STRUCTURE magazine | June 2015

A Joint Publication of NCSEA | CASE | SEI

STRUCTURE

®

June 2015 Tall Buildings/High Rise

Special Section

Tall Buildings

A new standard for exposed structure Learn more via CEU - http://ceu.construction.com/article.php?L=418&C=1269 Inset: Whitney Museum - Renzo Piano Building Workshop Above: Painswick Library - ZAS Architects

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STRUCTURE

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June 2015 34

Feature

Skyscraper Watch

By Daniel Safarik The Council on Tall Buildings and Urban Habitat provides a snapshot of tall buildings, worldwide, after an excellent construction year in 2014.

44 editorial

7 Structural Standards Coordination Council

By Robert Bachman, P.E., S.E.

39

Feature

ConStruCtion iSSueS

Construction of tall Buildings Going Strong

30 Basic Fire Precautions during Construction of large Buildings

and Ronald Hamburger, P.E.,

By Dr. Kuma Sumathipala, P.Eng

S.E., SECB

and Chief Ronny Coleman

enGineer’S noteBook

hiStoriC StruCtureS

11 the nonlinear load Path

46 the Pratt truss

By Larry Kahaner Companies involved with tall building construction continue to innovate and grow, and they’re bringing new products and services to their customers. For most, business is strong.

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

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

44

StruCtural deSiGn

StruCtural SuStainaBility

26,000 Gallons of Coatings

14 Post-installed reinforcement

50 Carbon reduction

By Richard T. Morgan, P.E.

By James A. D’Aloisio, P.E., SECB

BuildinG BloCkS

CaSe BuSineSS PraCtiCeS

18 Strengthening of Concrete Structures using FrP Composites

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

52 CaSe on Contracts

22 a Practical approach to aSr Mitigation in existing Structures

By Craig E. Barnes, P.E., SECB and Sofia Zamora, EIT

leGal PerSPeCtiVeS

By Matthew R. Rechtien, P.E., Esq. SPotliGht

59 enhanced Seismic design of the new San Bernardino Justice Center

By Mark P. Sarkisian, P.E., S.E.,

teChnoloGy

26 Structural engineers add Value with Constructable Models

By Stuart Broome

By Dee McNeill The Ohio Department of Transportation’s Interstate 90 Innerbelt Bridge replacement project is the largest project ever undertaken by the State. The project addressed corrosion issues by replacing this historic bridge – the main eastwest artery into and through downtown Cleveland, Ohio.

By Steve Schaefer, P.E.

56 an ounce of Prevention PraCtiCal SolutionS

Feature

Peter Lee, P.E., S.E., SECB and Lindsay Hu, P.E.

in eVery iSSue 8 Advertiser Index 43 Resource Guide (Tall Buildings) 60 NCSEA News 62 SEI Structural Columns 64 CASE in Point

On the cover At 300 meters (984 feet), the Torre Costanera building is the first super tall building is South America. The 62-story project was designed by Pelli Clarke Pelli Architects and Rene Lagos Engineers with Thornton Tomasetti as peer reviewer. See feature article on page 34.

StruCtural ForuM

66 engineer with your eyes open

By Scott R. Harpole, P.E.

STRUCTURE magazine

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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.

June 2015

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Editorial

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Structural Standards Coordination Council new trends, new techniques and current industry issues Rising to the Challenge of Coordination

By Robert Bachman, P.E., S.E. and Ronald Hamburger, P.E., S.E., SECB

oday’s building codes and the consensus standards they adopt – including ASCE-7, ACI-318, AISC-360, and others – are a complex web of inter-related documents.

Each refers to, and in some cases, modifies or takes exceptions to materials contained in the others. Coordination of structural design standards among each other and with the building code takes proactive efforts from many groups. The recently founded Structural Standards Coordination Council (SSCC), whose membership includes the major structural standards development organizations, is off to a successful start as it endeavors to fulfil its mission.

an unexpected, unilateral decision, the ICC modified its process, which resulted in shortening the adoption schedule for the 2012 IBC by 18 months for some standards (such as for ASCE/SEI 7), and lengthening the adoption process for other standards. This created a disaster for the coordination effort. While the ASCE/SEI 7 committee, in a highly-focused effort, met the new IBC schedule and produced ASCE 7-10, several of the structural material standards could not meet the highly accelerated ASCE/SEI 7 development schedule and some material standards became out of sync with ASCE/SEI 7 and the IBC. Furthermore, some of the material standards adopted late in the 2012 IBC development process included uncoordinated exceptions in the IBC, resulting in incorrect references. The upshot was an uncoordinated suite of structural design standards adopted into an uncoordinated building code.

How Did We Get Here?

Most building departments in the United States currently adopt the 2012 edition of the International Building Code (IBC). For structural design criteria and loadings, the 2012 IBC in turn references ASCE/ SEI 7-10 Minimum Design Loadings for Buildings and Other Structures for most loading requirements. In addition to ASCE/SEI 7, the IBC adopts many other standards including: the American Concrete Institute (ACI) standard Building Code Requirements for Structural Concrete and Commentary (ACI 318-2011); American Iron and Steel Institute (AISC) standards Specifications Structural Steel Buildings (AISC 360-2010) and Seismic Specifications for Structural Steel Buildings (AISC 341-2010); American Wood Council (AWC) standards National Design Specifications for Wood Construction Including Supplements (AWC NDS-2012) and Special Design Provisions for Wind and Seismic (AWC SDPWS-2008); and The Masonry Society (TMS) standard Building Code Requirements and Specification for Masonry Structures (TMS 402-2012). Each of these design material standards were developed by large dedicated volunteer groups of experts representing the structural engineering profession, regulatory bodies, researchers, and material interests.

In addition to direct adoption into the IBC, the material standards are also adopted in ASCE/SEI 7, with the adopted standards listed in Chapter 23. The building code and ASCE/SEI 7 adopt the material standards for somewhat different reasons. The building code broadly adopts these standards for regulating many aspects of design, construction and inspection of structures for all loadings. ASCE/SEI 7 primarily adopts these standards to reference their seismic detailing criteria. The materials standards in turn reference ASCE/SEI 7 for loading criteria and load combinations. Because of these interdependencies, and in order to avoid conflicts in the way these requirements are referenced and to insure that appropriate reference of requirements are made, it is very important – especially for seismic requirements – that the developers of ASCE/SEI 7 and the developers of primary structural material standards work closely together.

Major changes have occurred in structural design standards over the past 25 years. The pace of change in these standards has resulted in requests by the structural engineering profession to slow down the change process to allow the profession to understand and implement the changes. To address this concern, the ASCE/SEI 7 committee decided after publication of ASCE/SEI 7-05 to publish major new editions of the standard every six years to coincide with publications of alternate editions of the IBC, which is revised every three years. Therefore, after completing the 2005 edition, it was expected that the next version ASCE/SEI 7 would be published in 2011 and would be coordinated with the publication of the associated material standards as had been done in 2005. However, in STRUCTURE magazine

Where Do We Go Now? As this was unfolding, the SEI Board of Governors recognized that the resulting lack of coordination among the structural material standards, ASCE/SEI 7, and the IBC needed to be addressed for the good of the design profession and the construction industry in the U.S. It therefore approved a strategic initiative in 2012 to improve coordination between structural standards organizations. Working informally with the primary standards organizations for a year, the Structural Standards Coordination Council (SSCC) was formed in 2013 with key members (staff and volunteers) from each of the primary structural standards organizations, as well as NCSEA, represented. The stated mission of the SSCC is to provide an organized mechanism for planning and coordinating the development schedules of structural standards developed and maintained by U.S. standards development organizations (SDO) for the benefit of public safety, health, and welfare, as well as for the benefit of structural engineering practice.

One of the first issues that the SSCC addressed was the ICC adoption schedule, which had changed to create an impossible environment for coordination. Working together, the SSCC communicated directly with the ICC to persuade it to reconsider the adoption schedule. This unified effort has been successful; the ICC schedule has been adjusted, which will enable coordination among and between the standards and the code via purposeful efforts of the SSCC. As the SSCC continues its work, the next version of ASCE/SEI 7 will be published in 2016 (actually it will be ASCE/SEI 7-16 with Supplement 1, in order to be coordinated) and it will be fully coordinated with structural material standards and is intended to be adopted by the 2018 IBC. Along with coordination of schedules and adoption intentions, the SSCC continues its work with twice yearly meetings and will take on other issues as appropriate.

The coordination and harmonization of structural design standards is obviously necessary, but does not happen without considerable effort. It is the intent that the new SSCC will cause this coordination to occur so that it appears seamless and organized to end users, and so that the volunteer development groups have a clear understanding of their coordinated development schedules.▪ Robert Bachman, P.E., S.E., is the chair of the Structural Standard Coordination Council and Ronald Hamburger, P.E., S.E., SECB, is the chair of the 2016 ASCE/SEI 7 Main Committee. For questions, please contact SEI Manager of Engineering, Jennifer Goupil, P.E. at jgoupil@asce.org.

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June 2015

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EDITORIAL BOARD Chair Jon A. Schmidt, P.E., SECB Burns & McDonnell, Kansas City, MO chair@structuremag.org Craig E. Barnes, P.E., SECB CBI Consulting, Inc., Boston, MA John A. Dal Pino, S.E. Degenkolb Engineers, San Francisco, CA Mark W. Holmberg, P.E. Heath & Lineback Engineers, Inc., Marietta, GA Dilip Khatri, Ph.D., S.E. Khatri International Inc., Pasadena, CA Roger A. LaBoube, Ph.D., P.E. CCFSS, Rolla, MO Brian J. Leshko, P.E. HDR Engineering, Inc., Pittsburgh, PA

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June 2015

Brian W. Miller Davis, CA Mike Mota, Ph.D., P.E. CRSI, Williamstown, NJ Evans Mountzouris, P.E. The DiSalvo Engineering Group, Ridgefield, CT Greg Schindler, P.E., S.E. KPFF Consulting Engineers, Seattle, WA Stephen P. Schneider, Ph.D., P.E., S.E. BergerABAM, Vancouver, WA John “Buddy” Showalter, P.E. American Wood Council, Leesburg, VA C3 Ink, Publishers A Division of Copper Creek Companies, Inc. 148 Vine St., Reedsburg WI 53959 Phone 608-524-1397 Fax 608-524-4432 publisher@structuremag.org June 2015, Volume 22, Number 6 ISSN 1536-4283. Publications Agreement No. 40675118.

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

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

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T

here was a time, which many readers may well remember, when elastic behavior of structures governed our thoughts when it came to their design.

For seismic design, we understood that the response reduction factor (currently designated ‘R’) was a reflection of system ductility and gave us the latitude of designing the system for much lower forces than standard elastic design might typically predict. Inherent within this was the understanding that actual displacements would be much higher than those calculated when using the response reduction factor. Likewise, forces would be at least marginally higher; the old (3/8) Rw multiplier comes to mind.

Advancements and widespread acceptance of nonlinear design methods, which more accurately predict actual conditions, coupled with verification in physical test models, continue to propel our understanding of how structural systems actually behave when moderate and major transient events occur. A previous Structure magazine article, How Big is that Beam? The ‘X’ Brace vs. ‘V’ Brace Conundrum (STRUCTURE, November 2014), presents an example. It prompted several worthwhile and meaningful comments from readers. Peers of the author have also presented other geometries for which actual nonlinear behavior varies widely from the behavior predicted using elastic methods. One of these is the “multi-tiered X” configuration. This article addresses differences between linear and nonlinear behavior for such a case, and the need to design members for forces that are dramatically different from those predicted by linear analyses.

Consider the multi-tiered ‘X’ frame of Figure 1. For this example, pseudo-static lateral forces of 100 kips and 75 kips have been applied at the diaphragm levels for illustrative purposes. Figure 2 shows the axial forces that develop in the frame members for these forces with a rigid diaphragm at each floor level, an assumption that makes only a minor difference in the overall outcome.

Seems quite intuitive, right? Except for some small participation due to flexural rigidity of the members, most of the load is resisted by axial compression and tension (in equal shares) in the braces and columns.

What happens during an actual seismic event? By virtue of detailing prescribed in the AISC Seismic Provisions for Structural Steel Buildings (AISC 341-10), we may have to design the connections to accommodate, if not promote, out-of-plane buckling of the braces in compression. While the AISC Provision allows for a relatively small degree of post-buckled compression capacity, we may conclude that once the braces have buckled, their contribution to the stiffness of the system is relatively small. This can certainly be demonstrated with nonlinear analysis methods, such as pushover or response history. For the sake of this discussion, let us assume that the braces acting in compression no longer are contributing to system stiffness in their buckled state, at least for the instant of time represented by the pseudo-static transient load.

Now what is the load path? Suddenly the beams between floors, which had no load under the

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

The Nonlinear Load Path

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

Jerod G. Johnson, Ph.D., S.E. (jjohnson@reaveley.com), is a principal with Reaveley Engineers + Associates in Salt Lake City, Utah.

Figure 1. Multi-tiered braced frame with pseudo static forces.

Figure 2. Development of linear elastic frame forces.

STRUCTURE magazine

11

A similar article was published in the Structural Engineers Association-Utah (SEAU) Monthly Newsletter (January 2012). Content is reprinted with permission.

elastic case, have significant axial force as dem- (322 kips) to resist the aforementioned brace Why are the design forces governed by the onstrated by the red members shown in Figure yield force, thereby developing a deliberate and tensile yield strength of the brace, and not by 3 and the forces shown in Figure 4. Note that reliable load path for the frame’s nonlinear per- the actual forces applied to the model? To answer this presumes an infinitely rigid diaphragm formance. Likewise, the connections must be this, we must examine a fundamental premise at the presumed floor levels where the loads designed for the full (adjusted) yield strength. behind the equivalent lateral force methods were originally applied. This approach gives prescribed by the building code. us a good handle on the nonlinear forces of When utilizing the R factor, our the frame, right? Actually, no; but we do have design forces become much lower a more realistic view of how alternate load (artificially) and we are indirectly paths develop as nonlinearity (in this case taking advantage of the inherent buckling) occurs. ductility of the system. Higher R Owing to the response reduction factors mean higher ductility. Use factor (R ), we should understand of R means that we are presuming that the distribution of forces in ductile behavior, which for most the system will likely be dictated systems means that we are presumby the maximum developed tening that materials (probably steel) sile forces in the braces – in other will yield. In fact, yielding will likely words, the yield forces adjusted occur long before forces commenwith the appropriate over-strength surate to the prescribed spectral factor (Ry Fy Ag), which for this case acceleration will develop. Hence, has a magnitude of approximately actual yield strengths become the 384 kips. The intermediate beams de-facto governing forces for the are then acting in compression to strength design of the system.▪ resist this force, not unlike the alternating web members of a The author acknowledges Brent truss or open web joist. Hence, the Maxfield for his conceptual compression capacity in the beams contribution with respect to needs to be designed accordingly Figure 3. Development of Figure 4. Nonlinear load path this article. nonlinear load path.

forces with pseudo static forces.

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STRUCTURE magazine

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June 2015

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Structural DeSign design issues for structural engineers

R

einforced concrete is a construction method that relies on widely understood and historically validated concepts.

Traditionally, reinforcing bars are placed in formwork prior to concrete placement.

However, many applications require reinforcement to be added to existing structures by means of reinforcing bars grouted into drilled holes, usually with injectable adhesives. This article provides an overview of how reinforcing bars can be designed in accordance with the development and splice requirements of the American Concrete Institute ACI 318, Building Code Requirements for Structural Concrete, using a post-installed adhesive anchor system. Specific reference to the 2012 International Building Code (2012 IBC) and ACI 318-11 will be made because the first International Code Council-Evaluation Service (ICC-ES) Evaluation Service Reports (ESRs) containing provisions for designing post-installed reinforcing bars as “reinforcement” are recognized within the 2012 IBC provisions.

Post-installed reinforcing bars, for the purposes of this article, to refer to reinforcing bars installed into hardened concrete using a qualified adhesive anchor system. The primary focus will be to discuss post-installed reinforcing bar design using the development length provisions within ACI 318-11. Alternative design methods for post-installed reinforcement based on anchor theory and shear-friction will also be mentioned.

Post-Installed Reinforcement Design Using Adhesive Anchor Systems

By Richard T. Morgan, P.E.

Anchor Design versus Reinforcement Design Richard T. Morgan, P.E., is the Manager for Software and Literature in the Technical Marketing Department of Hilti North America. He is responsible for PROFIS Anchor and PROFIS Rebar software. He can be reached at richard.morgan@hilti.com.

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

Before discussing the new provisions to design post-installed reinforcing bars for development, it is a good idea to review the current provisions for post-installed anchor design. Post-installed adhesive anchor systems are commonly designed with the Appendix D, Anchoring to Concrete, provisions of the ACI 318 code. Anchor elements used with adhesive anchor systems include threaded rod, internally threaded inserts, proprietary anchor elements and reinforcing bars.

ACI 318-11 Appendix D contains provisions for calculating design strengths corresponding to anchor failure modes. Bond strength provisions are given in Part D.5.5, Bond strength of adhesive anchor in tension. The key concept when using Appendix D to design with reinforcing bars is that the bars act as “anchors” (Figure 1). Essentially, when using Appendix D provisions, the bars are designed in the same manner as anchor bolts.

This concept assumes the “anchorage” is subject to three possible failure modes in tension: steel failure, concrete breakout and bond failure; and three possible failure modes in shear: steel failure,

14 June 2015

Figure 1. Reinforcing dowels designed using anchor theory.

concrete breakout and concrete pryout. The bars can be treated as a group, such that the effects of spacing and edge distance relative to a specific embedment and characteristic bond strength are considered. Consideration is also given to splitting via the modification factors ψcp,N and ψcp,Na; however, calculation of these parameters is concerned with the increased edge distance required to preclude splitting failure rather than the embedment required to develop the bar to preclude splitting failure.

The predictive expressions for concrete breakout, pryout, etc. in Appendix D do not explicitly consider the influence of reinforcement. However, Appendix D does permit consideration of “supplementary reinforcement” or “anchor reinforcement” to enhance the capacity of an anchorage. The term “supplementary reinforcement” in Appendix D refers to reinforcement capable of controlling splitting, or providing an increased calculated concrete breakout capacity. Reinforcement designed for the strength and serviceability of a concrete member should not automatically be assumed to act as supplementary reinforcement for an anchorage.

The term “anchor reinforcement” in Appendix D refers to additional reinforcement specifically designed to preclude concrete breakout failure by transferring the loads applied to the anchorage into bars that will be developed. Reference ACI 318-11 D.5.2.9 (tension) and D.6.2.9 (shear) for more information about Appendix D anchor reinforcement provisions.

In contrast to development length provisions, Appendix D anchorage provisions are not predicated solely on design controlled by the steel strength of the anchor element. Rather, Appendix D provisions simply provide the means to calculate various strengths corresponding to possible anchor failure modes. Furthermore, Appendix D provisions consider “steel strength” to be defined by the specified ultimate tensile strength (futa)

of the steel element. This assumption differs from what is assumed when designing a reinforced concrete member (RCM), in which steel reinforcing bars are designed to yield.

RCM design assumes the reinforcing bars will provide the necessary strength, serviceability and ductility via yielding. RCM design further assumes the reinforcing bars will yield if they are installed at a deep enough embedment to preclude either a splitting failure (small cover) or a pullout failure (large cover).

Bars installed at an embedment to obtain yielding are assumed to be “developed”, and the embedment required to “develop” the bar is referred to as the “development length” (Figure 2). All of this is well understood by Structural Engineers. The reason it is noted here is to draw a distinction between reinforcing bars designed with the provisions of Appendix D, and reinforcing bars designed specifically for development. Therefore, unlike Appendix D, design of reinforcing bars for development assumes (a) the bars reach their specified minimum yield strength (fy), (b) the bar design is controlled by the yield strength instead of the ultimate bar strength and (c) the embedment required to yield the bar will be deep enough to preclude splitting or pullout.

Post-Installed Reinforcing Bar Testing and Assessment The ICC-ES Acceptance Criteria for PostInstalled Adhesive Anchors in Concrete Elements (AC308), establishes requirements for post-installed adhesive anchor systems to be recognized for compliance with the International Building Code (IBC). Anchor systems that satisfy these requirements receive an (ICC-ES) Evaluation Service Report. The ESR will note the IBC versions for which recognition has been obtained, describe the materials and components that comprise the anchor system, note design, application and installation parameters, provide tables with design data, and provide Manufacturer’s Printed Installation Instructions (MPII).

