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B&SE_Volume 45_Number 2_June 2015

The Bridge & Structural Engineer JOURNAL OF THE INDIAN NATIONAL GROUP OF THE INTERNATIONAL ASSOCIATION FOR BRIDGE & STRUCTURAL ENGINEERING

Strengthening, Repair and Rehabilitation of Structures


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The Bridge and Structural Engineer

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Volume 45 Number 2 June 2015  i


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ii  Volume 45

Number 2 June 2015

The Bridge and Structural Engineer


The Bridge & Structural Engineer ING - IABSE

Indian National Group of the International Association for Bridge and Structural Engineering

Contents :

Volume 45, Number 2 : June 2015

Editorial • From the desk of Chairman, Editorial Board : Mr. Alok Bhowmick • From the desk of Guest Editor : Mr. P.Y. Manjure

Highlights of ING-IABSE Events • ING-IABSE Annual Day-2015 and Technical Presentations held on 23rd May 2015 at New Delhi

x

• Workshop on “Project Preparation and Repair/Rehabilitation of Bridges and Flyovers” held at Lucknow on 10th & 11th June 2015

xii

1. Rehabilitation of Bridges & other Structures –The Challenging Discipline Padmakar Manjure

1

2. Rehabilitation of Steel Bridges Amitabha Ghoshal

13

3. Condition Assessment and Rehabilitation of an Impact Damaged Concrete Bridge Rajeev Goel, Surjit K. Sharma, Lakshmy Parameswaran

21

4. Strengthening, Retrofitting, Repair and Rehabilitation of Bally Road Over Bridge No. 15A, Howrah Division, Eastern Railway by Using External Prestressing S.J. Deb, V.L. Deshpande

29

5. An Overview of Repair and Rehabilitation / Strengthening of Concrete Bridges and A Case Study A. K. Banerjee

39

6. Investigation and Rehabilitation of Fire Damaged Structures with Case Studies R.K. Jaigopal

45

Contents

Special Topic : Strengthening, Repair and Rehabilitation of Structures

7. Replacement of Expansion Joints of 2nd Hooghly Bridge, Kolkata  53 Santanu Majumdar, Shibnath Lahiri, Arijit Ghosh, Pratik Sen  8. Evaluation of In-Situ Stress in Concrete Structures by Core Trepanning Technique S. Parivallal, K. Ravisankar, K. Kesavan, B. Arun Sundaram 9. Effect of CFRP Fabric in Enhancing Torsional Capacity and Twist Angle of Strengthened RCC Beams Pardeep Kumar, Surjit K. Sharma, Lakshmy Parameswaran

63

70

Research Paper 1. Classification of Concrete Bridges and Damage States for Seismic Evaluation: A State-of-the-Art Review Dnyanraj Patil, Rakesh Khare

77

Panorama • Obituary

87

• Office Bearers and Managing Committee Members 2015

88

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Volume 45 Number 2 June 2015  iii


The Bridge & Structural Engineer JOURNAL OF THE INDIAN NATIONAL GROUP OF THE INTERNATIONAL ASSOCIATION OF BRIDGE & STRUCTURAL ENGINEERING

September 2015 Issue of the Journal will be a Special Issue with focus on

AESTHETICS OF STRUCTURES SALIENT TOPICS TO BE COVERED ARE : 1.     Architecture & Aesthetics in general 2.     Aesthetics of Structures other than Bridges 3.     Aesthetics of Bridges 4.     Aesthetics and Heritage Structures 5.     Aesthetics attributes and quantification

The Bridge & Structural Engineer JOURNAL OF THE INDIAN NATIONAL GROUP OF THE INTERNATIONAL ASSOCIATION OF BRIDGE & STRUCTURAL ENGINEERING

December 2015 Issue of the Journal will be a Special Issue with focus on

GEOTECHNIQUES & FOUNDATION DESIGN FOR STRUCTURES SALIENT TOPICS TO BE COVERED ARE : 1. 2. 3. 4. 5. 6.

Geotechnical Investigations & Interpretations Liquefaction Analysis for Foundation Design Ground Improvement Techniques Foundations in difficult Ground conditions Choice of Foundation System for Buildings and Bridges Any other topic of relevance

Those interested to contribute Technical Papers on above themes shall submit the abstract by 7th November 2015 and full paper by 22nd November 2015 in a prescribed format, at email id : ingiabse@bol.net.in, ingiabse@hotmail.com

iv  Volume 45

Number 2 June 2015

The Bridge and Structural Engineer


B&SE: The Bridge and Structural Engineer, is a quarterly journal published by ING-IABSE. It is one of the oldest and the foremost structural engineering Journal of its kind and repute in India. It was founded way back in 1957 and since then the journal is relentlessly disseminating latest technological progress in the spheres of structural engineering and bridging the gap between professionals and academics. Articles in this journal are written by practicing engineers as well as academia from around the world.

Disclaimer :

Editorial Board

All material published in this B&SE journal undergoes peer review to ensure fair balance, objectivity, independence and relevance. The Contents of this journal are however contributions of individual authors and reflect their independent opinions. Neither the members of the editorial board, nor its publishers will be liable for any direct, indirect, consequential, special, exemplary, or other damages arising from any misrepresentation in the papers.

Chair :

The advertisers & the advertisement in this Journal have no influence on editorial content or presentation. The posting of particular advertisement in this journal does not imply endorsement of the product or the company selling them by ING-IABSE, the B&SE Journal or its Editors.

Jose Kurian, Chief Engineer, DTTDC Ltd., New Delhi

Alok Bhowmick, Managing Director, B&S Engineering Consultants Pvt. Ltd., Noida

Members : Mahesh Tandon, Managing Director, Tandon Consultants Pvt. Ltd., New Delhi A K Banerjee, Former Member (Tech) NHAI, New Delhi Harshavardhan Subbarao, Chairman & MD, Construma Consultancy Pvt. Ltd., Mumbai Nirmalya Bandyopadhyay, Director, STUP Consultants Pvt. Ltd., New Delhi S C Mehrotra, Chief Executive, Mehro Consultants, New Delhi

Advisors : A D Narain, Former DG (RD) & Additional Secretary to the GOI N K Sinha, Former DG (RD) & Special Secretary to the GOI G Sharan, Former DG (RD) & Special Secretary to the GOI A V Sinha, Former DG (RD) & Special Secretary to the GOI S K Puri, Former DG (RD) & Special Secretary to the GOI

Front Cover :

R P Indoria, Former DG (RD) & Special Secretary to the GOI

Top Right: Picture shows external prestressing of Girders for old Nizamuddin Bridge over river Yamuna, Delhi

S S Chakraborty, Chairman, CES (I ) Pvt. Ltd., New Delhi

Top Left: Picture shows collapse of cut-roller bearings for Kairana Bridge across river Yamuna in Uttar Pradesh Bottom Right: Picture shows external prestressing of Girders to compensate for loss of prestress and use of structural steel brackets for supporting distressed hammerheads, for Sharavathy Bridge on West Coast at NH-17 Bottom Left: Picture shows Kairana Bridge across river Yamuna in Uttar Pradesh, in which settlement of more than 1200 mm in one well foundation is observed, resulting in collapse of cut-roller bearings. Suspended Span bearings are also affected • Price: ` 500

B C Roy, Senior Executive Director, JACOBS-CES, Gurgaon Published : Quarterly : March, June, September and December Publisher : ING-IABSE C/o Secretary, Indian National Group of the IABSE IDA Building, Ground Floor (Room Nos. 11 and 12) Jamnagar House, Shahjahan Road New Delhi-110011, India Telefax: 91+011+23388132 Phone: 91+011+23386724 E-mail: ingiabse@bol.net.in, ingiabse@hotmail.com, secy.ingiabse@bol.net.in Submission of Papers : All editorial communications should be addressed to Chairman, Editorial Board of Indian National Group of the IABSE, IDA Building, Ground Floor, Jamnagar House, Shahjahan Road, New Delhi – 110011. Advertising: All enquiries and correspondence in connection with advertising and the Equipments/Materials and Industry News Sections, should be addressed to Shri RK Pandey, Secretary, Indian National Group of the IABSE, IDA Building, Ground Floor, Jamnagar House, Shahjahan Road, New Delhi-110011.

The Bridge and Structural Engineer

Journal of the Indian National Group of the International Association for Bridge & Structural Engineering

June 2015

The Bridge & Structural Engineer, June 2015

The Bridge and Structural Engineer

Volume 45 Number 2 June 2015  v


From the Desk of Chairman, Editorial Board

This issue of the journal is focused on the theme of “Strengthening, Repair and Rehabilitation of Structures”. Evaluation, repair, rehabilitation and strengthening of existing infrastructure has become increasingly an important topic within the construction industry. The need for repair and strengthening of a structure may arise from usual deterioration due to ageing or problems of durability, due to likely change in functional use of the structure, changes in the relevant design codes subsequent to the construction, change in loadings conditions subsequent to construction, structural defects or due to any unforeseen disasters (like earthquake, floods, cyclone …etc.). Strengthening, rehabilitation repair and retrofitting of structures is usually a challenging task for Engineers, due to uncertainties associated with the behavior of distressed structures. The Engineers involved in such works needs to have sufficient work experience and skill since there are no applicable codes and standards, which gives a formatted unidirectional approach to any solution. The Engineer has to explore amongst plenty of possibilities, after studying all the constraints in a given situation, to come out with the optimum solution. vi  Volume 45

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Accuracy of evaluation of any structure can be improved by using the recent advancements and developments in structural diagnostics, structural tests, material tests, structural analysis and probabilistic methods of design. Considering the above scenario, a need was felt by the editorial board of ING-IABSE for dissemination of current knowledge and for exchange of recent experiences gained by the practicing engineers as well as research institutions in the field of Repair and Rehabilitation. Our Guest Editor for this issue is Mr. P Y Manjure, who is a well known personality in the field of Repair and Rehabilitation in India and overseas. I am sure, the papers in this journal will reveal the intense amount of activity going on in India and in various parts of the world on topics of damage detection, diagnosis and evaluation, repair, rehabilitation and strengthening of engineering structures. It is hoped that readers will find the information of value.

ALOK BHOWMICK The Bridge and Structural Engineer


From the Desk of Guest Editor

This issue of “The Bridge & Structural Engineer” is specially devoted to ‘Rehabilitation of Structures’. Subject of rehabilitation is fairly new and is emerging in all spheres of construction. The topic is under evolution and touches variety of constructional; design and maintenance aspects. Population of old structures is increasing over the years and it is in the fitness of things that such issue is coming out which is timely and at appropriate juncture. Variety of requirements arises in respect of old structures which include normal concrete repairs, structural strengthening, enhancement of sections, replacement of bearings and joints; addition of reinforcement and making up prestress losses etc. Adverse effects on structures caused by natural disasters such as excessive floods, earthquakes and landslides etc., on the functions of structures are to be tackled in such a manner that the utility of the structure is restored in minimum possible time. Eventually it brings up several issues which need to be handled adroitly by the rehabilitation engineers. Factors such as increasing capacity of the Railway Bridge structures as it happens with conversion of meter gauge bridges which need to take Broad Gauge loading; call for upgradation. Similarly increase in axle loads of vehicles plying on highway bridges may take place in times to come and would therefore call for increase in load carrying capacity of the bridges. Besides, due to increase in density of traffic, roads and bridges need to be widened to cope with large traffic. Techniques of rehabilitation

The Bridge and Structural Engineer

would be useful in such situations and thus topic of rehabilitation becomes much more relevant. Bridges are more vulnerable and many of them need measures for strengthening and rehabilitation sometime or other during their service life. Type of measures would depend upon the distress and its severity, structural details, materials used and functional requirements etc. In sixties and seventies, few and far in between bridges had to be tackled for rehab. In late eighties, Thane Creek Bridge near Mumbai gave a wake up call. Need for revision of maintenance manuals standards for rehabilitation work was strongly felt. Standard methods for investigation and remedial measures were prepared by Indian Roads Congress and are now periodically reviewed. One of the important aspects in the rehabilitation process is assessment of the structure. The assessment of a structure differs in many ways from the design of a new one. At times, the most basic data about design and drawing of the structure as constructed is not available which fact makes the assessment more difficult. The engineer responsible for assessment has to resort to some assumptions and had to bank upon his engineering judgement. The data collected from the non-destructive tests and condition surveys do supplement the assessment and help in formulating remedial measures. There is substantial growth in recent years in development of materials and techniques for rehabilitation of structures. Issues of normal

Volume 45 Number 2 June 2015  vii


maintenance, ageing and consequent deterioration are fairly addressed. However a need is felt for techniques to deal with maintenance design for service life requirements, durability, fatigue and vibration problems. The situations arising from extreme events such as bomb explosion, fire, earthquake, landslides and very high floods have to be tackled for which innovative techniques need to be developed. The role of instrumentation is also significant in the scheme of repairs and rehabilitation. The structural remedies used for correcting or containing the distress can be checked for efficacy with the use of appropriate instrumentation. For example while augmenting the prestress in a member, measurement of strain gives confidence about the method used. In fact, instrumentation would be useful even after the rehabilitation work is completed. Such periodical monitoring would help timely action and prevent any untoward happening to the structure. Various aspects of rehabilitation as briefly mentioned earlier have been covered to some extent in 9 papers appearing in this issue. Apart from Bridges, there are other structures such as buildings, silos, jetties and dams etc, which also need to be strengthened. While elaborating the nature and cause of distress, I have covered such structures giving brief case studies. Besides, I have tried to highlight the challenges inherent in such works. The technique of supporting the truss in cantilever situation from the adjoining span is novel and Mr. Ghoshal has brought out the innovation appropriately in his article. Mr. Rajeev Goel has brought out recommendation about rehabilitation of impact affected girders. How deficient PSC members of an ROB were strengthened by additional pre-stressing has been elaborated by Mr. Deb and Mr. Deshpande in their paper. Paper of Mr. A.K. Banerjee gives an overview of sequential

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activities for any rehabilitation project together with an illustrative case. There are interesting case studies of fire affected structures by Mr. Jaigopal. Replacement of modular joints on Hooghly bridge with very heavy traffic was difficult task. Mr. Majumdar has brought out the complexity of the work in his paper. To know the residual prestress in any prestressed concrete member has been a nagging question. Structural Engineering Research Centre has done considerable work and research on this problem in recent years and has developed successfully a viable test-method to find out this parameter. Dr. Parivallal’s paper throws light on this requirement and provides important data which I am sure would help in assessment and developing proper remedial measure. Carbon fibre material is being used in rehabilitation of structures in the last few years. Further work done on this in the laboratories of CRRI by Dr. Lakshmy Parameswaran, Mr. Pardeep Kumar and their colleagues would certainly be useful in developing schemes of rehabilitation. As I said earlier rehabilitation is a developing science and there is great potential to innovate and make this discipline richer. All in all, I must say this issue would make an interesting reading and provoke engineers to greater innovations and novel solutions. Finally I would like to thank IABSE Secretariat – Mr. R.K. Pandey, Mr. K.B. Sharma and Chief Editor Mr. Alok Bhowmick and all authors for their wonderful co-operation and guidance in making this issue a success.

(P.Y. MANJURE)

The Bridge and Structural Engineer


Brief Profile of Mr. P.Y. Manjure Graduated with Honors in Civil Engineering from College of Engineering, Pune, Mr. P.Y. Manjure was actively engaged with Construction of Pre-stressed and RCC bridges for the first 6 years of his career. After joining The Freyssinet Pre-stressed Concrete Company Limited in 1970, he has specialized in the field of Pre-stressing, Repairs and Rehabilitation, Heavy Lifting and Special Civil Engineering Projects. During his career of 52 years, he was closely involved in rehabilitation of more than 350 structures including Bridges, Jetties, Aqueducts, Dams, Silos and Industrial Buildings, etc. He has been trained in France for pre-stressed Concrete and in Holland with M/s. European Structural Bonding Division bv., for repairs to Concrete. He has been an active member of Bridges Committee, Maintenance and Rehabilitation of Bridges Committee, Bearings Committee of Indian Roads Congress. He was also in the Managing Committee of IABSE. He is on the panel of Bureau of Indian Standard (BIS) for Revision of IS:456. He was selected ‘Vice President’ of Indian Roads Congress for the 50th Session in the year 1991. He was selected by FIP as a Member on Commission 10, dealing with Management and Maintenance of Concrete Structures for the period 1994-1998. He has written several Papers in Technical Journals and his Paper on Nizamuddin Bridge and Sharavathi Bridge won IRC Medals. His paper on ‘Erection of Buddha Statue’ brought him Indian Concrete Journal – V.K. Kulkarni Award for the Best Paper. He was awarded the IRC Medal for presenting the Best Paper on Rehabilitation and Strengthening of Zuari Bridge by Indian Roads Congress in January, 2004. The Institution of Engineers, Maharashtra Centre, Mumbai presented him the S.B. JOSHI MEMORIAL AWARD for the year 1994-95 for his contribution to Bridge Engineering. Received Citation & Award from Indian Chapter of American Concrete Institute for Outstanding Work of ‘Rehabilitation of Zuari bridge’ in December 2004. He has presented Papers at number of International Forums such as fib Congress in Amsterdam in 1998, IABSE Congress in Zurich in 2000, at American Concrete Institute during the Centennial convention in Washington in 2004, IABSE Symposium at Lisbon in 2005 and in Weimar in Germany in 2007, in June 2009 at fib Symposium 2009 held in London, in May 2013 at Rotterdam and recently in 2015 at Porto in Portugal. He was awarded the ‘S.B. Joshi Smruti Puraskar’ together with the Citation for ‘Excellence in Bridge and Structural Engineering’ by Alumni Association of College of Engineering, Pune in November 2005. The Institute of Engineers, (India) has felicitated him recently with “Eminent Engineer Award” for the year 2012 during convention held at Roorkee. The ‘Indian Concrete Institute’ has conferred on him ‘Life Time Achievement Award’ in September 2014. He is at present WHOLE TIME DIRECTOR of The Freyssinet Pre-stressed Concrete Company Limited.

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Volume 45 Number 2 June 2015  ix


HIGHLIGHTS OF THE ING-IABSE ANNUAL DAY-2015 AND TECHNICAL PRESENTATIONS HELD ON 23RD MAY 2015 AT NEW DELHI The Indian National Group of the IABSE had organised its Annual Day-2015 along with technical presentations on “Hammersmith Flyover and Forth” by Shri Mike Needham, Team Director, Ramboll and “Walton Bridge – A new Arch Bridge over the River Thames, UK” by Shri Chris Hendy, Atkins Fellow,

Head of Bridge Design & Technology, Transportation, Atkins at India International Centre, Lodhi Road, New Delhi on 23rd May 2015. The Annual Day 2015 and presentations was attended by about 75 delegates from various parts of India. The presentations was highly acclaimed.

A view of the Dais during the Inauguration

Shri Mike Needham during his Technical Presentation

Shri Chris Hendy during his Technical Presentation

A view of the audience during the technical presentation

A view of the audience during the technical presentation

Shri DO Tawade, Chairman, ING-IABSE Delivering his welcome address during the Annual Day and Technical presentations

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In the 55th Annual General Body Meeting, elections

under different rules were held for Managing Committee Members. In the 104th Managing Committee meeting, the elections were held for Members of the Executive Committee. Shri DO Tawade was elected as Chairman, Shri Divakar Garg, Shri MP Sharma, Shri Alok Bhowmick and Shri MV Jatkar were elected as Vice-Chairmen of the Group. Shri RK Pandey and Shri Ashish Asati would continue to act as Secretary and Director of the Group.

A view of the Dais during the 103rd Managing Committee meeting

A view of the audience during the 55th Annual General Body Meeting

Besides the above, the following Annual Meetings of the Group were also held on the 23rd May 2015 at India International Centre, New Delhi. 

103rd Managing Committee

55th Annual General Body

104th Managing Committee

A view of the audience during the 104th Managing Committee meeting

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HIGHLIGHTS OF THE WORKSHOP ON “PROJECT PREPARATION AND REPAIR/ REHABILITATION OF BRIDGES AND FLYOVERS” HELD AT LUCKNOW ON 10TH & 11TH JUNE 2015 The Indian National Group of IABSE in co-operation with Govt of Uttar Pradesh, PWD and UP State Bridge Corporation Ltd had successfully organised two day Workshop on “Project Preparation and Repair/ Rehabilitation of Bridges and Flyovers” at Lucknow on 10th and 11th June 2015. The Workshop was well attended by more than 200 delegates from various Govt Departments as well as other private and public organizations. The aim of the workshop was to provide a detailed understanding of the various aspects of a good project preparation for bridges and flyovers etc to the Engineers of State PWD and consultants. The Workshop was inaugurated by Shri Shivpal Singh Yadav, Hon’ble Minister of State, Uttar Pradesh for Public Works Department, Irrigation, Co-operative, Flood Control, Land Development & Water Resources, Waste Land Development, Irrigation (Mechanical), Revenue, Disaster & Rehabilitation and Public Service Management by lighting the traditional lamp. Shri Surendra Singh Patel, Hon’ble Minister of State, Uttar Pradesh for Public Works Department and Irrigation was the Chief Guest on the occasion. Other dignitaries, S/Shri KS Atoria, DO Tawade, RK Pandey, AK Banerjee, AK Gupta, Rajan Mittal and RC Beranwal also graced the occasion. During his inaugural address, Shri Shivpal Singh Yadav expressed that the deliberations of the Workshop will be highly educative with guiding parameter to meet any challenges in the matter of repair and rehabilitation of bridges by the practicing engineers and participants. Shri KS Atoria, Principal Secretary, Govt of Uttar Pradesh extended warm welcome to the participants of the Workshop. Shri DO Tawade and Shri RK Pandey delivered his address during the Inauguration. Shri Rajan Mittal, Managing Director, UP State Bridge Corporation Ltd proposed Vote of Thanks. The Workshop on “Project Preparation and Repair/ Rehabilitation of Bridges and Flyovers” was addressed by the following eminent experts covering the following Sessions: xii  Volume 45

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Session 1 – Project Preparation of Bridges & Flyovers 1 Shri AK Banerjee

– Feasibility Study & DPR – An Overview

2

– Geo-technical Investigation for Bridges

Shri Ravi Sundaram

3 Shri Alok Bhowmick

– Design of Substructure

Foundation

4

Shri Vinay Gupta

– Design of Superstructure

5

Shri Jitendra Rathore

– Bearings & Expansion Joints

6

Shri Somnath Biswas

– Reinforced Earth Walls

&

7 Shri GK Sahu,

– Instrumentation & Bridge Health Monitoring

8 Shri AK Banerjee

– Quality Control in Design and Construction

9 Shri AC Srivastava

– Construction of Bridges – Some Elementary Thoughts

Session 2 – Repair and Rehabilitation of Bridges & Flyovers 10 Shri AK Banerjee

– Overview of Investigation and Rehabilitation

Inspection, Repair /

11 Dr Lakshmy Parameswaran – Condition Survey and Detailed Investigation 12 Shri PY Manjure

– Rehabilitation of Bridges & Other Structures – The Challenging Discipline

13 Shri Upendra Ji Shukla

– Rehabilitation of Substructure of Yamuna Bridge on NH 73 – A Case Study

The Valedictory Session was held on 11th June 2015 (afternoon). Shri KS Atoria, Principal Secretary to the Govt of Uttar Pradesh, gave the Valedictory Address. He expressed the hope that the outcome of the Workshop would have enriched the delegates. The concluding remarks of the Workshop were presented by Shri DO Tawade, Chairman, ING-IABSE. The delegates who attended the Workshop mentioned that the subject matter of the Workshop is very timely. Shri RC Baranwal, Chief Engineer (NH), Govt of Uttar Pradesh proposed a Vote of Thanks. A cultural programme was organized in the evening of 10th June 2015 for the participants who rejoiced the evening. The Workshop was a great success. The Bridge and Structural Engineer


Shri Shivpal Singh Yadav, Hon’ble Minister,UP, PWD lighting the traditional Inaugural Lamp along with high dignitaries

A view of the Dais during the Inaugural Function

Shri KS Atoria, Principal Secretary, Uttar Pradesh, PWD Delivering his welcome address

Shri DO Tawade, Chairman, ING-IABSE Delivering his address

Shri RK Pandey, Secretary, ING-IABSE Delivering his address

Shri AK Banerjee, Chairman, Scientific Committee Delivering his address

Shri Surendra Singh Patel, Hon’ble Minister of State, Uttar Pradesh, PWD Delivering his address during Inaugural Function

Shri Shivpal Singh Yadav, Hon’ble Minister, Uttar Pradesh, PWD Delivering his address during Inaugural Function

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Volume 45 Number 2 June 2015  xiii


A view of the audience during the Inauguration

Another view of the audience during the Inauguration

A view of the Dais during the Valedictory Function

Call for Papers – Seminar on “Urban Transport Corridors” The Indian National Group of the International Association for Bridge and Structural Engineering (ING-IABSE) is organising a Seminar on “Urban Transport Corridors” in co-operation with Ministry of Road Transport and Highways and National Highways Authority of India from 6th to 7th February, 2016 at India International Centre, New Delhi. The Seminar will have four Technical Sessions covering each theme in one Session as per the following: i) ii)

Policy and Planning  Unified Urban Transport Development Authority  Planning for Multi-modal Transport for Urban Corridors  Transit Oriented Development including Land Use Planning System and Engineering Demand and Supply Management in Urban Transport  Infrastructure Requirement for Integrated Urban Transport  Use of ITS – Coordination, Efficiency, Monitoring, etc. in Urban Transport.  Safety and Security 

iii) Financing  Innovative Financing for Urban Transport Corridor.  Congestion Charging for Demand Management (including Parking) iv)

Case Studies Metro  Mono-Rail/LRT  BRTS  Intermediate Public Transport (Auto, Taxi etc.) 

Technical papers under various themes are invited for inclusion in the Seminar Report. The paper should be neatly printed including figures, tables etc. on A4 size paper with 25 mm margin on all side using 11 size Font (Times New Roman). Those who are interested to contribute a paper, kindly send their paper (maximum 9 pages plus one cover sheet) by 16th November 2015 at the following address. Selected authors will be invited to present their papers in the Seminar. Shri RK Pandey Secretary Indian National Group of the IABSE IDA Building, Ground Floor, Room No.12 Jamnagar House, Shahjahan Road New Delhi-110011 Telefax: 011-23388132

Phone: 011-23386724

E-mail: ingiabse@bol.net.in, ingiabse@hotmail.com

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Rehabilitation of Bridges & Other structures – The Challenging Discipline Padmakar MANJURE Director The Freyssinet Prestressed Concrete Co. Ltd., Mumbai ( India) pym@fpccindia.com

Graduated in Civil Engineering in 1963 from Pune university. Specialized in the field of Rehabiliation and prestressing. Done rehabilitation of more than 350 structures in last 5 decades.

Summary The structures are affected due to variety of reasons. Some cases of bridges and different type of structures are briefly described. Though symptoms of distress may be same, the solutions evolved would vary depending upon the assessment and requirement of each structure. Key words: Corrosion, cracking, deflections, external prestressing, bearings, mis-alignments

1. Introduction Deterioration of structures over a period of time and also due to variety of external influencing factors is found to be a universal phenomenon. It is not confined to any one country or particular part of the world. Whether it is an advanced country or a developing country, it has been widely experienced that problems do occur with the structures. Degradation of structures is also not governed by the type of materials used or type of structure adopted. Experience has shown that whether it is in steel or in concrete, it is vulnerable and looses its original characteristics and eventually the structure is unable to perform as envisaged. Irrespective of the type of structure, it has to face the problems of stability, safety and service life. Our country is no exception. It is a vast country, almost a sub-continent. It has a huge network of roads and rail systems, which are dotted with several hundreds of bridges. Besides, innumerable utility structures such as Storage Silos, Industrial factories, Power Stations etc., have come up in the length and breadth of the country. (Photo No.1A and 1B) The Bridge and Structural Engineer

Photo No. 1A-Important National Highways National Highways : 79116 km State Highways : 1,55,116 km No. of Road Bridges : Approx 100000 Nos

Photo No. 1B-Railway Network

Railway Network : 69000 Kms. No. of Railway : 1,33,000 Nos. Bridges

Population of old structures is increasing. Once a structure is built, it is considered to be almost permanent. This myth is however exploded as several structures are being discovered having deteriorated condition threatening their service life. There is growing realization about durability aspects and serviceability of the structures. The criteria for these parameters are regularly reviewed and are being established. Keeping this in mind, precautions are being taken during design and construction. New materials, methods of construction techniques are used to ensure durability of structures. In spite of growing realization for improved construction and maintenance, distresses are observed in the structures and rehabilitation measures are required to be taken. Volume 45 Number 2 June 2015  1


At times the structures are adversely affected due to natural disasters such as huge landslides on the bridges or extra ordinary floods over topping the bridges. Sometimes there are accidents such as tilting of bridge piers by traffic vehicles or barges. There are public and commercial structures de-capacitated by fire. All such structures are required to be made serviceable.

constructed during the last 6 decades.

Rehabilitation of structures calls for ingenuity and innovativeness. In spite of lack of sophisticated equipments, many complicated structures have been successfully rehabilitated by using indigenous materials and techniques. How this has been achieved by us is described in this article.

All these structures have to be maintained to keep the wheels of growth moving. In this context, rehabilitation of structures becomes more relevant.

2.

Panorama of our Structures

After Independence, there has been a spectacular growth in the construction field in India in all spheres of life. Systematic development of National Highways and Road and Railway network led to construction of bridges. There are several mighty rivers such as – Ganga, Brahmaputra, Godavari etc., and bridging these rivers was a great challenge. Ganga Bridge at Patna with its length 5500 Metres was considered to be longest river bridge in Asia at that time (1982). (Photo No.2). India has a vast coastline and building bridges over creeks and straits was challenging.

Storage facilities for grains, cement etc., were created and silos were constructed throughout the country. Besides, several Industrial Structures, Factory buildings, Power Stations have come up. As a matter of fact, all sorts of structures have come up in the pursuit of developmental activities on all fronts.

3.

Maladies and Remedies

Several rehabilitation works have been successfully completed by us in the last three or four decades. Over the years, many measures have been evolved and adopted in practice. Some of the important ones with proven efficacy are highlighted here. 3.1 Treatment of cracks by Epoxy It is known that every crack is not structurally significant. The crack in a structure signifies distress. However, what matters is not their occurrence, but their size, frequency and cause for occurrence. The integrity of the structure is restored by epoxy treatment. Solvent free epoxy resin compounds which cure by chemical reaction between resin and hardener are used for the treatment of cracks. Epoxy is advantageous in faster development of strength. This consideration is important in putting back the structure in service. Their bond with concrete is excellent. Prior to injection, cracks are cleaned and prepared. Equipment with automatic mixing and continuous flow type is effective for injection.

Photo No.2-Ganga Bridge at Patna

The range of bridges constructed is very vast. The materials used are: Reinforced concrete, Pre-stressed concrete and steel as well. The range of method of construction adopted covers simply supported, cantilever construction, balanced cantilever, arch, segmental and cable stay etc.. With the emphasis on Agriculture, several irrigation projects were taken up. As a result, Dams, Aqueducts, Syphons and similar hydraulic structures have been 2  Volume 45

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Sometimes, porosity of concrete is required to improved. In such case, even though there are cracks, treatment by epoxy injection can help improving impermeability properties. Injection done through inlets formed on a suitable grid.

be no in is

Epoxy treatment is not the panacea in the scheme of repairs. This can however be well combined with other techniques for better results. 3.2 Treatment of Honeycombs and Damaged concrete Fast setting repair mortars are found suitable for The Bridge and Structural Engineer


patchwork repairs of concrete. Cement based mortar containing admixtures are used when high early strength and increased resistance is needed. Polymer based special mortars are also used. The reinforcement encountered here is treated with passivating paint.

are prepared duly de-greased in a bath and covered with primer. The plates are applied under pressure to squeeze the film of glue and allow the plate to follow the profile of the member. The plates are protected against corrosion.

