STRUCTURE magazine | November 2015

November 2015 Steel/Cold-Formed Steel

A Joint Publication of NCSEA | CASE | SEI

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November 2015 40 editorial

7 Should We Be Concerned about resiliency?

By Carrie Johnson, P.E., SECB iNFoCuS

11 all Good things…

34

Feature

iNSiGhtS

BrBFs in NYC – Fugettaboutit!

32 Beware the Stamp?

By Jim Peloquin, Esq. hiStoriC StruCtureS

43 Queensboro Cantilever Bridge

By Jon A. Schmidt, P.E., SECB

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

StruCtural deSiGN

eNGiNeer’S NoteBook

12 design of Vehicular Barrier Walls

By Mohammad Iqbal, D.Sc., P.E., S.E., Esq. BuildiNG BloCkS

16 New twists and turns in Structural Bolting

46 Perfectly Symmetrical but extremely torsional?

By Jerod G. Johnson, Ph.D., S.E. StruCtural FailureS

48 Snow load Collapse of a manufacturing Building in oregon

By Robert E. Shaw, Jr., P.E.

By Dilip Khatri, Ph.D., S.E.

StruCtural PerFormaNCe

Code uPdateS

20 Seismic Strengthening of Buildings in los angeles

51 aiSi Cold-Formed Steel design manual updated

By Michael Cochran, S.E., SECB,

By Joshua Buckholt, S.E., P.E.,

Dilip Khatri, Ph.D., S.E.,

Richard C. Kaehler, P.E. and

Kevin O’Connell, S.E. and

Helen Chen, Ph.D., P.E.

Doug Thompson, S.E. ProjeCt deliVerY

24 Working in the iPd Framework

By Jay Love, S.E., Panos Lampas and John Leuenberger, S.E. StruCtural liCeNSure

a Cold-Formed Steel Gym

By Matthew L. Mlakar, S.E. To achieve a goal of constructing a small gymnasium with a modest price tag for the Language Academy of Sacramento elementary school, structural engineers took inspiration from two very different types of optimized designs: typical residential construction and pre-engineered metal buildings.

a Systems approach for Structural Framing

By Amie Sullivan, P.E., S.E. StruCtural Forum

66 how to make Better use of experienced Staff

By Phillip C. Pierce, P.E.

30 NCeeS Votes on Structural licensure and engineering education

By Marc S. Barter, P.E., S.E., SECB

On the cover Cold-Formed Steel Framing (CFSF) offers incredible flexibility, design creativity, and efficient and effective construction technologies. See feature article on page 40.

5

Feature

Feature

59 Brelsford Visitor Center

STRUCTURE magazine

37

40

SPotliGht

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

By A. Christopher Cerino, P.E., SECB, Michael Rogatsky, P.E. and Tim Nordstrom, P.E., S.E. While many New York City skyscrapers benefit from the support of billion year-old Manhattan Schist, other sites contend with fill and deep organic layers, saddling low-rise structures with amplified seismic design forces. Seismic analysis for the major modernization program of the Bronx Psychiatric Center resulted in building Seismic Design Category D. Structural engineers suggested using a BRBF system to enhance performance, reduce member size, and reduce cost.

By Steve Farkas, M.B.A. and Georgi Hall, P.E., M.S.C.E. Beyond the known benefits of CFSF systems, designers often ask what options are available that are not only efficient and effective, but also increase the overall strength of a structure while reducing the most expensive component of new construction – labor. CFSF systems may be the answer.

iN eVerY iSSue 8 Advertiser Index 55 Resource Guide (Software Updates) 60 NCSEA News 62 SEI Structural Columns 64 CASE in Point

November 2015

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Editorial

Should new trends, new We techniques Be and Concerned current industry issues About Resiliency?

By Carrie Johnson, P.E., SECB

T

he concept of resiliency has been a topic of interest in a lot of emails I have received lately. There are two definitions on Dictionary.com for resilience (or resiliency).

1) The power or ability to return to the original form, position, etc., after being bent, compressed, or stretched; elasticity.

2) Ability to recover readily from illness, depression, adversity, or the like; buoyancy.

I find these definitions thought-provoking when considering what we need to do to make our communities resilient. Although the first definition applies more to structural principles and addresses some of the concepts we need to use to make our communities more resilient, it is really the second definition that rings true to me. I have been involved several times with assessing structures that were affected by natural disasters, and the ability to recover readily is key. The words illness and depression don’t really apply, but the concept of dealing with adversity certainly does. It often involves very unfamiliar adverse conditions. It can be devastating to communities if there isn’t the infrastructure and ability to quickly recover.

At the NCSEA Structural Engineering Summit, we had a very interesting panel discussion on current efforts to provide new ordinances to address resilience. The panelists were all from the Structural Engineers Association of California (SEAOC), and the ordinances they are working on focus on resilience for seismic events. The topics they discussed covered building rating systems, performance based design, and renewed efforts for retrofit ordinances. The discussion was lively. There has been a wave of discussions, innovations, and political involvement by California’s structural engineering community. Efforts are underway to establish a rating system that can be used to describe the performance of buildings during earthquakes and other natural hazard events.

The concept of developing resilient communities to resist natural disasters certainly doesn’t stop with seismic events. They can include both natural disasters like tornadoes, hurricanes, snowstorms and floods (both from Hurricanes and Tsunamis) and man-made disasters such as electrical outages, water contamination, wildfires, and explosions. Each of these types of disasters will require a new set of considerations. It also doesn’t stop with buildings.

I remember the first time I fully realized how complex the issues involved with resiliency are. It was after an earthquake in South America. One of the engineers I met had visited the area in the aftermath and said that, while most of the buildings fared fairly well, the roads and bridges did not. Prior to this, my thoughts were focused mostly on buildings during disasters. People were sitting, waiting for food and supplies in buildings that were essentially intact.

Without roads and bridges to bring in supplies, it took months and even years to get back to what would be considered normal.

The tsunami in the Indian Ocean in 2004 raised awareness about the need to address both warning systems for tsunamis and the unique recovery requirements. The damage recovery involved cleaning huge volumes of debris and dealing with contaminated water STRUCTURE magazine

and soils, as well as extensive damage to the infrastructure. Another popular presentation at the Summit was a session by Gary Chock where he presented the new ASCE 7-16 Tsunami Loads Design Standard. The states of Alaska, Washington, Oregon, California, and Hawaii are most at risk for experiencing a tsunami event, and this standard will help address a need for missing information on what loads should be anticipated.

Hurricane Katrina uncovered issues with our aging infrastructure.

Portions of the coast were designed for hurricane wind and wave forces, but proved to be inadequate. It also raised many questions about the ability to quickly get basic necessities such as electricity and water into damaged areas. Hurricane Sandy on the east coast in 2012 brought to light the weakness of our infrastructure in response to flooding in urban environments. Most of the current codes are really not applicable for urban conditions. Engineers from the Structural Engineers Association of New York (SEAoNY) have been involved with efforts to help cities and agencies develop criteria for what is appropriate. They are in the process of assessing how different types of construction responded and making recommendations for how to rebuild so the recovery happens more quickly.

There are tornados each year that should also be considered when designing for resilient communities. When wind forces in excess of 250 mph strike an area, there are multiple issues that have to be dealt with during recovery. Like tsunamis, the amount of debris can be overwhelming. Flooding is common and the need to restore electricity and clean water are issues that must be addressed. In Oklahoma, recent tornados have accentuated the need for quality special inspections. Buildings that were essential facilities, and should have been able to resist the winds better than surrounding structures, did not. Investigators found problems with the construction quality that should have been addressed with special inspections.

These are just a few examples of the long list of issues that need to be considered as we move forward with improving our communities to be more resilient. My resounding answer of “should we be concerned about resiliency?” is YES! We should be concerned and we should be willing to get involved. The concept of developing resilient communities will require structural engineers to team with other branches of engineering and community leaders to develop communities that are adaptable enough to respond quickly after a natural disaster. I think structural engineers are poised to lead the charge. We have been working with the concepts of designing structures to withstand disasters for years, and we should be ready and willing to take the lead as these efforts move forward.▪ Carrie Johnson is a principal at Wallace Engineering Structural Consultants, Inc., Tulsa OK, and a Past President of NCSEA.

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November 2015

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EDITORIAL BOARD 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 Brian J. Leshko, P.E. HDR Engineering, Inc., Pittsburgh, PA

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November 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 November 2015, Volume 22, Number 11 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.

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InFocus

All new trends, Good new techniques Things… and current industry issues

By Jon A. Schmidt, P.E., SECB

I

n October 2005, I received a call from Ron Hamburger, who was nearing the end of his term as President of NCSEA. He informed me that Jim DeStefano had resigned as chair of the Editorial Board for STRUCTURE magazine, and he asked me if I would be interested in succeeding him. He described the job as primarily coordinating the work of the other members, which consisted of soliciting, shepherding, and editing articles for publication.

Ron gave me a week to think it over, during which I obtained more information about the associated expectations from Craig Cartwright, who was acting as interim chair; Jeanne Vogelzang, the Executive Director of NCSEA and Executive Editor of the magazine; and Marc Barter, who oversees the business aspects.

Based on those conversations, I accepted the position and attended my first meeting that same month at the 13th Annual NCSEA Conference in Kansas City. A decade later, I look back on it as easily one of the best decisions of my career.

Ten years seems like a nice, round number; so effective January 1, 2016, I am stepping down. Fortunately, I am leaving the role in good hands – Barry Arnold, who has written multiple articles over the years and just finished his term as President of NCSEA, is taking over. As a result, this will be my last bi-monthly InFocus column, but I hope to continue writing on an irregular basis for Structural Forum in the future … or maybe Outside the Box would be more appropriate for my usual philosophical topics!

My very first article in this space (“A Charge to Keep,” January 2006) outlined the vision, mission, objectives, and goals that I established for the editorial board when I joined it. I believe that we have achieved them, by and large; STRUCTURE magazine is indeed the premier resource for practicing structural engineers. I have a lot of people to thank for this, starting with those already mentioned above – my predecessors, Jim and Craig; Ron for giving me this opportunity; Jeanne and Marc for managing the enterprise; and Barry for volunteering to carry on from here.

The publishing staff at C3 Ink (a division of Copper Creek Companies, Inc.) obviously deserves a lot of credit, as well – Christine Sloat, Nikki Alger, Rob Fullmer, and Will Radig currently; Dawn Sloat, Brenda Schwartz, Pat Blinderman, and Nic Stage in the past. They have always cared as much about the quality of our product as anyone, and have taken great pains to assist with every step of the process. In particular, their initial setup and ongoing maintenance of an online Intranet – in fact, two completely different versions, because the vendor for the first one discontinued it – has been absolutely critical to keeping all of our operations running (mostly) smoothly. Furthermore, the distinctive “look and feel” of the magazine largely sprang from their creative efforts.

Another secret to our success was the sustainable business model developed by Jeanne and Marc, which ties the number of pages printed in each issue to its volume of advertising sales. One of my least favorite tasks was deciding which articles to cut each month

STRUCTURE magazine

during the Great Recession. I appreciate Chuck Minor and Jerry Preston, as well as Dick Railton previously, for selling as many ads as they could – and for continuing to beat the bushes even in (somewhat) improved economic conditions.

I am grateful, as well, for the continuity of the editorial board itself. Greg Schindler deserves special recognition for serving as our unofficial secretary throughout my tenure as chair, vigilantly keeping track of the ever-changing schedule of articles. Brian Leshko, Evans Mountzouris, Steve Schneider, and Buddy Showalter all started before I did and will remain after I am gone. Craig Barnes rode off into the sunset just last month, and although David Biggs technically left the board in 2006, he has graciously continued to help populate the masonry-themed May issue ever since.

It has been a pleasure to interact with the various others who have been involved, as well. Some were there when I began and have since departed: Steve Schaefer (2006), the late Bill Liddy (2007), the late Dan Falconer (2007), Richard Hess (2012), and John Mercer (2014). Two joined and left under my watch: Matt Salveson (2006-2010) and Amy Trygestad (2013-2015). Several others are still in the mix: Mark Holmberg (2006), Brian Miller (2007), Mike Mota (2007), Roger LaBoube (2010), Dilip Khatri (2012), John Dal Pino (2014), and newcomer Jessica Mandrick.

I must also acknowledge those at Burns & McDonnell who have steadfastly supported my “extracurricular” activities throughout my 21 years (and counting) with the firm: Don McLaughlin, David Yeamans, Randy Pope, Joel DeBoer, Mike Fenske, and Dave Griffith. My colleague Phil Terry reviewed the very first technical article that I ever composed, way back in 1997, and wrote on it, “I think you may be a writer.” I guess he was right!

Of course, a magazine has nothing to print without authors, and I have had the privilege of working directly with more than a hundred of you to put your ideas into words. Furthermore, a magazine has no purpose without readers, and I sincerely thank all 30,000-plus of you for giving us your time and attention month after month.

That leads me to close with a quote from Charles Sanders Peirce, the subject of my last column (“Representation and Reality,” September 2015): “The writer of a book [or article] can do nothing but set down the items of his thought. For the living thought, itself, in its entirety, the reader has to dig into his own soul. I think I have done my part, as well as I can. I am sorry to have left the reader an irksome chore before him. But [I hope] he will find it worth the doing.”▪

11

Jon A. Schmidt, P.E., SECB (jschmid@burnsmcd.com), is an associate structural engineer at Burns & McDonnell in Kansas City, Missouri. He chairs the STRUCTURE magazine Editorial Board and shares occasional thoughts at twitter.com/JonAlanSchmidt.

November 2015

Structural DeSign

12"

A s3 (typ.)

Barrier Wall P = 6k

A s4 (typ.)

18" 27"

A s1 A s2

design issues for structural engineers

12"

Slab Beam

Elevation

Section

Figure 1. Load assumed to be resisted by 1-foot width of the wall.

T

he perimeter of parking garages, and the edges of split ramps in the interior of parking garages, are required to have barriers, restraints or guardrails to stop the vehicles inside the structure from plunging down. The design and detailing of the perimeter walls has been a concern to public safety. The author has published three articles in STRUCTURE magazine on the subject calling for a rational design method for vehicular barrier systems. The first two articles presented a method on how to calculate the impact load on rigid and linearly elastic barrier systems. It was shown that the magnitude of the vehicular impact force depends on four factors: mass, speed, crushing characteristics of the vehicle, and barrier stiffness.

It was also shown that the code-prescribed load to design the barriers was unreasonable and arbitrarily set too low, and that there was a need for a rational approach to design the vehicular barriers.

The third article discussed the deficiency in the wall-slab joint, which causes cantilever concrete barrier walls to fail prematurely. The scope of this article is limited to the barrier walls. The article reviews the code requirements for design of the barrier walls using language of the current code, and provides suggestions on analysis and design of the walls. Specifically, it addresses the provisions of section 4.5.3 of ASCE 7-10 Minimum Design Loads for Buildings and Other Structures which prescribes the loads on vehicle barrier systems:

Design of Vehicular Barrier Walls ASCE 7-10 Requirements

By Mohammad Iqbal, D.Sc., P.E., S.E., Esq.

Mohammad Iqbal is a licensed attorney in the state of Illinois. A fellow and life-time member of ASCE, he serves on several ACI and ASCE committees. Dr. Iqbal can be reached at mi@iqbalgroup.us.

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

4.5.3 Loads on Vehicle Barrier Systems.

Vehicle barrier systems for passenger vehicles shall be designed to resist a single load of 6,000 lb (26.70kN) applied horizontally in any direction to the barrier system, and shall have anchorages or attachments capable of transferring this load to the structure. For design of the system, the load shall be assumed to act at heights between 1 ft 6 in. (460 mm) and 2 ft 3 in. (686 mm) above the floor or ramp surface, selected to produce the

Figure 2. Distribute-andSpread scheme for a single load.

maximum load effect. The load shall be applied on an area not to exceed 12 inches by 12 inches (305 mm by 305 mm), and located as to produce the maximum load effects…

The two underlined clauses (underline added by author) are prescribed in the Code to be used in design of barrier systems. The author asked the ASCE Standards Committee, ASCE 7, for a formal interpretation of the clauses. The questions submitted for the formal interpretation are summarized below: 1) Are the clauses ambiguous?

2) Are the clauses superfluous and can be ignored in design?

3) Does the clause “to produce the maximum load effects” mean that the single load of 6,000 lb distributed over an area of 12 inches by 12 inches (305 mm by 305 mm) shall produce the maximum shear force, the maximum bending moment and the maximum deflection in the 12-inch wide strip of wall directly under the area, such as shown in Figure 1?

4) Does the phrase “to produce the maximum load effects” mean that the single load of 6,000-lb shall be distributed over an area not to exceed 12 inches by 12 inches (305 mm by 305 mm) and then spread down to the wall base at the maximum slope reducing the wall bending moment on per unit length basis, such as shown in Figure 2?

The ASCE Standards Committee responded that the language in the section 4.5.3 was not ambiguous, and would not be clearer if the words “to produce the maximum load effect” were removed.

The author concurs with Standards Committee’s response. This paper provides a historical perspective of the reinforced concrete barrier wall design and provides design guidelines.

Barrier walls are commonly termed bumper walls. A bumper wall design example was published in the 1970s in the Handbook of Concrete Engineering (Editor: Mark Fintel). The design example used a 6-inch thick cantilevered concrete

12 November 2015

Distance above Base (in)

25 21 17 13 9 5 1 0

2

4

6 8 10 Bending Moment (kip-ft)

45° spread

12

Calculate base plate connection designs

14

No spread

Figure 3. Comparison of wall moments for No-spread and Distribute-and-Spread for a 6-kip load applied 27 inches above wall.

“To Produce the Maximum Load Effect” In engineering terms, the phrase “to produce the maximum load effect(s)” means to produce the maximum shear, torsion, bending moment and deflection in a barrier system under a single point live load. Generally, this point live load needs to be moved and applied at various points within the system to produce the maximum load effects. It is foreseeable that applying the load at any one point may not produce the maximum effects everywhere.

For example, the load applied at a wall corner may have one set of “maximum load effects” and the load applied at the wall’s free edge

may have another. The ASCE 7 standards section 4.5.3 defines the influence surface within which the load should be applied strategically in order to produce the maximum load effects.

For bumper walls, this influence area is the full length of the wall in the horizontal direction and from 18 to 27 inches in height above the floor in the vertical direction.

Building codes generally do not prescribe how the single load should be resisted by a barrier wall. There are many ways the wall can be designed for the load to flow from the point of application to the wall base, and then into the structure. The wall segment that participates in resisting the point load depends on the amount and pattern of the wall reinforcement. Consider the code-prescribed load spread provision of “not to exceed 12 inches by 12 inches”. Two examples of load-carrying mechanisms concerning the provision are shown in Figures 1 and 2. The figures show the part of wall assumed to resist the point load, P. In Figure 1, a 1-foot wide wall strip is assumed to act as a cantilever. Using the strip mode, the wall requires only A s1-type reinforcement. The temperature reinforcement is required by the code but is excluded from being part of the flexural reinforcement.

For the 6-inch concrete wall referenced earlier, subjected to the 10,000-lb point ultimate load at 18 inches above the floor, the steel requirement is about #4@3 inches on center, when considering only a 12-inch wide strip. For the ultimate point load applied at 27 inches above the floor, the steel requirement would increase further for each strip. Such closelyspaced reinforcement may not be desirable or practical and, therefore, an increase in wall thickness and other design options need to be considered. As such, the strip or non-spread method provides a safe, lower bound and conservative design for the bumper wall.

Figure 2 shows the point load, P, distributed over a 12-inch (305 mm) length and then assumed to spread downward at 45-degree

STRUCTURE magazine

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wall reinforced with a single layer (A s1-type) of steel. No other longitudinal, transverse or temperature reinforcement was provided in the example. It was assumed that the point load, P, spreads over a 4-foot width of wall.

The load spread scheme used in the Handbook is shown in Figure 2. It was shown that for a 10,000-lb point ultimate load, which equals a 6,000-lb allowable load, applied at 18 inches above the floor, the wall reinforced with A s1 = # 4 @12 inches on center was “OK”. No justification for the load spread was given in the Handbook. Though the design example has been commonly followed in the design and construction of bumper walls in concrete parking garages, the underlying 1:1 load spread assumption has not been examined or tested for validity. Assuming any failure pattern or load spread in structural design is generally unsafe and has been termed “half-truth” in the treatise Yield Analysis of Slabs (Jones et al., 1967) A proper failure mechanism is one that requires the maximum reinforcement in the bumper wall. This article examines cantilever bumper wall design in light of the ASCE 7-10 language and the principles of structural mechanics. Design guidelines are provided at the conclusion.

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Figure 4. Corner break-off mode with a point load at the corner of the barrier wall.

Figure 5. Fan mechanism formation with a point load on the corner of a long wall.

inclinations on both sides of the load. The spread assumption connotes that a 4-foot length of the wall at the floor level would be engaged in resisting the load. It further implies that the wall design moment reduces to 25% of the no-spread moment. For a barrier load located 27 inches above floor, the wall moment at its base reduces to a mere 18% of the strip mode (Figure 3, page 13).

This means an 82% reduction in the design moment. The load spread assumption minimizes the design by distributing the load over a larger load. Therefore, the use of the load spread scheme and the associated moment reduction must be justified using structural mechanics and experimental work in order to avoid design deficiency in the wall.

length of the yield-line formed at an angle θ with the x-axis is given by:

The ACI-318 Approach The ACI-318 code permits a new structural system or a new design approach if its adequacy has been shown. One way to show this is to successfully test the new system.

