STRUCTURE magazine | December 2015

A Joint Publication of NCSEA | CASE | SEI

STRUCTURE

®

December 2015 Soils & Foundations

NCSEA EXCELLENCE

IN

STRUCTURAL ENGINEERING AWARDS

Banking center strengthened with MAPEI’s CFRP products

Scotiabank’s concourse and ground levels at Scotia Plaza in Toronto are undergoing structural strengthening in order to increase the live load capabilities of the floors to greater than 50 lbs. per square foot. The center’s vertical support columns are being strengthened by MAPEI’s MapeWrap C Uni-Ax 300 and MapeWrap C Uni-Ax 600 uni-directional carbon fiber fabrics in combination with MapeWrap resins.

Two pultruded carbon fiber plates – MAPEI’s Carboplate E 200 and Carboplate E 250 – are being used on the floors themselves and on the underside of load-bearing beams on the two levels. The Carboplate products on the floors are being covered with MAPEI’s Planibond EBA bonding agent and Topcem Premix screed to provide a flat, level surface for floor coverings.

MAPEI products used:

• Carboplate™ E 250 (100 mm and 150 mm plates) • Carboplate E 200 (50 mm, 100 mm and 150 mm plates) • MapeWrap™ C Fiocco anchors • MapeWrap C Uni-Ax 300 • MapeWrap C Uni-Ax 600 • MapeWrap Primer 1 • MapeWrap 11 • MapeWrap 31 • Topcem™ Premix • Planibond ® EBA

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STRUCTURE

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FEATURE

Working at a Congested Urban Site

By Jay Love, S.E. and Alan Loving The site of the California Pacific Medical Center is ringed by major thoroughfares and the neighborhood is fully developed with established uses, leaving no surplus area for the staging of vehicles and materials. This article, the second in the series, outlines how the construction team developed a logistics plan that supported construction related activities and resulted in unique processes and staging requirements.

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FEATURE EDITORIAL

7 2016: A Year of Leadership and Innovation through Collaboration and Partnering

INSIGHTS

40 Design Snow Loads and Metal Buildings

By Vincent E. Sagan, P.E.

By David J. Odeh, P.E., S.E., SECB HISTORIC STRUCTURES BUILDING BLOCKS

10 Increase Steel Service Life Using Hot-Dip Galvanizing

By Laura Hanson STRUCTURAL REHABILITATION

14 Monitoring the Health of a Building during and after Rehabilitation

By Dominick R. Pilla, P.E., C.E., S.E., Jorel Vaccaro, P.E. and Justin Wilde

42 The Quebec Bridge – Part 1

By Frank Griggs, Jr., D.Eng., P.E. CASE BUSINESS PRACTICES

47 Another Fine Mess We Have Gotten Ourselves Into!

NCSEA Excellence in Structural Engineering Awards The NCSEA Excellence in Structural Engineering Awards program annually honors the best examples of structural ingenuity from around the world. The winners of the 2015 program were announced on October 3rd at the NCSEA Summit, held at the Red Rock Resort in Las Vegas, NV. STRUCTURE magazine is pleased to report on the structural solutions developed for these unique projects. Please join NCSEA in congratulating these exceptional winners.

By John Dal Pino, S.E. STRUCTURAL FORUM

58 The Engineering Way of Thinking: The Idea

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

STRUCTURAL PRACTICES

21 New Design Guide for Pile Caps

IN EVERY ISSUE 8 Advertiser Index 9 Noteworthy 50 Resource Guide (Earth Retention) 52 NCSEA News 54 SEI Structural Columns 56 CASE in Point

By Mike Mota, Ph.D., P.E. and Timothy W. Mays, Ph.D., P.E.

On the cover The Malone Cliff View Residence’s steel spiraling staircase was constructed of one spiraling steel box beam that was only connected at each floor access point. Cantilever steel plates supported the wood treads. The Residence is an NCSEA Outstanding Project winner in the NCSEA Excellence in Structural Engineering Awards program. See page 31 of this issue. Courtesy of Charles Davis Smith.

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Publication of any article, image, or advertisement in STRUCTURE® magazine does not constitute endorsement by NCSEA, CASE, SEI, C3 Ink, or the Editorial Board. Authors, contributors, and advertisers retain sole responsibility for the content of their submissions.

December 2015

Editorial

2016: A Year of Leadership and Innovation new trends, new techniques and current industry issues through Collaboration and Partnering

By David J. Odeh, P.E., S.E., SECB, F.SEI, M.ASCE

2016 will mark many key milestones for our profession, and will have many exciting opportunities to shape our future.

As we enter this important time in the history of structural engineering, let’s not forget that our greatest achievements and innovations always come when we work together in teams. Structural engineers often cite inspiration from other fields, such as physics, chemistry, or art, when they develop a novel idea or solution to an important problem. Furthermore, the increasing complexity of design and the related body of engineering knowledge together necessitate our interaction with specialists in all manner of disciplines, from soils to advanced composite materials. Even within our own discipline, there are numerous specialists and component engineers – each having their own custom tools and methods – who must interact to make a project succeed. Today, no structural engineer can practice in a silo.

With this in mind, I would like to draw your attention to some important upcoming events in the new year, all of which are the result of collaboration and teamwork: • First, 2016 will be the 20th anniversary of the founding of the Structural Engineering Institute. SEI was the first technical institute of ASCE, and today has grown to over 25,000 worldwide members in research, academia, and practice.

SEI operates with an independent board of governors and engages in all manner of activities to advance the profession of structural engineering. However, SEI also benefits from collaboration and partnership with its nine sister technical institutes in such diverse areas as: geotechnical engineering (G-I); architectural engineering (AEI); and coasts, oceans, ports, and rivers (COPRI). SEI also has developed important partnerships with peer organizations including NCSEA, CASE, SECB, SELC, ATC, IStructE, and IABSE. • Second, 2016 will mark the release of a new edition of SEI’s flagship standard, ASCE/SEI-7 Minimum Design Loads for Buildings and Other Structures. In addition to important updates to every section, ASCE/SEI 7-16 will for the first time include a chapter on tsunami loads, driven by a worldwide need to address this critical hazard for which no generally accepted structural design standards previously existed.

Research for this new chapter was jointly funded by SEI and our partner institute, COPRI. Only through this unique combination of resources, combined with a global team of experts, could the important work be done to develop this new standard which will enhance public safety.

• In February 2016, SEI and CASE will partner for the first time with the Geo-Institute (G-I) for a unique and fascinating conference in Phoenix called the Geotechnical and Structural Engineering Congress. This one-time event will feature all of the great things that participants have come to expect from Structures Congress – excellent short courses (including one on ASCE/SEI 7-16 taught by leading experts who worked on the standard), networking opportunities, and tracks on such key topics as earthquake engineering, blast and impact loading, and the popular CASE Risk Management Convocation.

STRUCTURE magazine

In addition, attendees of the 2016 conference will benefit from a unique opportunity to interact with the world’s top geotechnical engineers and learn about topics crucial to structural engineers, such as the latest ground-improvement methods and soil-structure interaction for earthquake engineering. With so much new scientific knowledge and technology being introduced in both fields, never has the interface between structural and geotechnical engineers been more important. The 2016 Geotechnical and Structural Engineering Congress promises to be a fantastic opportunity for structural engineers to expand their knowledge and build new relationships with fellow design professionals in our two related fields.

• Finally, in 2016 SEI will launch a new Global Activities Division. With an important mission to address the needs of a worldwide membership, this new division will be a tremendous opportunity to create new links between structural engineers around the world. Stay tuned this spring for more information on this exciting initiative.

Our capacity to innovate hinges on our ability to draw talent and inspiration from many different fields and from each other – each one of us with a different background and perspective on the critical issues we face. 2016 promises to be a year of great opportunity for those who can leverage these partnerships effectively. We must build more links between our organizations, both inside and outside of our discipline, to ensure a vibrant future of innovation and leadership for structural engineers.▪ David J. Odeh is the President of the Structural Engineering Institute of ASCE. He is a principal at Odeh Engineers, Inc. of Providence, Rhode Island.

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December 2015

ADVERTISER INDEX

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ADVERTISING ACCOUNT MANAGER INTERACTIVE SALES ASSOCIATES sales@STRUCTUREmag.org Eastern Sales Chuck Minor 847-854-1666 Western Sales Jerry Preston 480-396-9585

EDITORIAL STAFF Executive Editor Jeanne Vogelzang, JD, CAE execdir@ncsea.com Editor Christine M. Sloat, P.E. publisher@STRUCTUREmag.org Associate Editor Nikki Alger publisher@STRUCTUREmag.org Graphic Designer Rob Fullmer graphics@STRUCTUREmag.org Web Developer William Radig webmaster@STRUCTUREmag.org

EDITORIAL BOARD

ERRATUM In the November 2015 issue, the feature article, A Systems Approach for Structural Framing, referenced Structo-Crete panels. During the months preceding publication while the article was prepared, the panels were re-branded to USG Structural Panels.

The online version of this article has been updated to reflect the new product name. Also, see USG’s ad on page 33 of the November issue.

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

Chair Jon A. Schmidt, P.E., SECB Burns & McDonnell, Kansas City, MO 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

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December 2015

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 December 2015, Volume 22, Number 12 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.

news and information

Noteworthy

In Appreciation…

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n January 1, 2016, STRUCTURE magazine will have a new Editorial Board chair. If you are not part of the inner circle that produces the magazine, you might not see the significance in the change. The importance is not that the magazine’s quality is in jeopardy or the content will change, but that the man who made the magazine what it is today is moving on. Jon Schmidt, P.E., SECB, the Editorial Board Chair for the last ten years is stepping down. This issue is his last.

In the November In-Focus column, Jon thanked everyone he has been associated with in his ten years with the magazine. That’s Jon, gracious, methodical, and thorough.

Not surprisingly, what Jon did not mention is the role he has played in the success of the magazine. Over the last five years, Jon has been responsible for the selection and editing of over 2200 pages of articles and content.

In 2015 alone, Jon will have managed the production of over 500 pages of content.

Every month starting with the January issue of 2006, Jon has reviewed, scheduled, edited, and decided which articles to print. It did not matter what else was going on in Jon’s life, every month for ten years he held a conference call with his Editorial Board, interfaced with the publisher, and read, edited, and decided what the content of STRUCTURE magazine would be. The magazine is what it is today because Jon said yes to then NCSEA President Ron Hamburger ten years ago and took on the “volunteer” position of Chairman of the Editorial Board.

STRUCTURE magazine is successful because it is written and produced by volunteers. It’s common knowledge that print publications are having a difficult time surviving because of cost increases in postage, printing, and publishing, combined with stagnation in advertising revenues and the competition from digital delivery of content.

If STRUCTURE magazine did not have a volunteer editorial board and contributed content, there would be no magazine; and, despite what’s trending regarding the move to digital, structural engineers overwhelmingly

want their magazine in their hands monthly, and Jon Schmidt helped make sure that was possible.

Jon’s successor, past-president of NCSEA, Barry Arnold, had this response when asked about filling Jon’s shoes. “As the incoming Chair of the Editorial Board, I deeply appreciate and am thankful for the great care and thought Jon Schmidt has put into shaping STRUCTURE magazine into a well-respected, widely-read publication for structural engineers. Throughout Jon’s ten years of service as the Editorial Chair, the magazine has increased in value for the practicing structural engineer by offering a variety of articles focusing on notable projects and engineering achievements, exemplary people, increasing technical competence, and business-related topics….”

Jon Schmidt gave NCSEA ten very demanding years in his role as a volunteer.

Very few people in the 20-plus year history of the organization come close to matching his generosity. When he decided it was time

to step down, he did so and immediately agreed to serve what is likely to be many more years on the NCSEA board.

Knowing Jon, he will be very active and involved in his new role.

In fact, it’s my understanding that when the draft minutes were issued after his first board meeting, Jon immediately sent in his edits.

On behalf of the NCSEA Media Board, and all of the volunteers who make the magazine what it is, I would like to say thank you to Jon Schmidt. You gave us ten years and a first class publication that has flourished when others have floundered. You were a pleasure to work with, and we are all very glad to have had the opportunity. Thanks Jon, and good luck!

Marc S. Barter, P.E., S.E., SECB Chairman, NCSEA Media Inc.

STRUCTURE Welcomes a New Chairman Effective January 1, 2016, Barry K. Arnold, P.E., S.E., SECB will take over as Chair of the STRUCTURE Editorial Board. Barry has been a practicing consulting structural engineer for 27 years and is currently a co-owner and vice-president of ARW Engineers in Ogden, Utah. He is a Past President of the Structural Engineers Association of Utah (SEAU), serves as the SEAU Delegate to NCSEA, and served as NCSEA President during the 2014-2015 year (Current Past President), as well as a member of the NCSEA Licensing Committee. Mr. Arnold is licensed in 40 states and 4 Canadian provinces.

On his vision for STRUCTURE magazine, Barry says, “I look forward to working with the Editorial Board and our readers to build on the foundation Jon provided and offer more in-depth articles and a wider variety of articles of interest to the readers, articles that they can use to improve their technical skills, professional acumen, and business practices. I encourage the reader to be part of the process by sending in your comments about current magazine content and suggestions on how it might be improved.”

Please join STRUCTURE magazine in welcoming Barry Arnold. To contact Barry with your input on the magazine, email him at Chair@STRUCTUREmag.org.

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December 2015

Building Blocks updates and information on structural materials

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120-year service life is achievable in buried galvanized structures. Hot-dip galvanizing (HDG) is the process of immersing fabricated steel or iron into a kettle (bath) of molten zinc. While in the kettle, iron in the steel metallurgically reacts with the zinc to form a tightly-bonded alloy coating.

Hot-dip galvanizing resists corrosion by providing barrier and cathodic protection, as well as through the development of the zinc patina. These three levels of corrosion protection provide galvanized steel with maintenance-free longevity for decades.

One common exposure for HDG steel is partially or fully buried in soil. Structural integrity of these items below grade is very important, but it is difficult, if not impossible, to inspect buried structures for corrosion. Furthermore, the corrosive forces experienced underground are quite unlike atmospheric conditions, and the performance of steel in these conditions is not as well understood as in above-ground applications.

Many factors affect the corrosion rate of galvanized steel in soil, and understanding them takes some measure of effort.

Chloride content, pH, and moisture content of the soil all affect the performance of galvanized steel. Having an understanding of and value for these characteristics provides the input necessary to estimate the service life of the galvanized steel based on the type of soil it is buried in

Increase Steel Service Life Using Hot-Dip Galvanizing

By Laura Hanson

Corrosion Rate in Soil

Laura Hanson is the Senior Marketing Coordinator with the American Galvanizers Association based out of Centennial, Colorado.

She manages www.galvaniziet.org along with the Association’s digital marketing initiatives.

There are countless soil types in North America, which makes predicting the performance of galvanized steel in soil difficult. A number of soil characteristics affect the corrosion rate of galvanized steel, and soil content conditions can vary significantly. These variances can lead to vastly different corrosion rates for zinc, ranging from 0.2 microns per year in very favorable conditions to 20 microns annually in very aggressive soils.

