STRUCTURE magazine | August 2015

A Joint Publication of NCSEA | CASE | SEI

STRUCTURE

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August 2015

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Feature

Binghamton university energy r & D Building

By Chris Latreille, P.E. A new 105,000-square-foot Energy R & D building is currently under construction at Binghamton University in Binghamton, New York. The extensive use of curved, round HSS members as a structural framing system and the primary visual components of the architecture are what makes this project unique. eDitorial

7 it is all about the People You Meet and the Connections You Make…

By Susan Jorgensen, P.E., SECB

CoDeS & StanDarDS

39 nSSa/iCC 500-2014 Storm Shelter Standard— Structural Provisions

By Ernst W. Kiesling, P.E., Ph.D., Jason Pirtle, P.E. and

StruCtural PerForManCe

9 analyzing Cold-Formed Steel roof trusses for Blast loading

JuSt tHe FaQS

42 Steel Deck FaQs

By Kurt Voigt, P.E.,

Mark Weaver, P.E., S.E. and

Ben Pitchford, P.E.

Mike Pellock, P.E.

and Joe Voigt, E.I.T.

StruCtural ForenSiCS

GueSt ColuMn

14 Corrosion Diagnostics and electrochemical repair for Historic Steel Frame Buildings

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18 non-Prismatic Composite Girders

By Sompandh Wanant, P.E. HiStoriC StruCtureS

21 kentucky river High Bridge

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

Feature

Wilshire Grand

57 a new Generation of Galvanizing

By Gerard Nieblas, S.E. and Phuoc Tran In a continuation of a series on the design and construction of the Wilshire Grand, this article discusses the balancing act of stiffness, strength and mass in the design of the structure for both seismic and wind considerations.

By Howard Levine SPotliGHt

59 aSCe & Sei recognize outstanding Structural engineers

45

Feature

Software Business ‘robust’

StruCtural ForuM

66 eor uses Construction Coordination Drawings to Finalize Design

By Dean Brown, S.E.

On the cover Construction phase of the Wilshire Grand in downtown Los Angeles.

A 73-story mixed-use office and hotel facility with a surrounding podium. See feature article on page 34.

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

STRUCTURE magazine

Pushing the Boundaries of timber Design

34

By Gina L. Crevello and Paul A. Noyce

Feature

By Holger S. Schulze-Ehring, Dipl.-Ing., Filippo Masetti, P.E. and Matthew H. Johnson, P.E. The design of the China Pavilion for the 2015 World Expo Milano centers on the ideas of sustainability and the coexistence of nature and cityscape. Sharp-edge angled timber rafter members resemble a large city skyline, while soft and curvy waves form the profile of a rolling landscape. Merging these inherently opposing profiles presented challenges.

James E. Waller, P.E.

By Brian Warfield, P.E., S.E.,

30

5

By Larry Kahaner The structural design and construction industries continue to see improvements in the number of projects on the books. As such, the software industry is tasked in keeping up with the needs of structural engineers in an ever evolving project environment.

in everY iSSue 8 Advertiser Index 52 Resource Guide (Software) 60 NCSEA News 62 SEI Structural Columns 64 CASE in Point

August 2015

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Editorial

It is all about the People You Meet and the Connections You Make…

new trends, new techniques and current industry issues

By Susan Jorgensen, P.E., SECB, LEED

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ooking to learn the latest technology updates for practicing structural engineers? Need information on improving your business practices? Interested in meeting the leaders of our profession to discuss the challenges of structural engineering?

Join us for the 2015 Structural Summit at the Red Rock Resort, Las Vegas, NV, and you will be able to do just that. Every year the Summit draws the best and brightest of our industry – from the leaders who have advocated for the profession and are the experts in our field to the up and coming enthusiastic young professionals who will be taking over our profession in the future. What better place to be a part of the action to influence our profession?

The conference will begin with The Profession, The Grandeur, and The Glory by Ashraf Habibullah of Computers and Structures.

Ashraf will keep us engaged with stories of his experiences throughout his illustrious career. His presentation will be followed by the Basis for ASCE 7 Seismic Design Maps by Ron Hamburger of Simpson, Gumpertz & Heger and a panel from the Structural Engineers Association of California discussing Building Ratings, Retrofit Ordinances, and Community Resilience.

This year’s Summit follows up with two tracks of sessions with information for engineers at all levels. The technical track includes information on the latest updates in our codes and standards, and some of the design challenges we face. Gary Chock, of Martin & Chock, will give a presentation on The ASCE 7-16 Tsunami Loads Design Standards, Don Scott will discuss the Changes to Wind Loading in ASCE 7-16, and Wood & Cold-Formed Light Steel Frame Construction – Deficiency in the IBC Special Inspections will be presented by Kirk Harman of The Harman Group.

Other technical topics include Lateral Design of Buildings with Sloped Diaphragms by Steven Call, Lateral Analysis: Right Way/ Wrong Way with Software by Sam Rubenzer, Concrete & CMU Elements in Bending + Compression by John Tawresey, and Problem Solving for Repairing Wood Structures by Kimberlee McKitish.

The second track furthers the development of your business practices. June Jewell of AEC Business Solutions will discuss Find the Lost Dollars: 6 Steps to Improve Profits, and Working with Multiple Generations will be addressed by a panel from the NCSEA Young Member Group Support Committee. Jon Schmidt of Burns & McDonnell will speak about The Decline of Engineering Judgement and Craig Barnes of CBI Consulting will discuss Business Ownership Transfer. Other business related topics will cover Effective Communication: Tips for Improving Your Skills by Kirsten Zeydel, BIM and Structural STRUCTURAL Engineering by Desiree Mackey, ENGINEERING and Quality Assurance for INSTITUTE Structural Engineering Firms

by Cliff Schwinger.

The Summit draws the best and brightest of our industry

a member benefit

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Beyond the outstanding presentations, perhaps the most important benefit of the Summit would be the people you meet and the connections you make. After spending two to three days with a wide variety of structural engineers, including those who are facing the same problems you do in your practice, you will leave with a list of professionals you can contact in the future to get advice, share ideas, and ask technical questions.

Don’t worry. It is not all presentations and panel discussions.

There is also plenty of Las Vegas-style fun planned for you.

Wednesday evening will include two receptions – hosted by the Young Engineers and SECB – to which all attendees are invited.

This is a great way to begin making those connections. Thursday evening is a Welcome Reception in the vendor hall followed by the (Red) Rock ‘n Bowl with NCSEA at the onsite VIP Bowling Suite.

Friday ends with the NCSEA Banquet & Awards Presentation in the evening. All of these are excellent opportunities to meet other attendees in a more social setting to celebrate all the good our profession does. Plan to stick around for the NCSEA Annual Business Meeting on Saturday morning, to learn more about how NCSEA operates. This year’s Summit promises to fulfill NCSEA’s Vision Statement: The National Council of Structural Engineers Associations will be recognized as the leading advocate for the practice of structural engineering. This is your organization – take this opportunity to get the most out of it.▪

STRUCTURE magazine

Susan Jorgensen, P.E., SECB, LEED, is President of Prairie Smoke Engineering, Highlands Ranch, CO and an NCSEA Board Member. She can be reached at SusieJorg315@comcast.net.

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August 2015

ADVERTISER INDEX

PLEAsE suPPOrt tHEsE ADVErtIsErs

ADAPT Corporation ............................ 38 Albina Co., Inc...................................... 17 Applied Science International, LLC....... 67 AZZ Galvanizing .................................. 56 CADRE Analytic .................................. 54 Canadian Wood Council ....................... 48 Clark Dietrich Building Systems ........... 25 Design Data .......................................... 44 Enercalc, Inc. .......................................... 3 Hardy Frame ......................................... 43 Independence Tube Corporation ............. 2 Intergraph CADWorx & Analysis Sol.... 47 Integrity Software, Inc. .......................... 36 Integrated Engineering Software, Inc..... 21 KPFF Consulting Engineers .................... 8

Legacy Building Solutions ............... 37, 58 Lindapter .............................................. 41 NCSEA ................................................. 11 Nemetschek Scia ................................... 50 New Millennium Building Systems ....... 20 Ram Jack Systems Distribution ............. 51 RISA Technologies ................................ 68 S-Frame Software, Inc. ............................ 4 Simpson Strong-Tie......................... 13, 29 Structural Engineers, Inc. ...................... 23 Struware, Inc. ........................................ 55 Tekla ..................................................... 46 USG Corporation ................................... 6 Weyerhaeuser ........................................ 53

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

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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

WINNER OF AN

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

American Institute of Architects Design Award

Brian W. Miller Davis, CA

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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

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STRUCTURE magazine

8

August 2015

August 2015, Volume 22, Number 8 ISSN 1536-4283. Publications Agreement No. 40675118.

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

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

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

Structural Performance performance issues relative to extreme events

Figure 1. Completed multi-use facility.

C

old-formed steel (CFS) trusses can be an economical framing option for many buildings, and are often the most economical option for those having a steeply sloped roof. Some advantages of CFS trusses are that they have an excellent span-to-weight ratio, can be shop-fabricated into custom shapes, and are non-combustible.

Despite these advantages, the use of CFS trusses on inhabited building projects funded by the Department of Defense (DoD) can be challenging because of the requirements imposed by Unified Facilities Criteria (UFC) 4-010-01, DoD Minimum Antiterrorism Standards for Buildings.

One of the primary design strategies of UFC 4-010-01 is to increase the standoff distance between buildings and potential explosive threat locations. In 2012, UFC 4-010-01 was amended to correlate the standoff distance at which no analysis for blast loads is required with the exterior wall and roof construction type. Buildings constructed of heavier and more robust materials, such as reinforced concrete or masonry, are permitted to have smaller standoff distances than buildings constructed of lighter materials, such as wood or CFS studs, as long as the structural design complies with UFC-prescribed detailing requirements. Provisions for several wall and roof systems are included in the UFC, but any wall or roof type that differs from the prescriptive requirements must be analyzed for blast loads.

One roof framing system not explicitly addressed is CFS trusses with metal roof deck.

CFS trusses are typically constructed of proprietary light-gauge steel shapes and designed using proprietary tools developed by CFS truss designers and manufacturers. The design of CFS trusses is generally delegated by the Structural Engineer of Record (SER) to a specialty engineer familiar with these proprietary member shapes and design tools. However, it is the responsibility of the SER to define the truss performance requirements – including the blast loading requirements for DoD projects – such that the specialty engineer can design the individual trusses and overall truss system including bracing, bridging, connections,

etc. For the SER, understanding and communicating the loading requirements so that the project can be bid appropriately is an important part of the design process. This article documents the method employed to address this challenge for one project and describes the analyses performed along the way.

Analyzing Cold-Formed Steel Roof Trusses for Blast Loading

Project Overview

The example project is a two-story, 11,800-square-foot, multi-use facility with retail, food service, and meeting spaces. The building was constructed using CFS roof trusses, composite steel and concrete floor framing, exterior load-bearing reinforced masonry walls, and shallow foundations (Figure 1).

The client desired a new facility to match the existing architecture of the area, which meant a Mediterranean-style building with a sloped roof.

Typically, CFS trusses would be an economical framing choice to achieve this slope; however, the mandated DoD requirements warranted further investigation.

The standoff distance to the controlled perimeter was more than 200 feet, and the standoff distance to parking, roadways, trash containers, and other obstructed spaces was nearly 100 feet. While UFC 4-010-01 allowed for smaller standoff distances based on the chosen exterior wall system, reducing the standoff distance would have significantly increased the blast loads on the roof structure, and therefore its cost.

Specifying CFS Trusses for DoD Project CFS truss designers are very familiar with codemandated environmental forces such as dead, roof live, snow, and wind loads. Software written by product manufacturers or third-party vendors is available that will size thin-wall steel members and their connections to resist these static loads based on design procedures established by the

STRUCTURE magazine

9

By Brian Warfield, P.E., S.E., Mark Weaver, P.E., S.E. and Mike Pellock, P.E.

Brian Warfield, P.E., S.E. (brian.warfield@haskell.com), is a Senior Structural Engineer with Haskell Architects and Engineers, P.A. Mark Weaver, P.E., S.E. (weaver@kcse.com), is a Senior Engineer with Karagozian & Case, Inc. Mike Pellock, P.E. (mpellock@mii.com), is Executive Vice President of Aegis Metal Framing, a MiTek Company.

American Iron and Steel Institute (AISI).

However, design for the high-magnitude, short-duration loads associated with explosives is less well-established.

The blast load analysis requirement introduced by UFC 4-010-01 placed the SER in a difficult position when specifying blast loads for the CFS trusses of the subject project. One option was simply to delegate the blast load analysis of the CFS trusses to the manufacturer, but this would assume that the manufacturer has engineering personnel who could properly apply these requirements and bid the truss package accordingly. If incorrect, such an assumption could lead to incorrect bids and costly delays in the submittal review process.

An alternative approach, which was utilized for this project, was to conduct a generalized dynamic analysis such that an equivalent static blast load could be included in the delegated design performance specification. Ideally, this approach would enable the truss manufacturer to size truss members properly at the bid phase and estimate costs accordingly.

Blast Effects Analysis of CFS Truss Conducting a generalized dynamic analysis such that an equivalent static blast load could be included in the delegated design performance specification requires an approach that approximates the global response of the truss while still accounting for localized phenomena.

The approach ultimately consisted of quantifying the external forces applied (i.e., blast load) and the mass, stiffness, and controlling limit state(s) of the system (i.e., the truss model) such that a dynamic analysis could be conducted.

Blast Load Considerations Blast loads applied to roof structural components are generally not uniform along the length of the truss, particularly when the span is oriented perpendicular to the direction of shock front propagation. A method of simplification espoused by UFC 3-34002, Structures to Resist the Effects of Accidental Explosions, allows the blast load to be idealized as uniform along a component’s length by summing the effects of the incident overpressure and drag. It should be noted that this involves two assumptions: • The shock wave is not reflected by the roof surface, but rather “drags” across it. For sloped roof systems, this may not be valid if the angle of incidence is less than 90 degrees.

• The wavelength of the blast wave is not significantly shorter than the

Figure 2. Example of shock spectra for inbound and rebound truss response.

length of the truss. In this case, a uniform load is not a valid idealization of the blast loading.

Blast loads consist of positive and negative phases. In many cases, ignoring the negative phase and simply analyzing the structural component for the positive phase will generate a conservative component response.

However, for situations where the structural component is lightweight and/or the blast loading is characterized by a long positivephase duration relative to the period of the response mode considered, as is often the case for CFS truss roof systems, consideration of the negative phase may dictate the peak response of the component. Therefore, it was important to consider both “positive phase only” and “positive plus negative phase” scenarios.

SDOF Truss Model Based on the lack of information concerning individual truss properties, a single degreeof-freedom (SDOF) model was utilized to model a generic truss in order to generate an equivalent static blast load. The use of an SDOF truss model implied that the load could be idealized as uniform, a single degree of freedom could adequately represent truss response for the idealized blast load, and a corresponding resistance function could be generated that would capture the controlling limit state.

The assumption concerning the controlling limit state of a CFS truss is important in selecting a suitable response limit. SDOF response limits applicable to DoD construction are documented in PDC-TR 06-08, Single Degree of Freedom Response Limits for Antiterrorism Design; however, there are no response limits indicated for CFS trusses.

In the absence of formalized guidance, the SDOF response limits for open web steel joists

STRUCTURE magazine

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August 2015

were assumed. Both systems are trusses, and thus rely on the axial strength and stiffness of constituent members to span large distances.

However, tensile chord yielding can be difficult to achieve in practice for CFS trusses, because they are generally much deeper and will have longer web members in compression than open web steel joists. Thus, it was considered reasonable, although perhaps conservative, to assume the failure mode for most CFS trusses would be some form of web member buckling. A ductility ratio (maximum deflection to yield deflection) of 0.9 for heavy damage was used as recommended in PDC-TR 06-08 for an open-web steel joist web member buckling response limit.

Given a uniform load normal to the truss top chord, the point of maximum truss deflection was assumed to occur at mid-span and the deflected shape was assumed to match that of a simply supported beam subjected to a uniform load. A closed-form expression for peak truss deflection that is a function of time, blast load pressure-time history, and the fundamental period of the truss, Tn, was derived and used to develop shock response spectra (SRS) for truss inbound and rebound response. The developed SRS assumed that the inbound and rebound stiffness of the truss were equal. An example of SRS developed for a “positive phase only” loading is shown in Figure 2, where the deformation response factor, Rd, is equal to peak truss deflection divided by the truss deflection induced by a statically-applied peak blast pressure, p0.

To determine Tn , the mass and stiffness of each truss were required. While mass could be assumed as the roof system dead load tributary to the truss, the stiffness was unknown at the time of performance specification development. As such, the equivalent static blast load was defined in the performance specification as a function of truss spacing, s; truss length, L; continued on page 12

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attachment at every rib, the top chord was able to maintain its axial load-carrying ability under the given load between panel points.

Similarly, web member connection requirements can be provided to prevent premature connection failure due to excited localized response modes. Using the ultimate resistance of the specified roof deck and the axial capacity of the web member in question, an upper-bound force requirement can be derived and included in the performance specification. This requirement is Figure 3. Nonlinear dynamic FE result for selected roof truss. particularly important if a higherfidelity analysis is conducted for the and truss stiffness, k – all properties that the CFS trusses, as will be shown below. truss manufacturer would readily know.

Finally, the stability of the trusses in three Truss stiffness was defined as the initial dimensions should be considered. Typically slope of the load-deflection curve, where the top chord is braced by the steel roof deck “load” is the summation of the uniformly- and the bottom chord by intermittent braces. applied vertical load tributary to each truss, For this project, because an elastic response of and “deflection” is the maximum truss deflec- the truss was assumed, no additional stability tion corresponding to the “load”. The three requirements were included in the perforparameters that varied (s, L, and k) were mance specification. collapsed into a single variable, x = (sL/k) 0.5, Finite Element Truss Model and a table was included in the performance specification that correlated different ranges At the construction phase, truss designs of x with an equivalent static blast load. were submitted by the truss manufacturer Thus, the truss manufacturer could deter- for review. For a select number of trusses, mine the equivalent static blast load to be the delegated design performance specificaapplied to each individual truss based on x. tion requirements were so restrictive that an The adjustment factors K a, Ks, and Kd shown alternative means of analysis was requested by in Figure 2 were set equal to 1.7, 1.05, and the truss manufacturer. As such, a transient 1.19, respectively – consistent with those nonlinear finite element (FE) analysis was currently used for open web steel joists in performed for a representative truss that was SBEDS – to provide an allowable load to among the stiffest, yet had a relatively large the truss manufacturer. In addition, the per- tributary area. formance specification stipulated that the Proprietary truss shapes were explicitly modtributary dead load be applied concurrently eled with fully integrated shell elements, and with the equivalent static blast load. the tributary steel deck was also modeled Alternatively, expressions that envelope the explicitly. A nonlinear material model for SRS could be derived and used to commu- 50-ksi steel was used for the truss members. nicate the equivalent static blast load, pst , to Because the truss members were designed the truss manufacturer. For the case shown in such that they would yield or buckle prior to Figure 2, pst is simply 10p0td / xm0.5 for pst and connection failure, the connections were not m in pounds per square foot, p0 in pounds explicitly modeled in the FE analysis, which per square inch, td in milliseconds, and x in greatly simplified the model. (in3/lb)0.5.

Deflection results (Figure 3) indicated that In addition to the global response of the while several of the members buckled out of truss, the non-uniform and time-varying plane, the truss was still able to support its nature of roof blast loads may serve to excite tributary dead load following the application localized response modes of individual com- of the idealized blast loading. ponents, particularly the flexural response of the top chord, and should be considered Conclusion in performance specification development.

For this particular project, it was shown that An equivalent static blast load was determined because of the relatively short spans of the using an SDOF model and incorporated top chord and the use of a self-drilling screw into the delegated design performance

STRUCTURE magazine

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August 2015

Figure 4. CFS roof trusses employed at the multiuse facility.

specification for the CFS trusses. In addition, a nonlinear transient finite element analysis was performed for a representative truss to analyze its response under a time-varying load.

The end result of this effort was an economical roof framing system capable of satisfying the aesthetic demands of the client while complying with the blast loading requirements of UFC 4-010-01 (Figure 4).

There is a paucity of guidance concerning the design, and test data documenting the response, of CFS roof trusses exposed to blast loading currently available to the structural design community. In particular, test data would be helpful in assessing the importance of the non-uniform and time-varying nature of roof blast loads on truss top chords and the stability bracing.

Furthermore, test data could be used to formalize an analytical approach for CFS truss blast design by validating various modeling assumptions and providing response limits consistent with observed failure modes.

Such testing could serve to promote the economical and consistent use of CFS trusses in DoD facilities.▪

Acknowledgment The authors would like to thank Jon A. Schmidt, P.E., SECB, BSCP of Burns & McDonnell for his comprehensive review of the article and assistance in developing an equivalent static blast load expression that envelopes the shock response spectrum.

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Structural ForenSicS investigating structures and their components

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orrosion related damages are the root cause of numerous façade failures on masonry clad steel frame buildings (Figure 1). Corrosion of the underlying steel frame or anchorage can lead to cracking, spalling, displacement, and eventually the loss of entire masonry units or severe section loss of structural components. Corrosion is a quantifiable reaction, whereby initiation, propagation, and deterioration can be projected through comprehensive assessments and durability modelling.

