STRUCTURE magazine | January 2016

January 2016 Concrete

A Joint Publication of NCSEA | CASE | SEI

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Guide to the Code for Evaluation, Repair, and Rehabilitation of Concrete Buildings—A Companion to ACI 562-13, 2015, 140 pp.

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The ACI 562 code provides standard requirements for evaluating existing concrete buildings and the subsequent structural repair, rehabilitation, and strengthening of those buildings. This code provides rules for a preliminary evaluation that determines the “design basis code,” that is, the version of 318 with which the repair design must comply. The code provides rules for determining strength of in-situ material, performing structural analysis, designing for repaired strength and durability, requirements for stability and shoring of construction, and inspection and testing of repairs. Commentary provides application guidance as well as references for additional information.

The new guide is separated into two main components: chapter guides that follow the organization of ACI 562, broken down by the corresponding sections and project examples that illustrate the use of the code for real world projects from inception through completion.

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STRUCTURE

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January 2016 29

FEATURE

38 EDITORIAL

7 When Opportunity Walks in the Door

HISTORIC STRUCTURES

50 Quebec Bridge – Part 2

By Frank Griggs, Jr., D. Eng., P.E.

By David W. Mykins, P.E. INSIGHTS INFOCUS

9 Toward a Bright Future

By Barry Arnold, P.E., S.E., SECB STRUCTURAL DESIGN

10 Durability of Reinforced Concrete

By Paul Noyce and Gina Crevello

54 3D Printed Structures: Challenges & Opportunities

By Caitlin T. Mueller, Ph.D. SPOTLIGHT

59 Malone Cliff View Residence Soars over Dallas

By Thomas W. Taylor, P.E., Stephen Price, P.E., Lee Christian,

STRUCTURAL REHABILITATION

14 Precast, Prestressed Thin Slabs in Parking Garage Structures

By D. Matthew Stuart, P.E., S.E., P.Eng., SECB

P.E. and Craig Rios, P.E. STRUCTURAL FORUM

66 The Engineering Way of Thinking: The Future

By William M. Bulleit, Ph.D., P.E.

By Douglas G. Fitzpatrick, P.E. and

23 Special Inspections for Wood Construction – Part 1

By David P. Tyree, P.E., James B. Smith, P.E. and Michelle Kam-Biron P.E, S.E., SECB

34

FEATURE

A New Era of Women’s Health for Central Florida

By Kevin Casey, P.E., S.E., Bill Mitzo, P.E. and Nathan Morrow, P.E.

38

FEATURE

Structural Repairs for Courthouse Square

By Tarek Alkhrdaji, Ph.D., P.E.

43

Integrating Sustainability and Structure

18 Tilt-Up and BIM

CODES AND STANDARDS

By Larry Kahaner

FEATURE

TECHNOLOGY

Joe Steinbicker, P.E., S.E.

Foundation Companies Had a Good 2015 and Look Ahead to a Strong 2016

IN EVERY ISSUE 8 Advertiser Index 56 Resource Guide (Anchor Updates) 58 Noteworthy 60 NCSEA News 62 SEI Structural Columns 64 CASE in Point

By Keith T. Bauer, S.E.

46

FEATURE

On the cover The Florida Hospital for Women, a 12-story, 430,000 square-foot facility located in Orlando, is situated on a tight urban site bordered by active rail lines. Design issues related to vibrations and a high water table resulted in additional vibration studies and foundation investigations. See feature article on page 34.

Enduring Devotion: The Sanctuary for Sufism Reoriented

By Steve Ratchye, P.E., S.E. and Graeme Ballantyne, P.E., S.E.

Publication of any article, image, or advertisement in STRUCTURE® magazine does not constitute endorsement by NCSEA, CASE, SEI, C 3 Ink, or the Editorial Board. Authors, contributors, and advertisers retain sole responsibility for the content of their submissions.

STRUCTURE magazine

5

January 2016

Editorial

When new trends, new Opportunity techniques and current Walks industry issues in the Door

By David W. Mykins, P.E., Chair CASE Executive Committee

S

ome time ago, one of our project engineers came to my office late in the day and asked if I had a minute to talk about something. “Sure,” I said, and he came in and quietly closed the door behind him. Now, I’ve learned that when someone wants to talk to you and then closes the door, whatever is coming is probably not good. So I took a deep breath and braced myself…

What he had come to tell me was that his wife’s career path was going to require that they relocate to another state for a couple of years. The town where they would be living was small and remote, and there were not many (or perhaps any) prospects for a structural engineer.

He was wondering if it would be possible to continue to work for us from this remote location. Compared to some of the things that ran through my mind when he closed the door, this came as somewhat of a relief and we agreed to both look into how it might work.

Remote working arrangements like the one suggested by our project engineer would not have been impossible 15 or 20 years ago. But with the advances in technology and collaboration software, telecommuting has not only become possible, it is quickly becoming an expectation of today’s workforce. A survey conducted

by SkiptheDrive.com in October 2015 showed that 22.5% of millennials work from home at least part of the time. Here are some additional statistics based on the 2014 US Census and compiled

by Global Workplace Analytics: • 50% of the US workforce holds a job that is compatible with at least partial telework, and approximately 20-25% of the workforce teleworks at some frequency • 80% to 90% of the US workforce says they would like to telework at least part time. Two to three days a week seems to be the sweet spot that allows for a balance of concentrative work (at home) and collaborative work (at the office).

• Fortune 1000 companies around the globe are entirely revamping their spaces around the fact that employees are already mobile. Studies repeatedly show they are not at their desk 50-60% of the time.

So, the reality is that, in order to attract and keep the best and brightest, structural engineering firms will need to address this issue. Most firms today probably have some means of allowing employees to work remotely at least part of the time. This typically involves the use of a networking solution that allows employees to connect to the office from home, such as a virtual private network (VPN). With the technical means of allowing telecommuting already in place, the next step is managing expectations.

There are some significant differences for someone who is going to work from home for a day and an employee who will be telecommuting full time, so it is important to have honest and open conversations in advance to set the ground rules and expectations. Some of these issues may depend on how long the telecommuting arrangement is expected to last. Is it temporary as in the case of our engineer, or open ended? There are practical considerations like what the work hours will be. This is especially true if the employee will be living in a different time zone. Who will provide and own the required office STRUCTURE magazine

equipment (computers, printers and telephone) and how will office supplies be provided? What about the reference materials and codes that are needed?

Perhaps some of the more relevant conversations involve what remote working means with respect to the employee’s career.

Working out of the house can be convenient and efficient. You are free from many of the minor distractions of the day to day office environment, but your ability to ascend to more senior leadership positions within the firm may be limited. This is often the tradeoff.

Additionally, the size, complexity or type of projects you can be assigned may be limited.

Consideration also needs to be given to how employees and projects will be managed. How will performance be evaluated, and on what schedule? How will quality control reviews be done and by whom?

For some firms, it is important to have remote employees physically in the office on some regular basis. This helps both the telecommuting employee and the regular office staff maintain personal relationships that promote teamwork and efficiency.

There are lots of other practical and functional details that will need to be discussed and agreed to before implementing a successful telecommuting arrangement. It is best to have either a written policy (if you have many employees in this situation) or a memorandum of understanding (if this is a unique situation) to ensure that the ground rules are understood by all. Aside from the obvious advantage of being able to keep a valuable employee, telecommuting can have other intangible benefits. Providing this type of workplace flexibility can both promote loyalty and be a substantial motivator.

A changing workplace environment is the new reality, and keeping up with the business best practices that are unique to the structural engineering community is a daily challenge for owners and managers. Fortunately, we are not alone in facing these challenges and we have many resources through our professional organizations to provide help and guidance. For example, CASE’s recently published National Practice Guideline on Project and Business Risk Management includes topics like project communication and the Standard of Care as well as staffing, continuing education and even a section on working remotely.

We are coming to the end of our project engineer’s telecommuting experience and are looking forward to his return to the office.

While this arrangement has had its challenges, in the end, it has been a success for both the firm and our engineer. And maybe I’ll be a little less nervous the next time I hear that door close, because it might just mean a window has opened somewhere.▪ David W. Mykins is the president and CEO of Stroud, Pence & Associates, a regional structural engineering firm headquartered in Virginia Beach, VA. He is the current chair of the CASE Executive Committee. He can be reached at dmykins@stroudpence.com.

7

January 2016

ADVERTISER INDEX

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ADAPT Corporation ............................ 28 American Concrete Institute ................... 3 Applied Science International, LLC....... 67 ASDIP Structural Software .................... 36 Cast ConneX........................................... 6 Concrete Reinforcing Steel Institute ...... 13 Construction Specialties ........................ 42 Dayton Superior Corporation ............... 19 Dlubal Software, Inc. ............................ 25 Fyfe ....................................................... 21 Geopier Foundation Company.............. 32 Halfen USA, Inc. .................................. 53 Hayward Baker, Inc. ........................ 30, 31 Integrated Engineering Software, Inc..... 37 KPFF Consulting Engineers .................. 45

Legacy Building Solutions ..................... 55 MAPEI Corp......................................... 57 NCEES ................................................. 49 Pile Dynamics, Inc. ............................... 29 Powers Fasteners, Inc. ............................ 27 PPI (Professional Publications, Inc.) ...... 11 RISA Technologies ................................ 68 S-Frame Software, Inc. ............................ 4 Simpson Strong-Tie............................... 17 Steel Deck Institute ............................... 12 Structural Technologies ......................... 41 Subsurface Constructors, Inc. ................ 33 Tekla ....................................................... 2 Wood Products Council ........................ 22

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name R U O Get Y his list! on t Visit our website to see what advertising opportunities are right for you! www.STRUCTUREmag.org

EDITORIAL BOARD Chair Barry K. Arnold, P.E., S.E., SECB ARW Engineers, Ogden, UT chair@structuremag.org John A. Dal Pino, S.E. Degenkolb Engineers, San Francisco, CA Mark W. Holmberg, P.E. Heath & Lineback Engineers, Inc., Marietta, GA Dilip Khatri, Ph.D., S.E. Khatri International Inc., Pasadena, CA Roger A. LaBoube, Ph.D., P.E. CCFSS, Rolla, MO Brian J. Leshko, P.E. HDR Engineering, Inc., Pittsburgh, PA Jessica Mandrick, P.E., LEED AP Gilsanz Murray Steficek, LLP, New York, NY Brian W. Miller Davis, CA Mike Mota, Ph.D., P.E. CRSI, Williamstown, NJ Evans Mountzouris, P.E. The DiSalvo Engineering Group, Ridgefield, CT Greg Schindler, P.E., S.E. KPFF Consulting Engineers, Seattle, WA Stephen P. Schneider, Ph.D., P.E., S.E. BergerABAM, Vancouver, WA John “Buddy” Showalter, P.E. American Wood Council, Leesburg, VA C3 Ink, Publishers A Division of Copper Creek Companies, Inc. 148 Vine St., Reedsburg WI 53959 Phone 608-524-1397 Fax 608-524-4432 publisher@structuremag.org

Courtesy of Nic Lehoux

Erratum In the December 2015 article on the NCSEA Excellence in Structural Engineering Awards, an incorrect photo was used for one of the winners. The image printed for the Kimbell Art Museum Expansion Project (Category 4) is a view of the interior of the original museum, not the expansion. This photo is a view of the final expansion. STRUCTURE apologizes for the error.

STRUCTURE magazine

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January 2016

January 2016, Volume 23, Number 1 ISSN 1536-4283. Publications Agreement No. 40675118.

Owned by the National Council of Structural Engineers Associations and published in cooperation with CASE and SEI monthly by C3 Ink. The publication is distributed free of charge to members of NCSEA, CASE and SEI; the non-member subscription rate is $75/yr domestic; $40/yr student; $90/yr Canada; $60/yr Canadian student; $135/yr foreign; $90/yr foreign student.

For change of address or duplicate copies, contact your member organization(s) or email subscriptions@STRUCTUREmag.org. Note that if you do not notify your member organization, your address will revert back with their next database submittal. Any opinions expressed in STRUCTURE magazine are those of the author(s) and do not necessarily reflect the views of NCSEA, CASE, SEI, C3 Ink, or the STRUCTURE Editorial Board.

STRUCTURE® is a registered trademark of National Council of Structural Engineers Associations (NCSEA). Articles may not be reproduced in whole or in part without the written permission of the publisher.

InFocus

Toward new trends, newatechniques BrightandFuture current industry issues

By Barry Arnold, P.E., S.E., SECB

J

on Schmidt, and the past and present editorial board, did an excellent job of building STRUCTURE magazine into a high-quality, sought-after publication. Under Jon’s leadership and the talent and commitment of the editorial board, STRUCTURE magazine has become a widely-read and wellrespected publication. The profession owes Jon, those who served with him, and those who have contributed content to the magazine, our sincere appreciation.

STRUCTURE magazine’s Vision Statement clearly defines the magazine’s destiny: STRUCTURE magazine will be the premier resource for practicing structural engineers. Its Mission Statement contains the road map of how the magazine will achieve its destiny: The Editorial Board will engage, enlighten, and empower structural engineers by publishing interesting, informative, and inspirational content in STRUCTURE magazine that is professionally relevant, technically reliable, and intellectually refreshing.

To guide the Editorial Board in making decisions regarding magazine content, they adhere to the following, equally important, objectives: First, disseminate useful tips, tools, and techniques that will help structural engineers increase the quality, productivity, and profitability of their work; Second, introduce new and innovative concepts in structural engineering through project descriptions, case studies, lessons learned, and other approaches; and Third, promote structural engineering as a true profession, not merely a technical avocation, and highlight how it is unique from the other design disciplines.

The Editorial Board, consisting of three members from ACEC/ CASE, three members from NCSEA, three members from ASCE/ SEI, and three members from industry, has done an excellent job of adhering to these objectives, mission, and vision. The Editorial Board’s work and contribution to the profession have been considerable and commendable. Having proven effective and valuable in the past, these are the objectives that the Editorial Board and I will continue following in pursuit of the magazines’ mission and vision.

In addition to the types of articles you are familiar with, the editorial board will continue to seek out articles highlighting unique design approaches and imaginative solutions. STRUCTURE magazine should be a safe place to learn. It should be a place where questions can be asked and discussed freely, as well as a place where structural engineers can express innovative ideas and opinions and receive a respectful critique from their peers. STRUCTURE magazine must be a place where quality education and enlightenment are received without fear or embarrassment. It must be a place where structural engineers can look to re-stock their technical, business, and managerial toolboxes with relevant information.

I may be the Editorial Chair, but I serve you and the profession.

STRUCTURE magazine is your magazine. The members of the Editorial Board are open to your comments and suggestions, and we will eagerly review any content you submit.

STRUCTURE magazine

I want to provide a magazine you want to read. I want this to be a magazine you look forward to receiving and spending time reading, devouring the ideas it contains and discussing the design approaches presented during inner-office, lessons-learned type meetings. I want to use this medium to inspire structural engineers and instill a vision of what we can accomplish. I want the readers to be inspired to dream big and speak proudly about the profession. I want you to be encouraged to bravely stand up, stand out, and stand for something. My hope is that every structural engineer will be inspired by the articles they read, that they will embrace the people they read about as mentors and find value in the insights they share. I want every structural engineer to wear the title structural engineer proudly as a badge of honor, and be willing to defend it fiercely and fearlessly. I want you to believe in yourself as much as I believe in you. I want STRUCTURE magazine to remain surprising, novel, and interesting by including the work of thought leaders. I want you to see a future with abundant opportunity and ways to express your creative and technical skills and ability.

Instead of worrying about changing the code every three years and complaining about having to obtain continuing education credits, we should worry that the value of being a structural engineer will plateau or decline. An engineer friend said that professional licenses were secure, and that the state would never take them away because they are a profitable revenue stream. Although his assessment and conclusion may be correct, it troubles me that, as a profession, we have missed the mark. If the only reason we are allowed to exist as a profession is because the states make money from licensing regulations, then somewhere along the way we have failed to adequately inform the public about the critical role we play in protecting their health, safety and welfare. Have the words professional and engineer become so over-used and so misused that they mean nothing? Have we spent so much time advocating structural engineering to structural engineers that our message hasn’t been heard by the public? Given all the accomplishments of the structural engineering profession, why, when the term engineer is mentioned, does the public only think of Howard Wolowitz?

While I am serving you as Editorial Chair of STRUCTURE magazine, I want the Editorial Board to support NCSEA, CASE, and SEI as they take action to strengthen and improve the profession in meaningful ways, so that it will exist in grand splendor in the future.▪ Barry Arnold (barrya@arwengineers.com), is a Vice President at ARW Engineers in Ogden, Utah. He chairs the STRUCTURE magazine Editorial Board, is the Immediate Past President of NCSEA, and a member of the NCSEA Licensure Committee.

9

January 2016

Structural DeSign design issues for structural engineers

H

istorically, reinforced concrete has been thought of as very forgiving when it comes to the amount of time the material performs in service. Although there is a lot of truth to this, the environment inevitably can shorten reinforced concrete’s life expectancy, resulting in costly repairs and disruption to everyday life.

When we think of durable concrete, the Pantheon in Rome comes to mind. This structure has been in service for well over 2000 years.

If Roman concrete can last for centuries, surely current construction materials should be suitable to serve a 50 or 100 year design life. In some ways, assumptions on material durability may have influenced early specifications which fail to address material performance over time.

As our understanding of durability increases, we expect increased performance of the materials we put into service. In the instance of landmarks or monuments, we want to build and preserve these structures in perpetuity.

As we are constantly striving to improve material performance, we simultaneously want to be more sustainable in our approach, and be proud of what we build. Like Roman engineering, attaining durable structures with an extended service life, like the Pantheon, should be our end goal.

A vast amount of research was carried out on the durability of concrete from the 1970s to the 1990s and a great deal of technical knowledge was achieved. It is now possible to utilize this information in our designs to provide a level of confidence to owners on the future performance of reinforced concrete structures.

To make reinforced concrete more durable, a design approach has to be considered; the

Durability of Reinforced Concrete

By Paul Noyce and Gina Crevello

Paul Noyce is a concrete and material durability expert. Paul is the Chairman of National Association of Corrosion Engineer’s (NACE) Standard Technical Group 01 for Reinforced Concrete. He may be reached at pnoyce@e2chem.com.

performance over time should be modeled where various dimensions and material specifications can be reviewed. This type of design is referred to as service life design (SLD), where the engineer can demonstrate performance of the selected structure over time, as seen in Figure 1.

The SLD has to demonstrate the performance and degradation of the engineering materials.

Both of these are heavily influenced by the environment which, in turn, is affected by local macro and micro climates. In addition to understanding the environment, knowledge of local materials is required, as this too varies greatly. Because of these variations, material performance and service life should be treated stochastically.

Performance and Degradation The performance of a structure is typically seen as how well it is functioning related to its use. This can be further expressed as the performance of key principles like load capacity, stability, safety and visual appearance. Performance is regarded by many as a quantifiable property and is always a function of time.

When considering time in evaluating performance, degradation of the structural materials is regarded as the most important factor. This links the structure’s performance directly with the durability of its materials. ASTM E632, Standard Practice for Developing Accelerated Tests to Air Prediction of the Service Life of Building Components and Materials, defines durability as the capability of maintaining the serviceability of a product, component, assembly, or construction over a specified time. Serviceability is viewed as the capacity of the above to perform the function(s) for which they are designed and constructed.

Degradation is the reduction or decrease in performance over time and can be understood

Gina Crevello is material conservator. Gina is on the board of the Association for Preservation Technology International. She may be reached at gcrevello@e2chem.com.

Figure 1. Probability distribution function of service life.

10 January 2016

as the inverse of performance; therefore, measuring degradation allows one to assess performance related problems. Performance is then measured by a minimum acceptable level, while degradation is set by a maximum acceptable level. These levels are known as durability limit states and can be defined for future performance measurements. The limit state can be set to either an ultimate or serviceability limit, which defines the service life and ultimately the performance requirements of the structure.

When looking at degradation problems in reinforced concrete, the two main materials, the concrete and the reinforcing steel, are what impact the durability of the structure.