Magnum Piering, Inc.’s helical pilings in Westchester, Ohio rely on hot-dip galvanizing for corrosion protection.

Hot-dip galvanizing protects the buried steel supports of the Discovery Light Solar Project in Beaverton, Ontario, Canada.

Therefore, the key to understanding how long galvanized steel will last in buried applications is through classification of the soil.

As a general rule of thumb, galvanizing tends to perform well in brown, sandy soils, and not very well in gray, clay-like soils. The reason for this difference is sandy soils with larger particles wick moisture more rapidly, limiting the galvanized piece’s exposure to wet conditions, while clay-like soils hold moisture for longer periods.

Similar to atmospheric exposure, galvanized steel performs best when it is exposed to both wet and dry cycles. However, there is more to the corrosion story when it comes to buried galvanized structures.

The four variables with the most profound impact on the corrosion rate of hot-dip galvanized steel in soil include chloride concentration, moisture content, pH, and resistivity.

The presence of chloride ions causes resistivity to be lower, making the zinc coating more susceptible to corrosion. Along with high moisture levels in the soil, high chlorides will increase the rate of the corrosion of the zinc coating.

For hot-dip galvanized steel, the soil moisture content primarily affects the activity of the chloride ions. If the moisture content of the soil is below 17.5%, the chloride ion concentration does not significantly affect the corrosion rate of the zinc. For soils with moisture content above 17.5%, the chloride ion concentration has a significant effect on the corrosion rate of zinc. Soils with pH values less than 7.0 have a higher corrosion rate on zinc coatings. If the pH of the soil is above 7.0, then the corrosion

10 December 2015

rate of the soil yields a longer service life of the zinc coating. The resistivity parameter follows the chloride ion concentration in that higher resistivity means lower chloride ion content and a lower corrosion rate of the zinc coating.

Because predicting the service life of HDG steel in soil applications is dependent on the type of soil it is buried in, the American Galvanizers Association (AGA) has developed the Service Life of Galvanized Steel Articles in Soil Applications chart for estimating HDG steel’s performance The chart uses a combination of the three most critical environmental parameters to estimate the service life of HDG steel buried in soil.

In this instance, the service life is defined as time to complete consumption of the zinc coating plus 25% loss of steel thickness. At this point, the buried structure has reached full service life and it would be time to replace it.

This chart is based on real world corrosion data from two major studies. First, the Corrpro Companies study for the National Corrugated Steel Pipe Association (NCSPA) in conjunction with the American Iron and Steel Institute (AISI), which examined soils from 122 US sites with varying pH conditions. The second study was conducted

Corrosion Rate Variables Chlorides The presence of chloride ions causes the resistivity to be lower and makes the zinc coating more susceptible to corrosion. Along with high moisture levels in the soil, high chlorides will increase the rate of the corrosion of the zinc coating.

Moisture For hot-dip galvanized steel, the soil moisture content primarily affects Content the activity of the chloride ions. If the moisture content is below 17.5%, the chloride ion concentration does not significantly affect the corrosion rate of the zinc. If the moisture content is above 17.5%, the chloride ion concentration has a significant effect on the corrosion rate of zinc. pH The lower pH (< 7.0) values of soil have a higher corrosion rate on zinc coatings. If the pH is above 7.0, then the corrosion rate of the soil yields a longer service life of the zinc coating.

Resistivity This parameter follows the chloride ion concentration in that higher resistivity means lower chloride ion content and a lower corrosion rate of the zinc coating. in the 1970s by Dr. Warren Rogers. With this study, Dr. Rogers developed a model to predict Mean Time to Corrosion Failure from a number of factors that were measured at Underground Storage Tank sites.

Ultimately, this study helped to determine the four variables mentioned previously (chlorides, moisture content, pH, and resistivity) that have the most profound effect on the corrosion rates in soils.

The Service Life of Galvanized Steel Articles in Soil Applications table has four different graphs based on the classification of the soil, including chloride content, moisture, and pH. Using the chart, the first classification is by chloride content – Charts 1 and 2 (top row) are used for soils with high chlorides (>20 PPM) and Charts 3 and 4 (bottom row) are used for soils with low chlorides (<20 PPM). Soils with high chlorides are then

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classified based on their moisture content.

Soils with low moisture levels of less than 17.5% are shown on Chart 1, while soils with high moisture, i.e. greater than 17.5% are shown on Chart 2. Soils with low chlorides are classified by their pH levels. Soils with pH levels greater than 7.0 are shown on Chart 3, while soils with pH levels less than 7.0 are shown on Chart 4.

The blue line on all four charts represents the average for soils surveyed in that characteristic group. The green line then represents the best soil in the category sampled, while the red line represents the worst soil sampled. The shaded areas show how the changes in pH and moisture content affect the estimated service life. Assuming 3.5 mils as a minimum thickness for HDG steel buried in soil, the chart shows the average life in the harshest soils (uncommon) would be approximately thirty years and in the best soils would exceed 120 years.

Summary By utilizing the Service Life of Galvanized Steel Articles in Soil Applications chart and having an understanding of the factors affecting the performance of galvanized steel in soil,

predicting the service life becomes slightly easier. Although soil types vary based on location and the factors mentioned above, hot-dip galvanizing’s superior corrosion protection will help lengthen the life of the ADVERTISEMENT–For Advertiser Information, visit www.STRUCTUREmag.org

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December 2015

buried steel by decades. The durability and relatively maintenance-free performance of hot-dip galvanized steel make it a high quality corrosion protection system for steel applications in soil.▪

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Structural rehabilitation renovation and restoration of existing structures

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uring site work and, specifically, underpinning work involving existing buildings, it is best practice to perform monitoring of any buildings in the vicinity that may be influenced by the work. This monitoring includes both optically surveying the existing structures for displacement and installing vibration monitors to continuously monitor and record peak particle velocities. Both movement and particle velocity data can be used as tools to alert the monitoring engineer of potentially damaging site conditions or construction prac- Figure 1. Installing an underpin beneath foundation. tices, and to provide valuable time necessary to prevent or mitigate damage due to specifically outlines these requirements. The the construction work. Excavation beneath or requirement applies specifically to landmarked adjacent to foundations and use of vibratory buildings because they are particularly susceptible equipment can have drastic to damage. This is due to several factors. impacts to soils beneath existLandmarked buildings can be structurally ing buildings. deficient due to their age. Many landmarked The New York City Building buildings that this author has reviewed were Code, Section 1814.3, requires originally constructed as shared-party-wall this monitoring during any buildings and, through decades of renovaunderpinning activities (Figure tions, often no longer possess robust lateral 1). Monitoring is also required systems. Adjacent building demolition and during any site work within the associated removal of floor diaphragms ninety feet of a Landmarked Building, a des- that brace these party walls, coupled with the ignation specified by the NYC Landmarks subsequent partial undermining of these walls Preservation Commission (LPC). Technical Policy during underpinning processes, can cause sub& Procedure Notice 10 of 1988 (TPPN 10/88) sidence and out-of-plane movement.

Monitoring the Health of a Building during and after Rehabilitation

By Dominick R. Pilla, P.E., C.E., S.E., R.A., Jorel Vaccaro, P.E. and Justin Wilde

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Dominick R. Pilla owns and operates Dominick R. Pilla Associates, P.C. In addition, Mr. Pilla is an associate professor at the Bernard & Anne Spitzer School of Architecture at City College of New York. He can be reached at dominick@drpilla.com.

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excessive based on an average depth of excavation, say 20 feet, and an average angle of soil repose of 45°, the 90 foot radius also takes into account the potential for vibratory equipment to affect soils under buildings at this distance as a vibration wave propagates outward. While direct effects of soil removal are not anticipated at a 90 foot distance, sandy soils can settle during pile-driving or rock blasting, and effects of these vibration loads can be observed at this distance.

A building’s structural monitoring program is comprised of three components: optical

Figure 3. Collimation of a target through a total station.

Often, monitored landmarked buildings possess rubble foundations. These foundations are comprised of mediumsized boulders. The material may have been assembled with or without mortar or grout. If used, often times the mortar has significantly deteriorated. The pieces of rubble perform poorly as pits are excavated beneath them for the underpin installation; they do not bridge over these pits as well as newer reinforced concrete foundations. Larger boulders typically perform better than smaller to bridge over these excavations. Monitoring performed by the author in these instances has revealed that when performing this excavation for installation of underpinning pits, local subsidence can occur, even with the commonly-specified excavation width of four feet per pin. Three feet is now often specified due to these observations. Optical monitoring in these instances is most useful and can reveal most vertical and out-of-plane displacements. Collection and review of the monitoring data helps the engineer evaluate the performance of the specified construction in real-time and react accordingly, possibly by specifying additional bracing and shoring prior to continuation of underpin installation and/or reducing the number and size of pin pits that may be open simultaneously.

Soil types can also impact how a building performs and reacts during construction work. When installing piles or removing rock, vibratory equipment can cause sandy soils to settle or spill out into inadequately-supported excavations. Vibration monitoring can provide forewarning of such events and help to proactively address potential undermining due to excessive vibratory loading.

The LPC requires monitoring of all landmarked buildings within 90 feet and in all directions of the work being performed (Figure 2). While this radius may seem

monitoring, vibration/movement monitors, and telltale crack gauges.

Optical monitoring consists of the installation of targets on the façade (Figure 3) of each building to be monitored. Typically, targets are installed at a height equal to the 2nd floor or 3rd floor framing and spaced along the façade every five to ten feet horizontally. The first signs of any settlement are easily observable in the data when arranging targets in this orientation. This is because placement in the lower floors allows for any localized settlement to be observed. Separation and cracking can

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STRUCTURE magazine

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December 2015

1/2

DP39

1/4 E

0

N Z

‐ 1/4

‐ 1/2 8/29/14

9/18/14

10/8/14

10/28/14

11/17/14

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12/27/14

1/16/15

Figure 5. Graph of the displacement of a monitoring point.

Case Study

Figure 4. Surveying of monitoring points.

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occur above due to arching and other factors. This can result in little movement in the upper portions of the façade being measured, skewing results. The placement also allows the targets to be maintained out of reach of pedestrians and above potential obstacles such as vehicles. The sighting of targets is performed from the sidewalk level, and located at a set station mark, typically on a sidewalk.

Targets may also be placed in a grid over portions of, or the entire façade to monitor for potential out-of-plane movement. This technique can be utilized if the building’s exterior wall is suspected of being inadequately connected to its floor diaphragm.

This may occur in the case of a party-wall building where the contiguous building has just been demolished to make way for new construction. The remaining building could potentially possess large unbraced lengths of wall due to a stair or other shaft extending the height of the building. continued on page 19

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In one particular instance, multiple brownstones are proposed to be renovated simultaneously in order to be combined into a single new building. The brownstones are landmarked and their façades must be preserved. One of the lots is on a corner, with a long wall of the brownstone facing the street, unbraced by any other building. New floors are proposed to extend beneath the existing foundation, and underpinning is necessary. A difficult situation arises. In this case, the corner building is braced with temporary horizontal steel that is extended through the neighboring buildings to be demolished and into the next building’s bearing wall, which is to remain. Bracing could have instead extended downward into the ground, but the temporary structure would have then caused coordination issues when installation of the new structure moves forward.

Timber floor framing and floor decking in the pre-existing corner building are deficient.

Efforts were made, prior to underpinning, to better connect the floor diaphragm at each floor into the load-bearing masonry walls. Floor framing was re-decked where appropriate, and all connections into the exterior façade, the front and rear walls, and the party wall were bolstered. In demolishing the adjacent building at the shared party wall, a long, slender building results.

The next stage, underpinning of the rubble foundation, then proceeds in sequenced excavations. Excavation width is limited to four feet, pin width is limited to three feet, and all efforts are made to minimize the disturbance of existing soils. Unfortunately, lateral movement and vertical settlement approaching the ¼ inch limit are observed during the underpinning process (Figure 5).

As a result, work is stopped and additional bracing and steel reinforcement is designed by the engineer to bolster the frame of the Figure 6. Typical target on landmarked building. building. Additional targets are applied to the exterior face of the building in order to record a more precise profile (Figure 6 ) and monitoring frequency is increased to a 48 hour schedule. The additional shoring is developed to essentially create a temporary steel diaphragm, “grab” the existing masonry façade, and connect it directly to the horizontal steel bracing attached to the adjacent building. This effectively arrests all movement and the contractor is able to proceed with underpinning, completing it without further movement.

Overall, an inadequate lateral system combined with subsidence of the soil during pin excavation to cause slight vertical settlement. This in turn caused out-of-plane movement of the wall. While the building was originally constructed as free-standing prior to construction of its adjacent building, excessive renovation eventually caused it to rely on its contiguous neighbor. Even after reconnection of existing diaphragms and horizontal bracing extending to farther neighboring buildings, the removal of the contiguous building combined with the excavation performed beneath the foundation for underpinning caused slight movement. Monitoring of the building alerted the engineer to the condition, and the design and installation of an additional temporary structure arrested this movement.

STRUCTURE magazine

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December 2015

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FA S T ER Figure 7. Attachment of a vibration monitor geophone.

1981 ASCE article regarding a case study of monitoring in a Historic District in downtown NYC during adjacent excavation. The conclusions of the article discuss the success in monitoring results reflecting measurable damage based on the peak particle velocity and movement criteria along with monitoring frequency utilized in the program.

The ideal result of monitoring, of course, is that no significant movement or vibration occurs and therefore none is detected.

A carefully prepared underpinning and Support of Excavation (SOE) design, along with an experienced, competent contractor can often result in an uneventful monitoring report. Proper due diligence must be performed. This includes the review of soil boring logs and collecting and documenting the existing condition of neighboring buildings. Any pre-existing conditions must be addressed before the contractor commences. This can be very difficult with adjacent occupied buildings or unfriendly, litigious neighbors. Some sites are difficult because of the site conditions themselves.

Soil bearing capacity may be low, or inadequate existing foundations are present.

When adverse site conditions are present, techniques such as jacking and shortening of pin pit widths should be considered.

A thorough monitoring plan is critical in every instance. The monitoring protects the owner, and provides a forewarning before common damages such as interior wall finish separation and brick masonry mortar joint separation are observed.

It is important to consider all aspects in the preparation of each monitoring plan.

A thorough understanding of existing soil conditions, structural conditions, along with the proposed scope of site work will help to develop an effective plan. Close coordination with the structural engineer, general contractor, and architect will help ensure a safe process that runs smoothly to address any building movement that may occur during construction.▪

STRUCTURE magazine

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December 2015

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Optical monitoring is performed with a total station (Figure 4, page 16) and typically occurs multiple times per week. The frequency is increased if the monitored structure is deemed particularly vulnerable or if any movement trends are observed. During data collection, reference points are recorded in the form of previously-set benchmark target locations.