The ultimate reason for carrying out corrosion assessment work on existing steel frame buildings is to determine the long term behavior of the corrosion process that could cause damage to the historic façade. The end result of the testing and analysis is two-fold: to provide a predictive outcome from corrosion damages in the future and, where suitable, to determine if an electrochemical corrosion mitigation system such as impressed current cathodic protection (ICCP) is a viable corrosion mitigation option.

This comprehensive approach to corrosion diagnostics and the use of ICCP has been used in historic steel-frame buildings since the early 1990s.

Corrosion Diagnostics and Electrochemical Repair for Historic Steel Frame Buildings

By Gina L. Crevello and Paul A. Noyce

Gina Crevello has extensive experience in building diagnostics, corrosion diagnostics, material assessments and mitigation.

Gina has been involved with the majority of ICCP Systems on landmark structures in the U.S. She may be reached at gcrevello@e2chem.com.

Paul Noyce is professionally trained as an electrical electronic engineer with a further diploma in electrochemistry. Paul has provided corrosion diagnostics, design engineering and installation support to over 100 ICCP systems for historic buildings in England and the U.S. He may be reached at pnoyce@e2chem.com.

Corrosion Diagnostics A corrosion assessment is one step towards understanding the root cause of deterioration and providing a maintenance, rehabilitation and repair plan (MR & R) that deals with service life. As the steel frame will impact the historic masonry it is embedded within, it is essential to understand the symbiotic relationship of the materials. Variations in masonry type, building envelope details, environmental parameters, and the performance of the overall building enclosure will impact conditions. The basis of investigations is to provide a service life model where the fundamentals are as follows: 1) Determination of mechanical and environmental loads (in laboratory tests and in service, real and simulated) to which materials or components are likely to be subjected, 2) Characterization (macro, micro, and surface) of materials and components, 3) Identification of degradation mechanisms of materials and components, 4) Determination of degradation kinetics of materials and components, 5) Identification and expression of performance requirements and performance criteria for materials and components, and

14 August 2015

Figure 1. Cracking of masonry due to corrosion of the steel frame.

6) Organization and representation of computerized knowledge of materials and components.

The corrosion condition assessment employs various non-destructive and semi-destructive test methods analysed in conjunction with a thorough visual and physical inspection of the structure.

Many of the tests were established to address concerns regarding corrosion of reinforcing steel in concrete.

In 1979, the first full scale trial of non-destructive testing was undertaken in England by the Department of Transport. As a greater understanding of corrosion related deterioration became established, the more comprehensive the testing procedures and condition analysis became. By 1990, service life predictions and determinations of the “maximum tolerable amount of corrosion corresponding to condition of failure” by the use of corrosion rates were being addressed.

During this time period, the notable effects of steel frame deterioration began having a visual and physical impact on landmark and listed buildings in the United Kingdom (UK). Historic Scotland funded a three year study which resulted in the publication of Technical Advice Notes (TAN) 20 Corrosion in Masonry Clad Early 20 th Century Steel Framed Buildings. This study was the first large scale research initiative to introduce a corrosion condition methodology to the historic steel frame building. As such, the test methods, as applied to concrete, required a more refined approach when applied to the historical building stock.

The non-destructive approach as initially outlined in TAN 20, and subsequently refined by the National Association of Corrosion Engineers Task Group 460 (NACE TG 460), requires an understanding of corrosion pathology, knowledge of historic construction methods, construction details, and nondestructive test methods. Upon successful completion of a test program and inclusion of an ICCP feasibility trial, one can determine the most appropriate long term repair option for corrosion mitigation.

Figure 2. Electrochemical test area of masonry corresponding to Figure 3.

Applicable Test Methods The test procedures utilized to determine corrosion conditions vary slightly from building to building depending upon the construction details, materials, location and exposure. A critical analysis of the results requires interpretation based on historic integrity as well as corrosion activity. What may be considered minor corrosion activity on an industrial concrete structure could be considered higher risk for a historic steel frame building or landmark concrete structure where there is a higher intrinsic and monetary value of the construction materials.

The mortar in-fill is essential for ensuring accurate test results and for the passage of the protective current to the steel member.

This condition must be established prior to expending significant time on testing.

Previous and current repair details must be understood as they relate to corrosion, interpretation of test results, future repairs or adverse effects on electrically discontinuous steel from stray current for future repairs, and how the steel and electrolyte function together. The following test methods are key elements of the corrosion condition investigation for masonry clad historic steel frame buildings: • Cover • Resistivity • Continuity • Ecorr or Half Cell Potential • Icorr or Corrosion Rate Testing • Carbonation • Chlorides (if applicable) • Compressive Strength • Knowledge of: previous repairs, masonry properties, and chemical make up steel geometry.

Figure 3. Contour maps of the test data of correlate probable corrosion risk (potential), high moisture, low oxygen and areas of active corrosion. Top contour corrosion rates, bottom contains half-cell potential.

Whereby: Cover provides protection to the steel from the elements and atmosphere.

Electrical continuity to the steel is required for corrosion testing and treatments, and must therefore be established in the investigative phases of work.

Resistivity is the ability of the electrolyte to pass current. Low resistivity values are conducive to, and have a direct correlation with, high corrosion rates (Icorr).

Ecorr or steel potential is established by the taking half-cell potential of the steel with a reference electrode (Figures 2 and 3).

Icorr or corrosion rates are measured by Linear Polarization Resistance. The resulting corrosion current and loss of electrons is equated to section loss based on Faraday’s Law of Metal Loss. This has a direct relationship with rust accumulation (Figures 2 and 3).

Carbonation: the presence or depth of carbonation should be confirmed at the embedded steel. This can be carried out by laboratory analysis of mortar and infill samples, or in situ with pH reagents or indicators.

Chlorides do not usually pose a significant risk in steel frame buildings unless the building is located in a marine environment, or a sidewalk near the base of the building is subjected to de-icing salts in the winter.

Compressive strength of the electrolyte and cladding play an important role in understanding the durability of the material from the effects of corrosion. The higher the

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compressive strength of the cladding material, and the better the compactness of the infill around the frame, the sooner the masonry cladding will exhibit damages from the accumulation of corrosion scale.

As the various elements tested all possess a function in regard to the corrosion behaviour of the building, knowledge of the conditions and the interpretation of the data is required in the overall corrosion assessment (Figure 4, page 16 ). This information sets the basis of assessing service life of the structure and durability of the repair. Utilizing durability models, time to cracking and time to critical section loss can be determined to ensure the most appropriate repair is used.

Impressed Current Cathodic Protection As a redox reaction, oxidation and reduction occur simultaneously in the corrosion reaction. The anodic reaction, or oxidation, is the loss of electrons. This causes the steel to revert to rust. The volume of the rust can be as great as ten times the amount of steel section loss.

Simultaneous to this is the reduction reaction at the cathode site. The cathode reaction is harmless, and the cathode gains electrons that have been lost at the anode site. The electrons pass from the anode as ionic current through the masonry, moisture, or mortar electrolyte to the cathode site. The electrons return to the anode site as electrical current,

Figure 4. Corrosion timeline: These charts illustrate corrosion activity and deterioration of certain elements of the building within their service life.

Figure 5. Cathodic protection schematic.

creating a full circuit. This reaction is the basis of cathodic protection, whereby the corrosion cell is controlled, thus limiting damage to historic building fabric and providing a life extension to steel-frame structures.

The accumulation of corrosion scale damages the exterior masonry cladding where the tensile forces of the corrosion are greater than the masonry can withstand. Prior to large-scale losses and cracking, minor damages become apparent, such as hairline cracking and open joints.

For masonry clad buildings, Impressed Current Cathodic Protection (ICCP), which utilizes an external power source (versus a galvanic system), is the only suitable electrochemical technique to afford protection to the embedded steel.

Impressed current systems are permanently embedded while galvanic systems are ephemeral in nature, based on the consumption rates of the metallic alloy consumed. For ICCP systems to be effective, the anodes are installed within the masonry and mortar back-up material, known as the electrolyte, and current is passed through the conductive medium. The anodes are never directly in contact with the steel or there will be a short circuit.

stonework and the mortar joints of brickwork. Theses anodes are installed using a specialized cathodic-protection grout, which is then pointed over with traditional masonry pointing techniques. During installation, all anodes are installed and interconnected with a Titanium feeder wire. The anode wiring is then terminated at the positive terminal of the DC power supply unit.

As all exterior components are installed within the backup and never through the façade stone, the particular advantages of this system are: • The anodes are not visible.

• Anodes can be installed using standard grouting and masonry pointing techniques at the time of external repairs.

• Anodes are usually situated parallel to beam and columns.

• There is minimal internal disturbance.

Cathodic Protection Materials

Monitoring Cells

The requirements for an ICCP System for historic masonry construction include the following components:

Reference electrodes which measure the steel potential are permanently embedded as part of the system. All systems require performance evaluations according to the National Association of Corrosion Engineers (NACE) and the British Standards European Norm (BSEN) standards.

Anodes The most suitable anodes for ICCP in a historic steel frame building are discrete rod anodes. These are most often titanium with a mixed-metal oxide coating. Expanded mesh probe anodes with integral ballast resistors are particularly useful for insertion into the backup masonry at the fine jointing of

Cathodes While anodes are installed to provide electrons to the steel, the areas of the steel frame targeted for treatment become the cathode.

Wire connections to the steel frame provide a return path to the power supply unit, as the negative portion of the circuit.

Power Supplies All external wiring is brought into the building and routed to the power supply units (PSU) or where most suitable for the

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structure. PSUs are generally placed on the interior of a building in a maintenance closet, drop-ceiling space, or basement.

PSUs or transformer rectifiers (T/Rs) utilized in steel-frame cathodic protection require finite control of current output and voltage limitation.

The systems require so little current to polarize or protect the steel that there must be adequate control measures to ensure that over-protection and hydrogen embrittlement do not occur.

A schematic is provided in Figure 5, showing the layout of a system in a masonry-clad, steelframe building. The rod anodes are attached to the [+] of the power supply (red), and the steel frame (cathode) is connected back to the [-] of the power supply.

Track Record The first cathodic protection (CP) system for the prevention of steel corrosion in a masonry structure was designed by Taywood Engineering Ltd. and completed in 1991.

The CP system provided protection for the entrance colonnade of the Royal College of Science, Dublin. The entrance colonnade is a limestone structure containing two parallel structural I-beam members. Since its completion in 1991, regular remote monitoring via embedded reference electrodes has shown no corrosion problems. This has also been confirmed via annual visual inspections. Since the development of this first CP system for masonry, over 150 systems have been designed and installed for masonry buildings in the UK. In the United States (US), the first full scale application was installed in 2004 to the façade of a prominent historic Chicago department store, which was built in multiple phases from the late 1800s to the early 1920s. Today, at least 20 of these systems exist in historic steel frame buildings in the US (Figure 6).

Conclusions

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

Figure 6. Completed system on steel frame buildings.

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Since the 1990s, corrosion diagnostics and ICCP has been used on hundreds of heritage buildings. These systems have shown the possibility of protecting full-building façades from imminent corrosion related deterioration for listed and land-marked buildings.

Where ICCP has been installed, it has been found to have a cost saving in excess of 50% in comparison with traditional repairs which require the removal of masonry, treating the steel, and reinstating or replacing masonry units. Additionally, the cost of ICCP is usually in the range of 10% of the overall exterior envelope repair scope.

The following conclusions can be made from the brief discussions presented: • Steel-framed buildings constructed prior to 1940 are prone to corrosion related problems such as the cracking and displacement of masonry.

• Impressed current cathodic protection systems have been shown as an appropriate method of repair for the prevention of corrosion in early 20th Century steel-framed buildings.

• Cathodic protection systems for masonry-clad steel-framed buildings require a specialist’s knowledge of historical construction techniques.

• A corrosion survey with in situ trials is necessary prior to moving forward with a design.

• The overall investment in a longterm corrosion mitigation system provides economic incentive to a proactive approach.

• The loss of historic masonry and façade damage can be minimized with a proactive, long-term repair strategy.

• ICCP is specifically tailored to each building.

• ICCP adheres to preservation and conservation guidelines.

The design life of the systems range from 25 to 50 years; this is dictated by the power supply technology and internal wiring systems. While the design life of the anode and titanium wiring can exceed 50 years, based on the amount of current passed, the design life of the control systems will change as rapidly as technology allows.▪

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

A

t the early stage of building design, most architectural designers start with functional block schematic floor plans and the structural floor system.

The selection of the floor system is one of the most important considerations in building design.

Each alternative demands a certain depth, which results in different building floor-to-floor heights.

Lowering this depth allows the amount of materials used – such as exterior cladding, interior walls, partitions, stairs and other non-structural components – to be reduced. In high-rise building construction, it allows extra floors to be added within the proposed building height. On expansion projects, it helps facilitate the need to match existing floor elevations.

Non-Prismatic and Simply Supported Girder In conventional composite steel-concrete floor construction, the beam and girder cross-sections are uniform throughout the length of the members; i.e., they are prismatic members. Figure 1 shows a typical floor framing plan with simply supported beams and girders, which are required to have the maximum moment capacity at mid-span; the required moment capacity near the supports can be much less. This article suggests that making the girder non-prismatic, by reducing its depth near the support to match the beam depth, will provide additional space to accommodate the largest mechanical ducts, thus reducing building floor-to-floor height (Figure 2). It should be noted that only the girders that are above and perpendicular to the ducts need to have their depth reduced; therefore, the number of girders to be modified can be kept to a minimum.

The procedure for designing the girder may be summarized as follows: • Design the girder as a conventional composite member; i.e., select a wide

Non-Prismatic Composite Girders Reducing Building Floorto-Floor Height Sompandh Wanant, P.E., M.ASCE

Sompandh Wanant, P.E., M. ASCE (swanant@co.pg.md.us), is Building/Structural Section Supervisor in the Division of Building Plan Review, Department of Permitting, Inspections and Enforcement, Prince George’s County, Maryland.

Figure 2.

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Figure 1.

flange steel section and determine the required number of shear studs.

• With the length of the reduced section required for the largest mechanical duct, find the bending moment at the start of the reduced section.

• Design the reduced section by selecting the bottom flange plate required; the depth of the reduced section should match the typical depth of the beams.

• Check the vertical shear capacity.

• Check the horizontal shear strength of the concrete slab and provide reinforcement as required. Note that such reinforcement is usually required for thin slabs. The amount of reinforcement also depends on the percentage of composite action (number of shear studs); the higher the percentage, the more reinforcement is required.

Serviceability Requirements The deflection formulae for non-prismatic members (reduced depth at both ends) subjected to uniform load and concentrated loads have been derived and shown in Figures 3, 4 and 5 respectively. Notation is defined as follows:

Figure 3.

Figure 4.

Figure 5.

I1 = Larger moment of inertia at center portion of the beam/girder I2 = Smaller moment of inertia at both ends of the beam/girder k = I1 / I2 > 1 b = Distance from support to the point where stiffness changes from I1 to I2 w = Uniform load; P = Point load; L = Span length; E = Modulus of Elasticity In the design example, the girder effective moment of inertia (Ieff) at the full and reduced sections will be determined and used in calculating the maximum deflection.

Section L5 of the AISC Specification for Structural Steel Buildings (ANSI/AISC 36010) requires that “the effect of vibration on the comfort of the occupants and the function of the structure shall be considered. The sources of vibration to be considered include pedestrian loading, vibrating machinery and others identified for the structure.” As in any floor system design, the vibration characteristics of the floor system – i.e., the natural frequencies and the amplitude/acceleration due to certain appropriate dynamic loading – must be evaluated and satisfied. Refer to AISC Steel Design Guide #11, Floor Vibrations Due to Human Activity, for further information and the design procedure.

mechanical and structural engineers. The layout of large mechanical ducts and other utilities must be defined on plans and sections in order to eliminate conflicts, and to take full advantage of the additional space created. It should be noted that the largest supply air duct originates from the mechanical vertical chase and, run horizontally, can usually be reduced in size along its length. This, in turn, may eliminate the need to reduce the girder depth near the end of the duct.

dead load = 47 + 5 + 5 = 57 psf. With reduction per IBC Section 1607.10.1, live load = (80 + 15) [0.25 + 15 / (2 × 10 × 30)1/2] = 82 psf. W14×30 with (33) ¾-inch diameter shear studs will satisfy the design loads.

Design of composite girder: Assumed weight = 60 plf, dead load = (57 × 10 + 30) × 30 = 18,000 pounds, live Load = 82 × 10 × 30 = 24,600 pounds. Reactions: RDL = 18.0 + (0.060) (30 / 2) = 18.9 kips, RLL = 24.6 kips, RTL = 18.9 + 24.6 = 43.5 kips. Moments: MDL = 18.0 (10) + (0.060) (30)2 / 8 = 186.7 kip-ft, MLL = 24.6 (10) = 246.0 kip-ft, MTL = 186.7 + 246.0 = 432.7 kip-ft. Try W24×55, calculate composite section properties: b = L/4 = 30 × 12 / 4 = 90 in, n = E s / Ec = 11, A ctr = b × t0 / n = 90 × 3.50 / 11 = 28.64 in2, yb = [28.64 (23.6 + 2 + 1.75) + 16.3 (23.6) / 2] / (28.64 + 16.3) = 21.71 in, Itr = 3,891 in4, Str = 3,891 / 21.71 = 179.2 in3, St = 3,891 / (23.6 + 2 + 3.5 – 21.71) = 526.5 in3, Vh = 0.85 × 4 × 3.5 × 90 / 2 = 535.5 kips or Vh = 50 × 16.3 / 2 = 407.5 kips, Seff = 432.7 × 12 / (0.66 × 50) = 157.3 in3, Vh´ = [(157.3 – 114) / (179.2 – 114)]2 × 407.5 = 176.9 kips > 0.25 (407.5) = 101.9 kips (OK), Ieff = 1,350 + (176.9 / 407.5)1/2 (3,891 – 1,350) = 3,024 in4. Allowable horizontal shear, q = 13.3 × 0.88 = 11.7 kips. Number of shear studs required for half span = 176.9 / 11.7 = 15.1, minimum required = 2 × 16 = 32 total.

Moment at reduced section: At 6 feet from column center line, MbDL = 112.3 kip-ft, MbLL = 147.6 kip-ft, MbTL = 259.9 kip-ft. At the reduced

Design Example

Design a typical interior composite girder for an office floor with a bay size of 30 feet × 30 feet and live load of 80 psf throughout for the flexibility of future corridor arrangements. The girder depth must be reduced to match the beam depth at one end (or both ends as required), the shallower depth beginning at a distance of 6 feet from the column centerline (Figure 6, page 20).

The governing code is the 2012 International Building Code (IBC). Assume shored construction to minimize the design calculation.

Given: Floor framing as shown in Figure 1, with column line dimensions of 30 feet × 30 feet. Concrete: 3.5 inches, 120 pcf lightweight concrete, f´c = 4 ksi. Composite steel deck: 20-gage, 2-inch deep. Structural steel: Fy = 50 Team Coordination ksi. Live load = 80 psf, partition load = 15 psf, Design team coordination is essential, MEP = 5 psf, miscellaneous allowance = 5 psf. particularly between the architect and the Concrete and steel deck weight = 47 psf; total STRUCTURE magazine

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section, the steel girder depth is 14 inches; try ¾ inch × 7 inches bottom flange plate to match the W24 flange width. Determine the composite section properties in similar fashion as before: Ix = 452 in4, Sx = 75.1 in3, A s = 13.85 in2. For composite section: Yb = 13.93 inches, Itr = 1,771 in4, Str = 1,771 / 13.93 = 127.1 in3, Vh = 50 × 13.85 / 2 = 346.2 kips, Seff = 346.2 × 12 / (0.66 × 50) = 94.5 in3, Vh´ = [(94.5 – 75.1) / (127.1 – 75.1)]2 × 346.2 = 48.2 kips < 0.25 × 346.2 = 86.6 kips, Ieff = 452 + (86.6 / 346.2)1/2 (1,771 – 452) = 1,112 in4. Number of shear studs required = 86.6 / 11.7 = 7.4; these studs are to be placed over 6 feet length, therefore the number of studs over half span should be 7.4 × 15 / 6 = 18.5 studs; use 19 studs (38 total).

Vertical Shear: fv = 43.5 / (0.40 × 13.25) = 8.21 ksi < 0.4 Fy = 20 ksi (OK).

Horizontal Shear: Check concrete slab reinforcement transverse to the girder span. At girder centerline, horizontal shear capacity provided = (19 × 11.7) / 15 = 14.8 kips/ft. Therefore, at a distance of 4 inches from the girder centerline where concrete slab thickness is 3.50 inches, the shear stress v1 = [14.82 / 2 (12 × 3.5)] × (45 – 4) / (45) = 0.161 ksi, v1u = 1.44 × 161 = 232 psi (combined load factor = 1.44). From ACI 318-11 section 11.6 and Vn = 0.8Avffy + AcK1, Avf = 0.095 in2, so use #3@12 inches.

Note that AISC 360-10 Commentary section

Figure 6.

I3.2.1 recommends minimum reinforcing area = 0.002 × 3.5 × 12 = 0.084 in2.