Additional information is given in a specific ESR. The ESR references the IBC, which in turn references the ACI 318 code. For example, an adhesive anchor system having an ESR that references compliance with the 2012 IBC can be used to design an anchorage per the provisions of ACI 318-11 Appendix D. AC308 (approved June 2013 for compliance with January 2014 and January 2015) now also addresses the assessment and design of post-installed reinforcing bars for use with the provisions of ACI 318-11 Chapter 12, Development and Splices of Reinforcement, and Chapter 21, Earthquake-Resistant Structures.

Figure 2. Post-installed reinforcement designed as a lap splice.

The AC308 post-installed reinforcing bar qualification test program includes consideration of the following: Service Condition Tests • bond resistance of the post-installed adhesive system • bond/splitting behavior of the postinstalled adhesive system at deep embedment Reliability Tests • sensitivity to hole cleaning • sensitivity to freeze/thaw conditions • sensitivity to sustained load at elevated temperature • decreased installation temperature • sensitivity to installation direction Installation Procedure Verification • installation at deep embedment • injection verification Durability • chemical and corrosion resistance Special Conditions • seismic qualification Some of these tests are mandatory and some are optional. Reference Section 2.0, USES, and Section 5.0, CONDITIONS OF USE, in the ESR for information about the parameters for which the adhesive system has been tested. Reference AC308 for specific details on all test parameters. The intent of the test program is to demonstrate equivalence with cast-in place bars, which will permit a reinforcing bar post-installed using an adhesive system to be designed in accordance with the development and splice requirements of ACI 318. Adhesive systems that successfully complete this test program will receive recognition by way of an ESR, which then permits the adhesive to be used with reinforcing bars

STRUCTURE magazine

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June 2015

designed as “reinforcement” per the provisions of ACI 318 Chapters 12 and 21. ESRs referencing 2012 IBC compliance will be the first such reports to recognize this type of design. Therefore, post-installed reinforcing bars can now be designed as either an “anchor” using the provisions of ACI 318-11 Appendix D, or as “reinforcement” using the provisions of ACI 318-11 Chapters 12 or 21.

This means that post-installed reinforcing bars can now be designed for a development length calculated using the provisions of either Chapter 12 or Chapter 21.

Successfully completing the AC308 test program for post-installed reinforcing bars permits the bars to be designed for development in tension (ld), or development in compression (ldc), in the same manner as a cast-in-place bar. AC308 qualification testing for design per the provisions of Appendix D limits the embedment depth of an anchor element to a maximum of 20(danchor). AC308 qualification testing for design per the provisions of ACI 318 Chapter 12 or Chapter 21 limits the embedment depth of a post-installed reinforcing bar to a maximum of 60(danchor). Therefore, a key parameter for using adhesive systems with the provisions of Chapter 12 or Chapter 21 is to qualify for installation at deep embedment via the test program defined in AC308 Table 3.8. Satisfying this parameter is one way in which the system demonstrates equivalence with cast-in-place reinforcing bars. Note that post-installed reinforcing bar installation is only relevant to straight bars. The structural analysis required to determine the area of reinforcement (As) for post-installed reinforcing bars will be per the relevant provisions of the ACI 318 code.

Designing Post-Installed Reinforcing Bars as Reinforcement Consider an application for a slab extension in which reinforcing bars post-installed with an adhesive will be used. The post-installed bars will need to be spliced to the reinforcement in the existing member (Figure 3, page 16 ).

Assume the slab is subjected to non-seismic tension loads, and design is per the 2012 IBC. Assume the adhesive has been qualified per the test program defined in AC308 Table 3.8.

Reinforced concrete design principles would be used to determine a post-installed bar size and grade. The development length for the post-installed bars would be calculated using ACI 318-11 Eq. (12-1). Lap splices would follow Section 12.15, Splices of deformed bars and deformed wires in tension. If the existing

Figure 3. New slab extension to an existing slab.

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reinforcement bar size was the same as the post-installed bar size, the lap splice length would be calculated using the provisions of Section 12.15.1. If the criteria of 12.15.2 could be satisfied, a Class A splice could be used; otherwise, a Class B splice would be used.

Likewise, if the existing reinforcement bar size was different from the post-installed bar size, the lap splice length would be calculated using the provisions of Section 12.15.3. Once a bar size and splice length has been determined, the detailing would be in accordance with ACI 318-11 Section 7.6, Spacing limits for reinforcement, and Section 7.7, Concrete protection for reinforcement; subject to any additional conditions per the required code parameters and the product-specific ESR. The MPII would be followed when installing the new bars.

Now, consider reinforcing bars postinstalled to permit extension of an existing special moment frame (Figure 4 ). Reinforced concrete design principles would be used to determine a post-installed bar size and grade.

Assuming the adhesive has been qualified per the test program defined in AC308 Table 3.8,

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Figure 4. Extension of an existing special moment frame.

the development length for the post-installed bars would be calculated using the provisions of ACI 318-11 Section 21.7.5, Development length of bars in tension. Specifically, Eq. (21-6) in Section 21.7.5.1 and the provisions of Sections 21.7.5.2 and 21.7.5.3 would be used to calculate the development length.

Once a bar size and development length has been determined, detailing would be in accordance with ACI 318-11 Section 7.6 and Section 7.7, subject to any additional conditions per the required code parameters and the product-specific ESR. The MPII would be followed when installing the new bars.

Adhesive systems qualified per AC308 permit design and detailing of post-installed reinforcing bars with the same criteria as that for cast-in-place bars. In order to complete the post-installed reinforcing bar design, the installation requirements given in the MPII must be followed. Determining the method for drilling the hole in the existing concrete, making sure that the hole is drilled to the required depth and properly cleaned, installing the adhesive in a manner that eliminates voids and permits proper bar insertion, and allowing the adhesive to cure without any disturbance are parameters that must be considered when post-installing the reinforcing bars.

Additional installation parameters are given in the ACI 318 building code and in the productspecific ESR. The ACI 318-11 code addresses adhesive anchor installation in Appendix D via D.9, Installation and inspection of anchors.

Adhesive anchor ESRs address installation requirements in Section 4.0, DESIGN AND INSTALLATION, and Section 5.0, CONDITIONS OF USE. The MPII, ACI 318-11 D.9 provisions, and product-specific ESR provisions must be followed when designing and installing post-installed reinforcing bars with an adhesive anchor system.

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Alternative Design Methods Design of post-installed reinforcing bars is an ongoing area of research and testing.

Charney et al have proposed an approach that utilizes anchor theory to calculate a post-installed reinforcing bar development length. This approach is premised on calculating a development length that takes into consideration concrete breakout failure and bond failure when splitting failure no longer controls. The calculations utilize the concrete breakout and bond strength equations of ACI 318-11 Appendix D. Palieraki et al have proposed an approach that does not require bar development for applications being designed for shear transfer.

The resulting bar embedment could be less than that required per ACI 318-11 Section 11.6.4, Shear-friction design method.

Developing a code-approved approach to design anchor bolts for development is another area where research would be beneficial.

Summary The focus of this article was post-installed reinforcing bar design using the development and splice requirements of ACI 318-11.

Only adhesive systems that have been qualified per the post-installed reinforcing bar provisions of the ICC-ES Acceptance Criteria AC308 are relevant for this design.

Recognition for this design will be given in a product-specific ICC-ES Evaluation Service Report. The importance of understanding the requirements and limitations given in the ESR, following the Manufacturer’s Printed Installation Instructions, and following all code-related provisions for design and installation, are emphasized.▪

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Building Blocks updates and information on structural materials

F

iber-reinforced polymer (FRP) composites have been used for structural strengthening in the United States for almost 25 years. During this period, acceptance of FRP composites as a mainstream construction material has grown, and so has the number of completed FRP strengthening projects.

As a result, the use of FRP for strengthening and retrofit is gaining more popularity among design professionals over conventional strengthening techniques, such as installation of supplemental structural steel frames and elements.

FRP strengthening of existing structures can involve complex evaluation, design, and detailing processes, requiring a good understanding of the existing structural conditions along with the materials used to repair the structure prior to FRP installation. The suitability of FRP for a strengthening project can be determined by understanding what FRP is and the advantages it offers, but more importantly, its limitations.

Strengthening of Concrete Structures Using FRP Composites

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

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

What is FRP Reinforcement?

FRP composite materials are comprised of high strength continuous fibers, such as glass, carbon, or steel wires, embedded in a polymer matrix. The fibers provide the main reinforcing elements while the polymer matrix (epoxy resins) acts as a binder, protects the fibers, and transfers loads to and between the fibers.

FRP composites can be manufactured on site using the wet lay-up process in which a dry fabric, made of carbon or glass, is impregnated with epoxy and bonded to prepared concrete substrate.

Once cured, the FRP becomes an integral part of the structural element, acting as an externally bonded reinforcing system. FRP composites can also be prefabricated in a manufacturing facility in which the material is pultruded to create different shapes that can be used for strengthening applications, such as rods, bars and plates.

The most common FRP systems for concrete strengthening applications are carbon fiber based (CFRP). Carbon has superior mechanical properties and higher tensile strength, stiffness, and durability compared with glass fiber based systems. The use of prefabricated CFRP bars and plates is typically limited to straight or slightly curved surfaces; for example, the top side or underside of slabs and beams. Prefabricated FRP elements are typically stiff and cannot be bent on site to wrap around columns or beams.

FRP fabric, on the other hand, is available in continuous unidirectional sheets supplied on rolls that can be easily tailored to fit any geometry and can be wrapped around almost any profile. FRP fabrics may be adhered to the tension side of

18 June 2015

FRP fabric is easily tailored to fit any geometry, including ‘U’ wrapping around beams.

structural members (e.g. slabs or beams) to provide additional tension reinforcement to increase flexural strength, wrapped around the webs of joists and beams to increase their shear strength, and wrapped around columns to increase their shear and axial strength and improve ductility and energy dissipation behavior.

The adhesive systems used to bond FRP to the concrete substrate may include a primer that is used penetrate the concrete substrate and improve bond of the system; epoxy putty to fill small surface voids in the substrate and provide a smooth surface to which the FRP system is bonded; saturating resin used to impregnate the fabric and bond it to the prepared substrate; and protective coating to safeguard the bonded FRP system from potentially damaging environmental and mechanical effects. Most epoxies for FRP strengthening systems are adversely affected by exposure to ultraviolet light, but can be protected using acrylic coatings, cementitious coatings, and other types of coatings.

The resins and fiber for a FRP system are usually developed as one system, based on materials and structural testing. Mixing or replacing a component of one FRP system with a component from another system is not acceptable and can adversely affect the properties of the cured system.

The bond between FRP system and the existing concrete is critical, and surface preparation

Wrapping FRP fabrics around columns increases the shear and axial strength to improve ductility and energy dissipation behavior.

is essential to most applications. Any existing deterioration or corrosion of internal reinforcement must be resolved prior to installation of the FRP system. Failure to do so can result in damage to the FRP system due to delamination of the concrete substrate.

Differences between FRP and Steel FRP composites are different from steel in that they possess properties that can vary in different directions (anisotropic), whereas steel has similar properties in all directions (isotropic).

The most common type of fiber sheets for concrete strengthening application are constructed with continuous unidirectional carbon or glass fiber that runs the length of the fabric. When loaded in direct tension, unidirectional FRP materials exhibit a linear-elastic stress-strain relationship until failure, with no yielding or plastic behavior. Due to the linear-elastic characteristics of FRP and the fact they are applied externally to structural elements, the standard methods used to design or determine the amount of steel reinforcement do not apply to FRP. Relatively more complex procedures are used to design FRP, which can involve iterative design methodology.

Because the fiber in an FRP material is the main load-carrying component, the type of fiber, orientation of fiber, and thickness of the fabric (quantity of fibers) dictate the tensile strength and stiffness.

FRP composites vary in strength depending on the type of fiber used. While glass provides a tensile strength nearly equal to mild steel yield strength, carbon composites provide a tensile strength that vary from twice to five times the yield strength of mild steel. While both FRP composites have tensile stiffness lower than that of steel, carbon composite stiffness is twice to five times the stiffness of glass composites. FRP composites have approximately one fifth the weight of steel.

The tensile properties of FRP strengthening systems can be obtained from the FRP system manufacturer. The tensile properties can also be determined using the test method described in ASTM D7565.

Additional tension reinforcement increases the flexural strength of slabs when FRP is adhered to the tension side.

To account for material durability, most available design guides identify environmental reduction factors for the tensile strength of the FRP that can be used in design. These factors depend on the type of FRP and the exposure conditions for the element to be strengthened. For CFRP, the typical environmental reduction factor for interior exposure conditions is 0.95 while the reduction factor for exterior and aggressive exposure conditions is typically 0.85.

FRP Application FRP systems provide a very practical tool for strengthening and retrofit of concrete structures, and are appropriate for: • Flexural strengthening, • Shear strengthening, and • Column confinement and ductility improvement.

FRP systems have also been successfully used for seismic upgrading of concrete structures.

These applications include mitigating brittle failure mechanisms such as shear failure of unconfined beam-column joints, shear failure of beams and/or columns, and lap splice failure. FRP systems have also been to confine columns to resist buckling of longitudinal steel bars. These FRP schemes increase the global displacement and energy dissipation capacities of the concrete structure, and improve its overall behavior.

Because of the resistance to corrosion, FRP composites can be utilized on interior and

exterior structural members in all almost all types of environments.

Codes and Standards There are several guides and codes published worldwide that address the design of externally bonded FRP reinforcement systems for concrete structures. In the United States, ACI Committee 440 has published ACI 440.2R, Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures. However, this document is not considered a code and is not referenced in any code documents, including the International Building Code (IBC) and the International Existing Building Code (IEBC).

Understanding the need for a repair code, the American Concrete Institute (ACI) published, in 2013, Code Requirements for Evaluation, Repair and Rehabilitation of Concrete Buildings (ACI 562), which is the first performancebased standard developed for the repair of existing concrete buildings. This standard works with the IEBC where adopted, or as a stand-alone document for jurisdictions that have not adopted an existing building code.

The provisions in ACI 562 are not new to design professionals and include many of the same requirements as for the traditional design of concrete structures. ACI 562 directs design professionals to consider the behavior of the structure at all times during the repair process and after the repair is completed. ACI 562 permits the use of FRP materials for concrete repair and strengthening, and refers to ACI 440 standards for design and detailing requirements.

FRP Strengthening Limits Minimum Existing Strength Limit Per ACI 440.2R, in order for structural element to qualify for FRP strengthening, the existing structural member must maintain a STRUCTURE magazine

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June 2015

or not the reduced strength is sufficient if the FRP fails. If it is, there is no need in fireproofing the FRP. If it is not, fireproofing materials should be evaluated for cost efficiency and the ability to meet satisfactory fire ratings.

Installation

Installation of CFRP on an industrial silo.

certain minimum strength. This requirement is intended to guarantee that the ultimate capacity of the structural member without the FRP reinforcement is greater than a design force corresponding to the expected service loads under typical situations.

The minimum strength requirement in ACI 440.2R is: Equation 1: fRn = 1.1DL + 0.75LL fRn = design strength of the existing member without FRP DL = new design dead load LL = new design live load This limit stipulates that externally bonded FRP reinforcement should be considered as secondary reinforcement and used to supplement the existing interior steel reinforcement. Should the FRP reinforcement be compromised, the structure must maintain sufficient capacity to carry existing service loads without collapse.

Since FRP composites are designed to last for the service life of the structure, the impact of possible future renovations and modifications should be considered where the FRP is accidentally damaged. Such damage may not be observed immediately and the structure, or structural component, may remain in service until the damage is identified and the affected areas are repaired. Equation 1 is intended to address these situations.

The limit of Equation 1 is intended to minimize the possibility of collapse due to FRP failure or damage. In cases where the design live load has a high likelihood of being present for a sustained period of time (such as storage areas), a live load factor of 1.0 should be used instead of 0.75.

This limit is independent from fire rating requirements. It must be satisfied, even if fire protection is applied to the FRP system.

The limit is applicable to all types of strength increase such as shear, flexure and axial strengthening, but it does not apply to extreme loading events (seismic events, blast loading or other loads classified by ASCE 7 as extreme events).

Depending on dead load to live load ratio, the strength increase using FRP that satisfies Equation 1 typically results in up to 40% increase in strength. If the strength increase is higher than 40%, other conventional strengthening options should be considered.

Concrete Strength Limit The existing concrete substrate strength is an important parameter for bond-critical applications, such as flexure or shear strengthening.

For FRP to develop and transfer the design stresses at the bond line, the concrete substrate should possess sufficient strength to transfer these stresses. And, in order for the concrete to provide the minimum bond strength of 200 psi (1.4 MPa) specified by ACI 440.2R, the compressive strength of concrete f'c must be more than 2500 psi (17 MPa). This limit does not apply for contact-critical applications like FRP column confinement which relies solely on contact between the FRP system and the concrete.

Fire Rating and Protection While carbon fibers are capable of resisting high temperatures, adhesive systems have a much lower threshold temperature.

Fireproofing of the FRP is an option, but the high costs for specialized fireproofing material aren’t always justifiable.

The fire rating of strengthened structures should be evaluated without FRP. A determination needs to be made as to whether

CFRP reinforcement on parking garage beams.

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Procedures for installing FRP systems have been developed by the system manufacturers and may differ slightly. Temperature and surface moisture of concrete at the time of installation are the main parameters that affect the installation procedure and performance of FRP systems.

Surface preparation to create a bond between the FRP system and the existing concrete is critical. Any existing deterioration and corrosion of internal reinforcing must also be resolved prior to installation of the FRP system. Strengthening can only be applied after all corrosion problems have been determined and resolved following the appropriate procedures. Failure to do so can result in locking in contaminants, which may cause further deterioration and result in failure of the FRP system due to delamination of the concrete substrate.

The International Concrete Repair Institute provides several guidelines for selection, surface preparation, and installation of repair materials. Once installed, the curing of the FRP system depends on the time after installation and temperature during curing. Similarly, temperature extremes or fluctuations can retard or accelerate FRP curing time. The higher the temperature, the faster the system will cure – anywhere from one to three days.

Several grades of resin are generally available through the system manufacturer to accommodate special situations.

Conclusion FRP systems have been successfully used to strengthen buildings, bridges, silos, tanks, tunnels, and underground pipes. The higher cost of FRP materials is offset by reduced costs of labor, use of equipment, and downtime during installation, making them more cost-effective than traditional strengthening techniques.

While strengthening with FRP can involve complex processes, this system offers a number of advantages compared to conventional strengthening methods.

Understanding the properties and limitations of FRP is important step in developing the right design solution and utilizing it for the right application.▪

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Practical SolutionS solutions for the practicing structural engineer

T

he alkali–silica reaction (ASR) occurs over time in concrete between the alkaline cement paste and reactive non-crystalline (amorphous) silica, which is found in many common aggregates.

This reaction causes the formation of a calciumsilicate-hydrate (C-S-H) gel that expands the affected aggregate. This gel increases in volume with water, and exerts an expansive pressure inside the material that causes it to spall and break the cement bond, leading to the failure of concrete elements. The mechanism of ASR concrete deterioration can be summarized in the following four steps (Tantawi, 2014): 1) Water mixed with cement powder becomes an alkaline solution that attacks the siliceous aggregate, converting it to viscous alkali silicate gel.

2) The reaction consumes alkali generating dissoluted Ca2+ ions that react with the gel and convert it to hard C-S-H. 3) This bulky hardened gel generates expansive pressure that cracks and spalls the aggregate.

4) The expanding aggregate then cracks the cement allowing water to infiltrate and accelerate the deterioration process.

Water deterioration is particularly critical in the U.S., especially the Northern regions because of the freeze-thaw cycles that occur during winter.

A large number of structures in northern climates suffer from ASR. Since a susceptible aggregate differs very little in appearance from an inert aggregate and, in the 1800s and 1900s, there was little understanding of the destructive nature of reactive aggregate, there was little thought about excluding such aggregate from concrete. In fact, ASR-prone aggregate, in the right environment, will have an indefinite service life, which adds to the challenge of correct identification.

As the process of deterioration in concrete structures became more widely known and more pronounced, contractors and designers shied away from the use of such aggregates and the concrete product became less of a concern. A recent reappearance of ASR in concrete aggregate may be the result of the reduced availability of natural stone aggregates of high quality, and a commercial need to resort to less durable aggregates.

