The Bridge and Structural Engineer by IABSE

The Bridge & Structural Engineer Indian National Group of the International Association for Bridge and Structural Engineering ING - IABSE

Contents :

Volume 48, Number 1 : March 2018

Editorial ●

Editorial column from Chairman, Editorial Board : Mr. Alok Bhowmick

●

From the Desk of Guest Editor : Dr. Mike Schlaich

Aspect of Design and Construction of Six Lane Extradosed Bridge on River Ganga Inki Choi, P R Vital Veera, R Kasiviswanath

Aspect of Design and Construction of Extradosed Bridge Over Durgam Cheruvu Lake Inki Choi, Vinayagamoorthy. M, Udagiri Rajesh Kumar

Specificities of Railway Extradosed Bridges Serge Montens

The Xianshen River Bridge – A Single Pylon Extradosed Bridge with Very High Pier Crossing a Deep Gorge Zhengrong LI, Jun LEI

An Emerging Extradosed Cable Technology Thierry Duclos

VSL’s Experience with Extradosed Bridges in India Edo Vonk, Kailash Basita

Contents

Special Topic : Extradosed Bridges

Research Paper 1.

Comparative Study of Behaviour of Bamboo and Steel Reinforced Concrete Beams Under the Influence of Static and Fatigue Loading in Nonlinear Range Sulata Kayal, Pardeep Kumar, Sushil Kumar

Panorma ●

Office Bearers and Managing Committee - 2017

●

List of ING-IABSE Publications

The Bridge and Structural Engineer

Volume 48 │ Number 1 │ March, 2018

The Bridge & Structural Engineer ING - IABSE

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

June 2018 Issue of the Journal will be a Special Issue with focus on Geotechnics of Transportation Infrastructure Salient Topics to be covered are : 1.

Challenges in design and construction of Pavements and Embankments.

Design and construction of substructures for Highways, High speed Railway and Metro Projects.

Advances in Bridge Foundations, Waterways, Airfields and Pipeline transport geotechnic.

Slope stability, Landslides, Debris flows and Avalanches on hilly roads and remedial measures.

Sub-surface sensing, Investigation and Monitoring in transport geotechnics

Use of Geosynthetics and Non traditional materials in transport geotechnics.

Transport geotechnics in complex Underground Construction

Ground Improvement techniques for transport geoetchnics

Emerging trends in transport geotechnics– Unsaturated Soil Mechanics, Macro and Nano Technology, Climate Change and Sustainability

The Bridge & Structural Engineer ING - IABSE

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

September 2018 Issue of the Journal will be a Special Issue with focus on

Recent Structural Engineering Developments in Malaysia Salient Topics to be covered are :

Large scale rail infrastructure projects

Large scale traffic dispersal projects

Innovative structures and construction methods.

Volume 48 │ Number 1 │ March, 2018

The Bridge and Structural Engineer

March, 2018

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.

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. 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.

Editorial Board Chair: Alok Bhowmick, Managing Director, B&S Engineering Consultants Pvt. Ltd., Noida

Members: D.O. Tawade, Chairman, ING-IABSE & Member (Technical), NHAI I.K. Pandey, Secretary, ING-IABSE & Additional Director General (Road Development), Ministry of Road Transport & Highways, New Delhi Harshavardhan Subbarao, Chairman & MD, Construma Consultancy Pvt. Ltd., Mumbai V.N. Heggade, President (Engg), Gammon Engineers & Contractors Pvt. Ltd., Mumbai Umesh Rajeshirke, Managing Director, Spectrum Techno Consultants Pvt. Ltd., Mumbai Rajiv Ahuja, Consulting Engineer, Arch Consultancy Services Pvt. Ltd., Gurgaon Nirmalya Bandyopadhyay, Director, STUP Consultants Pvt. Ltd., Kolkata

Advisors: A.D. Narain, Former DG (RD) & Additional Secretary to the GOI A.K. Banerjee, Former Member (Tech) NHAI, New Delhi

Front Cover :

S.K. Puri, Former DG (RD) & Special Secretary to the GOI

Top : Elevation of Arrah–Chhapra Bridge or Veer Kunwar Singh Setu which is a four lane highway bridge across the Ganges river Connecting Arrahand Chhapra in Bhojpur and Saran districts of Bihar. This 4.35 Km long bridge is the longest known multi-span extradosed bridge in the world. The bridge was inaugurated on 11 June 2017. Bottom Left : Artistic impression of the New Narmada Bridge which is a 1.4 kilometre-long Extradosed Bridge, built over Narmada on NH-8 and constructed at Bharuch, India. This bridge was inaugurated by Indian Prime Minister Narendra Modi on March 7, 2017. Bottom Right : Photograph of Nivedita Setu (also called Second Vivekananda Setu) which is an Extradosed Bridge over Hooghly River in Kolkata, West Bengal. It runs parallel to and around 50 m downstream of the old Vivekananda Setu. The bridge is 29 m wide carrying 6 lanes of traffic and is 880 m long. The bridge is named after Sister Nivedita, the social worker-disciple of Swami Vivekananda. The bridge was opened to traffic in July 2007.

Prof Mahesh Tandon, Managing Director, Tandon Consultants Pvt. Ltd., New Delhi B.C. Roy, Advisor Transportation, AECOM & Chief Executive RUPL, New Delhi

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 Phone: 91+011+23388132 and 91+011+23386724 E-mail:

The Bridge & Structural Engineer, March 2018

Disclaimer :

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:

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

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All enquiries and correspondence in connection with advertising and the Equipments/Materials and Industry News Sections, should be addressed to Shri I.K. Pandey, Secretary, Indian National Group of the IABSE, IDA Building, Ground Floor, Jamnagar House, Shahjahan Road, New Delhi-110011.

The Bridge and Structural Engineer

Volume 48 │ Number 1 │ March, 2018

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Editorial column from Chairman, Editorial Board

This Journal has gained considerable popularity in the structural engineering circles over last five years. The journal is read and liked by many structural engineers who may not be members of ING-IABSE. It is heartening to observe that structural engineers are enquiring about the ‘Theme of next issue?’ at ING-IABSE secretariat as well as directly from the CEB. This clearly indicates the fact that the journal is serving the fraternity well. The editorial board is also delighted by the fact that many international experts are coming forward and contributing to the journal by writing articles, as well as taking the leading role as guest editor. This has further boosted the morale of editorial board members and at the same time it has helped us to improve the quality of this journal in leaps and bounds. While these developments are encouraging, there are some recent trends that are also cause for concern. Unfortunately the circulation of this journal did not increase over last 5 years in the same proportion as its readership. Hard copies of the journals are circulated to only members of ING-IABSE and non-member subscribers. These numbers have not grown over the years due to which, the journal circulation is restricted. This has a cascading effect on allocated resources for the journal. Our effort to make this journal as an indexed journal is not progressing at the expected speed essentially due to budget crunch. The only way forward is to increase membership of ING-IABSE and to look for more and more non-member subscriber to the journal. This special issue of the journal is dedicated to the theme of Extradosed Bridges. The conceptual design and the structural behaviour of an “Extradosed Bridge” lies in the transition between “Girder Bridge” and the “Cable-Stayed Bridge”. Extradosed Bridges are an emerging bridge technology, applicable to bridges in the 100 m to

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250 m span range. Though the concept of Extradosed Bridge dates back to beginning of 20th century, the large scale use of this type of bridges started only from the 1990s. The first such structure was the Odawara Blueway Bridge, which was designed and constructed in Japan (completed in 1994). We are very fortunate to receive consent of Prof. (Dr.) Mike Schlaich for guest editing this special issue of the journal. Prof. Mike Schlaich is no stranger to India. He has been involved with Indian Bridges since his childhood, along with his illustrious father, Prof. (Dr.) Jorg Schlaich. Presently he is involved in the design of famous Signature Bridge over river Yamuna at Delhi. He is at present the chair of Working Commission 3 (WC3) of International Association of Bridge &Structural Engineering. The mission of WC3 is to promote the rational use of structural concrete, alone or in combination with other materials, and to improve the analysis, design, execution and maintenance of concrete structures. Currently the commission is working on a state of the art report on Extradosed Bridges. There could not have been a better choice of Guest Editor for us for this special issue and we are thankful to him for agreeing to be the guest editor. I sincerely hope that the readers will find this issue informative, educative, insightful and thought provoking. Happy reading !

(Alok Bhowmick)

The Bridge and Structural Engineer

From the Desk of Guest Editor

In 2014 the members of Working Commission 3 of IABSE, namely Nirmalya Bandyopadhyay, Don Bergmann, Alok Bhowmick, Xu Dong, Thierry Duclos, Akio Kasuga, Serge Montens, Guido Morgenthal, José Romo, Chithabaram Sankaralingam, Robin Sham, Juan Sobrino, José Turmo, Edo Vonk, Zhao Liu, chaired by the writer of this text decided to gather and share their knowledge on cable-supported bridges to prepare a state-of-the-art-report on Extradosed Bridges. The report will be published this year and the activities of the group have also triggered the idea to dedicate this issue of the Indian National IABSE Group´s magazine to Extradosed Bridges. The text that follows is the slightly adjusted introduction to the IABSE report and shall serve here to prepare the reader for the seven very interesting articles by national and international experts on Extradosed Bridges compiled in this volume. Extradosed Bridges are a relatively new bridge form that offers a competitive alternate to more traditional forms such as arches and trusses used in the span range between 100 m and 250 m. Since this bridge type came up in the 1980s hundreds such bridges have been built all over the world but mainly in Japan. For spans up to 100 m concrete box girders are the most common choice but for spans above 100 m the height of the boxes above the piers becomes increasingly unacceptable for formal, constructability and cost reasons. For spans above 250 m, cable-stayed bridges are usually the most economical solution. Conceptual and structural design of this bridge type with bridge decks made of steel, concrete or a combination of

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the two materials are widely published. For spans below 250 m cable-stayed bridges often cannot fully exploit their strengths and lose their economic advantages. Here are four definitions of the extradosed bridge: ●

An extradosed bridge can be considered as a hybrid type of concept in the area of transition between girder bridges and cable stayed bridges. A large number of options are available to designers for configuring such a bridge to suit specific constraint for a particular project. The large number of extradosed bridges built over the last two decades is testament to that.

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Extradosed bridges are considered as “inbetween” girder bridges and cable stayed bridges. In a cable stayed bridge the loads (permanent as well as moving loads) are carried by the stay cables. In a girder bridge loads are carried by shear and flexure of the girder and internal prestressed or posttensioned cables which produce permanent and constant stresses that act opposite to those produced by self-weight and moving loads.

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With a stiff deck and shallow cables, an extradosed girder behaves like a prestressed concrete box girder although it has similarity in looks with cables stayed bridges. The shallowness of the cables ensures that the extradosed cables directly carry only a small portion of the moving load. This is the basic behavior of an extradosed bridge. However, the actual configuration of the bridge decides how close it behaves to a prestressed girder bridge. Volume 48 │ Number 2 │ March, 2018

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An extradosed bridge has its deck partially supported by a system of stays, which are connected to a pylon of small height. The pylon’s height measured above the bridge deck level is in between 7 to 13% of the main span (unlike to the classic cable-stayed bridge where the pylon has a height between 20 to 25% of the span length), thus making it easy to build. Having this geometrical arrangement, extradosed bridge stays have a small inclination with respect to the roadway and, therefore, provide less vertical stiffness to the deck compared to a cable-stayed bridge. Extradosed bridges are suitable for spans between 100-250 m depending on specific site constrains. For medium spans they compete with continuous pre-stressed concrete, steel girders, trusses or arches. For larger spans (more than 250 m) cable-stayed structures are likely more economical than extradosed bridges depending on site constrains.

thus contributing to the post-tensioning of the girder. For larger spans the forces increase and pose the risk of overloading the deck. While the cables can be tensioned so that they carry part of the permanent loads (the rest is carried to the supports by the deck itself), due to their strong inclination their stiffness is small therefore the cables are hardly activated by live loads. A deck of sufficient stiffness is therefore a necessary component of an extradosed bridge. ●

Deck stiffness: as a matter of fact most extradosed bridges built so far have very strong decks, when compared to cable-stayed bridges. They generally carry live loads primarily in bending. For decks of constant depth typical values are L/40 to L/45. The elegant Sunniberg Bridge by Christian Menn in Switzerland with its slender concrete slab deck is certainly an exception to this.

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Low masts: the shallow cables allow for very low and robust masts, which often are placed in the centre of the deck, because the already strong box girder decks are ready to also take torsion resulting from one-sided traffic loads.

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deck: often deck and masts are monolithically connected. This way the low mast can be stabilised more economically than through the cables. Such monolithic connection between mast and deck improves robustness and durability further. Some extradosed bridges are fully integral, i.e. deck and piers are also monolithically connected. For the spans discussed here, strains due to temperature and time-dependent effects can be handled, at least if the piers are high or longitudinally flexible or the soil is soft. Mid-span jacking can help to reduce the temperature and time dependent effects. This approach has been used successfully in numerous extradosed bridges.

●

No back stays: it is striking that, contrary to cable-stayed bridges, extradosed bridges rarely have backstays to connect the mast tops to the abutment. Cables are typically anchored in the deck short of the abutments thus relieving the cables from stresses due to

Comparison of the typical layout of a box-girder, an Extradosed and a cable-stayed bridg In the figure above the three bridges types mentioned and typical dimensions are shown. When comparing them, the characteristics of a typical extradosed bridge become apparent: ●

Shallow cables: they are often anchored closely spaced in groups which subdivide the main span length L into sections of 0.2L. Carrying the permanent loads of the bridge with such inclined cables leads to high cable forces. At the anchorages the horizontal components of these cable forces are introduced into the deck

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The Bridge and Structural Engineer

live load but exposing the deck and mast to bending which would otherwise typically be resisted by back stays in a cable stayed bridge. All these properties, which appear to be disadvantageous to the engineer of cable-stayed bridges, result in live loads basically carried by the deck and, therefore, very small stress changes in the cables for these loads. The cables of extradosed bridges are mainly there to carry permanent loads, i.e. to reduce bending moments in the deck due to these loads. Actually, in a typical extradosed bridge stress changes due to live loads are well below 5% of the breaking load of the cable. Usually parallel strands are used for extradosed bridges as they can be anchored easily and, depending on the manufacturer, even be replaced strand by strand. Because of the small stress changes in the cable, saddle systems which pass the cables through the mast top, become possible and desirable, especially if the mast is placed in the middle of the deck and little space is available.

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In this volume the reader will find three articles on Extradosed Bridges in India, two on large crossings over the Ganga river and one across the Durgan Cheruvu Lake. These bridges clearly illustrate that India today is a world leader in the field of long Extradosed Bridges. Another two papers provide valuable information on Extradosed Bridges for rail traffic and the Chinese context. Two views on the issue of cables for Extradosed bridges nicely complete this document. The readiness of the authors to prepare their contributions is most gratefully acknowledged. Finally, the guest editor also wants to express his sincere thanks to Mr. Alok Bhowmick for the invitation to contribute to the ING-IABSE.

(Mike Schlaich)

Volume 48 â&#x201D;&#x201A; Number 2 â&#x201D;&#x201A; March, 2018

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Brief Profile of Dr. Mike Schlaich Prof. Dr. sc. techn. Mike Schlaich, born 1960, received his civil engineering degree from the Federal Institute of Technology (ETH) Zurich in Switzerland. He is Managing Director of schlaich bergermann partner, Professor of Conceptual and Structural Design at the Technische Universität Berlin and certified German Proof Checking Engineer. With more than 25 years of experience, his executed projects extend from signature bridges, light-weight and long-span structures ranging from footbridges to stadium roofs, office and highrise buildings, tower structures and all the way to large solar thermal power plants. As expert for cable-supported bridges Mike Schlaich has an extensive experience as Project Director and coordinator of trans disciplinary and international design teams as well as experienced independent checker of complex bridge projects. Examples of his designs can be seen all over the world, from the Ting Kau cable-stayed bridge in Hong Kong to the new Yamuna cable-stayed bridge in New Delhi. He was also Independent Consultor of the Second Vivekananda Bridge in Kolkata, India, a multi-span extradosed bridge with a total length of 6,100 meters. All the projects reflect his belief that engineering should always strive to be elegant.

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He has been a member of IABSE since 1991 and is Chairman of WC-3 group, which is preparing a SED on Extradosed Bridges, that will be published this year. His projects have been awarded national and international prizes such as the German Bridge Award and Footbridge Award 2017 for a curved arch bridge in Rathenow near Berlin. In 2015 he has been awarded the Gold Medal by The Institution of Structural Engineers, London and is now a Fellow Member. He organized the 7th international Footbridge Conference, which took place in September 2017 in Berlin. A holistic approach to design and structural design as a conscious act is what Mike Schlaich is teaching at the TU Berlin where his research work includes extradosed bridges, bending and fatigue of strands for bridge cables, carbon fibre tension elements, movable and adaptive lightweight structures, as well as the use of new materials such as carbon and infra-lightweight concrete. Mike Schlaich believes in the joy of engineering and the engineer’s responsibility to contribute to “Baukultur”, the culture of building. His ambition and curiosity drive him to always look beyond the horizon and seek new opportunities, using a holistic approach to design wherever possible. Mike Schlaich is also the author of numerous publications including the book Footbridges, (Birkhäuser Verlag).

The Bridge and Structural Engineer

Aspect of Design and Construction of Six lane Extradosed Bridge on River Ganga

Inki Choi Head- Design Special Bridges, L&T Construction, Chennai, Tamilnadu, India inkichoi@lntecc.com

P R Vital Veera Manager- Design Special Bridges, L&T Construction, Chennai, Tamilnadu, India vital@lntecc.com

Post Graduated in structural engineering from Hanyang University, Seoul, South Korea in the year of 1999. 21 years’ experienced in bridge design. He has been involved several cable stayed projects such as Wando bridge, Incheon bridge in South Korea and Subiyah Causeway tender design for Kuwait. Also has experience in designing of iconic arch bridges.

Post Graduated in Geotechnical engineering from IIT Delhi in the year of 2007. He is having 11 years of experience in bridge design. He has good experience in Extradosed Bridges, Prestressed Concrete Bridges and Soil Structure Interaction. Experienced in Well Foundation designs for long span bridges over perennial rivers.

Summary The paper contains the design philosophy for six lane extradosed bridge of 9.759 km long as an iconic bridge project crossing immense river ganga in Patna, India. The bridge is going to be a linking express roadway between State capital of Bihar (Patna)and northern Bihar. Described the necessity of extradosed and well foundations concept in river Ganga for the bridge. Illustrated about the design development for extradosed bridge span configuration, planned construction sequence and conferred about formation of structural concepts for each component in the bridge and development of expansion joint between each typical block of the extradosed bridge.

1. Introduction Bihar State Road Development Corporation Limited under Government of Bihar has taken up steps for

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R Kasiviswanath Manager-Design EDRC, Special Bridges, L&T Construction, Chennai, Tamilnadu, India

kasi-viswanath@lntecc.com Post graduate in Structural engineering from IIT Delhi in the year 2009. He is having 8 years of experience in bridge design. He has good experience in Steel, Steel concrete composite Rail and Rail-cum Road bridges, Prestressed concrete bridges.

the development of infrastructure in the State of Bihar. As a part of this development, BSRDCL1 has proposed the “Construction of Green Field Six Lane Extradosed Cable Bridge over river Ganganear Kacchidargah on NH-30 to near Bidupurin DistrictVaishali on NH-103 at Patna in the State of Bihar under Engineering Procurement and Construction (EPC)”. With the total length of 22.76 km, the project mainly consists of construction of the extradosed main bridge section over River Ganga, ramp bridges, Viaduct bridge section and embankment portion. The objective is to improve transport connectivity for Patna, the state capital of Bihar, and the surrounding regions, in particular the northern Bihar across the Ganga River. The existing bridge (Mahatma Gandhi Setu) is restricted to two-lanes in deteriorating condition. The proposed New Ganga Bridge will

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provide an alternate crossing and become a critical link connecting Northern Bihar to Patna and Southern Bihar, ensuring access to basic services, increasing business opportunities, and promoting social cohesiveness. This project is a part of transport master plan for improving connectivity between northern and southern Bihar, and is integral to the overall road section improvements. The width requirements for the main bridge deck also produced in Table 1 as per client requirements and also has to satisfy the provisions as per Indian Standard “IRC:SP:87-2013[2] - Manual of Specifications and Standards for six Laning of Highways through Public Private Partnership”. Extradosed concept adopted for the entire 9.759 km as an Iconic bridge to Patna & Bihar in terms of Tourism and Business Development.