However, no test data on the 6-inch thick cantilever bumper wall system or the spread assumption could be found. Analytically, the load-carrying mechanism that produces “the maximum load effects” can be determined using the principles of structural mechanics.

Both elastic and plastic methods are available for analysis and design of the barrier wall.

Finite element analysis is one method and yield-line theory is another method. The ACI Code commentary refers specifically to the yield-line analysis as an acceptable approach.

Yield-line Analysis A yield-line in a slab (or a bumper wall in this case) corresponds to a plastic hinge in concrete beams. There are two types of yield-lines.

A yield-line formed by yielding of positive reinforcement is called a positive yield line.

Similarly, a yield-line formed by yielding of negative reinforcement is called a negative yield-line. The moment capacity per unit

mθ = m x cos2 θ + my sin2 θ

Equation 1

where mx and my are moment capacities of the reinforcement about the x- and y-axis, respectively.

In contrast to the finite element method, which is a computer-based method, the yield-line method requires hand-calculations along with some knowledge of how a bumper wall could fail. The yield-line method is an upper-bound method and provides the bumper wall load-carrying bending capacity when a proper yield-line mechanism is used. For example, consider the cantilever wall shown in Figure 1 subjected to a single point load, P. In order to design the wall, the load should be moved and applied at various points within the influence surface area in order to produce the maximum load effects. Two load locations significant for design are: the corner and the free edge of the wall.

Point Load at the Corner of the Bumper Wall Consider a single load, P, applied at the corner of the wall, as shown in Figure 4. The simplest failure mode occurs when the wall corner fails as a triangular piece with a negative yield-line at distance, a, from the corner. Consider the 6-inch thick concrete wall reinforced with #4@12 inches on center next to the interior (vehicle side) face of the wall, with the moment capacity of approximately 4ft-kip/ft. Using Equation 1, mx = 4 (ft-k)/ft my = 0 θ = 45° mθ = (4)(cos2 45) + (0)(sin2 45) = 2 (kip-ft)/ft Yield-line length, l = a + a = 2a Moment at the yield-line = P * a = mθ * l Therefore, P * a = (2) (2a) or P = 4 kips < 10 kips Though the anticipated failure load of 4,000-lb is much less than the design load of 10,000-lb, it is still an upper-bound and unsafe solution.

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This is because the implicit assumption in this failure mode is that the wall has sufficient positive reinforcement to eliminate formation of positive yield-lines. Because the bumper wall has no positive reinforcement and is only singly-reinforced with As1-type negative steel, its capacity is expected to be lower than that anticipated by the Figure 4 mechanism.

If a bumper wall is reinforced with both positive and negative steel, a fan-type mechanism may form which has radial and circumferential yield-lines, as shown in Figure 5. The circumferential yield-lines are formed when the negative steel yields and the radial yieldlines are formed when positive steel yields. If the positive steel is omitted altogether, then a quarter-circle of radius, r, could develop with no resistance along the radial lines. Further, the moment capacity As1-type steel varies along the periphery of the quarter-circle as angle changes. Therefore, the average moment capacity along the circumferential yield-line, mθ is one-half of the maximum moment the steel can develop. Thus, the failure load, P, can be computed as follows: Moment at the circumferential yield-line = P * r = mθ (2πr/4) Therefore P = (2)(π/2) = 3.14 kips < 10 kip Now, consider an 8-inch thick cantilever bumper wall reinforced with both positive and negative steel in longitudinal and transverse directions, i.e. each way, each face, (As1 thru As4) with #4@ 12 inches on center. Using a concrete cover of 1.5 inches, the average moment capacity in both the x- and y-directions is approximately 5.2 ft-kip/ft length of the wall. It has been shown that, with positive and negative reinforcements being equal, the fan type mechanism would not materialize and it would be replaced by the single yieldline mechanism (Figure 4). Using Equation 1, mx = my = 5.2 (ft-k)/ft θ = 45° mθ = (5.2)(cos2 45) + (5.2)(sin2 45 ) = 5.2 (kip-ft)/ft Yield-line length, l = 2a Moment at the yield-line = P * a = m θ * l Therefore, P * a = (5.2)(2a) or P = 10.4 kips >10 kips In addition to the failure modes described above, other modes are also possible. The failure mode that predicts the lowest capacity is the most credible upper-bound solution.

Point Load on the Free Edge of a Long Wall Similarly, for a point load on the free edge of a long wall, both failure modes shown in Figures 6 and 7 are possible. The mechanisms are similar

Positive yield line (typ.)

P

Negative yield line

h Wall

Fixed Base

Figure 6. Fan system of yield-lines in wall caused by a point load on the free edge.

Figure 7. Total collapse mode under a point load applied on the free edge of a wall.

in nature to the mechanisms discussed while addressing the corner load earlier. Figure 6 shows a general fan mechanism in which the fan and the adjacent yield lines meet. For a wall reinforced with only As1-type steel, the half-circle long yield negative line could develop with no moment resistance along the radial yield-lines.

As noted in the quarter-circle case, the solution is independent of the radius, r, and thus the anticipated failure load is given by:

Simply put, one needs to find the worst (i.e. gravest) layout for the system of yield-lines that produces the smallest load the wall can carry. In corollary, for a prescribed load, one needs to determine the system of yield-lines that produces “the maximum load effects”.

Thus, every assumption regarding the loadcarrying mechanism should be verified using the lower-bound solution.

The mode in Figure 7 shows the collapse of the entire wall, with the wall-floor joint being the weakest link and developing the yield-line. There are several ways this failure mode can form. One way is to reinforce the wall sufficiently with positive steel to eliminate formation of positive yield-lines. The wall may also collapse as a whole if the wallslab joint is inefficient. This type of failure mode was also discussed by the author in the April 2014 issue of STRUCTURE magazine.

Another reason the entire wall may collapse is the limited extent of the wall length, so that the wall acts as a one strip. Additional failure modes, such as progressive failure or zipper effect, are also possible.

The above examples show how the yield-line method can be used in the analysis and design of the barrier walls. This is generally an upperbound method, and consequently the true load a wall can resist may be less than the calculated load. This is a recognized concern, since a reasonably prudent design professional prefers to be correct and limit his/her liability by being somewhat conservative. Therefore, the upper-bound solution used in the design of a barrier wall must coincide with the lower-bound solution which gives a conservative or, at most, correct value of the collapse load. Its conditions are: 1) A complete stress field must be found, everywhere satisfying the differential equation of equilibrium.

2) The forces and moments at the edges must satisfy the boundary conditions.

3) At no point can the principal stresses violate the yield criterion.

It is the customary duty of a design professional to determine the failure pattern which is the most critical and produces “the maximum load effects”. The ASCE 7-10 phrase “to produce the maximum load effect” is proper as a design requirement.

The yield-line theory provides a satisfactory method in predicting the ultimate load a bumper wall would be able to resist. A proper yield-line or failure mechanism is one that requires the maximum reinforcement in the wall, consistent with analytical and experimental work. While there is a dire need for the code load requirements to be rationally-based, conservative design guidelines for barrier walls using the ASCE 7 code language are: 1) Before assuming any load spread or failure mechanism, verify it experimentally.

2) If no experimental data is available, use the strip mode shown in Figure 1.

3) Provide reinforcement each way on each face of the wall, as shown in Figure 1 and use a minimum bumper wall thickness of 8 inches.

4) Provide a fully efficient wall-floor joint which can transfer the load from the wall to the structure. One way to achieve this is to have the wall supported on a beam, as shown in Figure 1.

5) Use the single load application provision “on an area not to exceed 12 inches by 12 inches” for the punching shear check.▪

STRUCTURE magazine

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November 2015

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Summary

P = (2)(π) = 6.28 kips

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Building Blocks updates and information on structural materials

Table 1. Minimum bolt pretensions (kips).

Bolt Size, in.

AISC Group A

AISC Group B

AISC Group C, Grade 2

(F3125 Grade A325 & F3125 Grade F1852)

(F3125 Grade A490 & F3125 Grade F2280)

(F3043 Grade 2 & F3111 Grade 2)

1/2 5/8 3/4 7/8 1 1 1/8 1 ¼ 1 3/8 1 1/2

12 19 28 39 51 56 64 71 81 85 97 103 118

15 24 35 49 64 80 102 121 148

S

everal significant changes have or will soon occur in high-strength bolting for steel buildings. These changes have been incorporated into the latest drafts of the upcoming AISC Specification for Structural Steel Buildings (AISC 360-16), and related AISC standards such as AISC 341 and AISC 358. The Research Council on Structural Connections (RCSC) is beginning work on a new version of the Specification for Structural Joints using High-Strength Bolts to address these changes. AASHTO bridge design and construction specifications are also in the process of addressing these changes.

These changes include: • A new consolidated high-strength structural bolt standard, ASTM F3125 • Higher tensile strengths and pretensions for large diameter Grade A325 and Grade F1852 bolts • The addition of the 1¼-inch diameter for twist-off type tension control bolts • New 200 ksi high-strength structural bolts, ASTM F3043 and ASTM F3111 • AISC standard hole diameter for 1-inch and larger diameter bolts • RCSC definition of the snug-tight condition • New structural bolting products and coating systems

New Twists and Turns in Structural Bolting

By Robert E. Shaw, Jr., P.E.

Robert E. Shaw, Jr., founder and President of the Steel Structures Technology Center, Inc., provides consulting services, technical resources and training related to steel-framed structures, and is actively involved in numerous steel construction standards. Bob can be reached at rshaw@steelstructures.com.

ASTM F3125, the New Consolidated High-Strength Structural Bolt Standard A new structural bolt standard, ASTM F3125 – 15, Standard Specification for High Strength Structural Bolts, Steel and Alloy Steel, Heat Treated, 120 ksi (830 MPa) and 150 ksi (1040 MPa) Minimum Tensile Strength, Inch and Metric Dimensions, was adopted by ASTM in Fall 2014 that not only consolidated six existing specifications on structural fasteners, but made significant

90 113 143

technical changes to product strength and range.

The six “old” specifications now replaced by ASTM F3125 are: • ASTM A325 and ASTM A325M, for steel heavy hex structural bolts; • ASTM A490 and ASTM A490M, for steel heavy hex structural bolts; and • ASTM F1852 and ASTM F2280, for “twist off” type tension control structural bolt/nut/washer assemblies.

To minimize confusion, the bolt head markings will remain unchanged, and the term “Grade” is applied to differentiate the six products that now fall under a common standard. Thus, ASTM A325 bolts are now specified and ordered as ASTM F3125 Grade A325 high strength bolts. The term “Type” remains to distinguish steel composition, with “Type 3” being the weathering type. The term “Style” is used to distinguish between heavy hex bolts and “twist off” fastener assemblies.

In addition, several technical modifications were made. The “drop” in minimum tensile strength from 120 ksi to 105 ksi at 11/8-inch diameter and above for ASTM A325 and ASTM F1852 fasteners has been eliminated in ASTM F3125, so that the minimum remains constant at 120 ksi for all diameters of AISC Group A fasteners. This has been a long-standing issue in bolted connection design. As a result of the increased minimum tensile strength of these large diameter bolts, the minimum specified pretensions for these same bolts has increased proportionately. This change is shown in Table 1 for pretensioned and slip-critical joints, with red strikethrough being the old values and green underline being the new values: “Twist off” type tension control bolts were previously limited to a maximum diameter of 11/8 inches under ASTM F1852 and ASTM F2280.

The new maximum diameter for ASTM F3125 Grade F1852 and Grade F2280 is 1¼ inches.

ASTM F3125 Annex A1 adds significant information about hot-dip galvanized coatings (ASTM F2329), mechanically galvanized coatings (ASTM B695), and two types of zinc/aluminum coatings (ASTM F1136 and ASTM F2833). Annex A2 provides rotational capacity testing procedures,

16 November 2015

ASTM F3043 “Twist Off” and ASTM F3111 Heavy Hex Structural Bolt/Nut Washer Assemblies.

when invoked by Supplement S4, that replicate those required for bridge applications in the AASHTO Bridge Construction Specifications and in the FHWA Guidelines.

New 200 ksi High-Strength Structural Bolts

AISC Standard Hole Diameter for 1 Inch and Larger Diameter Bolts Reports of large diameter structural bolts not fitting into standard holes, even when properly aligned, led AISC to study and draft language for AISC 360-16 that increases the standard hole diameter (STD) and slot width for structural bolts 1-inch diameter and above to 1/8-inch larger than the bolt diameter, replacing the old criteria of 1/16-inch larger than bolt diameter.

Bolt manufacturing criteria in ASME B18.2.6 allow for swells and fins under the bolt head, and die seams on the body, up to 0.060 inch for high-strength bolts 3/4 inch through 1¼ inch diameter, and 0.090 inch for bolts over 1¼-inch diameter. As such, with a hole allowance of 1/16 (0.062) inch, there is risk that bolts may not physically fit in the specified hole.

Issues with bolt hole alignment and bolt fit have existed for many years, even for bolts without swells, fins or die seams. To quote from the Fisher and Struik’s Guide to Design Criteria for Bolted and Riveted Joints (1974): “Since the first application of highstrength bolts in 1947, bolt holes 1/16 inch larger than the bolts have been used for assembly. A similar practice was adopted in Europe and Japan, where a hole diameter 2 mm greater than the nominal bolt diameter became standard practice.

Restricting the nominal hole diameter to 1/16 inch in excess of the nominal bolt diameter can impose rigid alignment conditions between structural members, particularly in large joints. Sometimes

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November 2015

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ASTM F3043 “twist off” type tension control structural bolt/nut/washer assemblies and ASTM F3111 heavy hex structural bolt/nut/ washer assemblies (see Figure), with 200 ksi tensile strength, are intended for connections where large diameter high-strength bolts are typically used. These include connections for large bracing elements, long-span trusses, heavy column splices, heavy girders, bolted moment connections, and similar locations where thick plies of steel are being joined.

Both the “twist off” type and heavy hex type assemblies were adopted as new fastener standards by ASTM in 2014.

The assemblies are available in 1-inch, 1⅛ -inch, and 1¼-inch diameters, and are pre-assembled with bolt, nut, and washer or washers as required, including factory lubrication. At 200 ksi, they provide higher shear and tensile strengths. The resulting pretensions, as shown in Table 1 as a new Group C, are significantly higher than those of Group A and Group B bolts of equal diameters. The higher design strengths and pretensions make possible a more compact connection with smaller diameter bolts and/or fewer bolts.

Because of their very high strength, the use of Group C assemblies is limited to specific building locations and noncorrosive environmental conditions by the ASTM standards.

The bolts use tightly controlled steel composition, production and heat treatment, with unique design features including a larger radius under the bolt head, a modified bolt shank with reduced cross-section near the threads, and a root profile on the bolt’s external thread significantly smoother than the UNC thread profi le used for other structural bolts. Two grades are included in each standard, addressing two thread profiles.

Grade 1 uses a standard UNJ thread profi le as defi ned in ASME B1.15-1995. Th is grade has not yet been manufactured, and pretensioning methods and performance have not been verified through testing. As a result, AISC 360-16 has been drafted to limit Grade 1 assemblies to snug-tight joints.

Grade 2 uses a unique thread profile, smoother than Grade 1. These bolts are currently manufactured in Japan by Nippon Steel & Sumikin Bolten Corporation (NSSB), a leading supplier of high-strength structural bolts. Bolts using this material and this design have been used successfully in Japan since 2000. Bolts of each type, in inch-series, were tested at the University of Cincinnati, at Virginia Polytechnic Institute and State University, and at private independent laboratories. AISC 360-16 has been drafted to permit their use in snug-tight, pretensioned and slip-critical joints.

erection problems occur when the holes in the plate material do not line up properly because of mismatching.

Occasionally, steel fabricators must preassemble structures to ensure that the joint will align properly during erection.

With a larger hole size, it is possible to eliminate the preassembly process and save both time and money…”

Research at the time addressing this issue led to permission for significantly larger hole diameters, termed Oversize (OVS) holes, that were subsequently incorporated into US and other standards. The use of OVS holes eased fit-up issues, but also led to decreased pretensions and slip resistance design values. Others researched slightly larger holes, on the order of 1/8 inch or 3 mm larger than bolt diameter, and found negligible effects on pretension and slip resistance when such holes were used, and supported the use of such hole diameters as standard (STD) holes for larger diameter bolts. A review of this research, as well as reviews of other major national and international standards, showed a 3 mm value for standard holes for larger bolt diameters, and a 2 mm value for smaller diameters, to be suitable for all joint types including snug-tight. Indeed, AISC’s Table J3.3M used such values. In addition, bearing pressure analysis for varying hole diameters, using acceptance criteria from earlier research, was performed to verify the increase in STD hole size.

The old (in red strikethrough) and new (in green underline) values for hole diameter as drafted for AISC 360-16 are shown in Table 2.

It is expected that the new larger hole diameters for larger bolts will reduce bolted connection fit-up time, reduce shop and field reaming and slotting, reduce the need for trial assembly and in-situ hole drilling, and reduce the size of connections because the reduction factor Ø for STD holes is 1.0, compared to 0.85 for OVS holes.

Table 2. Nominal hole dimensions, inch.

Bolt Diameter 1/2 5/8 3/4 7/8 1 ≥ 1 1/8

Standard (Dia.) 9/16 11/16 13/16 15/16 1 1/16 1 1/8 d + 1/16 d + 1/8

Oversize (Dia.) 5/8 13/16 15/16 1 1/16 1 ¼ d + 5/16

Hole Dimensions Short-Slot (Width x Length) 9/16 x 11/16 11/16 x 7/8 13/16 x 1 15/16 x 1 1/8 1 1/16 x 1 5/16 1 1/8 x 1 5/16 (d + 1/16) x (d + 3/8) (d + 1/8) x (d + 3/8)

all of the bolts in the joint have been tightened sufficiently to prevent the removal of the nuts without the use of a wrench.”

A related change clarified the inspection requirements for the snug-tight condition, as stated in Section 9.1 of the 2009 RCSC Specification: “After the connections have been assembled, it shall be visually ensured that the plies of the connected elements have been brought into firm contact and that washers have been used as required in Section 6. It shall be determined that all of the bolts in the joint have been tightened sufficiently to prevent the turning of the nuts without the use of a wrench. No further evidence of conformity is required for snug-tightened joints. Where visual inspection indicates that the fastener may not have been sufficiently tightened to prevent the removal of the nut by hand, the inspector shall physically check for this condition for the fastener.”

While the 2009 definition was suitable for installation and inspection of snugtightened connections, that definition was found to be inadequate to define a suitable starting point for the turn-of-nut method of pretensioning bolts. This was evidenced RCSC Definition of the by lower and sometimes inadequate pretensions when the new definition was used as Snug-Tight Condition the starting point during pre-installation Long-standing issues with definitions of verification testing for the turn-of-nut the snug-tight condition in the RCSC method. Therefore, the definition of the Specification led to revision of the definition snug-tight condition in the August 1, 2014 for the 2009 edition. Such issues included (with April 2015 Errata) RCSC Specification what constituted “full effort on an ordinary was returned to its 2004 version: spud wrench”, as well as “a few hits of an “The tightness that is attained with a impact wrench,” especially when small pneufew impacts of an impact wrench or matic impact wrenches, electric wrenches or the full effort of an ironworker using hydraulic wrenches were used for snugging. an ordinary spud wrench to bring the Inspectors were also concerned about “not plies into firm contact.” snug enough” as well as “too tight for snug.” This restored definition still fails to address The new RCSC definition adopted in 2009 “full effort” or use of other wrench types, for “snug tight condition” was: but it was deemed better to have proper pre“The condition that exists when all of the tensions achieved when using turn-of-nut plies in a connection have been pulled into methods than to retain the older definition. firm contact by the bolts in the joint and However, the 2009 inspection description STRUCTURE magazine

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November 2015

Long-Slot (Width x Length) 9/16 x 1 ¼ 11/16 x 1 9/16 13/16 x 1 7/8 15/16 x 2 3/16 1 1/16 x 2 1/2 1 1/8 x 2 1/2 (d + 1/16) x (2.5 x d) (d + 1/8) x (2.5 x d)

used in section 9.1 was retained for 2014, as it is still appropriate for inspection purposes.

New Structural Bolting Products and Coating Systems Some new structural bolting products and their ASTM standards were too late to be included in the balloting for AISC 360-16.

One new system, covered by ASTM F3148, is LeJeune Bolt Company’s TnA® Fastening System, in which TnA stands for Torque and Angle. The system incorporates 144 ksi minimum tensile strength bolt material, with installation using an electric wrench that drives a spline similar to that of a twist-off bolt, but without twisting off the spline. The snug condition is torque-controlled, and the pretension is nut rotation controlled, set to achieve Group B pretensions.

Another zinc-based fastener coating system, ASTM F3019, was approved in November 2014, also too late for inclusion in AISC 36016. Because this is the third zinc flakesystem for use on ASTM F3125 Grade A490 bolts, with more expected, the ASTM F16 committee is looking to consolidate all manufacturer’s product lines, and their ASTM standards, into one standard, thus making for a more consistent standard that is easier to use and reference.

Conclusions Structural engineers and others involved in steel construction need to keep abreast of new and changing standards, especially with the number of significant issues that affect not only design but fabrication, erection and inspection practices. These new technologies and standards offer several advantages that engineers and constructors may wish to implement soon, even before official adoption of AISC 360-16, and before the next version of the RCSC Specification is issued to address these new standards, products and methods.