Mr. Barnes’ first experience with compromised aggregate occurred approximately 30 years ago, when he was hired to determine why a concrete retaining wall was crumbling without apparent signs of deterioration of the reinforcing bars within the wall. At the time, Mr. Barnes performed the initial tests for known deterioration causes such as chloride contamination and carbonation. After the initial assessment, the tests

A Practical Approach to ASR Mitigation in Existing Structures

By Craig E. Barnes, P.E., SECB and Sofia Zamora, EIT

Craig E. Barnes, P.E., SECB, is the Founding Principal of CBI Consulting Inc. Craig is also a member of the STRUCTURE Editorial Board.

Mr. Barnes can be reached at cbarnes@cbiconsultinginc.com.

Sofia Zamora, E.I.T., is a Structural Designer at CBI Consulting Inc. Sofia co-founded the SEAMASS YMG and leads Professional Networking efforts at the NCSEA YMG Support Committee. Sofia can be reached at szamora@cbiconsultinginc.com.

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

22 June 2015

Typical look of a wall suffering from severe ASR damage. The failure is occuring due to the aggregate of the wall expanding and pushing out the outer layer.

did not have to extend further since both of these known deterioration mechanisms affect the steel reinforcement and yet no damage of this sort was observed on the wall. Concrete cores revealed a reasonable compressive strength (3500 psi) and laboratory analysis quickly ruled out reductions in concrete durability due to low air content; although, the air content was estimated at no more than 2-2.5%. At a time when petrographic analysis had not become widely accessible, the engineer had to rely on visual observation of concrete through a magnifying glass to estimate its constitution. The aggregate was large, up to an estimated 2-inch diameter and well graded. Its texture hinted that it was not river washed but taken from a pit. Finally, after what appeared as multiple aimless hunts, the first solid pattern of failure was established: the larger aggregate appeared quite fragile as it split in several directions, although some looked intact.

Upon removal of the concrete binder, the aggregate consistently would fall apart while being held. After comparing these observations with concrete deterioration literature, Mr. Barnes hypothesized that the aggregate was suffering from Alkali-Silica Reaction. This theory was confirmed when the results of a through-wall excavation revealed that the water dependent reaction receded upon further excavation into the center of the wall and then increased again as the excavation approached the other side of the wall. The phenomenon seemed appropriate, as the surface on both front and back of the wall was subjected to greater moisture compared to the concrete within the depth of the wall.

Through the years, CBI Consulting, Inc. has tried to deal with ASR deteriorated concrete in a variety of ways. Some of these projects have benefited from new chemical technology and largely from common sense. CBI has observed that concrete with ASR aggregate, which has not deteriorated, does not suffer a strength reduction. Removing the deteriorated concrete to a depth where sound concrete is recovered, followed by pinning and recasting of concrete, has extended the life of affected structures. Although

Illustration of aggregate protection through lithium electrolysis.

Upturned beams at a stadium.

only one of the repairs CBI has guided over the years have been fortunate enough to have detailed post repair studies, it has been their experience that in an exposed environment, cement-based patches over ASR-prone aggregate concrete do not stop the deterioration; rather, they only slow it down.

To provide additional protection, CBI also recommends applying waterproofing

membranes. In the U.S., the most commonly applied preventive and remedial measures are those which control the ingress of water in the concrete (Tantawi, 2014).

Waterproofing coatings are commonly used for this purpose. A successful coating has to fulfill the following requirements: • Be chemically resistant to the alkalinity of concrete.

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STRUCTURE magazine

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• Have sufficient adhesion and water vapor permeability (prevent water from being trapped inside the concrete).

• Be compatible with the expansion of concrete and be water repellent.

The research paper by Santos, et al. (Lisbon, Portugal) indicates that a large number of studies have been conducted to evaluate the ability of coatings to mitigate the advancement of ASR and many present contradictory results.

These results have spurred a new research interest in testing methods that modify the expansive properties of the ASR products, one of them being the use of lithium salts. This phenomenon was first published in 1951, when the American Concrete Institute issued a study by McCoy and Caldwell that provided data showing that the incorporation of various lithium compounds (LiCl, Li2CO3,

Exposed concrete deck and beams suffering from ASR. Area was patched 20 years ago and the lifetime of the patches has been reached.

Waterproofing coating after replacing concrete surface would extend repair lifetime.

LiF, Li2SiO3, LiNO3, and Li2SO4) in mortars (ASTM C227) containing highly reactive silica could help control the alkali-silica reaction provided the lithium was present in sufficient quantity. In 2007, the FHWA published a report titled The Use of Lithium to Prevent or Mitigate Alkali-Silica Reaction in Concrete Pavements and Structures. Within the document, the FHWA establishes that the required amount of lithium to suppress expansion is based on the reactivity of the aggregate and the ratio of alkali to sodium plus potassium in the original concrete mix.

The following molar ratio is used to obtain the recommended dose to control ASR (FHWAHRT-06-133 Section 4.1):

of topical applications on shallow and small repairs. No significant improvement results have been observed in larger specimens. This triggered a study by Whitmore and Abbot in 2000, where they used electrochemical impregnation techniques to increase the penetration of the lithium compound on large structures. The technique is very similar to that of electrochemical chloride extraction technique. An electrode anode is applied to the concrete surface. The lithium electrolyte is ponded at the surface and a D.C. voltage is applied between the anode and the embedded steel (reinforcement) to drive the electrolyte into the concrete. A current of 60 volts appears to be the most effective, achieving a significant decrease in alkali reaction 2 inches into the surface. Electrochemical applications should be considered when large areas are affected and a long term protection mechanism is feasible.

In summary, practical suggestions for the determination of ASR in the field and employing feasible treatments include the following: 1) Where appropriate, such as with upturned exposed beams, copings, parapets, buttresses, and piers, wrapping to exclude water can extend the surface life.

2) As an engineer, when you encounter deteriorating concrete, run through your mind the usual culprits: chlorides, carbonation, mechanical abuse and now, ASR. In a salt-free environment (a concrete building façade), look for reduced concrete cover over the reinforcement made all the more sensitive by carbonation of that concrete. Carbonation reduces the natural alkaline passivity of cement around reinforcement.

[Li] ≥0.74 [Na+K ] The report also indicates that lithium additives appear to be more effective when applied to rapidly reacting aggregates such as those containing opal, chert or volcanic glass; meanwhile, they are less effective with slowly reacting aggregates such as those containing microcrystalline or strained quartz. In this report, Section 4.3, the FHWA provides recommended testing methods to help estimate the effectiveness of the lithium to control the ASR under evaluation.

In restoration cases where minor patching will take place, the surface application of lithium compounds can help slow down the ASR. Laboratory studies (Stark et al, 1993; Stokes et al, 2000) have confirmed the positive effect STRUCTURE magazine

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ASR deterioration.

3) In marine environments along the coast, or in parking structures where salts can be brought in by vehicles, look for chloride contamination that can lead to electrical chemical deterioration (rust) of reinforcing steel.

4) In older structures, look for the characteristic “map cracking” on the surface of the concrete that may be an indicator of an expansive aggregate (ASR) that is increasing the volume of the concrete, which exceeds the cement paste binder aggregate’s tension capacity. This phenomenon has also been referred to as a “varicose-vein” surface.

5) In recent years, chemical admixtures have come on the market that improve the durability of the concrete by increasing impermeability. Some of those products are marketed under manufacturer trade names. Using some of those same products in a topical application may be helpful.

Where deteriorated surface concrete can be removed and replaced to extend the service life, but it is not possible to provide a waterproofing wrap, consider the possibility of improving the waterproofing characteristics of the concrete internally by applying a densifying material topically to the interface between the ASR-prone aggregate and the new concrete surface treatment.▪

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

T

he value of constructable Building Information Modeling (BIM) to projects is evident, yet it remains a common misconception that structural engineers get the least benefit from it. But, as many structural engineering firms can attest, it doesn’t have to be that way. Instead of following the lead of architects who suggest or require the use of BIM, structural engineers should assume the lead by building “constructable” models that can be used downstream by all subcontractors throughout the life of the project. This seems straightforward, yet many structural engineers are still wondering, “what’s in it for me?” To answer that question, it is first important to understand constructable models and how they have the potential to be an added revenue source for the structural engineer, while at the same time providing the owner with a streamlined process that should reduce overall costs.

Structural Engineers Add Value with Constructable Models

By Stuart Broome, B.Eng (Hons)

Stuart Broome, B.Eng (Hons) (stuart.broome@tekla.com), is Business Manager for Engineering at Tekla, Inc., a Trimble Company.

He is a structural engineer with 21 years of experience in the U.S. and Europe.

What is Constructable BIM?

All 3D models are not BIM and also are not necessarily constructable. For example, models that contain only visual 3D data but no object attributes, or those that allow changes to dimensions in one view but do not automatically reflect those changes in other views, are not BIM. These types of models are useful for architects to communicate a building concept and vision to the owner and subcontractors, but they lack the data to support construction, fabrication and procurement, and thus are not constructable models. In reality, this is typically the way structural engineers work, taking an architect’s model, adding the structural elements and then supplementing the 3D model with a set of 2D drawings, usually created from a homemade library of standard details for things such as steel connections and concrete reinforcement. And to be fair, there is nothing fundamentally wrong with the structural engineer’s end product from this process; a full set of 2D construction documents is produced and conveys the design intent. This is usually what a structural engineer is requested to do and is often referred to as Level of Development (LOD) 300 in the contract.

However, this approach can be very inefficient for the structural engineer; there are two potential problems. Change management is time consuming and, as the 2D drawings are not always a product of the 3D model, the structural engineer is required to do twice as much work for the same result. Secondly, the 3D model is not useful downstream to others in the process because it does not contain enough detail or information and often is not accessible, meaning constructability and clash detection cannot be checked.

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Constructable models can provide an added revenue source for structural engineers along with a streamlined process that should reduce overall costs for the owner.

An Opportunity for Structural Engineers Expecting a structural engineer to spend time creating a model that contains all the information requested for fabrication and construction is not realistic. It is also unreasonable for a structural engineer to spend additional time creating a model solely for the benefit of someone else, unless fees are incurred for the additional work.

However, if the owner was prepared to spend a little more money at this phase of the project, the overall savings of the construction phase as a result of reductions in change orders and RFIs could be significant. This is the advantage of a constructable model.

So why should a structural engineer be interested in creating a constructable model? You could argue that structural engineers should want to create buildings that fit together purely for professional pride, but pride alone doesn’t pay the bills. Arguably, structural engineers are perhaps in the best position to harness BIM for their own advantage as well as the benefit of the entire project, from design to fabrication to construction. Constructable models can provide an added revenue source for the structural engineer, while at the same time providing the owner with a streamlined process that should reduce overall costs.

Constructable Models Offer a Wide Range of Benefits Improving Communication & Collaboration Constructable BIM breaks down communication barriers between project stakeholders. It provides a source of detailed unified information that becomes a trusted repository of collective accurate data and measurements to ensure consistency as each trade builds their own models.

Because everyone works on models that share common source data, the models can be overlaid to detect clashes before materials are ordered or construction begins.

In this way, constructable models foster frequent communication between architects, design engineers and trades because they are the product of collaboration. This open and frequent communication produces the opportunity for better and more efficiently built structures completed within even the most demanding schedules. The entire project team benefits from speedier, clearer communication and improved coordination. Fabricators and erectors, in particular, will benefit from better planning and management tools, and greater understanding through visualization.

can include a text description of the problem along with a screen capture, enabling the involved parties to immediately understand the issue and its impact. The model can be marked up and passed back-and-forth in real time, much like an attachment can be attached to an instant message.

National construction services company Barton Malow is taking the practice of using constructable models to resolve RFIs and reduce change orders a step further for the remodel and expansion of the Daytona

International Speedway grandstand, which is scheduled for completion in 2016. The company requires all of the trades to post open standard Industry Foundation Classes (IFC) files of their updated models to Dropbox each week.

The McGill Engineering office in Tampa, Florida, downloads the updated models from the other trades into their structural steel model, and uses a clash detection function in their BIM software to discover problem spots. When a clash is found, the other

Estimate and Material Accuracy

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Creating a detailed, information-rich structural model allows structural engineers to extract accurate material quantities to produce more competitive bids with much lower contingencies.

In addition to giving structural engineering firms a competitive edge for winning business, constructable models enable materials to be sequenced and ordered with confidence to reduce waste and the cost of fixing mistakes discovered at the jobsite.

French structural engineering firm Sarl Patrick Millet was tasked with extensively remodeling and expanding the 60-yearold skating rink in the Alpine town of Gap, France. Because of the accuracy of the constructable model detail, such as the dimensions and quantities of the steel required for the project and the ability to generate accurate drawings from the model, Millet issued its fabrication orders with confidence. Despite the project’s geometric complexity, there were no fabrication errors.

Estimating for atypical jobs such as remodels and expansion projects can also be achieved with constructable models. In these cases, the model is created using a combination of source data such as 3D laser scans of the existing structure, drawings and as-built information. This process creates an accurate project scope and produces accurate material quantities.

Clash Detection RFIs delay projects. When progress stops because a problem is discovered or someone needs more information, the project schedule suffers a setback. Using constructable models brings clarity to RFIs and leads to quicker resolution because they allow structural engineers to communicate and resolve issues with trades through the model. A model-based RFI STRUCTURE magazine

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trade’s model is imported into McGill’s working structural steel model and the problem is fixed. If it can’t be fixed in the steel model, McGill takes a snapshot of the clash and sends it along with an RFI to the appropriate trade for redesign.

Structural engineering and building firm Gregory P. Luth & Associates, Inc. in Santa Clara, California, started using constructable building information models in 2006.

Constructable BIM has allowed them to resolve conflicts and congestion during the design phase, which streamlines construction. Even when change orders are issued for design changes, making those changes to a constructable model reduces latency. Instead of taking weeks, the firm can have rebar in the field within seven days of receiving the change order because they can generate revised shop drawings direct from the updated model for the fabricator. This practice allows jobs to proceed much more efficiently, with no second-guessing.

Reducing Waste

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Building and sharing constructable models reduces waste throughout a project, from time wasted during the design phase to material waste, which translates to time and cost savings. Over the last 10 years, Walter P Moore has developed a spectrum of constructable models, ranging from Advance Bill of Material (ABM) model to a fully-connected detailed model. To further leverage model sharing, the firm wrote custom API interoperability tools for several design and analysis, and documentation platforms. These translators allow their structural engineers and steel detailers to quickly and automatically build models in their BIM software from models created in other platforms by other trades. Not only do these translators save project time, but they allow the firm’s engineers to spend more time designing; not remodeling.

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Structural engineering firms that routinely build and share constructable models add tremendous value to projects.

Reducing Risk & Liability

What’s Stopping Structural Engineers?

available and choosing the right one isn’t always easy. In an ideal world, the structural engineers should be able to use a BIM solution which: • Has been designed specifically for structural engineers, not architects.

• Enables the creation of a 3D model intelligent enough to generate all of the 2D drawings.

• Enables the 3D model to be created more quickly than creating the 2D drawings manually.

• Integrates seamlessly with the structural engineers chosen analysis design software.

• Would be accurate enough to pass downstream to be used by the detailer for detailing purposes (LOD 400).

• Provides the structural engineer with the option to include more detail than LOD 300 if required (with very little additional modeling time required).

Structural engineering firms that routinely build and share constructable models add tremendous value to projects through better designs, enhanced collaboration, better cost management, less waste and jobsite efficiencies that go right to bottom line. And, this tool leads to delighted owners, more repeat business and referrals, lower risk and even reduced liability insurance premiums.▪

The reality is that, in many cases, structural engineers are simply using the wrong BIM software. There are a number of options

All graphics courtesy of Nucor Buildings Group.

Perhaps one of the most frequent arguments against building constructable models and sharing them is the perception that this practice increases risk and liability. This likely comes from the counsel of overly cautious attorneys and insurance agents during the early days of computer-aided design and 3D modeling technology. The truth is actually the opposite, according to structural engineering firms that routinely do this. In fact, it can actually reduce liability insurance premiums by reducing a firm’s claims, one of the factors in determining premium costs.

A large percentage of claims stem from miscommunication, a problem that is greatly improved when design engineers produce constructable models in collaboration with others on the project team such as architects, steel detailers and steel fabricators. Sharing constructable models reduces risk for structural engineers because it gives everybody access to the same information at the same level of detail and allows them to comment within the model, thereby enhancing communication.

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ConstruCtion issues discussion of construction issues and techniques

T

he topic of fire precaution and safety during construction of large buildings is timely and relevant.

The frequency and consequence of this type of fire is attracting attention in both public and private arenas. These types of fires may also impact nearby buildings, can interrupt neighborhood business operations, and can have longer-term effects on the surrounding community. Often they result in property damage, have the potential for worker and first responder casualties and injuries, and can have a longer-term effect on the reputation of companies involved. But most importantly, they can be prevented to a large degree by strict adherence to existing model codes and standards that have been written for just such purposes.

These include requirements and references to standards that are almost universally accepted by local governments that oversee most construction in the United States.

To that end, the American Wood Council has joined with Fireforce One, a fire protection consulting firm, along with a coalition of stakeholder organizations involved in the construction of large buildings, to develop education and training materials on how to reduce the frequency and severity of fires during construction. The project is expected to be completed in mid-2015 and will make available video and print materials that can be used by developers, builders, fire services, and the design community to enhance fire safety on the jobsite. This article provides an overview of the areas on which the education and training materials will focus.

Basic Fire Precautions during Construction of Large Buildings

By Dr. Kuma Sumathipala, P.Eng and Chief Ronny Coleman

Dr. Kuma Sumathipala, P.Eng (ksumathipala@awc.org), is Director of Fire and Energy Technologies with the American Wood Council.

Chief Ronny Coleman is a retired California State Fire Marshal with fire protection consulting firm Fire Force One. He can be reached at ron@fireforceone.com.

Fire Safety Plan In order to manage risks and hazards and reduce catastrophic events, there needs to be a plan and management model in place. In order to have an effective program there must also be a system of accountability.

Fire Protection Program According to the Occupational, Safety, and Health Administration (OSHA) a building site must have a Fire Protection Program (FPP) incorporated into its Health and Safety Plan (29 CFR Part 1926 Subpart F). The Model building codes further require that an owner/developer implement a pre-fire plan for each new construction or renovation project site in coordination with the fire department. The program implemented is expected to incorporate the guidelines of NFPA 241 Standard for Fire Safety during Construction, Demolition or Alteration of Buildings.

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Model building codes require that an owner/ developer implement a pre-fire plan for each new construction or renovation project site in coordination with the fire department, which is expected to incorporate the guidelines of NFPA 241 Standard for Fire Safety during Construction, Demolition or Alteration of Buildings.

Site Fire Prevention Manager A person with appropriate knowledge should be designated as the Fire Prevention Program Manager for the site, in accordance with NFPA 241. This manager will coordinate their activities with the overall Site Safety Manager. The Fire Prevention Program Manager is responsible for developing and implementing a written, comprehensive Site Fire Safety Plan (FSP).

Enforcement Just like location is stressed for real estate, construction site fire safety emphasis must be on training and enforcement. The best Site Fire Safety Plan is ineffective unless training has been provided and the Plan is strictly enforced. Post-fire incident review often reveals that the very cause of a fire was explicitly addressed in the FSP but ignored.

Model Code Every State in the U.S. has an adoption process for fire and building codes, and many jurisdictions use available model codes for this purpose. All of the principal U.S. model building and fire codes follow a similar path in setting requirements for buildings under construction.

Best Management Practice (BMP) BMPs would require all people working on or visiting a construction site to be made aware of the importance of fire prevention and the content of the Fire Safety Plan, including what to do in the event of fire, emergency procedures, location of assembly points, and good housekeeping

practices. Appropriate training in relation to the use of portable firefighting equipment, safety precautions for those undertaking hazardous operations, and site-specific emergency procedures would be provided. Records are also kept of fire safety training and instructions given to site personnel and visitors.

Additional area-specific BMPs that are to be addressed in any Site Fire Safety Plan include : • Housekeeping • Hot Work • Electrical Supplies and Equipment • Smoking Activities • Food Preparation • Open Fires/Waste Fires and Temporary Heating Equipment • Plant Equipment and Vehicles • Stored and Waste Materials • Storage of Combustible Building Materials • Exposed Combustible Materials • Flammable Liquids and Gases • Waste/Garbage Chutes Once a building is under construction, there are two primary agencies that have an interest in compliance. The local building official inspects for compliance with applicable codes.

The other interested agency will be the fire department that may have ongoing enforcement responsibilities for completed buildings.