Deflections: From Figure 4, k = I1 / I2 = 3,024 / 1,112 = 2.72. ∆LL = 23 (24.6) (30 × 12)3 / 648 (29,000 × 3,024) + 24.6 (2.72 – 1) (6 × 12)3 / 3 (29,000 × 3,024) = 0.46 + 0.06 = 0.52 inch < L / 360 = 1.00 inch (OK). Using the deflection formulae shown in Figures 3 and 4, ∆TL < L / 240 (OK).

Conclusion The above design example demonstrates that by reducing the depth of the girder near its support, and with proper coordination among the design team members, the building floorto-floor height can be reduced. The increase in

girder deflection is very small, and therefore, the effect on the floor vibration is minimized.

The additional cost of the girder fabrication is likely to be less than the savings in cost on the exterior wall and various interior constructions.▪

Acknowledgements The author would like to thank Malee Kaolawanich, P.E. at the Building Mechanical System Branch, Office of Research Facilities, National Institutes of Health, Bethesda, Maryland, who reviewed the article as it relates to the space required for the HVAC system.

He would also like to thank Mike Rosenberger at Cates Engineering, Gainesville, Virginia, for his effort in drawing the figures.

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Historic structures significant structures of the past

W

hen engineers think of cantilever bridges, the Quebec Bridge with its 1,800-foot span and the Firth of Forth Bridge with its 1,710-foot spans come to mind. The cantilever principle in metal originated in Europe and the United States, but examples of cantilevers in wood and stone were found in many countries in the Far East, such as India, Tibet, China and Japan, as well as Norway and South America. The best known are Shogun’s Bridge in Nikko, Japan and the Wandipore Bridge in Tibet, both built in the mid 17th century. Lewis Wernwag built small cantilevers in wood and iron across Frankfort and Neshaminy Creeks outside Philadelphia around 1812 that he called “Economy Bridges.” Albert Cottrell patented and built several cantilevers similar to the Wandipore Bridge in New England between 1840-1860, calling them “Solid Lever Bridges.” It wasn’t until Heinrich Gerber built his cantilever in iron across the Main River at Hassfurt, Germany in 1866 that the merits of the cantilever system in iron began to be appreciated.

John Fowler and Benjamin Baker illustrated the principle of the cantilever bridge in 1887 to indicate how the Firth of Forth Bridge was designed. Working from the left is the anchorage, the anchor span, a tower, a cantilever arm, a suspended span, a tower and another anchor span and anchorage. The arms of the two tower men are in tension with the struts up from their chairs in compression. The counterweights (anchorages) at the ends balance the suspended and cantilever arms. Before this illustration was published, a competition in the 1870s was held for a bridge to span the East River in New York City across Blackwell’s Island. Several men proposed iron cantilevers, including William Petit Trowbridge who originally proposed one in 1868 and again in the 1870s competition. Henry Flad, Charles Macdonald and others submitted designs, but no action was taken.

In 1851, the Lexington & Danville Railroad, with Julius Adams as Chief Engineer, retained

Kentucky River High Bridge First Major Iron Cantilever Bridge in the United States

By Frank Griggs, Jr., Dist.

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

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

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

Firth of Forth cantilever illustration.

John A. Roebling to build a railroad suspension bridge across the Kentucky River for a line connecting Lexington and Danville, Kentucky.

It was clear to Adams that a bridge across this gorge would be the most difficult part of building the 33-mile long railroad. The longest iron truss spans for railroads in the early 1850s were built by Squire Whipple, 147 feet on the Albany Northern Railroad, and by Albert Fink, who built a three span, Fink Truss, each of 205 feet, across the Monongahela River for the B&O. It was also obvious to Adams that, with the turbulent nature of the river and the great depth of the gorge, the required false work for a truss bridge would not be possible at this site. The site selected for the bridge was just west of the intersection of the Dix and Kentucky Rivers. The gorge was described as, The Kentucky River...flows between two walls of limestone rock from 300 to 450 feet highalmost perfectly vertical, and varying from 1,000 to 1,300 feet apart. This canyon is extremely tortuous, and the stream flowing through it is about 300 feet in width at ordinary stages. The maximum rise above low water is 57 feet, and the extreme flood speed observed was eight miles per hour.

After building the towers, anchorages and with wire to spin the cables on site, the company ran out of money in 1855. It wasn’t until 1873 that the Cincinnati Southern Railroad solicited proposals to build a bridge at the same site. C. Shaler Smith, and the Baltimore Bridge Company (STRUCTURE, April 2008) in the first competition, submitted a plan for a five span continuous truss bridge with three river piers in which they assumed points of contraflexure for calculation

Smith erection detail for cantilever span using Roebling’s towers and anchor chains.

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Erection progress showing temporary wood pier and permanent iron pier. Note extra erections diagonals to right of temporary pier.

the opposite shore and the process repeated until the trusses met at mid span. What Smith did can best be told by a contemporary account that appeared in The Railroad Gazette of January 19, 1877, written while the bridge was under construction. It said in part, The viaduct as now being constructed consists of three spans of 375 feet each, resting on the bluffs and on two iron piers, which latter in turn are supported by stone piers, each 120 feet long by 42 feet in width at the base. The iron piers consist of four legs each, and while having a base of 71 feet 6 inches by 28 feet, their longitudinal profile terminates in a point at the top, or rather in a 12-inch pin upon which the truss rests as on a rocker. The entire pier is a complete structure within itself and can be rolled about on the masonry, the pedestal resting on double roller beds for this purpose.

The truss itself is, during erection, a continuous girder of the Whipple type; but after erection it will be converted into one continuous girder 525 feet long, projecting at each end 75 feet over its points of support, and carrying from each of these cantilevers a 300-foot span, which bridges the distance from the end of the cantilever to the bluff. It was necessary to make the bridge a continuous girder in order to raise it without false-work; and the hinges were obligatory because the rise and fall of the pier from thermal changes will amount to fully two inches, and would vary the strains hourly in a true continuous truss. The truss

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is 37.5 feet deep and 18 feet wide, and each bay is divided into 20 panels of 18.75 feet each. All connections between ties, posts and chords are hinged on pin connections but the chords are riveted to each other throughout, with the novel addition that the pin carrying the tie bars is forced into the chord splice by hydraulic pressure, and thus does duty as a rivet.

After the bridge seat was cut out of the cliff, the end posts were set up and the first section of bottom chord laid in place, each chord being continued back to the rock by a large screw jack placed between its rear end and the face of the bluff. Then the top of each end post was bolted back to Roebling’s towers by anchor bolts, which has a screw adjustment… continued on next page Software and ConSulting

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purposes. The problem with continuous trusses was the danger of unequal settlement of the piers and that temperature changes could place large stresses on the bridge members. In addition, it was difficult to purchase iron with a constant modulus of elasticity that was necessary to make the required calculations. Flad & Pfeiffer, a firm from St. Louis, submitted a plan for a continuous girder bridge with the chords cut following the plan adopted by Gerber. In the second round of submittals, a number of meritorious plans were presented; the one finally accepted was that prepared by Smith for a cantilever bridge, erected as a continuous truss, in wrought iron erected by a new and novel method using Roebling’s towers as anchors.

Thomas Lovett, the Chief Engineer for the Cincinnati Southern, decided that there should only be two piers on the banks of the river, 375 feet apart and set 375 feet from the abutments. Smith chose to utilize Whipple Double Intersection Trusses and to run the trains on the top chords of the trusses.

Smith cantilevered the first 196 feet 10 inches of his trusses out from the abutments to temporary wooden piers. This was unlike Eads who, at St. Louis, had built temporary wooden towers on the tops of his piers and extended iron bars from the top of the towers down to the deck to support cantilevered arch segments until they met at mid span.

Given the height of the piers and length of span, Smith could not use this process.

He chose to place a heavy beam built up of 12-inch x 12-inch oak timbers, in 11 rows and 11 columns, approximately 40 feet long, across the backs of Roebling’s columns. He then drilled six holes on each side through the timber on the line on each truss and inserted 4-inch diameter bolts with one end threaded and the other end with a forged eye. He then connected the bolts to a series of eight 7-inch x 11/4-inch anchor chains salvaged from Roebling’s anchorages. Using the links, he extended a chain to a connection at the end of the top chord of the trusses.

In order to have the cantilever arrive at the proper elevation when it reached the temporary piers, he simply adjusted the nuts at the ends of the bars, and used jacks, braced against the abutment rock, to push against, or relax, the ends of the lower chord. After the trusses reached the temporary pier, they were adjusted for elevation with jacks and then extended to a permanent iron pier 375 feet off the abutment.

From that point, they were cantilevered another 187½ feet to mid span of the river span. The erection process, the temporary wooden pier was then reused and moved to

It will readily be seen that with these connections once made the structure could be built out panel by panel until the limit of strength of the anchorage bolts or of the top chord or the available resistance of the Roebling towers had been reached. This last was the governing factor, and the other parts were proportioned to suit accordingly…

The next flight was to the permanent pier, 178 feet 2 inches. When the span left the bluff the iron pier was started upward from the masonry, and the two met in mid-air, the working force of each arriving at the point of junction within two hours of each other. The weather was cold and the span short, owing to the compression of the lower chord and the effect of temperature; but this had been foreseen, and the huge pier weighing 400,000 lbs. was moved on its rollers toward the span until the pier that connects the two could be put in place. This done the truss was built out as before until the middle of the river was reached…

The last operation will consist in taking out the bottom chord pins in the fourth panel north and south of each pier in arbitrarily and without ambiguity the strain in all parts of the truss in order that there may be no double action at the hinging points, both web systems are concentrated into one in the two panels adjoining the point at which the chord is cut [note this article was written before the bridge was completed]…

Altogether, in the novelties introduced in both construction and erection, and in strict adherence to theory throughout, this great viaduct-the most important in the world in regard to length of span in connection with its height-is probably unsurpassed by any similar work now existing.

Once the span left the temporary wooden tower’s additional diagonals, with inclinations towards the permanent iron pier were placed as “the diagonal tension members of the trusses slope toward the abutment, and consequently give no support for erection purposes. To erect this section of the trusses, use was therefore made of false diagonals. These were 4 x 7/8-inch iron bars, with end pinholes, and were slipped over the pins outside of the permanent diagonals. Two bars were used on each side of the chords, the pins being extended to provide for their use.” Once the permanent pier was reached, these bars and the temporary wooden piers were removed and moved to the opposite shore and reused. As is the case in any bridge erected by cantilever methods, the truss

Bridge erected to mid-span awaiting erection from opposite shore. Note extra diagonals removed when temporary pier was removed.

Bridge complete with locomotive and Roebling towers.

Lindenthal’s Bridge being built around Smith’s 1911.

members had to be sized to handle erection loads, dead plus traveler, as well as operational live and dead loads.

The official load test on the bridge was conducted on April 20, 1877, with the greatest deflection less than two inches. It was not formally dedicated until September 17, 1879, when President Rutherford B. Hayes and General William T. Sherman were in attendance. The Railroad Gazette finished its coverage of the bridge by stating, “the whole work was carried out very successfully, and reflects great credit upon the engineer, Mr. C. Shaler Smith, who designed the work, and the Baltimore Bridge Company, which executed it.” The bridge cost $404,373.31 and used 3,654,280 pounds of iron. It was estimated that an additional 40,000 pounds of iron was required as the result of building the bridge by the cantilever method.

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What Smith had done, with the assistance of the Edgemoor Iron Company of Wilmington, Delaware, was to develop an entirely unique design and construction technique, and to implement this “novelty” in bridge building over a river that was 275 feet below. In addition, he built the entire iron superstructure in four months and four days in the middle of a Kentucky winter.

The Railroad Gazette wrote the bridge parts went together, “like a Springfield musket.”

Smith went on to build major cantilevers over the Mississippi and St. Lawrence Rivers. The first cantilever to use a central suspended span was by C. C. Schneider across the Niagara River in 1883. In 1911, Gustav Lindenthal built a steel bridge around Smith’s bridge at a higher level that still serves.▪

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BINGHAMTON UNIVERSITY ENERGY R&D BUILDING This is the first article in a two-part series and highlights the development and design of the building.

The second article will be presented in a future issue and will focus on the fabrication and erection.

By Chris Latreille, P.E.

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new 105,000-square-foot Energy R & D building is currently under construction at Binghamton University in Binghamton, New York. It represents one of a series of laboratory research facilities planned for the university.

This $45 million research facility will house physics and chemistry programs focused on energy technologies of the future.

The extensive use of curved, round HSS members as a structural framing system and the primary visual components of the architecture are what makes this project unique. Use of BIM was essential to creating and visualizing the many complex shapes needed to model each element and produce the Construction Drawings. Autodesk Revit was used as the BIM platform.

The building consists of four distinct programmatic components (Figure 1): two laboratory Pods, an Atrium between them, and a Link rotunda structure that connects the new facility to the recently completed Center of Excellence (COE) to the east. Laboratory Pods D and E continue the research block programming of the COE, which houses Pods A through C. The design and construction of the building is broken up in to two phases; the first is the majority of structure and the second is the architectural fit-out, exterior skin, MEP systems, final site design, and landscaping. Phase 1 construction is mostly complete and should be finished during this summer, 2015. Phase 2 will commence in late summer 2015 with a targeted completion in late 2016.

The building is steel-framed and has a full concrete basement. The foundations consist of concrete spread footings bearing on glacial till.

The three-story Pods form the largest features of the building and consist of conventional steel framing and composite slab construction. The Pods are braced by moment frames in each direction, and portions of the first floor for each Pod were designed for floor vibrations due to human activity. Pod D and the Atrium are 7 feet higher at each level than Pod E. Pod D is also offset 45 degrees with respect to Pod E, creating the triangular-shaped Atrium that separates them.

Atrium Roof The use of curved round HSS began in the Atrium. The Architect modeled a fan-shaped space with a mono-sloped roof between the Pods. This clerestory space is tall on the east side and slopes down almost 30 feet to the west. The roof is symmetrical about a centerline running east to west, and the north and south edges of the roof splay out at an angle of 22.5 degrees along the walls of each Pod. One of the Architect’s initial goals was to expose a structure that would create visual interest from both the interior and exterior. The desired openness of space ruled out the use of numerous columns and diagonal bracing for lateral resistance. The Structural Engineer (SE) STRUCTURE magazine

Figure 1. Key plan.

Figure 2. Revit rendering of full atrium roof.

could only locate one line of columns at the interior of the Atrium.

The Architect envisioned the rest of the columns supporting the east and west ends of the roof to be exterior to the glass window walls with large roof overhangs beyond the glass façade.

Based on these criteria, it was evident that a structure consisting of moment frames for lateral resistance was needed. The geometry was created in Revit using round HSS. The idea behind the development of the geometry was an organic theme that fits with the “smart energy” initiatives of the facility. The Architect stipulated the guiding principles and overall massing of the space for the design, while allowing the SE the freedom to develop the structural concept and geometry based on the vision of his aesthetic and the SE’s knowledge of what is structurally feasible.

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Figure 3. Revit rendering of Link rotunda.

The framing layout consists of purlin trusses supported by girder trusses or “spine trusses”. Both types of trusses consist of a straight top chord and curved bottom chord. The web members consist of doublecurved round HSS giving the appearance of a series of wishbones, which led to the predictable nickname “wishbone truss.” The web members are separated by 8 inches, center-to-center at connections to top and bottom chords (Figure 2). This was done for appearance but also to eliminate highly skewed intersections of web members and complicated welding. The web members intersect the chords at 90 or near-90-degree angles and are separated enough to allow for all-around welding. Welding was preferred early on for appearance but also for transfer of large forces, particularly at chord members.

The top chords of the spine trusses frame over the tops of the columns, and the curved bottom chords intersect with the shafts of the columns below the top. This was done to simplify the connections and to create the necessary frame action needed for lateral resistance. The purlin trusses are top chord bearing with discontinuous bottom chords.

From a design perspective, the trusses function as modified Vierendeel trusses and each web member must accommodate bending, axial, and

shear forces. Since the members are curved, the axial forces also induce additional bending away from the connections to the chords. An elevation was created for each truss profile in Revit, and the wishbone members were modeled with splines and adjusted using detail lines laid out with the desired geometry. The spine trusses at the center of the Atrium were the starting point for spacing and sizing the wishbones, and locating purlin truss bearing points. The geometry of the spine trusses along the Pods was determined using similar triangles based on the 22.5 degree offset. Luckily the symmetry of the space allowed for a lot of mirroring, which reduced modeling time. More purlin trusses were required at the west side of the Atrium due to longer spans and drifted snow loading.

The sequence of analysis included exporting the Revit truss profiles to AutoCAD in order to locate four or five nodes along the length of each wishbone web member. The AutoCAD geometry was then exported to RISA 3D to perform 2D analysis to get initial member sizes based on gravity loads. The profiles were then assembled into a RISA 3D model for the entire structure, including the columns. The final model took about three hours to run all of the load combinations.

There are 10 columns that support the Atrium roof. Each has struts that are double-curved, similar to the web members of the trusses.

The struts or “branches” intersect with the top and bottom chords of the trusses, providing vertical support and also enhancing the frame action and stiffness of the system. It is no surprise that the nickname “tree column” was born.

The truss connections are generally all welded. However, six of the ten tree columns, eight purlin trusses, and portions of the spine trusses are outside of the building envelope. Welded joints at the envelope boundary would create large thermal bridges which, if nothing else, seemed contrary to the spirit of a “Smart Energy” facility. As such, custom bolted splices were designed and detailed that utilize thermal isolation material (TIM) and stainless steel bolts. The roof deck is also broken at the envelope boundary and utilizes similar connections to reduce thermal bridging. This technology was used at other locations in the Pods and Link. Hot-dip galvanizing was specified for all steel outside of the building envelope.

Link Rotunda The 40-foot-diameter rotunda continues a theme prevalent at other buildings on campus. However, this one is unique in that it is supported by a single 4-foot-diameter concrete column below the floor and a single 18-inch-diameter round HSS tree column above extending to the roof. The branches of the tree column are double-curved, similar to the tree columns in the Atrium. They are set at two elevations using two different round HSS sizes and are offset in plan by 45 degrees.

The branches of the columns primarily carry gravity loads for the floor and roof at each level, but also provide frame action to resist lateral drift. Lateral drift was a concern in design since lateral deflection in the column is magnified as vertical deflection in the floor and roof framing. It was necessary to analyze the rotunda as an inverted pendulum structure due Figure 4b. FEM results from RISA 3D.

Figure 4a. Structural detail of Link collar.

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Figure 5. Revit rendering of Tree Stair.

Figure 6. Revit rendering of east entrance canopies.

to the lack of redundancy with the single column support. As such, the seismic forces used for design were three times higher than other parts of the building due to the reduced response modification factor.

Part of the solution for controlling deflections was to create a hub of moment connections for all beams framing into the tree column at the roof and floor. Even though the branches carry a large amount of vertical load, the moment connections reduced the hinge effect at the hubs producing lower deflections.

The framing for the Link connects into the northeast corner of Pod D, which is structurally isolated from the rest of Pod D above the first floor. This corner consists of a stair with a concrete wall running up through the middle between flights and a concrete elevator shaft.

These concrete elements provide the rest of the lateral resistance for the Link. The stair stringers form drag struts connecting the Link floor and roof framing to the concrete walls. There is another expansion joint northeast of the rotunda, and a small bridge connects back into Pod C of the COE building.

The tree column for the Link is interior, and the concrete column below is exterior. A large TIM plate was detailed between the leveling plate and base plate to reduce thermal bridging. The connection of the branches for the interior steel column are similar to the Atrium. Connecting the steel branches to the concrete column proved challenging since the connections are structural and are exposed. Several options were considered, including individual embedded plates for each branch and embedding the bottom section of the round HSS in the concrete. However, it was determined that the individual plates would have been difficult to place and secure, and there was also concern about the logistics of building forms and consolidating concrete around all faces of an embedded branch member while avoiding chips and spalling. The solution was a custom galvanized steel collar embedded in the concrete column at two levels to support the two offset sets of curved branches that are welded to it. The collar is connected with internal tie plates and skewed reinforcing plates for areas of high stress.

The branches serve a similar dual purpose of carrying gravity loads from the stringers and landing framing while providing frame action to laterally brace the entire stair system.

Exterior Canopies The canopies are the only ornamental steel component relegated to Phase 2. There are a total of four canopies; two at the main (east) entrance of the Atrium, one at the southwest corner of Pod E near the Tree Stair, and one at the northwest corner of Pod D for an exit.

The canopy steel mimics the organic theme of the Atrium and Link rotunda, incorporating wishbone elements and tree columns.

The canopies are structurally separate from the building wall and are supported by only two columns each. The structural steel for the canopies will be highly visible from all vantages as they support large sheets of 1-inch-thick glass as the roof deck. Hot-dip galvanizing was specified for all canopy steel.

For the Structural Engineer, the design and development of these unique components was a rare opportunity to balance form and function while staying true to the mission of the research goals of the facility. The Binghamton University Energy R & D Building will be a welcome addition to the campus.

Stayed tuned for Part 2.▪

Tree Stair The southwest corner of Pod E features another prominent entrance that is highly visible from the adjacent road. To provide continuity with the aesthetic of the Atrium and the Link rotunda, the design team decided to incorporate another structural tree element into the two-story staircase at the entrance.

The stair stringers consist of HSS rectangular members supported by floor framing at each floor. At the intermediate landings, a single, round HSS tree column provides support for the landing and stringers.