Fig. 1 : Site Location Project Corridor Stretch

Table 1 : Functional Requirement of the Bridge (6 Lanes with median) Description Carriageway Crash Barrier Footpath Shy distance + Paved shoulders Railing Kerb Median (Including 2 x 0.45 median crash barriers) Total Width of Bridge

2. Design 2.1 Design Concept The present live channels in the entire bridge length would be 2.7 km only, however the entire main bridge needs to be considered for navigational clearance as the River Ganga can be meandering in due course as per the past 100 years morphology data of River Ganga. The location has been treated as Nation Waterway 01 (NW01) as per IWAI (Inland Waterway Authority of India) hence expected barge or cargo movement in the river shall be high. Accordingly class VII water way barges considered as per IRC:06-2014 then the navigational requirements as 100 m for horizontal clearance and vertical clearance (below soffit of girder) of 10 m above HFLis provided. As shown in the Fig. 2, typical block has the span length of 450 m and defined between two expansion 2

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Dimensions 2 X 10.5 2 X 0.45 2 X 1.50 4 X 0.50 + 2 X 1.5 2 X 0.30

= 21.0 m = 0.90 m = 3.00 m = 5.00 m = 0.60 m

2 X 0.45 + 2.00

= 2.90 m 32.4 m

joints (Needle Beams Method) for smooth traffic from previous block to next block. The connection between superstructure and substructure is made monolithic toensurest ability during construction and to reduce life time maintenance cost. Stay cables are anchored in deck in the median. There are 7 stay cables on each side of pylon considered in Design as per Value Engineering. Due to stiffness of deck and less height of upper pylons, stress variation due to traffic load in stay cable is much lessor than conventional cable stayed bridge thus the concern about fatigue is mitigated. 2.1.1 Aesthetical aspect Extradosed bridgeis proposed in order to improve architectural view of bridge rather than conventional massive girder bridge. The Aesthetic appearance of Kachidaragh Bridge is shown in Fig. 3.

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Fig. 2 : Elevation of the Typical Block

Fig. 3 : Aesthetic Appearance of Kachidaragh Bridge

and SETRA Recommendations for stay-cable design, testing, and installation. Further construction stage analysis is carried out considering the erection sequence, time dependent material property and changes of boundary conditions. Also detailed FEM analysis using plate model has been carried out in order that the load transferring mechanism from the deck to cable is clarified. Analysis of the bridge model is done by using MIDAS Civil software.

2.1.2 Structural aspects

2.2.1 Geometry

Minimum concrete strength requirements for various components of structure are as follows as per design requirements satisfying IRC provisions. Young’s modulus of Elasticity for normal weight concrete is considered as per Table 6.5 of IRC:112-2011 & Coefficient of thermal expansion for normal concrete is considered as 1.2 x 10-5/ºC.

The Extradosed Main bridge consist of 22 blocks of two span continuous with span arrangement of 75 m + 2 X 150 m + 75 m with three pylons monolithic system and internal needle beam at expansion joints. Lower pylons are of heights 18.35 m (Typ.). Well foundations are adopted considering scour conditions of the river Ganga. Part of the Span load from superstructure is transferred to upper pylons by 7 number stay cables on each side of pylons.

Table 2 : Concrete Grade Element Minimum Grade Superstructure for Main bridge M55 Crash Barrier M40 Upper Pylon/ Lower pylon M55 Well foundation M35 Grade of reinforcement is Fe 500 & Fe 500 D confirming to IS:1786-2000. The modulus of elasticity (E) is equal to 200,000 MPa. Design speed adopted in the project as 100 kmph for Main Carriageway and 40 kmph for loops in the Junctions. 2.2 Analysis and Design The design of Kachidargah Bridge has been developed in accordance with IRC bridge design specifications

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2.2.2 Superstructure and pylon Depth of box girder is typically 4 m and it varies over a length of around 14.5 m near the pylons location. As Deck width of superstructure is 32.4 m and bridge is located in highly seismic area (Zone IV), in order to minimize the weight of the superstructure deck has been provided with internal and external struts along with Transverse PT for the top slab of the deck. Internal struts at cable anchorage zone is strengthened by internal tendons to transfer the stay force to webs. Typical Cross sectional view of precast segmental box girder with internal and external struts is shown in Fig. 4.

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maintenance cost. However in order to mitigate the long terms displacement due to creep/shrinkage, pre-set back of both cantilever tip by using push back before closing the key segment is adopted. 2.2.3 Well Foundation

Fig. 4 : Sectional Elevation of Girder

Double leaf reinforced concrete column is adopted for lower pylon which is connected to the girder as a monolithic connection. This proposed lower pylon shape has key merits as follows. It’s flexibility against thermal or long term displacement provide feasible solution to eliminate bearing. Obviously the issue of bearing maintenance is not a concern with this arrangement. Expansion joints are located every 450 m spacing typically and provide better comfort level to the drivers and also reduce the overall

Based on field and laboratory test results, sub-surface profile along the main bridge portion is generally consists of loose, dense and very dense sand were found in the order below the ground surface and hard and stiff clay layer was spread in upper part of ground at a few boring locations. The Governing parameter for designing of well foundation stability and design is scour. Scour is basically dependent on silt factor, well foundation depth needs to be decided preliminarily based on the scour depth to proceed for further design checks like Safe Bearing Capacity, Stability. Graphical representation of wetted average silt factors for every pier location were distributed as shown in Fig. 5.

Fig. 5 : Silt Factor Distribution for all Pier Locations and Design Silt Factor

The silt factor of 0.9 is finalized after detailed investigation over the entire pier locations checking on a conservative side with several discussions with approving authority.

sinking methods also adopted like air and water jetting. The following construction progress activity at site shown in Fig .7.

The Scour parameters of the bridge under consideration is as follows as per preliminary calculations and observations from available Hydrological and Geotechnical Reports.

High Flood Level (HFL)

50.00 m

Low Water Level (LWL)

41.00 m

Design Scour Level

03.50 m

Design Discharge

Maximum Scour Depth

106,839 cumecs 46.5 m

General arrangement of foundation and pylon is shown in Fig 6. Construction Methodology adopted for well foundation is self-sinking and specialized 4

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Fig. 6 : Scour Parameters and Well Foundation Details

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Fig. 7a : Rebar Arrangement

Fig. 7b : Concrete Pouring

Fig. 7c : Mucking & Sinking

Fig. 7d : Ready for Next Lift

The scour depth for the analysis of extradosed bridge is considered to cover all load cases mentioned in IRC:78-2014 covering Seismic and non-Seismic conditions under High Flood Condition. Also Analysis is done for Low water level condition as well. The above cases have been modelled using soil structure interaction with linear spring constants in the model by using software MIDAS Civil.

is that the number of end span pier is minimized and there is no additional temporary structure required for end span erection. However it has been reported that excessive deflection at joint in the middle of span mainly due to long term deflection inducing very poor comfort level to the driver as well as significant maintenance cost.

The depth of the bottom portion of well foundation from the scour level is called the grip length. In order to design the well foundation, the minimum grip length, the maximum depth of scour and bearing capacity of soil strata should be determined to define the depth of the well foundation. Stability checks have been performed as per IRC:45-1972 for working loads and ultimate limits. The well foundation needs to be embedded or sunk below the maximum scour level to a required depth in order that the resistance from the sides of well is able to withstand the lateral forces on the well before monsoon season strikes while working in live water channels to avoid high tilts and shifts during high flood. 2.2.4 Needle Beam Expansion joint at middle of span proposed as shown in Fig. 8. This type of joint is commonly used for balanced cantilever erection. Merit of this type joint

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Fig. 8 : Needle Beam Arrangement near EJ

In order to mitigate the concern about the expansion joint in the middle of span, structural beam as shown in the Fig. 9 is adopted. This beam once installed at final construction stage will restrain the deflection due to traffic loads and provide better comfort level to the driver as well. Volume 48 â&#x201D;&#x201A; Number 1 â&#x201D;&#x201A; March, 2018

Fig. 9 : Needle Beam Detail

2.2.5 Stay cable Stay cablesare planned to be tensioned form the inside the deck spaced at a distance 6 m typical and 1.5 m along the Pylon height. A single plane consisting of 7 x 2 = 14 Number of cables per pylonare located on the bridge centerline.

The Cable design is under process of review and the SLS, ULS verification and Resistance verification for rupture of extradosed cable is done using SETRA Recommendations (SETRA 2001)the results are as follows in Fig 10. In the Present design condition, ULS is governing the design of cable.

*ULS - Verification Fed - Actual Frd - Resistance

Fig. 10 : Stay Cable Verification

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Construction Methodology

The construction methodology of the typical block of main bridge is the precast segmental balanced cantilever method using derrick crane. The pier table is considered cast-in situ method. The precast

segment of the deck will be fabricated at facility yard first, transported to the site and erected by the derrick crane in balanced cantilever method. The construction scheme of the main bridge is as per the following.

1. Construction of well foundation (Sinking and Concreting for steining is staggered process. 2. Closure with Bottom Plug, 3. Filling material inside, 4. Well Cap concreting.

1. Fabrication of reinforcing bar and casting concrete for lower pylon. 2. Install the temporary support system for pier table. 3. Construction of pier table and pylon

1. Transport segments by trailer. 2. Install segment in due sequence by derrick crane. 3. Tensioning the cable and tendon in due sequence.

Lift key segment formwork by derrick crane. 2. Lift internal movement joint. 3. Construct key segment. 4. Install internal movement joint (Needle Beam)

1. Install the expansion joint. 2. Install wearing surface and road facilities

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The construction load considered in the analysis model is divided into two groups. One is for the stage by stage analysis and the other for stability check during construction. In general, construction loads are very varied and the IRC:6 do not define the characteristic values of the construction loads to be taken into account during erection. Thus, we referred Eurocode 1991-1-6 as for the construction loads.

4. Conclusion The Kachhidargah extradosed bridge would be longest extradosed bridge in the world once construction is completed having total length of 9.759 km having consecutive 67 pylons every 150 m spacing. 32.4 m wide deck with precast segmental erection is challenging in design and construction. Both internal and external strut as well as transverse tendon are adopted in decks in order to minimize the segment weight and overcome this challenging project. In order to minimize maintenance cost, double leaf column is adopted without bearing. Needle beam

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expansion joint in the middle of span also adopted in design in order to provide comport to the public. This project would be one of the Iconic Bridge in the world and land mark for Patna. This project is considered as 9.759 km not only to make aesthetic presence but also improve the connectivity between Patna, Island and Northern Bihar by providing high class transportation with express way speed of 100 kmph to the public and cargo. Going to set recordable Bench Mark in long span bridge construction industry and encouragement to develop further more over Mighty Rivers in India.

References 1.

Feasibility Report on Project Provided by Client Bihar State Road Development Corporation Limited (BSRDCL).

Manual of Specification and Standards for Six Laning of Highways through Public Private Partnership - IRC:SP:87-2013.

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Aspect of Design and Construction of Extradosed Bridge Over Durgam Cheruvu Lake

Vinayagamoorthy. M

Inki Choi Head- Design Special Bridges, L&T Construction, Chennai, Tamilnadu, India inkichoi@lntecc.com

Udagiri Rajesh Kumar

Manager- Design Special Bridges, L&T Construction, Chennai, Tamilnadu, India mvmdil@lntecc.com

Manager- Design Special Bridges, L&T Construction, Chennai, Tamilnadu, India rajeshudagiri@lntecc.com

Post Graduated in structural engineering from Government College of Technology, Coimbatore, Tamilnadu, India in the year of 2006. Perusing PhD. He has experience in prestressed concrete structures, Computational fluid dynamics. He has 14 years of experience which includes Research and consultancy. He has authored 4 technical papers

Post graduate in structural engineering form IIT Bombay in the year 2007. He is having 11 years of experience in design and last 6 years in Bridges. He has good experiences in balanced cantilever bridges and prestressed concrete bridges and dynamics of structures.

Summary Appearance related to a cable-stayed and extradosed bridges are similar. Moreover,comparing the extradosed bridge to a girder bridge of similar span, an extradosed bridge with shorter pylonsenables the designer to makedeck significantly shallower than a girder bridge. This arrangement results in the typical extradosed appearance of a fan of shallow-angle stay cables. Extradosed bridge, which may belong to cable-stayed bridge in some way, is an innovative type of bridge having similarity from traditional girder bridge and conventional cable-stayed bridge. It has lessor girder depth than conventional girder bridge and lessor height of pylon than cable stayed bridge. Accordingly it becomes competitive design solution in terms of cost and constructability where the span range becomes 100 m to 200 m , thus number of construction of extradosed bridges are increased in India.

The Bridge and Structural Engineer

In order to provide full clearance over the lake and considering the limited space in back span, the 233.85 m main span with 96 m back span extradosed bridge were planned and under construction in Hyderabad India. In general, extradosed bridge has symmetric shape and cable arrangement about the pylon considering the balanced cantilever erection method. However this bridge is planned asymmetric with technical challenges such as controlling the uplift at back span and pylon displacement. The characteristics of the Durgam Cheruvu extradosed bridge were introduced including design aspect as well as construction.

1. Introduction Durgam Cheruvu extradosed bridge consist of the comparably longer main span with asymmetric span arrangement. It has amain span length of 233.85 m and the ratio of side span to main span is 0.410 having considerably shorter back span. Volume 48 │ Number 1 │ March, 2018

Fig. 1 : Elevation and Span Arrangement

India’s first extradosed roadway bridge was built by Larsen & Toubro Ltd for the second Vivekananda Bridge toll corporation over river Hooghly, Kolkata. This bridge is 880 metres long, with a span of 110 metres. First extradosed bridge in state of Telangana will be constructed soon across Durgam Cherevu Lake in Hyderabad. Although few extradosed bridges are constructed in India,this bridge having 233.85 m main span will be the longest main span extradosed bridge in India. Greater Hyderabad Municipal Corporation, Hyderabad (GHMC) under the aegis of Municipal Administration & Urban Development Department

(M.A. & U.D) Government of Telangana (GOT) has taken up steps for the development of infrastructure in Hyderabad. As a part of this development,GHMC has proposed the “Construction of Cable Stayed Extradosed Bridge across Durgam Cheruvu Lake at Madhapur in Hyderabad under Engineering Procurement and Construction (EPC) Turnkey”. The location of the bridge is shown in Fig. 2. L&T Construction, Special Bridges division carried out the detailed design of the project. This paper was prepared to describe the summary of main issues in design and methodology adopted in the detailed design.

Fig. 2 : Site Location of the Durgam Cheruvu Bridge Project

The Total length of the road bridge project is 735.639 m. The project mainly consists of extradosed main span bridge portion, approach span viaduct portion and RE wall approaches. The purpose of

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the bridge is to improve transport connectivity from knowledge circle to jubilee hills. The functional requirements of the bridge are specified in Table 1.

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Table 1: Functional Requirement of the Bridge Description Carriageway

Crash Barrier Footpath Railing kerb Median (Including 2 x 0.45 median crash barriers) Sub Total

Dimensions 2 x 9.0 = 18.0 m (Extra Widening if required) 2 x 0.45 = 0.9 m 2 x 1.5 = 3.0 m 2 x 0.4 + 2 x 0.38 = 1.56 m 2.5 m 25.96 m (Extra Widening if required)

2. Design

ribs, enhance night view of the bridge over the lake. The asymmetric single plane stay cables sustained byiconic shape pylon is proposed together with architectural lighting on top of the pylon. And this iconic bridge will be a beautiful land mark over the Lake Durgam Cheruvu. b)

Structural aspects:

Minimum concrete strength requirements for various components of structure are given in Table 2 below, as per tender specifications/design requirements satisfying IRC provisions. Young’s modulus of Elasticity for normal weight concrete is considered as per Table 6.5 of IRC:112-2011 & Coefficient of thermal expansion for normal concrete is considered as 1.2 x 10-5/ºC. Table 2 : Material Properties & Design Parameters

2.1 Design Concept As shown in the Fig. 1, three span continuous PSC box girder Extradosed bridge with main span of 233.85 m and side span of 96m each is proposed. Because of comparably shorter back span to main span length and unbalanced dead load during the erection, balance cantilever erection is ruled out from the construction scheme. In addition, there is a possibility of getting uplift in anchor piers in permanent loading condition itself. Due to asymmetric span arrangement of this order, control of pylon bending moment during construction stage and uplift at end-pier in-service state are a challenging issues in design. To overcome above mentioned difficulties, it is decided to make the section in back span much stiffer than main span section. Consequently weight of back span increased and uplift reaction at end-pier is eliminated. Hence, construction of back span is proposed to erect on ground-supported staging and main span is erected by cantilever method. The stiffness (Moment of inertia) of back span to main span is in the ratio of 1.7. (Refer Figs. 6 & 7).

Element

Minimum Grade

Superstructure for Main bridge

M60

Crash Barrier

M40

Upper Pylon/ Lower pylon

M60

Foundation

M40

PCC

M15

Operating speed for Geometry Design

35 kmph

Design of structural Components

80 kmph

Grade of reinforcement is Fe 500 confirming to IS:1786-2000. The modulus of elasticity (E) is equal to 200,000 MPa. 2.2 Analysis and Design: The design of Durgam Cheruvu Bridge has been designed in accordance with IRC bridge design specifications and PTI recommendation for stay-cable design, testing, and installation.

The connection between superstructure and substructure is made monolithic to overcome stability issue easily during construction and to reduce life time maintenance cost. Stay cables are anchored in deck in the median as per Client’s requirement. There are 13 stay cables on each side of pylon.

Forward construction stage analysis is carried out considering the proposed erection sequence, time dependent material property and changes of boundary conditions. Also detailed FEM analysis using plate elements has been carried out in order that the load transferring mechanism from the deck to cable is clarified.

a) Geometry:

Aesthetical aspect:

Client has proposed fish belly shape box girder consisting of rib as a mandatory requirement in order to improve architectural view of bridge. Architectural LED lighting provided under the deck toward the

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The bridge is a three span continuous with span arrangement of 96 m + 233.85 m + 96 m with two pylons,supported over bearings at the end-pier and connected monolithically with pylons. Lower pylons

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are of different heights due to different ground levels. Height of lower pylon P1 is of 15.78 m and P2 is of 19.0 m. Open foundation is adopted. Client proposed single plane stay cables in the median. Part of the load from superstructure is sustained by 13 nos. stay cables on each side of pylon.

traffic direction in order to relieve and nullify the residual bending moment induced by unbalanced permanent loading at final construction stage. General arrangement of foundation and pylon is shown in Fig. 5.

Fig. 3 : Aesthetic Appearance of Durgam Cheruvu Bridge

Fig. 4 : Rock Sample from Bore Hole at Pylon P1

Depth of box girder is typically 4.819 m and it varies to 7.8 m over a length of around 20 m near the pylons.

Study on the connection between the deck and pylon has been carried out comparing the bearing connection and monolithic rigid connection which restrains the rotation of girder at pylon location. It is concluded that monolithic connection without bearing has merits of reducing the deflection of the main span as well as reducing the uplift force at end pier location. Although the moment induced at lower pylon induced by the thermal movement and creep/shrinkage is noticeable range, monolithic connection at pylon is adopted as connection option to pylon.

Pylon and Foundation:

Based on field and laboratory test results, sub-surface profile generally consists of completely weathered rock underlain by granite bedrock. Reference photo of sample bore hole at pylon location is shown in Fig. 4. Hence Open foundation with 17 m(W) x 18 m(L) is adopted for the pylon. Center of foundation is shifted to 2.0 m from the center of pylon along the

Fig. 5 : General Arrangement of Pylon and Foundation

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In addition, monolithic connection is also preferred as it provide maintenance free in terms of bearing replacement which would be potential risk unless sophisticated care given such as restricting the movement of girder during the replacement. In order to ensure the lower pylon has enough structural strength as well as capacity to accommodate the thermal displacement and creep shrinkage, detailed analysis on pylon has been carried. Based on the assessment on effect due to thermal movement and creep/shrinkage, it is concluded that the force induced by long term displacement has to be reduced otherwise difficult to find the suitable cross section satisfying the design requirement such as stress limit in long-term. Pre-adjustment of long term displacement is adopted by applying push back of 7 mm before installing the key segment. Finally it is concluded that 233 m main span with monolithic connection without bearing is feasible also reduce the uplift force at end pier. Size of lower pylon is varying in both longitudinal and transverse directions, along the height. Size of pylon at top is 4.5 m x 3.8 m and at bottom it is 7.0 m x 5.0 m.