Interface with the Fire Department Regular liaison with the fire department is important. The fire department needs to have full knowledge of a building site before a fire emergency occurs. This allows for a more effective response. Areas to be reviewed with fire authorities, and for which a number of National Fire Protection Association (NFPA) standards exist to provide guidance, include: • Pre-Fire Planning • Water Supplies • Fire Department Access • Emergency Procedures

Built-In Fire Protection Features Better use can often be made of the additional fire protection that is built into a structure.

Planning their use as part of construction staging will allow their installation and operation as soon as reasonably practicable. Components that fall into this category include: Permanent Features • Fire stairs, including fire-resistant walls • Fire compartment boundaries, including fire doors, penetration seals and general protection of other openings

A coalition of stakeholder organizations involved in the construction of large buildings has joined together to develop education and training materials on how to reduce the frequency and severity of fires during construction.

• Fire-protective materials to structural steel and fire-preventative coverings over combustible construction • Automatic fire sprinkler systems and other automatic suppression systems, where usable • Automatic detection and alarm systems Temporary Systems • Temporary detection and automatic alarms • Manual pull-stations • Emergency telephones strategically located Means of Egress • Adequate paths of travel to fire exits • Regularly checked for obstructions • Clearly signed Fire Extinguishers • Appropriately sized and widely available at all times • Additional extinguishers for fire watch personnel • Always at hot works locations • Maintained and regularly inspected • All staff fully trained in their use Hydrants and Hose Reels • Fully operational as soon as possible Standpipe Risers • Installed and commissioned progressively with construction • Locations well marked • All staff fully trained in their use

Temporary Systems The construction process often results in a need for temporary installations. These are

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defined as those that will be removed before finalization and occupancy of the project.

Temporary systems may include building, exiting, and heating systems.

Such temporary systems are needed, but must never be placed in locations where they compromise the ability to maintain fire safety. The planning process should include and plan for any temporary system, with monitoring of such systems included in oversight and implementation of the fire plan.

Site Security Security is required on a construction site for many purposes. It includes preventing theft, vandalism, and reducing liability.

Notably, preventing arson is one of the most difficult tasks faced at building sites.

Depending upon the size and physical configuration of a building, guard services may be required to maintain levels of safety.

Additional details are available in NFPA 601, Standard for Security Services in Fire Loss Prevention.

Fire Reporting When an emergency occurs, time is of the essence. Emergency responders need to be notified immediately, even for events considered small. Research indicates that it is not uncommon for these types of fires to become catastrophic in size before the fire department is even notified or arrives on scene. continued on next page

Alternative Solutions The International Building Code, International Fire Code, and NFPA 5000 Building Construction and Safety Code allow alternative materials, designs, and methods of construction and equipment to be used. However, where such systems are used, care must be taken to ensure they are recognized and addressed in the FSP.

Construction within Occupied Buildings Final punch-out, renovation, and maintenance activities are often undertaken after buildings have received their certificate of occupancy and may even be occupied. This often presents unique challenges to ensuring fire and life safety during such processes. As with new buildings, the planning phase is critical to ensure that acceptable safety levels are maintained during final construction tasks, renovation, and maintenance. Principal contractors should take the lead in preparing a site Fire Safety Plan for these conditions, but representatives from among those working on the premises and the building owner should also be involved in developing an appropriate and responsive FSP.

The International Building Code and International Fire Code, both published by the International Code Council, and NFPA 5000 Building Construction and Safety Code allow alternative materials, designs, and methods of construction and equipment to be used.

Conclusion National fire organizations, including the U.S. Fire Administration and NFPA have been monitoring losses in construction fires in large buildings for decades. The trend and pattern of these fires is significant, as it shows that a greater percentage result in large financial losses compared to fires in completed, occupied buildings. Research that looked into the causes and outcomes of these fires repeatedly point to construction site accountability and enforcement of existing fire and building codes as primary

reasons for such losses, indicating a strong need to improve in these areas.

The joint American Wood Council/ Fireforce One project, along with a very engaged group of affected stakeholders, was created to specifically address this need.

Later this year, the project will be providing very specific print and video materials, training, and guidance for adoption and implementation to the construction, fire, and design communities. We hope the result will be a highly enhanced awareness of the problem, and a resulting reduction in construction site fire losses.▪

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SkyScraper

Completed 2014, Height 1251 Feet Owner: Aldar Properties Architect: Foster + Partners Structural Engineer: Halvorson and Partners

Watch 2014 Was Impressive, and 2015 Will Be Even More So

By Daniel Safarik

I

f construction completion is used as the main basis of comparison, it is hard to conclude anything other than the global tall-building industry is burgeoning, seemingly despite emerging signs of global economic doldrums. The Council on Tall Buildings and Urban Habitat (CTBUH) has determined that 97 buildings of 200-meter (656-foot) height or greater were completed around the world in 2014 – a new record. This is a 20% increase from the previous record of 81, set in 2011. Not surprisingly, 60% of these 2014 buildings were in China.

Key Market Snapshots • A total of 11 supertalls (buildings of 300 meters [984 feet] or higher) completed in 2014 – the highest annual total on record. Since 2010, 46 supertalls have been completed, representing 54% of the supertalls that currently exist (85).

The number of 200-meter-plus (>656 feet) buildings in existence has hit 935, a 352% increase from 2000, when only 266 existed.

• The year 2014 was the “tallest year ever” by another measure: The sum of heights of all 200-meter-plus buildings completed across the globe in 2014 was 23,333 meters (76,552 feet) – setting another all-time record and breaking 2011’s previous record of 19,852 meters (65,131 feet).

• Asia’s dominance of the tall-building industry increased yet again in 2014. Seventy-four of the 97 buildings completed in 2014, or 76%, were in Asia.

• Once again, for the seventh year in a row, China completed the most 200-meter-plus buildings (58). This represents 60% of the global 2014 total, and a 61% increase over its previous record of 36 in 2013.

• The Philippines took second place with five completions, the United Arab Emirates and Qatar share position three with four completions each, and the United States, Japan, Indonesia and Canada tie for fourth, with three completions each.

• Japan marked its first entry into the supertall stakes with the completion of the 300-meter (984-foot) Abeno Harukas in Osaka, becoming the country’s tallest building.

• South America also welcomed its first supertall, the 300-meter (984-foot) Torre Costanera of Santiago, Chile, which was also the only building of 200 meters or greater to complete on the continent in 2014.

STRUCTURE magazine

Burj Mohammmed Bin Rashid Tower, Abu Dhabi.

Courtesy of Arabian Construction Company.

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June 2015

• Tianjin, China, was the city that completed the most 200-meter-plus buildings, with six. Chongqing, Wuhan, and Wuxi, China, along with Doha, Qatar, all tied for second place with four completions each.

• In 2014, 47 all-office buildings were completed (48% of the total), the largest total ever, versus 31 (38% of the total) in 2011, the previous record high.

• At 541 meters (1,775 feet), One World Trade Center was the tallest building to complete in 2014 and is now the world’s third-tallest building.

Completed 2014, Height 984 Feet Owner: Cencosud Architect: Pelli Clarke Pelli Structural Engineer: Rene Lagos Engineers

Completions by Structural Material A majority of tall buildings completed in 2014 were of composite construction – 52 out of 97 (54%), as compared to 24 out of 71 (34%) in 2013, while the number of buildings whose predominant structural material is concrete declined to 37 of 97 completed (34%) in 2014, from 43 of 71 (61%) in 2013.

All-steel continued its decline as a primary structural material, comprising only 5% of 2014’s 200-meter-plus completions and 13% of the world’s 100 tallest buildings, though it showed a slight uptick from 3% in 2013.

The World’s 100 Tallest Buildings: Impact of 2014 In 2014, the number of buildings entering the World’s 100 Tallest list was 13, one more than in 2013. The shortest building on the 100 Tallest list in 2013 was the Columbia Center, Seattle, at 284.4 meters (933.1 feet). In 2014, the shortest building became the 291.6-meter (956.7-foot) SEG Plaza in Shenzhen, having moved down the rung from number 87 to number 100.

The average height of buildings in the 100 Tallest list has thus increased to 350 meters (1,148 feet) in 2014 from 344 meters (1,129 feet) in 2013 – the figure in 2000 was 285 meters (935 feet).

The number of all-office towers in the 100 Tallest ranking continues to decline, with 39 all-office buildings, down from 42 in 2013. In context, as recently as 2000, 85 of the world’s 100 tallest buildings were all-office buildings.

In the 100 Tallest rankings, 39 buildings were composite construction, versus 36 in 2013. Despite the somewhat surprising increase in 2014, all-steel continued its decline as a primary structural material, comprising only five of 2014’s completions and 13 of the world’s 100 tallest buildings.

Analysis What can be made of this skyscraper surge? It could very well be that pent-up demand has returned to real-estate markets after a lull during the recession. Now that six years have passed since the global economic crisis/recession began in 2008, and given the long gestation and construction periods common to tall buildings, we are almost certainly seeing the results of a post-recessionary recovery.

Clearly, the Chinese juggernaut has not yet run out of steam. The country continues to see new 200-meter-plus completions in cities that previously had few or no such buildings, indicating that the massive plan to urbanize the country – requiring the urban relocation of some 250 million people – is underway. Its effects have begun to percolate into smaller regional cities beyond the first tier of Beijing, Shanghai, Guangzhou, Shenzhen, and Hong Kong. It is tempting, but dangerous, to take this as an undiluted sign of economic health, as the STRUCTURE magazine

Torre Costanera, Santiago, Chile. Courtesy of Pablo Blanco Barro.

Chinese national and regional governments are principal stakeholders in many of these projects, and the “cause and effect” of the situation is not always clear. Is the government subsidizing tall buildings in order to attract businesses, and in anticipation of future masses, or are business and population needs organically driving growth?

The other major trend that would seem to justify further analysis is the increase in the number of all-office buildings, something that has not happened since the previous record year of 200-meter-plus completions across the board that occurred in 2011. The use of all-steel structures also increased slightly, which is counter to the overall trend of a steep decline since 2000. These 2014 figures are likely correlated.

The reason most office skyscrapers were historically made of steel is due to the spanning capabilities that steel affords the large, columnfree spaces office tenants desired. But in the past decade, the use of composite construction, such as concrete-encased steel – most often working in conjunction with a concrete core – has risen with the increasing number of mixed-use buildings, and has provided the flexibility needed to accommodate all kinds of uses in one building.

On its face, then, the small uptick in all-steel use in 2014 seems somewhat anomalous.

The number of all-steel cases is small enough to analyze as a group.

All of the buildings have an office component, but two are mixed-use.

Three of the five buildings completed are in Japan, which has extremely high seismic requirements. The methods used to satisfy those requirements, such as base isolation and in-plane dampers, are easier to implement in steel. Also, steel has inherent flexural properties superior to that of concrete. The Cathay Life Xinyi A3 building in Taiwan is an office building in a high seismic zone as well. London’s Leadenhall

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June 2015

Global Completed 2014, Height 977 Feet Owner: Silverstein Properties Architect: Maki and Assoc. / Adamson Assoc.

Structural Engineer: Leslie E. Robertson Asssoc.

The US Department of Agriculture’s $2 million Tall Wood Building Prize Competition closed in February 2015 and, as of press time, the agency was considering technical proposals. The winning proposal team will go on to construct a wood building based on their design at least 24 meters (79 feet) in height. It’s looking like 2015 will be a critical year in the development of this new/old building technology.

Plans for tall wood buildings have been announced in Vienna and Stockholm, while a project in Bergen, Norway is under construction.

To capture all the great learning that is happening now in this field, CTBUH has formed a Tall Timber Working Group.

Changsha Brushing off the apparent cancellation of its plan to build the world’s next tallest building (220 stories, 838 meters [2,749 feet]) out of prefabricated modules in a matter of months, the Broad Sustainable Building company finished a 57-story skyscraper using the same techniques in March 2015 – in 19 days – a stunning achievement.

Dubai The long-planned Burj 2020 is back in action, according to CTBUH insiders. In late 2014, shortlisted architecture-engineering teams were being interviewed, making the claimed start of construction in 2015 seem plausible. If the 660-meter (2,165-foot) tower’s developers want to keep its original plan to have the highest observation deck, it will have to top the Burj Khalifa’s 555.7-meter (1,823-foot) perch.

Las Vegas The erstwhile Harmon Hotel, a planned 47-story building, was stopped in 2008, having completed only 26 stories, after it was determined to be structurally unsound due to construction defects.

The deconstruction began in June of 2014, and should complete by June 2015. The traditional Vegas-style implosion was eschewed, due to its proximity to the surrounding $8.5 billion CityCenter.

London

4 World Trade Center New York, NY. Courtesy of Fadi Asmar / LERA.

Building, which entirely consists of office space for lease, had many particular site constraints that resulted in prefabrication being selected as the optimal construction method. Steel lends itself to the lifting and adjustment requirements of prefabrication, of course, and the project’s architect, Rogers Stirk Harbour + Partners, is widely known for its use of expressive steel exoskeletons in its work.

Moscow The burgeoning Moscow-City complex has begun to pick up pace, after several economy-related delays and at least one fire. The Vostok Tower, at 373 meters (1,224 feet) the higher of the two Federation Towers, will also become the tallest building in Europe in 2015.

Shanghai

Trend-Watching If anything, 2015 will be more active than 2014 and, indeed, any year previous. We currently project the completion of between 105 and 130 buildings of 200 meters’ height or greater, eight to 15 of which will be supertalls, and one of which will be a megatall – Shanghai Tower. Once again, China is expected to lead by a wide margin. China is on track to complete or top out 106 buildings of 200 meters or greater – that’s 86% of the low-range estimate (105) and 72% of the high-end estimate (130).

Here are some of the developments that will be making headlines in 2015: STRUCTURE magazine

The beleaguered Pinnacle, a mere “stump” since 2011 due to the recession, was promised another lease on life under PLP Architecture and new owners Axa/Lipton Rogers in late 2014. In February, it was revealed that the unfinished twisting skyscraper would be demolished and replaced in a $480 million plan. The new building is more rectilinear in form, and will be called 22 Bishopsgate when it opens in 2018.

The 632-meter (2,073-foot) Shanghai Tower will complete by midyear, becoming the tallest building in China and the world’s second-tallest building. The project is also highly anticipated due to its extensive use of double-skin façades and skygardens.▪

36

Daniel Safarik is the Director of the China office of the Council on Tall Buildings and Urban Habitat (CTBUH) and is editor of the CTBUH Journal. Daniel can be reached at dsafarik@ctbuh.org.

June 2015

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CONSTRUCTION OF TALL BUILDINGS GOING STRONG Companies Innovate, Offer New Products and Services

By Larry Kahaner

C

ompanies involved with tall building construction continue to innovate and grow, and they’re bringing new products and services to their customers. For most companies, business is strong.

At RISA Technologies (www.risa.com) in Foothill Ranch, California, Vice President, Operations, Amber Freund says, “We continue to hear from engineers that projects are coming in and design work is keeping them busy.” She adds: “With a well-trained team of engineers and software developers, RISA is working to meet the needs of our growing client base by implementing new design features and expanding the suite of software tools that we offer.

Providing exceptional customer service is a priority to us, and is something we continue to strive for in our day-to-day operations.

We have a wide variety of engineering design experience within the office, which gives us a great perspective for future development goals. Our focus is squarely on our clients.”

Freund notes that the company released RISAFloor ES in 2014 “so RISA now offers everything you need for concrete design.” She adds, “For concrete floors, including beams and two way slabs, nothing beats RISAFloor ES for ease of use and versatility. The design of columns and shear walls with RISA-3D offers total flexibility. Integration between RISA-3D and RISAFloor ES provides a complete building design.”

She says that the company introduced RISAFloor because companies asked for it. “RISAFloor customers had been asking for elevated concrete slab design with the same easy to use interface they were used to. Adding this feature was a good fit and expansion of our design features within RISAFloor.” (See ad on page 68.)

Also on the software side, Tekla, Inc (www.tekla.com/us). in Kennesaw, Georgia, has launched a new building analysis and design solution in March called Tekla Structural Designer (TSD).

“TSD utilizes some of the technologies from previous CSC solutions, Fastrak and Orion,” says Stuart Broome, Engineering Business Manager. “TSD has been developed with BIM integration in mind and enables structural engineers to model, analyze, design and produce drawings for complete buildings in a single interface. Capabilities include: steel, composite and concrete, and it is versatile enough to include floors, complex roof structures such as trusses, slopes, and hangers, as well as gravity and lateral systems all in the same model.”

Broome also says the company had introduced version 21 of Tekla Structures in March, bringing much more drawing capabilities to STRUCTURE magazine

their BIM solution. “Tekla Structures is well known around the world as being the most widely used and complete solution for steel and concrete detailing, but is less well known as a structural engineer’s tool for producing construction documents and general arrangement drawings. V21 includes many new features to make drawing production quicker than ever before. Because all of the detail is contained in the actual model, there is no need for additional 2D line work. Even dimensions and labels are automatically produced on the drawings.

This also makes dealing with changes very quick,” says Broome.

StructurePoint (www.structurepoint.org), formerly the Engineering Software Group of the Portland Cement Association (PCA), located in Skokie, Illinois, considers itself “a convenient single point of access to the vast resources and knowledge base of the entire cement and concrete industry including Library services, training, R&D, publications, building codes, specialty engineering, concrete material and testing, concrete repair, codes and standards consulting,” according to Heather Johnson, Marketing Director.

Johnson wants SEs to know about StructurePoint’s release of spMats v8.00, which was issued in the fall of 2014. “It provides foundation designers a sophisticated, brand new finite element solver. This increases capacity and substantially speeds solutions for larger and more complex models such as commercial building foundations, industrial facilities, slabs on grade, and equipment foundations. Also introduced are new results sections, including a report of reaction values for restraints, soil, spring, pile, and slaved nodes.”

She notes: “StructurePoint is now focused on incorporating ACI 318-14 code changes into our software suite. We are very pleased with the new code organization and find its new member based chapters a perfect match to our member design programs. Now there is a code chapter that correlates exactly to spBeam, spSlab, spColumn, spWall, and spMats. Our end users can easily account for all the 318 code provisions directly in their corresponding StructurePoint software output and results.”

Johnson says that they continue to support and gain credibility with international clients along with a definitive expansion in the Middle and Far East. “Meanwhile, our U.S. clients continue to consolidate and refine their software choices by increasing StructurePoint licenses for increasing work in retrofit and occupancy changes. These opportunities can sometimes make for very tough and long days, so we are continuing to add staff to address the consulting and educational projects that are no longer addressed by departments of Portland Cement Association.” (See ad on page 40.) continued on page 41

39

June 2015

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

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CONSTRUCTION CEMENT

FA S T ER STRONGER MORE DURABLE 3000 PSI IN 1 HOUR and fabrication costs dramatically increase.

Replacing those complex, built-up joints with castings is ideal. In fact, there are a number of high rises in Asia where this approach has been implemented with great success, and where this use of castings provides a higher degree of confidence in the quality and robustness of the joints. Note, too, that because machining is a standard part of casting production, cast nodes can be produced with machine-level dimensional precision at locations where structural steel elements are to mate with the casting. As such, shop jointing and field fit-up can be improved in projects which leverage castings.” (See ad on page 4.)

At CTS Cement Manufacturing Corporation (www.ctscement.com), in Cypress, California, Janet Ong Zimmerman, the company’s marketing director, says: “Business is very good.

Restoration, tilt-up, and flooring are growing for us and our customers. Residential is still a little slow, but coming back. Engineers, architects, contractors and other construction professionals are turning to innovative products to help solve and simplify their construction needs. For instance, they are looking for products that are fast, strong, durable, and easy to use.”

She suggests that SEs will be interested in their Rapid Set V/O Repair Mix (Vertical Overhead Repair Material). “Damaged concrete, even in vertical or overhead locations, can be dealt with quickly and easily using Rapid Set V/O Repair Mix,” says Zimmerman. “V/O Repair Mix is a high performance, polymer-modified blend of Rapid Set Cement with additives and specially graded fine aggregates, so it bonds well with existing concrete and is freeze/thaw and corrosion resistant. It is ideal where rapid strength gain, high durability, and low shrinkage are desired.” continued on next page

STRUCTURE magazine

41

June 2015

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Cast Connex Corporation, headquartered in Toronto, Ontario (www.castconnex.com), works with structural engineers and architects to enable them to incorporate cast steel components into their designs, and then assist contractors successfully integrate Cast Connex products into the structures they construct, according to Carlos de Oliveira, the founding Chief Executive Officer. “In so doing, we simplify the design and enhance the performance of structures. And when we say ‘enhance performance,’ we mean performance in the broadest terms: from architectural to structural performance.”