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Chris Latreille, P.E. (clatreille@ryanbiggs.com), is a Principal Associate with Ryan Biggs | Clark Davis Engineering and Surveying, P.C., and works in the firm’s Finger Lakes office in Skaneateles Falls, NY. Chris has provided the structural design of educational facilities, medical buildings, concrete repair projects, and contractor support service projects.

Project Team Owner: Binghamton University, Binghamton, NY Structural Engineer: Ryan Biggs | Clark Davis, Engineering and Surveying P.C., Skaneateles Falls, NY Architect: William Hall, Binghamton University, Binghamton, NY General Contractor: Fahs Construction Group, Binghamton, NY Structural Steel Fabricators: Schenectady Steel, Schenectady, NY and JPW Companies, East Syracuse, NY

August 2015

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Pushing the Boundaries of Timber Design

By Holger S. Schulze-Ehring, Dipl.-Ing., SIA, Filippo Masetti, P.E. and Matthew H. Johnson, P.E.

The China Pavilion for exPo Milano 2015 Figure 1. Rendering of the pavilion. Courtesy of Studio Link-Arc.

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andmark projects often develop from visions that push boundaries of modern design, forcing designers to think creatively and innovatively. Expanding on the World Expo Milano 2015’s principal theme, Feeding the Planet – Energy for Life, the China Pavilion, designed by Tsinghua University and New York based architecture firm Studio Link-Arc in collaboration with structural engineer Simpson Gumpertz & Heger, centers on ideas of sustainability and the coexistence of nature and cityscape. Its sustainable aspiration presented a challenge and inspiration to architects and engineers alike. Close collaboration and a holistic approach to architecture, engineering, and fabrication enabled the vision of an almost floating wavy timber roof signature structure to be realized (Figure 1).

Engineering Informed Architecture

intersects with the longitudinal, mostly straight discontinuous purlin members at regular intervals, creating an evolution of the diagrid, a three-dimensional orthogonal system with moment connections in each primary member axis. This timber structure, utilizing bi-axial moment connections for each orthogonal member connection, is reinforced by substituting exposed steel members of equivalent size and at distinct locations which act as collectors for the long-span diagrid elements.

Several materials and material combinations were considered for the roof structure. The long spans and cantilevers, the complex geometry, the continually varying elevations, and the visual exposure of the structure provided a particular structural challenge; glue-laminated timber (glulam) was selected for strength and stiffness requirements, geometric flexibility, and aesthetics. Glulam members are typically manufactured in standard sizes, but can be custom fabricated into a wide variety of shapes and sizes. The configuration of the laminations allows for complex curved geometries without greatly compromising strength and stiffness. The radius of curvature is limited to roughly 3.3 feet (1 meter). To achieve such a small radius, the laminations must be relatively thin, which can increase cost. If the radius of curvature is roughly 4.4 feet (1.33 meters) or greater, standard 1-inch (25 millimeters) thick laminations can be used and the cost greatly reduced (Figure 2).

While sharp-edge angled timber rafter members, resembling a large city skyline, shape the back of the pavilion’s roof, gentle, soft and curvy waves forming the profile of a rolling landscape define the front.

Promoting the coexistence of city and nature, these inherently opposing profiles are merged by longitudinal timber members connecting cityscape and landscape to create a ruled surface in between them.

An array of parallel rafters forms this gradual transition; sharp angles dominating the roof ’s back end are progressively eliminated, allowing the curved portions of the rafters to become predominant towards the front. The rafters, spaced at 6.5 feet (2 meters) on center, and each following a curved line with varying radii, are different in overall shape. The varying curvature of the rafters results in unique shapes for each parallel timber member.

Overall, a rafter-and-purlin solution forming a timber grid system defines the roof ’s major concept and geometry. The array of parallel but curved continuous rafters Figure 2. Roof skeleton and deformation contours.

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Figure 3. Wood member in extreme curvature.

Tradition and Innovation in Detail Key to the successful execution of significant timber structures is the detailing. Extensive timber engineering knowledge founded on firsthand experience, paired with the team’s drive to innovate and think creatively, led to unique customized detailing that responded to the distinct challenges of the three-dimensional timber grid structure.

The radical geometric form of the structural members plus the very nature of the glulam material (i.e., its orthotropic structural properties and behavior) represent key factors to be understood, considered, and incorporated into the design and detailing. Specific wood-design considerations became paramount through the development of the roof structure including the careful design and detailing of intersections, connections, and bearings, as well as the design of glulam members with extreme curvature.

Extremes in Curvature

engineering-mechanics principles: the free-body diagram of a curved member subjected to a bending moment requires both circumferential and radial stresses for the free-body to remain in equilibrium.

This is a well-known effect covered in several design standards including the American National Design Specification® for Wood Construction (NDS®) and the Eurocode for wood design (EC5), which have been used to estimate radial stresses in extreme curvature regions, such as the peak of the undulated front rafters.

Due to its orthotropic nature, glulam’s characteristic tensile strength for radial stresses perpendicular to the fibers of the laminations is only 72 pounds per square inch (psi) (0.5 megapascals); this is a very small fraction of the material’s strength for stresses parallel to the fibers and is insufficient for locations of extreme curvature of the rafters. The issue was addressed through a series of long, stainless steel, self-tapping screws, designed to be installed along the radial direction, to resist high radial stresses in regions of extreme curvature. The spacing of the screws diminishes as the radius of curvature decreases (Figure 3).

Detailing Rigidity Providing sufficient stiffness to the overall roof system in the two orthogonal directions became paramount to limit member sizes and shapes in line with the designers’ vision and led to the design of semi-rigid momentconnections at the rafter purlin interfaces. Considered key parameters are the achievable bending strength and stiffness in the two perpendicular directions (i.e., strong- and weak-axis bending). Following intensive research of literature on the topic (see the online version of this article for detailed references), several moment connection types were considered and evaluated in detail, including steel fin plates, serrated surfaces joints, friction welding, embedded and bonded steel plates, through-bolting of cross-laminated wood members, and embedded steel rods with end plates.

Steel fin plates embedded in adjoining wood members and connected to the glulam member by steel bolts provided the most direct load path. However, even when strengthened with an array of self-tapping screws installed perpendicular to the wood grain, these connections did not achieve the required level of moment-resistance and stiffness due to stress concentrations at the bearing surfaces around bolt holes.

Serrated surfaces, when clamped together by steel bolts, eliminate stress concentrations, but experimental results showed this type of connection was not sufficient.

Friction welded wood-to-wood connections work by creating an oscillatory movement between the two surfaces clamped together which, through friction, heats these surfaces to allow a thermochemical decomposition of the organic material causing it to be “welded” together. Although very innovative and promising, friction welding could not be selected for this project due to constructability considerations as the purlins needed to be field-connected to the rafters and laser welding in the field is not ideal. continued on next page

The design of curved members requires accounting for two phenomena: the peculiar distribution of the circumferential stresses parallel to the member’s longitudinal axis and the creation of radial stresses perpendicular to the member’s longitudinal axis.

In straight members, plain sections (before the application of a bending moment) are assumed to remain plain sections after bending occurs. Thus, as a result of bending, both longitudinal deformations and material strains (i.e. deformations per unit length) at any given fiber of the section are proportional to the distance of the fiber from the neutral axis. In curved members, however, only longitudinal deformations are proportional to the distance of the fiber from the neutral axis. Strains are not proportional to these distances because the fibers, as viewed across member’s depth, are not equal in length. This leads to larger strains (therefore stresses) at the inside (concave) surface of curved beams; the magnitude of these stresses is directly related to the radius of curvature at any particular point of a beam. As the radius of curvature decreases, stresses increase.

In consideration of this phenomenon, during the iterative design process targeted at identifying the roof ’s ideal support points, an overlap and interaction of these inherent stress spikes with potentially coinciding maximum bending moment stresses was avoided.

The creation of radial stresses is another phenomenon of significance that was addressed within the design process. These stresses are a direct result of fundamental Figure 4. Rafter and purlin connection – initial detail and as built.

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Figure 6. Interior view of long span structure.

placement of the purlins over through-steel rods protruding from the already-erected rafter.

During the pre-construction phase, due to considerations about procurement and lead times and as a result of fabricator specific detailing and fabrication preferences and associated value engineering, the design team decided to relax the established dimensional limits on the depth of the rafters and purlins. The increased member sizes allowed for more flexible purlin-to-rafter connections which became achievable with a simplified embedded steel fin-connection and custom fit steel bolts (Figure 4).

Bearing Figure 5. Roof support bearing detail.

The selected connection detail addressed constructability concerns as well as strength and rigidity demands of the overall roof structure. The purlins are connected to the rafters through embedded, glued, high-strength steel rods connected to steel end plates. A specific resin was specified along with proper embedment lengths and spacing of the rods to establish the desired rigidity for the connection (Figure 4, page 31). The proposed connection limits stress-concentration effects, sufficiently strong, provides the desired bi-axial rigidity, and ensures fast assembly in the field. The end plates are connected to the purlins during fabrication in the shop, and include a second steel plate with an offset to allow field STRUCTURE magazine

The geometrical location of the roof structure supports was the result of extensive studies, but was far from being the finish-line of the design.

In fact, complex geometry and several constraints in the number and position of the roof supports lead to fairly high reaction forces acting on often-sloped glulam members. A vertical reaction force acting on a sloped section causes longitudinal and perpendicular stresses to the fibers of the laminations. Utilizing the bearing capacity of the wood for the perpendicular component of the reaction, and bolts connected to a steel fin plate (embedded into the member section) to resist the longitudinal component of the reaction, was key to the design of the supports (Figure 5). The introduction of a vertical steel plate embedded through the bottom rafter (the fin plate) interrupts the continuity of the laminations and reduces the capacity of the section. The use of high-strength steel rods brought the section to its original strength.

The rods were envisioned to be installed into grooves cut into the

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Figure 7. Exterior front view of the pavilion.

laminations during construction of the laminated section in the shop, thus allowing for quality control.

The design of these connections also needed to consider (and avoid) the effects of eccentric loading conditions at the reaction points. In fact, the component of the reaction longitudinal to the rafter acts along the centroid of the section, while it is resisted below the rafter, at the interface with the top of a steel column. This configuration creates an arm between reacting forces, and secondary moments may be introduced in the section. A series of slotted holes for the bolts was used to achieve pinned connections to bypass the additional stresses caused by this configuration in the already highly-stressed rafters.

Finally, the volume changes that wood undergoes when subjected to variations in its moisture content was an important consideration.

As moisture content increases, wood tends to swell; when moisture content decreases, wood tends to shrink. Steel is not subjected to this phenomenon, and undesirable effects such as cracking may occur if the difference in the behavior of the two materials is not considered in design.

By limiting spacing of the bolts connected to the fin plate, the total change in length of the rafter between two consecutive bolts was accommodated through the play between the bolt-hole and the shank of the bolt. This allowed avoiding additional local stresses in the rafters.

Aspirations in Timber Modern design standards, fabrication techniques, and research allow pushing the envelope of timber design and achieving signature structures like the China Pavilion for the Milano World Expo 2015 (Figures 6 and 7). The devil sometimes literally lies in the details, and great visions cannot materialize without careful review of the interplay of the most fundamental structural components, connections, and members. When profound design aligns with technical advances in engineering and fabrication, new sustainable opportunities can be showcased, an example for what a pavilion hopes to achieve as an educational facility.▪

Project Team

Holger S. Schulze-Ehring, Dipl.-Ing., SIA, is a Vice President at Simpson Gumpertz & Heger Inc. He can be reached at hsschulze-ehring@sgh.com.

Structural Engineer: Simpson Gumpertz & Heger Architect: Tsinghua University + Studio Link-Arc Architect and Engineer of Record: F&M Ingegneria Timber Manufacturer: Stratex SpA General Contractor: China Arts Construction and Decoration Company + Unique Europe + Bodino Engineering

Filippo Masetti, P.E., is a Senior Staff II engineer at Simpson Gumpertz & Heger Inc. He can be reached at fmasetti@sgh.com.

Matthew Johnson, P.E., is a Principal at Simpson Gumpertz & Heger Inc. He can be reached at mhjohnson@sgh.com.

The online version of this article contains detailed references.

Please visit www.STRUCTUREmag.org.

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Wilshire Grand

By Gerard Nieblas, S.E., LEED AP and Phuoc Tran

Project DescriPtion

In the early development of the design, the structural team studied four lateral-load-resisting systems (with variations in vertical load-carrying systems) and presented them to the Contractor for evaluation and pricing: 1) Steel braced frames in the core.

2) Steel plate shear walls.

3) Concrete core wall.

4) Concrete core wall with outriggers and belt trusses.

A lateral system consisting of a concrete core wall with outriggers and belt trusses emerged as the best option, because it provided adequate lateral stiffness for wind comfort without the need for a tuned mass damper.

The final selection of the structural system was a collaborative effort with the Architect and Contractor to consider cost, ease of construction and schedule.

Ease of construction is somewhat of a misnomer, as this has not at all been an “easy” structure to design or construct. It has many geometric challenges, along with construction tolerances that are tighter than what would be considered the industry standard.

The vertical load-carrying system inside the core wall consists of concrete beams and slabs to accommodate the challenging construction schedule. Outside the core wall, it is comprised of steel box columns filled with concrete (for added rigidity), and steel floor beams and girders with lightweight concrete over metal deck.

The Wilshire Grand in downtown Los Angeles is a 73-story mixed-use office and hotel facility with a surrounding podium. The main tower will offer 900 guest rooms, 400,000 square feet of office space, and various restaurant and retail space. The top of the structure will feature restaurants, bars and a sky lobby overlooking the skyline. The surrounding podium structure will include additional retail and restaurant spaces for a bourgeoning resurgence of the surrounding area. The project achieves LEED Silver certification in the current eco-conscious setting. The new structure is located adjacent to the 7th Street Metro Station, which is a connection point to much of the Los Angeles County rail system.

An article discussing the building’s foundations appeared in the December 2014 issue of STRUCTURE magazine. In February 2015, the construction of the concrete core wall was 19 floors ahead of the erection of steel framing. At the time of this article, the core wall will be constructed to the 56th floor and the structural steel will be at the 45th floor. The construction phase schedule is a critical factor to consider in designing tall buildings.

The tower structure has buckling restrained brace (BRB) outriggers at the lower levels (28th to 31st), the middle levels (53rd to 59th) and the upper levels (70th to 73rd). The structure also has two three-story tall belt trusses around the perimeter, at the lower and upper outrigger levels. These belt trusses help increase torsional stiffness, distribute vertical loads more uniformly around the entire perimeter of the structure, and add redundancy in the gravity-load-resisting system.

BrB selection

selection of structural system Tall buildings in seismically active zones are required to balance both wind and earthquake design considerations. When selecting the structural system for the Wilshire Grand, the building needed to be rigid enough for comfort under service-level wind loads, and yet not so stiff that seismic forces would increase. The design of the structure was thus a balancing act of stiffness, Figure 1. Transverse building strength and mass. elevation.

STRUCTURE magazine

34

The core wall of the structure in the transverse direction is 30 feet wide and nearly 1,000 feet tall (Figure 1). The use of an outrigger system allows overturning forces in the transverse direction to be resisted by a force couple between the perimeter columns, which increases the overturning strength and stiffness of the structure. The outrigger braces at the lower and upper levels span multiple floors. Utilizing BRBs allowed the team to design for a slender brace. In addition, BRBs provide for predictable limits on member and connection forces.

August 2015

Figure 2. Lower outriggers with “Double-Double” BRBs.

Figure 3. Embed plate for lower.

Early in the design stage, the structural team investigated the use of conventional brace elements as part of the outrigger system. These conventional braces were sized based on compression buckling, making them much larger than necessary for the tension forces. This caused the brace connections to be much larger, as well, and increased the tensile demands on the outrigger box columns and the foundation.

This proved to be too heavy-handed a solution.

Therefore, BRBs were selected so that the brace area could be sized based on tensile capacity, since BRBs have essentially the same capacity in either axial direction. This made the connections to the core wall and outrigger columns less demanding, and also made the jamb forces to the outrigger columns smaller. The BRBs serve as a fuse for the vertical wind and seismic jamb forces. They provide a repeatable, predictable load to the foundation via the columns.

There are 170 BRBs in the structure, arranged at three locations along its height as follows: 1) Lower Outrigger – ten “Double-Double” (2x2), 2,200-kip BRBs from the 28th to the 31st Floor (40 BRBs total).

2) Middle Outriggers – ten BRB frames over six stories (53rd to 59th Floor), each comprised of twelve 800-kip BRBs (120 BRBs total).

3) Upper Outriggers – ten single 2,200-kip BRBs from the 70th to 73rd Floor (10 BRBs total).

Figure 4. FEA model for connection at core.

Courtesy of SIE, Inc.

Figure 5. Tekla model for connection at core. Courtesy of Schuff Steel.

lower outrigger BrBs The Lower (Figure 2) and Upper Outrigger BRBs are connected to the core wall with steel embed plates. Shear studs and half-couplers are welded to the back of the embed plates to satisfy the required force demands.

The steel embed plates are up to 4 inches thick and stand over 34 feet tall (Figure 3). Gusset plates are welded to the embed plates to receive the double-pinned connections for the “double-double” BRBs (Figure 4).

Due to the height of the embed plates, the Contractor proposed the addition of a “backbone” plate to allow erection of the embed plate as a single unit from the fabrication shop. The “backbone” plates allowed the Contractor to maintain an aggressive construction schedule by eliminating the need to field-weld multiple plates together to provide the required height (Figure 5). The sensitivity of concrete to heat from the welding of the gusset plates led to the use of electroslag welding with tight tolerances of +/- 3/8 inch for horizontal control of the embedment plate.

SIE, Inc. used a finite element model to analyze and confirm the design of the Lower Outrigger gusset plate connections to the core wall and box columns (Figure 6). continued on next page STRUCTURE magazine

Figure 6. Gusset plates and BRBs installed.

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Gerard M. Nieblas, S.E., LEED AP, is President of Brandow & Johnston Inc. Gerard may be reached at gnieblas@bjsce.com.

Phuoc Tran is a design engineer with engineering, design and CAD production experience in a variety of market sectors: office commercial tenant improvements, mixed-use developments and public works projects. Phouc can be reached at ptran@bjsce.com.

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STRUCTURE magazine

DETAIL @ BOX COLUMN @ LEVEL 53

The structural steel for the building will be substantially complete around March 2016. The scheduled opening date for the hotel and office is the first quarter of 2017. The use of BRBs provided the necessary strength and stiffness in the transverse direction to provide for occupant wind comfort, drift control for wind and seismic, and strain compatibility with creep and shrinkage of the concrete core.▪

View our Solutions page, Managing Bentley® Licenses

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After completion of the structure, the elastic shortening of the steel will be complete except for that associated with occupant live loads. Due to the thickness of the concrete core walls, it will take approximately 50 years for 75% of the concrete shrinkage to occur. As the core wall shrinks and creeps, the BRBs will go into tension.

The Upper Outrigger BRBs (Figure 8) are single 2,200-kip braces, which are sensitive to the differential movement between the shrinkage, creep and elastic shortening of the core wall and the elastic shortening of the structural steel box columns. The structural team conducted an extensive study to approximate the anticipated total creep and shrinkage in the core wall. This included a year-long creep TB and shrinkage testing program of the actual concrete mix used for the core construction, as well as a core construction sequence analysis to evaluate the force transfers based on a construction schedule prepared by the Contractor.

To mitigate the large force transfer due to differential building movements, the BRBs will be jacked with a pre-compression force to 1,000 kips each. This pre-compression in the BRBs will result in a temporary tension force in the exterior box columns. Over time, as the core wall creeps and shrinks, the BRBs will transition from compression to tension, while the exterior box columns will transition from tension to compression.

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August 2015

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Codes and standards updates and discussions related to codes and standards

Large community shelter.

S

ince the industry’s birth in the 1970s, storm shelter protection has risen from dank, dark, underground storm cellars found in backyards to above ground shelters fully integrated into residential or commercial construction. To enforce the proper design of these storm shelters, the ICC 500: ICC/NSSA Standard for the Design and Construction of Storm Shelters was developed. This article focuses on the structural provisions of the 2014 edition of ICC 500, how the provisions differ from typical structural design, the NSSA’s role in the development of the ICC 500, and new storm shelter trends.

Historical Perspective In 2001, the leading professional engineers involved in extreme wind resistant design founded the National Storm Shelter Association (NSSA) and developed the first industry standard to provide guidance for the design, construction, and performance of storm shelters. By establishing design wind speeds, debris impact resistance, and occupancy safety requirements, engineers and architects now had a document on which to rely for sound storm shelter design. The NSSA standard became the foundation document for the ICC/NSSA Standard. First published in 2008, this standard was developed by the ICC/NSSA Consensus Committee on Storm Shelters (ISSTM) that operates under the ANSI-approved ICC Consensus Procedures for the Development of ICC Standards with public meetings and organizations from across the country participating.

By co-publishing the ICC/NSSA Standard and a commentary in development, the NSSA, in partnership with the ICC, continues its leadership position in the storm shelter industry.

The design industry has recognized the importance of occupancy life safety in high wind events by making shelters a mandatory component of certain building types constructed in storm prone areas. The 2015 edition of the International Building Code (IBC), in Section 423, requires

construction of storm shelters in certain Group E, Educational Facilities, and in critical facilities such as 911 call stations, emergency operation centers, fire, rescue, ambulance and police stations in higher wind areas. These shelter designs must meet the ICC/NSSA Standard.

