STRUCTURE magazine | August 2016 by structuremag

A Joint Publication of NCSEA | CASE | SEI

STRUCTURE

August 2016 Steel/Cold-Formed Steel

SPECIAL

SOFTWARE

S EC T IO N

We Have The Smartest Customers In The Industry

We Want To Keep It That Way. Independence Tube is launching a major educational initiative. Independence Tube Corporation University – ITC U. Tube and pipe products are becoming more and more a first choice material for conventional as well as non-conventional applications. On-line Training We will offer on-line tutorials that will provide industry knowledge and training to empower architects, engineers, designers, fabricators and service center professionals on the manufacturing and benefits of HSS and the industries it supplies. Team of Experts We will have a dedicated web page where you can submit your questions. Our team of experts, including an engineer and metallurgist, will answer all your concerns. From our rolling practices to exploring the grades and sizes we produce. We will let you determine how HSS can fit into your next design, fabrication or structure. School is now in session. Sign up today, it’s free.

Celebrating Forty Years of Quality Tube Products CH ICAGO, I L

1-800-376-6000

MARSEILLES, IL

www.independencetube.com

D E C AT U R , A L

www.itcpiling.com

T RI NI T Y, AL

Increase Productivity with Trimble’s Structural Software Suite Powerful Structural Software to: Analyze, Design, Detail and Construct Buildings Tekla Tedds

- Calculation Production Suite - Automate all your structural calculations & deliver high quality documentation

Come see us at: NCSEA Convention Booth 149 tek.la/ncsea2016

Tekla Structural Designer -Analysis & Design Suite -Focused Analysis & Design for Steel & Concrete Buildings

Tekla Structures -BIM Solution for Structural Engineers -Produce construction documents and shop drawings from one solution

“Tekla Structures is the most exhautive form of communication that we require on our projects. Just as important, Tekla has shown a willingness to incorporate the needs of designers, such as making it easier to produce construction documents from models” — Stephen E. Blumenbaum, Walter P Moore TRANSFORMING THE WAY THE WORLD WORKS

Transform the way you work with Tekla’s complete software suite:

http://tek.la/eng

The integrated solution versatile enough for Commercial Industrial Institutional Utilities Power Generation Bridge structural analysis and design and backed by the industry’s most dedicated and responsive engineering support team.

STRUCTURE

August 2016 34

FEATURE

Transforming a Historic Auto Plant

34 EDITORIAL

7 Add Some Magic to Your Practice!

STRUCTURAL FAILURES

25 Hyatt Regency Skywalk Collapse Remembered

By Carrie Johnson, P.E., SECB

By Randall P. Bernhardt, P.E., S.E.

STRUCTURAL DESIGN

STRUCTURAL PERFORMANCE

10 General Principles of Fatigue and Fracture – Part 1 By Paul W. McMullin, S.E., Ph.D.

30 The 2015 Nepal Earthquake

Rediscovering a World Class Terminal

By James P. Mwangi, Ph.D.,

STRUCTURAL PRACTICES

By Dave Schubert, P.E.

By Shane E. Sweeten, S.E. Renovation of Terminal 3 at Phoenix’s Sky Harbor Airport required major structural alterations and additions. Excellent Team coordination and use of BIM allowed for the successful tackling of analysis, design and constructability issues head-on in the design-build project.

INSIGHTS

54 Seismic Retrofits Using the IEBC By John Dal Pino, S.E.

STRUCTURAL ANALYSIS

18 The Influence and Modelling of Warping Restraint on Beam By Angus Ramsay, M.Eng., Ph.D.,

ENGINEER’S NOTEBOOK

56 Flexure Design of Built-up Box Beams By Roger LaBoube, Ph.D., P.E.

C.Eng. and Edward Maunder, MA, Ph.D. PRACTICAL SOLUTIONS

22 Long-Span CFS Trusses Reach New Heights By Mike Pellock, P.E. and David Boyd

FEATURE

P.E., S.E.

14 Long-Span, Open-Web Trusses

By Klaus H. Ohrnberger, P.E. and Tito R. Marzotto, P.E. Fiat Chrysler Automobiles concluded that investing in an older plant in the Detroit area to make way for a new generation of minivans made sense from both economic and historical perspectives. Structural engineers were tasked with providing upgrades under a fast track schedule while maintaining an active assembly line for the current model.

SPOTLIGHT

59 2016 ASCE Structural and SEI Awards STRUCTURAL FORUM

FEATURE

Software Makers See Strong Demand By Larry Kahaner As firms get busier and technology continues at a rapid rate of change, Structural Engineers continue to demand more from software vendors. For improved efficiency, faster modeling, new user interfaces, interoperability, BIM, and more, vendors have lots of new offerings.

66 A Personal Call to Regain Seismic Design Code Simplicity By David W. Anderson, P.E., SECB

On the cover A rendering of the new Phoenix Sky Harbor International Airport Terminal 3, created with BIM, shows how alterations to the existing building improved views and daylight inside the terminal. (Photo courtesy of Hunt-Austin Design Build). See the article on page 38. 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

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

August 2016

Elastocolor beats the elements

After

Before

The facades of the 608 units in the Blue Lagoon Condominiums complex in Miami, Florida, are subject to aggressive environmental effects from heat, humidity and high levels of sea salt as well as carbon emissions from proximity to expressways and the Miami International Airport. The condo association’s board of directors turned to MAPEI’s Elastocolor Coat protective/decorative coating for defense against the elements. MAPEI supplied three custom colors of Elastocolor Coat to meet aesthetic requirements. And thanks to superior performance characteristics – such as carbonation resistance, high elongation, chloride resistance and water-vapor permeability – Elastocolor Coat offered protection against the environment.

Scan this code to view our standard color selection or request a special color.

Editorial

Add new trends, Some new techniques Magic and current to Your industry issues Practice! By Carrie Johnson, P.E., SECB, NCSEA Past-President and Summit Chair

Malley will discuss Upcoming Changes to AISC 341 – Seismic Provisions for Structural Steel Buildings. Non-technical topics will include information you can use to improve your practice. Annie Kao will present Becoming a Trusted Advisor: Communication and Selling Skills for Structural Engineers. The NCSEA Young Member Group will have a panel of engineers who will discuss an array of technical and non-technical issues in a presentation titled Has THIS Ever Happened to You? It will be presented via the short, fast-paced and automated PechaKucha style that limits presenters to an allotted amount of time and number of slides. Then Tom Grogan will discuss Florida SE Licensure: How the Bill was Created and Almost Became Law and Larry Novak will present Top 10 Useful Lessons for Structural Engineers. Also starting Thursday morning will be our Trade Show. Each year, we have an impressive number of exhibitors who are there to discuss their latest products and answer any questions you may have. It is an excellent opportunity to keep up by obtaining the latest manuals and product literature in one location. Thursday night, there will be a reception on the trade show floor, and Friday night will be the awards banquet. The NCSEA Banquet and awards presentation on Friday evening include the transition of officers, followed by awards that will be presented to individuals who have provided outstanding service and commitment to the association and to the structural engineering profession. Then, structural engineers will receive awards for projects that highlight some of the best examples of structural ingenuity throughout the world. The NCSEA Excellence in Structural Engineering Awards have been presented annually since 1998, and competition for the awards has continued to improve each year. I encourage you to come see the awards and be inspired! The NCSEA Summit also serves as an Annual Meeting of NCSEA’s 44 Member Organizations. Each of NCSEA’s Member Organizations has a delegate that represents their structural engineering association. The delegates will meet for breakfast on Thursday morning and then during a delegate collaboration session on Friday morning. The Summit concludes with NCSEA’s Annual Business Meeting on Saturday morning, September 17. This is an open meeting and includes reports on the activities of NCSEA’s committees and Member Organizations. These updates will highlight all of the hard work everyone is doing to enhance our profession further. I hope you agree that the outstanding technical program and exciting activities make this year’s NCSEA Structural Engineering Summit a “can’t-miss” event. For more information, including special offers for Disney Park tickets, please visit www.ncsea.com and select the Meetings tab. I hope to see you in Orlando!▪

a member benefit

STRUCTURE

hope you are planning to attend the 2016 NCSEA Structural Engineering Summit. I think it is going to be great this year, and I know it will be our highest attendance ever! The dates are September 14 thru 17 at Disney’s Contemporary Resort at Walt Disney World in Orlando, Florida. The official start to the Summit will be Wednesday evening, and we plan on starting with some fun! We will have a welcome reception at the Contemporary sponsored by the Young Engineers, followed by a special dinner at the Orlando Museum of Art. The dinner will be hosted by our Platinum level sponsor, Computers & Structures, Inc. (CSI). It promises to feature endless food, bottomless champagne, open bar, and unforgettable entertainment. Anyone who has attended an event sponsored by CSI can attest that this promise will be met. Given that NCSEA focuses on the practicing structural engineer when planning the program for the Summit, you can be assured that Thursday and Friday, September 15 and 16, will provide outstanding educational opportunities for learning from, and interacting with, leaders of the structural engineering profession. On Thursday morning, our keynote speaker will be Kent Estes, an Imagineer with Disney, who will tell us his remarkable story about Structural Engineering for Walt Disney Theme Parks. Then, since we will be in Florida, our program will highlight wind design with featured speakers Don Scott, discussing ASCE 7-16 Wind: How it Affects the Practicing Engineer, and Emily Guglielmo, discussing Wind Loads on Non-Building Structures for the Practicing Engineer. Subsequent programming at the Summit will include two concurrent tracks of sessions on Thursday afternoon, as well as all day Friday, featuring both technical and non-technical topics. Each of these tracks will provide information that practicing engineers can take back to their office and use. Technical topics will include discussions on a wide variety of materials and loading conditions. A panel from the Structural Engineers Association of California will discuss the SEAOC Structural / Seismic Design Manuals, Thomas Mendez will present Strut and Tie Design: What they Didn’t Teach You in School, Michelle Kam-Biron will discuss 2015 / ASCE 7-10 Special Design Provisions for Wood Construction, Gene Stevens and Chuck Larosche will present New ACI Standards and Repair of Existing Concrete Structures, Ed Huston will talk about TMS 402-13, The Masonry Design Standard, Donald Harvey will discuss Great (and Horrible) Masonry Design Practice, Kirk Harman STRUCTURAL ENGINEERING will present So you Want to INSTITUTE Delegate Connection Design – How to do it Right, and Jim STRUCTURE magazine

Carrie Johnson is a Principal at Wallace Engineering Structural Consultants, Inc., Tulsa OK.

August 2016

ADVERTISER INDEX

PLEASE SUPPORT THESE ADVERTISERS

ADAPT Corporation ............................ 58 Alpine TrusSteel .................................... 21 Applied Science International, LLC....... 67 ASDIP Structural Software .................... 48 Bluebeam Software ................................ 45 Canadian Wood Council ....................... 49 Clark Dietrich Building Systems ........... 37 Design Data .......................................... 46 DEICON.............................................. 51 Dlubal Software, Inc. ............................ 44 Integrated Engineering Software, Inc..... 24 Independence Tube Corporation ............. 2 Integrity Software, Inc. ............................ 8 KPFF Consulting Engineers .................. 28 Legacy Building Solutions ..................... 57

Lindapter .............................................. 50 LNA Solutions ...................................... 33 MAPEI Corp........................................... 6 NCEES ................................................. 53 Nemetschek Scia ................................... 42 New Millennium Building Systems ....... 13 Redbuilt ................................................ 47 RISA Technologies ................................ 68 S-Frame Software, Inc. ............................ 4 Simpson Strong-Tie........................... 9, 29 Structural Technologies ......................... 55 Struware, Inc. ........................................ 40 Super Stud Building Products, Inc......... 11 Trimble ................................................... 3 Wood Products Council ........................ 41

Opinions Matter…

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

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

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

EDITORIAL BOARD Chair Barry K. Arnold, P.E., S.E., SECB ARW Engineers, Ogden, UT chair@structuremag.org

Based on feedback, STRUCTURE’s Structural Forum columns are popular reads. Have you considered writing a Forum piece? What excites you or frustrates you about the profession? Would you like to see a change in the realm of Structural Engineering? Do you have an opinion you would like to share? Start a conversation with your peers about a topic you have a passion for. If you can express your opinion in 900 words, we would like an opportunity to consider it for a future issue of STRUCTURE. Email your draft to Publisher@STRUCTUREmag.org today!

Jeremy L. Achter, S.E., LEED AP ARW Engineers, Ogden, UT John A. Dal Pino, S.E. FTF Engineering, Inc., San Francisco, CA Dilip Khatri, Ph.D., S.E. Khatri International Inc., Pasadena, CA Roger A. LaBoube, Ph.D., P.E. CCFSS, Rolla, MO Brian J. Leshko, P.E. HDR Engineering, Inc., Pittsburgh, PA

Important news for Bentley Users

Jessica Mandrick, P.E., LEED AP Gilsanz Murray Steficek, LLP, New York, NY Brian W. Miller Davis, CA Mike Mota, Ph.D., P.E. CRSI, Williamstown, NJ

SofTrack controls Bentley® usage by Product ID code and counts (pipe, inlet, pond, and all others) and can actively block unwanted product usage

• Prevent Quarterly and Monthly Overages • Control all Bentley® usage, even licenses you do not own • Give users visibility of who is using licenses now • Warn and Terminate Idle usage

SofTrack also supports Autodesk® Cascading Licensing and

SofTrack directly reports and controls ESRI® ArcGIS license usage

Additionally, SofTrack provides software license control for all your applications including full workstation auditing of files accessed and websites visited. Many customers also benefit from SofTrack’s workstation specific logon activity reporting. © 2016 Integrity Software, Inc. Bentley is a registered trademark of Bentley Systems, Incorporated

STRUCTURE magazine

STRUCTURE

August 2016

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 August 2016, Volume 23, 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.

Field Adjustable Can be field trimmed and drilled

EASY TO SPECIFY

INSTALL INSPECT

Stronger Wall Narrow panel widths have higher loads Shear Transfer Plate for Header/Top Plate Attachment Ships with every wall and installs with nails

More Applications Residential, multi-family and light-frame commercial construction

Code Listed ICC-ES ESR-2652 and City of L.A. RR 25730 evaluated to the 2015 IRC/IBC

Easy to Install Front, back and side access for easy installation and inspection

The new Strong-Wall® Wood Shearwall has arrived and is better than ever. Standing up to 20 ft. tall, the new walls have significantly higher allowable loads than our original prefabricated wood walls and are now much easier to install and inspect. With visible ttps://widendtp.com/ssttoolbox/uqnjmzfgnn/metal_plate_look_36percent.psd?res=proxy front, back and side access for anchorage attachment, and a simplified top-of-wall connection, they can be installed before or after framing. Learn more about our new high-performance, field-trimmable Strong-Wall Wood Shearwalls ( WSW ). Call (800) 999-5099 and visit strongtie.com/wsw.

Strong-Tie Company Inc. WSW16

Structural DeSign design issues for structural engineers

he intent of this 3-part series is to expand the engineer’s understanding of the realities and opportunities in fatigue and fracture design. After reading this segment, the reader may have more questions than answers. This is not because the reader will not learn anything, but because they will better know the questions they should be asking.

Have Crack? What’s Next? Have you ever had a crack in a structure or been called on to evaluate one? It can be rather unsettling. Cracks like the one in Figure 1 are pretty easy. We replace the segment of pipe. However, what if you have a crack like the one in Figure 2? Alternatively, the UT inspector tells you there is a crack inside a key portion of your structure that you cannot even see. Under these circumstances, the solutions become less obvious and more difficult. Complicating matters is the fact that there is nothing in the codes that guides the engineer in evaluating cracks, leaving a big hole in the engineer’s ability to assess them and provide recommendations for repair. Fortunately, there are ways to evaluate these challenges, which will be discussed in the next two articles in this series.

Figure 1. Rupture in a gas pipeline.

General Principles of Fatigue and Fracture Part 1 By Paul W. McMullin, S.E., Ph.D.

It’s Complicated – and that’s OK

Paul McMullin is a founding partner at Ingenium Design in Salt Lake City. He is an Adjunct professor and the lead editor of the Architect’s Guidebooks to Structures series. Paul can be reached at Paulm@ingeniumdesign.us.

Embrace the complicated nature of cracks. The variables that influence fatigue and fracture behavior are truly legion. Figure 3 shows numerous inputs into fatigue and fracture design. It is certainly not complete, but it is a good start.

Figure 3. Inputs into fatigue and fracture design.

10 August 2016

Figure 2. Crack in a steel truss.

Fantasy vs. Reality The greatest disservice we can do in our approach to fatigue and fracture design is to oversimplify things. Crack design is full of oversimplifications. Why? It makes the design easier – initially. Who would not like that? In the real world, the problem and solution are much more complex. Oversimplifying the problem results in the engineer missing important variables that affect performance.

By looking at the way engineer’s talk about fatigue and fracture, we see where fantasy distorts reality. The fatigue constant, C f , is a common fixture in the fatigue design tables of the American Institute of Steel Construction (AISC), the American Association of State Highway and Transportation Officials (AASHTO) and the American Railway Engineering and Maintenance-of-Way Association (AREMA). However, it varies in each table. How can a constant have many different values? The mere fact we call Cf a constant shows we have room for improvement in the way we think about fatigue. Two examples are illustrative of the fantasy in fatigue design. Let’s take a look at the S-N curve and the assumed crack in an eyebar. S-N Curve The textbook stress-number of cycles (S-N) curve is nice and smooth and comes complete with a threshold for steels. However, when we look at the test data represented in Figure 4, we see scatter – lots of it. Fantasy is a simple curve; if we keep our stresses low enough, we do not ever have to worry about cracks. Reality tells us there will be outliers that lead to cracks.

Eyebar The assumed crack location in an eyebar is at the pin, perpendicular to the bar length, illustrated in Figure 5. This makes a lot of sense and is a great place to start. However, if we only looked for cracks at the assumed location, we might miss all the other cracks. Reality shows us cracks do not just occur where we expect them to. Why? Let’s get into that.

Why Complicated? So why is it so complicated? Mother Nature. Seriously. Materials are not perfect, environments are not benign, and loads are never what we think. More specifically, the following profoundly affect crack formation, growth, and critical size: • Size • Location • Detailing • Grain Structure • Residual Stress • Corrosion • Load spectrum These parameters are where many of the outliers originate. Laboratory testing simply cannot

Figure 4. Scatter in fatigue data.

Figure 5. Assumed and actual crack locations in an eyebar.

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

www.buysuperstud.com/DeflectionClips or call 800.477.7883 US Patent 6213679; other patents pending

STRUCTURE magazine

August 2016

The first three phases are shown in Figure 6. The nucleation phase is the period required for a crack to form. Next, the short crack path depends heavily on grain structure, and often described as “tortuous”. The long crack phase is smoother, larger, and less influenced by grain structure. Final instability is often fast fracture, with the crack moving at the speed of sound in the material. Crack Modes

Figure 6. Crack growth phases.

pick up all the variables that a structure will experience. This is unsettling if all we have available is a chart that tells us our structure will live forever if our stress is low enough. So what should the design engineer do? First, come to terms with the reality that cracks are complicated. As the engineer embraces all the parameters, it will become clear what is important and what needs additional attention. Second, use improved tools such as fracture mechanics to quantify the problem better. Third, use realistic material testing. Fourth, inspect. At some point, get out in the field and look at the problem. Observing the problem first-hand is the only way to know what is going on. Finally, embrace the vast array of knowledge that is available. To this point, Pellini, while at the Naval Research Labs stated: In summary, the present trends in fracture research emphasize an ever-increasing sophistication in the treatment of the problem – building upon rather than eliminating past knowledge. The great variety of fracture research evolves from the need for attention to widely different problems which have special features. Therefore, the engineer should not expect that fracture-safe design should ultimately evolve to a single generalized procedure, but rather to a variety of procedures that overlap and integrate into a coherent pattern. (Pellini 1969, p. 87) More than a nice quote – it is wisdom for the ages.

Crack Growth Basics Crack Growth Phases Getting into some specifics, consider the following four stages of crack growth: nucleation, short and long growth, and final instability.

There are three modes of crack loading: opening (Mode I), sliding (Mode II), and tearing (Mode III). In Mode I, cracking is characterized by stresses and displacements normal to the crack surfaces. In-plane shearing stresses with associated crack displacements in the plane of the crack, and perpendicular to the crack leading edge, produce Mode II cracking. Mode III cracking is caused by out-of-plane shear with displacements also in the plane of the crack, but parallel to the crack front. Crack Growth Mechanisms While fracture mechanics is interested in dealing with the critical crack size and how fast a crack will reach this size, it tells us nothing about how the crack originated. Without understanding how the crack formed, one can only superficially deal with the crack. However, when the processes of cracking (the physics of failure) are understood, the crack can be treated in a holistic manner. This results in a safer, more reliable structure. A broad range of mechanisms cause cracks and influence a crack’s potential propagation and propagation rate. Figure 3 lists many of the factors that affect both crack nucleation and growth. As seen from the table, the causes of cracks and influencing factors on propagation are intermingled. Focusing on one variable, as is so often the case with stress, and not considering other factors will likely result in a design that is unconservative, possibly by orders of magnitude.