De Oliveira says that casting manufacturing offers the ability to produce monolithic, high integrity structural steel components of virtually any geometry. “Designers across the United States and the world over are leveraging cast steel components in innovative ways to economically address design challenges and to enable unparalleled architectural design opportunities – enhancing structural performance, improving quality, refining aesthetics, and saving money all at the same time.”

He adds: “Aesthetics aside, castings provide an opportunity to improve connection load path and connected member efficiency. For example, cast joints can be used to eliminate or reduce shear lagging effects in connections, allowing for higher member utilization.

Also, given their isotropic material properties, castings are ideal for use at heavily loaded, multi-axis connections. In high rise construction, a common practice is to build up nodes from plates ‘laminated’ to one another.

However,” says de Oliveira, “when the loading on built-up nodes is multi-axis and results in the need to transfer load perpendicular to the direction of lamination, the engineering of such built-up nodes can be challenging

Zimmerman says: “Use V/O Repair Mix in thicknesses from ½ inch to 6 inches (1.2 to 15.2 cm) for general concrete repair, resurfacing, vertical and overhead applications and mortar beds. It can be applied full-depth with a single coat. V/O Repair Mix sets in 45 minutes and is ready for loading in 2 hours. It does not need to be wet cured in most applications, because it uses a cutting-edge self-curing technology (SCT). The mix is tinted gray to match most Portland concrete surfaces, and can be used indoors or outdoors.”

The impetus for this product came from customers. “We did market research and found a lot of products for patching, but not many products that do what V/O Repair Mix does. V/O Repair Mix is versatile and can be used on different types of projects. It is innovative due to its built-in corrosion inhibitor, fiber reinforced, and self-curing technology. It allows contractors to apply from a very thin to thick application in a single lift, which is rare for this kind of product,” says Zimmerman.

New Millennium Building Systems (www.newmill.com) has developed the Flex-Joist Tension-Controlled Steel Joist design approach, in part to address a growing interest in ways to resolve roof overloading.

The approach provides for an overall increase in steel joist strength, reliability, and safety, according to a company spokesperson. “The safety advantage relates to the joist’s ability to flex before it breaks. A Flex-Joist system can be equipped by a third-party sensoring installer to establish an early warning system for roof overloads. This is a ductile tensile yielding design approach that has been well researched.

The method was published last spring in the AISC Engineering Journal. Flex-Joist also meets the design requirements of the Steel Joist Institute.”

Company officials see a trend in steel building design and construction around the concept of composite joists. “The approach has been

around for many years, but is now more top-of-mind due to the rise in multi-story building construction,” the spokesperson continued.

“A composite steel joist achieves a higher density floor structure, compared to more conventional methods. This is achieved by integrating the structural elements into one compact system. Floor-to-floor elevations can be narrowed due to the thinner floors. Mechanical runs can be passed through the open web steel joists, rather than under a solid wide flange beam. Longer spans mean fewer columns and a more space-efficient design. Lighter and fewer joists also mean less cost at every step, including joist erection and joist fireproofing.”▪

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STRUCTURE magazine

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June 2015

4/28/15 7:57 AM

expertise in tall building design and construction Software ADAPT Corporation Phone: 650-306-2400 Email: florian@adaptsoft.com Web: www.adaptsoft.com Product: ADAPT-Edge for Load Takedown and Column Design Description: The ideal tool for rapid load takedown and column design of concrete buildings. Offers both tributary-based and 3D FEM analysis loading of columns. Use Edge’s integrated column design module or export all tributary and load values into a flexible XLS format. Seamlessly imports building models from Revit Structure.

Bentley Systems Phone: 800-236-8539 Email: structural@bentley.com Web: www.bentley.com Product: RAM Structural System Description: Quickly design, analyze and create documentation for your building projects, saving time and money. Design anything from individual components to large scale building and foundations.

Product: RAM Connection Description: Perform analysis and design of virtually any connection type, verify your connections in seconds, all with comprehensive calculations, including seismic compliance. Increase your productivity to optimize workflows and full integration of 3D design models, including the ability to customize the application with your preferences.

Computers & Structures, Inc. Phone: 510-649-2201 Email: sales@csiamerica.com Web: www.csiamerica.com Product: ETABS 2015 Description: New special-purpose options and algorithms for the practical and efficient application of Performance Based Design (PBD). PBD represents the future of earthquake engineering, giving reasonable assurance that a specific design will meet a desired level of performance during a given earthquake.

POSTEN Engineering Systems Phone: 510-275-4750 Email: sales@postensoft.com Web: www.postensoft.com Product: POSTEN Multistory Description: Efficient and comprehensive posttensioned concrete software in the world that, unlike other software, not only automatically designs the tendons, drapes, as well as columns, but also produces highly efficient, cost saving, sustainable designs with automatic documentation of material savings for LEED.

TALL BUILDINGS GUIDE

Powers Fasteners

Tekla

Phone: 845-230-7533 Email: Mark.Ziegler@sbdinc.com Web: www.powers.com Product: Powers Submittal Generator Description: A new submittal and substitution online tool that helps contractors create submittal packages in just a few steps,. and allows them to include all applicable code reports and technical details with a few clicks. Contact us for a free demonstration!

Phone: 770-426-5105 Email: kristine.plemmons@tekla.com Web: www.tekla.com Product: Tedds Description: A powerful software that will speed up your daily structural and civil calculations, Tedds automates your repetitive structural calculations.

Perform 2D Frame analysis, utilize a large library of automated calculations to US codes, or write your own calculations while creating high quality and transparent documentation.

Product: Powers Design Assist (PDA) Description: Anchor design software now includes the ACI 318-11 code provisions. Download or update to version 2.2 today, to take advantage of the most current code.

RISA Technologies Phone: 949-951-5815 Email: amberf@risa.com Web: www.risa.com Product: RISAFloor and RISA-3D Description: Modeling has never been easier whether you’re doing a graphical layout, importing a BIM model (from Autodesk Revit Structure), or prefer spreadsheets. Full code checks and optimization for six different material types makes RISA your first choice in buildings.

S-FRAME Software Phone: 604-273-7737 Email: info@s-frame.com Web: www.s-frame.com Product: S-FRAME Analysis Description: A powerful, efficient 4D structural analysis and design environment with fully integrated steel, concrete and foundation design & optimization tools. Use S-FRAME to perform linear or advanced non-linear analysis on commercial and industrial structures. Includes feature-rich BIM and CAD links.

StructurePoint Phone: 847-966-4357 Email: info@structurepoint.org Web: www.StructurePoint.org Product: spColumn and spSlab Description: spColumn: design of shear walls, bridge piers as well as typical framing elements in buildings and structures. spSlab: analysis, design and investigation of reinforced concrete floor systems.

Product: spMat and spWall Description: spMats: analysis, design and investigation of commercial building foundations and industrial mats and slabs on grade. spWall: design and analysis of cast-in-place reinforced concrete walls, tilt-up walls, ICF walls, and precast architectural and load-bearing panels.

All Resource Guide forms for the 2015 Editorial Calendar are now available on the website, www.STRUCTUREmag.org. Listings are provided as a courtesy. STRUCTURE® magazine is not responsible for errors.

STRUCTURE magazine

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June 2015

Product: Tekla Structures Description: Move from design-oriented to construction-oriented engineering and enable structural engineers proved additional services.

Through our open and collaborative software environment, you can work with other disciplines and reduce RFIs. From concept to completion, Tekla software gives you collaboration and control.

Suppliers American Wood Council Phone: 202-463-2766 Email: info@awc.org Web: www.awc.org Product: Code Conforming Wood Design (CCWD) Description: The CCWD documents summarize allowable wood use in buildings in accordance with ICC’s 2009 and 2012 IBC. Emphasis is on design flexibilities permitted for wood in commercial construction. Eight occupancies including Groups A, B, E, F, I, M, R, and S in construction Types I – IV are discussed.

CTS Cement Manufacturing Corporation Phone: 800-929-3030 Email: jong@ctscement.com Web: www.ctscement.com Product: Rapid Set® Cement Products Description: For concrete repairs, restoration and new construction, and to achieve high durability, fast strength gain and structural or drive-on strength in one-hour. Install concrete structures and industrialsize floors using Type-K shrinkage-compensating cement products with no curling, no drying shrinkage cracking and no intermediate saw cut joints.

Simpson Strong-Tie® Phone: 800-999-5099 Email: web@strongtie.com Web: www.strongtie.com/srs Product: Simpson Strong-Tie® Strong-Rod™ Systems Description: Anchor tiedown systems for shearwall overturning restraint and uplift restraint for roofs address many of the design challenges specifically associated with light-frame, multi-story buildings that must withstand seismic activity or wind events.

Simpson Strong-Tie engineers can help optimize your designs with tested, code-listed solutions.

Contact us today.

26,000 GALLONS OF COATINGS PROTECTION FOR THE OHIO DOT’S LARGEST PROJECT

By Dee McNeill Roughly 1.8 million square feet of steel comprise the finished westbound span of the Innerbelt Bridge over the Cuyahoga River, shown with finished coatings.

T

he Ohio Department of Transportation’s (ODOT) Interstate 90 (I-90) Innerbelt Bridge replacement project in Cleveland, Ohio, is the largest project ever undertaken by the State. The old bridge over the Cuyahoga River had fallen subject to the effects of the city’s harsh winters and hot, humid summers. After 55 years in service, ODOT needed to address corrosion issues by replacing the historic bridge – the main east-west artery into and through downtown Cleveland.

ODOT is currently in the midst of replacing the old Innerbelt Bridge with two new bridges, one to carry traffic in each direction. The pair of bridges has been named in honor of Ohio statesman George V. Voinovich. The decision to replace one bridge with two allows ODOT to maintain traffic during construction and increase capacity on I-90.

The connection serves more than 140,000 vehicles per day.

The first of the pair is now open and temporarily carrying traffic in both directions while the second bridge is being constructed. The first new bridge, which will eventually carry westbound traffic, is 4,347 feet long and stands 120 feet over the Cuyahoga River Valley at its highest point.

To expedite work and minimize disruption to both local motorists and those traveling between Chicago and the Northeast, ODOT used a value-based design-build approach, versus a design-bid-build approach, for the first time.

Choosing the Right Contractor Aesthetics played a vital role in choosing a general contractor for the westbound bridge project. The bridge’s architecture has distinctive delta-shaped girders, made of A709 Grade HPS 70W steel, that complement the Cuyahoga Valley topography without dominating it. The design teams that competed for the work were evaluated on their ability to deliver not just on cost and an ambitious schedule, but also on preserving the aesthetics that define this part of Cleveland’s landscape.

Inspections Lead to Action In 2008, inspections conducted by ODOT concluded that the old Innerbelt Bridge was showing signs of aging sooner than expected.

Harsh de-icing chemicals in the winter months, its location in a highly industrial area, roadway, waterway and vehicular traffic, and businesses located under the structure all presented corrosion threats to the bridge.

STRUCTURE magazine

All structural steel corrodes or rusts when exposed to water and oxygen. The major ways to mitigate the corrosion of the structural steel are protective coatings applied to the steel and the closed drainage system.

Not all states require steel bridges to be coated, but ODOT stipulates protecting its bridges in a specific manner. Bridges in northeast Ohio must stand up to some of the most rigorous inspections there are, given the constant expansion and contraction caused by thermal cycling, and exposure A painting contractor applies the intermediate coat to the steel girders to road salt and airborne contami- under the Innerbelt Bridge. He uses nants from Lake Erie winds. To a light mounted on his hard hat to achieve all of its requirements, improve visibility while stripe coating ODOT needed products with the bolts. high gloss, a low film build of 2-4 mils with higher-build performance, superior weathering capabilities and that were easy to apply.

ODOT decided on a proven coating system in this part of the country for structural steel protection, specifying an inorganic zinc, epoxy and urethane coating system. Sherwin-Williams was chosen to supply coatings for the new span to provide a high-gloss finish and protect the structure from the harsh Cleveland elements.

Painting a Bridge is Like an Obstacle Course One of the challenges was the bridge’s proximity to high-trafficked areas in the Cleveland metropolitan area.

The biggest challenges for a painting contractor include rigging and containment, not only to provide safe surface access to painters, but also to contain overspray, from application practices, falling onto passing motorists.

Other challenges for the applicator include temperature and humidity. Dew point may affect the ability to apply coatings in general and to apply coatings within their stated recoat window. A contractor does not always have a realistic idea of the challenges an applicator may face during a project like this. In addition, ODOT painting

44

June 2015

specifications require work to be completed within certain calendar dates to minimize disruption to the public.

Painters must schedule this work appropriately to complete all work within time and temperature parameters. Painters must also work in conjunction with the prime bridge contractor to avoid interfering with crucial operations.

With so many potential complications, it was important to establish how the coatings would be applied as early on as possible. A combination of spray guns, rollers and brushes are used. The entire area must be encapsulated with tarps. The tarps have to be secured and free of tears to prevent the paint and construction materials from escaping.

Why the Coating System Works Zinc-rich primers have been proven through years of testing in various environments to provide the best corrosion protection for steel substrates in all types of environments, including salt, fresh and atmospheric water. The inorganic zinc prime coat is considered sacrificial once in direct contact with the structural steel – because zinc is weaker on the galvanic scale when exposed to oxygen and moisture, it sacrifices itself and corrodes instead of the steel.

The epoxy intermediate coating is a barrier coating. It prevents exposure to moisture and oxygen by adhering well to the inorganic zinc primer and protects the steel components from early corrosion.

Epoxies break down when exposed to ultraviolet rays. This is where the urethane topcoat comes into play.

The gloss retention properties of a topcoat are crucial to determining its ability to resist the negative effects of UV exposure and protect the intermediate coating from degradation. In this instance, an off-white high-gloss polyurethane topcoat known to demonstrate gloss retention after 9,000 hours of exposure was used (5,000+ hours of UV exposure in QUV accelerated weathering testing is Ohio’s standard).

This doubles the maintenance-to-recoat cycle and provides unprecedented value for the taxpayers. In addition, the topcoat’s good color retention would enhance the bridge’s appearance and make it easier to keep clean throughout the years.

A final component was an organic epoxy, which was used by field painters to touch up shop-primed steel sections and splice plates that may have been damaged in the transportation and steel erection processes. In total, more than 26,000 gallons of coatings were used on the massive bridge project.▪

The Cleveland Innerbelt Bridge project facing north. The original bridge, which opened in 1959, is the main east-west artery into and through the city’s downtown.

All photos courtesy of Ohio Department of Transportation.

STRUCTURE magazine

45

CASE SUMMARY Project Construction of the westbound span of Cleveland’s George V. Voinovich Bridge required protective coatings to prevent corrosion of the structural steel and provide a 30-year service life.

Coating System Sherwin-Williams Macropoxy 646 intermediate and HP DOT Acrylic topcoat Field Touch-up Zinc Clad IV organic epoxy Project Owner Ohio Department of Transportation Design-Build Team: Walsh Construction (Chicago, IL), HNTB Corporation (Columbus, OH), HDR (Omaha, NE) Subcontractors: Atlantic Painting (Oak Lawn, IL), Corrosion Resistance LTD (Stow, OH), APBN Inc. (Campbell, OH) Dee McNeill is regional market director (U.S and Canada), Bridge & Highway, Sherwin-Williams Protective & Marine Coatings.

With more than 35 years of coatings experience, he is responsible for bridge and highway coating specification approval and for facilitating the development and acceptance of new technologies to protect the nation’s bridge inventory.

June 2015

Historic structures

M

ost bridge historians and bridge textbooks state that a bridge with a single tension diagonal in each panel and a compression vertical with parallel chords and an inclined end post is a Pratt Truss. The usual truss profile is shown in Figure 1.

significant structures of the past

Figure 1. Pratt Truss, even number of panels.

The Pratt Truss Whipple, Single Canceled, Trapezoidal Truss

By Frank Griggs, Jr., Dist.

M. ASCE, D. Eng., P.E., P.L.S.

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

Dr. Griggs can be reached at fgriggs@nycap.rr.com.

This, however, is not what Pratt had in mind when he designed his truss in 1843. Thomas Willis (T. W.) Pratt and his father Caleb were well known engineer/architects in New England in the middle of the 19th Century. T. W. attended college in Troy, NY at the Rensselaer Institute, later Rensselaer Polytechnic Institute. He did not graduate, which was not uncommon in those days, as only about a third of those who matriculated graduated. He returned to Massachusetts to work on the Boston and Worcester RR and the Providence & Worcester RR in the mid 1840s under Ellis Chesbrough and James Laurie, later the first president of the Boston Society of Civil Engineers and the American Society of Civil Engineers. There was a need for many bridges to cross the rivers and streams along the routes. At the time of his entry into bridge design, S. H. Long, Elias Towne, and William Howe (STRUCTURE, November 2014) were the primary wood bridge designers for railroads. Long’s and Towne’s bridges were all wood, even though they indicated they could be built with iron. Howe’s, however, replaced the wooden verticals with iron. His diagonals were in compression which, with wedges at both ends, were able to place a small amount of pre-stress in

Figure 3. Pratt Patent Drawing.

46 June 2015

Figure 2. Thomas Willis Pratt.

the structure. With nuts on the threaded ends of his verticals, he was able to camber the truss so that, under loading, the deck would approach a horizontal position.

Pratt no doubt had seen Howe’s Springfield Bridge, patented in 1840, across the Connecticut River and was aware it was adopted by many railroads replacing the Long and Towne Trusses.

The span of the Howe Truss was limited, as the diagonal compression members were susceptible to buckling as their length increased with increase in span. Over time, the wedges came loose requiring frequent adjustment of the tension verticals.

Pratt basically took the Long Truss and replaced the wooden diagonal members with two iron rods with threads and nuts, while keeping wooden verticals in compression, on both ends to make necessary adjustments to obtain the required camber and pre-stress. Since longer spans were possible with the long members in tension, the bridge appeared to correct some of the problems with the Howe Truss.

T.W., along with his father, obtained a patent, #3,523, on April 4, 1844 for a TRUSS FRAME OF BRIDGES (Truss Bridge). There is no evidence that his father had anything to do with the design, and it has been suggested that T. W.

Figure 4. Aldrich Change Bridge, originally built 1858.

the other-parts of the frame, whereby the tie beam or lower stringer is more or less relieved of a portion of its strain, according to the disposition of the weights producing the said strain. The bracing by means of tension bars extending diagonally across each panel of a bridge truss has been long known and used; but the system of bracing and counterbracing, by means of tension bars crossing each other in each panel, is believed to be new, and not only affords the means of regulating the general camber of a bridge, but allows it to be drawn up, or depressed, in any particular segment, at pleasure, and thus furnishes a means of regulation not derivable from the single tension braces in each panel.

He concluded his patent application with, The above described method of constructing a truss, that is to say the combination of two diagonal tension braces and straining blocks, in each panel of the truss frame of a bridge by means of which the camber may be regulated so as to increase or to diminish it, either in whole or in sectional part of the bridge, the whole being constructed and operating, substantially as herein before set forth.

Not many bridges in wood and iron were built to this Patent. When compared to the

Howe truss, it was necessary to adjust two rods instead of one, and the fact that the rod ends were inclined made it more difficult to tighten the nuts. In many cases, the tightening also caused the washers to press into the top and bottom chords damaging the wood.

George Vose wrote in his 1878 book, Manual for Railroad Engineers and Engineering Students, “the prominent defects of the old fashioned Pratt Truss were the crushing of the top chord between the washer and nut.” As a result, most railroads of the time adopted the Howe Truss.

In the 1850s and 1860s, iron started to replace wood as the material of choice by the railroads. (STRUCTURE, January 2015, February 2015 and April 2015). The first man to design and build a truss with a single tension diagonal in each panel was Squire Whipple. In his 1846/47 book on bridges, he analyzed, using the method of joints, all the loads in each member of the truss. He built several change bridges over the Erie Canal in the mid to late 1850s using cast iron for his compression members and wrought iron for his diagonals and lower chord. A change bridge was used when it was necessary to change the tow path from one side of the canal

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Figure 5. Wrought Iron Pratt Truss with pinned connections and Phoenix Compression Members.

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included his father’s name as a tribute to his work as an engineer. It will be noticed that Caleb’s name is the first name on the patent.