Communication and coordination between all involved will be needed.▪

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Structural Performance performance issues relative to extreme events

L

os Angeles is no stranger to earthquakes and, like other cities in California, has experienced extensive damage in previous seismic events, which has led to significant advancements in earthquake engineering. Some might say that L.A. has been the epicenter of seismic code development since the 1933 Long Beach Earthquake. Because of its long history with seismic events and their aftermath, Los Angeles has embarked in a leadership role to create a long-term program to educate the public, help building owners to seismically strengthen their buildings, and improve overall community resiliency after the next earthquake.

The impetus for this retrofit program started with a few articles published in the Los Angeles Times when a reporter got wind of a study being done at the University of California at Berkeley on non-ductile concrete buildings, which indicated that potential “collapse hazards” exist. This news spread like wildfire, and since then, the Times has been on top of this story with periodic coverage that has raised public interest in the topic of seismic strengthening and community resiliency. Mayor Eric Garcetti has issued a report to help improve the seismic preparedness of the city which addresses telecommunications, water system infrastructure, and building vulnerability.

The report calls for proposed ordinances, several of which relate to buildings and structures: 1) Seismic Retrofit of Existing WoodFramed Soft-Story Buildings 2) Seismic Retrofit of Existing Non-Ductile Concrete Buildings 3) New Cell Phone Communication Tower Design Requirements The mayor created an Earthquake Technical Task Force, among several task groups, which brought together people from the City, Dr. Lucile Jones from the United States Geologic Survey (USGS), and structural engineers from the Structural Engineers Association of Southern California (SEAOSC). This task force provided advice and recommendations to Mayor Garcetti as the mayor’s office went about writing a report that summarizes some of the city’s vulnerabilities to a major seismic event: Resilience by Design (www.lamayor.org/earthquake).

The report, released in December 2014, covers major seismic risks to the city’s infrastructure, and documents past disaster events that had serious impacts on other local economies. One fascinating observation is the effect that the 1906 San Francisco Earthquake had on California’s demographics. Prior to that year, San Francisco was California’s largest city (population approx.

400,000), but the earthquake and fire aftermath produced considerable migration south to Los Angeles as the U.S. population moved westward,

Seismic Strengthening of Buildings in Los Angeles

By Michael Cochran, S.E., SECB, Dilip Khatri, Ph.D., S.E., Kevin O’Connell, S.E. and Doug Thompson, S.E.

approximately doubling the population from 150,000 to over 300,000 in the City in just four years. By 1920, the population of Los Angeles had surpassed that of San Francisco, making it the new economic center for California (Figure 1). After 100 years, San Francisco and the bay area have only recently, in the last two decades or so, been able to recover to a similar relative economic status with the development of Silicon Valley and the growth of powerhouse internet software/manufacturing companies like Apple and Google.

In a similar context, the economic damage to New Orleans from 2005 Hurricane Katrina is illustrated in Figure 2 with a comparison to a similarly sized city with a similar economy and demographic, Nashville, Tennessee. The immediate financial loss suffered by New Orleans ($80 Billion) is exceeded by its lost potential financial gains over the next 7 years when compared with Nashville.

It has also been observed that when the immediate financial loss from the disaster approaches or exceeds the annual real growth domestic product of the community, it becomes very difficult to rebuild the community as existing resources (infrastructure, building stock, financial services, labor pool, available commodity goods and services, etc.) have been greatly depleted or wiped out. Resulting shortages greatly restrain the recovery effort, often for many years afterwards, as communities attempt to rebuild, in some cases from nothing. It has been ten years since Hurricane Katrina, and New Orleans has still not recovered to its original economic capacity.

The obvious conclusion in both of the above scenarios is that major disasters have long-term economic effects that can be irreversible, or at least take many decades to economically recover.

Los Angeles City and Los Angeles County have the largest population concentration (approx. 3.8 million/10.1 million respectively) in California and constitute a major economic hub within the state, which is a significant component of the United States gross domestic product (GDP) – approximately 10%. A major earthquake in the communities that make up the Los Angeles basin, or San Francisco bay area, could severely cripple the state economy and have a corresponding impact on the U.S. economic output. Mayor Garcetti’s initiative to create a seismic strengthening program is a unique approach, different than that attempted by his predecessors, and reflects his willingness to take on a monumental challenge.

The agenda of the program covers many topics beyond just buildings. Telecommunication facilities, water delivery, and power substations are among the lifeline infrastructures that are also addressed in the Mayor’s Resilience by Design report. But the seismic retrofit of both existing wood-framed soft-story buildings and non-ductile concrete buildings are of the most interest to the structural engineering community.

20 November 2015

Real Gross Domestic Product (in Billions of Dollars)

84

Population of Los Angeles vs San Francisco 1890-1920

700000

600000 576673

1906 Earthquake 506676

500000

416912

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400000 348782

300000

319198 298997

280000

200000 150000 102479

100000

Los Angeles

50395 0

1890

San Francisco 1900

1906

1908

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1920

Figure 1. The population of the cities of San Francisco and Los Angeles (U.S. Census Data). The population of Los Angles grew fourfold in the decade after the 1906 earthquake struck San Francisco (Los Angeles Resilience by Design Report, 2014).

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Wood-framed soft-story buildings and non-ductile concrete buildings are considered to have a high collapse potential during an earthquake, putting the occupants at great risk. The poor performance and loss of life in these existing building types during the 1971 San Fernando, 1989 Loma Prieta, and 1994 Northridge Earthquakes have confirmed their vulnerability.

The creation of the LA Mayor’s task groups to look at the threat of loss of life and impact on the economy from building failures in the aftermath of an earthquake afforded the local structural engineering community the opportunity to offer their technical advice on how to improve the performance of these buildings. An important distinction has to be made when participating in a task group such as the Earthquake Technical Task Force. As structural engineers, we can provide the professional technical expertise on how to help mitigate building failures during earthquakes and discuss associated risks associated with doing nothing. But this is where our advice typically needs to stop when working to develop a mandatory or voluntary seismic retrofit ordinance to be adopted by a local jurisdiction.

Besides the technical engineering aspects of any ordinance, there are also the economic, social, and political aspects that must be considered by the government jurisdictions. As engineers, we typically want to see hazard mitigation methods implemented as soon as possible.

Here is where we have to learn patience. Time frames for adoption and implementation of any seismic retrofit ordinance have to be left in the hands of the local government officials and staff to determine the amount of time it will take to get community buy-in regarding adopting such ordinances. As the costs increase for any mandated seismic retrofit, the time frame for compliance must also increase so as not to immediately impact building valuations, and building owners need time to strategize the best methods for mitigating the earthquake hazard given their particular property.

There will be occasions when the local jurisdictions decide not to move forward on adopting and implementing any mandatory seismic retrofit ordinances. This has been the case in Los Angeles for many years, since the 1994 Northridge Earthquake, with the City only able to adopt a voluntary seismic retrofit ordinance for several vulnerable building types.

In such cases, the only thing the structural engineering community can do is attempt to further educate the general public about the seismic risks and the necessity for adopting mandatory seismic retrofit ordinances.

Ultimately, the general public has to buy-in to implementing mandatory seismic retrofit ordinances, as elected government official’s work on behalf of their communities and cities. continued on next page

In the cases of the proposed wood-framed soft-story building ordinance and the nonductile concrete building ordinance, the Mayor’s office task groups did something different than had been done before while developing seismic retrofit ordinances. They engaged the stakeholders, including the apartment building and commercial office/retail/ manufacturing building owners, to understand their concerns and get their input regarding seismically retrofitting their buildings. These owners were specifically targeted since their buildings have high occupancy loads. This was a fundamental change in approach, as now the building owners were becoming part of the development process, instead of being typically placed in a reactionary position where they may be uninformed about the issues and have to respond to city mandates. Having all parties involved in the initial conversations has led to better developed ordinance language, with a greater chance of successful adoption.

The Mayor’s report also addresses adopting a voluntary rating system for estimating individual buildings’ earthquake performance.

The voluntary building rating system is designed to encourage building owners to invest in their existing facilities and to consider new construction that exceeds current minimum building code requirements. This will likely make their buildings able to be re-occupied and put back in use sooner after a major earthquake, and thereby help the overall community recover faster.

A building rating system informs the community about building risks such as earthquakes related hazards. It creates a system that evaluates new and existing buildings based on three separate dimensions: Life Safety, Damage (Repair Cost), and Recovery (Time to Regain Basic Function). A rating can be given for each dimension. The concept is to “encourage” building owners to design new buildings to a higher performance level or to perform seismic retrofit projects voluntarily. Strengthened facilities will be more desirable to the earthquakeaware public and their tenants than older buildings that are still vulnerable or new buildings that are not designed to higher performance standards.

An offshoot of such a rating system is that the community can have a better understanding of their building stock’s vulnerabilities to natural hazards such as earthquakes. This information allows the community to be able to formulate preparedness plans to help reduce the impact when the next earthquake occurs, and implement recovery plans after an event to help the community recover faster economically.

To encourage the residents of Los Angeles City to pursue voluntarily rating of their own buildings, the Mayor’s office is proposing to lead by example and is tentatively looking to have some city-owned buildings rated for earthquake performance. The city has consulted with the United States Resiliency Council (USRC) regarding how the city’s building department might proceed in rating city-owned buildings. More information about the USRC, building rating systems, and getting one’s building professionally rated can be found at (www.USRC.org).

moving forward towards better performing buildings and a more resilient community, we will be no better off than if we did nothing.

We can’t afford to do nothing.▪

Ordinance Status

Dilip Khatri, Ph.D., S.E., is the Principal of Khatri International Inc. located in Pasadena, California. He serves as a member of STRUCTURE’s Editorial Board and can be reached at dkhatri@aol.com.

The mayor’s office is currently working through the details of the ordinances identified in his report with the City Council, and has the goal to adopt and implement them into law before the end of this year. This program initially created quite a stir locally, putting structural engineers in the center of the discussion with owners, public officials, and the general public through extensive coverage by the Times and public town-hall meetings around the city. The ordinance adoption process by any jurisdiction can be lengthy, as the ordinances usually must pass through both economic and legal due-diligence reviews by a series of the jurisdiction’s own internal committees.

Preliminary drafts of the building seismic retrofit ordinances recommended in the Mayor’s Resilience by Design report were submitted to the Los Angeles City Council in January 2015. The ordinance requiring construction of new cellular communication towers to be designed for an importance factor of 1.5 passed rather quickly, and was adopted in March 2015. In September 2015, both the wood-framed soft-story building and nonductile concrete building ordinances were heard by the City Council and forwarded to the city attorney’s office for final review. It is anticipated the City Council will vote on the approved ordinance language from the city attorney’s office sometime in October.

SEAOSC has been actively involved with the mayor’s office and the Los Angeles City Building Department to provide support in developing the technical engineering recommendations for these seismic retrofit ordinances. The seismic retrofit ordinance compliance timelines, currently under consideration by the City Council for implementation, range from five years for wood-framed soft-story buildings to thirty years for non-ductile concrete buildings. It seems like a long time, but the big issue with earthquakes is that we simply do not know when the next “big one” will hit, and without

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Michael Cochran, S.E., SECB, is Vice President of Thornton Tomasetti in Marina del Rey, Califorinia. He is the SEAOC Past President, serves on the AISC – Prequalified Connection Review Panel and is a member of the Mayor’s Earthquake Technical Task Force for the City of Los Angeles. He can be reached at mcochran@thorntontomasetti.com.

Kevin O’Connell, S.E., is an Associate Principal with Simpson Gumpertz & Heger, Inc. in Los Angeles. He is the immediate past president of the Structural Engineers Association of Southern California and is a member of the Mayor’s Earthquake Technical Task Force for the City of Los Angeles. He can be reached at kdoconnell@sgh.com.

Douglas Thompson, S.E., is president of STB Structural Engineers, Inc. in Lake Forest and he a past president of the Structural Engineers Association of Southern California (SEAOSC). He has authored several articles and publications, including the light-frame design examples in the Seismic Design Manuals, the Guide to the Design of Diaphragms, Chords and Collectors and Four-story/Five-story Wood-frame Structure over Podium Slab. He was also a member of the Mayor’s Earthquake Technical Task Force for the City of Los Angeles. He can be reached at dougt@stbse.com.

City Council Update On October 9, 2015, the Los Angeles City Council adopted both the mandatory WoodFramed Soft-Story seismic retrofit and the mandatory Non-Ductile Concrete Building seismic retrofit ordinances. The Los Angeles City Department of Building and Safety now begins the task of implementing both of these ordinances, and notifying the building owners identified as owning either of these two types of buildings that they are required to comply with these mandatory ordinances.

It is likely that first notices will be sent out to the building owners towards the end of this year or the first few months in 2016.

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Project Delivery alternative approaches for getting from concept to completion

Working in the IPD Framework

By Jay Love, S.E., Panos Lampas and John Leuenberger, S.E.

Jay Love is the Structural Engineer of Record at Degenkolb Engineers. He can be reached at rjlove@degenkolb.com.

Panos Lampas is the Regional Program Manager at Sutter Health. He can be reached at lampsasp@sutterhealth.org.

John Leuenberger is Project Manager Site & Structure at HerreroBoldt. He can be reached at jleuenberger@herrero.com.

Figure 1. Site before demolition.

Sutter Health and Integrated Project Delivery Fifteen years ago, Sutter Health, a not-for-profit Northern California healthcare system with 24 acute care hospitals, decided that the traditional project delivery system was broken. Too often, projects ended badly for everyone, namely the owner, the construction team, and the design team. Between change orders, late projects, busted budgets, and litigation, there had to be a better way. Sutter started a journey to change the behavior of all the parties, itself included, by leading the way in the development of Integrated Project Delivery (IPD).

In 2004, Sutter Health formally announced this change in direction at a conference it hosted for its design and trade partners in the AEC community. Central to this launch were what came to be known as the Five Big Ideas, which act as the initial foundations of this new vision: 1) Optimize the Whole Project 2) Tightly Couple Learning with Action 3) A Project is a Network of Commitments 4) Increase the Relatedness of the Participants 5) Collaborate, Really Collaborate In 2006, in support of this new vision, Sutter created and implemented a brand new contract form called the Integrated Form of Agreement that binds multiple project partners together under a single contract, single business deal with a single set of objectives.

During the period 2007 to 2015, using this vision and this contract, Sutter delivered several

large hospital projects and multiple smaller clinic projects on time, on budget and most importantly, with no compromise to the clinical operational vision for these facilities. This was a total of $1.5 billion across fifteen separate projects. Currently, it has almost $3 billion in projects in progress using the same model of delivery. Much of this current investment is tied up in the single largest project in its history, the Van Ness & Geary Campus Hospital – and the subject of this article.

A primary component of the IPD approach is Lean Design and Construction, defined as “a production management-based approach to project delivery … that extends from the objectives of a lean production system – maximize value and minimize waste – and applies them in a new project delivery system.” The IPD project team strives to improve total project performance instead of reducing cost or increasing speed of any particular activity. (Lean Construction Institute: www.lean construction.org)

The Seismic Legislative Background As Sutter Health embarked on new ways to procure, design and construct healthcare projects, California was in the early stages of implementation of Senate Bill 1953, the seismic safety legislation for hospitals.. Immediately following the 1994 Northridge (M6.7) earthquake, older hospitals in the epicentral region were unable to provide acute care services. The SB 1953 legislation required all hospitals to be seismically

24 November 2015

with an additional 230,000 square feet of underground parking (Figure 2).

Assembling the Team

Figure 2. New hospital, looking southwest from Van Ness Avenue.

strengthened, replaced or taken out of acute care service in accordance with a series of milestone dates between 2008 and 2030. By 2030, the legislation requires all hospitals to be able to provide immediate services after an earthquake. With the need to replace older facilities on several of its affiliate campuses, and with a large construction outlay anticipated, the impetus for Sutter Health to implement IPD on these projects was paramount.

With seismic issues identified in its older buildings at all four Sutter Health California

Pacific Medical Center (Sutter CPMC) campuses in San Francisco, Sutter Health developed a $2 billion plan to consolidate a wide range of its services in a new hospital at Van Ness Avenue and Geary Boulevard.

This site, covering an entire city block of over 100,000 square feet, had an existing 1960s era hotel and office building (Figure 1). The Van Ness and Geary Campus (VNGC) hospital, currently under construction, will open in the 1st quarter of 2019 as an 800,000 square foot, 274-bed hospital housed over 12 floors

With its goal to implement its IPD approach at the Van Ness and Geary campus, Sutter invited two teams to present their qualifications. Boldt Construction, an early developer and practitioner of Lean Construction, headquartered in Wisconsin, joined with Herrero Builders, a long-time San Francisco general contractor, and the San Francisco office of SmithGroupJJR (SGJJR), an architectural firm with decades of experience in California hospital planning and design. HerreroBoldt, in turn, selected Rosendin Electric Inc., and Southland Industries to join the IPD team, while SmithGroupJJR selected Degenkolb Engineers (Structural), Ted Jacob Engineering Group (Mechanical/Plumbing), and Silverman & Light (Electrical), to compete for the project based on hospital construction experience, experience working together, quality of work, and, perhaps most importantly, a willingness to join Sutter Health in doing things differently to achieve a different, better outcome than before.

Once Sutter Health selected the HerreroBoldt team, Sutter Health brought their

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4/28/15 7:57 AM

Figure 3. Start of foundation construction with excavation shoring in place.

project management experts in IPD, together with the major construction team members and design professionals, to form the IPD environment. The Core Group, consisting of representatives from Sutter Health, SmithGroupJJR, HerreroBoldt and Pankow Builders, signed the Sutter Health Integrated Form of Agreement, a three-way contract in which stakeholders are involved early to define project targets and to deliver the best value for the client. The IPD team agreed it would provide a project to meet the Client’s target cost, or Estimated Maximum price (EMP). The IPD team built into the EMP the cost of the work, a contingency pool, and the Risk/Reward pool. Seventeen Risk/ Reward Members agreed to put 100% of their profit at risk in the Risk/Reward Pool and developed a contingency pool shared by the team, creating an environment that promotes collaboration to solve problems and implement cost-effective ideas. In this environment, any “fix” is funded from the contingency pool. By having their profits at risk, companies are energized to collaborate early on to avoid problems, even if that means crossing organizational boundaries to find solutions with partners in the team.

Each month, the Risk/Reward members meet to review the previous month’s financial billing report across the entire team. They track the actual cost of work versus the forecast cost of work and review changes to the forecast cost of work that affect the contingency pool available to cover such changes.

Additionally, each month the Risk/Reward members review the risks (increased costs), and the rewards (cost savings) identified. With

this monthly process involving all the Risk/ Reward members, everyone has an eye on the financial aspects on an ongoing basis. There should be no surprises building up behind the scenes.

Project Start The Sutter-HerreroBoldt-SGJJR IPD team started work in 2007 with a Validation Study phase to assess whether the program developed by CPMC could be designed and constructed with Sutter’s target budget. The entire team, design consultants side by side with the contractors, rapidly studied various options in each of the major disciplines, identifying the various tradeoffs in cost to achieve values for the owner.

Not too long after the HerreroBoldt-SGJJR team formed, one of its most important first tasks was the selection of the steel trade partner. The IPD team interviewed four steel fabricators and selected Herrick Steel to join the team. With all of the interviewed companies very experienced in steel construction, the primary differentiator in the selection was Herrick’s willingness to do things differently to achieve a better outcome.

Sutter Health has invested a large effort to make the VNGC project successful. The IPD team has created an environment to promote communication, collaboration, and learning, but how is IPD really different?

Starting with colocation in a downtown San Francisco office building, the IPD team members began the learning process to understand the interconnectedness of all the members and the benefits to working towards a common

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November 2015

goal of success, measured first by the success of the project. Colocation of the project team companies brought everyone together, but it has taken a continually evolving effort to make it successful. Because of the many specialty teams involved, the natural inclination is to “work in silos” even though everyone’s work directly impacts and influences the IPD team success in achieving the ultimate goal.

Thus, the project leaders were tasked with a big challenge of breaking this industry habit and opening the lines of communication.

“Having already completed a number of Sutter IPD projects, Herrick was extremely pleased to be again invited to the table early on the Van Ness and Geary project. One of the main differences this time around was the opportunity to begin our final design coordination and shop detailing activities more than six months earlier than usual. This allowed us to take two passes over the Tekla Structures model and shop drawings prior to going to fabrication. The majority of the work was completed on the first pass, with the second incorporating any last minute design or trade coordination packages. Between the two passes, we worked closely with Degenkolb and HerreroBoldt to prioritize Inquiries, Requests for Information (RFI’s), and Amended Construction Documents (ACD’s) to ensure these activities were closely tied to the structural steel fabrication schedule. This marked a shift in the standard Contractor / EOR / Fabrication relationship and behavior patterns. The end result was that all the fabrication packages were issued to the shop 100% complete and on time – something that is almost unheard of in the industry today.”

Wayne Morrison – Pre-Construction Manager – The Herrick Corporation A main venue of communication and coordination is accomplished through weekly “Big Room” meetings where all key project participants, including Sutter’s IPD project managers, meet and discuss design, construction, and schedule. Everyone has the opportunity to have his or her voice heard and to weigh in on decisions. The team utilizes vPlanner software, a Last Planner® System to produce predictable, continuous work flow in planning, design, and construction, to review the prior week’s work and to plan or re-plan future work. Daily check-in meetings, usually for only 15 minutes, supplement the Big Room meetings, engaging main system leaders to exchange the work in progress, identify constraints, and “swarm” items that need to be addressed in the short-term. continued on page 28

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Figure 4. Steel erection on-going.

have eliminated as many obstacles as possible before the work starts. Part of the process for small work batches is using easily definable displays that communicate flow and sequence with the entire team in a visual format for all to follow. “ Joe McKeown – Concrete Senior Superintendent – Pankow Builders Realizing information overload will likely happen when communicating with such a large team, the IPD team created special cluster groups to concentrate on their areas of expertise and filter necessary information to each other. The structural cluster team, primarily comprised of HerreroBoldt (GC), Degenkolb Engineers (structural engineer), The Herrick Corporation (structural steel contractor), and Pankow Builders (concrete contractor), was the first sub-group “out of the gate” to move from design completion into the construction

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Building Information Modeling, or BIM, provides the ultimate coordination, allows the team to ‘build’ the hospital in the virtual world before going to the site to build the real thing. All construction trades, architects, and engineers are required to design and model in BIM software, which allows for the creation of a centralized coordination model. The entire team can then observe each other’s work and adjust systems/components before they create real-world clashes.