The recorded monitoring data is compared to these benchmark locations to calculate any displacements that have occurred in three directions – the in-plane lateral (sideways) direction, out-of-plane lateral direction, and vertical (Z) direction. The directions are not always described in the same fashion as typical surveying coordinates, i.e. as Northing and Easting, because the direction relative to the face of the material being monitored is of primary concern.

The vibration monitoring equipment, commonly utilized to collect seismic data and blast activity monitoring during mining, consists of a tri-axial geophone (Figure 7) to convert movement into an electrical signal.

The signal is then recorded and, when coupled with a modem or internet-connected hardware, can be uploaded to the monitoring engineer’s server for real-time data review and immediate event alerts. The vibration monitors are placed on all adjacent and contiguous foundations surrounding the project site. A microphone can also be incorporated into these systems, which allows for the recording and monitoring of decibel level caused by the construction.

The third component in the monitoring program is a gauge that is applied across existing cracks and other deficiencies. These crack gauges consist of two plates that are attached on either side of the separation. One clear plate crosshairs overlaps the other plate which contains graduations. If the two sides of the separation shift relative to each other, the crosshair plate shifts compared to the graduated plate and this shift can be read by the crosshair end locations. These gauges are regularly observed, and separations are documented and reported in conjunction with optical and vibration data.

Monitoring criteria varies between industries, jurisdictions, and the composition of the building being monitored. The established criteria in NYC are specified in TPPN 10/88. The criteria specify a threshold of ¼ inch of movement displacement, and ½ inch/sec velocity limits. The monitoring plan must detail the procedure if these limits are exceeded. The engineer of record and the Department of Buildings are typically alerted as part of this procedure. The technical bulletin is largely based on the conclusions of a

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lthough pile caps are an important structural element, they are generally neglected in textbooks on structural design. This article is intended to offer a brief introduction to the new CRSI/DFI (Concrete Reinforcing Steel Institute/Deep Foundations Institute) Pile Cap Design Guide referred to henceforth as the Guide. The Guide was authored by Dr. Timothy W. Mays, P.E. with The Citadel.

The new Guide has been developed as a standalone publication to provide the practicing engineer with a detailed overview of pile cap design, detailing, and analysis methodologies that represent the current state of practice in the industry, and meet the latest codes and standards including the 2015 International Building Code (IBC) and ACI 318-14.

The Guide is much more than an updated version of Chapter 13 of the CRSI Design Handbook (2008). When the Design Handbook pile cap design tables were developed, pile allowable loads exceeding 200 tons were not common. The advent of new 16-inch and 18-inch HP sections with higher allowable loads has necessitated the need of an expanded scope that includes pile allowable loads up to 400 tons. Assuming a factor of safety of 2, this implies in place pile loads up to 800 tons.

The Guide also features expanded design tables to account for the higher allowable loads.

The complex and often misunderstood load path fundamentals associated with pile caps, and the fact that most pile caps are not open to visual inspection under service, warrants a conservative design approach. Complete nonlinear finite element modeling of pile caps is not practical in routine design practice, and applying geometry specific strut-and-tie design models for all pile caps can actually be unconservative when certain modes of failure control the pile cap’s response.

For this reason and others, ACI 318-14 does not permit strut-and-tie modeling for all pile caps.

In fact, only “deep pile” caps may be designed by this approach.

The Guide provides an overview of load types considered and how these loads are appropriately combined to design pile caps, followed by an overview of assumptions used to determine the load distribution to piles when caps are subjected to different load cases. Thirty pile cap configurations with dimensioning requirements are considered in the Guide, and the overall recommended layout of steel reinforcement in the pile cap is also provided (Figure 1).

Pile cap design procedures for vertical and lateral/overturning loads, respectively, are considered, along with a special chapter devoted to seismic design of pile caps. The Guide offers several practical pile cap design examples including complete manual solutions for vertical and lateral load situations as well as complimentary access to design spreadsheets.

Structural PracticeS practical knowledge beyond the textbook

Figure 1. Arrangement of piles and minimum plan dimensions of pile caps.

Tabulated pile cap designs for both vertical loads and combined, vertical, lateral, and overturning actions are available for pile loads up to 400 tons allowable load. The appendices are also replete with practical information. Appendix A presents detailed derivations for several simplified design equations presented in the Guide. Column-to-pile cap and pile-to-pile cap connection details are discussed in Appendix B and C, respectively.

Research performed during the development of this Guide suggests that deeper pile caps associated with larger and stronger piling than was considered in the Design Handbook warrant some new steel details. In addition, lateral loads on pile caps (Figure 2) are considered for the first time in a CRSI publication in the new Guide. A complete design example for detailing a pile cap under combined vertical loading, lateral loading, and overturning is presented. The use of larger and stronger high load piling typically requires deeper pile caps with larger edge distances. To better understand the behavior of deep pile caps, a finite element study (Figure 3, page 22) was performed and recommendations obtained from that study are presented and incorporated into new details

New Design Guide for Pile Caps

Figure 2. Pile cap resisting column applied axial, shear, and bending moment. Pile head assumed pinned.

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By Mike Mota, Ph.D., P.E., F.ASCE, F.ACI and Timothy W. Mays, Ph.D., P.E.

Mike Mota is the Vice President of Engineering for the Concrete Reinforcing Steel Institute (CRSI).

He is an active member of several ACI and ASCE committees, Member of ACI 318 and 318 sub B and sub R and Chair of ACI Committee 314 on Simplified Design of Concrete Buildings and is a member of the Editorial Board of STRUCTURE magazine. Mike can be reached at mmota@crsi.org.

Timothy W. Mays is a Professor of Civil Engineering at The Citadel in Charleston, SC. Dr. Mays previously served as Executive Director of the Structural Engineers Associations of South Carolina and North Carolina. He currently serves as NCSEA Publications Committee Chairman. Timothy can be reached at mayst1@citadel.edu.

Figure 3. Sample finite element study results.

obtained using the design provisions presented in the Guide are verified using hand calculations. The examples were selected in order to help the reader fully understand assumptions associated with the design procedures, and to provide adequate applications for the different pile cap configurations such that the user could design other pile cap configurations as necessary.

Example 1: 16 Pile Cap – This example is a symmetrical cap (i.e., square in plan) with two rows of piles on all 4 sides of the column.

The larger pile cap plan dimensions result in straight bars and it is one of the easiest pile configurations to work with calculation-wise.

Low pile service loads are used in the example.

Example 2: 5 Pile Cap – This example is also a symmetrical cap (i.e., square in plan) but it has only 1 row of piles on each side of the column. The smaller pile cap plan dimensions result in hooked bars and it has a unique pile

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used for all pile caps utilizing pile allowable loads greater than 200 tons.

For very high load piles, an additional prescriptive requirement of hoop steel reinforcement is presented in the Guide (Figure 4). This additional steel reinforcement provides confinement to resist high bursting stresses created in the concrete around the head of the pile due to the high load piles and allows for piles to be installed without the use of bearing plates at the top of the pile. Tabulated designs are also provided for all CRSI considered pile cap configurations and a wide range of vertical loading, lateral loading, and overturning effects. Users of the Guide have access to spreadsheets that include all pile configurations and allow the user to consider both gravity and lateral loads.

The Guide provides a series of six (6) design examples where tabulated design solutions

Figure 4. Additional prescriptive steel requirement when high load piles are used.

layout. It is the only cap that utilizes 45-degree angles in the pile plan geometry. Moderate pile service loads are used in the example.

Example 3: 6 Pile Cap – This example is an unsymmetrical cap (i.e., rectangular in plan).

It was also chosen since it is one of the special caps where Limit State 4 calculations require an average width “w” in orthogonal directions.

Example 4: 7 Pile Cap – This example is an unsymmetrical cap. It was chosen since it is one of only two caps that are uniquely detailed for round columns (rather than equivalent square columns).

Example 5: 5 Pile Cap – This example was selected as a comparison design with Example 2 and it utilizes high load piles.

Example 6: 16 Pile Cap – This example was selected as a comparison design with Example 1, but it is designed for combined gravity and lateral loading.

The Concrete Reinforcing Steel Institute is fully committed to providing timely and accurate guidance regarding steel reinforced concrete design and construction concerns. To enable convenient access to CRSI resources, many are available in both digital (pdf download) and print media.

This publication is available from the CRSI and DFI website.

Scheduled and on-demand webinars are also available as introductions to topics which are the subject of new or updated technical guides. The scheduled webinar format provides an opportunity for interactive discussion with the authors of CRSI’s Design Guides. For more information on these, and other, continuing education resources visit the CRSI website at www.crsi.org.▪ All graphics courtesy of CRSI Design Guide for Pile Caps 1st Edition 2015.

STRUCTURE magazine

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December 2015

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WORKING AT A CONGESTED URBAN SITE California Pacific Medical Center

By Jay Love, S.E. and Alan Loving Figure 1. Aerial view of site.

T

he California Pacific Medical Center is the San Francisco-based affiliate of the Sutter Health System. The November issue of STRUCUTRE magazine included an article on the use of the Integrated Project Delivery (IPD) framework on the project.

This month, the topic shifts to the challenges of constructing the project in a congested, urban environment.

Project Site In seeking a location for a new acute care hospital in San Francisco, Sutter Health/CPMC was fortunate to find in a ‘built-out’ city, an available full city block (2.5 acres) that also happened to be at the intersection of two major transportation routes: Geary Boulevard and Van Ness Avenue. In doing so, the hospital will be located in an area of the city that will allow it to serve the highest percentage of seniors and children living in San Francisco, as well as provide convenient medical care to the wider Bay Area region.

Geary Boulevard is the major arterial connecting the downtown to the western part of the city. The bus line on Geary Boulevard carries the highest volume of passengers of any line west of the Mississippi River, and serves as a transfer point to major north-south bus lines on Van Ness Avenue that serve both San Francisco and the North Bay counties of Marin and Sonoma. The bus lines on both transportation routes also connect to the Bay Area Rapid Transit System (BART) serving the greater Bay Area. Van Ness Avenue is also State Highway 101, the north-south route connecting points south of San Francisco to the Golden Gate Bridge and also to points north. On the west edge of the site, Franklin Street serves as a one-way arterial route that carries a large volume of local and regional traffic parallel to Van Ness Avenue. The northern edge of the site is bordered by Post Street, a one-way connector to downtown San Francisco (Figure 1).

Physically, the site presented a number of challenges to the construction team, from demolition of the hotel and office building that occupied the entire site through construction of the hospital.

The site is ringed by major thoroughfares and the neighborhood is fully developed with established uses including churches, residential units, businesses and commercial establishments, leaving no surplus area for the staging of vehicles and materials. As a result, the construction team worked closely with the City and County of San Francisco (City) and state agencies to develop a logistics plan that allowed for the use of adjacent sidewalks, parking and traffic lanes in support of construction related activities. This plan varies depending on the STRUCTURE magazine

type of work being done, the equipment needed, and the location of the work on the site. It requires permits from the City with fees in excess of $6 million.

Approvals and Permitting Sutter Health/CPMC spent over eight years seeking approvals from the City for the medical campus. This process included extensive public outreach to neighboring residents, property and business owners, and community organizations to inform them about the project and to get input about how to minimize impacts.

Prior to the commencement of construction work, commitments were made to neighboring property owners that construction activities would not result in excessive noise, vibration, dust or traffic. These commitments were in addition to, and at times more restrictive than, City requirements. For example, City regulations allow construction to occur every day of the week between 7:00 a.m. and 8:00 p.m.

Permits may be issued to allow work to occur outside of these hours.

CPMC agreed to limit construction work to between 7:00 a.m. and 7:00 p.m. Monday through Friday, and 7:00 a.m. to 5:00 p.m. on Saturday. No work is allowed on Sunday. While this results in a longer construction period, the limitations are important to protecting the quality of life of the project’s neighbors.

A community liaison was hired to interface with the community on a regular basis to disseminate information about current and upcoming construction activities. These activities are provided in the form of one week and six week reports. The community is encouraged to contact the liaison, 24 hours a day, should a problem arise.

The project’s location in San Francisco means that it is subject to city, state, and federal permitting agencies, including several City and County of San Francisco departments: Public Works, Municipal Transportation Agency (SFMTA), Building Inspection and Planning.

The state’s Office of Statewide Health Planning and Development (OSHPD) is responsible for the review and approval of the hospital building; the California Department of Transportation (Caltrans) is responsible for issuing permits for construction activity along Van Ness Avenue, which is State Highway 101. Federal Aviation Administration (FAA) permits are required for the height of the hospital building and the two tower cranes that will be used to construct it, as they exceed 200 feet in height. As the project progresses, and the site changes from demolition to excavation to foundations and the erection of steel, the need for access to the site has varied. continued on next page

25

December 2015

Demolition of the Existing Buildings Before construction could begin on the hospital, a 10-story, 120-foot tall, 455,000 square foot hotel and an 11-story, 180-foot tall office building had to be demolished. To reduce the impact of noise and dust on neighboring properties during demolition, implosion or the use of a wrecking ball were ruled out. Instead, high reach excavators with jaws and water spray attachments were used to demolish the building in sections from the inside of the site, using the walls along the exterior edges of the project as buffers. This type of operation is referred to as “munching.” To prevent debris from falling onto adjacent streets, cranes were used to hang large mesh screens around the exterior of the buildings. All materials were crushed and sorted on site prior to disposal or recycling. In the end, 99.7% of the materials were recycled.

After seven months of demolition work, the site was cleared and excavation work began. This work included archaeological and environmental testing of the soils. See Figure 2 for the site during the munching operations.

Excavation and Shoring Prior to the start of the shoring, an extensive pre-construction survey of adjacent buildings was undertaken to document interior and exterior structural conditions. These records will serve as source materials should any claims be filed against HerreroBOLDT, the general contractor, for damages caused by construction activities. Vibration and noise monitors were installed at key locations on or in neighboring buildings to provide the contractors with real time alerts of excessive noise or vibrations.

Figure 2. Demolition phase.

To achieve the three levels of underground parking and foundation system for the hospital, soldier piles and wood lagging shoring was installed during the site excavation to support the soil beneath the streets around the perimeter of the site. The shoring walls were held in place by tiebacks that extended into the roadways, avoiding existing utilities and foundations of neighboring properties. Inclinometers installed in the shoring system ensure that no unusual deformities occur from the pressure of the adjacent streets before the hospital walls could be poured.

The concrete foundation consisting of a combination of slab, continuous, and spread footings was placed. The site slopes upward more than 30 feet from east to west. On the west side of the site, the excavation was 65 feet deep. See Figure 3 for the site during the shoring work.

Figure 3. Site during excavation.

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December 2015

The site generated over 100,000 cubic yards of soil, mostly sands.

These soils were removed from the site in approximately 10,000 truckloads over a four month period. A logistics plan was created to minimize truck traffic on surrounding streets by directing trucks on-site to be loaded. Throughout the excavation phase, ramps were constructed to provide efficient site ingress and egress for the trucks.