He wrote of the top drawing, “Should it at any time be desirable to increase the strength of the truss beam F, of suitable length, may be arranged centrally and directly under and in contact with the upper stringer, as seen in Figures 1, 5, and from each extremity of this beam an inclined beam, G may extend to the lower stringer into or upon which it maybe stepped in any convenient manner, the said central and side timbers forming what may be termed an arch beam.” This form is similar to the Wernwag/Latrobe Truss built at Harper’s Ferry for the B&O Railroad (STRUCTURE, August 2014). As to the lower profile he simply wrote, “Figure 6 exhibits a modification of the truss, wherein the upper stringer is crowned or arched.” This is similar to the later McCallum Truss patented in 1857. The additional depth at mid-span more closely followed the moment along the truss, resulting in lower section sizes.

The main feature of the truss, however, was the placement of crossing iron rod diagonals in each panel. He wrote of this feature, The several iron braces are subjected to a tension strain and being arranged as hereinbefore described, they draw or confine the posts and stringers together. More or less camber may be easily given to the truss by means of the nuts upon the screws of the braces, which on being turned in the requisite direction, lengthen or shorten the distances between the heads and nuts of the braces to such degrees as may be requisite to produce the necessary camber. In the truss represented in Figure 1, the braces of each panel being coupled by means of the straining block, with the counter braces of the succeeding panel, and the counter braces also of the same, being in a similar manner coupled with the braces of the succeeding panel, a connected strain is thus kept on the tension braces, independent of

Figure 6. Vicksburg, Fairgrounds Avenue Bridge.

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to the other without unhitching the mules.

The writer was part of a team that restored an 1858 change bridge that was originally built in Rochester and placed it in a park near Palmyra, New York.

The top chord and inclined end post were cast iron tubes. The cast iron verticals were cast to provide support for cross beams at various heights so that the deck surface would parallel the curved top chord at about the height of mules, so the tow rope would slide easily along the top chord without snagging.

This style truss became a standard design for spans of up to 200 feet. Later in the 1880s, wrought iron replaced Whipple’s cast iron compression members. Frequently the top chord, verticals and end diagonals were built up Phoenix sections (by the Phoenix Bridge Company and others) or Keystone sections (by the Keystone Bridge Company), and the diagonals were eyebars and lower chords of wrought iron links. These bridges were prefabricated in shops and easily erected by local craftsmen. They became what was called by some “catalog bridges’ in that a local government would simply state the span and number

of lanes required, and a bridge company would supply and frequently erect the bridge.

The writer was also part of a team proposing the removal, rehabilitation and relocation of the two-span Fairgrounds Avenue Bridge. It has Keystone, polygonal, compression members connected by cast iron junction blocks and links for the main diagonals, bars for the counter ties and links for the bottom chord.

The two spans were originally built as a total of eight approach spans to a bridge across the Mississippi River at Dubuque, Iowa. It was designed by the Keystone Bridge Company under Jacob Hays Linville.

The next stage in the evolution of the truss type was the design of the compression members of built up steel shapes, such as angles and channels. The Waterford Bridge across the Hudson River was built in 1909 by Alfred P. Boller and Henry Hodge to replace Theodore Burr’s wooden bridge that was built in 1804 and, after a life of 105 years, was destroyed in a fire.

The top chord was built up with two channels, a solid plate on top and lattice bars connecting the lower flanges of the channels. The verticals are made of two latticed

channels, and the diagonals and lower chords are steel links.

This style was replaced with an entirely riveted steel structure of rolled shapes in the late 19th century. This made the truss very rigid and durable, and it was adopted by many leading engineers including J. A. L. Waddell who used it up to spans of 200 feet both with parallel and arched chords. In addition, he made many of his lift spans to the design.

An example of its rigidity was when several trusses crossing the Kansas (Kaw) River were pushed off their piers in the Kansas City flood of 1903. They were simply pulled and jacked into place with little or no damage.

According to Turneaure and Kinne’s book dated 1916, an “even number of panels were recommended for a riveted structure, while an odd number of panels was best for a pin-connected structure. The even number of panels permits symmetrical joint details and avoids the use of a double set of rigid diagonals in a centre panel. In pin-connected spans, an odd number of panels simplifies the lower chordbar packing near the centre of the span.”

In summary, Pratt never designed a bridge with inclined end posts, with a single tension diagonal in each panel, nor calculated the loads in each of his members, and never built a bridge in iron or steel, and yet the bridge style is called a Pratt Truss. Squire Whipple, however, designed a bridge with inclined end posts, with a single tension member in each panel and calculated the load in each member.

In addition, he built several bridges in this style in cast and wrought iron. The author wrote an article entitled, It’s a Pratt! It’s a Long! It’s a Howe! No It’s a Whipple for Civil Engineering Practice, Journal of the Boston Society of Civil Engineers in 1995 trying to correct this and other misnamed truss styles.

Whenever the author gets the chance, he calls a Pratt Truss by its proper name – a Whipple, single cancelled, trapezoidal truss.▪

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Figure 7. Waterford, NY, Hudson River Bridge 1909 with built up posts and top chord, pinned links for diagonals.

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Structural

SuStainability sustainability and preservation as they pertain to structural engineering

Carbon Reduction The New Structural Design Parameter

By James A. D’Aloisio, P.E., SECB, LEED AP BD+C

James A. D’Aloisio, P.E., SECB, LEED AP BD+C, is a Principal with Klepper, Hahn & Hyatt in Syracuse, NY. He is Chair of the SEI Sustainability Committee, and can be reached at jad@khhpc.com.

E

conomically ensuring the strength and stability of structures while adequately addressing serviceability concerns has always been the main goal of structural engineers. As members of design teams, engineers typically leave the nonstructural aspects of the project’s design requirements to others on the team. It’s now time to acknowledge our role and responsibility in another aspect of design: reduction of emissions of carbon dioxide and other global warming potential (GWP) gases from the construction and operation of our projects.

Of course, it’s not just structural engineers who need to take this into account – it’s everyone.

Human activities generate emissions of over 30 billion tons a year of CO2. This has resulted in nearly a 40 percent increase in the amount of CO2 in the earth’s atmosphere since the 18th century. Other greenhouse gases have increased as well. Scientific evidence shows that this is causing substantial problems with our climate, such as increased average land-ocean temperatures, and increased number and severity of storms and periods of drought. Engineers, who have an obligation to use Earth’s resources responsibly, have a particularly important role to play in reducing GWP gas emissions.

Increasingly, attention is being paid to the resilience of structures – their ability to adequately perform when exposed to greater service loads as storms’ intensities increase and shoreline development is subject to higher water levels and wave action. This is important work, and consistent with our fundamental engineering responsibility to protect the public. Yet, taking these changing conditions into account in our designs – also known as adaptation – is only part of our appropriate response. As we acknowledge that these changes are beginning to negatively affect our safety, we also need to acknowledge the activities we have engaged in that have led us to this point. Such actions will continue to create larger and long-term problems in the future unless we make changes to reduce those effects, which is called mitigation.

In 2009, the ASCE Board of Directors passed Policy Statement 488, Greenhouse Gases. This Statement acknowledged the problem of anthropogenic greenhouse gas emissions, and identified several actions that engineers can take to reduce these emissions. Identified strategies include use of existing technologies, as well as researching and implementing new technologies and materials that reduce emissions. How many of us have responded to this call for action to mitigate climate change effects?

Concrete, masonry, steel, wood, and other materials that structural engineers design and specify

50 June 2015

have significant carbon dioxide-equivalent (CO2-e) emissions, or footprints, released during their manufacture and construction. The emissions can fairly easily be quantified on a project. Rather than playing the materials off against each other (e.g. the classic “concrete versus steel” comparison), engineers can use strategies to reduce the emissions of the selected structural system: • Concrete can be produced with less Portland cement, which generates nearly a pound of CO2-e emissions for each pound of Portland cement in the mix, by using the pound-for-pound substitution of Supplementary Cementitious Materials (SCM). The required strength, cement content, and volume of material can also be refined and not over specified for the design task at hand. Where appropriate, one effective strategy is the use of FrostProtected Shallow Foundations (FPSF).

• Concrete Masonry Units (CMU’s) can frequently be produced with up to onethird less Portland cement at little or no additional cost, simply by requiring SCM to be used. Grout, which is frequently a cement-rich material, can be specified to have SCM as well. The cement content can usually be significantly reduced by avoiding the prescription-based specification in favor of prism tests and the strength method.

• Structural steel, with close to 1 pound of CO2-e per pound of material emitted during manufacturing, fabrication, and erection, warrants extra effort in design optimization to reduce a project’s tonnage.

Specifying and designing products produced in Electric Arc Furnaces, which use more recycled content material than

Basic Oxygen Furnaces, can result in carbon reduction. Other potential lifecycle carbon-reducing strategies include Design-for-Deconstruction (DFD); that is, designing with the intention of deconstructing a structure at the end of its service life so the members can be reused, rather than recycled, the use of salvaged steel when circumstances allow it, and the use of innovative, material-efficient structural forms such as diagrid systems.

• The carbon footprint of structural wood products is usually less than concrete, steel, or masonry systems.

Its use obliges the engineer to have an awareness of wood’s possibilities and limitations. Also, wood’s carbon footprint is dependent on the source of the material, including travel distance and management of the forest and the fabrication process. Jobsite waste can be minimized by careful planning and design choices.

Of course, carbon emissions of buildings do not stop at the completion of construction.

Emissions associated with building operation, including heating and cooling over a building’s service life, frequently exceeds

the construction emissions. Here too, structural engineers can, and should, play a bigger role than they previously imagined was necessary. Structural thermal bridging, especially of continuous elements such as shelf angles and roof edge conditions, can be responsible for a significant portion of a building’s envelope energy loss. Foundation insulation is not always addressed properly by the design team, particularly at slab edges and transitions in construction details.

Effective, continuous insulation of buildings in heating and cooling climates is not always accomplished unless the structural engineer carefully coordinates the details with the project architect.

Many of these emission reducing measures can be advanced by the structural engineer with or without the explicit directive or encouragement of the rest of the project team, provided, of course, that there is no negative impact on the performance, construction schedule, or cost of the project.

Other strategies, which may incur some costs, might need to be reviewed by the client and the rest of the project team before they are implemented. This is the really exciting and important challenge for structural engineers today. No matter what your experience level, ADVERTISEMENT–For Advertiser Information, visit www.STRUCTUREmag.org

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June 2015

taking on this challenge has the potential to lead one down an engaging path of shared learning and growth.

As engineers who are major specifiers and designers of carbon-intensive structural materials, we should educate ourselves and be leaders in advancing the mitigative actions necessary to reduce GWP gas emissions.

It may be that the level of change needed will not happen until carbon is given some economic value. Should we, as structural engineers, assume a role as advocates in the political realm?

We need to fill the role that engineers have historically played: Solving society’s problems and meeting its needs, in order to advance the human enterprise. It may be that history is calling us to be the engineers that we can be, in the largest sense of the word.▪ This article was peer reviewed by the Control Group of the SEI Sustainability Committee.

Statistics included in this article were provided by the U.S. Environmental Protection Agency www.epa.gov/climatechange/ science/causes.html

CASE BuSinESS PrACtiCES

business issues

CASE on Contracts Survey of SE Firms’ Contracts Practices

By Steve Schaefer, P.E.

I

n preparation for a presentation on Contracts for Structural Engineers at the SEI Structures Congress last year, the presenters surveyed members of CASE to determine how they dealt with several contract issues that pose business risks to their firms. Topics included: dealing with onerous contracts, getting paid by architects even when a contract is in place, use of limitation of liability clauses, use of standardized CASE contracts, and who within a firm writes and negotiates contracts. The following are those results.

If you try to explain the contract problems with the client in order to negotiate a more reasonable contract, how often is this effective?

A big problem that structural engineering firms face is clients/owners who supply their own contracts. These contracts are typically written by the clients’ lawyers and worded to shift as much potential liability as possible for any problems away from the owner and onto the project designers and contractors, even when the owner may be the negligent party or should bear some or all of the responsibility for certain problems. Often these onerous contracts require the designers to indemnify and defend (provide the owner’s legal defense) against claims against the owner by third parties, even when the designer has not been negligent. Although many engineers believe this situation would never occur in practice, a hospital in the Midwest is currently trying to get its designers for a new building, who signed one of these onerous contracts, to defend the hospital against claims by patients who developed Legionnaires’ disease while at the hospital. These contracts also frequently require the designers to perform at the “highest quality” or guarantee a “perfect design” or “successful” project. By contrast, the professional liability insurance policies for architects and engineers only cover designers for their negligence relative to the normal standard of care. Thus, there is no insurance coverage to pay for claims based on many of these onerous contract clauses; one of these claims can easily force a design firm into bankruptcy and out of business.

The CASE survey asked members how often they were successful in negotiating a

% of firms

% of firms

3% 10% 38% Negotiation is beneficial Hardly ever Occasionally Frequently

52%

Figure 1.

Dealing with Onerous Contracts

Are you willing to accept the risk and sign an onerous contract?

18%

15%

32% 32%

Figure 2.

more reasonable contract after explaining the problem terms to the client. See Figure 1 for the results. Figure 2 shows how often firms are willing to sign an onerous contract when they can’t get the client to renegotiate to fairer terms.

Why do firms sign these contracts? Some of the reasons given were: • It’s a small project with small risks.

• They need the work.

• The contact at the client’s organization says that the offending clause is required by their legal department, but not to worry, they have never sued an A/E provider.

As another example, the author’s SE firm designed some temporary shoring on a project for a large contractor on a rush basis. The contractor did not return a signed copy of the contract provided by the SE’s firm but, after the design was completed, the contractor presented an onerous contract saying it needed to be signed before the firm could be paid. The author’s firm waited until after the shoring installation was successfully completed and dismantled before agreeing to sign the contract since there was no longer any risk of a claim being made.

The responding CASE firms try to deal with these onerous contracts in the following ways: • Always provide an industry-standard contract first.

• Explain to the client that the engineer’s professional liability policy doesn’t cover claims made under these one-sided terms.

STRUCTURE magazine

How often we accept the risk and sign the contract 0% 1% – 10% 15% – 30% 50% 80% – 95%

52

June 2015

Percent of onerous contracts where you turn down the project after explaining the problem to the clients % of firms 7% 10%

Turndown rate 0% 1% – 10% 25% > 70%

32%

62%

Figure 3.

• Do as much work as possible with repeat clients based on initial good client selection processes.

• Implement a more thorough quality control process for the project.

• Put their best project managers on the project.

• Increase the fee to cover the additional risk (which can be somewhat successful).

• Respectfully decline to submit a proposal (if the engineer knows about the onerous terms in advance).

• Put their firm in a stronger negotiating position by working as a consultant to the owner rather than as a designer contracted to the project architect.

Table A.

Table B. Don’t do

Not effective

Sometimes effective

Relatively effective

Stop work if invoices not paid after grace period

42%

8%

42%

8%

Require architect to notify us if not paid within 30 days by owner

69%

27%

0%

4%

Refuse to process shop drawings

44%

11%

6%

6%

Call architect about unpaid invoiced after certain amount of days

4%

15%

48%

38%

Payments

• Keep a record of contract mark-ups and negotiation conversations to establish their inequitable bargaining position.

Payments from Architects Getting paid in a timely manner by architect clients is a common problem for structural engineering firms. Table A shows various methods and their effectiveness in producing more prompt payment. Some of these actions can be specified in the contract with the architect.

Other methods reported by the survey respondents were: • Refuse to sign off the completed project for the building department.

• File a lien if not paid in 90 days (this is difficult or unavailable in some states) • Contact the architect’s client to see if the architect has been paid.

• Involve a collection agency.

• Don’t work for architects who don’t pay in a timely manner.

• Before reviewing the shop drawings or 90 days after completing the design work, whichever comes first, require the architect to sign a promissory note.

Limitation of Liability Clauses

0% of the time

30%

1% – 10% of the time

26%

15% – 25% of the time

11%

50% – 60% of the time

19%

75% – 90% of the time

11%

99% of the time

3%

Table C.

CASE has produced 16 standard contracts for various conditions encountered by structural engineering firms. Table F (page 54) shows the percentage of firms that use the more popular CASE contracts, either directly or by adopting various terms from the CASE contracts in their own contracts.

The most widely used is Contract #1, An Agreement for the Provision of Limited Professional Services, which is useful for smaller projects with a limited scope. It is a very simple and easy to use contract for most of the miscellaneous-type projects performed at an SE firm, such as adding a loading dock or adding equipment on the roof of an existing building.

Contract #2 is used when the SE contracts directly with the owner but is not the prime consultant, while Contract #13 is to be used when the project primarily involves structural work and the SE is the prime or the only consultant.

The author feels that Contract #14A, Supplemental Form A – Additional Services Order (ASO), should be used more often and should be readily available for every project manager to use. Most medium to large projects run into situations where some unanticipated structural services are required, and it is important for the SE to get paid for these. If the SE waits until the end of the project to bring these to the client’s attention, there is a high risk of not being paid for the extra work, since there is no leverage.

Having a client sign the ASO before the SE does the work makes it much easier to get paid.

If the SE doesn’t want to “nickel and dime” the client, he/she should send an ASO describing

How often is the Limitations of Liability a fixed dollar amount?

% of firms

0% of the time

12%

1% – 20% of the time

24%

25% – 45% of the time

6%

50% – 60% of the time

12%

75% – 80% of the time

18%

100% of the time

29%

Table D. When it is fixed, what is the mount of the Limitations of Liability?

% of firms

Equal to the design fee

6%

Greater of $50,000 or the design fee

19%

$50,000

19%

$100,000

13%

$250,000

6%

Amount of insurance

13%

Varies

25%

the additional scope of work on smaller items and indicate “No Charge”. Then after a few minor items are designed for free, if more or larger issues arise, the SE can justify finally charging for some of these. continued on next page

Attention Bentley Users Have you received your automatic quarterly invoice from Bentley?

Would you like to reduce or eliminate these invoices?

Table E. When based on multiple of fee, what is the mount of the Limitations of Liability?

% of firms

1 x fee

63%

10 x fee

25%

25 x fee

12%

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% of firms

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June 2015

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Professional liability insurers encourage structural engineers to include a limitation of liability (LOL) clause in their contracts.

Table B shows how frequently LOL clauses were used in the firms’ contracts with architects. Relative to all clients (not just architects), Table C shows how often the LOL is a fixed dollar amount and Table D shows the amount of the fixed limit.

If the client doesn’t agree to one of the lower LOL amounts, the SE can usually get them to agree to a limit on the amount of professional liability insurance proceeds available to them. Although this doesn’t do much to reduce the amount that the insurer would pay in a claim, it does keep a large claim from putting the SE’s firm out of business. When firms base the LOL on a multiple of their fee, Table E shows the multiple that firms use.

Case Contracts Most Often Used

How often do you see a Limitation of Liability clause in architectural contracts?

Table F.

Table G.

CASE Contracts

% of Firms

#1 – Limited Professional Services

77%

Who writes and negotiates contracts with the client?

% of firms

#2 – Client & SER for Professional Services

68%

Firm Principals

96%

#11 – SER & Contractor, transfer CAD files

59%

Designated Contract Officer

11%

#3 – SER & Sub-consultant

50%

Select Project Managers

15%

#6 – CASE Commentary on AIA C401

46%

All Project Managers

7%

#4 – Structural Peer Review Services

46%

#13 – Prime Contract, Owner & SE

41%

#16 – Client & SE for Structural Condition Assignment

41%

#4 – Owner & SE for Special Inspections

36%

#15 – CASE Commentary on AIA A201 “General Conditions of Contract for Construction”

32%

#14A – Supplimental Form A, ASO

32%

The purpose and need for most of the listed contracts is fairly obvious; however, the importance of Contract #11 for the Transfer of CAD or BIM files should be emphasized. On most projects, the sub-contractors or fabricators want to use the SE’s CAD or BIM files to prepare their shop drawings. The SE firm exposes itself to additional risk if the terms and conditions under which the files are provided are not defined. Contract #11 makes it clear to the users of the files that they are responsible for the files once they are turned over to them.

The contract also makes provisions for the SE to charge a small fee for providing the files.

Although some firms have charged substantial amounts for this, CASE recommends that the charge be in line with the time necessary for a technician to prepare the files for transfer and to make the transfer. In this way, the files can still be considered “Instruments of Service” rather than a “Product” which has higher liability associated with it.

Who Writes the Contracts

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above regarding Additional Service Orders, the project manager must fully understand the contract so that they know when services are outside the scope for the project and an ASO should be issued. The author’s firm believes that the project manager should be the one doing most of the coordination and engineering on a project, and over 70 percent of the firm’s engineers have project manager positions or higher. The project manager will take more ownership in the success of the project if they are the one negotiating with the client, determining the scope and fee, and preparing the contract. Thus all project managers prepare at least some of their own contracts. The size and complexity, along with the project manager’s experience, will determine the level of responsibility that a project manager has in preparing the contract. The project manager’s team leader reviews all contracts and a fee committee reviews all larger or unusual projects even for the most experienced project managers and principals.