3.3 Jacketing Jacketing involves fastening of external material such as concrete, steel etc., over the existing members to provide required performance characteristics. Interface between old concrete and new concrete has to be treated by suitable bond coat. Besides, positive connection between two elements is achieved by providing dowels in the old concrete. On several Indian bridges, this method has been used for piers, arches, columns and even for footings of open foundation with success. 3.4 Replacement of Damaged Concrete Situations like delamination of concrete, contamination of concrete by chloride ions or severe cracking of concrete can be tackled by removing the defective concrete and rebuilding them. Equipment used should be such that it does not damage good concrete. Use of Concrete Saw, Power Operated tools etc., is effective. Fresh concrete is added by casting or spraying after priming the surface with a suitable material. It is necessary that replacement concrete has matching properties with existing concrete as close as possible. 3.5 Addition of Reinforcement Additional rebars are provided in place of damaged or corroded bars. This is a simple method and is being practiced here regularly. Precaution is taken to ensure that proper anchorage is established by suitable lapping or bolting and welding/coupling methods. 3.6 Bonding of Steel plates or Carbon Fibre Sheets Beams, columns and slabs etc., are strengthened by gluing metallic plates in appropriate manner. The addition of steel plates enhances the resistance of existing elements in bending, tension and shear. The aim of this technique is to modify or improve load bearing capacity of the structure. (Photo No.3) Before gluing the plates, the surface should be well prepared by use of sand blasting, water jetting or similar method. The plates of 2 to 3 mm. thickness The Bridge and Structural Engineer

Photo No.3-Bonding of Steel Plates – Bassein Creek Bridge

Fibre reinforced plastic and carbon fibre sheets are now available in India and this technique is increasingly being adopted on rehabilitation projects. These sheets have an advantage over the steel plates as they can assume any shape being thin and can be wrapped/ bonded with the structure more easily. Besides, they are not prone to corrosion. 3.7 External Post-Tensioning This is a versatile technique. There are number of prestressed concrete and reinforced concrete structures effectively strengthened in India by using this technique during the last two decades. (Photo No.4). Some steel deckings of the bridges comprising of trusses and plate girders are also strengthened by this method. The method envisages use of pre-stressing cable around the structure in such a manner that it augments the load carrying capacity or creates beneficial stresses as desired. The cable could be of bars, wires or strands. The design is generally on the same lines as for conventional pre-stressing. Lot of attention is required for detailing the scheme. Care is necessary in design and location of anchor plates, deviator blocks and protection of the cables. The pre-stressing forces are transmitted through the anchorages and due regard should be given to the fact that existing concrete and embedded reinforcement can cater to these forces. The support conditions for anchorages and use of deviators in structures being Volume 45 Number 2 June 2015  3


repaired should be studied in conjunction with tendon layout used.

Photo No.4-Nizamuddin Bridge – View of External Prestressing

Many bridges located on the Indian coastline are affected due to corrosion and stability of the decking is threatened. Bridges across Thane Creek, Zuari River and Sharavathi etc., are rejuvenated by using this technique.

4.

Case Studies

There are several bridges on the highways and railways systems which are rehabilitated successfully in the recent years. These are classified considering the type of distress observed. One typical case of each type of major distress is covered. Apart from bridges, other structures such as silos, industrial buildings and irrigation structures are also described.

5.2 Distress Noticed and Causes After few years of opening the bridge to traffic, it was observed that the suspended span between P-5 and P-6 had shifted towards the downstream side by 24 mm. The shifting was progressive and was found to be increasing. At the time of rehabilitation, the bearing had shifted as much as 110 mms. On inspection, it was found that the bearings were not placed in line and level. The bearing on downstream was inclined by 20 mms. whereas the upstream bearing was tilted by 7 mms. The bearings were also sloping along the axis of the bridge to some extent due to deflection of the hammerhead. This slope was of the order of 9 mms. and 4 mms. for upstream and downstream bearings respectively. The PSC girders were found curved in plan. The bearings, which might have been fixed normal to the axis of the girders, were, therefore, not at right angles to the axis of the bridge. Besides, the level of downstream bearing was lower by 35 mms. with respect to upstream bearing. On account of these factors, the bearings started shifting in transverse direction. Later on, after lifting the span, it was discovered that the guide strips were not an integral part of the bottom plate but were fixed by using flimsy screws. These screws had sheared off due to transverse force thus allowing the span to move. 5.3 How this was rectified

This bridge is on State Highway connecting Uttar Pradesh and Madhya Pradesh. It is built across River Chambal near Etawah in Uttar Pradesh.

First, an access platform was provided to reach the bearing for thorough inspection. As the piers were tall, it was not possible to erect any scaffolding from the riverbed. Therefore, a steel inspection cum working platform was suspended from the bridge deck near the roller end articulation. A scheme was prepared to lift the suspended span by using steel trusses (Photo 5), which were fixed to the hammerhead at one end and to the PSC girder at the other end. Between the trusses, traffic in one lane was permitted. The span was lifted by using flat jacks and was then supported on sliding arrangement for side shifting.

On well foundations, concrete piers of 24.4 M. height were built. The superstructure comprises of hammerhead and suspended span arrangement. The hammerhead is a single cell RCC box girder of 11.1 M. length. The suspended span comprises of 2 PSC ‘I’ girders each of 40.6 M. length. Cast steel Rocker and Roler bearings have been provided at articulations.

It was observed that on release of horizontal side shifting force, the span came back by 12 mms. As such, the span was shifted additionally for 12 mms. so that it moved back to original position. After achieving the required rotation of the span, new bearings were installed and the suspended span was lowered on to them.

5.

Bearing Displacement

On many bridges, Steel Rocker and Roller Bearings are commonly used. Many cases of displacement of bearings have been observed. Sometimes, the cut rollers get excessively tilted or fallen flat. One such case is that of Chambal Bridge. 5.1 Chambal Bridge Near Etawah

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The Bridge and Structural Engineer


The shift and loss of height was as under: Over P-3 Over P-4 a) Drop in height 200 mms. 500 mms. b) Shifting of bridge alignment 1070 mm. 409 mms. towards downstream (P-3/P-4)

Photo No.5-Chambal Bridge near Etawah – Lifting Arrangement

6.

Damage due to Floods

6.1 Vansadhara Bridge This bridge is situated on Behrampur-Raigada State Highway No.4 in Orissa State. There are 9 spans of 104 ft. each and two end spans of 35 ft. with floating spans of 5 ft. The superstructure consists of RCC box girder with twin cells and balanced cantilever supported on solid piers. Rocker and Roller Steel bearings were provided on the piers supported by dumb-bell shaped well foundations. The river has a sharp turn of almost 90° at about 1500 M. upstream of the bridge. During one of the high floods, the transmission tower and cables on it got toppled. Similarly, thousands of mango trees got uprooted and this entangled mass got blocked under the bridge. The water was blocked thereby creating a dam-like situation. Due to this, the abutment on the right bank together with P-1 and P-2 and decking got washed away. (Photo No.6). The superstructure on P-3 and P-4 shifted towards the downstream side and rested on 2 pedestals only.

The piers P-3 and P-4 were tilted towards the upstream side. The main span P3 – P4 and suspended span P4 – P5 were saved from getting washed away. However, they got misaligned badly in 3 directions. It was decided to rehabilitate span P3 – P4 and also set right the adjoining suspended span. The washed out span P1 – P2 and P2 – P3 were planned to be reconstructed. The following remedial measures were taken to restore span P3 – P4: 

 

The damaged concrete with cracks was treated with epoxy injection for the piers and box girder. Both piers were provided with RCC cladding. The anchoring of reinforcement was done with well cap and existing pier. The span was lifted to the original level. The lifted span was rotated for achieving proper alignment. The span was lowered on the Neoprene Bearings.

By adopting the above techniques, the span P3 – P4 was successfully restored.

7.

Settlement of Foundations

7.1 Thevally Bridge in Kerala In this bridge, one pier and an abutment suffered considerable settlement and tilting thereby adversely affecting the stability and alignment of the bridge. (Photo No.7) The bridge is located on a State Highway near Thevally town in Quilon district. It has balanced cantilever decking with two main units of 30.48 M. and central suspended span of 15.24 M. The end approach spans are supported by cantilever tips. In the transverse direction, four girders are provided for the two lane decking with footpaths on both sides.

Photo No.6-Vansadhara Bridge – Washed Spans

The Bridge and Structural Engineer

The abutment on Kadavur side and adjoining pier had settled and tilted. The settlement was 1.26 M. and 0.7 M. respectively for abutment and pier on Volume 45 Number 2 June 2015  5


upstream side. The span had shifted longitudinally and transversely. Due to settlement RCC rocker and roller bearings had cracks. Due to rotation of the span in plan, expansion gaps too varied substantially. The shear strength of the soil in which well foundations were located was found to be poor, thus resulting in the settlement. It was considered not to rely on existing foundations of P-1 and the abutment. Hence it was decided to construct new trestles around these foundations and transfer the load of the spans over them. For pier and abutment 20 and 12 bored piles of 550 mm φ were constructed respectively. On the top, new pier cap was provided.

8.

Deficiency in Construction

8.1 Restoration of Cement Silo Problems of deficiency in construction and workmanship manifest during the service life of the structure. The case of a Cement Silo which had excessively tilted and restored is relevant in this regard. (Photo No.8) There are 4 Cement Silos in Cement Plant near Bilaspur in Madhya Pradesh State. Each silo is 14 M. in diameter and 37 M. tall. The silos were constructed by slip-form method. When the height of 7 M. was reached, the shuttering got stuck up. It took quite some time to resume concreting work. The joint at the interface of old and new concrete remained weak. Therefore, when the silo was filled to its full capacity, it failed at this weak plane and tilted by 2 M. It rested against the adjoining silo and got supported. Experts from within the country and abroad were consulted. However, the proposal for restoration of this silo was received only from our organization. The following measures were proposed:

Photo No.7-Thevally Bridge-Settlement

The rehabilitation work was executed in the following sequence: 

Construction of piles and raising pier on them for some height below the soffit of superstructure. By lifting the spans, the superstructure was brought to the original level position.

Articulations were repaired.

Balance height of the trestles was constructed.

Side shifting of the span to bring to original alignment Neoprene Bearings were installed on new trestles and the superstructure lowered on to them.

In this manner the work was completed successfully without any problem. The magnitude of lifting and shifting operations for decking was considerable and there was no agency to undertake this risky work. The challenge was taken by FPCC and the job was done well. 6  Volume 45

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Photo No.8-Raymond Cement Silo – Tilted Position 

The silo to be brought back to its vertical alignment by controlled lifting operation. For this purpose, a portion of the silo above the crack level was supported by hydraulic jacks against steel The Bridge and Structural Engineer


required locations for joining new cables and then stressing them for making up the loss of pre-stress. A new concrete block was constructed inside the box girder in which cables from either side were anchored in cross shape giving overlap. Transverse cables were also provided to take care of the bursting forces on account of longitudinal pre-stressing.

brackets fixed on the tilted silo and diagonally on the opposite side. The jacks were supported on the concrete jacket built around the silo in lower portion. 

The concrete of the silo at 7 M. height was broken on the opposite side of the crack. Tilting the silo on the opposite side of the cracks by controlling carefully, lifting and lowering the jacks in stages of 100 mm. After bringing back the silo to its vertical alignment, concreting was done to the damaged portion. The outer jacket was integrated with existing silo. A pre-stressed concrete rig beam was provided on the top of the jacket.

After restoration, the silo is performing well.

9.

9.1 Khuni Nallah Bridge This bridge is on Jammu Srinagar Highway and is situated in the Himalayan terrain, which is prone to landslides. For providing safety to the bridge and traffic, a buffer system is provided on the hillside 13 M. from the bridge. (Photo No.9) The superstructure is a box girder constructed over 2 piers by free cantilever method and anchor spans. The cantilevers are 39.02 M. and 19.82 M. on Srinagar and Jammu side respectively. The anchor spans are 18.6 M. and 8.23 M. The central suspended span is 30.49 M. A mass of about 20 M3 of landslide fell on the valley side girder on Srinagar side pier. The impact was so big that the deck was punctured in an area of 6 M. x 3 M. besides damaging the pre-stressed cables of 12 φ 8 size. Out of 46 cables, 23 cables were completely sheared off and 9 cables were bent or exposed. Concrete was crushed and damaged severely. Suspenders and strands of the buffer system were also snapped. 

Photo No. 9-Khuni Nallah Bridge – Damaged Girder

Accidental damage to the Structure

Traffic was restricted to one lane with speed restrictions. The subway nearby was opened to traffic. The following measures were taken to restore the integrity of the decking: Cutting all snapped and damaged cables at

The Bridge and Structural Engineer

Repairing damaged concrete.

Stressing and grouting of cables.

A load test was carried out for maximum flexural and shear effect as per IRC loading. The recovery of deflection measured at the tip of cantilever was excellent.

10. Corrosion of Pre-Stressing Steel 10.1 New Shorrock Mills at Nadiad For this textile unit, roof arrangement consists of prestressed concrete girders over which pre-cast RCC elements are supported. The PSC girders rest on RCC corbels. Humid air is circulated in the weaving section as per quality requirement. Over a period, this led to corrosion of reinforcement as well as pre-stressing steel. Number of RCC corbels has developed distress on account of loss of steel section. Spalling of concrete along the cable profile had taken place in PSC girders. (Photo No.10) Additional supports were provided to the corbels by fixing bolted steel brackets under RCC corbels. In addition to bolting, pre-stressing cables were used to fix the brackets firmly to the parent box girder. Strengthening of roof girders was done by external pre-stressing cables. Two cables were provided on either side of the girder. Cables of 1T15 were anchored Volume 45 Number 2 June 2015  7


at the ends on steel brackets, which were fixed to the walls by wedge bolts. In this manner, 22 corbels and girders were strengthened successfully.

up for the loss of pre-stress at least by 18 to 20%. The cables were located on the underside of the deck and over the soffit by deviating them from the web. The load test was carried out successfully proving the efficacy of the measures taken. 10.3 Don Bridge in Karnataka State This bridge is 230 M. long with 7 spans out of which 5 spans of 40 M. length are in pre-stressed concrete. The superstructure consists of 3 “I” girders connected by cross diaphragms. RCC deck is laid on the top. (Photo No.12).

Photo No.10-New Shorrock Mills, Nadiad – External Cable

10.2 Zuari Bridge in Goa This bridge is situated on NH-17 near Panjim in Goa and is across River Zuari over the estuary portion. The superstructure consists of ‘T’ arm cantilevers over 5 piers and is in pre-stressed concrete. The decking for the main span consists of variable depth box girders constructed by free cantilever segmental construction method. A central hinge arrangement is provided where 2 faces of the cantilever meet. Each cantilever arm is about 61 M. long and depth of the box varies from 8 M. at the pier to 2 M. at the top of the cantilever. (Photo No.11) After 14 years, it was observed that there were excessive deflections of the cantilevers combined with vertical cracks in the web near the pier. One of the important factors contributing to the distress was loss of pre-stress on account of corrosion of cables.

Photo No.11-Zuari Bridge – General Elevation

To improve the serviceability of the structure, a scheme of external cables was developed to make 8  Volume 45

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The condition survey and inspection of the bridge revealed girders are weakened due to loss of pre-stress on account of corrosion of steel etc. The bearings were also damaged. The girders were strengthened by providing external cables. Due to geometry of the girder, the cables had to be deviated twice. In order to absorb the movements of the girder under load, pendulum type of arrangement was used for the deviator. As there was no sufficient space for anchoring the cables at the deck level, new deck slab was laid which was also required for enhancing the shear rating. In addition to external cables, other measures for rehabilitation taken included replacement of bearings, treatment to cracks and spalls in concrete by epoxy and providing protective coating and cement grouting of existing cables etc. The entire work was completed in 6 months.

11. Excessive Decking

Deflection

of

Cantilever

11.1 The Ganga Bridge situated on NH 19 near Patna city is a vital link between north and south Bihar and is considered to be the longest river bridge in Asia. It has two carriage ways resting on common RCC pier and well foundation. There are 46 “T” arms each of 121m length and two floating end spans of 5 meters each. The superstructure is in prestressed concrete and done by using pre-cast segmental cantilever construction. Each cantilever is 61 meter long and is a single cellular box with 8m depth on pier and 2.2m at the end and is prestressed with 70 cables of 24 φ 8 Freyssinet Tendons. Total prestressing force applied was 7915 tonnes. At the junction of two cantilevers central hinge bearings are provided. The Bridge and Structural Engineer


Photo No.12-Don Bridge

11.2 The Distress and causes Upstream carriageway was commissioned in 1982 and down stream in 1987. Signs of distress started appearing since late nineties. Periodical inspections of the superstructure revealed the following distress :

Excessive sagging of cantilever tips which was attributed to lack of adequate compression in the box girder and creep. Opening of joints between two precast segment at the deck level. Level differential at the junction of two adjoining cantilevers affected the riding surface. Though grade of concrete in both cantilevers was same perhaps, actual creep strains and relaxation losses in prestress could be different leading to such phenomenon. The deflections were observed by and large to be varying from 50 mm to 100 mm barring a few exceptional cases. Damages to central hinge bearing (CHB) in some cases plunger was separated and in some, plunger was found cracked at the root level. The wearing of top and bottom plates was commonly noticed leading to gaps of 20 to 40 mm in many bearings. Corrosion of prestressing steel :- Cables near road level were corroded and some wires were observed to be snapped due to corrosion.

11.3 Strengthening measures Most important requirement of this turnkey rehabilitation job was to provide adequate prestressing force to restore stability of the decking to the design level. Based on condition survey of each span and The Bridge and Structural Engineer

regular NDT tests done, it was established that the concrete strength was excellent and varied from 45 to 55 MPa. Assessment for additional prestress was done considering changes in codal provisions in IRC-18-1965 which was revised in 2000. There was major change in computing relaxation losses. Due to peculiar configuration of external cables and to take care of extra weight added due to cable anchorage system prestress to be applied was modified. Thus total external prestress applied originally was of the order of 19 to 20% of design prestress. During course of rehab work it was discovered that the cables were corroded. To compensate loss on account of corrosion, total external prestress was enhanced to 25%. In nutshell, various measures taken to strengthen this bridge are as follows :

External prestressing of the box girder by 12 nos of 9K15 cables anchored in the soffit. In a few spans, separation of vertical joints in precast segments was noticed. Local stitching across the joints by prestressed rods was carried out in addition to external cables. Central Hinge bearings were replaced by new ones. Due to geometrical limitations, sizes of bearings were generally maintained. However review of metallurgy and design aspects was taken and new bearings made.

Spalling in concrete was repaired by epoxy mortar and cracks were treated by low viscosity epoxy.

11.4 Instrumentation Main objective of instrumentation was to check behavior of the structure before and after applying additional prestress. Different parameters such as compressive strains, deflection of the cantilevers and variation due to temperature etc. were recorded. Electrical strain gauges were used to check strains in the box girder. Deflection was measured similarly at every stage. The uplift of the cantilever was recorded and was fairly in agreement with the theoretical deflections. 11.5 Re-construction of span P44 In March 2011, one cantilever of this span sagged excessively by 500 mm while replacement of bearing was being done. The sagging continued and stabilized Volume 45 Number 2 June 2015  9


at 659 mm in the following days. Temporary measures were immediately taken by connecting the sagging cantilevers at tip level by providing longitudinal structural steel members within the box. However the subsequent studies revealed that the cantilevers are not stable and it was not feasible to strengthen them any more.

Over the years, the mortar has leached and as a result, the stones have become loose. In order to restore the integrity of the structure and give them further lease of life, following measures were taken for strengthening of the bridge:

In view of this, it was decided to demolish the cantilevers with pier segment and re-construct the span. The work of demolition was very tricky as nearly half the length of cantilever was separated. The cantilevers were prestressed and there was residual prestress. During the process of dismantling, it was difficult to predict the behavior of cantilever and as such various measures were taken to ensure structural safety. (Photo.13) Photo No.14-Thane Creek Railway Bridge – Arch Bridge

 

Photo No. 13 - Demolition of span no.P44

The work of demolition is very challenging and is in advance stage. Reconstruction would be taken soon thereafter. Out of 92 spans, strengthening of 81 spans is over and the entire bridge would be strengthened during this year.

12. Ageing of the Structures 12.1 Arch Bridge on Central Railway near Mumbai In India, the railway system was introduced in the year 1853 between Mumbai (Bombay) and Thane for the first time. The arch bridges constructed 162 years ago on this line near Thane are still used. The bridges No.33/2 and 33/3 between Thane and Kalwa suffered distress due to loss of jointing mortar etc., between the arch stones. (Photo No.14) The superstructure constructed in stone masonry is supported by stone piers resting on open footings. In all, there are 23 arches of 9.14 M. span and barrel length of 21 M. 10  Volume 45

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Drilling of holes along the entire surface of the arch and pier and injection of neat cement grout. Fixing dowels over the entire masonry surface. Excavating the area around the foundation up to the founding level and constructing RCC jacket up to the springing point level. Internment of the arch by RCC jacket.

On the face of it, the work appeared to be simplistic. However, it was quite challenging and complex because of the tidal problem and long length of the barrel. The cofferdams were constructed to isolate the foundations and to enable us to carry out the work. Concreting the arch along the entire length was possible due to use of concrete pumps. Special scaffolding and formwork had to be devised for this purpose.

13. Design Deficiency 13.1 Diamond Cement Silo In Madhya Pradesh Two raw meal silos constructed in RCC in the year 1983 for a capacity of 5500 M.T. suffered heavy damage due to vertical cracks, spalling etc.. The 15 M. diameter silo is 33 M. in height and is located near Narsingarh in Madhya Pradesh State. (Photo No.15) Investigations were carried out by conducting NonDestructive Tests and Visual observations. Apart from the distress mentioned above, it was observed The Bridge and Structural Engineer


that the circumferential reinforcement is not adequate. In order to restore the design capacity of the silos and extend their service life, it was decided to provide external cables outside the silos. Full size circular cables were provided and anchored by using ‘Freyssinet’ special connectors. In all, 216 monostrand cables were provided. The strands were housed in suitable HDPE pipe with a layer of grease. The assembly of strand and pipe was housed in bigger HDPE pipe and the inter space was grouted with neat cement grout, thus providing multiple protection to the pre-stressing steel.

concrete and rest of the length is earth filled. The dam was completed in 1957. (Photo No.16). During inspection, it was observed that there is heavy leakage through the right spillway. The leakage was traced to several horizontal cracks formed along the spillway length.

Photo No.16-Hirakud Dam

Photo No.15-Diamond Cement Silo

Special equipment was used to carry out survey of the entire spillway surface and map the defects such as honeycombs, spalling, cracking etc. For this purpose, suitable grid was formed on the upstream surface. Underwater epoxy system was used to seal and treat the cracks. The efficacy of various sealants and injection materials as well as equipment was tested in Central Water and Research Station, Pune, by independent experts. Trained divers from abroad and within the country were used to actually execute the job. Video filming was done to monitor the job and document the work. Concrete cores were taken from the repaired area to check the penetration of the epoxy and they were found to be satisfactory.

14 . Hydraulic Structures

Due to the success achieved on Right Bank, similar treatment was carried out on Left Bank. Due to these repairs, it was possible to stores the water in the dam to full capacity without appreciable loss on account of leakage.

14.1 Repairs to Hirakud Dam

15. Upgrading of Structures

Leakage through the body of the dam not only results in loss of storage capacity buy also threatens the stability of the structure. This problem was discovered in Hirakud Dam and was tackled effectively.

15.1 Strengthening of Cauvery Bridge

After strengthening the silos are in service for 8 years and are working well and to full capacity without any problem.

Hirakud is one of the major dams in the country across River Mahanadi in Orissa State. The Dam is 4.8 Kms. long and is a combination of concrete, masonry and earth section. The Spillway portion is in The Bridge and Structural Engineer

On Indian Railways, there are three different gauges used namely Broad Gauge, Meter Gauge and Narrow Gauge. To optimize the operation and inventories, it was decided to phase out two latter gauges over a period of time. Therefore, as a part of gauge conversion programme, two bridges over River Cauvery were chosen for converting them from Meter Gauge to Volume 45 Number 2 June 2015  11


Broad Gauge. Preliminary studies indicated that there is sufficient reserve in foundations and substructure and only decking would have to be strengthened. These two bridges over River Cauvery are situated on Mysore-Bangalore Section of Southern Railway and are near Srirangapattinam. The decking consists of two PSC girders in each span of 12.19 M. length and 1.2 M. apart, with RCC decking and ballast (Photo No.17).

With these cables, full-scale load test was carried out on the released girders. The test was monitored by Research & Design Standards Organization (RDSO) of Indian Railways. After the test it was concluded that the external pre-stressing of PSC girders designed for Meter Gauge loading had increased the capacity of the girder and made them suitable for carrying Broad Gauge loading. Accordingly, detailed scheme was worked out and all 47 spans of these bridges were strengthened. These bridges are being used for Broad Gauge loading for the last 12 years and are in excellent working condition.

16. Conclusion

Photo No.17-Cauvery Bridge

For Broad Gauge loading and spacing of Broad Gauge track rails, it was found that the existing deck and girder are not safe. It was therefore decided to use external cables for the girders and cast additional 150mm deck slab to resist additional bending moments in cantilever due to Broad Gauge track. Two cables of 12 φ 5 Freyssinet system were used for each girder. These were anchored in the deck. The cables passed over steel saddles fixed at the soffit of the girders at diaphragm points.

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Rehabilitation of Civil Engineering structures is a complex activity. India, being a developing country, resources are limited and have to be conserved for the developmental work. As such, many structures which otherwise would have been demolished in developed countries, have been restored here. For this purpose, indigenous resources have been used with innovative ideas. With the experience gained and newer techniques developed, it is now possible to tackle any difficult job.

17. Acknowledgements The author gratefully acknowledges the assistance and guidance received from the Owners and Consultants of various structures referred to in this article. Help rendered by FPCC Management and Staff is gratefully appreciated.

The Bridge and Structural Engineer


REHABILITATION OF STEEL BRIDGES Amitabha GHOSHAL Chief Advisor to Board of Directors STUP Consultants Pvt. Ltd. Kolkata, India gamitabha@yahoo.com

Amitabha Ghoshal graduated in Civil Engineering from Calcutta University in 1957. He has been Director & Vice President of STUP Consultants Pvt. Ltd., Kolkata. He has interesting experience of retrofitting and rehabilitation of engineering structures.

Summary

record experiences of successful projects in this area.

Steel has emerged as the longest sustained Structural Material globally. In India we have many structures and bridges that have survived their design life of 100 years and are still in serviceable condition, with some planned Rehabilitation.

By extending useful life of a structure, one contributes to sustenance of earth’s limited resources, which is of great importance in today’s world. However, before undertaking Rehab work of a major structure, one needs to assess carefully the feasibility and viability of such a high resource-intensive undertaking.

Before Rehabilitation of any structure is taken up, it is important to assess its residual life and strength. Rehab work can, by extending the life of a structure, contribute to sustenance of non renewable assets of the world. It is, however, essential to examine the cost benefit aspect before taking up such work that need investment of resources and skill. Bridges require systematic rehabilitation with change in Loads, Seismic coefficients, Fatigue considerations and changes in clearances required. The need for adequate scientific documentation of Rehabilitation work has been emphasised by citing case studies of some important bridges in India and abroad. Keywords : Steel Bridges, Retrofitting, Residual life, Rehabilitation Plan.

1. Introduction Steel has proved to be the longest lasting structural material across the globe, in widely diverse environmental conditions, and continues to be the preferred material of choice for long span bridges. In India steel is being used for Bridges, commencing end of 19th century, for Railways and Road network. Some of the bridges in the subcontinent have been functioning more than 100 years and, given their physical condition, can continue to serve with some rehabilitation. There is very little published material for guiding Rehabilitation work and it is important to The Bridge and Structural Engineer

It is important to assess condition of the materials, the components as also the jointing elements. Physical damage like corrosion and internal stress effects due to fatigue generation need be assessed carefully, before attempting to undertake costly rehab process. Often, rehabilitation work, undertaken without adequate prior investigation, leads to uncontrolled expansion of work load and makes the rehabilitated structure unviable. Such work requires meticulous planning in advance, care in selection of new jointing materials that need to be compatible with the parent materials and a work plan that will keep the structure safe and stable all through the restoration work. Bridge structures need to carry vehicles of varying loads and cater for the dynamic effect. Through type Bridges need to cater for clearances needed from the envelope of moving vehicles. Rehabilitation needs of a Bridge usually arise due to the following reasons :

Local damage caused due to accidents,

Serviceability deficiency due to excessive deflection or vibration caused due to slippage of joints and splices,

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Increase in design vehicle loads and impact effect,

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Change in codal provisions for imposed loads like Wind or Seismic effect, Deterioration of structures due to atmospheric effect like corrosion, Fatigue effect due to Long term use, Inadequacy of clearance from vehicle moving dimensions.

Case Studies

Steel bridges can be modified and / or strengthened to address most of the above situations, so that they can continue to serve the users. Many such instances are available for study and can provide good guideline to practising engineers. Some case studies of rehabilitation are given hereafter as illustration, defining the circumstances that created the need for rehabilitation and detailing the innovative solutions adopted in each case to restore the structure to its original use, thereby enhancing the life of the structure. 2.1 Case Study I : Rehabilitation of Flood Damaged Ulhas Railway Bridge near Mumbai

The Damage Ulhas Railway Bridge situated on Diva-Vasai Road Section of Central Railways near Mumbai in India, has two Railway tracks carried by two sets of 6 x 76.2 M span Warren type girders. Both the sets of girders rest on common substructure. The first set was constructed in 1980-81 and serves as up-line, while the adjoining down line bridge was completed in 2001-02.

14  Volume 45

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On 27 July, 2005, during extraordinary heavy floods, when recorded high flood level was exceeded by 2.5M, two barges loaded with river sand hit the 4th span from Diva end on the upstream side, dislodging the roller bearings at Diva end. Detailed inspection revealed that the 4th span on the upline had suffered severe damages at the free end. Bottom chord members of six panels from the free end, the middle vertical, lateral gussets including some lateral bracings got severely bent, twisted and dented, resulting in apparent overstressing and locked-in stress in several members. There was a loss of camber by 50 mm. Elevation of the damaged 4th span along with temporary connecting members, is shown in Fig.1. In general, about 50% of the bottom chord of the 4th Span of the up line bridge was deformed and/ or severely damaged, rendering the span unfit for traffic, without retrofitting or replacing. The Railway authorities decided that the downstream girders would be used for both up and down-line traffic until the upstream girder was brought back into operation, though this would cause serious handicap to traffic movement in this busy route.

Restoration Operations Various options for repair, strengthening and replacement of damaged members were examined carefully. However, no satisfactory long-term solution could be found. It was finally decided to remove the entire damaged span and replace it by a new 76.2M span of MBG Standard, which providentially, was available readily with Railway Stores.