The symbiotic relationship between reinforced concrete and steel ensures that, if defects exist within the original design or material selection and if load factors that enhance corrosion are present, deterioration will ensue. In turn, the environment in which these materials are installed impacts and defines their long term performance and degradation.

Service Life Service life of materials can be assessed by their expected lifetime, or their acceptable period of use in service. As service life can be

expressed in three ways, technical, functional or economic, then different use requirements are needed. In assessing service life as a business policy, financial tools and mathematical calculations can be carried out to develop a maintainability and reliability analysis.

The questions regarding service life and maintenance are always related as maintenance routines are carried out during the service life of the structure. Maintenance activities, which influence service life, need due consideration. This changes the overall definition of service life which is stated as “when routinely maintained” as defined in TC 71-PSL Systematic Methodology for Service Life: Prediction of Building Materials and Components (Masters and Brandt, 1989).

It is always the requirement of the owner to define the service life requirements and set forth the duration requirements, which sets the target service life.

Probability of Failure When a target service life is set, a stochastic durability design will involve a definition of the maximum probability of not reaching a certain limit state. These limit states can be either an ultimate limit state (ULS) or a serviceability limit state (SLS).

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January 2016

Two distinct types of failure exist, as either a durability failure or mechanical failure. However, in most instances, a material durability failure will be responsible for the mechanical failure.

A maximum failure probability has to be set and defined by evaluating the consequences of the risk of failure. The risk is defined as the multiplication of the probability of failure by the amount of damage (Kraker, de Tichler and Vrouwenvelder, 1982).

When considering how to set the required probability of failure, social, economic and environmental criteria should be considered.

For social criteria, the importance of the structure and the consequences of failure, where human lives are at risk, is essential. Economic criteria should consider the financial consequences of disruption due to failure when these are considerably more than the construction cost. As with environmental and ecological criteria, consideration is due to either an environmental disaster or in line with ecological principles.

Probability of failure can be applied during the design phase of new structures or to existing structures, as the principles are the same.

The only significant difference is that the margin of safety used for existing structures will be much lower than new construction. continued on next page

Table 1. Exposure categories and classes (ACI 318R-14 Table 19.3.1.1).

Durability Design Conceptually, a durability design is based around safety, where the structure must resist failure by various hazards it is exposed too. Safety has typically been applied to structural mechanics; however, we should not be so restricted in our design when dealing with the performance of materials. The use of this technique is increasingly advocated for dealing with durability and service life problems (Siemes, Vrouwenvelder and van den Beukel, 1985).

By incorporating time into the design, we can now value the degradation of the materials as part of the overall problem. This time-based design has to set performance related requirements to ensure that the structure fulfils its long term service life goals for safety. This then has the effect of forcing the designer to ensure that the material selection will achieve the long-term durability requirement for the service life goals.

Category

Class

Freezing and Thawing (F)

Sulfate (S)

Condition

F0

Concrete not exposed to freezing-and-thawing cycles

F1

Concrete exposed to freezing-and-thawing cycles with limited exposure to water

F2

Concrete exposed to freezing-and-thawing cycles with frequent exposure to water

F3

Concrete exposed to freezing-and-thawing cycles with frequent exposure to water and exposure to deicing chemicals Water-soluble sulfate (SO42-) in soil, percent by mass[1]

Dissolved sulfate (SO42-) in water, ppm[2]

S0

SO42- < 0.10

SO42- < 150

S1

0.10 < SO42- < 0.20

150 < SO42- < 1500 or seawater

S2

0.20 < SO42- < 2.00

1500 < SO42- < 10,000

S3

SO42- > 2.00

SO42- < 10,000

The Environment

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Concrete dry in service W0 In Contact Concrete in contact with water and low permeability is not required When considering a durability design, a with Water key understanding of the environment and (W) W1 Concrete in contact with water and low permeability is required the exposure of the materials is essential in achieving a good design. The building code requirements for structural concrete, the C0 Concrete dry or protected from moisture American Concrete Institute’s ACI 318-14, Corrosion defines exposure categories and classes as Concrete exposed to moisture but not to an external source of Protection of C1 shown in Table 1. BS EN 206:2013: Concrete chlorides Reinforcement Specification, Performance, Production and (C) Concrete exposed to moisture and an external source of Conformity, also provides exposure classes C2 chlorides from deicing chemicals, salt, brackish water, seawater, for concrete durability, as shown in Table 2. or spray from these sources Although both these tables differ overall, 1 Percent sulfate by mass in soil shall be determined by ASTM C1580. it can be seen that they both consider the degradation of the materials. ACI categories 2 Concentration of dissolved sulfates in water, in ppm, shall be determined by ASTM D512 or ASTM D4130. are broken down by a damage mechanism and then class, with a variation of severity. As with BS EN 206:2013, the class is broken down based on wet and dry cycles, with various corrosion risks associated with a letter in the exposure class.

As with most situations, a series of environments and contaminants can coexist on the same structure, so the design engineer must pay attention to this in the durability design. This can be extremely

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January 2016

Table 2. Exposure classes and class descriptions (BS EN 206:2013).

Exposure Class

Class Description

Corrosion Risk

X0

For concrete without reinforcement or embedded metal where there is no significant freeze/thaw, abrasion or chemical attack

No risk of corrosion or attack

XC1

Dry or permanently wet

XC2

Wet, rarely dry

Corrosion induced by carbonation

XC3/4

Moderate humidity or cyclic wet and dry

XD1

Moderate humidity

XD2

Wet, rarely dry

XD3

Cyclic wet and dry

XS1

XS1 Exposed to airborne salt but not in direct contact with sea water

XS2

Permanently submerged

XS3

Tidal, splash and spray zones

XF1

Moderate water saturation without de-icing agent

XF2

Moderate water saturation with de-icing agent

XF3

High water saturation without de-icing agent

XF4

High water saturation with de-icing agent or sea water Chemical attack (ACEC classes) Refer to BS 8500–1 and Special Digest 111

Corrosion induced by chlorides other than from seawater

Freeze/thaw with or without de-icing agents

term performance of a building or a structure can be drastically affected. QA is still, in our opinion, one of the major factors in achieving long term durability of concrete

structures. Whether designing new or fixing existing, attention to the installation of the work is paramount to the structure’s long term survival in our ever changing environment.▪

Design Aids and Solutions.

Analysis, design, done.

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complex on some structures but, if overlooked, can result in a degradation failure in an unacceptable period, which can cost many millions of dollars.

As we repair structures today, durability and the environment are not considered enough in their role in leading to premature and costly maintenance repairs.

The most deleterious durability failure of concrete is related to corrosion of the embedded reinforcing steel, which subsequently causes damage to the surrounding concrete and results in millions of dollars in damage, repair and associated ‘indirect’ costs.

Corrosion induced by chlorides from seawater

Summary In summary, it is essential that a holistic approach is used for the design of durable concrete structures by considering multi-faceted aspects of the structure, the structure’s relationship to its surroundings, appropriate material selection, the utilization of proper construction methods, adequate quality control and planned maintenance. Figure 2 provides an overall holistic approach to the considerations required to provide durable concrete structures.

As we can see from Figure 2, the overall approach to durability goes beyond the design engineer’s work. By reducing QA on a construction project due to cost and budget constraints, the long

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STRUCTURE magazine

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January 2016

Structural rehabilitation renovation and restoration of existing structures

Figure 1.

Precast, Prestressed Thin Slabs in Parking Garage Structures Or, When Thin is a Not a Win-Win

By D. Matthew Stuart, P.E., S.E., P.Eng., F.ASCE, F.SEI, SECB

D. Matthew Stuart (MStuart@Pennoni.com) is the Structural Division Manager at Pennoni Associates Inc. in Philadelphia, Pennsylvania.

R

ecently, Pennoni Associates was involved in the investigation and assessment of several existing parking garages constructed with precast, prestressed thin slabs. In this type of structural system, precast planks function as stay-in-place formwork and become a part of an overall composite slab once a field-cast topping is placed and the shoring is removed. Although this type of construction is common in bridge decks, it is more unusual in parking garages, except perhaps in the Delaware Valley and surrounding region. In those areas, it is popular in cast-in-place concrete building construction as a voided system and is referred to as Wideslabs. There appear to be no similar precast, prestressed thin slab products available for commercial use in the remainder of U.S.

The System The cross-section of the thin composite slab typically consists of a 2¼-inch-thick by 8-footwide solid precast, prestressed concrete planks in combination with a minimum 4-inch-thick castin-place concrete topping. The system is capable of clear spans of roughly 20 feet between beams that act compositely with the topping – either structural steel (Figure 1) or precast U-shaped beams that are infilled when the field-cast concrete is placed (Figure 2). The erection of the planks and beams requires the use of temporary shoring that remains in place until the field-cast topping is placed and has achieved adequate compressive strength.

The composite capabilities of the combined precast planks and cast-in-pace topping is provided

14 January 2016

primarily via vertical lattice or “filigree” reinforcing that is cast into the precast planks but protrudes above the top of them in order to engage the topping. The primary positive or bottom flexural reinforcing of the resulting system is provided by the prestressing strands (typically 3/8-inch diameter) in the precast planks, while the top or negative flexural reinforcing is provided via conventional deformed bars in the topping.

Temperature and shrinkage reinforcing is also provided transverse to the slab span in both the precast planks and the cast-in-place topping.

Unlike similar thin precast components used in parking garage construction, such as double tee flanges, mechanical plank edge connections (e.g., embedded plate weldments) are not employed along the abutting joints of adjacent planks. As a result, the nominal transverse reinforcing in the topping and aggregate interlock of the cast-inplace concrete are the only mechanisms available for transferring moving, concentrated vehicular wheel loads across the open joints below, as well as the tooled joints in the topping that generally align with the plank joints. A search of the available literature indicated that the structural capability of this portion of the thin slab system to function properly in a parking garage appears to be untested.

The Problem Similar to an aged and failed, tooled and sealed topping joint in a typical double tee parking garage structure, joints in a thin slab garage structure will allow for moisture intrusion into the joint. The moisture, which is typically contaminated with chlorides from deicing salts either applied to the surface or brought in from the road by vehicles, tends to migrate through the

Petrographic testing of thin slab planks revealed additional susceptibilities of the product, including the lack of sufficient airentrainment and concrete cover beneath the strands that was less than the 1-inch minimum recommended by ACI for precast slabs.

In addition, laboratory testing revealed significant coarse aggregate segregation due to high-slump concrete and/or over-vibration, as well as carbonation as deep as 1 inch from the bottom of the soffit.

The Solution for Older Garages

Figure 2.

joint. The moisture flows horizontally into the interface between the topping and precast via capillary action, and across the bottom surface of the soffit of the precast (Figure 3). As a result, any reinforcing steel that is adjacent to the joint will begin to corrode, causing the surrounding concrete to deteriorate.

In a double tee flange edge, this can result in isolated damage to the connectors and mesh reinforcing, which can often be repaired conventionally. In a thin slab plank, however, the proximity of the outside strand to the joint edge can result in the corrosion of a portion of the primary positive flexural reinforcing in the composite slab system. If the two outside strands of a typical 6-strand plank become corroded to a point at which a considerable amount of cross-sectional area is lost, or the strand is completely consumed – which is frequently the case because of the relatively

small diameter of the strand (Figure 4) – the associated 8-foot-wide section loses 33% of its positive moment capacity.

This vulnerability of the thin slab system is exacerbated by the lack of an adequate vertical load transfer mechanism at the joints. This susceptibility was evident even in garages that were only 5 to 10 years of age in which the condition of the tooled topping joint sealant appeared to be in very good condition. Test results indicated that the same level of contamination existed at both the driving surface above and the plank soffit joint edge below, with water-soluble chloride content as high as 2.63% by mass of cement versus an ACIrecommended limit of 0.06% for prestressed members. Similar planks in bridge decks do not appear to exhibit this phenomenon, primarily because tooled and sealed joints in the topping are not routinely used in such construction.

Figure 3.

Figure 4.

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The inability of individual deteriorated planks with completely corroded strands to share the support of imposed vertical loads with adjacent intact planks, due to the lack of mechanical connections at the thin slab joints, caused concern for the structural integrity of these planks. Furthermore, it was also not unusual for adjacent strands in adjoining planks to be corroded as well. This led to the development of the following mitigation strategy for the unsafe conditions created in garages, that were approximately 30 years of age, by the loss of one or more strands out of the available six in each plank.

Based on the age of these older garages, the original design live load was probably 50 psf.

Comparing this with the current minimum garage live load of 40 psf suggested a reserve capacity of 10 psf, or 20% of the assumed original live load capacity of the planks. A loss of only one out of six strands equated to a strength reduction of approximately 17%, which was less than the 20% reserve capacity. Therefore, planks that had only lost one strand were deemed to be still capable of safely supporting the minimum imposed live load. continued on next page

Figure 5.

The loss of two out of six strands, which was the maximum strand loss documented in any of the 30-year-old planks, equated to a strength reduction of approximately 33%, which was greater than the 20% reserve capacity. These planks required the installation of aluminum shoring beams immediately below the location of the corroded strand, which were shimmed tight to the underside of the plank soffit. The shoring beams spanned between, and were supported by, the existing steel beams that provided the original support of the planks (Figure 5).

The composite nature of the plank and topping, made possible by the vertical lattice shear reinforcing, also makes it difficult to facilitate conventional repairs to both the precast and cast-in-place components of the slab system. This is because the vertical shear reinforcing is not robust enough to avoid being significantly damaged when subjected to the renovation demolition of the surrounding concrete. Supplanting the existing shear reinforcement with alternate means of providing composite action was also not considered practical or economical. As a result, any repairs from the top surface or bottom soffit that encountered the shear reinforcement would cause a loss of composite action between the planks and topping.

This condition meant that practical options for conventional concrete repair were extremely limited. Additional challenges in the older garages included the absence of a chloride extraction or re-alkalization system that would not risk hydrogen embrittlement of the strands, insufficient concrete cover over the reinforcing, and non-uniform

air-entrainment and the resulting susceptibility of the concrete to freeze-thaw damage.

Because of these impediments, the most practical and cost-effective method of renovating the older garages involved the complete demolition, removal, and replacement of the existing composite slab system. A review of several options led to the selection of a 3¼-inch-thick cast-in-place slab on top of a shored 3-inch-deep composite metal deck, for a total thickness that matched the original slab system.

The Solution for Newer Garages The mitigation strategy for the newer garages, where the extent of chloride contamination and carbonation had not yet resulted in corrosion of the plank strands, was different. Due to the limited ability of the filigree vertical lattice reinforcing to withstand renovation demolition of the CIP topping and the difficulty of replacing it with an alternate method of ensuring composite action between the prestressed planks and the topping, the success of repairs to the surface delaminations was difficult to predict. This led to the recommendation to conduct a limited test program at one of the deteriorated surface areas in order to assess the potential for successful repair.

In order to prevent further moisture intrusion at the plank joints and the subsequent introduction of road salts, the top wearing surface would be coated with a waterproofing membrane after such repair.

The presence of significant chloride contamination of the plank soffits at the joint edges, even with the elimination of further

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January 2016

chloride-contaminated moisture migration due to the presence of a new surface membrane, would result in the eventual corrosion of the affected strands. This potential existed because of the exposure of the concrete to ambient conditions, which would allow for enough humidity in the concrete to be present to enable corrosion cells to develop. The recommended solution was installation of a surface-applied, metalized cathodic protection system on the plank soffit at the area of chloride contamination.

The recommended proprietary system was capable of providing long-term galvanic protection without damaging the prestressing steel via hydrogen embrittlement. The location and extent of the metalized cathodic system was established based on the results of an Electrical Resistivity survey. This allowed for the extent of the potential for corrosion to be mapped in areas not immediately adjacent to the plank joints, to ensure that the protection system did not have to be installed over the entire soffit.

Conclusion The results of the investigation revealed the susceptibility of precast, prestressed thin slab parking structures to corrosion and resulting loss of strength over the life of this type of construction. It is interesting to note that the International Parking Institute began discouraging the use of this type of product in parking garages in 2004. In addition, a number of reputable consulting engineering firms that specialize in the design of parking structures do not recommend the use of precast, prestressed thin slab members in garages.▪

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Technology information and updates on the impact of technology on structural engineering

Tilt-Up and BIM The Value Proposition

By Douglas G. Fitzpatrick, P.E. and Joe Steinbicker, P.E., S.E.

Douglas G. Fitzpatrick is President of Fitzpatrick Engineering Group in Cornelius, NC and is an avid BIM advocate. He can be reached at dfitzpatrick@fegstructural.com.

I

remember my first day of work as a young engineer like it was yesterday. The firm where I was starting my career was ceremoniously ditching the teletype machine that had provided them with computing power from a timeshared computer in a remote office building, in downtown Charlotte, NC, in favor of a desktop computer – a Wang SVP. It sported 32,000 characters of user memory (yes, characters – this was before MB and GB), a 500,000 character 8-inch diskette drive, and a 4 million character Winchester fixed disk drive. Some of you may have had one of these in your office.

The ability to run our little programs from the main frame computer downtown via the teletype punch tape reader had been a significant improvement over hand calculations, although each time you hit the run button there was a charge. “Garbage in = garbage out” had a price tag to it back then. While our new Wang had a not so insignificant price tag, we quickly discovered it gave us much more computing power than we could have imagined and many more opportunities to experiment with programming and our designs.

It didn’t take very long before we needed more computing power. We were really seeing benefits of local accessibility of the computer in the office but, more importantly, we were saving a significant amount of time. The computer had easily replaced hand number crunching with the enviable benefit of knowing if the programming was right, the answers would be right – every time – eliminating human error.

The mundane repetitive calculations we were doing by hand could be automated and free us to focus other things.

Of course, the rest is history. Computing power has grown by leaps and bounds. The sophistication

of our analysis and design software has allowed us to economically analyze buildings that would have been unthinkable when I first graduated.

The engineering community has been a significant beneficiary of what technology and computing power has to offer.

And now, we have BIM – a way to virtually construct a building before anyone lifts a hammer. Architectural and engineering disciplines can perform an electronic mash-up of their work before handing it off to the construction team. For the first time, they have an opportunity to know that all of their systems work and play together well.

Similarly, our construction partners have all seen significant improvements due to technology as well. Construction simulations, electronic tracking of materials at a job site, even laser scanning of existing conditions are common technologies at many of today’s construction sites.

But Some Things Have Not Changed Sadly, though, that’s where the significant technological improvements end. The way we get from design intent to construction has remained essentially unchanged since that first day as a young engineer (Figure 1). Our use of all of this wonderful 3D rich content dies with a hand-off of 2D paper drawings for construction. Both sides of the equation benefit greatly from technology individually, but the missing link – the gap between our two processes – is hindering the true efficiency improvements technology could really bring to bear on our projects.

In 2004, I left my old firm and started out on my own. We adopted BIM in 2006 and quickly recognized its potential. As my new firm expanded our use of BIM, this gap between design and construction became more apparent.

Joe Steinbicker is a charter member and past chairman of ACI Committee 551, Tilt-Up Concrete Construction. He is also a founding member of the Tilt-Up Concrete Association and past member of their Board of Directors.

He recently co-authored the book, Engineering Tilt-Up. He can be reached at joes@tilt-werks.com.

Figure 1. Traditional shop drawing process overly reliant on 2D documents.

18 January 2016

SIGN UP FOR A FREE TRIAL TODAY Figure 2. Complete steel and tilt BIM combined together for visual coordination.

The Process Needs to Change In 2012, we set out to change the old outdated process. We figured out a way to share our structural data, multiple times during the design phase of the project, with a steel detailing partner to shorten the delivery of steel to

our projects by 8 weeks. And, we eliminated the RFIs and change orders in the process by creating the steel fabrication package during design. Problem solved, with case studies to demonstrate the savings.

The key factor here was leveraging our structural data and sharing it downstream. We could use it both to improve our productivity from analysis to construction documents; and also make downstream processes more efficient, not just faster, by eliminating the recreation of data.

Once we saw the benefit this new process brought to the construction of our steel buildings, we started looking for other building types that could leverage what we had learned from steel. Our tilt-up projects seemed to be handicapped by many of the same problems.

