STRUCTURE magazine | July 2013

July 2013 Wind

A Joint Publication of NCSEA | CASE | SEI

®

STRUCTURE Special Section: Seismic Products

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FEATURES 21 Special Section

Growing Optimism Spurs Innovation for Seismic Companies

By Larry Kahaner

In general, there appears to be some optimism in the market.

Companies are seeing a slight upsurge in the demand for related products and an increase in requests for innovations.

Read what some seismic suppliers are hearing and offering.

CONTENTS July 2013

COLUMNS 5 Editorial Contribute to Your Profession and it Pays You Back

By Andrew Rauch, CASE Chair

New York State Capitol Restoration

26

By Susan L. Knack-Brown, P.E. and Nicholas T. Floyd, P.E.

By the late 1990s, the New York State Capitol, designed and built in various stages between 1869 and 1899, was losing its luster due to neglect, insensitive major modifications and chronic leakage. This award winning project has finally addressed all of the reported leakage, as well as restored to prominence the three monumental staircases by returning natural light and lost historic features to the spaces.

University of Washington Invests in Student Housing

30

By Jennifer Cover, MS, P.E.

STRUCTURE

®

In 2012, the University of Washington completed a fivebuilding construction project, adding nearly 1,700 student housing beds. The use of light-frame wood construction met both the University’s ambitious design goals and a tight budget, in addition to providing design flexibility and creating elegant, durable, urban structures.

A Joint Publication of NCSEA | CASE | SEI

The Intellectual Virtue of Engineering

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

8 Structural Performance Across-Wind Response of High-Rise Buildings

By Rafik R. Gerges, P.Eng, Ph.D., S.E., SECB, and Kal Benuska, P.E., S.E.

12 Practical Solutions Foundations for Metal Building Systems

By Alexander Newman, P.E.

16 Codes and Standards Wind Farm Tower Design

By Nestor A. Agbayani, P.E., S.E., SECB and Rolando E. Vega, Ph.D., P.E.

34 Professional Issues Façade Attachments

By Filippo Masetti, P.E., Milan Vatovec, P.E. and James C. Parker, P.E., S.E.

Special Section: Seismic Products

ON

THE

DEPARTMENTS

COVER

The largest collection of Salvador Dalí’s art outside of his hometown in Spain is in St. Petersburg, Florida. Walter P Moore was named an Outstanding Award Winner in the 2012 NCSEA Annual Excellence in Structural Engineering awards program for their work in building a new iconic facility that would not only protect Dalí’s artwork, but would also attract worldwide attention. This project is the Spotlight article on page 43.

July 2013 Wind

7 InFocus

IN EVERY ISSUE 6 Advertiser Index 40 Resource Guide (Concrete) 44 NCSEA News 46 SEI Structural Columns 48 CASE in Point

A Look at Insurance Options

By Gail S. Kelley, P.E.

41 InSights ASCE 7 and the Standards Development Process

By Jennifer Goupil, P.E.

43 Spotlight A Treasure Box for Dalí

By Scott D. Martin, P.E.

50 Structural Forum

Publication of any article, image, or advertisement in STRUCTURE® magazine does not constitute endorsement

by NCSEA, CASE, SEI, C 3 Ink, or the Editorial Board. Authors, contributors, and advertisers retain sole responsibility for the content of their submissions.

STRUCTURE magazine

38 Legal Perspectives

4

July 2013

Increasing the Velocity of Knowledge

By Gene Frodsham, MS, S.E.

Editorial

Contribute to Your Profession new trends, new techniques and current industry issues and it Pays You Back

By Andrew Rauch, CASE Chair

F

irst, I would like to extend my condolences to the family, friends, and colleagues of Doug Ashcraft who recently passed away after a battle with cancer. Doug was instrumental in developing many of the CASE Risk Management Tools and served for a time as CASE Chair. He was a tremendous person who was committed to the structural engineering profession. He will be missed by all of us.

As I begin my two year term as CASE chair, I wanted to take this first opportunity to introduce a little of my background to you. I am a principal in a mid-size firm, about 40 people, that practices civil and structural engineering in the upper Midwest. Our practice is a rather “salt of the earth” type of practice. We design schools, courthouses, and jails, apartments, office buildings and warehouses.

Along with those common project types, we also have had the opportunity to design some rather interesting structures including a South American Embassy and the first LEED® platinum building in the State of Minnesota. We also have done some unusual projects like moving a 90 year old vaudeville theater a block and a half so that it could be salvaged and then remodeled into a fine dance theater. But, in general, we are a typical firm that tries very hard to provide great service for our clients.

So why is it, then, that I am able to say that I am the third person from our firm to hold this position? I truly believe that it is because our firm has a culture and expectation of being involved. It is not sufficient or acceptable to simply pay your dues and be a member of a professional organization. Rather, you are expected to become involved and contribute to the activities of the organization. This active involvement not only allows you to contribute to your profession, it pays back many times over.

The first way that it pays back is in a better understanding of our profession. The first project that I was involved in with CASE, about 12 years ago, was to help write a commentary on the AISC Code of Standard Practice. To prepare for that effort, I needed to read through the entire document. Sure, I was already familiar with it and had read parts of it that I was interested in. But this time was different. I read through it making sure that I understood what it was saying. I also had to read it with an eye towards how my expectations during a project might differ from what was written in the Code of Standard Practice and just what the Code of Standard Practice expects from the design profession. Then, as we met and discussed the document, I more fully understood just how differently engineering is practiced in various parts of the country.

STRUCTURAL The second way involvement ENGINEERING pays back is information sharing.

INSTITUTE At that first meeting, I was introduced to engineers with far more

“...it is because our firm has a culture and expectation of being involved. It is not sufficient or acceptable to simply pay your dues and be a member of a professional organization. Rather, you are expected to become involved and contribute to the activities of the organization. This active involvement not only allows you to contribute to your profession, it pays back many times over.”

Celebrating

years

1993-2013

a member benefit

structurE

®

experience than I had. It was fascinating to listen to their experiences, and insights into the document and engineering practice. Over the years, I have been able to ask questions and gain insight about a variety of topics like hiring practices and bonuses and incentive programs.

This insight has come from engineers in large and small firms and from all parts of the country. One of my fellow committee members made it a point to come to each meeting with a list of questions to which he wanted to get an answer. What a great way to maximize the benefit of your involvement!

Finally, this involvement pays back in networking and friendships.

My involvement has allowed me to meet conscientious, committed engineers from around the country. I am glad to call many of these people my friends. I can count on this network of people for advice if I need to know about local construction practices for a project, if I need design advice about a system or technique with which I am not familiar, or if I might need consulting services on a project requiring expertise that our firm does not have.

So, how do you become involved? If you have an interest in business practice and risk management issues and your firm is an ACEC member, think about becoming involved in CASE. You can contact me or Heather Talbert at ACEC (htalbert@acec.org). If your firm is not already an ACEC member, contact your state ACEC organization and get the process started.

If you have an interest in national structural engineering issues such as licensing and building codes, become a member of your state Structural Engineering Association and become actively involved at the state and national level. If you have an interest in structural engineering standards or the other activities of ASCE’s Structural Engineering Institute, become a member, find out about their committees and seek to join one that interests you.

There are many other ways for you to get involved. There is the old saying, “the world is run by those who show up.” Get involved, contribute to your profession and watch that involvement pay you back many times over.▪

STRUCTURE magazine

Andrew Rauch is a principal with BKBM Engineers in Minneapolis, MN. He can be reached at arauch@bkbm.com.

5

July 2013

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Editorial Board Chair

Burns & McDonnell, Kansas City, MO chair@structuremag.org

Brian W. Miller

CBI Consulting, Inc., Boston, MA

Mark W. Holmberg, P.E. Dilip Khatri, Ph.D., S.E.

Greg Schindler, P.E., S.E.

Khatri International Inc., Pasadena, CA

KPFF Consulting Engineers, Seattle, WA

Roger A. LaBoube, Ph.D., P.E.

Stephen P. Schneider, Ph.D., P.E., S.E.

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John “Buddy” Showalter, P.E.

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American Wood Council, Leesburg, VA

Chase Engineering, LLC, New Prague, MN

EditoriAL stAFF Executive Editor Jeanne Vogelzang, JD, CAE

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STRUCTURE® (Volume 20, Number 7). 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 $65/yr domestic; $35/yr student; $90/yr Canada; $125/yr foreign. For change of address or duplicate copies, contact your member organization(s). 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

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inFocus

new trends, new techniques and current industry issues The Intellectual Virtue of Engineering

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

B

ased on the work of Allison Ross and Nafsikas Athanassoulis, I have identified safety, sustainability, and efficiency as “The Internal Goods of Engineering” (March 2013). Based on the work of Gene Moriarty, I have identified objectivity, care, and honesty as “The Moral Virtues of Engineering” (May 2013).

However, I have also acknowledged the potential for dissonance among the individual goods or virtues in each list. How is an engineer supposed to harmonize them when that happens?

One way to look at this issue is to recall that engineering involves the exercise of skill (“The Nature of Competence,” March 2012).

Rules and maxims can help novices and advanced beginners learn to incorporate safety, sustainability, and efficiency into their designs; but it takes someone who has enough experience to be at least competent, if not proficient, to do so consistently. Successfully integrating all three could be seen as the mark of a true expert.

Many philosophers have drawn a strong analogy between virtues and skills (“Virtue as a Skill,” May 2012), so the same terminology applies to those who characteristically exhibit objectivity, care, and honesty in the proper proportions.

Ross and Atahanassoulis seem to agree, observing that engineers internalize these goods and virtues to the point that they are able to balance them rightly in particular cases, having developed “a reliable capacity to respond to risk with the appropriate attitude.” They affirm that “professionals acquire, through training and thought, settled dispositions to judge in accordance with their distinctive professional values and thus can be said to exemplify a kind of professional practical wisdom”; i.e., phronesis (“Knowledge, Rationality, and Judgment,” July 2012).

This notion strikes me as closely related to a faculty that engineers constantly take for granted but rarely try to explain: engineering judgment. Michael Davis, a philosophy professor at Illinois Institute of Technology, addressed the challenge of delineating exactly what it is in a 2012 paper (“A Plea for Judgment,” Science and Engineering Ethics, Vol. 18, No. 4, pp. 789-808). As he says, “One who otherwise knows what engineers know but lacks ‘engineering judgment’ may be . . . a handy resource much like a reference book or database, but cannot be a competent engineer.”

Similar to Ross and Athanassoulis, Davis defines judgment as “the disposition (including the ability) to act as competent members of the discipline act.” It involves more than just (theoretical) knowledge-that or even (technical) knowledge-how; it is “the embodiment of a high likelihood of making certain decisions in the appropriate way at the appropriate time.” Such judgment is neither arbitrary nor algorithmic, and the reference to peers as the benchmark is consistent with the legal notion of the standard of care – the level or quality of services that is ordinarily provided by practitioners of good standing in the same field under similar circumstances.

Davis portrays judgment as the key to integrating ethics into any discipline that requires it. “Once we see judgment as central to the discipline, we can also see how central ethics is to its competent practice. There is no good engineering, no good science, and so on without good judgment and no good judgment in these disciplines STRUCTURE magazine

without ethics.” However, Davis is quick to clarify what kind of ethics he has in mind and reveals a deontological orientation: “I mean those (morally permissible) standards of conduct (rules, principles, or ideals) that apply to members of a group simply because they are members of that group. Engineers need to understand (and practice) engineering ethics to be good engineers, not moral theory, medical ethics, or the like.”

As Davis acknowledges, this approach – unlike that of Ross and Athanssoulis – treats applied ethics as a matter of technical rationality (techne), rather than practical judgment (phronesis). Despite recognizing that engineering judgment, like phronesis, is “a disposition to act in an appropriate way,” he defines the latter much more broadly as “the ability reliably to respond to any situation with a course of action that makes life better … Phronesis is (more or less) a global term; judgment is not global … We should speak of the art, craft, or skill of [an engineer] rather than his phronesis when he shows good [engineering] judgment.”

Nevertheless, Davis explicitly wonders whether engineering judgment is a virtue, since it admittedly “is a disposition that contributes to living well (both to the engineer’s living well and to others living well).” Ultimately, though, Davis remains worried about the limited scope of judgment in this sense; as he notes, “The traditional virtues (courage, hospitality, truthfulness, and so on) concern the whole of life. No traditional virtue concerns only a single discipline as, for example, engineering judgment does.”

Personally, I do not see this as a problem, given MacIntyre’s situation of virtues within distinct practices. Engineering judgment is, in fact, a discipline-specific form of practical judgment, which Aristotle classified as an intellectual virtue – importantly, the one that guides and ultimately unifies the corresponding moral virtues.

As Moriarty summarizes: Phronesis is at work in discerning and choosing appropriate goals of ethical virtue. Thus, ethical virtue without phronesis remains directionless. But, discernment of the good and perfection of deliberation are dependent on having good character. Hence, without ethical virtue, one might have cleverness in figuring out the means to any end, but one would not have phronesis, the virtue of choosing the appropriate means to the right end.

This intellectual virtue of practical judgment – i.e., engineering judgment – is thus what makes it possible for engineers steadfastly to achieve their practice’s internal goods of safety, sustainability, and efficiency, while conscientiously exhibiting its moral virtues of objectivity, care, and honesty.▪ Jon A. Schmidt, P.E., SECB (chair@STRUCTUREmag.org), is an associate structural engineer at Burns & McDonnell in Kansas City, Missouri. He chairs the STRUCTURE magazine Editorial Board and the SEI Engineering Philosophy Committee, and shares occasional thoughts at twitter.com/JonAlanSchmidt.

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July 2013

performance issues relative to extreme events

ONCOMING WIND

STRUCTURAL PERFORMANCE

Along-Wind Torsional-Wind

Across-Wind

S

Figure 1: Components of tall building response to wind excitation.

tructural design of tall buildings is driven by forces of nature, including wind and earthquakes. As buildings get taller, windinduced dynamic response dictates the design of the lateral system to meet both serviceability and survivability limit states. Structural engineers rely upon wind tunnel consultants to determine equivalent static loads (ESL) and top floor accelerations (TFA). This becomes increasingly important for tall and slender towers where across-wind effects dominate. After the building has been tested, the structural design continues to develop, resulting in changes to the mass and/or the stiffness. To quantify the increase or decrease in ESL and TFA, the structural engineer needs to send an updated set of dynamic properties to the wind consultant for a new cycle of post-processing. This article presents an alternative to this process in the form of design charts that enable the design engineer to adjust ESL and TFA for changes in mass and/or stiffness. The interaction between the design team and the wind consultant could then be saved for

Across-Wind Response of High-Rise Buildings Adjusting for Changes in Mass and Stiffness

By Rafik R. Gerges, P.Eng, Ph.D., S.E., SECB, LEED AP, BSCP and Kal Benuska, P.E., S.E.

Rafik R. Gerges, P.Eng, Ph.D., S.E., SECB, LEED AP, BSCP, is a Project Manager at John Martin & Associates, Inc., Los Angeles, California. Dr. Gerges can be reached at rgerges@johnmartin.com.

Kal Benuska, P.E., S.E., is a Principal of John A. Martin & Associates, Inc., in Los Angeles, California.

Mr. Benuska can be reached at benuska@johnmartin.com.

major design milestones to confirm wind loads and responses.

How does Wind Excite a Tall Building?

Under the action of wind, tall structures are loaded simultaneously in the along-wind, acrosswind and torsional directions as shown in Figure 1. The loads can be broken down into static loads due to mean wind pressure and dynamic loads due to fluctuating pressure. The fluctuating pressure induces two distinct responses; a low-frequency background component and a resonant component at the fundamental frequency of the structure. While all three sources contribute to the along-wind loading, only the fluctuating wind pressure – the background and resonant components – results in the across-wind and torsional loadings. TFA is a result of the resonant response only. The mean and background components are primarily dependent on the building geometry and the turbulence environment, while the resonant response, in addition to geometry and turbulence, depends on the structure’s dynamic properties; mass, stiffness and damping.

fp Design Range

Aerodynamic Fitted Relationship f

S

( f ) /σ M 2

M

f B /U H

Figure 2: Across-Wind Spectra.

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July 2013

Aspect Ratio

Aspect Ratio

Frequency Ratio

Exposure B Exposure C Exposure D

Frequency Ratio

Figure 3: Upper bound for ESL adjustment factor for buildings with square floor plan.

Figure 4: Lower bound for ESL adjustment factor for buildings with square floor plan.

Does the Building Code Address All Three Components?

across-wind response and limited guidance on the torsional response.

ASCE 7 provides a comprehensive treatment of the along-wind response of flexible structures based on the Gust Factor Approach.

However, ASCE 7, similar to many codes and standards, provides no guidance on the

Are There Any Tools to Estimate Across-Wind Response?