The Bridge and Structural Engineer


The damaged upstream girder was located within 2.5 metres of the undamaged downstream girder. This proximity made it mandatory that utmost caution had to be The damagedinupstream girderofwas withinspan 2.5 exercised dismantling thelocated damaged metres of the undamaged downstream girder. This and erection of the new span. proximity made it mandatory that utmost caution had of the Damaged Span toRemoval be exercised in dismantling of the damaged span and erection of the new span. A number of alternative schemes were critically examinedoffor the damaged span. Removal thedismantling Damaged of Span Some of these were: A number of alternative schemes were critically examined for dismantling the damaged span.chords Some (a) Strengthen the of damaged bottom in the forward 6 panels (L0 to L6) and of these were: dismantle the span by reverse cantilever (a) Strengthen method.the damaged bottom chords in the forward 6 panels (L0 to L6) and dismantle the (b) spanRemove thecantilever damaged span by floatation by reverse method. method, using barges with temporary (b) Remove the for damaged span by flotation method, trestles the task. using barges with temporary trestles for the task. (c) Support the damaged span by temporary (c) Support the damaged temporary suspenders hung span from by suspension cables and the span.cables and suspenders hungdismantle from suspension dismantle the span. The first scheme, i.e. dismantling by reverse cantilever method was considered be the The first scheme, i.e. dismantling by reversetocantilever safest, considering the proximity of the running method was considered to be the safest, considering traffic the adjacent therailway proximity of along the running railway spans. traffic along the adjacent spans. Construction work was carried out in the following stages Construction work :was carried out in the following

stages : (I) The damaged 4th span was connected to undamaged 5thwas spanconnected at the top (i) The the damaged 4th span to and the th bottom chord levels with the 5 span to th undamaged 5 span at the top and bottom chord act as anchorth span while the fourth span levels, with the 5 span to during act as anchor span became cantilevered dismantling when the fourth cantilevered process. In span this gets condition thereduring was dismantling In this condition reversal process. of stresses in the chords there and members of both thechords cantilever and was web reversal of stresses in the and web anchorof both spans. was found that members the Itcantilever and anchor additional strengthening was required for spans. It was found that additional strengthening the end two bottom chords of the 4th was required for the end two bottom chords (cantilever) span and the end two bottom th th of the the endspan. two (anchor) and4 top(cantilever) chords of span the 5and th bottom and top chords of the 5 (anchor) span. Additional strengthening materials were Additional strengthening materials were fixed to fixed to the relevant members in the form members of webin theplates priorplates to the relevant form of web commencement of the dismantling work. prior to commencement of the dismantling work.

safety by providing an adequate load path for compressive force of the cantilever span to the anchor span during dismantling operations. (Fig. 2 & 3)

Fig. TypicalSection Section of Strengthened Bottom Fig.2:2: Typical of Strengthened Bottom Chord Chord

(iii) Erection crane was erected at the forward node point of the top chord of the anchor span. (iv) Kentledge was provided at the rear end panel of the anchor span to prevent uplift.

Fig-3 : Strengthening of bottom chords L4 – L5 – L6

(III)

Erection crane was erected at the

node ofpoint of Chords the top of Fig. 3forward : Strengthening Bottom L4 chord – L5 – L6

the anchor span. (v) The damaged 4th span was connected to the th at theat top chordend level span (5 (IV) anchor Kentledge wasspan) provided the rear by panel fixing of link-pin system span for transmitting the anchor to preventthe tension uplift.forces developed at the rear of the cantilever span and by buffer at bottom chord (V) level. The(Fig. damaged 4th span was connected 4) to the anchor span (5th span) at the top chord level by fixing link-pin system for transmitting the tension forces developed at the rear of the cantilever span and by buffer at bottom chord level. (Fig. 4)

(ii) Temporary repair/strengthening of the distorted bottom chords between L0 and L6 of the –3– upstream truss of the damaged span was done to ensure safety by providing an adequate load path for compressive force of the cantilever span to the anchor span during dismantling operations. Fig. 4 : Link Arrangement at Top Chord Level to Connect the Damaged Span and the Anchor (Fig. 2 & 3) The Bridge and Structural Engineer

Volume 45 Number 2 June 2015  15


The bearings on Diva end were removed, thus cantilevering the damaged span from the anchor span.

Erection of the New Span by Cantilever Method

(vi) Stringers and cross girders between L0 and L4 of the damaged span were removed by gas cutting in order to reduce dead load of the cantilever span. (Fig. 5).

The new 76.2 M MBG span was erected by forward cantilever method with the 76.2 M RBG span behind acting as an anchor span, reversing the process adopted for dismantling of the damaged span. The erection work was done in following stages: i)

The crane was placed at the forward end of the top chord of the anchor span.

ii) Additional kentledge was provided at the rear end panel of the anchor span as the new MBG span to be cantilevered was heavier than the RBG anchor span.

Fig. 5: View of Damaged Span after Removal of Stringers and Cross Girders

(vii) Components of the first four forward panels were dismantled by flame cutting. The dismantled materials were removed from the site using the existing railway track, back to the approach bank. (viii) The crane was brought forward to U6 and components of the 5th panel were dismantled after cutting rivets in the joint. Repeating the process, the balance panels were dismantled by the crane, which progressively receded panel by panel as the dismantling work proceeded. Placing the crane at U1 of anchor span, the link members and buffer arrangements were removed (Fig. 6).

Fig. 6 : Flame Cutting of End Rakers of Damaged Span

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iii) Adequacy of the sections of the bridge components of both the new and the anchor spans was checked for erection loads during cantilevering. Accordingly, additional strengthening plates were fixed to the web of the bottom chords of the first two panels of the new span prior to erection. iv) Temporary vertical members were erected at the forward end of the anchor span followed by the 1st link member at top chord level. v)

The erection was done with the help of the crane, panel by panel.

vi) After completion of erection of the entire span, the tensile force in the link member was neutralized by jacking at the forward end of the cantilever span. The crane was then moved backwards and temporary link system removed.

Advantages of Scheme Dismantling of the 4th span of the damaged Ulhas Bridge and erection of a new span in its place presented a challenge, (i) because of the proximity of a second bridge located within 2.5 m of the damaged bridge on the same substructure, (ii) because of the heavily damaged bottom chords. The adopted options viz., dismantling by ‘reverse cantilevering’ and erection of the new span by ‘cantilevering’ proved to be safe methods for restoration of the bridge. The work was completed without any unwarranted incident at worksite or affecting the adjoining spans of the downline through which traffic movements continued uninterrupted all through the work duration. The Bridge and Structural Engineer


2.2 Case Study II : Rehabilitation of Blast Damaged Hardinge Railway Bridge in Bangladesh

History of Damage This Bridge across Lower Ganges was built as a part of Eastern Railway system in undivided India and linked Kolkata with North Bengal and Assam. It was part of East Pakistan till the birth of Bangladesh as a country, when this became a vitally important railway link between North and South of the country. The bridge carries two tracks of broad gauge railway and is configured as fifteen nos. 105 m Petit type through spans and six, 23 m approach spans of deck type. The bridge was opened to traffic in 1915 and has just completed 100 years of its existence. The bridge was very seriously damaged during the liberation war of Bangladesh at four locations. The twelfth span from the western end was totally damaged by exploding dynamite attached to girder members and fell into the river. The girder was removed with help of submarine barge but finally sunk into the river bed more than 1km away downstream. Temporary restoration work was done by bringing in a new span from an ongoing bridge work across river Godavari in South India. This temporary span was replaced by a new girder similar to the original spans.

Damage to 9th Span The ninth span from the Western bank suffered excessive and unusual damage due to a missile attack (from the eastern bank of the river), which blew off 18 m length of the bottom chord in the central part of the downstream truss. Several web members of truss were blown off or twisted beyond repair. Additionally the deck system in the central panel of the bridge was substantially damaged, with part of the cross girder and one set of stringers blown off. Effects of the explosion were very severe, causing lifting of the steel rocker bearing at one end; the downstream truss sagged by 105 mm and the upstream truss sagged by 25 mm. The span titled out of plumb by a gradient of 1 in 250 at the centre towards the downstream side. Normal truss analysis indicated the span to be nonfunctional and irreparable. However, it was observed that the extensive and heavy system of top and bottom lateral bracings along with portal type sway bracings at every cross frame location made the girder work as space frame and prevented collapse of the structure. The Bridge and Structural Engineer

The damaged span was analyzed in a mainframe IBM computer at IIT Kanpur and the analysis revealed that the dead load stress in undamaged members did not exceed the yield stress. Therefore it was deemed possible to use the span with proper rehabilitation work. The rehabilitation work had to be done in position as it was not possible to remove the span weighing 1250T from its location, to a yard for replacement of the damaged members. The depth of water at the location was more than 12 m in dry season and during the wet season, the river rose fast by another 6 m. Velocity of water exceeded 4m/sec during monsoon. The rehabilitation of this bridge was of supreme importance to the newly formed nation of Bangladesh as this was the only bridge linking northern part of the country with the southern region and the lifeline for export of jute fibres, the only exportable product of the country at that time. The monsoon starts in July and the repair work had to be completed ahead of same, with earliest possible start by end of February. The rehabilitation scheme had to be planned for completion within 4 months, and therefore had to be innovative.

Rehabilitation Scheme It was reckoned that the span could be lifted to its designed configuration if an uplift force of 240T could be applied at two middle third points of the damaged truss. This, it was concluded, was only be possible if such a force could be imparted from a floating craft. It was envisaged that this could be done by pumping water into the hold of the watercraft and then pumping same out to create the necessary buoyant force. This unique scheme was developed by bringing in two large barges (used for ferrying Railway wagons) from the recently abandoned ferry services at Farakka, after the new barrage provided railway link. These barges could carry 24 wagons i.e., upto 480T of load. It was decided that these steel bodied barges should be strengthened by fixng rigid diaphragms inside the barge cavity such that it was capable of carrying concentrated load of 240T at the centre. The barges were refurbished in position under the span and then anchored under the 8th and 14th panel points, with the help of concrete cubes of 1m size that were cast on top of the deck of the barges. Four anchors were Volume 45 Number 2 June 2015  17


dropped at appropriate places for keeping each barge reasonably stable. Steel trestles capable of carrying 240T of load were designed, fabricated and built on the barge decks. After considering various possibilities it was decided that span would be jacked up by using Archimedes Principle. Prior to jacking up operation, the barges were filled in with water and the truss supported at two nodal points of the bottom chord with steel packs fitted in the space between trestles on the barges and the bottom chord of the span. The water was pumped out from the two barges synchronizing the 8 pumps on each Barge so as to deliver a jacking force, equivalent to water removed, through the trestles onto the two nodal points of the truss bottom chords. It had been calculated that 240T jacking force delivered at each trestle could restore the span to its original shape. The span did restore to its original position recovering upto 80% of the original designed camber. (Fig. 7) At this stage, specially designed and fabricated steel links were introduced between the ends of the top chord of the distressed truss and ends of the adjacent spans. The design of links was done such that the half of truss in cantilever position could be held by adjacent spans, thereby permitting dismantling of the damaged truss. Once this task was completed, the barges with the trestle were moved away and restoration work undertaken bringing in newly fabricated members of original dimensions, (fabricated at Kolkata) and fixing them in position, replacing the damaged members. However, the splice plates of central joint of the bottom chord of the span were left blank. The barges were brought back to their original position and once

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again span was jacked to theoretical position for final restoration. Rivet holes were drilled in-situ to match with the holes on the chord member made in workshop and the truss was fully jointed and closed. This ensured that there were no secondary stresses in the members and span restored to its original shape. Simultaneously temporary link members and buffers were released, to disconnect the ninth span from the adjacent ones. The span was thus completely rehabilitated.

Challenges Unforeseen problems were faced during the restoration. The river water level rose between two jacking operations by 4 m and the trestles had to be truncated to fit in. The insertion of link plates at the end of the damaged span and the adjacent spans was an extremely challenging operation as the stability and safety of the structures had to be ensured when cover plates at the joint between top chord and raker members were removed temporarily for inserting link plates. Bangladesh, as a new born country, had no resource to provide even the basic facilities for this operation and every little bit of equipment, jointing material and even fuel had to be brought from India for completing the operation within the tight schedule. The final jacking was completed in mid July just ahead of the monsoon fury of the river thus providing a great relief to Bangladesh economy at that point of time in history. This rehabilitation operation was lauded at that time as one of the finest achievements of Indian engineering fraternity.

The Bridge and Structural Engineer


2.3 Case Study III : Rehabilitation of Railway Bridge In Malaysia By Structural Re-Arrangement

Background In the early nineties, the Railway network in Malaysia was in dire need of repairs and maintenance and the country decided to rehabilitate its existing railway assets and to expand the network for carrying a larger share of goods and passengers, reducing dependence on roads.

Problem The Sungie Karayung bridge, located in Kuala Lumpur, is a Pratt Truss bridge with 31.3m span and carried two meter gauge tracks. Built in early 19th century, the bridge structure had unconventional details e.g., top lateral bracing system was not continuous and was formed by cross beams connected on top of the top chord. The deck system was hung from the bottom chord with the longitudinal stringers connected to the cross girders as simply supported beams. There were no portal bracings provided at the top of the rakers (Fig. 8). Some of the diagonals and bottom chords were formed by two separate structural members, not connected by lacings and battens. The bridge truss was prone to vibrate and oscillate

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when trains passed, even at low speed. Malaysian railway had decided to upgrade the Rolling Stock with new locomotives having 20T axle load running at a maximum speed of 120kmph. The design of the bridge had to be checked for this enhanced capacity, apart from correcting the in-built inadequacies.

Solutions It was concluded that the following improvements could successfully accommodate the enhanced requirements :

The top chord bracing system required to be made continuous and connected to portal bracing system at either end to ensure effective transfer of the transverse loads.

The cross beams, on the top of the top chord that extended by about 1.2m beyond the chords, to be rigidly connected to the verticals by appropriate knee bracings both outside and inside of the verticals.

Lacing members introduced, to connect isolated structural elements of web and bottom chord, to improve structural function.

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Local deteriorations due to poor maintenance and corrosion were improved by local repair and high quality protective painting system adopted. (Fig. 9)

With above mentioned restoration work, the span was rehabilitated by using only 20T of new steel material and thereby rendered adequate for the enhanced axle load. The oscillation of the bridge during passage of trains got substantially reduced, and complete replacement of the span was avoided.

3. Conclusion India has a large numbers of old bridges in Steelwork construction that are still giving good service. It would be desirable to have a systematic appraisal of such bridges by appropriate agencies and where required, take up Rehabilitation programme for effective

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extension of their service life. This action will not only save valuable resources of the country but also avoid the disruption that is caused by unplanned closure of a bridge, due to sudden disfunction.

References : 1.

Ghosh U. K., Ghoshal A., Baul S., “Restoration of a Railway Truss Girder Damaged during Flood”, Journal of IRICEN, Sep. 2010.

2.

Ghoshal A., Ganguly J. C., Banerjee H. K., Kapoor M. P., “Hardinge Bridge Span Repair”, Journal of the Construction Division, ASCE, Vol. 100, No. CO4, Proc. Paper 11034, Dec 1974.

3. Ghosh U. K., Ghoshal A., “Experiences in Rehabilitation of Steel Bridges”, Journal of the IABSE, Structural Engineering International, Vol. 12, No. 4.

The Bridge and Structural Engineer


CONDITION ASSESSMENT AND REHABILITATION OF AN IMPACT DAMAGED CONCRETE BRIDGE

Rajeev GOEL Principal Scientist Bridges & Structures CSIR-Central Road Research Institute, New Delhi, India rgoel.crri@nic.in

Surjit K. SHARMA Principal Technical Officer Bridges & Structures CSIR-Central Road Research Institute, New Delhi (India) sksharma.crri@nic.in

Lakshmy PARAMESWARAN Chief Scientist Bridges & Structures CSIR-Central Road Research Institute, New Delhi-11025 lakshmy.crri@nic.in

Dr. Rajeev Goel, born 1967, did B.E. (Civil Engineering) from MNREC, Allahabad; M.e. (Structural Engineering) from University of Roorkee; and Ph.D from IIT Roorkee. His areas of specialisation are Analysis & Design; Instrumentation, Performance Monitoring, Health Assessment, Evaluation & Rehabilitation of Structures; and Rating of Bridges. He has published more than 60 Research papers in International/ National journals/Conferences/ Seminars etc.

Dr. Surjit K. Sharma, born 1958, received PhD (Civil Engineering) from the Delhi College of Engineering, Delhi. His areas of specialisation are Analysis & Design, Evaluation & Rehabilitation of Structures and Rating of Bridges.

Dr. Lakshmy Parameswaran, born 1962, received her PhD (Civil Engineering) from IIT, Roorkee, Roorkee. She has more than 28 years experience and is currently working in CSIR-CRRI as a Chief Scientist. Her main area of research includes bridge management, health monitoring of bridges, bridge aerodynamic and sustainable construction materials.

Summary Concrete bridges show the sign of distress during their service life due to different causes such as damage due to oversize vehicles, use of sub-standard materials for construction and lack of quality control during construction, exposure to aggressive environment, theft of bridge components/vandalism etc. Condition assessment is a pre-requisit for selecting an appropriate repair and rehabilitation scheme. It helps in assessing the severity, extent and cause of distress with the help of visual inspection as well as non-destructive and partially destructive testing. In this paper, a case study on condition assessment and rehabilitation of an impact damaged RCC bridge due to passing of oversize vehicle has been presented. Keywords: Impact damage, Distressed RCC bridge, The Bridge and Structural Engineer

Non-destructive testing, Repair and rehabilitation, Oversize vehicle

1. Introduction Kalimati Bridge (better known as Howrah Bridge) was built in year 1967 as a Road Over Bridge across Kalimati road in Jamshedpur, India, primarily to cart away blast furnace slag from the TISCO steel plant. Over a period of time, slag got accumulated over the bridge carriageway due to pilferage from the trucks and its average thickness increased to about 800mm by year 1996. TISCO proposed to use this bridge for regular transport of Hot Rolled Coils using heavy duty trailers and requested CSIR-Central Road Research Institute, New Delhi (CRRI) to examine it during April 1996. As the structural drawings of the bridge Volume 45 Number 2 June 2015  21


were not available with TISCO, CRRI team carried out Non-destructive testing of various structural elements of the bridge during September 1996 and recommended strengthening measures for the various structural elements along with other corrective measures vide CRRI report of January, 1997 [1]. Subsequently, in October 2009, M/s Tata Steel Ltd., Jamshedpur noticed damages to the soffit of some of the longitudinal girders of the bridge, caused due to impact of over height vehicle passing underneath the bridge and again approached CRRI to suggest the strengthening measures for the bridge. CRRI investigated this bridge in detail as shown in Fig.1 and found that the bridge was severely damaged and recommendations for strengthening were submitted vide CRRI report of March, 2011 [2]. Assess Damage -Visual Observation -NDT Methods Degree of Damage

Minor (Concrete cracks and nicks, shallow spalls and scrapes)

Moderate (Wide concrete cracks and spalls, exposed & undamaged rebars)

Severe (Exposed and damaged rebars, loss of concrete, beam offset)

Fig.1 : Assessment of Impact Damage of a Concrete Bridge

2.

Salient Features of the Bridge

Kalimati Bridge is a 4-span RCC T-girder bridge built with a skew angle of 30° in plan. The superstructure consists of seven main T-shaped longitudinal girders and four diaphragms. The total length of skew span bridge is about 50 m arranged in a four span configuration of 7.6 m, 17.4 m, 17.4 m and 7.6 m length (approximately) resting on five supports through steel plate bearing. The longer bridge portion over the roadway is a two span continuous unit with overhangs on either side to create half joints (articulation). The end spans are suspended units supported at the articulations and on the multileg portals which serve as open abutments. The main span (continuous unit) have diaphragms at articulations, mid support (over the road divider), mid spans over each carriageway of Kalimati road and at the quarter span closer to mid support. The depth of the diaphragms is small in comparison to the longitudinal girders and they are attached either at the top or bottom side depending on the location. The depth of longitudinal girders of two span continuous units is more than that of the suspended spans. Mild steel reinforcement was used in construction and concrete of mix 1:1.5:3 was stated to be used which corresponds to M20 grade.

Fig. 2 : General View of the Bridge

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The Bridge and Structural Engineer


The five supporting structures are 7-leg portal frames with rhombus shaped columns inter connected at the top with a horizontal beam. The horizontal (portal) beam serves as the load transfer member from the superstructure to the columns. The longitudinal girders and columns are equally spaced and evenly aligned in plan for direct transfer of the load from the longitudinal girders to the columns. The size of the column supporting the two span continuous unit is larger compared to those at end portals due to higher

load transfer. Stone pitching was done on the slopes of earth work and infilling made at the end portals to retain the backfill of open abutments. Fig.2 shows a general view of the bridge.

3.

Condition Assessment

The longitudinal girders and diaphragms of one of the carriageway of the bridge were found to be damaged. The damaged portion in question was

Fig. 3 : Views of the Impact Damaged Girder of the Bridge

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on the carriageway, catering for the traffic from Railway station to Sakchi in Jamshedpur. Mild steel reinforcement bars were exposed and bent at several locations. Cracks in the various members were also noticed. Typical views of the damages are shown in Fig.3. Also, all the longitudinal girders, diaphragms and columns of the bridge were found to be guinited. Further, the bearing plates were noticed to be covered with guiniting material and thus were ineffective for the intended use. The approach road from the slag gate was quit steep and the loose slag is getting deposited over the bridge. Also, the drainage spouts were observed to be partially blocked. Accumulation of water over the bridge deck was also observed. CRRI noticed that this water flows over the bridge from the steel plant and the accumulation of the water leads to seepage from the articulation joints. Vegetation growth over the footpath portion of the bridge was also observed. The seven longitudinal girders were numbered as G1, G2, G3, G4, G5, G6 and G7 from the railway station side. The two vertical faces of the longitudinal girders are described as G1R & G1S, G2R & G2S and so on, where R and S represent ‘Railway station end’ and ‘Sakchi end’ respectively. The region between central support and diaphragm (D1) is designated as Bay-1. Eight numbers of 32 mm diameter mild steel bars were found to be provided in two layers in longitudinal girders as main reinforcement. Table-1 shows the details of damages observed in longitudinal girders. Table 1: Damages in Longitudinal Girders Girder Length of the damaged / Length of Number exposed portion from the damaged diaphragm D1(m) reinforcement (m)

4. Detailed Investigation Elements

of

Damaged

CRRI team carried out the following investigations on this particular carriageway of the bridge: 

Schmidt Rebound Hammer test for estimating the compressive strength of concrete in longitudinal girders, diaphragms and deck slabs. Ultrasonic Pulse Velocity test to find out uniformity of concrete and strength of concrete in longitudinal girders and diaphragms. Core test to assess the insitu strength of the concrete Rebar Locator Test Carbonation test to assess the extent of depth of carbonated concrete

Typical views of field testing are shown in Fig.4 and Fig.5. Testing locations on this particular carriageway are shown in Fig.6. 4.1 Schmidt Rebound Hammer Test In the present investigation, ten rebound numbers were taken at each location using Schmidt rebound hammer according to IS: 13311 (Part-2) [3]. From this data of Schmidt hammer test, compressive strength of existing in-situ concrete was assessed and is summarised in Table-2. 4.2 Ultrasonic Pulse Velocity Test Ultrasonic pulse velocity test (UPV) was carried out using 20 KHz frequency transducers by direct method of testing. Transit time was measured with 1.0 micro-second accuracy. From the values of transit time, velocity of propagation of ultrasonic waves has been computed. Based on this wave velocity, grading of the existing concrete was estimated as per IS:13311(Part-1) [4]. Quality of concrete of various structural elements is found to be as follows:

G1

1.30

1.00

G2

1.00

1.00

G3

1.20

0.80

G4

1.00

-

G5

1.00

-

‘Good’ in columns C1, C2, C4, C6 and C7

G6

0.60

-

‘Medium’ in columns C3 and C5

G7

0.40

-

‘Doubtful’ to ‘Good’ in longitudinal girders

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‘Doubtful’ in diaphragms between Girder G1 and G2, G2 and G3, G3 and G4, G4 and G5, G5-G6 and G6-G7

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Fig. 4 : Views of Non-destructive Testing

Fig.5 : Views of Core Cutting

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Table 2 : Results of Schmidt Rebound Hammer Test Sl. No.

Element

Estimated Concrete Strength (MPa) Average Strength

Standard Deviation

Characteristics Strength

test to avoid cutting of steel reinforcement during core extraction. In the present study, three cores of 70 mm diameter and 150 mm length were extracted from the longitudinal girders for the evaluation of quality and in-situ strength of concrete. Core test were conducted as per IS:516 [5]. The equivalent in-situ cube strength of concrete as assessed by this test varied from 24.81 MPa to 27.94 MPa. Quality of concrete in these cores was also checked using Ultrasonic pulse velocity test and was found to be ‘GOOD’.

1

Longitudinal 53.69 Girder G1

8.30

39.99

2

Longitudinal 53.43 Girder G2

9.63

37.55

3

Longitudinal 57.91 Girder G3

9.53

42.19

4

Longitudinal 50.81 Girder G4

10.70

33.16

4.4 Rebar Locator Test

5

Longitudinal 48.08 Girder G5

8.35

34.30

6

Longitudinal 47.83 Girder G6

11.17

29.41

7

Longitudinal 53.39 Girder G7

11.18

34.95

This investigation has been carried out using the “Profometer” known as digital cover meter which is capable of detecting the cover to reinforcement, location of reinforcement, bar diameter and any discontinuity in the reinforcement bars [6].

8

Diaphragm between G1 and G2

53.97

4.16

47.11

9

Diaphragm between G2 and G3

62.12

4.50

54.69

10

Diaphragm between G3 and G4

53.77

6.90

42.38

11

Diaphragm between G4 and G5

46.66

8.76

32.20

12

Diaphragm between G5 and G6

44.86

3.93

38.38

13

Diaphragm between G6 and G7

44.11

5.08

32.72

14

Central Column C1

32.48

-

-

15

Central Column C2

42.84

-

-

16

Central Column C3

43.55

-

-

17

Central Column C4

35.60

-

-

18

Central Column C5

49.86

-

-

19

Central Column C6

61.87

-

-

20

Central Column C7

60.16

-

-

4.3 Core Test Before starting the core extraction, the locations of steel reinforcement were detected using rebar locator 26  Volume 45

Number 2 June 2015

4.5 Carbonation Test To determine the depth of carbonation [7], 10mm diameter holes were drilled in stages at several locations on the longitudinal girders. As the hole was being drilled, the phenolphthalein solution was sprayed at different depth of hole to check the alkalinity of the concrete. Results of this test reveal that carbonation depth at the tested locations varied from 6mm to 31mm.

5. 

Analysis and Discussions

Schmidt hammer test results showed that average compressive strength of concrete at the testing locations was in the range of 47.83 to 57.19 MPa, 44.11 to 62.12 MPa and 32.48 to 61.87 MPa for longitudinal girders, diaphragms and columns respectively. The characteristics compressive strength of concrete at test locations was estimated to be in the range of 29.41 to 39.99 MPa and 32.20 to 54.69 MPa for longitudinal girders and diaphragms respectively. This wide range of variation may be due to the presence of guiniting layer over the concrete surfaces. UPV test results indicated that quality of concrete was ‘Medium’ to ‘Good’ in columns, ‘Doubtful’ to ‘Good’ in longitudinal girders and ‘Doubtful’ in diaphragms. Doubtful quality of concrete may be due to debonding of guiniting layer from concrete. It is to mention that the UPV tests were conducted mostly on the guinited surface as it was The Bridge and Structural Engineer


Railway Station

Sakchi NOTES :– TESTING LOCATION IN GIRDERS IS 60 CM ABOVE ITS SOFFIT – TESTING LOCATION IN DIAGPHRAMS IS AT ITS MID DEPTH

Fig. 6 : Plan Showing Non-destructive Testing Locations of Bridge Superstructure

not possible to peel-off the layer of guiniting. At some locations, the bond between guiniting layers and the parental concrete substrate was not proper. Therefore, the quality of concrete as ‘Doubtful’ has appeared at many locations. The interfacial bond of guiniting layer and the concrete substrate was lacking in all the diaphragms, which was evident from the UPV data indicating quality of concrete as ‘Doubtful’. The Bridge and Structural Engineer

Depth of carbonation at tested locations of longitudinal girders varied from 6mm to 37mm. As the thickness of guiniting layer varied from 28mm to 55mm, so it was inferred that carbonation has not reached up to the steel reinforcement. From the core test, average equivalent cube compressive strength of insitu concrete in longitudinal girders was estimated to be 26.37 MPa. Volume 45 Number 2 June 2015  27


Cracks observed in the various members were found to be in guinited portion only. These had not penetrated into the parent concrete.

6. Recommendations Based on the results of condition assessment and detailed investigation of the bridge, which had occurred due to the collision of the oversized vehicle with the bridge deck, following remedial measures were suggested: 

 

Repair scheme for damaged longitudinal girders and diaphragms which includes replacement of damaged longitudinal reinforcement of 32 mm and 10 mm dia. stirrups, repair of unsound concrete areas around the reinforcement and pouring fresh concrete of M25 grade. Repair scheme for columns and articulation joints.

As the bearings supporting the superstructure were buried by the shotcrete material and had become non-functional so replacement of bearings with new elastomeric bearings was suggested.

Construction of side drain to channelized the waste water / liquid flowing from the steel plant. Regular cleaning of drainage spouts. Construction of approach slabs on both the ends of the bridge.

It was advised that the repetitive laying of bituminous layers on road level under the bridge shall not be undertaken to avoid the reduction in the head room under the bridge. For this, cement concrete pavement should be provided in lieu of the existing flexible pavement under the bridge.

7. Conclusions For suggestion of suitable and appropriate rehabilitation scheme for a distressed structure, condition assessment plays an important role. This has been illustrated with the case study of Kalimati bridge, Jamshedpur.

8. Acknowledgement Authors are thankful to Director, CSIR-Central Road Research Institute, New Delhi for granting permission to publish the paper. Sincere thanks are due to those CRRI officials who directly or indirectly contributed in this project work. Thanks are also due to M/s Tata Steel Ltd., Jamshedpur for assigning the work of condition assessment of Kalimati bridge to this institute and also providing support in conducting the field studies.

9. References 1. CRRI report entitled “Non-destructive testing of slag road bridge over Kalimati road in Jamshedpur” January, 1997.

Frequent removal of the slag from the deck slab to reduce the dead load over the bridge.

2. CRRI report entitled “Strengthening measures for Kalimati road bridge (Howrah Bridge), Jamshedpur” March, 2011.

Repair the existing parapets on both the sides of the carriageway or replace the existing parapet with steel parapet.

3. IS: 13311, Part-2, “Non-destructive testing of concrete - Methods of tests - Rebound hammer”, Bureau of Indian Standards, New Delhi, 1992.

4. IS: 13311, Part-1, “Non-destructive testing of concrete - Methods of tests - Ultrasonic pulse velocity”, Bureau of Indian Standards, New Delhi, 1992.

Remove the growth of vegetation on the abutment/ pier

Erection of height restriction gates on both the carriageways, at the entrance of the underpass to stop the recurrence of damage to the bridge by oversized vehicle. Removal of all the hoarding sign boards except the informatics signage erected on both the railing. Shifting of existing eatable shops, under the bridge to other suitable locations to prevent the distress due to heat.

28  Volume 45

Number 2 June 2015

5. IS: 516, “Indian standard code of methods of tests for strength of concrete”, Bureau of Indian Standards, New Delhi, 1956. 6. BUNGEY, J.H., Testing of Concrete in Structures, Chapman and Hall, New York, 1989, pp.28-109. 7. RAINA, V.K., Concrete Bridge Practice, Tata McGraw-Hill Publications, 1989. The Bridge and Structural Engineer


STRENGTHENING, RETROFITTING, REPAIR AND REHABILITATION OF BALLY ROAD OVER BRIDGE NO. 15A, HOWRAH DIVISION, EASTERN RAILWAY BY USING EXTERNAL PRESTRESSING

SJ DEB FPCC Ltd. Kolkata Office kolfpcc@gmail.com

VL DESHPANDE Managing Director Structcon Designs Pvt. Ltd. Mumbai, India structconconsultants@gmail.com

S. J. Deb received his graduation degree from University of Roorkee (Now I.I.T, Roorkee). Main area of specialization is Prestressed Structures including Incremental Launched & Stay Bridges, Heavy Lifting, Rehabilitation of structures & PSC Flat Slab.

V. L. Deshpande received his graduation degree from I.I.T. Kharagpur in 1973 and post graduation from I.I.T. Mumbai in 1975.