Fig. 7 : Cross Section of Running Section Main Span

Fig. 8 : Section Properties of Running Section Main Span

Superstructure Superstructure is of segmentalpost-tensioned prestressed box girder with deck width 25.5 m. The soffit slab is provided with curvature of radius 10m. Concrete ribs are provided at middle of segments to support cantilever arms in transverse directions. Shape of the ribs are proposed to keep in harmony with the curvature of soffit slab. Curvature of soffit slab and ribs forms a fish belly shape. Main span section is provided with internal strut to support deck as well as to transfer the stay force to webs, whereas back span is a 3 cell box girder. Running sections of main span and back span are shown in Figs. 6 & 7 respectively. Section properties of the sameare shown in Figs. 8 & 9 respectively.

Fig. 6 : Cross Section of Running Section Back Span

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Fig. 9 : Section Properties of Running Section Back Span

Tendon Arrangement: Internal tendons with strands conforming to IS: 14268-1995, of class 2 low relaxation uncoated stress relieved, of 15.2 mm diameter are used. Tendons are provided to limit the stresses within the permissible limits as per specified in IRC:112. Jacking stress is limited to 0.765 fpu, as per tender requirements. As Main span is erected by free cantilever method, two (2) nos top tendons are provided for every segment to cater the top tension stresses. Mid span bottom continuity tendons are provided to cater the serviceability stresses due to SIDL, live load, temperature etc. Longitudinal Design: The global design of the main bridge deck has to comply with the IRC standard for the service and strength limit states. At the service limit state, fiber stresses must remain within permissible limits and at the strength limit Volume 48 â&#x201D;&#x201A; Number 1 â&#x201D;&#x201A; March, 2018

state the shear, torsion and flexural strength must be adequate.

crack width, no tensile stress is permitted in precast segmental construction, whereas in the cast in-situ portion the tensile stress is limited to permitted tensile stress as per IRC:112. Below figures (Figs. 12 & 13) shows the envelope of stresses for both top and bottom considering long term.

Fig. 10 : Section Showing Cantilever Tendons at S1

Serviceability limit state: The maximum compression in concrete during construction and service is limited to 0.48 fck. In order to satisfy the requirement of

Fig. 11 : Section Showing Mid Span Continuity Tendons at Key Segment

Fig. 12 : Girder Top Stress Considering Long Term (100 Years)

Fig. 13 : Girder Bottom Stress Considering Long Term (100 Years)

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Ultimate limit state: Figure below shows the ULS bending moment capacity (Both sagging and hogging)

of the superstructure including the demand from the critical loads.

Fig. 14 : ULS Bending Moment, Capacity vs Demand

Transverse Design: Results from global model with plate elements as shown in Fig. 15 are considered for design of box section in transverse direction. Struts are modelled as truss elements. Both ULS and SLS checks are carried for reinforcement design of box. Forces to design struts are taken from the same model. Fig. 16 shows the strut forces for one of the critical SLS combination. The design of diaphragms at end piers and pylon location has been done using “strut and tie” model. Finite element modelling has been carried out to investigate the flow of forces in

diaphragm in order to establish proper strut and tie model.

Fig. 15 : Global Plate Model

Fig. 16 : Strut Forces for SLS Combination

Fig. 17 : 3D Rendered view of Junction of Strut and Stay Blisters

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Design of Stay cable

A single plane consisting of 13 x 2 = 26 No cables per pier is located on the bridge centerline. Stay cables are arranged on Main span side at 7.0 m c/c, whereas on back span side first eight cables near to pylon are arranged at spacing of 7.0 m c/c and remaining stay cables are at 3.5 m c/c. Stressing end of stay cables is proposed at deck level. The maximum number of strands provided are 73. As stiffness of deck is high and less height of upper pylons, horizontal component of stay forces are higher compared to Volume 48 │ Number 1 │ March, 2018

vertical component. Stay cables transfer dead load of 20% to upper pylon. Stay cables are designed as per PTI recommendation for stay-cable design, testing, and installation (6th edition).Stay cables are designed for strength limit state as per clause 5.3 and cable loss case as per clause 5.5. In case of strength limit state, the strength factor to be considered varies from 0.65 to 0.75 (Fig 18) depending on forces in stay due to live load and wind loads, whereas for loss of cable case it is recommended as 0.95.

Fig. 21 : Foundation Covered with Sand Fill and Polythene Sheet

Fig. 18 : Strength Resistance Factor φ (Fig. 5.1of PTI Recommendations)

e) Durability: As considerable mass concrete of 1100 m3 planned to be poured continuously for pylon foundation, development of thermal cracks due to heat of hydration is investigated. Hence, heat of hydration analysis is carried for foundation to check the stresses due to loss of moisture. The selected cementitious content was 380 kg/cum. However, to reduce the hydration temperature the cement content is replaced by 50% of GGBS content as per clause 1715.2 of MORTH specifications. From analysis, it is found that peak temperature due to hydration is reaching to 62 degree at core and 42 degree at surface after 120 hours of concreting. To maintain the difference in temperature between core and surface less than 20 degrees, selfcuring concept by covering the foundation with polythene sheet and sand filling over the sheet is adopted (Fig. 22).

Fig. 19 : Temperature Contour showing at Mid Cross Section (120 Hours)

Fig. 20 : Foundation Model with Subsoil

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Fig. 22 : Completion of Concreting of Foundation P1

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3. Construction 3.1 Construction Methodology In general extradosed bridge is constructed using balanced cantilever erection although there is choice of either cast-in-situ or precast construction. It is concluded that controlling the unbalanced force during the erection is not feasible if it is erected by conventional balanced erection for this bridge. Hence construction of back span is planned by using full staging from the ground and main span will be constructed by cantilever erection with precast segment using derrick crane (Fig. 23) as described in Fig. 24.

Fig. 23 : 3D view of Derrick Crane

Fig. 24 : Construction Stages

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Currently foundations are constructed and pylon and piers are under construction. Pier table including lower pylon will be constructed soon and back span including variable depth of deck will be completed by mid of 2018. Precast segment will be fabricated in the casting yard near by the Durgam Cheruvu Lake and transferred to the site by barge. Maximum weight of segment will be 153 ton with 3.5 m length. Derrick crane designed and fabricated by L&T will be used for the erection of precast deck segment for the main span and bridge is planned to be open to the public in December 2018.

4. Conclusion Longest span extradosed bridge in India is under construction in Hyderabad. Although there are challenges in design such as unbalanced span arrangement, controlling uplift reaction at end pier, fulfilling the architectural requirement of fish belly shape box girder with reinforced concrete ribs, design of the bridge is completed successfully by L&T inhouse design department. The other challenge is ongoing in order to complete the construction and open the bridge by end of 2018.

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Longer span bridge construction has been challenged in India recently and the Durgam Cheruvu extradosed bridge will be one of the remarkable structure creating grand land mark in Hyderabad.

Reference 1.

Final Report “Durgam Cheruvu Extradosed Bridge” from L&T ECC, Special Bridges, EDRC, Chennai.

Design Report (2017), “Durgam Cheruvu Extradosed Bridge” Detailed Design of Main Bridge and Approach Viaduct Report.

IRC:6-2014 Standard Specifications and Code of Practice For Road Bridges, Section-II, Loads and Stresses (Revised Edition).

IRC:112-2011 Code of Practice for Concrete Road Bridges.

Recommendation for Stay Cable Design, Testing and Installation by Post Tensioning Institute, 6th Edition, 2012.

Cable Supported Bridges by Niels Gimsing, Published by John Wiley& Sons, 1983.

MORTH 5th Revision Specifications for Road and Bridge works.

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Specificities of railway Extradosed Bridges Serge Montens, born 1956, received his civil engineering degree from the ESTP, Paris, France. He worked for Sogelerg, Figg & Muller Engineers, Scetauroute, Jean Muller International, and is now scientific director of the Bridge Department of SYSTRA.

Serge MONTENS Civil Engineer, SYSTRA Paris, FR smontens@systra.com

Summary The paper describes the specificities of railway Extradosed Bridges, compared to highway Extradosed Bridges, and provides some examples of railway Extradosed Bridges designed by the author and built in India.

1. Introduction Extradosed Bridges have developed a lot during the last twenty years. Although most of the existing Extradosed Bridges carry roadways, some have been built for railways. The purpose of this paper is to explain the specificities of railway Extradosed Bridges, and to show some railway Extradosed Bridges built in India.

Requirements for Railway Bridges

2.1 Vertical Stiffness Railway bridges must have a sufficient vertical stiffness in order to fulfil comfort criteria and safety of railway traffic. This is generally expressed as a maximum allowable vertical deflection under live load. The ratio between the allowable deflection and the span is between 1/600 and 1/2500 depending on the train speed, the value of the span itself, and the static scheme concerning deck continuity. 2.2 Vertical Acceleration The vertical acceleration of railway decks must be checked under live load, in order to avoid ballast liquefaction in case of ballasted tracks, and to have a proper wheel-rail contact. The maximum vertical acceleration must be lower than 3.5 m/² for a ballasted track, and 5 m/s² for a slab track. This acceleration depends on the vertical and torsional vibration

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frequencies, on the deck stiffness, on the deck mass, on the deck damping, and on the train speed and axles spacing. 2.3 Fatigue On a railway bridge, the frequent live load value is generally close to the design live load value used for Service Limit State, which is not the case for a highway bridge. This means that the fatigue loading could govern the design of elements sensitive to fatigue. So it is important to check fatigue for a railway bridge.

3. Consequences for Railway Extradosed Bridges Design 3.1 Vertical Stiffness The vertical stiffness of an Extradosed Bridge depends mainly on the deck inertia and on the extradosed cables areas and angles. In order to get the necessary vertical stiffness it will be necessary, either to have a quite high vertical bending inertia for the deck, or high stiffness from the extradosed cables. For the Pragati Maidan bridge[1], on Delhi metro, the first Extradosed Bridge for LRT in India with a 93 m main span, we used a U shape deck because we wanted an architectural continuity between the Extradosed Bridge and the adjacent spans, made from U shape concrete deck simple spans, and because a deeper deck would have required to lift too much the longitudinal profile of the line, which crosses many existing railway lines. This U shape deck has a relatively low vertical bending inertia, although it is sufficient for typical 30m long simple spans. The allowable vertical deflection under live load was Volume 48 │ Number 1 │ March, 2018

small. In order to fulfil this criteria, it would have been necessary to provide extradosed cables with

very large areas compared to the axial forces applied to them.

Fig. 1 : Pragati Maidan Bridge Elevation

Fig. 2 : Pragati Maidan Bridge Cross Section

We found it was more economical to put the extradosed cables in some concrete walls. This type of bridge is sometimes called a cable panel bridge. The stiffness of the concrete wall can be taken into account for the analysis under operation conditions. But when live loads are applied to the deck, some tension stresses occur in the concrete walls, which could be higher than the concrete tension strength, and then a cracked wall would loose its stiffness. So, the extradosed cables have been tensioned at a lower value than the final value before concreting these walls, and then tensioned to their final permanent value once the walls had been concreted. This introduced a compression stress in the walls, such that there are no more residual tension stresses in the walls under live loads. The Moolchand bridge[2], also on Delhi metro, has a 65.5 m main span. As the typical spans, on both sides of the Extradosed Bridge, used a concrete box-girder

deck, we decided to use the same type of deck for the Extradosed Bridge. We designed the extradosed cables areas as usual, and when we calculated the vertical deck deflection under live load, we saw that it was allowable. Due to the higher inertia of the deck (and may be also to the smaller span than for Pragati Maidan bridge), it was not necessary to add concrete walls around the extradosed cables. However a small concrete wall was provided in order to protect the extradosed cables from train impact. For the Weh bridge [3], on Mumbai metro, with a 86 m main span, the deck has a U shape cross section, for architectural continuity with the adjacent spans. It was not possible to use a box-girder deck because of the clearance above the existing highway fly-over below the bridge, and because the longitudinal rail profile could not be lifted since this bridge was very near from a station.

Fig. 3 : Weh Bridge Cross Section

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So we used a pylon with increased height compared to the typical height of Extradosed Bridges pylons. The ratio between the pylon height and the span was 18.36/86 = 0.21. So this can be considered nearly asa cable-stayed bridge. The angle between

the extradosed cables and the deck is higher than for typical Extradosed Bridges, and then extradosed cables bring a higher vertical stiffness to the system. So, the strict deflection criteria were fulfilled, despite a relatively low deck bending inertia.

Fig. 4 : Weh Bridge Elevation

3.2 Vertical Acceleration For the three above examples, the vertical acceleration criteria under live load were fulfilled. They were not governing the design. For high speed rail bridges, this acceleration check could govern the design, because the high frequency excitation coming from the high speed train would excite the relatively high natural vertical vibration frequencies of such small or moderate spans. For longer extradosed spans, vertical acceleration would probably not govern the design because they have smaller natural vertical vibration frequencies.

the cables and the concrete. This was very important for the economy of the bridge, since prestressing anchors and much more cheaper than stay cables anchors, specially in India.

3.3 Extradosed Cables Fatigue

Fig. 6 : Moolchand bridge

Fig. 5 : Pragati Maidan Bridge

For the Pragati Maidan bridge, we calculated the extradosed cables stress variations under frequent live loads. Due to the presence of the concrete walls, they were relatively small. They were allowable for typical ordinary prestressing cables. This means that it was possible to use ordinary prestressing anchors for the extradosed cables. In a certain way this was quite logical since these cables were encased in concrete elements, like ordinary prestressing cables, so the forces variations under live load were spread between

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For the Moolchand bridge, the stress variations in the extradosed cables under frequent live loads were much higher, since there were no concrete walls around the cables. So we checked the fatigue according to the French Recommendations for stay cables [4], which has a chapter for extradosed cables. We used the Palmgren-Miner criteria to check the fatigue. The owner provided the number of expected trains per day, with a percentage for full loaded trains, and a percentage for partially loaded trains. The fatigue criteria for extradosed cables according to[4] was checked, so specific anchors for extradosed cables could have been used. But due to the fact that no specific anchors for extradosed cables were manufactured at that time, classical stay cable anchors were used. The minimum curvature radius provided

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in[4] was used for the saddles of the extradosed cables at the pylons.

Fig. 7 : Weh Bridge During Cantilever Construction

4. Conclusion The main specificities of railway Extradosed Bridges come from the following requirements for railway bridges: vertical stiffness, vertical acceleration, fatigue. The required vertical stiffness can come from concrete walls encasing the extradosed cables, or from the use of a stiff deck, or with specific layout of extradosed cables. The vertical acceleration generally does not govern the design for LRT extradosed bridges, due to the reduced train speed. The fatigue of extradosed cables must be checked carefully, in order to choose either conventional prestressing anchors or stay cables anchors for the the extradosed cables anchors.

References

Fig. 8 : Weh Bridge General View

For the Weh bridge, the consequence of the higher global vertical stiffness of the extradosed cables was that the stress variations under frequent live loadswere quite high, and then stay cablesanchors had to be used. This seems logical, as the bridge looks similar to a conventional cable-stayed bridge.

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Y. Gauthier, “Pragati Maidan Bridge – First Extradosed LRT Bridge in India” in Future Technology for Concrete Segmental Bridges, ASBI, San Francisco, 2008.

S. Montens, G. Mauris, P. Jain, M. Shahid, A. Mhedden, “Moolchand Extradosed Bridge for Delhi Metro”,IABSE Symposium, London, 2011.

T. Duclos, M. Ketfi, H. Amami, C. Aubazac, “A Signature Bridge in a Congested Urban Area”, IABSE Symposium, Seoul, 2012.

Stay cables- Recommendations of French Interministerial commission on prestressing, SETRA, 2002.

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The Xianshen River Bridge – A Single Pylon Extradosed Bridge with Very High Pier Crossing a Deep Gorge

Zhengrong LI Senior Engineer CCCC Highway Consultants Co., Ltd., Beijing, China lizhengrong@hpdi.com.cn

Jun LEI Doctor Candidate, Tongji University Shanghai, China 1310269@tongji.edu.cn

Zhengrong Li, born in 1964, received his civil engineering degree from Chongqing Jiaotong University.

Jun Lei, born in 1991, received his civil engineering degree from Tongji University.

Summary

1. Introduction

The Xianshen River Bridge is one of the many high bridges in the Jinji state highway system that connects the Jiyuan City, Henan Province and the Jincheng City, Shanxi Province. In order to keep the vertical alignment flat and smooth, mountain tunnels are built in this project. The Xianshen River Bridge, as a key part, connects the two longest tunnels in this region. This bridge is a single pylon extradosed bridge with very high pier and its span arrangement is 131 m + 136 m. This paper introduces the background of the project, the selection of bridge type, the design and the construction of the bridge, which can serve as a source of reference for similar projects in the future.

The Erenhot-Guangzhou (G55) Highway is an important branch of the National Highway System in China. It is a major north-south link in this system, which crosses six provinces of China, as shown in Fig. 1a. As a key structure in the part of G55 highway that connects the Jincheng City, Shanxi Province, and Jiyuan City, Henan Province, the construction of Xianshen River Bridge controls the schedule of the project. As shown in Fig. 1b, the bridge is located in mountainous area composed of deep gorges and crags. In order to keep the vertical alignment flat and smooth, mountain tunnels are used in the project and are constructed by blasting method. At the same time, many bridges are constructed to connect the tunnels in adjacent mountains. Among all these bridges, the Xianshen River Bridge is a very representative one.

Fig. 1 (1) : Location of the Xianshen River Bridge in G55 Highway (left figure) (2) Satellite Photograph for the Surroundings of the Xianshen River Bridge (right figure)

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In the following sections, this paper will introduce the location of the bridge, the principles for the selection of bridge type, the technical standards and the construction method for the Xianshen River Bridge.

bridge and the approach bridge. Hence, the design is mainly carried out using the aviation measurement data.

According to the project schedule, the total time period is 4 years, including the plan, survey, design and construction of the roads, bridges and tunnels that are 30 km in total.

Location of the bridge

The Xianshen River Bridge is located in the southern foot of the Taihang Mountains. The two tunnels that the bridge connects are located at two steep crags over 400 m high. A deep gorge is formed between the two crags, as shown in Fig. 2. The superstructure is located in the middle of the crags while the abutments of the bridge are placed at the entrance of the tunnels.

Fig. 2 : The Original Appearance of the Region

The Xianshen River is a seasonal river lying at the bottom of the gorge. The width of the gorge at the bottom is around 20 m. The river only exists during the rainy season in summer and is dry in the remaining seasons. The vicinity of the bridge is a nature reserve protecting the habitation for macaques. This is a remote and uninhabited region that is full of inaccessible crags. In addition, no road was built previously. The nearest village to the bridge is Luohe Village in Jincheng City. It is around 5km from this village to the bridge site by walking. According to the geological survey, the stratum at the bridge site is mainly composed of limestone and dolomitic limestone. At the entrance of the tunnels where the abutments are located, fissures are fully developed and there are many bare rocks. Any explosion or other relevant disturbance is likely to lead to collapse and rockfall, which is hazardous for the construction of the bridge. Due to the complexity of the topographical condition, a deep geological survey at the bridge site cannot be implemented unless the tunnels are finished. As a result, detailed topological and geological data are not available for the design of the abutments as well as the main

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Selection of bridge type

Due to the complicated topographical conditions, the construction period of the bridge is very tight. Hence, the primary principles for the selection of bridge type include: (1) the synchronization of the design and construction of both bridges and tunnels; (2) the feasibility of the construction of bridge; (3) the cost efficiency and (4) the minimum disturbance to the environment. In the preliminary design, several schemes are compared regarding the technical and economic aspects. The studied schemes include a single pylon extradosed bridge, a concrete filled steel tubular arch bridge and a single pylon cable-stayed steel-concrete composite girder. The single pylon extradosed bridge only requires a main pier erected from the bottom of the gorge. The geotechnical condition and the space at the bottom of the gorge is very suitable for the construction of high piers, which can ensure the quality and the construction feasibility as well as the least disturbance to the environment. On the other hand, the design of the arch and the cable-stayed schemes highly depends on the V-shaped gorge and the geological survey data, which are not available before the completion of the adjacent tunnels. Meanwhile, the construction of these types of bridges may interfere with the construction of tunnels. This is to say, the construction of bridge cannot start until the completion of the construction of tunnels. Apart from all these drawbacks, the technical uncertainties and high construction costs rule out the possibility of the arch bridge and the cable-stayed bridge. After these comparisons, the single pylon extradosed bridge turns out to be the most suitable scheme regarding all the principles mentioned above. Also, this bridge type can adapt to the potential design change (such as the change of the span arrangement) due to further detailed geological survey after the breakthrough of the tunnels. Besides, the construction method for this type of bridge is conventional and thus easy to handle. Finally, the single pylon extradosed bridge scheme is recommended.