Storm Shelter Performance Requirements

NSSA/ICC 500-2014 Storm Shelter Standard— Structural Provisions

Design wind loads and performance requirements for storm shelters far exceed normal building code requirements. Different failure modes and loadings must be considered since the majority of adjacent non-shelter structures will be destroyed or damaged during an extreme wind event. These include envelope perforation due to windborne debris, collapse of adjacent taller structures onto the shelter, laydown of nearby objects such as trees, signs, or towers that could impact the shelter, and rollover of vehicles or small buildings impacting the shelter. Some failure modes (sliding, overturning, uplift, foundation connection failure, etc.) are similar to those encountered in other structural design.

But with much higher wind load demands, design solutions can be harder to achieve and ensuring a continuous load path from all shelter components to the supporting foundation is paramount.

Storm shelters are required to be designed with the assumption that surrounding or host buildings are completely destroyed, leaving the shelter fully exposed to the wind forces of a storm. If components such as stud framing and roof trusses of the host building are attached to the shelter’s structure, the loads imparted from these elements must be accounted for in the shelter’s design. The 2014 edition of the ICC 500 provides a rational procedure for determining the maximum force that a connected host building element can transmit to a storm shelter. continued on next page

STRUCTURE magazine

39

By Ernst W. Kiesling, P.E., Ph.D., Jason Pirtle, P.E. and James E. Waller, P.E. Ernst W. Kiesling, P.E., Ph.D., is the Executive Director of NSSA since 2001, Research Professor at the National Wind Institute, Texas Tech University and ICC/ NSSA Consensus Committee (ISSTM). Ernst can be reached at Ernst.Kiesling@ttu.edu.

Jason Pirtle, P.E., is the President at Remagen Corporation, Vice President of NSSA and Committee Member for ICC 500 Commentary.

Jason can be reached at jason@ remagensaferooms.com.

James Waller, P.E., is Director of Engineering at Remagen Corporation, and Founding President of NSSA and ICC/ NSSA Consensus Committee (ISSTM). James can be reached at Remagen6@blomand.net.

Design Wind Speeds Design wind speeds found in ICC 500 are based on records of measured wind speeds in hurricanes and estimated wind speeds for tornadoes based on a 10,000 year Mean Recurrence Interval (MRE – the inverse of the probability that the event will be exceeded in any one year). Contour maps are presented in ICC 500 for both tornadoes and hurricanes for the continental U. S. and its territories.

For site-built storm shelters, design wind speeds may be determined using these maps.

For factory-built, or relocatable storm shelter structures that may be installed in any location, the ‘worst case’ design wind speed should be used. These design wind speeds are as high as 250 miles per hour for tornado shelters and 235 miles per hour for hurricane shelters. These elevated speeds can result in wind pressures that are nearly five times as great as the wind pressures typically required for the design of buildings.

Wind-Induced Pressures Wind pressures for storm shelters are calculated using ASCE 7-10, Minimum Design Loads for Buildings and Other Structures. Due to the unique nature of extreme wind event loadings, ICC 500 specifies the variables required to calculate the Main Wind Force Resisting System (MWFRS) and Components and Cladding (C & C) loadings. Values are specified for the directionality factor, exposure category, and topographic factor and guidance is given on selecting the proper internal pressure coefficient, GCpi. Wind-induced internal pressures from winds acting through openings are added to external pressures. Internal pressures have a large effect on the forces acting on the shelter’s structure and its connections to the foundation. Atmospheric pressure change due to the reduced pressure in the vortex of a tornado can also result in internal negative and external positive, or ballooning, pressures.

While significant in tornadoes, atmospheric pressure change is not a large factor in hurricanes where winds are more straight-line in behavior (due to the storms diameter) and somewhat cyclic in nature.

The internal pressure coefficient, GCpi, accounts for these pressure induced positive and negative load changes. The value of this coefficient varies with the ratio of openings to shelter volume or the degree of enclosure as defined by ASCE 7, i.e., whether the building is considered enclosed or partially enclosed.

Small residential shelters are usually designed as enclosed spaces. Community shelters are

Third Party Review, Quality Assurance, Special Inspections, and Structural Observations

Below the garage slab shelter.

typically defined as partially enclosed buildings due to the ICC 500 requirement for the largest operable opening on a windward side of the shelter to be considered open during peak wind speed of the storm.

Testing for Pressure and Debris Impact Resistance The mature field of structural engineering enables analytical approaches to be applied to the wind-induced pressure analysis and design for most storm shelters and their components.

When analytical analysis for wind pressure is not practical, ICC 500 gives requirements and procedures for laboratory pressure testing of walls and roof assemblies, door assemblies, glazing, and impact-protective systems.

Debris impacting the shelter is a major design issue that engineers must consider. Although a substantial science base has been developed for terminal ballistics, such as bullets striking armor plate, much less is known about the impacts of a large variety of wind-borne debris missiles, such as wind-driven lumber or roof decking striking shelter surfaces, doors, vents, glazing, and impact-protective systems.

Therefore, to ensure occupant protection, ICC 500 requires laboratory impact testing of the storm shelter structures and all impactprotective systems.

Extensive and specific requirements are in ICC 500 regarding numbers and locations of debris impact tests that must be performed on storm shelter components to ascertain their suitable performance.

For example, a storm shelter door must be impacted in at least three locations – in a central location, within 6 inches of a corner, and within 6 inches of the main latch. Similar specificity is given for other components. Systems (such as a door system consisting of a door, frame, hardware, and fasteners) must be tested in a configuration as similar as possible to the intended shelter configuration. It is not sufficient to test the components separately to predict performance of the assembled system.

STRUCTURE magazine

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August 2015

The design, construction, and installation of storm shelters are all critical to their performance. ICC 500 requires safeguard checks to ensure quality in each of these phases.

Peer-reviews or independent third-party evaluations are required for community shelters with 50 or more occupants, daycare shelters with 16 or more occupants, school shelters, and shelters in Risk Category IV as defined by the IBC. A Quality Assurance Plan covering quality control issues must be part of design drawings and specifications which are sealed by a design professional, and the contractor must submit a written statement of responsibility acknowledging these special requirements to the authority having jurisdiction, the design professional, and the owner prior to commencing work.

During construction, special inspections are required, many of which are similar to those required by the IBC, with some special inspections added such as on-site inspections to verify the locations and installation of postinstalled anchors in hardened concrete or masonry and verification of the structural adequacy of existing foundations used for shelter support. Community shelter construction also requires structural observations to be performed by a registered design professional during significant phases of construction.

Other Life Safety Considerations Only the structural provisions of the ICC 500 have been covered in this article. The Standard also gives requirements on other life safety issues in shelter design, such as shelter siting, occupancy density, egress, mechanical and natural ventilation, lighting, fire safety, sanitation facilities, locks and latching, and signage, among others.

NSSA’s Role in ICC 500 and the Shelter Industry The National Storm Shelter Association has played a major role in the development and promotion of quality storm shelter design, manufacturing, and construction since its inception. The primary purpose of the association is to ensure the highest quality of manufactured and site-constructed storm shelters for protecting people from injury or loss of life due to tornadoes, hurricanes and other extreme windstorms. The ICC/NSSA

Standard has significantly contributed to the stability and orderly progress of development of the storm shelter industry. NSSA continues to play an important role in development of the ICC/NSSA Standard by being represented on the ICC/NSSA Consensus Committee on Storm Shelters (IS-STM). NSSA members are participating in development of the ICC 500 Commentary, whose development cost is also sponsored by the NSSA.

New Storm Shelter Trends Under the guidance of the ICC/NSSA Standard, a remarkable variety of storm shelters has emerged. Shelters range from above ground or underground residential, which offer space for as few as three occupants to large community shelters housing thousands of occupants and serving multiple purposes such as school corridors, gymnasiums, or auditoriums. Solutions have also been developed to effectively retrofit existing buildings with ICC compliant shelters. The wide variety of storm shelters is a testament to the free enterprise system of the U.S., and the creativity and entrepreneurship of storm shelter and shelter component designers, builders, and manufacturers.

School corridor shelter retrofit.

Participation in NSSA by structural engineers offers a challenging and exciting professional involvement. Since its founding in 2001, NSSA has grown from twenty Producer Members to over sixty members of various membership categories (Producer, Installer, Professional, Associate, Media Partner). Technical information and continuing education are available at NSSA seminars, annual association meetings, and via webi-

nars. For more information on membership opportunities, visit www.nssa.cc.▪ The ICC 500-2014: ICC/NSSA Standard for the Design and Construction of Storm Shelters is available for adoption and use by any jurisdiction. To learn more about the standard, visit www.iccsafe.org.

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STRUCTURE magazine

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August 2015

Just the FAQs questions we commonly receive about ... Steel DeckS

Steel Deck FAQs

By Kurt Voigt, P.E., Ben Pitchford, P.E. and Joe Voigt, E.I.T.

General Questions

Q

This is counter-intuitive at the surface. Standard effective deck properties are typically reported such that the section moduli used for bending are calculated assuming a maximum bending stress in the extreme fiber of the deck equal to the design yield strength (Fy) of the deck steel.

Moments of inertia are typically calculated and reported at a stress level equal to 0.6Fy, to capture the deck in its state at the maximum anticipated service level stress for serviceability limit states, like deflection. In calculating these effective section properties, effective flange and web widths are used in lieu of actual widths such that, under a given amount of compression stress, an entire flange or web may not be completely effective due to the buckling shape of the flat elements under compression stress. So, as the design yield strength increases, the effective compressed element widths tend to decrease due to the higher stress levels being analyzed.

These smaller effective element widths result in smaller effective section properties. However, the increase in design yield strength when calculating global flexural strength outweighs the reduction in section properties, so increasing design yield will nearly always increase the deck strength and associated allowable spans, even though the section properties get smaller.

Q

Kurt Voigt, P.E., is an Engineering Manager at New Millennium Building Systems. He can be reached at kurt.voigt@newmill.com.

Ben Pitchford, P.E., is an Engineering Manager at New Millennium Building Systems.

He can be reached at ben.pitchford@newmill.com.

Joe Voigt, E.I.T., is an Assistant Engineering Manager at New Millennium Building Systems.

He can be reached at joe.voigt@newmill.com.

Why do section properties decrease as the yield strength increases?

Why do properties vary among manufacturers?

There are many reasons for this. Since effective section properties vary with design yield strength, if two manufacturers publish different design yield strengths for similar decks, the effective section properties will be different.

Also, each manufacturer has their own tooling, which may have slight differences in bend radii, web angles, sidelap lips, flange widths, overall depth, flange stiffener configuration, etc. Typically, for truly comparable products, section property differences at the same yield strength are within 5% of one another. The Steel Deck Institute (SDI) publishes industry minimum effective section properties for standard profiles in its Floor Deck Design and Roof Deck Design manuals, based on all active member company data. If the deck is not the limiting component in a design, specifying SDI minimums in lieu of specific manufacturer published minimum properties will limit the amount of manufacturer specific approvals the Structural Engineer of Record has to handle for a particular project.

42 August 2015

Q

I specified 80 ksi steel; why are you providing me design information for 60 ksi design yield?

80 ksi steel and other high-strength or full-hard steel coils typically have lower ductility than lower strength steels. The American Iron and Steel Institute (AISI) S100 specification limits the maximum permissible design yield stress to 60 ksi for these lower ductility steels (with potential exceptions for the flexural yielding limit state).

Neither AISI S100 nor the SDI prohibits the use of higher strength steels, we just typically cannot take advantage of the increased steel strength.

Q

Can screws be used at supports in lieu of welds?

Q

What differences are there when butting steel deck over supports as compared to lapping the ends related to the transfer of diaphragm loads, and is it stronger to lap when possible?

Yes; mechanical, power-driven, or powderactuated fasteners of many types may be used in lieu of welds at the discretion of the Structural Engineer of Record (SER). It typically will not be a one-for-one substitution; it will require design consideration by the SER of the particular fastener chosen.

The Steel Deck Institute (SDI) Diaphragm Design Manual and American Iron and Steel Institute (AISI) S310 do not distinguish lapped ends from butted ends in the diaphragm strength and stiffness design equations, so there is no difference if using those published design equations to determine the strength and stiffness of the diaphragm. Using specific product testing, manufacturers can potentially gain additional stiffness using lapped ends as compared to butted, but often do not distinguish. Butted

deck ends require both ends of adjoining sheets over the support be welded with their own line of welds, compared to a lapped joint where a common weld line is shared by the two lapped deck ends.

Roof Deck Questions

Q

Can roof deck be curved in the strong direction by the erector in the field, to fit a radiused roof?

This is dependent on the experience of the erector, gage of the deck, deck support spacing, and roof radius. Contact the deck manufacturer and erector for guidance. If it can’t be field-curved, shopcurving prior to jobsite delivery may be an option depending on project location and required schedule.

If required, this question should be asked on a project and manufacturer specific basis.

Certain profiles, finishes and gages have a higher likelihood of availability than others.

In general for New Millennium, heavier gages, white primer finishes and some composite decks are not always available in higher yields.

However, if higher yields than published are desired, consult the manufacturer.

Q

Where do I find design information if the slab depth used on my project is not published in your catalog?

Consult the manufacturer’s website or contact the manufacturer. New Millennium has additional tables available on our website, and our engineers are available to prepare tables for nearly any condition needed.▪

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Why does the required concrete volume for a slab on steel deck vary based on deck profile when the overall slab depth is the same?

The width and spacing of the deck flutes varies by profile. Wider rib openings at the top of the deck and closer spacing of open top ribs results in more concrete nested down in the profile of the deck, requiring more concrete than a profile with narrower and/or further spaced top open ribs.

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August 2015

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The slab must be designed with the required capacity to support anticipated loading, such as a scissor lift. The Structural Engineer of Record (SER) is responsible for the design of slabs on steel deck and should be made aware of any anticipated vehicle traffic as early in the design process as possible. For slabs on composite steel deck, the SER can refer to the Steel Deck Institute (SDI) C-2011 Standard for Composite Steel Floor Deck-Slabs for design requirements and guidance, applicable limit states, and other design considerations. The SER should refer to ACI 318 for the design of slabs on noncomposite steel floor deck. The SDI Floor Deck Design manual is also a great resource with example problems to help guide the SER through the design of composite and non-composite steel deck-slabs.

Q

Is higher yield strength deck available than is published by the Steel Deck Institute or individual manufacturers?

Nearly two decades ago Hardy Frames created the first steel shear wall

Floor Deck Questions

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Software Business

ROBUST UPGRADES APLENTY

By Larry Kahaner

T

he software segment of the construction industry is doing very well, according to those involved in the business. And most expect it to get even better.

“Business is robust and appears to be strong through the remainder of the year. We have seen a record number of new customer additions, and available talent is becoming short in supply,” says Doug Evans, Vice President of Sales for Design Data (www.sds2.com).

To help ease the talent crunch, companies are taking advantage of technology. “With the strong market, we are seeing firms trying to optimize their investment in technology to meet project timelines.

With BIM workflows and qualified personnel shortages, many firms are trying to leverage technology resources over people resources to meet short-term project crunches. Longer term, we are seeing firms place an emphasis on developing the technical expertise to plan these projects under new BIM workflows in an attempt to meet customer and market requirements.”

Stuart Broome, Engineering Business Manager (USA) for Tekla (www.tekla.com), agrees that the market is strong. “We’re very busy.

The recent release of Tekla Structural Designer was received very positively by engineers who tell us they’re excited by the concept of combining code-based design for both concrete and steel buildings with general structural analysis all in one software tool that has a fresh, easy-to-use interface and a fast, powerful core. Our sales engineers are rushing around the country demonstrating Tekla Structural Designer and TEDDS to engineers who are updating their analysis and design tools now that the construction market is back on solid ground.”

When it comes to products, Evans says: “SDS/2 Engineering provides all the tools and features to design and analyze a steel structure. SDS/2 is a very illustrative product, allowing you to visually add and inspect your structure. In 3D, you can graphically add all loads and easily review the results, such as deflected shape diagrams, stress analysis and much more. In addition, the industry-leading automatic connection design has been enhanced to enable you to design around specific variables within each connection, including plate thickness or weld size. This robust product has many benefits that can be used throughout the engineers’ project.” To make reviewing and approving easier, Evans recommends SDS/2 Approval. “A rapidly growing workflow of model approval over drawing approval is gaining momentum, and SDS/2 Approval was created to service this demand. You can save many hours, and increase the depth and understanding of communication to all project partners, using the model as a project center.”

Adds Evans: “SDS/2 Detailing is the flagship product of Design Data’s software solutions and has set the standard for all other structural steel detailing systems for over three decades. The automatic connection design and automatic drawing production combination are unparalleled in the industry. Moving your design model into a manufacturing model STRUCTURE magazine

is time critical. SDS/2 Detailing can help you meet short timelines through its ability to import models and quickly start creating connections and drawings to manufacturers’ specifications.”

Tekla’s Broome also notes that the company launched version 21 of Tekla Structures in March, bringing more drawing capabilities to 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. We have introduced these new features based on required deliverables that engineers are facing.” (See ad on page 46.)

Tekla has also launched its 2015 version of TEDDS. “In this software, users can choose from one or more of the Tekla calculation library, or they can write their own,” Broome says. “Professional documentation can also be created from the software. Forget time-consuming hand calculations and cumbersome spreadsheets. Instead, automate your repetitive structural and civil calculations with TEDDS and transform the way you work.” Also new is Tekla Structural Designer (TSD).

“TSD was developed using some of the technologies from previous CSC solutions, Fastrak and Orion,” says Broome. “Developed with BIM integration in mind, TSD enables structural engineers to model, analyze, design and produce drawings for complete buildings in a single interface. Capabilities include: steel, composite and concrete and is versatile enough to include floors, complex roof structures, gravity and lateral systems all in the same model.”

At GT STRUDL (www.intergraph.com), Executive Technical Director Leroy Z. Emkin also sees a healthy business environment ahead. “We expect a significant surge in new business opportunities for GT STRUDL as a consequence of its new CAD Modeler and GTMenu user interfaces, which make GT STRUDL far easier to use by engineers at all levels of knowledge and experience while continuing to deliver the important structural engineering benefits for which it is widely known.”

The company has recently released GT STRUDL 2015. “Among the most important new features and enhancements included with this version are the new CAD Modeler Graphical User Interface (GUI), and a significantly updated GTMenu GUI,” says Emkin. “As an extension to AutoCAD, CAD Modeler enables structural engineers to take full advantage of AutoCAD’s powerful, robust and easy-touse 3D graphical manipulation features in order to create models for structural analysis and design. CAD Modeler includes a rich collection continued on page 47

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August 2015

Tekla Structural Designer is here.

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of easy-to-use dialogs to specify information required, and to display the results of structural analysis and design. It also incorporates the ability to automatically create GT STRUDL input command files, and the ability to automatically execute GT STRUDL using menu picks in the CAD Modeler ribbon within the AutoCAD screen. CAD Modeler creates an environment within which structural engineers can far more easily create simple to highly complex models in less time, at less cost, and in a more reliable manner.”

Emkin says that GTMenu also has been updated to provide a more modern GUI look, feel and features. “Significant improvements include easy navigation through dockable dialogs, improved mouse control, increased display speed, easier-to-follow workflows, and display features that provide very smooth graphical manipulation of model displays. It also provides the ability to display two concurrent and interconnected views of the model which improves the review of model details, analysis and design results.”

Ahmed Khalil, Senior Structural Consultant at Applied Science International (www.appliedscienceint.com) says they will soon release Extreme Loading for Structures Software (ELS) v4.0. “The new version allows creating numerical models of structures for nonlinear dynamic analysis with more than a million elements; and yet, the advanced level analysis runs in a reasonable amount of time, with reliable accuracy, on a standard PC. ELS allows building three-dimensional nonlinear solid models for complete structures, taking into consideration the contribution of secondary members and slabs.”

The timing is excellent, says Khalil. “This new release of ELS could not come at a better time as the trend in the United States and all over the world is to use explicit building code requirements for preventing disproportionate collapse of a structure due to local damage of any of its components. The Alternate Path Method is increasingly becoming the

standard of practice for preventing progressive collapse in all government building codes. Performing nonlinear dynamic analysis is preferable when using the Alternate Path Method, as it leads to a more uniform factor of safety and a more cost-efficient design.” He adds: “With ELS, structural engineers can perform nonlinear dynamic analysis for the column removal scenarios, taking into consideration three-dimensional effects such as membrane action from slabs or arching action in masonry walls. Contribution of non-structural members as well as secondary structural members can also be evaluated. This allows an accurate estimation of the inherent strength of structures that is not possible using traditional beam and shell element linear models. This becomes particularly important when evaluating existing buildings or new buildings with non-traditional structural systems.” (See ad on page 67.)

“Business is the best it has been in over a decade,” states Michael D. Brooks, president of Enercalc (www.enercalc.com). “There is a huge amount of work on the boards, and users are updating long-outdated software. We are seeing strong new license sales. Once this design work comes into construction, the economy will be flooded with dollars, creating a great economic boom.” Says Brooks, “We have discussed our Cloud deployment before, and after some delays, which were actually just subscription management related, we are now up and running. We use a scalable Amazon Web Services platform to provide our user base with our same proven software system running in the cloud through any HTML5 browser. There is nothing else like it in the Structural Engineering community.