Over the years, wind tunnel testing has provided valuable aerodynamic data for the ADVERTISEMENT–For Advertiser Information, visit www.STRUCTUREmag.org

STRUCTURE magazine

Exposure B Exposure C Exposure D

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July 2013

across-wind response. The across-wind spectra exhibits an evident peak around the Strouhal number, as shown in Figure 2. The Strouhal number is measured in terms of non-dimensional reduced frequency, f * = f x B/UH, where f is the natural frequency of the building, B is the building width perpendicular to the approaching wind and UH is the mean hourly

Mass Ratio

wind speed at the building height. The structural response peaks when f * matches the peak frequency (Strouhal number), fp. Tall building designers always tune the structural system to have a reduced frequency, at the strength level wind speed, that is greater than fp as shown in Figure 2.

Relationships have been developed using curve-fitting to predict the across-wind Power Spectral Density (PSD) as shown in Figure 2, as well as the Root-Mean-Square (RMS) of the base moment coefficient. These relationships take into account the turbulence environment, building aspect ratio and building side ratio.

In particular, the model by Gu & Quan is reported to produce a good fit for a wide range of buildings and turbulence environments.

How are Across-Wind Models Used?

Frequency Ratio

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Non-dimensional across-wind models can be used to compute wind-induced response of any structure having architectural features and a turbulence environment that are within the limits of the model. The model by Gu & Quan was calibrated for aspect ratios of 4 to 9, side ratios of 0.5 to 2 and four different wind exposures. Using this model, the upper-bound ESL adjustment factor chart is developed and is shown in Figure 3 (page 9) for buildings with a side ratio of 1.0. The adjustment factor is plotted vs. the frequency ratio (original frequency / new frequency) on the horizontal axis and the aspect ratio on the vertical axis. Similarly, a lower-bound ESL adjustment factor chart is shown in Figure 4 (page 9). Figures 3 and 4 indicate that the base moment decreases with an increase in the natural frequency of the structure, but increases more rapidly with a decrease in the natural frequency. This is consistent with the increased slope of the PSD as f * moves toward fp. The charts show a slight dependency on the wind exposure.

230

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Exposure B Exposure C Exposure D

Figure 5: TFA adjustment factor for buildings with square floor plan and aspect ratio of 7.

A TFA adjustment factor chart is shown in Figure 5 for buildings with a side ratio of 1 and an aspect ratio of 7. The adjustment factor is plotted vs. the frequency ratio (original frequency / new frequency) on the horizontal axis and the mass ratio (original mass / new mass) on the vertical axis. Figure 5 indicates that TFA decreases with an increase in frequency and/or mass of the structure, as expected. The dependency on the exposure is insignificant.

Design Example Consider a 76-story residential concrete tower located in Los Angeles, California. The overall height of the building is about 260 meters (858 feet) with a square floor plan roughly 37 meters (121 feet) on each side. The wind exposure category is close to B as defined by ASCE 7. The lateral system consists of a reinforced concrete shear wall core with rigid outriggers (in one direction), and the gravity system consists of concrete flat plates supported by concrete columns. The resonant wind response, reported by the wind tunnel consultant, was mainly due to across-wind effects, with TFA of 18 milli-g. During the design development phase, the design team learned that the original target strength of 10,000 psi for concrete would not be achievable using local aggregate. The owner asked the design team to reevaluate the structural system using a maximum concrete strength of 7,000 psi. This concrete strength reduction resulted in a stiffness decrease of about 16%, which then reduced the natural frequencies by approximately 8%. Figure 5

STRUCTURE magazine

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shows an increase in TFA of about 12%. From a strength point of view, the force increased by approximately 12-18% based on Figures 3 and 4. Increasing the flexural strength of the shear walls was not an option due to seismic considerations in shear.

The design team decided to add post-tensioning to the concrete flat plates in order to reduce their thickness by about 20%. This reduced the generalized mass by about 15%, restoring the building’s original fundamental frequencies so that the wind strength design could remain unchanged. However, the mass decrease also resulted in a TFA increase of about 20% per Figure 5. To deal with this, the design team proposed a damped outrigger system (90° to the rigid outriggers) to increase the sway mode equivalent damping ratio from 1% to 3% (in one direction), thus achieving TFA of 13 milli-g.

Conclusion Changes in mass and stiffness during design affect a structure’s dynamic response to wind effects, which in turn require revisions to the associated equivalent static loads and top floor acceleration. Charts such as those in Figures 3, 4 and 5 provide a “quick and dirty” tool to estimate the impacts of such changes on strength and serviceability.

However, confirmation from revised wind tunnel post-processing is still strongly recommended at design milestones. Engineered damping provides an economical alternative to meet serviceability (and possibly strength) design requirements, even at the final stages of structural design.▪

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(a)

Practical SolutionS

H HL

WIND

H HL

HR VL

VR

solutions for the practicing structural engineer

HR

VL

VR

L

L

(a)

(b)

Figure 1: The direction of horizontal column reactions in a single-span rigid frame: (a) from gravity loads; (b) from wind or seismic loads.

M

etal building systems (MBS), also known as pre-engineered metal WIND H buildings, are proprietary structures designed and manufactured HL HR by their suppliers.

Metal buildings are extremely VL and they account for a substantial VR popular percentage of low-rise nonresidential buildings in the L United States. The design of foundations for these (b)structures often involves special challenges. The design procedures are often not well understood, because they are not specified in the building codes and technical design guides. Until the recent publication of Foundation and Anchor Design Guide for Metal Building Systems (McGraw-Hill, 2013), there have been no authoritative books on the subject. As a result, the foundation designs produced by different engineers for the same metal building structure could range from those that cost a trivial amount to those that are quite expensive to construct. This article discusses the reasons for such disparity and misunderstanding and examines the available design options.

Foundations for Metal Building Systems Finding a Practical Solution for Your Project

By Alexander Newman, P.E., F. ASCE

Alexander Newman, P.E., F. ASCE, is a forensic and structural consultant in the Boston area. He is the author, most recently, of the Foundation and Anchor Design Guide for Metal Building Systems (McGraw-Hill, 2013). He can be reached at Alexander-Newman@ Outlook.com.

The Main Challenges Several challenges make foundations for metal building systems different from those used in conventional buildings: • Single-story MBS are extremely lightweight. The total weight of the structure could be between 2 and 5 pounds per square foot (psf ), which means that a strong wind results in a net uplift loading on the foundations.

• The most popular types of the primary frames used in MBS – gable rigid frames – exert significant horizontal column reactions on the foundations.

Such reactions could be present in some conventional building foundations as well, but rarely at every column, and in combination with uplift.

• Because MBS are proprietary structures, the manufacturers often report slightly

12 July 2013

different column reactions for the buildings with identical loading and configuration.

In the construction projects that use public funding and require competitive bidding, the MBS manufacturers cannot be selected prior to the foundations being designed.

Accordingly, the column reactions must be estimated by the foundation designers, running the risk that the final reactions will exceed those used in the design.

• Unfortunately, in many situations the owner of the building decides to procure the metal building superstructure first and design the foundations later, as an afterthought.

Without a structural engineer involved in establishing the design parameters for the MBS, some manufacturers might choose to provide the cheapest design possible. One such example is a building with fixed-base frame columns, which might result in minor cost savings for the manufacturer but in major cost increases for the foundation vis-à-vis pin-base columns.

• The lack of clear design procedures naturally results in uneven design solutions. Some foundation designs for metal buildings have been overly complicated, and some have been barely adequate for the imposed loads (or not adequate at all).

Uplift and Horizontal Column Reactions In single-story MBS, the dead load is generally insufficient to counteract the effects of wind-generated uplift. In addition, building codes require that no more than 60% of “the dead load likely to be in place” be used in combination with wind uplift (the International Building Code (IBC) “basic” load combination for the allowable stress design method). Thus the weight of the “ballast” must be substantial. For a typical shallow foundation, such as an isolated column footing, the “ballast” consists of the footing, column pedestal (if any), and the soil on the ledges of the footing.

Some engineers also include a contribution of the soil frictional resistance.

Quite often, the minimum size of column foundations is dictated by the minimum amount of “ballast,” not by the soil-bearing capacity for downward loads. This often comes as a shock to the foundation designers unfamiliar with MBS specifics. The design example in the sidebar illustrates the process of sizing an isolated column footing for uplift.

Gable rigid frames exert horizontal column reactions on the foundations. This occurs under gravity loading, when the reactions are numerically the same but act in opposing directions (Figure 1a), as well as under wind or seismic loading, when the reactions usually act in the same direction (Figure 1b).

Some Available Foundation Systems The vertical and horizontal column reactions can be resisted by a variety of foundation systems, such as those listed below and illustrated in Figure 2 (page 14). Properly designed, each system can resist the required level of horizontal and vertical frame reactions. However, experience shows that some systems could be more or less applicable in various circumstances. Each system has advantages and disadvantages, as summarized in Table 1.

Table 1: Comparative cost, reliability and degree of versatility of selected foundation systems for metal building systems.

Foundation System

Cost

Reliability

Versatility

Low to high

Low to high

Low to medium

Hairpins and Slab Ties

Low

Low

Low

Moment-Resisting Foundation

High

High

High

Tie Rod

Slab with Haunch

Medium

Low to high

Low to medium

Medium to high

High

High

Mat

High

High

Low

Deep Foundations

High

High

High

Trench Footing

The table compares cost, reliability and degree of versatility of the selected foundation systems used in pre-engineered buildings.

Here, reliability refers to the probability of the foundation system performing as intended for the desired period of time under various field conditions. The most reliable systems can tolerate inevitable irregularities in construction, loading and maintenance. The overall reliability of a foundation system depends on three factors that define the system’s ability to function in adverse circumstances: • Simplicity of installation. The foundations that are difficult to install or require a perfect installation tend to

be less reliable, because some placement errors are common and perfection in foundation construction is rare.

• Redundancy. Redundant systems have more than one load path for transferring the column reactions to the soil. If one load path is blocked, another path takes over.

• Survivability. Can the system maintain its load-carrying capacity after some of the adjoining building elements have become damaged? For example, what happens if the slab on grade is cut or partly removed? continued on next page

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Versatility, as noted in Table 1, is possessed by the systems that can be used with various floor and soil conditions (e.g., floor trenches and pits).

Some foundation systems commonly used in MBS are: • Tie rods (Figure 2a). In this intuitively appealing solution, the foundations at the opposite building columns are tied together, “extinguishing” both horizontal column reactions. Tie rod construction ranges from the cheapest and least reliable, such as a couple of reinforcing bars placed in a thickened slab, to the relatively expensive and much more reliable, such as concrete grade beams. The survivability of the former is low, because there is a distinct possibility that the slab on grade will be cut or partly removed at some point, while the grade beams placed below the slab will likely survive such a scenario. There are also the issues of elastic elongation of the tie rod under load and whether the tie rod is considered a “tension- tie member” under the provisions of the American Concrete Institute standard ACI 318.

The versatility of this system is at the lower end of the spectrum, since tie rods cannot be used in buildings with deep trenches, depressions, and pits.

• Hairpins with slab ties (Figure 2b). The general idea behind this design is the same as in the tie-rod system, but the tension force is resisted by distributed steel reinforcement in the floor slab (slab ties) rather than by discrete tie rods. This is the least expensive method of resisting horizontal column reactions and, for this reason, hairpins have been widely used in the past. But the system suffers from multiple disadvantages. Among them is a total reliance on the floor slab, which makes the system vulnerable to

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FH Column pedestal

Hairpin Tie rod

FH

FH (a)

(b)

Slab ties

FH

FH

(d)

(c)

Figure 2: Common Foundations Used in Metal Building Systems: a) Tie rod; b) Hairpins with slab ties; c) Moment-resisting foundation; d) Slab with haunch.

the slab being cut or partly removed.

Other issues include construction joints in slabs on grade, where the slab reinforcement generally stops, and even the fundamental issue of treating slabs on grade as structural elements. Slabs on ground are excluded from the scope of ACI 318, except when they transmit lateral forces from other portions of the structure to the soil. If the designer intends to have the slab on grade comply with ACI 318, the slab must be designed and constructed with greater care than the prevalent practices. At the very least, it should be reinforced more substantially than with a layer of light welded-wire fabric, to provide for a minimum percentage of “shrinkage” reinforcement.

• Moment-resisting foundations (Figure 2c). These foundations work similarly to cantilevered retaining walls: the weight of the foundation, and any soil on top of it, resists overturning and sliding caused by external horizontal forces. Because it does not depend on a contribution of the slab on grade, the moment-resisting foundation represents one the most reliable systems available. It also is one of the most versatile, since deep trenches, depressions, and pits in the floor – or no floor at all – do not affect its function. The system can even be used in hillside installations, where one end of the building is lower than the

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other. However, the design procedures for moment-resisting foundations are relatively lengthy and the construction costs could be high.

• Slab with haunch (Figure 2d ). This system has been widely used in residential construction, and some have tried to use it for supporting large pre-engineered buildings as well.

The slab with haunch, also known as a downturned slab, works similarly to the moment-resisting foundation, and a rigorous design would result in the “haunch” of the size similar to the footing of the moment-resisting foundation. Needless to say, this is not the size the proponents of this system hope for. The reliability and versatility of the slab with haunch depends on whether the design relies on the contribution of the slab on grade. If it does, both reliability and versatility would be at the low end of the spectrum, similar to the hairpin system.

• Trench footing (Figure 2e). In this design, a deep trench is excavated and filled with concrete. The resulting foundation could be made heavy enough to resist uplift and deep enough to develop passive pressure of the soil. Since the design does not depend on the contribution of the slab on grade, both reliability and versatility of this system are high. Obviously, the trench footings (also known as mass foundations or

(f) Widen trench footing at columns Slab Slabon ongrade grade

FFH H

FFH H

(e)

FFH H

FH

(f) (f) Widen Widentrench trench footing footing at at columns columns

(e) (e)

Figure 2 (continued): Common Foundations Used in Metal Building Systems: e) Trench footing; f ) Mat; g) Deep foundations.

FFH H

(g)

formless footings) can only be used in the soils that allow for the excavated trench to be stable during construction.

This typically requires clayey soils.

• Mats (Figure 2f ). Using mats might be advantageous in metal building

foundations bearing on poor soils.

According to one rule of thumb, when isolated column footings cover more than 50% of the building’s footprint, mats become economical. Mats are typically reinforced in two directions,

A Simplified Design Example for Sizing an Isolated Column (g) (g) Footing for Downward Forces and Uplift.

Given: Select the size of an isolated column footing to support an interior column of a single-story multiple-span rigid frame. The spacing of the interior columns within the frame is 60 feet; the frames are 25 feet on centers. The following loads act on the roof: 3 psf dead load, 30 psf design roof snow load, and 14 psf wind uplift. The depth of the footing must be at least 3 feet below the floor. The column is supported by a 20 inch by 20 inch concrete pedestal extending to the top of the floor. Use allowable soil bearing capacity of 4000 psf. Assume the average weight of the soil, slab on grade and foundation is 130 lbs/ft3. The building is not located in the flood zone. Use IBC basic load combinations.

Solution. The tributary area of the column is 60 x 25 = 1500 (ft2). The design loads on the column are: Design dead load D = 4.5 kips Design snow load S = 45 kips Design wind uplift load W = –21 kips Total downward load D + S = 4.5 + 45 = 49.5 kips Total uplift load on foundation (0.6D + W ) = 0.6 x 4.5 – 21 = –18.3 kips Weight of the soil, slab on grade and foundation is 0.130 kips/ft3 x 3 ft. = 0.39 kips/ft2 (ksf) Net available soil pressure is 4.0 – 0.39 = 3.61 (ksf ) Required area of the footing for downward load is 49.5/3.61 = 13.71 (ft2) For downward load only, the sign of the footing is 3.7 feet by 3.7 feet at a minimum.

Check stability against wind uplift. Minimum required weight of the foundation, soil on its ledges and tributary slab on grade (Dmin, found) can be is found from: 0.6Dmin, found + W = 0 Dmin, found = 18.3/0.6 = 30.5 (kips) This corresponds to 30.5/0.130 = 234.62 (ft3) of the average weight of “ballast” With the depth of footing 3 feet below the floor, this requires the minimum square footing size of (234.62/3)1/2 = 8.84 (ft.)

To reduce the footing size, try lowering the bottom of the footing by 1 foot. Then the minimum required square footing is (234.62/4)1/2 = 7.66 (ft.).

To arrive at a nominal size, use 8.0 by 8.0-foot footing, with a depth of: 234.62/(8)2 = 3.67 (ft.).

The final footing size is 8.0 ft. x 8.0 ft. x 3 ft. 8 in. deep, as controlled by uplift.

The complete version of this design example, including concrete design for various loading conditions, can be found in the new book, Foundation and Anchor Design Guide for Metal Building Systems (McGraw-Hill, 2013).