The Bridge and Structural Engineer

4. Design of the single pylon extradosed bridge The final scheme for Xianshen River Bridge is a single pylon extradosed bridge with prestressed concrete girder. This type of structure is featured by the low height of its tower that is normally half the tower height of a cable-stayed bridge [1,2]. The stress variation in the cables of extradosed bridges is also much lower than that in cable-stayed bridges. The structural behavior of extradosed bridges lies between continuous girder bridges and cable-stayed bridges. In extradosed bridges, the stiffness contributed by the girders is significant compared with that contributed by the extradosed cables, such that the girder carries the majority of the live load [3,4]. The bridge serves a two-way four-lane traffic. The general configuration is showed in Fig. 3. The span arrangement for the main bridge is (131 + 136) m. The heights of the tower and pier are 53.0 m and 161.0 m, respectively. The girder is rigidly connected with the tower and the pier.

anchored. The girder adopts the longitudinal, vertical, horizontal prestressing techniques. According to the requirement of the seismic design, two dampers are installed at the bottom of both ends of the girder.

Fig 4. Typical section of the girder (unit: cm)

The height of the tower above the deck is 53.0 m. The section of the tower is uniform and is a solid rectangular with chamfer at each corner. The dimension of the section is 6.0 m by 3.5 m, as shown in Fig. 5.

Fig. 3 : General configuration

The cross section of the main girder is a single box with three cells having inclined webs, as shown in Fig. 4. The depth of the girder is 11.0 m over the pier and 4.0 m at the end of the beam. The variation of the depth of the girder follows a polynomial of the order 1.75. The width of the top slab is 26.0 m while the width of the bottom slabs varies from 10.0 m to 14.0 m. The overhanging slab is 5.0 m long. The thickness of the top slab is 30 cm while the thickness of the bottom slab increases from 30 cm (at midspan) to 150 cm (over the pier). According to the shear forces sustained by the girder, the thicknesses of the outermost webs are set as 50 cm, 60 cm and 80 cm in different segments. The thickness of the inner web is 120 cm in pier segments while it is 50 cm in other segments. Diaphragms are set in each segment where cables are

The Bridge and Structural Engineer

Fig. 5 : Cross section of the tower

The pier adopts an octagonal-shaped hollow section with 1.2 m thick wall. The dimension of the pier varies linearly along the vertical direction. The dimensions and the cross section of the pier are shown in Fig 6. To enhance the ability of the pier to resist the impact load from the floating stones during the flooding period, internal bracing beams are provided inside the pier within 21.9 m from the cap. Regarding the stability of the ultra-high hollow pier, 15 stiffening ring beams are provided every 9 m inside the pier along the vertical direction. In addition, stairs and lighting system are installed in the pylon and the pier for maintenance purpose.

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for the saddle to balance the unequal tension forces on both sides of cables during the construction and operation period.

Fig. 6 (a) : Elevation of the Pier;(b) Cross Section of the Pier (unit:m)

2×11 pairs of extradosed cables are used in the bridge, covering the range of 34.5 m to 114.5 m away from the tower. The cables are anchored every two segments on the girder. The transverse and longitudinal distances between cables are 1.5 m and 8.0 mon the girder, while they are 1.5 m and 1.2 m on the pylon. The OVM250-55 strands are used for the cable system. This system is featured by the usage of a specialized saddle, which is composed of 55 welded parallel steel guide tubes (Fig. 7a).The cables are unbonded in the saddle region while are bonded in the anti-sliding key region. Different from the traditional way of deviating the whole cable together in one pipe (Fig. 7b), each strand of the cable is individually deviated by one tube. This saddle type deviator avoids the issue of local stress concentration in the pylon that arises when the traditional saddle is used. It is capable of alleviating the stress concentration in pylon, distributing and transferring the load evenly into the tower.

Fig. 7 : (a) Detailing of the cable system (b) traditional antisliding key (c) the adopted anti-sliding key

The sliding of the extradosed cables is undesirable for its adverse effect on the overall structural behavior of extradosed bridges[5]. In the anti-sliding key region next to the saddle (Fig. 7a), the strands are well separated and the epoxy mortar grips each strand adequately (Fig. 7c). As a result, the interfaces between the mortar and all strands contribute evenly to the anti-sliding, which makes the anti-sliding force uniform, strong and thus reliable. This is beneficial 26

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At the same time, the cable adopts epoxy-coated prestressing steel strands with multiple protective layers. No grouting is required at the saddle section and there is no need to peel the PE of the unbonded prestressing tendons. All these measures solve the erosion issue of the traditional saddle type. A waterproof system is used to prevent the penetration of water into the cables. In addition,a specialized anchorage for the cable system with excellent anchoring and anti-fatigue performance is developed and applied, which provides a reliable solution for the anchorage of cables. The foundation of the main pier is located at the bottom of the gorge and is composed of 25 bored piles of the diameter 2.8 m. The pile cap used the C30 concrete and has the dimension of 30m×30m×6m. A 4 m high octagonal pedestal is constructed between the pile cap and the pier.

5. Construction Before the construction of the main structure, a concrete pavement construction access road, which is about 5km long from Luohe Village to the bridge site was built. In order to ensure the personnel safety at the construction site, a dam was built at the higher part of the river to block the water. In the meanwhile, a 500 m long spillway tunnel was used to divert and guide the river flow to the lower part of the river. In this way, the possibility of the construction area suffering from the flood is eliminated. During the construction of the bridges, the inspection and maintenance of the construction access road and the guarantee of the personnel safety is a continuous task. The foundation of the pier adopts group piles of large diameters. Due to the requirement of the blasting and the removal of debris at the entrance of the tunnel, the construction of the bridge was suspended for 5 months after the completion of the group piles. After the breakthrough of the tunnel and the removal of hazard debris created during the blast, the construction of the pile cap started. A self-climbing formwork system was used for the construction of the pylon and the pier (Fig. 8). The segments of the pylon and the pier are 4.5 m long. The construction time for each segment is 4 to 5 days. Due to the tight construction period, the construction was continued during winter by maintaining the required temperature for the curing of concrete.

The Bridge and Structural Engineer

The completed structure is shown in Fig. 10.

Fig. 10 : The completed structure

6. Conclusion

Fig. 8 : Construction of the pier by self-climbing formwork

The girder adopts the cast-in-situ balanced cantilever construction (Fig. 9). Due to the existence of extradosed cables, the erection of segments can use the existing cables, which is more convenient than the balanced cantilever construction of continuous girders[2].Apart from the pier segments, there are 30 pairs of segments. The pier segments are 13.0 m long while the other segments are 4.0 m long. The time period for finishing one segment is around 7 to 9 days. A 4.4 meter long segment and a 7.4 m long segment are cast on the falsework at the starting side and the other side of the bridge, respectively. A 2 m long closure segment is cast to connect the cantilever and the end of the bridge.

Xianshen River Bridge is the key engineering project connecting the Jincheng City, Shanxi Province and Jiyuan City, Henan Province. The height of its pier rank first in extra-dosed bridges in Asia. This paper introduces the background of the project, the principles for the selection of bridge type, the technical details and the construction of the bridge. It can provide reference for structures of similar type in the future. The bridge is completed in October 2008 and is open to traffic in December 2008. Until now, it is the longest single pylon extradosed bridge in China. Its superior aesthetic style integrates with the rocky landscape seamlessly and perfectly, forming a spectacular view in this region.

7. References 1. 2.

5. Fig. 9 (1) : Pier segment (left figure) (2) balanced cantilever construction (right figure)

The Bridge and Structural Engineer

Kasuga, A. “Extradosed bridges in Japan.” Structural Concrete, Vol.7 No.3, 2006, pp. 91-103. Chen, C., & Xiao, R., “Method of cable/beam live-load ratio for distinguishing extradosed cable-stayed bridges”. Journal of Tongji University,Vol.35, No.6, 2007,pp. 724-727 Chen, C., Zhou, H., & Xiao, R., “Recent research advancement of extradosed Cable-Stayed Bridge”. World Bridges, No.1, 2006, pp.70-73. Collings D., Gonzalez A.S. “Extradosed and cable-stayed bridges, exploring the boundaries”, Proceedings of the Institution of Civil Engineers Bridge Engineering, Vol.166, No.4, 2013, pp. 231-239. Liu Z., Meng S., Zang H., Zhang Y., “Model test and design investigation on saddle deviator zone of extradosed bridge”, Journal of Southeast University, Vol. 37, No.2, 2007, pp. 291-295.

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An Emerging Extradosed Cable Technology Thierry Duclos born 1956, received his civil engineering degree from the National Public Work School (ENTPE): Civil engineer specialized in structures and bridges, diploma 1979, France. He worked for several Consultants Companies as Thales EC, Arcadis, Systra and now for a contractor VCGP in France. For more than 20 years he is lecturer at the National School for Bridges and Roads (ENPC) of Paris East University for bridges projects courses.

Thierry DUCLOS Civil Engineer VINCI Construction Grands Projets Thierry.duclos@vini-constuction.com

Summary Issued from the working commission 3 of IABSE, this paper deals with the state of the art related to the extradosed cable technology. After a period of attraction for the cable stayed bridges, the extradosed bridges give to the owners’ possibilities to project signature bridges or specific design in particular cases. But these bridges don’t support the same constraints as cable stayed bridges. In generality the extradosed bridges support less live loads stress range in a stiffer structure. So the constraints are not as high as for cable stay bridges and the technology developed for these specific bridges never suits the extradosed bridges. Savings can be done. Through the given main goals to integrate in a design of an extradosed cable directions of evolution are proposed. These considerations should help the designer to define a durable technology and an economic design. A state of the technology is given through different main requirements found in the stay cable technology. A quick recall of the technology used for transition in mast is completed by a synthetic table and a view of the proposed technology by manufacturers. Main points are listed to help the designer and owners to make the best choice. Keywords: extradosed cables, standards, durability, fire, waterproofing, corrosion, saddle, anchorage, strands, barriers.

1. Introduction The Extradosed Bridges has been becoming one of the most famous concept used in the design of bridges at the moment. Avoiding the issues of dynamic responses and fatigue met in the cable stayed bridges, 28

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they offer to the owners the economical possibility of creating Signature Bridges with lower maintenance constraints than cables stayed bridges, bowstrings or others arch structures. The deck materials are concrete, steel or composite. Through the background of the Extradosed Bridges design, the domain progresses on several issues:   



Technology of cables Structural design robustness, impact analysis Parametric excitations: traffic effect, wind effects… Typology according to structural materials

Nevertheless Extradosed Bridges bring to the owners’ possibility to cross rivers or others obstacles in limiting the environmental impacts less of piles and also less materials in comparison with classical structures. The owners take into account in their choices characteristics of the concept in terms of durability which gather life time, maintenance strategy, protection against major event like fire and protection against corrosion for the steel parts and so on. This paper will deal with technology of cables which has a significant weight in the maintenance strategy.

Standards in consideration

This technology is not defined yet but through the feedback of this concept two types of technology are used. The first is coming from the cable stayed bridges through typical standards established at the beginning of this century as:



SETRA - CIP Stay Cable Recommendations 2002[1],

The Bridge and Structural Engineer

  

PTI Recommendations 6th edition, 2012 [2]. FIB Bulletin 30, 2005[3] JPCEA 2000 the Japanese Recommendations: Specifications for Design and Construction of Cable-stayed Bridges and Extradosed Bridges [4].

The maintenance strategy and the life time will permit to define also the constraints of serviceability according to the extradosed cable technology. Accessibility and replace ability are the first concerns for the designer. Dispositions against corrosion of the system will be fixed accordingly.

These publications concern specifically stay cables technologies. They gave a lot of specifications due to numerous lessons learned. Concerning extradosed cables several information are given but there are too limited to help the designer. Plus technologies and materials have evolved and these publications may be dated.

Life time must be calibrated according to the level of environmental aggressiveness. Several information are given in the aforementioned standards. These life times must be adjusted in accordance with the owners’ objectives, the strategy maintenance and the results of the risk analysis, but also in regard to the kind of technology eventually chosen. (see [1], [2], {3], [4])

Already the concerned working groups intend to provide up dated version as for the FIB bulletin 30, or for the PTI 7th version now in progress. So specifications for extradosed bridges will be provided with for these standards.

During the last 20 years large progress have been done in cables technologies to avoid corrosion of the system and insure a water-tightness. The three parts, anchorages, free length, and crossing mast zone have been treated with the concept of barriers against corrosion applied on different parts of the cable technology. For example the strands can offer internal and external barriers completed by wax or grease in interface between these barriers. Something equivalent is proposed at the scale of the bundle of strands. The internal barrier is generally applied on the wires of strand with a metallic coating on each wire. The external barrier for a strand is a PE sheathing forming a watertight outer casing. For a bundle of strands the external barrier could be a stay pipe from high density polyethylene (HDPE) or steel stay pipes. The retained technology for a given project can be a mix of these guidelines with redundant dispositions against corrosion.

Durability, a main goal

Waiting for a specific publication, the engineers have been continuing to design extradosed bridges trying to propose durable and low priced structures to the owners. The feedback of this technology show us at the moment that stay cable technology remains a referenced solution. But providers and engineers try to mix this technology with the external prestressing technology in order to integrate the right demand of strength of the extradosed bridges. These bridges offer stiffer decks and masts than cable stayed bridges. The masts are shorter with a slenderness ratio around 0,15 instead 0,25 for the cable stayed bridges. The maximum span length is around 200 to 250 m. So dynamic and fatigue loads have less impact due to lighter stress range than in a stay cable bridge. So the conceptual design of extradosed cables must integrate these facts. The durability is one of the main goal the designer must integrate in his conceptual analysis. Behind this generic term we find specific terms as life time, waterproofing, fire stability, fatigue, impact of dynamic loads, construction tolerances and so one. So defining this kind of technology must begin with a risks analysis, a work to do with the owner and his advisers. Through this analysis, parameters will be defined as life time, maintenance strategy, fire risks but also the fatigue risks with the level of traffic or others vibrating actions.

The Bridge and Structural Engineer

For the fire stability, the designer must take into account that extradosed cables are closer to the deck than for a cable stayed bridge and their free length are more exposed to an accidental event as a truck fire. Two main projects in France ([5] and [6]) took into account this constraint. The engineers and cables providers created a specific protection layer between the bundle of strands and the external pipe. These conceptions were tested following PTI 6th edition. Boundaries conditions were fixed according to the owners’ specifications and the French standards. Solutions were found without a perceptible effect on the cables size. PTI specifications could be adjusted as suggested by W. Brand in [7]. As the length of extradosed cables are short, they are less sensitive than stay cables to the fatigue effects. Local bending moments are less significant due to the shorter length and the less sagging so the impact at

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the wedge anchors is significantly lower. But if any, dispositions can be defined or taken from the stay cable technology to control the stress bending at this location. At the moment fatigue test are calibrated for stay cable. But it is showed in [8] that tests must be defined accordingly to the real using conditions. So for cable with strands bundle covered by a cement grout interface these tests did not yet exist and should be defined. Dynamic loadings can impact the life time of the cables. Under the road transit loads this risk is low and generally less significant than for a cable stayed bridge. But under rail transit loads, the alternative impact of loads depending of speed and weight of axle loads the stress range can become significant with an impact on the using time of cables. Technical answers can be given in using the solutions developed for the stay cables. But the solution must be appropriate to the specific impact of vibration and the used technology of the extradosed bridge. Tests can be necessary. The use of external prestressing technology with a cement grouted interface for example involves a specific concern to insure the integrity of grout over time.

to the extradosed cables constraints with certainly decrease of the costs.

A state of technology â&#x20AC;&#x201C; few aspects

4.1 Transition at mast If durability is the main scope to define the extradosed cable technology, specific devices coming from cable stayed bridge design are often used in the extradosed bridges for the transition of the mast head. There are two main design: a first which cuts the continuity of cables and a second keeping this continuity with specific devices. The first is classically used in the cable stayed bridges. Stay cables are anchored in the masts or out of the masts thanks to steel shapes. It involves a thicker mast and accessibility dispositions for maintenance. (see type A and B) The second has been declined in different technology summarized below in the Table 1 (type C and D) which integrate the main system types for transition in mast:

Durability depends also on the construction stages due to the tolerances which can create internal and unfavorable stress range. Tolerances must be carefully specified for construction and must be considered as part of the design of the cable stays. Errors in construction or fabrication which result in bending of the cables can contribute to fatigue due to live load stresses increase and fretting at the anchorages or deviation points. The positioning of saddles or anchorages in mast and the deck anchorages must be done with care, in consideration of the specified tolerances in order to control bending and fatigue effects in thestays But for the moment these progress and defined technologies have enhanced essentially the stay cable technology which was developed to take into account a durability heeding of fatigue, dynamic effects and specific behavior of stay cable. This costly technology should be adapted to integrate the decrease of constraints with obviously savings. Certain dispositions coming from the external prestressing technology could be mix with the stay cable technology in order to prioritize the relevant elements in regard to the savings and the durability. As we see progress are expected for extradosed cable and existing technologies are going to be adapted 30

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Table 1: type of anchorages in mast with the courtesy of IABSE WC3 members

Saddles are limited to type C and D. This technology has a positive effect on the aspect with a slender and elegant mast. And no access in mast is necessary. 4.2 Saddles type C In type C an anchor link is disposed internally in the concrete. This link is generally a steel element using steel welded plates or steel tubes with external noses on which the cable is anchored. After the hardening of concrete, the tension of stay cables creates an inward pressure. The steel element works in tension. (see Fig. 1).

The Bridge and Structural Engineer

The system needs external anchorages and a specific design of noses to assure at first an intermediate anchor for the cable and at end its replaceability.

This technology was already used in Japan on the Nonthaburi Bridge in Thailand. 4.3 Saddles type D These saddles have been used in several extradosed bridges. They allow the continuity of tensile elements without gap and limit the sizes of the pylons. They provide the anchorage of the cable while avoiding their slippage. There is a saddle per cable. The advantages of this continuity is the savings of anchorages and the absence of tension elements buried in concrete. With the continuity of the cable the dispositions for watertightness are facilitated. So the respect of all durability points aforementioned gives to the saddle system a high level of strength for axial or bending fatigue behavior.

Fig. 1: Sketch of internal steel link at mast (with the courtesy of Alok Bhowmick)

But a technology with curved steel elements connected to the concrete has been developed working as composite system and as a saddle. The Extradosed cable is not continuous and anchored on each side of an external nose section. Lateral openings can be outfitted to allow an easy exchange of single strands or even whole cable. (Fig. 2).