Keywords Bridge, Pre-stressed, Rehabilitation, Strengthening Epoxy concrete & injection grouting, Polymer mortar & grouting, External Pre-stressing, pre-stress losses, external girder.

1. Introduction In general Pre-stressed concrete bridge girders show distresses due to several reasons like corrosion of H.T. steel and reinforcement, changes in actual loadings over design load additional losses over those considered in design and non functioning of bearing etc. In general, it is more economical and convenient to strengthen deficient girders than to replace the entire bridge. The external pre-stressing method is used for repair and strengthening existing girder along with the application of epoxy concrete, epoxy injection, polymer mortar patching, grouting etc. in order to restore the structural capacity of the girders.

2.

Salient Feature of the Bridge

This R.O.B. has main span of 35.598 m with 08 nos P.S.C. Girders 07 nos R.C.C. cross diaphragms having depth of 1.88 m stressed with 16 nos The Bridge and Structural Engineer

12ø7 mm wire and 02 nos end spans with 14.80 m. Deck slab thickness is 152 mm with 75 mm wearing coat. The total carriageway is two lanes of 7.10 m each in each direction with a central median of 0.90 m and two footpaths of 0.61 m each on either side. (See figure 1). Two spills through abutments are provided on either end. The R.C.C. piers consist with 08 nos. columns one under each girder with a continuous R.C.C. pier cap. The bearings are steel roller and rocker type. The R.O.B. connects NH34 via Vivekananda Bridge at Dakshineswar end to NH6 & NH2 at Dankuni end. So bridge serves as a vital link between the Eastern and Northern part of the country. The bridge is extremely busy mostly with passenger bus and heavy vehicle transport during day and carries heavy loaded trucks at night.

3.

Problem Identification

3.1 Inspection During routine bridge inspection by Eastern Railway Authority, Wide Vertical cracks were observed from soffit of the longitudinal girder at approx. L/3 location of the span. The cracks were on both sides of web and connected at girder soffit. These cracks were Volume 45 Number 2 June 2015  29


showing progressively upward trends. (See in Fig.5). Since this ROB is located on main line of Eastern Railway connecting New Delhi and Howrah track with 25,000V overhead lines, track can not be shut down for repair. After close inspection followed by chipping the existing surface near crack a very severe and wide crack which started from the soffit of the beam and extended right up to the deck slab was observed. The path of the crack was not linear and it branched in several directions. Condition of the bridge was alarming. 3.2 Other Defects Other defects of the R.O.B. noticed during condition survey are as listed below:-

4.

Locking of roller bearing

:

This has led to creating additional axial tension in girder

-

Why was distress only in Extreme Girders

These carry maximum load however prestress provided is same for all girders.

-

Why at 1/3 span

Cable profile provided was very peculiar (See in Fig. 4). This profile made 1/3 span more critical than mid span because at this location reduction in bending moments is much smaller than reduction in eccentricity of cables. This was probably due to use of 12 Ø 7 system. Large no of cable were required needing anchorages to be located in deck.

A) Pre-stressing cables situated at the soffit of the girders were found exposed in certain locations. Existing sheathings were badly corroded. Some of the cables were not only corroded but some wires had snapped. ( See in Fig. 6 )

Reference Drawings

B) The roller and rocker bearings: Roller bearings were non-functional due to the blocking by dirt etc.

2) Drg. No.SC/489/CD-03 : CONSTRUCTION DETAILS.

C) The wearing coat was damaged at several location and expansion joints were practically non-functional. D) The R.C.C. railings were damaged at certain location. Distress was noticed in end girders and near one third of span. Internal girders showed only minor distress. 3.3 Analysis the Causes Distress has occurred due to various reasons as given below: 1.

Poor workman ship

:

Less or reduced cover, honeycombs etc.

2.

Losses due to creep, shrinkage & relaxation

:

Specially relaxation was under estimated (use of old codal provision)

3.

Specific environment

:

Emission of CO2 by coal based train engines (Heavy goods traffic)

30  Volume 45

Number 2 June 2015

1) Drg. No.SC/489/GA-01 : GENERAL ARRANGEMENT & EXTERNAL PRESTRESSING.

4

Remedial Measures

4.1 Method Of Analysis Structural analysis was done by using STAAD Pro Software. Superstructure is discretized as a mesh representing deck slab and beam elements representing girders and diaphragms. The superimposed dead loads (SIDL) are applied as joint and member loads as applicable. Following critical sections are checked. ….. 0.1L, 0.2L, 0.34L, 0.5L 4.2 Assessment of Existing Stress Levels From the analysis of the existing PSC girders of superstructure, checks are made w. r. t present codes 20% additional losses due to time dependent factors like Creep Shrinkage Relaxation were neglected for present stage of stresses (as these are for abundant precaution) but included in developing remedial measures and following were noticed: 1. Section at 0.34L is more critical than the midspan. The stress at 0.34L is tensile -5.018 N/mm2 at the midspan -1.679 N/mm2 bottom section at 0.34L. The Bridge and Structural Engineer


Stresses at 0.34L are higher than Modulus of Rupture. Hence, the girder is likely to crack first at 0.34L. Loss of section properties after cracking has induced progressive crack almost upto deck.

Stress at midspan is -1.679 m/mm2 which indicates that though tension exists at the bottom it may not lead to rupture. 2. The state of stress in the internal girders G2 to G7 were also assessed. it is found that 0.34L is a critical location and the stress is -3.513 N/ mm2. While codes do not allow tension, this is a marginal value where crack may not appear. However there is a probability that cracks will develop in these girders too in the future. 4.2.1 Ultimate Checks The ultimate checks for the existing structure have already been carried out. It was found that the structure due to untensioned steel will not lead to immediate collapse. 4.2.2 Check for Shear The check for shear given for the existing structure has been found that the structure is safe for the shear reinforcement already present in the structure. 4.3 Remedial Measures Structural Additional prestress was provided to improve bottom stress levels. 2 Nos. 12T13(S) system, external cables one on either side of the web were provided. Initial stress after wobble and seating was restricted to 0.45 times UTS to control relaxation losses and fatigue effects, in the cable. Profile generated helped in shear with the proposed addition bottom stress improved to + 1.5 n/mm2 (compressive). Due to limitations on ‘Scope of Work’ only external girders were strengthened with a recommendation that internal girders also be taken up later. Based on condition survey lot of non structural repair work with epoxy injection, epoxy mortars, polymer concrete etc. was under taken.

5.

Brief Methodology for Repair the Bridge

On the basis of visual survey following methodology was adopted. The Bridge and Structural Engineer

1. Erection of continuous type hanging scaffolding for inspection, mapping of distresses and complete condition survey. 2. Repair of the main major crack by use of epoxy injection grouting and epoxy mortar with quick set and high early strength properties before external prestressing. 3. Spalling of concrete / honeycombing of cover concrete etc were repaired by polymer modified cement mortar and polymer base cement grout. 4. Fixing deviator blocks and creating anchorage pockets. 5. Provide external pre-stressing by FREYSSINET “12T13S” SYSTEM. 6. Lift the entire superstructure to enable cleaning, resetting and rest removal & greasing of bearings. The entire span was lifted by placing one jack below each girder at each end and connecting all jacks to a common manifold. 7. Provide protective polymer cement base coating on the entire exposed surface of the bridge including the substructure for improving durability of structure.

6.

Detail Methodology and Sequence

1) The work was started on 14/01/2005. Erection of the hanging type wooden platform and hanging type scaffolding platform by bamboo, platform with bridge railing is erected. Most of the work had to be carried out at night between 12.30A.M. – 3.00A.M. and by obtaining a typical schedule of staggered block over the groups of line without stopping the trains. (See in Fig. 7 ) 2) A through inspection of the entire soffit of the bridge deck was carried out. All loose / laminated/ spalled concrete below all the girders and deck slab was chipped off & removed and cracks were mapped. 3) For the injection of the main structural cracks was also carried out at the night. The road traffic was diverted. The power and traffic block for railway lines was obtained 12.30 A.M to 3.30A.M. During repair following steps were undertaken:

i) Chipping out the large amount of loose concrete from the main wide cracks and Volume 45 Number 2 June 2015  31


pipe for external pre-stressing cables. A curing period for 14days was allowed for the concrete. These operations were followed for other three deviator blocks also. Steel specification adopted for the deviator block was as per IS-4000-1992.

cleaning the cracks and the surface by compressed air jetting supplemented by manual wire brushing etc.

ii) For this cracks V notch was formed create space for pouring of epoxy concrete.

iii) Prior to application of the epoxy concrete CICO BOND EPOXY bonding agent was applied on the entire exposed surface of the crack. Epoxy concrete was prepared using the following proportion 2: 1: 22 [2 Resin Brand CICOPOXY-21 PART-A & Hardener Brand CICOPOXY-21 PART-B : & Filler Aggregates (quartz sand + 6 mm coarse aggregate). The chemicals were retested by recognized test hours. Time gap between application of bonding agent & epoxy concrete was five minutes. (See Fig.8).

iv) PVC nozzles were placed at 300 mm c/c intervals in position to ensure sealing of the fine cracks by grouting epoxy resin.

v) This grouting operation was done till refusal of grout.

vi) Existing cables of P.S.C. girders were also re-grouted. Wherever the sheathing cables are damaged re-grouting was done by fixing PVC nozzle.

Where the cables were not exposed, they were located by means of Electronic Locator for fixing the PVC nozzles. Cebex-100 with O.P.C. 43 grade cement was used and injected by FREYSSINET GROUT PUMP. 3550 kg grout was thus injected (30 days operation) indicating substantial ungrouted cable lengths. 6.1 External Prestressing After these external prestressing was taken up. The sequence of activities of the major activity is as follows:a) Fix deviator blocks on the either side of the diaphragm at either end both the longitudinal girders. The deviator block was lifted to position manually under power and traffic block and fixed in position by fixing the bolts. After fixing the deviator block, concrete of M40 grade was cast below it to fix the 100NB angle pipe in position to provide a guide path for the HDPE 32  Volume 45

Number 2 June 2015

b)

Fixing end anchors.

1) Required portion of road deck concrete was broken by pneumatic equipments to create recess for the fixing anchorages.

2) FREYSSINET 12T13(S) system guides were fixed both ends at each cable.

3) Reinforcement bars were place as per design with the existing deck slab reinforcement.

4) HDPE sheathing was profiled and inserted into the guide mouth on both sides and seal that portion properly in position as per working drawing.

5) Threading operation was done strand by strand.

6) For the actual pre-stressing both the girders were tackled the same day. Both end stressing was adopted.

6.2 Resetting of Bearings After the external pre-stressing of girder was over, the superstructure was lifted up using FREYSSINET FLAT JACKS with lock nuts. Jacks were fixed at pier level. 1) 1st of all the jacks were fixed with manifolds and connected with FREYSSINET hydraulic pump. All the eight girder were lifted simultaneously. 2) The lifting is done till bearings were made free and placed on necessary packings. 3) The surfaces were cleaned by air jetting, wire brush and derusted by emery paper. 4) Protective red oxide coating paint was applied on bearing all the exposed surface and bearings greased. 6.3 Overall Protection The remaining work of provision of protective polymer cement base coating 2 coats TAPECRETE MARINE COATING (anti- corrosive paint) over the exposed surface of bridge including the substructure was completed. The Bridge and Structural Engineer


Cost of the Repair The total cost of the repairs came to Rupees 85 lakhs only. (See Fig.9 : Completed Bridge).

Summary and Conclusions In order to prevent such type of distress, the following needs to be ensured in construction and maintenance in PSC girder. i) Use of LRPC strands is preferable to reduce long term losses.

References 

1960’s as per the prevalent code.

IRC - 6 - 2000 --------- Loads and stresses.

IRC – 18 – 2000 -------- Pre-stressed concrete road and bridges. (Post tensioning concrete)

FREYSSINET literatures for

(a) 12T13(S) Anchorage.

(b) Grouting.

FIP guidelines.

Technical report –-- use of external prestressing on Kalyani R.C.C. R.O.B. @ Belgharia expressway for restoration and repair.

ii) During construction adequate precautions must to be taken to improve durability. This shall include:

a) Use of high strength concrete.

b) Proper grouting of sheathing ducts.

c) Adequate attention to cover

Acknowledgement

d) Use of protective coatings.

The authors expresses gratitude to Eastern Railway authority of the sr. Divisional Engineer (co-ordination), Assistant Engineer AEN/1/LLH and Section Engineer – Bally for their whole hearted support while carrying out the repair on turnkey basis.

iii) In built provisions for future prestressing requirements. iv) Adequate maintenances & inspection schedule.

The Bridge and Structural Engineer

IRC guidelines for inspection and maintenance of Bridges – Special publication no 35 – 1990.

Volume 45 Number 2 June 2015  33


Fig. 1 : Details Drawing of General Arrangement drg. no: SC / 489 / RC - 02

34  Volume 45

Number 2 June 2015

The Bridge and Structural Engineer


Fig. 2 : Details Drawing of Superstructure General Arrangement, Schematic Arrangement of External Pre-stressing drg. no: SC / 489 / GA - 01

The Bridge and Structural Engineer

Volume 45 Number 2 June 2015  35


Fig. 3 : Details Drawing of Construction Details drg. no: SC / 489 / CD - 03

36  Volume 45

Number 2 June 2015

The Bridge and Structural Engineer


Fig. 4 : Details Drawing of Cable Geometry of P.S.C. Girder Note no: 489/N-01

The Bridge and Structural Engineer

Volume 45 Number 2 June 2015  37


Fig. 5 : Photograph close view of the crack at l/3 location of end Girder Howrah end

Fig. 7 : Photograph of view of the Scaffolding and hanging type staging under erection

Fig. 6: Photograph for corroded existing Sheathing

Fig. 8 : Photograph of major crack repair by epoxy concrete with fixing the PVC Nozzle

Fig. 9 : Photograph after Complete the Repair of P.S.C. Girder Main Span Side view

38  Volume 45

Number 2 June 2015

The Bridge and Structural Engineer


An Overview of Repair and Rehabilitation / Strengthening of Concrete Bridges and a Case Study

A K BANERJEE Former Member (Technical), National Highways Authority of India ak_banerjee@hotmail.com Mr Banerjee graduated in Civil Engineering from Calcutta University in 1963 and later did his post graduation from IIT, Delhi. After a brief stint of two years in West Bengal State PWD, he joined Ministry of Road Transport & Highways in 1965 and rose through various ranks to became Chief Engineer in 1997. In 2002, he joined NHAI as Member (Tech) and retired from this post in 2003. Since then, he had been associated with the Consulting Firms for more than a decade and is currently associated as Advisor to a Private Construction / Concession Company. During his entire career, Mr Banerjee has been responsible for planning, design and supervision of several major road and bridge projects, as also repair and rehabilitation of some major bridges in the country. He has been a Member of various Technical Committees of IRC, including Bridges Specifications & Standards (BSS) Committee and is also the Convenor of Loads & Stresses Committee dealing with IRC:6. He is also a Member of the Managing Committee and Executive Committee of ING-IABSE.

Abstract Concrete Bridges, if properly designed and constructed, normally should not require much maintenance and repairs during their design service life. However, in practice it may not be the situation always on ground. This is evident from the fact that a large number of bridges have undergone distresses in the recent years much before their design life, requiring major repair and rehabilitation / strengthening of these structures and eventually warranting their replacement by new bridges. This paper gives an overview of the major causes of distress, importance of routine inspection and preventive maintenance, detailed investigation and project preparation and modalities of implementation of repairs and rehabilitation / strengthening, besides briefly illustrating a case study for rehabilitation / strengthening of a major pre-stressed concrete bridge in the coastal area of Karnataka state.

1. Introduction Premature ageing and early deterioration of concrete bridges has been a relatively common phenomenon in The Bridge and Structural Engineer

the past not only in India but also abroad, mandating the Authorities to conduct detailed condition survey, investigation, testing and carry out large scale repair and rehabilitation / strengthening of these bridge structures. While aggressive environment has been in most cases the main causative factor for development of premature distress in the structure, deficiencies in design and quality of construction, as well as lack of inspection and preventive maintenance, have also aggravated the situation on ground. Prohibitive cost of new bridges as replacement of the distressed bridges has left us with no option but to go in for extensive repairs and rehabilitation / strengthening of the existing bridges to extend their service life till such time new bridges could be planned in the near future. The task of detailed project preparation, comprising detailed condition survey, investigation, testing, assessment of distress and formulation of repair plan to undertake such a specialized job, is normally entrusted to a reputed Consultant having expertise in this field. Load testing is generally done after completion of the rehabilitation work to validate the efficacy of repairs vis-Ă -vis design assumptions. Volume 45 Number 2 June 2015  39


2.

Major Causes of Distress

Analysis of data of condition survey, detailed investigation and testing of the distressed bridges in the past broadly indicate the following major causes of distress in the concrete bridges: (i) Deficiencies in quality of construction like porous concrete, less cover, inadequate compaction, use of rusted steel, improper grouting of cable ducts etc; (ii) Inadequate durability measures in using slender sections and deficiencies in design / detailing of reinforcement; (iii) Malfunctioning of bearings and expansion joints; (iv) Effect of corrosion on reinforcing and prestressing steel, chloride attck and carbonation in marine environment, leaching action, sulphate attack etc; (v) Improper drainage and water proofing of bridge deck ; (vi) Higher intensity of traffic and higher axle loads of vehicles; (vii) Damages due to accidents and natural calamities; (viii) Abnormal flood in river There is also a marked aggravation of distress for want of preventive maintenance or due to deferred maintenance of the bridges either due to paucity of fund or lack of awareness among the Engineers of the possible fall out of lack of regular inspection and preventive maintenance. If the minor distresses are not attended in time, it may lead to major repair and rehabilitation work at a later date at a huge cost and in some cases, the existing bridges, either partly or wholly, may need replacement, being beyond the scope of economic repairs and rehabilitation.

3.

Major Signs of Distress

Major signs of distress in concrete bridges may be identified as:

Rust stains;

Deformations;

Excessive deflection / movement

4. Approach to Repair and Rehabilitation / Strengthening 4.1 Repair and Rehabilitation of bridges is a specialized job and understanding of the magnitude and seriousness of distress is very important, which unless analyzed by an experienced Bridge Engineer, may lead to panic reaction from the Authority. This requires an experienced Consultancy Firm for detailed inspection, investigation, testing, analysis of data and formulation of repair plan. While sudden distress in a bridge due to earthquake, abnormal flood or accidental damages would warrant an immediate response from the Authority, management of existing bridge assets and prioritization of repairs and rehabilitation, however, require a proper Bridge Management System (BMS), keeping in view the paucity of funds for maintenance and repairs. Analysis of data of routine inspection and normal maintenance of bridges assume great importance in this context and constitute the basic parameters of an effective BMS. 4.2 Once the need for repair and rehabilitation / strengthening is identified by the Authority, the next step is to select an experienced Consultant for detailed project preparation. NIT for such jobs shall indicate the salient features and signs of distress observed during visual condition survey. Broad Terms of Reference for such a consultancy job may be identified as: Phase I – Detailed condition survey; – Detailed investigation of causes and extent of distress;

Cracking;

– Formulation of repair and rehabilitation / strengthening plan;

Scaling;

– Rough cost estimate

Spalling and Delamination;

Phase II

Leaching;

– Detailed design and drawings;

40  Volume 45

Number 2 June 2015

The Bridge and Structural Engineer


– Detailed Cost estimation;

– Identification of causes of distress;

– Specifications and bid document;

– Assessment of nature and magnitude of distress and urgency of repairs / strengthening;

– Advise Authority for selection of a suitable contractor Phase III – Assist the Authority in supervision during execution of repairs / rehabilitation; – Suggest alternative materials of repairs depending on availability in India

– Examine options for Repair / Rehabilitation comprising: 

4.3 Detailed Scope of work in Phase I Condition Survey – Use of bridge inspection unit with hanging platform or boats and binoculars; – Mapping of locations and extent of distress like cracking, spalling, honey combing, exposed reinforcement etc;

Total replacement in case of extensive damages and prohibitive repair cost; Partial replacement and repair based on severity of localized damages; Extensive repairs / strengthening; Economic effectiveness of repairs vis-à-vis increase in service life;

Need for evaluation of load carrying capacity;

Need for retrofitting

– Formulation of Repair plans – Broad Criteria: 

Available repair techniques;

– Adequacy of drainage;

Technical feasibility;

– Condition of bearings and expansion joints;

– Deflection / movement of bridge deck; – Anchorage zones of pre-stressing cables

Detailed Investigation – Theoretical studies comprise: 

study of original records of design and construction;

Cost of repairs / rehabilitation both short term and long term;

Least estimate of remaining service life and anticipated increase in service life after repairs; Availability and efficacy of repair materials and equipment;

Availability of suitable contractor

study of reports of earlier inspections;

Traffic management during repairs;

study of environmental conditions and;

Access for repairs;

Estimated time for repairs;

study of present loading pattern and intensity of axle loads vis-à-vis loads adopted in original design;

– Laboratory tests on Concrete Cores:

– Major Repair Materials: 

Cement mortar or grout;

Petrography i.e. mineral composition;

Latex modified cement mortar or concrete;

Compressive strength of concrete;

Epoxy resin mortars;

Cement content and aggregate-cement ratio;

Epoxy concrete;

Permeability and water absorption;

Synthetic silica shotcrete

Chloride content;

– Repair / strengthening Techniques:

Depth of carbonation

– Analysis of data of inspection, investigation and testing; The Bridge and Structural Engineer

Patch repair with mortar concrete; Crack repair with epoxy grouting and cement mortar; Volume 45 Number 2 June 2015  41


Guniting / shotcreting for large patch repairs;

Epoxy injection for sealing fine cracks;

 

– Suggest suitable alternative material etc. where necessary;

Vacuum grouting of cable ducts with epoxy resin / cement grout;

– Ensure quality control;

External pre-stressing with HDPE sheathing for cable ducts;

– Maintenance manual for future inspection / maintenance

Epoxy bonded steel plates; Concrete overlay over existing deck slab / deck slab replacement;

– Suggest solutions to problems during execution;

5. Rehabilitation of Sharavathy Bridge on NH 17 in Karnataka – A Case Study 

Salient Features of Bridge:

Resetting / replacement of bearings;

Resetting / replacement of expansion joints;

– Total length 1048 m – completed in the year 1970;

Jacketing of piers;

– 34 spans of 30.2 m c/c of piers;

Underwater repairs / strengthening of concrete piles in foundation;

Repair / replacement of wearing coat and crash barriers / railings

4.4 Detailed Scope of Work in Phase II – Design calculations and detailed drawings for repairs / strengthening;

Hammerhead piers with suspended span of 24.4 m length;

– Carriageway width 7.32 m with 1.53 m wide footpath on either side; – 5 nos. simply supported precast PSC I girders in superstructure;

– Realistic cost estimate;

– Cross pre-stressed deck comprising girder flanges and gap slab;

– Tender document comprising:

– Cantilever footpath from precast girder flanfes;

General conditions and special conditions of contract;

– Cross pre-stressed diaphragms 2 nos. end and 3 nos. intermediate diaphragms;

Detailed technical specifications for various items of work, e.g. materials, methodology of construction, quality assurance etc.;

– Hammerhead portion of superstructure cast integrally with RCC piers;

Bill of quantities;

Drawings

– Guidelines and specifications for load testing and instrumentation; – Assist client for selection of expert agency for execution of repairs / rehabilitation

– Twin dumbbell shaped well foundations; – Cast steel segmental roller / rocker bearings under each girder at articulations; – Located in coastal area in aggressive marine environment 

4.5 Detailed Scope of Work in Phase III

Condition survey done by Central Electrochemical Research Institute (CECRI), Chennai in 1989 after the bridge showed signs of distress:

– Associate with client in supervision of repairs / strengthening works;

– Severe damages due to corrosion observed in superstructure;

– Consultant to be present during execution of critical items of repair / strengthening work, including load testing;

– Assessment of strength of superstructure and repair / strengthening recommended

– Render general guidance for execution; 42  Volume 45

Number 2 June 2015

Decision to involve an Expert Foreign Consultant in association with Indian Firm to carry out The Bridge and Structural Engineer


detailed inspection, investigation, testing and formulate repair plan duly ensuring transfer of the state-of-the art technology to the Indian Firm 

Design consultancy done by M/s STUP Consultants in association with M/s ACER, STATS Ltd. and TRL of U.K in early 1992

– Visual inspection done by Mobile Bridge Inspection Unit (MBIU); – Field and laboratory testing done both in India and U.K; – Analysis of data and assessment of residual strength; – Long term and short term rehabilitation measures suggested in Phase I; – Decision taken to adopt long term measure of strengthening by adopting external pre-stressing of two cables on each side of an I-girder; – Detailed design and drawings prepared for long term rehabilitation – Recommend closure of Bridge to heavy vehicles 

Major Distresses Observed

– Poor quality of concrete in piers and; – Damages to deck slab and wearing coat over suspended spans 

Major Repairs / Strengthening Done

– 150 mm thick M35 concrete jacketing of piers; – External pre-stressing of main girders and cross diaphragms by 4 nos. 15.2mm dia strands per girder with HDPE sheathing; – External steel brackets on either side of pier to support girders of hammer head and suspended span and provision of new elastomeric bearings below suspended spans to relieve load on the articulations; – Cement grouting of existing cables; – Grouting of cracks in concrete with epoxy resin; – Anti-corrosive reinforcement;

treatment

to

exposed

– Dismantling the wearing coat and laying new RCC deck slab with shear connectors; – Reconstruction of footpath, kerb and handrails;

– Spalling of concrete;

– Fixing of new expansion joints;

– Cracking in webs of longitudinal and cross girders;

– Resetting and replacement of roller bearings and provision of grease box;

– Exposed corroded reinforcement;

– Fixing new sets of drainage spouts at closer spacing

– Corrosion of pre-stressing wire cables and sheathing and loss of cable sections;

Traffic Management Rehabilitation

during

Repairs

/

– Severe corrosion in exposed cable and anchorages of cross girders;

– Round the clock ferry service for heavy vehicles;

– Severe cracking, spalling and corrosion of steel in precast footpath slabs;

– Only light vehicles allowed on the bridge by erecting gantry portal at either end;

– Honeycombing of concrete around bearings; – Severely corroded cable ducts and some ungrouted ducts detected in Endoscopy; – Malfunctioning and leakage of expansion joints and drainage spouts; – Severe carbonation penetrating significant depth in concrete; – Voids in grouts in cable ducts and high level of chloride in grout; – Poor compaction and honeycombing of concrete around cable anchorages; The Bridge and Structural Engineer

– Limited traffic restriction during external prestrssing; – One lane of traffic allowed at all time; – Speed breakers erected to limit speed of vehicles on bridge to 10 kmph

6. Conclusions Bridges need repairs / rehabilitation primarily due to ageing, lack of routine maintenance, higher loads, natural calamities and aggressive environment. At the initial stage, detailed condition survey is required Volume 45 Number 2 June 2015  43


to identify the nature and extent of distress followed by detailed investigation and testing to assess the causes of distress, serviceability level of the bridge and determine the necessary repairs / strengthening of the bridge. Corrosion of reinforcement, pre-stressing steel, cable ducts and carbonation of concrete are major causes of distress in a RCC or PSC bridge. Repair / rehabilitation measures should be decided after study of various options, cost vis-Ă -vis increase in service life in each option, availability of repair materials and repair techniques. There is a need for load testing and instrumentation of the bridge after

44  Volume 45

Number 2 June 2015

repair to determine the efficacy of repairs. Tender documents for a repair / rehabilitation work should include detailed specifications, method of execution of major repairs and quality control measures. Terms of Reference for the Consultant to be engaged by the Authority for detailed project preparation of repairs / strengthening measures shall provide for the Consultant to guide and assist the Client in supervision of repairs / rehabilitation works at site. Finally, due importance should be given to traffic management during repairs and strengthening including diversion of heavy traffic across major rivers.

The Bridge and Structural Engineer


INVESTIGATION AND REHABILITATION OF FIRE DAMAGED STRUCTURES WITH CASE STUDIES RK JAIGOPAL Managing Director Struct Geotech Research Laboratories Pvt. Ltd., # 588, 6th Block, 2nd Main Hosakerehalli Cross, BSK 3rd Stage, 2nd Phase Bangalore – 560 085 sgrlpl@yahoo.com

R.K. Jaigopal, born 1955, received his Post graduate in Structural engineering from Bangalore University. He has more than 36 years of experience in the field of design, construction, structural investigation and rehabilitation which includes buildings and bridges.

Summary

industrial structures and also cricket stadiums.

Investigation and rehabilitation of fire damaged structures needs higher level of technical expertise and knowledge about structural aspects of buildings as well as integration of new materials on to the structure while repairing. Hence the investigation expert is a key figure in addition to site testing and laboratory testing. Formulation of repair scheme is an important aspect. The two case studies given are from important structures where the author himself has carried out investigation and repair of said structures.

The emphasis of investigation shall be for assessing the concrete structure after a fire and as such determining the extent of repairs required. In addition to structural damage there may be smoke damage to partitions, glass facades, electrical systems and mechanical systems. It shall be noted that the associated cost of cleaning and replacing such systems will be very significant.

1. Introduction Fire resistance of concrete is an inherent property and generally concrete structures are capable of taking repair after the fire, even it is of high intensity. This happens as concrete is a poor conductor of heat. Heating of concrete results in physico-chemical conditions shifting in and out of thermo dynamic stability field of specific phases in minerals in concrete effectuating their appearance and disappearance. Here we will have to maintain the metamorphic petrology which is a branch of geology deals with study of mineralogy. Chemical composition, heating history of concrete during fire is important to determine whether concrete structure subjected to fire and its components are still structurally sound or not. Analogous to metamorphic petrology thermally triggered reactions in concrete result in changes in specific cases which may be used to trace isograds. Rehabilitated structures, after fire, generally performed well after repair and are restored back to service. It is noticed that when structures are demolished and replaced it was generally for reasons other than damage sustained during the fire. There are many structures affected by fire, like commercial multi storied buildings, port administrative buildings, The Bridge and Structural Engineer

When a fire has occurred, the requirements are generally for an immediate and thorough appraisal to be carried out, with clear objectives. Such an appraisal shall begin as soon as building can be entered safely and generally before the removal of debris. In order to establish whether the building is safe or not, a competent person shall inspect the structure. While inspection structure shall be observed for load sustainability condition and it shall also be observed for whether few members have become weak needing support. The fire damage assessment shall be mainly based on; (a) On-site evaluation of the structure (b) Laboratory testing (c) Physical examination (d) Any specific separate assessment. The focus shall be on on-site measurement of residual strength in structural members, deformation if occurred and to obtain evidence of actual temperature reached during the fire. The focus shall be on methods for onsite measurement of residual strength in members, deformation of members and also to obtain evidence for actual temperatures reached during the fire. All the more, an experienced and competent Engineer is Volume 45 Number 2 June 2015  45


an important factor while assessing the fire damage. The Engineer shall be aware of limits of applicability of all construction. Immediately after the fire, a thorough appraisal needs to be carried out with clear objectives. The appraisal shall commence once the building can be entered safely and normally before removal of debris. The said expert or the competent person shall establish whether the building is safe or not and if it is unsafe, methods of propping shall be advised. It has been observed that after detailed appraisals, the reinforced concrete structures mostly, can be repaired by means of suitable techniques. In case of severe damage, certain elements in the structure shall be replaced. The active fire resistance of a concrete structure is normally well above minimum requirements and hence the reserve strength in the structure enables it to survive, severe fires, and often, it can be reinstated. Safety plays a major role in the structure at all stages from initial assessment to completion of repair. Wherever necessary, members like beams and slabs shall be propped up with temporary supports. In some circumstances phased breaking may be required. Temporary false work may be required to secure the structure not just for individual members but for the stability of the entire structure. All types of loads coming on the structural members shall be calculated in specific for doubtful members.

2.