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both at the top and at the bottom.

Heavyweight mats work well in resisting wind uplift, and their continuous reinforcement solves the problem of “extinguishing” the horizontal column reactions at the opposite ends of the frames. One challenge of using mats in metal buildings with multiple-span rigid frames is the placement of anchor bolts for interior columns. This often requires placing a separate “mud slab,” which can be used to temporarily support anchor bolts. Mats possess high reliability – they are unlikely to be cut casually – but a low versatility, because they do not work with deep trenches, depressions, and pits. Their cost is relatively high.

• Deep foundations (Figure 2g). There are two main types of deep foundations: deep piers (also called caissons, or drilled shafts) and piles. Deep piers typically possess enough dead load to counteract moderate wind uplift.

If additional “ballast” is needed, a contribution of the perimeter grade beams could be considered. The grade beams also engage the passive pressure-resistance of the soil and thus help resist horizontal column reactions. Piles can resist both uplift and horizontal forces in a variety of ways, including friction in cohesive soils and flexure. Because deep foundations generally do not depend on a contribution of the floor slabs, these foundations are both reliable and versatile. But they are also costly and are typically used in only poor soils, particularly those where weak strata are underlain by competent materials.

By understanding the advantages and disadvantages of various foundation systems used in pre-engineered buildings, designers should be able to select the foundation design that most closely matches the expected use, configuration and performance of the building as a whole.▪

Codes and standards updates and discussions related to codes and standards

I

n the CASE Business Practices article titled, “Too Many Codes Spoil the Design?

Conflicts and Hidden Requirements Can Hurt You!” published in the September 2012 issue of STRUCTURE® magazine, Kirk A. Haverland wrote about a topic familiar to US engineers in the wind energy industry. Mr. Haverland describes the situation where a professional structural engineer “if presented with the opportunity to design a structure that is a little different” hopefully should be able to do his homework and “research the idiosyncrasies of industry practice, design requirements, different codes and standards, etc.” The piece further describes a problematic scenario where the building code (i.e., “Code” based on 2009 IBC and ASCE 7-05) may not necessarily govern the design. That is, various reference standards are in conflict, and design may be governed by undocumented and un-codified information known only to those engineers “in the know.” Unfortunately, this accurately describes the situation faced by US engineers trying to engage in wind turbine support structure analysis, design and permitting.

The primary difficulty is the lack of a dedicated wind turbine generator system (WTGS) support structure design standard. The US wind industry has been developing utility-scale wind farms for over three decades, and yet in that time there has been no clear guidance in the US for the design and permitting of WTGS support structures. The domestic wind industry utilizes foreign design standards used by the European wind turbine original equipment manufacturers (OEM) who had initially dominated the global wind energy market.

Wind Farm Tower Design Introducing ASCE/AWEA RP2011

By Nestor A. Agbayani, P.E., S.E., SECB, M. ASCE and Rolando E. Vega, Ph.D., P.E., M. ASCE

Nestor A. Agbayani, P.E., S.E., SECB, M. ASCE, is a Principal Engineer at Agbayani Structural Engineering. Nestor may be reached at nagbayani@sbcglobal.net.

Rolando E. Vega, Ph.D., P.E., M. ASCE, is the Director of Renewable Energy Research at the University of Texas at San Antonio, Texas Sustainable Energy Research Institute. Rolando may be reached at Rolando.Vega@utsa.edu.

Introducing RP2011 In the absence of specific domestic design guidelines or standards, demonstrating Code compliance has been a challenge. In 2009, the American Society of Civil Engineers (ASCE) and the American Wind Energy Association (AWEA) formed a joint committee to provide US design guidance. This article introduces one of the results of that effort: a new reference document for the analysis, design and permitting of utility-scale wind farm towers titled ASCE/AWEA RP2011: Recommended Practice for Compliance of Large Land-based Wind Turbine Support Structures (Figure 1 ).

RP2011 is a resource for structural engineers engaged in utility-scale wind farm tower design or permitting. The recommended practices are intended to help engineers establish an appropriate design basis for producing tower and foundation designs that meet established

16 July 2013

Figure 1: ASCE/AWEA Recommended Practice for Compliance of Large Land-based Wind Turbine Support Structures (ASCE/AWEA RP2011) © The American Wind Energy Association.

wind industry standards and that comply with Code. RP2011 is also intended to assist Authorities Having Jurisdiction (AHJ) who are responsible for permit process plan review of WTGS towers and foundations. RP2011 is available as a free download at the AWEA website: www.awea.org.

As an example, this article will describe some of the major idiosyncrasies of wind industry structural design practice for WTGS steel fabricated tube towers. Applying conventional Code provisions alone as a design basis would likely result in an under-designed structure. Similarly, applying Code provisions alone for plan review compliance would be too permissive and give a “pass” to that same under-designed structure. It has been argued that the Code is a minimum standard for compliance and that the wind industry is free to meet a higher standard.

Unfortunately, that argument is misapplied, since the Code minimum standard does not capture the correct governing structural design basis in terms of loading, WTGS behavior, and industry norms.

The Tower The steel fabricated tube tower is currently the most typical structure type in use in the domestic and international utility-scale wind industries. While WTGS machine components may fail and be repaired or replaced through maintenance, the tower support structure must perform more reliably and without failure (Figure 2 ). At this time, RP2011 addresses only this tower structure type. To most engineers and others who are wind industry outsiders,

the tube tower appears to be a simple structure. In reality, structural engineers “in the know” understand that the simple appearance belies the inherent design complexities.

CONSTRUCTION CEMENT

Primary Design Issues

FA S T ER

Wind Design

Earthquake Design Applying Code seismic provisions is immediately problematic because a steel fabricated tube WTGS support structure does not appear in ASCE 7-05 Table 15.4-2, Seismic Coefficients for Nonbuilding Structures not Similar to Buildings. Faced with this, the engineer may use engineering judgment to apply the R factor for a similar structure: perhaps a steel stack with R=3, an inverted pendulum with R=2; or a steel pole telecommunications tower with R=1.5. Note that “all other self-supporting structures …” with R=1.25 has a 50 feet height limitation in SDC D and greater, which would be

STRONGER MORE DURABLE 3000 PSI IN 1 HOUR

Figure 2: WTGS with steel fabricated tube tower.

Courtesy of Rolando Vega.

too short for utility-scale towers. This is a reasonable approach, but there are other considerations. Virtually all utility-scale WTGS towers are thin-shell steel tubes whose design strength is governed by the limit state of local buckling and, therefore, they have very low ductility and little overstrength. Moreover, there are other unfavorable characteristics: the tower is a single member with no redundancy; the system is top heavy with the wind turbine concentrating up to one-half of the total system mass at the tower top; and, the tower itself has very little inherent structural damping. Finally, the Code earthquake load combinations do not capture the wind industry’s governing earthquake load combination.

RP2011 Section 5.4.4.5 recommends the consideration of two earthquake loading conditions: • IBC-compatible loading: gravity plus earthquake.

• IEC-compatible loading: gravity plus earthquake plus operational load.

For the IBC loading, RP2011 recommends R=1.5 along with the Code design response spectrum adjusted to a 1%-damped spectrum. The earthquake load is used in Code seismic load combinations. The wind turbine is assumed to be at standstill, so there is no effective structural damping contribution from the turbine’s interaction with the wind in the form of aerodynamic damping. For this reason, RP2011 recommends adjustment of the Code’s 5%-damped design response spectrum to a level of 1% damping, resulting in an increase in spectral ordinates by a factor of about 1.4. continued on next page

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Typical application of the Code’s wind provisions would entail ASCE 7’s Section 6.5 Method 2 – Analytical Procedure. However, this loading may not be the governing wind loading for the WTGS tower. In fact, the Code’s extreme wind (1-in-50 year, 3-second gust) represents only one of many design load combinations (DLC) considered by the wind industry standard IEC 61400-1 published by the International Electrotechnical Commission (IEC). While the Code’s extreme wind may result in high design forces, the turbine OEM’s loads may contain other DLCs that produce even higher design loads that have no parallel in the Code, such as “turbine emergency stop” or “extreme annual operating gust plus electrical fault.” Code loading alone may be insufficient for WTGS tower design. Complete IEC WTGS design loading is obtained from a complex time series simulation, modeling the turbine’s proprietary aerodynamic, mechanical and physical properties. This analysis is usually performed by the turbine OEM’s specialists who compile the design loading into a comprehensive “loads document.” RP2011 Sections 5.4.8 and 5.4.9 provide strategies for reconciling building Code wind design loading with IEC site class extreme loading and recommends appropriate ASCE 7 design parameter values. Section 13 provides guidance on understanding the turbine OEM’s loads document. Section 14 also discusses the differences in wind speed and turbulence intensity profiles between ASCE 7-05 and that of the IEC standard wind site class definitions.

For the IEC loading, RP2011 recommends R=1.5 in conjunction with the IEC seismic plus operational load combination that considers the somewhat likely situation where the WTGS is operating in a power production mode when the design earthquake event strikes. In this case, the effective damping contribution from the operational turbine is considered sufficient to allow use of the Code’s standard 5%-damped design response spectrum. However, the operational load of the turbine must be included. One such operational load is the “emergency stop load.” In this scenario, sensors (accelerometers) within the operating turbine detect the excessive tower top motions induced by the earthquake event. The “emergency stop” protocol is triggered, engaging the rotor and yaw brakes to rapidly halt the turbine so that it can ride out the excessive tower top motions. It so happens that this creates large tower design loads.

The industry idiosyncrasies do not end here, as there are different ways to combine the earthquake and operational loads.

Without an actual full-blown time series simulation, in practice the engineer separately calculates the Code’s design seismic force and then combines these with the maximum operational loads provided by the turbine OEM. Recognizing that these peak loads do not necessarily occur at the same point in time nor in the same direction, RP2011 recommends a square-root-sumof-squares (SRSS) combination. In contrast, the IEC standard suggests an absolute sum of the peak loads, but it recognizes that this is conservative.

Fatigue Design At this stage of the design, the engineer may have applied Code wind and earthquake provisions along with the additional related IEC criteria. Nevertheless, the tower or portions of the tower may still be under-designed because fatigue may be the governing design condition. Even if the engineer were to have applied American Institute of Steel Construction (AISC) fatigue provisions, the design would still be unconservative with respect to wind industry practices. RP2011 Section 7.3.1 describes and reconciles Eurocode (EN 1993-1-9) fatigue S-N curves with the AISC (ANSI/AISC 360-05) S-N curves. Section 7.3.2 discusses the additional fatigue safety factors required by IEC that do not appear in AISC. Sections 7.3.4 and 7.3.5 introduce the Miner’s Rule linear damage summation method and the fatigue damage equivalent load (DEL) concept, respectively. The point is worth repeating that fatigue often governs all or part of the WTGS tower.

Frequency Separation Assuming all the aforementioned design calculations were performed, the engineer may assume that the tower design is complete. Unfortunately, it is still possible that the tower design may be completely unusable if it does not meet frequency separation criteria. RP2011 Section 5.4.7 states that “to avoid resonance, WTGS should be designed with sufficient separation between system natural frequencies and turbine operational frequencies.” The section provides separation criteria that are in current widespread use in the wind industry practice. Adequate frequency separation is an imperative serviceability condition for WTGS. Upon start of operation, a WTGS with inadequate frequency separation will undergo large and violent backand-forth resonant oscillations. Sensing this, modern turbines will then shut down, preventing any further power production. However, older turbines without such a detection system could reach resonant oscillations large enough to damage or fail the tower. Inadequate frequency separation is remedied during the tower design phase by thickening the tower shell or widening the overall diameter of the lower sections to stiffen the tower, thereby increasing the system mass and natural frequency.

Design for Stress Concentrations Localized portions of the wind tower may still be under-designed. In particular, tower shell areas subject to stress concentrations, i.e., “hotspot” stresses, usually require thickening. For example, stress concentrations occur around wall penetrations such as doorways and cable openings. The wind industry utilizes specific methods of finite element analysis (FEA). RP2011 Section 7.4.2 references an International Institute of Welding (IIW) standard, which gives guidelines on FEA mesh sizes and recommended hotspot stress extrapolation functions.

Other Design Issues Specialized Design Procedures RP2011 Section 7.4 briefly mentions specialized design procedures used in the wind industry for the strength and fatigue design of bolted ring flanges. These bolted flange design methods (such as the “Petersen Model” or “Seidel Method,” so named for their inventor) are more amenable to hand calculation in lieu of FEA. Foundation Design Like the tower, the WTGS foundation design has its idiosyncrasies. RP2011 Section 8.6.1.5 describes “ground gap” limitations that amount to additional overturning stability requirements.

One ground gap criterion requires that under IEC DLCs such as normal power production,

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no ground gap (i.e., zero bearing pressure) shall occur at the foundation-soil contact.

Stated differently, this means that the contact stresses under the entire foundation footprint must remain in compression. Another ground gap criterion states that under service extreme loads, the ground gap shall not extend beyond the center of gravity of the foundation bottom area. Fatigue design of a reinforced concrete foundation is atypical in conventional building design, but WTGS foundations must be designed for high-cycle fatigue loading. This includes anchor rods and non-prestressed steel reinforcement bars. RP2011 Section 8.5 mentions a few alternative international standards used in the wind industry.

The Future of RP2011 Although RP2011 is a first-of-its-kind design guidance document for WTGS support structures in the US, as a “recommended practices” document it is certainly far from being a design standard. At this time, there are two goals for RP2011’s future: (1) The first goal would be the evolution of RP2011 or its future successor document into a standard, specifically into an ANSI standard to give the document credibility in the structural engineering community. Next would be an effort to achieve the status of a “code referenced standard” in future editions of the IBC. This would give the standard some “teeth,” i.e., the regulatory authority of Code.

(2) The second goal would be the incorporation of future research to address and improve current gray areas in design knowledge. These include the following topics: a more comprehensive scope to include alternative tower structural systems and materials; improved understanding of tower response to earthquake plus operational loads; better understanding of seismic response and performance at near-fault locations; effective supplementary damping systems; improved understanding of concrete anchor bolt resistance to fatigue; a reliability-based soil-structure interaction framework for Load and Resistance Factor Design of WTGS foundations and improved coordination with future Code editions.

Conclusion WTGS support structure design is subject to many idiosyncratic wind industry practices. It is of critical importance that structural engineers and plan reviewers recognize that many of those practices are beyond Code (from international standards) and may often be above Code (more conservative). RP2011 is an excellent resource to learn about current wind industry design practices and un-codified requirements.▪

Appalachian State University (ASU) Boone, NC

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rowing optimism in the construction industry is bringing provide the most state-of-the-art performance levels and keep our with it new products and services, as companies offer more fabrication processes as economical as possible.” value and advanced features to keep up with customer Other companies see better times, too. “The construction environdemand and their own competitors. ment is becoming more optimistic. It appears that, as the economy At West Jordan, Utah-based CoreBrace, LLC (www.corebrace.com), continues to recover, construction jobs are returning,” notes Aura Chief Engineer Brandt Saxey says that growth in the steel industry is Joyce, Marketing Communications Manager for Aegion Corporation increasing his sales. “We have continued to see strong growth in the (www.aegion.com), headquartered in St. Louis, Missouri and the steel industry and in particular the use of buckling restrained braces parent company of Fibrwrap Construction Services and Fyfe Co. (BRBs) within that industry. The use of BRB systems can bring the “One new and innovative application for the Tyfo Fibrwrap Systems overall construction cost for a building down, often helping to make on light-frame construction is the Tyfo G Wrap System,” says Joyce. the project more feasible and funding more available. Projects incor- “The Tyfo G Wrap System utilizes advanced composite materials to porating BRBs often use less steel; offering not only significant cost strengthen existing gypsum walls, and makes them behave like properly savings, but also contributing to true sustainability.” detailed plywood shearwalls. This is critical in strengthening existing The company supplies a large number of braces for typical buildings apartment buildings that suffer from what is called soft story or weak such as schools, office buildings, and hospitals, but also provides braces story deficiencies.” She adds: “The Tyfo G Wrap systems allows for for large industrial facilities, existing building retrofits, warehouses, the strengthening of these buildings by applying advanced composite bridges, and essentially any structure that an engineer might be materials over existing painted gypsum wall boards without having to designing, Saxey notes. “As the engineering community continues to tear into the wall. This allows for faster construction schedules and become more familiar with the behavior and advantages that BRBs provide, we see designers continually finding novel uses and new applications for them. This sometimes means that new kinds of performance requirements must be met from engineering and fabrication perspectives, which we work constantly to achieve.”