Fig. 2: DYNA® Link Curved Anchor Box with two DYNA Grip® Stay Cable Anchorages

This technology have structural advantages due to the strength of mast concrete. The transfer of loads is easily done with the shear studs without bond stresses. There is no mechanical wear due to strand deviation. Possibilities are given to mix size of cables at the same link and to adapt the links in order to integrate different inclinations at each side. No tests are necessary for the design justifications fully in accordance with conventional steel construction standards. Dispositions taken to protect the anchorages can induce difficulties of accessibility for maintenance. Unbalanced dispositions have an impact on the pylon efforts. So the designer must take it into account to adjust the slenderness of the mast. The Bridge and Structural Engineer

Two type of saddles are proposed, the monotube saddle and the multitube saddle. The monotube saddle was the first technology proposed two decades ago. The system was close to the deviator for the external prestressing technology. In case of eventual damages in the cables, it was necessary to change all the cable. More,due to the stress range between the sides of the masts it appeared that the level of friction had to be reliable. So to respond to these issues, the providers developed then the concept of multitube saddle to control better the friction coefficient and to make the replacement of cable elements easier and less costly. These last developments in saddles have led to systems where the protection of the strands is maintained with multiple nested barriers similar to modern stay system. This saddle systems permit there placement of each strand without changing the cable. Cable suppliers provide various proprietary multitube saddle with different shapes and characteristics. Few systems have been developed. In some of them the anchorage of strands that have locally been unsheathed is ensured by the friction of the strands in each groove. In this case a final injection is needed within each tube to ensure the corrosion protection of strands. In others a specific technology of sheathed strand avoids the sliding of the wires in the HPDE sheath which its keeps its integrity without interruption. The saddle with recesses allowing to pass the strands through is filled with a UHPF concrete. Each strand is replaceable. These saddles are buried in the pylon concrete. Below two saddles examples of these systems Figs. 3 and 4. Volume 48 │ Number 1 │ March, 2018

The stay cable assembly impacts cycle times for cantilever construction.

In some systems the removal of the PE sheathings of each strand is needed in order to obtain the transfer of differential forces into the pylon by friction. Dispositions against corrosion must be applied to obtain again a continuous protection.

The saddle structures need generally qualification tests: fatigue, friction coefficient which consume time.

The exchange of individual strands is sometimes not possible or only feasible through a full cable replacement as for monotube saddle.

Inspection of the saddle is possible from the outside of the pylon only. However, strand inspection in the deviation area for type D can only be conducted by replacements of individual strands or of the complete cable.

Installation and tensioning of each cable in C system create alternative efforts in the mast possibly inducing cracks and are more aggressive than in systems A or B where the mast is less narrow. (the same for the last system)



Fig. 3:3 D CAD View (with the courtesy of VSL)



These comments are elements to be taken into account in the analysis to compare each solution if there are. 4.5 Friction Fig. 4: Current section of the saddle (with the courtesy of Freyssinet)

A medium position has been also developed between the type C and type D. The stay cable is not continuous through the mast and it is completed with a short cable anchored on each side of the mast. The saddle is a multi-tube saddle system. The system is buried in the pylon concrete. It mixes post tensioning system with the stay cable system. So sliding is not possible. The system offers a continuity in the strength of compression in the pylon. Each strand is replaceable. A specific coupling anchorage devices must be installed to ensure the continuity of the tensile element.

The prevention of slippages is a fundamental design requirement for saddles with mono-tube or multitubes. All loads or events must be taken into account. The friction coefficient analysis should be set at SLS and ULS. In the EC3-1-11 [12], this analysis is limited to ULS considerations but this can be extended to ELS in adding specific requirements. This standard proposes the formula below with a partial factor for friction resistance γM, fr = 1,65 reducing the value of the friction coefficient.

4.4 Choice of a saddle To expect from future developments new types of cables, the technologies exposed in C and D type impose to take care of several specificities in order to be able to choose. They are given below:



The appearance of each system needs to be studied with the owner to assess the rendering. Volume 48 │ Number 1 │ March, 2018

Where μ is the coefficient of friction, α the angle in radians of the cable passing through the saddle, γM,fr is the partial factor for friction (recommended value is 1,65), FEd1 or FEd2 the design values of maximum and minimum forces respectively on each side of saddle.

The Bridge and Structural Engineer

The next PTI publication should be close to this approach. The cable supplier will provide friction values for saddle system giving different deviation angles. The designer will fix the required geometry of the cables to achieve the required friction value for the structure. It is typical to require testing to demonstrate the friction value for the saddle system. The reader is invited to refer to the revisions of both PTI and fib bulletin 30 to come for the proper assessment and qualifications of friction coefficients 4.6 Saddle fatigue According to fib bulletin 30 [2] the objective of the saddle fatigue test is to confirm the performance of the saddle in terms of fretting fatigue at the entrance into saddle.

So this solution is not far from the technology used on Odawara Blueway Bridge as exposed by A. Kasuga in [11].

5. Conclusions The technology for extradosed cables has evolved in recent years as the extradosed bridge form has become more prevalent. Similar to cable stays it is expected that the systems for extradosed cables will continue to develop, resulting in effective systems for anchorages, saddles and cable that provide the required performance of extradosed stays in the best possible manner giving to the designer durable and adapted system. Acknowledgements: This article is part of the works of the Working Commission 3 of IABSE. The technical direction of several cable suppliers gave their advices.

Test have been related in several articles [8], [9],[10]. They focused at first on stress range for fatigue and after on specific issues coming from the analysis of the contact of the cable at the entrance of the saddle. More recently the last tests showed that the requirements of the standards needed to be adapted to take into account the current conditions which take place during the design life of the cable to obtain valuable test.

6. References 1.

Cable Stays: Recommendations of French Interministerial Commission on Prestressing. Bagneux Cedex: SETRA, 2002.

As aforementioned, the updated recommendations should bring clarifications.

D. Jungwirth, Acceptance of Stay Cable Systems using Prestressing Steels: Recommendation. Lausanne: Internat. Federation for Structural Concrete, 2005.

DC45.1-12: Recommendations for Stay-Cable Design, Testing, and Installation, 2012.

4.7 Evolution of saddle

As aforementioned the external prestressing technology was evoked and several suppliers of stay cables technology try to propose a technology using a part of it and ensuring all the goals discussed previously regarding durability.

Japan Prestressed Concrete Engineering, Japanese Recommendations (170621 Ref. 4, 93, 104): Specifications for Design and Construction of Prestressed Concrete Cable-Stayed Bridges and Extradosed Bridges.

The grout seems to offer a weak barrier against water ingress. The effort must be provided by the outer pipe and the high quality of the links at connection to the saddle or to the anchorages.

A. Grison and J. Tonello, “Le Pont de St Rémy de Maurienne sur l’A 43, un Parti Original : la Précontrainte Extradossée,” Revue Ouvrages d’art, vol. 27, no. Juillet 1997, 1997.

P. Charlon and J. Baumgartner, “Protection au feu des Câbles Extradossés et des Haubans (Fire Protection of Curved Cables and Câble Stays),” Revue Travaux, vol. 843, pp. 30–36, 2007.

W. Brand and A. Märzluft, “Fire Protection For Stay Cables,” in fib Congress, Mumbai, 2014, Mumbai, 2014.

S. Mohareb, A. Goldack, M. Schlaich, and S. Walbridge, “Effect of Relative Displacement of Strands Bent over Circular Saddles on

Some current developments involves the use of external post-tensioning tendons with an external anchorage allowing the replaceability of cable. To assure the replacement of the cable which is grouted, the saddle is not buried in the concrete but dragged and dropped in an outer steel box which is buried in the concrete. The water-tightness must be assured at the junctions of the free length at the anchorage zone and at the saddle. All the system is grouted. In this technology, the stress range due to fatigue loading should be lower than Δσ=80 MPa referring to [1].

The Bridge and Structural Engineer

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Fatigue Life under Fretting Conditions,” in fib Symposium, Mumbai, 2017, Maastricht, 2017.

Saddle System,” in fib Congress, Washington, 2010, Washington, 2010.

S. Mohareb, A. Goldack, and M. Schlaich, “Simple Model for Contact Stress of Strands Bent Over Circular Saddles,” Report (Iabse Congress), Vol. 18, No. 1, to be Published, 2016.

11. A. Kasuga, “Extradosed Bridges in Japan,” in Future Technology for Concrete Segmental Bridges, San Francisco, 2008.

10. M. Schlaich, A. Abdalsamad, and R. Annan, “Fatigue and Tensile Tests of a 55 Strands

Volume 48 │ Number 1 │ March, 2018

12. Eurocode 3: Design of Steel Structures Part 1-11: Design of Structures with Tension Components, EN 1993-1-11, 00.2010.

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VSL’s Experience with Extradosed Bridges in India

Edo VONK Engineering Manager VSL International Singapore edo.vonk@vsl.com

Kailash BASITA Managing Director VSL India Pvt Ltd Chennai, India kailash.basita@vsl.com

Edo Vonk, born in 1973, received his Civil Engineering degree from the Univ. of Technology Delft, Netherlands. He has extensive experience in bridge engineering, working for both consultants and contractors.

Kailash Basita, born in 1978, obtained his Civil Engineering degree in Gujarat and post-graduation in Construction Management from CEPT, India. Hehas extensive experience in bridge construction, especially in segmental and cable-stayed bridges.

Summary

1. Introduction

VSL has been active in India since 2000, and has been involved in a large number of extradosed bridge projects. VSL has several state-of-the-art solutions available for application on this kind of structures. This paper gives an overview of the bridges that have been constructed and that are currently planned to be constructed by VSL India.

This paper will discuss the main characteristics of cables used in extradosed bridges and how VSL technology can be applied on these structures. It will then give an overview of the extradosed bridges that have been constructed in India and of the bridges that have recently been awarded to VSL.

Fig. 1 : Veer-Kunwar Singh Setu Bridge, Bihar (Arrah-Chhapra Cable-Stayed Bridge)

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Volume 48 │ Number 1 │ March, 2018

Cable technology for extradosed bridges

2.1 Behaviour of extradosed bridges and tendons To give some background on the characteristics of extradosed tendons, a simplified definition of extradosed bridges is given below. The behaviour of cable-stayed bridges is dominated by the stays and the majority of the loads are carried by the stays. The stress variations due to live loads, introducing fatigue, are significant in stay cables and can easily reach values of 100 MPa and more. On the other end of the spectrum are the girder bridges, with only tendons inside the girder. The behaviour is dominated by the girder bending capacity. The prestressing tendons carry only a very limited part of the live loads and the stress variations are small. Extradosed bridges are situated between the girder bridge and the cablestayed bridges and thus also for the characteristics of the live load stress variations and the fatigue sensitivity. Since the super structure of extradosed bridges tends to be relative stiff, the deformations of the deck and consequently the angular rotations of the tendons at the anchorages are small. Another aspect that needs to be mentioned is the fixity of the tendons at the pylon. External tendons applied in girder bridges are often considered fully unbonded and intend to need relatively little force increase in the tendons for superstructure live loads. Therefore, external tendons are usually not anchored at the deviators. Similarly, for extradosed bridges, saddles in pylons could be like deviators with relatively little friction or bond in the saddle. 2.2 Performance characteristics of extradosed tendons Similar to the definition of extradosed bridges, one can define extradosed tendons as tendons that are situated somewhere between external tendons and stay cables. Important characteristics for the performance of the tendons are the maximum stress in the tendon, the stress range under fatigue live loads, the angular rotations at the anchorages and the corrosion protection. A summary of typical values are given in Table 1. For a typical corrosion protection for the most aggressive environment (called category C5 in accordance with ISO12944), an external tendon for a girder bridge would be uncoated strands inside an HDPE external pipe with a cementitious grout filler. For a cable-stayed bridge, zinc coated strands with an individual PE sheating and filler would be

Volume 48 â&#x201D;&#x201A; Number 1 â&#x201D;&#x201A; March, 2018

applied inside an external HDPE pipe. For extradosed tendons,we could easily follow the solution for the cable stay bridges. For less aggressive environments, uncoated strands inside an external HDPE pipe with a cementitious grout filler could also be considered acceptable. Table 1: Summary of tendon characteristics Type of Cable

Maximum Initial Stress in Tendon

Fatigue Stress Range (Mpa)

Angular Rotation at anchorage (mrad)

Stay cable

45 - 50% GUTS

160 - 200

External tendon

70 - 80% GUTS

Extradosed tendon

60 - 65% GUTS

120 - 140

2.3 VSL technology for extradosed tendons Based on the above explanations, VSL can offer three different solutions: 1.

VSL SSI 2000 Stay Cable System

VSL Monostrand Tendon System

VSL External Multistrand PT System

VSL SSI 2000 System The VSL SSI 2000 System is typically used for stay cables and can thus also be employed for extradosed tendons. It would satisfy or even exceed the requirements for mechanical and durability performance. Reference is made to the VSL brochure for details and dimensions. For cable stay bridges, often a guide deviator is applied to guide the stay cable transversally to avoid the forces and bending stresses of the angular deviations to reach the anchor. For extradosed bridges, a tension ring can instead be applied to form a compact bundle in the free length. Saddles for the SSI 2000 System consist of a steel box filled with ultra-high-performance concrete and featuring V-shaped guide voids for each individual strand. The VSL Saddle allows unrivalled single strand installation, inspection and replacement. Strands can be individually stressed and de-stressed. Injecting the guide tubes with a special, polymerised and bonded flexible gel filler prevents any ingress of oxygen, hence eliminating the risk of fretting corrosion. The result is a saddle with fully replaceable strands that achieves the same fatigue performance as standard SSI 2000 anchorages.

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VSL Monostrand System This system uses uncoated 7-wire strand, individually greased and PE sheathed, encased in a HDPE external pipe and filled with a high performance cementitious grout. Saddles for such tendons consist of a general saddle pipe in which the bundle of monostrands is installed. The sheathing of the strands is continuous through the saddle. The free length and saddles are filled with a high performance grout. Replacement of the extradosed tendon is possible through the provision of a double pipe through the pylon. 3.1 Mumbai Metro WEH Bridge, Mumbai Table 2: Description of Mumbai Metro WEH Bridge Bridge parameters

Description

VSL External Multistrand PT System This system uses uncoated bare strands encased in a HDPE external pipe and filled with a high performance cementitious grout. Saddles for this system are similar to the solution of the monostrand, but the tendons are considered to be fully bonded inside the saddle.

Completed bridges in India

This section presents three bridge projects that have been completed by VSL in India. For each bridge, the basic data is given in form of a Table, together with a few Photos. 3.2 Moolchand Crossing, Delhi Table 3: Description of Moolchand Crossing Bridge Bridge parameters

Description

Bridge length

175 m

Bridge length

167.5 m

Span articulation

2 x 23 + 83 + 2 x 23

Stay arrangement

Saddles at pylon

Stay arrangement

Saddles at pylon

No.of stays per pylon

5 pairs per pylon

Total stays

8 (2 pylons)

Total stays

20 (2 pylons)

Strand coatings

Galvanised, sheathed and waxed

Stay cable size

6-31, 6-37

Anchorage type

Adjustable with ring nut

Total no. of stays

Stay cable size

6-31

Anchorage type

Adjustable with ringnut

Total no. of anchorages

Span articulation

51 + 61.5 + 51m

Strand tonnage

35t

Strand tonnage

15t

Year of completion

2013

Year of completion

2010

Fig. 2 : Mumbai Metro WEH Bridge

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Fig. 3 : Moolchand Crossing, Delhi

Fig. 4 : Ganga Bridge between Arrah and Chhapra

3.3 Ganga Bridge between Arrah and Chhapra, Bihar

4.1 Re-construction of B.P. Mandal extradosed bridge, Bihar

Table 4 : Description of Arrah-Chhapra Bridge

Table 5 : Description of B.P. Mandal extradosed bridge

Bridge parameters Bridge length Stay arrangement No. of stays per pylon Total stays Strand coatings

Description 1.9 km Saddles at pylon 5 per pylon 80 (16 pylons) Non-galvanised, sheathed and waxed Stay cable size 6-61 Anchorage type Fixed without ring nut Total no. of saddles/ 80/160 anchorages Span articulation 60 + 15 x 120 + 60 m Strand tonnage 417t Year of completion 2017

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Description

Bridge length

290 m

Span articulation

75 + 140 + 75

Pylon shape/ Total number H-Shaped/4 number Stay arrangement

Link units at pylon

No. of stays per pylon

7 pairs per pylon

Total stays

28 (7/ pylon)

Strand coatings

Non-galvanised, sheathed and waxed

Stay cable size

6-19, 6-22, 6-31, 6-37

Total no. of anchorages

112

Erection method

Balanced cantilever construction

Expected year of completion

2018

Extradosed bridges under construction

VSL has been awarded three new extradosed bridges that are under construction as of January 2018.

Bridge parameters

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Fig. 5(a) :

Fig. 5(b) :

Fig. 5(c) :

Fig. 5 : Re-Construction of B.P Mandal Extradosed Bridge (a) Elevation (b) Cross-Section of the Bridge (c) 3D view of Pylon with Link Units

4.2 Hatnia-Doania extradosed Bridge, West Bengal Table 6 : Description of Hatania-Doania extradosed bridge Bridge parameters Bridge length Span articulation Pylon shape/Number Stay arrangement No. of stays per pylon

Description 340 m 85 + 170 + 85 H-Shaped/2 number Link units at pylon 5 pairs per pylon

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Bridge parameters Total stays Strand coatings Stay cable size Total no. of anchorages Erection method Expected year of completion

Description 20 (5/ Pylon) Non-galvanised, sheathed and waxed 6-31, 6-37 80 Balanced cantilever construction 2018

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Fig. 6(a) :

Fig. 6(b) :

Fig. 6(c) :

Fig. 6 : Hatania-Doania Extradosed Bridge (a) Elevation (b) Cross-Section of the Bridge (c) 3D view of Pylon with Link Units

4.3 Ganga cable-stayed bridgebetween Sultanganjand Aguwani Ghat, Bihar Table 7 : Description of Ganga cable-stayedbridge between Sultanganj and Aguwani Ghat Bridge Parameters Bridge length

Span articulation

Total no. of pylons

Description 1562.5 m 125 + 2x 162.5 + 125 (Unit 1) 125 + 2 x 162.5 + 125 (Unit 2) 125 + 1 x 162.5 + 125 (Unit 3) 8

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Bridge Parameters Stay arrangement No. of stays per pylon

Description Saddles at pylon 7 stays on all pylons except for P10 with 9 stays Total stays 58 stays Strand coatings Galvanised, sheathed and waxed Stay cable size 6-31, 6-43, 6-55, 6-61, 6-73 & 6-85 Total no. of anchorages 116 Erection method Balanced cantilever construction Total strand quantity 540MT

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Fig. 7(a) :

Fig. 7(b) :

Fig. 7(c) :

Fig .7 : Ganga Stay Cable Bridge between Sultanganj and Aguwani Ghat (a) Elevation (b) Typical Cross section view of Stay Cable Pylon (c) Typical Cross Section view of extradosed Pylon

5. Conclusions The appropriate choice of type of tendon technology depends mainly on the behaviour of the structure and the environmental conditions. A range of VSL’s systems are available which satisfy the typically

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specified performance requirements for extradosed tendons. These systems have successfully been applied in several bridge projects in India which also have been presented in this paper.

Volume 48 │ Number 1 │ March, 2018

COMPARATIVE STUDY OF BEHAVIOUR OF BAMBOO AND STEEL REINFORCED CONCRETE BEAMS UNDER THE INFLUENCE OF STATIC AND FATIGUE LOADING IN NONLINEAR RANGE

Sulata Kayal Former Deputy Director CSIR-CRRI, New Delhi New Delhi, India sunil_kayal@yahoo.com

Pardeep Kumar Sr. Technical Officer CSIR- CRRI, New Delhi New Delhi, India pardeep.crri@nic.in

Sushil Kumar Former Prinicpal. Technical Officer CSIR- CRRI, New Delhi New Delhi, India sushilarora57@gmail.com

Sulata Kayal received her Bachelor of Technology in Civil Engineeringand Masters Degree from I.I.T, KGP,India and Ph. D from I.I.T, Delhi. She was former Deputy Director of CSIR-CRRI, New Delhi.

Pardeep Kumar received his Three year Diploma in Civil Engineering from Thapar Polytechnic Patiala, A.M.I.E. in Civil Engineering from Institution of Engineer (India), Kolkatta and Master Degree in Structures from Delhi Technical University, Delhi. He is currently as Senior Technical Officer in Bridge Engineering and Structures Division, CSIRCRRI, New Delhi.

Sushil Kumar received his Three year Diploma in Civil Engineering from K.L.Polytecnic, Roorkee and A.M.I.E. in Civil Engineering from Institution of Engineer (India), Kolkatta He wasformer Principal Technical Officer in Bridge Engineering and Structures Division, CSIRCRRI, New Delhi.