During much of the excavation, a large conveyor was used to load the trucks with dirt, reducing the travel area within the site and saving time and effort. Creating a truck route that directed the trucks onto and off the site as soon as possible reduced the impact on city streets and traffic. Truck arrivals were timed to avoid stacking on streets and departures were designed to direct the trucks to outbound city truck routes. Street sweepers were employed by the project to reduce any dirt and dust carried by the trucks onto streets in the area of the project.

To minimize the impact to surrounding streets and traffic from material deliveries, loading and staging areas were created within the expanded construction zone around the site. All deliveries are scheduled in advance and timed to ensure that no trucks wait outside the site. This is achieved by coordinating off-loading with production schedules, tower crane and crew availability. Any unusual deliveries of oversized equipment or items that can’t be delivered during normal construction hours are approved by the City in advance with outreach to the neighbors.

Erection of Structural Steel Once the foundation was completed, erection of structural steel began – which is the current state of the project as this article is written. The project will use more than 12,000 tons of steel in the construction

of the 12-story structure. In order to support the large amounts of equipment typical in a hospital, the building has columns that weigh as much as 52,000 pounds. Two tower cranes erected on the site during this phase of work were supplemented by large mobile cranes used to install larger, heavier columns. Once column and beam placement began, walls and decks began to be formed and poured. An aggressive schedule anticipates a 10-month completion period for this phase of work. See Figure 4 (page 28) for the site during steel erection.

Impact on Public Transportation and Pedestrian Traffic Both diesel powered and electric powered buses are used by the San Francisco Municipal Railway (MUNI) in this area of San Francisco.

The electric buses connect to an overhead catenary system. Overhead lines run adjacent to the site on two streets; on Post Street to the north and to the east on Van Ness Avenue.

In order to provide greater access to the site and maximize public safety during demolition and the erection of steel, MUNI allowed the project to move the lines on Post Street one lane north. The construction team developed a plan with the City to temporarily deenergize and physically relocate the lines during early morning hours when service on those bus lines was limited. All costs were borne by the project. The move allowed the project to expand its work area by using the adjacent sidewalk and parking lane. Although there are no overhead lines on the remaining three streets adjacent to the site, a similar expansion of the site was permitted by the City and the state to provide critical space to the construction team for staging, delivery of materials, concrete pumping, column placement and other activities. continued on next page

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Figure 4. Steel erection.

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The sidewalks adjacent to the site are closed on three sides in order to provide more space for construction activities and to ensure the protection of pedestrians in the area. Through the use of signage, pedestrians are directed to use the sidewalks on the opposite side of the street. Given the high volume of pedestrian traffic on Van Ness Avenue, a covered pedestrian walkway was constructed in the parking lane.

Tunnel under Van Ness Avenue The hospital project includes a 125-foot long pedestrian tunnel beneath Van Ness Avenue, providing a safe connection for medical center patients and staff between the hospital and a medical office building, located on the east side of Van Ness Avenue. The 10-foot by 10-foot tunnel (essentially a box culvert) is approximately 13 feet below the surface of the roadbed and required three separate closures of Van Ness Avenue to complete. Extensive potholing was performed in the road to locate existing utilities beneath Van Ness Avenue prior to the drilling of 37 shoring piles that serve as the structural support of the earth during the tunnel construction (Figure 5).

HerreroBOLDT determined that the cut and cover method would be the best way to construct this tunnel. Use of a boring machine was not economically feasible nor physically practical, given the length of the tunnel and the constraints of working directly adjacent to the construction of the hospital.

Excavation of the top 8 feet of the road (+/- 30 feet wide) allowed for the installation of cap beams that support precast concrete panels beneath the temporary roadbed while the tunnel was constructed below. The utilities were supported in place from these panels. The temporary roadbed allowed traffic to resume normal flow on Van Ness Avenue while excavation; formwork and pouring occurred below. The first two road closures were dedicated to installing the soldier piles, removing the road surface and installing the precast panels. The final

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closure will see the removal of the temporary roadbed and pre-cast concrete panels, and the placement of the permanent roadbed.

In order to minimize traffic delays on Van Ness Avenue while this surface work was done, the city block in which the tunnel is located was closed and traffic was detoured to parallel north-south arterials. Only city and regional buses were allowed to travel through the work zone during the closures. The work was performed during three 72-hour weekend closures over the course of eight months.

These closures required the close coordination and cooperation of HerreroBOLDT, the City’s transportation agency for traffic control and de-energizing of the overhead catenary system within the work area, and the police department for additional traffic control. In addition to approving the detour plan, Caltrans provided regional traffic control assistance through the use of highway message signs that notified motorists of the dates and the status of the closure well in advance of the work. These notifications, combined with a public outreach campaign that included community meetings, mailed notifications, electronic, print and social media significantly reduced the number of motorists travelling in the area during the three designated weekends. This outreach was a key factor in the success of the closures.

With fewer vehicles in the area, the construction crews could focus on completing their tasks safely within the 72 hours scheduled. There were no significant traffic delays created by the detours and the work was completed on the first two closures hours earlier than expected.

From a cost standpoint, the tunnel represents a small percentage of the overall budget – $10 million of the $1.1 billion total. The coordination required to successfully construct it in a way that had minimal impact on the construction of the hospital and traffic in the area was, however, quite significant.

Project Labor Any discussion about the cost to build must include a discussion about labor. As a commitment to the City, Sutter Health/CPMC works with its trade partners and subcontractors to ensure that a minimum of 30% of trade hours (30% of journeyman and apprentice trade hours) are performed by San Francisco residents. In a challenging economic environment that has priced many construction workers out of San Francisco, the project is meeting this goal.

In addition, the project continues to work to reach a goal of contracting 14% of the cost of construction, over $140 million, with San Francisco-based businesses.

Figure 5. Tunneling under Van Ness Avenue.

who use public transportation and gifts are made available for people who walk or bike. To date, over 45% of workers participate in the program.

Working With the City and the Community Constructing a major hospital in the center of San Francisco has presented the contractor and owner with major challenges in the way the project has been approached from demolition through construction. Decisions made about the construction of the project are made to maximize safety and productivity, limit waste, and minimize the impact on the community. Maintaining good relations with the neighborhood and the representatives from the various government agencies that have jurisdiction over the site is very important to the success of the job. The team values their input and their assistance. The project is on schedule to be open for patient care in 2019.▪ Jay Love, S.E., is the Structural Engineer of Record at Degenkolb Engineers. He can be reached at rjlove@degenkolb.com.

Alan Loving is the Manager of Permitting and Public Commitments at HerreroBOLDT. He can be reached at alan.loving@boldt.com.

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Employee Transportation and Parking One of the concerns raised by the community about the project in early discussions was the impact of workers parking in the neighborhood around the job site.

HerreroBOLDT assured the community that workers would not be allowed to park on the street. To achieve this, a program was created that encourages workers to carpool, take public transportation, bike or walk to the job site. A limited number of off-site parking spaces are provided for workers in local garages, but incentives like gas cards and gifts are provided to those who carpool.

Monthly transit passes are provided to those

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Malone Cliff View Residence. Courtesy of Charles Davis Smith.

EXCELLENCE

in

STRUCTURAL ENGINEERING

NCSEA 18th Annual Awards Program

T

he National Council of Structural Engineers Associations (NCSEA) is pleased to announce the following 2015 Excellence in Structural Engineering Awards. The awards were announced on the evening of October 2nd during the Awards Program at NCSEA’s 2015 Structural Engineering Summit in Las Vegas. The awards have been given annually since 1998 and highlight some of the best examples of structural ingenuity throughout the world.

All structures must have been completed, or substantially completed, within the past three calendar years. Awards were given in eight separate categories, with one project in each category named an Outstanding Project. The categories for 2015 were: • New Buildings under $10 Million • New Buildings $10 Million to $30 Million • New Buildings $30 Million to $100 Million • New Buildings over $100 Million • New Bridge and Transportation Structures • Forensic / Renovation / Retrofit / Rehabilitation Structures under $20 Million • Forensic / Renovation / Retrofit / Rehabilitation Structures over $20 Million • Other Structures The 2015 Awards Committee was chaired by Carrie Johnson (Wallace Engineering Structural Consultants, Inc., Tulsa OK). Ms. Johnson noted: “Seeing the quality of the entries each year makes me proud to be a structural engineer. We had a great group of judges from the Structural Engineers Association of Washington this year. They had the enormous task of evaluating a wide variety of quality projects from twenty-five different states and five different countries. The judges did an outstanding job of thoroughly analyzing each entry and thoughtfully discussing which ones should receive the award.”

Please join NCSEA and STRUCTURE® magazine in congratulating all of the winners. More in-depth articles on several of the 2015 winners will appear in the Spotlight section of the magazine over the course of the 2016 editorial year.

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2015 PANEL OF JUDGES The judging was held Saturday August 1, 2015, at the offices of Brown and Caldwell in Seattle, WA. The awards jury included the following engineers from the Structural Engineers Association of Washington: Ade Bright, P.E., S.E. Bright Engineering Inc. Tom Corcoran, P.E., S.E. Integrus Architecture Scott Douglas, P.E., S.E. Douglas Engineering Chun Lau, P.E., S.E. Brown and Caldwell Jane Li, Ph.D., P.E., S.E. RHC Engineering Marjorie Lund, P.E., S.E. Lund Opsahl LLC William McVitty, CPEng KPFF Consulting Engineers Tim Nordstrom, P.E., S.E. Star Seismic Ignasius Seilie, P.E., S.E. Integrated Design Engineers Craig Stauffer, P.E., S.E. PCS Structural Solutions Anne Streufert, P.E., S.E. KPFF Consulting Engineers

December 2015

Category 1 New Buildings under $10 Million

OUTSTANDING PROJECT Malone Cliff View Residence Dallas, TX

Datum Engineers, Inc.

This handsome residence, sitting on top of a bluff, was only made possible by a unique and innovative structural system. Post-tensioned concrete cantilever slabs, 10 inches thick and 17 feet long, soar out over the cliff creating dramatic views from balconies and from spaces on thin concrete slabs. The two-story tall spiraling steel tube that supports the stair is the centerpiece of the architecture.

The foundation was built through a 60-foot deep trash fill that required a creative and innovative structural solution.

Photos courtesy of Charles Davis Smith.

Category 2 New Buildings $10 Million to $30 Million

OUTSTANDING PROJECT The Stack New York, NY

The Harman Group, Inc.

The Stack, a 38,000 square foot, seven-story, 28-unit apartment building was the first modular building constructed in Manhattan. Modules for the 1, 2 and 3 bedroom units were constructed off-site at DeLuxe Building Systems in Berwick, Pennsylvania. The modules were transported to Manhattan and stacked atop a steel-framed podium level. Key to the success of the project was lightweight construction and repetition of design to facilitate assembly line production. The 56 modules were erected in nineteen days with a single crane and crew of 14 workers.

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Category 3 New Buildings $30 Million to $100 Million

OUTSTANDING PROJECT Columbia University Medical Center Graduate Education Building New York, NY

Leslie E. Robertson Associates

The Columbia University Medical and Graduate Education Building is a 100,000 square-foot, 15 story state-of-the-art educational facility. The project’s main feature is a “Study Cascade” that contains interconnected study and social spaces to encourage collaboration between students. Envisioned as a vertical campus of stacked neighborhoods, the main structural challenge was to find vertical load paths that could respect the varied spatial planning of the stacked neighborhoods, while providing floor spans that could accommodate the tight deflection performances required for coordination with the curtain wall. A concrete structure was used because it facilitated the changing floor-to-floor slab edge positions required for the spaces and related façade.

Category 4 New Buildings over $100 Million

OUTSTANDING PROJECT Grove at Grand Bay Coconut Grove, FL

DeSimone Consulting Engineers

Grove at Grand Bay, the first truly twisting buildings in the United States, is an iconic residential project located at the former site of the Grand Bay Hotel in Miami. Grove at Grand Bay features two towers rising 20 stories above a lush landscaped two-story podium. The two towers are low density, with 98 spacious custom homes featuring 12-foot high ceilings and 14-foot deep balconies. In order to capture the full panoramic views of Biscayne Bay and the Miami skyline, the architect rotated the towers incrementally along the height for a total rotation of 38 degrees.

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Category 5 New Bridges or Transportation Structure

OUTSTANDING PROJECT South Park Bascule Bridge Replacement Seattle, WA

HNTB Corporation

The original South Park Bridge was a Scherzer Rolling Lift bridge listed in the National Register of Historic Places. It was unstable and seismically vulnerable because shallow foundation piles caused active tilting and cracking of the main piers. Designing the new bridge to be fully functional after an Operational Level (108-year return) earthquake, and experience only moderate, repairable damage during a Design Level earthquake, was unprecedented. Innovative design features, including sunken caisson foundations, isolated trunnion frames and collapsible center joints on draw spans, provided required seismic performance.

Additionally, “trussed” plate girders improved constructability, maintainability, safety and aesthetics.

Category 6 Forensic / Renovation / Retrofit / Rehabilitation Structures under $20 Million

OUTSTANDING PROJECT Dolphin Towers Condominium – Remediation Sarasota, FL

Morabito Consultants, Inc.

This 12-story residential condominium was constructed over a 3-story garage, with a 24-inch thick concrete transfer slab at the 4th level supporting the apartments above. This transfer slab failed along several columns. A value engineering solution to strengthen the existing building saved the Condominium Owners several million dollars. The scope of work included the strengthening of the existing building structure to support live and dead loads and wind loads required by the original 1971 Standard Building Code or the present 2010 Florida Building Code. Constant communication was a necessity to adapt to continuously changing conditions that required quick solutions.

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Category 7 Forensic / Renovation / Retrofit / Rehabilitation Structures over $20 Million

OUTSTANDING PROJECT 2040 Market Street Philadelphia, PA

The Harman Group, Inc.

2040 Market Street, built in the 1960s, was acquired in 2011 for residential use with ground floor level retail and a vertical and horizontal expansion of the existing five-story concrete framed building. The Harman Group, using a system of loadbearing steel wall panels, added eight residential floors and horizontally expanded the building’s footprint by 68,000 square feet. This vertical and horizontal expansion turned a 120,000 square-foot vacant office building into over 300,000 square feet of residential rental units. By using an Ecospan floor system and Integrity Max panel, they were able to add a maximum number of floors with a minimum weight.

Category 8 Other Structures

OUTSTANDING PROJECT Hy-Fi Long Island City, NY

Arup

As part of MoMA’s annual Young Architects Program, Arup provided structural engineering support to The Living on Hy-Fi – a tower made entirely of mushroom bricks. Mushroom bricks, created by Ecovative Design, are grown from mycelium and agricultural waste to create a styrofoam-like material, and are ultimately compostable. Arup worked with Ecovative and the architects to develop a testing regime to examine the properties of this innovative material.

The result – mushroom bricks are 200,000 times more flexible than steel, but quite strong. The resulting structure is heroic. Ten thousand organically grown bricks soar 40 feet in the air, creating a cathedral to experimental construction.