Damage Assessment

Concrete due to fire can be result in variety of structural changes like cracking, spalling, debonding of aggregates and rebars, expansion and mineralogical, chemical changes such as discoloration, dehydration, and disassociation. When concrete is exposed to fire, differential expansions and contractions of various components and constituents within the concrete takes place. For aggregates the heat can induce cracking around and across the aggregates, loss of bond with the cement paste also with the reinforcement. In case of cement paste, it can be evaporation and dissolution. Dehydration and dissolution of ettringite, gypsum, calcium hydroxide, calcium carbonate and other

46  Volume 45

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phases in the cement phase such as calcium silicates, hydrates can occur. Structural and mineralogical changes will affect the integrity of structure in turn the mineralogical changes can be used to deduce heating history of the structure. Combining metamorphic petrology and concrete petrology will provide a suitable investigation tool for assessment of structure. The sole aim of damage assessment is to decide if any structural elements are to be demolished or whole structure needs to be demolished or structural elements that are retained need any rehabilitation. Damage classification of various structural members shall be carried out systematically. At best, structural members need no repair due to inherent residual strength and at worst, demolition may be required. The damage assessment shall follow two methodologies as stated below of which one or both shall be applied A. In order to calculate residual strength of concrete and reinforcement, fire severity shall be estimated so as to deduce temperature profiles. The A above can be sub-classified as; a)

Estimation of fire severity

b)

Determination of temperature profiles by numerical methods.

a)

Estimation of fire severity by careful examination of debris and quantification of fire, as fire load in calorific energy of whole contents contained in the area, or applying numerical evaluation methods such as computational fluid dynamics.

Important factor in assessing and quantifying the heat caused, will be careful examination of debris and prehistory of materials which caught fire. This shall be in terms of kgs of materials, their respective colorific values and finally wood equivalent values. This can be obtained from National Building Code of India-2005 vide table-26 of chapter-IV, which also specifies the allowable fire load density for affected portions. Refer Table-1 which provides for Fire expressed as fire load in calorific energy of whole materials contained in the specific space.

The Bridge and Structural Engineer


Table 1 : Certain Selected Combustible Materials from a Case Study Sl No.

Materials

No’s*

Weight in Kgs*

Calorific Value

Wood equivalent Kg/Kg

1.

UPS (polyvinyl chloride)

5

5

522.5

29.75

2.

CPU (Polyvinyl chloride)

5

5

522.5

29.75

3.

Printer (Polyvinyl chloride)

2

5

209

11.90

4.

System table

5

15

1320

75

5.

Office chairs

10

5

790

45

6.

Papers

-

1000

15400

880

7.

Cloth

-

50

790

45

8.

Steel racks

20

20

-

-

9.

Benzene

50

1980

112.5

10.

AC Ducts (Nylon)

-

500

11000

625

11.

Plywood

-

250

4400

250

12.

LED/LCD panels

1000

15

528000

30000

13.

Electric switch box

10

1

41.8

23.8

14.

False ceiling

-

150

2370

135

15.

Wooden Drawer

-

500

8800

500

16.

Miscellaneous & other items

-

500

8800

500

17.

Plastic

1000

41800

2380

18.

Thermocol

500

7900

450

19.

Wooden box 37592.70

1500

26400

1500 37592.70

20.

Considering additional of heat energy due to steel articles at 20% of combustible articles it will be

7518.50

Total

45111.20

The fire load density for the affected portion having 400 sq.mt. will be at 45111.50/400=112.78 Source: One of the investigation reports of author.

The typical allowable values for the fire load density of this category of building vide table-26 of, chapter-IV of National Building Code of India-2005 is upto 150, however there it is only 112.78 in the present case. Therefore it is less than the values prescribed in NBC. b)

Determination of temperature profiles by applying numerical methods or any relevant calculation techniques.

With the above methods, damage classification can be a realistic actual condition of fire damaged structure. The strength of unaffected concrete shall be assessed The Bridge and Structural Engineer

to confirm the design assumptions. Normally concrete changes colour due to heating. It changes to pink/red discoloration above 300oC which is important since it coincides approximately with onset of significant loss of strength due to heating. Any pink/red discolored concrete shall be regarded as being suspect and potentially weakened. The colour changes are most pronounced for siliceous aggregates and less for limestone and granite. A Summary of mineralogical and strength changes to concrete caused by heating are furnished in Table-2; Volume 45 Number 2 June 2015  47


Table 2 : Summary of Mineralogical and Strength Changes to Concrete Caused by Heating Heating Temperature: oC

Changes caused by heating Mineralogical changes

Strength changes

70-80

Dissociation of ettringite

Minor Loss of strength possible (<10%)

105

Loss of physically bound water in aggregate and cement matrix commences, increasing capillary porosity

120-163

Decomposition of gypsum

250-350

Oxidation of iron compounds causing pink/red discolouration Significant loss of strength of aggregate. Loss of bound water in cement matrix and commences at 300oC associated degradation becomes more prominent

450-500

Dehydroxylation of portlandite. Aggregate calcines and will eventually change colour to white/grey

573

5% increase in volume of quartz (-to-quartz transition) Concrete out structurally useful causing radial cracking around the quartz grains in the after heating in temperature in aggregate excess of 500-600oC

600-800

Release of carbon dioxide from carbonates may cause a considerable contraction of the concrete (with severe microcracking of the cement matrix)

800-1200

Dissociation and extreme thermal stress cause complete disintegration of calcareous constituents, resulting in whitishgrey concrete colour and severe micro-cracking

1200

Concrete starts to melt

1300-1400

Concrete melted

B. Quality assessment by testing the fire damaged concrete

proportions, aggregates present and the applied load during heating. For temperatures upto 300oC, the residual compressive strength of structural quality concrete is not significantly reduced, while for temperatures greater than 500oC, the residual strength may be reduced significantly of its original value. However temperature of 300oC is normally taken to be the critical temperature above which concrete is deemed to have been significantly damaged, the most direct method of estimating the compressive strength of concrete is by testing core samples cut from structure.

There are several levels and methods to test fire damaged concrete, a) Physical examination and hammer soundings. The assessment of extent of damage shall be carried out in field by detailed and careful physical examinations for various structural elements. Examination of rubble shall indicate temperature in the air, this however might not truly reflect the heat intensity reached on the concrete, which is likely to be less than air. The effect of heat will be in its full energy deployed on outer surface of concrete and gradually the intensity will decrease in proportion to the depth. The surface temperatures are usually different from temperatures at different depths. As such Non Destructive tests indicate strength characteristics at various depths. The strength of concrete after cooling varies depending on temperature attained, the heating duration, mix 48â&#x20AC;&#x192; Volume 45

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Changes in both cement paste and aggregates of fire affected concrete will result in conversion of certain phases into new ones which may alter the colour of concrete also original mineralogical composition of cement paste. Both effects can be used to trace isograds in the concrete element. Since these isograds occur in response to the temperature they will roughly coincide with The Bridge and Structural Engineer


isotherms and can be further used to trace the temperature variations with depth from surface. Tracing of temperature history of fire effected concrete is of vital importance in determining the depth of damage in a particular concrete member that can eventually be discarded with 60% reduction in compressive strength when heated upto 300oC.

(i) UPV to ascertain internal integrity of concrete.

b) Non destructive testing like Ultrasonic Pulse Velocity Tests, Cover Meter tests, Rebound Hammer tests are most suitable tests. c) Laboratory testing of samples collected from cross section of structural member to be tested for core compressive strength, Ph values, Chlorides, Sulphates and Petrographic examination of concrete and relevant tests for steel. C. Steel reinforcement and structural steel In the event of fire, steel will also reach higher temperature along with concrete, loss of strength in a steel will be a significant factor. Recovery of yield strength after cooling is generally complex for temperature upto 450oC for cold worked steel and 600oC for hot rolled steel. Above these temperatures there will be loss in yield strength after cooling. The effect of heating on structural steel will include reduction in physical properties, distortion, axial shortening of column, over stressing of bolts, connections and welds.

Fig. 2 : Ultrosonic pulse velocity test in progress

(ii) Core extraction and testing to assess compressive strength and to inspect internal concrete also laboratory test can be conducted for pH, Chlorides and sulphates.

Fig. 3 : Concrete core extraction in progress

Fig. 1 : showing exposed steel and delaminated concrete

3.

Testing of fire damaged structures

Structure will have to be tested for its internal integrity, strength characteristics,, degree of damage and change in composition with respect to depth. Following tests are carried out to diagnose the depth of damage. The Bridge and Structural Engineer

(iii) Stereo microscopic inspection of concrete cores. This test will reveal the alterations and colour changes in the cores as well as the surface features such as cracking, spalling and popouts, to estimate the possible temperature variations in the concrete as a function of depth from surface. Here important aspects are colour variations with depth from the surface, pattern of cracking in and around the aggregate particles, width and depth of cracks, dissolution and loss of bonding to the aggregate particles and integrity of cement paste. (iv) Rebound hammer test to ascertain the compressive strength of concrete on various surfaces at required depths of concrete. Volume 45 Number 2 June 2015â&#x20AC;&#x192; 49


examination of fluorescent thin sections with the aid of; Combined polarizing and fluorescent light microscope. This sections are normally prepared from drilled cores for testing. (viii) Condition of steel will have to be assessed for damage from heating.

Fig. 4: Rebound hammer test in progress

Invariably steel expands resulting in delamination of power concrete also steel will buckle out of its portion.

(v) Petro graphic analysis to check the concrete dehydration. Number of laboratory tests are available for determining concrete condition. Petro graphic examination and compressive strength testing of core samples are those most commonly used in the fire damaged investigations. Petro graphic examination is the definitive technique for determining depth of fire damage in concrete.

Fig. 6 : Steel expanded, delaminated and buckled

4.

Effects of fire on masonry elements

Clay bricks in the buildings can withstand temperature in the region 1000oC or more without any damage. The heat can also damage the size stone masonry in the similar way as that of concrete.

5. Fig. 5 : Petrographic analysis

(vi) Fluorescence macroscopic analysis Detailed information regarding distribution of cracks, including fine micro cracks, integrity of concrete with respect to depth from surface can be obtained by flatpolished fluorescent sections can be prepared from the drilled cores and examined under ultraviolet light to study cracks in concrete. (vii) Polarizing and fluorescent microscopy In case of requirement for further detailed information this can be derived from polarizing and fluorescent microscopy. This technique is based on

50â&#x20AC;&#x192; Volume 45

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Formulation of repair schemes

Upon visual inspection and Non destructive testing a suitable restoration scheme will have to be formulated to bring back the structure to serviceable condition. Important factor here is concrete will have to be removed upto the depth to where it is damaged due to fire. Assessing this damaged thickness is a important factor in rehabilitation. The reinforcement if damaged also need to be replaced. Replacing concrete material can be in the form of made to order concrete, microconcrete, shotcrete, polymer modified mortar or epoxy mortar etc. Few typical examples of restoration of columns, beams and slab are shown Figures 7 to 9. The Bridge and Structural Engineer


6.

Load test to confirm the regain of carrying capacity

After completion of rehabilitation process the structure needs to be load tested to confirm it is satisfactory for carrying design loads. The load testing can be carried out as per IS 456 -2000.

7. Conclusions With experience in evaluation of fire damaged structures unless severely damaged, most of the structures are fit enough to be repaired rather than replaced. The structures can be assessed for fire damage by various testing techniques and a suitable repair solution can be given to bring back the structure to its original serviceable condition.

Appendix A Fig. 7: Typical example of rehabilitation of column

Case Study -1 â&#x20AC;&#x201C; Stadium in Bangalore A portion of the stadium where club/bar is located was fire damaged. The affected building is a RCC framed structure of column, beam and slabs. Here the quantification of fire was meticulously done as debris was not disturbed. As such the temperature levels were calculated to a reasonable accuracy. Investigation was carried out by physical examination, Non destructive test, core extraction etc. A suitable rehabilitation scheme was formulated which consisted of removal of damaged surface concrete, replacement of additional thickness with shotcrete with application of epoxies etc. The structure was brought back to its original serviceable condition. Below photographs shows the stages of rehabilitation.

Fig. 8: Typical example of rehabilitation of column

Fig. 9 : Typical example of rehabilitation of slab and beams

The Bridge and Structural Engineer

Fig. 10 : Reinforcement placing is complete

Volume 45 Number 2 June 2015â&#x20AC;&#x192; 51


Fig. 11 : Shotcrete work in progress

Case Study – 2 – A software technology park A multi storied structure housing software industry caught fire due to short circuit and here also assessment of the temperature was fairly accurate, because the debris was not disturbed. The fire load densities were meticulously calculated as per National Building Code of India- 2005. Physical investigation, condition survey, Non destructive

52  Volume 45

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tests and laboratory analysis was carried out to assess the damage due to fire. A rehabilitation method was formulated which was a unique one in order not to increase the size of the columns. As such steel plates were used and anchored on all four sides of the column. Slab concrete was virtually replaced by one third of its thickness by shotcrete and necessary adding of reinforcement wherever steel was damaged.

The Bridge and Structural Engineer


Replacement of Expansion Joints of 2nd Hooghly Bridge, Kolkata Santanu MAJUMDAR Chief Executive Officer Mageba Bridge Products Pvt. Ltd., Kolkata, WB, INDIA smajumdar@mageba.in

Santanu Majumdar graduated in Civil Engineering from Jadavpur University, Kolkata in the year 1991. He started his career as a bridge and structural engineer, has served the industry of Bridge Bearings and Expansion Joints for the last 22 years.

Shibnath LAHIRI Technical Head Mageba Bridge Products Pvt. Ltd., Kolkata, WB, INDIA slahiri@mageba.in

Shibnath Lahiri graduated in Civil Engineering from Jadavpur University, Kolkata in the year 1991. He has vast experience in construction industry in hydel power, cement plant etc. He is associated with mageba India for the last 7 years and functioning as the head of the Technical and Design office.

Arijit GHOSH Sr. Project Manager Mageba Bridge Products Pvt. Ltd., Kolkata, WB, INDIA arijitg2@gmail.com

Arijit Ghosh graduated in Civil Engineering from Jadavpur University, Kolkata in the year 2006. He started his career as a design engineer with a consulting firm and is presently associated with mageba India as Sr. Project Manager.

Pratik SEN Sr. Project Manager Mageba Bridge Products Pvt. Ltd., Kolkata, WB, INDIA psen@mageba.in

Pratik Sen graduated in Civil Engineering from NIT Calicut in the year 2008. Over the 7 years of work experience, he was initially associated with the Cement industry and is presently working as Sr. Project Manager with mageba India.

Abstract Vidyasagar Setu also known as Second Hooghly Bridge is a toll bridge over River Hooghly in West Bengal, India. The bridge serves as a major link in between the twin cities of Kolkata and Howrah. Being in service since 1992, spanning over a total length of 823metres, Vidyasagar Setu is the first major cablestayed bridge built in India. The bridge serves as the major feeder route to all the major National Highways emanating from/connecting the metropolitan expanse of Kolkata and thus experiences high traffic load almost all throughout the day. The Bridge and Structural Engineer

Main cable stay portion of the bridge was equipped with Matt Slab seal (Matt type) expansion joint at one end an eleven cell Modular Expansion joint of 880mm movement capacity at the other end. The eleven cell Modular Expansion joint was also the first application of large movement modular joint in India. Being into service for more than two decades the condition of the Modular joint deteriorated over time and finally got damaged to an extent that immediate replacement became necessary. Replacement of the existing expansion joints, particularly the Modular Expansion joint involved Volume 45 Number 2 June 2015â&#x20AC;&#x192; 53


its own challenges e.g., defining proper traffic management; implementing necessary safety assurance; proposing appropriate technical solution and work methodology etc. The entire replacement job was to be carried out ensuring uninterrupted flow of traffic and that too avoiding blocking of any carriageway for more than a few hours.

concrete comprises of built-up steel girder system in longitudinal and transverse direction along with 230 mm thick RCC deck slab.

The paper discusses the entire work of replacement, including traffic management and replacement methodology adopted for this extremely challenging work.

1. Introduction

Fig. 1.1 : Aerial view of 2nd Hooghly Bridge

1.1 A Brief Overview

1.3 Elementary Structural Arrangement

The twin cities of Kolkata and Howrah are located on the eastern and western banks of River Hooghly respectively. In 1874, the Pontoon Bridge near Howrah station was the first fixed structure across river Hooghly, followed by Bally bridge, known as Vivekanda Setu at Dakhineswar in 1932. In 1943, the elegant Rabindra Setu (also known as the Howrah Bridge) came into being, replacing the age old Pontoon Bridge. But in only two decades it was rendered inadequate to cater for the growing need of the transriver communication. In October 1992, Vidyasagar Setu came into existence at 1.5 Km downstream near Princep Ghat. This pencil slim, elegant engineering marvel redefined the skyline of Kolkata and made India proud to have its first major cable stay bridge.

At both end the Cable stay portion is supported on two hollow box RCC anchor piers constructed on twin circular well foundation. The bridge is stayed by 152 number of main-stay cables and holding down cables at the anchor pier location. The bridge deck is restrained along both longitudinal and transverse direction thr ough bearing supports at Kolkata end and only along transverse direction at Howrah end which allowed the longitudinal movement of full length of the main cable stay bridge portion.

This magnificent structure, connecting Kolkata to its suburbs, a vast land bank of industrial and fertile agricultural zone, caters to almost 80,000 vehicles per day and thus in turn has an immense impact on the socio-economic life of its citizens. 1.2 The Geometrical Aspects The cable stay portion is a single span bridge of 823 meters long with a central span of 457.20 meters between two â&#x20AC;&#x153;Aâ&#x20AC;? frame pylons and two equal end spans on either side. The total deck width of 35 meters is divided in dual-carriageway separated by a median strip wherein each carriageway comprises of three lanes. A cross-fall of 2% is maintained across each carriageway to facilitate surface run-off and 4% gradient is maintained in the longitudinal direction to match a central vertical curve of 5000 metre radius. The carriageway composite section in steel and 54â&#x20AC;&#x192; Volume 45

Number 2 June 2015

In view of the restraint arrangement, the Kolkata end expansion joint was required to cater for the movement contribution only from the approach part, which is limited to 230 mm. Slab seal (matt type) expansion joint, an option which was available in India at that time, was used at Kolkata end. The expansion joint at the Howrah end was required to be designed for a huge longitudinal movement of 880 mm, contributed primarily by the main cable stay bridge and an eleven cell Modular Expansion joint was required, which had to be imported from Germany.

2.

The Background

In the year 2014, the bridge authority undertook a comprehensive inspection of the bridge with an a aim to estimate its structural health and to enhance the operational life. Based on the inspection and assessment of the condition, a decision was taken to replace the expansion joints of the main bridge portion. The existing modular joint at Howrah end was an early generation swivel-joist type eleven cell modular joint. Structural behaviour and performance of the joint started to deteriorate within 10 years The Bridge and Structural Engineer


from opening of the bridge to traffic. The mechanical steering system, which controls the gap width of the modules got defunct hindering the free movement of the joint. Jamming of the moving parts caused locked-in stresses in the system and as an effect the top lamella beams were found to be bent in plan with non-uniform gaps between modules. The severity of the problem grew fast with time and finally the lamella got snapped into pieces to relieve the huge accumulated locked-in stress built up over time. The situation was so grave that the existing joint was required to be buried under steel cover plates to facilitate traffic movement. It became critical for the bridge authority to replace the joint as early as possible.

which was of rubberised Slab seal (Matt) type, were found to be in workable condition. However, being into service for more than two decades, there were signs of wear and tear at the top rubber surface facing road traffic but there was as such no serious structural damage. It was also emphasized that since the joint had crossed the design service life of 15 years with sporadic signs of weathering and ageing of rubber causing local exposure of internal steel parts, it was decided to replace this joint as well.

3.

Execution and Planning for the Job

3.1 The working principle Replacing expansion joints of a bridge in service is always very critical. The issue becomes manifold with the complexity in the bridge structure. The replacement methodology adopted addresses both technical and administrative aspects under the following boundary conditions: 3.1.1 Keeping uninterrupted traffic flow

Fig. 2.1 : Rubberised Slab Seal (Matt) Expansion joint prior to replacement

Heavy traffic volume on the bridge demanded a robust and efficacious traffic management plan so that free flow of traffic is ensured on the bridge at all times while replacement work would take place simultaneously. It was therefore inevitable that the joint replacement had to be done in a lane by lane manner i.e. to take up activity of replacement at one lane of a carriage way at a time and allowing traffic over the other two lanes of the same carriageway. 3.1.2 Complexity of the Bridge structure The average daily movement of the bridge is about 200 mm which is facilitated at the Howrah end only. The bridge is of sophisticated cable stay construction with composite deck and approaches made of concrete. So the replacement of the modular joint at the Howrah side involved removal of existing expansion joint by controlled breaking and preparing the edge faces for concrete connection at one end and introducing an appropriate steel connection at the other during installation. 3.1.3 Complexity of joint types

Fig. 2.2 : Swivel-joist type 11 cell Modular joint prior to replacement

On the contrary, the joint installed at Kolkata end, The Bridge and Structural Engineer

Replacement of slab seal joints at Kolkata end of the bridge involved little difficulty, as the elastomeric slab units are modular in nature and were replaceable easily from top with new slab unit. Accordingly, Volume 45 Number 2 June 2015â&#x20AC;&#x192; 55


the challenge was mostly limited only to the traffic management requirement. In case of modular joint the complexity was manifold. The sequential replacement scheme of expansion joint was envisaged by segregation of the entire 11 Module joint into two parts; first part being the edge beams of the entire joint, split into appropriate segments along with the primary internal support system of the joint and in second part all the ten central (lamella) beams having length of full carriageway width and including the complete elastic steering system, was lowered collectively in one go. 3.1.4 Product Selection and distinguishing features Owing to the mentioned boundary conditions and the replacement methodology needed to be adopted, the technical features of the product played a very vital role. The features of the products were compatible with the replacement methodology. 3.1.4.1 Slab Seal (Matt) joint at Kolkata end Only the elastomeric slab units of the Slab Seal (Matt) joint were required to be replaced and it was possible to use slab units of same model and brand used during the first installation. Since the embedded steel housing was found to be in good condition even after more than two decades of service, the entire replacement work could be done in a non-invasive way. This proved the efficacy of the Elastomeric Slab Seal (Matt) joint for mid-range movement capacity not only from the durability point of view but also from the ease of replacement. The replaced new slab units have improved abrasion resistance, better flexibility and strength. 3.1.4.2 Modular Expansion joint at Howrah end The new modular expansion joint used is a 4th generation modular joint. Unlike rigid and intolerant mechanical steering system of the existing joint, the new joint uses elastic steering systems, which is a natural and forgiving system. Adopting such a system shall help to avoid the constraint forces due to unforeseen movements or obstacles. The new joint is made of bolted connection which not only improves the durability of the joint against fatigue but also helps to facilitate future replacement of joint components easily and quickly. Sleek shape and construction of the joist box helps to provide

56â&#x20AC;&#x192; Volume 45

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adequate reinforcement bars with proper detail for concrete connection. The most important feature of the new joint is that the support system and gap control steering systems are independent of each other. This unique feature is of primary importance in detailing the new joint in a manner such that the support system of the joint of one carriageway may be placed in 3 parts to meet the lane by lane placement requirement. Once the support system along with the edge beams are in place the lamella beams, complete with steering system, are placed in single piece for full length. Then the lamella beams are connected to the support system through bolted connection. 3.2 Execution of the work 3.2.1 Traffic Management System The elaborate temporary traffic management and control system that has been adopted on bridge during the replacement activity was planned ensuring smooth and hassle free traffic movement. While adhering to the same, safety to the motorist and the workers was also emphasized on. Subsequently, mitigating emergency situations like fire break-out or breakdown of vehicles had been planned beforehand. The guiding principle of the traffic management system was to reduce the number of conflict point by establishing a stream-flow of traffic on bridge. The traffic management system has been developed in the following phases: 3.2.1.1 Planning Phase This involves analysis of raw data supplied by the bridge authority. The vehicular characteristic varies widely between day and night demanding separate study for both the phases. Toll data available from the bridge authority was the reference sample data which was analyzed.

Fig. 3.1 : Traffic Volume analysis and study based on toll data

The Bridge and Structural Engineer


ii) Approach Transition Zone After the Advance Warning Zone there is a Transition Zone where the traffic is redirected from a normal path to a new path. A suitable taper length and geometry have been provided to meet the requirement of the design speed. Fig. 3.2 : Directional split of the up and down traffic with respect to category of vehicle

3.2.1.2 Design Phase Based on the volume study and mandatory clearances as per IRC SP: 55-2001 a basic layout plan had been prepared to mitigate the situation taking into consideration the basic principle stated above. a) Components of Basic layout i) Advance Warning Zone The information in this zone have been conveyed through a series of traffic signs along the length of the zone. Detailed Signage posting and other relevant Informatory Signs, Regulatory Signs, and Warning Signs has been posted for the Advance Warning of Traffic. Length of the Advance Warning Zone has been considered to be 200 m in this case.

The Merging Taper used here merges three lanes into two lane. It needs a longer distance for the drivers to adjust their speed to merge with an adjacent lane before the end of transition. The length of the merging taper depends on the average approach speed of the vehicles which has been considered to be 80kmph. According to the provisions of IRC:SP:55-2001, Table 2.1 the length of The Approach Transition Zone is taken as 100 m with the gradient of transition smoothly merges the three lane carriageway into Two lane carriageway. Delineation of the Transition Zone has been done by using continuous steel Barricades and Traffic Guards rails.

Fig. 3.4 : Graphical representation of Approach Transition Zone

iii) Activity Zone Fig. 3.3 : Graphical representation of Advance Warning Zone

The activity zone is where the actual work is taking place. It contains the work area and the working space, lateral safety buffer zone and the longitudinal zone.

Determination of available carriageway from basic layout plan Design criteria Minimum width of each lane Number of lane kept open for traffic Carriageway width in each direction Mandatory clear space as per IRC guidelines Calculation basis: Available carriageway width

Width of working zone

The Bridge and Structural Engineer

= = =

3.25 m 2 12.300 m

=

(existing carriageway width in each direction â&#x20AC;&#x201C; width of working zone) (width of activity area + lateral buffer zone)

=

Volume 45 Number 2 June 2015â&#x20AC;&#x192; 57


Direction of Traffic

Lane Designation*

Width of Activity area (m)

LL

KOLKATA TO HOWRAH

HOWRAH TO KOLKATA

Lateral Buffer zone (m) RHS

LHS

Width of Activity zone (m)

4.50

1.20

-

5.70

6.60

ML

3.30

1.20

1.20

5.70

6.60

RL

4.50

-

1.20

5.70

6.60

LL

4.50

1.20

5.70

6.60

ML

3.30

1.20

1.20

5.70

6.60

RL

4.50

1.20

5.70

6.60

Available width of Carriageway (m)

*LL : Left Lane; ML : Middle Lane; RL : Right Lane

In all possible sequences of execution of the bridge work:

Number of lanes that can be kept open to traffic

=

2

Width of each traffic lane

=

3.30 m

The length of the Working zone is considered to be 950 m approximately. The available carriageway width, number of trafficable lane, and lane width was consistent and in line with the contract document and satisfied the codal provision of minimum lane width.

Fig. 3.5 : Graphical representation of Activity Zone

iv) Termination Zone Considering the existing lane width to be 4.100 m the termination zone length can be calculated to be 45 m for the project, thus the exit taper slope is greater than 1: 10 slope which also conforms to the codal provisions. The termination zone is marked by the End of Restriction sign. It is recommended to keep the entire activity lane within the working zone preceded by adequate approach transition and advance warning zone. Due to ease of handling, Steel Barricades and Concrete Delineators are used to separate the traffic control zone from the surrounding as and when required. 58â&#x20AC;&#x192; Volume 45

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3.2.1.3 Implementation Phase Implementing Temporary traffic management and control in practice is found to be an uphill task particularly in situation with a daily traffic volume of 80,000 vehicles and peak hourly volume of 4,000 PCU. The Plan had been thoroughly scrutinized by the officers of the State Traffic Control and their recommendations were suitably incorporated in the plan before implementing. Deploying adequate number of trained Flagmen under the supervision of senior Flag Marshalls, erecting Informative, Prohibitive or Warning signage, placing Barricades and Delineators as per the basic layout plan was instrumental in implementing the robust traffic management and control. 3.2.1.4 Operation and Maintenance Phase This is to ensure that the traffic management plan as implemented is being abided by the working crew, the responsible flagmen and marshals to maintain disciplined flow of traffic on bridge. Relevant checklist control is made which has been instrumental in imposing discipline at site. 3.2.2 Enabling Structure The bridging plate is designed as a simply supported span of 3.5 m capable of withstanding Class AA wheeled loading as per IRC regulation. The Bridge and Structural Engineer


Fig. 3.6 : Placement of the Bridging Plate

were done by unfastening the fasteners system holding the pad firmly to steel housing underneath. The steel housing was then cleaned thoroughly by in-situ sand blasting, removing scales, rusts and other substances prior to the application of anti-corrosive treatment. The corrosion protection system has been designed for severe exposure condition. Furthermore, the threads of the tapped hole holding the primary fasteners have been made good for fastening the new bolts.

The striking characteristics of the enabling structure, which made the plan of sequential replacement possible, are described as below: 

The support system of the plate is capable of accommodating the movement of the bridge due to thermal variation with one end being restrained in both longitudinal and transverse movements. The design of the bridging plate was optimized to the level that it remains light, facilitating easy handling while maintaining adequate strength to allow heavy traffic over it. The bridging plate and its support system being modular in nature can be handled as independent units. The surface of the plate facing the traffic is made skid proof. Adequate head-way space is kept underneath the plate. The curved vertical profile of the plate accompanied with adequate smooth transition curves at either ends by flexible bituminous course help easy maneuvering of vehicles.

3.2.3 Mitigating Emergency situations Towing equipment and necessary fire-fighting arrangements are made available on bridge throughout the implementation phase. Lastly, since the traffic management and control system has to encounter unforeseen situations, reserve resources were maintained to mitigate such undesirable occurrences. 3.3 Replacement of Slab Seal (Matt) Expansion joint Owing to the strikingly remarkable features of the Slab Seal (Matt) joint, it could be replaced in a non-invasive manner. Removal of the existing Elastomeric Slab Units The Bridge and Structural Engineer

Fig. 3.7 : (a) The Steel housing after removing the older Elastomeric slab units, (b) Surface preparation of the Steel housing after sand blasting and corrosion protection treatment prior to placement of new Elastomeric Slab units

Prior to the placement of new slabs the steel housing has been neatly cleaned by compressed air. The new slabs are placed in position keeping the center of the slot in the pad and the center of the hole in the housing as close Volume 45 Number 2 June 2015  59


as possible. Temperature plays a key role in this regard. The slotted hole in the slab is capable of accommodating the differences within a tolerance range. Precision is necessary in placement to avoid cumulative differences. After being positioned properly, the fastener accessories are fastened to their respective position in an orderly manner. Care has been taken so that male-female groove of one slab and the immediate adjacent one develops a mechanical water-tight interlocking. Water-proofing sealant has been applied at all possible locations, susceptible to water-leakage, to make the system perfectly watertight. Finally, prior to opening of the lane to traffic, trial run using light commercial vehicles was made and only after satisfactory results the lanes were opened to traffic.

surfaces ready to accept the new joint. For the steel side of the main girder, mechanical cleaning was done followed by sand blasting and anticorrosive treatment complying with the requirement to meet severe exposure condition. However, on the concrete side, the recess preparation was far more elaborate. It involved cleaning the cutout concrete edges neatly, removing loose particle with chiseling tools, chipping of the base and placing adequate rebar held or anchored firmly in position imparting flexural and shear strength to the section. This has been designed as sufficient to withstand the force responses of the new structure. A new support interface is introduced at the prepared surface of the steel side to minimize the interference and involvement of fabrication with the existing steel girders, and at the same time developing the load transmission mechanism through the existing bracket systems of the main girder.