Constraint We hear from seasoned engineers to avoid over-welding joints. Why? It certainly has an economic and environmental impact, but, more importantly, it reduces constraint. Reduced constraint increases toughness and energy absorption. Constraint refers to the materials inability to deform because the surrounding material restrains it. When a material is constrained, a tensile stress is created in both directions perpendicular to the applied stress (Y and Z directions if X is in the

STRUCTURE magazine

direction of applied stress) due to Poisson’s effect, illustrated in Figure 7. Triaxial stress states reduce the principal shear stresses in materials. This, in turn, diminishes plastic deformation, which occurs on planes of principle shear stress due to slip. To come full circle, the reduction in a materials ability to plastically deform reduces its toughness, or ability to absorb fracture energy.

Fracture Toughness Toughness is to the boxer as strength is to the weightlifter. Toughness is a measure of the amount of abuse a material can take. More technically, fracture toughness measures crack resistance. Toughness Trends Fracture toughness and all structural properties are influenced by size. As size increases, toughness – and strength, stiffness, and stability – decrease, as shown in Figure 8. As we move from a test specimen to component test to full-scale performance, there is a general trend of decreasing properties. Unique to fracture toughness, as the material gets thicker, the toughness decreases. After a certain point, the toughness remains the same – known as the plane strain fracture toughness. Toughness is also highly influenced by temperature. Figure 9 shows the transition curves for a Charpy and Dynamic Tear Test. As temperature decreases, so does fracture toughness. Note how the test type changes the location of the curve. The curve to the right is a 1-inch thick specimen, while the Charpy curve is based on the standard one-half inch thick specimen. If the material was ½-inch thick and relied on the Charpy test, we would grossly miss the actual transition temperature. This was the case in the Liberty Ship failures during World War II. Finally, strain rate affects fracture toughness. As the strain rate increases, the toughness decreases. It is worth considering this for impact type loads.

Figure 7. Triaxial stress states due to a notch.

August 2016

Figure 8. Conceptual material property variation with change in size (source: Introduction to Structures, P. W. McMullin, J. S. Price, 2016, Routledge).

Toughness Tests Characterizing fracture toughness is key to good fracture design. We will briefly look at Charpy, Drop Weight Tear, and Fracture Mechanics type tests. The reader may remember the Charpy test from mechanics lab where a ½-inch thick specimen is notched in the middle and a weight swings through it. The amount of

Figure 9. Temperature and specimen size effect on fracture toughness (source: Principles of Structural Integrity Technology, 1976, Office of Naval Research).

energy the specimen absorbs is the toughness. Charpy tests should only be used for quality control, not a direct correlation to structures with a thickness greater than ½-inch thick. Fracture Mechanics type tests take us from general correlations to direct analysis of crack behavior. The most common specimen is the plane strain, compact test specimen that determines KIc . To conduct this test, the specimen is pre-cracked so that it reflects the conditions of

an actual crack. Then the specimen is loaded until the crack unstably propagates. Using a stress-intensity solution, we can calculate the fracture toughness and then apply it to design. This article has introduced some fundamental concepts in fatigue and fracture design. Hopefully, the reader is beginning to develop some questions. The next article presents details of AISC and Fracture Mechanics-based fatigue design.▪

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

www.newmill.com/7

We’re building a better steel experience Our collaborative approach will help you achieve the architectural vision while optimizing construction related costs. New Millennium is your nationwide resource for the broadest range of custom-engineered steel products and systems. We can support you with our industry-leading BIM-based joist and deck design, backed by a dynamic manufacturing and delivery process.

14-NMBS-18_struc-horiz.indd 1

STRUCTURE magazine

August 2016

1/5/16 1:56 PM

Structural PracticeS practical knowledge beyond the textbook

n the engineering and construction industry, any truss spanning more than 60 feet is considered to be “long span”, thus requiring engineering consideration (per International Building Code (IBC) 2015 Section 2303.4, “Trusses” [for design of ]). The purpose of this article is first to explore and explain various aspects of building with long-span, open-web trusses, including manufacturing, architectural design options, engineering considerations, and installation practices and, second to provide examples of structures where long-span, openweb trusses are featured (Figure 1). Two types of wood trusses are found in today’s market: • Metal-plate-connected wood trusses are typically manufactured with chords and webs of solid-sawn wood fastened together with metal plates. These types of trusses are typically used in roof applications, yet are sometimes used in floor systems. • Open-web pin-connected trusses have chords made of either solid-sawn or engineered wood, and tubular steel webs attached using pinned connections. These trusses are suitable for either roof or floor systems. With their open-web construction, both truss styles allow for easy installation of plumbing, electrical lines, and HVAC ductwork. The trusses are custom designed and manufactured for each job, yet pin-connected trusses offer designers and builders the advantages of both wood and

Long-Span, Open-Web Trusses By Dave Schubert, P.E.

steel that generally allow for a shallower truss. They can also be attached to a variety of wall types, and their high strength-to-weight ratio and long-span capabilities give architects more design freedom with large open spaces. Although much of the following design and installation information could be applied to either style of truss, the balance of this article will focus on pin-connected trusses.

Profile Options Pin-connected open-web trusses come in a variety of profiles and chord configurations allowing for unique designs. Although the trusses are industrial grade and come with cosmetic imperfections, some designers elect to leave them exposed for visual effect. Following is a list of the various open-web truss profiles (Figure 2). Parallel Chord: An economical workhorse ideal for flat roofs and floors. Tapered: Allows for built-in roof drainage and a dramatic look when designed with a more extreme depth differential. Pitched and Radius Pitched: Provides varying slopes to create different looks for roofs and ceilings. Bow String: Offers a radius pitch continuous arc across the top chord while creating a flat interior ceiling at the bottom chord. Barrel and Compound Barrel: Both the top and bottom chords have radii to provide curved ceilings. Pitched Top Chord/Radius Bottom Chord: An unusual chord combination that allows curved ceilings with a pitched roofline.

Dave Schubert (DSchubert@ redbuilt.com) is a Technical Representative for RedBuilt™, a manufacturer of engineered wood products.

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

Figure 1. Exposed trusses create visual appeal for the Taylor Middle School cafeteria and public meeting space.

14 August 2016

Figure 2. Open-web truss profiles.

Scissor: Ideal for shallow depth trusses with vaulted interiors. Lenticular: A lens-shaped truss (curved top and bottom).

Design and Engineering Considerations IBC 2015 Section 2303.4.1.3, “Trusses spanning 60 feet or greater,” requires that a registered professional be responsible for the design of both temporary and permanent bracing. Temporary bracing is any non-permanent element used to stabilize the trusses during the construction process. The primary component of permanent bracing is typically the plywood or oriented strand board (OSB) roof diaphragm that laterally braces the top chords of the trusses. Other permanent bracing elements are used for conditions in which the bottom chord is in compression, such as wind uplift or cantilever conditions. Even without compressive forces, the bottom chord should be braced to hold the truss in proper alignment, which is usually perpendicular to the roof deck. Providing adequate temporary bracing enhances safety and prevents truss damage during installation. Permanent bracing helps ensure the truss will support the intended design loads. Structural Roof Panels Top chords in compression can buckle laterally if not properly braced. It is recommended that plywood or OSB-rated panels that form the roof diaphragm be fastened directly to the tops of the trusses to provide permanent lateral stability. If the truss top chord is a double-chord member, both top chord members should be independently fastened to the roof diaphragm to prevent lateral buckling. Alternate decking materials may lack adequate top chord buckling restraint. For example, structural insulated panels have large, single fasteners that may fall between truss chords or split the truss chords. Cementitious fiber panels not only use large fasteners but may require structural adhesive to create a bond to

brace the truss top chord adequately. Wood tongue-and-groove decking may not provide a diaphragm to brace the trusses unless the boards are fastened together or have structural panels installed over them to create the diaphragm. Metal decking may also lack diaphragm action if not properly designed. A wood cap attached directly to the top chords of the trusses may help address issues of oversized or closely spaced fasteners.

• Uniform design dead loads for top and bottom chords • Any wind or seismic lateral loads • Wind uplift loads • Other loads, including those for mechanical units or loads suspended from the trusses Engineers must also address other loads, such as sprinkler mains, which often are not known until after contract drawings are completed.

Diaphragm Design with Modular Erection

Connections

Modular erection involves a group of trusses that are assembled on the ground with most of the permanent plywood or OSB panels fastened in place to the truss top chords. Also, 2x4 top and bottom chord bridging with cross bracing is installed – typically ten foot on center – to brace the bottom chords. This entire assembled unit, which is very stable relative to a single truss, is referred to as a “truss module”. When trusses are erected in modules, the permanent roof diaphragm will have a continuous edge at eight-foot-on-center (based on standard panel dimensions). The engineer must take this panel layup into account when designing the diaphragm. Most long-span open-web trusses have double chords, meaning the top chord consists of two separate members (usually 2x6 members), connected with pins and lock washers at truss panel points. It is common for the manufacturer to factory install a plywood cap on the trusses to transfer shear across the joint. Diaphragm nails should be long enough to penetrate through the plywood cap and into the truss chord. IBC 2015 section 2306.2 on woodframe diaphragms references the American Wood Council’s Special Design Provisions for Wind and Seismic (AWC SDPWS). The AWC SDPWS provides diaphragm assembly Tables 4.2A, 4.2B, and 4.2C, in which nailed diaphragms can be used to determine allowable diaphragm shear. When using these tables and designing with double-chord open-web trusses, a nominal framing width of three inches should be employed when determining allowable shear. The engineer should review the truss manufacturer’s allowable nail spacing into the truss chord to verify the closest allowable on-center spacing is not exceeded. Loading The structural engineer’s drawings should provide all design loads, along with load duration factors and/or required load combinations. Following are some examples: • Snow loads, including any snow drifting or non-snow live loads

STRUCTURE magazine

August 2016

Open-web trusses typically include factoryinstalled bearing hardware. The engineer should work with the manufacturer to verify gravity, uplift and lateral capacities during the design process and confirm if the engineer or the manufacturer is responsible for the design of any given connection. Usually, if the hardware is factory-installed on the truss, the truss manufacturer assumes design responsibility for the connection, but only if the engineer specifies the design loads. Be aware some truss hardware may only be designed for gravity or uplift load conditions. Additional hardware from another manufacturer may be required to resist lateral loads. Wall anchors and straps specifically designed for use with open-web trusses are available. It is important to choose an anchor or strap that has fasteners compatible with the truss chords and bearing hardware. It is up to the engineer to specify the correct model. Bearings Specifications for truss bearing hardware required bearing lengths, allowable field tolerance, slope bearing requirements, and minimum chord cut-off lengths all vary based on the truss series and the specific design application. The engineer should address all of these requirements during the design process to ensure that there are no installation issues related to the bearing details. Deflection Long-span trusses can experience significant vertical deflection when loaded. It is advisable for the engineer of record to review the design deflections and specify the truss camber for long spans. The following situations are examples of when camber and deflection should be evaluated: • Trusses located next to fixed elements such as walls • Deflection limits related to suspended/ movable partition walls • Gap requirements over non-bearing partition walls • Top-of-wall bracing details continued on next page

• Long-term creep and short-term creep that can vary depending on truss chord moisture content and construction loads • Roof designs with potential for ponding With scissor profile trusses, limiting horizontal deflection should also be considered. Truss Length Truss design length may exceed what the manufacturer can build or ship to a given area. Trusses can sometimes be manufactured in two sections and assembled in the field using special connections where the sections meet. Although they are designed much the same way as any standard length open-web truss, long-span trusses present some additional considerations. It is recommended that the engineer works in close collaboration with the manufacturer during the design process, thus avoiding potential design and installation issues.

Open-Web Truss Installation Methods Due to their long length and narrow chords, steps must be taken during installation to prevent buckling or rolling of the trusses. Open-web trusses less than 70 feet in length are usually installed one truss at a time with the use of strut bracing. Strut bracing is manufactured using light gage steel tubing with flattened ends that include punched nail holes positioned over the truss chords. They are designed to fit common truss spacing such as 16 inches, 24 inches, 32 inches, or 48 inches on-center. The bracing is temporary in that the struts can be removed once the trusses are permanently braced with the diaphragm. Instability of the truss chords due to the truss self-weight, as well as temporary construction loads, is amplified as the span increases. For

Figure 3. Workers are guiding a module of pitched trusses into place.

spans over 70 feet, modular erection is recommended to avoid material damage, or worse yet, a work-site injury. Some manufacturers contractually require modular erection when spans exceed 70 feet. In addition to improving safety, modular erection can speed up the installation process (Figure 3). When using the modular erection method of stabilizing long-span trusses during installation, the structural engineer should include appropriate information in the contract drawings to let the contractor know modular erection is required. Following is an example of appropriate verbiage: “The trusses shall be installed in rigid modules at least 8 feet in width, accurately assembled in a jig with final sheathing permanently attached while on the ground. Specified bridging and bracing shall be installed in each module as detailed in the manufacturer’s drawings.”

Figure 4. Proper forklift spacing and fork locations ensure trusses are not damaged during handling.

STRUCTURE magazine

August 2016

Trusses typically arrive at the job site on a flatbed trailer in banded bundles. When banded, the bundles are relatively stable, but it is still important to have the pick points spaced far enough apart to provide stability (Figure 4). Using a single forklift to move long span trusses should be avoided. The truss bundle should be placed on dunnage and all trusses braced in preparation for removing the banding. Once the bands are removed, the trusses can be moved one truss at a time into a prebuilt jig to assemble the truss modules. A crane with nylon rigging straps long enough to widely space the pick points is typically sufficient to move the single trusses into the jig. Jigs should be located on level ground, be designed to support the trusses in multiple locations, and take the truss camber into consideration. The purpose of the jig is to provide a safe way to space and align

Figure 5. Spreader bar with proper pick locations lifted by a crane. Notice the second module in assembly jig on the ground.

Figure 6. Delivered segments before assembly. Once assembled, they will form a 75-foot-long scissor pitched truss. Note the required steel-tube crossbracing in the foreground.

trusses squarely for attachment of bracing and sheathing while still on the ground. Once the modules are constructed, they will be ready to lift into place in a safe and efficient manner (Figure 5). As with truss design, the design professional can receive assistance from the manufacturer regarding bracing methods.

Figure 7. The multi-purpose building for Lighthouse Baptist Church includes a second story basketball gymnasium.

Examples and Applications Some common applications for long-span open-web roof trusses are school gymnasiums, church gathering rooms, and light commercial construction – anywhere a big, open room is desired. Trusses can be installed in buildings with wood, concrete or masonry walls, including those located in high seismic zones. While spans can extend over 100 feet, the most common long-span applications range between 60 and 100 feet. Taylor Middle School Located in Millbrae, California, the 15,694 square-foot cafeteria of Taylor Middle School not only serves school lunches but is also a venue for graduations, board meetings, community meetings and even basketball and volleyball games. The design team selected a scissor truss system that spans the width of the cafeteria and then left it exposed to create an open feel. The 75-foot-long double-scissor trusses are eight-foot-on-center and meet seismic and other loading requirements (Figure 6). Lighthouse Baptist Church MultiPurpose Building While it is typical for a gymnasium to be located on the ground-floor level, not so for Lighthouse Baptist Church, where their only option was to go up. The design and construction team created a first-floor with offices, classrooms, and a sanctuary, and a second-floor that hosts a basketball gymnasium with roll-out bleachers (Figure 7), to develop this unique multi-purpose building.

Figure 8. Modules of 89-foot-long pitched profile trusses for multi-purpose building hoisted into place by crane.

The two-story, wood-framed building is 45 feet high and 22,464 square feet in size. Its 89-foot-long, pin-connected open-web trusses are spaced at 48 inches on-center and span the entire gymnasium. Left exposed, they create an attractive, clean-looking roof structure. The team built the entire roof in modules on the ground and then lifted them into place by crane to keep construction simple (Figure 8). Morrell’s Electro Plating Located in Compton, California, Morrell’s is a metal finishing provider for the aerospace and military defense industries. Their 80,000-square-foot structure features 62 trusses, each 73 feet long. The clear span of the trusses allows an obstruction-free interior to the warehouse. The truss depths of just 36 inches were required to accommodate building height restrictions of the city. The building includes concrete block walls with wood ledgers that support the trusses. Two hold-downs per truss end were used to anchor the walls laterally to the trusses (Figure 9).

STRUCTURE magazine

August 2016

Figure 9. These single-piece 73-foot-long, top-chordbearing parallel profile trusses will be installed onto wood-ledgers-connected concrete block walls.

Long-span, open-web trusses provide architects with design freedom and engineers with a choice in material selection. The trusses are custom designed, detailed, and manufactured to meet the structural needs and design intent for the specific application. They are economical and provide the added benefit of building with wood, which is considered a green alternative to steel or concrete.▪

Structural analySiS discussing problems, solutions, idiosyncrasies, and applications of various analysis methods

Figure 1. Cross-sectional and other geometric and material properties.

aint Venant established his theory of torsion (1853) by assuming axially invariant modes of tangential and axial (warping) displacements. In conjunction with known static boundary conditions, the equations of elasticity were satisfied leading to an exact solution for pure torsion. His theory assumes free warping displacement and, when this is restrained, the torsional stiffness is increased depending on the cross-sectional shape. The basic beam finite element formulation assumes free warping, but there are also elements that include a warping freedom thereby allowing warping to be controlled. This article details a design scenario where the manufacturing of an I-shaped structural steel member was changed from rolled to machined. This change enabled thick, integral end plates to be machined to allow bolting to adjacent members. Before the design change, warping restraint had not been considered. With the addition of integral end plates, it became apparent a study would be required to establish how warping restraint changed the (torsional) stiffness of the member. Beam elements were used to model the structural members and the influence of different element formulations on the structural response were compared. Also, verified three-dimensional solid models were used to provide validation for the beam solutions. To verify the modeling approach adopted, and to provide solutions that may be checked with closedform solutions, members with other cross sections were also considered. In preparing this article, benchmark studies on warping restraint were not found, even in the documentation of ANSYS (the FE software used for this study). It is hoped, therefore, that this article might be useful to fellow structural analysts when considering how to model beams with warping restraint. The three cross sections and other geometric and material properties considered are shown in Figure 1.

The Influence and Modelling of Warping Restraint on Beam By Angus Ramsay, M.Eng, Ph.D., C.Eng, FIMechE and Edward Maunder, MA, DIC, Ph.D., FIStructE

Angus Ramsay is the owner of Ramsay Maunder Associates, an engineering consultancy based in the UK. He is a member of the NAFEMS Education & Training Working Group and acts as an Independent Technical Editor to the NAFEMS Benchmark Challenge. He can be contacted at angus_ramsay@ramsaymaunder.co.uk. Edward Maunder is a consultant to Ramsay Maunder Associates and an Honorary Fellow of the University of Exeter in the UK. He is a member of the Academic Qualifications Panel of the Institution of Structural Engineers. He acts a reviewer for several international journals, such as the International Journal for Numerical Methods in Engineering, Computers and Structures, and Engineering Structures. He can be contacted at e.a.w.maunder@exeter.co.uk.

18 August 2016

Closed-Form Solutions The theory of pure torsion defines the torsional stiffness of a beam of length, L, as the torque, T, divided by the relative rotation, θ, of the two ends of the beam measured in radians: Where G is the shear modulus and J is the polar second moment of area of the cross section. The torsional stiffnesses, T/θ, for the three beams defined above are 3293 kNm/rad, 2269 kNm/rad and 16.6 kNm/rad, respectively, for the circular, rectangular and I-shaped beams.

Boundary Conditions For pure torsion, the end sections of the member are assumed to rotate such that the circumferential displacement is proportional to the distance from the axis of rotation. Longitudinal distortions of the cross-section at the element ends depend on the warping restraint which may vary between the free and restrained conditions: 1) Free Condition – nodes on the end sections are free to move independently in the axial direction. 2) Restrained Condition – nodes on the end section remain in the same plane which is free to translate axially (although as a result of symmetry this translation will be zero). To implement these kinematic conditions, one first needs to recognize that nodes of solid elements possess only translational degrees-of-freedom. As such, one simple method to compute rotation where torque may be applied or rotation constrained at the ends of a solid model is to add a beam element. This element should be collinear with the centroidal axis of the solid model, with one node positioned at the centroid of each end section of the solid model. The axial rotation of this node may then be coupled, appropriately, to the in-plane translations of the nodes on the end section of the solid model to give a pure rotation of the end section.

Figure 2. Boundary conditions. The coefficients a and b are determined from the relative positions of the master and slave node. Translations, U, and Rotations, R, have subscripts indicating the asix and superscripts, where required, representing slave or master nodes.

Figure 3. Solid finite element models.

rectangular section warped but those warping distortions were significantly less than for the open I-shaped section. The values for free warping agree well, exact for the circular and rectangular sections, with values of the theoretical, closed-form solutions. Given the degree to which restraining the warping of the I-beam increases the stiffness, it is not surprising to see that the addition of integral end plates will have a similar but partial effect (Table 2). For this example, the stiffness is increased by a factor of nearly three over the standard I-beam. Figure 4 shows contours of axial displacement together with the maximum value of axial displacement computed, rounded up to the nearest micrometer. Symmetric contour ranges were chosen, with red indicating +ve displacement and blue –ve displacements. For the prismatic members (those without end plates) with unrestrained warping, the longitudinal distortion of the cross-section is invariant along the element axis and exhibits the typical warping distribution with opposite signs at adjacent corners of the section. When warping is restrained, member warping still occurs away from the ends but has to transition to zero at the ends of the member.

Results for Beam Models

Figure 4. Contour plots of axial displacement (maximum values in μm).