Corebrace recently tested braces specifically designed for bridge applications as well as near-fault earthquake effects B U C K L I N G R E S T R A I N E D B R A C E S such as occurred in Christchurch, New Zealand. This testing included braces fabricated out of standard steel, galvanized steel, and stainless steel, and included both pseudo-static and dynamic rates of loading. Adds Saxey: “Each of these different material types produced a unique set of brace performance data, but each can be fit for any project type. We’ve also WWW.COREBRACE.COM 801.280.0701 recently tested braces designed specifically for retrofit use. These braces are installed ✔ Bolted, Pinned, and Welded Connections— in two separate pieces and spliced in the Fully Qualified and Exceeding AISC 341 Requirements middle, allowing them to be brought in ✔ Real-Time Engineering Assistance and fit-up in tight spaces where the use of a traditional brace would not be possible. ✔ Non-linear Modelling Design Guides These recently tested braces underwent ✔ Maximum QA/QC and Scheduling Control some of the most rigorous testing we have ✔ Integration with RAM Structural System and REVIT ever performed – far exceeding the AISC341 code requirements. Our ongoing ✔ New! “Near Fault Effect” Testing R&D program allows us to continually

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limits the potential exposure of asbestos or other airborne particles that could be hidden within the walls of these buildings.”

Also seeing an improvement is Lyle Simonton, Director of Business Development at Subsurface Constructors in St. Louis, Missouri (www.subsurfaceconstructors.com). “We are seeing a big increase in the use of ground improvement methods in the transportation and commercial sectors. We have performed the design-build of ground improvement solutions for MSE (mechanically stabilized

STRUCTURE magazine

earth) walls for several large DOT projects in several states,” says Simonton. “Additionally, we are seeing several of the big-name retail companies who are building new stores across the country require the use of ground improvement in lieu of remove and replace to speed up construction of these new stores.”

At Subsurface, innovation is key, Simonton says. “As a specialty contractor, we must continue to innovate with our equipment and services so marginal sites can be improved economically, while trying to maintain a technological advantage over our competitors.” He adds: “Engineering consultants and the owners they’re working for seem to be spending more time than ever on trying to bring value to their projects. They’re asking designbuild speciality contractors like us to work closely with them to develop valueadded foundation solutions, which often times means using vibro stone columns/ aggregate piers in lieu of deep foundations or substantial over-excavation.” (See ad on page 20.)

Mo Ehsani, President of QuakeWrap Inc. (www.quakewrap.com) in Tucson, Arizona, says that a major concern in seismic retrofit of structures is the strengthening and confinement of concrete columns. The company in the early 1990s introduced Fiber Reinforced Polymer (FRP) products which had been successfully used worldwide, he says.

However, these repairs use the FRP in what is known as a wet layup procedure, where the fabrics of carbon or glass are saturated in the field with epoxy resins and wrapped around the column. The method requires the column surface to be smooth, and in some post-earthquake repairs this may take additional time so masons can repair the damaged concrete before wrapping. The technique also requires trained contractors who have prior experience with these products.

Now, Ehsani says that QuakeWrap has come up with a new generation of products called PileMedic that make these repairs much faster and easier. “We can now apply heat and pressure to saturated fabrics in our plant to produce a very thin FRP laminate sheet. These sheets are four feet wide by hundreds of feet long and are sold in rolls. The challenge in this technique has been to make these sheets with thicknesses as little as 0.01 inch; the typical sheet is 0.025 inch and has a tensile strength in excess of 150,000 psi. The relatively flexible sheets can be

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continued on page 24

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formed to virtually any shape in the field. In a typical installation, the sheet is wrapped twice around the column and glued to itself to create a very strong “sonotube”-like shell that leaves a small annular space. This annular space between the shell and the column is filled with grout. The entire operation takes about 1-2 hours.” Videos of these applications are available at www.pilemedic.com.

“Like most engineers, we like to solve problems. So we’re continually researching and developing new ideas and asking ‘what can we do better?’.” says Henry Gallart, President of SidePlate (www.sideplate.com), Laguna Hills, California. “CJP welding is expensive and time-consuming, so SidePlate FRAME was developed as an easier way to realize the SidePlate design benefits without having to do any CJP welds. It’s been a huge success by any measure, but many areas of the US still prefer field-bolting. The SidePlate bolted connection was the logical follow-up to that.”

Adds Gallart: “In April, we unveiled a new low-seismic, R=3 system that is field-bolted. The industry response has been tremendous. For higher-seismic areas, just a few years ago we developed a new, more economical system called SidePlate FRAME, that uses only fillet welds in the shop and field. The field-bolted connection is tailored to low-seismic applications and delivers the same SidePlate cost-saving benefits to the overall design, but also solves many of the fit-up issues inherent with other bolted moment connections. For higher-seismic applications, the fillet-welded SidePlate FRAME configuration meets all of the AISC criteria for Special Moment Frames, saves cost on the overall design, and saves a significant amount of construction cost by eliminating CJP welding.” (See ad on page 23.)

Jim Hussin, Director, Hayward Baker, Inc., (www.haywardbaker.com) headquartered in Odenton, Maryland, says that his company is involved in all industries and sectors since nearly all are confronted with geotechnical challenges. “Since its inception over 60 years ago, HBI has established itself in the forefront of geotechnical specialty contracting, evolving and expanding to meet the increasingly complex needs of the construction community. HBI is recognized by the industry to be reliable and innovative experts, and offers full DesignBuild services for virtually any geotechnical construction application.”

Hussin adds: “Soil mixing is a relatively new technology that is growing in use to solve issues related to soft soils and seismic applications. HBI has used this technology to improve ground for a wide variety of structures, especially those subjected to seismic and wind loading.” As for business conditions in general, he notes: “Although not close to the peak levels seen several years ago, Hayward Baker has seen a steady, healthy growth in the construction market over the past couple of years. Hayward Baker has a strong engineering staff and is available to assist SEs with evaluating geotechnical challenges and provide Design-Build services.”▪ STRUCTURE® magazine is planning several additional Special Advertorials in 2013 and 2014. To discuss advertising opportunities, please contact our ad sales representatives Chuck Minor and Dick Railton at Sales@STRUCTUREmag.org

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STRUCTURE magazine

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July 2013

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New York State Capitol Restoration

By Susan L. Knack-Brown, P.E. and Nicholas T. Floyd, P.E.

T

Figure 1: East elevation of the Capitol. Courtesy of Laurie Donald, Bernstein Associates Photographers, for OGS.

he New York State Capitol, designed in various stages by a succession of architects including Leopold Eidlitz and H.H. Richardson, was built between 1869 and 1899.

This landmark building illustrates both Second Empire and Richardsonian Romanesque elements and is an architectural masterpiece with ornate carved stone, vibrant paint finishes and decorative glass, and decorative tiled floors. A number of monumental public spaces such as the Senate and Assembly Chambers, and three monumental staircases (the Assembly, Senate, and Great Western Staircases) help to architecturally define the building. By the late 1990s, the building was losing its luster due to neglect, insensitive major modifications and chronic leakage, dating as far back as 1874, that damaged the exterior stone and interior finishes.

In 1996, the New York State Office of General Services (OGS) embarked upon a study to address the chronic leakage, which grew into a four-phase, 12-year restoration of the roofs and the three staircases, at a cost of approximately $85 million. This award winning project has finally addressed all of the reported leakage through the roofs, as well as restored to prominence the three monumental staircases by

Figure 2a and b: Original mortar-set terra cotta hip installation and new system with stainless steel strut attachments.

STRUCTURE magazine

returning natural light and lost historic features to the spaces. This project’s success has also fostered other, separate restoration efforts within the Capitol that continue OGS’s efforts to restore the landmark to its original prominence.

Accomplishing this project took a team of consultants and contractors from the initial investigation in 1996 through construction in 2012. Success involved a partnership of OGS, contractors, and the design team to ensure quality and craftsmanship befitting this monumental building.

Architectural Terra Cotta Roofing The Capitol has a complex roof arrangement, including several slate and clay tile roofs accented by architectural terra-cotta hips and railings (Figure 1). The original hung slate and clay tile roofing was replaced in the 1960s, incorporating decking and underlayment for added weather protection, but the terra-cotta was the original material dating to the late 1800s. These terra-cotta units were mortar set directly onto the shingled roofing and steel bar stock framing (Figure 2a), and were a source of ongoing leakage that deteriorated the terra-cotta and mortar setting beds and corroded supplemental steel anchors. Prior to this roof project, tiles had been face-fastened with through-anchors and covered with sealant in attempts to address the attachment and leakage concerns; these repairs exacerbated the leakage and resulted in further cracking and degradation of the terra-cotta. Full replacement was deemed necessary.

The replacement design required a water-tight system, with structurally sound attachments that maintained the original appearance and had durability comparable to the terra-cotta material (approximately 100 years). The design team elected to hang the new terra-cotta hip and apron tiles with stainless steel struts and attachment clips, which allowed for a drainable, water-tight copper flashing and continuous membrane underlayment below (Figure 2b). In order to attach these struts and provide a continuous substrate for the copper and membrane, the design included new steel framing and clips at each hip, ridge, and finial configuration to carry the terra-cotta loads back to the existing metal roof structure. The existing roof planes and framing on the Capitol varied significantly, so the design provided dimensional tolerances in the attachment system by use of the struts (allowing

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Figure 3: Granite tower during installation of new substructure and after reinstallation of granite.

adjustability along the roof slope) and shims between the various attachment clips (allowing up/down adjustability). The individual terra-cotta tiles were also shimmed off the strut to accommodate variations in the tiles themselves. Finials and ridge tiles were set as more traditional stacked masonry with new stainless steel attachments.

Pyramidal Granite Towers The Capitol has four pyramidal masonry tower roofs, originally constructed with a granite exterior and a brick masonry vault backup.

Chronic leakage plagued the rooms below these towers, which contained a combination of office space and rooms housing sensitive voting equipment and elevator machinery. A successful design solution needed to eliminate all leakage, while retaining the existing granite cladding, an integral part of the exterior appearance, and without relocating the equipment or machinery below.

During the initial field investigation, it was observed that each course of granite included a back cut in the stone to interlock successive courses. While helping to interlock the tower structurally, this back slope channeled water runoff into the granite bed joints, exacerbating mortar deterioration and leakage. This systemic issue accounted for the previous pointing and sealant repairs’ failure to provide long-term relief from the ongoing leakage.

The design team’s solution was to rebuild the pyramidal roofs as a typical masonry veneer, albeit on a monumental scale. Each pyramidal tower was deconstructed down to the cornice level and all granite units were salvaged, numbered, and stored for reinstallation. The towers were then rebuilt with a steel and precast pyramidal sub-structure on a reinforced-concrete ring beam designed to take the thrust of the new framing (Figure 3). New membrane and copper roofing, and through-wall flashing, were then installed for water management and the original granite was reinstalled with an open drainage cavity.

The final appearance of the rebuilt tower exactly matched the original tower from the exterior.

Assembly and Senate Staircase Restoration Due to safety concerns during World War II, the skylights over the three monumental staircases were painted black. Ongoing leakage through the then dysfunctional skylights prompted their later removal and overclad with copper or slate roofing. In the late 1940s, space pressures within the Capitol prompted the State to infill the upper reaches of the Assembly and Senate Staircases with offices. These major modifications showed little regard for the staircases, as the designs STRUCTURE magazine

Figure 4: Assembly Staircase attic before and after installation of new skylight, laylight, and staircase lighting.

Before photo courtesy of Laurie Donald, Bernstein Associates Photographers, for OGS.

were now out of fashion, and many of the staircases’ iconic features were removed or damaged including hand-blown, hand-painted glass laylights, carved stone features, and decorative paint finishes.

The roofing restoration work at the Capitol created an opportunity to replace the skylights over all three staircases and restore natural light to these remarkable public spaces. The Great Western Staircase was part of the first phase of construction. Work here included providing new modern aluminum framed skylights (including providing a new steel structure to support the side skylights where subsequent roof reconfigurations had removed the previous support framing), and restoring the glazing and paint on the original laylight frames that were still intact. The skylight and laylight were unveiled in August 2003.

The success of the Great Western Staircases’ restoration paved the way for the state Office of General Services to pursue restoration of the remaining two monumental staircases. These two staircases posed an even greater challenge, as their restoration required removal of the infill construction, which included connecting corridors, floors, and the design and installation of new laylights to replicate the long-since removed original laylight framing and glass.

Structural Concerns The staircases are constructed with load bearing masonry stairs and perimeter walls, and each is rectangular in plan with a long dimension of approximately 50 feet. The staircase roofs are constructed with long span iron trusses, perpendicular iron purlin members, and rafters which supported the original skylight glass but had since been modified to support wood decking and roofing. While there was little documentation of the original laylight framing grid pattern or attachment, the thick perimeter masonry walls are capped with a stone cornice that clearly supported the original laylight frame’s perimeter. Remnants of the original laylight framing hangers on the roof trusses were also identified. Using this information, the design team developed a gridded framing structure specific to each laylight that used the same methods of structural support as the original laylight frame (Figure 4).

To meet building code requirements and contemporary performance expectations, the new laylight installation included an additional layer

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Figure 5: Assembly Staircase before and after restoration work. After photo courtesy of Laurie Donald, Bernstein Associates Photographers, for OGS.

of laminated glass as safety glazing, and the replacement skylight was a contemporary aluminum-framed system with insulating glass units, attached to the existing structure. These necessary upgrades increased the dead load of both the laylight and roof/skylight systems, both of which are supported by the original iron roof trusses. Using historical material property data, initial analysis indicated that portions of the original Senate Staircase would be overstressed by the new laylight and skylight loads. Material testing, including tensile testing, chemical analysis, and Rockwell hardness testing provided quantified material properties that allowed the design team to refine the design and confirm that the trusses could be reused with minimal additional framing to redistribute the loads.

In addition to analysis of the new loads, the design considered the consequences of the load reductions resulting from the removal of the infill floor space. Portions of the Capitol already had reported settlement and foundation concerns due to the varved clay layer, and there were concerns that this load reduction could result in swelling of the clay that could cause damage to the existing masonry structure or interior finishes. Fortunately, in both staircases, the design team found that the infill construction represented a reasonably small percentage of the total staircase dead load, minimizing potential concerns.

Staircase Finish Work The Assembly and Senate Staircases’ appearances are in stark contrast to each other. The Assembly Staircase is notable for its lavish, bright polychromatic painted plaster finishes, brightly colored laylight, and carved

Figure 7: Senate Staircase before and after restoration work. After photo courtesy of Laurie Donald, Bernstein Associates Photographers, for OGS.

sandstone accents (Figure 5 ). Within the restored space, this staircase also included an ornately carved stone balcony and wood windows and doors looking into the space from the surrounding circulation areas. Unfortunately, all of these features, along with the laylight and skylight, were removed during the infill work. Restoring them required a careful preservation effort of documenting the painted-over colors and patterns; designing the new wood windows and doors based on remnants of the originals; replicating the detailed sandstone carvings that had been removed or damaged by the infill work; and designing a complimentary laylight based on limited original documentation.

Restoring the balcony required not only careful architectural detailing of the carved stonework, but a creative structural design, as it was no longer feasible to deeply embed the supporting stone brackets and floor into the load bearing walls (as was done in the original design). The project design instead utilized a horizontal steel truss fastened to the surrounding masonry walls to support a sandstone stone cladding that mimicked the bracket and floor slab appearance (Figure 6 ). The stone railing was similarly reinforced with steel posts that were clad with sandstone.

In contrast to the lavishly colored Assembly Staircase, the Senate Staircase is monochromatic and constructed with extensively carved red sandstone and capped with an opalescent glass laylight above (Figure 7 ). Similar to the Assembly Staircase, careful preservation efforts were required to replicate the damaged, intricately carved stone finishes and to clean the exposed stone of both general soiling and of mastics, markings, and staining left behind by the infill construction.

The Assembly Staircase restoration was unveiled in January 2012. The Senate Staircase restoration, the final portion of the project, was unveiled by Governor Andrew Cuomo in January 2013.▪ Susan L. Knack-Brown, P.E., is a Principal at Simpson Gumpertz & Heger Inc. (SGH). Susan’s work includes a range of building enclosure investigations and designs, with a specialty in large-scale preservation. She can be reached at slknack@sgh.com.

Nicholas T. Floyd, P.E., is a Senior Staff II at SGH. He supervised the roof restoration design and construction administration work on multiple phases of the Capitol restoration project. He can be reached at ntfloyd@sgh.com.

Figure 6: Balcony steel frame and sandstone cladding installation during construction. Courtesy of Laurie Donald, Bernstein Associates Photographers, for OGS.

STRUCTURE magazine

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July 2013

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University of Washington Invests in Student Housing UW Uses Wood Framing to Meet Ambitious Design Goals on a Limited Budget

By Jennifer Cover, MS, P.E. For the new University of Washington campus buildings, the design team used wood-frame construction to create a community with an iconic identity, exceptional energy efficiency and integrated sustainability – all within a tight budget.