Make Up of Case Survey Respondents Twenty seven firms responded to the CASE survey: one third of the firms had 20 or fewer employees, one third had 25 to 50 employees and one third had over 100 employees. Seventy percent of the firms were primarily structural engineers while the remainder were multi-discipline. The number of structural engineers at the participating firms ranged from one to over four hundred.

Summary By being aware of other SE firms’ contract practices, SEs can compare their own practices relative to their peers. The results of the

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June 2015

Table H. How often do you specify the Limitations of Liability to be equal to the amount available from Professional Liability insurance?

% of firms

0% of the projects

39%

15% – 25% of the projects

22%

40% – 50% of the projects

22%

90% – 100% of the projects

17%

survey also indicate the need for NCSEA, ASCE/SEI, ACEC and CASE to work together to educate clients that they don’t have the insurance protection they thought, because their onerous contract clauses may not be covered by the designers professional liability insurance policies. Also, if SEs and other designers through their various professional associations agreed to turn down contracts with these onerous clauses, owners may realize that they can’t get good design firms to do their work. One last thing to ask the client who presents a contract with these onerous terms, “If our competitor is so ill informed about business and insurance issues that they are willing to sign this contract, what makes you think they are any more knowledgeable about good design practices? Do you really want them designing your facility?”

The contracts, guidelines and other publications developed by CASE are available for purchase. Go to www.ACEC.org, and on the right side of the page click on “Coalitions”, then scroll down and click on the CASE hyperlink labeled “Council of American Structural Engineers.” Then select “News & Resources” then “Publications” and finally “Contract Documents”. All publications are free to CASE members.▪ Steve Schaefer, P.E., is the founder and chairman of Schaefer, a 60-person structural engineering firm, with offices in Cincinnati and Columbus, Ohio, and is a member of CASE’s Programs Committee. Steve may be reached at steve.schaefer@schaefer-inc.com.

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LegaL PersPectives

discussion of legal issues of interest to structural engineers

An Ounce of Prevention One Lawyer’s View on Professional Writing for Engineers

By Matthew R. Rechtien, P.E., Esq.

Y

ou probably did not go to engineering school to learn to write… and you probably did not take your job for its writing opportunities. Admit it; you probably look forward to drafting written communications about as much as you do reviewing steel shop drawings. However, if you have read any of the author’s earlier articles, you know the importance of the latter task. The former is just as critical.

However much one may discount the value of good writing to structural engineering, it is essential to the business and legal aspects of the job. Of course, good writing is critical to prudent contracting. It is also critical to the daily management of the business of structural engineering.

There are two major components of construction disputes: the facts and the law. As a legal matter, construction projects are large, complex commercial transactions. Moreover, in any given commercial transaction, emails and other correspondence are the heart of the evidence; along with drawings, RFIs, submittals and the like, they tell the story. They establish and corroborate the facts to which the law is applied.

That makes attorneys the end-users of your writing. Do witnesses matter? Of course.

However, the documents are key. It is from that perspective that this article is formulated, which lays out recommendations for your written communications. As you read, keep in mind that for every general recommendation, there are exceptions. You must use your professional judgment, in light of the whole context.

Recommendation No. 1 No Secrets Write assuming that the person you least want to see your writing one day will. Modern lawsuits go through discovery, a period in which parties may serve on each other, and on third parties, requests that they produce documents. The law protects litigants’ rights to access evidence, including documents.

Under the Federal Rules of Civil Procedure, for example, “[a] party may serve on any other party a request… to produce… any designated documents or electronically stored

information – including writings” so long as they are not privileged and are “relevant to any party’s claim or defense.” Responding to these requests, and producing responsive documents, is not optional.

With modern technology – servers, backup tapes, and internet service providers – your writing is likely to exist, in some form (more likely, multiple forms: hard copy, pdf, email, etc.) in some repository, long after it was created, and long after you would have hoped it would disappear. If you end up in a legal dispute, you should assume that communications will come out.

Conduct yourself accordingly. Keep in mind that what you write today is tomorrow’s evidence. Write as though your letter will eventually be on display to a jury. Write as though you will be in the witness box, answering questions about your writing from a hostile lawyer. If you only do that, you are likely to avoid many of the problems this article is meant to avoid.

Recommendation No. 2 The Toothpaste Doesn’t Go Back Into the Tube The second recommendation closely relates to the first. Because you will assume that everything you write, from a formal report to draft email, will endure long into the future, you will and should draft your professional writings with commensurate sobriety. There are no take-backs. If you write it, you will not be able to un-ring the bell later. This is especially true once correspondence leaves your office. At that point, you have no control, no document retention policy that will dictate the document’s longevity.

What does all of this mean? That you can write something does not mean you should.

Consider your choice before you proceed.

Consider whether you would be better off not writing it at all.

Recommendation No. 3 “Just the Facts, Ma’am” Professional writing should be prosaic, not poetic. If a lawyer is reading your writing,

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it is because a legal dispute is brewing. In that situation, the lawyer will know little of the nuanced context in which your communication was written. It may be years later. Without context, emotion, hyperbole, humor, irony and sarcasm may be impossible to interpret. While these rhetorical tools certainly have their value in screenplays, poems, speeches and conversations, their use in professional writing is generally very risky. Your professional writing is not art, and it is not supposed to entertain. Emotion or hyperbole that make sense at the time, in light of the complete picture, will come across differently when your communication is, as it likely will be, viewed in isolation.

The same can be said for any unnecessary characterization of the facts. Try to avoid words that end in “ly.” Characterizations are usually debatable and therefore are not facts.

Admittedly most of us are offenders here.

Sometimes a person just cannot avoid the bait, and we respond to emotion with emotion, to insult with sarcasm. Resist the urge to respond in kind, or to be too cute; resist the urge to write how you might casually speak.

Take care with respect to how you state the facts; facts you state in writing are likely to become admissions in later litigation. If you are involved in a case, what you stated as a fact in 2007 is more believable than your contrary testimony today.

Recommendation No. 4 Be Nice, or at Least Truthful “Sticks and stones may break my bones but words will never hurt me.” Baloney. Little is as powerful as an idea. Words express ideas. As that great jurist, Oliver Wendell Holmes Jr., said: words are “the skin of a living thought…”

As a legal matter, words matter. Our founders did not ratify the First Amendment for nothing. Words are not just statements, but actions. They carry legal consequences. Black’s Law Dictionary defines defamation as “[a] false written or oral statement that damages another’s reputation.” It defines the tort of tortious interference as “[a] third party’s intentional inducement of a contracting party to break a contract…” And, finally, it defines

extortion as “[t]he act… of… compelling some action by illegal means, as by force or coercion.” Each of these defined terms can lead to civil or criminal liability. Each can be accomplished by little more than an injudiciously drafted letter. It may be hard for you to imagine one of your writings falling within one of these definitions. That is reasonable.

However, the bottom line is that words are acts to which the law attaches consequences.

Write carefully. To the extent you can, avoid reducing to writing disparaging comments, threats or intermeddling. If you must wade anywhere near those waters, be relentlessly and scrupulously truthful, avoid threatening things you have no right to do, and, as a segue, follow recommendation No. 5 below.

Recommendation No. 5 “Brevity is the Soul of Wit” – Shakespeare, Hamlet

A Couple of Cautionary Examples With these recommendations in mind, a couple of cautionary examples are in order.

Both are loosely based on actual correspondence (with the names changed to protect the guilty).

Consider example 1, a vendor letter: To whom it may concern, We would like to introduce Acme as your new local source of anchors. In the past we have sold through John Doe. His recent defrauding of us, however, caused us to decide to serve your area directly. We would also ask that if you owe John Doe money, you contact us before paying. He owes us $15,000.00.

We look forward to serving you.

Acme This is a high-risk letter a client wanted to circulate. It is obviously an extreme, but illustrative, example. Not only does the author open the door to defamation (first underlined passage) and tortious interference liability (second), but by reducing these words to writing and circulating them to a broad audience, he or she is guaranteeing zero control over the longevity and endurance of the evidence. About the only thing the letter has going for it is that it is brief, and arguably to the point.

Consider as well example 2, a written response to a project-related communication about compensation for “extras”: Mike: Your letter is so full of crap, I hardly know where to start.

Try this – Issue No. 7: We have not received written direction for this extra. An apparent difficulty of yours!

Issue No. 8: More crap! You have hardly completed anything because of your terrible mismanagement! If you pursue your threats, I will have my attorney shut the job down and will show the owner your lousy work. You are out of line in your letter. I can prove it!! Retract it, pay me for all the extras, and we will continue.

Very Sincerely, Bill

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Again, an extreme example, but instructive still. It contains potentially extortionate threats, defamatory statements, unhelpful emotion, and sarcasm. It is unnecessarily personal. It generally looks horrible, reflecting very poorly on its author. If this were your letter, your attorney would be on damage control in dealing with it in a lawsuit. This is exhibit A of what not to do.

Conclusion These recommendations and examples are not intended to over encumber you in your daily work. You need not suffer from paralysis by analysis. Rather, they are intended to give you some broad themes to keep in mind as you write, and to remind you just how important this otherwise mundane task may be. The professionalism that goes with being a professional engineer should never stop at the drawings’ edge.▪ Matthew R. Rechtien, P.E., Esq., (MRechtien@BodmanLaw.com), is an attorney in Bodman PLC’s Ann Arbor, Michigan office, where he specializes in construction law, commercial litigation, and insurance law. Prior to becoming a lawyer, he practiced structural engineering in Texas for five years.

Disclaimer: The information and statements contained in this article are for information purposes only and are not legal or other professional advice. Readers should not act or refrain from acting based on this article without seeking appropriate legal or other professional advice as to their particular circumstances. This article contains general information and may not reflect current legal developments, verdicts or settlements; it does not create an attorney-client relationship.

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

“I didn’t have time to write a shorter letter.”

Whether coined by Mark Twain or Blaise Pascal, this truism expresses the final recommendation. If brevity is not the ideal in love letters, it is, as the saying suggests, in written engineering communications. However, the saying also affirms that brevity requires time and effort to achieve. You probably do not have the time to endlessly draft, review and edit each communication just to ensure its brevity. You will have to strike a balance based on its importance, but the goal should generally be succinctness. Each communication has an objective. Be aware of that objective and say no more than needed to accomplish it. Edit aggressively and often; remove any unnecessary language.

One tip is to avoid the passive voice.

Consider, for example, the question: “subsequent to your termination from the project, what did you do with respect to finding other work?” “What did you do to find work after the owner terminated you” works much better: shorter, clearer, more effective.

The reasons for this recommendation are self-evident. Brevity enhances clarity by removing distractions; and if it is worth writing something, it is worth doing it clearly. Think of it as form following function. The contents of the letter should be singularly driven by what you are trying to accomplish. With brevity as a goal, and a focus on the purpose of the communication, you will also naturally reduce the risk of violating the other recommendations. And when, should things go awry, that letter is in your lawyer’s hands, he or she will have a much better prospect of

making use of it. Finally, brevity is something your readers will appreciate, which is reason enough for the rule.

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Enhanced Seismic Design of the New San Bernardino Justice Center

By Mark P. Sarkisian, P.E., S.E., LEED AP BD+C, Peter Lee, P.E., S.E., SECB, LEED AP, and Lindsay Hu, P.E., LEED AP BD+C Skidmore, Owings & Merrill LLP was an Award Winner for the San Bernardino Justice Center project in the 2014 NCSEA Annual Excellence in Structural Engineering awards program (Category – New Buildings over $100M).

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s one of the tallest seismically base isolated buildings in the United States, the Justice Center creates a visible landmark for the city while engaging the public with vibrant open space. The new 400,000 square-foot building improves the efficiency of the courts by consolidating functions that had previously been spread across 12 different buildings throughout the county. Located in one of the most active seismic regions in the U.S., the Justice Center replaces more vulnerable existing facilities.

It is designed to meet the Judicial Council of California (JCC) standards to achieve enhanced seismic performance objectives to limit damage and loss of operations under expected moderate to major earthquake events.

The complex consists of two building elements: an 11-story courtroom tower, and a linear, three-story podium. The building’s main entrance is a three-story public lobby.

The courthouse tower and podium sit on a one story below-grade level which integrates site sloping grades with building access, courthouse functions and support facilities.

Originally targeting LEED® Silver certification by the U.S. Green Building Council, the courthouse achieved LEED Gold certification at no added cost.

The Justice Center is located in the central business district of the City of San Bernardino in close proximity to known active earthquake faults, including the San Jacinto (M=7.4, 3.9 km), San Andreas (M=7.8, 9.1 km) and the Cucamonga (16.1 km). Site-specific seismic hazards and ground motions, including near fault normal and parallel components, were developed based on Next Generation Attenuation (NGA) relationships – two times greater than ASCE 7-05 code based requirements. The SBJC utilizes seismic base isolation bearings and viscous damping devices as energy dissipation systems to manage the large ground motions and meet the client’s enhanced seismic performance objectives. Seismic assessment and life-cycle analysis (LCA) based on a 25-year return period was conducted during design development. The

studies showed an 18.5% return on investment for the seismically isolated superstructure which included estimated mean annual losses from damage to structural, non-structural (drift and accelCourtesy of Bruce Damonte. eration sensitive) and building contents, as well as, loss of use and business foundation slab system. The isolation plane interruption impacts. was carefully selected at below the lowest occuSuperstructure Gravity Framing. The grav- pied level and at building perimeter conditions ity steel-framed structure consists typically of a to minimize the number of building utilities 3¼-inch lightweight concrete fill over a 3-inch and service elements required to be detailed to 20-gauge metal deck slab. Composite steel accommodate movements across the seismic floor framing at mechanical, roof penthouse, isolation plane. Locating the isolation plane Level 1 and below grade levels consists of above the mat foundation required approxi4½-inch normal weight concrete fill over a mately 55,000 square feet of additional steel 3-inch 18-gauge metal deck slabs. The typical framing at the lowest building level. levels with an open, column-free floor plan Courthouse Security. Additionally, the and story height of 16 feet accommodates the design of the building superstructure incorcourtrooms with clear ceiling heights of 12 feet. porates physical security measures to further Superstructure Lateral Frame. The lateral protect the facility and its inhabitants, consisforce resisting system features a cost-effective tent with JCC (2006) requirements to provide steel-framed superstructure with two-way spe- security and blast resistant mitigation stratecial moment-resisting frames on essentially all gies. Redundant perimeter two-way moment frame lines in each direction, utilizing both frames at the grade level are designed to steel wide flange cruciform and built-up box reduce the potential for progressive collapse. columns with 184 distributed supplementary viscous damping devices (VDD) with extender Conclusions brace elements supported on an energy dissipating seismic isolation system above the SBJC is currently the largest project conlowest mat foundation level. The VDD brace structed for the JCC and the first to embrace elements have a 440-kip design force with a life-cycle analysis considering the long-term +/- 5-inch stroke capacity. Pre-qualified steel structural performance and return on investmoment frame connections include reduced- ment in a region of high seismicity. The design beam section “RBS” ductile detailing. of the seismic isolation system and viscous Seismic Isolation System. The seismic damping devices provide an enhanced seismic isolation bearing system, as manufactured performance protecting the structure, nonby Earthquake Protection Systems, Vallejo, structural elements, and building contents CA, consists of 69 Triple Concave-Friction against future damage, as well as loss of use Pendulum (TC-FP) bearings located above under the severe demands of expected MCE the base mat foundation. The TC-FP isola- ground motions.▪ tion bearing system will accommodate up to 42 inches of lateral movement at the seismic Mark P. Sarkisian, P.E., S.E., LEED AP isolation plane and perimeter moat walls. The BD+C, Partner; Peter Lee, P.E., S.E., SECB, TC-FP bearings transfer gravity and lateral LEED AP, Associate Director; Lindsay Hu, forces to the supporting foundation subgrade P.E., LEED AP BD+C, Associate. via reinforced concrete pedestals and mat

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Nominations open for NCSEA Board of Directors

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NCSEA News

News form the National Council of Structural Engineers Associations

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NCSEA is seeking nominations for the NCSEA Board of Directors. The upcoming elections, which occur annually, are for Vice President (elected for a one-year term as Vice President and a succeeding one-year term as President), Secretary (twoyear term), and two out of the four Directors (two-year terms).

Candidates for Officer positions are drawn, for the most part, from current or past NCSEA Board members.

Nominations are requested for motivated, practicing structural engineers within your NCSEA Member Organizations.

Nominations should be emailed to Brian Dekker, Chairman of the NCSEA Nominating Committee, brian@soundstructures.net.

The Nominating Committee will be recommending a slate of candidates by the end of June, and ballots will be distributed prior to July 10.

As stipulated in the NCSEA By-Laws, the Board of Directors is policy-based and defined as a deliberating body which has fiduciary, legal and strategic responsibilities and focuses on continuous strategic planning, determination of desired outcomes, development and approval of policy imperatives to guide operations, and ensuring that NCSEA works toward meeting its vision and fulfilling its goals.

Given that NCSEA represents structural engineers spanning the country, the nominating committee gives consideration to maintaining a diverse geographical representation when selecting candidates. Directors remaining on the Board are Barry Arnold, SEAU (Utah); Brian Dekker, SEAOI (Illinois); Susie Jorgensen, SEAC (Colorado); Chad O’Donnell, SEA-WI (Wisconsin); and Bill Warren, SEAOC (California).

Safety Assessment Program Class Scheduled for June 11 Interested in using your engineering expertise to assist postdisaster efforts following earthquakes, tornadoes, hurricanes or other natural disasters? Obtain certification through the California Office Of Emergency Services (CalOES) Safety Assessment Program (SAP), presented by NCSEA on June 11.

The CalOES SAP program is highly regarded as a standard throughout the country for engineer emergency responders.

The training has been reviewed and approved by FEMA’s Office of Domestic Preparedness.

Based on ATC-20/45 methodologies and documentation, the SAP training course provides engineers, architects and

NCSEA Committee Positions open in June

NCSEA Webinars June 16, 2015 Safe Room Designs and Examples

NCSEA Committees will be requesting new members in June.

An email will be sent to all members of NCSEA Member Organizations with a listing of those NCSEA Committees requesting new members.

Available committee positions are open to any current member of an NCSEA Member Organization. NCSEA is appreciative of its excellent volunteer base and strives to retain that quality and keep committee membership “fresh”, through 3-year terms and an annual call for new committee members.

A complete listing and description of NCSEA’s committees can be found on the website, www.ncsea.com.

Young Engineer Scholarships to NCSEA Summit The scholarship covers registration to the Summit, which includes 3 breakfasts, 2 lunches, 2 receptions, refreshment breaks, trade show access, all educational sessions, and the NCSEA Awards Banquet, as well as a $500 stipend that may be used toward transportation and hotel costs. Qualified applicants will be under 36 years of age and be a current member of an NCSEA Member Organization. Application can be found at www.ncsea.com/members/younggroups.

The application deadline is July 1.

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code-enforcement professionals with the basic skills required to perform safety assessments of structures following disasters.

Licensed design professionals and certified building officials will be eligible for SAP Evaluator certification and credentials following completion of this program and submission of required documentation.

Course cost is $500 per connection, and a proctor is required, who may also take the course.

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William Coulbourne, P.E., Director of Wind & Flood Hazard Mitigation, Applied Technology Council June 25, 2015 HSS Design with the Latest Codes and Material Specifications

Kim Olson, P.E., Structural Engineer, FORSE Consulting

July 14, 2015 The Most Common Errors in Wind Design & How to Avoid Them

Emily Guglielmo, S.E., Associate, Martin/Martin July 21, 2015 ACI Development of a Building Code for Repair of Existing Concrete Structures

Keith Kesner, Ph.D., P.E., S.E., Chair, ACI Committee 562

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

Non-CalOES courses award 1.5 hours of continuing education. Approved for CE credit in all 50 States through the NCSEA Diamond Review Program. Time: 10:00 AM Pacific, 11:00 AM Mountain, 12:00 PM Central, 1:00 PM Eastern. NCSEA offers three options for registrations to NCSEA webinars: Ala Carte, Flex-Plan, and Yearly Subscription. Visit www.ncsea.com for more information or call 312-649-4600.

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Register and get your hotel room today!

Join us in Vegas!