“IPD is different because it breaks down the work into small batches, and details the work, workers and equipment required to complete the small batch of work (“level out the workflow”). When the team reviews the specific batch of work, the team includes all the people involved with the scopes of work, and details out their experiences to ensure we

phase. The other cluster groups included the Interiors Design, Exterior Design, and MEP Design Cluster Groups. Each of the cluster groups included members from both the design firms and the construction firms.

The primary structure received its approval and building permit from the California Office of Statewide Health and Planning Development (OSHPD) to start construction in May 2014. However, the design and preconstruction coordination by the other cluster groups continued over the next 14 months, creating a big challenge – approval of changes to the already-approved structural design documents that resulted from the ongoing design and coordination activities of the other cluster Groups. OSHPD must approve any material change to the permitted construction documents prior to construction. There is no “proceeding at risk” with unapproved construction documents.

Ongoing changes to the structural design required an extensive review and approval process with OHSPD. The Structural Engineer of Record, the Architect, and the Contractor meet weekly with OSHPD staff to present material changes for approval in order to maintain continuous work flow in the field.

“At the VNGC project, one of our earliest missions was to establish a culture with OSHPD that was different. The IPD team knew that, in order to be successful, we needed to form a partnership, not only amongst ourselves, but also with OSHPD so that we could align ourselves to complete the common goal of a providing a state of the art hospital. With complete backing from Sutter Health, the IPD team defined new electronic submittal and review processes, loaned new hardware and software to the OSHPD reviewers, and implemented training specifically tailored to their day-to-day needs to bridge the gap between a new electronic review process and the old paper review process. This added a collaborative, real-time approach with comments/ responses/and approval all occurring in the ethereal web-based cloud to make every issue transparent to all.”

Juan Restrepo, OSHPD & Commissioning Manager – HerreroBoldt

Preliminary Results and Lessons Learned The project is on schedule. Figure 3 (page 26) shows the site nearing the excavation completion at one end of the site with simultaneous construction of the STRUCTURE magazine

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November 2015

“The IPD culture is one combining old school tactics with new age technology. The IPD team is a continuous improvement environment with employees with 20 plus years engaging with young energetic engineers who take the knowledge of their managers and streamline it into a leaner, more productive solution. There is no single leader who makes all the decisions, but rather a group of peers educating each other and working together to make it the best project possible.”

Joe McKeown – Concrete Senior Superintendent – Pankow Builders

As the AEC industry goes through a fundamental transformation, Sutter Health and the IPD Team chose to embrace this change and to create a collaborative and innovative project team to design and build VNGC. Implementation of collaborative delivery process and BIM technologies offered a unique environment to AEC professionals and created a high performing team.∎

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Conclusions Sutter implemented the Integrated Project Delivery system to create a team environment amongst the owner, design consultants, and construction team. A target was set with open understanding of the team’s goals and requirements. As demonstrated in this article, this radical change requires constant effort to alter behaviors, try new techniques, and promote continual learning. Having the owner and all Risk/Reward Members in a collaborative environment is the key to the success of IPD; people that are willing to embrace the IPD environment while making sure not to lose sight of the design and construction methodologies that have worked in the past, but that can be improved upon and refined in the spirit of creating value and reducing project risk.

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foundations at the other end. Figure 4 shows the site, with steel and metal deck erection at the end of August 2015. At that time, the project was 30 percent complete, with a forecast to be 50% complete by the end of Q2 in 2016. The contingency fund has held very constant over the last six months, with 75% of the fund remaining. Construction is proceeding rapidly with concrete placements occurring up to four days each week.

Structural steel erection will be essentially complete by the end of 2015. The mechanical and plumbing trades are ramping up quickly with installation beginning at the bottom level, starting with preset embeds in the concrete decks to hand plumbing, ducts and electrical conduits.

With the model coordination that has been done to date, on-going construction has increased the team’s focus on coordination to an even higher level.

There is nothing like continuous concrete placement to convince people that the design is complete, and there can be no more changes. Based on Sutter Health’s experience on previous projects, the leadership has been direct and adamant that the IPD team will coordinate the design using the BIM models, the contractors will build to the coordinated BIM models, and the results will be checked using LIDAR to scan the as-built construction to compare to the BIM model. Coordination at the interfaces between interior and exterior construction has been the most challenging, because the interfaces involve so many disciplines.

Structural licenSure issues related to the regulation of structural engineering practice

A

t its 2015 Annual Meeting in August, the National Council of Examiners for Engineering and Surveying (NCEES) voted on Motion 1 submitted by the Advisory Committee on Council Activities (ACCA) (see www.structuremag.org/downloads/ NCEES_Committee_Report.pdf for the full text of the committee’s charge and rationale). If passed, Motion 1 would have ultimately modified the Model Law and Model Rules to limit both the use of the structural engineer title and the practice of structural engineering. The motion stated: Move that the Generic P.E. Licensure Plus Protected S.E. Title and Restricted S.E. Practice approach as defined under Charge 2 of the ACCA report be incorporated into the Model Law and Model Rules and that the appropriate committee or task force be charged to develop specific language for that purpose, including the Thresholds definition as described under Charge 2. Further, move that the language be presented to NCEES for approval before being charged to the UPLG Committee for final incorporation into the Model Law and Model Rules.

Unfortunately, after no debate whatsoever, the motion failed by a single vote. Debate did not take place because no one rose in opposition to the motion, which under the NCEES rules, prevented a need for a statement of support or rebuttal. Moreover, the overwhelming majority of the boards had already decided how to vote before the meeting started.

The failure of the motion was disappointing, but an understandable and even expected outcome.

Just the fact such a motion was presented is a victory for proponents of structural licensure.

Opposition within NCEES has been deep, persistent, and unabashed for many years. It was thus an accomplishment for the S.E. licensure movement to have a committee charged with the issue, and an even greater accomplishment for a committee composed of non-structural engineers and land surveyors to recognize that the threat to the public from unqualified practitioners is real and should be addressed by NCEES. NCEES is composed of members of 70 separate licensing boards representing all fifty states plus other United States jurisdictions. Of the 70 boards, 56 license engineers and 14 license surveyors. 31 boards voted in favor of Motion 1 and 32 opposed it; six boards abstained and one was absent. Three boards from states that currently recognize structural engineering to some degree opposed the motion. Of the 14 surveyor boards, eight opposed the proposal, one abstained, and five voted in the affirmative. Removing the

NCEES Votes on Structural Licensure and Engineering Education

By Marc S. Barter, P.E., S.E., SECB

Marc S. Barter is the president of Barter & Associates, Inc., a structural engineering consulting firm in Mobile, Alabama. He is a past president of NCSEA and chair of the Alabama Board of Licensure for Professional Engineers and Land Surveyors.

He can be reached at mbarter@barterse.com.

surveying boards from the voting, the measure would have passed, 26 to 24.

The primary opposition to structural licensure is from civil engineers and NSPE members. Despite the best efforts of ASCE to be supportive of the SEI position, many of ASCE’s members are opposed to any recognition of structural engineers or any restriction on the practice of structural engineering. By and large, the vote of each surveying board mirrored the vote of the engineering board from the same state. Where it did not, the engineering board abstained. The takeaway is to convince the engineering licensing boards of the need for structural licensing, and the surveying boards will likely follow their lead the next time such a measure is proposed.

Of particular interest, considering the surveying board votes, is the composition of the ACCA. Six of the eight members are licensed as surveyors, as is the president of NCEES. Based on this demographic, the lack of support from the surveying boards is not systemic of surveyors, but rather more of a “me too” approach.

Based on comments from the incoming NCEES president, Michael J. Conzett, in his acceptance speech following his induction as president, the matter is not dead and will be raised again in the future. This is good news in that board memberships are constantly changing, with older engineers leaving and (marginally) younger professionals replacing them. With this transition, this proposal (or a similar one) has a better chance for passage in the future.

ACCA Motion 8 is also of interest to the structural engineering community, because it dealt with engineering education (see www.structuremag.org/ downloads/NCEES_Committee_Report.pdf for the full text of the committee’s charge and rationale). This motion was pulled from the NCEES meeting’s consent agenda and voted on separately. The motion is as follows: Move that Position Statement 35 be adopted as follows: PS 35 Future Education Requirements for Engineering Licensure One of the goals of NCEES is to advance licensure standards for all professional engineers. Those standards describe the technical and professional competency needed to safeguard the health, safety, and welfare of the public. The Council recognizes that future demands for increasing technical and professional skills and the reduction that has occurred in the formal education requirements needed to obtain a bachelor’s degree in engineering from a program accredited by the Engineering Accreditation Commission of ABET (EAC/ABET) have resulted in the need for additional education beyond the bachelor’s degree for those entering the

30 November 2015

also watered down the proposition. Although less potent than the original Model Law provision, the position statement is an affirmation of what NCSEA’s Basic Education Committee has proposed for the last dozen years or more: the curriculum for a bachelor’s degree in civil engineering does not prepare the civil engineering graduate to practice structural engineering; more education is needed.

On balance, the NCEES meeting was good for issues that concern the structural engineering profession. ACCA Motion 1 failed, but in failing it provided proponents of structural licensure a roadmap for the future, as did the passing of the education position statement.

NCSEA’s Structural Licensure Committee learned which state boards are receptive to structural engineering licensure, and the NCSEA Basic Education committee received validation of their work for the last decade or more.

Structural engineers view their license as critical to their livelihoods. Many of the other disciplines view it more as a merit badge.

They never use their seal, their jobs are with industry or government, and they do not perform design or analysis whereby a professional credential is required. Additionally, many accepted jobs after college that required

a technical degree, but relied on extensive on-the-job training. Increased education requirements are not supported by these individuals to the extent that civil engineers – especially structural, geotechnical, and environmental engineers – support them.

The demographics of the attendees at NCEES meetings also play into the decision-making process. A significant number of NCEES members graduated when a BS degree required 145 semester hours or more of coursework, versus the current trend toward only 120 semester hours. They do not support, nor will they ever support, any change perceived to diminish the significance of the P.E. license. They also view education through a historically unadjusted viewport. Change does not come easy and is seldom embraced.

To them, and everyone concerned with structural licensing, both in favor and opposed, I say wait; time is on the side of the public’s best interest. After all, engineering licensure is about protection of the public, and its future can only be assured if it holds true to that purpose. Increased engineering education and structural licensure are changes that will demonstrate adherence to that purpose; the status quo does not.▪

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November 2014

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engineering profession. NCEES has identified several future pathways by which a candidate for licensure as a professional engineer might obtain the body of knowledge needed to meet these educational requirements, including the following: A. A bachelor’s degree in engineering from a program accredited by EAC/ABET and a master’s or earned doctoral degree in engineering in the same technical area from an institution that offers EAC/ABET accredited programs, or the equivalent.

B. A bachelor’s degree and a master’s degree in engineering from a program accredited by EAC/ABET. C. A bachelor’s degree from a program accredited by EAC/ABET that has a minimum of 150 semester credit hours, of which at least 115 semester credit hours are in mathematics, science, or engineering combined and at least 75 of these semester credit hours are in engineering.

D. A bachelor’s degree in engineering from a program accredited by EAC/ABET and at least 30 additional semester credit hours of upper-level undergraduate or graduate-level coursework in engineering on topics relevant to the practice of engineering (e.g., engineering-related science, mathematics, or professional practice topics such as business, communications, contract law, management, ethics, public policy, and quality control) from approved course providers (e.g., institutions that have EAC/ABETaccredited programs, or institutions or organizations accredited by an NCEESapproved accrediting body).

NCEES will continue to explore alternative educational pathways for candidates for licensure as professional engineers to develop the body of knowledge needed for entry into the profession. These alternatives will be developed through collaboration with technical engineering societies and other stakeholders engaged with the engineering profession.

Position Statement 35 was proposed after last year’s vote by NCEES membership removing Model Law language requiring a master’s degree for engineering licensure starting in 2020. Removal of the Model Law language was in response to the fact that very few (if any) boards were proposing legislative changes accordingly.

Position Statement 35 passed, but only after an amendment was defeated that removed language regarding ABET that

InSIghtS new trends, new techniques and current industry issues

An engineer’s stamp, or seal, is a symbol of professional pride and accomplishment. It signifies that the engineer has attained a level of education, competence, and experience so that he or she may be relied upon by private and public clients to prepare a set of plans and specifications that conform to the standard of care in the engineer’s area of practice. But does the mere act of stamping a set of plans create any additional liability concerns for the engineer?

Not long ago, an opposing attorney argued to me that my client, a structural engineer, was legally liable for a design-related claim – regardless of the standard of care – simply because “he stamped the plans.” He suggested that the mere act of stamping a set of plans carries with it some form of express warranty tantamount to strict liability. While I’d never heard such a claim before, this led me to question whether my client’s compliance with the standard of care would be sufficient, as it usually is, or if I had a broader concern simply because my client had stamped the drawings in question.

I was relieved, but not surprised, that in my state I found no case law supporting the attorney’s position – nor did I find any authority actually addressing the subject. A design professional’s potential liability typically is measured against the applicable standard of care, and if my opponent had an alternative liability theory it surely would be his burden to back it up with some legal authority.

In my jurisdiction, there was nothing of the sort.

In fact, the only reported case that touched on the use of a design professional’s stamp was a disciplinary proceeding against an architect for sealing plans that had not been prepared either by himself or by his subordinates.

But, my curiosity having been piqued, I looked at other jurisdictions. Though my survey was limited to higher level court cases, I was pleased to find that even if my adversary reaches outside the boundaries of our state, he is not likely to find support for his liability theory unless it is based on the engineer’s contract terms or the commonly asserted breach of the duty of professional care.

For example, in a non-published Sixth Circuit opinion, Conopoco, Inc. v. Allen & Hoshall, Inc., 129 Fed. Appx. 131 (6th Cir. 2005), the architect had affixed his seal to plans that ultimately included a floor design by another design professional. The architect specifically had disavowed knowledge of the special nature of this particular floor design. The plaintiff claimed “that because the plans were issued under seal, any defects in them are professional negligence even if [the architect] was not contractually responsible.” 128 Fed. Appx. at 145. The court flatly disagreed. “[T]here is no basis for the claim that issuing

Beware the Stamp?

By Jim Peloquin, Esq.

Jim Peloquin is a partner at the Boston law firm of Conn Kavanaugh Rosenthal Peisch & Ford, LLP. For over 30 years, Jim has specialized in the construction litigation arena representing all actors, including design professionals, owners, and contractors. He can be reached at JPeloquin@ConnKavanaugh.com.

plans under seal creates liability for professional negligence. [The plaintiff] cites no authority for the proposition that tort liability can result from … any placement of a seal whatsoever … There is nothing in the language of the statute or case law to support the idea that misapplication of a seal can create an additional professional duty apart from contract.” Id. The Conopoco court left no room for misunderstanding: Stamping a set of drawings does not create an independent basis for liability separate and apart from the usual contract and tort claims.

Other jurisdictions were consistent. See McConnell v. Servinsky Engineering, PLLC, 22 F. Supp. 3d 610, 616 (2014). “The plaintiff argues that [the engineer] assumed legal duties beyond the contract by affixing his professional engineering seal to the foundation plans. However, there is no support under [applicable] law for the argument that an engineering seal creates an independent tort duty …”

If confronted with this contention in your professional design practice, your attorney will have to scour the law in your jurisdiction to satisfy himself that there are no peculiar statutes, regulations, or cases that say otherwise. When I surveyed the question of independent stamp-related liability, it appeared that engineers and other design professionals most often encounter trouble in this area when stamping plans prepared by others who were not under their immediate supervision or control. This action is typically a violation of state-enacted licensure regulations, and a pitfall that has become increasingly problematic in an age of computer-aided design technology and pre-engineered building components.

Needless to say, all registered professionals need to be intimate with the dos and don’ts of plan stamping in their particular jurisdictions. But, assuming you comply with those, and you otherwise have exercised professional competence in accordance with the standard of care in your field and geographic area, the good news is that you shouldn’t be concerned about an independent basis for strict liability arising from the mere use of your hard-earned professional stamp.▪

32 November 2015

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BRBFs in NYC

Fugettaboutit!

West Coast Seismic System Invades NYC

By A. Christopher Cerino, P.E., SECB, Michael Rogatsky, P.E. and Tim Nordstrom, P.E., S.E. Rendering of Adult Behavioral Healthcare Facility.

T

he New York State Office of Mental Health (OMH), in association with the Dormitory Authority of the State of New York (DASNY), is implementing a major modernization program for the Bronx Psychiatric Center, including a new 180,000 square feet, 156-bed, Adult Behavioral Healthcare facility.

The amorphously-shaped five-story building creates a supportive and humane environment for both consumers and providers while maximizing natural light, emphasizing the connection with the outside environment and improving spatial orientation. The Adult Behavioral Health Center will be the first new adult inpatient facility in New York State in nearly two decades.

While many New York City skyscrapers benefit from the support of billion year-old 60+ tsf (tons per square foot) Manhattan Schist, other sites contend with fill and deep organic layers, saddling low-rise structures with amplified seismic design forces. Located in the Westchester Square section of the Bronx, the site was originally a wetland through which the Westchester Creek flowed. The facility sits on 4 million cubic yards of fill materials generated from the construction of the Cross Bronx Expressway. The fill was placed over salt marsh deposits and river alluvium overlying Pleistocene glacial and glaciofluvial sediments. While a bedrock bearing surface was found an average of 58-feet below grade, the presence of up to 15 feet of very soft, highly compressible, organic silt and clay with peat resulted in a Site Class F categorization. The site-specific ground motion analysis performed in SHAKE 2000 yielded acceleration parameters of SDS = 0.80g and SD1 = 0.17g – resulting in building Seismic Design Category D. With no practical height limitations, structural steel was selected for the superstructure to minimize the gravity load on the 63-ton, 12-inch diameter concrete filled pipe piles, and a special concentric braced frame lateral system was developed. As the non-linear time history design progressed, even with a seismic response coefficient of 6, the frame members and associated foundation elements were enormous for a low-rise building, creating many space-planning challenges where walls needed to expand and bump out around elements. With design collaboration across STV offices, structural engineers in Los Angeles suggested using a buckling restrained braced frame (BRBF) system to enhance performance, reduce member size, and reduce cost.

STRUCTURE magazine

Historic map showing Westchester Creek in the site.

Now widely used in high seismic zones, BRBFs are codified and a performance leader among post-Northridge systems. BRBFs do not exhibit the unfavorable buckling characteristics of conventional braces and have a full, balanced, hysteretic behavior, with compression-yielding similar to tension-yielding. This performance is achieved by decoupling the stress resisting and flexural buckling resisting aspects of the compression strength. The primary brace component is actually a simple steel plate, called the core; with its size calculated based on required tension area.

The core is then surrounded by a steel tube, filled with concrete, and capped on each end so that it exists unbonded in the end elongation zones. Because the steel core is restrained from buckling, it develops nearly uniform axial strains across the section resulting in efficient energy dissipation. In addition, the near balance between tension and compression capacities greatly reduces the brace connections since they are sized based on the expected yield capacity of the member that is not controlled due to a buckling limit state. With an enhanced seismic response coefficient (R=8), better overall performance, reduced member sizes, and smaller, easier connections, estimated structural system savings are on the order of $2.40 per gross square foot for a representative 6-story building with a Special Concentric Braced Frame (SCBF) [cost

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November 2015

Wildcat braces installed.

savings data acquired from a study presented at American Institute of Steel Construction’s (AISC 2007 NASCC Steel Conference).

While the overall project benefits seem obvious, there were still two major hurdles to overcome for this project – introduction of a new system to East Coast steel erectors and use of a proprietary component in a state funded project. STV’s LA office worked with Star Seismic to develop a schematic BRBF layout for the new Adult Facility and findings were presented to DASNY and LiRo, the construction manager. The presentation described the system components and outlined how the BRBF’s would reduce architectural and service interference with slender elements and smaller gusset plates, and also reduce erection time with single pin connections. With the BRB system, no stiffener plates are required due to its patented collar and there is a significant reduction in welding since only simple fillets are required. Erection is fast and simple since each element has a tolerance of +/- 2 inches. However, what quickly won over the audience was the estimated $500,000 in material savings alone for the combined superstructure and foundation.

LiRo used the presentation and contacted several steel erectors, confirming that the only hurdle for an East Coast project location would be the shipping time for the brace elements coming from Star Seismic’s facility in Utah. In addition, LiRo explored the other two companies that manufacture similar bracing systems, getting project-specific quotes for comparison. After analyzing the pros and cons of each system, STV and LiRo recommended to DASNY that the proprietary Star Seismic Wildcat system be specified exclusively for this project to gain the time benefits of including Star Seismic as a design team member, since the costing due diligence exercise was performed. DASNY agreed and prepared a project specific waiver that allowed this proprietary system to be included as a component of the competitively bid structural steel package.