The nodes at the ends of the beam lying in the plane of the end sections are created distinct from the nodes of the solid model and coupled using the CERIG function in ANSYS. In this manner, the correct constraint equations are written between the freedoms of the beam element (master) node (including rotations) and the translations of the slave nodes on the end plane of the solid model. The model also needs single point constraints to remove any rigidbody motions and to deal with the incomplete coupling. The model is driven with a 1kNm torque applied to the node at the left-hand end of the left-hand beam. The boundary conditions are illustrated in Figure 2.

element. The section properties of the beam were defined per Figure 1 with a step transition in properties at the junction between I-beam and end plates. Models have been meshed appropriately and verified to produce stiffness values within 1% of the converged value.

Results for Solid Models Table 1 illustrates, qualitatively, what an engineer already knows – the axisymmetric circular section did not warp, the solid

BEAM188 has two formulations; one which does not explicitly include warping and one which does. For the formulation that includes warping, an additional warping freedom is added to each node. An extract from the ANSYS Help Manual is shown in Figure 5 (page 20) together with the corresponding dialogue box for setting the element’s Key Options. The following definitions are adopted to aid in understanding the beam formulation: KO(1)=0 – standard (default) formulation without warping freedoms KO(1)=1 – formulation with warping freedoms For KO(1)=1 – the nodes have additional warping freedoms which may be unrestrained or restrained continued on next page

Table 1. Stiffnesses for three sections (kNm/rad).

Finite Element Models Solid models were constructed using twentynode reduced integration brick elements (SOLID186), with the level of mesh refinement as indicated in Figure 3, and beam element BEAM188 was used (with default Key Options) to model the collinear frame

Table 2. Stiffness for the I-shaped section with and without end plates (kNm/rad).

STRUCTURE magazine

August 2016

Figure 5. BEAM188 key options. Table 3. Stiffnesses for three sections (beam elements).

Table 4. Stiffnesses for ‘I’ section with and without end plates (beam elements).

KO(1)=1f – formulation with warping freedom unrestrained KO(1)=1r – formulation with warping freedom restrained at the ends of the model The default formulation in ANSYS is KO(1)=0, but for sections that are recognized as open ANSYS provides a warning that the user should consider using KO(1)=1, presumably with the appropriate constraint of warping freedom. Table 3 lists the stiffness for the beams with the value in brackets equal to the percentage increase over the values obtained for the corresponding solid model. While there is a difference between the stiffnesses of the beam and solid models, with the beam models tending to be stiffer than the solid model, the results are consistent and, with no greater than a 5% difference, can be considered to be within reasonable engineering approximation. The results for KO(1)=0 and KO(1)=1f are identical. This reminds us that the formulation without explicit warping (KO(1)=0) actually models free warping. It is also seen that the ANSYS dialogue box is misleading since, with KO(1)=1, the warping remains unrestrained until the user changes the default free warping freedoms. The results for the I-section are compared in Table 4. Again, the numbers in brackets are the percentage change in stiffness compared with the solid model. Note, however, that for the beam with end plates, the beam model is now less stiff than the solid model. The second row of Table 4 is for the member including end plates. The first point to note is the massive discrepancy between the results for the KO(1)=0 beam model and the solid

model with free warping. The explanation is that this beam formulation does not ensure continuity of warping between beams (there are no warping freedoms). As such, the partial restraint on the warping expected (and seen for the solid model) is not captured. The beam formulation KO(1)=1f offers a far more realistic solution as it is only 2% less than the result of the solid model. For the beam with restrained warping (KO(1)=1r), the stiffness increases but significantly less than that for the solid model and the stiffness is underestimated by some 20%.

Conclusions The results for the I-beam are summarized in Figure 6 which shows that the basic beam element, without warping control, is clearly unsuitable for modeling situations where warping is partially or fully constrained. The more advanced element, which includes

Figure 6. Summary of stiffnesses for the ‘I’ section.

STRUCTURE magazine

August 2016

warping control, performs significantly better, particularly when end plates are not included. When end plates are included, the advanced beam model can lead to error. However, for the geometry considered in this article, the free warping case produces a good correlation with the solid model. The machined member in this study is to be bolted to thick members. So, it is likely that warping at the member ends would be almost entirely restrained by the adjacent structure. As such, if the member had been modeled with beam elements without warping restraint then the stiffness would have been underestimated by some 72/16=4.5 times! Although, when warping is restrained, the beam model still underestimates the stiffness but by only 72/60=1.2 times. The error in the results shown above for beam elements reminds us of the importance of considering the appropriateness of the choice of idealization carefully. The sort of study presented here is thus necessary if the engineer is to make a sound, evidence-based decision as to the nature of the idealization to choose. An alternative approach, which may have both simplified the analysis and led to more reliable results, would have been to replace the I-sections with circular sections for which warping would not have been an issue. This indicates the potential virtue of adopting a ‘design-for-analysis’ philosophy which, particularly for one-off structures, has many potential virtues. Unless the torsional stiffness is captured in a realistic manner, natural frequencies involving torsional modes of deformation in a member will be poorly approximated which could be important, particularly if the structure is to be seismically qualified. The absence of suitable benchmark verification problems for warping in beam finite elements provided part of the motivation for writing this article. In this study, it was found that the dialogue for setting the element Key

Options in ANSYS was highly misleading. It suggests that warping is restrained when, in fact, it is not without further user intervention. The default option for BEAM188 is KO(1)=0. This, however, is only appropriate for axisymmetric cross sections. As such, a more appropriate default might be KO(1)=1 which, of course, should also apply to nonwarping axisymmetric cross sections. The following recommendations are therefore suggested to ANSYS Inc: 1) Change the dialogue text from ‘Restrained’ to ‘Included’, 2) Add some benchmark examples and advice to the Help Manual, and, 3) Change the default value for KO(1) from 0 to 1.▪

Post Script Following the publication of this article in the NAFEMS Benchmark Magazine (July 2014) ANSYS acted on one of the recommendations that was made by modifying the element type options dialogue for BEAM188:

The online version of this article contains detailed references. Please visit www.STRUCTUREmag.org. This article was originally published in the NAFEMS Benchmark Magazine (July 2014). It is reprinted with permission. ADVERTISEMENT–For Advertiser Information, visit www.STRUCTUREmag.org

TrusSteel Provides Peak Performance The innovative TrusSteel cold-formed steel truss system offers proven and reliable solutions for virtually every roof or floor application. TM

 Delivers strength and stiffness  Transfers structural loads efficiently  Facilitates clear spans over 80 ft.  Provides greater stability for easier handling and installation  Utilizes integrated software for design flexibility That’s why it’s the most accepted and specified cold-formed steel truss system available. Visit www.trussteel.com to obtain a copy of the popular Truss Design Manual and see why the most demanding building professionals prefer TrusSteel.

The World Leader in Cold-Formed Steel Trusses (888) 565-9181



www.trussteel.com

STRUCTURE magazine

August 2016

Practical SolutionS solutions for the practicing structural engineer

hen starting something new, it is a good idea to start small, work out the kinks and make the inevitable mistakes on a small scale before expanding a product or a process. Businesses do not start off as Fortune 100 companies. Musicians do not purchase Stradivarius violins or P. Mauriat saxophones before they spend hours of practice honing their skill. Churches begin meeting in school gymnasiums before breaking ground on their first small building, with hopes to expand as their memberships grow. Such has been the case with cold-formed steel trusses. When steel trusses were first introduced as a framing option for commercial and institutional projects, they were used in areas of relatively short spans. For example, small mansard trusses on a store front or a small office building with sloped roofs. These trusses paved the way for larger and more complex roof shapes. Today, it is safe to say that the cold-formed steel truss industry has advanced to the point where architects are taking advantage of the strength capabilities and design flexibility of CFS trusses to regularly stretch the envelope with longer clear spans, complex intersecting roof planes and girders supporting large roof areas. One example of starting small and growing is the First Baptist Church of Lake St. Louis (FBCLSL). From the small original chapel to the current expansion of the sanctuary and office, this church building has seen many changes over the last several decades. Moreover, in 2013, they were ready to expand again. As with any successful construction project, there must be a vision from the owner, combined with the construction expertise of the building designers to bring that vision to life. LePique & Orne Architects, Inc. has worked with FBCLSL several times during previous projects and understood

Long-Span CFS Trusses Reach New Heights By Mike Pellock, P.E. and David Boyd

Mike Pellock is the Executive Vice President for Aegis Metal Framing. Member of CFSEI, AISI and SFIA. He can be reached at mpellock@mii.com. Dave Boyd is a Sales Representative for Aegis Metal Framing. He can be reached at dboyd@aegismetalframing.com.

Figure 1.

22 August 2016

the goals. According to Dennis Elledge (architect), “Based on the client’s requirements and to more fully integrate the building facade design into the primarily residential community of Lake St. Louis, we were led to the use of sloped and shingled roof construction. With this sloped roof direction in mind, the use of pre-engineered trusses seemed to be the right fit. After considering the various pros and cons of wood trusses versus steel trusses, we concluded that steel trusses were the correct solution, especially regarding longevity, strength and deflection requirements.” Ædifica Case Engineering had worked with cold-formed steel trusses in the past and agreed that the strength, as well as the design versatility, would be the best fit for the long spans of almost 80 feet (Figure 1). Throughout the design phase, several critical discussions were required so that all systems involved would work in conjunction with the new roof structure. The open dialogue between the architect, structural engineer, and cold-formed steel truss designer was instrumental in assuring that all systems went together well. Stephen Sacco, P.E., structural engineer and principal at Ædifica Case stated, “During the design phase, our structural engineers needed to take into account the additional horizontal deflection due to live loading (snow, etc.), and take this lateral movement into account when reviewing outward movement of exterior bearing walls and detailing the interior drywall joints at the wall/ceiling interface. An Aegis representative ran various load conditions for dead and live loads at our request to get a range of deflections we would need in design and detailing, so we could consult with and advise the architect and owner.” For Elledge, his focus was on the goal of the client. “The new and larger sanctuary required open and vaulted space to accommodate state-of-the-art audiovisual elements as well as the impressive and open worship environment they desired. The unobstructed sanctuary space was accomplished with the use of CFS scissors trusses.”

Figure 2. Example use of spreader bar.

Figure 3.

As if 78-foot scissors trusses were not enough of a challenge, the church expansion faced delays due to a significant rainy season, substandard soil properties as well as an increase in the project scope half way through the project. The timeline for design, manufacture, and delivery of the trusses was squeezed significantly to minimize any delays in the construction schedule. To meet the new time restraints, the design expertise of the specialty truss engineer, Aegis Metal Framing, and the extensive truss experience of the truss fabricator, Engineered Steel Products, were put to the test. With 441 individual trusses to build and 153 unique truss profiles to design to form this roof, it was critical that all parts of the roof system fit together, with all trusses and connections properly designed and installed, to create the desired architectural look that blended in with the neighborhood. The variety of truss shapes and connections, along with the long-span scissors trusses, created the potential for a challenging installation for the truss installer, Bender Construction. However, using the appropriate spreader bar for the long trusses, the crew set 19 of the 78-foot scissors trusses in one 8-hour shift (Figure 2), which was quite an accomplishment. Installation included all required lateral and diagonal restraint bracing for the webs and chord members. As trusses were erected, hat channel was installed for bracing using self-drilling screws as required per the plan. Although the installation crew was a little timid when setting the first of those large clear span truss, after getting a few set and braced, they found their rhythm and made quick work of the 24,700 square foot of roof area. Adding to the efficiency of the installation was the fact that the truss-to-truss and truss-to-bearing connections were simple to install. Connection to the supporting walls

was made with standard Aegis HD clips with self-drilling screws into the trusses and supporting walls. Truss to truss connections were aided by factory installed skewable connectors on the tie-in trusses and receiving girder plates on the girder trusses (Figure 3). As illustrated by the FBCLSL project, long clear-span CFS truss projects can present a variety of challenges to consider during the roof layout and design phase of the project. One such challenge results from the combination of slope and span of the truss that creates a truss profile that is too tall to ship from the manufacturing plant to the job site. One common solution is to design the truss in multiple pieces: a base truss designed with a height feasible for shipping (10-12 feet) and a cap truss, sometimes called piggyback truss, designed to be installed on top of the base trusses to finish the slope. In this application, it is critical that lateral and diagonal bracing is installed along the flat portion of the top chord of the base truss to ensure stability before installing the cap trusses, and to provide permanent lateral bracing/restraint of the unsheathed flat portion of the base truss. The Building Code, by reference to the Code of Standard Practice for Cold-Formed Steel Structural Framing, AISI S202, provides for three options for truss member restraint/bracing: Standard Industry Details, Substitution with Reinforcement, or Project Specific Design. The specialty truss engineer is an excellent resource for specifying and designing member lateral and diagonal restraint/bracing for the roof system. They are generally more informed regarding requirements, limitations and general understanding of the CFS roof system than the EOR or building designer. Handling, storage, delivery and installation are critical processes for all CFS trusses and

STRUCTURE magazine

August 2016

require careful and thorough attention. With long-span CFS trusses, the importance is magnified. Particular care must be taken to ensure trusses are not damaged and are installed properly, with all required connections and bracing, so they function as designed. The Cold-Formed Steel Building Component Safety Information (CFSBCSI), published by The Cold-Formed Steel Council of the Structural Building Components Association, is one reference for standard industry details as well as information covering truss handling, storage, and installation. There are many different types of buildings that can take advantage of the long-span capabilities of cold-formed steel trusses. Church sanctuaries with an open cathedral ceiling are one excellent example. Fire stations with open mechanical bays are another. As Stephen Sacco closed out his discussion of the expansion of the First Baptist Church of Lake St Louis, his words fit well for other projects. “In the end, long-span, cold-formed steel roof trusses proved to be the correct and obvious choice for this high-profile project.”▪

FBCLSL Project Team Owner: First Baptist Church, Lake St. Louis, MO Structural Engineer: Ædifica Case Engineering, Fenton, MO Architect: LePique & Orne Architects, Inc., St. Charles, MO Truss Engineer: Aegis Metal Framing, Chesterfield, MO Truss Fabricator: Engineered Steel Products, Wright City, MO General Contractor: Demien Construction, Wentzville, MO Truss Installer: Bender Construction, St. Louis, MO

“ St��ct�ral desig� is what we do. IES tools help our engineers do it well. ” Design Your World VisualAnalysis See your work more clearly. Then have summer fun time with family.

IES, Inc.

800.707.0816 info@iesweb.com

www.iesweb.com

t was a time of celebration at the Kansas City Hyatt on July 17, 1981, 35 years ago. Between 1,500 and 2,000 people were in attendance at the Tea Dance, enjoying the band, the music, the food, the drink and the dance contest. Unfortunately, what began as an evening of celebration would be remembered for the tragic deaths resulting from the most catastrophic failure of a structural connection in the United States. The collapse caused the death of 114 people and the injury of more than 180, and traumatized countless others. The effects were felt throughout Kansas City and the United States and served as a wake-up call to the engineering community. This event highlights the importance of following appropriate procedures and processes involved in structural engineering. The consequences of a structural failure can be catastrophically high – and can be the result of inattention to details, inadequate quality reviews, and lax shop drawing reviews. The following article describes the events leading to the construction and failure of the Hyatt Regency Skywalks, post-event actions, and lessons learned – especially about quality reviews.

Background Planning for the Hyatt Regency project started in 1976. The plan for the hotel included a 35-story tower with sleeping (guest) rooms and a four-story conference center. A walkway spanning across the atrium at the second, third and fourth stories connected the two buildings. Initially, the walkways were intended to be supported from columns at the ground level. In a later design change, the walkways were suspended from the roof (Luth 2000).

In the final configuration, the fourth-floor walkway was positioned directly above the second-floor walkway. The third-floor walkway was offset from the other two (Figure 1). The distance that the walkways spanned from the tower structure to the conference center was approximately 120 feet. The 120-foot length was split into four equal spans of approximately 30 feet each, using two (2) W16x26 longitudinal stringers per walkway. The ends of the walkways were supported by the tower and conference center structures, but each interior span support consisted of a built-up box beam suspended from the roof structure by two steel hanger rods. The box beams consisted of two MC8x8.5 channels welded toe to toe. The hanger rods were 1¼-inch diameter steel with a yield stress of 36 kips per square inch (ksi) (Marshall et al. 1982). The roughly 8-foot wide walkway was comprised of 3½-inch thick lightweight concrete on 1½-inch steel form deck that spanned longitudinally between W8x10 floor beams (Figure 2, page 26). This was a “fast track” project intended to provide the owner with a completed product in the shortest amount of time. Speed was of the essence, where construction often preceded a completed design and structural design preceded architectural design (Luth 2000). While this method became popular in the 1970s, the coordination of all the processes under these conditions to ensure quality was not fully developed. At the time of the project, it was customary in the Kansas City area to delegate design of most of the typical steel connections to the steel fabricator (Luth 2000). continued on next page

investigating failures, along with their consequences and resolutions

Hyatt Regency Skywalk Collapse Remembered

Figure 1. After the event; the fourth-floor hanger rods remain next to the intact third-floor walkway.

STRUCTURE magazine

Structural FailureS

By Randall P. Bernhardt, P.E., S.E.

Randall P. Bernhardt is a Senior Consultant for forensic structural engineering in the St. Louis, Missouri Office of Engineering Systems Inc. He has been active in structural engineering licensure issues and chairs the Structural Engineering Institute’s Professional Activities Committee. He is also a member of the Structural Engineering Licensure Coalition and the NCSEA Licensing Committee. He can be reached at rpbernhardt@engsys.com.

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

Figure 3. The perspective of the critical connection showing the double rod configuration. (Marshall, R.D., et.al, 1982. Page 30.)

Figure 2. Cross section of the walkway. (Marshall, R.D., et.al, 1982. Page 26.)

Chronology The following important points and missed opportunities can be found in Luth’s chronology of events (Luth 2000). 1) The initial project engineer and senior designer, who were familiar with the background of the design, left the structural engineering firm early in the design process. Their departure impeded the communication of the original design intent to those who completed the design. 2) Similarly, the fabricator transferred incomplete shop drawings to an outside detailing firm for completion, further impairing the flow of information. The outside detailer assumed the connection had been designed because it was shown on the shop drawings and not flagged for design check, as no loads were provided in the initially drafted sketch. 3) The project manager conditionally approved a change request from the fabricator to use a double rod configuration in lieu of a single continuous rod (Figure 3). This essentially doubled the load on the rod-to-box-beam connection at the fourth-floor walkway. The structural engineering manager requested it be submitted as a formal change request, delaying the final review until a later date. The fabricator did not formally submit the change from one continuous to two offset rods as requested by the structural engineer. 4) The structural engineer’s technician reviewed the shop drawings and questioned the yield stress of the steel hanger rod. The project

manager did not give the question his full attention but responded from memory. If the question had drawn the structural engineer’s focus, the deficiencies in the design might have been noticed. Expansion bearing connections for the steel atrium roof failed early during construction due to erection deficiencies. This failure prompted an internal check of the atrium roof design. During this internal check, the grade of steel hanger rod was again questioned, but no follow-up was made. At approximately 7:05 pm on July 17, during the Tea Dance, with less than 10 people on the fourth-floor walkway and less than 60 people on the second-floor walkway, the bottom flange weld connecting the two MC8x8.5 toes ruptured. The rupture was caused by the force of the fourth-floor walkway-to-roof hanger rod nut on the bottom surface of the box beam. Before the rupture, the welded channel flanges acted continuously between the webs. After the rupture, the flanges were cantilevered. They rotated upward from yielding in the web which allowed the bolt and nut to slip through the hole (Figure 4). The impact from the bolt and nut on the upper flange of the box caused failure of the upper flange, with the bolt and nut slipping through the hole in an instant at that point. The fourth-floor walkway became disconnected from the roof support, and both walkways collapsed onto over one hundred people standing below (Figure 5) (Luth 2000).

Figure 4. Deformed box beam failed connection.

Figure 5. The collapsed second- and fourth-floor walkways on the floor of the atrium after the rescue operation.

Fourth Floor Hanger Rod to Box Beam Force Code Required Loading Actual Loading at Collapse Actual Tested Ultimate Capacity

STRUCTURE magazine

August 2016

Total Unfactored Load (Kips) 40.7 21.3 18.6

Post-Event Investigation After the collapse, the National Bureau of Standards conducted an exhaustive investigation (Marshall et al. 1982). The following conclusions can be drawn from their report: 1) The loads on the hanger rods and hanger-rod-to-box-beam connections at the time of the collapse were significantly less than the loads required by the Kansas City Building Code as seen in the Table. 2) According to the applicable AISC Specification (1969), the 1¼-inch hanger rods with a yield stress of 36 ksi had an allowable tensile capacity of 20.9 kips. If the 60 ksi rods had been used as intended, they would have had an allowable tensile capacity of approximately 34.9 kips. This is still less than the code required dead and live load on the fourth-floorto-roof hanger rod of 40.7 kips that would be imposed for both the single continuous rod configuration or the offset double rod configuration. The original 1¾-inch diameter hanger rods would have an allowable tensile capacity of 41.0 kips using 36 ksi steel and would have satisfied all load requirements. Though the failure of the hanger rods was not the cause of the walkway collapse, they were still under-designed. 3) The dynamic effects of walking or dancing on the walkways did not significantly increase the load effect on the walkways. 4) The box-beam-to-rod connection detail did not satisfy the requirements of the 1969 AISC provisions, i.e., it was not a typical detail that could be designed by the fabricator: No bearing stiffeners to accommodate concentrated loads were provided and web crippling requirements were not met through the use of distribution plates. Further, the AISC provisions did not anticipate significant eccentricities of the load from the plane of the web as were actually used where the rod load was applied at the flange toe. 5) Though the original continuous rod configuration did not meet the requirements of the Kansas City Building Code, the hanger rod connection to the box beams under that configuration would have had the capacity to resist the actual loads estimated to have occurred at the time of the collapse.