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The NCSEA Structural Engineering Summit will take place at the Red Rock Resort in Las Vegas. The hotel features seven restaurants, spa, bowling alley, movie theatre, and arcade along with a casino. There is a complimentary scheduled shuttle to and from McCarran Airport and the Las Vegas Strip. A reservation link for the NCSEA group rate at the hotel, as well as a link to register for the Summit, are available at www.ncsea.com.

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Full Summit registration includes all educational sessions, plus breakfasts, lunches, receptions, and the NCSEA Awards Banquet. Special discounted registration rates are available for first-time attendees and young engineers!

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• Structural Engineering Education • Trade Show • Awards Banquet, including the NCSEA Excellence in Structural Engineering Awards and the NCSEA Special Awards • Receptions for networking and meeting structural engineers from across the country

Saturday, October 3 8:00 – 12:00 NCSEA Annual Business Meeting 12:30 – 2:00 NCSEA Board of Directors Meeting

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The NCSEA Summit will feature:

News from the National Council of Structural Engineers Associations

Thursday, October 1 7:00 – 8:00 Delegate Interaction Meeting 8:00 Welcome & Introduction 8:15 – 9:30 Keynote: Ron Lynn, Director, Department of Building & Fire Prevention Bureau, Clark County, Nevada 9:45 – 11:00 Basis for ASCE 7 Seismic Design Maps, Ron Hamburger, Senior Principal, Simpson Gumpertz & Heger 11:00 – 12:00 Building Rating, Retrofit Ordinances, and Community Resilience, Panel from Structural Engineers Association of California 1:00 – 2:15 A. The ASCE 7-16 Tsunami Loads Design Standard, Gary Chock, President, Martin & Chock; Chair, ASCE 7 Tsunami Loads & Effects Subcommittee B. Working with Multiple Generations, Panel Discussion with the NCSEA Young Member Group Support Committee 2:45 – 3:45 A. Wood & Cold-Formed Light Steel Frame Construction - Deficiency in the IBC Special Inspections, Kirk Harman, P.E., S.E., President, The Harman Group B. The Decline of Engineering Judgement, Jon Schmidt, P.E., SECB, Associate Structural Engineer, Burns & McDonnell 4:00 – 5:00 A. Changes to Wind Loading in ASCE 7-16, Don Scott, S.E., PCS Structural Solutions; Chair, NCSEA Code Advisory Committee Wind Engineering Subcommittee B. BIM and Structural Engineering, Desiree Mackey, BIM Manager, Martin/Martin 6:30 – 8:30 Welcome Reception on Trade Show Floor

Friday, October 2 8:00 – 10:00 Member Organization Reports 8:00 – 10:00 Vendor Product Presentations 10:15 – 11:30 A. Lateral Design of Buildings with Sloped Diaphragms, Steven Call, P.E., S.E., Call Engineering B. Effective Communication: Tips for Improving Your Skills, Kirsten Zeydel, S.E., President, ZO Consulting & Annie Kao, P.E., Field Engineer, Simpson Strong-Tie 1:00 – 2:30 A. Lateral Analysis: Right Way/Wrong Way with Software, Sam Rubenzer, P.E., S.E., Structural Engineer, FORSE Consulting B. Quality Assurance for Structural Engineering Firms, Cliff Schwinger, P.E., Vice President & Quality Assurance Manager, The Harman Group 2:45 – 3:45 A. Concrete & CMU Elements in Bending + Compression, John Tawresey, retired, KPFF Consulting Engineers B. Find the Lost Dollars: 6 Steps to Improve Profits, June Jewell, CPA, AEC Business Solutions 4:00 – 5:00 A. Problem Solving for Repairing Wood Structures, Kimberlee McKitish, P.E., Nutec Group B. Business Ownership Transfer, Craig Barnes, Founding Principal, CBI Consulting 6:00 – 7:00 Awards Reception (formal attire encouraged) 7:00 – 10:00 NCSEA Banquet & Awards Presentation, featuring the NCSEA Excellence in Structural Engineering Awards and the NCSEA Special Awards

NCSEA News

Wednesday, September 30 8:00 – 5:00 Committee Meetings 8:00 – 12:00 NCSEA Board of Directors Meeting 5:30 – 6:30 Young Engineer Reception 6:30 – 8:30 SECB Reception

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ETS 2015 – Registration Now Open

Structural Columns

The Newsletter of the Structural Engineering Institute of ASCE

Electrical Transmission & Substation Structures Conference 2015 September 27 – October 1, 2015, Branson, Missouri Grid Modernization – Technical Challenges & Innovative Solutions

Pre-Conference Workshop

The ASCE/SEI Electrical Transmission & Substation Structures Conference is recognized as the must-attend conference that focuses specifically on transmission line and substation structures and foundation construction issues. This event – for utilities, suppliers, contractors, and consultants – offers an ideal setting for learning and networking.

Conference Highlights Technical Program – presentations, panel discussion, and case studies by leaders in the field Exhibit Hall – the most comprehensive display of products and services in the industry Demonstration Hours – unique opportunity to see several overhead power line construction and supplier demonstrations in a single day

Panel Discussion of Storm Handling, Resiliency and Security Issues Sunday, September 27, 2015 Kick off your participation in the conference early with a workshop on some of the most pressing issues in the industry. The workshop panel will include industry experts who represent federal, state, research and utility perspectives. After the panel’s presentations, there will be ample time for open discussion and interaction with the audience on these key topics: • Current and trending FERC and NERC regulations • State regulations, response to federal rules and trends • Utility emergency response, recovery and mutual assistance during major events • Updates on current, relevant research for utility applications Visit the conference website at www.etsconference.org for complete information and to register.

Local Activities West Virginia University Graduate Student Chapter The West Virginia University GSC was actively involved in organizing an event attracting about 150 high school students and their families. The high school visitation event was organized to encourage interest towards civil/structural engineering among the participating students. There were presentations on several technical topics that research groups at WVA are working on. See the News page of the SEI website for complete details.

University of Texas at Arlington Graduate Student Chapter The University of Texas at Arlington GSC has presented two programs to enhance the education of their members. In March they presented a training on PGSuper Bridge Design Software

ASCE Forensic Engineering 7 th Congress Performance of the Built Environment

The more we understand failure, the better we can understand design. Learn alongside professionals who share the same challenges in their work to identify and address the root causes and consequences of design errors and construction defects. The Forensic Congress will be in Miami, Florida, November 15–18, 2015. See the Forensic Congress website at www.forensiccongress.org for more details.

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which included an overview, program configuration, working with the PGSuper library, and designing bridges with prestressed girders. In April chapter members attended a webinar on tornado and high wind shelter design. Upcoming events include a field trip, guest speakers, and collaborating with the SEI Fort Worth Chapter on a Habitat for Humanity project.

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

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

Share your Expertise – Become an ASCE Instructor Do you have practicing knowledge of technical, management, or regulatory topics, as well as strong presentation skills? ASCE needs your training expertise to develop and present continuing education. As an ASCE presenter, you will earn the prestige of a nationally recognized program, monetary compensation, and the opportunity to advance the profession. Learn more and submit a proposal at www.asce.org/become_an_instructor.

June 2015

December 10 –12, 2015, Hyatt Regency San Francisco

Demolition Engineering Committee A new Technical Activities Committee on Demolition Engineering has been formed within SEI and held its first meeting April 22 at the Structures Congress 2015. The focus of the committee is currently proposed to provide guidance on proper means, methods and design for demolition. While related, these are separate from issues of the health, safety and welfare of those carrying out the demolition process. The committee’s initial focus will be on developing guidelines for professional engineers involved in this sector of construction, in the hope that this will lead to safe practices and more accountability to all engaged in demolition. Ultimately, the hope is that these guidelines will be further developed into a national standard.

The first set of activities will be to develop the membership (which is currently underway), develop a plan of activities and commence work on the manual. To join the committee, fill out the on-line form on the SEI website at www.asce.org/ structural-engineering/sei-tad-committee-application.

For more information about the committee, please contact James Cohen, P.E. at james.cohen@wai.com.

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Confirmed Keynote Speakers and Topics Ken Elwood: Observations of building performance in recent earthquakes, with a special focus on the devastating event in Christchurch in 2011, and a discussion on where codes still need improvement.

Lucy Jones: Resilience by design in Los Angeles – The Los Angeles Mayor’s Plan to improve the seismic performance of buildings.

Curt Haselton: The evolution of building seismic evaluation and loss estimation methods, with a focus on recent technical developments that could both transform the approach to loss estimation and support resilience-based design.

William Holmes: A new cost-effective method to evaluate and identify older concrete buildings with the highest potential to collapse during severe earthquakes.

David Mar: Innovative seismic retrofit solutions, with a focus on new and emerging concepts.

Laurie Johnson: Building a foundation for resilience at the community scale.

Visit the conference website at www.atc-sei.org for complete details and to register.

Save the Date

Geotechnical & Structural Engineering Congress 2016 February 14 –17, 2016 Phoenix, AZ Connect | Collaborate | Build www.Geo-Structures.org

Take Any of ASCE’S Live Webinars This Summer for $99 Each Sign up for any ASCE live webinar to be held in June, July, or August – either 60 or 90 minutes – and get a special individual member rate of $99, applied automatically when registering.

Take advantage of convenient, efficient training that provides practical knowledge and earns PDHs. This offer does not apply to site/group webinar registrations, on-demand webinars, or P.E. exam review courses, and cannot be combined with other offers. Visit the ASCE Continuing Education website at www.asce.org/continuing_education for more information.

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The Newsletter of the Structural Engineering Institute of ASCE

The Second ATC-SEI Conference on Improving the Seismic Performance of Existing Buildings and Other Structures will provide a forum for the presentation and exchange of new information on the seismic evaluation and seismic rehabilitation of existing buildings, including case studies, new discoveries, innovative use of new technologies and materials, implementation issues, needed improvements to existing standards and methods, and socio-economic issues. The goal is to provide an invaluable opportunity to advance the understanding of the tools, techniques, and innovations available to assist the attendees in meeting the challenges of seismic evaluation and rehabilitation.

Who Should Attend • Structural engineers • Civil engineers • Bridge engineers • Business owners • Researchers working in the structural engineering discipline • Students • Users of ASCE/SEI 31, Seismic Evaluation of Existing Buildings, and ASCE/SEI 41, Seismic Rehabilitation of Existing Buildings • Members of ASCE/SEI • Professional engineers looking for additional PDH opportunities

Structural Columns

RegistRation open Second ATC-SEI Conference on Improving the Seismic Performance of Existing Buildings and Other Structures

The Newsletter of the Council of American Structural Engineers

CASE in Point

Case Risk Management Tools Available Foundation 3 Planning: Plan to be Claims Free Tool 3-1 A Risk Management Program Planning Structure This tool is designed to help a Firm Principal design a Risk Management Program for his or her firm. The tool consists of a grid template that will help focus one’s thoughts on where risk may arise in various aspects of their engineering practice and how to mitigate those risks. Once the risk factor is identified, then a policy and procedure for how to respond to that risk is developed. This tool contains 10 sample risk factors with accompanying policies and procedures to illustrate how one might get started. The tool is designed to insert custom risks and policies to tailor it to individual firms.

Tool 3-2: Staffing and Revenue Projection Firms are provided a simple to use and easy to manipulate spreadsheet-based tool for predicting the staff that will be necessary to complete both “booked” and “potential” projects. The spreadsheet can be further utilized to track historical staffing demand to assist with future staffing and revenue projections.

Tool 3-3: Website Resource Tool This tool lists website links that contain information that could be useful for a Structural Engineer. A brief description of the website is also included. For example, there is information about doing business across state lines, information regarding the responsibility of the Engineer of Record for each state, links to each State’s Licensing Board, etc.

Tool 3-4: Project Work Plan Templates Preparing and maintaining a proper Project Work Plan is a fundamental responsibility of a project manager. Work Plans document project delivery strategies and communicate them to the team members. Project Managers will use this template to create a project Work Plan that will be stored with the project documents.

Foundation 4 Communication: Communicate to Match Expectations with Perceptions Tool 4-1: Status Template Report This tool provides an organized plan for keeping your clients informed and happy. This project status report is intended to be sent to your Client, the Owner and any other stakeholder whom you would like to keep informed about the project status.

Tool 4-2: Project Kick-Off Meeting Agenda Effective communication is one of the keys to successful risk management. Often times we place a significant amount of effort and care into communication with our clients, owners and external stakeholders. With all that effort, it’s easy to take for granted communication with our internal stakeholders – the structural design team. If a project is not started correctly, there is a good chance that the project will not be executed correctly either. Tool 4-2 is designed to help the Structural Engineer communicate the information that is vital to the success of the structural design team and start the project off correctly.

Tool 4-3: Sample Correspondence Guidelines The intent of CASE Tool 4-3, Sample Correspondence Guidelines, is to make it faster and easier to access correspondence with appropriate verbiage addressing some commonly encountered situations that can increase your risk. The sample correspondence contained within this tool is intended to be sent to the Client, Owner, Sub-consultant, Building Official, Employee, etc., in order to keep them informed about a certain facet of a project or their employment.

Tool 4-4: Phone Conversation Log Poor communication is frequently listed among the top reasons for lawsuits and claims. It is the intent of this tool to make it faster and easier to record and document phone conversations.

Tool 4-5: Project Communication Matrix

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

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This tool is to provide an easy to use and efficient way to (1) establish and maintain project-specific communication standards, and (2) document key project-specific deadlines and program/coordination decisions that can be communicated to a client or team member for verification.

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The CASE Summer Planning Meeting is scheduled for August 6–7 th in Chicago, IL. The night of August 6 th will feature a roundtable discussion on risk management and business practice topics. Firms can develop business relationships leading to growth and success through the CASE roundtables held twice each year. 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. If you are interested in attending the roundtable/meeting, please contact CASE Executive Director Heather Talbert at htalbert@acec.org.

April 19–22, a record 1,400 ACEC members attended the ACEC Annual Convention in Washington, D.C., meeting with 300 Senators, Congressmen, and Capitol Hill staffers to urge passage of long-term transportation, energy legislation, tax reform and design-build/procurement reforms. 600-plus attended the blacktie Engineering Excellence Awards Gala, which recognized 170+ preeminent engineering achievements from throughout the world.

The San Francisco-Oakland Bay Bridge New East Span, Oakland, CA, was honored with the 2015 Grand Conceptor Award on April 21st. The engineering work for the project was done by a joint venture of T.Y. Lin International/Moffatt & Nichol.

ACEC’s Annual Convention also marks the induction of a new ACEC Executive Committee. Ralph Christie, Chairman of Merrick and Company, succeeded Richard Wells as ACEC Chairman for 2015-2016 at the spring meeting of the ACEC Board of Directors.

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

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

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

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

Follow ACEC Coalitions on Twitter – @ACECCoalitions.

Expectations and Requirements To apply, you should • be a current member of the Council of American Structural Engineers (CASE) • be able to attend the groups’ two face-to-face meetings per year: August, February (hotel, travel reimbursable) • be available to engage with the working group via email and conference call • have some specific experience and/or expertise to contribute to the group Please submit the following information to htalbert@acec.org • Letter of interest • Brief bio (no more than 2 paragraphs) Thank you for your interest in contributing to your professional association!

A/E Industry’s Premier Leadership-Building Institute Filling Fast for September Class Since its inception in 1995, the American Council of Engineering Companies’ prestigious Senior Executives Institute (SEI) has attracted public and private sector engineers and architects from firms of all sizes, locations and practice specialties. Executives – and up-and-coming executives – continue to be attracted by the Institute’s intense, highly interactive, energetic, exploratory, and challenging learning opportunities.

In the course of five separate five-day sessions over an 18-month timeframe, participants acquire new high-level skills and insights that facilitate adaptability and foster innovative systems thinking to meet the challenges of a changed A/E/C business environment.

The next SEI Class 21 meets in Washington, D.C. in September 2015 for its first session. Registration for remaining slots is available.

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Executives with at least five years’ experience managing professional design programs, departments, or firms are invited to register for this unique leadership-building opportunity. As always, course size is limited, allowing faculty to give personal attention, feedback, and coaching to every participant about their skills in management, communications, and leadership.

SEI graduates say that a major benefit of the SEI experience is the relationships they build with each other during the program.

Participants learn that they are not alone in the challenges they face both personally and professionally, and every SEI class has graduated to an ongoing alumni group that meets to continue the lifelong learning process and provide support.

For more information, visit http://sei.acec.org/ or contact Deirdre McKenna, 202-682-4328, or dmckenna@acec.org.

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CASE is a part of the American Council of Engineering Companies

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CASE in Point

Case Summer Planning Meeting – Save the Date

2015 Annual Convention and Legislative Summit

Structural Forum

opinions on topics of current importance to structural engineers

Engineer with Your Eyes Open

By Scott R. Harpole, PE

G

iven the choice, and the apparent difficulties of the alternative, this may seem like superficial advice for navigating a daily routine.

This bit of counsel, however, has impacts far beyond mere cognizant awareness of the surrounding environment. Most have heard or been given the guidance, “keep your head on a swivel” – often in relation to sports, or perhaps even before entering precarious situations, but these recommendations may not be expected among the cubicle warriors of engineering firms. Taking time to look around may just save a project schedule and budget in a matter of minutes.

Rarely is it more important for an engineer to be omniscient than on a site visit. Never mind the direct task at hand – walking down systems, updating project staff, identifying progress, or ensuring quality – staying out of harm’s way is a full-time (not to mention the most important) responsibility. Too often in an efficiency-driven industry this awareness is lost in the “I’m here to do this … or I need to look at that ...” mentality, and engineers lose sight of the bigger picture: the whole project’s goals.

A recent site visit to investigate the failure of slide plates on a flue gas ductwork system reinforced this concept as well as any class, design concept, or code document ever has. As a structural engineer, my eyes are continually drawn to the steel and concrete infrastructure that dominates the power industry in which I work. On the trudging climb to the top of a precipitator structure to walk down the subject ductwork, an oddity in the braced frame structure jumped out. To the chagrin of many architect counterparts, this structure was intended to be concentric, aligned, straight, square, the whole bit – but it was no longer.

One of the large first-tier vertical braces had shifted noticeably out of plumb (Figure 1).

After further investigation, I discovered that the gusset and web splice connection plates had buckled, further causing the web of the wide flange brace to begin tearing down the axis of the member (Figure 2).

The piece of the story that has yet to be told regards the large new ductwork support

Figure 1.

Figure 2.

structure that was in mid-design back at the office, soon to be built adjacent to the precipitator. It would be counting on this existing structure for both lateral and vertical support in varying capacities. As is typical in retrofits, the client had provided a set of existing structural drawings, the contract was written such that the new design could reasonably rely upon the owner-provided documents, and consequently the small proverbial snowball of design began rolling, formed around the nucleic assumption that the structure would look and act as the drawings indicated. Though it was later determined that the existing structure had likely relieved its excess load through the displacement of the brace, thus finding a new path to its foundation, and was stable in its current condition, it most certainly would not have been sufficient for the new loads that were going to be introduced.

Luckily, that snowball had not yet reached terminal velocity – about which a structural engineer knows nothing, but it sounds great in print – on its way down the hill of the project schedule toward construction, and thus the design could be redirected to stand on its own without the help of the failed bracing system. Though a more expensive approach, it was certainly the prudent one given the developments, and it would provide the client with the expected reliability and safety.

So why tell this little story? Investigation of the existing ductwork slide plate was a separate scope of work, under a separate agreement, largely unrelated to the major

air quality control system design/construction project taking place at this site; but the impact of that climb up the stairs became far-reaching. Probable schedule and budget impacts were averted due to the early detection of the existing conditions, not to mention the potential for a catastrophic failure in the future. There were certainly no “atta boys” or accolades provided for the find, nor should there have been. This was not a personal victory, but one for the project and the long-term interest of the owner – after all, it is the fundamental obligation of all engineers to protect the safety, health and welfare of the public and their clients (in that order) – it is just doing the job. It is a reminder that – with all the metaphorical blinders of contract language, performance pressure, future repeat business, and economy of design – there is no relief from the overarching duty of due diligence in project work. That includes simply paying attention to the “that looks odd” moments.

Though it is likely feasible to scratch out a few pages of calculations while staring at the back of closed eyelids, this certainly does not stand as a challenge to try. Instead, think of it as a reminder that an engineer’s responsibility on a project goes far beyond the tasks at hand, and entails always – ALWAYS – keeping those eyes open. Clients depend on it.▪ Scott R. Harpole, P.E., is a senior structural engineer in the Energy Group at Burns & McDonnell in Kansas City, Missouri. He can be reached at sharpole@burnsmcd.com.

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

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