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AWARD WINNER – CATEGORY 2 Wallis Annenberg Center for the Performing Arts Goldsmith Theater Beverly Hills, CA Structural Focus The Wallis Annenberg Center for the Performing Arts project includes the restoration of the historic Beverly Hills Post Office and the construction of the new 500seat state-of-the-art Goldsmith Theater. The structural engineering effort required precise coordination with architects, acousticians and mechanical engineers to ensure premium acoustic performance. Sunken 30 feet and rising some 50 feet above street level, the Goldsmith Theater is constructed of a steel composite frame and reinforced concrete walls and slabs. Inside, steel braced frames support shaped wood overhead reflectors, a complex system of catwalks, and sidewall panels to achieve functional and acoustic perfection.

Courtesy of John Linden.

AWARD WINNER – CATEGORY 2 The Cubes New York, NY

Gilsanz Murray Steficek LLP

The most dramatic newcomer to Midtown’s 42nd Street commercial corridor is The Cubes, comprising nearly 90,000 square feet of above-grade and below-grade retail space. Challenging excavation and foundation work included digging 32 feet below street level adjacent to an operational subway tunnel. Additionally, the column grid of the new superstructure did not align with the preserved/ existing substructure, requiring the use of transfer girders to distribute loads to the foundation. A series of “bent” transfer girders solved issues with grade differences across the site. The superstructure frame is designed to support a 60-foot billboard above the roof, as well as a full-span LED display anchored to the north façade.

AWARD WINNER – CATEGORY 3 170 Amsterdam New York, NY

DeSimone Consulting Engineers

Located in New York, 170 Amsterdam Avenue is, at 250 feet, the first high-rise exposed concrete diagrid structure.

Zoning provisions limited floor plate size, so an innovative solution was found to increase valuable interior square footage. The diagrid, or exoskeleton, is a system of triangles which carries both lateral and gravity loads through the exterior members. By having the same members carry all of the loads on the exterior, unnecessary interior columns and walls were eliminated, creating more useable square footage. The successful implementation of the concrete diagrid in 170 Amsterdam Avenue will further influence structural design on a local and global level.

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AWARD WINNER – CATEGORY 3 Aspen Art Museum Aspen, CO KL&A, Inc. The Aspen Art Museum is an iconic 33,000 square-foot venue in Colorado designed by the Pritzker Prize winning architect, Shigeru Ban. The museum uses wood products in unprecedented ways. Most notably, in the structure of the roof above the top floor terrace is a 2-way wood space frame that is unique in the world in terms of its form, its use of innovative wood materials, its fabrication and its construction, not to mention its architectural effect. The floating plane of the 3-D space frame roof is supported on a few clustered columns, cantilevering from interior to exterior and covering the roof terrace.

AWARD WINNER – CATEGORY 4 Kimbell Art Museum Expansion Fort Worth, TX Guy Nordenson and Associates The Kimbell Art Museum Expansion is a free-standing, 89,000 square-foot addition that includes several parts.

An East Pavilion consists of gallery and lobby space where the column-free structure is a combination of architecturally exposed concrete walls and 102-foot glued-laminated timber beams with custom metal hardware supporting a glass roof. A new West Building features additional gallery space, an auditorium, and education rooms which is framed with CIP concrete, with a green roof that blends into the surrounding parkscape. Additionally, a basement underneath the full building site, with a parking garage, provides a connection between the new and existing buildings.

AWARD WINNER – CATEGORY 4 Marriott Marquis Convention Center Hotel Washington, DC

Thornton Tomasetti

The Marriott Marquis is a 15-story hotel surrounding a grand lobby, five ground-floor retail and restaurant outlets, a 5,200 square-foot terrace and a two-story fitness center.

The lobby features a 270,000 pound, 56-foot tall stainless steel sculpture. Supporting the building’s seven belowgrade levels, including 105,000 square feet of meeting / event space, hotel and convention operations, mechanical spaces and parking, required an innovative structure and atypical construction methods. The structure consists of 18- to 24-inch thick concrete flat-plate slabs with mild steel-reinforcing bars, W14 steel wide-flange members and steel plates up to two inches thick, supported by concrete-encased composite steel columns.

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AWARD WINNER – CATEGORY 5 The Bridge over Taxiway R Phoenix, AZ Gannett Fleming In April of 2013, Phoenix Sky Harbor International Airport opened the first stage of its new automated transit system, the PHX Sky Train. One of the biggest challenges during Stage 1 was the crossing of Taxiway Romeo, an active taxiway that handles planes as large as Boeing 747s.

The taxiway crosses over Sky Harbor Boulevard, thereby putting planes, trains and automobiles all within close proximity. Nowhere in the world had this been done before. The project team worked for six months with Federal Aviation Administration (FAA), control tower personnel and airline representatives to develop acceptable criteria for the elevated guideway.

Courtesy of Bob Perzel.

AWARD WINNER – CATEGORY 5 I-70 Stan Musial Veterans Memorial Bridge St. Louis, MO

HNTB Corporation

The Stan Musial Veterans Memorial Bridge connects downtown St. Louis, Missouri to southwestern Illinois.

At 2,772 feet long, this three-span, cable-stayed bridge has a main span of 1,500 feet and is the third longest cable-stayed bridge in the U.S. Designed in half the time of similar bridges, the four-lane bridge carries 55,000 vehicles daily, can carry two additional lanes of traffic, and will accommodate an adjacent future four-lane bridge.

The team’s design innovations, including a Conditional Mean Spectrum approach to the seismic analysis never before used in bridge design, transformed the unattainable project into an affordable, buildable, $290 million project.

AWARD WINNER – CATEGORY 6 Checkered House Bridge Design-Build Richmond, VT

Finley Engineering Group, Inc.

An incremental side-launch concept was developed for widening this 350-foot steel truss bridge. The falsework and jacking system preserved 80% of the existing bridge, and added 12 feet 6 inches to the width. Ten specially designed 18-inch stroke capacity hydraulic ram systems were carefully monitored to move the 65-ton north truss to its new location. An Exodermic deck, consisting of steel formwork and lightweight concrete, was used to reduce dead load while providing a strong and durable deck.

Challenges included Historic Registry restriction, ice flows, wind loading, maintaining aesthetics and sensitive environmental issues.

Courtesy of CHA Consulting, Inc.

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AWARD WINNER – CATEGORY 6 Bethel Park Renovation Houston, TX Walter P. Moore Bethel Park is a unique restoration that preserves the architecture of Bethel Missionary Baptist Church. A 2005 fire destroyed the interior of the church. Creative strengthening and restoration techniques salvaged the exterior masonry walls. The design preserved the walls in place to maintain the church’s historical integrity.

The strengthening techniques – which included new or repaired reinforced backup walls, strengthened coatings, and a galvanized steel frame that visually recalls the church’s original gabled roof lines – resulted in exposed masonry walls where the strengthening contributes to the overall original aesthetics of the church. Contributions by the shotcrete subcontractor, Epoxy Design Systems of Houston, TX, assisted in the success of this project.

AWARD WINNER – CATEGORY 7 The Forum Inglewood, CA

Severud Associates Consulting Engineers

The Forum is a cable-suspended structure – not unlike a suspension bridge. The entire roof structure sits on the cables. The building required enhanced capacity to support heavier video boards, lighting, LED arrays, speakers, and rigging required by bands today. This could not be realized with conventional reinforcement techniques. A modern-day version of a dome was created to marry a new compression structure to the existing tension structure. It relieves the forces on the existing outside ring and generates the extra capacity. The combined structure is the only structure in the world that has both a tension ring and a compression ring at its center.

AWARD WINNER – CATEGORY 7 The Strand, American Conservatory Theater San Francisco, CA Skidmore, Owings & Merrill LLP The renovation and retrofit of The Strand transformed an abandoned, century-old cinema with a colorful history into a highly visible second stage for the company. The project focused on respecting the historic character of the original building by inserting a new structural system into the existing shell. This structure consists of a metal deck roof diaphragm over the original auditorium trusses, ductile reinforced concrete shear walls, and steel and composite metal deck floor framing all supported on new, shallow, reinforced concrete foundations and grade beams.

The project team worked diligently to retain and reuse as many of the original materials and features as possible.

Courtesy of Bruce Damonte.

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AWARD WINNER – CATEGORY 8 Ballard Drive Bridge – Bascule Seattle, WA D.H. Charles Engineering, Inc. The Ballard Drive Bridge is just one of many historic bridges scattered throughout the Pacific Northwest that have maintained regular service for nearly 100 years. Due to their age, continuous use, and exposure to the elements, these bridges require regular inspection, maintenance, and repainting. The complex loading of this fully functional bascule bridge presented extreme design challenges beyond that of a traditional horizontal suspended platform. Such items included intense wind loading on the underside of the platform, stabilization during raising, analysis of all bridge framing from irregular loading, and counterweight restrictions.

AWARD WINNER – CATEGORY 8 TILT at 360 Chicago Chicago, IL

Thornton Tomasetti

Sitting on the 94th floor of the John Hancock Center, TILT at 360 Chicago is an operable steel and glass structure that allows patrons to hover 1,000 feet over the city. TILT’s mechanism is a two-part system composed of a stationary base, directly connected to existing steel, and a movable viewing platform. The mechanism rotates 30 degrees on one axis and is supported at three locations by the base.

Patrons stand in one of eight individual partitions along the length of the 26-foot wide platform. Holding onto handrails, three hydraulic cylinders overhead extend to give them an adrenaline filled site seeing experience.

Courtesy of 360 Chicago.

Malone Cliff View Residence. Courtesy of Charles Davis Smith.

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InSIghtS new trends, new techniques and current industry issues

T

hroughout a significant portion of the United States, the design snow load on roofs typically exceeds the roof design live load, so many structural engineers need to be familiar with snow load determination.

The level of complexity in calculating the design snow loads for a building or other structure can vary from simple to complex, depending on the building location, the roof geometry, and the roof finish. The design snow load calculations for a flat roof with no parapets on a big-box store located in Iowa is relatively simple. A roof with multiple levels and slopes on a ski lodge located in the Rocky Mountains of Colorado will likely involve a site-specific case study to determine the ground snow loads, and include consideration of windward, leeward, and intersecting snow drifts, and sliding snow.

Metal buildings are similar to other buildings when calculating the design snow loads.

The design loads are determined according to the building code adopted by the local jurisdiction, typically an edition of the International Building Code (IBC), which references ASCE 7, Minimum Design Loads for Buildings and Other Structures. In addition, the geometry of metal building roofs can be simple, complex, or something in between, since metal buildings are typically custom-designed.

Design Snow Loads and Metal Buildings

By Vincent E. Sagan, P.E.

Metal Building Considerations

Vincent E. Sagan is a Senior Staff Engineer for the Metal Building Manufacturers Association and a member of ASCE 7 Subcommittee on Snow and Rain Loads. He can be contacted at vsagan@mbma.com.

There are applications and features of metal buildings that are not as common with many other building types, which result in different provisions being applied when calculating the design snow loads according to ASCE 7-10. These applications and features include: Unheated Buildings Metal buildings are commonly used in agricultural applications for the storage of equipment and grain. These building can be unheated. Other examples of unheated structures are commercial warehouse/freight terminals; raw material storage; parking and vehicle storage; some recreational facilities such as ice rinks, exhibition buildings, and fair buildings; and refrigerated storage facilities. For unheated buildings, the thermal factor, Ct, from ASCE 7 Table 7-3 is 1.2. For heated buildings, Ct is 1.0.

Sloped, Slippery Roofs Metal roofs are considered to be slippery surfaces.

When the roof is sloped, the design snow load can be reduced by the roof slope factor, Cs, provided that the roof is unobstructed and there is sufficient space below the edge of the roof slope to

Metal building gable roof snow loading. Courtesy of the Metal Building Manufacturers Association.

accommodate the sliding snow. Obstructions to sliding snow can include snow retention devices or other roof projections. ASCE 7 Section 7.4 refers to Figure 7-2 to determine Cs for various conditions, accounting for the slope, the surface, and the thermal factor, Ct. When snow slides off a sloped roof onto a lower roof, the design snow load on the lower roof due to sliding snow is determined using Section 7.9. According to this section, “Sliding loads shall be superimposed on the balanced snow load and need not be used in combination with drift, unbalanced, partial, or rain-on-snow loads.”

Roof Overhangs The sloped roof provisions also include Section 7.4.5, Ice Dams and Icicles Along Eaves. As stated in the commentary, “The intent is to consider heavy loads from ice that forms along eaves only for structures where such loads are likely to form.”

It also states, “This provision is intended for short roof overhangs and projections …”

Gable Roofs Gable roofs, common in metal buildings, are susceptible to snow drifting on one side of the ridge, creating an unbalanced loading condition.

ASCE 7 Section 7.6.1 defines the snow load cases, balanced and unbalanced, for gable and hip roofs.

Loading diagrams for these load cases are shown in Figure 7-5.

Snow Load Design Resources Several resources are available that are helpful in obtaining snow load design information, as well as determining appropriate snow design loads.

These resources include the following: • Applied Technology Council (ATC) Ground Snow Load Website, http://snowload.atcouncil.org, provides a way for engineers to easily obtain ASCE 7 site-specific ground snow loads. A location can be selected by directly entering the GPS coordinates or the mailing address.

If needed, a map of the United States can

40 December 2015

Montana, New Mexico, Oregon, and Washington). For each of these states, Figure 7-1 will include a reference to a table that contains approximately forty locations and their ground snow load and elevation, similar to what is done for ground snow loads in Alaska (Table 7-1). Note that the last time this figure was revised was in the 1995 edition!

• New provisions for snow loads on airsupported structures.

• New provisions for snow loads on open frame equipment structures.

• New provisions for intersecting drifts (Section 7.7.3).

• Addition of definitions to Section 7.1, including drift, freezer building, and ventilated roof.

• Addition of the importance factor, Is, to drift heights (Figure 7-9).

• Changes and clarifications on thermal conditions for freezer buildings, partial loading on continuous beams (Section 7.5.1), drift criteria, including canopy drifts and the effect of parapets (Sections 7.7 and 7.8), and snow retention devices and sliding snow (Section 7.9).

For future editions of ASCE 7, the changes to the ground snow load map, Figure 7-1, should

continue. The net effect will be more information that is more accurate, especially in areas that are identified as CS, which require site-specific Case Studies to establish ground snow loads.

In addition, design snow loads on photovoltaic systems will likely be addressed. Recent research on solar paneled roof snow loads was recently completed by Dr. O’Rourke and Nicholas Isyumov, Ph.D. P.Eng., of Western University. The project, sponsored by the American Iron and Steel Institute, FM Global, and the MBMA, will result in a guideline for snow loads on solar paneled roofs, which will be published by ASCE.

Summary Although metal building applications and features may require different ASCE 7 provisions to be used in the determination of design snow loads, the design load process is similar to other buildings.