6) Poor quality of workmanship and materials did not contribute to the collapse. 7) The critical portion of the structure, and where the collapse initiated, was at the fourth-floor hanger rod to fourth-floor box beam connection. This connection had a tested ultimate capacity of 18.6 kips, with a coderequired load demand of 40.7 kips.

Legal and Professional Actions The damages awarded to victims and families of victims exceeded $100 million. A grand jury found no evidence of illegal action on the part of the design professionals. The Missouri Board for Architects, Professional Engineers and Land Surveyors investigated and brought charges of gross negligence and misconduct against the structural engineer of record and the structural engineering project manager from the firm that had provided the structural design of the Hyatt. An administrative judge found them guilty of the charges. Both engineers lost their licenses (Roddis 1993) (Pfatteicher May 2000)

Lessons Learned Many lessons can be drawn from this tragedy, including the following (Luth 2000): 1) Connections should be designed by a qualified engineer at some point in the design and construction process. 2) An internal quality review should be thorough – more than spot checking – and should include a formal check of details on the structural drawings 3) Questions posed during design and construction should not be disregarded, but should be given the utmost attention on a project with an accelerated schedule. 4) When there are changes in personnel, steps should be taken that ensure a smooth transition and full transfer of knowledge about the design activities leading up to the personnel change. 5) Even small, seemingly insignificant changes in concept should be handled through a process that compels the participants to focus on potential issues. 6) Engineers in city building departments should not be depended upon for finding errors in the design. Internal quality reviews should catch any errors before documents are issued for construction.

STRUCTURE magazine

August 2016

Discussion Additionally, many more valuable lessons can be extrapolated from the Hyatt Collapse including issues about communication during the project, design quality control, design responsibility, shop drawing review, construction inspection, and structural observation (Delatte 2009) (Morin 2005). These issues were also discussed in House Report 98-621, Structural Failures in Public Facilities, that was prepared in part as a result of the Hyatt tragedy and other structural failures in the United States (House Committee on Science and Technology, 1984) and other papers. Structural engineers can be pulled in many different directions on projects, but in particular on a project with an accelerated schedule and tight budget. There may be temptations to skip steps in normal procedures and not give the focused attention that design or construction issues require. Some say that if you have quality and speed, the cost will be high. If you want speed and low cost, the quality will suffer. When faced with a highpressure project, many have been tempted to relax the guard on quality. Like the engineering mistakes made in the Hyatt, “There but for the grace of God, go all of us.” It is essential that there be an independent checking process, a conviction to follow the process, and a focus on protecting the public by providing safe designs. Comprehensive quality control reviews during the design, effective shop drawing reviews, and vigilant structural observation during construction are three significant steps that structural engineers can use to ensure that the design conforms to accepted practice and that the fabricator and constructor understand and deliver a final product that meets the engineer’s design intent.

Quality Review Process during Design Every project should have a clearly documented quality review process for design deliverables. Project engineers should be instructed about its importance and procedures, and should demonstrate a commitment to adhere to it. Given the magnitude and complexity of the Hyatt construction, which included a revolving restaurant on top of the tower, the walkways were a relatively small part of the project (Luth 2000). It would be easy to focus on the complexity of the tower and revolving restaurant, and pay less attention to the details of the atrium. continued on next page

Some takeaways from the Hyatt event and the author’s experience with different firms regarding quality control are: 1) The originators of calculations and drawings need to provide a self-check of their work. 2) An independent internal review should be required for calculations and deliverables. This may be completed by the structural engineer of record or a senior engineer in the firm. Some firms require drawings to be highlighted for compliance and red lined for disagreements. 3) The reviewer should have a commitment to quality for the firm’s deliverables and should assume a sense of responsibility. It should be required that the reviewer’s comments be resolved by the originator of the work product. 4) The review should not focus on only the details on the structural plans, but should envision the “big picture”– how the discipline specific design fits into the whole project. Coordination with other disciplines is necessary to provide fewer change orders during construction.

5) The engineering firm should not depend on the client or a government agency to find errors. The design and plans should be correct when delivered for a permit or issued for construction. 6) Corrections made by a drafter need to be thoroughly reviewed to ensure that the corrections are accurate before submittal to the client. This review process is intensive, but essential, especially for more complex or innovative projects. Only by adhering to this process can effectiveness and a high degree of accuracy in the final product be provided. Self-check is important but equally important is that another set of experienced eyes review design calculations and details on a project. ASCE’s Quality in the Constructed Project, A Guide for Owners, Designers and Constructors provides useful information on different facets of quality reviews for civil engineering projects.

Shop Drawing Review Shop drawing review is another step in the process of delivering a quality project. The fabricator or vendor should submit detailed fabrication drawings and information for the materials that meet the designer’s intent.

These submittals need to be approved by the engineer of record or a delegate before construction. The reviewer needs to be someone who is familiar with the design and who is knowledgeable in the structural engineering requirements. Shop drawing review should not be depended on as a quality review to find the designer’s errors. Rather, it is a step to ensure accurate communication of the design for fabrication before construction. Like quality reviews, the ASCE guide, Quality in the Constructed Project, has useful information on shop drawing submittals and review.

Structural Observation during Construction Having a site presence during construction was requested by the structural engineer of record at the Hyatt three times. Presence at the site by a qualified structural engineer may have finally prompted the attention to the critical detail that was required and the tragedy could have been averted. As with shop drawings, observation of the construction by a structural engineer should not be used as a tool to find errors in the design, but it can be another layer of the safety net to ensure that the structural details are constructed as the engineer intended in the design. The House Report 621 suggested that building codes require structural inspections of critical components. This is currently included in the International Building Code, Chapter 17.

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

Conclusion

UC San Diego Jacobs Medical Center, Central Utility Plant, San Diego CA Photograph © Tim Hursley

SUPPORTING 2015 AIA

INNOVATION SAN DIEGO IN ARCHITECTURE MERIT AWARD

Seattle Tacoma Lacey Portland

Eugene Sacramento San Francisco Los Angeles

Long Beach Pasadena Irvine San Diego

Boise St. Louis Chicago New York

KPFF is an Equal Opportunity Employer. www.kpff.com

STRUCTURE magazine

August 2016

Many factors could have affected the outcome of this tragedy. Imagine if the structural project manager and engineer were not overloaded – or, the original project engineer and designer had not left the firm. Consider what might have happened had the project manager and engineer realized the critical nature of the detail when questioned. Our clients and the public at large should be aware of the importance of high-quality structural engineering on all projects. We, as structural engineers, should operate with a heightened level of discipline and conviction to ensure that projects are not deemed, or delivered, as complete without adherence to a proper quality control process. Additionally, we should not avoid our responsibility to provide quality in our structural reviews of construction submittals and observation in the field during construction.▪

Loads of Anchoring Options You now have tabulated design values for anchorage. The new SCHA slide‑clip connector is designed and tested to accommodate several different methods of anchoring to concrete or steel, which helps you easily account for the buckling capacity of the anchored leg and mitigate risk. The SCHA also features a wider support leg to decrease eccentricity on anchors and provide a variety of anchorage options. With pre‑punched holes to accommodate ¼"‑diameter Titen HD® concrete screw anchors or 0.157" PDPAT pins for attachment to steel, the SCHA connector is easy to specify and to install. To learn more, call (800) 999‑5099 or visit strongtie.com/scha.

Strong-Tie Company Inc. SCHA16E

Structural PerFormance performance issues relative to extreme events

epal, located within the subduction zone created by the massive Eurasian tectonic plate to the north and the smaller Indian tectonic plate to the south, has eight of the world’s tallest mountains, including Mount Everest and more than 240 peaks over 20,000 feet dotting the northern region of the country. Over the last 180 years, Nepal has encountered nine major earthquakes with two having moment magnitudes (Mw) of 8.0 and 8.4, in 1833 and 1934 respectively. The latest 7.8 Mw earthquake occurred on April 25, 2015, followed by a 7.3 Mw earthquake on May 12, 2015. Both earthquakes had epicenters close to Kathmandu, the country’s capital, as shown in Figure 1. The earthquakes killed over 9,000 people, injured over 23,000 and damaged over 500,000 structures that included schools, hospitals, public buildings, residences, and UNESCO heritage sites. More than two million people were left homeless not only in the city of Kathmandu, but in the surrounding villages in the greater Kathmandu Valley.

The 2015 Nepal Earthquake Building Assessment and Masonry Construction Performance By James P. Mwangi, Ph.D., P.E., S.E.

Dr. Mwangi is Professor of Architectural Engineering, California Polytechnic State University, San Luis Obispo (Cal Poly). He has participated in post-earthquake building structural assessments in California, Haiti and Nepal. He is a Director of the Masonry Society representing Zone 1 and is also an active member of the society’s Technical Activities Committee. Dr. Mwangi can be reached at jmwangi@calpoly.edu.

Building Assessment Team According to data from the Nepal Engineers’ Association (NEA) (www.neanepal.org.np), the country has an estimated 15,000 engineers, with only about 400 of them in structural engineering practice, serving the country of close to 29 million people. About 50% of the country’s structural engineers were working out of the country when the earthquakes occurred. Following the earthquakes, the Government of Nepal (GON) contacted international non-governmental organizations (NGO) requesting assistance in bringing international structural engineers to Nepal to help in the much needed expert evaluation of the safety of the earthquake-damaged structures. There was an urgency in the exercise in order to

Figure 2. Assessment team 1 at a press conference.

30 August 2016

Figure 1. Epicenters of 2015 earthquakes and resulting aftershocks (USGS).

get the displaced population from tents to safe homes before the heavy monsoon rains arrived, which were on the horizon. The Global Fairness Initiative (GFI) (www. globalfairness.org), a Nepal NGO based in Washington D.C., reached out to the International Masonry Institute (imiweb.org) seeking personnel willing to travel to Nepal for the structural assessment of the building structures. IMI assisted GFI to assemble a team of 13 structural engineers, including the author, selected from various parts of the United States and three from Australia and New Zealand. Many members were from The Masonry Society and the National Council of Structural Engineers Association (NSCEA). GFI wanted engineers familiar with post disaster assessment to hit the ground running once in Nepal. The selected structural engineers were experts in seismic analysis of building structures and had global experience in post disaster needs assessment. Two teams were formed, with the first one arriving on May 12, 2015 and the other on May 21, 2015. Each team was in Nepal for nine days with exercises ending on May 29, 2015. Figure 2 shows the first team, made up of all American engineers, at a press conference on the building assessments.

Structural Assessment of Building Structures The primary goals for the assessment of the building structures were to either get people back into undamaged structures or out of unsafe structures. A secondary goal was to provide on-the-job training to the available Nepali engineers on structural assessment of building structures. Through the coordination of GFI and NEA, at least two Nepali engineers were teamed up with each international engineer in order to do the training and equip the Nepali engineers with the knowledge to continue with the assessments once the international engineers left the country. This also made it possible to accomplish more assessments. The Terms of Reference (TOR) for the international engineers was provided by the Ministry of Urban Development, while the Kathmandu Valley Development Authority provided the list of buildings with high public use for the safety evaluation. The National Society for Earthquake Technology-Nepal (NSET)’s Seismic Vulnerability Evaluation Guideline for Private and Public Buildings, Part II: Post Disaster Damage Assessment was used as a building assessment guide. The procedures in the document and the field forms are similar to those of the United States’ ATC 20 procedures, including the placard postings of Green – Inspected, Yellow – Restricted Use and Red – Unsafe. The document is also adopted by the United Nations Development Program (UNDP). Both rapid and detailed evaluations were conducted as needed. The international team received liability protection from the Nepal government. By the end of the assessment period, both teams had evaluated about 3,000 structures including education facilities, commercial

Figure 3. American and Nepali engineers with Nepali family at their evaluated home.

buildings, hospitals, residences, world heritage sites, shopping malls, high-rise apartments, and other building structures in Kathmandu, Lalitpur, Bhaktapur, Kavre and Sindhupalchok. An estimated 75,000 people benefited from the building evaluations conducted by the international team. Thousands of people living in tents were able to move back to homes which were determined to suffer no structural damage. Recommendations were also offered to building owners whose structures were identified as structurally unsafe or damaged, either demolition or possible repair procedures. Figure 3 shows a happy family who was living in a tent when they learned from several American and Nepali engineers that they could move back to their three-story building, which had not suffered serious structural damage.

Figure 4. Building construction in urban and rural areas.

STRUCTURE magazine

August 2016

Building Construction Adobe, brick and reinforced concrete are the main building materials in Nepal. There are approximately 150 brick kilns throughout Nepal, but the quality varies greatly. The country has limited domestic Portland-cement production capabilities. It is heavily dependent upon imports from India. Therefore, newer commercial masonry construction uses cement-based mortars but many buildings still use mud mortar. Currently, the building code in Nepal is poorly enforced. It includes prescriptive Mandatory Rule of Thumb (MRT) guidelines published by the Department of Urban Development and Building Construction under the Ministry of Physical Planning and Works of the GON. The common Nepal National Building Code (NBC) chapters are:

and 10x10-inch lower level columns with 4 – #4 or 4 – #5 bars, respectively, and #3 ties at 5-inch spacing are used. Footing sizes and reinforcements are also given for different columns depending on their location in the buildings (interior, corner, face) for weak, soft, medium and hard soil conditions. The infill bricks used are unreinforced. As seen in Figure 4, buildings in the urban areas exceed the three story requirement. In the rural areas, buildings are either rubble stone in mud mortar or adobe in mud mortar. Some of the multi-level construction has bamboo floors. The MRT covers rubble stone but not adobe construction. Where the guidelines of the MRT were followed or where buildings were engineered, there was minimal damage to the infill brick systems as shown in Figure 5. Figure 5. Brick in cement mortar infill in RC frame systems in Kathmandu.

1) NBC 105: 1994, Seismic Design of Buildings in Nepal. 2) NBC 201: 1994, Mandatory Rules of Thumb Reinforced Concrete Buildings With Masonry Infill. 3) NBC 202: 1994, Mandatory Rules of Thumb Load Bearing Masonry. 4) NBC 205: 1994, Mandatory Rules of Thumb Reinforced Concrete Buildings Without Masonry Infill. 5) NBC 205: 2012, Ready to Use Guideline for Detailing of Low Rise Reinforced Concrete Buildings Without Masonry Infill. Due to the shortage of Nepali structural engineers in the country, most buildings are constructed by self-taught or on-thejob trained contractors in consultation with home owners. In these cases, the above MRT procedures are used, which are essentially prescriptive techniques. The more modern buildings are engineered. It appears that the majority of the construction uses the MRT guidelines with unregulated variations. The MRT defines one type of un-engineered building as a reinforced concrete (RC) frame structure with or without masonry infill. The building is limited to three stories, or 36 feet in height, and a plan of 80 feet by 80 feet maximum. Each direction is limited to a maximum of six bays of at most 14 feet width. 4-inch concrete slab panels with a maximum of 145 square feet of area are required to be reinforced by #3 bars at 6-inch center-to-center each way. 9-inch wide by 12-inch deep concrete beams with two or three #4 or #5 bars tension reinforcement, top and bottom, and ¼-inch diameter wire stirrups. 9x9-inch upper level

Performance of Masonry Structures Use of adobe and brick in Nepal dates back to the 3rd through the 10th centuries when the world heritage royal palaces (Durbar) and temples were built. The majority of the older historic construction, also currently practiced in the villages by the economically marginalized population, are comprised of either unreinforced brick with mud mortar or adobe with mud mortar bearing wall systems. Adobe is currently made using the same ancient back-breaking methods in sites located in the vast valleys. Bricks are fired in large kilns. A single kiln fires up to one million bricks per

run. Figure 6 shows a photograph at a brick plant site. The unreinforced brick kiln was also damaged by the earthquake. The residential and historical floor systems are either a) unreinforced mud or cement plaster over wooden planks and floor joists, or b) mud plaster on bamboo floor systems. The roofs consist of either a) fired clay tiles over wooden planks over wood roof joist with mud mortar, or b) corrugated metal deck over wood joists. The foundation systems consist of rubble stone. Bricks used as infill in the reinforced concrete frame systems were all unreinforced. The bearing wall brick and mud mortar buildings were heavily damaged, as seen in Figure 7. In URM buildings located mostly in the rural villages, failures were triggered by outof-plane failure of the exterior walls due to a lack of positive connection of the floors and the walls, as shown in Figure 8. There was also disconnection of interior walls at the corners due to lack of proper connection details.

Conclusions The building assessment teams accomplished their goals, as thousands of people were able to return to their homes or were given guidance on how to repair homes with minor non-structural damages. The teams also participated in capacity building by teaching the few available Nepali engineers about the principles of earthquake behavior of building structures and associated structural safety assessments, including repair procedures.

Figure 6. Many adobe and brick plant sites are located in the Kathmandu Valley.

STRUCTURE magazine

August 2016

Brick and adobe are the materials of choice and the only sustainable construction materials in Nepal, especially in the rural villages located in remote mountainous sites that lack adequate road access. Based on observations from the building assessments after the 2015 earthquakes, the multi-story brick and mud mortar buildings performed very poorly. The brick infills in RC frame buildings performed generally well. The dated historic monuments, palaces and temple structures, most of which are recognized as UNESCO heritage sites, performed poorly.

Recommendations

Figure 7. URM wall failure of the Kathmandu Durbar square.

Figure 8. Out-of-plane failure of exterior adobe walls.

Connect Steel to Steel without Welding or Drilling • Full line of high-strength, corrosion-resistant fasteners • Ideal for secondary steel connections and in-plant equipment • Easy to install or adjust on site • Will not weaken existing steel or harm protective coatings • Guaranteed Safe Working Loads

BoxBolt® for HSS blind connections. ICC-ES certified.

FastFit universal kits for faster, easier steel connections.

A K E E S A F E T Y C O M PA N Y

STRUCTURE magazine

For a catalog and pricing, call toll-free 1-888-724-2323 or visit www.LNAsolutions.com/BC-2 August 2016

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

Nepal is in urgent need of help from the international structural engineering community, both to repair damaged historic structures and to network with the government in developing sound building construction procedures, sustainable national building codes and enforcement procedures. In enhancing the continued use of masonry construction, this may include but is not limited to: 1) Outlaw the use of mud mortar in construction. Develop a cementbased mortar mix that is affordable for poor villagers. 2) Develop guidelines that expand the MRT for rural homes to include provisions on how to build adequate horizontal diaphragms. 3) Develop details for adequately anchoring exterior walls of load bearing structures, including parapets to roof and floor diaphragms for new construction, and repair of existing structures. 4) Urgently educate homeowners, contractors and engineers on ways to build or rebuild earthquake resistance structures through workshops and other media outlets. 5) Develop details and train Nepali professionals on how to repair the massive brick and mud mortar historic structures. 6) Provide recommendations for the implementation of regulatory processes for design-andconstruction permitting of new construction and repairs. 7) Implement more engineering training for the design and assessment of masonry structures. 8) Improve the quality of brick manufacturing and develop a quality assurance program for materials.▪

TRANSFORMING A HISTORIC AUTO PLANT

By Klaus H. Ohrnberger, P.E. and Tito R. Marzotto, P.E., F.ASCE

Figure 2. Crane lift.

orth American automobile manufacturing and assembly plants, from the origins of the industry in the early 20th century, have held an iconic heritage position in our culture. Consider the Albert Kahn designed factories for Henry Ford. Aside from nostalgia, are these plants still useful and are they fulfilling a role in society today? The answer is, yes they are, thanks to the steel and concrete of their construction and the ingenuity of design engineers. Our case study is the Fiat Chrysler Automobiles (FCA) assembly plant in Windsor, Ontario (WAP). Created at a time of major consolidation in the domestic auto industry, former General Motors executive Walter P. Chrysler started his namesake company in 1925, incorporating the Maxwell, Chalmers, and Dodge companies. A bold step for him was building a new greenfield site plant, in 1928, on the outskirts of Windsor, Ontario, to serve markets in Canada and the British Commonwealth. Designed by the Hamilton, Ontario, engineering firm of Hutton & Souter, the

original structure has been expanded and updated over the years with more than 15 major expansions (Figure 1). The site today sits on 170 acres (70 hectares) and comprises a facility campus of over 4,000,000 square feet (380,000 square meters) of floor space, supporting body manufacturing, painting, and assembly. The plant’s many additions and transformations over the years have kept pace with advances in technology, so that today WAP is an efficient and productive high volume plant turning out about 1,400 vehicles per day on three shifts, sometimes six or seven days per week, while maintaining Silver status in the FCA World Class Manufacturing (WCM) production system. (WCM is a methodology that focuses on eliminating waste, increasing productivity, and improving quality and safety in a systematic and organized way). Through the years, the steel superstructure has continued to reinvent itself and has kept up with the demands of the market and the dictates of company chief executives from the founder to Lee Iacocca to today’s Sergio Marchionne, CEO of FCA N.V.