Abstract Numerous investigations have been carried out for evaluation of performance of bamboo reinforced concrete beams. No study has been reported on the comparative evaluation of performance of bamboo reinforced concrete beams vis-à-vis steel reinforced concrete beams. The present study has made an attempt in this direction. It presents comparative study of behavior of both types of reinforcements under static and fatigue loading. To fulfil this objective four pairs of steel reinforced concrete and bamboo reinforced concrete beams have been tested to destruction. Three pairs are subjected to static bending and one pair is subjected to fatigue loading. These pair of beams is designed for the same moment of resistance corresponding to balanced state of failure of the cross-section using working stress method. Various 42

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comparisons related to strength and serviceability has been outlined in the paper. Under fatigue loading fatigue strength and fatigue life have been compared Keywords: - Bamboo Reinforced, Static and Fatigue Loading, Non-Linear Range

1. Introduction Problems encountered with the commonly used construction material like steel are rise in cost; degradation of the non-renewable material, the pollution of the environment due to industrial process etc. However, with sustainability as a key issue in the last decades the environmental load of building materials has also became a more important criterion. The building industry, directly or indirectly causing a considerable part of the annual environmental damage, can take up the responsibility The Bridge and Structural Engineer

to contribute to sustainable development by finding more environmentally benign ways of construction and building. One of the directions for solution is to look for new material applications: recycling and reuse, sustainable production of products, or use of renewable resources. Attention has to be given to materials such as vegetable fibres including bamboo, jute and glass, wastes from industry, mining and agricultural products engineering applications to central environmental degradation and to minimize cost out of these various alternatives, the advantages of bamboo reinforcement are its low cost, its good mechanical strength (~370 N/mm2 intension), its replenishable nature, and the lack of requirement of expensive and artificial forms of energy for its manufacture. Due to the above advantageous characteristics of bamboo, studies have been made on bamboo as structural material and reinforcement in concrete. Although the tensile strength of bamboo is reasonably comparable to steel reinforcement, it is weak in compression, modulus of elasticity, shear strength and bond. Besides the deficiency in mechanical properties, it suffers from several durability related problems. Therefore, all its merits as mentioned above can be fully exploited only when these drawbacks are overcome by intensive program of research. These knowledge base generated through research would pave the way of making national and international standard on this subject, which would open the way for engineers and designers to the world of bamboo. Review of literature reveals that research efforts on bamboo reinforcement during 1950 to 1980 are mostly concentrated on determination of physical and mechanical properties of bamboo of different countries and devising of various remedial measures to overcome the durability related problems. Various investigators throughout the world have put efforts in determination of physical and mechanical properties of local bamboos. Ibrahim et al (2001) and Seethalakshmi et al (1998) conducted a survey of literature reporting the values of these properties of bamboo culm of different countries. The ranges of properties of bamboo culms are as follows: Density (kN/m2) 5.6 – 9.0; Moisture content (5) 9.7 – 12.5; Tensile strength (N/mm2) 110.0 – 331.0 (inter nodal), 79 – 117 (nodal); Modulus of elasticity (kN/mm2) 1.6 – 21.0; Shear strength (N/mm2) 5.5 – 95.7; Bond strength (N/mm2) 0.24 – 1.47; compressive strength (N/mm2) 24.0 – 100.0. Comparing the highest value

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in the range of various properties of bamboo culm with that of Indian mild steel reinforcement, it can be seen that steel is 8 times heavier than bamboo. Tensile strength of bamboo is almost comparable with that of steel but compressive strength is ¼th of that of steel. Shear strength of bamboo is almost half of that of steel. Modulus of elasticity intension is almost one tenth of that of steel. Although the bond strength is shown to be half of that of steel, it is an impossible task to achieve this bond strength in real structure. Apart from these limitations of mechanical properties bamboo-culms suffer from various limitations related to durability. Durability includes moisture susceptibility, lack of natural bond with concrete and vulnerability to attack by insects such as borers, termites and rot fungus. Numerous investigators have dealt with these durability related problems. Durability related to moisture susceptibility and consequent problems of lack of natural bond with concrete and its remedial measures have been reported in details in references (Subramanyan, 1984), (Geymer and Cox, 1970), (Ghavami, 1995), (Ghavami, 2005), (Siddhpura et al, 2013). Various prophylactic treatments like varnish, resin-alcohol mixture, paraffin-resin-linseed oil mixture, epoxy or polyester resin, molten sulphur (at 1450C) have been reported in these references. Siddhpuraet at (2013) have reported an interesting study on the effectiveness of three types of prophylactic treatments such as araldite, epoxy resin and coal tar. They have used these coatings on splint bamboo and conducted flexural test on these bamboo reinforced beams by applying two point loading and plotted load vs. midpoint deflection curve till collapse of the beam. Treating, the cross-section of these BRC beams as a homogenous one, the modulus of elasticity of the equivalent sections were calculated using the deflection corresponding to load at linear elastic point of the load-deflection curve. They concluded that coal tat treated reinforced beam have 37.45% and 25.16% higher modulus of elasticity than that of beam elements having reinforcement as bamboo treated with Araldite and Epoxy Resin respectively. BRC Beams (Bamboo Reinforced Concrete) Beams The possible use of bamboo as tensile reinforcement in flexural members such as beams and slabs has long been recognised. During 1950 to till date numerous investigators, namely, Glenn (1950), Narayana and Rehman (1962), U.S. Naval Civil Engineering

Volume 48 │ Number 1 │ March, 2018

Laboratory (1966, 2000), Cox and Geymer (1969), Cox and Geymer (1970), Kankam, Ben-George and Perry (1988), Ghavami (1995), Kankam and Odum – Ewuakye (1999), Ghavami (2005), Khare(2005), Jung (2006), Lima et al ( 2008), Terai and Minami (2011), Terai and Minami (2012), Sevalia et al (2013), Siddhpura et al (2013), Sethia et al (2014), Karthik (2017) and many others throughout the world have contributed to the evaluation of the feasibility of the use of bamboo as a potential reinforcement in concrete structural members. As mentioned above, a review of the above references also reveals that these references primarily dealt with two aspects: one is the exploring the feasibility of the use of various species of bamboo, which are locally available in different parts of the world, in the concrete matrix; and the other one is devising various measures to overcome the various drawbacks of bamboo to be used as potential reinforcement. Out of all the references mentioned above, Sevalia et at (2013) and Siddhpura et al (2013) merit special mention, Sevalia et al have experimentally determined, equivalent young’s modulus of elasticity of singly reinforced and doubly reinforced composite cross section of bamboo and concrete. They have concluded that modulus of elasticity of the doubly reinforced beam is more than twice of modulus of elasticity of the singly reinforced beam. The work of siddhpura et al (2013) has been described above. Lima et al (2008) have established the durability of bamboo in the alkaline medium of cement concrete. Karthik et al (2017) have explored the possibility of replacing the river sand with manufactured sand and the cement by 25% of combination of admixtures such as fly ash and Ground granulated blast furnace slag and they concluded that it improves the mechanical properties of BRC. The various prophylactic treatment devised by various investigators throughout the world using locally available water proofing agents of different countries are systematically listed in reference (Subramanyan, 1984). All the works reported so far are restricted to evaluation of performance under static loading. No work has been reported on the fatigue strength of BRC beams. Besides this, no systematic study has been carried out on the comparative performance of beams reinforced with these two types of reinforcement-bamboo and steel except Mark et al (2011) and Adewuyi et al

Volume 48 │ Number 1 │ March, 2018

(2015). Mark et al (2011) presented a comparative study using different stirrup materials and concluded that steel stirrups are the most economical. Adewuyiet al (2015) presented a comparative studies of twisted steel rebars, Nigerian bamboo and rattan as reinforcing bars in concrete. The tensile and flexural characteristics were compared. They have concluded that the experimental ultimate failure loads of bamboo and rattan RC beams were 51% and 21% respectively of the conventional steel RC beams. The main objective of the present study is comparative evaluation of various performances of steel reinforced beams with bamboo reinforced beams. Such comparative investigation on steel and bamboo under similar geometric and loading conditions would determine the relative capacities and thereby establish the limits to the applicability of the natural rebars as against the steel reinforcement. A review of literature on application of bamboo reinforcement in various structures reveals that various species of bamboo have been successfully used either in full or in part replacement of structural steel in different types of structures. These are mostly temporary structures (Arocksamy et al 1976, Ramaswamy 1977). It is well known that apart from other strong mechanical strength, bamboo has good ductility , which is very important for earthquake. Therefore, it is necessary to establish data bank consisting of comparative evaluation of bamboo reinforcement with respect to steel in prototype structures. This knowledge would enable one to use bamboo as a partial substitution of steel in permanent structure. It would lead to substantial capital savings and increased rural employment. The aim of the present study is to provide a preliminary contribution towards the collection of data to this end.

Static Study

2.1 Test Program 2.1.1 General In order to fulfill the above objective, an experimental investigation has been contemplated. In this program of comparative study four pairs of steel reinforced concrete and bamboo reinforced concrete beams have been tested to destruction. These pairs of beams are designed for the same moment of resistance (6.6 kN.m) corresponding to balanced state of failure of the cross-section using Working stress Method of

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design. The same factor of safety of 0.55 has been used to obtain the permissible tensile strength of both steel and bamboo reinforcements. A simple prophylactic treatment in which a single coat of water proofing treatment consisting of 1:0.25 mixes of bitumen and kerosene has been applied to the bamboo surface followed by dusting with ordinary sand. The test beams are of 1.8 m span and they are subjected to two points loading as shown in Fig. 1. Out of four pair of specimens, three pairs are subjected to static bending test and one pair is subjected to flexural fatigue test with similar type of load application. The prime variables used in this program are strength of concrete, type of reinforcement and type of loading. The test program is documented in Table 1.

Fig. 1 : Test Beam Under Two Point Loading

Fig. 2 : Cross-Section of Rectangular Beams with Steel Reinforcement

Fig. 3 : Cross-Section of Rectangular Beams with Bamboo Reinforcement

Table 1 : Details of Test Program for Comparative Study Beam Designation

Location of reinforcement in the cross-section (Refer to Figures)

Reinforcing materials in the tensile zone

Grade of concrete

Cube strength of concrete(N/mm2)

Type of testing

Fig. 2(I)

Steel

M-20

23.7

Static Bending

Fig. 3(III)

Bamboo

M-20

23.7

Static Bending

Fig. 2(I)

Steel

M-20

22.1

Flexural Fatigue

Fig. 3(III)

Bamboo

M-20

22.1

Flexural Fatigue

Fig. 2(II)

Steel

M-20

22.3

Static Bending

Fig. 3(IV)

Bamboo

M-20

22.3

Static Bending

Fig. 2(I)

Steel

M-30

32.5

Static Bending

Fig. 3(III)

Bamboo

M-30

32.5

Static Bending

2.1.1.1 Geometric properties The test beams are of 1.8 m span and they are subjected to two point loading placed at one-third span as shown in Fig. 1. The span and the size of the cross-sections are assumed and the reinforcement details of both steel and bamboo are determined on the basis of same moment of resistance to be developed by both types of reinforcements. Two types of reinforcement lay out in the cross-section are shown in Figs. 2 and 3 for steel reinforced beams and bamboo reinforced beams The Bridge and Structural Engineer

respectively. It should be noted in these figures that primarily one type of reinforcement has been used in the tensile zone and two types of reinforcements have been used in the compression-zone. In the compression-zone two steel reinforcements have been provided primarily to hold the stirrups in position as well as to act as compression reinforcement. For steel reinforced beams high strength deformed bars conforming to IS: 1786-1986 (ISI, 1985) of 8 mm dia have been used for longitudinal reinforcement. Volume 48 â&#x201D;&#x201A; Number 1 â&#x201D;&#x201A; March, 2018

The similar dia bars have been used for stirrups also for both types of beams. Steel stirrups are preferable to bamboo stirrups (Mark et.al., 2011).

stick has been described in details in reference (Kayal et.al, 2007). The comparative engineering index of this specie and high strength deformed bars Fe 415 conforming to IS: 1786-1986 (ISI, 1985) is given in Table 2. This specie of Dendrocalamus Strictus is of 14.1 mm outer diameter and 7.0 mm inner diameter. The various physical and mechanical properties have been experimentally determined and documented in Table 2.

In order to select suitable bamboo culm which can be used for reinforcing the concrete beams, the specie named Dendrocalamus Strictus has been chosen out of 130 species grown in India. This selection is made because the slim tubes are preferable to bigger tubes as these are stronger in various mechanical properties. The basis of selection of this slim bamboo Table 2 : Comparative Engineering Indices Density (Kn/M3

Moisture Content%

Tensile Strength (N/mm2)

Compressive Strength (N/ mm2)

Modulus of Elasticity (kN/ mm2)

Modulus of Rupture (N/mm2)

Bending Stress (N/mm2)

Tensile Strength/ Weight Ratio (mmx10-6)

Shear Strength (N/mm2)

Dendrocalamus Strictus Round

8.20

9.70

179.60

78.74

11.76

115.42

85.95

21.90

7.08

High Strength Deformed Bars Fe-415

78.50

485.00

200.00

415.00

228.25

6.18

415.00

Item Description

Table 3 : Mix Proportion of Various Types of Concrete Ingredients

M20

M30

Cement 43 Grade(Kg)

426.60

540.00

Coarse Aggregate(Kg)

977.42

921.30

Fine Aggregate (Kg)

651.60

641.20

Water (Litres)

208.00

2.1.2 Material Properties Two types of concrete mixes, namely M 20 and M

30 have been used which are shown in Table 3. Mix proportions of concrete per one cum of concrete have been determined by using absolute volume method of mix design as per IS: 10262-1982(ISI, 1982). The properties of fresh concrete are given in Table 4. Size and grading of coarse aggregate satisfying IS: 383-1963(BIS, 1970) specification has been used which are shown in Table 5. Size and grading of fine aggregate satisfying the zone III of IS: 383-1963 (BIS, 1970) specifications have been used which are shown in Table 6.

Table 4 : Properties of Fresh Concrete Designation of Beams

Compressive S rength (N/mm2)

Tensile Strength (N/mm2)

Slump(mm)

Compacting Factor

Grade of Concrete

Beams - A

23.7

1.6

13.0

0.82

M-20

Beams - B

23.7

1.6

13.0

0.82

M-20

Beams - C

22.06

1.6

23.0

0.81

M-20

Beams – D

22.06

1.6

23.0

0.81

M-20

Beams - E

22.3

2.18

18.0

0.83

M-20

Beams - F

22.3

2.18

18.0

0.83

M-20

Beams - G

32.5

2.3

18.0

0.83

M-30

Beams - H

32.5

2.3

18.0

0.83

M-30

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Table 5 : Size and Grading of Coarse Aggregate IS Sieve Designation

Percentage Passing

Percentage as per IS:383:1970

20 mm

100

10 mm

89.5

85-100

4.75 mm

20.75

0-20

2.36 mm

2.50

0-5

Table 6 : Size and Grading of Fine Aggregate IS Sieve Designation

Percentage Passing

Percentage as per IS:383:1970

10 mm

100

4.75 mm

98.45

90-100

2.36 mm

96.10

85-100

1.18 mm

89.90

75-90

600 μ

78.00

60-79

300 μ

12.01

12-40

150 μ

3.6

0-10

(Zone-III)

The load has been measured by a load cell as shown in this Figure. 2.2 Discussion of Results under Static Loading The results obtained from experimental and analytical investigations under static loading are presented in Tables 7, 8 and 9 and in Figs. 4-11. Table 7 presents comparative study of various responses of steel reinforced concrete beams with those of bamboo reinforced concrete beams related to strength, under the influence of static loading. Table 8 presents various responses related to serviceability of both types of beams as mentioned above. Table 9 presents comparative study of both types of beams at common load level. It should be noted here that although both types of beams have been designed for the same moment of resistance, they are not able to reach the same load due to the difference in the type of reinforcement. Bamboo reinforced beams are not able to reach the same load as the steel reinforced beams due to inadequate bond developed by the former. Therefore, one to one correspondence between the two types is not possible. Therefore, comparison of various responses has been made at common load levels, i.e., the failure loads of bamboo reinforced beams, and is presented in Table 9.

2.1.3 Instrumentation of Test Specimens Only one electrical resistance strain gauge has been fitted at the mid-point of the middle longitudinal reinforcement of both steel and bamboo reinforced concrete beams for measurement of strain under the various stages of loading up to failure. This electrical resistance strain gauge (RohitRoorkee) is known under the trade name FFG-10 (10 x 2.00mm) grid size with 120ohm resistance and gauge factor equal to 2 which has been used on the reinforcements to measure electric strain. Reinforcement surfaces are made ready by filing and grinding with 150-180 grain emery paper and washed with tolouene wash. Then these spots were cleaned with acetone or ethyle acetone. Space equal to twice the size of the strain gauge is to be prepared. The strain gauges were fixed with adhesive called “Araldite” and soldering was done at least after 24 hours after fixing the strain gauges. Wire were kept in position with the help of molten wax and hot bitumen. Banana plugs were fitted at the other end of the wire. Strain has been recorded by a portable data logger with liquid crystal display. The test set up under static loading is shown in Fig. 9.

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Fig. 4 : Comparison of Load Deflection Response Between Steel Reinforced Beam (A) and Bamboo Reinforced Beam (B)

Fig. 5 : Comparison of Load Deflection Response Between Steel Reinforced Beam (E) and Bamboo Reinforced Beam (F)

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Fig. 6 : Comparison of Load Deflection Response Between Steel Reinforced Beam (G) and Bamboo Reinforced Beam (H)

Fig. 7 : Comparison of Load Strain Response Between Steel Reinforced Beam (A) and Bamboo Reinforced Beam (B)

Fig. 10 : Typical crack pattern of a steel reinforced beam.

Fig. 11 : Typical crack pattern of a bamboo reinforced beam.

Fig. 8 : Comparison of Load Strain Response Between Steel Reinforced Beam (G) and Bamboo Reinforced Beam (H) Fig. 12 : Experimental Test set up for a Fatigue Loading.

Fig. 9 : Experimental test set up for Static Loading

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Fig. 13 : A typical Display of deflection on monitor.

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Fig. 16 : Variation of Mid-Span Deflection at Maximum Load Limit with Number of Load Cycles - Steel Reinforced Beam Fig. 14 : Crack pattern of a steel reinforced beam at failure.

Fig. 17 : Variation of Mid-Span Deflection at Maximum Load Limit with Number of Load Cycles - Bamboo Reinforced Beam

Fig. 15 : Crack pattern of a bamboo reinforced beam at failure

Table 7 : Comparative Study of Various Response (Related to Strength) of Steel Reinforced Beams with those of Bamboo Reinforced Beams under the Influence of Static Bending Beam Designation (Refer Table 1 for description)

Ultimate Strength in Ultimate Strength in Flexure(kN.m) Shear(kN.m)

Failure Load (kN) (Tests)

Type of Failure

Analytical Method

Tests

Analytical Method

Tests

Pull out Tests

Encountered by the Beam at Experimental Failure Load

20.7

19.35

88.19

32.25

2.08

2.05

64.5

Combined Effect of Flexure and Bond

17.55

7.5

63.62

12.5

0.244

0.328

25.0

Bond

22.19

21.15

88.19

35.25

2.08

2.24

70.5

Flexure

17.69

10.5

63.62

17.50

0.244

0.45

35.0

Bond

24.2

21.3

88.8

35.50

2.6

2.25

71.0

Flexure

20.7

10.8

63.96

18.0

0.48

0.49

36.0

Bond

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Ultimate Bond Stress (N/mm2)

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Table 8 : Comparison of Various Response (Related to Serviceability) of Steel Reinforced Beams with those of Bamboo Reinforced Beams Beam Designation

Type of Tensile Reinforcement

Ultimate Load (kN)

First Crack Load (kN)

Deflection At

Deflection Index At

Ultimate Load (mm) (Test)

First Crack Load (mm) (Test)

Ultimate Load (mm) (Test)

First Crack Load (mm) (Test)

Ductility Factor (Test)

Crack Width At Collapse Computed (mm)

Tests (mm)

Steel

64.5

55.0

21.0

3.1

.0116

.0017

6.82

.111

.12

Bamboo

25.0

10.0

2.5

0.55

.0014

.0003

4.54

.836

.85

Steel

70.5

20.0

29.0

1.38

.016

.00076

21.0

.111

.119

Bamboo

35.0

13.0

34.6

2.10

.019

.00117

16.5

.836

.84

Steel

71.0

20.0

33.0

1.18

.018

.00065

27.96

.111

.119

Bamboo

36.0

14.0

24.2

1.38

.013

.00076

17.53

.836

.84

Table 9 : Comparative Study of Test Results at Common Load Level Load Deflection Level Of (mm) Comparison (kN) Steel Reinforced 25.0 1.7 Beam - Beam A Description of Beam and Its Designation

Strain at Mid Point

Type of Cracking

No. of Main Cracks (Nos)

Crack width (mm)

Mode of Failure

0.00025

Diagonal Tensile crack

0.04

Flexural Crack at mid point Flexural Crack

0.85

Combined influence of bond and Flexure Bond

0.06

Flexure

Flexural Crack

0.84

Bond

Flexural Crack Flexural Crack

0.06

Flexure

0.84

Bond

Bamboo Reinforced Beam - Beam B

25.0

2.5

0.001

Steel Reinforced Beam - Beam E

35.0

3.0

Bamboo Reinforced Beam - Beam F

35.0

34.6

Steel Reinforced Beam -Beam G Bamboo Reinforced Beam - Beam H

36.0

3.5

Strain could not be recorded Strain could not be recorded 0.00205

36.0

24.2

0.0032

Figs. 4-6 present load-deflection responses of three pairs of specimens, namely Beams A-B, Beams E-F and Beams G-H respectively. Figs. 7-8 present loadmid strain (longitudinal reinforcement) responses of two pairs of specimens, namely Beams A-B and Beams G-H respectively. Strain values cannot be recorded for the pair Beams E-F. Fig. 10 shows the crack pattern of steel reinforced beam G at failure under static loading. Fig. 11 shows the crack pattern of bamboo reinforced beam H at failure under static loading. 50

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Table 7 presents ultimate strength in flexure, ultimate strength in shear and ultimate bond stress by both analytical methods and tests. The failure loads of the specimens have been determined by test only. Ultimate strength in flexure has been analytically determined using an iterative method based on strain compatibility approach. In this approach non-linear stress-strain curve of concrete (Kayal, 1984), bi-linear stress-strain curve of deformed steel reinforcement (BIS 2000) and linear stress-strain curve of bamboo reinforcement (Youssef, 1976) have been used.