Our analysis is done in 3D, yet the method of communicating our design is 2D. Someone else is typically responsible for coordinating the minutia of details, completing the engineer’s design intent and delivering it to the field in the form of shop drawings. And, much like our steel buildings, all of the construction phase work involves the recreation of data the engineer already has, and is subject to the same RFI and change order hazards.

Leveraging Lessons Learned In 2014, we started looking for tilt-up design software that would address the following criteria and allow us to really take advantage of BIM: • Working with walls as opposed to individual panels to minimize the bookkeeping while the design was changing, i.e., four walls instead of 100 individual panels • Adding loads globally to walls and the program divides the loads to individual panels continued on next page

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January 2016

TILT-WERKS.COM Tilt-Werks is a Unique & Powerful New Technology • Developed specifically for the tilt-up industry • Web based — Can be accessed anywhere, anytime

Tilt-Werks Automatically Generates: • Structural design for all walls/panels • Panel design/shop drawings • Panel reinforcing design & placing drawings • Complete panel reinforcing cut list • Material quantities & cost estimates • Dayton Superior product parts list & pricing • Building Information Models (BIM)

info@tilt-werks.com

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We do our work in BIM and hand off our design via 2D drawings, only to learn later that the contractor has recreated most of the original design models himself.

Schedules are generally a driving factor in most of our projects. It seems like everyone needs to get into their building quickly and the current economy has only escalated the need. One of the ways the construction industry has responded is by involving construction trade partners earlier. Identify the tasks on the critical path and get those players involved earlier. On most of our projects, that usually means getting the steel fabricator involved at some point during the design phase.

While I think we could agree that schedules have improved, it has been accomplished by taking an old, out dated process and simply making it faster, not more efficient. This is apparent by the increasing amount of RFIs and change orders we engineers have to deal with. Earlier involvement means our drawings are less developed, which translates into lots of clarifications. On our projects, early involvement typically means the fabricator is hired based on a GMP before the design is finished which has consistently resulted in change orders.

The constant parade of change orders for our steel buildings is not good for the industry, regardless of whether they’re justified or not.

Owners won’t tolerate having to pony up for more cost forever when they think they have been given a GMP.

• Adding panel geometry, openings and embeds • Associativity of components – move a support line, and loads and embeds move with it • Automated determination and design of the panel • Automated generation of panel layout drawings and reinforcing drawings • A BIM ready 3D output of the walls – an IFC complete with panel joints and openings • Quantity take-offs that we could share with downstream users.

Tilt-Werks® satisfied all of those criteria.

So, what can you do with all of this design information to add value to your tilt-up projects with BIM? With some careful planning of modeling and origins, the BIM you get from your steel design program can be attached to the IFC model you get from the tilt-up software.

The automated panel layout shop drawings from the tilt-up software – complete with embeds and openings – could be repurposed by attaching each drawing to the inside face of the wall IFC model at its respective panel location. That puts the steel framing, panels, openings and embeds all in the same context.

As the design evolves, the steel BIM gets updated from the analysis program, and the exported IFC and panel drawings are refreshed from the tilt-up software. You could end up with something like Figure 2 (page 19).

But Doug, you say, this looks like all the other images found on any company’s website on the internet. Where’s the value in another pretty picture? Not only that, this looks really tough to review and coordinate in 3D.

Leveraging BIM So, let BIM do all the work! By cutting sections at the face of the walls, coordination becomes very easy. The steel and tilt-up elements are all shown in context to one another and errors can be easily uncovered.

If you set your view attributes correctly, you can see which members are on the near side of the wall (solid) and which are on the far side (dashed). If you develop an embed naming convention that distinguishes between embeds on the upcast and downcast faces of the panel, you can visually verify that the embed labeling matches the location of the steel members – before the panels get built.

In our case, we use an asterisk to identify embeds on the downcast face. For coordination, we scan the extracted elevations (Figure 3) to make sure all embeds with an asterisk

Figure 3. Using BIM to verify embeds and framing in complicated areas.

Figure 4. Using BIM to resolve coordination errors for tilt-up construction.

have a dashed member at their location. If a solid member is found, one of the two is wrong and the correction can be made. Figure 3 is an example of a section cut with framing on both sides of the wall.

This composite BIM can also be used to check for errors as well, not just the upcast or downcast location of embeds. Because there are two analysis programs (steel and tilt-up), it’s not unthinkable that a change in one program doesn’t get picked up in the other, particularly while the design is changing. BIM is a perfect environment to do this error checking (Figure 4). This is an example where a new bay was added, the steel framing was modified but the tilt-up embeds had not been adjusted accordingly.

So, BIM can do a really great job of coordinating our steel design and tilt-up design. But, what if we take this a step further to add even more value? What if the quantity take-offs from the tilt-up software were shared with the tilt-up sub-contractor? If the take-offs are

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robust enough and include all of the items that the contractor needs to price the project – length of forming, gross and net square footage of the panels, length and size of reveals, quantities of embeds, tonnage of reinforcing, etc. – they could all be used at any point during the design to help monitor the cost of the structure. What contractor or owner doesn’t want to know where they stand during the design phases instead of waiting until the design is finished? At any point during the design you can provide a take-off that could easily have dollar amounts applied to it.

The Value Proposition Some of this may seem like a lot of extra work; some of it may not. The first time or two will require some trial and error as you home in on a system that works for your office. But once set up, updating is almost automated.

You are getting design information from your steel design program pushed down to your

lesser fee than you. Even though you know you do a better job than those other guys, trying to sell subjective benefits to a client (“better” engineering, faster response time to questions, always accessible, and just plain nice guys) is difficult at best and generally a waste of time.

However, if you can show you can add real value to a project – specifically time and/ or money – now you have their attention.

A difference in design fees could pale in comparison to the additional revenue an owner receives by getting in their building

The Bigger Picture I think we could all agree that the last seven years have been pretty tough on both the design and construction communities. Design fees are under constant pressure and it seems there is always someone willing to take a project for a STRUCTURE magazine

a month early. Leveraging BIM on your tilt-up projects is a great place to start for adding tangible value your clients will notice immediately.

By the way, if you’re doing what everyone else is doing, you’ll get paid what everyone else is getting paid. Find something your firm does better than everyone else, leverage it to the max to differentiate your firm from the rest and figure out how to translate it into real value for your clients. Hopefully, the thoughts presented here give you a decent starting place for your tilt-up projects.▪

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steel BIM multiple times during design, and as the tilt-up design continues to mature you can generate updated drawings, an IFC and quantity take-offs at any time.

Here’s a summary at some of the key valueadd you gain by doing this extra work: • Single source responsibility for the design and detailing. You are the EOR for the project. Your seal is on the building drawings. Who best knows how the building needs to go together.

Why not leverage that knowledge and put it to good use. Do the coordination yourself and know you have everything covered. You have to review the shop drawings anyway.

• Better coordination. If you have worked in BIM (3D) before, surely you have discovered something you wouldn’t have caught in 2D until the project was in construction.

Why wait for something to get caught later, regardless of who is “responsible”, and have to deal with the RFI (or change order) in panic mode during construction.

Coordinate early, save time later.

Leverage BIM to help with all of that work.

• Speed to market. If your tilt-up design program is able to generate the panel layout and reinforcing drawings automatically, you can easily generate a complete set of field use drawings when you issue your construction documents.

Think of the time savings you can offer your client by shortening the typical construction schedule.

• Quantity take-offs. If your tilt-up software gives you robust quantities (surface areas, embeds, weights, tonnages, reveals, etc.) at any time during design, allow that information to be used downstream.

This can be particularly helpful if you are working with a design/build or fast-tracked project. Everyone has their finger on the pulse of the project cost these days. Anything you could do to help with that would be valuable.

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January 2016

This article is a two part series which discusses special inspection provisions for wood construction in the 2015 International Building Code (Part 1) and perspectives from several States (based on the 2012 International Building Code) on suggested handling of special inspections regionally (Part 2).

S

pecial inspection is not a new term to the building code. The International Conference of Building Officials’ (ICBO) Uniform Building Code (UBC) has had special inspection requirements in the code since the 1961 edition. The Building Officials and Code Administrators’ (BOCA) National Building Code first introduced special inspection provisions in 1988. The ICBO and BOCA codes had a slightly different philosophy and emphasis, which resulted in very different special inspection implementation approaches in ICBO jurisdictions from BOCA jurisdictions. When the International Code Council’s (ICC) International Building Code (IBC) was first issued in 2000, it merged the ICBO and BOCA special inspection requirements into its Chapter 17. Today, the IBC continues this practice with criteria included in 2015 IBC Chapter 17, titled Structural Tests and Special Inspections. The Special Inspections in Chapter 17 are in addition to the inspections identified in Chapter 1 Section 110 and although Chapter 1 will not be covered in this article, Section 110.3.4 Frame Inspection is specific to wood construction elements.

Background Special inspection is a quality control measure intended to ensure that certain critical – mostly structural – features incorporated into a structure are constructed properly. This requires inspection by professionals (usually registered design professionals) with specialized skills and experience to verify that the material and workmanship comply with approved plans, specifications, and industry standards. Some aspects of construction may only need periodic inspection, while other aspects of construction require continuous inspection. In

most cases, wood construction is only required to have periodic inspections. The authority to enforce provisions contained in the building code for special inspections rests solely with the local building official. Since a building official certainly cannot be expected to be an expert on all technical building systems contained in a modern structure, inspectors are necessary who have special expertise to evaluate critical building components.

The purpose of special inspections is to provide additional evaluation and inspections above and beyond inspections which are normally performed by the building department, particularity in areas of construction where strength, safety, and construction practices have been determined by the building code, registered design professional, or building official to be sufficiently critical to warrant a special inspector.

Ensuring competence of the special inspector has always been and continues to be the responsibility of the building official.

The registered design professional in responsible charge and engineer of record involved in the design of the project are permitted to act as the approved agency, and their personnel are permitted to act as the special inspector for the work designed by them, provided those personnel are qualified to perform the inspection and are approved by the building official.

Codes and standards updates and discussions related to codes and standards

Special Inspections for Wood Construction – Part 1

By David P. Tyree, P.E., C.B.O., James B. Smith, P.E. and Michelle Kam-Biron P.E, S.E., SECB

Pre-fabricated Wood Members The definition of a pre-fabricated item is located in Section 202 of the IBC. The definition notes that any item that is manufactured in accordance

Figure 1. National Design Specification® for Wood Construction,Table A1 Standard Common, Box, and Sinker Nails.

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David P. Tyree is the Central Regional Manager, James B. Smith is the Midwest Regional Manager, and Michelle KamBiron is the Director of Education at the American Wood Council, Washington, DC.

to provide written documentation to the building official demonstrating that the special inspectors are qualified individuals who demonstrate competence, and relevant experience and training, for the inspection of the particular type of construction or operation requiring special inspection or testing.

Generally, it is the opinion of most building officials that the increased involvement by the registered design professional in responsible charge during the construction process of a project will help facilitate early detection of code and structural problems, which can be resolved much more easily when caught at an earlier stage of construction.

The building codes do not specifically state how a special inspector is to be considered qualified. Minimum qualifications are somewhat clarified in IAS Accreditation Criteria for Special Inspection Agencies (AC291), but additional assistance can be found in other documents concerning special inspection as well and can be of help to the building official.

Figure 2. Special design provisions for wind and seismic – high load diaphragm nailing details.

with one of the standards referenced in the code (Chapter 35) is not to be considered a fabricated item and thus is not subject to the special inspection requirements of Section 1704. However, this exception is only permitted if the fabricator maintains approved detailed fabrication and quality control procedures that provide a basis for control of the workmanship and the fabricator’s ability to conform to approved construction documents and the code. As an example, most metal plate connected wood trusses, glued laminated timbers (glulam), and I-joists are manufactured to a referenced standard (such as ANSI A190.1 for glulam). Therefore, unless there is an unusual situation where a reference standard is not being used, special inspection of these items is not required by the IBC. Chapter 23 of the IBC specifies requirements for wood design and construction. Section 2303 specifies the minimum standards and quality control procedures for various wood products. Quality control certification programs such as those implemented by APA– The Engineered Wood Association, Truss Plate Institute, International Accreditation Service (IAS), etc., are covered under provisions specified in IBC Section 1704.2.5.1 for “fabricator approval.” These requirements include a comprehensive audit to stringent industry-specific performance criteria by trained auditors and industry professionals.

IBC Section 1704 outlines requirements for special inspections and tests, contractor

responsibility and structural observation.

Since the 2000 IBC was published, this section of the code has changed several times and provides much more guidance for the building official.

Special Inspection and Tests Where application is made to the building official for construction as specified in Section 105, the owner or the owner’s authorized agent, other than the contractor, shall employ one or more approved agencies to provide special inspections and tests during construction on the types of work listed under Section 1705.

Per Section 1704.2, there are exceptions as to where special inspections are required including: construction of a minor nature or in situations where the building official does not feel special inspection is necessary; portions of structures designed and constructed in accordance with Section 2211.7 for cold-formed steel light frame construction or conventional light-frame construction in accordance with Section 2308; and, a Group U occupancy which is accessory to a residential occupancy including but not limited to those uses listed in Section 312.1. Additionally, it is noted in this section that the contractor is permitted to employ the approved special inspection agency where the contractor is also the owner.

Prior to the start of construction, the approved special inspection agency is required

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Special Inspection for Wood Construction Sections 1705.5.1, 1705.11 and 1705.12.2 of the IBC specify special inspection requirements for wood construction, and these are in addition to basic requirements of the frame inspection in Section 110.3.4. The IBC does not contain special inspection requirements for conventional wood frame construction per Section 2308, which is specifically exempted from special inspection as noted previously.

The IBC specifies generally that all wood special inspections be “periodic” as opposed to “continuous”, except in Sections 1705.11.1 and 1705.12.2 where continuous special inspection is required during field gluing operations of the main wind force-resisting system in certain high wind areas and of the seismic force-resisting system in seismic areas.

Therefore, the special inspection frequency is usually left to the special inspector’s discretion unless the structural engineer specifies a specific frequency of inspections in the Statement of Special Inspections.

Statement of Special Inspections IBC Section 1704.2.3 requires a “Statement of Special Inspections.” The extent and duration of special inspections, as well as their frequency, should be clearly stated. Not all buildings are created equal; therefore, when considering the statement of special inspections, the required number of inspections for specific elements should take a number of factors into

consideration such as complexity of construction details, the general contractor’s wood construction skill and experience, building size, and staffing of the building department.

High-Load Diaphragms Under the 2015 IBC, section 1705.5.1 requires special inspection of high-load diaphragms designed and constructed in accordance with Section 2306.2. Per Section 1705.5.1, the special inspector is required to complete the following when inspecting high-load diaphragms: • inspect the wood structural panel sheathing to determine whether it is the grade and thickness shown on the approved construction documents • verify the nominal size of framing members at adjoining panel edges • verify the nail or staple diameter and length (Figure 1, page 23) • determine the number of fastener lines • verify that the spacing between fasteners in each line and at edge margins agrees with the approved construction documents (Figure 2) Additional special inspection requirements for high wind and high seismic areas are listed in

Sections 1705.11.1 for wind and 1705.12.2 for seismic.

Metal-Plate-Connected Wood Trusses Spanning 60 Feet or Greater The 2015 IBC section 1705.5.2 requires special inspection when a metal-plate connected wood truss has a clear span of 60 feet or greater. The special inspector is required to verify that the temporary installation restraint/ bracing, and the permanent individual truss member restraint/bracing, are installed in accordance with the approved truss submittal package. This section specifically requires that the owner or his/her authorized agent employ one or more approved agencies to perform inspections on the temporary and permanent truss bracing during construction to verify installation is in accordance with the truss submittal package.

Special Inspections for Wind and Seismic Resistance Section 1705.11 requires special inspections for wood buildings in Exposure B

areas where design wind speed, Vasd , as determined in accordance with Section 1609.3.1, is equal to or greater than 120 miles per hour; and in Exposures C & D areas where Vasd is equal to or greater than 110 miles per hour. Continuous special inspection is required during field gluing operations of elements of the main wind force-resisting system, and periodic special inspection is required for nailing, bolting, anchoring and other fastening of elements of the main wind force-resisting system, including wood shear walls, wood diaphragms, drag struts, braces and hold-downs. Section 1705.11.3 goes further to state that special inspections should include periodic inspection for fastening of the following systems and components: roof covering, roof deck, roof framing connections, exterior wall coverings, wall connections to the roof, and floor diaphragms and framing (Figure 3b, page 26).

Section 1705.12.2 requires special inspections for wood buildings when the building is located in Seismic Design Categories C, D, E or F. In these Seismic Design Categories, continuous special inspection is required during field gluing operations of elements of the seismic force-resisting system and periodic inspection is required for: nailing, bolting,

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January 2016

Dynamic Analysis

(a)

(b)

Figures 3a and 3b. Periodic special inspection is required for nailing, bolting, anchoring and other fastening of elements of the seismic and main wind forceresisting systems, including wood shear walls, wood diaphragms, drag struts, braces and hold-downs.

anchoring and other fastening of the elements of the seismic force-resisting system, including wood shear walls (Figures 3a and 4), wood diaphragms (Figure 3b), drag struts, braces, shear panels, and hold downs.

Sections 1705.11.1 and 1705.12.2 further provide for an exemption from special inspection for wood shear walls, shear panels, and diaphragms, including nailing bolting, anchoring, and other fastening to other elements of the main wind force-resisting system where the diaphragm fastener spacing is greater than 4 inches. This exception is intended to exempt less highly-stressed lateral force resisting systems from special inspection. Additionally, a general exception to special inspection for seismic force resistance is provided in Section 1705.12 for buildings of light-frame construction not exceeding a building height of 35 feet and located in areas where SDS does not exceed 0.5.

The purpose of special inspection requirements in these areas is to provide additional public safety in higher wind and seismic zones, and to provide assurance for the structural engineer of record and the building department that the structure is being built in accordance with the proper design and performance specifications.

with all of the requirements of the approved construction documents. Structural observation does not waive nor is it an alternative to the inspections in Section 110 or the special inspection requirements in Section 1705.

Typically, observation occurs during significant construction stages and at the completion of the structural system. The objective of the structural observation is to become familiar with the progress and quality of the contractor’s work, and then determine if the work is being completed in general conformance with approved plans and specifications.

Observation is a contract-negotiated activity which is usually performed by the structural engineer as a part of the normal scope of services. Structural observations are mandated for certain high wind or high seismic areas, Risk Category III or IV buildings, and in other circumstances in accordance with IBC Section 1704.6. At the conclusion of the work included in the permit, the structural observer is required to submit to the building official a written statement that the site visits have been made and identify any reported deficiencies that, to the best of the structural observer’s knowledge, have not been resolved.

Structural Observations When required by Sections 1704.6.1 for those structures assigned to Seismic Design Category D, E or F or Section 1704.2 for those structures sited where Vasd , as determined in accordance with Section 1609.3.1 exceeds 110 mph, structural observations are to be provided on a project. Structural Observation is the visual observation of structural systems by a Registered Design Professional (i.e., licensed engineer or architect) for general conformance with approved construction documents. Structural Observation is intended to assist and supplement the work of the Building Official.

Structural Observation by itself does not certify, guarantee, or ensure conformance

Figure 4. Shear wall nailing details.

STRUCTURE magazine

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January 2016

Conclusion Requirement for special inspections in the model building codes have been mandated since 1961; however, special inspections pertaining to wood construction have only been required for the past twenty-five years.