Figure 1. Windsor Assembly Plant expansion plan.

STRUCTURE magazine

August 2016

The current transformation began during the two-week Christmas holiday break in 2014 and continued through a 14-week new model launch from mid-February to the end of May in 2015. This was to prepare the plant for production of the new minivan, the 2017 Chrysler Pacifica, that arrived in dealer showrooms in early 2016. A unique aspect of the launch was that the current models (Town & Country and Grand Caravan) continue to be built alongside the new platform. As was necessary for this and past launches, aggressive fasttrack scheduling was required to minimize production downtime. The result was additional challenges for the structural engineering team. The construction program began with modest footprint additions to complement the FCA-WCM product quality initiatives. It continued with remodeling and renovations within the existing building to accommodate new process loading and to provide space for advanced technologies, improved conveyance and robotic assist equipment. Structural modifications included truss, column, and footing reinforcing and removal; floor, pit and tunnel construction and replacements. From the many examples of unique and challenging projects, this case study focuses on two areas representative of the grand scope of modifications: the rooftop enclosure and the alignment pit.

Empty Carrier Return Conveyor Structural Steel Enclosure The process layout called for the empty body carrier conveyor to be returned from the end of the line to the head of the line. Due to restricted floor space and insufficient headroom, the logical pathway for 200 feet of conveyor was over the roof in the middle of the 1928 building. The 1928 plant was a milestone structure in its time, incorporating an expansive wide-open bright space created by a floor to ceiling height of 27 feet with 16 feet clear height to the bottom chord of the modified Warren and Fink trusses. The ceiling was the underside of the lightweight concrete roof deck at the continuous monitor window sash. Columns were spaced 20 feet in the north-south direction, and 40 feet east-west, and were supported on slender 8 x 6½ H-section columns. The 87-year-old steel trusses and columns were reinforced, and footings were underpinned in advance of erection of the superstructure during the Christmas shutdown. Reinforcing and erection were staged to accommodate added possible snow drift loading with systematic roof weight removal. Some columns and truss members required intricate and innovative reinforcing and welding at locations already previously reinforced between two or possibly even four times. Environmental concerns were treated responsibly. Standard red lead structural prime paint was abated and soils were tested for contamination and properly remediated. The decision was made to lift about 200 steel members into place over the roof, to avoid construction traffic through the plant. The original thought was to do this by helicopter, but the contractor suggested using a 600-ton Swedish crane (Figure 2) to save cost and improve safety. An exclusion zone for the crane boom swing covered about 200,000 square feet of plant area. The lift of the steel members was completed in three days. During the 14-week shutdown, the existing roof deck, and monitor structure was removed and opened up to be exposed to the production floor (Figure 3).

Manufacturing Process Concrete Pits In-plant renovation construction progressed during windows of opportunity that included weekends and holiday non-production days, and working in non-production areas and external site areas where plant traffic could be re-routed. However, when it came to in-plant STRUCTURE magazine

Figure 3. Rooftop enclosure.

production areas where the “heart” of the new product upgrades and changeover took place, the 14-week production shutdown was used to accomplish the necessary demolition and reconstruction. Although the 2015 model build was accelerated in order to stock dealer inventory during the shutdown, it was critical that production of the current minivan resumed at the end of May 2015. Dozens of independent construction projects were undertaken simultaneously in this compressed time frame, including line underpasses, truck loading dock upgrades and an in-line water test booth. Also, a new ergonomic “skillet” conveyor line, a platform that cradles the vehicle during assembly and adjusts its height to ideal levels for assemblers, thereby improving quality with better sight lines, was installed. The project that attracted the most attention during the shutdown was the pit construction, underground utility rerouting, and column extensions for the new caster, camber, and toe-in alignment station. Originally constructed as part of the 1982 model launch, the alignment station followed the wheel roll-test station where vehicles were driven under their own power to alignment. However, as production increased, a backlog would occur because of a limited number of alignment stations. The alignment stations needed to be expanded from three to five within four-20-foot x 40-foot bays. The ambitious schedule involved demolition in February, construction in March, and equipment installation in April. May was devoted to getting the new processes commissioned for the quality production of the first vehicle off the line when production resumed. From start to finish, the removal, demolition, excavation, utility rerouting, shoring, construction and installation (Figure 4), was accomplished in a remarkable four weeks. This could only have been done with a well-organized plan conceived by FCA, implemented by experienced and determined consultants, contractors, subcontractors and suppliers in an environment that was carefully monitored for safety and quality. Contractor coordination meetings took place every day of the shutdown. The workforce was focused and well trained. To handle the multiple and varying concrete construction conditions of depth, loading pattern and rebar placement, contractors were given standard design approaches to allow on-site decisions during round the clock construction. To fast track concrete curing operations, high early strength concrete was utilized throughout and was consistently tested to allow work to proceed with cylinder test reports at critical stages of construction; results varied from 2,800 psi (19.5 MPa) at 30 hours to 6,500 psi (44.6 MPa) at 28 days. continued on next page

August 2016

Figure 4. Alignment pit.

In addition to steel reinforcing bars, concrete base slabs and walls were reinforced with polypropylene/polyethylene synthetic macro-fibers. Because of high wheel loads, floor slabs were reinforced with steel fiber.

Acknowledgment A program of this magnitude involves many teams of individuals that deserve to be recognized. Although not all can be mentioned, the following were noteworthy players: FCA US Corporate Building Group: Ben Monacelli, R.A. and Sam Sedghi FCA Canada WAP Facilities: Colin McLellan, P.Eng. and Eric Wilson, P.Eng. SNP Technical Services, Inc.: Joe Zabolotny R.A. and Jacqueline Ymana Structural Engineering Consultants: Irfan Ahmed, P.E. and Ryan McGoff, E.I.T. (Engineering Design Solutions), Tim Averill, CET (Valdez Engineering) and in memory of Hector Valdez, P.Eng. (1934 – 2015), and Harry Papadopoulos, Ph.D. (Testing Engineers & Consultants) Structural Fabricators and Erectors: Andy Bas, P.Eng. (Victoria Steel) and A. Tedesco (AC Metal Fabricating) General Contractors: Mike Leslie, P.Eng. and Colin O’Donnel (Elmara Construction), Frank Matassa and John Miller (Matassa Construction) STRUCTURE magazine

Conclusion Although many factors influence the decision to invest in either a greenfield manufacturing site or to renovate an existing one, the decision by FCA to invest in the Windsor plant was an acknowledgment that an 87-year-old structure was not a deal breaker. This is an important consideration for the future of the many historic factories in the Midwest and Great Lakes area. As this example at WAP shows, with proper planning in competent hands, older structures still have the resiliency and adaptability to be transformed into a space that can serve the needs of America’s reawakening manufacturing prominence.▪ Klaus Ohrnberger, P.E., is the facilities structural engineer for the FCA US Corporate Building Group, responsible for capital project structural work, based in the FCA US headquarters in Auburn Hills, MI. He has been involved in structural design and construction assignments at the Windsor Assembly Plant since the 1994 minivan project. He may be reached at klaus.ohrnberger@fcagroup.com. Tito Marzotto, P.E., F.ASCE, is the Executive Consultant to SNP Technical Services, Inc. with offices in Troy, MI and Windsor and Burlington, Ontario. He first became involved in building design assignments at the Windsor Assembly Plant with the original 1982 minivan program and has continued with each major new product launch since then. He may be reached at tmarzotto@snp-tech.com.

August 2016

CONNECT WITH US TODAY. [CONNECT THIS TOMORROW.]

FastBridge™ Clip

FastClip™ Slide Clip

Holdown Clip

Moment Clip

CLARKDIETRICH CLIP EXPRESS. It stands alone as a

product line, support service and single-source philosophy. And now, with new clips to cover more installation needs, the industry’s widest selection of steel framing connections is even wider. As always, overnight shipping options keep your projects on the fast track. Plus, getting the whole system—studs, tracks, accessories and more—from one trusted name keeps you working smart. STRONGER THAN STEEL. SM

Interior Framing ∙ Exterior Framing ∙ Interior Finishing ∙ Clips/Connectors ∙ Metal Lath/Accessories∙ Engineering

clarkdietrich.com

Rediscovering a

WORLD CLASS TERMINAL

By Shane E. Sweeten, S.E., LEED AP BD+C Created with BIM, the rendering represents the integration of all major design disciplines. Alterations of the terminal building substantially improved quality views and daylight inside the terminal. Courtesy of Hunt-Austin Design Build.

ositioned in the heart of Phoenix, the Phoenix Sky Harbor International Airport strives to serve the air transportation needs of the public and earn the reputation as the nation’s friendliest airport. To meet the ever changing needs of the future, the Airport is faced with improving and expanding their aging facilities. The Phoenix Aviation Department hired a design-build team to transform the existing Terminal 3 facility into a modern world class airport terminal that will meet the anticipated demand of 51 million annual passengers by the year 2024. The full terminal modernization effort is comprised of several components, including a new 15 gate concourse, upgraded security checkpoints, and remodeling and expanding the existing terminal building. One component in particular that deserves special attention is the renovation of the 36-year-old Terminal 3 building. Renovating an existing building is generally more sustainable than demolishing and building new, as fewer new raw materials are required

The addition of angled skylights diverts sunlight into the interior of Terminal 3. A welder puts the frame in place.

STRUCTURE magazine

and the building is already integrated with public transportation infrastructure. Renovations also present the opportunity to improve the interior comfort and appeal to occupants, while taking measures to improve the energy efficiency of the building’s cooling systems. Transforming an existing airport terminal into a modern, thriving, and expanded version of itself that is capable of meeting the demands of the future requires a major overhaul. A feat of this size is no easy task because the project includes major structural alterations and additions. Changes to the building affect the loads applied to the building, and also the ability of the frames to resist them. This remodel and expansion also requires architects and engineers to apply analysis techniques and constructible designs to an existing structure to make the Airport’s vision a reality.

Alterations According to the 2012 International Existing Building Code (IEBC), adopted by the City of Phoenix, the alterations for this project are classified as Level 3 because the work area exceeds 50 percent of the total floor and roof area of the building. The structural alterations were substantial, ranging from adding weight or removing gravity members, to modifying portions of the floor and roof diaphragms and lateral force resisting frame elements. In accordance with the IEBC, an engineering evaluation and analysis were required to establish that the building with the alterations is structurally adequate and compliant with the current adopted building code. Alterations of the terminal building substantially improved quality views and daylight inside the terminal. Views to the outside were enhanced by removing the bulky 1970s style precast window frames and replacing them with modern window wall glazing. Nearly 5,000 square feet of the second floor, 15,600 square feet of the third floor and 36,000 square feet of the fourth floor were removed. This created a vaulted space with a full height window wall providing exterior views

August 2016

The building alteration included removal of large floor areas to create vaulted ceilings. These changes made significant impacts to the structural design of the building.

on the north side of the building. Additionally, select precast roof members were removed for the installation of skylights that provide natural lighting to the interior of the building. Renovations also included changes to escalators and elevators. In several cases, this required the structure to be altered by cutting new holes through floors for new elevator shafts or escalators. Additionally, the terminal’s large central escalator well-way was filled in to make more floor space, as the escalators were relocated elsewhere in the building. This work required framing in the open space with steel beams spanning over 30 feet and making heavy steel anchorages to the existing concrete columns and beams. Connections of steel beams to concrete using post-installed anchorage were designed for loads as high as 6,600 pounds. New mechanical units will improve the energy efficiency and performance of the building system. Approximately 387 feet of the length and 20% of the total roof area is allocated to a new roof level mechanical penthouse. Also, a portion of the adjacent garage will be converted to interior space for the terminal building. This alteration includes increasing first floor ceiling height and building a new 13-foot-long steel beam cantilevered off an existing round concrete column.

Team Coordination and BIM A team of expert drafters carefully reviewed original design drawings and major renovation drawings to create a computerized replication of the physical terminal building. Computer models have been constructed of various surrounding airport buildings, including the PHX Sky Train® infrastructure, that are integral to the terminal building. Major design disciplines, including architectural, structural, electrical, and mechanical, modeled their respective building components and joined them together in a 3-D Building Information Model (BIM) using Autodesk® Revit® software. Even piping and conveyor equipment contractors modeled their equipment in Revit so that it could be inserted into the 3-D model and checked for conflicts. Amidst the capabilities of exchanging information, a 3-D model is only as useful as the accuracy of the information put into it. Building a computer model that had sufficient accuracy for the project included reconnaissance of several different types. Information gathering included researching original design drawings and major renovation drawings, and making numerous site visits to verify the original design drawings. Three-dimensional point cloud surveying was used to verify interior dimensions and conduit routing. This created a

Additions In order to gain much needed floor-space, the project design included an expansion of the terminal building toward the west. This addition features a full height atrium with window wall glazing, glass wall partitions, and visible landscaping consistent with the goal to create plenty of open space and quality views. The terminal building will be extended 75 feet to the west with 29,380 square feet of new floor area. The roof of the addition will include a cantilever of 37 feet to the west and 21,410 square feet of new roof area. Under the IEBC, the addition is new construction and must comply with the current building code. The new addition attaches to the existing building at each floor and at the roof on the adjoining grid line, and is dependent on it for lateral and vertical support. Even though the existing building was built under a past building code, the IEBC requires it to be analyzed for compliance with the current building code because it was impacted by more than 10%. STRUCTURE magazine

Structural expansion of the building adds 29,380 square feet of floor space. The steel structure attaches to the existing concrete, including a 37-foot cantilever.

August 2016

comparison and verification of the actual building to the computer model generated using the original design drawings. With a design-build project, multiple design packages, and an existing building, the investigation and gathering of information was a continual process. Communication between the contractor and the designers about discoveries during construction was crucial to the success of the project. The contractor discovered conditions about the structure after removing drywall and ceiling tiles that could not have been seen before. Some of these instances are considered repairs according to the IEBC. This is the nature of dealing with an existing building. However, the design team and the construction team needed to communicate and cooperate to quickly resolve new complications in order to maintain the quality and schedule of this world class effort.

Structural Analysis and Design A project of this sort challenges the creativity of architecture and engineering to make an old building into something new and relevant. Team collaboration on this project tackled the issues of code compliance, function, and aesthetic form all within the confines of cost, schedule, and limitations of an existing structure. With all of the technology available to vastly expand design collaboration and exchange of information, the computer will always be a tool and will never replace sound engineering judgment. As described above, the magnitude and extent of the additions and alterations were significant reasons to analyze the entire existing building and ensure the new condition was compliant with the current building code. The modeling of the structure in 3-D drafting software added the benefit of exporting building frame members from drafting software to structural design software. The structural model was checked for correctness and intuitive behavior. Constructability is an important consideration in making connections and modifications to an existing structure. A good design must include tolerances and consider difficulties such as accessibility and maneuverability. There is a good chance that conditions in an existing building will not perfectly match what is drawn on a piece of paper.

Ready for the Future

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

When faced with the problem of renovating the airport’s Terminal 3, the design-build team creatively pursued ideas of open space and ways to make this building modern, inviting, and a source of pride for the community. The renovated terminal serves to improve the experience of customers through open interiors, views to the outside and modernized security, baggage claim and ticketing. The creative

Originally, escalators connected levels 1 and 3 through a well-way that was decorated to resemble the majestic walls of the Grand Canyon. The biplane will be relocated, the well-way filled in with steel sub-framing, and two-story escalators will be along the north building line, with modern vaulted ceilings against a glass curtain wall.

renovations to the building made vaulted open spaces where there were ceilings and transformed something outdated into something modern and ready for the future. There were many factors that came together for a successful renovation of the Terminal 3 building. These included construction and design team communication, design team collaboration using the latest forms of computer modeling and information exchange, and good practical structural engineering design with due consideration given to the challenges of an existing building. These efforts combined to fulfill the vision of the Phoenix Aviation Department for a world class facility.▪ Shane E. Sweeten, S.E., LEED AP BD+C, is a Structural Project Engineer at Gannett Fleming, Phoenix, Arizona. He can be reached at ssweeten@gfnet.com.

Demos at www.struware.com Wind, Seismic, Snow, etc. Struware’s Code Search program calculates these and other loadings for all codes based on the IBC or ASCE7 in just minutes (see online video). Also calculates wind loads on rooftop equipment, signs, walls, chimneys, trussed towers, tanks and more. ($195.00).

Project Team

CMU or Tilt-up Concrete Walls Analyze solid walls for out of plane loading and panel legs next to or between openings by automatically calculating loads to the wall leg from vertical and horizontal loads at the opening. ($75.00 ea)

Owner: Phoenix Sky Harbor International Airport Structural Engineer, Terminal 3 Renovations: Gannett Fleming, Inc. Design-Builder: HuntAustin, a Joint Venture Architects: DWL Architects + Planners, Inc., Corgan Associates, Inc. and SmithGroup JJR

Floor Vibration Program to analyze floors with steel beams and/or steel joist. Compare up to 4 systems side by side ($75.00). Concrete beam/slab Program to provide bending, shear and/or torsional reinforcing. Quick and easy to use ($45.00).

STRUCTURE magazine

August 2016

A NEMETSCHEK COMPANY

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.

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 adventage 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-to-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

“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 Engieer 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.scia.net/en/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. 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. Request your FREE Trial.

Daniel Monaghan is the U.S. Managing Director of SCIA, Inc., developers of leading software products for AEC software industry. He can be reached at d.monaghan@scia.net

(410) 207-5501

www.scia.net

SOFTWARE MAKERS SEE STRONG DEMAND Resolved to Offer New and Updated Products By Larry Kahaner

he construction software business is doing very well thanks to new products, services and structural engineers who are finding great use and economy in the latest software offerings. “Business across all our regions is booming,” says Dan Monaghan, Managing Director, North America for SCIA, Inc. (www.scia.net), part of the Nemetschek Group. “We see a particular uptick in the United States and Europe as engineers are looking for easier ways to plug analysis and design into BIM.” The company introduced SCIA Engineer 16 in late spring and response has been strong, says Monaghan. “The reception around the world has been tremendous. With this release, we focused on usability. In fact, over 70 percent of the version 16 updates and features were born from customer feedback. The result is an improved structural design program that provides engineers an easier and faster way to deliver quality results.” He adds: “For steel buildings, we partnered with the Steel Joist Institute to incorporate their new Virtual Joists and Joist Girder tables and enhanced Composite Floor capability [AISC 360, EN 1994]. We also teamed up with the Steel Tube Institute and developed a free suite of HSS design software to make it easier for engineers to design with Hollow Structural Sections. For concrete, engineers will find new workflows and improved design of concrete beams and columns [Eurocode 2]. There is also a new concrete shear wall & frame module that includes Pushover [ACI 318-14, ASCI/ SEI 7-10, and FEMA 356] and improved concrete slab and shell design [NBR 6118:2014].” At the high end of the market, Monaghan sees more M&A as large AE and EC look to expand beyond their current maturing markets. “These firms are looking to save costs. With SCIA Engineer’s broad set of analysis and design functionality, these businesses can standardize and consolidate the number of software programs they use and maintain. At the middle of the market, we are seeing an awareness for how the right structural software can streamline workflows making companies more efficient and more competitive. These firms are looking for structural design software that can do more and let them take on larger more complex projects.” To help SEs with their work, Bluebeam, Inc. (www.bluebeam.com) offers Revu which delivers PDF creation, editing, markup, and collaboration technology to Windows desktop and tablet users. “Structural engineers can use Revu to harness the rich data created during the design process to expedite reviews and preserve value,” says Nick Decker, Senior Industry Specialist. STRUCTURE magazine

“For example,” Decker notes, “the new Batch Markup Summary feature in Revu 2016 allows a project team to review an entire document set and run one consistent report from all files. Expanded data sorting and filtering capabilities make running multiple reports in both PDF and Excel formats easier than ever. Additionally, improved document tagging and drawing log features allow users to automate document naming and metadata formulation. This process was previously compiled manually in an external spreadsheet or database. Now, the data can be associated with the sheets themselves and automatically updates as drawing revisions are released.” “Finally,” says Decker, “the new Legends feature enables engineers to visualize the markup data directly on the PDF, which was a highly requested workflow enhancement. By summarizing the markup data in a customizable table, the legend on the PDF automatically updates, providing the user with the data at a glance… We have some fantastic customer success stories we can share, detailing the impact Bluebeam’s intuitive and collaborative workflow solutions have made on projects and on their ability to deliver on time and on budget. Eighty-six percent of the top contracting firms in the United States use Revu because it lets them do what they do, better. Our customer’s success is our success.” (See ad on page 45.) Doug Evans, Vice President of Sales at Design Data (www.sds2.com), says that the construction industry has been stable for the last couple of years, and they are continuing to see the benefits. “Our growth of new customers has been as high now as it has been at any time in our 30-year history.” Adds Evans: “Design Data has two new technologies that are continuing to emerge within the BIM segment of the industry. The first is the SDS/2 Erector product and the second is the Model Approval workflow using the SDS/2 Approval product. The SDS/2 Erector gives general contractors and erectors an opportunity to plan the site and the steel erection visually, with tools and information not available in the past. All needed documentation for critical lifts and lift plans are capable with SDS/2 Erector, making it much easier to satisfy the AISC erector certification process. This product can help companies optimize the construction of steel structures.” “The Model Approval workflow continues to gain momentum as an alternative to sifting through stacks of paper and rolls of drawings,” Evans continues. “Using the SDS/2 Approval, this process can save weeks by reducing the time to communicate information along with much more clarity by using the model as a tool. Instead of using 2D drawings and hand sketches, the SDS/2 Approval allows

August 2016

users to view the model and review all metadata associated with the members in 3D space.” Concludes Evans: “We continue to see the model as a means to more completely communicate information to project partners. We are also seeing the benefits of early involvement of steel suppliers in the overall project timeframe and quality.” (See ad on page 46.) At RISA Technologies, Inc. (www.risa.com), Vice President, Operations Amber Freund says that RISAConnection has a number of HSS connections available, and the company is currently working on developing more HSS connection types to add to the RISAConnection library. “More variations to our current connections and new HSSspecific connection types will be released in 2017,” she says. “We see much interest in HSS and Truss Connections. The ability to design connections is a growing and exciting option for many of our users. Capacity to see the complete details of each limit state check is also an easy way for users to better understand the overall behavior of the connection and verify the completion of the design,” says Freund. “We recently introduced Seismic Braced Connection design per the AISC Seismic Design Manual in RISAConnection version 6,” she says. “This new feature designs OCBF and SCBF diagonal brace and chevron braced connections to the code provisions of AISC 341-10. Now, you can complete a very complicated design – including loading cases of reversible lateral loads and post-buckling compression – in just a matter of minutes.” (See ad on page 68.)