Fig. 3.8 : Positioning of the new Elastomeric slab units

3.4 Replacement of Modular Expansion joint The lane by lane replacement of modular joint is a multi-fold activity done in different phases. The existing swivel type joint was detailed with fixed joist box at the steel connection end and with movable joist box at the concrete end. Due to the swivel geometry of the joint the selection of the segment to be removed has been done judiciously. Auxiliary support system has been devised to hold the free end of the lamella beams. The lamella beams and supporting frames are then removed in an orderly manner. The concrete is then dismantled to remove the extralarge joist box structure. Adequate precision and control has been imposed during dismantling work keeping in consideration the PSC girder system of the viaduct portion. The process of surface preparation was also demanding since the new joint would be supported between the steel girder of the main bridge and the concrete recess of the viaduct. Separate preparatory process has been adopted to make both 60â&#x20AC;&#x192; Volume 45

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Fig. 3.9 : (a) The older swivel type joist boxes prior to dismantling; (b) Stage wise and planned dismantling of the old lamella beams

The Bridge and Structural Engineer


The support system of the modular joint is then lowered and put to position as marked on the bridge. A robust holding system has been developed to avoid any type of local or system distortion. A strict quality control system is devised to monitor that the level and line of each joint segment are in line with the subsequent or preceding one and vice-versa, and at the same time matching the bridge gradient in either direction. After obtaining necessary clearances from the quality control team, welding of the support system of the joint to the support interface was carried out maintain properly designed sequence of welding. Finally, the joist-boxes in the concrete recesses were held in position through tack welding with the newly placed reinforcing bars.

After successful completion of the preceding activity in all the lanes of the carriageway, the entire lamella assembly of full length as that of the entire carriageway width, fitted with the complete steering system, was lowered and placed over the Joist beams of the support system already installed. The lamellas are now ready to be fastened with the Joist beams of the support system in their respective locations. Final connection of the joint has been established at the steel side by completing all required welding.

Fig. 3.11 : The newly installed joist boxes along with the edge beams in position

Fig. 3.12 : The entire assembly of lamella of the new Modular joint being lifted to be placed and positioned along with the edge beams and joist boxes

Fig. 3.10 : Surface preparation prior to positioning of the new edge beam and support system on the steel side

The Bridge and Structural Engineer

Controlled concrete of defined grade, strength and workability was adopted for the project. Development of early strength guides the selection of plasticizers for the design mix. Prior to pouring of concrete, bonding agents were applied in prescribed manner to the neatly prepared concrete recess. Desired compaction is attained by using mechanical vibrators. After initial setting time of couple of hours, traffic was allowed over the bridging plate spanning over the installed joint and new concrete. The concrete is then cured adequately before removal of the bridging plates and exposing the new joint and the concrete back to full traffic Volume 45 Number 2 June 2015â&#x20AC;&#x192; 61


4. Conclusion Expansion joints are key functional component of a bridge. For longer span bridges, Modular Joints are the most preferred and adopted engineering solution, which makes it one of the most critical components. Efforts should be made in selecting Expansion joints with longer service life, structural adaptability and incorporating scope for easy replaceability. Replacement work of expansion joint on a major and busy bridge in service is extremely complex, and challenging. The challenge becomes manifold when the entire task is to be coordinated at a fast pace also simultaneously ensuring uninterrupted smooth flow of traffic. The most difficult part is to foresee hurdles from all corners and to design the work procedure in a manner so that there is no unforeseen surprise during the actual execution of work.

Fig. 3.13 (a) The Howrah bound flank of the bridge was opened to traffic after the successful installation of the new eleven module Modular Expansion joint; (b) The eleven module Modular Expansion joint after second stage concreting

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In the subject case, replacement work has been taken up for a very large expansion joint for the first time in India with precise planning and has been carried out through well-coordinated execution within the estimated time, posing least trouble to the traffic. Vidyasagar Setu, the lifeline of Kolkata, has got rejuvenated through this refurbishment work. It is expected that the experience and knowledge gathered through this work will not only remain as precedence but also will provide reference for similar challenging work to be taken up in future.

The Bridge and Structural Engineer


Evaluation of In-Situ Stress in Concrete Structures by Core Trepanning Technique S PARIVALLAL Principal Scientist CSIR-SERC Chennai, INDIA paris@serc.res.in

Dr. S. Parivallal is presently Principal Scientist in the Structural Health Monitoring Laboratory of CSIR-Structural Engineering Research Centre, Chennai. He obtained his B.E (Civil) from PSG College of Technology, Coimbatore, M.E (Structural Engineering) form Govt. College of Technology, Coimbatore and Ph.D from Anna University, Chennai. He has been with CSIR-SERC since 1994. His areas of interest include experimental Mechanics, condition monitoring of structures, existing stress evaluation in prestressed concrete structures and Remote health monitoring of structures. He has published around 100 papers in International / National Journals and in Conference proceedings and over 150 technical reports. He has been associated with many industrial projects including full scale testing of important structures.

K. RAVISANKAR Chief Scientist CSIR-SERC Chennai, INDIA kravi@serc.res.in

Dr. K. Ravisankar is a Chief Scientist at CSIR-Structural Engineering Research Centre (CSIR-SERC), Chennai and heading the Structural Health Monitoring Laboratory. He has been associated with CSIRSERC since 1979. He has vast experience in experimental techniques for stress analysis and has been actively engaged in the development of various experimental techniques and their applications, through in-house R&D programmes, for the solution of a variety of practical engineering problems. He has been associated with more than 110 industrial projects, particularly in critical application areas such as nuclear power, space, aeronautics, civil infrastructure and Defence where safety and integrity are of paramount importance. He has published around 170 technical papers (in Journals and Conferences) and 270 technical/research reports. Two patents have been filed so far. He is a member of many professional bodies and is serving in several national committees.

K. KESAVAN Principal Scientist CSIR-SERC Chennai, INDIA kesav@serc.res.in

Dr. K. Kesavan is a Principal Scientist in CSIR-Structural Engineering Research Centre, Chennai. He obtained his B.E (civil) from Anna University, Chennai and M.Tech (Structural Engineering) from Indian Institute of Technology, Chennai and Ph.D from Anna University in the area of application of Fiber Optic Sensor for structural health monitoring of civil engineering structures. He has been working in the area of experimental stress analysis since 1995. His current areas of interest include condition monitoring of structures, existing stress evaluation in prestressed concrete structures and health monitoring of civil engineering structures using fiber optic sensors. He has contributed more than 50 technical papers in International and National Journals and more than 50 papers in seminars and more than 150 technical reports.

B. Arun SUNDARAM Scientist CSIR-SERC Chennai, INDIA arunsundaram@serc.res.in

Mr. B. Arun Sundaram obtained his B. E (civil) and M.E (Structural Engineering) from Anna University, Chennai and he has been with CSIR-Structural Engineering Research Centre since 2008. His current areas of interest include remote health monitoring of civil engineering structures, experimental stress analysis. He has contributed about 20 technical papers in Journals and Conferences and more than 50 technical reports.

The Bridge and Structural Engineer

Volume 45 Number 2 June 2015â&#x20AC;&#x192; 63


Summary Determination of in-situ stress on the concrete surface is one way to assess the prestressing force available in the prestressed concrete members. Core trepanning technique is a versatile semidestructive method, can be used to evaluate the insitu stresses on structural elements of different sizes and shapes. Concrete core trepanning technique has been developed for assessing the existing stress in prestressed concrete structures in-service. This technique is based on the measurement of strain release due to local elastic stress relief, caused by core drilling and creation of normal stress-free boundaries. Laboratory studies were carried out to formulate proper procedure to measure and assess reliability of concrete core trepanning technique for the determination of existing stress in prestressed concrete structures. Developed concrete core trepanning technique was used in assessing the existing level of stress / prestress in various prestressed concrete structures. Case studies of assessment of residual prestress in prestressed concrete structures using core trepanning technique are also presented. Key words : in-situ stress, Core trepanning technique. prestressed concrete structures, Civil infrastructures

1. Introduction Civil infrastructures are essential for economic health and prosperity of any country. These structures such as tall buildings, bridges, pressure vessels, power plant structures etc. are constructed using reinforced/ prestressed concrete. These structures undergo distress with time due to environmental and other unfavorable operating conditions. It is well known that the time dependant phenomenon such as creep and shrinkage of concrete also reduces prestressing force over time. Thousands of concrete bridges presently in operation worldwide are in need of rehabilitation through major works of repairs. In the future, the rehabilitation of existing structures will constitute an exceptionally large field of operation that will extend for many years. Timely retrofitting measures help to reduce damages and improve service life. In order to assess the safety and serviceability and to take a decision about the possible repair measures to rehabilitate the distressed concrete structures, it is necessary to estimate the existing level of stress. 64â&#x20AC;&#x192; Volume 45

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To assess the safety and serviceability of distressed structure and to take a decision on the possible repair and rehabilitation measures, it is necessary to estimate the existing level of stress. Assessing the existing stress of prestressed concrete structures in service is fairly a difficult task and the researcher is often faced with lack of actual design/construction information and environmental service conditions. It is first necessary to generate scientifically and systematically required data relating to the existing level of prestress, in order to take a decision about the residual strength and possible repair measures to rehabilitate the distressed prestressed concrete members. Determination of insitu stress in the concrete surface is one way to assess the prestress available in the prestressing steel. There are few methods available to assess the existing stress in concrete structures and are given below. Owens [1] described a method called steel stress relief hole method for determining prestress in a prestressed concrete member by drilling a relatively small hole in prestressed steel (or reinforcing steel) existing in the beam. Owens[2] discussed centre hole stress relief method for measuring in-situ stress in concrete bridges by using vibrating wire strain gages. Mehrkar-Asl [3] developed a stress-relief coring technique for in-situ stress measurement in concrete structures. Trial tests were performed on structures in service and calibrations carried out in the laboratory on uniaxially and biaxially loaded slabs. Ryall[4] used instrumented hard inclusion technique for measurement of in-situ stresses in concrete bridge decks, which involves drilling a small pilot hole of about 40 mm diameter in concrete and bonding to it an instrumented mild steel inclusion. The inclusion is over cored and the resulting strain changes in the inclusion used as a basis for determining the local stresses. Abdunur[5] proposed an approach which can be summed up as forming a slot in the structure rather than a cylindrical hole. A â&#x20AC;&#x153;jackâ&#x20AC;? is then inserted into the slot to pressurise the sides of the slot until the surrounding structure has readopted to its original position, that are predominantly under uniaxial stress state. These methods have some limitations which include the strain release is very less, difficult to apply for in-situ stress measurements in existing structures, ease of measurement, level of preliminary work, level of expertise required, etc. The Bridge and Structural Engineer


2.

Concrete core trepanning technique [6]

Concrete core trepanning technique has been developed for assessing the existing stress in prestressed concrete structures in-service. This technique is based on the measurement of strain release due to local elastic stress relief, caused by core drilling and creation of normal stress-free boundaries.

10 locations, 30 mm size linear strain gages were bonded (five each at top and bottom) along the longitudinal direction. A special test set-up was designed and fabricated to apply axial compression to the beam, by means of a hydraulic jack (Fig.2). A core of 50 mm diameter was formed by diamond core drilling, till the depth equals to diameter of the hole. For every 10 mm depth of cutting, the released strains were noted.

Fig. 1 : Concrete core trepanning technique

In this technique, a strain gage is fixed at the center of the intended core aligned in the direction of maximum stress (for uniaxial stress condition). On drilling the annular hole around core, the strain gage measures the complete elastic strain relief due to core drilling. Arrangement of strain gage in the core is shown in Fig.1. An annular hole of 50 mm dia. is formed by diamond core drilling and the strain release is recorded till the cutting depth reaches to the required depth. Special instrumentation procedures, water proofing of gauges and lead wire connections are developed to minimize errors during measurements. This technique has the advantage of measuring full strain release and data reduction is also simpler. The released strain is of the opposite polarity to the in-situ stress. After a sign change, the strain is multiplied by the elastic modulus of concrete to determine the in-situ stress. The core samples taken from measured locations can be used, to determine elastic modulus of concrete.

3. Laboratory Studies using Trepanning Technique [7]

From these studies, it is observed that for 50 mm diameter core drilling using 30 mm gage size, the maximum release occurs at a cutting depth of 20 to 30 mm and there is no need to cut deeper, nor it is required to remove the core (Fig. 3). Also it was observed from the studies conducted on beams that the average of released strain due to core cutting is around 80-90% of existing strain.

Core

Laboratory studies were carried out to formulate proper procedure to measure and assess reliability of concrete core trepanning technique for the determination of existing stress in prestressed concrete structures. Experiments were carried out to assess the depth of cutting required to get maximum strain release in core trepanning technique. For this purpose, two reinforced concrete beams (150 x 100 x 1500 mm) were cast. On each beam at The Bridge and Structural Engineer

Fig.2 : Experimental setup for existing strain measurement on RCC beam

Fig.3 : Released strain in axially compressed RCC beam

4. Existing Stress Measurement Pretensioned PSC Beam [8]

in

In order to carry out further reliability studies on core trepanning technique, a seven year old pretensioned PSC beam (T-section) was chosen. Instrumentation

Volume 45 Number 2 June 2015â&#x20AC;&#x192; 65


details of the beam are given in Fig. 4. The beam was prestressed with 18 numbers of 5mm diameter high tensile steel wires with an initial prestressing force of 360kN. Seven sections were identified for instrumentation and measurement.

Fig. 5 : Released strain vs. depth for the Prestressed Concrete Beam Fig. 4 : Instrumentation Details of the Pretensioned PSC Beam

The easiest way to calculate the existing prestress is by finding the stress at the neutral axis of the beam, where all the bending stresses due to prestress as well as gravity loads vanish. The calculated neutral axis of the T-beam in consideration is found to fall very close to the top flange and hence it was not possible to cut a core at the neutral axis and hence to be interpolated by cutting at least two cores in the same cross section. One core at top of the flange (normal to the top surface) and two cores below the neutral axis on either side of the beam were cut out at every section and from the released strain values, the strain at the neutral axis was calculated. Fig.5 shows the released strain for a typical core of a seven year old PSC beam. It is seen that the released strains at web left and web right are identical, which shows the reliability of the measurements and absence of significant lateral bending. From the measurement of strain at top and bottom, the strain released at the neutral axis position is calculated. The existing prestressing force at various sections is evaluated using the appropriate material properties. The average prestress calculated is 283.8kN, which is in good agreement with the applied prestress, after taking into account the losses due to shrinkage, creep etc. 66â&#x20AC;&#x192; Volume 45

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Developed concrete core trepanning technique was used in assessing the existing level of stress / prestress in various prestressed concrete structures.

5.

Case Studies

Developed concrete core trepanning technique was used in assessing the existing level of stress / prestress in various prestressed concrete structures. Case studies of assessment of residual prestress in prestressed concrete structures using core trepanning technique are presented here. 5.1 Existing Stress Determination in Vierendeel Girder of the Roof Truss System [9] An experimental investigation was carried out by CSIR-SERC, to assess the safety and serviceability of the roof system of a Workshop building ( Fig.6). The scope of the project includes assessing the existing level of prestress in the Vierendeel girders of the roof truss system from the knowledge of existing stress levels in the bottom chords of the Vierendeel girder. Concrete core trepanning technique was used for the measurement of existing stresses. In all, nineteen locations (four locations on the top surface and the remaining in the centroidal line of the sides) of the bottom chord were instrumented on 10 different trusses (out of total 36 trusses). From this investigation, it was possible to estimate the level of prestress in the bottom chords of the girders. The Bridge and Structural Engineer


5.3 Assessment of Residual Prestress in a Balanced Cantilever Prestressed Concrete Bridge [9]

Fig. 6 : Vierendeel girder truss roof system of a workshop building

5.2 Determination of Existing Level of Prestress in PSC Girders of the Iron Ore Berth[9] This is a 37 years old iron ore berth structure consisting of an approach deck having a length of about 143m of steel gratings supported by RC beam on either side. These beams rest on the RC pile cap supported by two RC piles. The iron ore berth deck has seven spans (varying from 16.44m to 17.69 m). The width of berth is about 22 m. The structural system for this consists of 20nos. of post tensioned beams arranged side by side @ 1m c/c. The groups of girders are also prestressed laterally through diaphragms, after laying the deck concrete (Fig. 7). The entire deck including PSC girders is supported over pier cap formed over prestressed concrete crip that rests on the ballast bed found over the sea bed available at -22m approximately from MSL. In order to obtain prestress in the identified PSC girders, the position of neutral axis was determined from the geometry of girder in order to avoid the bending stress contribution. The trepanning technique was carried out at three selected spans. The instrumented locations in PSC girder is as shown in Fig.9. The stress in the beam was calculated from measured strain.

The bridge comprising ten spans and supported on cylindrical piers with the end spans on abutments. The overall length of the bridge is 530.36 m and span length is 48.77 m. The piers are hammerhead type with articulations supporting the suspended spans. Each of the piers was constructed integral with prestressed cantilever girders on either side of the pier head, extending for 9.14m length from centre of pier to serve as hammer heads. The gaps between the cantilever arms having a span of 30.48m were bridged with suspended girders resting on the cantilever ends. Based on the request made by the sponsor, an experimental investigation to assess the loss of prestress was carried out on the hammer head supported by pier P7, which is highly deteriorated. The hammer head is a cast - in - situ multi â&#x20AC;&#x201C; cell box section, consisting of five girders with top and bottom flanges to form an integral box section (Fig. 8). Due to inaccessibility, only the outer surfaces of the extreme girders of the hammer head were available for instrumentation. Four locations on each of these extreme girders of the hammer head were selected for instrumentation. Out of these four locations, two were on the cantilever portion on pier P7 projecting towards one side and the other two on opposite side. In all eight locations were instrumented at the centroidal axis of the hammer head (Fig. 8). The residual prestress forces were obtained from the investigation.

Fig. 8 : Instrumentation details of prestressed hammer head

5.4 Experimental investigations on super-structure of the Mahatma Gandhi Bridge [9] Fig.7 : Instrumentation details of typical PSC girder of Iron Ore Berth

The Bridge and Structural Engineer

An experimental investigation was carried out to assess the residual prestressing force of the Mahatma Volume 45 Number 2 June 2015â&#x20AC;&#x192; 67


Gandhi Bridge at Patna. The bridge is a balanced cantilever bridge having 59 m span on each side of the pier as shown in Fig. 9. In order to evaluate the residual prestress, two different pier spans, namely

Fig. 10 : Experimental investigations on Sone River bridge

6. Summary

Fig. 9 : Experimental investigations on super structure of the balanced cantilever bridge

span P23 at upstream side and span P26 at down stream side were identified for the investigation. Out of the two selected span P23 of U/S side is older and distressed compared to the span P26 of D/S side. In each span, both cantilever girders were instrumented at the inner surface of the box girder. In each arm three sections were identified and at each section four locations were instrumented at two locations on the centre of gravity of the cross section and the other two are at the top and bottom of the web. From the measured strains at CG of the section, the residual prestressing force in each girder is obtained. 5.5 In-Situ Stress Evaluation of Sone River Bridge [10] Experimental investigation on the Sone River bridge was carried out by using concrete core trepanning technique for evaluating the in-situ stresses in the girders. The bridge is 1006.5 m long with 22 spans of 45.75 m centre to centre and 7.32 m wide carriageway (Fig.10). Three spans were identified for evaluating the existing stress. Totally 18 locations were instrumented with strain gages for evaluating the existing stresses in the girders. Concrete core trepanning technique is used to measure the released strain. From the measured strain the existing stress is calculated by using the modulus of elasticity of concrete and the calibration constant. From the investigations, the existing stresses in the girders were evaluated and used to assess the present condition of the bridge. 68  Volume 45

Number 2 June 2015

For assessing the existing stresses on distressed prestressed concrete structures, concrete core trepanning technique can be used. Laboratory studies were conducted to evaluate the reliability of the concrete core trepanning technique. Case studies of assessment of residual prestress in prestressed concrete structures using core trepanning technique are presented here. Using this concrete core trepanning technique, it is possible to estimate the probable value of existing prestress with a high degree of reliability in prestressed concrete members. This will go a long way for the designer to design suitable rehabilitation measures.

7. Acknowledgements This paper is published with the permission of the Director, CSIR-Structural Engineering Research Centre (SERC), Chennai. The cooperation and support extended by the sponsors during the investigations are gratefully acknowledged.

8. References 1.

Owens, A. ‘Application of Residual Stress Techniques in the Determination of In-situ Load in Reinforced Bars’, Experimental Techniques, 12, 5, 1988, pp. 23–27.

2.

Owens, A. ‘In-situ Stress Determination used in Structural Assessment of Concrete Structures’, Strain, 29, 4, 1993, pp. 115-124.

3. Mehrkar-Asl, S., ‘Concrete stress-relief coring: theory and application’, Proceeding of FIP Symposium on Post-tensioned Concrete Structures, London, UK, 1996, pp. 569-576. The Bridge and Structural Engineer


4.

Ryall, M.J. ‘The Measurement of In-situ Stresses in Concrete Bridge Decks using an Instrumented Hard Inclusion Technique’, Proceedings of the Centenary Year Conference on Bridge Assessment, Management and Design, Cardiff, Amserdam, 1994, pp. 417–422.

5. Abdunur, C. ‘Direct Access to Stresses in Concrete and Masonry Bridges’, Proceedings of the Second International Conference on Bridge Management, University of Surrey, Thomas Telford, London, April 1993. 6. Ravisankar.K, Narayanan.T Kesavan. K, Parivallal.S , and Narayanan.R, “Experimental Techniques for Existing Stress Determination in Prestressed Concrete Structures”. CSIR-SERC Report No.EML-RR-98-2, September 1998. 7. Kesavan. K, Parivallal.S , Ravisankar.K, Narayanan.T and Narayanan.R,”NonDestructive Evaluation of Existing stress in

The Bridge and Structural Engineer

Prestressed Concrete Members”, Proceeding of the National Seminar NDE-2000,pp 39-45. 8. Parivallal.S,

Kesavan.K, Ravisankar.K, Narayanan.T and Narayanan.R, “Assessment of Existing Prestress in Prestressed Concrete Structures” Proceeding of the National Seminar on Trends in prestressed Concrete, 2001, pp 271-279.

9. Parivallal.S,

and Kesavan.K, “Evaluation of residual pre-stress in concrete structures” Structural Health Assessment and Management of Bridges CBA Publishers, Chennai 91, February 2011

10. Parivallal, S., et.al, “In-situ Stress Measurement on Super structure of Sone River Bridge at Chopan near Varanasi”, Sponsored Project Report No. R&D 02–SSP 14941-SR-01, July 2014.

Volume 45 Number 2 June 2015  69


EFFECT OF CFRP FABRIC IN ENHANCING TORSIONAL CAPACITY AND TWIST ANGLE OF STRENGTHENED RCC BEAMS

Pardeep KUMAR Sr. Technical Officer Bridges & Structures CSIR-Central Road Research Institute, New Delhi (India) pardeep.crri@nic.in

Surjit K. SHARMA Principal Technical Officer Bridges & Structures CSIR-Central Road Research Institute, New Delhi (India) sksharma.crri@nic.in

Lakshmy PARAMESWARAN Chief Scientist Bridges & Structures CSIR-Central Road Research Institute, New Delhi-11025 lakshmy.crri@nic.in

Mr. Pardeep Kumar, born 1971, received M.E. (Structure) from the Delhi College of Engineering, Delhi. He is also pursuing PhD from IIT Delhi. His area of research includes rehabilitation of distressed bridges, fatigue study of strengthened RC members, analysis & design and Rating of Bridges.

Dr. Surjit K. Sharma, born 1958, received PhD (Civil Engineering) from the Delhi College of Engineering, Delhi. His areas of specialisation are Analysis & Design, Evaluation & Rehabilitation of Structures and Rating of Bridges.

Dr. Lakshmy Parameswaran, born 1962, received her PhD (Civil Engineering) from IIT, Roorkee, Roorkee. She has more than 28 years experience and is currently working in CSIR-CRRI as a Chief Scientist. Her main area of research includes bridge management, health monitoring of bridges, bridge aerodynamic and sustainable construction materials.

Summary Torsional failure is an undesirable brittle failure. Only few researches were reported in the past on torsional capacity of the RC beams strengthened with FRP. This paper presents an experimental investigation on reinforced concrete beam strengthened with externally bonded Carbon Fibre Reinforced Polymer (CFRP) fabric under the action of pure torsion. The main objective of this study was to determine the contribution of CFRP fabric to the ultimate and cracking torque, angle of twist and ductile behaviour. Two RC beams were tested in the laboratory, reference beam (REF) and beam originally deficient in torsion and strengthened with CFRP fabric (STCF). During the studies, it was observed that the failure of beam REF was due to crushing of concrete and yielding of tension steel, whereas, beam STCF failed due to failure of anchorage, debonding of the CFRP fabric strips, yielding of reinforcement provided in the compression zone at mid span, and finally due 70â&#x20AC;&#x192; Volume 45

Number 2 June 2015

to crushing of the concrete. It was observed that the Beam STCF exhibited an enhancement of torsional capacity by 58% only as debonding and anchorage failure of CFRP fabric led to the utilisation of only 7% of its ultimate strain. Keywords: Pure Torsion, Rehabilitation, CFRP Fabric.

1. Introduction The repair and retrofitting of existing structures have become a major part of construction activity in many countries. Some of the structures are damaged by environmental effects, which include the corrosion of steel, variations in temperature and freeze-thaw cycles. There are always cases of design and construction related deficiencies that need correction. Many structures need strengthening to meet the requirements of updated codes. This last case applies mostly to seismic regions, The Bridge and Structural Engineer


where new standards are more stringent than the old. Deterioration may occur due to material degradation, aging, lack of maintenance and severe earthquakes and so on. The continuous deterioration of the world’s civil concrete structures highlights the urgent need for the effective rehabilitation technique in terms of low cost and fast processing time with minimum traffic interruption. In most of the developing countries, there is a requirement to widen and retrofit the existing structures due to increase in traffic volume on account of growing population. The reinforced concrete structural members such as peripheral beams in each floor of multi-story buildings, beam supporting canopy slabs and helical stair cases, edge beams of shell roof, ring beams at the bottom of circular water tanks are subjected to torsional loading in addition to flexure and shear. Also, girders of skew and curved bridges also experience torsion. There are different methods adopted for torsional strengthening of concrete members, such as (1) increasing cross-sectional area of member as well as by providing additional reinforcement, (2) using externally bonded steel plates and (3) applying an axial load to the member by post-tensioning and (4) strengthening using Fibre Reinforced Plastics (FRP).

2.

Fibre Reinforced Polymer (FRP)

FRP has been used since 1980’s for strengthening of RC beams. There are certain advantages of FRP in comparison to traditional construction materials such as concrete and steel are that they are easy to apply, possess high strength and light weight, cost effective, non-corrosive, non-magnetic, resistant to various type of chemicals and require less maintenance. Also, they can be used for preservation of existing bridges, as it can minimize/eliminate traffic disruption during retrofitting, minimize the use of heavy equipments and it offers greater flexibility and conformity for repairing areas where other means of repair are difficult to perform. However, the unknown durability characteristics which affect the service life, lack of quality control standards and manual application, contribute to variation in material parameters of composites. Strengthening the structural elements using FRP enable the designer to selectively increase their ductility, flexure, and shear capacity in response The Bridge and Structural Engineer

to increase in seismic and service load demand. Flexural and shear strengthening of reinforced concrete beams using composite materials were studied in detail by many researchers. However, study of strengthening of structural elements using FRP for torsion has not received much attention. The reasons for the lack of research in the area include the specialized nature of the problem and the difficulties in conducting realistic tests and representative analyses. Also, one reason is that only few structural members need to be strengthened to increase the torsional capacity.

3.

Literature Review

Most of the research projects investigating the use of FRP mainly focused on enhancing the flexural and shear capacity, ductility, and confinement of concrete structural members. The structural members such as beams when subjected to torsion show spiral cracking on all surfaces of the beam as shown in Fig. 1, where as the crack pattern for shear is different as shown in Fig. 2, if they are not designed and detailed properly Further, change in loading and deterioration of the member reduce the torsional capacity. The available strengthening option for torsion are found to be similar to shear strengthening schemes, with the strips applied around the beam such as full wrap and U-wrap at angle of 90° and 45°. However, only limited studies were conducted to investigate torsional strengthening of RC members using FRP like Ghobrah, et. al (2002), Panchacharam and Belarbi (2002), Ronagh et al (2004), Hii and Al- Mahaidi (2006, 2007), Ameli et. al ( 2007) and Constantin (2008) [1-7].

Fig. 1: Spiral Cracking Pattern Due to Torsion

Fig.2 : Cracking Pattern Due to Shear

Ghobrah et al. (2002) [1] evaluated the FRP strengthening of RC beams subjected to torsion. They carried out experimental investigations on 11 beams with different orientation of CFRP and GFRP wrap Volume 45 Number 2 June 2015  71


and found that complete wrap was found to be more effective and 45 degree orientation of fibers proved to be more efficient. Panchacharam and Belrabi (2002) [2] studied the performance of RC beams strengthened with externally bonded GFRP sheets, subjected to pure torsion. They reported that combination of FRP sheets in longitudinal direction of the beam followed by allwrapped strips, showed an increase in both ultimate strength and ductility of the beam. Shantakumar et al. (2007) [8] presented FEM analysis of un-retrofitted and retrofitted RC beam subjected to combined bending and torsion. They reported that FRP laminates used for strengthening was effective only after initial cracking of the beam and did not contribute significantly to the stiffness of the beam. The laminates with ± 45° fibre orientation were more effective for higher values of twisting to bending moment ratios. Ameli et al. (2007) [6] reported experimental and FEM using ANSYS of twelve rectangular beams strengthened by CFRP/GFRP wrap with different configuration. They reported significant improvement in ductility with GFRP wrapping in comparison to CFRP. Also, very few analytical models are available for predicting the section capacity because of complexity of the problem associated with torsion and lack of adequate experimental results required for understanding the behaviour. The analytical method proposed by Ameli and Ronagh (2007) [9] for evaluating the torsional capacity of FRP strengthened RC beam consider the interaction of concrete, steel and FRP. Their study showed that the enhancement of torque was conservative for fully wrapped beams and found slightly un-conservative for strip wrapping and found to be more trust worthy than the FIB (2001) [10]. Users of the FIB (2001) [10] have so far assumed that the contribution of concrete and steel reinforcements in the ultimate torque of FRP strengthened beams can be calculated based on models applicable to unstrengthened reinforced concrete (RC) beams and this assumption may produce erroneous results. In a strengthened beam, FRP, concrete, and reinforcements interact and as such, the distribution of stresses among these elements and within the body of concrete is not similar to that of unstrengthened RC beams. 72  Volume 45

Number 2 June 2015

4.