Resources are available to assist engineers in determining the loads more easily and accurately. Design snow load provisions for all buildings, including metal buildings, are changing with the new edition of ASCE 7. The changes should add clarity to the requirements.▪

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Engineers familiar with ASCE 7 know that the standard is continually changing, incorporating the latest research on building loads and performance. While significant changes to the wind and seismic provisions of the load standard have occurred frequently, the changes to the snow load provisions have been more modest. The changes in the snow provisions in the 2016 edition of ASCE 7 will be more substantive than in past years, including the following: • Revision of Figure 7-1, the ground snow loads map for the continental United States: The contours and values will be removed for six western states (Colorado, Idaho, STRUCTURE magazine

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be used to find the GPS coordinates of a particular location. This website overcomes the challenges in using the snow loads map (Figure 7-1) that is printed in ASCE 7. These challenges include insufficient spatial resolution of the map to determine some sitespecific ground snow loads and the lack of reference cities or towns on the map. These ground snow loads can then be used with the equations provided in ASCE 7 to determine design snow loads for buildings and other structures. The Metal Building Manufacturers Association (MBMA) assisted in the development of the website.

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Historic structures significant structures of the past

The first in a three part series on the Quebec Bridge.

I

n the middle of the 19th Century, the St. Lawrence River had not been bridged. In early 1852, the City Council of Quebec City requested Edward W. Serrell to make a study of the problem and make recommendations for a bridge. His major bridge at this time was the suspension bridge he built across the Niagara River connecting Lewiston and Queenstown.

At the time of its construction (1851), it was the longest suspension bridge in the country.

Serrell’s report to the City Council recommended a bridge site about six miles above the city where the Chaudiere River intersects the south bank of the St. Lawrence River. His suspension bridge had a central span of 1,610 feet, and the bridge would carry a single track and a roadway. He concluded his report to the Board with, “Gentlemen of Quebec, you must either build a bridge or a New City.”

The Acts of Confederation signed in 1867 included the creation of the Intercolonial Railroad connecting the Provinces of Nova Scotia, New Brunswick, and Prince Edward Island (indirectly) to the south bank of the St. Lawrence River at River Du Loup.

The Quebec, Montreal and Occidental Railroad running southwesterly along the northern shore of the St. Lawrence connected Quebec City to Montreal and was seeking its own outlet to the south and the United States, particularly a route to Portland, Maine, so that the railroad could provide transportation to the Atlantic Ocean during the winter months when the river was impassable due to ice.

In 1887, the Quebec Bridge Company was incorporated with Edward Hoare, a well-known Canadian Engineer, retained to survey the various sites and make another recommendation as to the best site for a bridge. In 1891, with activity at a standstill, the charter was re-enacted “with the provision that work start in three years and be completed by July, 1897.” Nothing happened until 1897, when the charter was renewed again with the bridge now scheduled to be completed in five years. In June 1897, the American Society of Civil Engineers (ASCE) held their annual meeting in Quebec. In attendance were John Sterling Deans, Chief Engineer of the Phoenix Bridge Company and Theodore Cooper. The Phoenix Bridge Company was one of the leading designers of iron bridges in the country.

Theodore Cooper graduated from Rensselaer Polytechnic Institute in 1858. Over the next forty years, he became one of the leading bridge engineers in the country.

Hoare wrote to Deans asking if he intended on attending the convention and, if he was, would

The Quebec Bridge Part 1

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 19th 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.

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Theodore Cooper.

he “call to see him” about the Quebec Bridge.

Hoare told Deans that if he was “interested in the bridge project, I shall be glad to send you a profile of the crossing at the proposed site and other necessary information so that you may, if you wish, be prepared to bid, if the project is carried out.” After the meeting, Deans returned to Phoenixville. When the profiles were received, the company took the calculated risk of preparing a preliminary plan for a 1,600-foot span cantilever bridge to span the St. Lawrence.

The first plan was submitted on November 30, 1897 or only five months after the ASCE Convention. The bridge company approved of the plan and called for “tenders” on the project.

They used the Phoenix Bridge design as a base plan, but indicated that they would entertain other designs. Hoare’s specifications went along with the request for tenders, as well as the same profile information he had sent to the Phoenix Bridge Company earlier.

Proposals (tenders) were submitted by the Phoenix Bridge Company, the Dominion Bridge Company, the Keystone Bridge Company and the Union Bridge Company, each of which had several proposals. The bridge company now needed someone with an international reputation to review the proposals and make a recommendation as to which design best met its guidelines.

They asked Cooper to review the plans and he agreed, reporting on the competitive plans on June 30, 1899. He reviewed all of the tenders and selected that of the Phoenix Bridge Company for a cantilever.

He wrote that the Phoenix plan was slightly lower in estimated cost and it was, “an exceedingly creditable plan from the point of view of its general proportions, outlines and its

42 December 2015

Phoenix Bridge Company – cantilever.

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reports of McLure who did not have a great deal of practical experience. Cooper’s staff in New York was small, so it did not have the resources to do all that Cooper had almost insisted on doing for a very small fee.

Between August 7 and August 27, a flurry of letters and telegrams were sent between McLure and Cooper and Deans discussing the distress of the lower chord member.

On August 9, for instance, Cooper wrote to McClure suggesting a way to bring the bends back into “proper line by use of 15 to 20 1-inch bolts, threaded through both ends for nuts, passing through the two webs...”

“If necessary, after getting the bent webs in line to hold them, spacers and possibly some through bolts may be used.” Cooper wrote to Deans describing his solution stating, “It is Software and ConSulting

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south cantilever arm, was completed in 1906. While designing the south cantilever span and the suspended span, Szlapka discovered that the bridge was coming in heavier than he had assumed. He brought this fact to the attention of Cooper. He now determined that the weight “exceeded the original estimated weight. There was no means of changing or correcting this work.

I made an estimate of the increased strains due to this increased weight and found it to be about 7 per cent... Realizing that there was no remedy and that this 7 per cent was not a fatal increase, I did say to Mr. Szlapka, in effect, that we would have to submit to it.” When Szlapka had designed the bridge for the 1,800-foot span, he used his earlier estimate for dead weight of the structure he had determined for a 1,600-foot span.

In August 1907, the heavy main traveler was being removed as it was to be moved to the north side of the river. A smaller traveler was at work extending the suspended span outward from the cantilever arm. Work proceeded to the fourth panel point outward from the end of the cantilever arm. At this time, early August, the splice in the lower chord 7-8 L of the anchor span showed additional signs of distress. Cooper later stated that he began to get “uneasy” about the lower chord members on August 8 when he got McLure’s report on apparent bending of the web plates. The design of this member consisted of a series of four web members stiffened by angle irons, with the top and bottom spaced using solid plates near the panel points and lattice angles between these areas. The cross sectional area of the plates was 781 square inches.

All compressive load was to be transferred through the carefully planed end surfaces of the web plates. Almost immediately after the beginning of construction of the suspended span in July, problems with member 8L started, setting into motion one of the most bizarre set of miscalculations, miscommunications and plain incompetence in the history of bridge building.

Cooper had not visited the bridge site since the beginning of steel erection due to failing health, so he had to rely exclusively on the

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constructive features.” He “recommended it as the ‘best and cheapest’ plan and proposal of those submitted to me...” Cooper, still acting in a consulting role, was asked to follow up on the suggestion made many years ago by Walter Shanley that an 1,800foot span might be more economical given the better foundation sites that would be associated with a span of this length. He reported on May 1, 1900, “after a careful consideration of all the conditions by your chief engineer, Mr. E.A. Hoare, and myself, it was decided that an 1,800-foot channel span was most desirable if the expense was not too great.” Back at Phoenixville, Deans told Peter Szlapka to prepare a preliminary design for a 1,800-foot central span. Szlapka prepared all the plans that Phoenix submitted to the Quebec people to date and would now be the designer of the largest cantilever bridge in the world, as well as the longest span bridge in the world.

During the period of mid-1900 to mid1903, some work continued on the design and details of the anchor and cantilever spans. The Quebec Bridge Company did contract with William Davis & Sons to build the substructure on August 22, 1899.

Work started shortly afterwards and was completed late in 1902.

With the financial support of the government in 1903, the project moved ahead with more speed than at any time since 1899. Cooper then sent in his “Proposed Specifications of June 30, 1903.” The main changes were a reduction in wind load, an increase in rolling loads, an increase in the allowable working stresses in the members to 20,000 pounds per square inch under a Cooper E-30 loading and 24,000 pounds per square inch under a Cooper E-50 loading over the entire length of the bridge. Deans testified later, “the changes in unit stresses for compression members carried them out of the field of past experience in bridge construction and detailing, and did not follow usual practice.”

It wasn’t until late 1903 that funding for the superstructure was finally approved and a contract signed with Phoenix Bridge.

Erection of the anchor span on falsework began in July 1905 and it, along with the

Quebec Bridge August 27, 1907 south cantilever. Small traveler on left and large traveler at end of cantilever arm.

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a mystery to me how both these webs have to be bent at one point and why it was not discovered sooner?” On August 13, Cooper wrote to Deans saying that he was getting conflicting information from Deans and McLure, and that he “can take no action on the matter until the exact facts are presented…Without going into it carefully, I think that there will be more compression at these points with more of the suspended span in place. Please report promptly regarding joint 7 and 8-L with the facts.” On August 21, Cooper wrote to Deans discussing his theory that the chord had been hit during erection and indicating that “I still believe that the bend can be partly removed by use of long bolts... I cannot consent to let it go without further action, as the rivets in the cover plates would not satisfy the requirements of my mind.”

In the meantime, the people at the bridge site had been showing a great deal more concern than Cooper or the people in Phoenixville were. Norman McLure sent a letter to Cooper on the 27th with his sketches and the statement that “the erection will not proceed until we hear from you and from Phoenixville.” It also contained the comment that “although a number of the chords originally had ribs more or less wavy, as I have reported to you from time to time, it is only very recently that these have been in this condition, and their present shape is undoubtedly due to the stress they are now receiving. Only a little over a week ago, I measured one rib of the 9-L chord of anchor arm here shown, and it was only ¾-inch out of line. Now it is 2¼

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Quebec Bridge August 29, 1907.

inches.” McLure arrived at Cooper’s office in New York City on the morning of the 29th. Cooper later testified: “After carefully reading and considering the letter, I called Mr. McLure into my office and cross-examined him to find out whether the facts given were actual or whether he had been scared, and satisfying myself that the data there were from actual measurement and actual observation, I said: ‘It is very serious.’ I immediately telegraphed them to add no more load to the bridge till after due consideration of facts. I then said to Mr. McLure; ‘You must go to Phoenixville immediately and tell the Phoenix Bridge Company that I do not want any delay such as that involved in the discussion that we have had heretofore on similar occasions, but I want immediate action to strengthen that chord and to protect the bridge.’…”

Cooper sent McLure to Phoenixville. He also thought that McLure would wire Kinloch at the bridge to stop work, but McLure did not do so. Work continued throughout the day at the bridge site as neither Hoare, Cooper, McLure, Deans nor Szlapka had told them otherwise. McLure met with the Phoenix Bridge people, who had received Cooper’s telegram telling them effectively to stop work and add no more load to the bridge. They decided to do nothing until the morning, awaiting A. H. Birks’ information. That decision was made shortly after McLure had arrived around 5:30.

The shift was to end at 5:45 with 86 men working on the bridge.

There were three riveting crews and one hoisting crew working on the anchor arm, and six riveting crews working on the cantilever arm. A locomotive had just delivered an eight-ton load of steel to the end of the bridge and was returning with another load of the same size. It was located at just about the end of the cantilever arm near the large traveler when witnesses reported a loud explosion.

In no more than 20 seconds, probably less, the massive 17,000ton structure just settled downward into the St. Lawrence River.

A total of 75 men were killed instantly, with 11 escaping with their lives. The Philadelphia Ledger summed it up very nicely when it stated: “The world’s confidence in the skill and judgment of the engineering profession will be seriously shaken unless it can be shown that the accident was the consequence of unforeseen and unavoidable contingencies.” Part II of the series discusses the investigation into the failure and the redesign.▪

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December 2015

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CASE BuSinESS PrACtiCES

Another Fine Mess We Have Gotten Ourselves Into!

By John Dal Pino, S.E.

I

had a conversation with a colleague recently while developing a fee proposal for a seismic project which was to use a national structural engineering seismic standard. Our discussion eventually got around to that often repeated question, “why are these provisions so constraining, rigid and detailed, leaving me no flexibility to make engineering judgments?” My colleague told me that the answer was that the writers of codes and standards are trying to force engineers to do the “right thing” in all situations, via the technical provisions. His point got the attention of the libertarian gnome that usually sits on my shoulder, who spoke up and asked “Is this the best and most efficient way for society to gain a safe result?” I thought about it for a second and answered, NO! The longer my colleague and I talked, the higher my fee went as I realized how much I was required to do, even when my experience told me otherwise!

The purpose of a building code or building standard should be to regulate a market that has gone astray by prohibiting (or at least discouraging through penalties) designs that are detrimental to the public interest or safety.

Certainly there have been building failures from which engineers have learned a great deal, and the resulting research into building performance has helped advance the state of our knowledge. But I am not sure that we have learned enough with requisite certainty to justify the extent and breadth of the building codes and standards that currently regulate the engineering profession. At times, well-meaning engineers rush to incorporate research into the code before it is settled science, having then to backtrack and change the code again when better data is discovered. A good example of this is the 1988 UBC change requiring welded moment frame connections in ductile frames that the 1994 Northridge earthquake showed to be a bad idea. I believe that we have lost our way through unnecessary bureaucracy and rigidity that stifles engineering creativity, increases costs and may not actually make the public safer. A change is needed.

When I was a young engineer, a favorite topic around the lunchroom table, particularly on Friday afternoons, was whether we needed building codes at all. The fun position for the older engineers to take, particularly those that wanted to stir it up a bit, was to advocate for the “no codes at all”, i.e. the laissez faire

approach, as being the most efficient way to provide safe buildings for society. The argument went that if codes didn’t exist at all, the best designers would be recognized as such, the lesser designers would fall by the way side since their lack of skills would be exposed and they wouldn’t have clients, and the world would be a safe and happy place. Shocked to hear such heresy, the young engineers countered with the question, “aren’t you concerned about public safety?” To the young engineers, the lack of a code would result in the design of many poorly conceived structures, some that might collapse in an earthquake due to shoddy design or construction, or both. The old guys countered that this might need to happen from time to time to keep the profession honest (this really got the young guys going!) and by the way, they reminded us, there are lots of perfectly safe buildings that were designed before modern codes were developed. The young guys, who really didn’t want to have their lives shortened dramatically in an unnecessary building collapse, argued that the lack of codes was just too scary to comprehend and something that the public would never accept anyway. After a while of this back and forth, a stalemate ensued, so we finished our drinks and went home, to resume the argument another day.