WoodWorks software sales over the past year have steadily been increasing for both the U.S. and Canadian editions, notes Robert J. Jonkman, Director Codes and Standards – Structural Engineering for the Canadian Wood Council (http://cwc.ca). “Our customers say that the Canadian Wood Council produces very affordable software that provides high value to users, and our customers purchase upgrades loyally.” In the U.S., their latest version of the software is Design Office 10 (SR4b), released in November 2015. “The current U.S. version conforms to the IBC 2012, NDS 2012, SDPWS 2008, and the ASCE-7-10. We are working on the development of the next major U.S. version of the software, and we expect to have it available by the fall of 2016. Relevant updated provisions in the IBC 2015, NDS 2015, SDPWS 2015 will be incorporated into Sizer, Shearwalls, and Connections,” Jonkman says. “The most significant changes will be to our Shearwalls program, as there have been many updates to how aspect ratios are handled in SDPWS 2015. Shearwalls will also be updated to include the 3-term deflection equation from SDPWS 2015. The software already includes the 4-term equation.” Jonkman adds: “In Canada, our latest version of the software is the Design Office 9 (SR3a), released in January 2016. This version of the software currently conforms to the CSA O86-14 and NBC 2010. As many jurisdictions across Canada have not yet adopted the

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

RFEM 5

Steel / Aluminum

Structural Analysis and Design Software

Concrete

Timber / CLT © www.mgm-ki.pl

Powerful, Intuitive and Easy

DOWNLOAD FREE TRIAL

Cable / Membranes Glass

www.dlubal.com

Join us: SEA NW & WC Aug 4-5, 2016 Bozeman, MT NCSEA Sep 14-17, 2016 Orlando, FL Wood Solutions Fair Oct 13, 2016 Philadelphia, PA

Dlubal Software, Inc. Philadelphia, PA (267) 702-2815 info-us@dlubal.com www.dlubal.com

STRUCTURE magazine

August 2016

E C N

F O

E R

E F IF

D E

H T

Software that

CONNECTS.

“Design Data, and the implementation of SDS/2, has bolstered Delta Structural Steel Services’ ability to elevate the quality of product that we offer our clientele. Prior to SDS/2, Delta was using another popular CAD program of which we were becoming increasingly disappointed. Our initial investment in SDS/2 began with two seats, and we have since grown to 17. Because of their outstanding product development and impeccable customer service, we feel Design Data has helped make Delta Structural Steel Services the multi-million dollar business we are today.” Paul Hemenway CM-BIM Estimating/Production Manager, Delta Structural Steel Services 1501 Old Cheney Rd., Lincoln, NE 68512 // 1-800-443-0782 // sds2.com

CSA O86-14, the current version of the software allows the user to toggle the design between the CSA O86-09 and CSA O86-14.” He adds: “Over the next year, we will be updating the Canadian version of the software to conform to the NBC 2015, in which significant seismic design provisions have been modified. We have also started to incorporate the new 6-story wood frame construction provisions introduced in the 2015 NBC.” (See ad on page 49.) Amy Heilig, Chief Executive Officer of Dlubal Software, Inc. (www.dlubal.com), would like SEs to know that the company has been in the structural analysis software industry for 30 years. “With several European offices, existing clientele in the United States and Canada, and offering U.S. and Canadian material design standards, we knew we were ready to make an impact in the local market with the opening of our Philadelphia, Pennsylvania office in July 2015. With existing competition in this same industry, we understand we must have a product that goes above and beyond engineers’ expectations.” Says Heilig: “Our FEA software RFEM is one of the most sophisticated yet user-friendly analysis programs available for member, plate, shell, and solid element modeling. RSTAB, with a similar interface as RFEM, is an alternative program for framework type structures only. These are software programs created by engineers for engineers. The photorealistic rendering, non-linear capabilities, and seamless BIM integration surpass what structural engineers settle for currently. Multi-material structures

are easily designed with not only steel, reinforced concrete, and timber, but also glass, cross-laminated timber (CLT), and reinforced plastics according to current U.S. and Canadian standards and codes. Only a few trial runs in RFEM or RSTAB will showcase the power, efficiency, and usability behind our German-engineered software.” How’s business? “Business is growing,” Heilig says. “With the physical presence of Dlubal Software in the United States, existing and new clientele are pleased to have a local contact for sales and technical support. Outreach at tradeshows around the country, free online webinars for PDH credit, and monthly email newsletters continue to broadcast who we are and how our products can significantly increase structural engineers’ productivity.” She concludes: “Engineers are busy people. As former practicing engineers ourselves, we understand this. However, if you simply need to make a change because you expect something more out of your current software, we encourage you to try Dlubal. With an incredibly intuitive interface, we guarantee the downtime to learn our software is minimal yet the outcome is beyond beneficial. There is a reason Dlubal is utilized by more than 25,000 satisfied customers in 71 countries.” (See ad on page 44) At ASDIP Structural Software (www.asdip.com), Founder and Owner Javier Encinas describes their product as a “structural engineering software conceived by and designed for structural engineers

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

74' LONG RED-W™ OPEN-WEB BARREL TRUSSES WITH A 7' CAMBER

OPEN When you design with RedBuilt engineered wood structural systems, long, free spans exceeding 100 feet become as economically attractive as they are beautiful. Installation is easier. And even your carbon footprint shrinks. Suddenly, your designs are as open as your imagination. See more at RedBuilt.com.

OPEN-WEB TRUSSES • RED-I™ JOISTS • REDLAM™ LVL

STRUCTURE magazine

August 2016

DESIGN SPACE MINDS

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

to work cost-effectively and complete common tasks in less time.” He says that they currently offer four products, each consisting of several modules. These are: • ASDIP Concrete – Design of continuous beams, biaxial columns, and out-of-plane bearing walls, • ASDIP Foundation – Design of spread footings, combined footings, and strap footings, • ASDIP Retain – Design of cantilever retaining walls and toprestrained retaining walls, • ASDIP Steel – Design of base plates, anchor rods, shear lugs, steel columns, and steel / composite beams. Says Encinas: “Our customers are mainly small companies and individual consultants, as well as some large design firms. ASDIP is utilized by structural engineers to design, analyze, check and optimize calculations for structural members such as beams, columns, walls, footings, and retaining walls. Also, ASDIP can be used as an educational tool because the reports include exposed formulas and code references.” He adds: “I provide the technical support directly through email or by phone. Being a practicing structural engineer with more than 30 years of experience, this is a big plus. I often provide structural engineering recommendations in addition to the software support. We focus on excellence in technical support and service, solving over 95 percent of the issues in the same day.” Stuart Broome, Business Manager, Engineering at Trimble (www.tekla.com) says there are three new developments within the Tekla Software portfolio that SEs should know about: Tekla Structures 2016, Tekla Structural Designer 2016, and Tekla Model Sharing. • Tekla Structures 2016 delivered a brand new user interface with its latest release. With a new, contemporary look, customizable menu ribbons, and brand new “quick launch feature,” version 2016 enables faster and more efficient modeling. In the new 2-D library, means for creating and

editing high-quality drawing is faster and easier for the Structural Engineer. Smoother collaboration among a wider design team was also enhanced in the new version with improved workflows with plant design systems such as Intergraph Smart3D, Aveva PDMS, and E3D. • Tekla Structural Designer 2016 was another new offering recently released. With new RSA and seismic design provisions for concrete, a whole new market for Trimble’s A&D solution has opened up on the West Coast. Major performance enhancements in modeling, processing times and IFC compatibility have also proved to be well received by customers. • Tekla Model Sharing now makes it possible for people all over the world to work on the same Tekla model at the same time. With the flexibility of working online or offline, along with the ability to sync only the changes they have made to a model, instead of the entire file, users are redefining how they work. This exclusive capability to Tekla Software is available with users’ current Tekla Structures software; no add-ons are needed. “Business is strong as the structural engineering community continues the search for improved productivity,” Broome says. “Structural engineers were historically very conservative when it came to adopting new technology, but the younger generation coming through the ranks understand that just because a software solution has been used for 10 years or more does not mean that it is the best on the market. This has led to an increased level of competition among software vendors and technology is moving quickly. The more forward-thinking engineers are capitalizing on the competitive advantage that newer tools can provide. This applies in particular to Tekla Structural Designer, Trimble’s new building analysis and design solution. With Response Spectrum Analysis (RSA) and seismic design for concrete structures, TSD offers many unique features that enhance productivity. TSD has been developed with BIM integration in mind, and while its primary function is analysis and design, it communicates at a very high level with BIM solutions like Tekla Structures and Revit.” Concludes Broome: “We are also seeing structural engineers looking to expand their scope of business by moving into Construction Services. This does not mean that engineers are trying to become detailers, but they are now creating truly constructible models which are useful downstream. This additional revenue stream has been very lucrative for our users. Tekla Structures produces construction documents as you would expect, but works to a higher level of detail (LOD) than some other BIM solutions. It does not take much additional work to design out clashes by using the automated steel connection and 3D rebar modeling functionality. The model can then be used by the detailer who is likely to be using Tekla Structures, too.” (See ad on page 3.) continued on page xx

STRUCTURE magazine

August 2016

Design wood structures effectively, economically and with ease!

Design Office

SIZER Gravity Design

SHEARWALLS Lateral Design

CONNECTIONS Fasteners

O86

Engineering design in wood

2x4

DATABASE EDITOR

PDF

Adobe

WOOD STANDARDS

(US version)

PDF

Adobe

WOOD STANDARD (CDN version)

Download a Free Demo at woodworks-software.com n sio l! r e S v is Fal U h w Ne ing t com

AMERICAN WOOD COUNCIL

US Design Office 10

Canadian Design Office 9

NDS 2012, SDPWS 2008, IBC 2012 and ASCE 07-10 compliant

CSA O86-09 and NBC 2010 compliant

Use Promo Code STRUCMAG2015 and receive a 10% discount towards your purchase!

www.woodworks-software.com

800-844-1275

Marinos Stylianou, Chief Executive Officer of S-FRAME Software (www.s-frame.com), is excited about S-FOUNDATION 2017. “It improves the ability for structural engineers to generate foundations of any shape easily, with any number of holes, pedestals, and walls. When engineers realize the simplicity and power of S-FOUNDATION, they immediately understand the direct benefits to their organization,” he says. Recently released updates for S-FRAME Analysis, S-CONCRETE, S-STEEL, and S-CALC have added improved functionality and integration, too. Says Stylianou: “Challenges in the software industry are a continued demand for ease of use combined with product integration. Recent releases of S-FRAME Analysis have significantly improved meshing automation and enhanced tighter integration with concrete and steel design, to help engineers streamline their workflow. We have seen strong growth in the U.S. and Asia, especially when the need is to analysis and design newer trend-setting tall buildings. Having software tools that are versatile enough to work for any industry type or region is key.” He adds: “We expect structural analysis and design software to continue to evolve in terms of supporting newer, advanced material models, to incorporating more design codes, providing more automation and allowing for the user’s ability to customize the software to fit individual, organizational needs. Newest releases of our products address these needs.” (See ad on page 4.) Paul Drace, Marketing Director at Redbuilt (www.redbuilt.com), says that business has been steadily improving, and they are experiencing growth across-the-board in their commercial segments in 2016. “We are planning for and expect the same upward trajectory for the next one to two years.”

“In the near term, we see an overall increase in the use of wood in commercial construction and particularly in large structures. The primary drivers are increases in steel prices associated new anti-dumping duties imposed on China, availability of skilled labor, and increasing emphasis and awareness of the environmental benefits of wood. The biggest impact in the long term is likely to be finding, training, and keeping skilled labor. As a result, RedBuilt is focused on the search for ways to ease the shortage of skilled labor on job sites by offering services and pre-assembled accessories.” Says Drace: “RedBuilt’s associates, products including Open-Web trusses, Red-I I-joists, [sic] and RedLam LVL, and services and accessories are directed toward one primary goal: being the premier supplier of structural solutions to the commercial construction industry. Our products are well suited for roof, floor, and wall framing in myriad applications including all wood, structural steel frame, and concrete/ CMU wall structures.” (See ad on page 47.) Wayne Golden, Marketing Manager at Lindapter International (www.lindapterusa.com), touts their work on the Wilshire Grand Center designed by AC Martin. “When it is finished in 2017, it will be the tallest skyscraper west of Mississippi and will be configured to maximize views of Santa Monica, the Pacific Ocean, the Hollywood Hills and the San Gabriel Mountains,” he says. “The main feature of AC Martin’s design is the swooping glass canopy which forms the lobby structure and main entrance to the building. The steel contractor was tasked with connecting the wavy structure made up of circular hollow structural sections.” “It was a taxing contract which required good organization skills because there were hundreds of unique sections, and their varying curves meant that each one had its own specific location. Safety and

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

Hollo-Bolt

The only expansion bolt with full A to F seismic approval Engineers can now specify Hollo-Bolt structural steel connections in all Seismic Design Categories A through F in compliance with both International and City of Los Angeles Building Codes. 4 4 4 4 4 4

For HSS and structural steel sections Fast, cost saving installation from one side High resistance to shear and tensile loads Unique high clamping force design Hot Dip Galvanized corrosion protection ICC-ES and LARR approved

HIGH CLAMPING FORCE ICC

Seismic Approved

Please download the catalog at www.LindapterUSA.com Find your regional Lindapter representative and more information at www.LindapterUSA.com STRUCTURE magazine

August 2016

durability were of paramount importance but due to the architecturally exposed steel design, the engineer also wanted a discrete finish. Thorough planning and research were carried out by the structural engineer who evaluated various connection methods. The engineer decided to avoid through-bolting to ensure that there was no deformation of the steel tubes, while welding was deemed undesirable due to the additional work required to prepare and finish the joints. The structural engineer began to research various alternative connection methods and, after evaluating factors such as resistance to wind and seismic loads, decided that Lindapter’s Hollo-Bolt was the best solution.” The Hollo-Bolt is an expansion bolt for structural steel and HSS that was invented by Lindapter in 1995. Unlike conventional bolts, the fastener can be installed from one side of the steel (i.e. the bolt/nut does not protrude out of the opposite side of the HSS), Golden notes. “It was recently approved by ICC-ES for use in all seismic zones and report ESR-3330 concludes that ‘Hollo-Bolt Fasteners may be used to resist wind loads and seismic loads in Seismic Design Categories A through F in accordance with Section 1613.3.5 of the 2012 IBC, and Section 1613.5.6 of the 2009 IBC.’ Also, the ICC-ES evaluation validates load data for LRFD and ASD design methods, confirming that Hollo-Bolt has achieved the highest resistance to tensile loading in accordance with AC437.” Further to the ICC-ES approval, the Hollo-Bolt has been awarded the Los Angeles Research Report (LARR approval) from the City of Los Angeles Department of Building and Safety, Golden says. “Although this is a state-based review, it provides architects, builders and specifying engineers with extra confidence when specifying the Hollo-Bolt. Following the specification of Hollo-Bolt to connect

the atrium’s architecturally exposed structural steel, the steel erector began the process of lifting the steel sections into place, and inserting size ⅝-inch Hollo-Bolts into the pre-drilled holes and tightening with standard tools. The simple process allowed over 3,000 HolloBolts to be quickly installed and avoided the need for drilling or welding in the field. Moreover, the quick and easy installation allowed the contractor to complete the atrium structure on time and on budget.”▪

ADVERTISING OPPORTUNITIES Be a part of upcoming

SPECIAL ADVERTORIALS in 2016.

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

CHUCK MINOR

JERRY PRESTON

Phone: 847-854-1666

Phone: 480-396-9585

Sales@STRUCTUREmag.org

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

STRUCTURAL VIBRATION CONTROL TUNED MASS DAMPERS DEICON provides the most effective passive and active tuned damping solutions for vibration abatement in: • Floor Systems • Pedestrian Bridges • Towers

• Industrial Structures • Monumental Staircases • And more

August 2016

DEICON.COM

SOFTWARE GUIDE

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

ADAPT Corporation

Bentley Systems, Incorporated

Pile Dynamics, Inc.

Phone: 650-306-2400 Web: www.adaptsoft.com Product: ADAPT-ABI 4D Construction Phase Analysis Description: Easily models construction phases including temporary structures, closure strips, pre- and post-tensioning. 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, super-positioning, and investigation of construction methods.

Phone: 800-BENTLEY Web: www.bentley.com Product: STAAD.Pro Description: Design any structure and share synchronized model data with confidence. Ensure on time, on budget completion of your steel, concrete, timber, aluminum, and cold-formed steel projects, regardless of complexity. Confidently design structures anywhere in the world using over 80 international codes, reducing the need to learn multiple software applications.

Product: ADAPT-PT/RC Strip Design Description: Popular software for design of posttensioned 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.

Design Data

Phone: 216-831-6131 Web: www.pile.com Product: GRLWEAP, PDI-Tomo, SPT Analysis Software Description: Revamped SPT Software, standard on SPT Analyzers and a Pile Driving Analyzer(R) option, quickly summarizes SPT hammer calibration results for reporting. PDI-TOMO is new software used for crosshole sonic logging data 3D visualization and interpretation. GRLWEAP, the classic wave equation analysis of pile driving program, underwent a significant update.

Applied Science International Phone: 919-645-4090 Web: www.appliedscienceint.com Product: SteelSmart System 7.3 (SSS) Description: Raises the bar for light steel framing analysis and design by seamlessly integrating the well-known analytic power of its predecessors with additional functionality and accessibility. SSS will streamline production through the design and detailing of members, connections, and fasteners. Product: Extreme Loading for Structures 4.0 (ELS) Description: An advanced non-linear structural analysis software tool designed specifically for structural engineers. ELS allows structural engineers to study the 3D behavior of structures through both the continuum and discrete stages of loading.

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

ATIR Engineering Software Phone: 847-677-1945 Web: www.atir.com Product: BEAMD Description: A complete and totally integrated solution for RC beam design, detailing, drafting, and scheduling. Use it on its own, with STRAP, or with CAD. Design is in accordance with ACI and other international codes.

Autodesk, Inc. Phone: 415-580-3872 Web: www.autodesk.com Product: Autodesk® Advance Steel Description: Easy-to-use software for structural steel detailing built on the AutodeskAutoCAD® platform. Intelligent 3D modeling tools help you accelerate more accurate design and detailing. Help speed time to fabrication by automatically generating shop drawings and deliverables. Interoperability with Autodesk Revit® software supports a more connected BIM workflow.

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

Dlubal Software, Inc. Phone: 267-702-2815 Web: www.dlubal.com Product: RFEM Description: Complete with USA and International Standards for steel, concrete, timber, CLT, glass, and aluminum. Allows for efficient modeling, a powerful analysis, and highly detailed design results. Direct interfaces with BIM and CAD software incorporate seamless and bi-directional data exchange.

Hilti, Inc. Phone: 800-879-8000 Web: www.us.hilti.com Product: PROFIS Anchor, PROFIS Rebar, PROFIS DF Description: Hilti offers three design programs for structural engineers. 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.

Integrity Software, Inc. Phone: 512-372-8991 Web: www.softwaremetering.com Product: SofTrack Description: Why choose SofTrack? Block unwanted Bentley® license usage. Control Bentley concurrent usage. Compliant with all of Bentley’s licensing policies. Discover who is using licenses via a real-time web page (any user can access). Alert users and administrators of idle application usage, stop application parking.

MDX Software Phone: 573-446-3221 Web: www.mdxsoftware.com Product: MDX Software Curved & Straight Steel Bridge Design & Rating Description: Used by many top design firms and DOTs to design and rate steel girder bridges for compliance with LRFD, LRFR, LFD, and ASD AASHTO Specifications.

STRUCTURE magazine

August 2016

Powers Fasteners Phone: 800-524-3244 Web: www.powers.com Product: Powers Submittal Generator Description: 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 Powers Fasteners for a free demonstration!

RedBuilt Phone: 866-859-6757 Web: www.redbuilt.com Product: RedSpec™ Description: Quickly and efficiently create floor and roof design specifications using Red-I joists, open-web trusses, and RedLam for a variety of applications. A central component is FloorChoice™; allows a floor to be evaluated while still in the design phase, providing an easy-to-understand numerical rating system.