Structural provisions in the building codes, including those for special inspection, have evolved based on experience following natural and manmade disasters. Certain types of wood construction require special inspections per IBC Chapter 17. Most commonly specified wood products have quality control and third-party auditing procedures in place that exempt the manufacturer from these additional requirements. High capacity (blocked) diaphragms and applications for certain high wind and high seismic zones, however, are the most common examples where special inspections for wood construction are required. Part 2 of this article will provide perspectives from several States (based on the 2012 IBC) on suggested handling of special inspections regionally.▪

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Foundation Companies Had

A GOOD 2015

and Look Ahead to

A STRONG 2016

STRONG DOLLAR MAY IMPACT OVERSEAS PROJECTS

By Larry Kahaner

I

STRUCTURE magazine

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January 2016

ADVERTISEMENT–For Advertiser Information, visit www.STRUCTUREmag.org

n a solid market for foundation services, companies are rampAt Geopier Foundation Company (www.geopier.com), President ing up new products and services to keep pace with demand. Kord Wissmann says that the ground improvement industry as a “Because foundations are the first step in construction, this whole is changing rapidly and interfacing with the structure engiindustry tends to experience trends a little bit before the rest of neering community in lots of ways. “It seems that this part of the the construction market. By analyzing economic trends, I suspect we’ll whole ground-support-for-structures segment is expanding rapidly. continue to see the American market recover and yield good results for Within our company we have two new things that SEs might like the foundation industry,” says Gina Beim, Senior Consulting Engineer to know about. One is within the rigid inclusion realm of things. and Marketing Director at Pile Dynamics, Inc. (www.pile.com). For We have developed something called a GeoConcrete Column that her own company, she notes: “Business has been good, but the strong is being used to support fairly heavy loads on very, very soft soil. dollar is affecting sales in some international markets, particularly in Most of that work is being done on the East coast, New England Asia. In the United States, however, sales increased in 2015 when compared to the previous year.”

Thermal Integrity Profiler (TIP) For 2016, Pile Dynamics will launch a new product called SQUID. Beim says, The Heat Is On. “SQUID is a large device that attaches to the end of the Kelly bar used in founShape, quality, cage alignment and dation drilling, and assesses the quality concrete cover of drilled shafts. of the bottom surface of the bored pile or drilled shaft hole. It is a disruptive New TIP Reporter Assesses the entire cross section, shows soil profile and no blind zones. technology, in that this assessment is reinforcing cage. currently made qualitatively only – visuTesting with the TIP is fast and ally, by means of a video camera lowered is done soon after casting, so down the hole. The SQUID instead meaconstruction can move on. sures stuff – it’s a quantitative assessment, Complies with ASTM D7949. which, of course, engineers prefer. The device measures the thickness of any soft material or debris still to be cleaned from the bottom of the hole. It can also take some measurements that evaluate the strength of the bearing layer, which is the layer at the bottom of the hole where www.foundations.cc www.pile.com/tip engineering@foundations.cc sales@pile.com the shaft is supposed to rest.”

and the mid-Atlantic regions,” Wissmann says. “GeoConcrete Columns are a form of rigid inclusions which are becoming quite popular to support structures. These are foundation, systems that are neither deep foundations nor are they shallow foundations, but something in between. Sometimes, when traditional forms of ground improvement don’t quite do the trick, then rigid inclusion is being used, a ground improvement element that’s constructed with cement.”

He adds: “The second item is improvements to our Rammed Aggregate Pier systems. We have a hybrid called the X1 system. It’s a way of constructing a Rammed Aggregate Pier where we can partially drill a hole and then use our tool to displace the remainder of the hole. This particular type of compaction device does a good job of compacting the Rammed Aggregate Pier in place. The advantage to SEs is that it’s a more efficient way of building Rammed Aggregate Piers, saving time and money on projects.”

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STRUCTURE magazine

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January 2016

Wissmann sees a trend towards increased use of ground improvement and more methods for SEs to choose from. “Business is up this year versus last year. Last year was a tremendous year for us, and this year is still better.” (See ad on page 32.)

Eric Droof, President of Hayward Baker (www.haywardbaker.com) says that some engineers are still not familiar with all the ground improvement services that are available. “I think these things are still not well understood by consulting geotechnical engineers. Consulting geotechnical engineers

typically don’t have the knowledge or skills to design these solutions. Some of the solutions include products like soil mixing, earthquake drains, jet grouting, aggregate piers and rigid inclusions.”

He says these methods are typically replacements for deep foundations, or solutions for very soft or difficult soil conditions. “They offer lower cost, reduced time for construction, reduced cost for foundation construction, and they also offer seismic mitigation in conjunction with foundation support.” continued on next page

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GROUTING Cement Grouting (High Mobility Grouting) • Chemical Grouting • Jet Grouting Compaction Grouting (Low Mobility Grouting) • Fracture Grouting • Polyurethane Grouting GROUND IMPROVEMENT Dry Soil Mixing • Dynamic Compaction • Injection Systems for Expansive Soils • Rapid Impact Compaction • Rigid Inclusions (Controlled Stiffness Columns) Vibro Compaction • Vibro Concrete Columns • Vibro Piers® (Aggregate Piers) Vibro Replacement (Stone Columns) • Wet Soil Mixing STRUCTURAL SUPPORT Augercast Piles Drilled Shafts • Driven Piles • Franki Piles (PIFs) • Helical Piles • Jacked Piers • Macropiles® Micropiles • Pit Underpinning EARTH RETENTION Anchors • Anchor Block Slope Stabilization Gabion Systems • Micropile Slide Stabilization System (MS3) • Secant or Tangent Piles Sheet Piles • Soil Nailing • Soldier Piles and Lagging ADDITIONAL SERVICES Earthquake Drains Sculpted Shotcrete • Slab Jacking • Slurry Walls • TRD Soil Mix Walls • Wick Drains DESIGN-CONSTRUCT SERVICES

STRUCTURE magazine

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January 2016

Says Droof: “Business is pretty good. The commercial markets in major urban areas have come back nicely. Places like New York, Miami, Atlanta and Los Angeles are all busy with the commercial sort of residential construction, as well as educational and hospital.”

He says that the company is excited about a new project in lower Manhattan. “It’s a 55-story residential tower. We’ve just completed the jet grouting for it.” He says that the alternative would have been 190-foot deep drift shafts. “We believe it will be the first high rise building in lower Manhattan that is not supported by a deep foundation.”

At Adapt Corporation (www.adaptsoft.com), President Florian Aalami says: “We have made major advancements in our ADAPTBuilder software platform for integrated design of concrete

buildings, in particular for the design of foundations using the ADAPT-MAT module. Structural engineers can now model a complete building, including all details of the foundation system.

Global gravity and lateral analysis results are available for detailed foundation design, all within the same model, without requiring the need to first export/import the solution between programs.

This saves time and reduces errors often introduced when translating global building analysis results into separate foundation design programs. ADAPT-MAT can be used to design any type of foundation system.”

Aalami notes that he sees a continuing trend towards BIM even though many practitioners are not completely clear about their BIM requirements. “We also continuously hear complaints about how it is much more efficient to design and detail steel buildings, compared to what is possible for concrete structures. The potential to deliver ever more efficient, complete concrete design solutions is what keeps us motivated.”

As for business, Aalami says, “The U.S. market has been very strong this year, but we are seeing some softening in international markets. We largely attribute this to the slowdown in their economies and the weakening of many international currencies against the U.S. Dollar.” (See ad on page 28.)

The company Subsurface Constructors (www.subsurfaceconstructors.com) has had a busy year, according to Lyle Simonton, Director of Business Development. “In addition to it just being an extremely busy year, Subsurface Constructors has had some exciting new experiences in 2015,” he says. “We completed Aggregate Pier ground improvement projects in several new states, including Washington, Alabama, and New Hampshire. We had some huge news with the opening of our New England office, just outside of Boston. Having a physical presence in this region will help us to remain competitive on bid day and provide better support to Give your structure stabilit y the engineering community.”

Simonton adds: “More than ever before, Work with Geopier’s geotechnical engineers to solve your ground we are working directly with structural improvement challenges. Submit your project specifications to engineers during the design phase of receive a customized feasibility assessment and preliminary cost projects to help develop the optimum foundation plan using Aggregate Pier estimate at geopier.com/feasibilityrequest. ground improvement. We are providing them with specific project information 800-371-7470 regarding bearing pressures, which can be geopier.com achieved with Aggregate Piers.” info@geopier.com He says that Subsurface Constructors was fortunate to have been involved with several high profile St. Louis area projects in 2015, including a large earth retention ©2016 Geopier Foundation Company, Inc. The Geopier® technology and brand names are protected under U.S. patents project at the Gateway Arch and trademarks listed at www.geopier.com/patents and other trademark applications and patents pending. Other foreign patents, patent applications, trademark registrations, and trademark applications also exist. and completing the ground improvement work for the St. Louis IKEA store.▪

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Geopier Ground improvement controls structure settlement

STRUCTURE magazine

32

January 2016

A New Era of Women’s Health for Central Florida

By Kevin Casey, P.E., S.E., Bill Mitzo, P.E. and Nathan Morrow, P.E.

T

he Florida Hospital for Women is located on the main campus of Florida Hospital South in Orlando, FL. It is a 12-story, 430,000 square-foot facility dedicated to the health and well-being of women and new born children, with a 322-bed tower. Opened in December 2015, the facility includes 14 labor and delivery suites, 13 operating rooms for obstetric and women’s services, 72 postpartum care beds, mother-baby beds, high-risk beds and 80 neonatal intensive beds. The operating rooms accommodate robotic surgeries for obstetrics, including the da Vinci Surgical System for robotic minimally invasive surgery.

The building is situated on a tight urban site bordered by CSX rail lines on the west, the 3-story Andersen Wing, an existing 40 year old hospital building, on the north, the 10 year old 7-story Walt Disney Pavilion for Children on the northeast corner, Rollins Street, a public street on the south and the main hospital entrance on the east.

Structural Frame A cast-in-place concrete building was the preference of the hospital, based on their previous success with concrete construction. The benefits to the hospital include: • Inherent fire protection • Accommodates future modifications and changes of use, with minimal disruption to ongoing operations in a sterile environment • Inherent ability to dampen vibrations The project team evaluated two framing systems during the schematic design phase. Preliminary designs were prepared by Paul J. Ford & Company (PJF) for a conventionally reinforced 27-inch deep module joist and beam system (5-inch slab + 22-inch pans) and a 12-inch conventionally reinforced concrete flat plate. Post-tensioning was not considered as conventional reinforcing is more easily modified for future floor penetrations and openings required for healthcare STRUCTURE magazine

Figure 1. Campus plan.

facilities. The designs were evaluated by the team and the flat plate was selected based on the following benefits: • Accommodated an irregular column layout dictated by the building’s unique curvilinear shape • Minimized the structural floor depth allowing increased interstitial space for high demand MEP systems necessary for a hospital • Reduced the overall height of the building by 12 feet, reducing the cost of the building envelope • Simplified the form work and reinforcing steel placement • Increased the speed of construction Columns are typically 30 x 30 inches from foundation to roof. Interior columns from the foundation to Level 7 are 30 x 36 inches. Concrete strengths varied from 7000 psi to 5000 psi.

Concrete reinforcing steel was specified to be Grade 60 for bars up to No. 9 and Grade 75 steel for No. 10 and No. 11 bars. Specifying the higher strength steel for the larger bars eased congestion by reducing the required number of bars, and saved placement costs. The material cost for the Grade 75 bars was 4% greater than the Grade 60 bars.

The primary lateral load resisting system is an ordinary concrete shear wall system. A “blade” shear wall was required at the south end of the building to supplement the stair and elevator cores, in order to maintain torsional rotation within allowable limits.

34

January 2016

Figure 2. Isometric view of Revit model.

Figure 3. Progress as of September, 2015.

An elevated pedestrian bridge located between the second and third levels connects the new hospital to the New Bedford Tower on the south end of the hospital. Escalators connecting the bridge lobby to the main lobby on Level 1 dictated the need for a transfer girder over the escalators. A one-story connector was included along the north east corner that connects to the existing Children’s Hospital.

RWDI to determine the expected vibrations in 1/3 octaves for several representative trains at various locations in the building.

Three types of trains travel the rail lines; passenger, freight and heavy freight trains. The predicted vibration levels on Level 1 and Levels 3 through 12 achieved the required 4000 mps criterion. The predicted vibration levels on Level 2 achieved the required 1000 mips criterion for the passage of passenger trains and freight trains. The predicted vibration levels on Level 2 due to the passage of a heavy freight train exceeded the required 1000 mips criterion for that level.

Vibration mitigation was implemented on Level 2 by stiffening the floor system to a 24-inch deep beam and slab (12 inch slab and 12 inch pan) system.

Additional measures were evaluated to further mitigate vibration from the heavy freight trains including a base isolation system, isolating the rail lines, or constructing a deep slurry wall between the building and the rail lines. The base isolation system was not a viable option, as it was cost prohibitive. Isolating the rail lines or constructing a deep slurry wall may be implemented in the future, if deemed necessary by the hospital.

Vibration Study and Design Minimizing vibrations is a design consideration in all healthcare environments in order to assure a comfortable environment for patients, and is necessary to allow uninterrupted medical procedures. All healthcare facilities must be checked for footfall induced vibrations. The heavily traveled CSX rail lines located immediately to the west of the new Women’s hospital presented a unique design challenge to the team.

Vertical vibration criteria used in the design were an ISO Operating Theater vibration criteria of 4000 micro-inches/second (mips) for patient rooms and other patient areas, and a VC-B vibration criterion of 1000 mips for the operating rooms on Level 2. A limit of 4000 mips is on the threshold of human perception. A limit of 1000 mips is suitable for micro-surgery, eye surgery and neurosurgery.

Preliminary structural calculations indicated the building structure met the 4000 mips criteria for patient rooms and other patient areas due to footfall, but did not meet the 1000 mips criteria for the L2 operating rooms. It was estimated that a 27-inch beam and slab system would be required to meet the 1000 mips criteria from footfall.

In order to measure the vibration effects from the adjacent rail lines and to conduct studies on the vibration performance of the building, RWDI was retained by the hospital. Part of that study included taking ground vibration measurements in the form of time-history accelerations and determining the vibration performance of the new hospital. RWDI created a model of the mat foundation and soil properties using the soil-structure interaction software Dyna5.4. A shear-wave velocity of 660 fps, provided by Terracon, the project geotechnical engineer, was used for the soil surrounding the foundation.

The measured time-history accelerations were applied to the Dyna5.4 model and the response of the foundation was then used as an input load to a SAP2000 finite element model. PJF’s ETABS model was used to generate the SAP2000 finite element model that was modified for dynamic analysis. The velocity responses were determined at specific points in the SAP model. These records were processed by STRUCTURE magazine

Geotechnical-Structure Iterative Foundation Design PJF and Terracon worked closely together on the foundation design for the new facility to arrive at a system that saved two months on the construction schedule.

Four foundation systems were considered for the hospital; auger cast piles, auger cast displacement piles, a mat foundation on improved soils, and a mat foundation.

Preliminary designs were carried out for a deep foundation system with auger cast displacement piles and a mat foundation.

The deep foundation system utilized 18-inch diameter, 50-foot long, auger cast displacement piles with a capacity of 100 tons. In addition to the construction of the piles and pile caps, a 2-foot thick heavily reinforced slab was required to resist the hydrostatic pressure due to the high water table common throughout Central Florida.

The mat foundation was designed to be 5 feet thick, sufficient to resist the hydrostatic pressure and punching shear from the columns.

PJF and Terracon worked together to evaluate the need for rigid inclusions under the mat to minimize overall settlement and differential settlement. The settlement for the mat without ground improvement was initially predicted to be on the order of 3 to 4 inches.

35

January 2016

continued on next page

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The team decided the predicted settlement was within an acceptable limit, and that further study of a mat foundation without ground improvement was warranted.

PJF and Terracan proceeded to study the mat foundation. The study was conducted based upon the following parameters: • The mat (raft) foundation was supported on ground without deep ground improvement elements, i.e., no rigid inclusions or similar ground improvement elements were included in the analysis.

• The thickness of the mat foundation was 5 feet.

• The modulus of sub-grade reaction values, i.e., the spring constants, ranged from 6 pci at the interior of mat foundation to 12 pci at the perimeter of the mat foundation.

• Four iterations of calculations were conducted between PJF and Terracon in order for settlement results to converge between the structural model and geotechnical model. The structural engineer utilized SAFE and ETABS for its analyses, and the geotechnical engineer utilized PLAXIS for its analyses.

The results of the study are summarized as follows: • The total settlement of the mat foundation was predicted to be in the order of 2.5 inches at the interior core area at the patient elevators to 0.90 inches along the east edge of the mat.

• Approximately 25% of the expected total settlement will occur due to the weight of the mat prior to the casting of the Level 1 structural slab.

• The expected differential settlement in the mat was a slope rate of 0.002 or L/500.

• The settlement of the structure along the existing Anderson Building and Disney Pavilion was expected to in the order of 0.75 inches to 1.50 inches.

• The maximum contact pressure below the mat foundation was 3800 psf.

The calculated settlement values were conservative and are on the upper bound of the expected actual values based upon previous experience with similar projects.

The project team concurred that the settlements were within acceptable limits.

Figure 4. Mat preparing for concrete placement.

Project Team Structural Engineer of Record – Paul J. Ford & Company Owner – Florida Hospital Office of Design and Construction Architect – HKS Gerneral Contractor – Brasfield & Gorrie The three story areas of the building on the south and east elevations were supported by shallow foundations. Construction of these areas of the structure was phased to occur simultaneously with the construction of the final three levels of the tower, in order to minimize the risk of differential foundation settlement.

Conclusions Measurement during construction indicated the overall settlement of the mat averaged about 1 inch with minimal differential settlement.

The majority of the settlement occurred during construction of the building frame, as predicted.

Schematic design of the new Florida Hospital for Women started in April, 2012. Construction broke ground on January 9, 2013. Concrete for the mat foundation was placed on February 8, 2014 and the concrete frame topped out October 31, 2014. The hospital opened in December, 2015.

The Florida Hospital for Women introduces a whole new era of high-technology care for the women of Central Florida.▪ Kevin Casey, P.E., S.E., is a Vice President and can be reached at kcasey@pjfweb.com.

Bill Mitzo, P.E., is an Engineering Manager and can be reached at bmitzo@pjfweb.com.

Nathan Morrow, P.E., is a Project Manager and can be reached at nmorrow@pjfweb.com.

All three work in the Orlando office of Paul J. Ford & Company.

STRUCTURE magazine

36

January 2016

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STRUCTURAL REPAIRS for COURTHOUSE SQUARE Completed complex.

By Tarek Alkhrdaji, Ph.D., P.E.

T

he Courthouse Square complex, located in the heart of Salem, Oregon, is owned by Salem-Keizer Transit and Marion County. The complex occupies an entire city block and consists of three structurally independent, architecturally contiguous structures; a five-story office building, a transit mall, and a future development site (North Block). An existing belowground parking facility extends under the three structures and occupies the entire block. The complex was first opened to the public in September 2000.

The original floors and roof of the office building consist of flat plate, 10-inch thick post-tensioned concrete slabs, supported by reinforced concrete columns and a perimeter reinforced concrete foundation wall at the basement level. The lateral force resisting system for the building consists of shear walls surrounding the two stairwells that are supported by a 5-foot thick reinforced concrete mat foundation.

The transit mall and the North Block are one-story below-grade reinforced concrete structures constructed with 10-inch elevated posttensioned slabs. The approximately 60,000 square-foot transit mall slab consists of six individual slabs segments that were constructed with

Installation of the FRP Composite Strengthening System.

STRUCTURE magazine

no pour strips between slabs. The post-tensioned slab was originally coated with a waterproof barrier and topped with a thin concrete overlay, a sand blotting layer, and brick pavers. The North Block slab has bonded post-tensioning with a 3-inch thick topping. Both structures are supported by 12- by 12-inch reinforced concrete columns and by the perimeter reinforced concrete foundation walls.

Between November 2012 and March 2014, the Courthouse Square complex went through a significant structural and building envelope rehabilitation program. The structural program included remediation to existing slabs, columns, lateral load resisting system, isolated column footings and matt foundation, and building envelope.

A Complex in Distress Issues with the building and transit mall began to emerge in 2002.

Cracks started to appear on interior partition walls and on the concrete foundation walls, and floor tiles started to crack and buckle.