Experimental Program

4.1 Specimen Details To carry out the pure torsion strengthening, two RC beam specimens of size 150 x 250 x 2050 mm were cast in the laboratory. One beam designated as REF was provided with each 2 nos. of 12 mm dia. bars at bottom and top of the beams and 2-legged shear stirrups of 8 mm diameter at a spacing of 75 mm c/c. The other designated STCF was provided with 2 nos. of 12 mm dia. bars at bottom and top of the beams and 2-legged shear stirrups of 8 mm diameter at a spacing 450 mm, thus the STCF beam was made deficient in torsion. The beam specimens were cast using a concrete mix proportion of 1:1.79:2.81 (one part Ordinary Portland Cement: 1.79 part sand: 2.81 part coarse aggregate maximum size 20 mm), all by weight, with a watercement ratio of 0.416. Compressive strength (fcu) of concrete was determined from cube (150 x 150 x 150 mm) and cylinder (150 mm diameter and 300 mm height) are 34.58 MPa, 24.98 MPa, respectively. The longitudinal reinforcing steel was of Fe500 grade having ultimate tensile strength and elastic modulus 620 MPa and 210 GPa, respectively. Carbon Fibre Reinforced Polymer (CFRP) fabric has ultimate tensile strength and elastic modulus as 3900 MPa and 260 GPa, respectively. The thickness, density and fiber weight CFRP fabric were 0.234 mm, 1.8 g/cm2 and 400 g/m2.The epoxy used as adhesive to bond the CFRP fabric strip has mixed density of 1.80±0.05 kg/ ltr, 7-days strength in compression, flexure, tension and bond as 60 MPa, 23 MPa, 20 MPa and more than 2.5 MPa respectively (as reported by manufacturer). 4.2 Strengthening Scheme Cracking moment (Tc) for both the beams (REF and STCF) was calculated analytically using the elastic theory [11] as 7.55 kNm (Eqn. 1) and 7.81 kNm (Eqn. 2) respectively. The computed ultimate torque capacity (Tu,RC) of the reference beam REF and deficient beam STCF was 17.31 and 7.426 respectively by using Equation 3 [12]. (1) (2) (3) Tf= 0.006 Af Ac Ef/sf

(4)

The Bridge and Structural Engineer


Where b is width of the beam, h is overall depth of the beam, α is angle of crack in radians, f’c is cylindrical characteristic concrete strength, b1 and h1 width and depth of beam within the shear reinforcement, fsy, As, s are yielding stress, cross-sectional area and spacing of shear reinforcement respectively, Af, Ef and sf are the area, elastic modulus and spacing of CFRP fabric strips respectively, Ac is the cross-sectional area of beam. The strengthening scheme of the deficient beam STCF was designed to increase the torque capacity(Tf) by 11.86 kNm (Eqn. 4) [1], assuming the design effective strain of CFRP fabric as 20% of the ultimate strain, i.e., 1.55%. The spacing of U-Shaped CFRP Fabric Strips of 50mm width was 125 mm c/c. Discontinuity of the fabric strips were intentionally provided in the strengthening scheme because in real life situation all the four faces of the beam are generally not available for strengthening. The end strip was 100 mm thick and fully wrapped to avoid the failure at the ends of the beam. 4.3 Instrumentation Scheme Each of three electrical strain gauges of resistance 120±0.2 ohms with gauge length 4.95 mm were bonded to the longitudinal (Top and Bottom) and shear steel reinforcement before casting of the beams to measure the magnitudes of the strain at various stages of the applied load.

Fig. 3 : Position of Electric Strain Gauges on Surface of CFRP Fabric

The eleven electric strain gauges were fixed on the surface of the vertical U-Shaped CFRP fabric strips and two electric strain gauges on longitudinal CFRP fabric strips as shown in Fig. 3. The locations of strain gauges on the strips were decided based on the observed crack pattern developed during the testing The Bridge and Structural Engineer

of the reference beam REF. Roller was applied to the CFRP fabric for removing the air bubbles between CFRP fabric and concrete surface as shown in Fig. 4. To produce torsional loading, steel plates 150x150x6 mm were welded to the stirrups on either end on opposite faces (support region). The load was applied

Fig. 4 : Applying Roller on CFRP-Fabric to remove air bubbles between the CFRP and Concrete Surface

through the hand operated hydraulic jack and was monitored through load cells housed on each end. The twist was monitored through dial gauges of least count of 0.01mm placed at both the ends. The development / propagation of the cracks during each increment of load were marked on the specimen. 4.4 Test Setup Two load cells were positioned on either end of the I-section ISWB150 as shown in Figs. 5 and 6, so that the eccentricity of the loading if any could be detected. To transfer the load from loading frame to load cell, ISMB150 was used, which was already stiffened with5 mm thick steel plate loaded at top and bottom flange. A hydraulic jack of 50 tons capacity was placed on the ISMB150 at mid span such that equal loading could be transferred to both ends of the beam. To measure the twist angle of beam specimens REF and STCF, 8 dial gauges were fixed at distance of 200 mm and 180mm from both the supports. The dial gauges were fixed at a distance of 50 mm from top and bottom fibre of the beam to give the complete profile of twist at any cross section of the beams. A 32-channel dynamic data logger “DEWETRON” was used to record the strains in longitudinal rebars and shear reinforcements of the beams at 9 different locations as well as the twist angle at 8 locations as shown in Fig. 7. Volume 45 Number 2 June 2015  73


Table 1: Summary of Experimental Results of REF and STCF Specimens Initiation of First Crack Torque (kNm) Specimen

Fig. 5 : Experimental Setup of REF Beam

Ultimate Failure

Twist angle °/m

Torque (kNm)

Twist angle °/m

Twist angle °/m 85% of ultimate load beyond peak

Maximum strain in CFRP (μm)

Failure Mode

REF

9.78

0.252

14.14

2.361

3.677

-

Yielding of steel followed by crushing of concrete (Fig. 8)

STCF

8.50

0.691

11.55

3.445

4.167

1127

Debonding of CFRP followed by yielding of longitudinal steel and crushing of concrete (Fig. 9)

Fig. 8 : Failure of REF at ultimate torque 14.14 kNm

Fig. 6: Experimental Setup of STCF Beam

Fig. 7 : Dynamic Data Logger “DEWETRON”-32 Channels

5.

Test Results and Discussion

During the experimental study, the torque and twist angle were measured at the initiation of first crack and ultimate failure of both REF and STCF and the results are summarised in Table 1. 74  Volume 45

Number 2 June 2015

Fig. 9 : Crushing Failure of Concrete and Debonding of CFRP Fabric Strips

The cracking moments also showed good agreement between theoretical and experimental results. The observed failure of STCF was due to failure of The Bridge and Structural Engineer


anchorage, debonding of CFRP fabric strips and crushing of concrete as well as yielding of steel provided in compression zone. Experimental twist angle at cracking and ultimate torque and ductility ratio [13] are presented in Table 2. Table 2: Comparison of ductility ratio

Where, φ y,e and φp,e are experimental twist angle at yielding and ultimate torque respectively

φ 0.85p,e is experimental twist angle at 85% ultimate torque beyond the peak μφ,e and μφ 0.85φ ,e are experimental ductility ratio.

6.

Concluding Remarks

From the experimental study discussed in this paper, it was observed that the Beam STCF which was originally deficient in torsion and strengthened using CFRP fabric strips exhibited enhancement of torsional capacity by 58%. The torsional capacity of strengthened beam STCF achieved was 81.69% of the reference beam. Though the crack pattern of beam STCF was similar to Beam REF under pure torsion but the specimen STCF had shown less ductility in comparison to REF as the percentage of increase in cracking twist angle was much more than that of ultimate twist angle. The measured strain of CFRP fabric was only 7% of the ultimate strain, as the failure of STCF was due to anchorage failure, debonding of CFRP fabric and no rupture of fabric was observed. The torsional capacity based on the strain recorded in CFRP fabric during the experiment shows good agreement with the theoretical values. The increase in twisting angle by 175%, 46% and 13% were significant at cracking torque, ultimate torque and 0.85 of ultimate load beyond peak respectively. Hence STCF showed significant increase in ductility during yielding. The internal longitudinal steel bars were observed to be yielded in both the cases. This implies that by improving the anchorages of CFRP fabric during their application, their effectiveness could be improved. This demands more research for better understanding. Also, more study is required by changing the direction of CFRP fabric strips, i.e., perpendicular to crack (450 to axis of the beam). The Bridge and Structural Engineer

In real situation, the crack pattern changes when strengthened RC beams are subjected to simultaneous flexure and torsion and detailed experimental studies are required to understand the contribution of CFRP fabric. Some effort is in progress in this direction. Based on the comprehensive experimental study there is a need to develop a methodology for design of strengthened RC beams, considering the contribution of both CFRP fabric and steel reinforcement.

7. Acknowledgments Authors are thankful to Director, CSIR-Central Road Research Institute, New Delhi for granting permission to publish this paper. Thanks are also due to staff of the Bridges and Structures Division, CSIR-CRRI for their assistance during laboratory work. Thanks are due to Sh. Alok Verma Associate Professor DTU, Delhi for his valuable guidance during the project of the first author. Thanks also due to Dr. Gopal Lalji Rai, Chief Executive Officer, R&M International, Mumbai by providing the Carbon Fabric and Adhesive.

8. References 1. Ghobarah, M. N. Ghorbel, and S. E. Chidiac, “Upgrading Torsional Resistance of Reinforced Concrete Beams Using Fiber-Reinforced Polymer,” Journal of Composites for Construction, vol. 6, pp. 257-263, 2002. 2. S. Panchacharam and A. Belarbi, “Torsional behavior of reinforced concrete beams strengthened with FRP Composites,” 2002, pp. 1-11. 3.

H. Ronagh, M. Ameli, and P. Dux, “Experimental investigations on FRP strengthening of beams in torsion,” in FRP Composites in Civil Engineering - CICE 2004, ed: Taylor & Francis, 2004, pp. 587-592.

4.

Hii Adrian K.Y., Al-Mahaidi Riadh,(2006), “An experimental and numerical investigation on torsional strengthening of solid and box-section RC beams using CFRP laminates”, Composite Structures 75 (2006), pp 213-221.

5.

A. Hii and R. Al-Mahaidi, “Torsional Capacity of CFRP Strengthened Reinforced Concrete Beams,” Journal of Composites for Construction, vol. 11, pp. 71-80, 2007. Volume 45 Number 2 June 2015  75


6. M. Ameli, H. R. Ronagh, and P. F. Dux, “Behavior of FRP strengthened reinforced concrete beams under torsion,” Journal of Composites for Construction, vol. 11, pp. 192200, 2007. 7. C. Constantin E, “Torsional strengthening of rectangular and flanged beams using carbon fibre-reinforced-polymers – Experimental study,” Construction and Building Materials, vol. 22, pp. 21-29, 2008. 8. Santhakumar R.,.Dhanaraj R, and Chandrasekaran E., 2007. “Behaviour of Retrofitted Reinforced Concrete Beams under Combined Bending and Torsion : A numerical study”, Electronic Journal of Structural Engineering, Vol. 7, pp 1 to 7. 9. Ameli Mehran and Ronagh Hamid R.,(2007), “Analytical Method for Evaluating Ultimate Torque of FRP Strengthened Reinforced Concrete Beams”, Journal of Composites for Construction © ASCE / July/August 2007, pp 384-390. 10. FIB,

(2001),

76  Volume 45

“Externally

Number 2 June 2015

Bonded

FRP

Reinforcement for RC Structures”, (CEB-FIB) Lausanne (Switzerland): The International Federation for Structural Concrete; 2001. Technical Report, 14, pp. 59-68. 11. Metin Husem, Ertekin Oztekin and Selim Pul, (2010), “A calculation method of cracking moment for the high strength concrete beams under pure torsion”, Sadhana Vol. 36, Part 1, February 2011, pp. 1–15 © Indian Academy of Sciences. 12. Thomas T. C. Hsu, (1968),” Torsion of Structural Concrete - A Summary of Pure Torsion”, American Concrete Institute Publication SP- 18, 165-178 (1968). 13. M.R. Mohammadizadeh and M.J. Fadaee, (2009),” Torsional Behaviour of High-Strength Concrete Beams Strengthened Using CFRP Sheets; an Experimental and Analytical Study”, Transaction A: Civil Engineering Sharif University of Technology Vol. 16 (4) (2009) 321-330.

The Bridge and Structural Engineer


CLASSIFICATION OF CONCRETE BRIDGES AND DAMAGE STATES FOR SEISMIC EVALUATION: A STATE- OF-THE- ART REVIEW

Dnyanraj PATIL PhD Research Scholar Shri G.S. Inst. of Tech. & Sc. Indore, MP, INDIA itsdmpatil@yahoo.com

Rakesh KHARE Professor Shri G.S. Inst. of Tech. & Sc. Indore, MP, INDIA rakeshkhare@hotmail.com

Dnyanraj Patil received his Bachelor degree in Civil Engineering in 1992 from Marathwada University and Masters degree in Structures in 2000 from Mumbai University. Presently, he is working as an associate professor in Sardar Patel Institute of Technology, Mumbai. He has registered himself for PhD at RGPV Bhopal in 2010.

Rakesh Khare received his Bachelor degree in Civil Engineering in 1985 and Masters degree in Stress and Vibrations Analysis of Machinery & Structures in 1987 from Bhopal University. He joined SGSITS in 1988 and did his PhD in 1996 from DAVV Indore. He has done One Semester certificate Course at IIT Kanpur on Earthquake Resistant Design of structures and six months Post Doctoral Research Training at University of Catenbury, Christchurch, NZ in 20052006. Presently, he is professor at SGSITS, Indore.

Summary In present study, a comprehensive review is carried out for classification of concrete bridges and damage states for effective and efficient use of performance based earthquake engineering. Key findings from different research studies are incorporated. The importance is highlighted of classification, for concrete bridges and damage states to have feasible, practical and economical seismic evaluation in performance based earthquake engineering. Also recommendations are given to incorporate in the seismic design codes of bridges. Keywords: Concrete bridge classification; seismic damage limit states; fragility curves; performance based earthquake engineering.

1. Introduction The general understanding of concrete bridges in terms of their structural attributes as well as their seismic behavior is essential for the generation of fragility curves. Considering each bridge in the inventory data individually and obtaining its fragility curve is neither feasible nor practical, when the total number The Bridge and Structural Engineer

of bridges is concerned. Each existing bridge has its own characteristics due to its structural properties and hence different seismic behavior. This makes it rather difficult to evaluate the seismic performance of each bridge in a large inventory in detail under an expected earthquake. Although each bridge has its own structural characteristics, they have some similarities at various aspects. Therefore, it is a rational way of classifying bridges into different groups considering their certain structural attributes. Similarly, determination of bridge damage parameters and their corresponding limit states is one of the significant steps in the development of analytical fragility curves. Bridge damage limit states have a direct influence on the reliability of the fragility curves, which represent the probability of reaching or exceeding a specific damage state under an earthquake ground motion considering its seismic intensity to decide on the performance level of the bridges. Therefore, realistic damage limit states need to be specified to obtain reliable fragility curves and hence to make a reasonable estimate of their seismic performance level. Volume 45 Number 2 June 2015â&#x20AC;&#x192; 77


Bridges can be regarded as a separate infrastructural facility owing to their distinct importance. Classification of the bridges allows us to deal with each bridge class in detail instead of investigating all bridge samples individually. In this approach, it is intended to generate fragility curves for the identified bridge classes not for individual bridges in the inventory data. The number of bridge classes depends on the structural system variability in the inventory as well as the level of accuracy required for the generation of fragility curves. If all the structural attributes are taken into consideration through the classification procedure, a very detailed classification can be made and considerable amount of bridge classes can be generated. Meanwhile, it should be kept in mind that it is not possible to include every structural characteristic of a bridge in the classification, nor is practical to specify a large number of bridge classes. The number of bridge classes needs to be as small as possible by considering the most important structural attributes of the bridges only. On the other hand, there should be sufficient number of bridge classes covering every bridge sample in the bridge inventory data. Therefore, the list of bridge classes has to be comprehensive in order to enable the classification of as many bridges as possible and at the same time it has to be simple enough to be manageable and applicable. Limit state can be defined as the ultimate point beyond which the bridge structure can no longer satisfy the specified performance level. Moreover, each damage limit state also has functional and operational interpretation. Various qualitative and quantitative limit states for different bridge damage are available in previous studies. Structural damage is related to the deformation of the bridge system and its components. That is why most of the available bridge damage limit states are specified in terms of deformations for the local and global response parameters, which can be expressed as engineering demand parameters. Local engineering demand parameters are utilized for certain structural components whereas global ones are considered for the estimation of overall structural response. Great care should be given to the selection of proper engineering demand parameters for defining the bridge damage limit states to obtain reliable fragility curves. The selected engineering demand parameters should have good correlation with the seismic damage of bridges. Because seismic damage of the bridge is represented by the bridge seismic 78â&#x20AC;&#x192; Volume 45

Number 2 June 2015

response in terms of the selected engineering demand parameter, which is used in the calculation of both capacity and demand of the bridge components. The physical damage of bridges due to seismic actions should be represented with a sufficient number of damage limit states, which should be quantified by appropriate engineering demand parameters. Although qualitative damage limit states for bridges are available in different codes and studies, widely accepted quantitative damage limit states are not readily available for bridges. Damage limit states for various components of bridges or bridge system as a whole is not a trivial task. Bridge damage states are one of the main sources of uncertainty engaged in the fragility curves due to the subjectivity involved in defining the limit states.

2.

Review of bridge classifications

In order to make the classification, structural attributes that best describe the seismic response of bridges and the parameters affecting their seismic behavior need to be specified for the bridge inventory. Different structural properties of the bridges were used in the previous studies to classify the bridges into groups. ATC- 13 (ATC, 1985) considers only two bridge classes according to their total length. Bridges having total length greater than 500 ft and less than 500 ft is classified as major bridge and conventional bridge, respectively. Conventional bridges are further classified into two groups as multiple simple spans and continuous monolithic. This is a very broad classification and neglects various structural characteristics that affect the seismic performance of a bridge, such as material, substructure properties, skewness, etc. In the classification developed by Basoz and Kiremidjian (1997), bridges are grouped according to number of spans, superstructure type, substructure type and material, abutment type, and span continuity. Using that classification, bridges damaged in the Northridge and Loma Prieta earthquakes were grouped first by the superstructure type and substructure material. Then, these bridges were further classified into sub-categories based on other structural characteristics, such as number of spans, abutment type; column bent type and span continuity. Empirical damage probability matrices and fragility curves were developed for each of these bridge The Bridge and Structural Engineer


sub-categories using the damage data from the Northridge and Loma Prieta earthquakes. The bridge sub-categories employed in the study of Basoz and Kiremidjian (1997) are given in Table 1. Table 1: Description of bridge sub-categories employed by Basoz and Kiremidjian (1997) Bridge SubCategory

Abutment Type

Column Bent Type

Span Continuity

HAZUS (FEMA, 2003) has a bridge classification based on the following structural characteristics: 

Seismic Design

Number of spans: single vs. multiple span bridges

Structure type: concrete, steel others

Single Span Bridges

Pier type: multiple column bents, single column bents and pier walls Abutment type and bearing type: monolithic vs. non-monolithic; high rocker bearings, low steel bearings and neoprene rubber bearings.

C1S1

Monolithic

Not Not applicable applicable

C1S2

Nonmonolithic

Not Not applicable applicable

C1S3

Partial integrity

Not Not applicable applicable

Classification scheme of HAZUS (FEMA, 2003) incorporates various parameters that affect damage into fragility analysis. In this way, a total of 28 bridge classes (HWB1 through HWB28) are defined as given in Table 2.

Multiple Span Bridges C1M1

Monolithic

Multiple

Continuous

C1M2

Monolithic

Multiple

Discontinuous

C1M3

Monolithic

Single

Continuous

C1M4

Monolithic

Single

Discontinuous

C1M5

Monolithic

Pier wall

Continuous

C1M6

Monolithic

Pier wall

Discontinuous

C1M7

Nonmonolithic

Multiple

Continuous

C1M8

Nonmonolithic

Multiple

Discontinuous

C1M9

Nonmonolithic

Single

Continuous

C1M10

Nonmonolithic

Single

Discontinuous

C1M11

Nonmonolithic

Pier wall

Continuous

C1M12

Nonmonolithic

Pier wall

Discontinuous

C1M13

Partial integrity

Multiple

Continuous

C1M14

Partial integrity

Multiple

Discontinuous

C1M15

Partial integrity

Single

Continuous

C1M16

Partial integrity

Single

Discontinuous

C1M17

Partial integrity

Pier wall

Continuous

C1M18

Partial integrity

Pier wall

Discontinuous

The Bridge and Structural Engineer

Span continuity: continuous, discontinuous (inspan hinges) and simply supported.

Table 2: HAZUS (FEMA, 2003) bridge classification scheme Class

State

Year Built

Design

Description

HWB1

Non-CA <1990

Conventional Major Bridge Length>150m

HWB1

CA

Conventional Major Bridge Length>150m

HWB2

Non-CA >=1990 Seismic

Major Bridge Length>150m

HWB2

CA

Major Bridge Length>150m

HWB3

Non-CA <1990

Conventional Single Span

HWB3

CA

Conventional Single Span

HWB4

Non-CA >=1990 Seismic

Single Span

HWB4

CA

Single Span

HWB5

Non-CA <1990

Conventional Multi-Col. Bent, Simple SupportConcrete

HWB6

CA

Conventional Multi-Col. Bent, Simple SupportConcrete

HWB7

Non-CA >=1990 Seismic

<1975

>=1975 Seismic

<1975

>=1975 Seismic

<1975

Multi-Col. Bent, Simple SupportConcrete

Volume 45 Number 2 June 2015  79


Class

State

Year Built

Design

HWB7

CA

>=1975 Seismic

HWB8

CA

<1975

HWB9

CA

Description Multi-Col. Bent, Simple SupportConcrete

Conventional Single Col. Box Girder -Continuous Concrete

>=1975 Seismic

Single Col. Box Girder -Continuous Concrete

HWB10

Non-CA <1990

Conventional Continuous Concrete

HWB10

CA

Conventional Continuous Concrete

<1975

HWB11

Non-CA >=1990 Seismic

Continuous Concrete

HWB11

CA

Continuous Concrete

HWB12

HWB13

>=1975 Seismic

Non-CA <1990

CA

<1975

Conventional Multi-Col. Bent, Simple Support-Steel Conventional Multi-Col. Bent, Simple Support-Steel

Class

State

Year Built

Design

Description

HWB19

Non-CA >=1990 Seismic

Multi-Col. Bent, Simple SupportPrestressed Concrete

HWB19

CA

>=1975 Seismic

Multi-Col. Bent, Simple SupportPrestressed Concrete

HWB20

CA

<1975

HWB21

CA

>=1975 Seismic

HWB22

Non-CA <1990

Conventional Continuous Concrete

HWB22

CA

Conventional Continuous Concrete

HWB23

Non-CA >=1990 Seismic

Continuous Concrete

HWB23

CA

Continuous Concrete

HWB24

Non-CA <1990

Conventional Multi-Col. Bent, Simple Support-Steel

HWB25

CA

Conventional Multi-Col. Bent, Simple Support-Steel

<1975

Conventional Single Col. Box Girder -Prestressed Concrete Single Col. Box Girder -Prestressed Concrete

HWB14

Non-CA >=1990 Seismic

Multi-Col. Bent, Simple Support-Steel

HWB14

CA

Multi-Col. Bent, Simple Support-Steel

HWB15

Non-CA <1990

Conventional Continuous Steel

HWB15

CA

Conventional Continuous Steel

HWB16

Non-CA >=1990 Seismic

Continuous Steel

HWB26

Non-CA <1990

Conventional Continuous Steel

HWB16

CA

Continuous Steel

HWB27

CA

Conventional Continuous Steel

HWB17

Non-CA <1990

Conventional Multi-Col. Bent, Simple SupportPrestressed Concrete

HWB18

CA

Conventional Multi-Col. Bent, Simple SupportPrestressed Concrete

80â&#x20AC;&#x192; Volume 45

>=1975 Seismic

<1975

>=1975 Seismic

<1975

Number 2 June 2015

HWB28

>=1975 Seismic

<1975

<1975

All other bridges that are not classified

In the study of Nielson (2005), bridges are assigned to one of 11 bridge classes based on their construction material, construction type and the number of spans. Bridge classes and their corresponding abbreviation defined by Nielson (2005) are presented in Table 3. The Bridge and Structural Engineer


Table 3: Bridge classes defined by Nielson (2005) Bridge Class Name Multi-Span Continuous Concrete Girder Multi-Span Continuous Steel Girder Multi-Span Continuous Slab Multi-Span Continuous Concrete Box Girder Multi-Span Simply Supported Concrete Girder Multi-Span Simply Supported Steel Girder Multi-Span Simply Supported Slab Multi-Span Simply Supported Concrete Box Girder Single-Span Concrete Girder Single-Span Steel Girder Others

3.

Abbreviation MSC Concrete MSC Steel MSC Slab MSC ConcreteBox MSSS Concrete MSSS Steel MSSS Slab MSSS Concrete-Box SS Concrete SS Steel

Review of Seismic Damage Limit States

ATC-32 (1996) adapted three damage levels: Minimal damage: Damage is limited to minor flexural cracking, and minor inelastic response is permitted to develop at structural elements. Repairable damage: Concrete cracking, reinforcement yielding and minor spalling is allowed, but limited to avoid closure of the structure during minor repair work. Significant damage: Similar to repairable damage, except during repair, the structure needs to be closed for major repair work. Priestley et al. (1996) specified limit states for both member and structure response. Qualitative descriptions were given for cracking, first-yield, spalling and ultimate limit states to define the member seismic response. Member limit states are schematically shown on a moment-curvature diagram in Figure 1-a. Priestley et al. (1996) considered three structural limit states, which are serviceability, damage control, and survival limit states. Both qualitative and quantitative limit state descriptions based on an average range of displacement ductility ratios were given. Schematic representation of the three structural limit states as well as the yield point of an idealized force-displacement curve are shown in Figure 1-b. The Bridge and Structural Engineer

Fig. 1 : Schematic representation of limit states (Priestley et al., 1996)

In the study of Basoz and Mander (1999), a total of five damage states were defined for highway bridge components, which are in accordance with the ones defined by HAZUS. Table 4 lists these damage states and the corresponding failure mechanisms. Also drift limits were specified to predict the various damage states for non-seismic and seismically designed bridges by Basoz and Mander (1999). These drift limits are applicable to bridges with weak piers and strong bearings. Displacement limits for girder bridges with weak bearings and strong piers increase as the bridge damage state increases. Slight and moderate damage states show initial damage to the bearings. Extensive and complete damage states show incipient unseating (i.e. when the girder seat becomes unstable and is equal to half the width of the girder flange) and collapse (i.e. the bearing topples). The given drift limits for each damage limit state were further utilized by Banerjee and Shinozuka (2007) to quantify the limit states in terms of rotational ductility of columns. Table 4: Drift and displacement limits for each damage state (Basoz and Mander, 1999) Damage state

Failure Mechanism

Drift limit for weak pier & strong bearings Nonseismic

Seismic

Displacement limits for weak bearings and strong pier (m)

Slight

Cracking, spalling

0.005

0.010

0.050

Moderate

Bond, abutment backwall collapse

0.010

0.025

0.100

Extensive

Pier concrete failure

0.020

0.050

0.175

Complete

Deck unseating, pier collpase

0.050

0.075

0.300

Volume 45 Number 2 June 2015â&#x20AC;&#x192; 81


Kowalsky (2000) considered two damage limit states, which are “serviceability” and “damage control”, for circular RC bridge columns. Qualitatively, serviceability limit state implies that repair is not needed after the earthquake, while damage control limit state implies that only repairable damage occurs. Quantitatively, these damage limit states were characterized with respect to concrete compression and steel tension strain limits in Table 5.

Table 6: Bridge damage assessment (Hose et al., 2000) Level

Damage Classification

Damage Description

I

No

II

Minor

III

Moderate

IV

Major

V

Local failure/ Visible permanent deformation, buckling/rupture of reinforcement

Table 5: Quantitative damage limit state definitions (Kowalsky, 2000) Limit state

Concrete strain limit

Steel strain limit

Serviceability

0.004

0.015

Damage control

0.018

0.060

Quantitative descriptions of the limit states were also given by Kowalsky (2000). The serviceability concrete compression strain was defined as the strain at which crushing is expected to begin, while the serviceability steel tension strain was defined as the strain at which residual crack widths would exceed 1 mm, thus likely requiring repair and interrupting serviceability. The damage control concrete compression strain was defined as the compression strain at which the concrete is still repairable. Steel tension strain at the damage control level was related to the point at which incipient buckling of reinforcement occurs. It was mentioned that the proposed strain limits for the serviceability limit states are widely accepted. On the other hand, damage control level strain limits were dependent on the detailing of transverse reinforcement. The given damage control strain limits valid for well detailed systems and they would not be appropriate for assessment of existing columns with insufficient transverse reinforcement. In the study of Hose et al. (2000), five levels of performance and damage states were specified. Seismic damage of the bridges was classified in relation with the socio-economic descriptions at five designated performance levels. Table 6 lists the classifications of bridge damage for each of the five levels as well as corresponding damage, repair, and social-economic descriptions. 82  Volume 45

Number 2 June 2015

Repair Description

Barely visible No Repair cracking Cracking Possible Repair Open cracks, Minimum onset of Repair spalling Very wide Repair cracks, extended concrete spalling Replacement Collapse

Socioeconomic Description Fully operational Operational Life safety Near collapse

Collapse

To explicitly relate bridge damage to capacity, engineering terms were selected for the performance levels rather than the socio-economic expressions for the five performance levels ranging from concrete cracking and member strength degradation. Qualitative and quantitative performance descriptions corresponding to the five performance levels were given in Table 7. Table 7: Bridge performance assessment (Hose et al., 2000) Level

Performance Level

Qualitative Performance Description

Quantitative Performance Description

I

Cracking

Onset of hairline cracks

Cracks barely visible.

II

Yielding

Crack widths < 1mm Theoretical first yield of longitudinal reinforcement

III

Initiation of local mechanism

Initiation of inelastic deformation. Onset of concrete spalling. Development of diagonal cracks.

Crack widths 1-2 mm. Length of spalled region >1/10 crosssection depth.

IV

Full development of local mechanism

Wide crack widths/ spalling over full local mechanism region.

Crack widths >2 mm. Diagonal cracks extend over 2/3 crosssection depth. Length of spalled region > 1/2 cross-section depth

V

Strength degradation

Buckling of main reinforcement. Rupture of transverse reinforcement. Crushing of core concrete.

Crack widths >2mm in concrete core. Measurable dilation > 5% of original member dimension.

The Bridge and Structural Engineer


The database attempts to explicitly define criteria at each level by providing quantitative guidelines such as crack widths, crack angles, and regions of spalling. In addition to the quantitative descriptions for each performance level, various engineering demand parameters were investigated for numerical determination of damage limit states using experimental results of several bridge column tests. The investigated engineering demand parameters are steel and concrete strain, curvature and displacement ductility, plastic rotation, principal compression and tension stresses, drift ratio, residual deformation index, equivalent viscous damping ratio and normalized effective stiffness. In the study of Hwang et al. (2001), two different approaches were considered for the seismic damage assessment and the seismic fragility analysis of bridges. In the first approach, a component-bycomponent assessment of seismic damage to a bridge was performed by defining damage states for the response parameters of bearings, columns in shear and columns in flexure. Two damage states were defined for the bearings considering their yield and ultimate shear capacity. The second response parameter was the column shear capacity, which is compared with the column shear demand to determine whether columns sustain any shear damage or not. Lastly, four damage states were defined according to the flexural capacity of the columns. Damage description of each damage state and its limit state criteria are given in Table 8. Table 8: Seismic damage assessment criteria for columns in flexure (Hwang et al., 2001) Criterion M1 > M My > M ≥ M1 M ≥ My , θ < θp M ≥ My, θ > θp

Description of damage No reinforcing steel yielding, minor cracking in concrete Tensional reinforcement yielding and extensive cracking in concrete Hinging in column, but no failure of column Flexural failure of column

Column status No damage (OK)

Cracking (C)

Hinging (H) Flexural failure (F)

M1 is the column moment at the first yielding of longitudinal bar, whereas My is the yield moment The Bridge and Structural Engineer

at the idealized moment curvature diagram of the column sections. θp is the plastic hinge rotation with εc equal to 0.002 and 0.004 for the columns with and without lap splices at the bottom of the columns, respectively. In the second approach of Hwang et al. (2001), damage limit states were defined to assess the overall seismic damage to bridges for the development of analytical fragility curves. For this purpose, damage states were defined using an engineering demand parameter of displacement ductility ratio of columns, which is defined by Equation

Δ is the relative displacement at the top of a column obtained from seismic response analysis, and Δcy1 is the relative displacement of a column when the longitudinal reinforcing bars at the bottom of the column reaches the first yield. Five damage states were defined using demand parameter of displacement ductility ratio of columns, μd. The damage states were quantified according to the criteria given in Table 9. μcy1 is displacement ductility ratio at the first longitudinal bar yield. Since displacement ductility ratio is defined in terms of the displacement at the first longitudinal bar yield, μcy1 is equal to 1.0. μcy is yield displacement ductility ratio of the column. μc2 is displacement ductility ratio with εc=0.002. μcmax is the maximum displacement ductility ratio, which is defined as; μcmax = μc2 + 3.0. Table 9: Bridge damage states by displacement ductility ratios by (Hwang et al, 2001) Damage States

Criterion

N

No damage

µcy1 > µd

S

Slight/ Minor damage

µcy > µd > µcy1

M

Moderate damage

µc2 > µd > µcy

E

Extensive damage

µcmax > µd > µcy2

c

Complete damage

µd > µcmax

Qualitative description of five damage states is defined for highway bridge components by HAZUS (FEMA, 2003). These are the none (ds1), slight/minor (ds2), moderate (ds3), extensive (ds4) and complete (ds5) damage states as defined in Table 10. Although very detailed qualitative descriptions are defined, Volume 45 Number 2 June 2015  83


quantitative description of these damage states is not given. Each damage state has its own functional and operational interpretation for the bridge components and/or bridge structural system as a whole. As a result, recovery time necessary of the bridges for each damage state differs considerably. As the bridge damage level increases, more recovery time is needed for the bridge to be operational and functional. Restoration functions for each damage state is also specified by HAZUS (FEMA, 2003) as shown in Figure 2. These curves are the smooth curves characterized by a cumulative normal distribution function using a mean and standard deviation for each damage state.