RISA Technologies Phone: 800-332-RISA Web: www.risa.com Product: RISA-3D Description: Designs and optimizes steel, concrete, masonry, wood, cold-formed steel and aluminum with a fast, intuitive interface. State of the art solvers, customizable reporting options and robust integration with other products such as RISAFloor, RISAFoundation and Revit Structure make RISA-3D a premier choice for general purpose structural analysis and design.

S-FRAME Software, Inc. Phone: 604-273 7737 Web: www.s-frame.com Product: S-FRAME Analysis Description: Versatile enough to model, analyze and design robust structures regardless of geometric complexity, material type, loading conditions, nonlinear effects, or design-codes. The model management environment efficiently integrates Steel, Concrete, and Foundation design solutions and BIM/ DXF data import to ensure maximum productivity. Product: S-CONCRETE Description: Interactive design solution for reinforced-concrete columns, beams and walls. Design and optimize a single section or evaluate thousands of concrete sections at once. Not a blackbox solution: S-CONCRETE’s comprehensive and multi-code support generates detailed reports that include clause references, equations employed, intermediate results and diagrams.

SCIA, a Nemetschek Company

StrucSoft Solutions Ltd.

StruMIS LLC

Phone: 410-207-5501 Web: www.scia.net Product: SCIA Engineer Description: Looking to migrate to, or improve 3D design workflows? Plug structural analysis and design into today’s BIM workflows with SCIA Engineer. Tackle larger projects with advanced non-linear and dynamic analysis. Plug into BIM with IFC, and bi-directional links to Revit, Tekla, and others. Free demo!

Phone: 514-538-6862 Web: http://strucsoftsolutions.com Product: MWF Advanced Metal Description: A Revit based modeling and engineering software allowing for automated modelling, quantification and design of structural and non-structural light gauge steel building elements including roof trusses. Outputs include panel drawings, BOM, engineering reports and CNC code. Visit the website for more details.

Phone: 610-280-9840 Web: www.strumis.com Product: StruMIS Steel Fabrication Software Description: Complete management information and production system for every steel fabrication company; minimize overheads and costs, maximize productivity and profitability; in every step of the steel fabrication process.

Simpson Strong-Tie Phone: 800-925-5099 Web: www.strongtie.com Product: Anchor Designer™ Software for ACI 318, ETAG and CSA Description: The latest anchorage design tool for structural engineers to satisfy the strength design provisions of multiple design methodologies. Anchor Designer will quickly and accurately analyze an existing design or suggest anchorage solutions based upon user-defined design elements in cracked and uncracked concrete conditions.

Standards Design Group, Inc. Phone: 800-366-5585 Web: www.standardsdesign.com Product: Wind Loads on Structures 4 Description: Performs computations in ASCE 7-98, 02 or 05, Section 6 and ASCE 7-10, Chapters 26-31 computes wind loads by analytical method rather than the simplified method, provides basic wind speeds from a built-in version of the wind speed, allows the user to enter wind speed, has numerous specialty calculators.

StructurePoint Phone: 847-966-4357 Web: www.StructurePoint.org Product: spSlab and spWall Description: spSlab: for analysis, design and investigation of reinforced concrete floor systems. spWall: for design and analysis of cast-in-place reinforced concrete walls, deep beams, coupling beams, tilt-up walls, ICF walls, and precast architectural and load-bearing panels. Product: spColumn and spMats Description: spColumn: for design of shear walls, bridge piers as well as typical framing elements in buildings and structures. spMats: for analysis, design and investigation of commercial building foundations and industrial mats and slabs on grade.

Trimble Solutions USA, Inc. Phone: 770-426-5105 Web: www.tekla.com Product: Tekla Structural Designer Description: 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 to cost-effective change management and seamless BIM collaboration, Structural Designer can transform a business. Product: Tekla Structures Description: Create and transfer constructible models throughout the design lifestyle. From concept to completion. Allows you to create accurate and information-rich models that reduce RFIs and enable structural engineers proven additional services. Models are used for drawing production, material take offs and collaboration with other disciplines.

Not listed? Visit www.STRUCTUREmag.org and submit your information for upcoming guides! Listings are provided as a courtesy. STRUCTURE magazine is not responsible for errors.

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

We do the exams. You do the math. Study with NCEES. PRACTICE EXAMS Developed by the same people who create the actual exams Include many questions used on past exams Simulate the format, style, and level of difficulty of the actual exam

SE Practice Exam $49.95 PE Practice Exams $39.95 each ncees.org/PracticeExams

STRUCTURE magazine

August 2016

inSightS new trends, new techniques and current industry issues

n the October 2010 Insights column (STRUCTURE®), Bruce Maison wrote an excellent article on ASCE 41-06 Seismic Rehabilitation of Existing Buildings, now called ASCE 41-13 Seismic Retrofit of Existing Buildings, and its inclusion in the International Building Code (IBC). A portion of Maison’s article discussed a survey of Structural Engineers Association of California (SEAOC) members regarding their satisfaction with ASCE 41 and areas where the respondents felt there were opportunities for improvement. Of particular relevance to this article is that 74% of respondents wanted to see a calibration or comparison with the building code, and 64% of respondents wished there was reduced conservatism in the linear static and linear dynamic procedures and acceptability criteria. When roughly two-thirds to three-quarters of a group of structural engineers agree on the need to make changes in a standard they use as the basis of a significant part of their work, this is a clear call for action. It is now 2016, and the author has a hunch that if the survey was conducted today, the results would be much the same. Several root questions need to be answered to address the concerns of engineers, namely: 1) Why are there two standards intended to accomplish the same result? 2) Why do retrofit designs developed using each standard often differ so much? 3) Is it appropriate to base seismic retrofit designs on the prescriptive provisions of the IBC which were written solely for the design of new buildings? 4) If there is one standard, does a “one-size fits all” approach work across all levels of seismicity? To answer the first question, one needs to step back in time to when seismic strengthening was an emerging field. At that point, 1) the building code (let’s say the UBC) was a far simpler and less prescriptive document, and 2) many practitioners and jurisdictions felt that it didn’t make sense to strengthen existing buildings to the same strength level as new buildings, because existing buildings had a shorter remaining useful life. The use of 75% of the UBC seismic forces was commonly used as the required seismic demands, with the “how” part left largely up to the engineer. In those days, engineers were “engineers,” much like doctors were “doctors”, so this “freedom” seemed to work fairly well. Of course, some engineers designed better seismic retrofits than others, just like new buildings. This is not to say that, at the time, the beginnings of the performance-based design revolution were not being discussed by the more elite of the profession and university researchers. However,

Seismic Retrofits Using the IEBC Should I use 75% of IBC or ASCE 41? By John Dal Pino, S.E.

John A. Dal Pino is a Principal with FTF Engineering located in San Francisco, California. He serves as a member of the STRUCTURE Editorial Board and may be reached at jdalpino@ftfengineering.com.

54 August 2016

the UBC predated ASCE 41 and its predecessor relatives (ASCE Proceedings, April 1951 Separate No. 66, ATC-14, NEHRP 178, FEMA 310/273, etc.), so it is natural that engineers, many of whom mostly design new buildings as their business, have some natural affinity for the “code.” Ignoring for a moment all of the assumptions condensed and contained in a single number, the R-value, which is built upon research for new systems, these engineers were looking for a “force” to design to and move on with the work. As engineers, we think it is fair to say this. So, to answer the first question in two or three words, “inertia, simplicity, and familiarity.” In a perfect world, there really ought to be just one standard; why do we need two standards that get us to the same result? Seismic is different from wind in that we all agree with the USGS about seismicity, while various aspects of wind design are based on different sets of physical measurements. The answer to the second question is a simple one, there should be no difference. In any world, not even a perfect world, the strengthening results shown on the construction documents for obtaining life-safety building performance should be the same regardless of the method used. To illustrate the potential discrepancy in seismic retrofit requirements, we calculated the length of plywood shear walls necessary for a wood frame residential structure using a linear static analysis approach. We picked a location in the center of San Francisco at latitude 37.777 deg. N and -122.444 deg. W, and found that the length of the wall using the ASCE 41 provisions was twice that required using 75% of the IBC. Some might argue that this result is an outlier and is not representative of the situation due to unique seismicity issues and the material selected (wood), although others might counter that if the IEBC standards do not work well in the heart of earthquake country where retrofits are common, we have a problem. So we tried another location, Oklahoma City, at 35.472 deg. N and -97.517 deg. W and found a smaller, yet still significant, difference of 25%. The third question stated another way is whether all of the “stuff” contained in the code R-value applies to the process of designing strengthening of existing buildings. The authors of ASCE 41 wrote a standard specifically for existing buildings built upon the research on existing buildings of past vintages, which do not comply with current code detailing requirements, and created an “m-factor.” To be fair, the authors of ASCE 41 also knew that engineers were also looking for a “force” to design to. The answer to the third question is “probably not.” Determining the seismic base shear force is relatively easy, but followers of the code-approach are almost immediately faced with a daunting problem. How do they calculate the strength of the existing elements in the building, particularly when the elements do not look like replicas of

State-of-the-Art Products STRUCTURAL TECHNOLOGIES provides a wide range of custom designed systems which restore and enhance the load-carrying capacity of reinforced concrete and other structure types, including masonry, timber and steel. Our products can be used stand-alone or in combination to solve complex structural challenges.

V-Wrap™

Carbon Fiber System

DUCON®

Micro-Reinforced Concrete Systems

VSL

External Post-Tensioning Systems

Tstrata™

Enlargement Systems

Engineered Solutions Our team integrates with engineers and owners to produce high value, low impact solutions for repair and retrofit of existing structures. We provide comprehensive technical support services including feasibility, preliminary product design, specification support, and construction budgets. Contact us today for assistance with your project needs.

www.structuraltechnologies.com

+1-410-859-6539 To learn more about Structural Group companies visit www.structuralgroup.com DUCON® trade names and patents are owned by DUCON GmbH and are distributed exclusively in North America by STRUCTURAL TECHNOLOGIES for strengthening and force protection applications. VSL is the registered trademark of VSL International Ltd.

STRUCTURE magazine

August 2016

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

modern materials that are described in the building code and related material standards? Simply stated, the fourth question is whether large and small earthquakes impact buildings the same way or, in other words, can the effects be scaled like wind? So should the reduction “factor” also be based on the seismicity? Amongst many other factors contained in the “stuff” is the nature of the earthquake, the acceleration and velocity components and, most important of all, the duration. Except for the most brittle of materials, is the duration of shaking in areas of low seismicity long enough to damage an ordinary or intermediate concrete shear wall (of any vintage)? By that, we mean really grind it up and put it into the non-elastic range for which ASCE 41 has rightly assigned low m-factors? We think the answer is “no.” There are earthquakes all of the time throughout the country in areas of low seismicity where buildings should be damaged (based on evaluation using ASCE 41 provisions), but aren’t. Perhaps it is not that ASCE 41 is too conservative but that the m-factors have been developed using research data for strong earthquakes, and then applied to small ones (i.e. scaled). It seems like a little nonlinear analysis to derive the required inelastic displacement would solve this in short order. Likewise, in a near source event in a region of high seismicity, would one expect the same ordinary or intermediate concrete shear wall (detailed to past standards) to stand up to 20 seconds of really strong shaking? Again, we think not. So the answer to the fourth question is also “probably not.” So what is the insight here? First, retrofit designs can obviously differ greatly depending on the standard being followed. Both of the standards might yield life-safe designs, with one more conservative than the other. Alternatively, one might not be life-safe while the other is. The first possibility is unfortunate but acceptable. The second option is clearly not acceptable. Therefore, 1) there ought to be one standard based on a performance-based approach, 2) the results need to make sense to most engineers (i.e. the strengthened building should look comparable to, but clearly weaker than, a new similar building), 3) the analysis and design techniques need to address only existing buildings, and 4) the force reduction and ductility “factors” need to be adjustable for seismicity and earthquake duration. There are minds out there far smarter than ours that will come up with other needed improvements, but it is not asking too much to have engineers and researchers sit down and come up with one accurate standard for retrofitting existing buildings, just like there is for designing new ones.▪

EnGInEER’S nOTEbOOk

aids for the structural engineer’s toolbox

Flexure Design of Built-up Box Beams By Roger LaBoube, Ph.D., P.E.

box beam configuration may be used at openings in a floor or wall framing assembly. The American Iron and Steel Institute’s AISI S100 contains design provisions for built-up flexural members consisting of two C-sections oriented back-to-back to form an I-shaped section, i.e. Section D1.1, but does not contain design guidance for a box-section formed by orienting two C-sections lip-to-lip. For built-up members to act as a single composite unit, the members must be connected with sufficient fasteners at the maximum spacing as calculated below. This article illustrates the extrapolation of S100 Section D1.1 provisions to a box beam configuration. The AISI S100 provisions are based on stabilizing the shear flow in the flanges. The same shear flow exists in a box-shaped section; therefore, the S100 provisions could apply to form a box-shaped section with the two C-sections oriented lip-to-lip. The AISI S100 provisions for Flexural Members Composed of Two Back-to-Back C-Sections (D1.1) are as follows: The maximum longitudinal spacing of connections (one or more welds or other connectors), smax, joining two C-sections to form an I-section shall be: 2gTs smax = L / 6 or , whichever is smaller mq (Eq. D1.1-1) where L = Span of beam g = Vertical distance between two rows of connections nearest to top and bottom flanges Ts = Available strength [factored resistance] of connection in tension (Chapter E) m = Distance from shear center of one C-section to mid-plane of web q = Design load [factored load] on beam for determining the longitudinal spacing of connections. The D1.1 provisions, Eq. D1.1-1, define the fastener spacing along the length of the member (Figure 1). Because the current D1.1 provisions are intended to stabilize the C-section and achieve equilibrium of the cross section for the single C-section (Figure 2), the D1.1 provisions may be adapted to box-shaped sections by recognizing that “g” is the vertical distance between the two rows of welds that interconnect the

overall buckling is not a limit state. This design check is achieved by evaluation of the following equation: 0.36Cbπ Lu = √EGJIy FySf If the span length is less than Lu, no intermediate braces are required to achieve the yield moment as computed by Section C3.1.1 of the AISI specification, Maxo = Sxe Fy / Ω Check Shear Alone (Section C3.2): Figure 1. Figure C-D1.1-2 (AISI S100C).

two C-sections. To evaluate “Ts”, the available strength of the welded connection, the provisions of AISI S100 Section E2.6, Equation E2.6-1, for flare groove welds applies. Using ASD, the safety factor is 2.55, and the nominal strength is as follows: Pn = 0.833 t L Fu (Eq. E2.5-1) Where, t is the thickness of the C-section, L is the length of the weld and Fu is the tensile strength of the C-section. Additional limit states that must be considered in the design of a flexural member are further defined in the AISI S100 provisions and include Bending, Shear, Combined Bending and Shear, Web Crippling, and Combined Bending and Web Crippling. The following example illustrates the design steps for a built-up box beam. Check Bending Alone (Section C3.1.2.2): The two interconnected C-sections are assumed to behave as a closed box member. Because for a closed box member in bending, lateral buckling is unlikely, the AISI Specification first requires the evaluation of the critical unbraced length for which

For cold-formed steel members, shear alone is typically not a controlling limit state. However, the available shear capacity per web may be computed based on the limit states of shear yielding, shear inelastic buckling or shear elastic buckling. Because of the thin web material, buckling is the controlling shear limit state. Combined Bending and Shear (Section C3.3): For continuous span members, the combination of high shear and bending stresses may occur at intermediate supports. Thus, this limit state is an important design check for continuous span beams. Web Crippling Alone (Section C3.4): If the box beam is uniformly loaded, web crippling need only be considered at the end support. Web crippling must be considered if the box beam is supported on its bottom flange, and no web stiffener or clip is provided at the support location. When checking web crippling, AISI Eq. C3.4.1-1 is applicable. The appropriate coefficients and safety factor are provided in Table C3.4.1-2. The coefficients and safety factor tabulated in Table C3.4.1-1 are not appropriate because these coefficients, although indicated to be valid for “built-up sections,” were experimentally developed for only I-shaped sections. Combined Bending and Web Crippling (Section C3.5):

Figure 2. Figure C-D1.1-1 (AISI S100-07C).

STRUCTURE magazine

August 2016

For continuous span members, the combination of high compression stresses resulting from concentrated loads and bending stresses may occur at intermediate supports. Thus, this limit state is an important design check for continuous span beams.

the application of Section D1.1 for a back-toback configuration, see page 303 of Cold-Formed Steel Design (Yu and LaBoube, 2010).▪

Studs – toe to toe

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

Figure 3. Typical boxshaped cross section.

Check the Interconnection of the Two C-sections (Section D1.1):

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

To interconnect the two C-sections forming a box beam configuration, flare groove welds are commonly used to interconnect the flanges (Figures 3 and 4). The available strength of a flare groove weld can be computed using AISI Section E2.6. The maximum longitudinal spacing for the welds, smax, as defined by AISI Section D1.1 is the lesser of 2gTs smax = L / 6 or (Eq. D1.1-1) mq Although not required by Section D1.1, it is suggested that the maximum unbraced length, Lu, to achieve the yield moment, Maxo, for the single C-section be considered. The author suggests that Lu is considered to ensure that the weld spacing is less than the unbraced length to preclude overall buckling of the single C-section between the welds. The AISI S100 Commentary provides an equation for Lu (Eq. C-C3.1.2.1-11). The evaluated Lu should be greater than smax. For a numerical example problem illustrating the design of a welded box beam, refer to Cold-Formed Steel Engineers Institute TN G104-14, www.cfsei.org. For a numerical example problem illustrating

This article was originally published in CFSEI Tech Note, July 2014, Welded Box Beam Flexure Design, and is reprinted with permission.

Figure 4. Typical groove weld.

STRUCTURE magazine

Roger LaBoube is Curator’s Teaching Professor Emeritus of Civil Engineering and Director of the Wei-Wen Yu Center for Cold-Formed Steel Structures at the Missouri University of Technology. Roger is active in several professional organizations and societies, including the American Iron and Steel Institute’s Committee on Specifications and Committee on Framing Standards. He also serves on STRUCTURE’s Editorial Board. He can be reached at laboube@mst.edu.

August 2016

award winners and outstanding projects

SpOTlIGhT

2016 ASCE Structural and SEI Awards

he Structural Engineering Institute (SEI) is proud to congratulate the winners of the 2016 ASCE Structural and SEI Awards:

STRUCTURAL ENGINEERING INSTITUTE AWARDS

2016 Chapter of the Year Award The 2016 SEI Chapter of the Year Award was given to the SEI Maryland Chapter. The SEI Maryland Chapter has strived to create programs with diverse content including bridge, building, waterfront, and geo-structural topics. The Chapter has partnered with local universities to create student-centered content during on-campus meetings that are free of charge for students and has conducted extensive K-12 outreach. 2016 Graduate Student Chapter of the Year SEI presented the 2016 Graduate Student Chapter award to the West Virginia University Graduate Student Chapter. The chapter has been active in providing educational opportunities, speaking opportunities to present research in conjunction with professional events and SEI Structures Congress, and outreach to undergraduate and K-12 students. In addition to these efforts, their members have been active on the SEI Graduate Student Chapter Leadership Council and have assisted in forming the policies and procedures that govern the SEI Graduate Student Chapters. W. Gene Corley Award The 2016 W. Gene Corley Award was given to Susan A. Jorgensen, P.E., LEED, AP BD+C, M.SEI, M.ASCE. Ms. Jorgensen is commended for her outstanding service to the engineering profession by distinguishing Structural Engineering as a profession through her persistent efforts to obtain Structural Engineering licensure nationwide and through her leadership of the Structural Engineering Licensure Coalition. Gene Wilhoite Innovations in Transmission Line Engineering Award The 2016 Gene Wilhoite Award was presented to Dana Crissey, P.E., M.ASCE. Mr. Crissey’s support, strong leadership and participation in ASCE/SEI spans over thirty years. His leadership, willingness to share his knowledge and experience and continuous education of his staff and peers in the electric utility industry were strong factors in his selection.