The young guys were clearly on the “winning side” in the court of public opinion as evidenced by not only the expansion of both the size and complexity of codes and standards, but also in the number of codes and standards and the variety of building types they are written to address. Now that I can safely put myself in the “old guy” category, I often ask myself, is this detailed and constraining regulatory approach the best way to ensure public safety and to do so in an efficient manner and at a reasonable cost? I think not.

It seems extremely futile and wasteful for a large number of code writers, who are arguably the best engineering minds the profession has, to spend their energies year after year, code cycle after code cycle, writing more and more detailed code provisions and standards to catch fewer and fewer “bad” buildings from being designed, those that heretofore have somehow slipped through their grasp, while at the same time making the design and evaluation of all of the other “good” buildings more and more complicated and more opaque.

Have they created a code that in my opinion

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unnecessarily applies to almost all buildings uniformly whether they are, to use an auto analogy, a basic compact or a Tesla Model S? Have they also unwittingly created a “safety net” which bails out engineers, with lets say less than average skills who are heavily reliant on computer models and technology to design buildings, at a cost to everyone else?

In addition to the safety net aspect, could the bureaucracy and rigidity of the codes be making the situation less safe? To save time and fee for the important creative design process, engineers have turned to technology to design almost all of the major components in a building in order to stay competitive and charge fees that can be accepted in the marketplace.

The technology, which was supposed to help engineers, has the opposite effect of intellectually distancing engineers from the design process and the end result can suffer. Has your staff engineer ever told you that he or she feels certain about the design because “everything was green” in the computer model?

In researching legal matters for a paper I recently wrote on the engineering Standard of Care, I came across the argument that the most efficient way for the court system to decide alleged negligence and breach of duty-to-protect cases (and in fact the way our courts do it today), is for the courts to rely on “custom” as defined by expert witnesses using the common law. Negligence is therefore behavior that falls outside of what engineers should have done or should not have been expected to do in specific cases as established by engineers as a group.

The alternative to “custom” would be for the courts to decide cases based on a “code” or a set of rules the courts established for themselves from a thorough understanding of the engineering profession, its technical nature, the economics of its business model, etc. or legislative actions that eventually result in code provisions that regulate how engineers do their work in addition to what they can and can’t design. Clearly the courts don’t have time to do this for engineering, let alone multiplying this effort by thousands of times to cover all of the cases from other industries, professions and occupations that find their way before the courts. So the courts rely on custom to the extent permissible by law. Most engineering projects don’t end up in court, so the majority of engineers must be doing the right thing for their clients a vast majority of the time. continued on page 48

Getting back to the code issue, my “old guy” argument is – why don’t we take the same approach as the courts to our building codes?

The code could be a fairly simple document (like the Uniform Building Code still was back in the mid-1980s, when I was “young”) that covered most buildings and laid out a general philosophy for proper building design. Required loadings (floor, roof, wind, seismic, etc.) and load conditions would be easy to understand and straightforward to implement, with little waste. Organizations such as the Structural Engineers of California (SEAOC) would write commentary documents (as they did in the past and continue to do) that would help engineers understand code intent and to provide guidance on how to incorporate best practices and current research into building designs. Equally important, the code would clearly state for the public what the structure was intended to provide in terms of safety, longevity and durability, and it would be up to the engineer to provide these through design. The engineering effort would be balanced against the risk in terms of loads and historic building performance. In terms of economic impact, it would be an efficient system because engineers and their clients would not be burdened by excessively restrictive and burdensome code regulations for buildings and legislative edicts which simply don’t justify the

extra effort required based on their size, use or construction type. Engineers could always incorporate whatever technical advances that seemed justified to them and the building owner, given the intended age and use of the building. Let’s face it, not every building needs to be designed to last 150-200 years or survive every natural event without some damage!

For larger, more complicated or unique buildings that fall outside the limits of a building code for “basic” buildings, rather than rely on overly detailed and restrictive codes like we do now, why not rely on the peer review process to decide if the building design is appropriate? If it works for the courts in terms of expert witness testimony and the establishment of custom, it should work for building design too. Besides, despite the efforts of code writers and legislators, the code provisions can never stay ahead of the creativity of engineers and architects working at the cutting edge. So why try? The building designer would develop a basis of design and the peer review panel (i.e. the experts) would either approve the project or require changes before final approval. This would be the purest form, and in my opinion the ideal result, of performance-based design. For those that aspire to engineering legend, what could be better?

The code currently has a similar system known as “alternative means of compliance”

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for buildings that don’t strictly comply with some aspects of the building code but that can be shown by test or calculation to provide the required measure of safety under expected loadings. The City of San Francisco already uses this process on buildings that are pushing the envelope, and there is no shortage of engineers eager to get involved on the review side. In theory, it should speed the review process because major projects won’t be funneled through the normal building department review process that is not equipped to deal with such buildings. My argument is that this type of approach isn’t used nearly often enough.

So as you can see, I am not advocating an entirely new approach to the building code, but just one that involves a sliding of the “complexity needle” considerably to the “left” (say from 910 toward 560 on the AM radio dial) so that many more buildings end up in the peer review process. Common, nothing-outof-the-ordinary, buildings can be designed in accordance with a streamlined building code.

This change would also have the added benefit of placing the burden of good design on skilled design professionals, and might even weed out the less skilled. I think that engineers and owners will be happier, money will be saved, and the public will be better off. What do you think?

I am not sure the change will ever happen.

Tectonic changes like this are akin to changing the tax code from a graduated progressive tax to a flat tax. Most people can see the overall benefit from the simplicity of a flat tax and the obvious incentives for economic growth, but people generally lack the courage to try something new because they either don’t see the immediate need (although it may exist), are worried about the disparate impacts on taxpayers, or for other reasons.

Others who would be against a significant code change are those that have vested interests in managing and propagating the current system, and selling services to help their clients navigate the minefields that have been created (by them).

There will always be a role for the true expert in design and consulting, so those engineers have nothing to fear and I suspect they would thrive in a freer environment.

I am advocating for a reform that will establish a healthier and more sustainable platform for everyone going forward.▪ John Dal Pino, S.E., is a Senior Principal in the San Francisco office of Degenkolb Engineers. John is a member of STRUCTURE’s Editorial Board and can be reached at jdalpino@degenkolb.com.

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December 2015

EARTH RETENTION GUIDE

news and information from earth retention companies RISA Technologies

S-FRAME Software

Tekla, Inc.

Phone: 949-951-5815 Email: amberf@risa.com Web: www.risa.com Product: RISAFoundation Description: Designs retaining walls, two-way mat slabs, spread footings, grade beams and pile caps all within an open modeling environment.

With synchronized load transfer from RISA-3D and RISAFloor models, foundation design has never been easier. Punching shear checks, rebar design, and international codes make it the smart choice for engineers.

Phone: 203-421-4800 Email: info@s-frame.com Web: www.s-frame.com Product: S-FRAME Analysis Description: A powerful 4D structural model management environment. Versatile enough for linear or advanced non-linear analysis on both commercial and industrial applications. Analyze, design and optimize using comprehensive integrated steel, concrete and foundation mutli-code design tools.

Includes advanced BIM and CAD links.

Phone: 770-426-5105 Email: kristine.plemmons@tekla.com Web: www.tekla.com Product: Tedds Description: Our built-in library of calculations allows you to quickly calculate the ASCE 7 wind and seismic forces for your structure. Then use one of our component design modules to design your beams, columns and foundations. Link the modules together to create a professional report for review submittals.

Schnabel Foundation Company Phone: 703-742-0020 Email: hank@schnabel.com Web: www.schnabel.com Product: Specialty Geotechnical Contractor Description: A nationwide geotechnical contractor that specializes in design-build earth retaining structures and deep foundations. Our services include deep soil mixing, secant pile walls, soldier piles and lagging, soil nailing, tiebacks, tiedowns, underpinning, jet grouting, and micropile foundations. We have offices throughout the United States.

StructurePoint Phone: 847-966-4357 Email: info@structurepoint.org Web: www.StructurePoint.org Product: Reinforced Concrete Design Software Description: spWall-for design and analysis of cast-inplace reinforced concrete walls, retaining walls, tilt-up walls, ICF walls, and precast architectural and loadbearing panels. spColumn-for design of shear walls, bridge piers, and typical framing elements in buildings and structures. spColumn complements spWall by generating axial/flexure (P-M) diagrams suitable for shear wall design.

VERSA-LOK Phone: 800-770-4525 Email: versalok@versa-lok.com Web: www.versa-lok.com Product: VERSA-LOK Standard Unit Description: Solid construction and unique pinning system that enables unparalleled design flexibility for building everything from erosion control and waterway installations to beautiful residential and commercial hardscapes with curves, corners, stairs and columns. Available in traditional split-face or vintage weathered textures.

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Helical Pile Technology Exclusive Patented Technologies for Foundation Solutions

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Patented threaded connection; Strongest, most rigid in industry

December 2015

Helical Piles stamped into true spiral shape; Penetrates loadbearing strata

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News form the National Council of Structural Engineers Associations

NATIONAL

Call for Summit Abstracts Open The 2016 NCSEA Structural Engineering Summit Committee is seeking 60-90 minute presentations that deliver pertinent and useful information that attendees can apply in their practices.

Submissions on best-design practices, new codes and standards, recent projects, advanced analysis techniques and other topics for practicing structural engineers, are desired. The 2016 Summit will feature education specific to the practicing structural engineer, both technical and non-technical.

Abstract proposals are due by February 22, 2016. A form for submission is available at www.ncsea.com/meetings/ annualconference.

Abstracts should be emailed to Carrie Johnson, Summit Committee Chair, cjohnson@wallacesc.com with a copy to Jan Diepstra, NCSEA Director of Education, jan@ncsea.com.

Speakers will be notified of acceptance

by March 18, 2016, and will be provided with required guidelines after acceptance of abstract. All speakers receive free registration on the day of their presentation.

New NCSEA Board Seated New NCSEA Board members took office at the 2016 Summit in Las Vegas.

The new President of the Board is Brian Dekker, P.E., S.E., president of Sound Structures Inc. and a member of SEAOI. Assuming the Vice President position is Tom Grogan Jr., P.E., S.E., a member of FSEA and Chief Structural/Civil Engineer and Director of Quality Assurance for The Haskell Company.

Jon Schmidt, P.E., SECB, will be the Secretary for the upcoming year.

Schmidt is an Associate Structural Engineer at Burns & McDonnell and a member of SEAKM. Assuming the Treasurer role is Williston “Bill” Warren IV, S.E., SECB, the Principal Structural

Engineer for SESOL, Inc., and a member of SEAOC. Barry Arnold, P.E., S.E., SECB, will serve as Past President and is a Principal/VP at ARW Engineers and a member of SEAU. Emily Guglielmo, P.E., S.E., and Jonathan Hernandez, P.E., SECB, have assumed Director positions. Guglielmo is an Associate at Martin/Martin and a member of SEAOC, and Hernandez is a partner at Gilsanz Murray Steficek and a member of SEAONY. Staying on as directors are Susan Jorgensen, P.E., SECB, and Chad O’Donnell, P.E., S.E. Retiring from the board are Carrie Johnson, P.E., Chris Cerino, P.E., SECB, and Ed Quesenberry, S.E.

NCSEA Webinars January 5, 2016 Carbon Emissions of Structural Systems

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

Michelle Kam-Biron, P.E., S.E., SECB, M.ASCE, Director of Education, American Wood Council January 19, 2016 Vibrations of Reinforced Concrete Floor Systems

Mike Mota, Ph.D., P.E., SECB, Vice President of Engineering, Concrete Reinforcing Steel Institute (CRSI) January 26, 2016 Code Applications for Nail-Laminated Timber and Cross-Laminated Timber

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NCSEA News

Jim D’Aloisio, P.E., SECB, Principal, Klepper, Hahn & Hyatt

Diamond Reviewed

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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December 2015

NCSEA THANKS THE 2015 STRUCTURAL ENGINEERING SUMMIT TRADE SHOW EXHIBITORS: AISC Alpine ITW American Concrete Institute Architects & Engineers for 9/11 Truth Armatherm Atlas Tube AZZ Galvanizing BASF Corporation Bekaert Blind Bolt Cast Connex Corporation CivilFEM Conxtech CoreBrace Buckling Restrained Braces Dlubal Software, Inc Euclid Chemical Fabreeka International INC Fyfe Co./Fibrwrap Construction Geopier Foundation/TENSAR Hayward Baker Hilti International Code Council Independence Tube Corporation ITW Buildex/Red Head/Ramset LafargeHolcim Lindapter Meadow Burke LLC MiTek Builder Products Nemetschek Scia New Millennium Building Systems Nucor–Verco Decking Nucor–Vulcraft Powers Fasteners RISA SidePlate Systems, Inc Simpson Strong Tie Star Seismic Steel Deck Institute Steel Joist Institute Steel Tube Institute Strand7 TEKLA USG Valmont Tubing Vector Corrosion Technologies Vulcan Materials Company

Project Delivery Workshop

Legal Update

How to achieve your business objectives while minimizing the risks of litigation. Topics include: • Hiring the Best Candidate...Lawfully!

• Properly Classifying and Paying Your Workers – Independent Contractor v.

Employee – Exempt v. Nonexempt • Preventing Discrimination and Harassment in the Workplace • The Handbook: Informing Employees of Policies & Procedures • Disciplining the Problem Employee • What to Expect when Facing a Lawsuit Speaker: Staci Ketay Rotman, Attorney, Franczek Radelet P.C.

John Malcolm, P.E. Vice President Peak Engineering, Inc. The WLF is a great way for structural engineering business leaders to get together in a noncompetitive environment and discuss issues facing their companies. I am looking forward to diving into our legal aspects at the 2016 WLF, hearing from the speakers and also from attending companies on how they personally deal with some of the topics.

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

Claims Management

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December 2015

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The Coronado Island Marriott Resort & Spa features stunning views of the San Diego skyline across the bay. The Resort includes a full-service health spa, three heated pools and convenience to beautiful sandy beaches, shopping and restaurants at Ferry Landing. The Winter Leadership Forum room rate is $239 with a complimentary resort fee (a $25 value).

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The first step is hysteria.

The second step is denial.

The third step is anger.

Finally, the fourth stage is resignation. There is recognition of the injustice and the necessity to mitigate the damage and end the nonsense. Settlement usually follows and life goes on. (Excerpted from a paragraph written for SERMC by John Tawresey.)

Structural engineers and defense counsel from three firms will present what happened to them when they were sued for professional negligence; and the audience will have an opportunity to predict the outcome.

Speakers: Seasoned [been sued] structural engineers and defense counsel Moderator: John Tawresey, S.E., Retired VP & CFO, KPFF

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Register online at www.ncsea.com!

Professional Liability Risk Management – Professional liability claims typically start with a real or perceived technical issue and evolve into a fullfledged claim because of a poor business decision.