Deflections up to 3.5 inches were measured on existing slabs. The paving stones on the bus mall were shifting and settling. Over the next eight years, several separate engineering studies were initiated to assess the structure. Most reviews concluded that, while repairs were necessary, the complex remained structurally safe to occupy.

In January 2010, a comprehensive assessment of the structural and serviceability problems was conducted and concluded that the original design of the complex was inadequate in several areas. Field investigation and detailed analysis confirmed the presence of significant structural/life-safety issues within the structure. A significant number of columns in the building were overstressed and prone to axial and bucking failures, and some slab locations were significantly overstressed in punching shear; one slab location exhibited signs of punching shear failure. The building envelope showed signs of water infiltration around windows and damage due to building movement. The brick masonry system exhibited compression of the expansion joints, and the brick façade appeared to be pushed out.

Clear separation was observed at slab-to-curtain-wall connections, indicating excessive shrinking and shortening of the post-tensioned floor slabs. The bus mall exhibited significant structural issues as well, most notably excessive foundation wall cracking, two rows of end columns that were leaning inward and several columns with significant and pronounced cracks. One of the major concerns was

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the safety of the transit mall slab which was found to be significantly overstressed in bending and punching shear, making the use of the facilities unsafe. In July 2010, Courthouse Square was closed, offices and services were relocated to other buildings, and the complex was declared too dangerous for the public.

A task force comprised of transit, county, and citizen representatives was appointed to evaluate remediation solutions and explore alternative uses for the site. Initial repair estimates exceeded $49 million, while the cost to demolish and replace the building was estimated at $56 million.

Remediation was favorable because the site of the complex is a centralized, easily accessible location in downtown Salem. Considering the complexity of the project, a three-tier design-build-bid process was developed by the owners. In the first phase, qualified design-build teams were selected and approved based on pre-established requirements for experience with evaluation and rehabilitation of structures with similar types of problems. In Phase 2, the selected teams submitted detailed reports that included review of the results of field assessment reports, performing preliminary structural analysis, identification of existing deficiencies, and development of remediation approach and cost estimate. In Phase 3, the teams were interviewed by a special panel that included the owners and third party reviewers in order to evaluate the design-build proposals and select a successful bidder. Structural Preservation Systems, LLC (STRUCTURAL) along with Whitlock Dalrymple Poston & Associates (WDP) were selected to lead the design-build team to complete the $22.9 million remediation in 2012.

Crews apply a traffic-bearing coating in the public transportation area.

Structural Deficiencies and Remediation Methods Remediation work for Courthouse Square was carried out based on the 2009 International Building Code (IBC 2009) – Oregon Structural Specialty Code, the 2008 edition of the American Concrete Institute’s (ACI) Building Code Requirements for Structural Concrete (ACI 318-08), and Minimum Design Loads for Buildings and Other Structures (ASCE 7-05), along with seismic hazard data from the United States Geological Survey. Modeling and analysis were performed using SAFE and SAP2000 software for nonlinear analysis of the existing structure. The main structural deficiencies and remediation techniques used to bring the structure to current standards included: • Isolated Footings – several of the existing column footings were found to be deficient in punching shear and in bearing capacity. These issues were resolved by enlarging the size and depth of the existing footings to increase their shear, flexural and bearing strengths.

• Slab Punching Shear – Deficiencies were identified at numerous locations throughout the building, including significant shear deficiencies at the transit mall slabs. Slab remediation was achieved utilizing cast-in-place concrete drop panels. A specialized technique was required to prepare the concrete surfaces and to place the concrete material in order to guarantee proper bond between the new and existing concrete – known as the form-and-pump technique. The size of the drop panel was proportioned to satisfy strength increase requirements and to minimize interference with existing mechanical, electrical and plumbing (MEP) systems. Steel dowels were used to supplement the bond between new and existing concrete, and improve load transfer to existing columns.

• Column Capacity (Slenderness and Strength) – Analysis indicated that a majority of the columns were deficient in STRUCTURE magazine

Columns wrapped with FRP for axial strength and enlarged for punching shear.

Enlargement systems were used to strengthen the column footers in the parking structure.

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axial and/or bending strength, or did not satisfy stiffness requirements. Column strengthening was achieved by installing 6- to 10-inch thick reinforced concrete jackets to increase the axial and bending strengths, and to increase buckling resistance of the columns. Similar to drop panels, the concrete jacket was placed using the form-and-pump technique. Specialized self-compacting concrete (SCC) January 2016

Placement of bonded overlay over the parking structure created a strengthened deck for the public transportation area.

material was developed, and used to pressurize the formwork and to produce optimum bond between the existing and new concrete. The size of the concrete jacket varied to satisfy strength requirements and to minimize interference with the existing MEP, building finishes, and parking spaces. Onesided, two sided, and full jackets were used, as needed, to address these conditions.

• Slab Bending Capacity – Several locations were identified that required additional tension reinforcement at the top or bottom sides of existing slabs. Flexural strengthening of slabs was achieved using externally bonded fiber reinforced polymer (FRP) reinforcement. The V-Wrap externally bonded FRP composites supplied by Structural Technologies provided a very low profile and did not change the appearance of the slabs or interfere with floor finishes.

The design of the FRP was achieved using the industryrecognized ACI 440.2R-08 design guide.

• Shear Walls – Deficiencies were identified on shear walls located on the west core of the office building. Strengthening of deficient walls was achieved by epoxy injection of existing cracks in addition to using concrete enlargement, bonded FRP reinforcement, or a combination thereof. The choice of the strengthening solution varied, and depended on the existing wall capacity and required strength increase. Form-and-pump concrete placement techniques were used to ensure proper load sharing between existing walls and new enlargements.

• Mat Foundation – The mat foundation supporting the west core element was found to be deficient in bending.

Strengthening was achieved using micropiles that were placed through the existing mat foundation to improve its load carrying capacity.

Strengthening of the transit mall slab included removal of the existing concrete overlay, sand and pavers, and installation of a new 5-inch thick bonded overlay, increasing the slab thickness from 10 inches to 15 inches. To ensure composite performance STRUCTURE magazine

of the existing slab with the new reinforced topping, the topside of the existing slab was roughened to ¼-inch amplitude, and steel dowels were installed in both directions. Using this approach, the total superimposed dead load was reduced while increasing the flexural and punching shear capacities of the slab. The concrete overlay was finished with an epoxy-based heavy traffic coating.

Cast-in-place shear capitals were also installed at several columns where high punching shear deficiency was identified. In addition, externally bonded FRP was utilized at the mid-span regions to increase the flexural capacity of the slab. All existing foundation wall cracks were repaired using epoxy injection.

Building Envelope Repairs The design-build team concluded that several of the building envelope issues were caused by the relatively high post-tensioning forces in the slabs. Over time, the large post-tensioning forces in the slabs resulted in excessive elastic shortening and creep of the slabs. The detrimental side effect of slab shortening is the distress it caused in the brick façade, as well as high shear forces on columns located near the expansion joints.

The compressive stress in the slabs due to post-tensioning varied between 350 psi and 500 psi. The long-term elastic shortening of the slab due to these forces was estimated using the GL2000 model provided in ACI 209.2R-08. Using this approach, an elastic shortening of 0.7 inches was estimated to occur at each end of the slab after 12 years. This calculated value compared well with the field-measured shortening of 0.75 inches at a slab edge.

As the long-term slab shortening was considered to be complete after 12 years, the overall repair approaches served to address distressed and displaced building envelope components. Additional shortening that may occur over the remaining service life of the structure was accounted for by installing additional strip joints onto the masonry façade, as well as widening existing joints. Repairs to the façade included replacement of the 5th floor brick façade, flashing repairs

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at window perimeters and shelf angles, and replacement of severely cracked/damaged window frames. Replacement and stabilization of significantly displaced brick panels on lower floors were also completed.

Conclusions

Tarek Alkhrdaji, Ph.D., P.E., is Vice President of Engineering with Structural Technologies. Dr. Alkhrdaji is an active member of ACI Committee 437 (Strengthening Evaluation) and ACI 562 (Repair Code); and he is the past Chair ACI 440F (FRP Strengthening). He can be reached at talkhrdaji@structuraltec.com.

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Delivery of a structurally safe complex, with sound engineering and a 50-year service life, was a primary focus of the owners. To this end, a third party consultant was hired to be the owners’ representative, ensuring a rigorous quality assurance program as the project progressed.

Over the course of the project, up to 100 construction workers were at the project site to perform the repairs. Throughout the project, a series of four stages of inspection process were developed that occurred during the construction of each repair.

Repairs moved forward to the next phase only when inspectors representing the various parties were satisfied with the quality of completed work.

Courthouse Square has been described as a model design-build structural repair project with design professionals, contractors, and vendors all focused on delivering a successful result. After eighteen months of construction, the Courthouse Square complex was reopened in April 2014, on schedule and within budget.

In 2014, the Courthouse Square project recieved an Award of Excellence by the International Concrete Repair Institute and was also a Project of the Year Finalist.▪

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I N T E G R AT I N G

SUSTAINABILITY

& STRUCTURE A Case Study

By Keith T. Bauer, S.E.

T

he Sacramento Municipal Utility District East Campus Operations Center (SMUD ECOC) is a six building, 350,000 square foot facility on a 51 acre site in Sacramento, California that was completed in May 2013.

The project served to relocate the operations headquarters for SMUD to a more centrally located and larger facility which would increase operational efficiency. SMUD also sought to lead by example by achieving LEED Platinum certification and Net Zero energy usage for sustainability. The project was awarded to Turner Construction and the design-build team of Stantec (lead architect, mechanical, electrical, and plumbing designs), RNL (sustainability and yard building architect) and Buehler & Buehler Structural Engineers, Inc. (structural) based largely on the team’s innovative use of an integrated structural and mechanical system which leveraged the use of the thermal mass of the concrete to reduce energy consumption. This design methodology was identified through the use of Integrated Project Delivery (IPD), and ultimately required the smallest area of photovoltaic panels.

Yard Buildings The yard buildings consisted of approximately 150,000 square feet of new construction spread amongst five primary structures: Fleet Maintenance, Tools/Shop, Warehouse, Electrical, and Truck Wash.

Structural considerations for these buildings centered on use of costeffective structural systems (open web joists, precast concrete panels,

cold-formed steel canopies), providing accommodations for bridge cranes within the structures, and minimizing thermal bridging through detailing to enhance the energy efficiency of the buildings.

A thermal bridge is defined as an area of a building component which has a significantly higher heat transfer than the surrounding materials, resulting in an overall reduction in thermal insulation of the object or building. For the yard buildings, the main source of thermal bridging was the connection of the shade canopies at the building perimeter to the exterior precast insulated concrete sandwich panels. The concrete wall panels consisted of a structural wythe (thickness varied dependent on building height and loading demands), 2½ inches of insulation and a 2½-inch architectural wythe. The thin architectural wythe was insufficient for anchorage of the perimeter shade canopies, therefore isolated areas of full-thickness concrete that penetrated the insulation layer were required.

These canopies were integral to the sustainable design of the structures. The shading elements controlled heat gain by preventing direct sunlight from entering interior space, while still allowing enough natural light to reduce the need for powered interior lighting. The IPD project environment allowed B&B’s structural engineers to work concurrently with the architects and energy modeling team to find a structural solution that met canopy anchorage demands, achieved the architectural aesthetic, and minimized the thermal bridging that was incorporated in the energy model. The canopy attachment detail is shown in Figure 1.

Office Building The largest structure on the site is the six-story office building, a fourstory tower over a two-story podium housing over 200,000 square feet of office space, a large conference/meeting space, cafeteria, and an emergency operations center at the upper level. Although not directly specified, the original project Request-for-Proposal implied that the office building was anticipated to be designed of steel. However, through coordination fostered by the IPD process, the concept of using radiant cooling that utilized the thermal mass of a concrete structure was developed and implemented.

There were several advantages to using this integrated structural and mechanical system. The thermal mass of the concrete structure allows the building itself to store and release heat at a rate similar to that of its environment. The ability of concrete to store heat during the warmest part of the day and release it as the ambient temperature cools at night reduces the need for mechanical climate control.

Secondly, the energy required to move water through radiant tubing in the slab is less than traditional mechanical systems that push air. continued on next page

Figure 1. Typical canopy attachment.

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with regard to providing a large open meeting space at the ground level as required per the RFP. The meeting space required 67-foot clear spans which were not possible utilizing a two-way post-tensioned slab.

Additionally, due to story height limitations, using concrete beams or girders at the second floor was also not an acceptable design solution.

To solve this issue, it was decided to suspend the second floor from the roof structure above. This was achieved by providing two upturned post-tensioned concrete girders with tube steel hangers at third points from which the second floor post-tensioned concrete deck was supported. To clear span 67 feet, the required girder depth was 5 feet 6 inches; this was not well received architecturally, as the girder would project over the parapet wall. Therefore the girder design was modified to provide a two-way taper at the south end (adjacent to the parapet); the girders were reduced in depth while increasing in width to maintain the necessary shear capacity and the beam-column interface. An elevation of the girder is shown in Figure 3.

Figure 2 Typical slab detail.

Air is circulated within the office building, but only by use of ceiling fans. Initially, the team proposed that, with the use of ceiling fans, the ambient temperature inside the building could be maintained at 82 degrees Fahrenheit. Ultimately, the owner decided that an ambient temperature of 78 degrees would be satisfactory. Compared to traditional forced-air office ambient temperatures in the range of 70-74 degrees, this increase in allowable ambient temperature also resulted in significant energy savings.

The structural detailing of the radiant slab system is shown in Figure 2.

The total slab section consists of a 10-inch thick 2-way post-tensioned slab. The bottom 2 inches of the slab is considered to be non-structural, as the radiant tubing is located in this zone. Because of the owner’s requirement to use a ‘walker duct’ system (for distribution of electrical and IT) at each floor, a topping slab over lightweight insulation was used to provide a flat finished floor surface. This insulation also served as an aid in managing the directionality of temperature control between floors.

Although the thermal mass of the concrete structure was a major benefit to the mechanical design, the connection of the post-tensioned floor slabs to the exterior concrete shear walls presented a ‘thermal bridging’ design challenge. To mitigate this thermal bridge, the bottom 2 inches of the non-structural portion of the floor slabs were omitted and filled with insulation that protected a suspended radiant tubing system. The width of the slab recess was defined through thermal gradient models, which determined at what point the external and internal temperature difference was sufficiently dissipated so as to not adversely affect the performance of the radiant slab system.

Energy Model and Monitoring Taking into account the structural systems, thermal bridging, anticipated demands as provided by the owner and the anticipated MEP design, the MEP team created a sophisticated and detailed energy model using the TRNSYS platform. As various components of the design evolved, the energy model was updated in real time to determine the amount of photovoltaic panels that would be required to meet the calculated energy demands and achieve ‘netzero’ energy consumption.

The main limitation to the energy model was its dependence on anticipated energy use information provided by the SMUD user groups. This included such detailed information as anticipated plug loads, frequency of roll-up doors at the yard buildings being opened and closed, and hours of operation at a site whose function is to be able to be at full use at a moment’s notice in the event of a storm or power outage. SMUD elected not to fully fund monitoring that would enable detailed tracking of power usage in comparison to the anticipated use information provided. Although global energy consumption on site can be monitored, specific usage cannot be tracked and adjustments made to ensure the site is operating at its maximum efficiency.

Girders Although the use of a concrete two-way flat slab for the building structural system had many advantages from an energy standpoint, it created a tremendous challenge Figure 3. Typical girder elevation.

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Figure 4. Building cost comparison between the SMUD ECOC and a similar office building.

Conclusion

SUPPORTING

INNOVATION IN ARCHITECTURE

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There is a common misperception that sustainable design equates to increased cost of construction. Based on energy modeling, the SMUD ECOC buildings consume 60% (office building) and 40% Figure 5: Annual energy cost comparison. (yard buildings) less energy than an ASHRAE 90.1 code design at comparable initial construction cost to similar buildings. Figure 4 provides a comparison between the SMUD ECOC and a project Turner Keith T. Bauer, S.E., is an Associate Principal with Buehler & Construction completed in northern California four years earlier.

Buehler Structural Engineers, Inc. Keith also enjoys mentoring high Project square footage, construction duration, and usage between school students as part of the ACE Mentor Program of Sacramento the two buildings were similar. While SMUD was certified LEED and is an adjunct lecturer at the University of California at Davis.

Platinum with Net Zero energy usage, the Caltrans project achieved He can be reached at kbauer@bbse.com. a LEED Silver rating. As shown in the figure, the MEP cost for the SMUD project was significantly higher than for the Caltrans project, as would be expected due to the high efficiency and technologically advanced systems required to achieve the target energy goals. However, due to a significantly lower structural cost on the SMUD project, the overall cost per square foot for the buildings is almost identical.

The efficiencies in the design and construction of the SMUD project also resulted in reduced annual maintenance costs. Figure 5 shows the annual energy costs of a “code minimum” building, LEED Silver building (Caltrans) and Net Zero, LEED Platinum building (SMUD). Based on energy modeling, the annual energy costs for the SMUD project are approximately 55% of the University of California, Merced Joseph E. Gallo Recreation and Wellness Center, Merced, CA Caltrans project and 33% of a code Photograph © 2015 Tim Griffith minimum project.

Overall, the SMUD ECOC project demonstrates how integrated structural and mechanical systems can lead to an optimum sustainable design, with reduced Seattle • Tacoma • Lacey • Portland • Eugene • annual operating costs and Sacramento • San Francisco • Los Angeles • Long Beach • Pasadena • Irvine • San Diego • building construction costs Boise • Phoenix • St. Louis • Chicago • New York comparable to those of less KPFF is an Equal Opportunity Employer. energy efficient code miniwww.kpff.com mum structures.▪

ENDURING DEVOTION: The Sanctuary for Sufism Reoriented

By Steve Ratchye, P.E., S.E., R.A., LEED AP BD+C and Graeme Ballantyne, P.E., S.E., LEED AP

Figure 1. Aerial photograph during construction. Courtesy Sufism Reoriented.

D

ecades in conception and planning, the new Sanctuary for Sufism Reoriented in Walnut Creek, California, aims for a design life of centuries. The Sanctuary consists of a series of one-story domes above grade and a basement below (Figure 1). The largest dome is 78 feet in diameter and covers the column-free Prayer Hall, and smaller domes cover a variety of other spaces around the perimeter. A striking 38-foot tall base-isolated bronze sculpture reaches up from the basement to the oculus of one of the medium domes.

In an effort to fit into the surrounding residential neighborhood, the above-grade structure is much smaller than the basement (Figure 1). The below-grade level features a sky lit rotunda, a gallery, offices and a recording studio.

The building will serve as the principal center of worship for Sufism Reoriented, a religious group with congregations in the San Francisco Bay Area and Washington, D.C. The congregation collaborated with Philip Johnson/Alan Ritchie Architects and Thornton Tomasetti as structural engineer, and hired Soga + Associates as the architect of record.

Elongated Design Life Cast-in-place concrete was selected for the building, a choice influenced by the owner’s desire for an elongated design life with minimal maintenance. Other materials such as structural steel, precast concrete and concrete masonry were judged to be less durable for a variety of reasons, and therefore unsuitable. The smallest domes stand as the exceptions and consist of precast glass-fiber reinforced concrete.

When the owner initially expressed a desire for a design life in the range of hundreds of years, the structural designers recommended the use of STRUCTURE magazine

Figure 2. Main dome over Prayer Hall during construction.

performance-based design concepts because of the high seismicity of the site. Sufism Reoriented decided not to pursue this design option, but they did maintain their desire for a more robust approach than minimum code compliance. They understood that, although the code aims at life safety for occupants, significant damage to the structure may occur during a major seismic event. As a result, the building was designed using an R-factor of 1.25, the lowest response modification coefficient in the California Building Code (CBC), rather than the R-factor of 5 for special reinforced concrete bearing walls. This approach reduces the ductility demands on the structure and aims to keep seismic forces largely in the elastic range of reinforced concrete.

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Figure 4. Boundary zone at drum wall.

Figure 3. Partial plan of drum wall on columns below.