“We’ve been in business for 32 years and have seen three large economic cycles. The United States is strong and will continue to lead the world. For the short term, business will be strong, and for the long term we can only hope.” (See ad on page 3.) continued on page 49

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GT STRUDL Structural Modeling, Design & Analysis ®

Intergraph GT STRUDL is one of the most widely-used, integrated and adaptable structural analysis solutions in the world. GT STRUDL has a proven track record in a variety of applications such as: nuclear and conventional power generation, on- and offshore facilities, marine, civil,infrastructure, and more. It can fully model, design and analyze structures for the following services: • Nuclear facilities • Industrial facilities • Offshore platforms/jackets • Roof supports • Power transmission • High-rise buildings • Stadiums • Bridges • Docks, Locks and Dams • Radar dishes and facilities • Construction equipment • Transportation equipment www.intergraph.com/go/gtstrudl

© Intergraph Corporation. All rights reserved. Intergraph is part of Hexagon. Intergraph, the Intergraph logo, and GT STRUDL are registered trademarks of Intergraph Corp or its subsidiaries in the United States and in other countries.

STRUCTURE magazine

47

August 2015

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When it comes to wood construction, Kevin Rocchi, WoodWorks (http://cwc.ca/woodworks-software) Technical Support Leader says their software continues to be the industry’s leading software of wood design for engineers. He would like SEs to know their latest software version, Design Office 10 (SR3a), was released in October, 2014.

“The current U.S. version conforms to the IBC 2012, NDS 2012, SDPWS 2008, and the ASCE-7-10. This summer, the WoodWorks software developers will begin the development of a new version of the software which will be updated to conform to the IBC 2015, NDS 2015, SDPWS 2015 and the ASCE 7-10. The current goal is to release the updated version before the end of 2015.”

He notes: “In Canada, our latest version of the software is the Design Office 9 (SR3), released in July, 2015. This version of the software was updated to conform to the CSA O86-14 and NBC 2010. In this latest version, there were significant changes to the Shearwalls module, as the shearwall resistance equations in the CSA O86-14 were updated to a mechanics-based approach and also now includes a check for the panel buckling for the sheathing of the shearwall.

Along with these changes, a new feature was added to the software.

The Detailed Shearwall Design shows the shear resistance and panel buckling calculations for all the shearwalls designed in a model. This feature is very useful for understanding the new shearwall resistance equations and checking the calculations made by the software.”

Sales have been strong, Rocchi says. “WoodWorks software sales over the past year have steadily been increasing for both the U.S. and Canadian editions. Currently, there are over 2,500 users of U.S. WoodWorks Design Office and over 1,200 users of the Canadian WoodWorks Design Office.

Nemetschek Scia (www.scia.net) is celebrating its 40th anniversary as an engineering software company, according to Dan Monaghan, Managing Director, North America. In addition, the company released Scia Engineer v.15, which is its most substantial release ever, he says.

“With the theme Open BIM and Open Checks, Scia Engineer v.15 is helping firms plug analysis and design into BIM and allowing engineers to expand their FEA workflow by letting them script their own custom checks. “ Says Monaghan: “With Open BIM, Scia Engineer v.15 offers bidirectional links to Revit 2016 as well as the 64-bit version of Tekla Structures, and continues to be the only engineering software certified for IFC. With IFC, Scia Engineer supports the ACI, PCI and ASIC new BIM interoperability initiatives. It also gives engineers an easy way to exchange models with over 150 BIM software programs.

And, for firms working with graphical scripting, Scia Engineer v.15 introduces new links to Rhino, Grasshopper, and Dynamo.

“Open Checks is being introduced in a new product called Scia Design forms,” Monaghan adds. “Scia Design Forms is similar to Mathcad and MATLAB but tuned for structural engineering. These checks can run as stand-alone or linked to Scia Engineer’s FEA modeling design environment. This ability to allow engineers to extend their FEA workflow by writing custom checks is ‘game changing.’

More than a ‘box of software,’ Scia Engineer is a platform upon which firms can centralize their design tasks and consolidate the number of engineering programs they need to own and maintain.”

STRUCTURE magazine

How’s business? “In general, we’re seeing an uptick in business across all sectors we serve,” Monaghan says. “The big drivers are the steady migration to BIM and a new emphasis that firms have to save money by consolidating the number of software they own and maintain. With Scia Engineer, firms have a very efficient engineering program for their day-to-day work, and a deep set of analysis capabilities they can tap for larger, more complex projects that require advanced non-linear and dynamic analysis. This desire for one program to handle all of a firm’s analysis tasks also extends into design. Engineers don’t want to check gravity in one system and lateral in another, or beam/columns in one program and floors in another. There’s a true efficiency to programs like Scia Engineer that can help firms integrate and consolidate their workflows.” (See ad on page 50.)

At Bentley Systems (www.bentley.com), Senior Product Manager Josh Taylor says that the company has some breakthrough capabilities coming this year. “We’ve begun to connect all the family products, not just the structural but Bentley wide, which is a successor to the current V8i generation. The exciting thing about this for structural engineers specifically is that we’ve given access to cloud-based analysis and design services that have orders of magnitude more power compared to what they’re using in the traditional desktop environment.

We’re doing this for both the STAAD and the RAM lines. A key point is that we’re not reinventing the way that users use these products and services. They will be accessible directly from the interface of the product and are aimed at bringing more power to the way that users currently use their products. This allows users to evaluate 10, 100, maybe even 1,000 times the number of design scenarios that they’re currently able to do purely in the desktop environment. We’re using analysis engines and design services based in the cloud as opposed to the desktop. This will all fall under a service we call CONNECT Edition scenario services. There will be a portal to this service available within each application. STAAD.Pro and RAM Concept will likely be the first to do this. “ The company also is simplifying their licensing. “We’re offering both STAAD and RAM products under one license. We call this structural enterprise. It’s a special license that gives the user unlimited access to products. It’s very favorably priced in comparison to purchasing each of these licenses as a stand-alone. The other big factor, aside from just the price, is that it enables the full use of interoperability across products.”

“Last,” says Taylor, “we’re continuing to develop the core analysis and design features within each of the products, and that includes color-coded activity enhancements that engineers find useful.”

Also supporting efficiency for clients is ADAPT Corporation (www.adaptsoft.com), a recognized leader in the detailed design of post-tensioned slabs and beams for over 30 years. According to Florian Aalami, President and CEO, “We are building on our long heritage of concrete design expertise to develop a comprehensive software solution for the integrated design of concrete buildings. Most software vendors are advertising the same complete solution for all design requirements, making it very challenging for the practicing engineer to distinguish between offerings and their respective ‘value.’ We have taken a very practical approach to our product development strategy. Instead of continued on page 51

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August 2015

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Plugging Analysis and Design into Your 3D Workflow

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ITH new processes like BIM (Building Information Modeling) and VDC (Virtual Design and Construction) and new project delivery methods like IPD (Integrated Project Delivery), more and more engineering firms are being asked to participate in collaborative, model-based workflows.

Migrating to these new processes can be made easier with software designed to support them— software like Scia Engineer from Nemetschek.

Scia Engineer is a new breed of integrated structural design software that goes beyond analysis and helps firms successfully join in today’s collaborative 3D workflows.

Fast and Efficient Modeling Modeling is an essential requirement for any 3D workflow. As projects become more complex and project timelines compressed, modeling needs to be fast and efficient, but also not restrictive. Engineers need to be able to keep up with the modern designs coming from architects and contractors who push the limits of new materials and methods.

“A unique feature of Scia Engineer is its modeling capabilities,” says Mark Flamer, M.I. Flamer & Associates. “It’s a very fast and efficient FEA (Finite Element Analysis) modeling tool. freeform modeling capabilities make it easy for me to work up designs in 3D and keep pace with my architect’s avant-garde designs. And, its parametric object technology has allowed me to automate routine and repetitive work. I can quickly work up and test design concepts. Then, when the design has gelled, I can develop an accurate structural model in Scia Engineer or link my design to another BIM program for model coordination or construction drawings.”

With support for open standards like IFC 2x3 and direct links to a number of BIM software programs, Scia Engineer makes it easier for engineers to reuse models created by others and leverage them into analysis.

This is a huge advantage when working in a collaborative workflow.

“For the new National Music Centre project in Calgary, Canada, the architect made frequent and sometimes dramatic changes,” says Andrea Hektor, KPFF Portland. “We needed to be able to give them a quick thumbs up or thumbs down on their revised designs. With Scia Engineer it was great. The architects would just send us their updated models. We would import them into

Scia Engineer, update our model, run a quick analysis, and give them enough information to continue moving forward.

I don’t think we would have been able to do this with any of the other analysis software we have in our office.”

Another advantage of Scia Engineer is its extensive functionality. Analysis and design is becoming more rigorous, and owners are looking for highly optimized structures to minimize materials, construction time, and costs. Being able to have one program that is efficient for your day-do-day work, and at the same time offers the ability to handle complex analysis tasks is a big benefit.

“With support for advanced FEA analysis and multi-material design I’ve avoided having to invest in disparate analysis programs,” continues Flamer. “Reducing the number of analysis programs we manage saves on maintenance costs and makes it less expensive to train new employees. Most importantly, it reduces the risks that come with manually coordinating multiple analysis models.

For occasions when I need to go outside Scia Engineer, the program’s Open Design technology, allows me to script my own checks to expand its built-in design capabilities.”

When Modeling Matters, Scia Engineer Delivers

“More in tune with the engineer’s workflow” “Eye-opening” “Extremely impressed”

Growing with Technology In addition, the right software makes a firm more flexible, allowing them to go beyond their usual projects, and take on work wherever they find it. “Scia Engineer allows our firm to confidently compete for bigger building projects as well as go beyond buildings,” says Flamer.

“While our expertise is in commercial, we just completed a bridge project and are ready to take on larger, complex structures. A flexible tool like Scia Engineer makes all the difference.”

He added: “I evaluated the usual list of structural analysis programs, and there isn’t another program in the market like it. Scia Engineer is the only program I found that integrates fast and efficient modeling, lets me script my own calculations, and easily reuse and share 3D models. For us, Scia Engineer was a logical choice.”

Read the AECbytes Article www.nemetschek-scia.com/review

Scia Engineer is a new breed of integrated structural design software that goes beyond analysis to help firms excel in today’s collaborative 3D workflows.

Discover fast, efficient modeling and intelligent FEM analysis. Recycle and leverage models created by others into analysis. And, centralize your design tasks with static and advanced nonlinear and dynamic analysis, plus multi-material design in ONE program.

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Daniel Monaghan is the U.S. Managing Director of Nemetschek Scia, developers of leading software products for AEC software industry. He can be reached at dmonaghan@scia-online.com

(877) (443) 808-7242 542-0638

www.nemetschek-scia.com

driving ahead with the implementation of marketing oriented features, we embedded ourselves in the workings of a few strategic clients and sought to discover critical bottlenecks that cause inefficiencies in their design workflows. This led us to discover practical design steps that almost every engineering firm still carries out manually, like the calculation of tributary-based areas and load takedowns for the gravity loading and verification of their vertical elements.”

Aalami describes how ADAPT went from discovery to a solution, “Learning about this requirement, we implemented a new feature as part of our ADAPT-Builder 2015 release that quickly calculates tributary-based loads in any simple or complex 3D model. Our tributary loading feature has added tremendous productivity gains to our clients, by freeing them of burden of having to develop a fully functioning FEM model before being able to calculate column and wall loads. A builder’s integrated column design module can be run with forces calculated using the tributary module or finite element method.”

And, striving to improve efficiency for the SE’s workflow results in other improvements to ADAPT’s offerings. “We are also leveraging our unique software architecture, which supports global and single-level analysis and design procedures in one model, to provide workflow efficiencies other disparate solutions can’t provide. For example, engineers can carry out the detailed design of slabs for lateral frame action forces in the same model they use to run the global building model for wind or seismic loads, eliminating the need to maintain multiple models and transfer data between them.” (See ad on page 38.)

According to Darin Willis Director of Engineering at Ram Jack (www.ramjack.com), the company has recently updated its ICC Evaluation Service Report (ESR-1854) for its helical and driven-steel piles to the 2015 International Building Code (IBC). “It’s important

to Ram Jack that engineers and building officials have peace of mind when specifying our products,” he says. “Who is more qualified to evaluate and rate a building product for compliance with the building code than the ones who publish it? Ram Jack also received our ISO 9001:2008 certification. This demonstrates our commitment to quality control, as well as assurance that our products are manufactured with the highest standards.”

Says Willis: “We are seeing a steady growth pattern of approximately 20 percent year-over-year, and the credit goes to our staff and franchises for never ceasing in our pursuit of giving our customers solutions that work. We always hold true to our mission statement: ‘To be recognized for providing peace of mind through engineered foundation solutions and exceeding customer expectations; nothing more, nothing less.’ “ Willis concludes: “Ram Jack’s core values include ‘complete integrity’ which means building our future by providing support for our customers. We furnish an incredible support system for our franchises that includes: IT support, marketing, technical coaches, business coaches, research and development, and professional engineers for our 60-plus installation locations throughout the U.S., Canada, Puerto Rico, and Central America. Providing the support to our franchises equates to providing the best support to our customers. We are continuing to grow all of these areas of Ram Jack support.”

Shannon Hughes, Product Manager – Services and Customer Experience at Weyerhaeuser (http://www.woodbywy.com), notes that the company, headquartered in Federal Way, Washington, continues to see customers struggle to find new efficiencies in today’s building environment. “This makes it all the more important that Weyerhaeuser delivers efficient tools that keep pace with technology, changing building codes, varied user sophistication and evolving customer needs,”

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August 2015

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says Hughes. “Structural engineers benefit from recent updates to two Weyerhaeuser software tools. Javelin software allows users to build a complete model of the entire structural frame. The 3D modeling, state-of-the-art CAD capabilities, and integrated design tools provide the power needed to specify products and track vertical loads from the ridge to the foundation. Javelin was updated in 2015 to include force orthogonal snapping, hatch beams and controlled spacing – all features to make designing easier and more flexible.”

Hughes adds, “Our Forte single-member sizing tool easily performs load calculations and to help identify solutions for specific conditions and geometry. The latest version of Forte offers the ability to analyze members for commercial loading with improved input and analysis.

It also offers load assistance for complex conditions, the ability to size engineered wood as well as dimension lumber and an intuitive workflow and user interface. The best part is that it is a free tool available for download.” In addition, Hughes notes an increase in the use of open floor plans. “Our software, design support, specification guidance and several of our product offerings help engineers and designers navigate these tricky open floor plans.”▪

SOFTWARE GUIDE

ADVERTISING OPPORTUNITIES Be a part of upcoming

SPECIAL ADVERTORIALS in 2015.

To discuss advertising opportunities, please contact our ad sales representatives:

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BIM, Bridges, Building Components, Business/Productivity, CAD, Concrete, Found./Retain. Walls, Gen./Packages/Suites, Light Guage Steel, Masonry, Steel, Wood

ADAPT Corporation

American Wood Council

Phone: 650-218-0008 Email: florian@adaptsoft.com Web: www.adaptsoft.com Product: ADAPT-PT/RC Strip Design Description: The most popular software for design of post-tensioned slabs and beams now includes a Reinforced Concrete design as option. This capability lets engineers learn and standardize on one software and design workflow for all of their concrete projects: PT or RC, saving time and becoming more efficient.

Phone: 202-463-2766 Email: lbalsavage@awc.org Web: www.awc.org Product: Connection Calculator Description: Provides users with a web-based approach to calculating capacities for single bolts, nails, lag screws and wood screws per the 2005 NDS. Both lateral (single and double shear) and withdrawal capacities can be determined. Wood-to-wood, wood-to-concrete, and wood-to-steel connections are possible.

Product: ADAPT-Builder with Column Design Description: An integrated analysis and design software for concrete buildings with integrated column design option. Includes unique tributary load takedown. Use it to efficiently analyze and design your complete concrete building from foundation to roof slab all in one model – post-tensioned or mild reinforced. Seamlessly integrates with Revit Structure.

Bentley Systems

Product: ADAPT-ABI 4D Construction Phase Analysis Description: 4D construction phase analysis of concrete bridge or building structures.Analyzes structure at each step and reports forces, creep, shrinkage and deflections using non-linear material behavior. Great tool for calculating long-term effects, camber, superpositioning, and investigation of construction methods.

Phone: 800-236-8539 Email: structural@bentley.com Web: www.bentley.com Product: ProStructures Description: Accurate 3D models for structural steel, metal work, and reinforced concrete structures.

Design drawings, fabrication details, and schedules, with automatic updates whenever your 3D model is changed. Easily customize the interface to meet your precise needs to take full advantage of the open working environment and programming interface.

STRUCTURE magazine

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August 2015

Product: RAM Structural System Description: Produce high quality and economical designs, using various concrete, steel and joist building materials; all in compliance with local building codes.

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: STAAD(X) Description: Design any type of structure and share your synchronized model data with confidence.

Ensure on time and on budget completion of your steel, concrete, masonry and cold-formed steel projects, regardless of complexity. Comprehensive analysis and design provides thorough compliance with design codes and multiple options for dealing with changes.

continued on page 54

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.

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Enercalc, Inc.

Phone: 425-392-4309 Email: cadresales@cadreanalytic.com Web: www.cadreanalytic.com Product: CADRE Pro – structural analysis Description: Solves virtually any type of structure for internal loads, stresses, displacements, and natural modes. Easy to use modeling tools including import from CAD. Complete structural validation with advanced features for stability, buckling, vibration, shock and seismic analyses. Latest version includes checks against the steel, aluminum and wood products codes.

Phone: 800-424-2252 Email: info@enercalc.com Web: www.enercalc.com Product: Structural Engineering Library Description: A collection of modules providing proven solutions to all the typical, repetitive and daily design tasks performed by engineers and architects. Combines building code provisions, proven analysis techniques, and standard materials into an integrated software package.

Concrete Masonry Association (CMACN) Phone: 916-722-1700 Email: info@cmacn.org Web: www.cmacn.org Product: CMD12 Design Tool Description: Structural design of reinforced concrete and clay hollow unit masonry elements for design of masonry elements in accordance with provisions of Ch. 21-1997 UBC, 2001 through 2013 CBC or 2003 through 2012 IBC and 1999 through 2011 Bldg.

Code Requirements for Masonry Structures (TMS 402/ACI 530/ASCE 5)

Decon® USA Phone: 707-996-5954 Email: frank@deconusa.com Web: www.deconusa.com Product: Studrails® Description: The North American standard for punching shear enhancement at slab-column connections. Studrails are produced to the specifications of ASTM A1044, ACI 318-08, and ICC ES 2494. Decon Studrails are also increasingly used to reinforce against bursting stresses in banded post-tension anchor zones.

Product: JORDAHL® Anchor Channels Description: Decon USA is the exclusive representative of Jordahl in North America. Hot rolled Anchor Channels are embedded in concrete and used to securely transfer high loads. Main application is for flexible connections of glazing panels to high-rise buildings. Anchor Channels with welded-on rebar or corner pieces are available.

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BIM, Bridges, Building Components, Business/Productivity, CAD, Concrete, Found./Retain. Walls, Gen./Packages/Suites, Light Guage Steel, Masonry, Steel, Wood

CADRE Pro 6 for Windows Solves virtually any type of structure for internal loads, stresses, displacements, and natural modes. Easy to use modeling tools including import from CAD. Much more than just FEA. Provides complete structural validation with advanced features for stability, buckling, vibration, shock and seismic analyses.

CADRE Analytic Tel: 425-392-4309

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Hilti, Inc. Phone: 800-879-8000 Email: us-sales@hilti.com Web: www.us.hilti.com Product: PROFIS Anchor, PROFIS Rebar, PROFIS DF Description: PROFIS Anchor performs anchor design using ACI 318 provisions. PROFIS Rebar calculates development lengths for post-installed rebar using ACI 318 provisions. PROFIS DF Diaphragm optimizes design of steel deck roof and floor diaphragms using SDI DDM and ICC-ES AC43 provisions.

IES, Inc. Phone: 406-586-8988 Email: business@iesweb.com Web: www.iesweb.com Product: VisualAnalysis Description: Model any structure, apply loads quickly, analyze with powerful nonlinear FEA, get concise results, and design to meet the code requirements.

Phone: 512-372-8991 Email: sales@softwaremetering.com Web: www.softwaremetering.com Product: SofTrack Description: Control use of all Bentley® applications; reduce or eliminate quarterly overage billings.Control by Calendar Hour or by Calendar Day. View active users via web page. Alert on idle usage and optionally terminate idle usage.

Automatically detects each Bentley license as used per workstation. Also controls AutoCAD usage.

Losch Software Ltd Phone: 323-592-3299 Email: LoschInfo@gmail.com Web: www.LoschSoft.com Product: LECWall – Concrete Sandwich Wall Panel Design and Analysis Description: Prestressed and/or mild reinforcing. Flat, hollow-core or double tee configurations. Column design, handling analysis, multi-story capability, zero to 100 percent composite. Free 30 day trial.

Nemetschek Scia Phone: 410-207-5501 Email: dmonaghan@scia.net Web: www.scia.net Product: Scia Design Forms Description: Integrate custom checks into your FEA workflow. Scia Design Form’s makes it easy script custom calculations that can run as standalone checks or link to Scia Engineer’s FEA workflow. Having the ability to write your own checks inside your FEA software is a real game changer. Try it for free!