An additional benefit to the project that was not originally realized was the inherent submittal expedition that naturally occurs with the interrelated design. Most of the design and coordination effort between STV and Star Seismic happened prior to contract award; therefore, Star Seismic was able to produce shop drawings and calculations in only two weeks after award. With the submittal approval, braces were manufactured and delivered to the job site within six weeks.

The Adult Behavioral Health Center is the first building in New York City, and the entire Northeast, to use the Wildcat buckling restrained braced frame (BRBF) with moment resisting beam-column connections as a lateral system. The project challenges were overcome thanks to the collaborative spirit encouraged by the owner, the designers and STRUCTURE magazine

Buckling restrained brace cross-section.

the contractors, all of whom began cooperating early in the design phase and continued to do so throughout construction. Completion of the LEED Silver facility is on target for the fall of 2015.▪

35

A. Christopher Cerino is the Structural Engineering Director at STV, Incorporated in the firm’s New York office. Christopher has overseen the design of various educational facilities, hotels, transit structures, and residential high-rise towers. He can be reached at chris.cerino@stvinc.com.

Michael Rogatsky is a Senior Structural Engineer at STV, Incorporated providing condition assessments, structural analyses, design, and construction oversight for a variety of transportation, education, and industrial facilities. He can be reached at michael.rogatsky@stvinc.com.

Tim Nordstrom is a Senior Structural Engineer at Star Seismic.

Tim has been involved with numerous new and retrofit projects in the U.S., Canada and New Zealand. In addition, he is currently working on the research and development of the next generation of BRBs. He can be reached at timn@starseismic.net.

Project team Owner: New York State Office of Mental Health (OMH); Dormitory Authority of the State of New York (DASNY) Structural Engineer, Architect, Geotechnical Engineer: STV Incorporated, New York / Los Angeles General Contractor: ARC Electrical & Mechanical Contractors Corp.

Steel Fabricator, Detailer and Erector: Orange County Ironworks (OCI) (AISC Member) Construction Manager: The LiRo Group November 2015

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A COLD-FORMED STEEL GYM Figure 1. A regular grid of HSS columns surround the main gym and auxiliary spaces.

SIMPLE AND ECONOMICAL

By Matthew L. Mlakar, S.E.

T

he Language Academy of Sacramento elementary school wanted a small gymnasium with a modest price tag. To achieve that goal, the design team took inspiration from two very different types of optimized designs: typical residential construction and pre-engineered metal buildings.

Overall Design Single-family houses often use identical trusses for roof framing, which allow for low fabrication and installation costs, and can, through the use of gable end trusses, provide identical top plate heights throughout the building, and avoid excessively long studs in the gable walls. A pre-engineered metal building (PEMB) is inexpensive partly because of its optimized use of metal deck and cold-formed steel members, its strategic limited use of the more expensive hot-rolled steel, and its modularity. The designers of the Language Academy gym decided to merge these systems. The main portion of the gym would have a metal deck installed on top of a cold-formed steel truss roof system.

The cold-formed steel stud walls would be laterally braced by flat-strap steel “X” braces and finished with steel panels.

The design team laid out a twelve-foot grid of HSS columns in the walls (Figure 1) to optimize the metal deck and make fabrication of the walls, X-bracing gusset plates, and trusses repetitive (Figure 2) and, therefore, economical. This grid was repeated in the gym’s auxiliary spaces – such as the coaches’ office, storage room, and toilet rooms.

Cold-formed steel box beams were used in the roof framing over the auxiliary spaces which provided economy in the construction of the roof and walls. Gable end trusses were incorporated in the design to allow for identical column heights throughout the main gym and keep the wall stud depths to a minimum (Figure 3). These design choices allowed: • the main roof to have only one truss design, • the main gym’s wall studs to all be the same length, and • quick erection.

Like a PEMB, the structural engineer used hot-rolled steel strategically but sparingly. Th e trusses sit on hot-rolled square hollow structural section (HSS) columns that also serve as the “holdown posts” for the cold-formed steel flat-strap lateral bracing system. The dual functions STRUCTURE magazine

Figure 2. The HSS columns support the cold-formed steel trusses and are the “holdown” posts for the cold-formed X-bracing.

Figure 3. Gable end trusses keep the wall stud depths to a minimum. Courtesy of Yaroslav Derdyk, Broward Builders, Inc.

37

November 2015

Figure 4. Profiled steel panels provide an attractive and economical exterior finish.

of the HSS columns created a very simple system with simple steel detailing, anchor bolt layout, and erection. The only hot-rolled steel beam inside the building supports an operable wall.

A small California gym would often have stucco as the exterior finish. However, the design team selected profiled steel panels as the exterior finish (Figure 4). This allowed for: • a lower-cost finish, • less stringent out-of-plane wall deflection requirements, permitting shallow wall studs to be spaced 24 inches on-center in most of the building, and • less seismic mass for the building’s lateral system to support.

Flat-strap Bracing Design

While designing flat-strap braces is not difficult, the author has found the Cold Formed Steel Engineer’s Institute (CFSEI) Technical Note L001-09, Design of Diagonal Strap Bracing Lateral Resisting Systems for the 2006 IBC helpful. It not only provides a clear, concise explanation of flat-strap bracing design, but it also has useful diagrams and a design example.

The process of designing the braces was very simple. The key to brace design was to make sure the brace was strong enough to resist the design forces, but small enough to be the “fuse” in the lateral design, much like special concentric brace frames.

The CFSEI Tech Note example uses metal studs for the compresTruss Design sion/holdown posts, but the project structural engineer chose to use The architect’s vision included exposed trusses with closed rectangular the HSS columns for this purpose (Figure 3). Advantages of this cross-sections in the main gym space (Figure 5). The engineer selected decision were: cold-formed steel box sections for all the truss chords and webs. These • the compression/holdown posts had plenty of compression chords consisted of two 1200S C-stud sections “boxed-in” by two capacity even though the walls were over 20 feet tall, 600T tracks. The webs consisted of two 600S C-studs boxed-in by • design lateral uplift at the “holdown posts” was resisted by two 400T tracks. The C-stud sections were designed to resist benddead load from the trusses, and ing and axial loads without the benefit of the tracks’ cross-sectional • the horizontal component and torsional eccentricity of the properties. This was done to avoid the labor cost of installing enough design brace force were easily designed to be transmitted to the screws to allow adequate shear flow between the C-studs and tracks. foundation through the gusset plate, HSS column, base plate, Roof box beams over the auxiliary spaces were designed similarly. and anchor bolts.

The truss top chords were designed to be continuous past the wall to support the eaves and create a look similar to a wood-framed Looking back building’s rafter tails. To achieve this, the trusses were designed as top-chord bearing. While this made the eaves’ structural detailing Designed in 2012 under the 2010 California Building Code, the simple, it required the top chord to be designed as a composite sec- Language Academy’s gym design was approved by the California tion, including both the 1200S C-studs and 600T tracks to resist a Division of the State Architect (DSA) in May of 2013, and was significant flexural moment at the heel joint. This resulted in very part of a larger campus modernization project built in 2014 and close screw spacing at the heel joint (one-and-a-half inches on-center) 2015. A few notes looking back on the design and construction between the tracks and the studs. of the gym: STRUCTURE magazine

38

November 2015

• The system of HSS columns, cold-formed trusses, metal deck, Figure 5. The cold-formed steel trusses and metal deck are part of the finished interior look. and metal studs made for a very clean job-site, requiring little staging space on this compact existing school site.

Project Team • Conduit and plumbing installation was very clean with the use of the metal stud “punch-outs.”

Structural Engineer: Barrish Pelham & Associates, • Dry rot, mold, and termites will obviously not be problems in Sacramento, CA the framing or exterior finishes.

Owners: Language Academy of Sacramento (K-8 charter • The Steel Stud Manufacturer’s Association catalog’s lowerschool) & Sacramento City Unified School District bound screw shear values were used for the design of the truss Architect: Rainforth Grau Architects, Sacramento, CA connections. However, for future projects, the author will Contractor: Broward Builders, Woodland, CA likely select a specific manufacturer with higher shear values and reduce the number of required screws.

• The design team considered proprietary pre-fabricated coldMatthew L. Mlakar, S.E., is an Associate at Barrish Pelham & formed steel trusses during schematic design, but decided Associates in Sacramento, CA. He can be reached at against using them because they did not have the desired mmlakar@barrish.com. aesthetic and because of concerns regarding DSA inspection requirements.

• Each of the box-section trusses took about 80 man-hours to fabricate, according to project SUPPORTING superintendent Hans Anderson.

Mr. Anderson suggested investigating the cost of using IN ARCHITECTURE HSS trusses for future gyms. This may be less expensive, provide the benefit of the trusses being fabricated in a shop, and accelerate construction.

• Mr. Anderson noted that before the insulation and finishes were Seattle Pasadena applied, the building “would talk Tacoma Irvine to you” as the steel expanded and Lacey San Diego contracted. A few screw heads Portland Boise Eugene Phoenix in the truss sheared off, and the Sacramento St. Louis screws had to be replaced due San Francisco Chicago to the day-night temperature Los Angeles New York Long Beach fluctuations.

Combining PEMB and typical residential construction design concepts provided a practical alternative to conventional framKPFF is an ing. The design team’s decision to utilize Equal Opportunity a modular design, with steel’s inherent Employer. strength and durability, delivered a gym www.kpff.com with a competitive initial Center for Math & Science at Los Angeles cost and minimized mainteMission College East Campus, nance costs for the Language Los Angeles, CA Academy of Sacramento.▪

INNOVATION

39

November 2015

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STRUCTURE magazine

A Systems App

By Steve Fark as

, M.B.A. and

roach for Struc

tural Framing

Georgi Hall, P. E

., M.S.C.E.

Figure 1.

C

old-Formed Steel Framing (CFSF) offers incredible flexibility, design creativity, and efficient and effective construction technologies when comparing options for use in design and construction of commercial, institutional, residential, and thematic/entertainment structures. Combined with the time-tested reliability of hot-dipped galvanized steel in framing systems, architects and engineers can feel confident that CFSF designs are valid choices when it comes to strength, stability, and cost effectiveness. With high-recycled steel content and dimensional stability, standard CFSF products, i.e. C-shaped studs/joists and tracks, are usually popular for commercial or residential framing conditions.

Beyond the known benefits of CFSF systems, designers often ask what options are available that are not only efficient and effective, but also increase the overall strength of a structure while reducing the most expensive component of new construction – labor?

From a manufacturer’s standpoint, the answer begins with a systemic approach to developing CFSF products. These products, as simple as they are in configurations, thicknesses, tensile/yield strength, and protective hot-dipped galvanized coatings, can provide a synergistic solution to accommodate typical framing applications. For example, a C-shaped member can be used in a typical floor condition as a horizontally placed joist with a top of wall box-rim distribution track.

Joined with structurally approved connectors at the ends, these floors perform very well in both residential and commercial applications.

Several options for sub-flooring are available due to the increased availability of fasteners specifically designed for CFSF members, some of which are concrete-based products. However, is a direct trade-off between a steel floor joist for a wood floor joist the best we can do STRUCTURE magazine

as manufacturers? The answer is NO, because the ability for manufacturers to offer CFSF members and components that can fit into a “system” are readily available. The key component to developing these products, however, is the substantial amount of research, testing, and evaluation needed to develop CFSF products and systems that do what they are intended to do: Satisfy the engineering and design communities’ needs, offer assemblies that are fire or sound rated, provide contractors with products that reduce installation time and costs, and meet current building codes. This solution – the systems approach to CFSF framing- has been around for some time and is readily available now!

An example of the use of a systems approach to a CFSF framing solution is the recently completed 158 bed, 107,000 square foot, Plaza at Pearl City Assisted Living Facility in Pearl City, Hawaii (Figure 1). The structure is five floors, primarily supported by CFSF load bearing walls, with some hot-rolled steel framing at lower levels to transfer the bearing wall loads and provide more open areas for activities. Designed by Wattenbarger Architects out of Bellevue, WA, and engineered by Steven Baldridge of BASE (Baldridge & Associates Structural Engineering) in Honolulu, HI, this assisted living facility brings together both hot-rolled members and cold-formed steel framing components to create a systems solution. Responsible for the delivery of these products and others was G.W. Killebrew-A.M.S., the Honolulu branch of Allied Building Services.

Starting with the floor framing (Figure 2), 12-inch deep cold-formed steel joists of varying thicknesses were used as the framing components supported on box-rim track (Figure 3). USG Structural Panels, when fastened to the joists, provided the horizontal load path, or floor

40

November 2015

Figure 3.

Figure 2.

Figure 4.

diaphragm action. USG Structural Panels offered the code required fire rated floor assembly. USG Structural Panels have a similar fire resistance as poured-in-place concrete subfloors, but are much lighter and faster to install. Combining the steel floor joist system with the USG Structural Panels allowed the builder to reduce the dead-load of the structure when compared to a more traditional floor system, yet maintain the non-combustible classification up to the roof line.

Sure-Board® wall panels were used as wall sheathing to provide lateral shear resistance for the five-story cold-formed steel wall framing assemblies. The Sure-Board composite panels for this specific project were made using 22 ga. thick hot-dipped galvanized steel sheet laminated to FIBEROCK® Aqua-Tough™ panels. The wall panels were an ideal solution for the interior wall application due to their resistance to abuse, moisture intrusion, mold, and fire.

The Simpson ATS Anchor Tiedown System was the perfect solution for anchoring the CFSF system to the foundations. The easy-to-install, high-capacity anchor restraint system provided flexibility for the design team as they considered options for the structural framing.

Each of the products created a synergist system that, when used in the construction of this project, allowed Group Builders of Honolulu the ability and confidence to meet a demanding construction schedule.

Group Builders, with its experience and expertise in load-bearing midrise construction, pre-fabricated the wall panels off site to maintain the highest quality and ensure accuracy and proper fit-up on the site.

Stringent tolerances were a must for this project due to the need to match the poured-in-place concrete shafts, and to incorporate the structural steel members (Figure 4) that were used in select areas within the building. Panelization, the key to the systems approach

for structural framing in a CFSF system, offered a high level of quality control to meet the required tolerances and project schedule.

Panelization also helped expedite erection (Figure 3) and aided in the ability to deliver the completed project to the client on time and within budget.

MW Group, the project’s developer, selected a load-bearing CFSF structure for the fourth of its Plaza Assisted Living facilities on Oahu, which was completed in September of 2014 for approximately $46 million. This was the first time such a system was used by MW for a Plaza structure. In May of 2015, this project was honored with a 2015 ColdFormed Steel Engineers Institute (CFSEI) Design Excellence Award.

Due to the ever-increasing demands upon the architectural and engineering communities to provide owners and developers with more efficient and effective designs, cold-formed steel framing products and systems continue to be more and more popular as true solutions. As CFSF research and development continues, they will create opportunities for manufacturers and structural engineers to come up with solutions that are cost effective, allow flexibility, and meet the constant demand for quality products approved for use by the building code officials.▪

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Steve Farkas is the Corporate Marketing Manager for California Expanded Metal Products, Co., dba CEMCO. Steve can be reached at sfarkas@cemcosteel.com.

Georgi Hall is the Director of Engineering for California Expanded Metal Products, Co. dba CEMCO. Georgi can be reached at ghall@cemcosteel.com.

November 2015

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Historic structures Delaware Bridge Company winning design.

T

significant structures of the past

he East River separating Manhattan Island from Long Island was long a barrier for people and goods traveling into and out of what was called New York City. Manhattan Island was formed by the East River, on the east, the Harlem River on the North, and the Hudson River, frequently called the North River, on the west. The East River is more like a strait connecting Long Island Sound with New York Harbor. Near the junction of the Harlem River, Long Island Sound and the East River is a zone of erratic currents called Hell Gate. Below Hell Gate, the river is variable in width, being only 1,300 feet between 86th street in Manhattan and Astoria on Long Island; 3,000 feet from 42nd Street to Hunter’s Point; 3,500 feet from 19th Street to Green Point, below which it narrows down to 1,700 feet as it flows southwest from the area of the United States Naval Yard to the Fulton Ferry opposite City Hall in Manhattan. However, from about 85th Street to 50th Street, Blackwell’s Island divides the river into two channels with widths of approximately 1,000 feet and 800 feet. As early as 1804, a proposal was made by Benjamin Latrobe to build a multiple span masonry bridge at this site. In 1837, R. Graves proposed a three span suspension bridge (four towers plus two side spans) bridge and in 1847 and 1856 John A. Roebling also proposed suspension bridges. The idea of spanning Blackwell’s Island with a cantilever bridge started with a design by William P. Trowbridge in 1868 that was updated in 1873. Nothing, however, ever got past the proposal stage until 1876 when a large design competition was held that resulted in 11 designs, some of which were cantilevers. The winner of the competition was Charles Macdonald and the Delaware Bridge Company with a cantilever.

The bridge company, however, chose to build a suspension design by the Phoenix Bridge Company, but work never started on the project. In 1887, C. C. Schneider, the designer of the Niagara Cantilever (STRUCTURE, January 2011) had a design approved and actually started constructing a pier but ran out of funding. Another cantilever was proposed in 1894 by Charles Jacobs, but, after working on two piers, he also ran out of money.

In 1898, the City got into the act and wanted a vehicular bridge rather than a railroad bridge.

It turned the design over to the City Bridge Department under John Shea, who was Commissioner of Bridges for the city, Samuel R. Probasco, Chief Engineer, and Richard S. Buck as Chief Engineer in charge. The City already had the Brooklyn Bridge completed and the Manhattan and Williamsburg Bridge under design or construction, and was now looking for a bridge north of the Williamsburg Bridge at Blackwell’s Island. The design, primarily by Buck, was for a cantilever.

It consisted of two cantilever spans with an anchor span on Blackwell’s Island, as well as anchor span on the Manhattan and Queens sides of the river. After construction started on the piers, Gustav Lindenthal was named Commissioner of Bridges and he made significant changes to the design.

It appeared to be quite similar to Buck’s design, but he removed the curved top chord of the island anchor span and completely eliminated the suspended spans. The top chords of the cantilevers were made up of massive nickel steel links and came to a

Queensboro Cantilever Bridge

Richard S. Buck design.

Lindenthal’s design.

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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.

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

Panel of Engineers Deck Structure.

Revised deck layout by Nichols/Buck.

Lindenthal’s Plan 1903.

point at mid span, thus removing any suggestion that it was a suspension bridge. He also modified the deck structure, narrowing it significantly.

Buck and his mentor Leffert L. Buck, who was building the Williamsburg Bridge, objected, resulting in a special panel being formed to review both designs. The panel consisted of William H. Burr, Charles Hodge and Palmer C. Ricketts, all of whom were RPI graduates as were the two Bucks and O. F. Nichols of the bridge department. The panel decided by a vote of 2 to 1 that if they had to make a choice, the Buck plan was the preferred plan. They went beyond their charge; however, and suggested a different deck layout that Mayor Low adopted while keeping the Lindenthal structure.

Lindenthal was very unhappy, but his trussing system was retained for cantilevers with no suspended span. His bridge was determinant under dead load, but indeterminate and continuous under live load.

Bids were called for on September 24, 1903, but only one bid was submitted. Lindenthal changed the specifications and went out to bid a second time, but only two bids were received, and both were well over the estimate.

Lindenthal awarded the contract to the high bidder, the Pennsylvania Steel Company, on the advice of the Corporation Counsel, even though an injunction was in place prohibiting him from awarding the contract.

Mayor Seth Low lost the next election, and Lindenthal was removed as Bridge Commissioner at the end of 1903 after a tumultuous two years in office fighting with the Buck team. He was replaced by a new team, much like the old, consisting of George Best as Commissioner, Mr. O. F. Nichols, Chief Engineer and R. S. Buck, consulting engineer with Leffert Buck also as consulting engineer. The new team made major changes to the bridge. Lindenthal fought the changes publically in the press and journals, even though he was out of office.

The foundation work was completed in June, 1904. The superstructure had the shore anchor spans and the main anchor truss on Blackwell’s Island built on steel falsework.

The cantilever arms were built out from the island following standard cantilever practice.

They were the longest cantilever arms built in America at the time. After the erection of portions of the bridge built on the island falsework, the cantilevers from the island towards the shores were cantilevered out to mid-span. The travelers were then taken down

and re-erected at the ends of the bridge for the construction of the anchor spans. The last step was to continue the cantilever arms from the river bank piers to the middle of each channel of the river, where they would be connected to the previously erected cantilevers from Blackwell’s Island.

By the end of December 1907, the 1,713foot long continuous truss over Blackwell’s Island was complete. The long river span consisted of two 591-foot cantilever arms over the westerly channel and the short river span of two 492-foot cantilever arms over the easterly channel. The shore anchor arms were completed in the early part of 1908, and the cantilevers over each channel were connected on March 12 and 18, 1908. The span lengths from Manhattan easterly were, 469.5, 1182, 630, 984 and 459 feet. The 1,182-foot cantilever span exceeded the Wabash Bridge over the Monongahela River at Pittsburgh, the longest since 1904, by 360 feet and was not exceeded until the Quebec Bridge opened in 1917 with its 1,800-foot span. An example of the “bigness” of the bridge was a 16-inch diameter, 10-foot long Nickel Steel pin that weighed 3½ tons. The heaviest prefabricated piece weighed 120 tons and was in the lower chord. This was the only United States example of a cantilever bridge built without a suspended span. Many engineers were very critical of Lindenthal’s design and expressed themselves in the journals of the day.