Seismic Design of Shear Walls and Domes Special reinforced concrete shear walls that are circular in plan serve as the lateral system for the above-grade portion of the Sanctuary. The twelve “drum walls” occur below the four 38-foot diameter medium domes and the eight small domes. The main dome sits on columns, as shown in Figure 2, and is stabilized by a concrete flat slab diaphragm at roof level that transfers the seismic forces to the drum walls.

Because the basement has a rectilinear geometry, the drum walls typically sit on columns below (Figure 3). In addition to serving as shear walls, the 12-foot high drum walls act as beams spanning between the basement columns. The drum walls supported on columns were treated as discontinuous lateral system elements for design, and seismic forces acting on the columns were designed for the CBC’s over-strength load combinations. The ground floor slab serves as a diaphragm to redistribute shears from the drum walls to the perimeter retaining walls, which serve as shear walls.

Boundary zones were detailed within the drum walls where the stress criterion in ACI 318-08 Section 21.9.6.3 was exceeded, and typically these elements occurred where drum walls sit on columns. Because of the way the drum walls intersected in plan, some of the boundary elements have unusual configurations (Figure 4). Additional vertical dowels were added to anchor the drum walls into the supporting columns for uplift loads.

A dome is such a stable structural form that an extremely thin shell is possible but, out of consideration for very long term durability, two mats of reinforcing were used with a minimum thickness of 7½ inches. The architects set the relatively shallow partial-sphere geometry of the domes initially, and it was confirmed by structural analysis. The domes and drum walls were modeled by finite element analysis with special attention paid to the intersections between the domes and the flat slab at the roof (Figure 5). The Morley Clark Nielsen method was used to calculate reinforcement for the domes from finite element results. Monolithic ring beams occurred at the top and bottom of each dome in order to carry the compressive and tensile hoop stresses respectively.

STRUCTURE magazine

Figure 5. Finite element model of domes and drum walls.

Small reinforcing bars were detailed in the domes, and in their top and bottom ring beams, in order to facilitate bending them to a curve.

Similar reinforcing bar sizes were specified for the curved bars in the drum walls. In addition, the clear cover specified was one-half inch larger than that required in ACI 318 in order to give the contractor more tolerance for rebar erection.

Formwork for the domes consisted of closely spaced radial ribs of dimensional lumber, cut to curve and spliced. Thin plywood forms cut in wedge shapes were bent to curve and fastened to the ribs.

The ribs were propped by conventional shores, which were braced at regular intervals for lateral stability. The concrete ring beams at top and bottom were placed first in order to insure that they, rather than the formwork, bore hoop stresses resulting from the wet concrete of the dome. The contractor shotcreted the domes in alternating pie-slice segments in order to minimize cracking from circumferential shrinkage.

Domes constructed with inflated formwork were considered by the owner, but the only version that held promise for economy included an integral roofing system that was considered to lack the desired long term durability.

The smallest domes are ¾-inch thick glass-fiber reinforced concrete with ribs. They are exposed to the elements, so thermal issues required

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Figure 7. Interior of triple friction pendulum isolator.

the mat was thickened by placing pads on top of the mat within the gravel layer, which minimized excavation.

Concrete for the mat slab was required to reach a 4000 psi compressive strength at 56 days. The longer than usual time period for the achievement of design compressive strength allowed for the use of less portland cement, just 282 pounds per cubic yard, and an equal proportion of Class F fly ash to create a more environmentally friendly mixture.

Sculpture

Figure 6. New Man sculpture. Courtesy Sufism Reoriented.

consideration. The other domes, on the other hand, are covered by roofing and insulation and are more massive, which prevents large temperature swings. Oversized bolt holes with Teflon shims at the base connections of the GFRC domes insured that the thin shells could expand and contract from temperature swings without being overstressed.

Buoyancy A recommended water table 10 feet below grade and a basement roughly 20 feet below grade, coupled with a single story above grade or none at all, made hydrostatic uplift a significant issue.

A concrete mat foundation was chosen because of its mass and the flexibility it afforded for future column placements during renovations. Additional ballast came in the form of a green roof over the ground floor slab outside the footprint of the above-grade story (approximately 250 pounds per square foot) and an eighteen-inch layer of gravel with a finish slab on top of the mat. Utilities such as plumbing lines were placed in the layer of gravel, which allowed for relatively easy future access. Near heavily loaded columns,

One of the highlights of the sanctuary is a 38-foot high bronze sculpture designed by a member of the congregation. The cloth-textured base of the sculpture supports the body, from which branches with butterflies rise to the full height (Figure 6). The body has numerous long holes cut in the surface, some as long as 15 feet.

The highest butterflies are acrylic, the only portion of the sculpture that is not bronze.

As with the building structure, the owner desired a long design life for the sculpture.

Using the CBC provisions resulted in bronze thicknesses of one inch. However, the fabricator stated it was not feasible to cast a structure that thick.

To reduce seismic forces and therefore the bronze thicknesses, Thornton Tomasetti suggested base-isolating the sculpture. Baseisolating the sculpture significantly lengthens the dynamic period of the sculpture and reduces the seismic forces. Friction pendulum isolators were selected because they use durable materials such as stainless steel and graphite, and are understood to return to equilibrium

after a seismic event (i.e. self-centering). The isolator supplier recommended four triple pendulum isolators for the sculpture (Figure 7). Each of the three surfaces of these isolators is tuned for a different type of seismic event: frequent smaller earthquakes, the design basis earthquake and the maximum considered earthquake. The upshot of this careful tuning is a fatter hysteresis loop than would be achieved by a single pendulum isolator, which means more earthquake energy absorbed with smaller displacements (Figure 8). The maximum expected horizontal displacement at the base isolators is 15 inches in any horizontal direction.

For the analysis of the sculpture, a twostep process was employed. A finite element model of the sculpture body was used to check local stresses acting on the bronze, particularly around the long openings, and also local buckling (Figure 9). An elastic “stick” model included the full sculpture and base isolators to check global behavior, overall displacements and confirm the finite element model.

The artist had a small scale model of the sculpture scanned to create a stereolithography (“.stl”) digital file, and the engineers took cross sections from this file in order to calculate member properties for the stick model.

For the finite element model, a new mesh was needed because a sterolithography file is made up of elements, many with acute angles, which are not ideal shapes for analysis. The .stl file was brought into the software Rhinoceros in order to create a new 3-D surface, which was then brought into the finite element program to create a satisfactory mesh.

The result of the base isolation and advanced analytical work was reduced bronze thicknesses that the fabricator could accommodate.

Because the base, with its folds and billows, was not an ideal structural shape, a stainless steel pipe was added that rose from the isolators to approximately mid-calf of the load-bearing leg. A “moat cover” of black granite on a steel plate covered the gap provided to accommodate the horizontal movements expected at the base isolators. The structural designers used Tekla to create the fabrication drawings for the sculpture’s steelwork.

Figure 8. Friction pendulum isolator hysteresis. Courtesy Earthquake Protection Systems.

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Conclusion The Sanctuary for Sufism Reoriented presented many challenges to its design team, including high seismicity, unusual geometries and a unique sculpture. The project is expected to open in mid-2016, providing an elegant, unique and durable worship space for its congregation, fulfilling a dream decades in the making.▪ Steve Ratchye, P.E., S.E., R.A., LEED AP BD+C, is a Vice President in Thornton Tomasetti’s San Francisco office and serves on ACI’s Committee 232 on Fly Ash in Concrete. Steve may be reached at SBRatchye@ThorntonTomasetti.com.

Graeme Ballantyne, P.E., S.E., LEED AP, is an Associate in Thornton Tomasetti’s San Francisco office. Graeme may be reached at GBallantyne@ThorntonTomasetti.com.

Project Team Structural Engineer: Thornton Tomasetti, San Francisco, CA Owner and Construction Manager: Sufism Reoriented, Walnut Creek, CA Design Architect: Philip Johnson/Alan Ritchie Architects, New York, NY Executive Architect: Soga + Associates, San Francisco, CA Geotechnical Engineer: DCM Consulting, Inc., Lafayette, CA Isolator Supplier: Earthquake Protection Systems, Vallejo, CA Concrete Contractor: Overaa Construction, Richmond, CA Sculpture Fabricator: Mussi Artworks Foundry, Berkeley, CA

Figure 9. Finite element model of sculpture.

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Historic structures significant structures of the past

Quebec Bridge Part 2

By Frank Griggs, Jr., Dist. M.ASCE, D.Eng., P.E., P.L.S.

Dr. Griggs specializes in the restoration of historic bridges, having restored many 19 th Century cast and wrought iron bridges. He was formerly Director of Historic Bridge Programs for Clough, Harbour & Associates LLP in Albany, NY, and is now an independent Consulting Engineer.

Dr. Griggs can be reached at fgriggsjr@verizon.net.

Part 1 of this article was published in the December issue of STRUCTURE magazine.

A

total of 75 men were killed instantly, with 11 escaping with their lives, in the bridge collapse on August 29, 1907. How could this have happened?

Weren’t Cooper and the Phoenix Bridge Company acknowledged to be leaders in the bridge building business? The Engineering News wrote: “It is with keenest regret that we record the collapse on Aug. 29 of the great cantilever bridge under construction over the St. Lawrence River at Quebec. We are sure this regret is shared by every engineer who takes the least pride in his profession and its achievements. And the feeling is even deeper than regret. When the newspapers of last Friday morning spread the news of the terrible disaster at Quebec to every corner of the country, thousands of engineers, as they read the story, were grieved and sick at heart. They felt not only horror at the fearful loss of life, sorrow and sympathy for their brothers whose professional and business reputation were dealt a cruel blow when the huge steel structure fell into the St. Lawrence, but also a sense of personal loss as well.

It could not be otherwise. Public confidence in engineers and engineering constructors and in the safety and reliability of their works is an asset of the whole engineering profession. To have this public confidence receive such a blow as this at Quebec is a loss almost incalculable. For decades to come, the Quebec disaster will be quoted, in public and in private, as an unanswerable proof of the unreliability of engineers and their work – of even the best engineers.”

The Engineering Record wrote of the collapse, “Engineers themselves know full well that probably no structure ever received more careful attention in design, manufacture and erection than the Quebec Bridge and they will be unwilling to attribute its collapse to defective proportions, inferior material or faulty erection until definite proof is established to the contrary.”

Several investigations were held, with the major one, the Royal Commission staffed by Canadian engineers, appointed on August 30, the day after the failure. The chairman of the team was Henry Holgate, assisted by two civil engineering professors, John Galbraith from the University of Toronto and J. G. G. Kerry from McGill University. The team visited the site immediately after the collapse, and took testimony in Quebec between September 9 and 24 and in Ottawa on September 26 and 27. They went to New York City to interview Theodore Cooper for a week

50 January 2016

and then went to Phoenixville to interview the Phoenix Bridge Company personnel. The team members also revisited Cooper and the Phoenix Bridge people later on in December.

The Commission also talked with Charles Macdonald, Henry Hodge, Ralph Modjeski, F. C. Kunz and John V. W. Reynders of the Pennsylvania Steel Company that was building the Blackwell’s Island Bridge across the East River in New York City. In addition, they spoke with some of the leading professors of the day, Mansfield Merriman, W. C. Kernot, William H. Burr, Edgar Marburg, H. M. McKay, and G. F. Swain.

In addition, the Board hired C. C. Schneider (STRUCTURE, January 2011) to advise them on structural design of the bridge. Schneider had seven conclusions, the most important ones being: 2. The trusses, as shown in the design submitted to this writer, do not conform to the requirements of the approved specifications, and are inadequate to carry the traffic or loads specified.

3. The latticing of many of the compression members is not in proportion to the section of the members which they connect.

6. The present design is not well adapted to a structure of the magnitude of the Quebec Bridge and should, therefore, be discarded and a different design adopted for the new bridge, retaining only the length of the spans in order to use the present piers.

Cooper’s testimony, as well as that of the Phoenix Bridge personnel, was extensive and published in the journals of the day. Cooper stated, “I had and have implicit confidence in the honesty and ability of Peter Szlapka, the designing engineer of the Phoenix Bridge Co., and when I was unable to give matters the careful study that it was my duty to give them, I accepted the work to some extent upon my faith in Mr. Szlapka’s ability and probity.” Another question and answer was, Q. Do you consider that the engineering data at our disposal are sufficient to enable engineers to design members similar to those in the lower chord with safety and economy? Would you now recommend any material changes in the detailing of these or any other members, and, if so, what would these changes be?

A. My responsibilities, gentlemen, end as soon as I have served my duty of aiding you in reaching the truth in regard to the destruction of this bridge. While I have my views and such views are at the service of those who have heretofore relied on me, I shall decline to take any executive or responsible position in connection with the corrections of the errors that we now recognize in this work; it must be referred to younger and abler men.

With all the testimony, the report of Schneider, and inputs of the leading cantilever bridge

designers and builders, the Commission released its report in March 1908. The report had fifteen findings. The most important were as follows: e. The failure cannot be attributed directly to any cause other than errors in judgment on the part of these two engineers. [Cooper and Szlapka] f. These errors of judgment cannot be attributed either to lack of common professional knowledge, to neglect of duty, or to a desire to economize. The ability of the two engineers was tried in one of the most difficult professional problems of the day and proved to be insufficient for the task. g. We do not consider that the specifications for the work were satisfactory or sufficient, the unit-stresses in particular being higher than any established by past practice. The specifications were accepted without protest by all interested. h. A grave error was made in assuming the dead load for the calculation at too low a value and not afterward revising this assumption. This error was of sufficient magnitude to have required the condemnation of the bridge even if the details of the lower chords had been of sufficient strength because, if the bridge had been completed as designed, the actual stresses would have been considerably greater than those permitted by the specifications. The erroneous assumption was made by Mr. Szlapka and accepted by Mr. Cooper and tended to hasten the disaster. n. The professional knowledge of the present day concerning the action of steel columns under load is not sufficient to enable engineers to economically design such structures as the Quebec bridge.

A bridge of the adopted span that will unquestionably be safe can be built, but in the present state of professional knowledge a considerably larger amount of material would have to be used than might be required if our knowledge were more exact. o. The professional record of Mr. Cooper was such that his selection for the authoritative position that he occupied was warranted and the complete confidence that was placed in his judgment by the officials of the Dominion Government, the Quebec Bridge & Railway Company and the Phoenix Bridge Company was deserved.

The Engineering Record wrote of the Report, “It is seldom that the responsible engineer for any work great or small has more authoritatively or more effectively impressed his engineering judgment upon

Peter Szlapka.

the work in his charge than in this case...

Perhaps the most painful part of the evidence is that in which the Consulting Engineer makes the plea of impaired health for not exacting from both the contractor and the Quebec Bridge Co. certain requirements of design and plans in the one case, and the necessary organization for the proper performance of the work on the other. Unfortunately such pleas are admissions of official shortcoming, however much a man may feel the disability of ill health, they give him no relief from official responsibility. There is one only clear way by which he can divest himself of the responsibilities of official position and that is by a formal withdrawal from it... The Consulting Engineer makes a further point in his evidence that the fee he received was quite insufficient to enable him to maintain a proper office work force for the discharge of the duties imposed upon him in his official capacity... When he accepted the fee he accepted all of the responsibilities of the position. No engineer has any right whatever to consider his responsibilities lessened because his fee is not as large as it should be... The failure of the Quebec bridge reflects in no way whatever upon the American engineering profession, it simply shows that the exactions of responsibility unfortunately make no compromise with the disabilities of age and ill health, even when combined with a meager compensation.”

The work was then turned over to the Transcontinental Railway Commission.

To ensure that there would not be any mistakes, they appointed an International Panel of bridge experts. H. E. Vautelet was appointed Chairman and Chief Engineer with

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Maurice Fitzmaurice, then chief engineer of the London County Council, and Ralph Modjeski (STRUCTURE, January 2013) from the United States.

The Panel went to Phoenixville to talk with Szlapka and J. Sterling Deans, the Reeves Brothers and others. After a great deal of study, they fully endorsed the Holgate Report, as well as that of C. C. Schneider. No part of the existing bridge would be usable in any new structure and they were to start over with an entirely new structure! The Board was initially in favor of a cantilever bridge, but they also looked at several suspension bridge designs before deciding on a cantilever.

Many questions were asked about the kind of truss to be used. Should they be vertical and parallel, or inclined as on the Forth Bridge?

Should they have straight or polygonal chords?

What kind of a web system should be used, single or double intersection or some entirely new system? The Board, with the full financial backing of the government, consulted freely with other engineers and bridge building companies to help them make their decision.

The Panel prepared its own design, largely that of Vautelet, which had parallel trusses, straight chords and an unusual web pattern. Modjeski and Fitzmaurice were still carrying on their own engineering careers and had reservations about the design, while Vautelet devoted full time to the project. The Panel, however, passed the following resolution of May 2, 1910: “It is resolved that the plans and specifications for a cantilever design, now completed, be approved and submitted to the Minister for tenders, and that, in the event of a better design being submitted by any of the bidders, shall be adopted.”

Prior to this official resolution, the Board had notified several bridge companies in late 1909 that they would be requesting tenders, and that they could view the Board’s design early in 1910.

Fitzmaurice resigned his position in June 1910 to return full time to his position in London. He was succeeded by Charles Macdonald (STRUCTURE, January 2009), who agreed to serve only as long as necessary to evaluate the tenders. In the same month, the Department of Railways and Canals officially requested tenders on their “superstructure design comprising 80 sheets of drawings, 6 or 8 feet long, and contract bids on them and on alternate plans which may be prepared by the contractors in accordance with the printed specifications.” In other words, the Panel had a design, which, even if they had some reservations about it, would work. If any tender could improve on it so much the better. continued on next page

A few of the tenders submitted, along with final design 1910.

After reviewing the tenders, Vautelet, Macdonald and Modjeski reported to the Minister of Railways and Canals that “design V of the Board and the scheme of erection proposed by any one of the bridge companies would result in a satisfactory structure.” They also recommended designs A, B, C of the St. Lawrence Bridge Company. The Minister, however, wanted a specific recommendation, from the Board.

The Panel, however, could not agree on a specific recommendation as Vautelet recommended one of the tenders on his own design and Macdonald and Modjeski recommended design B of the St. Lawrence Bridge Company. The minister would not accept a split recommendation, so he appointed two more engineers to the Panel to help in making the decision. They were M. J. Butler, a Canadian, and Henry Hodge, an American. After an extensive review of the tenders, they agreed with Macdonald and

Modjeski that the plan B submitted by the St. Lawrence Bridge Company was the best tender. Their reasons were as follows: a. The type of design offers greater safety to life and property during erection, as well as economy and rapidity of construction. b. The design contains the minimum of secondary members and requires few, if any, temporary members during erection. c. The system of triangulation, by dividing the web stresses, reduces the members to more practical sections and simplifies the details of construction. d. The general appearance of the structure is, in our opinion, improved.

Vautelet resigned on February 22 while deliberations were ongoing and Macdonald took over as acting Chairman. The Minister, upon considering the high cost of building highway approaches to the bridge, decided to omit the two roadways and accepted plan B of the St. Lawrence Bridge Company.

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A contract was signed with the St. Lawrence Bridge Company, a joint venture of the Dominion Bridge Company and the Canadian Bridge Company, on April 4, 1911.

With the signing of the contract, Macdonald resigned as acting chairman and was replaced

by Lt. Col. Charles N. Monsarrat who was engineer of bridges for the Canadian Pacific Railway. On May 17, 1911, C. C. Schneider was appointed a full member of the Board, which then consisted of Monsarrat, Modjeski and Schneider. Erection of the approach spans on the North end of the bridge was completed

by November 7, 1913. Work on the bridge proper began on May 21, 1914, when the traveler moved out onto the falsework for the anchor arm. Everyone associated with the bridge believed that with all the precautions taken and checking done, nothing could possibly go wrong during construction, and the bridge would open in 1916.▪

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InSIghtS

new trends, new techniques and current industry issues

3D Printed Structures: Challenges and Opportunities

By Caitlin T. Mueller, Ph.D.