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Opti-Mate, Inc. Phone: 610-530-9031 Email: optimate@enter.net Web: www.opti-mate.com Product: Bridge Engineering Software Description: Software titles include Merlin Dash for steel and prestressed concrete girders, Descus I and Descus II for curved plate and box girders, SABRE for sign bridges and TRAP for truss bridges. All software packages include AASHTO WSD, LFD or LRFD code check and rating.

POSTEN Engineering Systems Phone: 510-275-4750 Email: sales@postensoft.com Web: www.postensoft.com Product: POSTEN Multistory Description: The most efficient & comprehensive post-tensioned concrete software that, 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.

Powers Fasteners

Integrity Software, Inc.

STRUCTURE magazine

Product: Scia Engineer Description: Scia Engineer links structural modeling, analysis, design, drawings, and reports in ONE program. Design to multiple codes. Tackle larger projects with advanced non-linear and dynamic analysis. Plug into BIM with IFC, and bi-directional links to Revit, Tekla, and others.

August 2015

Phone: 845-230-7533 Email: Mark.Ziegler@sbdinc.com Web: www.powers.com Product: Powers Submittal Generator (PSG) Description: PSG is a 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!

Product: Powers Design Assist (PDA) Description: PDA anchor design software now includes ACI 318-11 and CSA A23.3 design provisions for mechanical, adhesive and cast-in place anchors. Download or update to version 2.3 for free.

RedBuilt Phone: 208-364-1322 Email: csprung@redbuilt.com Web: www.redbuilt.com Product: RedSpec Description: A proprietary product sizing software.

Allows engineers and architects to quickly and efficiently create floor and roof design specification using Red-I joists, open-web trusses, and RedLam for a variety of commercial and multi-family applications.

A central component is FloorChoice™, a propriety floor performance rating system.

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.

BIM, Bridges, Building Components, Business/Productivity, CAD, Concrete, Found./Retain. Walls, Gen./Packages/Suites, Light Guage Steel, Masonry, Steel, Wood

SOFTWARE GUIDE

RISA Technologies

Strand7 Pty Ltd

Phone: 949-951-5815 Email: amberf@risa.com Web: www.risa.com Product: RISA-3D Description: Developing leading edge structural design and optimization software for over 25 years, RISA products are used around the world for buildings, stadiums, bridges and everything in between. The seamless integration of RISAFloor and RISA-3D creates a powerful structural design environment, ready to tackle your next design challenge.

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

S-FRAME Software

StrucSoft Solutions

Phone: 203-421-4800 Email: info@s-frame.com Web: www.s-frame.com Product: S-CONCRETE Description: For reinforced concrete structural design, displays instantaneous results for concrete columns, beams and walls. Optimize a single section design or evaluate thousands of concrete sections at once. With comprehensive ACI1 318-11 design code support, S-CONCRETE produces detailed reports that include clause references, intermediate results and diagrams.

Phone: 514-538-6862 Email: info@strucsoftsolutions.com Web: http://strucsoftsolutions.com Product: Metal Wood Framer Description: Metal Wood Framer is a template-based and rule-driven extension to Autodesk® Revit® for framing. It empowers users to automate the modeling, engineering, clash detection and manufacturing of CFS framing including shop drawings, cut lists, BOM, optional CNC output and more.

Product: S-STEEL Description: S-STEEL generates comprehensive design reports that include equations employed and clause references. Code-check and auto design for both strength and serviceability to multiple design codes. S-STEEL supports composite beam design, staged construction, and numerous optimization criteria and constraints.

Structural Engineers Inc.

Product: S-FRAME Analysis Description: A powerful 4D structural analysis and design environment with integrated steel, concrete and foundation design & optimization tools. Ideal for linear or advanced non-linear analysis, domestic or international design.

Simpson Strong-Tie

Product: Simpson Strong-Tie® Anchor Reference Tool Description: The new web-based Simpson StrongTie Anchor Reference Tool (ART) helps users locate recommended Simpson Strong-Tie mechanical or adhesive anchor products for common competitor products. ART selects products that most closely match the alternate manufacturer’s products in performance, application or code listing, using the product name or code listing.

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

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

Tekla Inc. Phone: 770-426-5101 Email: kristine.plemmons@tekla.com Web: www.tekla.com Product: Tedds Description: Perform 2D frame analysis, access a large range of automated structural and civil calculations to US codes and speed up daily structural calculations.

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Product: Tekla Structures Description: From concept to completion.

Tekla Structures allows you to create accurate and information-rich models that reduce RFIs. Models are used for drawing production, material take offs and collaboration with disciplines like architects, consultants, fabricators and contractors.

Weyerhaeuser Phone: 800-833-9491 Email: software@weyerhaeuser.com Web: www.woodbywy.com/software Product: Forte, Javelin, Stellar and Estima Software Description: Take advantage of the predictable strength and consistency of Weyerhaeuser engineered and performance tested lumber. With Forte, Estima, Javelin and Stellar Software, quickly implement high-quality structural framing solutions and optimize material use – while reducing construction cycle time, cost and waste.

WoodWorks® Software Phone: 800-844-1275 Email: sales@woodworks-software.com Web: www.woodworks-software.com Product: WoodWorks® Design Office Suite Description: Conforms to the IBC 2012, ASCE7-10, NDS 2012, SDPWS 2008; SHEARWALLS: designs perforated and segmented shearwalls; generates loads; rigid and flexible diaphragm distribution methods.

SIZER: designs beams, columns, studs, joists up to 6 stories; automatic load patterning. CONNECTIONS: Wood to: wood, steel or concrete.

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.

StruWare, Inc

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

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

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

Concrete beams with/without torsion ($45.00).

Demos at: www.struware.com

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Phone: 800-999-5099 Email: web@strongtie.com Web: www.strongtie.com Product: Strong-Wall® Bracing Selector Web App Description: Provides pre-engineered Strong-Wall shearwall alternatives to code-prescribed braced wall panels. Strong-Wall model numbers and foundation anchorage designs are established to meet job-specific requirements and provide the narrowest bracing solutions possible. This new tool replaces the Strong-Wall Shearwalls Prescriptive Design Guide.

FLOORVIBE Phone: 540-731-3330 Email: tmmurray@floorvibe.com Web: www.floorvibe.com Product: FloorVibe v2.20 Description: Analyze floor vibrations due to walking and rhythmic activities and for floors supporting sensitive equipment. Version 2.20 includes recommendations in the just released SJI Technical Digest 5, as well as the AISC Design Guide 11 “Floor Vibrations due to Human Activity”.

Product: Tekla Structural Designer Description: Revolutionary software that provides the power to analyze and design buildings efficiently and profitably. Fully automated and packed with many unique features for optimized concrete and steel design, from the quick comparison of alternative design schemes through to cost-effective change management and seamless BIM collaboration.

AZZ Galvanizing now offers GalvXtra® in rustic brown.

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dedicated to the dissemination of information from other organizations

Guest Column

A New Generation of Galvanizing

By Howard Levine

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n 1837, Stanislaus Sorel received a patent for galvanizing. Even though the process has been around for over 175 years, it’s not your great, great, great grandfather’s galvanizing!

Of course, many of the same principles still apply…outstanding corrosion protection, metallurgical bonding,100% surface protection of the interior and exterior of steel fabrications… but the galvanizing industry has adapted to the demands of the 21st century by recognizing that there is more to it than stopping rust. This article will highlight some of the technical and marketing trends benefitting the engineering community.

On the technical side, there are several issues currently being addressed by the industry, with the charge being lead by the American Galvanizers Association. Of particular note and impact on the engineering community are Slip Factors for Slip Critical Connections and Hydrogen Embrittlement/Galvanizing A-490 Bolts.

A slip factor study by the American Galvanizers Association is in the final stages of research. The goal of the study is a guideline or specification with instructions on preparing a galvanized surface to achieve a Class B slip coefficient.

With a higher slip coefficient, designers will be able to use galvanized steel in applications previously not considered or decrease costs by using less connections. Previous phases of testing indicate that obtaining the required 0.50 slip coefficient through roughening or other treatments is not possible. Therefore, the testing is focused on the use of a zinc-rich paint over the galvanized surface to obtain the Class B slip coefficient. The final phase of testing is slated to occur in 2015.

Another study deals with the feasibility of hot-dip galvanizing A490 bolts without a danger of hydrogen embrittlement. Hydrogen embrittlement originates in the cleaning step of the hot-dip galvanizing process. During the process, the heating of the steel causes some of the atomic hydrogen absorbed from the pickling acid to migrate into “trap sites” within the steel matrix. Once in the trap site, the hydrogen atoms can cause a premature failure of the steel fastener when installed in the field. Removing the source of hydrogen atoms (pickling acids) from the galvanizing process essentially eliminates the concern for hydrogen embrittlement failure. To accomplish this, the time the steel spends immersed

in the pickling acids must be eliminated, as this is the only source of hydrogen atoms in the process. Mechanical surface preparation (blasting or wheel abrading) of the steel after the degreasing stage will solve the problem.

The study tested several bolts galvanized with this modified process for compliance with ASTM and other standards. Results of these tests were typical for hot-dip galvanizing, showed no adverse effect on the coating from the modified process, and met the requirements of ASTM A153. The A490 bolt study has been completed and is being introduced to ASTM for inclusion in the specification.

There may be further testing to explore other steel base materials to prove there is no difference in their hydrogen threshold after galvanizing. More tests will be done in 2015, and the total report will be published with a change proposed to the new specification on high strength bolts. It should be noted that these practices have been utilized in Europe for many years, and the use of hot-dip galvanized A490 bolts is an accepted practice in design and construction.

In addition to addressing technical issues, the galvanizing industry has come to realize that there are other initiatives that can benefit both the galvanizer and engineer. These areas fall into three basic categories: Education, Sustainability, and Marketing Opportunities.

Educating the next generation of architects and engineers is a priority. Many have little or no knowledge of the galvanizing process.

Their college curriculum skims over (or ignores) the need for corrosion protection.

Visits to college campuses and A/E/C offices across the United States and Canada are being held to educate future architects and engineers about hot-dip galvanized steel. Through these presentations, students and “emerging professionals” will learn about the galvanizing process, design, sustainability, performance, specification, cost, and inspection.

Hot dip galvanizing is universally recognized as environmentally friendly. In reference to LEED® category Materials and Resources – Credit 4.1 and 4.2 Recycled Content, the steel and zinc used in the hot dip galvanizing process contain 56.1% post-consumer recycled content and 31.17% pre-consumer recycled content. Recently, the U.S. Green Building Council approved the new LEED v4 rating system, which revamped the Materials

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& Resources credit area. The change targets more transparency in materials to assist in selecting more sustainable building products.

The requirements have been changed to more objective measures – Environmental Product Declarations (EPDs) which are based on life-cycle assessment (LCA) data. This more objective and transparent measurement of sustainability favors hot-dip galvanized steel because of its durability, low life-cycle cost, and 100% recyclability – unmatched by most competitive systems.

The old marketing adage “grow or die” also pertains to the galvanizing industry. The galvanizing process can no longer remain an afterthought. Through the efforts of the American Galvanizers Association as well as some individual galvanizers, great strides have been made to advance the use and knowledge of hot dip galvanizing. By reaching out, the galvanizing industry has seen trending growth in zoos, short span bridges, and parking structures to name a few market segments. By utilizing empirical data to prove long-term effectiveness, there has been increased growth in the use of duplex coatings (both liquid and powder) in the bridge & highway and structural markets.▪ Howard Levine is Senior Vice President of Duncan Galvanizing in Everett, MA. A Fellow of the Construction Specifications Institute, he has represented Duncan and the galvanizing industry to Architects and Engineers throughout the Northeast for over 30 years.

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award winners and outstanding projects

Spotlight

ASCE & SEI Recognize Outstanding Structural Engineers

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he Structural Engineering Institute (SEI) proudly recognized the following recipients at the Structures Congress 2015 in Portland, Oregon on April 23, 2015:

Structural Engineering Institute Awards 2015 Chapter of the Year Award The 2015 SEI Chapter of the Year Award was given to the SEI Boston Chapter. The Boston Chapter has been very active in a variety of initiatives including technical presentations, conferences, tours, college outreach, and networking opportunities. They also made significant contributions to the Structures Congress 2014 local planning committee.

2015 Graduate Student Chapter of the Year SEI presented the 2015 Graduate Student Chapter award to the University of Central Florida Graduate Student Chapter for their work in partnering with the local ASCE and SEI Chapters and branches to present seminars, training programs for high school students, and enrichment for the UCF Student Body.

W. Gene Corley Award The 2015 W. Gene Corley Award was given to Stan R. Caldwell, P.E., SECB, F.SEI, F.AEI, F.ASCE, for his outstanding and generous leadership in many critical SEI initiatives and committees. An ASCE member since 1972, his contributions include Charter Member of SEI, founding member of AEI, the first person elected to the ASCE Board of Direction from the Technical Region, the ASCE Executive Committee, SEI Board of Governors representing ASCE, the SECB Board of Directors, the SELC Steering Committee, and establishment of the SEI Futures Fund.

Dennis L. Tewksbury Award The 2015 Tewksbury Award was presented to Charles W. Roeder, Ph.D., P.E., F.SEI, M.ASCE. Dr. Roeder has been an ASCE member since 1970 and his contributions include charter member of SEI, SEI Technical Activities Division ExCom, Chair of the Dynamic Effects TAC, member of the SEI Awards Committee, 1998 Structures Congress Steering Committee, Chair of 2003 Structures Congress Steering Committee, and

a member of several SEI committees in both the Technical and Codes and Standards Divisions.

Walter P. Moore, Jr. Award The 2015 Walter P. Moore, Jr. Award was given to Gary Yet Kong Chock, Left to right: Don Dusenberry, Dharma Pasala, Ozen Celik, Benjamin Schafer, Satish Nagarajaiah, Yozo Fujino, S.E., D.CE, F.SEI, F.ASCE. Based in Charles Roeder, Jon Schmidt, Stan Caldwell, Roberto Leon, Hawaii, Mr. Chock’s project portfolio Larry Fahnestock, Mehrdad Sasani, Daniel Cox, John van includes wind, tsunami, earthquake, and de Lindt, Andy Herrmann, Laura Champion. hurricane hazard research, building risk assessments, hazard mitigation planning, coastal Walter L. Huber Civil flooding hazard analysis, building code developEngineering Prize ment, and emergency response planning. He has Up to five Huber Prizes are awarded each year worked on developing wind speed GIS-based for achievements in civil engineering research. mapping and topographical design provisions Larry A. Fahnestock, Ph.D., P.E., M.ASCE for adoption as State code amendments to the is one of the 2014 winners of the Huber Prize.

IBC. He led a group from ASCE/SEI to survey Dr. Fahnestock is known for his achievements of tsunami-damaged areas of Japan with an in seismic behavior and design of steel wall and interest in improving building codes. braced-frame systems. He combined large-scale SEI President’s Award experimental testing with nonlinear analysis to The 2015 SEI President’s Award was given develop pioneering practical guidance and has sigto Jon A. Schmidt, P.E., SECB, BSCP, nificantly influenced the codes. He is a dedicated M.ASCE. Mr. Schmidt has more than 20 educator, seeking to motivate and encourage curyears of experience working on aviation, com- rent and future generations of engineers. mercial, industrial, and institutional facilities Moisseiff Award for government, military, and private-sector The 2015 Moisseiff Award was presented to clients. He is a nationally recognized thought Dharma T.R. Pasala, Ph.D.; Apostolos A. leader and speaker on antiterrorism design of Sarlis, Ph.D., M.ASCE; Andrei M. Reinhorn, buildings, philosophy of engineering, and Ph.D., P.E., F.ASCE; Michael Constantinou, engineering ethics. Mr. Schmidt has served Ph.D., P.E., M.ASCE; Satish Nagarajaiah, on many SEI/ASCE committees including Ph.D., F.SEI, M.ASCE; Douglas P. Taylor, Blast, Shock & Impact; Building Security P.E, M.ASCE, for the paper titled “Simulated Council; BPAD Executive Committee; chair Bilinear-Elastic Behavior in a SDOF Elastic of the Editorial Board for STRUCTURE; Structure Using Negative Stiffness Device,” puband the Engineering Philosophy Committee. lished in the February 2014 issue of the Journal of Structural Engineering. In selecting them for American Society of Civil this award, the committee particularly noted the Engineering Structural Awards team’s findings to provide a seminal advance in influencing accepted design paradigms.

Shortridge Hardesty Award The 2015 Shortridge Hardesty Award was Raymond C. Reese Research Prize given to Benjamin W. Schafer, Ph.D., P.E., The 2015 Raymond C. Reese Prize was preM.ASCE. Dr. Schafer earned great respect sented to David B. Linton, P.E.; Rakesh for his solid analytical background, his deep Gupta, Ph.D., M.ASCE; Daniel T. Cox, knowledge of numerical techniques of struc- Ph.D.; Mary Elizabeth (Oshnack) tural analysis, and his rich experience as an Berkes, P.E.; John Van De Lindt, Ph.D., experimentalist. He has produced design tools F.ASCE; Milo Clauson, for their paper that are widely used to characterize the buck- titled “Evaluation of Tsunami Loads on ling behavior of thin-walled members. He has Wood Frame Walls at Full Scale,” published served on the Structural Stability Research in the August 2013 issue of the Journal of Council, as an Associate Editor of the Journal Structural Engineering. The selection commitof Structural Engineering, and as a member of tee particularly noted the team’s research was several ASCE committees. accompanied by full-scale experimentation.▪

Visit the SEI Website at www.asce.org/structural-engineering/structural-engineering-awards to submit a nomination for the 2016 awards.

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August 18, 2015 Wind Design of Solar Photovoltaic Arrays

Dr. David Banks, CPP, and Ron LaPlante, S.E., Division of the State Architect, California August 25, 2015 Seismic Design of Solar Arrays on Flat & Low-Slope Roofs

Karl Telleen, S.E., Maffel Structural Engineering September 10, 2015 Wind Engineering – Beyond the Code

Roy Denoon, CPP Wind Engineering & Air Quality Consultants

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and agreed to speak with other members and provide SEAoO feedback regarding moving forward. His feedback informed SEAoO that the Ohio legislature would also weigh input from OSPE (the Ohio branch of NSPE) in deciding how to approach legislation involving the practice of engineering. OSPE expressed opposition to structural licensure. The representative suggests that SEAoO coordinate with other engineering organizations such as OSPE to build a consensus prior to seeking any legislative action. The SEAoO Licensure Committee is working to build support among other stakeholders before approaching the legislature again.

The Missouri committee has met with possible allies such as Missouri Association of Building Officials, AIA, MODOT and the Design Alliance which includes MSPE, Board members, ACEC, AIA and others. So far no hard core opposition. They have developed a one-page position statement and intend to meet with educators, contractors and then MSPE. Their next step will be to write the language and possibly work with ACEC’s lobbyist to lay the ground work with all the groups and possible sponsoring legislators.

A number of other states have made progress in developing a licensure committee, garnering support within the engineering community and developing proposed legislative changes.

These include Arizona, New York, Minnesota, Tennessee and South Carolina.

All in all, there is a great amount of energy being expended across the country in attempts to get specialty licensure for structural engineers. Member organizations in a significant number of states are developing strong relationships with their engineering boards and their legislators. They are making it known that they are the voice for structural engineers in their respective states.

If you visit the Structural Licensure page under Resources on the NCSEA website, you will find information on state licensing rules, NCSEA’s participation in the Structural Engineering Licensure Coalition (SELC), licensure articles, and, soon, sample legislation templates for states seeking licensure. This should help develop consistency in the licensing language between states.

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News form the National Council of Structural Engineers Associations

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he NCSEA Structural Licensure Committee works with the Member Organizations to influence states to adopt consistent licensing laws and rules in the interest of public safety, especially relating to licensure of structural engineers.

As part of that mission the Committee has been monitoring the efforts of state Member Organizations and assisting them in those efforts. This past year we have seen a number of state Member Organizations make strides in their attempts to gain specialty licensing in their state. Following is a short description of current efforts across the country: Great strides were made by Florida this legislative session.

Proposed legislation was put before the legislature in 2015. The bill was passed by both houses of the legislature. Only a veto by the Governor kept the bill from becoming law. It was reported that the Governor believed that all engineers who wanted to become structural engineers should pass the SE exam. He did not agree with the grandfathering clause. Florida’s Licensure Committee is to be congratulated for their efforts and their success. Tom Grogan will give a more detailed account of Florida’s efforts in a later article.

The licensure committee in Texas continued working within the state to silence the opposition as they prepared to again go before the legislature. Their biggest opponent is TSPE, which is following the policies of the parent organization, NSPE. For the third legislative session in a row (six weeks every two years), licensing legislation has been crushed. But SEAoT remains steadfast with the support of their membership. They are determined to become a voice regarding all engineering issues at the legislature and the engineering board along with TSPE and Texas ACEC. The licensure committee in Georgia is also making progress.

Georgia House Bill 492 was sponsored in the 2015 session and will be voted on in the 2016 session. Though there did not appear to be major opposition, it was tabled this year because of a Supreme Court decision concerning licensing boards and North Carolina dentists. This decision created some doubt about how Georgia handles its licensing boards in general and was specific to the licensing bill.

In Connecticut, the licensure committee took their changes to the legislature for a second year in a row but it did not make it out of committee. They are a member of the ACEC structural engineers’ coalition and are able to utilize their lobbyist. The challenge for 2015 will be to separate the structural licensure issue from continuing education as they were in the same bill this previous year.