Unfortunately, the Quebec Cantilever Bridge collapsed while under construction on August 29, 1907, raising concerns about the safety of the Queensboro Bridge. Panels of experts were called in again, and they issued reports along with a lengthy report by the Pennsylvania Steel Company. One report was by William H. Burr

Queensboro Bridge looking to top of tower showing Links, Pinnacle, etc.

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November 2015

Queensboro Bridge December 1907.

and a second by Alfred P. Boller and Henry Hodge. The Pennsylvania Steel Company retained Charles Macdonald, C. C. Schneider, H. R. Leonard and J. E. Greiner to review a report by F. C. Kunz. The reports varied widely in their findings. The city now had distinctly different professional opinions given by leaders within the bridge building community. All findings of the experts were correct, based on their assumptions. The question to be answered was which assumptions were appropriate for this case. Burr, Boller and Hodge had determined the highest possible live load and placed it in the worst possible location. The other board asked themselves whether that was a realistic loading situation or was it “the placing of impossible loads in an impossible manner.” The bridge department, and the city, decided to keep two

Ed Koch Queensboro Bridge. Courtesy of HAER.

of the four tracks on the upper deck and to lighten the pavement. They accepted Burr’s recommendation that two elevated rail lines (the same recommendation as the Pennsylvania Bridge Companies experts) would not overload the bridge and that no additional loads be placed on the upper deck without a reduction in weight elsewhere on the bridge.

With this last hurdle out of the way, the Pennsylvania Steel Company finished its work on the bridge. It opened on March 30, 1909.

The approaches were finished about the same

time and on June 12, 1909, the bridge was formally opened, 105 years after the first proposal by Benjamin Latrobe. It remained the longest cantilever bridge until the opening of the Quebec Bridge in 1917. The bridge continues to serve after a recent major rehabilitation. In 2009, the America Society of Civil Engineers named it a National Historic Civil Engineering Landmark. The bridge was renamed in honor of former Mayor Ed Koch in 2011, and is now known officially as the Ed Koch Queensboro Bridge.▪

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EnginEEr’s notEbook aids for the structural engineer’s toolbox

A

mong the most powerful innovations in recent years in the structural engineering profession is the widespread adaptation and use of nonlinear analysis methods for seismic issues. The concept of nonlinear behavior has been around for decades, but only recently – say, within the last 15 years – have practical analysis methods been introduced and embraced by many. Among these is the static pushover method, which enables a representation of nonlinear behavior without the need to develop and run sophisticated response history analyses.

Admittedly, the pushover procedure is not without its shortcomings – no analysis method is – but even such simplified methods can provide a useful glimpse of actual behaviors that could never be captured with traditional elastic analysis. In fact, they can expose the limitations of conventional analysis approaches, as well as the limitations of conventional structural assemblies and geometries long thought to be reliable.

Simple questions may sometimes haunt our experience and cause us to re-think designs and concepts that we once embraced uncritically.

For example: What is the consequence of a brace buckling in compression?

There are obvious local consequences in the structure that need no further elaboration here, but what about beyond the localized failure?

Consider the perfectly symmetrical braced frame structure shown in Figure 1. This three-bay by five-bay, one-story (12-foot high) building has columns spaced at 24feet in each direction. Brace sizes are typical, and are controlled by the limiting slenderness parameters found in AISC 341-10.

This simplified model is the “big dumb box,” shunned by architects and embraced by engineers for a common reason, its regularity. By all conventional definitions, this structure is regular and symmetrical.

Indeed, lateral analyses using equivalent force methods demonstrate this to be the case, with perfectly uniform displacement under application of centered lateral load in the transverse direction. If the diaphragm is rigid, we know that we must accommodate a minimum of 5% accidental eccentricity. Doing this still yields a structure characterized as “regular,” since the peak drift is not greater than 1.2 times the average (ASCE 7 Table 12.3-1). The design thus appears sound; we need not do anything more to address potential torsional effects.

Next, consider the buckling question.

Buckling can of course be characterized as a form of nonlinear behavior, but even more, a brace with the potential for buckling in compression and yielding in tension should also be characterized as potentially exhibiting

Perfectly Symmetrical but Extremely Torsional?

By Jerod G. Johnson, Ph.D., S.E.

Jerod G. Johnson is a principal with Reaveley Engineers + Associates in Salt Lake City, Utah. He can be reached at jjohnson@reaveley.com.

hysteretically asymmetric nonlinear behavior – a complex way of saying that nonlinear behavior is different in tension vs. compression.

There is nothing earth-shattering here. For the compression case, a buckled brace essentially loses its stiffness, and for the ‘X’ configuration the tensile brace then becomes the primary bracing element in the bay – at least until a load reversal occurs and the compression members and tension members switch roles.

What happens next? For perfectly balanced behavior, we should see simultaneous buckling of the brace on the opposite side of the building. However, the 5% accidental eccentricity alone is enough to cause the braces on one side of a building to buckle before those on the other side. For this scenario, nonlinear static analysis methods predict a peak diaphragm deflection equal to 1.24 times the average diaphragm deflection at the prescribed target displacement, thereby breaching the 1.2 threshold of a “regular” diaphragm.

Consider also the altered bracing configuration (chevron) of Figure 2. For this case, a brace buckled in compression not only reduces the frame stiffness by about 50%, but also significantly reduces the counteracting resistance that would enable effective performance of the tensile brace. For this case, nonlinear analyses show that peak diaphragm displacements are 1.47 times the average displacement, well into a range that would qualify as an “Extreme Torsional Irregularity.”

This example is purely hypothetical, and the structure could certainly be designed using conventional procedures and not be tagged as extremely torsional. However, the simple nonlinear analysis methods clearly show that a potential for extreme torsion exists as a consequence of braces buckling. Another case where buckling of a brace might introduce an irregularity in an otherwise regular condition is a multi-story braced frame. As a brace buckles, frame stiffness could easily be reduced to the degree that vertical irregularities are introduced (ASCE 7 Table 12.3-2).

The potential irregularities mentioned previously stem from one phenomenon common to any conventionally braced system: nonlinear asymmetric hysteretic behavior. To a degree, this is accounted for by response modification factors with a lower magnitude than other systems demonstrating nonlinear symmetric hysteretic behavior. However, a diminished value of R does little to reduce the potential for irregular behavior.

So what are the other options? Simply put, the effects of nonlinear asymmetry can largely be overcome by other lateral systems, such as special moment frame, eccentric braced frame, and buckling restrained braced frame (BRBF).

46 November 2015

Figure 1. ‘X’ Braced Frame under transverse loading.

For other materials, similar symmetry of hysteretic behavior may be developed – e.g., concrete shear walls, concrete moment frames, and wood shear walls. Each of these systems has its advantages, the BRBF being particularly attractive because it captures the ductility of a moment frame without the limber consequences.

Figure 2. Chevron Braced Frame under transverse loading.

Whereas earlier codes commonly allowed the use of ordinary bracing systems, the code development and adoption process has gradually nudged such systems to the realm of Occupancy Category I, where there is low risk to human life in the event of failure.

Currently, special concentric braced frames are the only conventional bracing system

qualified for use in standard occupancies (or greater) in high seismic regions. What will future changes to the code include? Will the day come when conventional bracing systems are no longer deemed suitable for any occupancies?▪

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Structural FailureS investigating failures, along with their consequences and resolutions

A

snowstorm in November 2014 hit Northern Oregon and was subsequently followed with freezing rain and arctic temperatures of -20° F. This event caused a large manufacturing plant’s roof to collapse, resulting in extensive structural damage to the facility. Of the 400,000 square foot plant size, approximately 80,000 square feet (20% of the facility) collapsed and shut down the plant’s operations. Structural damage extended to approximately 100,000 square feet of the facility, which was observable by visual means. In this article, the author explores the cause of the failure, collapse load analysis, and provides a brief overview of the structural system that was designed in the 1940s which remained in operation until the date of this event. The U.S. and Canada have thousands of buildings built over 60 years ago that are aging, deteriorating, and experiencing long term fatigue which are prone to failure/collapse. This article explores these issues and offers methods to evaluate existing facilities, which require attention before such fatal events can harm occupants.

The November 2014 snowstorm was a combination of sudden snow fall, arctic like temperatures, and freezing rain that caused the roof of this steel moment frame facility to collapse.

Fortunately, this failure occurred in the early hours of the morning and no fatalities were experienced. Figures 1 through 5 show the extent of the damage and loss of inventory. The building was constructed in the 1940s and comprises approximately 400,000 square feet of space, which was designed through successive permits over several decades. In its entirety, the design of this facility ranges from the 1940s-1960s vintage, and remained in operation until the 2014 storm event.

The ownership of the facility was advised to reduce their occupancy/use of the remaining facility (i.e., “undamaged” sections) until further investigation could be completed. This meant the entire building of 400,000 square feet was approximately 50% shut down due to

Snow Load Collapse of a Manufacturing Building in Oregon

By Dilip Khatri, Ph.D., S.E.

Dilip Khatri is the Principal of Khatri International Inc. located in Pasadena, California. He serves as a member of STRUCTURE’s Editorial Board and can be reached at dkhatri@aol.com.

Figure 2.

Figure 1.

the possibility of extenuating damage beyond the immediate collapse zone. Specifically, approximately 80,000 square feet was a total collapse, and an additional 120,000 square feet remains suspect or partially damaged, pending further analysis/study. Since this forensic investigation is ongoing, and this is an active file, the details of this study are still confidential.

The focus of this article is on the collapse zone, specifically, and recommendations for other facility owners (and their design firms) to take note that such events can occur in their areas, to similar structures that may experience large sudden loading.

Forensic Investigation of the Roof Collapse As can be observed from Figures 1 through 5, and after doing a collapse load analysis, the reasons for the failure are attributed to several causes: 1) Excessive snow/ice loading due the storm event that exceeded the capacity of the steel moment frame system.

2) Plastic Hinge Failure at several locations in the steel moment frame system, including compression flange failure of the top chord of the truss.

3) Footing failure at the base reaction.

The structural analysis of the steel moment frame system shows the collapse load is approximately 5 to 7 psf of snow/ice load. This varies somewhat based on the assumption of load distribution. If we assume uniform loading, then the answer will be slightly different from unbalanced snow/ice loading because the load distribution changes the stress concentration points. Figure 6 shows the structural model using RISA 3D and the resultant moment diagram.

However, the conclusion from the structural analysis definitively shows that the analytical collapse load agrees reasonably with the estimated ice load at the approximate time of failure during the storm event.

The structural analysis also confirms that the collapse load is far below the required design requirement of 20 psf as a minimum snow load capacity, and well below current code requirements, which would exceed 50 psf in certain areas of Northern Oregon.

48 November 2015

Figure 3.

Figure 5.

Survey of the Structural Alignment

Figure 6.

can move in three translational directions (x,y,z) and this is very difficult to determine with crude measurement devices such as a plumb bob, laser level, or visual means. The alignment survey of this facility showed certain frames had serious misalignment issues that render them potentially unsafe. This was further compounded by the fact that the collapse load analysis showed the failure deflection was less than 2 to 3 inches on certain moment frames. A low collapse load capacity, which translates into a low deflection tolerance, means that these structural frames are a collapse hazard in storm events and must be retrofitted/repaired.

Conclusions and Application to Other Similar Facilities

Figure 4.

There are thousands of facilities similar to this one that are spread across the U.S. and Canada. They are old and designed for a different era of application, and should be investigated for possible premature collapse hazard conditions. The tools utilized in this investigation are readily available and may be implemented to evaluate existing facilities STRUCTURE magazine

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November 2015

with similar construction so as to forewarn owners of potential hazardous situations.

The use of Forensic Analysis combines the analytical tools of structural modeling with the physical survey tools of measurement devices that can assist structural engineers to better evaluate such failures and prevent new ones from occurring. In this case, the owners are exploring several retrofit schemes to repair the remainder of their facility to retain their occupancy/use, and maintain the safety of their employees.▪

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As part of the structural investigation, the forensic analysis of the cause of failure was performed using analytical methods (RISA 3D) and additionally with a physical geometric survey of the remaining structural frames.

In many investigations, engineers can visibly observe the movement of a structure, but in certain cases the misalignment/movement may be too small to detect by visual observation. In these situations, engineers should consider retaining a professional surveyor to perform a physical geometric alignment survey of the structure to provide accurate three dimensional coordinate data of the facility’s main structural frames.

In this case, the structural frames span approximately 100 to 120 feet in length, which translates into deflection criteria of about L/180 ~ 6.7 to 8 inches. This may seem visually observable, but in mathematical terms it’s about 0.5% (0.005) of the length and cannot necessarily be observed with the naked eye. In fact, our investigation utilized a laser system, which in some cases could not measure this alignment because it occurs in three dimensions. The frames

code developments and announcements

Code Updates

AISI Cold-Formed Steel Design Manual Updated

By Joshua Buckholt, S.E., P.E., Richard C. Kaehler, P.E. and Helen Chen, Ph.D., P.E., LEED AP-BD+C

M

unicipalities have, or are in the process of adopting, the 2015 edition of the International Building Code (IBC). The 2015 IBC incorporates by reference AISI S100-12, North American Specification for the Design of Cold-Formed Steel Structural Members, 2012 Edition. To facilitate the use of AISI S100-12, the American Iron and Steel Institute (AISI) developed the 2013 edition of its Cold-Formed Steel Design Manual (Manual).

The Manual includes 63 worked example problems, tabulated and graphical design aids, and supplemental information relevant to the design of cold-formed steel. In addition, AISI S100-12 and the Commentary on the North American Specification for the Design of Cold-Formed Steel Structural Members (AISI S100-12-C) are included in the Manual. The Manual is presented in two volumes with eight parts. The following discussion highlights significant changes to the document.

Dimensions and Properties The table of referenced ASTM steels has been updated to reflect recent changes in steels approved for cold-formed steel design.

Information regarding steel deck products has been updated to reflect the latest requirements published by the Steel Deck Institute (SDI).

The cross-sections provided in Part I include: “representative cross-sections,” such as purlins or girts and light-steel framing cross-sections (joists, studs, or track).

Similar to the previous edition of the Manual, formulas for calculating grosssection properties used for compression or flexure, and the properties for distortional buckling analysis, have been provided for commonly used C-, Z- and Hat-Sections.

The effective section property examples have been updated to reflect changes in Chapter B of AISI S100-12.

Two new examples have been added: 1) Effective section properties of a panel section with large radii This example illustrates the effect of large corner radii on effective section properties by using the rational engineering method provided in Section B1.3 of the AISI S100-12-C Commentary.

2) Effective section properties of cellular deck with intermittent fasteners between deck and cover plate This example illustrates the application of the new design provisions of AISI S100-12 Section B2.5 for determining cellular deck effective section properties.

AISI M ANUA L

Cold-Fo

rmed St eel Des ign

9RO

Beam Design The introductory sections have been updated to include expanded discussions on coldformed flexural member behavior and limit states, including distortional buckling, in order to assist in an overall understanding of cold-formed steel beam behavior and design.

The strength tables for joist/stud and track sections have been updated and reflect only the thicknesses readily available for each steel grade.

Tabulated strengths for Grade 50 are provided for sections with a thickness greater than or equal to 54 mils. Similarly, tabulated strengths for Grade 33 are provided for sections with a thickness less than or equal to 43 mils. Table values based on Grade 50 material are differentiated with bold-faced type and shading.

Four new example problems have been added: 1) Four span continuous standing seam roof system This example outlines a comprehensive procedure for designing a standing seam roof system and applies to both the panel and its supporting purlins. This example illustrates the application of AISI S100-12 Section D6.1.2 to determine the flexural strength of purlins under gravity loads.

2) Flexural strength of a C-Section with web perforations by the Direct Strength Method This example shows how to determine the flexural strength of a perforated member using the Direct Strength Method (DSM).

3) Shear strength by Direct Strength Method This example illustrates how to calculate the shear strength and the combined bending and shear strength of a C-Section using the DSM. 4) Inelastic reserve strength by Direct Strength Method This example demonstrates how to use

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2013 Ed ition

the DSM to evaluate the inelastic reserve strength of a flexural member.

In addition to the four new design examples, the design example for a C-Section with combined bending and torsional loading has been expanded to include design calculations for flexural and torsional shear stresses.

Column Design Discussion of cold-formed compression member behavior and limit states located in the introductory section has been updated.

In addition, two new example problems have been added: 1) Compressive strength of C-Section members with openings using the Direct Strength Method This example illustrates the Direct Strength Method for a compression member with web holes. A methodology, utilizing manual calculations, is outlined that determines the compressive strength of the member including the influence of the holes based on local, distortional, and global buckling.

2) Braced frame design with consideration of second-order analysis This example demonstrates the verification of the strength and stiffness of a lateral bracing member (tension strap) against given design criteria applicable for a second-order analysis using AISI S100-12 Appendix 2. continued on next page

Built-Up Section Members • Clarifications are made to Section D1.1, Flexural Members Composed of Two Back-to-Back C-Sections.

Connection Design The introductory discussions of design limit states were updated for welded, bolted, screwed, and power-actuated fastened connections. The following new example problems were added: 1) Flare bevel groove weld with t>0.10 in.

This example illustrates how to apply the new design provisions for flare bevel groove welds in AISI S100-12 Section E2.6.

2) Flare V groove weld This example illustrates how to apply the new design provisions for flare V groove welds in AISI S100-12 Section E2.6.

3) Top arc seam sidelap weld This example illustrates how to apply the new design provisions in AISI S100-12 Section E2.4 for top arc seam sidelap welds that are used in diaphragm deck systems.

4) Power-actuated fasteners in shear and tension This example presents a comprehensive procedure for determining the shear and tension strengths of power-actuated fasteners (PAF) and how to check the interaction of PAFs subject to shear and uplift loads. The calculations utilize the provisions of Section E5 of AISI S100-12.

Supplemental Information Section 4, “Suggested Cold-Formed Steel Structural Framing, Engineering, Fabrication, and Erection Procedures for Quality Construction,” has been updated to reflect the 2011 Edition of the AISI Code of Standard Practice for Cold-Formed Steel Structural Framing which can be downloaded from www.aisistandards.org.

Test Procedures The fourteen AISI test standards included in previous editions of the Manual have been removed and are available online as free PDF downloads at www.aisistandards.org. The Bibliography of test procedures has been updated, and a new example problem was added:

1) Computing φ and Ω factors from test data using Section F1.1(b) This example shows how to apply AISI S100-12 Section F1.1(b) to determine the resistance and safety factors for a derived design equation.

2012 Edition of AISI S100-12 AISI S100-12 is included as an integral part of the Manual. The major technical changes contained in AISI S100-12 are: Materials • Material standard ASTM A1063 is added.

• All referenced ASTM material standards are reorganized in accordance with the ranges of the minimum specified elongation.

Elements • Section B1.3, Corner Radius-toThickness Ratios, is added, which limits the applicability of the design provisions in Chapter B to members with corner radius-to-thickness ratio not exceeding 10.

• Section B2.5, Uniformly Compressed Elements Restrained by Intermittent Connections, is added, which determines the effective widths of multiple flute built-up members.

Members • Country-specific provisions on tension member design (Section C2) are unified and moved from Appendices A and B to the main body of the Manual.

• Revisions are made in Section C3.1.1, such that the resistance factor for bending is the same for stiffened, partially stiffened, or unstiffened compression flanges.

• The simplified provisions for determining distortional buckling strength of C- or Z-Section beams (Section C3.1.4) and columns (Section C4.2) are moved to the Commentary.

• The reduction factor, as given in Section C3.6, for combined bending and torsional loading is revised.

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Member Bracing • Sections D3 and D3.1 are revised for clarifications.

• Section D3.3 is revised to be consistent with the AISC bracing design provisions. Second-order analysis is now permitted to determine the required bracing strength.

Wall Stud and Wall Stud Assemblies • Reference to nonstructural members is removed from Section D4.

• Reference to AISI S213, North American Cold-Formed Steel Framing Standard – Lateral, is moved from Section D4 in Appendix A to the main body of the Specification.

Metal Roof and Wall System • The following applicability requirements in Section D6.1.1 are revised or added: member depth, depth to flange width ratio, flange width, and ratio of tensile strength to design yield stress.

• Clarification is made to Section D6.2.1a regarding the application of the 0.67 factor specifically to clips, fasteners and standing seam roof panels.

Connections The whole chapter is reorganized with the rupture check consolidated to Section E6. In addition, the following provisions are added or revised: • New provisions (Section E2.2.4) on combined shear and tension on arc spot welds are added.

• New provisions (Section E2.4) on top arc seam sidelap welds are added.

• Section E2.6, Flare Groove Welds, is revised to be consistent with the provisions in AWS D1.1-2006.

• Section E3, Bolted Connections, is revised with added provisions for alternative short-slotted holes, applicable to connections where the deformation of the hole is not a consideration and the bolt diameter equals 1/2 in.

• Table E3.4-1, Nominal Tensile and Shear Strengths for Bolts, in Appendix A is revised to be consistent with the values provided in ANSI/AISC 360.

• New provisions (Section E4.5) are added for screw combined shear and pull-over, combined shear and pull out, and combined shear and tension in screws.

• N ew provisions (Section E5) on power-actuated fasteners are added.

• The reduction factor due to staggered hole patterns is eliminated in Section E6.

Tests • Determination of available strength (factored resistance) by evaluation of a rational engineering analysis model via verification tests is added.

Appendix 1 • The geometric and material limitations of prequalified columns and beams for using the safety and resistance factors defined in Sections 1.2.1 and 1.2.2 are expanded.

• Provisions for determining the flexural and compressive strength of perforated members are added in Sections 1.2.1 and 1.2.2.1.