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Ultimate strength in shear has been analytically determined by the method enumerated in BS: 81101985. formerly CP 110 (1972). Here, shear strength is calculated by a) considering the concrete section alone, b) the concrete section and the tension reinforcement, c) Contribution by stirrups and d) Contribution of longitudinal reinforcement by dowel action, where ultimate shear strength of longitudinal reinforcement determined by test has been used. Ultimate bond strength has been experimentally determined by standard pull-out test as per BIS: 2770-2008 (BIS, 2008). Bond stress encountered by the specimen at failure has been determined by the standard formula of bond by putting the appropriate values corresponding to collapse. A review of Table 7 reveals that steel reinforced beams E and G have undergone flexural failure whereas Beam A has undergone failure due to the combined influence of flexure and bond. All the bamboo-reinforced beams have undergone failure due to insufficient bond. These beams cannot reach the predetermined flexural strength due to insufficient bond as they failed due to bond. As evident from Table 7, the bond stress encountered by these beams at failure exceeds the bond strength of these specimens determined by Pull-out tests. Table 7 also reveals that none of the beams have undergone shear failure. Both steel reinforced beams and bamboo reinforced beams have been designed for moment of resistance of 6.6 kNm corresponding to balanced failure of the cross-section using method of working stress design. A study of Table 7 also reveals that maximum experimental flexural moment of resistance of the cross section reached in steel reinforced beams varies from 19.35 kNm to 21.3 kNm depending on various parameters mentioned in Table 1. Maximum analytical flexural moment obtained by the method based on strain-compatibility approach varies from 20.7 kNm to 24.2 kNm. It can be seen that agreement is excellent except Beam -A which has undergone failure due to the combined influence of bond and flexure. The load factor involved in these steel beams varies from 2.93 to 3.23 (19.35/6.6 or 21.3/6.6). For bamboo reinforced beams, there is no agreement between analytical and experimental flexural moments. All the beams have undergone bond failure due to ordinary prophylactic treatment adopted in the present investigation and many other parameters. Under this circumstance, it is very difficult to make comparative study between the performances of two The Bridge and Structural Engineer

types of beams. Table 8 presents various responses related to service-ability. All the quantities namely ultimate load, first crack load, deflections at ultimate load and first crack load and the deflection indices at both the loads, ductility factors as obtained from the load deflection response and crack width at collapse are presented in Table 8. For comparative study Table 9 has documented various test results at common load level, i.e., at the failure load of bamboo-reinforced beams. This table has been described later. 2.2.1 Load Deflection Response Figs. 4-6 present load-deflection response of three pair of specimens. A study of these figures and Table 8 reveals the following: 2.2.2 Deflection Indices Defining the first crack load as working load, the deflection indices (deflection at the first crack load divided by the span length) of steel reinforced beams designated by A,E and G vary from 0.00065-0.0017, which are well below the permissible deflection index 0.004 stipulated by IS: 456-2000 (BIS, 2000). The deflection indices of bamboo reinforced beams identified as B, F and H, vary from 0.00030.00117, which are also well below the permissible deflection index. Therefore, it can be seen that both types of beams satisfy the criterion of limit-state of serviceability-deflection as the stiffness of both types of beams is quite satisfactory. 2.2.3 Ductility Indices It may be recalled that ductility index is defined as the deflection at collapse divided by the deflection at first crack load (defined as the working load). It can be seen from Table 8 and Figs. 4, 5 and 6 that the ductility factors of Beams designated by A, E and G are 6.82, 21.0 and 27.96 respectively. Ductility factor of Beam A is quite less as compared to those of Beam E and Beam G as the former has undergone failure due to combined action of bond and flexure and the latter two beams have undergone flexural failure. It can be seen from Table 8 and Figs. 4, 5 and 6 that the ductility factors for bamboo reinforced beams identified as B, F and H are 4.54, 16.5 and 17.53 respectively. It should be noted that ductility factors of Beam F and H are almost 4 times of Beam B because of the fact that former two beams have compression reinforcement and higher grade of concrete (Table 1 and Fig. 3III, Fig. 3IV) which Volume 48 â&#x201D;&#x201A; Number 1 â&#x201D;&#x201A; March, 2018

leads to higher failure load and deflection at collapse. For the same reason the ductility factors of steel reinforced beams are higher. A study of Table 8 and related figures also reveal that bamboo reinforced beams are less ductile than steel reinforced beams. It can be attributed to the fact that ductility factors are directly proportional to the grade of concrete, amount of tensile and compression reinforcement and type of stress-strain curve of reinforcement. The stress-strain curve of steel reinforcement is non-linear giving rise to more ductility than that of bamboo-reinforcement whose stress-strain curve is linear which leads to less ductility. 2.2.4 Load-Strain Response As mentioned before electric resistance strain gauge has been fitted at the mid-span of the middle tensile reinforcement (Figs. 2, 3) for the measurement of tensile strain under the various stages of loading up to failure. Strain readings have been taken by a portable data logger with liquid crystal display. Figs. 7 and 8 show comparison of load strain response between pairs of steel and bamboo reinforced beams A, G and B, H respectively. It can be seen from Fig. 7 that at 20 kN, the strain in Beam A is 224x106 and in Beam B, it is 895x10-6. In other words, the strain experienced by bamboo beam is 4 times of the strain experienced by the steel beam A. It is mainly due to the fact that Young’s modulus of elasticity of bamboo reinforcement is 1/17 times that of steel reinforcement. Fig. 8 shows that at 36 kN, the strain in bamboo reinforcement (Beam H) is 1.55 times that of steel reinforcement (Beam G), the reason being the same as mentioned above. 2.2.5 Crack Pattern under Static Loading Fig. 10 shows the crack pattern of steel reinforced beam G at failure and Fig. 11 shows the same for its companion bamboo reinforced beam H. By comparing these two figures it can be seen that due to the poor bond characteristics of bamboo reinforcement, cracks form at wide spacing and are not numerous. Such wide cracking is to be expected, in view of the large crack spacing, poor bond characteristic, and the large strains in bamboo (due to low modulus of elasticity). For steel reinforcement cracks are numerous, spacings are less due to improved bonding characteristics and higher modulus of elasticity. 2.2.6 Crack Width Table 8, also presents the crack width of all the six beams obtained from experiment and computed by 52

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the equation stipulated by IS: 456-2000 (BIS 2000) at experimental failure load. Experimental crack width was measured by Crack microscope. The crack width formula given in IS: code is taken from CP-110 (CP-110, 1972) and is originally proposed by Beeby (1971) by least fit of experimental results. The formula takes care of the load level through the depth of neutral axis. It also takes care of position of crack and the tension stiffening effect of concrete. The depth of neutral axis adopted in the present investigation has been determined by strain compatibility approach. The various stress-strain curves of the constitutive materials adopted have been already mentioned earlier in section “Load-Deflection Response”. A study of Table 8 shows that agreement between the test values and computed values is quite satisfactory. The crack widths at the experimental failure loads of bamboo reinforced beams are almost 7 times of those of steel reinforced beams. It can be attributed to the facts that along with many other parameters, tensile strength of steel and Young’s modulus of elasticity of steel are 2.7 and 17.0 times of those of bamboo reinforcement respectively. Failure loads are also quite different in both the cases. From these tables it is also evident that the formula of crack width given in IS: 456-2000 is valid for both steel reinforced beams and bamboo reinforced beams. From consideration of aesthetics and the prevention of corrosion of the reinforcement, the current practice with steel reinforced concrete members is to limit the average crack width to 0.3 mm, 0.2 mm, or 0.1 mm, for interior structures, for outdoor structures not exposed to severe condition, and for structures exposed to aggressive environment respectively (BIS 2000). Crack width values obtained from computed and test corresponding to experimental failure loads satisfy these permissible limits in the case of steel reinforced concrete beams. But in the case of bamboo reinforced concrete beams crack width values are materially in excess of these permissible limits. These values may not violate aesthetics requirements, but adequate durability cannot be assured. 2.2.7 Comparison of Performance at Common Load level Table 9, presents comparative performance of both types of reinforced beams at common load level i.e., the failure loads of bamboo reinforced concrete beams. It can be seen from Table 9. that deflections of bamboo reinforced beams identified by B,F and H are 1.5, 11.5 and 6.9 times of those of the respective

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pairs of steel reinforced beams designated by A,E and G respectively. It is mainly due to low modulus of elasticity of bamboo reinforcement and the crosssectional characteristics of both types. The young’s modulus of elasticity of steel reinforcement is 17 times that of bamboo reinforcement (Table 2). Table 9, also presents the tensile strain of mid-point of the longitudinal tensile reinforcement of bamboo reinforced beams B, and H to be 4, 1.56 times of those of the respective pairs A and G respectively. It is mainly due to the fact that tensile strength of steel reinforcement is 2.7 times that of bamboo reinforcement (Table 2). Apart from this, low modulus of elasticity of bamboo reinforcement is also responsible for this. Due to low modulus of elasticity and low tensile strength of bamboo reinforcement, the numbers of cracks are less and crack spacings are more in case of bamboo reinforced beams. Due to larger crack spacings, crack widths are also more in these beams. Table 9 shows that crack widths of bamboo reinforced beams identified as B,F and H are 21,14, and 14 times of those of the corresponding pairs designated by A,E and G respectively.

Fatigue Study

3.1 Test Program

the test beams are of 1.8m span and they are subjected to two points loading as shown in Fig. 1. As in static study, the prime variables used in this program are strength of concrete, type of reinforcement and type of loading as mentioned in Table 1. 3.1.2 Test Program under Fatigue Loading A detail of test program under fatigue loading is presented in Table 10. The static bending failure load of Beam A which is identical to Beam C is 64.5 kN and the static bending failure load of Beam B which is identical to Beam D is 25.0 kN. The stress range for the run out test of steel reinforced beam is taken as 60-65% of the failure load. The stress range for the run out test of bamboo reinforced beam is taken as 3032% of the failure load. Bamboo being a new material less load has been selected for stress-ranges. Rate of loading or frequency of loading has been decided keeping in view the natural frequency of the MTS machine to avoid resonance. For steel reinforced beam the frequency of loading is taken as 20 cycles/ sec. For bamboo reinforced beam the frequency of loading is taken as 5 cycles/sec. The steel reinforced beam survived 18, 00,000 cycles in 25 hours. The bamboo reinforced beam survived 4, 50,000 cycles in 25 hours. In both the circumstances the specimens developed a large number of cracks. Fig. 12 shows the experimental test set up for fatigue loading. Mid-span deflections were monitored throughout the loading cycle. Fig. 13 shows a typical display of deflection on monitor. Fig. 14 shows crack pattern of steel reinforced beam C at the end of runout test under fatigue loading. Fig. 15 shows crack pattern of bamboo reinforced beam D at the end of run-out test under fatigue loading. Fig. 16 shows the no. of cycles vs. mid-length deflection of Beam C. Fig. 17 shows the no. of cycles vs. mid-length deflection of Beam D.

3.1.1 General

In this program of comparative study four pairs of steel reinforced concrete beams and bamboo reinforced concrete beams have been tested to destruction. Out of these four pairs one pair has been tested under flexural fatigue loading. The various specifications of these four pairs have been documented in Table 1. The test specimens designated by Beam C and Beam D in Table 1, have been tested under flexural fatigue. As mentioned under ‘Static Study’, Table 10 : Test Program and Test Results under Fatigue Loads Description of Beam and its Designation

Run out Test Stress Range (kN)

Frequency Duration of Loading of Test (Cycles/ (Hours) Secs)

Rerun Test No. of Cycles

Stress Range (kN)

Frequency Duration of Loading of Test (Cycles/ (Seconds ) Secs)

No. of Cycles

Steel Reinforced Beam - (Beam-C)

38-42

18,00,000

58-62

354

Bamboo Reinforced Beam (Beam-D)

7.5-8.0

4,50,000

10.011.25

400

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After 18, 00,000 cycles in 25 hours, run-out test was terminated for steel reinforced Beam C. A new test, called a rerun test, was initiated, using the run-out specimen. In order to achieve fatigue fracture in rerun test, the steel reinforced concrete beam specimen of run-out test was subjected to escalated stress range. As documented in Table 10. A stress range of 58-62 kN has been selected. It is 90-96% of the static bending strength of the specimen. Frequency of loading has been also escalated to 30 cycles/sec. The specimen failed due to fatigue fracture after 354 cycles after 12 seconds. No reading could be taken in such short duration.

3.1.4 Crack Pattern under fatigue loading

Similarly, for bamboo reinforced beam D, rerun test was conducted. As shown in Table 10 for rerun test, the stress-range for this beam has been escalated to 40 to 45% of the static bending test. Thus, the stress range is 10.0-11.25 kN. The frequency has been increased to 20 cycles/sec. The specimen failed due to fatigue fracture after 400 of such cycles in 20 seconds. Due to short duration no reading could be taken.

Fig. 14 shows crack pattern of steel reinforced Beam C at failure under fatigue loading. Fig. 15 shows crack pattern of its bamboo reinforced counterpart Beam D at failure under fatigue load. Like under static loading the number of cracks is numerous in case of steel reinforced beam whereas in bamboo reinforced beam the numbers of cracks are very few. As mentioned under static loading it can be seen that due to the poor bond characteristic of bamboo reinforcement, cracks form at wider spacings and are not numerous. The crack width of bamboo reinforced beam is 7 times (1.23/.17) of the crack width of steel reinforced beam. Such wide crack width is to be expected, in view of large crack spacing, poor bond characteristic, and the large strain in bamboo due to low modulus of elasticity of bamboo reinforcement. For steel reinforced beams, cracks are numerous spacings are less due to improved bond characteristics and higher modulus of elasticity.

In all the above tests, the specimens have been subjected to sinusoidal variation of loading.

3.1.5 Load-Deflection Response under Fatigue Loading

3.1.3 Crack Width under Fatigue Loading

Fig. 16 shows variation of mid-span deflection at maximum load of the stress-range with the number of load cycles of the steel reinforced beam. Fig. 17 shows the similar variation of the bamboo reinforced beam.

The crack width at the end of run-out test has been measured by crack microscope. The crack width of Beam A is 0.12 mm (Table 8). The crack width of Beam C (the counter part of Beam A under static bending) is 0.17 mm. Similarly for Bamboo reinforced Beam B under static loading it is 0.85 mm. The crack width of Beam D (the counterpart of Beam B under static loading) is 1.23 mm. In both the cases it is 45% higher than the value under static loading. The reason for increase in crack width under cyclic loading can be attributed primarily to the increase in rebar slip at crack locations. The increase in rebar slip is caused by bond deterioration under repeated loads (Bresler and Bertero, 1968). No direct formula is available for calculation of crack width under fatigue loading. Balaguruet. Al (Balaguru, 1982) has outlined a procedure for computation of crack width under fatigue loading. This procedure takes care of various parameters such as (i) the cyclic creep of concrete in the compression zone, (ii) the reduction in stiffness contribution of the tension zone concrete due to fatigue tensile cracking and the progressive deterioration of the bond between steel and concrete, and (iii) the cyclic strain softening of reinforcing steel. The procedure is quite involved, hence not attempted in the present investigation. 54

Volume 48 │ Number 1 │ March, 2018

Mid-span deflection increases with the number of cycles due to the fact that dynamic modulus of elasticity decreases along with the number of cycles. The decrease in dynamic modulus is indirectly related to the following facts: i)The cyclic creep of concrete in the compression zone, ii) the reduction in stiffness contribution of the tension zone concrete due to the fatigue –tensile cracking and the progressive deterioration of the bond between steel and concrete, and iii) the cyclic strain softening of the reinforcing steel. Contribution of these three mechanisms and how to predict them are discussed in detail in reference (Balaguru et al, 1982). It is realized that in the absence of sufficient results, it is difficult to throw light in the behavior of these beams under fatigue loading. However, discussion presented here will nevertheless be useful in offering an insight into the comparative behavior between the two types of reinforcements under fatigue loading.

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The experimental ultimate failure loads of steel reinforced beams designated by A.E and G are 2.58, 2 and 1.97 times that of their bamboo reinforced counterparts designated by B, F and H respectively (Table 7).

The fatigue strength of steel reinforced beam is 62 kN corresponding to a fatigue life of 18,00,000 cycles where a cycle is comprised of 62 kN as maximum stress and 58 kN as minimum stress. The fatigue strength of its bamboo reinforced counterpart is 11.25 kN corresponding to a fatigue life of 4,50,000 cycles where a cycle is comprised of 11.25 kN as maximum stress and 10.0 kN as minimum stress.

The residual capacities after the first crack of steel reinforced beams designated by A,E and G are 15%, 72% and 72% respectively. While bamboo reinforced beams designated by B, F and H had exhausted 40%, 37% and 38% respectively of their load carrying capacities after the first crack.

10) The mid-length deflection of a steel reinforced beam is 7.65 mm for 1900,000 cycles where a cycle consists of 42kN as maximum stress and 38 kN as minimum stress. The same for bamboo reinforced counterpart is 7.25 mm for 1700,000 cycles where a cycle comprises of 8.0 kN as maximum stress and 7.5 kN as minimum stress.

Both steel reinforced beams and bamboo reinforced beams satisfy the criterion of limit state of serviceability-deflection.

Tensile strain at the middle longitudinal reinforcement of steel reinforced beams vary from 1.5 to 4 times of that of bamboo reinforced beams due to the fact that young’s modulus of elasticity of bamboo reinforcement is 1/17 times that of steel reinforcement.

11) The crack widths under fatigue loading for both steel and bamboo reinforced beams are 45% higher than the value under static loading. The reason for increase in crack width can be attributed to the increase in rebar slip which is caused by bond deterioration under repeated loads.

4. Conclusions

The following salient conclusions can be drawn from the present study.

All the steel reinforced beams have undergone flexural failure while bamboo reinforced beams have undergone bond failure. None of the beams have undergone shear failure (Table 7). For steel reinforcement cracks are numerous, spacings are less as compared to bamboo reinforcement (Figs 10 and 11) due to improved bond characteristic and higher modulus of elasticity, compared to bamboo reinforcement. In both types of beams cracks are flexural cracks only. The crack widths at the experimental failure loads of bamboo reinforced beams are almost 7 times of those of steel reinforced beams due to low tensile strength and low modulus of elasticity of bamboo reinforcement. The ductility factors of steel reinforced beams identified as A, E and G are 1.5, 1.27 and 1.6 times the ductility factors of their bamboo reinforced counterparts designated by B, F and H respectively (Table 8). It is due to the nature of stress-strain curve of the two types of reinforcement and other parameters mentioned in section 2.2.3.