In Oklahoma, the licensure committee has obtained agreement with the licensing board for a title act with a transition period. Specific changes to the board rules and state laws are being developed for consideration during the 2016 legislation session. The board’s executive director made a presentation on this at OSPE’s state wide meeting in June. OSEA licensure committee members attended this session to gauge interest, positive and negative, on the topic.

Ohio’s SEAoO Licensure Committee was able to meet informally with a member of the Ohio legislature to discuss the idea of structural licensure. The representative, an engineer himself, expressed general agreement with the goals of structural licensure

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Diamond Reviewed

August 2015

Non-CalOES courses award 1.5 hours of continuing education. Approved for CE credit in all 50 States through the NCSEA Diamond Review Program.

Ashraf Habibullah, S.E., President and CEO, Computers & Structures, Inc Structural Engineering: The Profession, The Grandeur, and The Glory Join Ashraf as he shares his passion and enthusiasm for structural engineering, a profession whose grandeur and glory are worth celebrating!

Other educational offerings include technical as well as non-technical sessions, on two tracks. Speakers include forward-thinking practicing structural engineers and panel discussions. Visit www.ncsea.com for a complete schedule of sessions.

Registration

Hotel

Reservations at Red Rock Resort, the Summit host hotel, are open.

A reservation link for the NCSEA group rate of $180 plus $15 resort fee, which includes complimentary valet and self parking, airport shuttle, in-room internet and Spa & Fitness Center access, is available at www.ncsea.com.

In addition to the educational sessions, the Summit offers opportunities for networking and social interaction.

Wednesday kicks things off with the Young Engineer reception, followed by the Structural Engineering Certification Board reception. You’ll have plenty of time to catch up with old friends and make new ones.

In addition to Thursday’s breakfast, lunch and breaks, the Welcome Reception on the trade show floor gives attendees the chance to visit with exhibitors while enjoying cocktails and food. After the Welcome Reception, join fellow attendees for some late-night bowling competition and fun at the Red Rock ‘N Bowl in the VIP Bowling Lounge at the Resort.

Friday’s evening will give attendees the chance to show off their finery and celebrate the best in structural engineering innovation at the NCSEA Awards Banquet. Black tie is encouraged, but not required.

If that’s not enough, the Red Rock area of Las Vegas has much to offer, whether it be gambling, entertainment, shopping or outdoor activities. The host hotel, Red Rock Resort, features restaurants, lounges, a movie theatre and bowling alley, and a walkway to Downtown Summerlin, with shops, dining and entertainment options. If you want to check out the Strip, the hotel has a shuttle to take you there.

If you prefer outdoor options, a high desert wonderland is located just minutes from the hotel. If you want to rock climb the 5th most popular destination in the country, mountain bike, hike or kayak, check out Red Rock Adventures through the hotel.

News from the National Council of Structural Engineers Associations

Discounts for Summit registration are available to NCSEA members, Young Engineers under the age of 36, and First-Time attendees. While Young Engineer and First-Time attendee rates are available until the Summit begins, Early Bird rates end August 28. Register today!

More than just education!

NCSEA News

Keynote Speaker:

NCSEA offers Short Courses on New Design Irregularities Book

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how to appropriately analyze and design lateral force-resisting elements for various types of irregular buildings located in Seismic Design Category (SDC) B and D. The book references the 2012 IBC and ASCE/SEI 7-10, and references material standards from the 2012 IBC by section number. It is also applicable to the later versions of these standards and the 2015 IBC. Four detailed design examples include an overview of applicable irregularities, a discussion of appropriate analysis and design requirements, determination of key lateral forceresisting system demands, and design of select example elements contained in the building’s load path.

The course instructor, Timothy Wayne Mays, Ph.D., P.E., is president of SE/ES and a Professor of Civil Engineering at The Citadel in Charleston, SC. He has served as executive director of the Structural Engineers Associations of South Carolina and North Carolina, and currently serves as NCSEA Publications Committee Chairman.

The publication is available for purchase through both the NCSEA and the International Code Council websites. NCSEA members receive a discount on the publication price.

ASS

With the release of the new NCSEA publication Guide to the Design of Common Irregularities in Buildings, 2012/2015 IBC and ASCE/SEI 7-10, NCSEA is offering an associated live course. The course provides an overview of the book material and includes approximately 25 percent new material not included in the actual publication to help the engineer better understand the fundamental theory behind the practical example problems, and to verify approaches used with hand calculations and simple computer modeling results. The 4-hour NCSEA Diamond-approved course can be provided as a stand-alone course or as part of an arranged program such as an NCSEA Member Organization meeting. All attendees will receive one copy of the new guide. Registration information is available at www.ncsea.com. There is a scheduled course available August 10 in Boston. Additional courses will be scheduled.

The new guide fully explains how and why building irregularities impact structural design and provides detailed examples of

COUNCI L

Electrical Transmission & Substation Structures Conference

Structural Columns

The Newsletter of the Structural Engineering Institute of ASCE

September 27 – October 1, 2015, Branson, Missouri EARN uP TO 19 PDHs

REGISTRATION NOW OPEN Grid Modernization – Technical Challenges & Innovative Solutions

• Industry executives • Consultants • Government-agency personnel • Design/build contractors • Anyone with an interest in improving the structural reliability of transmission lines and substations Visit the conference website at www.etsconference.org for complete information and to register.

Can you afford to wait until 2018? Don’t miss out on an excellent opportunity to network with professionals in your industry.

The conference will feature three days of technical sessions, four days of exhibits, one workshop, and an exciting constructionoriented demonstration day that will offer many opportunities to share international knowledge on grid modernization from a structural and construction standpoint. Attendees will experience a unique setting in which to learn and network with peers, industry leaders, and knowledgeable suppliers. Who Should Attend: • Civil engineers • Structural engineers • Electrical transmission engineers • Substation engineers • Engineering students

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

Local Activities Lehigh Valley Chapter

Maryland Chapter

The SEI Lehigh Valley Chapter is offering a half day structural engineering seminar on August 12, 2015. Partnering with the Lehigh University Graduate Student Chapter and the ASCE Leigh Valley Section, the seminar will offer up to 4PDHs. Four sessions will be offered on topics from steel structures to retrofit solutions.

This year the SEI Maryland Chapter has presented a very active program of activities for their members. These include presentations on stabilizing a deflected I-495 bridge, the Seagrit Marine Terminal, and a construction tour of a new health sciences facility.

West Coast Florida Chapter

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.

The SEI West Coast Florida Chapter recently held a seminar about the extradosed prestressed bridge in Pearl Harbor. The chapter also presented an in-depth structural tour of a hospital expansion project.

See the News page of the SEI website for details.

Get Involved in SEI Local Activities

Design of Steel Transmission Building Information Modeling: Towers Standards Committee Applications and Practices The Design of Steel Transmission Towers Standards Committee recently completed the latest revision of ASCE 10. Design of Latticed Steel Transmission Structures (ASCE 10-15) is now available as a published softcover standard or as an E-Book in pdf format. In the next few months the existing committee will be discharged and the committee will seek to re-form for the next revision. The goal of this future volume is to “modernize” the document with the inclusion of relevant photos, add more examples and perhaps revisit the format of those currently included, review other industry criteria for relevance and review other relevant Standards for possible changes in this Standard.

For more information, see the full story on the SEI news page.

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Building information modeling (BIM) has become a significant area of endeavor in the architecture, engineering, construction, and operations (AECO) industry. Building Information Modeling contains 13 chapters, contributed by international researchers and practitioners, that present a comprehensive overview of the recent advances in the application of BIM across the AECO industry. The table of contents and abstract for each chapter are viewable for free in the ASCE Library. Engineers, architects, contractors, building owners, facility managers, as well as researchers, will find this publication a valuable resource.

Visit the ASCE Bookstore at www.asce.org/publications to learn more.

August 2015

December 10 – 12, 2015, San Francisco, California REGISTRATION NOW OPEN The ATC-SEI Conference on Improving the Seismic Performance of Existing Buildings and Other Structures is an opportunity for structural engineers, business owners, and users of ASCE seismic standards to learn the latest in seismic evaluation and rehabilitation.

Reasons to Attend: • Earn up to 14 Professional Development Hours (PDHs) • Each day starts with two Key Note Speakers • Learn from educational technical sessions • Network with colleagues and leaders in your field • Exhibitor and sponsorship opportunities are available • Honor the Champions of Earthquake Resilience at the Awards Dinner

New Infrastructure App from ASCE – FREE!

ASCE has launched a new “Save America’s Infrastructure” app. The app shares key data from the Report Card along with Sign up for any ASCE live webinar to be held in June, July, or news, prompts users via notifications to take action, and with August – either 60 or 90 minutes – and get a special individual just a few clicks can connect with legislators or social media. As member rate of $99, applied automatically when registering. stewards of the nation’s infrastructure, civil engineers know and Take advantage of convenient, efficient training that provides understand the challenges our country’s roads, bridges, dams, practical knowledge and earns PDHs. This offer does not apply levees and drinking water pipes are facing. The app provides to site/group webinar registrations, on-demand webinars, usable data to illustrate the problem, and then offers ways to or P.E. exam review courses and cannot be combined with tell lawmakers and social networks about it, too. Visit the App other offers. Visit the ASCE Continuing Education website at Store to download. www.asce.org/continuing_education for more information.

Save the Date

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

Joint Congress highlights will include: • Joint networking events • Technical sessions on both geotechnical & structural topics • Special lectures • Short courses • Young professional and student member events • Impressive exhibit hall Visit the Joint Congress website at www.Geo-Structures.org for more information.

STRUCTURE magazine

Reach SEI Members with SEI Sustaining Organization Membership Join SEI as a Sustaining Organization Member to raise recognition for your organization with decision makers in the structural engineering community year-round, and to show your leadership and support for SEI to advance and serve the structural engineering profession. Demonstrate your commitment and increase your organization’s visibility with more than 25,000 SEI members and at SEI conferences through www.asce.org/SEI, the monthly SEI Update e-newsletter, and STRUCTURE magazine.

We hope you will join Hayward Baker, International Code Council, and Simpson Strong-Tie in support of SEI as an SEI Sustaining Organization Member. Learn more at www.asce.org/SEI-Sustaining-Org-Membership.

Questions? Contact Suzanne Fisher at sfisher@asce.org.

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The Newsletter of the Structural Engineering Institute of ASCE

Take Any of ASCE’s Live Webinars This Summer for $99 Each

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

Structural Columns

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

CASE Risk Management Contracts Available

CASE in Point

The Newsletter of the Council of American Structural Engineers

CASE #10 An Agreement between Structural Engineer of Record and Geotechnical Engineer of Record The Structural Engineer of Record may be required to include geotechnical engineering services as a part of its agreement. If a geotechnical engineer & laboratory must be subcontracted for this service, CASE #10 may be used. It can also be altered for use between an Owner and the Geotechnical Engineer of Record.

CASE #11 An Agreement between Structural Engineer of Record (SER) and Contractor for Transfer of Computer Aided Drafting (CAD) files on Electronic Media Fabricators and suppliers are requesting CAD or BIM files from the designer. By providing CAD or BIM files, changes may be made to the files by others that would not be distinguishable without a critical review. CASE #11 is used so that both the Structural Engineer of Record and recipient of the CAD or BIM files understand the limitations and extent to which the files may be used. This is an agreement to allow for the transfer of CAD or BIM files to others.

CASE #12 An Agreement between Client and Structural Engineer for Forensic Engineering (Expert) Services This is a sample agreement when the engineer is engaged as a forensic expert. It is designed primarily for when the Structural Engineer is engaged as an expert in the resolution of construction disputes, but can be adapted to other circumstances where the Structural Engineer is a qualified expert.

CASE #13 Prime Contract, an Agreement between Owner and Structural Engineer for Professional Services This agreement is intended for the Structural Engineer to serve as the Prime Design Professional. It addresses projects which may require other engineering disciplines and architectural services which are more than incidental. Examples are parking garages, warehouses, light industrial buildings, sports facilities and structural renovations. It should be distinguished from CASE #2 which is to be used when the Structural Engineer of Record has an agreement with the Owner but does not serve

as the Prime Design Professional. This document is written to be compatible with CASE #3, which can be used by the Structural Engineer as Prime Design Professional to contract with consultants on the same project in conjunction with this agreement CASE #14A Supplemental Form A, Additional Services Form A one-page Additional Services form to be signed by both the Structural Engineer and the Client.

CASE #14B Standard Form for Request for Information (RFI) The purpose of this document is to provide the design team with a standard Request for Information (RFI) form that can be included in the bid documents and used by all contractors and subcontractors on the project.

CASE #15 Commentary on AIA Document A201 “General Conditions of the Contract for Construction”, 1997 Edition The purpose of this Commentary is to point out sections and paragraphs of AIA document A-201 which, in the opinion of CASE, merit special attention, or which other reviewers have found to contain “pitfalls.” (See also CASE Contract Document 6.)

CASE #16 An Agreement Between Client and Structural Engineer for a Structural Condition Assessment The purpose of this Document is to provide a sample Agreement for structural engineers to use when providing a structural condition assessment directly to a client. Examples are – earthquake evaluation, seismic retrofitting, fire or wind damage, changes in occupancy or historic preservation.

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

WANTED

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

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

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

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

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

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

August 2015

October 13 –17 ACEC is holding its Fall Conference at the Westin Copley Place, Boston, MA. CASE will be holding convocation on Thursday, October 15. Sessions include: 10:45am How to Reduce Your Risk on Alternative Delivery Projects Moderator: Beth Larkin: HNTB Speakers: Mary Conway, HNTB; George Wolf, Shook Hardy & Bacon; David Hatem, Donovan Hatem 1:45pm

5:15pm

Non-Neotiable Contracts: What’s Plan B? Karen Erger & Bob Fogle, Lockton Co.; Eric Miller, Ice Miller; Jennie Muscarella, Kenny, Shelton, Liptak, Nowak LLP ACEC / Coalition Meet and Greet

Member Firm CEOs Forecast Future of Engineering at ACEC Fall Conference in Boston, MA

Managing Uncertainty and Expectations in Building Design and Construction Clark Davis, Cameron MacAllister Group; Stephen Jones, Dodge Data & Analytics Building Resilient Infrastructure for Future Cities Terry Bennet, Autodesk Inc.; Donna Huey, Atkins Global; Marty Janowitz, Stantec Missouri’s Peer Review Law–Should Your State Have One? Karen Erger, Lockton Companies How to Reduce Your Professional Liability Costs Tim Corbett, SmartRisk The Conference also features: • General Session addresses by Pulitzer Prize-winning author Doris Kearns-Goodwin; 2015 ACEC Distinguished Award of Merit Honoree Dr. Robert Ballard • CEO roundtables; • Exclusive CFO, CIO, Architect tracks; • Numerous ACEC coalition, council, and forum events; and • Earn up to 21PDHs

ACEC BUSINESS INSIGHTS ISI Makes Strides in Promoting Infrastructure Sustainability

More than 3,300 professionals from more than 170 engineering firms and public agencies have been credentialed as Envision™ October 13 –17 Sustainability Professionals (ENV SP) by the Institute for Sustainable Infrastructure (ISI).

Three leading Member Firm CEOs will provide their forecasts The Envision sustainability program rates the environmental on Change and Innovation in the A/E Industry during the ACEC and economic benefits of infrastructure projects as well as lifeFall Conference in Boston, MA, October 13-17, 2015. On the cycle sustainability. panel will be Stephen Hickox, Chairman/CEO, CDM Smith; ISI was founded in 2010 by ACEC, the American Public Eric Keen, Eningeering President & Vice Chair, HDR; Tom Works Association (APWA) and the American Society of Civil Scarangello, Chairman/CEO Thornton Tomasetti Engineers (ASCE).

Also speaking at the Conference will be a panel on People and For more information on the Institute for Sustainable Practices that Build Success featuring Mike Carragher, President, Infrastructure, www.sustainableinfrastructure.org.

VHB; Larry Smith, President/CEO, Haley & Aldrich; Lisa Brothers, President/CEO, Nitsch Engineering The Conference also features more than three dozen bottom-line-focused educational sessions; CEO roundFollow ACEC Coalitions on tables; exclusive CFO and CIO tracks; the CASE Convocation; and numerous ACEC coalition, council, Twitter – @ACECCoalitions. and forum events. For more information and to register, www.acec.org/conferences/fall-conference-2015/registration.

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CASE is a part of the American Council of Engineering Companies

3:30pm

Dead in the Water: A Case Study of Claims Facing Civil Engineers Dan Buelow & Bob Stanton, Willis A/E

You will not want to miss these additional important risk management sessions:

CASE in Point

ACEC Fall Conference Features Case Risk Management Convocation and More!

Structural Forum

opinions on topics of current importance to structural engineers

EOR Uses Construction Coordination Drawings to Finalize Design

By Dean Brown, S.E.

D

o Owners, Building Officials, and even Professional Engineers really understand each other’s respective roles and responsibilities, especially on the use of deferred submittals? Many of today’s engineered designs are not so much linear (i.e., design then build), but cyclic (i.e., iterations of design then build then design then build, etc.).

Let me relate an experience from another project in which my employer was the Construction Manager (agent) for a federal government agency constructing a post-tensioned structure. The project involved not only the post-tensioning system with associated reinforcing steel, but precast wall panels as well. Each of these products were part of the contractor’s scope of responsibility. My involvement on the project began basically mid-stream (i.e., after design documents were submitted, and contracts awarded, and construction delays had occurred). For the sake of simplifying this discussion, the Owner and Building Official were one and the same… a government agency.

As was typical of all individual projects on this complex, structural engineers used stamps from their respective states (i.e. any of the 50 state seals could be used).

Project documents correctly defined respective roles and responsibilities for each party.

The project specifications included language directing the prime contractor to perform “concurrent coordination” of all submittals.

The general notes section of the structural drawings indicated that all structural submittals needed to be reviewed by the EOR. Even the Post-Tensioning Manual (published by the Post-Tensioning Institute) concurs by stating, “It is essential that details for the tendons, mild steel reinforcement, conduit, ductwork, and other embedment items be reviewed and coordinated by the … Engineer and General Contractor during preparation of installation drawings. The installation drawings prepared by the different material suppliers may show incompatible or conflicting layouts.” The Manual goes on to say, “When conflicts arise either during the development of installation or during construction, the tendon layout should govern over other element or

embedment locations unless otherwise indicated by the Engineer of Record.”

On the contractor’s side, actual practice was far from reality as documents submitted to the owner were staggered. Coordination drawings were never prepared and conflicts were difficult to pinpoint.

The government contributed a misstep also by not contracting with the EOR (as a cost savings measure) for “construction support services.” This obviously resulted in limited structural engineering reviews.

Weeks turned into months, each side pointing the finger at the other as to causation for delays. And though all stakeholders eventually met together to get coordination issues worked out, the project ran into cost overruns and a late opening.

Herein lies the main issue regarding deferred submittals; after stamped documents have been given to the owner, is further involvement by the EOR part of “construction support services” or continuance of the original design process? When is final design … FINAL? Furthermore, given the differing language of all 50 states on the use of a seal, does one state’s stamp provide an EOR better control over deferred submissions than another state’s? That is a legal question I am not qualified to answer.

The need for an EOR’s involvement during the “construction phase” is absolutely essential. It is this engineer’s opinion that it should be a building code mandated requirement.

As demonstrated, design issues are not all resolved once the contract documents have been handed over to the owner (or building official). Allowing conditional statements adjacent to the seal better communicates the need for ongoing involvement by the EOR and easily informs the owner, contractor, and building official what stage of completion has been reached. Please refer to my earlier discussions on these issues beginning in the August 2014 issue of STRUCTURE magazine.

In his discussion relating engineering failures, the late Paul Munger, Ph.D., P.E. (30 Years Later – The Kansas City Hyatt Regency Skywalk Collapse found at www.asce.org), emphasizes the need that engineers not relegate their authority to industry trends

or management influences. He emphasizes that there is indeed a difference between an engineer’s authority and responsibility.

Authority has more to do with the power to control or give directives. Building Officials have authority on building projects within their jurisdiction. Responsibility is an expected duty. Professional Engineers demonstrate their Responsible Charge (i.e., responsibility) by use of their seal.

If you don’t understand the difference between authority and responsibility, just file a complaint of suspected wrongdoing on a Professional Engineer to his/her respective state board and a preliminary investigation may ensue regarding Responsible Charge. File a similar complaint on a building official (if you can determine who regulates them) and you will most likely get a letter deflecting any city or county responsibility. I would argue that Building Officials have authority but little responsibility. The two are not necessarily the same.

More conditional control on the use of the stamp gives more authority to the Professional Engineer and provides better communication on the use of deferred submittals.

In Mr. Hung’s article (STRUCTURE, December 2003 – January, 2004), he writes, “What are the design phases in a project?

What work product is required in each phase of a project? How much information does a structural consultant need for his/her design…on each phase.”

Until these questions are clearly defined (i.e., clarifying what Standard of Care actually means), Professional Engineers need to question current industry practices and be determined to improve that which we can have influence on. This author believes the first step is in providing better statute language on the conditions surrounding the use of the seal.▪ Dean D. Brown, S.E. (browndean57@yahoo.com), is a Professional Structural Engineer in the state of Utah. He works as a senior structural engineer for Lauren Engineers & Constructors in Dallas, TX.

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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