• Provisions for determining the web shear strength using the Direct Strength Method are added as Section 1.2.2.2.

• Provisions for considering beam or column reserve capacity are added in Section 1.2.2.1.

Appendix 2 • For braced members, the requirement to meet the specified maximum-out-ofstraightness is added.

2012 Edition of the Commentary The Commentary on AISI S100-12, which provides background information and reasoning for the provisions, is also included in the Manual.

Conclusion The 2013 AISI Cold-Formed Steel Design Manual represents a refinement and updating of the previous edition. The changes will make the Manual both more convenient and useful to the range of users it serves.

This Manual has been dedicated to Richard (Dick) Kaehler, P.E., who has produced each edition of the AISI Cold-Formed Steel Design Manual since 1996. As a highly respected professional in structural analysis, design, and testing, Dick is noted for his expertise in developing design manuals, design guides,

and computer programs. Engineers, students, and general users have greatly benefited from his many contributions.▪ Joshua Buckholt, S.E., P.E., is an associate at Computerized Structural Design and assisted with the development of the 2013 AISI Cold-Formed Steel Design Manual. Joshua may be reached at jbuckholt@csd-eng.com.

Richard Kaehler, P.E., in memoriam, was a Vice President at Computerized Structural Design and was responsible for the production of the 2013 AISI ColdFormed Steel Design Manual.

Helen Chen, Ph.D, P.E., LEED AP-BD+C, is manager of the Construction Standards Development of the American Iron and Steel Institute. She is directly involved in the development and update of AISI construction standards. Helen may be reached at hchen@steel.org.

The online version of this article contains a reproduction of Appendix 1 – Complete List of Design Examples. Please visit www.STRUCTUREmag.org.

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Strong Structures Come From Strong Designs

With RAM™, STAAD® and ProStructures, Bentley offers proven applications for:

Build it with Bentley! Integrated projects, teams and software.

Bentley’s Structural Software provides you the tools you need for strong designs and supports an integrated workflow all the way around. Having all the applications you need for the tasks at hand, along with the ability to easily synchronize your work with the rest of the project team, helps you get your job done right, fast and profitably.

Visit www.bentley.com/Structural to learn more! © 2014 Bentley Systems, Incorporated. Bentley, the “B” Bentley logo, ProjectWise and MicroStation are either registered or unregistered trademarks or service marks of Bentley Systems, Incorporated or one of its direct or indirect wholly owned subsidiaries. Other brands and product names are trademarks of their respective owners.

• Metal Buildings • Steel/Steel Composite • Aluminum • Reinforced Concrete • Foundation Design • Steel Connections • Structural Drawings and Details

… all easily coordinated with the Architect and other team members and their design applications – such as AutoCAD, Revit, MicroStation® and more.

news and information from software vendors

Software UpdateS

ADAPT Corporation

Bentley Systems

HALFEN USA Inc.

Phone: 650-306-2400 Email: florian@adaptsoft.com Web: www.adaptsoft.com Product: ADAPT-PTRC 2015 Description: An indispensable production tool for the fast and easy design of concrete slabs of any form, beams, and beam frames.

Uses equivalent frame method to design posttensioned or conventionally reinforced projects.

Easily switch between PT and RC modes.

Phone: 800-236-8539 Email: structural@bentley.com Web: www.bentley.com Product: ProStructures Description: Enables engineers to reduce documentation production time and assists them in eliminating errors and design flaws, and to design and document composite structures.

Phone: 800-423-9140 Email: pschmidt@halfenusa.com Web: www.halfenusa.com Product: HSD-LD Calculation Software Description: Allows calculations of slab-to-slab and slab-to-wall connections. Offers quality printouts of the calculations and an easy to follow, detailed parts list of the required HSDLD system. Enables the designed to combine multiple conditions in one file, and offers 2D and 3D illustrations of the calculated situations.

Product: ADAPT-Edge 2015 with Tributary Load Takedown Description: Edge offers fast and reliable gravity load takedown of concrete structures in minutes.

Easily model buildings from scratch or import from Revit to take down loads in seconds. No need for FEM solution or complicated analytical modeling; just simple and fast load takedown results. Integrates with comprehensive column design module.

Product: ADAPT-Builder 2015 with Column Design Description: The only fully integrated solution for the design of complete concrete buildings using one model: gravity design of reinforced concrete or post-tensioned floor systems, lateral analysis, column design, shallow foundation design, and automated inclusion of lateral frame actions in slab and foundation design.

Seamlessly integrates with Revit Structure.

American Wood Council Phone: 202-463-2766 Email: info@awc.org Web: www.awc.org Product: Connections Calculator Description: Provides users with a webbased approach to calculating capacities for single bolts, nails, lag screws and wood screws per the 2012 NDS. Both lateral (single and double shear) and withdrawal capacities can be determined. Wood-to-wood, wood-to-concrete, and wood-to-steel connections are possible.

ASDIP Structural Software Phone: 407-284-9202 Email: support@asdipsoft.com Web: www.asdipsoft.com Product: ASDIP Suite Description: For more than two decades, ASDIP has provided the design tools for structural engineers. Footings, bearing walls, composite beams, concrete and steel columns, retaining walls, base plates, continuous beams, anchoring to concrete, and much more can be designed with our products.

Product: ProSteel Description: Provides detailing for structural steel and metal work, and ProConcrete detailing and scheduling of reinforced insitu/precast and post-tensioned concrete structures.

Product: RAM Structural System Description: The RAM Structural System is the only fully integrated engineering software with complete building analysis, design, and drafting for BOTH steel and concrete structures.

Product: STAAD(X) Description: Provides the comprehensive analysis and design of monopoles, self-supporting and guyed communication towers through physical modeling and parametric tools, ensuring minimum user interaction.

Design Data Phone: 402-441-4000 Email: doug@sds2.com Web: www.sds2.com Product: SDS/2 Description: Provides automatic detailing, connection design, and other data for the steel industry’s fabrication, detailing and engineering sectors. SDS/2’s data sharing between all project partners reduces the time required to design, detail, fabricate and erect steel.

Dlubal Software, Inc. Phone: 267-702-1815 Email: info-us@dlubal.com Web: www.dlubal.com Product: Dlubal Software Description: A worldwide leader in structural analysis and design software. Our highly sophisticated yet user-friendly programs with additional design modules will cater to each engineer’s individual project requirements.

Seamless workflow is offered with BIM integration, accurate non-linear finite element analysis, and precise module design capabilities.

Hilti, Inc. Phone: 800-879-8000 Email: us-sales@hilti.com Web: www.us.hilti.com Product: PROFIS Anchor Description: Performs design calculations for Hilti post-installed anchor systems and cast-in-place anchors using the anchoring to concrete provisions of ACI 318.

Product: PROFIS Rebar Description: Performs calculations for Hilti adhesive anchor systems and post-installed reinforcing bars using the development and splice provisions of ACI 318.

IES, Inc. Phone: 800-707-0816 Email: info@iesweb.com Web: www.iesweb.com Product: VisualAnalysis Description: Model what you need to build, applying loads (yes, you are skilled), get quick results for your design, with great reports to make you shine. In this way, your work is fast, solving problems is a blast. VisualAnalysis helps you get, engineered success: no sweat.

Integrity Software, Inc. Phone: 512-372-8991 Email: sales@softwaremetering.com Web: www.softwaremetering.com Product: SofTrack Description: Provides absolute control of each different type of Bentley license in your portfolio to prevent Bentley overage fees; additionally, SofTrack monitors, reports and optionally controls use of ESRI ArcGIS products by extension code, as well as reporting for Autodesk Cascade Licensing Sequences. Call today for your free trial! continued on next page

All Resource Guide forms for the 2016 Editorial Calendar are now available on the website, www.STRUCTUREmag.org. Listings are provided as a courtesy. STRUCTURE® magazine is not responsible for errors.

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Software UpdateS

news and information from software vendors

Intergraph®

Opti-Mate, Inc.

RISA Technologies

Phone: 281-890-4566 Email: icas.marketing@intergraph.com Web: www.coade.com Product: 2016 GT STRUDL® Description: Includes an intuitive user interface and AutoCAD-based modeler, enabling you to quickly create innovative design & analysis projects while maintaining structural integrity & uniformity never before possible. As always, GT STRUDL works how you do: quickly, globally, and with safety always top of mind.

Phone: 610-530-9031 Email: optimate@enter.net Web: www.opti-mate.com Product: Bridge Engineering Software Description: Engineering software for transportation bridges. Software titles include Merlin Dash for steel and prestressed concrete girders, Descus for horizontally curved plate and box girders, TRAP for trusses and SABRE for sign bridges. The software packages include analysis, AASHTO code check and ratings.

Phone: 949-951-5815 Email: toddr@risa.com Web: www.risa.com Product: RISAConnection Description: The latest version of RISA’s steel connection design software, RISAConnection, was released earlier this year and included seismic design of moment connections per AISC 341 and 358. The next version will be released later this year, and will include seismic brace connections, wide flange vertical braces, and design per CSA S16-14.

POSTEN Engineering Systems

Product: RISAFoundation Description: The latest version of RISAFoundation has introduced the analysis and design of battered (tapered) retaining walls. In addition, the capability to model pinned joints between slabs has been added, and design for all elements can now be performed under the new ACI 318-14 code.

Losch Software Ltd. Phone: 323-592-3299 Email: Loschinfo@gmail.com Web: www.LoschSoft.com Product: LECWall Description: Precast Concrete Column and Sandwich Wall Panel Design and Analysis.

Prestressed and/or mild reinforcing. Flat, hollowcore or double tee configurations. Column design, handling analysis, multi-story capability, zero to 100 percent composite.

National Concrete Masonry Association Phone: 703-713-1900 Email: ncma@ncma.org Web: www.ncma.org Product: Direct Design Software Description: Updated to the 2013 edition of TMS 403 (referenced by the International Building Code and Residential Code) this software allows users to generate final structural designs for whole concrete masonry buildings in minutes.

Product: Structural Masonry Design Software Description: Version 6.1 is now updated to include the 2012 International Building Code and the 2011 MSJC. Includes new larger allowable stresses per code. Design walls, lintels,columns and much more.

Phone: 510-275-4750 Email: sales@postensoft.com Web: www.postensoft.com Product: POSTEN X Description: The most efficient and comprehensive post-tensioned concrete software in the world that, unlike other software, not only automatically designs the Tendons, Drapes, as well as Columns, but also produces highly efficient, cost saving, sustainable designs with automatic documentation of material savings for LEED. The others simply Analyze – POSTEN DESIGNS.

Powers Fasteners Phone: 845-230-7533 Email: Mark.Ziegler@sbdinc.com Web: www.powers.com Product: Powers Design Assist® Description: PDA anchor design software now includes ACI 318-11 and CSA A23.3 design provisions for mechanical, adhesive and cast-in place anchors. Download or update to version 2.3 for free today at the website to take advantage of the most current code standards.

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RedBuilt

StruWare, Inc

Structural Engineering Software The easiest to use software for calculating wind, seismic, snow and other loadings for IBC, ASCE7, and all state codes based on these codes ($195.00).

CMU or Tilt-up Concrete Walls with & without openings ($75.00).

Floor Vibration for Steel Bms & Joists ($75.00).

Concrete beams with/without torsion ($45.00).

Demos at: www.struware.com

Phone: 866-859-6757 Email: csprung@redbuilt.com Web: www.redbuilt.com Product: RedSpec Description: Quickly and efficiently create floor and roof design specification using Red-I joists, open-web trusses, and RedLam FloorChoice™, RedBuilt’s propriety floor performance rating system. Allows a floor to be evaluated while still in the design phase, providing an easyto-understand numerical rating system fully integrated into the RedSpec sizing software.

Product: RISAFloor ES Description: Designs elevated concrete twoway slab floors including the optimization of rebar and full code checks for punching shear. RISAFloor ES designs concrete-only buildings or a mixture of concrete and nonconcrete floors. New features in the latest version allow you to model thickened regions or drop panels.

Product: RISA-3D Description: The latest version of RISA-3D has introduced Time History Analysis. This feature is very useful for the analysis of frames or slabs which support vibrating equipment.

Time History can also be used to simulate a specific earthquake on a structure, or apply a blast load.

SCIA, a Nemetschek Company Phone: 410-290-5114 Email: dmonaghan@scia.net Web: www.scia.net Product: Scia Engineer Description: Looking to migrate to, or improve your 3D design workflows? Scia Engineer links structural modeling, analysis, design, drawings, and reports in one program. Design to multiple codes. Tackle larger projects with advanced non-linear and dynamic analysis. Plug into BIM with IFC, and bi-directional links to Revit, Tekla, and others.

All Resource Guide forms for the 2016 Editorial Calendar are now available on the website, www.STRUCTUREmag.org. Listings are provided as a courtesy. STRUCTURE® magazine is not responsible for errors.

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news and information from software vendors

Software UpdateS

S-FRAME Software Inc.

StructurePoint

Phone: 204-421-4800 Email: info@s-frame.com Web: s-frame.com Product: S-CALC 2016 Description: Generates over 19 section properties for sections of any size, any shape, any material combination. Marks a major advancement in ease of use, enhanced features, and product integration.

Access built-in CISC, AISC, UK and other databases, import DXF, Revit, and other files or design sections within S-CALC.

Phone: 847-966-4357 Email: info@structurepoint.org Web: www.StructurePoint.org Product: spColumn and spMats Description: spColumn; for design of shear walls, bridge piers as well as typical framing elements in buildings and structures. spMats; for analysis, design and investigation of commercial building foundations and industrial mats and slabs on grade.

Simpson Strong-Tie® Phone: 800-925-5099 Email: web@strongtie.com Web: www.strongtie.com Product: Steel Deck Diaphragm Web App Description: Enables engineers to quickly and efficiently identify the best design and fastener solutions for steel decks given shear and uplift loads. The app, which is accessible from any web browser, provides diaphragm shear strengths of a steel deck when using Simpson Strong-Tie screws.

Strand7 Pty Ltd

StrucSoft Solutions Phone: 514-538-6862 Email: info@strucsoftsolutions.com Web: www.strucsoftsolutions.com Product: Metal Wood Framer Description: Take cold-formed steel and wood framing from modeling to fabrication using the Autodesk Revit platform. MWF provides usercontrolled, automated modeling, clash detection and manufacturing of light gauge steel and wood framing as well as shop drawings, cut lists, bill of materials and CNC machine output.

Phone: 904-302-6724 Email: mail@struware.com Web: www.struware.com Product: Struware Code Search Description: Imagine getting all pertinent wind, seismic, snow, live and dead loads for your building in just minutes. The program simplifies ASCE 7 & IBC by catching the buts, ifs, insteads, footnotes and hidden items that most people miss. Demo at website. Current users: a new update is available for download.

Tekla, Inc.

Software and ConSulting

FLOOR VIBRATIONS FLOORVIBE v2.20

Phone: 770-426-5105 Email: kristine.plemmons@tekla.com Web: www.tekla.com Product: Tedds Description: Perform 2D frame analysis, access a large range of automated structural and civil calculations to US codes and speed up your daily structural calculations.

Product: Tekla Structural Designer Description: Fully automated,with many unique features for optimized concrete and steel design, Structural Designer helps engineering businesses to win more work and maximize profits. From the quick comparison of alternative design schemes through to cost-effective change management and seamless BIM collaboration, Structural Designer can transform your business.

online All past issues

News, Events, Book Reviews, Letters to the Editor and more!

www.STRUCTUREmag.org

STRUCTURE magazine

Phone: +49 711 518573 30 Email: melanie.engel@vcmaster.com Web: www.vcmaster.com Product: VCmaster 2016 Description: Ranks as the most comprehensive tool in the structural design industry for digital technical documentation. The t2W-interface makes it a technical computing software that does what spreadsheets, word processing and other programming applications alone can’t do.

Bring blueprints, texts, images and calculations into one single, reusable, professionally presented document.

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• Software to Analyze Floors for Annoying Vibrations • Demo version at www.FloorVibe.com • Calculations follow AISC Design Guide 11 and SJI Technical Digest 5 2nd Edition Procedures • Analyze for Walking and Rhythmic Activities • Check floors supporting sensitive equipment • Graphic displays of output • Data bases included

CONSULTING SERVICES

• Expert consulting available for new construction and problem floors.

Structural Engineers, Inc. Radford, VA 540-731-3330 tmmurray@floorvibe.com

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Phone: 252-504-2282 Email: anne@beaufort-analysis.com Web: www.strand7.com Product: Strand7 Description: An advanced, general purpose, FEA system used worldwide by engineers, designers, and analysts for a wide range of structural analysis applications. It comprises preprocessing, solvers (linear and nonlinear static and dynamic capabilities) and postprocessing. Features include staged construction, a Moving Load module and quasi-static solver for shrinkage and creep/ relaxation problems.

Struware, LLC

Veit Christoph GmbH

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Product: CFS Designer™ Software Description: For cold-formed steel designers, automates product selection and helps navigate the complicated design provisions of AISI while offering more robust design tools. The program has an upgraded user interface that makes input faster and more intuitive. CFS Designer is the new version of LGBEAMER software.

Product: spWall and spSlab Description: spWall; for design and analysis of cast-in-place reinforced concrete walls, tilt-up walls, ICF walls, and precast architectural and load-bearing panels. spSlab; analysis, design and investigation of reinforced concrete floor systems.

Product: Tekla Structures Description: Create and transfer constructible models throughout the design lifestyle. From concept to completion. Allows you to create accurate and information-rich models that reduce RFIs and enable structural engineer’s proven additional services. Models are used for drawing production, material take offs and collaboration with disciplines like architects, consultants, fabricators and contractors.

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Finite element analysis & design of reinforced, precast ICF & tilt-up concrete walls

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StructurePoint’s suite of productivity tools are so easy to learn and simple to use that you’ll be able to start saving time and money almost immediately. And when you use StructurePoint software, you’re also taking advantage of the Portland Cement Association’s more than 90 years of experience, expertise, and technical support in concrete design and construction.

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award winners and outstanding projects

Spotlight

Brelsford Visitor Center Washington State University

By Amie Sullivan, P.E., S.E. KPFF Consulting Engineers was an Award Winner for the Brelsford Visitor Center project in the 2014 NCSEA Annual Excellence in Structural Engineering awards program (Category – New Buildings under $10M).

T

he Brelsford Visitor Center sits near the junction of the Washington State University (WSU) campus and downtown Pullman at the corner of Main and Spring streets. The location was chosen to recognize the historical significance and celebrate the vitality of the town-gown relationship that has existed between the City of Pullman and WSU for more than 123 years. The $1.3 million facility was delivered using the design-build method with a team lead by Sellen and Olson Kundig as contractor and architect. KPFF provided structural and civil engineering for the new 4,277 square-foot building that now serves as a showcase for the university’s wide-ranging activities.

WSU awarded the project in February 2013, construction began on May 20, 2103, and the Grand Opening was celebrated in October 2013. Driven by the aggressive schedule and a tight budget, the team pushed boundaries and responded to design and construction challenges with creative solutions. Ultimately, the team was able to deliver the iconic structure the University was looking for in just eight short months.

The most prominent architectural statement, the 40-foot-tall illuminated tower, is also a primary structural element. Composed of two curved steel segments, the west segment supports a series of cantilevers at the roof edge.

The east segment is a free standing element.

To maintain the project budget and schedule, the tower was stitched together with several curved sections rather than one piece of steel.

To avoid a segmented look, KPFF worked closely with the steel fabricator to create discrete welded splices, successfully giving the tower the seamless look the architect desired.

Three 15-foot-high concrete letters that spell W-S-U are another distinctive feature. The letter “U” serves as a building column supporting the overhanging roof on the west end. To meet budget and schedule, the letters were cast in concrete on-site and tilted

up in place. To control cracking and provide durability, the letters were reinforced with a welded rebar mesh. KPFF designed the lifting brackets and erection assemblies to support the letters and minimize stresses while they were being erected.

The board formed concrete wall on the south elevation of the building is an example of how creative problem solving was used incorporate the structural systems within the framework of the architectural vision. This concrete wall was an important feature in the architectural design of the building. By making this wall a primary lateral element used to support the lateral loads both in-plane and out-of-plane (in a cantilevered manner), KPFF eliminated braced frames or moment frames that would have otherwise been required, saving money and keeping the rest of the glass pavilion very light and open.

The Visitor Center is one of the first commercial applications of cross laminated timber (CLT) in the country. The panels are made up of three layers of 2-by-6 planks that are stacked crosswise and glued together. The CLT roof spans

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14-feet between supports and cantilevers in both directions at the roof edge.

The site was constrained by numerous Environmentally Critical Area buffers, and these constraints pushed the building to the corner of the site atop a combination of bedrock and uncontrolled fill. KPFF worked with the geotechnical engineer to provide a foundation system that would fit the budget and control differential settlement.

Efficiency in systems and finishes was achieved by integrating the structural elements into the architectural design in other ways, as well. The building features polished slab-on-grade floor, exposed steel and glulam beam framing, steel angle columns nested into the re-entrant corners of the window wall system, and an exposed CLT ceiling finish.▪ Amie Sullivan is an associate at KPFF Consulting Engineers in their Seattle office. She can be reached at amie.sullivan@kpff.com.

November 10, 2015 Designing for Wind Loads Using the Directional Procedure in ASCE 7

T. Eric Stafford, P.E., Eric Stafford & Associates

November 17, 2015 Calculating Wind Loads for Components and Cladding

T. Eric Stafford, P.E., Eric Stafford & Associates

December 1, 2015 2015 International Building Code – Significant Structural Changes

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Sandra Hyde, P.E., Senior Staff Engineer, International Code Council, Product Development Group

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News form the National Council of Structural Engineers Associations

NCSEA News

NCSEA Webinars

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Brian Dekker President, NCSEA Board of Directors

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STRUCTURE magazine

resource, but no one ever knows about it, all of that effort goes to waste.