I

n 2012, the University of Washington (UW) completed a five-building, $109 million construction project, adding nearly 1,700 student housing beds. Known as West Campus Student Housing – Phase I, the 668,800-square-foot project is the first of four phases planned by UW to add much-needed student housing to its Seattle campus, which has an enrollment of more than 42,000 students.

UW’s housing need is great, but budgets were limited since the buildings are owned by the University. Since Seattle’s building code allows five stories of wood over two stories of concrete podium, Mahlum Architects worked with engineers from Coughlin Porter Lundeen to make the most of the urban campus location by using light-frame wood construction to meet both ambitious design goals and the University’s tight budget. As a result, the entire project was constructed for just $177 per square foot.

Traditional Wood Construction Designed to connect students with their university, West Campus Student Housing – Phase I includes three residential halls (Alder Hall, Elm Hall, and Poplar Hall) and two apartment buildings (known collectively as the Cedar Apartments).

The decision to use wood was made early in the design process.

Mahlum Architects performed some initial cost analysis, even considering concrete at one point because they thought concrete was needed to provide thermal mass. But they quickly found that concrete’s higher cost did not justify the additional thermal mass, which drove their decision to use more cost-effective wood framing.

All five buildings in West Campus used a combination of five upper floors of Type V-A construction over two lower floors of Type I-A concrete podium, which is a common construction type in Seattle.

STRUCTURE magazine

The two types were separated by a 3-hour rated floor assembly and all floors were fully sprinklered per NFPA 13. The five upper floors used 2x4 and 2x6 wood studs in both exterior and interior load-bearing walls and partition walls. Interior shear wall assemblies included plywood sheathing. Floors consisted of engineered wood I-joists and plywood sheathing.

Stair treads and stair landings on the primary staircases are constructed from glued laminated beams, and laminated strand lumber (LSL) is used for the rim boards. Roof structures are comprised of engineered wood trusses and plywood sheathing, and heavy timber blocking was used throughout for fire protection. The building’s exteriors were then clad in manganese flashed brick extending to grade. Mahlum Architects added wood as a finish material on portions of the exterior to add richness and warmth to the material palette, especially around the main building entries. Inside, they used wood paneling, casework and trim for durability and to bring warmth to the public spaces.

Structural Design Strategies Started with Non-load-bearing Exterior Walls Cost-effective design and engineering strategies started with a decision to make the exterior walls essentially non-load-bearing for all five buildings; interior walls provided both primary structure and shear.

With a few exceptions (e.g., at the corners) the strategy allowed the design team to space exterior wall studs at 24 inches on-center instead of 16 inches on-center. This saved money in material and allowed for more insulation, a decision that will help UW save energy over the life of the structures.

In addition, the relatively random window pattern chosen, provided variable load paths in the exterior walls. Interior load bearing walls

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alleviated the floor load from the exterior walls, which simplified load path calculations. The non-load bearing exterior walls also allowed for larger windows, which improves daylighting and reduces energy use over the long term.

strategy. Doing so allowed the designers to save money on materials; it allowed them to combine their shear walls with the load bearing walls, which reduced the size of hold downs.

Brick Fascia Required Careful Structural Detailing All five structures were fully clad on the exterior with brick, which increased load demands on the structure. Framing members in the exterior walls supporting the brick were sized with a deflection limit of L/600.

The design team took great care to make sure that the masonry to wood structure connection was engineered appropriately. Recognizing that shrinkage and compression occurs naturally with both wood framing and brick veneer (albeit at different rates), they anticipated the movement through proper detailing.

The International Building Code (IBC) allows brick to be stacked up to 30 feet above the non-combustible foundation when there is a wood stud wall backing the veneer. Above that level, the brick has to be supported every 12 feet. However, to avoid problems caused by incompatible shrinkage between wood and brick systems, the West Campus Housing design team closely evaluated the wood building movement and then chose an interval to hang brick veneer that was specifically compatible with that analysis. They isolated the brick panels at each level by using veneer ledger angles hung from the rim board at each floor above the podium. So, the first story of bricks sits on top of the concrete foundation and is re-supported at the concrete podium slab and then at every level of wood floor framing. Brick wall gaps were detailed at every floor with enough tolerance to allow wood to shrink without causing the brick to crack.

The design utilized a 3½ x 12-inch LSL beam set on edge, which spans the same dimension as the floor joist and extends between the interior bearing walls. The LSL carries the ledger angle, while also helping to alleviate the random load path around the windows in the exterior walls.

Seismic Protection Lateral loading was also a consideration, since Seattle is in a high seismic area. Because wood systems are ductile, Coughlin Porter Lundeen engineers took advantage of wood’s flexible properties to meet the requirements. And, by combining the shear walls and the load-bearing walls, they were able to reduce the size of the required hold-downs.

The staggered studs used for acoustical benefits (2x4 studs staggered on a 2x6 plate) also provided an additional advantage. Because the interior shear walls were stacked, floor-to-floor all-thread hold downs and multiple 2x6 compression studs were able to be used, which provided better strength. A standard 2x4 stud wall would not have been able to accommodate the larger 2x6 compression studs.

The West Campus Housing design team’s decision to locate the main structural components in the interior of the building was a good

The first of four planned phases, the new UW campus project includes five buidlings, each with five stories of wood-frame construction over a concrete podium.

Acoustics Acoustics are important for any multi-family housing unit, but particularly so for student housing. Mitigation measures must be weighed against the budget, which is why the design team brought in experts from Seattle-based SSA Acoustics.

While the science of sound is fairly complicated, many mitigation measures are relatively simple. For example, SSA recommended a strategic combination of staggered stud and double stud walls to minimize sound transmission between residential units themselves, between the units and common spaces, and between the units and service areas.

Because single stud walls would not provide adequate “sound” performance, SSA recommended staggered stud walls between residential units. Since there is no rigid connection between the gypsum board on each side (except at the plate), a staggered stud wall performs better than a single stud wall. Double stud walls perform better than a staggered stud design because plates are separated by an air space; so, double stud walls between residential units and common spaces (lounges, staircases, elevators, etc.) and service areas were used.

Little details also count when it comes to acoustics, so all penetrations were sealed using resilient caulk. Whenever possible, junction boxes were located using minimum 24-inch spacing and back to back placement was avoided. When this was not possible, contractors placed putty pads on the backside of the junction boxes.

In the floor/ceiling assembly, careful attention was paid to the installation of resilient channels, which are often one of the main causes of failed floor to ceiling assemblies from an acoustical standpoint.

In fact, there is a difference of 8 to 10 IIC and STC points between

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thermal, and moisture barriers. Their efforts made a significant impact on the buildings’ energy performance while also increasing the structures’ lifespan.

The design team worked with an envelope consultant and the contractor to test full-scale mockups; they also did thermal imaging and conducted blower tests to measure infiltration. In addition, a number of simulation studies were performed to locate and size windows, maximizing daylighting and summer ventilation while maintaining winter comfort and minimizing energy loss through assemblies.

Like many mid-rise housing structures, codes require a substantial number of air changes, which also helps avoid mold and moisture problems. Field testing was conducted to identify and correct any air barrier deficiencies.

Their hard work paid off. Four of the five buildings in the West Campus Student Housing – Phase I meet the AIA 2030 Challenge (requiring 60 percent reduction over baseline fossil fuel energy consumption) with the purchase of green power. Cedar Apartments has already received certification at the LEED (Leadership in Energy and Environmental Design) Silver level, while Poplar Hall and Elm Halls earned a LEED Gold certification. Alder Hall is also on track to earn a LEED Gold rating.

Flexibility for the Future

Wood was used as both a structural and finish material throughout the UW project.

assemblies with resilient channels versus those without. Channel installation has fairly straightforward requirements; for example, screws for the gypsum board should never touch the framing behind the resilient channel.

Since carpet is the best material for reducing impact noise and footfall impact, carpet was installed throughout the West Campus complex (except in bathrooms and kitchens). Bathrooms and kitchens used a drop ceiling to accommodate ducting and plumbing, which provides additional noise reduction between units. Where the finish floor was stained concrete, a resiliently suspended gypsum wallboard ceiling was installed, using neoprene clips to reduce footfall impact noise below.

Fire protection measures often benefit acoustical efforts. Where putty pads were required at electrical boxes for fire code (in 1- or 2-hour fire rated wall assemblies), there was no additional acoustical mitigation required. Penetrations through 1- or 2-hour-rated demising walls, corridor walls, shaft walls, floor to ceiling assemblies and others were sealed with fire resilient caulk, which also met acoustical recommendations.

Structural changes were also implemented for acoustic performance.

SSA increased live load deflection to L/480 (the code only requires L/360) on interior walls. They also recommended that plywood sheathing be placed only on the outer side (not the inner side) of double stud walls as the air space between layers of mass on each side of the studs is critical for achieving acoustical performance.

The UW challenged their design team to create a community that could be built within a very tight budget, yet provide iconic identity, exceptional energy efficiency, and integrated sustainability to set the stage for future development. The decision to use wood as the primary structural material achieved all that and more. Wood framing also provided design flexibility, increased speed of construction, cut overall carbon emissions, and utilized local materials and a skilled labor force. Careful attention to detailing created an air- and watertight, thermally-efficient building envelope, providing long-term durability for the University.

The five buildings are testament to the fact that wood construction can not only save time and money, but also create elegant, durable, urban structures that contribute positively to city and campus vitality.The West Campus Housing project represents a paradigm shift at the University of Washington, symbolizing its first embrace of large-scale light wood-frame construction.▪

Moisture and Energy Management Mahlum Architects used careful detailing and oversight to reduce envelope air infiltration and thermal bridging with continuous air, STRUCTURE magazine

32

Jennifer Cover MS, P.E., is National Director of the Architectural & Engineering Solutions Division of WoodWorks. Since 2006, she has also been an adjunct professor teaching timber design at the University of California, San Diego. She can be reached at jennifer@woodworks.org.

Project Overview Project Name: University of Washington West Campus Student Housing – Phase I Owner: University of Washington Structural Engineer: Coughlin Porter Lundeen | Seattle, WA Architect: Mahlum Architects | Seattle, WA Acoustical Consultants: SSA Acoustics | Seattle, WA General Contractors: Walsh Construction | Seattle, WA WG Clark Construction | Seattle, WA Total size: 668,800 square feet (five buildings) Completed: July 2011 (Cedar Apartments and Poplar Hall) July 2012 (Alder Hall and Elm Hall) July 2013

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Professional issues issues affecting the structural engineering profession

W

hile some of the more complex design, detailing and critical coordination on a building construction project occur at the interface of the structure and the building enclosure, building design teams often consider façade-system attachments as ancillary components of the project. In fact, design, fabrication, and erection of façade systems are often subcontracted out to a specialty contractor, who is part of the construction team. The specialty contractor’s team also typically includes façade system manufacturers, erectors, designers, detailers, and sometimes other various consultants.

As a result of this arrangement, the project design team often delegates the façade-system and associated connection design work to the specialty contractor’s team. This allows the specialty contractor to consider efficiency and cost effectiveness of fabrication and erection in their design methodology. However, the specialty contractor is typically required to adhere to the overall design intent outlined in project specifications and contract documents developed by the design team; this direction may include specific requirements relative to overall system performance, loading, etc. The design team’s documents typically also provide guidance on submittal and review procedures, as well as general design-responsibility delineation; the design documents often also define specific portions of the design work that is delegated. Many project documents, however, come a bit short and end up with general façade-related requirements that are a mix of prescriptive direction (e.g. where the façade is in plan and where it gets attached to the structure) and performance-specified direction (e.g. loads and deflection limits for façade elements and their attachments).

Due to the delegated design arrangement, coordination is vital between the design professionals for the overall building project and the design professional that performs the delegated design of the façade systems. Without sufficient clarity and information in the design documents, as well as coordination and follow-through during submittals, the design-responsibility demarcation line is often blurred, and project deliverables, schedule, and overall quality can suffer; in worst cases, failures can ensue. This article provides a summary review of the current industry documents and their guidance on the topic, discusses the importance of clear delineation of design responsibility for façade-system connections and associated components, and provides some insight on how to potentially improve coordination between the design and construction professionals. In the upcoming sequel to this article, the authors plan to expand upon the topic, focus in some depth

Façade Attachments Who is Designing Them?

By Filippo Masetti, P.E., Milan Vatovec, P.E. and James C. Parker, P.E., S.E.

Filippo Masetti, P.E., Senior Staff II at Simpson Gumpertz & Heger Inc. Mr. Masetti has been involved in numerous design, investigation, and rehabilitation projects involving concrete, steel, masonry, and wood structures. He may be reached at fmasetti@sgh.com.

Milan Vatovec, P.E., Senior Principal at Simpson Gumpertz & Heger Inc. Mr. Vatovec is the head of structural engineering in the firm’s NY office. He may be reached at mvatovec@sgh.com.

James C. Parker, P.E., S.E., Senior Principal at Simpson Gumpertz & Heger Inc. Mr. Parker is the head of structural engineering in the firm’s LA office. He may be reached at jcparker@sgh.com.

34 July 2013

on specific issues, and discuss upcoming industry changes with respect to design (delegation) of facade attachments.

Review of Current Industry Standards The following industry references provide broad information on the subject: 1) PCI Architectural Precast Concrete MNL-122, Third Edition, 2007 2) PCI Design Handbook MNL-120, Seventh Edition, 2010 3) PCI Connections Manual for Precast and Prestressed Concrete Construction MNL-138-08, First Edition, 2008 4) AISC Design Guide 22, 2008 – Facade Attachments to Steel-Framed Buildings 5) AAMA CWG-1-89 – Installation of Aluminum Curtain Walls, 1989 The majority of the industry reference documents emphasize the importance of coordination between the design professional (Engineer of Record – EOR, or Structural Engineer of Record – SER) and the design professional performing the delegated design (Specialty Structural Engineer – SSE).

• As referenced in The PCI Deign Handbook: “Coordination and communication between the […] SER and the […] SSE are of paramount importance. This aspect and its importance are recognized on the national level by the Council of American Structural Engineers (CASE): ‘The primary failure in projects involving SSE is the lack of coordination

problems that designers should be aware of and avoid when designing the support and anchorage systems for precast concrete wall panels… Lack of clarity in the division of responsibilities for designing and providing attachment and support components.

Responsibility for the design of miscellaneous angles, embedment plates, and similar items must be clearly indicated in the contract documents.”

(Para. 8.10) The references above also point to the EOR to review the submittals relative to the delegated work for completeness and coordination with the contract documents. The following list of selected excerpts summarizes the guidance relative to the submittal review process: • The PCI Architectural Precast Concrete MNL-122 states: “The Engineer of Record (EOR) has the responsibility of reviewing the precast concrete design work for compatibility with the overall structural design and structural stability. This does not, however, relieve the EOR from the overall design responsibility for the safety and proper performance of the completed structure. The Engineer of Record (EOR) should determine and

show on the contract documents the locations for supporting the gravity and lateral loads of the precast concrete units, including intermediate lateral (tieback) connections, if necessary. The EOR’s review of the erection drawings confirms that the structure is adequate, within defined deflection limitations, to resist the anticipated loads and forces from the precast concrete, and verifies that the magnitude and location of the loading points on the structure agree with the original design intent.” (Para. 4.1.3) • The PCI Design Handbook MNL120 states: “[…] This does not relieve the EOR from reviewing the designs, ensuring that the designated loading requirements have been properly interpreted and interactive forces with other construction are fully coordinated.” (Para. 14.5.3) • The AISC Design Guide 22 states: “The EOR reviews submittals by the Specialty Engineer and the facade contractor specifically for the effect of the facade and its attachments on the primary building structure.” (Para. 3.3) • AISC Design Guide 22 also states: “The SER normally has the design

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and delineation of responsibility.

When interfacing with the SSE, the SER should always be the one who delineates responsibility for the various structural requirements.’” (Para 14.5.4.3).

The industry references describe the architect and/or the EOR (the design team) as those responsible for delineating the delegated work, for providing all design requirements relative to the delegated work, and for overall coordination between the delegated work and the rest of the project. The contract documents (drawings and specifications) are the means to convey this information. The following list of selected excerpts summarizes specific industry guidance on the topic: • The PCI Architectural Precast Concrete MNL-122 states: “The design team should provide complete, clear, and concise drawings and specifications.

Contract documents should clearly define: (1) precast concrete components that are to be designed by the precaster (state who takes responsibility for design of elements at interfaces with other parts of the structure, such as secondary steel bracing of the structure, to prevent rotation of beams or columns); (2) details or concepts of supports, connections, and clearances that are part of the structure designed by the design team and that interface with the precast concrete components; and (3) permissible design load transfer points and indicate generic connection types to avoid having the precaster make assumptions on connection types and piece counts during bidding and design.