Complete (ds5)

Any column collapsing and connection losing all bearing support, which may lead to imminent deck collapse, tilting of substructure due to foundation failure.

Karim and Yamazaki (2003); Nateghi and Shahsavar (2004) considered five damage states for the development of analytical fragility curves. These are the No, Slight, Moderate, Extensive and Complete damages. Park-Ang damage index based on energy dissipation was employed for the quantification of each defined damage states. In the study of Liao and Loh (2004), a total of four damage states were defined for highway bridge components, which are in accordance with the ones defined by HAZUS. Liao and Loh (2004) determined analytical fragility curves using the above mentioned damage states, which were quantified in terms of ductility and displacement (Table 11). Table 11: Ductility and displacement limits for each damage state (Liao and Loh, 2004)

Fig. 2 : HAZUS restoration functions for highway bridges (FEMA, 2003)

Table 10: Definitions of damage states by HAZUS (FEMA, 2003) Damage States None (ds1) Slight/ Minor (ds2)

Moderate (ds3)

Extensive (ds4)

Definitions No bridge damage Minor cracking and spalling to the abutment, cracks in shear keys at abutments, minor spalling and cracks at hinges, minor spalling at the column (damage requires no more than cosmetic repair) or minor cracking to the deck. Any column experiencing moderate (shear cracks) cracking and spalling (column structurally still sound), moderate movement of the abutment (<2”), extensive cracking and spalling of shear keys, any connection having cracked shear keys or bent bolts, keeper bar failure without unseating, rocker bearing failure or moderate settlement of the approach. Any column degrading without collapseshear failure- (column structurally unsafe), significant residual movement at connections, or major settlement approach, vertical offset of the abutment, differential settlement at connections, shear key failure at abutments.

84  Volume 45

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Ductility limits for weak pier and strong bearings Conventional design (non-seismic design)

Displacement limits Weak bearings and strong pier

Damage state

Seismic design

Slight

µ = 2.0

µ = 1.0

Yield displacement

Moderate

µ = 4.0

µ = min (1+µf -1)/2, 2.0)

10 cm

Extensive

µ = 6.0

µ = min (µf, 3.0)

20 cm

Complete

µ = 9.0

µ = 4.5 or pier reach its ultimate capacity

Min (40 cm, 2N/3)

µf : corresponding ductility at occurrence of flexure to shear failure. N: seat length of a girder at the support.

For each damage state, ductility limits were specified for weak pier and strong bearings by considering the design type of the bridge, which is either seismic or conventional design. Whereas, displacement limits were specified for the bridges having weak bearings and strong pier. Available girder seat length is taken into account for the definition of complete damage state. However, in the definition of moderate and extensive damage states, numerical values are given without any physical meaning for the associated damage state. Five post-earthquake damage states were employed by Elnashai et al. (2004). The Bridge and Structural Engineer


Table 12: Definition of damage states for bridge components (Choi et al., 2004)

These are as follows:  

 

Undamaged; Slightly damaged, but usable without repair or strengthening; Extensively damaged, but still repairable; No collapse, but so severely damaged that must be demolished; Collapse.

Four limit states were defined to assess the bridge damage state including both qualitative and quantitative descriptions. Below the first limit state, no damage should take place and the expected response is of small displacement amplitude. This limit state is defined as the point that the first yielding of longitudinal reinforcing bars. Below the second limit state, bridge can experience minor structural damage and it is usable after the earthquake. Member flexural strengths may have been reached and limited ductility developed, provided that concrete spalling in plastic hinges does not occur and that residual crack widths remain sufficiently small. Cover concrete strain εc, is employed to identify this limit state. Below the third limit state, significant structural damage is expected. The bridge will be out of service after the earthquake unless significant repair is undertaken. However, repair and strengthening is feasible. Rupture of transverse reinforcement or buckling of longitudinal reinforcement should not occur and core concrete in plastic hinge regions should not need replacement. Below the final limit state extensive damage is expected, but the bridge should not have collapsed. Repair may be neither possible nor cost-effective. The structure will have to be demolished after the earthquake. Beyond this limit state, global collapse endangering life is expected since it corresponds to the inability of the structure to sustain gravity loads. A steel strain of 9% was assumed by Elnashai et al. (2004) to identify the final limit state. In the study of Choi et al. (2004), damage states of bridges were defined for column ductility demand, steel fixed and expansion bearing deformations, and elastomeric bearing deformations. The damage state definitions were based on the qualitative descriptions of the damage states as provided by HAZUS. The quantitative definitions of each damage states for the mentioned engineering demand parameters are presented in Table 12. The Bridge and Structural Engineer

Engineering Demand Parameters Damage state

Columns (µ)

Steel Bearings (δ, mm)

Expansion Bearings (δ, mm)

Fixed Dowels (δ, mm)

Expansion Dowels (δ, mm)

Slight

1.0 < µ <2.0

1< δ <6

δ< 50

8<δ<100

δ <30

Moderate

2.0< µ <4.0

6< δ <20

50<δ <100

100 < δ < 150

30<δ<100

Extensive

4.0< µ <7.0

20< δ <40

100<δ<150

150<δ <255

100<δ <150

Complete

7.0< µ

40< δ

150<δ<255

255<δ

150<δ <255

Choi et al. (2004) mentioned that the damage states were quantified according to the recommendations from previous studies and experimental test results. The quantified damage states for the columns were described by the column curvature ductility and based on tests of non seismically designed columns, of which the lap-slices at the base were taken into account. The damage states for the bearings in the pre-stressed concrete girder bridges were based on fracture of the bearing and the displacement necessary for unseating. The problem of instability and unseating is a function of the size of the bearings and the width of the supports. The displacement at the complete damage limit state was assumed to be δ=255 mm by Choi et al. (2004), which accounts for the unseating of prestressed concrete girders. Nielson (2005) utilized bridge damage states described qualitatively by HAZUS. Engineering demand parameters of column curvature ductility, steel fixed and rocker bearing deformations, elastomeric fixed and expansion bearing deformations, and abutment displacements were employed for the quantification of damage states. Column curvature ductility values for each damage limit state were computed using the displacement ductility ratios specified by Hwang et al. (2001). In the CALTRANS (2006) approach, ordinary bridges are not allowed to collapse under the safety evaluation earthquake (SEE). The bent top displacement capacity to demand ratio is limited to ΔC/ΔD > 0.1 Based on the correlation of seismic response measures with damage levels, T. Yilmaz and A. Caner (2011) suggested displacement capacity-demand ratios of 1.1, 1.5 and 2.5, for significant, repairable and minimal Volume 45 Number 2 June 2015  85


damage levels for the safety evaluation earthquake with a return period of 1000 years, respectively.

4. 

Conclusion

The review on the subject reveals that work on the classification of concrete bridges and damage states is still inadequate and deserve attention for more understanding of the subject and for providing definite guidelines for seismic evaluation and performance based design of bridges. Classification of concrete bridges and damage states is very important step in seismic evaluation to have possible, practical and economical aspects for seismic design of bridges using Performance Based Earthquake Engineering. Therefore it must be included in seismic design standards of bridges. As per ATC-32 bridges with single span and span length less than 20 m does not require seismic evaluation due to less vulnerability. Bridges having similar geometric and material attributes with closely ranged spans must be grouped together for seismic evaluation.

5. References 1.

ATC-13, “Earthquake Damage Evaluation Data for California”, Applied Technology Council, Redwood City, California, 1985.

2. ATC-32, “Improved Seismic Design Criteria for California Bridges: Provisional Recommendations”, Applied Technology Council, Redwood City, California, 1996. 3.

BANERJEE S., AND SHINOZUKA M., “Nonlinear Static Procedure for Seismic Vulnerability Assessment of Bridges”, Computer-Aided Civil and Infrastructure, Vol. 22, pp. 293-305, 2007.

4.

BASOZ N., AND MANDER J., “Enhancement of the Highway Transportation Lifeline Module in HAZUS”, National Institute of Building Sciences, 1999.

5.

BASOZ N., AND KIREMIDJIAN A.S., “Evaluation of Bridge Damage Data from The Loma Prieta and Northridge, CA Earthquakes”, Technical Report No. 127, John A. Blume

86  Volume 45

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Earthquake Engineering Center, Stanford, CA (also Technical Report MCEER-98-004), 1997. 6.

CALTRANS, “Seismic Design Criteria Version 1.4.”, California Department of Transportation, Sacramento, CA, 2006.

7.

CHOI E., DESROCHES R. AND NIELSON B., “Seismic Fragility of Typical Bridges in Moderate Seismic Zones”, Engineering Structures, Volume 26, No. 2, pp. 187-199, 2004.

8.

ELNASHAI A.S., BORZI B., AND VLACHOS S., “Deformation–Based Vulnerability Functions for RC Bridges”, Structural Engineering and Mechanics, Volume 17, No. 2, pp.215-244, 2004.

9.

FEMA, HAZUS-MH MR1: Technical Manual, Vol. Earthquake Model. Federal Emergency Management Agency, Washington DC, 2003.

10. HOSE Y., SILVA P., AND SEIBLE F., “Development of a Performance Evaluation Database for Concrete Bridge Components and Systems under Simulated Seismic Loads”, Earthquake Spectra, Volume 16, No. 2, pp. 413– 442, 2000. 11. HWANG H., LIU J.B., AND CHIU Y.H., “Seismic Fragility Analysis of Highway Bridges”, Report No. MAEC RR-4, Center for Earthquake Research Information, 2001. 12. KARIM K.R., AND YAMAZAKI F., “A Simplified Method of Constructing Fragility Curves for Highway Bridges”, Earthquake Engineering and Structural Dynamics, Volume 32, pp. 1603-1626, 2003. 13. KOWALSKY M.J., “Deformation Limit States for Circular Reinforced Concrete Bridge Columns”, ASCE Journal of Structural Engineering, Volume 126, No. 8, pp. 869-878, 2000. 14. LIAO W.I., AND LOH C.H., “Preliminary Study on the Fragility Curves for Highway Bridges in Taiwan”, Journal of the Chinese Institute of Engineers, Volume 27, No. 3, pp.367-375, 2004. 15. NATEGHI F., AND SHAHSAVAR V.L., “Development of Fragility and Reliability Curves for Seismic Evaluation of a Major The Bridge and Structural Engineer


Prestressed Concrete Bridge”, 13th World Conference on Earthquake Engineering, Paper No. 1351, Vancouver, B.C. Canada, 2004.

17. PRIESTLEY M.J.N., SEIBLE F., AND CALVI G.M., “Seismic Design and Retrofit of Bridges”, John Wiley & Sons, Inc., New York, 1996.

16. NIELSON B.G., “Analytical Fragility Curves for Highway Bridges in Moderate Seismic Zones”, PhD Thesis, Georgia Institute of Technology. Atlanta, Georgia, 2005.

18. YILMAZ T., AND CANER A., “An Improved Seismic Design Approach For Two-Column Reinforced Concrete Bents Over Flexible Foundations With Predefined Damage Levels”, TDMSK, Ankara, 2011.

OBITUARY The Indian National Group of the IABSE express their profound sorrow on the sad demise of Late Shri Tapan Kumar Basu, Managing Director, Basu & Associates Pvt. Ltd. on the 9th April 2015 at New Delhi. He was an active member of the Indian National Group of the IABSE. The Group prays the almighty God to grant strength and courage to the bereaved family to bear the loss. May his soul rest in peace. Shri Tapan Kumar Basu

With profound grief, the Indian National Group of the International Association for Bridge and Structural Engineering condoles the sad and untimely demise of Shri Chander Rupchand Alimchandani, on the 12th July 2015, Chairman and Managing Director of M/s STUP Consultants Pvt. Ltd.

Shri Chander Rupchand Alimchandani

this group.

Late Shri Chander Rupchand Alimchandani was one of the founder Member of the Group and was closely associated with various activities of this Group. He served as a Members on the Executive Committee and Managing Committee of the Group for many years. He was a member of numerous Technical Committees in India and abroad and also member of the Permanent Committee of the International Association for Bridge and Structural Engineering. Shri Alimchandani was a man of great ability. His contribution to the activities of engineering profession and group, will remain as landmark in the history of

Shri Alimchandani was well known for his dedication in the profession. Indian National Group of the International Association for Bridge and Structural Engineering sincerely appreciates his contribution to the Group and deeply mourns his untimely death. The Group prays the almighty God to grant strength and courage to the bereaved family to bear the loss. May his soul rest in peace. Shri DM Siddesh The Indian National Group of the IABSE express their profound sorrow on the sad demise of Late Shri DM Siddesh, Chitradurga (Karnataka) on 10th July 2015. He was an active member of the Indian National Group of the IABSE. The Group prays the almighty God to grant strength and courage to the bereaved family to bear the loss. May his soul rest in peace.

The Bridge and Structural Engineer

Volume 45 Number 2 June 2015  87


INDIAN NATIONAL GROUP OF THE IABSE OFFICE BEARERS AND MANAGING COMMITTEE MEMBERS – 2015 Chairman 1. Shri DO Tawade, Chief Engineer (Coordinator-II), Ministry of Road Transport and Highways

Past Member of the Executive Committee and Technical Committee of the IABSE 11. Prof SS Chakraborty, Past Vice-President, IABSE

Vice-Chairmen

12. Dr BC Roy, Vice President & Member, Technical Committee, IABSE

2. Shri Divakar Garg, Director General, Central Public Works Department

Honorary Secretary

3. Shri MP Sharma, Member (Technical), National Highways Authority of India

13. Shri RK Pandey, Chief Engineer (Planning), Ministry of Road Transport and Highways Members of the Executive Committee

4. Shri Alok Bhowmick, Managing Director, B&S Engineering Consultants Pvt. Ltd.

14. Shri AD Narain, Former DG (RD) & Additional Secretary

5. Shri MV Jatkar, Executive Director (Technical), Gammon India Ltd.

15. Shri AK Banerjee, Former Member (Technical), NHAI

Honorary Treasurer

16. Shri AV Sinha, Former DG (RD) & Special Secretary

6. The Director General (Road Development) & Special Secretary to the Government of India, Ministry of Road Transport and Highways Honorary Members 7.

Shri Ninan Koshi, Former DG (RD) & Additional Secretary

8. Prof SS Chakraborty, Honorary Member & Past Vice-President, IABSE

17. Shri G Sharan, Former DG (RD) & Special Secretary 18. Shri RP Indoria, Former DG (RD) & Special Secretary 19. Shri OP Goel, Former DG (Works) 20. Shri Shishir Bansal, Chief Project Manager, Delhi Tourism & Transportation Development Corp. Ltd. Secretariat

Persons represented ING on the Executive Committee and Technical Committee of the IABSE

21. Shri RK Pandey, Secretary, ING-IABSE & Chief Engineer (Planning), Ministry of Road Transport and Highways

9. Dr BC Roy, Vice President & Member, Technical Committee, IABSE

22. Shri Ashish Asati, Director, ING-IABSE & General Manager, National Highways Authority of India

10. Dr Harshavardhan Subbarao, Member, Technical Committee of IABSE & Chairman a nd Managing Director, Construma Consultancy Pvt Ltd

88  Volume 45

Number 2 June 2015

23. Shri KB Sharma, Under Secretary, Indian National Group of the IABSE

The Bridge and Structural Engineer


MEMBERS OF THE MANAGING COMMITTEE – 2015 Rule-9 (a): A representative of the Union Ministry of Road Transport and Highways 1.

Shri DO Tawade, Chief Engineer (Coordinator-II), Ministry of Road Transport & Highways

Rule-9 (b): A representative each of the Union Ministries/Central Government Departments making annual contribution towards the funds of the Indian National Group of the IABSE as determined by the Executive Committee from time to time 2.

Shri Divakar Garg, Director General, CPWD

3.

NHAI - nomination awaited

4.

Ministry of Railways - nomination awaited

Rule-9 (c): A representative each of the State Public Works Departments/Union Territories making annual contribution towards the funds of the Indian National Group of the IABSE as determined by the Executive Committee from time to time 5.

Govt of Andhra Pradesh – nomination awaited

6. Shri Katung Wahge, Chief Engineer, Western Zone, Govt of Arunachal Pradesh 7. Shri AC Bordoloi , Commissioner & Special Secretary to the Govt of Assam 8.

Govt of Bihar – nomination awaited

9.

Govt of Chattisgarh – nomination awaited

10. Shri Mukund Joshi, Engineer-in-Chief, Govt of Delhi 11. Shri UP Parsekar, Chief Engineer (NH, R&B), Govt of Goa 12. Govt of Gujarat – nomination awaited 13. Shri Rakesh Manocha, Engineer-in-Chief, Govt of Haryana 14. Govt of Himachal Pradesh – nomination awaited 15. Govt of Jammu & Kashmir – nomination awaited

17. Govt of Karnataka – nomination awaited 18. Govt of Kerala – nomination awaited 19. Govt of Madhya Pradesh – nomination awaited 20. Shri CP Joshi, Chief Engineer, Govt of Maharashtra 21. Shri O Nabakishore Singh, Additional Chief Secretary (Works), Govt of Manipur 22. Shri CW Momin, Chief Engineer (Standard), PWD (Roads), Govt of Meghalaya 23. Shri Lalmuankima Henry, Chief Engineer (Buildings), Govt of Mizoram 24. Govt of Nagaland – nomination awaited 25. Govt of Orissa – nomination awaited 26. Govt of Punjab – nomination awaited 27. Govt of Sikkim – nomination awaited 28. Shri KC Parameswaran, Chief Engineer (H), Projects, Highways Depatment, Govt of Tamil Nadu 29. Govt of Tripura – nomination awaited 30. Shri Yogendra Kumar Gupta, Chief Engineer (Bridges), Govt of Uttar Pradesh 31. Govt of Uttarakhand – nomination awaited 32. Shri Sagar Chakraborty, Suptd Engineer, Bridge Planning Circle, Govt of West Bengal 33. UT Chandigarh Admn – nomination awaited Rule-9 (d): A representative each of the Collective Members making annual contribution towards the funds of the Indian National Group of IABSE as determined by the Executive Committee from time to time 34. Major VC Verma, Director (Mktg), Oriental Structural Engineers Pvt Ltd Rule-9 (e): Ten representatives of Individual and Collective Members 35. Shri G Sharan, Former DG (RD) & Special Secretary

16. Govt of Jharkhand – nomination awaited The Bridge and Structural Engineer

Volume 45 Number 2 June 2015  89


36. Shri AK Banerjee , Former Member (Technical), NHAI

Rule-9 (h): Four representatives Engineering Firms

37. Shri AV Sinha, Former DG (RD) & Special Secretary

51. Shri AD Narain, President, ICT Pvt Ltd

38. Shri RP Indoria, Former DG (RD) & Special Secretary 39. Shri V Velayutham , Former DG (RD) & Special Secretary 40. Shri Alok Bhowmick, Managing Director, B&S Engineering Consultants Pvt Ltd

of

Consulting

52. Shri Bageshwar Prasad, CEO (Delhi Region), Construma Consultancy Pvt Ltd 53. Dr Nirmalya Bandyopadhyay, Director, STUP Consultants Pvt Ltd 54. Shri Aditya Chander Sharma, Director – Transport, Ramboll India Pvt Ltd

41. Shri OP Goel, Former DG (Works)

Rule-9 (i): Honorary Treasurer of the Indian National Group of the IABSE

42. Shri Ranjan Kumar Datta, Former ED, JacobsCES

55. The Director General (Road Development) & Special Secretary to the Govt of India

43. Shri Inderjit Ghai, Chief Executive Officer, Consulting Engineers Associates

Rule-9 (j): Past-Chairman of the Society, for a period of three years, after they vacate their Chairmanship

44. Shri RS Mahalaha Rule-9 (f): Four representatives of Bridge and Structural Engineering Firms 45. Shri MV Jatkar, Executive Director (Technical), Gammon India Ltd 46. Shri Rajan Mittal, Managing Director, UP State Bridge Corporation Ltd 47. Shri Surjit Singh, Vice President & Project Director, IL&FC Engineering Construction Co Ltd 48. Shri T Srinivasan, Vice President & Head – Ports, Tunnels & Special Bridges, Larsen & Toubro Ltd Rule-9 (g): Two representatives of the Engineering Colleges / Technical Institutes / Universities /Research Institutes 49. Dr K Ramanjanelu, Structural Engineering Research Centre, Madras 50. Shri VL Patankar, Director, Indian Academy of Highway Engineers

--Rule-9 (k): Secretary of the Indian National Group of the IABSE 56. Shri RK Pandey Rule-9 (l): Persons who have been awarded Honorary Membership of the Parent Body 57. Shri Ninan Koshi 58. Prof SS Chakraborty Rule-9 (m): Persons represented ING on the Executive Committee and Technical Committee of the IABSE 59. Dr BC Roy 60. Dr Harshavardhan Subbarao Rule-9 (n): Past Members of the Executive Committee and Technical Committee of the IABSE 61. Prof SS Chakraborty 62. Dr BC Roy

90  Volume 45

Number 2 June 2015

The Bridge and Structural Engineer


Ministry of Road Transport & Highways, Government of India Transport Bhavan, Parliament Street New Delhi-110001 (International Competitive Bidding) Notice Inviting Tender No. RW/NH-12037/1240/2014/J&K/NH-1 

Dated: 30.07.2015

1. Ministry of Road Transport & Highways (MoRT&H) invites RFQ Applications and RFP Bids under single stage two cover system (referred to as the “Bidding Process”) for selection of the Bidder for award of the Project from the Applicants/Bidders interested in design, engineering, construction, development, finance, operation & maintenance of the following project to be executed on Design, Build, Finance, Operate and Transfer (DBFOT) (Annuity) basis for a pre-agreed concession period (the “Concession Period”): State

NH No.

Name of work

Jammu & NH-1 (Old Construction, Operation and Maintenance of Zozila Tunnel Kashmir NH-1D) including approaches on National Highway No. 1 (Srinagar Sonamarg - Gumri Road) in the State of J&K on Design, Build, Finance, Operate and Transfer (Annuity) basis

Length

Total Project Cost (TPC)

14.083 km long Single Rs. 9090 crore Tube bi-directional tunnel with parallel egress tunnel

Concession period 22 Years (including construction period of 7 years)

The MoRT&H has adopted a single stage two cover system (referred to as the “Bidding Process”) for selection of the Bidder for award of the Project. Under this process, the RFQ application as well as RFP Bid shall be invited at single stage under two covers. Eligibility and qualification of the Applicant will be first examined based on the details submitted under first cover (RFQ Application) with respect to eligibility and qualifications criteria prescribed in this RFQ document. The RFP Bid under the second cover shall be opened of only those Applicants whose RFQ Applications are responsive to eligibility and qualifications requirements as per RFQ document. The MoRT&H shall open on-line received RFP Bids after the evaluation of RFQ Applications (which shall be intimated separately), in the presence of the Bidders, who choose to attend.

2. The scope of work broadly includes Civil, Electrical and Mechanical works of Zozila Tunnel (Single tube bidirectional tunnel with parallel egress tunnel) including approaches (10.820 km Approach road, 60 m span Major Pmt Bridge and 700 m Snow Gallery) in between Appx km 94 to 119 on Srinagar Sonamarg Gumri Road (NH-1) in the state of J&K on Design, Build, Finance, Operate and Transfer (DBFOT) (Annuity) basis. 3. The Detailed RFQ and RFP documents can be viewed/downloaded from official portal of MORTH http://www.morth.nic.in or e-procurement portal of MORTH https://morth.eproc.in from 1st August 2015 up to 1st November 2015 (17:00 Hours). Last date of sale of RFQ and RFP documents is 1st November 2015 (upto 17:00 Hours). Due date for submission of Applications/Bids is on 2nd November 2015 up to 11:00 Hrs. Opening of Applications/Bids will be on 2nd November 2015, 11:30 Hrs. 4. To participate in bidding, Bidders have to pay a sum of Rs. 27,30,000 (9,10,000 + 18,20,000)/- (Rupees twenty seven lakh thirty thousand only) as the cost of RFQ and RFP process (non-refundable) to “Ministry of Road Transport & Highways” and Rs. 1,295/- (Rupees one thousand two hundred and ninety five only) towards tender processing fee (non-refundable) to “M/s C1 India Pvt. Ltd.” one-tender portal of MORTH https://morth.eproc.in through integrated online payment gateway enabled on E-Tender portal. 5. It is mandatory for all Bidders to have Class-III Digital Signature Certificate (in the name of person who will sign the Application/Bid) (with both Signing and Encryption Certificate) from any of the licensed certifying agency (“CAs”) [Applicants can see the list of licensed CAs from the link www.cca.gov.in] to participate in e-tendering of MoRT&H.

DSC should be in the name of the authorized signatory as authorized in Appendix II of RFQ and Appendix III of RFP. It should be in corporate capacity (that is in Applicant/Bidder capacity / in case of Consortium, in the Lead Member capacity, as applicable). The Applicant/Bidder shall submit document in support of the class III DSC.

The authorised signatory holding Power of Attorney shall only be the Digital Signatory. In case authorized signatory holding Power of Attorney and Digital Signatory are not the same, the Application/Bid shall be considered Non-Responsive.

6. Pre-bid meeting will be held on 7th September 2015 (11:00 Hrs) at Transport Bhawan, Parliament Street, New Delhi-110001. The Bidders who have paid the cost of RFQ and RFP process of Rs. 27,30,000 /- only shall be permitted to attend the meeting. 7. Complete bid document can be submitted at e-tendering portal of MORTH https://morth.eproc.in. For participating in the bidding through E-tendering mode, please refer the “Procedure Under E-Tendering (Instructions to Bidders)” attached as a separate document. Please note that MoRT&H reserves the right to accept/reject any or all applications/bids without assigning any reason therefor. 8. To participate in the E-Bid submission, it is mandatory for the Bidders to get their firm/ Consortium registered with e-tendering portal of MORTH https://morth. eproc.in and to have user identification number & password (collectively referred to as the “ID and Password”) which has to be obtained in Bidder’s own name by submitting an annual registration charges (non refundable) of Rs.2280/- (Rs. 2,000 plus service tax @ 14%) (Rupees two thousand two hundred eighty only) to M/s C1 India Pvt. Ltd. through online payment only. The registration obtained, as mentioned above shall be valid for one year from date of its issuance and shall subsequently be got renewed. 9. Amendments/Corrigendum for RFQ and RFP documents, if any, would be hosted on the e-tendering portal of MORTH https://morth.eproc.in.

Address for Communication:

Mr. Dheeraj,

Superintending Engineer (P-1), Room No. 144, Transport Bhawan, Ministry of Road Transport & Highways, No.1, Parliament Street, New Delhi - 110001 Phone: 011-2331 4328 Fax: 011-23710358 Email: dheeraj.rth@nic.in,

The Bridge and Structural Engineer

Volume 45 Number 2 June 2015  91


Ply-Krete Joint Systems PlySeal

Ply-Krete

Joint Width

Foam Seal

FRP Nosing

High Movement Ratings Zero Mentenance Waterproof

Joint design of Armorless Elastomeric Expansion Joint System

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Installing Armorless Elastomeric Expansion Joint System for Bridges

Quick replacement of old expansion joints of Bridges

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Consultancy against corrosion problem for right solution

Rehabilitation of damaged Concrete & Bridge structures

92  Volume 45

Number 2 June 2015

The Bridge and Structural Engineer


The Bridge and Structural Engineer

Volume 45 Number 2 June 2015â&#x20AC;&#x192; 93


FORTHCOMING EVENT OF ING-IABSE The Indian National Group of the International Association for Bridge and Structural Engineering (ING-IABSE) in association with Govt of Telangana, R&B is organising two day Workshop on “Code of Practice for Concrete Road Bridges: IRC:112” on 30th and 31st October 2015 at Hyderabad. Programme of the Workshop is as under:

PROGRAMME Friday, October 30, 2015 0830 – 0930 0930 – 1000 1000 – 1030

Registration Inauguration High-Tea

Session-1 1030 – 1100 1100 – 1130 1130 – 1215 1215 – 1300 1300 – 1330 1330 – 1415

– Prof. Mahesh Tandon – Prof. Mahesh Tandon – Mr. Alok Bhowmick – Prof. Mahesh Tandon

Overview & Scope Basis of Design Actions and their Combinations Material Properties and their Design Values Discussions for Session-1 Lunch

Session-2 1415 – 1500 1500 – 1530 1530 – 1600 1600 – 1630 1630 – 1715 1715 – 1745

Analysis ULS of Linear Elements for Bending and Axial Forces Tea Worked Example for Bridge Design with IRC 112 Serviceability Limit State Discussions for Session-2

– Mr. Vinay Gupta – Mr. Umesh Rajeshirke – Mr. Umesh Rajeshirke – Mr. Vinay Gupta

Saturday, October 31, 2015 Session-3 0930 – 1100 1100 – 1130 1130 – 1200 1200 – 1230 1230 – 1315 1315 – 1330 1330 – 1415

ULS of Shear, Punching Shear and Torsion Tea ULS of Induced Deformations ULS of Two and Three Dimensional Elements for Out of Plane and In–Plane Loading Effects Prestressing Systems Discussions for Session-3 Lunch

– Mr. JS Pahuja – Mr. VN Heggade – Mr. VN Heggade – Mr. Alok Bhowmick

Session-4 1415 – 1500 1500 – 1530 1530 – 1615 1615 – 1645 1645 – 1730

94  Volume 45

Durability and Deterioration of Concrete Structures Tea Detailing Requirements Including Ductility Detailing Discussions for Session-4 Valedictory Session

Number 2 June 2015

– Mr Vinay Gupta – Mr Alok Bhowmick

The Bridge and Structural Engineer


With Best Compliments From: DILIP BUILDCON LIMITED INFRASTRUCTURE & BEYOND

BHOPAL

Plot No. 5, Inside Govind Narayan Singh Gate, Chuna Bhatti, Kolar Road, Bhopal (M.P.) - 462 016 Phone: 0755 - 4029999 â&#x20AC;˘ Fax: 0755 - 4029998 Email: db@dilipbuildcon.co.in

The Bridge & Structural Engineer  

The Bridge & Structural Engineer Vol 45, Number 2, June 2015

The Bridge & Structural Engineer  

The Bridge & Structural Engineer Vol 45, Number 2, June 2015