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12) The behavior such as deflection, crack width and crack pattern of both types of reinforced beams under fatigue loading is similar to that under static loading. It should be noted that the conclusions enumerated above are valid within the ranges of parameters used in the present investigation.

References 1.

Adewuyi, A.P., Otukoya, A.A., Olaniyi, O.A., and Olafusi, O.S.(2015), “Comparative Studies of Steel, Bamboo and Rattan as Reinforcing Bars in Concrete: Tensile and Flexural characteristics”, Open Journal of Civil Engineering, Vol 5, June 2015, PP. 228-238.

Arockiasamy, M. and Vijayaraghavan, K.V. (1976) “Low-Cost Housing Slum clearance Project in Madras City-case Studies”, Proc. IAHS Inst. Symp. Housing problems, Vol 1.

Balaguru,P and Shah, S.P.,(1982), “A method of Predicting Cracks widths and Deflections for Fatigue Loading”, ACI SP 75-7, Fatigue of Concrete Structures, Shah, S.P.(Ed), ACI Special Publication, 1982, PP. 153-175.

Bebby, A.W., (1971). “A study of cracking in reinforced concrete members subjected to pure Volume 48 │ Number 1 │ March, 2018

tension”. Technical Report 42.46.6, Cement and Concrete Association, Wexham springs, slough, England. 5.

Bresler, B. and Bertero, V. (1968), “Behaviour of Reinforced Concrete under repeated load, Journal of the Structural Division, ASCE, June 1968, PP.1567-1589.

Bureau Indian Standards (BIS), Recommended Guidelines for Concrete Mix design (1983), IS: 10262-1982, New Delhi, India.

Bureau Indian Standards (BIS). (2000), “Indian Standard Code of Practice for plain and reinforced concrete, IS: 456-2000., Bureau Indian Standards, New Delhi, India.

Bureau Indian Standards (BIS, 2008) Indian Standard for pull-out test, BIS: 2770-2008, Bureau Indian Standards, New Delhi, India.

Cox, F.B. and Geymer, H.G. (1969) Expedient reinforcement for concrete for usein Southeast Asia Report1, Preliminary Tests on Bamboo, Technical Report No. C-69-3, U.S. Army, Waterways Experiment Station, Vicksburg, Mss., U.S.A. 135.

10. CP 110: Part (1972), Code of Practice for the Structural use of concrete, British Standard Institution, London, 1972, PP.154. 11. Geymayer, H.G., and Cox, F.B., (1970), “Bamboo Reinforced Concrete”, ACI Journal, Vol. 67, No. 51 Oct 1970, PP. 841-846. 12. Ghavami, K. (1995), “Ultimate Load Behaviour of Bamboo-Reinforced Lightweight Concrete Beams”, Cement and Concrete Composites, Vol. 17., May,1995, PP. 281-288. 13. Ghavami, K. (2005), “Bamboo as Reinforcement in Structural Concrete Elements”, Cement and Concrete Composites, Vol 27, No. 6, July 2005, PP. 637-649. 14. Glenn, H.E., (1950), “Bamboo Reinforcement in Portland Cement Concrete”, Bulletin No. 4, Clemson Agricultural College, Clemson, South Carolina, U.S.A, 171. 15. Ibrahim, N.H. and Mously, H.I. (2001), “Study of Physical and Mechanical Properties of Bamboo in Egypt in Agribuilding 2001”, Sio Poulo Brazil. 16. Indian Standard Specification for Coarse and Fine aggregates from natural sources, (1970),

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IS: 383-1963, Bureau Indian Standards (BIS), New Delhi, India. 17. IS: 1786: 1985 Specification for high strength Deformed Bars and Wires for Concrete reinforcement, IS: 1786-1985, New Delhi, India. 18. Jung, Y. (2006). “Investigation of Bamboo as Reinforcement in Concrete”, Thesis submitted to the University of Texas at Arlington in partial fulfillment of the requirements of M.Sc, in Civil Engineering, August, 2006. 19. Kankam, C.K., and Odum-Ewuakya, B., (1999), “Structural Behaviour of Baleadua Reinforced Concrete Beams”, Construction and Building Materials, 13(1999), April 1999, PP. 187-193. 20. Kankam, J.A, Ben-George, M. and Perry, S.H., (1988) Bamboo-Reinforced Concrete Beams Subjected to Third-Point Loading”, ACI Structural Journal, Title no. 85-S7, Jan-Feb, 1988, PP. 61-67. 21. Karthik, S. (2017), “Strength Properties of Bamboo and Steel Reinforced Concrete Containing manufactured Sand and Mineral Admixtures”, www.sciencedirect.com/ science/ article/pii/S1018363916300484. 22. Kayal, S. (1984). “Finite Element method for uniaxially loaded RC Columns”, Journal of Structural Engineering, Vol. 110., No. 5, PP. 1114-1133 23. Kayal, S., Kumar, S., and Kumar, P. (2007), “Evaluation of Suitability of Bamboo Culms for use as Structural Reinforcements in Concrete”, The Bridges and Structural Engineers, IABSE, September (2007), Vol. 37.,No.3., PP. 21-38 24. Khare, L. (2005). “Performance Evaluation of Bamboo Reinforced Concrete Beams”, Thesis submitted to the University of Texas at Arlington in partial fulfillment of the requirements of M.Sc in Civil Engineering, Dec, 2005. 25. Lima, H.C., Willrich, F.L., Barbosa, N.P., Rosa, M.A, and Cunha, B.S. (2008). Durability Analysis of Bamboo as Concrete Reinforcement”, Materials and Structures, 2008, Vol. 41, PP 981-989. 26. Mark, A.A. and Russell, A.O.(2011), “A comparative Study of Bamboo Reinforced Concrete Beams using Different Stirrup Materials for Rural Construction”,- International

The Bridge and Structural Engineer

Journal of Civil and Structural Engineering, Vol 2, No.1, Nov., 2011, PP. 407 – 423.

Journal of current Engineering and Technology, Vol. 3 No.2., June 2013, PP. 476-483.

27. Ramaswamy, G.S. (1977) “Research and Development on low cost Housing”, Proc. Int. Seminar, Low Cost Housing, Madras, Vol, 1., IP3/1-22.

32. Subrahmanyam, B.V. (1984)., “Bamboo Reinforcement for Concrete Matrices”, “New Reinforced Concretes”, Edited by R.N. Swamy, London, PP. 141-194.

28. Sethalakshmi, K.K. and Muktesh Kumar, M.S. (1998),“Bamboo of India”, INBAR, New Delhi.

33. Terai, M. and Minami, K. (2011), “Fracture Behaviour and Mechanical Properties of Bamboo Reinforced Concrete Members”, 11th International Conference on the Mechanical Behavior of Materials, Vol. 10. DVD.

29. Sethia, A. and Baradiya, V. (2014), “Experimental Investigation on Behaviour of Bamboo Reinforced Concrete member”, International Journal of Research in Engineering and Technology, Vol 3, Issue 2, Feb-2014, PP. 344 – 348. 30. Sevalia, J.K., Siddhpura, N.B., Agrawal, C.S., Shah, D.B., and Kapadia, J.V. (2013), “Study on Bamboo as Reinforcement in Cement Concrete”, International Journal of Engineering Research and Applications, Vol 3, Issue 2, March–April 2013, PP. 1181–1190. 31. Siddhpura, M.B., Shah, D.B., Kapadia, J.V., Aggarwal, C.S. and Sevalia, J.K., (2013), Experimental Study on Flexural Element using Bamboo as Reinforcement”, International

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34. Terai, M. and Minami, K. (2012), “Research and Development on Bamboo Reinforced Concrete Structure”, www.iitk,ac.in/nicee/wcee/article/ WCEE 2012-2020. Pdf. 35. U.S. Naval Civil engineering Laboratory (1966, 2000) Bamboo Reinforced Concrete Construction,http://www.,romanconcrete. com.does/bamboo/1966/BambooReinforced Concrete, PP. 1-19. 36. Youssef, M.A.R (1976), “Bamboo as a Substitute for Steel Reinforcement in Structural Concrete”, New Horizons in Construction Materials, Vol. 1, H.Y.Fang (ed).,Envo Publishing Co., Lehigh Valley, U.S.A., PP. 525-554.

Volume 48 │ Number 1 │ March, 2018

Indian National Group of the IABSE Office Bearers and Managing Committee - 2017 Chairman 1.

Shri D.O. Tawade, Chairman, ING-IABSE & Member (Technical), National Highways Authority of India

Vice-Chairmen

Members of the Executive Committee 13. Shri N.K. Sinha, Former Director General (Road Development) & Special Secretary 14. Shri A.K. Banerjee, Former Member (Technical), NHAI

Shri B.N. Singh, Additional Director General, (I/C) Ministry of Road Transport and Highways

15. Shri G. Sharan, Former Director General (Road Development) & Special Secretary

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

16. Shri A.V. Sinha, Former Director General (Road Development) & Special Secretary

Shri A.K.S. Chauhan, C.O.O., GR Infraprojects Ltd.,

Shri Vinay Gupta, Chief Executive Officer, Tandon Consultants Pvt. Ltd.,

Honorary Treasurer 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, Honorary Member, IABSE & Former Director General (Road Development) & Addl. Secretary

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

Persons represented ING on the Executive Committee and Technical Committee of the IABSE 9.

Dr. Harshavardhan Subbarao, Vice President & Member, Technical Committee of IABSE & Chairman and Managing Director, Construma Consultancy Pvt. Ltd., Past Member of the Executive Committee and Technical Committee of IABSE

10. Prof. S.S. Chakraborty, Past Vice-President, IABSE 11. Dr. B.C. Roy, Past Vice President & Member, Technical Committee, IABSE

17. Shri R.P. Indoria, Former Director General (Road Development) & Special Secretary 18. Dr. Lakshmi Parameswaran, Chief Scientist, Bridges & Structures Div., CSIR-Central Road Research Institute 19. Shri Ashwinikumar B. Thakur, Group Engineer, Atkins India 20. Shri Sarvagya Kumar Srivastava, Engineer-inChief (Projects), Govt of Delhi 21. Dr. Mahesh Kumar, Engineer Member, Delhi Development Authority 22. Shri R.K. Jaigopal, Consultant, Concrete Structural Forensic Consultant 23. Prof Mahesh Tandon, Managing Director, Tandon Consultants Pvt. Ltd.

Past Secretary of the Society, for a Period of Two Years, after they Vacate their Secretaryship 24. Shri R.K. Pandey, Member (Projects), National Highways Authority of India

Secretariat 25. Shri I.K. Pandey, Additional Director General (RD), Ministry of Road Transport and Highways,

Honorary Secretary

26. Shri Ashish Asati, General Manager, National Highways Authority of India

12. Shri I.K. Pandey, Additional Director General (RD), Ministry of Road Transport & Highways

26. Shri K.B. Sharma, Under Secretary, Indian National Group of the IABSE

Volume 48 │ Number 1 │ March, 2018

The Bridge and Structural Engineer

MEMBERS OF THE MANAGING COMMITTEE – 2017 Rule-9 (a): A representative of the Union Ministry of Road Transport and Highways 1.

Shri Manoj Kumar, Director General (Road Development) & Special Secretary

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 IABSE as determined by the Executive Committee from time to time 2.

CPWD - nomination awaited

Shri D.O. Tawade, Member (Technical), National Highways Authority of India

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 IABSE as determined by the Executive Committee from time to time 5.

Govt of Andhra Pradesh – nomination awaited

Govt of Arunachal Pradesh – nomination awaited

Govt of Assam – nomination awaited

Govt of Bihar – nomination awaited

Govt of Chattisgarh – nomination awaited

10. Govt of Delhi – nomination awaited 11. Govt of Goa – nomination awaited 12. Govt of Gujarat – nomination awaited 13. Govt of Haryana – nomination awaited 14. Govt of Himachal Pradesh – nomination awaited 15. Govt of Jammu & Kashmir – nomination awaited 16. Govt of Jharkhand – nomination awaited

20. Govt of Maharashtra – nomination awaited 21. Shri K Radhakumar Singh, Commissioner (Works), Govt of Manipur 22. Shri PR Marwein, Chief Engineer (Standards), 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. Shri Anil Kumar Gupta, Suptd Engineer, Central Works Circle, Govt of Punjab 27. Govt of Sikkim – nomination awaited 28. Govt of Tamil Nadu – nomination awaited 29. Govt of Tripura – nomination awaited 30. Govt of Uttar Pradesh – nomination awaited 31. Govt of Uttarakhand – nomination awaited 32. Govt of West Bengal – nomination awaited 33. Union Territory Chandigarh – 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 V.C. Verma, Director (Mktg), Oriental Structural Engineers Pvt. Rule-9 (e): Ten representatives of Individual and Collective Members 35. Shri A.K. Banerjee, Former Member (Technical), NHAI 36. Shri G. Sharan, Former DG (RD) & Special Secretary

17. Govt of Karnataka – nomination awaited

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

18. Shri S Saju, Joint Director (EE) & Highways Design, DRIQ, Govt of Kerala

38. Shri R.P. Indoria, Former DG (RD) & Special Secretary

19. Shri LD Dube, Chief Engineer (Bridge Zone), Govt of Madhya Pradesh

39. Shri Rakesh Kapoor, General Manager, Holtech Consulting Pvt Ltd

The Bridge and Structural Engineer

Volume 48 │ Number 1 │ March, 2018

40. Shri Ashwinikumar B Thakur, Group Engineer, Atkins India

53. Shri Bageshwar Prasad, CEO (Delhi Region), Construma Consultancy Pvt. Ltd.

41. Prof Mahesh Tandon, Managing Director, Tandon Consultants Pvt. Ltd.

54. Shri G.L. Verma, Proprietor, Engineering and Planning Consultants

42. Shri R.S. Mahalaha, Advisor, ITL

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

43. Shri R.K. Jaigopal, Consultant, Concrete Structural Forensic Concrete 44. Shri Inderjit Singh Ghai, CEO, Consulting Engineers Associates Rule-9 (f): Four representatives of Bridge and Structural Engineering Firms 45. Shri V.N. Heggade, Director & President (Engineering), Gammon Engineers & Contractors 46. Shri A.K.S. Chauhan, C.O.O., GR Infraprojects Ltd. 47. Shri Shishir Bansal, Chief Project Manager, Delhi Tourism & Transportation Development Corporation 48. Shri S.P. Singla, Managing Director, SP Singla Constructions Ltd Rule-9 (g): Two representatives of the Engineering Colleges / Technical Institutes / Universities / Research Institutes 49. Dr Lakshmi Parameswaran, Chief Scientist, Bridges & Structures Div., CSIR – Central Road Research Institute 50. Shri VL Patankar, Former Director, Indian Academy of Highway Engineers Rule-9 (h): Four representatives Engineering Firms

Consulting

51. Shri N.K. Sinha, President, ICT Pvt. Ltd. 52. Shri Alok Bhowmick, Managing Director, B&S Engineering Consultants Pvt. Ltd.

Volume 48 │ Number 1 │ March, 2018

55. The Director General (Road Development) & Special Secretary to the Govt of India Rule-9 (j): Past-Chairman of the Society, for a period of three years, after they vacate their Chairmanship Rule-9 (k): Secretary of the Indian National Group of IABSE 56. Shri I.K. Pandey Rule-9 (l): Persons who have been awarded Honorary Membership of the Parent Body 57. Shri Ninan Koshi 58. Prof S.S. Chakraborty Rule-9 (m): Persons represented ING on the Executive Committee and Technical Committee of the IABSE 59. Dr. Harshavardhan Subbarao Rule-9 (n): Past Members of the Executive Committee and Technical Committee of the IABSE 60. Prof S.S. Chakraborty 61. Dr. B.C. Roy Rule-9 (o): Past Secretary of the Society, for a period of three years, after they vacate their Secretaryship 62. Shri R.K. Pandey

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Volume 48 │ Number 1 │ March, 2018

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With the growing population and increasing congestion on intersections leading to larger waiting time, LASA has provided solutions in the form of design, construction and project management of flyovers. LASA has always provided most cost effective solutions with the use of latest technology and materials. Engineering Surveys and Investigations Ground Improvement Detailed Design Construction Supervision Quality Assurance and Technical Audit Project Management Contract Administration Proof Checking Bridge Rehabilitation and Replacement

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Volume 48 â&#x201D;&#x201A; Number 1 â&#x201D;&#x201A; March, 2018

LIST OF ING-IABSE PUBLICATIONS Available for Sale S. No.

Name of the Publications

Price Rs. Postage Rs.

Technical Presentation on “Maintenance and Rehabilitation of Bridge Structures” held at New Delhi in November 1994

200/-

100/-

Seminar Report on “Elevated Transport Corridors” held at Maysore (Karnataka) on 27th and 28th June, 2014 Themes of the Seminar are as under:Planning Preparation, Economic benefits & Value Engineering Technical Session - I Technical Session - II Design and Construction Operation and Maintenance Technical Session - III Case Studies Technical Session - IV Hard Copy Out of Stock – CD is available

250/-

100/-

36th IABSE Symposium on “Long Span Bridges and Roofs – Development, Design and Implementation” held at Kolkata from 24th to 27th September, 2013

250/-

100/-

Vol. 43 No. 3, September, 2013 Special Issue – Urban Flyovers (Structure, Architecture, Sustainability)

500/-

100/-

Vol. 43 No. 4, December, 2013 Special Issue – Bearings, Expansion Joints & STUs for Bridges (Selection, Design, Testing Installation, Maintenance) Hard Copy Out of Stock – CD is available

250/-

100/-

Vol. 44 No. 1, March, 2014 Special Issue – Building Structures

500/-

100/-

Vol. 44 No. 2, June, 2014 Special Issue – Codes & Standards in Structural Engineering (Developments & Need for Improvement)

500/-

100/-

Vol. 44 No. 3, September, 2014 Special Issue – Reinforced Soil Walls (Current Practices & Future Directions)

500/-

100/-

Vol. 44 No. 4, December, 2014 Special Issue – Structural Failures (and Lessons Learnt)

500/-

100/-

Vol. 45 No. 1, March, 2015 Special Issue – Earthquake Resistant Design of Structures

500/-

100/-

Vol. 45 No. 2, June, 2015 Special Issue – Strengthening, Repair & Rehabilitation of Structures Hard Copy Out of Stock – CD is available

250/-

100/-

Vol. 45 No. 3, September, 2015 Special Issue – Aesthetics of Structures

500/-

100/-

Vol. 45 No. 4, December, 2015 Special Issue – Geotechniques & Foundations Design of Structures

500/-

100/-

Vol. 46 No. 1, March, 2016 Special Issue – Enabling Works, Formworks & Scaffolding Systems

500/-

100/-

Vol. 46 No. 2, June, 2016 Special Issue – Steel & Composite Bridges Hard Copy Out of Stock – CD is available

250/-

100/-

Vol. 46 No. 3, September, 2016 Special Issue – Tall Structures

500/-

100/-

Vol. 46 No. 4, December, 2016 Special Issue – Challenges Facing the Civil & Structural Engineering Industry

500/-

100/-

Vol. 47 No. 1, March, 2017 Special Issue – Bridge Engineering

500/-

100/-

Vol. 47 No. 2, June, 2017 Special Issue – Urban Transportation Structures

500/-

100/-

Vol. 47 No. 3, September, 2017 Special Issue – Structural Engineers for Sustainable Development

500/-

100/-

Vol. 47 No. 4, December, 2017 Special Issue – Wind Sensitive Structures

500/-

100/-

Annual Subscription Charges for Quarterly Journal - 2018 “The Bridge and Structural Engineer” Published in March, June, September & December

800/-

200/-

Note: These Publications are available on cash payment or through cheque drawn in favour of the “Secretary, Indian National Group of the IABSE, New Delhi” at the following address:

The Secretary, Indian National Group of the IABSE, IDA Building, Ground Floor, Room No. 12, Jamnagar House, Shahjahan Road, New Delhi -110011 Phone No. 91-11-23388132, 23386724, E-mail: ingiabse@bol.net.in; ingiabse@hotmail.com

Volume 48 │ Number 1 │ March, 2018

The Bridge and Structural Engineer