It is preferable to leave specific panel and connection design to precasters so they can design details and connections suitable for their production and erection techniques.” (Para 4.1.2) • The PCI Design Handbook MNL120 states: “A critical function of the contract documents is to clearly define responsibility among involved design professionals.”

(Para. 14.5.3) • The AISC Design Guide 22 states: “The structural drawings should delineate the structural steel elements from the attachment elements to be designed by the Specialty Engineer.” (Para. 3.3) • AISC Design Guide 22 also states: “The following is a list of potential

responsibility for the following: …

The review and approval of shop drawings and field erection drawings for the effect of precast panels and attachments on the primary building structure.” (Para. 8.4) Finally, the references generally agree that the SSE is responsible for the design of the delegated system, but that this design is subject to review by the EOR. However, the design responsibility for the physical connections between the delegated system and the primary building structure varies among the reference publications. Examples of the industry’s attempts to draw the demarcation line between the delegated and the non-delegated components are summarized below: • The PCI Architectural Precast Concrete MNL-122 indicates that the design of these interface connections is the responsibility of the delegatee: “The precaster designs the precast concrete panels and connection hardware for the design loads defined by the EOR and is responsible for selecting, designing, and locating hardware and panel reinforcement or items associated with the precaster’s methods of handling, storing, shipping, and erecting the precast concrete units. (Para. 4.1.5) • The PCI MNL-138-08 design guideline provides design examples for numerous types of precast-panel connections to the main structure.

All the examples show a list of the components of the connection for which design checks are performed.

In particular, the list of Example 6.5, Bolted Tieback to Concrete or Steel Beam, includes the precast-panel embed insert, a connection rod connected to a steel angle, in turn welded to a plate embedded in the cast-in-place concrete.

This example considers the plate embedded in the cast-in-place concrete (part of base building) to be part of the precast-panel connection.

• The AISC Design Guide 22 states: “The Specialty Engineer is the design professional responsible for the design of the facade and/or its attachments to the structural frame. […] The Specialty Engineer prepares calculations and drawings for submittal in accordance to the project specifications. The Specialty Engineer is responsible for the design of the attachments.” (Para. 3.4) • The AISC Design Guide 22 also states: “The SER normally has the design responsibility for the following: The design of the primary building

structure, including the slab, slab edge detail, column, spandrel beam, roll beams, kickers, embedded bearing plates, etc., to support the forces imposed by the precast concrete panel system with due consideration to stiffness requirements… The precast manufacturer and SSE normally have responsibility for the following: …

The precast panel bearing and lateral connection design, including all supplemental hangers, kickers and other structural steel elements required to support the panels.” (Para. 8.4) • Finally, the AISC Design Guide 22 states: “The curtain wall manufacturer and the Specialty Structural Engineer “normally have responsibility for … [t]he design of the curtain wall frame and its attachments to the primary building structure” and “[t] he preparation of shop drawings including details of all attachments to the primary building structure, types and locations of anchors clearly noted, and installation procedures and potential difficulties with field attachment considered and addressed in the shop drawings”. (Para. 9.4) • The AAMA CWG-1-89 states: “Adequate anchor design is more likely to be attained if the curtain wall designer follows the load along its path from ‘start’ (e.g. glass or infill panel) to ‘finish’ (i.e. floor slab or spandrel beam). Often this tracking process will disclose potentially weak parts in the trial design.” (p. 26).

Conclusions In summary, the industry points to the design team as the responsible party to safeguard adherence to the intent and requirements in the design documents, which includes compliance to the submittal-review protocols.

In addition, the design team is expected to define, through their contract documents, which professional is responsible for what portion of the façade design, including its connections. In the absence of a clearly defined line of demarcation in the contract documents, the industry attempts to provide guidance to “fill the gaps” but, based on the authors’ experience, these attempts are often not sufficient to avoid potential miscommunication or issues on deliverables, schedule, and overall quality of the project.

Situations where controversy can arise are usually related to different interpretations between the EOR and the SSE on where

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the façade components stop, and where the original building structure starts; for example, when façade-system anchors are embedded or post-installed into a column or slab of the main building structure, or when customized attachments connect a curtain wall to the main building structure. Based on the authors’ experience, as well as the authors’ interpretation of the intent of industry standards, the SSE (construction team) would be responsible for all facade-related connection design. Furthermore, the SSE’s design responsibility should include examining the ability of not only the connections themselves to resist loads at the actual point of attachment, but also to examine that the loads get into the building structural component (through the connection) without detriment to the structure. In other words, the SSE should examine the entire load path from the façade component through (and into) the building structural component. The SSE’s responsibility, however, should not include confirming that the base-structure component is able to resist the design loads in the ‘global’ sense (e.g. the overall bending moment, shear, and torsion demands on say a perimeter beam or column due to the façade-attachment loads); this responsibility remains with the design team. Unfortunately, unless the contract documents are very specific on defining the delineation between the responsibilities to this level of detail, room for interpretation remains, and potential for problems exist.

Design gaps and/or blurred responsibility situations would generally be avoided if the design team would list (or indicate) in the contract documents all the items and components that are part of the delegated work, the performance and design criteria that the delegated work must satisfy, and all the submittals and associated procedures required for the delegated work. Design-delegation clarity would be further improved if, during the course of the project, the design team would also verify that all components of the delegated work are addressed by the construction team, and that reviewed submittals satisfy the performance and design criteria indicated in the contract documents. It is the authors’ opinion that an owner should always be able to rely on the experience and thoroughness of the design team to lead this process, even if the above arrangement is not required by the code or written into the design contract with the owner. In general, the design professionals should always strive to identify and prevent potential areas of controversy in the design documents, regardless if they are related to façade attachments or any other component of building design.▪

LegaL PersPectives

discussion of legal issues of interest to structural engineers

A Look at Insurance Options Excess Versus Umbrella Insurance

By Gail S. Kelley, P.E.

A

lthough the terms “excess insurance” and “umbrella insurance” are often used interchangeably, an excess insurance policy is not the same as an umbrella insurance policy.

Both policies provide liability coverage, i.e. coverage that protects against claims of damage or injury to others or their property. Both increase the policyholder’s liability limits above those of specifically listed underlying policies and both protect against catastrophic risks, with coverage typically only provided in multiples of $1,000,000. However, excess liability policies only provide coverage above the limits of the underlying primary insurance; true umbrella insurance will provide coverage for additional risks.

Excess Insurance Coverage Excess insurance policies can be either selfcontained (stand alone) or “follow form”.

A self-contained policy has its own insuring agreement, conditions, definitions and exclusions; coverage applies to the extent described in the policy. In contrast, a follow form policy will simply state that it only applies if the loss is coverd by the underlying insurance. Coverage is subject to the same basic terms and conditions as the primary insurance. Neither self-contained nor follow form excess liability policies offer broader protection than what is provided by the underlying policies. In fact, excess liability policies, even those written as follow form, often have exclusions that make them more restrictive than the underlying coverage.

Excess Insurance Limits Most excess insurance policies will increase both the each-occurrence limit and the aggregate (total) limit of the underlying policy. For example, if the underlying policy is a Commercial General Liability (CGL) policy with an each-occurrence limit of $1,000,000 and an aggregate limit of $2,000,000, an excess insurance policy for $1,000,000 would increase the eachoccurrence limit to $2,000,000 and the aggregate limit to $3,000,000.

Umbrella Liability Coverage While excess insurance policies typically provide coverage for one underlying policy, umbrella policies typically provide coverage for several underlying policies. In addition, umbrella policies typically provide coverage not available in the underlying policies; such policies are often written in an “A/B format.”

Coverage A represents excess coverage and is written to “follow form” the underlying policies. The policy increases the each-occurrence limits of the underlying policies and drops down when an underlying policy’s aggregate limit is exhausted or reduced by payment.

Coverage B is the umbrella coverage; it applies when there is no coverage under an underlying policy. However, Coverage B will not apply to any claim for which applicable insurance is listed in the schedule of primary policies, even if the underlying insurance is uncollectible. In addition, Coverage B will specifically exclude coverage for various risks.

Common exclusions are liability for asbestos, expected or intended injury or damage, workers compensation, aircraft, watercraft, unemployment compensation, pollution, liquor liability, contractual liability, damage to the insured’s product; and damage to property in the insured’s care, custody or control.

Some umbrella policies also exclude coverage for professional liability.

Coverage B is typically subject to the insured’s assumption of a self-insured retention (SIR). An SIR is similar to a deductible, in that it is the amount the insured is obligated to pay. However, when a liability policy has a deductible, the insurance company pays the entire amount and then bills the insured for the deductible. When the policy has an SIR, coverage does not begin until the insured has paid the SIR. In addition, deductibles usually only apply to judgements and settlements; an SIR usually applies to defense costs as well as judgements and settlements.

Umbrella Versus Excess Policies Excess policies are sometimes designed to cover a risk that cannot be covered under an umbrella policy, such as liability arising out of

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the operation of a plane or high performance speed boat. Such policies are generally much more expensive than umbrella coverage in terms of premium costs versus amount of coverage. Excess insurance can also be used to bring coverage up to the limits required for an umbrella policy, or can be designed to “sit on top of ” an umbrella policy to provide additional coverage for certain risks.

Duty to Defend Excess policies are typically written such that the insurer has the right to defend against a claim, but is not required to do so. This is referred to as claim participation; a typical claim participation clause will state: “The Insurer may, at its sole discretion, elect to participate in the investigation, settlement or defense of any claim covered by this Policy even if the Underlying Insurance has not been exhausted.” If the excess insurer elects not to participate, the primary insurer must pay for the attorney fees and other legal costs to defend against a claim, even if the amount of the claim is such that the excess policy would be reached.

Umbrella policies usually do include the duty to defend. Although defense coverage may be limited to occurrences not covered by underlying insurance, some umbrella insurance policies provide defense coverage once the limits of the underlying insurance have been exhausted. An example of when this might apply is when there are several claims resulting from the same occurrence. If the first claim is settled for the each-occurrence limit of the underlying insurance, the umbrella insurer would have the duty to defend against the additional claims.

Sub-limits Liability insurance will often have specific sub-limits, such that coverage for certain risks is much lower than the policy limits. As an example, under a standard CGL policy, the coverage limit for fire damage to property leased by the insured is $50,000, regardless of the CGL each-occurrence coverage. Most umbrella or excess insurance policies do not drop down to provide coverage in excess of any sub-limits; specialty insurance is needed to provide such coverage.

Loss of Underlying Coverage Neither excess nor umbrella policies will drop down to provide coverage when the underlying insurer denies coverage because the insured did not comply with provisions of the underlying policy. Likewise, they will not drop down when underlying coverage is uncollectible due to insolvency of the insurer.

The insured becomes liable for costs up to the limits of the underlying policy.

In some cases, the underlying insurer may state that a claim does not fall within its policy and thus denies coverage. Rather than suing for coverage, the insured may prefer to settle with the insurer for some amount less than its policy limits. If the claim is such that an excess or umbrella policy would be reached, the law in most states holds that the insured is entitled to coverage under that policy once it has paid the limits of the underlying policy.

Claims Against an Umbrella Policy Umbrella insurance with a policy limit of $1,000,000 will increase the limits of each of the underlying policies by $1,000,000.

However, the umbrella coverage available for all of the underlying policies is reduced by the

amount of any payment from the umbrella policy. A catastrophic claim on one underlying policy could completely exhaust the umbrella coverage for all of the policies.

Nevertheless, the premium for an umbrella policy will be considerably less than the cost to increase the limits of each of the underlying policies by the amount of the umbrella policy. Umbrella policies are thus an attractive way to increase coverage, provided the risk of catastrophic claims is low.

Conclusion There are no standardized forms for umbrella and excess insurance policies, and coverage definitions are developed by the individual insurance companies. As a result, excess insurance policies from different insurers can vary greatly in what they cover. For example, an excess policy might increase the limits of the each-occurrence coverage, but not the aggregate coverage.

Likewise, when considering an umbrella policy, it is worth comparing several policies to see what additional coverage is provided and what defense costs are covered.

Although insurers typically state that umbrella

insurance will help close or eliminate “gaps” in the underlying insurance, policies tend to have a long list of exclusions. Some of the exclusions are reasonable because coverage is available under other policies, such as workers compensation and pollution liability policies. Other exclusions, such as damage to the named insured’s product or work, are viewed as a business risk that the insured should be responsible for. However, when all of the exclusions are considered, it may not be clear what additional risks are covered.▪ Gail S. Kelley, P.E., is a LEED Accredited Professional as well as a licensed attorney in Maryland and the District of Columbia. Ms. Kelley is the author of Construction Law: An Introduction for Engineers, Architects, and Contractors, published in 2012 by John Wiley & Sons. Gail would like to thank Keith Bouchard of CBI Consulting for his review of, and comments on, this article. Ms. Kelley can be reached at Gail.Kelley.Esq@gmail.com.

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InSIghtS

ASCE 7 and the Standards Development Process

By Jennifer Goupil, P.E.

T

he consensus standard Minimum Design Loads for Buildings and Other Structures (ASCE 7) is developed and maintained by the Structural Engineering Institute (SEI) of the American Society of Civil Engineers (ASCE).

One of 28 standards currently in development

by SEI, ASCE 7 is the most widely used; although the process is similar for all SEI standards, ASCE 7 is unique in many ways.

History The American National Standards Institute (ANSI) published the first consensus standard for structural loads, ANSI A58.1, in 1972.

In 1985, ASCE assumed responsibility for developing and disseminating the standard and received accreditation for its Codes and Standards Program from ANSI. This essentially means that ASCE created rules for its consensus process, ANSI agreed that the rules are satisfactory, and ASCE is periodically audited by ANSI to ensure that the rules are being followed. ASCE first developed its Rules for Standards Committees in the late 1970s and updates them from time to time; the current version is posted online.

When ASCE assumed responsibility for the minimum loads standard, it created an open committee membership policy and increased participation from the profession.

Membership on some of the subcommittees doubled, and a new process was born.

Committee Although changes have been made since the first edition of ASCE 7 in 1988, the process is essentially the same now as it was then. A subset of the committee, typically a defined subcommittee, develops proposals for changes to the existing provisions, and the main committee vets them.

Currently, a new ASCE 7 committee is formed for each development cycle. Interested participants apply for membership on the main committee, a subcommittee, or both.

Members are selected for the main committee in two categories: voting and associate.

There are strict balance requirements for the committee composition per the ASCE rules.

The voting membership consists of a group of technical experts from a range of stakeholders.

The total number of voting members is limited to approximately 50 individuals and includes the following balance requirements: • Consumers (consultants): 20-40% • Producers (vendors or industry): 20-40% • General interest (academics or others, including regulatory): 20-40% • Regulatory (building officials): 5-15% Regulatory members are identified as a special category, but for balance requirements are included under general interest. The current voting membership includes 22 consumers, 13 producers, and 20 general interest, including 4 regulatory members.

Associate members must meet the same requirements to join as voting members, and have all the same rights with the exception of a counted vote. Associate members can participate in all of the ballots, and their comments must be resolved in the same manner as voting member comments. Voting and associate members combine for a total of 115 participants on the current main committee.

The two membership categories enable the main committee to achieve the necessary participation to validate every ballot while allowing interested parties to participate in the process, even with limited knowledge of the technical issues. Also worth noting is that ASCE membership is not a requirement for joining an ASCE standards committee. The volunteer effort to develop ASCE 7 is unparalleled, with more than 350 main committee and subcommittee members participating.

or new ideas or information impacting the provisions. Additionally, ASCE 7 employs a “Call for Proposals” period, during which the public can submit proposals to the main committee for consideration.

Once a proposal is generated, it is sent to the full subcommittee to be “balloted,” which is the term used for the evaluation process or voting. Every ballot is open for a finite period of time, and when it closes, any and all comments must be resolved. The original proposal is often modified and then re-balloted until it passes and all comments are resolved. This cycle can take multiple attempts for many proposals, as the consensus process ensures wide participation. Once the proposal passes the subcommittee ballot, it is ready for the main committee to ballot.

This cyclic process continues at a larger scale with the main committee. Comments are given back to the subcommittees to resolve in the same way discussed above. This cycle occurs at the main committee several times until all ballots are passed and all comments are resolved. Proposals not passed by the main committee do not make it into the standard even if passed by the subcommittee.

The last step in the consensus process is public comment. This is a minimum period of 45 days, during which anyone can submit comments to the main committee. As with every previous ballot, every comment must be resolved. Once the public comments are resolved, the standard is ready for publication and adoption into the building code … which is another process entirely!

Process

Conclusion

What does it mean to be a consensus standard? Consensus is a process for group decision making that seeks consent from all participants. This means that all voices are heard and vetted; it does not, however, mean that everyone agrees! Relative to standards development, the consensus process includes balloting by the balanced committee and a public review period.