T

echnologies for 3D printing, or more broadly additive manufacturing, have proliferated in recent years, and have captured the public’s imagination as a revolutionary way to democratize small-scale, customized manufacturing for the DIY community. In the design of buildings and bridges, 3D printing has proven to be a valuable technique for creating intricately detailed scale models in a fraction of the time required by traditional methods. In both cases, the generalized layer-by-layer material deposition process is a compelling way to achieve geometries of nearly infinite complexity with ease.

But 3D printing has also permeated markets beyond the consumer and model scale, with increasing buzz about applying the technology to large objects, such as full-scale buildings.

This prospect is exciting for several reasons: reduced construction waste through highly precise material placement, increased capacity for complex geometries for both functional and aesthetic purposes, and new possibilities for integrating building component functions into a single, streamlined assembly.

Recent developments internationally have provided increasing evidence that such advantages can be realized, and that 3D printing may represent a viable pathway for the future of construction. For example, at the University of Southern California, researchers have developed Contour Crafting, a robotic fabrication system that uses a large-scale gantry to deposit a low-slump concrete-like material in layers to produce vertical wall systems and structural elements for housing [Khoshnevis, 2004].

This technology has also garnered interest from NASA as a way to construct habitats on the moon and Mars using mostly local materials. A similar technique has been used by a Chinese company, Winsun, to produce several housing units, produced in parts and then assembled on-site, including a five-story apartment building [Stampler, 2015].

In the Netherlands, DUS Architects and collaborators are building a full-scale 3D-printed replica of a traditional Amsterdam canal house, using a custom-made, room-sized 3D printer (called the KamerMaker, or “room maker”) that deposits an extruded, heated thermoplastic material [Wainwright, 2014]. As a scaled-up version of commercially available printers like those from MakerBot and Ultimaker, this technique can produce double-layer walls and other components with compelling geometric

variation, allowing for storage and furniture to be integrated, and for acoustical and structural properties to be tuned.

Most recently, Skidmore, Owings & Merrill (SOM) and the U.S. Department of Energy’s Oak Ridge National Laboratory produced a small, transportable 3D-printed habitat with integrated photovoltaic panels, printed using ABS plastic reinforced with 20% carbon fiber and post-tensioned with steel rods [SOM, 2015]. The printing technique produced the building in 2-foot wide wall and roof sections that integrated structural and building envelope functions, acting as vacuum-insulated panels for thermal insulation.

3D printing is also being investigated at the component scale for buildings. For example, Arup developed and produced a customized 3D printed steel structural connection for a tensile structure, using topology optimization to generate complex, highly efficient forms that are responsive to the specific forces at each node [Galjaard et al., 2015]. With a 3D printing technique called direct metal laser sintering, which selectively melts and fuses metal powder with lasers in a layer-bylayer approach, a stainless steel component was produced that weighed 75% less than a conventional plate-based version.

These advances offer compelling support for a new vision of construction for civil structures. However, several key challenges remain to be met before these techniques can be used in a widespread, cost-effective manner, especially in terms of structural behavior and performance. There is an exciting and important opportunity for the structural engineering community to have a strong voice in the further development of these new techniques to ensure that safety and material efficiency are prioritized.

One set of challenges relates to the materials and composites proposed for 3D printing of civil structures, many of which are new to this application or new in general. While a great deal is known about traditional structural materials such as steel, concrete, and timber, the behavior and properties of materials produced through heated extrusion, layered deposition, and sintered powders are less well understood, and need to be studied and developed with long-term building applications in mind.

Furthermore, the layer-by-layer fabrication approach should be reconsidered for applications with structural functions. In many

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materials and techniques, this leads to significant anisotropy in strength and ductility, due to poor bonding between layers, limiting the efficacy of printed parts. Current research at MIT’s Digital Structures research group offers one alternative: a new process called stress line additive manufacturing (SLAM) uses a robotic arm to deposit material along threedimensional lines of principal stress, ensuring material connectivity in the most critical directions [Tam et al., 2015] (see Figure).

A final set of challenges relates to the question of formwork. While 3D printing promises to reduce or eliminate construction waste, the difficulties of supporting a structure as it is constructed remain for geometries that cannot be fabricated as vertical extrusions. Small-scale 3D printers address this problem by printing support structures concurrently with the final objects, which can be dissolved or detached once the print is complete. A similar approach could work at the building scale, but more research is needed to determine how to implement this effectively, ideally in a way that involves re-usable or recyclable support material.

Looking forward, it is clear that many such challenges lie ahead before the promise of 3D printing can be broadly achieved for building structures, but the recent, rapid development of increasingly realistic proofs-of-concept is highly encouraging. The continued contributions of pioneering structural engineers are critical to help push this transformative technology from small-scale geometric representation to highperformance, full-scale structures.▪ Caitlin T. Mueller (caitlinm@mit.edu), is an Assistant Professor at the Massachusetts Institute of Technology in the Departments of Architecture and Civil and Environmental Engineering. She leads the Digital Structures research group, which focuses on new digital technologies for the design and fabrication of innovative structures.

The online version of this article contains detailed references. Please visit www.STRUCTUREmag.org.

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All Resource Guide forms for the 2016 Editorial Calendar are now available on the website, www.STRUCTUREmag.org.

Banking center strengthened with MAPEI’s CFRP products

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Noteworthy

news and information

NCSEA Past-President Bob Paullus Passes Away

T

he structural engineering profession lost a colleague and friend on November 26, 2015 with the passing of Robert Paullus, Jr. Bob, as most know him, had an amazing career.

He touched the lives of many, contributed tirelessly to our profession, and became the well-respected Structural Engineer that we all enjoyed conversing with and working alongside. He did so exemplifying the qualities of humility, generosity, hard-work, and humor that only Bob could bring together so well.

Bob began his career in 1981 with a Bachelor of Science in Civil Engineering from Christian Brothers University, followed 20 years later with an MSCE from the University of Memphis. His project experience included work in the plate fabricating industry, design of water and wastewater treatment facilities, design of refineries, chemical processing plants, commercial buildings, schools, churches, military facilities, and seismic rehabilitation of existing structures.

In the 1990s, Bob came to realize the impact of structural engineering and what could be achieved by working together for the common good of our profession and safety of the public.

He held this belief through the remainder of his career, and wrote in the TNSEA 2015 State Convention welcome letter, “The heavy work for the betterment of our profession is directly on the local organizations. As the foot soldiers, we are the ones that quickly see the benefits and the shortcomings in our industry.

Each of us must step up and do the necessary work. We cannot pass this off to others. Our state and regional chapters are dedicated to this mission.”

Three milestone events occurring in the late 1990s resulted in Bob’s significant contributions to our profession: The introduction of the International Building Code, formation of the West Tennessee Structural Engineers Association (WTNSEA), and his attendance as a delegate to the NCSEA annual meeting and conference in 1999 and 2000.

The International Building Code (IBC) had an impact on all practicing structural engineers and the public during its early adoption.

Bob quickly became known to many as the go-to guy for code questions and interpretations…the “Code Master”. He realized the impact that the code would have on seismic design in Memphis and the surrounding area. NCSEA past-President Ron Hamburger

writes, “He was one of the few engineers in the mid-south that came to realize that there really is great earthquake risk in the region, and that pretending it was not an issue was not appropriate.” He worked for the adoption of the IBC, including the seismic provisions.

Bob attended meetings and provided public testimony, emphasizing the need for municipalities to adopt the seismic provisions in the IBC. As a founder of WTNSEA, Bob strived to bring together the efforts of all engineers in the State of Tennessee to form what would become the Tennessee Structural Engineers Association (TNSEA). On November 13, 2015, Bob was made a Distinguished Member of the Tennessee Structural Engineers Association for his contributions.

It was during Bob’s first two NCSEA Conferences, 1999 and 2000 that he realized that, if structural engineers worked together, we would be a much stronger profession. Bob was recognized for his dedication to the profession in 2001, when he was asked to join multiple committees, including the Code Advisory Committee Seismic Subcommittee and the Structural Engineering Certification Board interest committee. It was through his work with NCSEA, serving on the NCSEA Board and holding the office of President in 20082009, that he developed a nationwide network of colleagues and friends. Bob would go on to serve as a board member of the Applied Technology Council (ATC) and a member of the ASCE 7 Seismic and Wind Committees.

Bob’s contributions to our profession never ceased. In his last days, and with the help of his family, he assisted in preparing for the TNSEA 2015 State convention, attended the NCSEA Structural Engineering Summit in Las Vegas, Nevada, and attended the ATC Board meeting in New Orleans, Louisiana.

He didn’t just talk the talk, but he walked the walk and set expectations high for all structural engineers and our profession.

Bob would not be satisfied with this article without the mention of his children, Ben, Kelly, Sarah-Beth, and Caleb. We are appreciative to them for allowing Bob to share his life with us. Most know that Bob enjoyed sharing family stories of what was happening in their lives, and we enjoyed hearing those stories.

STRUCTURE magazine

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Bob was a humble man, with a humor that resulted in smiles and laughs every time you saw him. This often disguised a man of great principle and reason. He enjoyed teaching and educating others, not just engineers – but everyone, about structural engineering. His dedication to the profession and his children is an example for all of us. He put himself last, and others first, and was a cheerful giver of all that he had.

Barry Arnold, past-president of NCSEA, shared this story. “I called him recently and what should have been a two-minute conversation turned into a chat that lasted a few hours. Even though he admitted his situation was dire, he wasted none of our time discussing his plight. Rather, he wanted to know how I was and what I was doing. And, in typical Bob fashion, even though he was in a situation of little hope, he concluded our conversation with, ‘Well, let me know if you need anything. I’d be happy to help you out.’ What an amazing attitude. What an amazing man.”

Jeanne Vogelzang, Executive Director of NCSEA, said: “Bob Paullus, always selfeffacing, forever genteel, a family man like none I’ve ever met. Bob will be missed.”

This was Bob Paullus, the man who gave so much of his time and succumbed to cancer on Thanksgiving Day at 2:15 in the morning.▪ Many thanks to the NCSEA Past-Presidents, NCSEA staff, ATC Board Members, Julie Furr and Mike Sheridan of the TNSEA, and other friends of Bob for contributing their sentiments and expressions of respect concerning Bob while preparing this article.

award winners and outstanding projects

Spotlight

Malone Cliff View Residence Soars over Dallas

By Thomas W. Taylor, P.E., Stephen Price, P.E., Lee Christian, P.E. and Craig Rios, P.E. Datum Engineers, Inc. was an Outstanding Award Winner for the Malone Cliff View Residence project in the 2015 NCSEA Annual Excellence in Structural Engineering awards program (Category – New Buildings under $10M).

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his unique residence sits on the top of a bluff which originally was a 60-foot deep landfill of trash, tires, and more. The Architects design intent for the residence created three specific amazing views of the Dallas skyline.

Parts of the house and balconies soar 17 feet out over the cliff with thin post-tensioned concrete slabs. These soaring cantilever floors accentuate the view in a dramatic way. The architectural centerpiece of the interior of the house is a two story spiraling steel stair which is also a part of the architectural appeal of the exterior of the house, as it can be seen through the glass window at the front entrance.

The site conditions, and desired architectural and functional expression, created numerous structural challenges not often found in residential construction. Four of these challenges were the major influence on the structural design concept.

First, the trash landfill created the need for deep vertical piers through the unstable fill to support the load of the residence, and battered piers to resist the horizontal sliding forces created by the bluff. A key to the success of the foundation was working closely with the contractor to identify sizes and location of both battered and vertical piers that could be accessed with special equipment. Finding the type of equipment that the contractor could drive out onto the bluff, and then designing the foundation around this restriction, was a major challenge. This was a difficult but successfully completed challenge with close teamwork between the structural engineer and the contractor.

Second, the only reasonable structural system that would accomplish the architect’s vision was a post-tensioned cast-in-place concrete slab. The architectural vision deserved thin concrete slabs. But, the thin slabs had to cantilever 17 feet. An added complication was that the cantilevered slabs needed to be supported on thin concrete slab bands that were formed flush to the bottom of the slab. Both the cantilevers and the slab bands were integrated into a 10-inch concrete slab with no drop beams.

The concrete slab design and construction was further complicated at the roof, which was formed as a slight hyperbolic parabola. Engineering analysis of the post-tensioned cantilever slabs to prevent differential deflections that could lead to glass breakage at the ends of the cantilevers was a major tedious engineering effort. Deflections at the tips of the cantilevers varied depending on the length of the cantilever slab and the length of the supporting slab band.

This required a thorough analysis of deflections at the tip of the cantilever and along the slab band to hold tight deflections and coordinate with the architect’s window wall details. No drop beams were used to stiffen the floor, in order to accommodate the air conditioning ducts and light fixtures in the low floor to floor height. Lee Christian P.E. used ADAPT-PT and ADAPT-Floor Pro software to analyze the slabs. Final measurements of deflections after construction were compatible with the calculations, and a successful solution to the architectural vision was accomplished.

Third, the two story architectural centerpiece stair was constructed of a single center-spiraling welded steel box beam that was only connected at each floor access point. Two cantilever steel cross plates, cut into the wood treads, were welded to the spiraling steel box beam, to support each tread. Structural considerations of a spiraling box beam and control of vibration characteristics, created a major analytical challenge to create an ultimately simple appearing, but structurally successful, architectural centerpiece. Craig Rios P.E. used SAP2000 to calculate the stresses, deflections and vibrations, and created a successful structural solution for the architectural centerpiece expression.

Fourth, originally there was no apparent method to support the circular steel roof over the stair without adding bulky columns behind the window wall. The ultimate solution to this structural challenge was to integrate small

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structural steel supporting tube columns into the glass exterior wall, eliminating any appearance of structural columns adjacent to the window wall. The steel tubes became the window mullions in addition to supporting the steel roof. This wall of steel and glass was meticulously detailed, and kept as thin and lightweight as possible. This allowed for views of the centerpiece from the outside, let light in, and created a dramatic architectural entry to the residence.

A strong aspect of this award winning residence is its integration into the environment.

The architectural vision, in large part, was made possible by the structural concept. A beautiful and dramatic home now sits on a bluff that was once a trash landfill.▪ Thomas Taylor is Principal Design Engineer of Datum Engineers. Thomas can be reached at thomas@datumengineers.com.

Stephen Price is the Technical Director and a Principal of Datum Engineers.

He functioned as the project manager on this project. Stephen can be reached at stephen@datumengineers.com.

Lee Christian is a Senior Associate at Datum and performed the concrete design on this project. Lee can be reached at lee@datumengineers.com.

Craig Rios is President of Datum|Rios in San Antonio, Texas and designed the spiral stair for this project. Craig can be reached at c.rios@datumrios.com.

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News form the National Council of Structural Engineers Associations

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Structural Engineering Education: Preparing for Our Future Engineers

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uring a spontaneous discussion at a National Council of Structural Engineers Associations (NCSEA) Annual Conference over 13 years ago, a group of practitioners and educators shared their concerns over the increasing lack of technical knowledge exhibited by recent college graduates. This informal gathering launched the formation of the NCSEA Basic Education Committee (BEC). The NCSEA BEC has expanded its efforts from its early beginnings to address different challenges that face the structural engineering profession.

The BEC along with other NCSEA efforts seek to maintain and strengthen the process of preparing structural engineering students to practice structural engineering as licensed professional engineers. The process of preparing students to become competent licensed professional engineers focuses on three main elements: education, examination, and experience.

The BEC is committed to sustaining and improving a future structural engineer’s educational experience, upholding a strong examination process, and encouraging licensed professional engineers to provide structural engineering students with an opportunity to receive a successful mentorship experience.

A sound educational experience is instrumental in the development of a competent licensed professional engineer. The recommended NCSEA Structural Engineering Curriculum encourages structural engineering students to receive instruction in the following subjects: structural analysis, matrix methods, steel design, concrete design, timber design, masonry design, dynamic behavior of structures, foundation design / soil mechanics, and technical writing. These subjects are further defined as twelve recommended courses. Each recommended course suggests topics and objectives that are encouraged to be covered as part of the curriculum.

The BEC has begun the arduous process of reviewing each recommended course’s suggested topics and objectives. The recommended curriculum, available on the committee’s page on the NCSEA website, was one of the first tasks completed by the BEC in an effort to improve the quality of structural engineering education.

This month the BEC is distributing the 2016 NCSEA Structural Engineering Curriculum survey, a triennial comparison of the recommended NCSEA Structural Engineering Curriculum, to college professors at nearly 300 engineering colleges across the country.

Participation by engineering colleges is important for the survey’s success, and we encourage interested NCSEA member organizations to contact the BEC to determine how they may assist with increasing the survey response. The results of the survey will be published in the August 2016 Issue of STRUCTURE magazine and will be posted on the NCSEA website later this year.

Over the years, the BEC has solicited and received feedback from practicing structural engineers and educators concerning the recommended NCSEA

The BEC is committed to sustaining and improving a future structural engineer’s educational experience, upholding a strong examination process, and encouraging licensed professional engineers to provide structural engineering students with an opportunity to receive a successful mentorship experience.

Structural Engineering Curriculum by (i) regularly publishing education articles in STRUCTURE magazine, (ii) engaging other organizations directly (AISC Partner’s in Education, ACI’s Faculty Network, AWC, etc.), and (iii) holding numerous informal conversations with engaged NCSEA members. The BEC is currently preparing a formal practitioner survey of the recommended curriculum, to be distributed later this year to all NCSEA members. The results of the practitioner survey will serve as a guide for the BEC to review and, if necessary, the BEC will revise the recommended curriculum to ensure that the curriculum continues to meet the demands of the structural engineering profession.

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The BEC continues to work with the Structural Engineering Certification Board (SECB) in an effort to develop and implement an SECB Education Certificate program at interested colleges. The SECB Education Certificate is a transportable document that will guide collegiate choices to ensure alignment between academic and professional goals.

The education certificate would also serve as a means to identify individuals that have met the educational requirements necessary for SECB certification.

The BEC believes it is critical that the profession recruits talented high school and collegiate students to ensure future successes. The BEC has created an NCSEA High School Outreach Guide to aid member organizations in creating a successful high school outreach program. The BEC is also in the process of developing an NCSEA College Outreach Program titled “Become a Structural Engineer” that includes a trifold brochure and slide presentation. The NCSEA High School Outreach Guide and “Become a Structural Engineer” brochure are now available for download from the NCSEA website, after login, under NCSEA Committee Documents and Resources. The “Become a Structural Engineer” slide presentation will be available later this year.

The BEC SE Connect group seeks to increase the effectiveness of its efforts by partnering with similar member organization committees or with interested members acting on their member organizations’ behalf. The BEC gathered potential contacts to assist with the SE Connect Group at the 2015 NCSEA Summit Annual Meeting and is looking for additional assistance. Please contact Brent Perkins, NCSEA BEC Chair at bperkins@dwase.com if you are interested in participating in the SE Connect Group.

Brent Perkins, P.E., S.E. Basic Education Committee Chair

Managing Risk Professionally, Collaboratively, and Transparently: • Project Delivery Workshop - Dale Munhall, Architect, Director of Construction Phase Services, Leo A Daly

• Legal Update - Staci Ketay Rotman, Attorney, Franczek Radelet P.C.

• Professional Liability - Dan Bradshaw, CPCU, Benchmark Insurance Agency, and Craig Coburn, Attorney, Richards Brandt Miller Nelson

NCSEA News

Don’t miss the 2016 Winter Leadership Forum

• Claims Management

- Seasoned [been sued] structural engineers and defense counsel; moderated by John Tawresey, S.E., Retired VP & CFO, KPFF

News from the National Council of Structural Engineers Associations

Register online and make hotel reservations now at www.ncsea.com!

The WLF is a great way for structural engineering business leaders to get together in a non-competitive environment and discuss issues facing their companies.

I’ve found it particularly informative in my role as a principal and leader of our firm.

The business practices sessions, management and communication techniques, and legal case studies have been very useful and interesting.

Sarah Appleton, P.E. S.E. Associate Wallace Engineering Structural Consultants

Bill Bast, P.E., S.E., SECB Principal Thornton Tomasetti

2016 W INTER L EADERSHIP F ORUM

March 10 & 11 Coronado Island Marriott, San Diego

NCSEA Webinars

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More detailed information on the webinars and a registration link can be found at www.ncsea.com. Subscriptions are available!