Attendees will learn (or be reminded of ) how these factors combine to spawn a professional malpractice claim and gain valuable insight on how to better identify, evaluate and manage professional liability risk before it becomes reality or, if it becomes reality, how sound up-front risk management can make this reality much more manageable and tolerable.

Speakers: Dan Bradshaw, CPCU, Benchmark Insurance Agency Craig Coburn, Attorney, Richards Brandt Miller Nelson

News from the National Council of Structural Engineers Associations

The root cause of projects ending badly is often a lack of actual teamwork among the owner, designers and contractors, the seeds of which were sown by poorquality contractual decisions made at the earliest stages of development. This interactive workshop will explore virtually every aspect of modern project delivery: formal methods, with an examination of advantages and disadvantages for each; details of various contractual tools and techniques; legislative history of QBS for design firms and future QBS prospects for the construction team; and a deep dive into results of major studies that document what works and what doesn’t in the design and construction industry.

Speaker: Dale Munhall, Architect, Director of Construction Phase Services, Leo A Daly

Your clients respect and value your technical knowledge. But what about running the ship? Owners and principals cannot do everything. I have found guidance, ideas and motivation to better address these important issues at the Winter Leadership Forum.

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ON FRIDAY Professional Liability: Manage the Risk – Reap the Rewards

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NCSEA News

The NCSEA Winter Leadership Forum draws principals and leaders from a diverse group of structural engineering firms to engage in thought-provoking sessions, roundtables, and networking. In 2016, the focus will be on managing risk professionally, collaboratively and transparently.

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The Newsletter of the Structural Engineering Institute of ASCE

Structural Columns

REGISTRATION NOW OPEN Geotechnical & Structural Engineering Congress 2016 February 14 –17, 2016, Phoenix, Arizona Connect | Collaborate | Build 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.

Earn 4 PDHs for these morning half-day courses • Cold-Formed Steel – History, Design, and Innovation • Introduction to the 2016 Edition ASCE 7 Minimum Design Loads for Buildings and Other Structures • Heave Prediction for Pier Foundation in Expansive Soils Earn 4 PDHs for these afternoon half-day courses • Seismic Design of Diaphragms • New Structural and Geotechnical Seismic Design Requirements in the 2015 NEHRP Provision • Data Acquisition Basics – Setting Up a Simple Automated Instrumentation System for Geotechnical and Structural Monitoring Visit the Joint Congress website at www.Geo-Structures.org for complete information and to register.

Extend Your Congress Experience – Register for a Pre-conference Short Course Short Courses take place on Sunday, February 14, 2016 Earn 8 PDHs for these full day courses • Recent Developments in Ground Improvement – Tools Every Geotechnical Engineer Should Have • Geotechnical and Structural Instrumentation and Monitoring During Construction • Bridge Scour • Risk Assessment in Geotechnical & Structural Engineering • FRP Composites for Struct. & Geotechnical Infrastructure

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.

SEI Members Receive Prestigious Awards William H. Wisely Award Longtime SEI members Robert E. Bachman, P.E., S.E., F.SEI, M.ASCE; and Kathy J. Caldwell, P.E., F.SEI, Pres.11.ASCE, were recently awarded the William H. Wisely Award from ASCE. This award is given to those ASCE members who have demonstrated continuing efforts to better the history, tradition, developments and technical and professional activities of the Society.

Don’t miss this opportunity to attend – register today Visit the conference website at www.atc-sei.org for complete information and to register.

Dream Big Contest In conjunction with the upcoming IMAX film on civil engineering, ASCE has launched the Dream Big Contest. ASCE members are invited to submit entries based on how civil engineering helped them pursue their personal dreams. Prizes include trips to filming locations and screenings. For full details and to enter see the contest website at www.asce.org/dream-big-contest.

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New ASCE Distinguished Members SEI members Lawrence C. Bank, Ph.D., P.E., Dist.M.ASCE; Barry J. Goodno, Ph.D., P.E., F.SEI, Dist.M.ASCE; Thomas T. Hsu, Ph.D., P.E., Dist.M.ASCE; and Roberto T. Leon, Ph.D., P.E., F.SEI, Dist.M.ASCE; were honored with Distinguished Membership in ASCE.

December 2015

Bridges 2016 offers spectacular images of bridges from the United States and around the world. This calendar is a celebration of the unique blend of technology and art that is the hallmark of great engineering. Every photo in the calendar was selected from entries to ASCE’s Bridges Photo Contest. Each bridge photo appears with a description of its technical or historical significance. Bridges 2016 is a full-sized wall calendar, perfect for jotting down daily activities or appointments. Order your calendar today at www.asce.org/calendar.

Promote Your Business All Year Long Print your company name and logo across the full 12-inch width at the bottom of customized Bridges 2016 calendars. Your brand and message will be in front of your clients and colleagues every day.

Learn more at http://ascelibrary.org/page/imprintcalendar.

WITH SEI SUSTAINING ORGANIZATION 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.

www.asce.org/SEI-Sustaining-Org-Membership

Celebrate structural engineering with a tie or scarf that shows structures from around the globe. Makes a great gift. Visit the SEI Website at www.asce.org/structural-engineering/ sei-merchandise to purchase yours today.

SEI Futures Fund The SEI Futures Fund Board recently met and approved the following strategic initiative funding proposals for FY16. Your gift of support provides critical funding for these visionary efforts that invest in the future of structural engineering: • Workshop for Committee for the Reform of Structural Engineering Education (CRoSE) • SEI Global Activities Division Executive Committee – Initial Meetings • SEI BoG Task Committee to Evaluate and Recommend SEI Global Initiatives • Joint Congress Registrations for Young Professional Scholarship Recipients • Research Evidence to Support the Promotion of SE Licensure • Local Chapter Webinars Learn more and invest in the future of structural engineering at www.asce.org/SEIFuturesFund. Gifts are fully deductible for income tax purposes.

Local Activities Nebraska Structural Technical Group

Maryland Chapter

The Structural Technical Group of ASCE’s Nebraska Section recently held their annual Structural Conference. More than 260 attendees enjoyed a full day of sessions and a pre-conference dinner meeting. Sessions covered a wide range of subjects including: concrete floor systems, masonry design practice, ethics, blast resistance design, hollow structural sections, and changes to the Nebraska Board of Engineers & Architects regulations and policies. For full details see the News page on the SEI website.

The SEI Maryland Chapter has had a busy late summer and fall. Members took tours of the historic Jericho Bridge, the Back River Wastewater Treatment Plant, and the Rec Pier Hotel construction site in the Fells Point neighborhood of Baltimore. General meetings featured presentations on research of aramid fiber reinforced polymers concrete bridge decks and the Sparrows Point Steel Mill. For full details see the News page on the SEI website.

West Virginia University Graduate Student Chapter

Get Involved in SEI Local Activities

The SEI Graduate Student Chapter at West Virginia University encouraged undergraduate students to consider civil engineering at the recent Freshman Engineering Visitation. Chapter members made presentations on their own experiences and provided information on civil engineering work culture, job prospects, and research opportunities. For full details see the News page on the SEI website.

STRUCTURE magazine

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.

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December 2015

The Newsletter of the Structural Engineering Institute of ASCE

REACH SEI MEMBERS

SEI Ties and Scarves Available

Structural Columns

ASCE Bridges Calendar Now Available

CASE in Point

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 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.

Follow ACEC Coalitions on Twitter – @ACECCoalitions.

CASE Practice Guidelines Available CASE 962 National Practice Guidelines for the Structural Engineer of Record The purpose of this document is to give firms and their employees a guide for establishing Consulting Structural Engineering Services and to provide a basis for dealing with Clients generally, and negotiating Contracts in particular. Since the Structural Engineer of Record (SER) is normally a member of a multidiscipline design team, this document describes the relationships that customarily exist between the SER and the other team members, especially the team leader. Further, this Guideline promotes enhanced Quality of Professional Consulting Structural Engineering Services, while also providing a basis for negotiating a fair and reasonable compensation.

Additionally, it provides a basis for Clients to better understand and determine the Scope of Services that the Structural Engineer of Record should be retained to provide.

CASE 962-A National Practice Guidelines for the Preparation of Structural Engineering Reports for Buildings The purpose of this document is to provide the structural engineer a guide for not only conducting conditional surveys, code reviews, special purpose investigations and related reports for buildings, but includes descriptions of services that aid with the client risk management communication issues. This Guideline is intended to promote and enhance the quality of engineering reports.

A section of this Guideline deals specifically with outlines for various reports. While it is not intended to establish a specific format for reports, it is believed there may be certain minimal information that might be contained in a report. The Appendix includes disclaimer language which identifies statements one might consider in order to clarify the depth of responsibility accepted by the report writer.

CASE 962-B National Practice Guidelines for Specialty Structural Engineers This document has been prepared to supplement CASE’s National Practice Guidelines for the Structural Engineer of Record STRUCTURE magazine

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by defining the concept of a specialty structural engineer and the interrelation between the specialty structural engineer and the Structural Engineer of Record. CASE encourages the concept of one Structural Engineer of Record for an entire project.

However, for many, if not most projects, there may be portions of the project that will be designed by different specialty structural engineers.

The primary purpose of this document is to better define the relationships between the SER and the SSE, and to outline the usual duties and responsibilities related to specific trades. This is done for the benefit of the owners, the PDP, the SER, the SSE and the other members of the construction team. The goal is to help create positive coordination and cooperation among the various parties.

CASE 962-D A Guideline Addressing Coordination and Completeness of Structural Construction Documents The guidelines presented in this document will assist not only the structural engineer of record (SER) but also everyone involved with building design and construction in improving the process by which the owner is provided with a successfully completed project. Their intent is to help the practicing structural engineer understand the importance of preparing coordinated and complete construction documents and to provide guidance and direction toward achieving that goal.

Currently, the coordination and completeness of Documents varies substantially within the structural engineering profession and among the various professional disciplines comprising the design team. The SER’s goal should be meeting both the owner’s and the contractor’s needs by producing a complete and coordinated set of Documents. Owners and contractors generally understand that some changes to the Documents will occur, because they realize that no set of Documents is perfect. The SER must focus on completeness, coordination, constructability, and the reduction of errors in order to minimize potential changes.

You can purchase these and the other Risk Management Tools at www.acec.org/coalitions/coalition-publications December 2015

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

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 Early-bird registration thru December 5th CASE Members – $424 ACEC Members – $674 Non-members – $924 Standard registration after December 5th CASE Members – $499 ACEC Members – $749 Non-members – $999

STRUCTURE magazine

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

SAVE THE DATE

CASE Winter Planning Meeting The 2016 CASE Winter Planning Meeting is scheduled for February 11–12 in Phoenix, AZ. If you are interested in attending the meeting or have any suggested topics/ideas from a firm perspective for the committees to pursue, please contact Heather Talbert 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 & Assoc.

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 Idea

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

A

t the 2013 annual meeting of the National Academy of Engineering in Washington, DC, Mitch Daniels, the former governor of Indiana and the president of Purdue University, said this about the possibility of educating too many engineers: “But even if we were to somehow outrun the market’s need for engineering talent, we will be a far stronger country if the engineering mentality takes a more prominent place in our national conversation.”

I would like to consider what Daniels called the ‘engineering mentality’ more broadly and refer to it as the “engineering way of thinking” (EWT). Like Daniels, I believe that more widespread use of the EWT will benefit society. For many if not most Americans, this idea makes no sense, is absurd on the face of it, or is potentially dangerous. I suggest that the naysayers are wrong, either because they are ignorant about engineering or are looking at engineering and engineering knowledge through mid-20thcentury glasses that distort their view of what engineering is supposed to entail.

Engineering is constantly evolving, and the main driver for that evolution is the emergence of better heuristics for design.

Heuristics are techniques – colloquially, rules of thumb – that allow problems to be solved that would otherwise be intractable.

Heuristics range from very crude techniques to very sophisticated methods. Billy Koen has said repeatedly that the engineering method is to use heuristics, but the EWT is more than just using heuristics. It encompasses how we choose which heuristics to use, what kinds of heuristics we use, how we use the heuristics that we choose, when we change heuristics, how we change heuristics, and why we change heuristics. To be fair to Koen, I suppose that we use heuristics – or perhaps “meta-heuristics” – to do all of these things.

None of the above decisions can be made without first thinking about design. Design is the process of taking something that appears in the mind’s eye, modeling it in one or more of a number of ways, predicting how that thing will behave if it is made, and then making it, sometimes modifying the design

Engineering is constantly evolving, and the main driver for that evolution is the emergence of better heuristics for design. as we make it. Design is what engineering is about. Furthermore, modeling is how engineering design is done. This includes mental models, mathematical models, computer models, plans and drawings, written language, and (sometimes) physical models.

Some historians of technology claim that what the Egyptians did to build the pyramids was not engineering. Certainly it was not engineering as we know it today, but it was indeed engineering. The pyramids were imagined, modeled in some way – probably with drawings – and then built. For its day, it was sophisticated engineering. The engineering ability of the Egyptians must have evolved from the first use by some hominid of a tool to do something, as well as the more sophisticated tools used in Egypt and elsewhere before the building of the pyramids.

Of course, engineering continued to evolve after the pyramids. From the Middle Ages, we have massive masonry buildings – e.g., cathedrals – in which post-construction efforts to fix inadequate design were used, such as flying buttresses. These are a good example of another aspect of the EWT: learn from failure. In this case, many of the failures were (fortunately) non-catastrophic.

Engineering continued to evolve, often in the context of military applications such as siege weapons and fortifications, up to and through the Renaissance, primarily as something that looked more like a trade than what we today call engineering. Strength of materials first developed as an analytical tool during the Renaissance. Of course, many other ideas and mathematical methods became available during that era and thereafter. Some of these proved useful for designing new artifacts such as the steam engine. Engineering began to use ideas and heuristics that had been unavailable in the past. This step in the evolution of engineering represents another aspect of the EWT: If an idea appears useful, try it.

The heuristics available to engineers advanced even more rapidly as the end of the 19th century approached. We refer to that time as the Industrial Revolution. It was then that engineering science became a distinct field. At that time, it was used only to a limited extent in engineering proper; widespread use of it was yet to occur. Engineering education was still emphasizing the trade origins of engineering.

Engineering students still took a significant amount of shop courses and drafting.

It was not until after World War II that engineering science became the primary component of engineering education and an integral aspect of engineering practice.

Once again, the heuristics for design were evolving. This evolution continued with the advent of the computer, and continues today.

If a tool appears to be useful, try it. If it works, use it. This approach is a major aspect of the EWT, and goes beyond just trying tools. It includes trying new ways to design and build the myriad of artifacts that engineers develop.

The EWT is something that the community of engineers uses and keeps alive. As individual engineers, we use only a small portion of the EWT, but we all need to be aware of it and learn more about it. The EWT is both science and art, both theory and practice, both analysis and synthesis, both philosophy and common sense, and more. It expects that methods and ideas will continuously evolve, and that much of that evolution will be driven by failures, both large and small. The EWT has been much maligned and often ignored. I will address it further in my next column.▪ 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.

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December 2015