Within the ASCE 7 committee, development efforts generally begin with the subcommittees. Individual members or small groups begin by developing proposals, which typically are generated from two sources: items unresolved from the previous standard cycle,

ASCE 7 is developed within a six-year cycle by a diverse and dedicated committee of volunteers under highly structured, well-established rules that encourage wide participation by all stakeholders. The next edition of ASCE 7 will be published in 2016.

To learn more about ASCE 7 and ASCE/ SEI standards development, or to apply for membership on a particular committee, visit www.ASCE.org/SEI.▪

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Jennifer Goupil, P.E. (jgoupil@asce.org), is the director of the Structural Engineering Institute (SEI).

award winners and outstanding projects

Spotlight

A Treasure Box for Dalí

By Scott D. Martin, P.E., LEED AP BD+C Walter P Moore was an Outstanding Award Winner for the Salvador Dalí Museum project in the 2012 NCSEA Annual Excellence in Structural Engineering awards program (Category – New Buildings $10M to $30M).

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he largest collection of Salvador Dalí’s art outside of his hometown in Spain is not in the Louvre, or a New York museum, but in St. Petersburg, Florida. Since the original Salvador Dalí Museum was opened in 1982, it was evident that the converted waterfront warehouse facility that housed the collection was too small and did not provide adequate protection from flooding and hurricanes. To build a new iconic facility that would not only protect Dalí’s artwork, but would also attract worldwide attention, the Museum’s Board of Directors hired internationally-renowned architect Yann Weymouth and his team at HOK, along with the structural engineering firm of Walter P Moore, to design the new museum.

All parties recognized that the new iconic museum needed to be designed for at least a 100-year life; however, the new site was only 200 feet away from Tampa Bay and five feet above sea level. Seasonal hurricanes can bring high winds and a storm surge of up to 25 feet.

To protect the priceless collection, the building pad was raised four feet, the structure was designed to resist wind speeds of 165 mph (42 mph above code minimums), and all gallery spaces, the vault, and rare book library were located on the upper floors.

An economical reinforced one-way, castin-place concrete slab and beam system was selected for the structural system. To create attractive exposed walls throughout the building, unfinished and architecturally exposed cast-in-place walls were used in lieu of architectural precast. Using exposed, unpainted concrete as the load-bearing structure and the architectural finish created several challenges: • Water Migration. 18-inch thick walls were specified, using a dense concrete mix with a low water-cement ratio, high cementitious material content, and 20% fly-ash replacement to minimize permeability of the concrete.

Penetron crystalline waterproofing admixture virtually eliminated any water infiltration. This water-activated admixture, which forms a crystalline structure in the pores in the concrete, was particularly important in the areas

where the glazing abuts the outer wall surface to prevent any water that seeps into the wall concrete from migrating around the glazing joints.

• Uniform, Blemish-Free Surface. The traditional method of pouring a concrete building, with pour joints below and above each floor level, was not desirable in the exposed walls.

The walls were poured full height floor-to-floor in 14-foot lifts, and the floor and roof structures were keyed in and mechanically doweled to the inside face of the walls. The Self-Consolidating Concrete flowed around door and window openings, minimizing surface blemishes.

• Openings. There are numerous potential holes in the concrete shell. Seven of Dalí’s master works are on display in the main gallery and are naturally illuminated by light-directing skylights.

Over the impact-resistant glass skylights, retractable aluminum covers are moved into place before a storm to take the initial impact force from flying storm debris. The largest potential hole, however, is the primary glazing system that encompasses the grand central atrium. The “Enigma” was designed to withstand the code minimum storm, but could not be designed to resist the 165-mph storm threshold and maintain its aesthetic quality. Assuming the Enigma system could be breached in the worst of storms, the interior walls and doors enclosing the gallery and vault spaces were designed for exterior exposure and 165-mph winds.

The “Enigma” and the smaller “Igloo” freeform glazing systems that encompass the lobby atrium and multi-purpose room are made up of more than 1,000 individual glass panels held in place by interior steel space frames connected to the concrete superstructure. HOK worked closely with glazing designer Novum Structures to define the shapes of the Enigma and Igloo, while Walter P Moore and Novum developed attachment strategies and details.

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Courtesy of Moris Moreno Photography.

This was the first application where Novum’s free-form glazing system would be fixed on all sides and serve as the primary weather barrier.

The welded connections along all sides of the frame, especially a frame with three dimensions and re-entrant corners, produced unmanageably large thermal stresses, which were controlling the design of the steel frame and the foundations.

By allowing vertical movement of the frames at the base, the maximum design forces greatly decreased and foundation uplift was eliminated.

Paying tribute to Dalí’s fascination with DNA structure and the Golden Section, a helical spiral shape was used for the grand stair connecting the ground floor to the galleries 30 feet above. The 41-inch deep wall stringer is the primary load-carrying element for the stair, while the treads and landings cantilever off of the stringer and add lateral stiffness to help prevent unwinding.

During construction, the stair was un-shored and re-shored between concrete lifts before locking it into the 3rd floor structure. This construction sequence minimized stresses in the stair and allowed most of the natural deflection of the coiled shape to be built into the treads and risers as the stair was erected.

The new $30 million, 66,400 square-foot museum is truly the crown jewel in the revitalization of St. Petersburg and the Tampa Bay area, and is a fitting architectural tribute to the talents of Salvador Dalí.▪ Scott D. Martin, P.E., LEED AP BD+C, is a senior associate with Walter P Moore in its Tampa office and was the Structural Project Manager for the Salvador Dalí Museum. He can be reached at SMartin@walterpmoore.com.

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NCSEA News

News form the National Council of Structural Engineers Associations

Celebrating

NCSEA Code Advisory Committee Report The Code Advisory Committee (CAC) is composed of 6 subcommittees: General, Existing Buildings, Seismic, Quality Assurance, Wind, and Evaluation Services, and an executive committee, composed of the chairs of each of the subcommittees, including Ed Huston (General), David Bonowitz (Existing Buildings), Kevin Moore (Seismic), Kirk Harman (Quality Assurance), Don Scott (Wind), Bill Warren (Evaluation Services) and this author.

The CAC’s charge is to improve the building codes to assure safe, economical and reliable construction. Building codes today consist of no single document, but rather, a complex suite of documents including the model codes themselves (there are several), the individual state and municipal adoptions of these codes, the ANSI consensus standards the codes adopt by reference, and a series of evaluation services reports that identify the code conformance of proprietary products of different types.

The committees’ specific activities include: 1) Monitoring the status of the model building codes, their referenced standards, and evaluation service approvals, to assure that our “codes” are providing safe and economical structures, and do not place undue burden on structural engineers either through unfair apportionment of professional responsibility/liability, or through imposition of unclear, conflicting, or hardto-implement requirements.

2) Through advocacy, suggesting, to the standards committees, proposals intended to address our membership’s concerns.

3) Providing public comment to the standards associated with revisions that are not in our member’s interests.

4) Developing and submitting code change proposals to the ICC, to address issues of concern.

5) Monitoring code change proposals submitted by others, to assure that these do not violate the principles indicated in 1 above.

6) Attending the ICC code hearings, and advocating for (or testifying against) proposals consistent with the goals indicated in item 1 above.

7) Partnering with the ICC-ES and other evaluation services, to improve the technical adequacy of their evaluation of acceptance criteria and product reports.

8) Providing public comment on acceptance criteria proposals, through the public hearing process, as appropriate to accomplish the goals in item 1 above.

In recent years, the CAC has also initiated activities aimed at providing continuing education to NCSEA members on the various code requirements and their proper implementation. This takes the form of development and publication of design manuals and webinars.

technical changes to the IRC and IEBC. Presently, we are in the middle of the cycle for Group B changes. Proposal submittals were due in January 2013; and ICC just public hearings in May to review and vote upon proposals submitted.

The IRC is a highly prescriptive code with a focus on the use of “conventional” construction requirements. Tables within the code prescribe minimum size and spacing of structural elements based on span, story height, wind speed and seismic zonation; however, these tables are often based on past common practice, rather than actual calculations of demand and capacity, and frequently result in lower-strength structures than the IBC. Structural engineers would like to see the IRC brought into closer alignment with the requirements of the IBC, thereby guarding against permitting prescriptive construction for complex structural situations, where the expertise of a structural engineer is required to assure an appropriate structure.

The IEBC is still new to many jurisdictions. The intent of this code is to govern the use of existing buildings, including additions, repairs and alterations, and to deal with unsafe conditions, traditionally the subjects of Chapter 34 of the IBC. The IEBC includes a series of requirements for structural evaluation and upgrade for an existing building, triggered by different project types (additions, alterations, repairs, change of occupancy, or relocation). In addition to evaluation and upgrade triggers, the IEBC also includes a number of alternative design procedures for specific types of buildings, such as unreinforced masonry bearing wall buildings and wood frame residential construction with unanchored cripple walls. Many of these design procedures have been developed over the years by NCSEA and our member organizations.

Code Change Proposals Participation in the ICC code change process is a major effort and is one of NCSEA’s most publicly visible activities. Effective action in this environment requires not only detailed technical knowledge, but also political sensitivity and superior

Building Codes ICC is in the process of developing its 2015 series of model building codes, including the International Building Code (IBC), the International Existing Building Code (IEBC), and the International Residential Code (IRC), among others. It does this in two groups, over a period of three years. Group A changes, which were administered in 2012, included technical changes to structural design criteria included in the IBC. Group B changes (administered this year) include administrative adoption of updated structural standards adopted by the IBC, as well as STRUCTURE magazine

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Silver:

Bronze:

NCSEA Webinar August 13, 2013 Checklist for Reviewing a Concrete Mix Design – There’s More to It than You Think!

Kim Basham, Ph.D., P.E., president, KB Engineering Register at www.ncsea.com.

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Don’t Forget!

• Nominations are due Monday, July 15 for the NCSEA Service Award and the Robert Cornforth Award, to be presented at the NCSEA Annual Conference in Atlanta in September. Nomination forms can be found at www.ncsea.com.

• Entries for the 2013 NCSEA Excellence in Structural Engineering Awards are due Friday, July 12. Up to three awards will be presented in eight categories. The Call for Entries is available at www.ncsea.com.

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Ronald O. Hamburger, S.E., SECB, is Chair of the NCSEA Code Advisory Committee.

NCSEA Annual Conference Sponsors to date:

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In the coming year, with fewer code development deadlines, the Existing Buildings Subcommittee hopes to develop a set of case studies illustrating the intent of the IEBC’s and IRC’s existing building triggers and exceptions.

The Seismic Subcommittee is working to recruit a few more authors interested in developing a Seismic Design Manual for SDC C. The subcommittee developed a general scope/ outline for the Seismic Design Manual at the Annual Meeting in St. Louis and is continuing its work with Tim Mays and the Publications Committee.

The Wind Subcommittee recently focused on educational activities, including a series of five webinars that were presented for NCSEA during the months of January, February and March, and is presently initiating the process of formulating submissions for Group A proposals for the 2018 I-Codes.

The Evaluation Services Subcommittee principally works with ICC-ES to monitor and assist in the improvement of that Evaluation Service’s products (Evaluation Service Reports qualifying the use of proprietary products in construction). The subcommittee chair participated with the ICC ES Task Force in developing testing and acceptance criteria for lateral force resisting components “equivalent” to timber shearwalls. In addition, our chair has reviewed the evaluation reports produced by ICC ES and begun to make recommendations, for either format or content revisions, to better serve the needs of the structural engineering profession and reduce any confusion in their use. Coordination is also ongoing with other Evaluation Service agencies, e.g. IAPMO.

News from the National Council of Structural Engineers Associations

Other Activities

Atlanta will be the center of structural engineering from September 18-21. Join NCSEA and leading structural engineers from across the country for targeted, timely educational programs and opportunities to network and learn from peers and leaders in the field.

Educational highlights will include a keynote by Bill Baker of Skidmore, Owings & Merrill, and sessions on Serviceability, ACI 550, ASCE 412, DoD Minimum Antiterrorism Standards for Buildings, and Complex Stability Bracing. A complete list of educational sessions can be found at www.ncsea.com.

The Annual Conference will include social events that facilitate networking with fellow structural engineers and a trade show featuring structural engineering products and services.

Special features for young engineers will also be offered, including a special reception and networking opportunities.

Registration is now open! Special discounted registration rates are available for first-time attendees, young engineers and NCSEA members. Register online at www.ncsea.com today!

NCSEA News

communication skills. The code hearings last almost two weeks and are a major effort by our delegates.

The Existing Buildings Subcommittee was active in code development, making 50 proposals (of which 48 were successful and one is still pending) for the 2015 I-codes. Major changes, which Existing Buildings supported, will include the update to ASCE 41-13 for seismic evaluation and retrofit with any of the IEBC’s three methods, and the introduction of certain proactive wind and seismic mitigation triggers into the IEBC’s Prescriptive method, to match the Work Area method. Perhaps the most obvious change in the 2015 I-codes will be the removal of Chapter 34 from the IBC, so that the IEBC will be the default code for existing building regulations (though users will still be allowed to choose one of three methods). The committee was neutral on this proposal, since the substance of the codes should not change, but is working now to ensure a smooth transition.

The General Requirements Subcommittee reviewed a total of 247 proposals submitted by others who wished to revise the IRC and provided public comment on thirty-seven of these.

The General Requirements Subcommittee was successful on 75% of the items they took positions on.

The Seismic Subcommittee has been actively engaged in the 2015 IRC code cycle. SEAOC submitted 9 code change proposals to CAC which we reviewed, endorsed and submitted to IBC as NCSEA proposals. These proposals sought to strengthen the technical requirements of the IRC to be more compatible with the requirements of the IBC. The ICC will produce a report on the Dallas hearings and public comments will be submitted in August. Final Action Hearings for Cycle B, for the 2015 IRC, will be held in Atlantic City, NJ in early October.

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2013 SEI and ASCE Structural Awards

Structural Columns

The Newsletter of the Structural Engineering Institute of ASCE

The Structural Engineering Institute (SEI) proudly recognized the following recipients at the Structures 2013 Congress in Pittsburgh, Pennsylvania on May 4, 2013:

Structural Engineering Institute Awards 2013 Chapter of the Year Award The SEI Chapter of the Year Award recognizes an SEI Chapter for its exemplary activities and efforts to advance the structural engineering profession. The 2013 SEI Chapter of the Year Award was given to the SEI Sacramento Chapter. The Sacramento SEI Chapter has been very active in a variety of activities including technical presentations, conferences, tours, community outreach events, and networking opportunities.

Gene Wilhoite Innovations In Transmission Line Engineering Award The Gene Wilhoite Award honors an individual who has made significant contributions to the advancement of the art and science of transmission line engineering. The 2013 Gene Wilhoite Award was given to Richard F. Aichinger, P.E., M. ASCE. Mr. Aichinger has spent much of his career in the tubular steel transmission pole fabrication industry, especially in the area of unique structural solutions to meet specific customer needs. In addition, Mr. Aichinger has served on several committees that developed ASCE standards and manuals of practice in the area of transmission line engineering.

Dennis L. Tewksbury Award The Tewksbury award recognizes an individual member of the Structural Engineering Institute who has advanced the interests of SEI. The 2013 award was presented to Roberto Leon, Ph.D., P.E., F.SEI, F. ASCE. Dr. Leon is currently the Past President of SEI and was an active member of five SEI technical committees. He is also an active member of the American Institute of Steel Construction, received the AISC T.R. Higgins award, and is a Fellow of the American Concrete Institute. He is currently serving on the editorial boards of four journals in the field of structural engineering, and has chaired or co-chaired the organization and delivery of six international conferences.

Walter P. Moore, Jr. Award This award is presented for significant contributions to the development of codes and standards. The 2013 Walter P. Moore, Jr. Award was given to Satyendra K. Ghosh, Ph.D., M. ASCE.

Award winners, left to right: Dennis Mertz, William Melbourne, Ahsan Kareem, Samuel Lewis, Satyendra K. Ghosh, Gintaris Kaklauskas, Masayoshi Nakashima, Joyce Copelan, Craig Copelan, Roberto Leon, Bob Nickerson, Sam Rihani, Ron Ziemian and Jennifer Goupil.

Dr. Ghosh is known internationally for his work in earthquake engineering. He has influenced seismic design provisions in the United States for many years. Dr. Ghosh is active on many national technical committees and is a fellow of the American Concrete Institute and Pre-stressed Concrete Institute. He is a member of ACI Committee 318 and the ASCE 7 Standard Main Committee and Seismic Subcommittee. He is a former member of the Boards of Direction of ACI and the Earthquake Engineering Research Institute.