1.5 hours of continuing education. Approved for CE credit in all 50 states through the NCSEA Diamond Review Program. www.ncsea.com.

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NCSEA

Diamond Reviewed

Michelle Kam-Biron, P.E., S.E., SECB, M.ASCE, Director of Education, American Wood Council

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January 26, 2016 Code Applications for Nail-Laminated Timber and Cross-Laminated Timber

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Duane K. Miller, Sc.D., P.E. G EN

Mike Mota, Ph.D., P.E., SECB, Vice President of Engineering, Concrete Reinforcing Steel Institute (CRSI)

February 23, 2016 Welded Connections: the Good, the Bad, and the Ugly

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January 19, 2016 Vibrations of Reinforced Concrete Floor Systems

Chuck Knickerbocker, Curtainwall Manager, Technical Glass Products

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Michelle Kam-Biron, P.E., S.E., SECB, M.ASCE, Director of Education, American Wood Council

February 11, 2016 Steel Curtain Walls

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January 12, 2016 2015 National Design Specification® (NDS®) for Wood Construction

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The Newsletter of the Structural Engineering Institute of ASCE

Structural Columns

REGISTER TODAY CONNECT DISCIPLINES, SOILS, AND STRUCTURES. COLLABORATE AND PROVIDE BETTER SOLUTIONS. BUILD STRUCTURES AND RELATIONSHIPS. The Geo-Institute (G-I) and Structural Engineering Institute (SEI) of the American Society of Civil Engineers (ASCE) are coming together to create this first-of-its-kind event. By combining the best of both Institutes’ annual conferences into one unique conference, you will profit from unmatched networking opportunities with colleagues within and across disciplines.

• 3½ days of premier educational and networking events • 15 tracks and 6 plenary sessions focusing on interdisciplinary and discipline-specific areas of interest for professional development hours • Prestigious awards and keynote lecture presentations • An impressive exhibit hall, with more than 100 exhibitors expected • Lively programs for students and young professionals

Who Should Attend: • Geotechnical Engineers • Geoprofessionals • Structural Engineers • Bridge and Building Designers • Civil Engineers and Researchers with an interest in cross-cutting topics • Young Professionals • Owners • Educators • Government Officials • Students Visit the Joint Congress website at www.Geo-Structures.org for complete information and to register.

2016 Fazlur R. Khan Distinguished Lecture Series

ASCE Innovation Contest

Lehigh University is pleased to announce the dates and speakers for the 2016 Fazlur R. Khan Distinguished Lecture Series. All lectures will be presented on the Lehigh University campus.

Performance-based Design: What, How, When, Why, and Why Not to Use It Ronald O. Hamburger, Senior Principal, Simpson Gumpertz & Heger Inc., San Francisco, CA Friday, March 4, 2016 – 4:30 pm Lessons Learned John Zils, Senior Structural Consultant, Skidmore Owings & Merrill LLP, Chicago, IL Friday, April 15, 2016 – 4:30 pm Structural Use of FRP Composites in Construction: Past Achievements and Future Opportunities Jin-Guang Teng, Chair Professor of Structural Engineering, The Hong Kong Polytechnic University, Hong Kong, China Friday, April 22, 2016 – 4:30 pm The Structural Engineering Institute-Lehigh Valley Chapter will be awarding 1 PDH credit for each lecture to eligible attendees. For additional information visit the Fazlur R. Khan Distinguished Lecture Series website at www.lehigh.edu/~infrk.

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Join the power of the crowd that will help transform the state of our nation’s infrastructure. Become part of the solution by sharing your best ideas, projects, and theories for how to build a better future. Contestants may submit a description of their innovations in any or all of four different topics: Innovative Business Models & Technologies, The Internet of Things, Green Engineering, and Resilience. Deadline is January 5, 2016. Learn more at www.asce.org/innovation-contest.

Applications are Invited for ASCE Scholarships and Fellowships ASCE offers tuition assistance to engineering students through seven Society Scholarships and four Society Fellowships. Awards vary depending on demonstrated academic success, financial need and career goals, but are typically $2,000 to $8,000. The Eugene C. Figg, Jr. Civil Engineering Scholarship and Y.C. Yang Civil Engineering Scholarship should be of particular interest to structural engineering students. Applications for 2016 are due February 10. For further details and downloadable application forms, please visit the Scholarships website at www.asce.org/Scholarships and the Fellowships website at www.asce.org/ASCE_Fellowships. For assistance, please contact ASCE Honors and Awards at awards@asce.org.

January 2016

The 2015 SEI Local Leaders Conference was held October 23 – 24 in Charlotte, North Carolina. Participants included representatives from 32 local SEI groups (Chapters, Graduate Student Chapters, and Structural Technical Groups), the SEI Local Activities Executive Committee, and SEI President David Odeh, P.E., S.E., F.SEI, F.ASCE, who gave an update on the SEI Vision for the Future of Structural Engineering Initiatives.

In addition to the general session meeting and exchange of SEI Chapter best practices, the conference included a technical tour of the Insurance Institute for Business and Home Safety (IBHS) Research Center, a technical presentation on the design and construction of the UNC Charlotte Football Stadium project by ASCE NC Structures Chair Garrett Overcash, P.E., M.ASCE, and leadership training by Jim O’Brien, P.E., M.ASCE, ASCE Managing Director of Professional and Educational Activities.

S.E. Exam Review Course

NIST Seismic Design Techbriefs Now Available

REACH SEI MEMBERS

The National Institute of Standards and Technology (NIST), in conjunction with the Applied Technology Council (ATC) and the Consortium of Universities for Research in Earthquake Engineering (CUREE), has produced a series of concise “techbriefs” on practical issues related to earthquake-resistant design of buildings. These compact volumes are authored by leading practitioners and researchers, and they combine summaries of code and standard requirements, latest research results, and design and construction experience. Visit the National Earthquake Hazards Reduction Program website at www.nehrp.gov/library/techbriefs.htm to download the 11 available techbriefs.

www.asce.org/SEI, SEI Update e-newsletter, STRUCTURE magazine, and at SEI conferences year round.

REACH SEI MEMBERS WITH SEI SUSTAINING ORGANIZATION MEMBERSHIP

www.asce.org/SEI-Sustaining-Org-Membership Increase your exposure to more than 25,000 SEI members through www.asce.org/SEI, SEI Update e-newsletter, STRUCTURE magazine, and at SEI conferences year round.

Local Activities Pittsburgh Chapter

Get Involved in SEI Local Activities www.asce.org/SEI-Sustaining-Org-Membership

The SEI Pittsburgh Chapter celebrated SteelDay with a tour of a steel fabrication shop and a site tour. In the morning, the chapter members visited the Sippel Fabrication Shop to see a presentation on a new structural floor system. The afternoon tour of the under-construction SkyVue Complex in the Oakland neighborhood highlighted the use of the new flooring system.

SkyVue general contractor, Massaro Construction Group provided remarks before the tour. For complete details see the Pittsburgh Section’s website, at www.asce-pgh.org/SEI.

Join your local SEI Chapter, Graduate Student Chapter, or Structural Technical Groups (STG) to connect with colleagues, take advantage of local opportunities for lifelong learning, and advance structural engineering in your area. If there is not an SEI Chapter or STG in your area, talk with your ASCE Section/ Branch leaders about the simple steps to form an SEI Chapter.

Visit the SEI website at www.asce.org/SEI and look for Local Activities Division (LAD) Committees.

San Francisco Chapter The SEI San Francisco Chapter had an extensive tour of the new San Francisco–Oakland Bay Bridge. Chapter members saw bridge structures not visible to motorists. In November, chapter members conducted their Inaugural Dinner and Presentation.

Terrence Paret with Wiss, Janney, Elstner Associates, Inc., gave a presentation on the seismic assessment of the Washington Monument. For complete details see the SEI news webpage.

STRUCTURE magazine

Errata SEI posts up-to-date errata information for our publications at www.asce.org/SEI. Click on “Publications” on our menu, and select “Errata.” If you have any errata that you would like to submit, please email it to Jon Esslinger at jesslinger@asce.org.

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The Newsletter of the Structural Engineering Institute of ASCE

ASCE’s live 11-part S.E. Exam Review courses are the most comprehensive and convenient way to prepare for and pass the S.E. exam. Interact with instructors, access free on-demand SEI SUSTAINING ORGANIZATION MEMBERSHIP recordings, andWITH feel confi dent on exam day. S.E. Exam Review Course begins February 1, 2016. Learn more and register today at www.asce.org/se_exam_review. Use code SHPE to save Increase your exposure to more $100 by January than12.

25,000 SEI members through

Structural Columns

2015 SEI Local Leaders Conference

The Newsletter of the Council of American Structural Engineers

JUST RELEASED: Updated 2015 CASE Contract Library For the first time since 2009, CASE has done a complete overhaul, with legal review, of all 17 CASE Contracts. The CASE Contracts Committee has spent the last two years revising and updating each contract to reflect current industry standards and practices. Major changes include: 1) Modified indemnification language 2) Modified risk allocation language 3) Additional commentary on AIA documents 4) Expanded language regarding attorney and expert fee costs

Donate to the CASE Scholarship Fund!

The ACEC Council of American Structural Engineers (CASE) is currently seeking contributions to help make the structural engineering scholarship program a success. The CASE scholarship, administered by the ACEC College of Fellows, is awarded to a student seeking a Bachelor’s degree, at minimum, in an ABET-accredited engineering program.

We have all witnessed the stiff competition from other disciplines and professions eager to obtain the best and brightest young talent from a dwindling pool of engineering graduates. One way to enhance the ability of students in pursuing their dreams to become professional engineers is to offer incentives in educational support.

In addition, the CASE scholarship offers an excellent opportunity for your firm to recommend eligible candidates for our scholarship. If your firm already has a scholarship program, remember that potential candidates can also apply for the CASE Scholarship or any other ACEC scholarship currently available.

Your monetary support is vital in helping CASE and ACEC increase scholarships to those students who are the future of our industry. All donations toward the program may be eligible for tax deduction and you don’t have to be an ACEC member to donate!

Contact Heather Talbert at htalbert@acec.org to donate.

CASE Winter Planning Meeting

CASE 2015 Bestsellers Now Available!!

February 11 – 12, 2016 Embassy Suites Phoenix Biltmore, Phoenix, AZ

Guideline Documents 962:

National Practice Guidelines for the Structural Engineer of Record (SER) 962-A: National Practice Guidelines for the Preparation of Structural Engineering Reports for Buildings 962-D: A Guideline Addressing Coordination and Completeness of Structural Construction Documents Contract Documents

CASE in Point

Details regarding specific updates for each contract are listed in their online abstracts.

CASE Contracts are developed and released with the sole purpose of ensuring CASE members manage risk and safety when engaging in structural engineering projects. We encourage you to download them and incorporate them into your business.

To view the updated library, go to www.acec.org/case/ getting-involved/contracts-committee.

#1: An Agreement for the Provision of Limited Professional Services #2: An Agreement between Client and Structural Engineer of Record (SER) for Professional Services #13: An Agreement Between Owner and Structural Engineer for Professional Services Risk Management Toolkits 1-1: Create a Culture for Managing Risks and Preventing Claims 5-1: A Guide to the Practice of Structural Engineering 9-1: A Guideline Addressing Coordination and Completeness of Structural Construction Documents These publications, along with other CASE documents, are available for purchase at www.acec.org/bookstore.

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The 2016 CASE Winter Planning Meeting is scheduled for February 11 – 12 in Phoenix, AZ. The planning meeting will kick-off the night of the 11th with a roundtable covering topics such as special inspections, new IBC codes, healthcare, business operations and more. The CASE Committees will meet all day on the 12th; if you are interested in what CASE is doing and are in town ahead of the Structures Congress, you are invited to sit in on any committee meeting. The agenda is below and we’ll be meeting at the Embassy Suites Biltmore. For more information, contact Heather Talbert at htalbert@acec.org.

CASE Winter Planning Meeting Schedule: Thursday, February 11 – Executive Committee/ Roundtable Discussion 12:30 pm Executive Committee Meeting 6:00 pm Roundtable Discussion – Junior Ballroom Friday, February 12 – Planning Meeting 7:30 am Continental Breakfast 8:00 am Welcome 8:30 am – 4:30 pm Committee Breakout Sessions CASE Contracts Committee CASE Guidelines Committee CASE Programs & Communications Committee CASE Risk Management Toolkit Committee 12:30 pm Buffet Lunch 4:30 pm Committee Updates January 2016

The CASE Risk Management Convocation will be held in conjunction with the joint Geo-Institute /Structures Congress at the Sheraton Phoenix Downtown and Phoenix Convention Center in Phoenix, AZ February 14 – 16, 2016. For more information and updates go to www.geo-structures.org.

The following CASE Convocation sessions are scheduled to take place on Monday, February 15: 10:00 am – 11:30 am Soil/Structure Interaction: Dialogue between Engineers to Create Good Soil Reports Moderator: Mr. Brent L. White, S.E., ARW Engineers Panel Speakers: Structural Engineer Panelist: Michael Murphy, P.E., m2 Structural Geotechnical Panelist: Michael S. Ulmer, P.E., S&ME, Inc. 1:00 pm – 2:30 pm Characteristics of Higher Performing Design Firms Moderator/Speaker: Mr. Timothy J. Corbett, SmartRisk

Follow ACEC Coalitions on Twitter – @ACECCoalitions.

2016 Small Firm Council Winter Seminar Next Stage Financials: Valuation and Exit Strategy Essentials for Small Firms February 12–13, 2016; Phoenix, AZ Presented by Matt Fultz of Matheson Financial Advisors, this 1½ day seminar will allow attendees to learn and apply key financial metrics driving value in an engineering firm. The speaker will explore the impact a volatile economy has on financial management beyond revenue, profits, backlog, and staff size. Attendees will broaden their understanding of engineering firm valuation and its relationship to ownership transition.

This seminar is for any employee within a small firm tasked with analyzing financial data, such as: owners, principals, CEOs and CFOs. ACEC’s Small Firm Council (SFC) was established to protect and promote the interests of the smaller engineering firms.

Its winter meeting provides an exclusive forum for small firm principals to attend seminars, network with peers, address key issues affecting their firms, learn and share new ideas. Attendees provide valuable input that helps SFC direct the business and legislative agenda for the coming year. To learn more, visit www.acec.org/coalitions/coalition-events.

Registration

Location Embassy Suites Phoenix Biltmore 2630 East Camelback Road Phoenix, AZ 85016 Hotel Main # 602-955-3992 Online Reservations Special Rate – $219/night until January 13, 2016 To register for the seminar: www.acec.org/calendar/calendar-seminar/ 2016-small-firm-council-winter-seminar

CASE Members – $499 ACEC Members – $749 Non-members – $999

Questions? Call 202-682-4377 or email at htalbert@acec.org.

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CASE is a part of the American Council of Engineering Companies

3:00 pm – 4:30 pm Tackling Today’s Business Practice Challenges – A Structural Engineering Roundtable Moderator: David W. Mykins, P.E., Stroud Pence & Associates

CASE in Point

CASE Risk Management Convocation in Phoenix, AZ

Structural Forum

opinions on topics of current importance to structural engineers

The Engineering Way of Thinking: The Future

By William M. Bulleit, Ph.D., P.E.

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s discussed previously in this space (The Engineering Way of Thinking: The Idea, STRUCTURE December 2015), engineering is continually evolving as engineers try new tools, develop new designs, and build new or modified artifacts. All of these expand the heuristics that engineers use, but many times lead to failures.

Henry Petroski has even argued that engineering advances through failures.

The engineering way of thinking (EWT) accepts the inevitability of failures because heuristics always have limits, and trying new tools and building new artifacts always pushes these limits. It is not feasible to wait until all scientific knowledge about whatever is being designed becomes available, since nothing would ever get done. Science is never done; there is always more to know.

The inevitability of failures causes engineers to be conservative about change. Engineers know that change is essential to the evolution of their profession and society; they also know that today’s heuristics have limits, and exceeding those limits can cause failures. Thus change must consider not only how we can advance engineering, but what the potential consequences are. The inability of engineers to imagine and predict such consequences has caused some to believe that today’s environmental and societal problems are due largely to engineers and engineering.

I suggest that the real problem is a society, including its engineers, that has not followed the EWT. People in general, and engineers in particular, have allowed themselves to get trapped in a narrow conception of what engineering should entail. Engineering needs to be perturbed; we need to use the EWT to re-engineer engineering.

Stephen Goldman has argued that engineers are socially captive – working for owners, firms, and others such that they just want to get a job done and not think beyond that. To a great extent, this is true – and it will always be true as long as engineers make a living doing engineering. Given that limitation, what can we do to get engineers to use the EWT more broadly?

First, even the most socially captive engineer works with documents developed by the engineering community: regulations, codes of practice, design guides, textbooks, and other compilations of engineering knowledge, each developed by individual engineers or groups of engineers. These individuals and groups are in a position to begin using the EWT in a broader context to perturb engineering. In the long run, even the socially captive engineer will then need to change in order to work within the updated system. However, the EWT is not dependent on any engineering discipline, individual engineer, or group of engineers.

With apologies to philosopher Wilfrid Sellars, the EWT is a means to approach design, in the broadest possible sense of the term, using heuristics, in the broadest possible sense of the term, to develop artifacts, in the broadest possible sense of the term.

The design needs to include as much of the system in which the artifact resides as is practical, based on the heuristics available to the engineer at the point in time when the design is being performed. Furthermore, the EWT must evolve as the available heuristics change to meet the demands of a constantly changing society. In fact, the EWT should be used to help engineer society.

This is not about how engineering was used to attempt to change society in the past, particularly some of the nearsighted efforts of the mid-20th century. These merely employed the engineering of the time, not the EWT; and we seem to be making the same kinds of mistakes today. The blame resides with not only engineers, but also among others, politicians, voters, teachers, and colleges and universities (including engineering schools).

Therefore, rather than engineering society, we should talk about “an engineering society”: a society that respects and uses the EWT in all its aspects. This is admittedly a radical suggestion, but only because the EWT has not been properly understood, even by engineers themselves.

What might this wide use of the EWT mean for engineers and society?

First, it would require engineers to broaden their horizons and develop mental models based on a wide range of disciplines. This idea is already being suggested by ASCE in its push for a broader undergraduate education and specialization at the graduate level. However, I would argue that the liberal undergraduate degree followed by engineering graduate school – modeled on law and medicine – is not the way to go.

The EWT requires a broad range of knowledge, with engineering deeply embedded in the other disciplines studied. To work toward better understanding of the EWT, we need an education that covers a fairly wide range of topics, but always keeps in mind how those topics will be used. Early engineering education needs to include subjects that have clear applications, even if they are not put to those exact uses when taught; mathematics is an obvious example. To suggest that nonengineering courses should come first, and then engineering later, is to build a structure that goes against the EWT. Second, it would mean that non-engineering majors in universities would need to take some engineering courses as part of their general education – much like engineers take humanities and social sciences as part of their general education. Engineers recognize, sometimes begrudgingly, the importance of non-engineering knowledge; the converse is typically not true.

The EWT is somewhat alien to many, perhaps most, engineers; but we realize that when confronted with a new problem, we will think broadly enough to determine what heuristics, new or old, we need to solve it. This is really nothing but a limited version of the EWT. In my next article, I will analyze the EWT with the aim of convincing you further that engineering is broader than we have allowed ourselves to recognize.▪ William M. Bulleit (wmbullei@mtu.edu), is a professor in the Department of Civil and Environmental Engineering at Michigan Tech in Houghton, Michigan, and the vice chair of the SEI Engineering Philosophy Committee.

Structural Forum is intended to stimulate thoughtful dialogue and debate among structural engineers and other participants in the design and construction process. Any opinions expressed in Structural Forum are those of the author(s) and do not necessarily reflect the views of NCSEA, CASE, SEI, C 3 Ink, or the STRUCTURE® magazine Editorial Board.

STRUCTURE magazine

66

January 2016