NCSEA plans to form a new committee in the next few months – the NCSEA Communications Committee. Our charge for this committee will be to ensure that all of NCSEA’s work is communicated to its intended audience. The committee will first gather information from other NCSEA Committees, NCSEA staff, and MOs. Subsequently, the committee will distribute that information using the most effective means: website, email, phone, snail mail, etc.

Another important task of the Communications Committee will be to establish a means for MOs to share ideas, successes, and challenges. It is likely that this resource will take the form of an internet forum or message board. Users will be able to post experiences related to topics such as membership engagement, quality content/speakers for meetings, maintaining active committees, developing a steady revenue and dues structure, attracting new membership, and leadership development. This new resource will help MOs learn from each other and avoid re-inventing the wheel.

Finally, using information gathered from the forum, NCSEA will develop How-To Guides for common topics. We’ve already completed guides on starting a young members group, starting a student chapter, and starting a high school outreach program.

In the future, we are likely to look at developing guides on topics such as building a website, publishing a newsletter, organizing continuing education seminars, getting sponsors/vendors, and starting an awards program.

In 2015-2016, we’ll be doing our best to advance the practice of structural engineering by representing and strengthening our Member Organizations. If you have ideas of how we can represent and strengthen your MO, please feel free to contact me directly – brian@soundstructures.net. NCSEA exists for the benefit of our MOs. We’re here to help. Just tell us where it hurts.

EN

Rick Warren’s book, The Purpose Driven Life, has encouraged over 60 million readers to ask themselves, “What on earth am I here for?” I often ask myself that question. There isn’t a simple answer. I think my purpose in life varies, depending on who I’m relating to at any particular moment. I have different purposes in my life as I relate to work, family, faith, and friends.

Fortunately, NCSEA’s purpose isn’t as complicated as pondering the meaning of life. Our focus is singular. We exist for the benefit of our Member Organizations. Last October, NCSEA updated our Mission Statement to better reflect our purpose.

NCSEA advances the practice of structural engineering by representing and strengthening its Member Organizations.

Are we fulfilling our purpose? I think so. Here are a few examples.

Representing 1) The Code Advisory Committee represents MOs at ICC code hearings.

2) The Structural Licensure Committee represents MOs in states that don’t yet have SE licensure.

3) The Advocacy Committee represents MOs to the media, general public, students, and educators.

4) The Basic Education Committee represents MOs to universities regarding their structural engineering curriculum.

5) The SEER Committee represents MOs on matters related to emergency response.

6) STRUCTURE magazine represents MOs as practicing structural engineers.

Strengthening 1) The Young Member Group Support Committee strengthens our organizations by encouraging the next generation of structural engineers.

2) The Grant Program strengthens MOs by financially supporting their programs.

3) The Summit strengthens MOs by encouraging delegate collaboration.

4) NCSEA Publications strengthen MOs by providing technical guidance.

5) The Continuing Education Committee strengthens MOs through webinars and the SE Review Course.

6) The Delegate model strengthens MOs by sharing knowledge and experiences with other MOs and with NCSEA. Does this mean our job is done? No. There’s always room for improvement. So what are we going to do in the next year?

Here are a few of our plans.

A. Assess and revise NCSEA’s organizational structure to better serve our new Mission Statement.

B. Improve the effectiveness and engagement of NCSEA delegates.

C. Streamline and improve communications between NCSEA and its MOs. D. Create a financially secure future for NCSEA. In all of our activities, we need to focus on communication. As in our businesses, work that is not reported is the same as work that is not done. Engineers may develop a complex computer analysis model to design a structure. But, if they don’t communicate that information on drawings, then it’s as if they never did the analysis.

The same goes for NCSEA. If a committee prepares a wonderful

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More detailed information on the webinars and a registration link can be found at www.ncsea.com. Subscriptions are available! 1.5 hours of continuing education. Approved for CE credit in all 50 states through the NCSEA Diamond Review Program. www.ncsea.com.

Diamond Reviewed

November 2015

Incoming President Brian Dekker; Outgoing President Barry Arnold and wife Debbie

Young Engineer Attendees

NCSEA News

NCSEA Structural Engineering Summit, Las Vegas

News from the National Council of Structural Engineers Associations

NCSEA Delegate Collaboration Session

Ashraf Habibullah and Computers & Structures Inc. (CSI) sponsored Thursday’s festive event

Mark your Calendars! 2016 Structural Engineering Summit: September 14 – 16, Disney’s Contemporary Resort, Orlando

Thank You to the Structural Engineering Summit Sponsors: Platinum

Gold

Young Member Summit Scholarship Recipients

Silver

Bronze

Copper

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NCSEA Past Presidents

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Geotechnical & Structural Engineering Congress Technical Sessions

Structural Columns

The Newsletter of the Structural Engineering Institute of ASCE

Monday, February 15, 2016 Soil – STrucTure inTeracTion

earThreTaining STrucTureS

10:00 AM – 11:30 AM

International Geotechnical Panel Discussion

Design, Construction & Performance of Deep Excavations

Bridge Scour & Erosion: The Way Forward

ASCE/SEI 41: What’s Coming in the 2017 Edition?

Structural Engineering Licensure as it Relates to Geotechnical Engineering

Innovative Systems for Seismic Resistance

Soil/Structure Interaction: Dialogue Between Engineers to Create Good Soil Reports

1:00 PM – 2:30 PM

Soil-Structure Interaction for Energy GeoStructures

Design, Construction & Performance of Retaining Walls

What Structural Engineers Need to know about Rain Loads

Seismic Evaluation of Cold-Formed Steel-Framed Structures

The Risk of Professional Practice

Structural Wall Research: Recent Research & International Collaboration

Characteristics of Higher Performing Design Firms

3:00 PM – 4:30 PM

Advancements in Micropile Foundation Technology: Design, Analysis, & Construction

The Future of Earth Retention: Construction, Design, & Practice

Dynamic Behavior

ASCE/SEI 7-16 Seismic: Learn From The Experts

Geotechnical & Structural Engineering: From Project Conception through Construction

Reliability-Based Design

Tackling Today’s Business Practice Challenges: A Structural Engineering Roundtable

Track

FoundaTionS/ rain loadS

codeS & BuildingS

BuSineSS & ProFeSSional PracTice 1

emerging ToPicS

caSe riSk managemenT convocaTion

Tuesday, February 16, 2016

Track

Soil – STrucTure inTeracTion

earThreTaining STrucTureS

FoundaTionS

codeS & BuildingS

BuSineSS & ProFeSSional PracTice 1

emerging ToPicS

develoPmenTS in earThquake engineering

10:00 AM – 11:30 AM

Interaction of Geotechnical & Structural Engineers for the Design of Tunnels & Underground Structures

Case Histories & Design Methods for Braced Excavations

Geo-Structural Solutions in Railroad Applications

Update on 2016 AISC Standards

Debate: Who is Better Qualified to Design GeosyntheticReinforced Walls: Structural Engineers, Geotechnical Engineers, or Both?

Novel Methods of Educating Geotechnical & Structural Enginers

Panel Discussion: Implementing NRC Recommendations Related to the Assessment of Earthquake-Induced Soil Liquefaction

1:00 PM – 2:30 PM

Tunnels & Underground Space

Analysis & Performance of MechanicallyStabilized Earth Walls

Shallow Foundations & Rafts

Seismic Performance of Tall Buildings

The Geoprofessional Business Association (GBA) Presents: Risk Management Case Studies from GBA Leaders

Life-Cycle Cost Design & Assessment in Structural & Geotechnical Engineering

Post-Earthquake Reconnaissance Findings From the M7.8 Gorkha Earthquake

3:00 PM – 4:30 PM

Instrumentation & Monitoring for Tunnels & Underground Construction

Internal Stability Design & Analysis of MSE Walls: Influence of Facing Elements

Case Studies on HydroCompressive (Collapsible) Soils in Western Colorado

Seismic Resiliency & Innovation of Structures

A Real Claim Presentation 2016

Managing Risk in Geotechnical & Structural Analysis & Design

Updated Earthquake Ground-Motion Maps for ASCE/SEI 7-16 & Beyond

Wednesday, February 17, 2016

Track

Soil – STrucTure inTeracTion

TeSTing & modeling

FoundaTionS

STrucTural healTh moniToring oF geoTechnical SySTemS

geohazardS

emerging ToPicS

SuSTainaBiliTy & reSilience

8:00 AM – 9:30 AM

Foundations: Case Studies & Applications

Structural Research

Better Drilled-Shaft Design Through Better Data

Case Studies: Large-Scale Sensing & Monitoring Projects for Structural & Geotechnical Systems

Hydraulic Fracturing & Geoenvironmental Issues

Closing The Gap: Probabilistic Methods for Decision Support Across Complex Structural & Infrastructure Systems

Lifecycle Analysis & Carbon Calculation: Part 1

10:00 AM – 11:30 AM

Simulation Methods for Performance Evaluation of Soil-FoundationStructural Envelope

Computational Modeling

Design & Construction of Pile Foundations

Monitoring & Health Assessment of Geotechnical Systems

PerformanceBased Liquefaction Assessment & Mitigation

Sustainability Rating

Life-Cycle Analysis & Carbon Calculation: Part 2

Register early and save. For more information including registration and housing, visit our website at www.geo-structures.org.

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PavemenTS/ Wind iSSueS

BridgeS

SeiSmic- & geo-hazardS

SuSTainaBiliTy/ reSilience

lighTning round

www.geo-structures.org

nonBuilding STrucTureS, nonSTrucTural comPonenTS & Their FoundaTionS

SiTe characTerizaTion

ground imProvemenT

Stability and Loading of Long Span Bridges under Wind Action

Stability & Stabilization of Slopes, Dams, & Embankments: Part 1

Disaster Resilience – Indispensable for Sustainable Design

Risk Analysis & Reliability Topics

Wind Loads on Solar Panels

Seismic Site Characterization

Soil Improvement for New Seismic Code Requirements

PerformanceBased Wind Engineering

Bridge Analysis

Site Factors: Code Issues

Alternative Approaches to Multi-Hazard Analysis & Design of Structures

Corrosion Topics

Analysis of Nonbuilding Structures

Vibrations: Serviceability

Condition Assessment of Structural Systems Under Service Loads

Subgrades & Unbound Layers

Structural Analysis of Bridge Substructure Components

Stability & Stabilization of Slopes, Dams & Embankments: Part 2

SEI Climate- Action Initiative

Geotechnical Topics

Modular Construction Practices for Industrial, Infrastructure, & Power Facilities

Advancements in Field and Laboratory Characterization of Coastal Deposits

Ground Improvement for Structures

SiTe characTerizaTion

ground imProvemenT

unSaTuraTed SoilS

lighTning round 2

Foundations & Slope-Stability for Collapsible & Expansive Soils

SeiSmic- & geo-hazardS

SuSTainaBiliTy/ reSilience

Structure Modeling, Investigation, and Evaluation

Liquefaction Testing & Modeling

ASCE/SEI 7-16 Tsunami: The New Resiliency Approach & Design Provisions

Grouting & Structures Structural Topics

Wind Energy Structures & Their Foundations

Dynamic Properties & Behavior of Soils

Ground Improvement: Testing, Modeling & Evaluation

Impact of Desiccation Cracks on the Behavior& Performance of Geo-Structures

Seismic Analysis of Bridge Components

Liquefaction: Case Histories

Experimental & Analytical Investigation of Robustness of Structures

Resiliency & Sustainability

Foundations for Specialized Structures

Advanced SiteCharacterization Techniques

Grouting & Structures: Advances in Grouting Materials & Testing

Soil-Structure Interaction in Unsaturated Soils

Innovations in Building Systems and Materials

Liquefaction Effects on Structures

Strategies for Enhancing Structural Robustness

Advance in PerformanceBased Design

Seismic Design of Large Buried Reservoirs

In-Situ Testing & Soil Properties

Soil Improvement Methods – Research & Practice: Part 1

SiTe characTerizaTion

ground imProvemenT

SeiSmic- & geo-hazardS

BlaST & imPacT

lighTning round

nonBuilding STrucTureS, nonSTrucTural comPonenTS & Their FoundaTionS

lighTning round

nonBuilding STrucTureS, nonSTrucTural comPonenTS & Their FoundaTionS

PavemenTS

BridgeS

Pavement Foundation Systems: Part 1

Bridge Scour: A Hydraulic, Geotechnical, & Structural Problem

The Effect of Lanslides, Avalanches & Debris Flows on Structures

Advances in BlastResistant Structures & Design: Part 1

Tunnels & Underground Spaces

Energy GEO-Structures Topics & Materials

Computer Modeling in Geomechanics

Grouting & Structures: Case Studies

Pavement Foundation Systems: Part 2

Structural Design of Deep Foundations

Potential Effects of Surface Fault Rupture on Infrastructure

Advances in Blast-Resistant Structures & Design: Part 2

Extreme Loads

Innovations in Structural & Geotechnical Engineering for Tunnels & Underground Structures

Small-Scale Testing Methods in Geotechnical Engineering

Soil-Improvement Methods – Research & Practice: Part 2

View the interactive Technical Program, including all presenters and abstracts at www.geo-structures.org.

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The Newsletter of the Structural Engineering Institute of ASCE

Modeling & Testing

Structural Columns

February 14 – 17, 2016 – Phoenix, Arizona

CASE in Point

The Newsletter of the Council of American Structural Engineers

CASE Practice Guidelines Available CASE 962-E Self-Study Guide for the Performance of Site Visits during Construction

CASE 962-G Guidelines for Performing Project Specific Peer Reviews on Structural Projects

This guide is intended for the younger engineer but will be useful for engineers of all experience levels. Structural engineers know that site visits are crucial construction phase services that help clarify and interpret the design for the contractor. Site visits are also opportunities to identify construction errors, defects and design oversights that might otherwise go undetected. Engineers should include adequate construction phase services as a part of their scope of services to insure the design intent is properly implemented.

Increasing complexity of structural design and code requirements, compressed schedules and financial pressures are among many factors that have prompted the greater frequency of peer review of structural engineering projects. The peer review of a project by a qualified third party is intended to result in an improved project with less risk to all parties involved, including the engineer, owner, and contractor.

Many aspects of the peer review process are important to establish prior to the start of the review, in order to ensure that the desired outcome is achieved. These items include the specific goals, scope and effort, the required documentation, the qualifications and independence of the peer reviewer, the process for the resolution of differences, the schedule and the fee. The intention of these guidelines is to increase awareness of such issues, assist in establishing a framework for the review and improve the process for all interested parties.

CASE 962-F A Guideline Addressing the Bidding and Construction Administration Phases for the Structural Engineer This document has been developed to assist all the parties associated with the bidding and construction administration phases of a project with the primary emphasis on those issues associated with the structural engineer (SER). It is important that the design team remains proactive in communicating with the contractor and the owner after the construction documents have been issued. This communication during the construction phase, as well as during the pricing and bidding process, should have as its primary goal the assistance, interpretation and documentation for the improvement of the constructed project.

This is a guide to the SER’s roles after the construction documents have been issued for construction. It provides guidance on pre-bid and pre-construction activities through the completion of the project. The appendices contain tools and forms to assist the SER in applying this guide to their practice. This guideline includes suggested approaches to the various components that can make up the bidding and construction administration phases.

CASE 962-H National Practice Guideline on Project and Business Risk Management This guideline is intended to assist structural engineering companies in the management of risk associated with projects and to provide commentary regarding the management of risk associated with business practices. The guideline is organized in two sections that correspond with these two areas of risk, namely Project Risk Management and Business Practices Risk Management. The goal of the guideline is to educate and inform structural engineers about risk issues so that the risks they face in their practices can be effectively mitigated, thus making structural engineering firms more successful.

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

WANTED

Engineers to Lead, Direct, and Get Involved with Case Committees!

If you’re looking for ways to expand and strengthen your business skillset, look no further than serving on one (or more!)

CASE Committees. Join us to sharpen your leadership skills – promote your talent and expertise – to help guide CASE programs, services, and publications.

We have a committee ready for your service: • Risk Management Toolkit Committee: Develops and maintains documents such as business practices manuals and policies for engineers under CASE’s Ten Foundations for Risk Management.

Please submit the following information to htalbert@acec.org: • Letter of interest • Brief bio (no more than 2 paragraphs) STRUCTURE magazine

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Expectations and Requirements To apply, you should • be a current member of the Council of American Structural Engineers (CASE) • be able to attend the groups’ two face-to-face meetings per year: August, February (hotel, travel partially reimbursed) • be available to engage with the working group via email and conference call • have some specific experience and/or expertise to contribute to the group Thank you for your interest in contributing to your professional association!

November 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: William M. Camp, III, P.E., D.GE., 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/sfc.

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 htalbert@acec.org.

CASE Winter Planning Meeting – SAVE THE DATE 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

Follow ACEC Coalitions on Twitter – @ACECCoalitions.

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

How to Make Better Use of Experienced Staff

By Phillip C. Pierce, P.E., F.ASCE

“W

hat are we going to do with Abcd? He’s not as up-to-date with design specifications as he used to be. He no longer wants to work long hours. He really doesn’t want to travel for work and is no longer able to do the more physically demanding field work. What ARE we going to do with Abcd?”

Chances are good that this scenario is familiar at your firm. If not, you are in the minority.

For purposes of this discussion, it is assumed that Abcd retains respect in the firm and has been viewed as a valuable staff person to date.

Furthermore, it is assumed that Abcd has been involved in the current line of work for a long period of time, and in most aspects of it. But it is clear that the end of his career is approaching.

So what are good ways to take advantage of the skill set of experienced staff? Consider these general ideas: • Identifying winning strategies for chasing new projects is an important requirement for all firms. The experienced staff person can often offer insights into what techniques have worked well in the past on similar projects, or “think outside the box” and suggest a new approach for consideration, with sound justification for it. Accordingly, include the person in initial and early strategy sessions.

• An experienced staff person has often developed good relationships with a large number of clients, but may not be assigned an active role in marketing for the firm for whatever reason. Pressing the person into a more active marketing role may open new doors for the firm.

• Mentoring of younger staff may often be assigned to mid-level staff, but the experienced staff person may provide a more seasoned exposure for young staff, helping them focus on what is important and avoid what is unnecessary or irrelevant.

• An experienced staff person may be a good choice to conduct group training sessions on various topics.

• Initial review of design products, looking at overall aspects while leaving the checking of minutiae to younger

staff, is a good way to use senior experience and, at the same time, early reviews can avoid having a younger staff person moving down a misguided path.

• The experienced person can serve as an advisor to deal with technical and/ or field problems and challenges.

There are often unusual situations that require prompt and effective solutions.

Many experienced staff perform admirably and enthusiastically when provided such challenges.

• Experienced staff often serve in a Quality Control (QC) or Quality Assurance (QA) role for the group.

• If not assigned a QC/QA role in general, the experienced person can do periodic, random reviews of designs or products with focus on assumptions, modeling, and accuracy.

• One of the more rewarding assignments may be to ask the experienced person to prepare articles or histories about various aspects of the work – background information that may not be known to younger staff or contained in current codes and specifications.

The above list can be true of experienced staff in any engineering discipline. Focusing on more specific issues for experienced staff involved in structural engineering: • Experienced staff may be able to suggest alternatives to default assumptions; e.g., when the yield strength of existing elements is not known, instead of relying on tables based on the age of the structure (which are generally conservative), coupon tests might indicate higher actual values.

• Experienced staff usually have more/ older/unusual reference materials and/or knowledge of the same that can become a rich resource at times; e.g., when determining allowable stresses for castiron elements, which are not typically provided in modern specifications.

• Experienced staff often have more knowledge of the intent of design specifications or the evolution thereof, which helps when there is a need to “bend the rules” a bit.

• Experienced staff often look for conservative assumptions that can indicate problems, and then find solutions to represent the situation better; e.g., concrete decks on steel beams without shear connectors act as composite elements until loss of bond along the interface is evident.

• Experienced staff usually have had more exposure to different situations or unusual structure types.

• Experienced staff can more readily find opportunities to use past experience in new ways; e.g., trussed floor beams, steel sheet pile abutments, retention and rehabilitation of existing foundations rather than automatic replacement, etc.

• Experienced staff almost always have more experience with estimating costs, and know where to focus attention during value engineering reviews or how to prepare quick initial estimates.

• Experienced staff have more knowledge of the total project picture; e.g., rightof-way, permitting, fabrication, and construction limitations and costs.

• Experienced staff are geared to look for simplification and not start automatically looking for software.

• Experienced staff have a better knowledge base of what is practical.

This use of experienced staff and their broader knowledge base benefits the firm, as well as the employee. New opportunities to contribute may renew enthusiasm and boost spirits, thereby yielding a more productive staff person. The firm also benefits by enhanced direct and indirect training of younger staff, improved product quality and more successful marketing efforts.

Returning to the initial question – what ARE we going to do with Abcd? We’re going to get him excited again, with renewed energy, by taking full advantage of the storehouse of experience that he has gained over the years.▪ Phillip C. Pierce (ppierce2@gmail.com), is a Senior Principal Structural Engineer in Upstate New York, working in both the public and private sectors over his career of more than 40 years.

Abcd is a fictitious staff person. The masculine gender was used for convenience.

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, C3Ink, or the STRUCTURE® magazine Editorial Board.

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