SEI President’s Award The SEI President’s Award recognizes exemplary contributions to the success of SEI. The 2013 President’s Award was given to Robert Elliott Nickerson, P.E., F.SEI, M. ASCE. Mr. Nickerson has been very active in the Technical Activities Division of SEI and is the current secretary of the Executive Committee of the Technical Activities Division. He is the past chair of the Special Design Issues Committee and the Electrical Transmission Structures Committee, and is current Chair of the Gene Wilhoite Awards committee. Mr. Nickerson is the Chair of the ASCE Standards Committee on Design of Lattice Steel Transmission Structures (ASCE 10) and has been a key member of the ASCE Standards Committees on Design of Steel Transmission Pole Structures (ASCE 48). In addition, he has served on the committees that developed the Guidelines for Electrical Transmission Line Structural Loading (Manual No. 74) and the Guide to Design of Guyed Transmission Structures (Manual No. 91).

American Society of Civil Engineering Structural Awards Jack E. Cermak Award This award was created by the Engineering Mechanics Institute/Structural Engineering Institute to recognize Dr. Jack E. Cermak’s lifetime achievements in the field of wind engineering and industrial aerodynamics. The 2013 award was given to William Melbourne, Ph.D., in recognition of his significant contributions through his life-long studies to increase the understanding of the effects of turbulence in problems of bluff body aerodynamics pertinent to wind engineering applications. In addition, he has made key contributions to international and local codes and standards in the field of wind engineering.

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Shortridge Hardesty Award The Shortridge Hardesty Award may be given annually to individuals who have contributed substantially in applying fundamental results of research to the solution of practical engineering problems in the field of structural stability. The 2013 award was given to Ronald D. Ziemian, Ph.D., A.M.ASCE. Dr. Ziemian’s research into direct analysis modeling of inelastic and elastic stability issues enables professional engineers to quickly and accurately model structural behavior. He has also served as editor of the Structural Stability Research Council’s Guide to Stability Design Criteria for Metal Structures, the guiding reference for developers of structural stability design provisions.

July 2013

Moisseiff Award The Moisseiff Award recognizes a paper contributing to structural design, including applied mechanics, as well as the theoretical analysis or construction improvement of engineering structures, such as bridges and frames, of any structural material. The 2013 award was presented to Gintaris Kaklauskas, Ph.D., Dr.Habil, M.NASc, and Viktor Gribniak, Ph.D., for the paper titled Eliminating Shrinkage Effect from Moment Curvature and Tension Stiffening Relationships of Reinforced Concrete Members, published in the December 2011 issue of the Journal of Structural Engineering.

ASCE Library Features Free Collection of Tornado Articles In response to the powerful tornado that devastated a 20-milelong and 2-mile-wide path through Moore, Oklahoma, the ASCE Library has provided free access to a selected group of papers that discuss strategies for reducing loss of life and property damage when this natural hazard occurs. These articles are free to registered users and subscribers through July 31, 2013; see Rebuilding after a Tornado on the ASCE Library at http://ascelibrary.org/ to download the articles.

Monday’s tornado occurred almost two years to the day after the deadly events in Joplin, Missouri. ASCE/SEI sent a postdisaster assessment team to Joplin; the team’s findings and lessons learned are included in the Joplin, Missouri Tornado of May 22, 2011 report, also available from the ASCE Bookstore at www.asce.org/bookstore/.

Two New Books from SEI Structural Identification of Constructed Systems

Tensile Fabric Structures

Approaches, Methods, and Technologies for

Design, Analysis, and Construction

Effective Practice of St-Id Structural Identification of Constructed Systems: Approaches, Methods, and Technologies for Effective Practice of St-Id offers an overview of nearly 20 years of research directed at bridging the gap in structural engineering between models and real structural systems. Structural identification, known as St-Id, can be defined as the process of creating and updating a model of a structure (for instance, a finite element model) using experimental observations and data. By developing reliable estimates of the performance and vulnerability of structural systems, St-Id produces improved simulations that, in turn, assist in decision making and the transition to performance-based civil engineering.

This report was prepared by SEI’s Structural Identification of Constructed Systems Committee. Structural engineers, educators, and researchers working in the areas of structural modeling, health monitoring, assessment, forensics, performance evaluation, predictive analysis, and decision making will find this book useful in covering critical and practical aspects of these concepts.

STRUCTURE magazine

Tensile Fabric Structures: Design, Analysis, and Construction summarizes the range of tensile membrane structure forms and their applications, and documents the current state of knowledge regarding loading, form finding, and nonlinear analysis of membrane structures.

Structural forms and details are generally left exposed in tensile membrane designs and are strongly tied to architecture and aesthetics. These environmentally friendly and economically competitive structures are found in a wide range of recreational and transportation facilities.

This report was prepared by SEI’s Task Committee on Tensioned Fabric Structures, and the will provide practical guidance to structural engineers, architects, and builders of tensile membrane structures.

To purchase these and other structural engineering books visit the ASCE Bookstore at http://www.asce.org/bookstore/.

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The Newsletter of the Structural Engineering Institute of ASCE

Raymond C. Reese Research Prize The Raymond C. Reese Research Prize may be awarded to the author(s) of a paper published by ASCE that describes a notable achievement in research related to structural engineering, and recommends how the results of that research (experimental and/

or analytical) can be applied to design. The 2013 award was presented to Zhongguo John Ma, PH.D., P.E., F. ASCE; Samuel Lewis; Zhiqi He; Qi Cao, PH.D., A.M.ASCE; Edwin G. Burdette, Ph.D., P.E., F. ASCE; and Catherine E.W. French, PH.D., P.E., M. ASCE, for their paper titled Transverse Joint Details with Tight Bend Diameter U-Bars for Accelerated Bridge Construction, published in the October 2011 issue of the Journal of Structural Engineering.

Structural Columns

Ernest E. Howard Award The Ernest E. Howard Award recognizes a member of the Society who has made a definite contribution to the advancement of structural engineering through research, planning, design or construction. The 2013 award was given to Masayoshi Nakashima, Ph.D., M. ASCE. Dr. Nakashima has been engaged in research and education in the field of structural and earthquake engineering for 30 years. He was the first director of the E-Defense shake table, one of the largest in the world, and had led more than 40 large-scale tests. He also pioneered the use of “pseudo-dynamic” tests in which quasi-static loading tests and numerical analyses are conducted side-by-side.

CASE in Point

The Newsletter of the Council of American Structural Engineers

Guidelines on Peer Review and Coordination/Completeness CASE Guideline 962-D: A Guideline Addressing Coordination and Completeness of Structural Construction Documents

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

This guideline discusses the background behind the issue, the important aspects of design relationships, communication, coordination and completeness, guidance for dimensioning of structural drawings, effects of various project delivery systems, document revisions, and closes with recommendations for development and application of quality management procedures. A Drawing Review Checklist is attached.

The key to achieving the desired level of quality throughout the profession is for each structural engineering firm to focus on and develop its own specific quality management plan and to implement that plan on each project. This guideline will assist the structural engineering profession in achieving that goal.

Please see the companion publication to this document: CASE Tool 9-1: A Guideline Addressing Coordination and Completeness of Structural Construction.

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.

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.

Please see the companion publication to this document: CASE Contract #5: An Agreement for Structural Peer Review Services.

You can purchase all CASE products at www.booksforengineers.com.

CASE Summer Planning Meeting August 6 -7, 2013; Chicago, IL The CASE Summer Planning Meeting is scheduled for August 6-7th in Chicago, IL. A new feature added to this meeting will be a roundtable discussion on topics relating to the business of Structural Engineering, facilitated by some of the CASE Executive Committee members. Topics in the past have included the Business of BIM, using social media within your firm, Peer Review and Special Inspections. Attendees to this session will also earn 1.5 PDHs. Please contact CASE Executive Director Heather Talbert (htalbert@acec.org) if you are interested in attending this roundtable or have any suggested topics for the roundtable.

Upcoming ACEC Online Seminars Get On the Pathway to Success August 6, 1:30-3:00 pm

Stop waiting for the economy to improve. In The Pathway to Success, Scott Hunter, president of The Hunter Partnership Alliance, will demonstrate how firms don’t need to be dependent on the economy for their success and will lay out four steps that firms can take to start building business today. For more information and to register, www.acec.org/education/eventDetails.cfm?eventID=1443.

Use Design Thinking to Build Business and Break the Commodity Trap August 13, 1:30-3:00 pm

Engineering firms use design thinking every day to solve their clients’ most pressing and complex design problems. In Using Design Thinking to Build Business and Break the Commodity Trap, find out how to use this core competency in your business planning.

Joseph Rei of MORF Consulting will demonstrate how firms can use design thinking to gain market share, strengthen their STRUCTURE magazine

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position with clients, and solve the ongoing problem of “engineering commoditization.” For more information and to register, www.acec.org/education/eventDetails.cfm?eventID=1446.

Top ACEC On-Demand Webinars from spring 2013: • Transportation Project Financing Through TIFIA: Major Expansion of Federal Assistance • Are You Fighting Fires Instead of Managing Your Employees?

• Accounting 101 for Project Managers • Creating a High-Performing Marketing & Business Development Organization • How to Write Division 00: Tips for Preparing Effective Bidding and Contracting • Seven Critical Mistakes Engineers Make During Contract Negotiation & Project Executing that Sabotage Their Projects & Invite Litigation • Successful Integration of an Acquisition

To see the full ACEC Bookstore selection, www.acec.org/bookstore.

July 2013

Gov. Mitch Daniels, FHWA Administrator Victor Mendez to Headline ACEC Fall Conference in Scottsdale, AZ Mitch Daniels, former Indiana governor and budget director for President George W. Bush, and FHWA Administrator Victor Mendez will keynote the 2013 ACEC Fall Conference in Scottsdale, AZ, October 27-30.

During his two terms as governor, Daniels turned the state’s $800 million budget deficit into a $370 million surplus, and funded a backlog of public transportation projects through a $4 billion public-private partnership. He also created a $500 million highway trust fund to maintain the state’s

roads. Mendez, who was director of the Arizona DOT prior to becoming FHWA administrator, has long grappled with the nation’s transportation challenges. His signature initiative is the Every Day Counts program to accelerate project delivery and innovation.

The Conference also features top industry CEO panels and more than three dozen educational sessions and business roundtables. For more information and to register, www.acec.org/conferences/fall-13/index.cfm.

CASE is on LinkedIn LinkedIn is a great virtual resource for networking, education, and now, connecting with CASE. Join the CASE LinkedIn Group today! www.linkedin.com.

CASE Business Practice Corner If you would like more information on the items below, please contact Ed Bajer, ebajer@acec.org.

Addressing Engineer-Caused Change Orders The engineer should educate the owner that a certain amount of imprecision and incompleteness is to be expected in the design documentation. An option in Appendix I of the EJCDC Engineer/Owner Agreement is intended to address engineercaused change orders, whether caused by professional negligence or imperfections within professional standards. 6.10.A.3 of Appendix I provides a “safe harbor” for covered change orders up to a certain percentage of construction costs. The blank percentage will need to be filled in. Any claims over that will be only for the amount in excess of the agreed-to percentage.

Limitation of liability is not intended to be a complete solution.

The engineer remains liable to the owner within the agreed limits and to third parties regardless of such limitation.

Being an Expert Witness: The Ph.D. Doesn’t Always Win It’s all about credibility. But how do you get it? Education counts of course, but it is more than that. Knowledge of the subject matter is important, as is knowledge of the case (do your homework). Manner of presentation is significant; simplify complex issues and use analogies that lay people understand.

You maintain your credibility by keeping a steady demeanor and not being defensive but, if necessary, stand up for yourself.

Identify any conflicts you have with other experts and explain why you are correct.

STRUCTURE magazine

Elements of a Bad Contract What would a bad contract look like? It would probably include a heightened standard of care, meaning you promised more than what is expected of a person in your position. This is important because, in court, if it is shown you raised the standard of care higher you are expected to meet it. Not meeting the expectations of the owner is a frequent trigger of this. The contract might also include a duty to defend the party with whom you have signed a contract, which could take effect even though you have done nothing wrong. An incomplete scope of services is also bad, as is the lack of an appropriate dispute resolution. Some form of limitation of liability is advisable. These are enforceable but there are nuances in the law from state to state.

Patent Trollers Take a Hit Major copy companies have filed a lawsuit that there is no basis for asking a licensing fee for use of scanning technology. The companies contend that the 426 patent is invalid, the infringement claims are without merit and the licensing demands are unsupportable. These involve the use of scanner/ copiers that scan a hard copy document into an electronic file and then transmit that file to someone else. Some firms have received letters saying that if they are using this technology they are infringing on a patent and must pay a license fee. The patent has become the subject of an aggressive patent licensing campaign by various entities that are targeting users of the products of virtually every manufacturer of multi-function imaging equipment.

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Structural Forum

opinions on topics of current importance to structural engineers

Increasing the Velocity of Knowledge

By Gene Frodsham, MS, S.E.

T

he complexity of calculations and the development of new materials and methods have increased the amount of knowledge necessary for engineers to learn. In response, the National Council of Examiners for Engineering and Surveying (NCEES) and the American Society of Civil Engineers (ASCE) propose increasing the education requirements for licensure to a bachelor’s degree plus 30 hours (B+30). The movement to require essentially a master’s degree was done without sufficient consultation with practicing engineers; there is a far more efficient solution available.

The leaders of these organizations are correct that the problem is one of time. However, it is not one of more time. Instead, we need to implement means of presentation that increase the rate of learning, also known as the velocity of knowledge.

The underlying principle has always been known, as shown by sayings like “a picture is worth a thousand words,” “seeing is believing,” and “experience is the best teacher”.

This describes a transfer of knowledge greater than the 300-500 words per minute that is typical when reading text with 2D pictures.

“Seeing” operates in four dimensions from any viewpoint. With the concept of “seeing”, we have an efficient way to display all human knowledge operating in reality.

The necessary technology is now off-theshelf. Computer gaming gives ready-made tools for developing 3D environments to show any process or procedure. Goggles are available for the display of this virtual reality.

MathCad and other programs give us the ability to show problems in the traditional calculation format.

We can thus create a world in which we build and watch every interaction in real time in any amount of detail, from any position, in four dimensions, and even be a part of them. From the present operating system of being in a room looking out a window on the far wall, we can now be immersed with knowledge all around us – on every surface, or suspended in space with the entire volume used for presentation.

There is no end to the density of information and the interconnection of knowledge that can be achieved. In every area, unlimited and flexible visualization will allow the tailoring of learning. Every child can have an education equal to the best prep schools with tutors for every class. Feedback from the virtual reality learning programs will provide the “educational research” to ascertain the methods of learning that are actually used by people in practice.

This concept applies to all areas of knowledge – from engineering, math and chemistry to biology and languages, and even to the skills of mechanics and other trades. Every process can be experienced as though the student were doing it. In virtual space, layers of information can be displayed at a glance – geometry, material specifications, installation instructions, nomenclature and traditional calculations.

In engineering, buildings and machines can be simulated in three dimensions; all loads can be shown and all code references can be indicated. There is then no more need for “black box” spreadsheets and other software that give more decimal places, but not more significant figures. In construction management, the student can see a project being planned and built and learn to do every position, inspection, calculation and report from the start.

Medical and biology classes can be conducted in the virtual world where every structure, chemical reaction and physical process is observed. The student can stand in the middle of space and see the atoms and chemical reactions, along with all the data, procedures and calculations.

Math and computer programming can be taught with all information available, including applied problems or proofs and derivations. Electronic designs can be seen operating at the level of the structure of the electrons, transistors or chips, a 3D operation in real time. Languages can be taught by intensive immersion.

We need a human interface language for creation and operation of the display of virtual knowledge. The interface language can

be acquired by children, becoming an inherent part of growing up as they progressively learn the complexity of the interface. By contrast, engineers currently must become familiar with multiple interfaces using large numbers of explanatory books. A common standard human interface will save great time and effort.

Increasing education requirements will not do what is necessary; increasing the velocity of knowledge will. The layering and interconnection allowed by “seeing” knowledge creates multiple paths for learning and the tailoring of lessons for each student, fostering both rigor and flexibility and allowing the student to choose the best way in which to learn. This would give everyone a powerful tool to extend their knowledge and the boundaries of their understanding, at the greatest possible velocity.

Coordination of these interfaces and the methods of displaying knowledge must be the responsibility of the engineering societies. It is time for engineers to take their fate into their own hands and start this process that will benefit every field, profession, and type of work.

The parts already exist. The programming has been created. The hardware is now in place. The coordination to create the protocols for the data and standards for presentation remains to be done. The benefits are far beyond just engineering – the whole of human knowledge can be displayed and experienced. It can be learned by immersion with the tutors and processes optimized for each individual, resulting in a revolutionary increase in the velocity of knowledge.

This method will cut years from traditional education programs and expand the scope and abilities of everyone. It is a project that is worth the effort of a generation, and an extraordinary inheritance to bestow upon future generations.▪ Gene Frodsham, MS, S.E. (gfrodsham1@gmail.com), is a structural engineer practicing in Nevada.

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

STRUCTURE magazine

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