Dennis L. Tewksbury Award The 2016 Tewksbury Award was presented to Marc I. Hoit, Ph.D., F.SEI, F.ASCE. Dr. Hoit has been committed to improving the quality and effectiveness of ASCE and SEI’s technical programs and has helped the annual Structures Congress grow in attendance and international significance. Walter P. Moore, Jr. Award The 2016 Walter P. Moore, Jr. Award was given to John D. Hooper, P.E., S.E., F.SEI, F.ASCE. Mr. Hooper has served as the Chair of the ASCE 7 Seismic Subcommittee for both the 2010 and 2016 cycles and has significantly improved the reliability and safety of structures subjected to seismic loads. SEI President’s Award The 2016 SEI President’s Award was given to Donald Dusenberry, P.E., SECB, F.SEI, F.ASCE. Mr. Dusenberry has made significant contributions to SEI through leadership roles in technical, publications and standards efforts, and through his leadership on the SEI Board, particularly in developing the Vision for the Future Structural Engineer. AMERICAN SOCIETY OF CIVIL ENGINEERING STRUCTURAL AWARDS Shortridge Hardesty Award The 2016 Shortridge Hardesty Award was given to Kim J.R. Rasmussen, Ph.D., M.ASCE. Professor Rasmussen is honored for his contributions to the development of practical design provisions and advanced analysis guidelines in the field of structural stability. Throughout his career, he has demonstrated exceptional talent both as a researcher and as a leader and administrator. Ernest E. Howard Award The 2016 Ernest E. Howard Award was given to Ron Klemencic, P.E., S.E., M.ASCE. Mr. Klemencic is honored for his leadership in the application of performance-based seismic design methods for tall building structures and the promulgation of this approach throughout the structural engineering profession. Walter L. Huber Civil Engineering Prize Up to five Huber Prizes are awarded each year for achievements in civil engineering research. Amit Kanvinde, Ph.D., M.ASCE, is one of the 2016 winners of the Huber Prize. Dr. Kanvinde is honored for significant contributions in modeling integrated with large-scale

STRUCTURE magazine

August 2016

Left to right: Shuxian Wassenius, Susan Jorgenson, David Odeh, Sheila Rimal Duwadi, John Hooper, Dana Crissey, Marc Hoit, Laura Champion.

experiments to advance the analysis and design of steel connections and members. Moisseiff Award The 2016 Moisseiff Award was presented to Matthew R. Eatherton, Ph.D., P.E., S.E., M.ASCE; Xiang Ma, A.M.ASCE; Helmut Krawinkler, Ph.D.; Gregory G. Deierlein, P.E., F.ASCE; and Jerome F. Hajjar, Ph.D., P.E., F.SEI, F.ASCE for the paper titled QuasiStatic Cyclic Behavior of Controlled Rocking Steel Frames, published in the November 2014 issue of the Journal of Structural Engineering. The team contributed to a multi-institution, international research project to develop the controlled rocking system. Raymond C. Reese Research Prize The 2016 Raymond C. Reese Prize was presented to Ronny Purba, Ph.D., and Michel Bruneau, Ph.D., P.Eng., F.ASCE for their paper titled Seismic Performance of Steel Plate Shear Walls Considering Two Different Design Philosophies of Infill Plates II: Assessment of Collapse Potential, published in the June 2015 issue of the Journal of Structural Engineering. The paper recommended design changes that have been implemented into the document that directly governs the design practice. George Winter Award The 2016 George Winter Award was given to Andrea Surovek, Ph.D., P.E., F.SEI, M.ASCE. Dr. Surovek has made significant technical contributions in structural engineering and accomplishments in the arts and theater. Also, she has been an active ASCE and SEI volunteer and has chaired several major committees. To submit a nomination for the 2017 awards visit the SEI website at www.asce.org/structural-engineering/ structural-engineering-awards.

GINEERS

ASS O NS

STRUCTU

OCIATI

RAL

COUNCI L

NCSEA News

News form the National Council of Structural Engineers Associations

NATIONAL

NCSEA Code Advisory Committee – Wind Engineering Subcommittee

Buildings Starting to be Designed for Resiliency The federal government provides a significant amount of disaster relief funds to state and local governments each year for emergency and major disasters. For example, Congress provided roughly $120 billion for Hurricane Katrina and $60 billion for Hurricane Sandy recovery. Even in years with relatively few major disasters, it is typical for the federal government to annually appropriate between $2 billion and $6 billion to help pay for recovery projects. Studies and analyses of disasters indicate that there has been an increase in the number of major disasters declared each year. In addition, scholars of disaster policy and other experts such as climatologists expect disasters to increase in both frequency and costs in the near future, with the effects of climate change being considered. Congressional interest in disaster assistance has always been high given the amount of money provided to states and localities, but also because of increasing disagreements over the appropriate role of the federal government in providing assistance. Other concerns include the use of supplemental appropriations to pay for disaster relief, offsetting expenditures for disaster assistance, and whether some of the federal burden for disaster assistance should be shifted to states and local governments. Over this last decade, there has been a significant increase in research, education and promotion for developing community based resilience plans for natural and man-made disasters. Thus, the current buzzword of choice in the federal government and in our building code organizations is “Resiliency”. Almost every agency in the federal government has some type of resiliency initiative being worked on, with currently in excess of 100 initiatives on the topic being studied. These efforts involve thousands of individuals from various professions and tens of thousands of man hours. “Resiliency is the ability to prepare for anticipated hazards, adapt to changing conditions, and withstand and recover rapidly from disruptions” (Ms. Penny Pitzker, U.S. Secretary of Commerce). This sounds simple enough; however, a major road block in achieving these goals stems from the current approach used to establish performance goals of the buildings that we, as structural engineers, design. Our current codes are based on a life safety approach only, for a majority of our buildings, and do not consider the loss of functionality that can result in extensive socioeconomic disruptions and slow recovery after a major hazard event. There are some exceptions in our current design approach, i.e., performance-based seismic design for essential facilities; but overall we need to rethink our current design approach to integrate more of a system, or communitylevel-performance objectives, into our design requirements. NCSEA has been involved in these efforts over the past few years, to monitor the recommendations of these resiliency initiatives as they relate to the buildings codes. Currently, the main recommendations have been to promote the requirements for special inspections and structural observations during the construction process. Many of the studies have shown that these increased inspections during construction will provide significantly better resistance to the loads imposed by natural hazards. Buildings are starting to be designed for “resiliency” by doing simple things like elevating the emergency power systems out of the flood plain, providing impact resistant glazing for hospitals in tornado zones, anchoring equipment to the structure in STRUCTURE magazine

seismic regions, and designing exterior cladding systems for blast loads. These are steps that will help in the return to functionality following the natural hazard. We as structural engineers have a unique position in the design team to help the owners, architects, and other design professionals involved in our projects consider what minor design options can be utilized to make the building more resilient. We have a greater understanding of the magnitude of these natural and man-made disasters and the effects that they will have on the structures that we design. Most of the general public, and many of our fellow design professionals, consider buildings that we design “earthquake proof ” or “hurricane proof ” while we know that they are designed to a life safety code. We can also provide valuable insight in the codes and standards process to help move to a more community-resilient-design approach. Donald R. Scott, S.E., F.SEI, F.ASCE, is Vice President, Director of Engineering for PCS Structural Solutions, and Chair of NCSEA’s Code Advisory Wind Engineering Subcommittee.

New NCSEA Executive Director Named As previously announced, Jeanne Vogelzang is retiring as NCSEA’s Executive Director, coinciding with her move to Orange Beach, Alabama. As part of her transition plan, the NCSEA Board of Directors formed a Search Committee to fill the position and lead us into the future of NCSEA. Following an assessment of needs and an evaluation of over 50 candidates, the NCSEA Board has selected Al Spada to assume the Executive Director position on July 25. Al comes to us from the American Foundry Society, where he spent the last 18 years, most recently as Vice President of Business Development and Publisher/Editor in Chief of the Society’s three trade magazines. “In the last 20 years, Jeanne has done an incredible job and has positioned us for success. Al has a great starting point, and I’m confident that he will help make NCSEA even more successful in the future,” stated NCSEA Board President Brian Dekker. Jeanne Vogelzang will be assisting in the transition, and both Jeanne and Al will be at NCSEA’s Structural Engineering Summit in Orlando in September.

NCSEA Webinars August 9, 2016 Multi-Hazard Design of Blast-Resistant Facades August 25, 2016 Assessment of Seismic Performance of Reinforced Masonry Wall Structures September 27, 2016 Case Studies in Evaluation & Instrumentation of Existing Buildings Detailed information on the webinars and a registration link can be found at www.ncsea.com. Subscriptions that include both live and recorded webinars are available! 1.5 hours of continuing education. Approved for CE credit in all 50 states.

August 2016

Structural engineers from across the country will be gathering at Disney’s Contemporary Resort in Orlando for the 2016 NCSEA Structural Engineering Summit, featuring timely and informative education specific to the practicing structural engineer. Sessions will be available on two tracks, covering a wide range of topics. The keynote for the Summit will be Kent Estes, S.E., Ph.D., of Walt Disney Imagineering, on Structural Engineering for Walt Disney Theme Parks. The full slate of educational sessions can be found at www.ncsea.com.

NCSEA News

©Disney

Hotel

News from the National Council of Structural Engineers Associations

The host hotel and site of the sessions and trade show is Disney’s Contemporary Resort. Rooms are also available at Disney’s Grand Floridian, which is on the same monorail line as the Contemporary. Links for online reservations can be found at www.ncsea.com. Reserve your rooms, as we expect to sell out our room block well before the start of the Summit.

Networking & Social Events Along with the stellar educational sessions, the Summit offers many opportunities for networking and social activities with your fellow engineers.

Silver

Copper EN

GINEERS

August 2016

O NS

NATIONAL

OCIATI

STRUCTURE magazine

Platinum

ASS

Friday – Engineering projects and leaders in the structural engineering field will be honored at the NCSEA Awards Banquet. The Banquet features the presentation of the NCSEA Excellence in Structural Engineering Awards, honoring the best examples of structural engineering ingenuity throughout the world. The Banquet also includes the presentation of the NCSEA Special Awards, given to NCSEA members who have provided outstanding service and commitment to the association and to the structural engineering field. Formal attire is encouraged, but not required. In addition to the functions listed above, attendees will have the opportunity to visit and network during the breakfasts and lunches, as well as refreshment breaks.

Summit Sponsors to date:

RAL

Thursday – Thursday evening is the Welcome Reception, held on the trade show floor. Enjoy cocktails, food and the opportunity to visit with NCSEA Trade Show exhibitors.

STRUCTU

Wednesday – The Summit kicks off with two opportunities to meet and reconnect with Summit attendees. A Reception sponsored by the NCSEA Young Member Group Committee will be held at the Contemporary Resort from 4:30-5:30 p.m. The Reception will include recognition of the Summit Scholarship recipients as well as the presentation of the Young Member Chapter of the Year award. All Summit attendees are welcome. Following the Reception, attendees will be treated to a Gala Dinner event at the Orlando Museum of Art, hosted by Computers & Structures, Inc. Continuous shuttle service will begin at 6 p.m. from the Contemporary Resort. The event will feature endless food, bottomless champagne, open bar and unforgettable entertainment.

COUNCI L

Structural Short Course and Technical Sessions at the ASCE 2016 Convention

Structural Columns

The Newsletter of the Structural Engineering Institute of ASCE

September 28 – October 1, 2016, Portland, Oregon The technical program for the 2016 ASCE Convention was recently announced. Join civil engineers from across ASCE to celebrate the best the profession can offer including sessions that will benefit structural engineers. Below is a small sample of what ASCE Convention attendees can expect. Short Course: Lifeline Performance – Tohoku Earthquake & Tsunami March 2010 Wednesday, September 28, 2016 11:00 a.m. – 5:00 p.m. This workshop will cover physical effects of the earthquake and tsunami, field observation of earthquake and tsunami damage to critical infrastructure systems (including roads and bridges, railway system, airports, marine ports, electric power, natural gas, liquid fuel, telecommunication, water and wastewater systems), interdependencies of lifeline systems, response and recovery of lifeline systems, and debris management. Technical Sessions: ASCE/SEI Assessment of the Chile Earthquake of 2010 Thursday, September 29, 2016 4:00 p.m. – 5:30 p.m. Challenges of Replacement and/or Rehabilitation of Local Bridges Friday, September 30, 2016 10:15 a.m. – 11:45 a.m. ASCE/SEI 7: Updates to the 2016 edition Friday, September 30, 2016 4:30 p.m. – 5:30 p.m.

Willamette River Bridges Tour Wednesday, September 28, 2016 12:45 p.m. – 3:30 p.m. Take a unique tour of Portland’s Bridges on the Portland Spirit Explorer. Downtown Portland has a wide array of historic and unique bridges crossing the Willamette River including vertical lift and bascule spans, an independent double vertical lift, a Rall-wheel bascule, the world’s second longest steel tied arch bridge, and a new cable-stayed bridge for transit, bikes and pedestrians only. The cruise will be narrated by Sharon Wood Wortman and Ed Wortman, well-known local authors of the Portland Bridge Book and the newly released Big & Awesome Bridges of Portland & Vancouver. Visit the Convention website at http://asceconvention.org for more information, download the Preliminary Program and to register.

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.

The New Chapter on Tsunami Loads and Effects in ASCE 7-16 Saturday, October 1, 2016 8:30 a.m. – 10:00 a.m.

ASCE Week Las Vegas

Dan Frangopol Receives Multiple International Honors

Earn up to 34 PDHs in one week

Don’t miss ASCE Week, September 26 – 30, 2016, at the Green Valley Ranch Resort Spa & Casino in Henderson, Nevada. ASCE Week offers ASCE’s most popular face-to-face seminars in one location. Structural seminars include Structural-Condition Assessment of Existing Structures, Seismic Analysis of Structures and Equipment, and Structural Engineering of a 4-Story, Combined Material Building Using the 2015 International Building Code. Also, there will be a special tour of Hoover Dam, Mike O’Callaghan-Pat Tillman Memorial Bridge, and Lake Mead. Register at www.asce.org/asceweek by September 2 for special discounts.

STRUCTURE magazine

Special Tour:

Dan M. Frangopol, Ph.D., P.E., F.SEI, F.EMI, Dist.M.ASCE, was elected as a foreign member of the Academia Europaea. He was one of only four foreign members elected in the Physics and Engineering Science section. Dr. Frangopol is a longtime SEI leader and is currently the chair of the Technical Council on Life-Cycle Performance. Earlier this year he received an honorary doctorate (Laurea Magistrale ad Honorem) from the Politecnico di Milano. This was the fourth honorary doctorate Frangopol has received in his career. Learn more on the Lehigh University website at www.lehigh.edu/~incee/news/frangopolinternational-awards.html. August 2016

Linda Kaplan, chair of SEI’s Young Professional Committee, recently completed the book Bridges...Pittsburgh at the Point...A Journey Through History. Co-written with Thomas Leech, the book is a truly distinctive and valuable coverage of this topic. It explains when and where bridges were built, who built them, how they work, the historical context of the time they were constructed, and how these bridges helped to transform Pittsburgh and the region. Learn more on the publisher’s website at www.wordassociation.com/ history%20book%20page/bridges.html.

SEI Welcomes Two New Graduate Student Chapters

On April 18, SEI President David J. Odeh, P.E., S.E., SECB, F.SEI, F.ASCE, spoke at the 2016 National Academy of Engineering (NAE) – American Association of Engineering Societies (AAES) Convocation of the Professional Engineering Societies. The NAE-AAES Convocation brought together engineering society leaders from a wide range of disciplines to discuss important topics not only to the engineering community but also with broader implications for the United States. As a panelist for The Revolution in Modeling and Simulation for Engineering session, Mr. Odeh took part in a discussion on computational modeling, simulation, and visualization tools as key drivers in providing accelerated innovation and cost reduction in processes and products. In particular, Mr. Odeh focused on building information modeling (BIM) during his presentation Virtual Design and Construction – New Tools to Manage Risk and Improve Outcomes for Building Projects. He highlighted how integrated models could improve the decision-making process and provide opportunities for collaboration. The event took place at the National Academy of Sciences Building in Washington, D.C.

SEI Local Activities West Coast Florida Chapter

Oregon Chapter

The SEI West Coast Florida Chapter has presented a variety of events for its members. These include recent presentations about the Longboat Bascule Bridge and a panel discussion on the New St. Pete Pier. Learn more about these and other chapter activities on the SEI news web page.

The SEI Oregon Chapter recently held a joint meeting with SEAO on the subject of seismic preparedness. The presentations by Chris Goldfinger, Amit Kumar, Carmen Merlo, and Steve Drohota, were well received by the 80 participants. Learn more on the SEI news web page.

Houston Chapter announces their Fall Technical Luncheons Dates and Speakers:

Get Involved in Local SEI Activities

Tuesday, September 13th: Ultra-Performance Concrete (UHPC) in Bridge Structures Gregory Nault, P.E., S.E., Project Manager – Ductal Bridge Engineering, Lafarge Holcim Tuesday, October 11th: Giving a Legal Deposition – An Engineer’s Perspective Narendra Gosain, Ph.D., P.E., Senior Consultant, Diagnostics Group, Walter P Moore Tuesday, November 8th: Enhanced Building Resilience Required for Community Continuity Stephen S. Szoke, P.E., F.ACI, F.SEI, F.ASCE, LEED AP, CSI-CDT, Senior Director, Codes and Standards Portland Cement Association

STRUCTURE magazine

Join your local SEI Chapter, Graduate Student Chapter (GSC), 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, GSC, or STG in your area, review the simple steps to form an SEI Chapter at www.asce.org/structural-engineering/sei-local-groups. Local SEI Chapters and Structural Technical Groups of the ASCE Sections/Branches serve local member structural, technical, and professional needs through a variety of innovative programs. SEI supports local SEI Chapters with opportunities for local Chairs to learn about new initiatives and best practices with other local SEI Professional Chapter and Grad Student Chapter leaders (quarterly conference call and annual funded SEI Local Leader Conference including technical tour and training). Those local structural groups that affiliate with SEI and establish local Chapters receive SEI Chapter logo/branding, complimentary webinar and banner, and more.

August 2016

The Newsletter of the Structural Engineering Institute of ASCE

• Georgia Tech, chaired by Sujith Mangalathu, sujithmss@gatech.edu • University of Wyoming, chaired by Bryce Fiore, bfiore@uwyo.edu There are now eight SEI Graduate Student Chapters (GSCs). GSCs conduct a variety of activities including presenting visiting speakers, helping members connect with peers, field trips, and outreach activities to prospective students. For more information visit the SEI website at www.asce.org/ structural-engineering/sei-local-groups.

SEI President Speaks at NAE AAES Convocation

Structural Columns

SEI Member Writes Book about Pittsburgh Bridges

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, 2015 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, the 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, 2015 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 utilized. 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, 2015 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, 2015 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, 2015 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), 2015 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, 2015 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 other CASE products at www.acec.org/bookstore.

Pathways to Executive Leadership A practical, focused program for new leaders facing the challenges of a continuously evolving business environment. To be successful at taking on higher levels of leadership responsibility and prepare for the demands of being owners, new practice builders need specific and relevant training in the intricacies of leading an AE firm in ever-changing, always uncertain economic times. Pathways to Executive Leadership is an intensive leadership program for early-career elites and promising mid-career professionals with 8 to 12 years of experience who are just beginning to lead and think strategically about their practices and careers. The reality-based curriculum focuses on the core skills necessary to becoming more influential (in team development, coaching, and client relationships) and more strategic (in business forecasting, team building, and client development), including: STRUCTURE magazine

• High-Level Business Development • Leading Teams of Teams • Managing Uncertainty • Personal and Career Visioning • Strength Identification and Self-Awareness • Building Personal Resiliency • Coaching, Managing Others and Intentional Influence • Strategic Market Analysis Pathways to Executive Leadership will span 7 months beginning October 18 – 21, 2016 at the ACEC Fall Conference in Colorado Springs, and ending April 22 – 25, 2017 at the ACEC Annual Convention in Washington, DC. To register for this program or get more information about schedule, go to www.acec.org/calendar/calendar-seminar/ consulting-by-design-pathways-to-executive-leadership. August 2016

Courtesy of Keith Knapp.

Follow ACEC Coalitions on Twitter – @ACECCoalitions.

You will not want to miss these additional important risk management sessions: Limiting Liability Risks on New Residential Development Mike Unger, WSP|Parsons Brinckerhoff and a Panel of Experts Public-Private Partnerships and Design-Build: Opportunities/ Risks for Consulting Engineers David Hatem & Patricia Gary, Donovan Hatem LLP Professional Liability Case Study Marathon Karen Erger, Lockton Companies, Eric Singer, Ice Miller, LLP Limitation of Liability for Small Firms Jeff Connelly & Charlie Geer, Greyling Insurance Brokerage The Conference also features: • General Session addresses by Colorado Governor John W. Hickenlooper; Stuart Rothenberg on the 2016 Election; Rich Karlgaard, Forbes Publisher • CEO roundtables; • Exclusive CFO, CIO, Architect tracks; • Numerous ACEC coalition, council, and forum events; and • Earn up to 21 PDHs

Member Firm CEOs Forecast Future of Engineering at ACEC Fall Conference Stantec President/CEO Bob Gomes, Arcadis North America CEO John Jastrem, and Louis Berger Chairman Nick Masucci will discuss The M&A Shake-Up in the A/E industry at the 2016 ACEC Fall Conference in Colorado Springs, CO, October 19 – 22. The panelists, all of whom have been active in the M&A market, will discuss principal motivators behind the surge in M&A activity; major challenges and financial complexities; key integration issues after closing; and lessons learned. For more information and to register, go to www.acec.org/conferences/fall-conference-2016.

WANTED

Engineers to Lead, Direct, and Get Involved with CASE Committees! If you are looking for ways to expand and strengthen your business skillset, look no further than serving on one (or more!) CASE Committees. Join us to sharpen your leadership skills – promote your talent and expertise – to help guide CASE programs, services, and publications. We have a committee ready for your service: • Risk Management Toolkit Committee: Develops and maintains documents such as business practices manuals and policies for engineers under CASE’s Ten Foundations for Risk Management. Please submit the following information to htalbert@acec.org • Letter of interest • Brief bio (no more than 2 paragraphs) STRUCTURE magazine

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

August 2016

CASE is a part of the American Council of Engineering Companies

ACEC is holding its Fall Conference at The Broadmoor, Colorado Springs, CO, October 19 – 22. CASE will be holding convocation on Thursday, October 20. Sessions include: 10:45 am Contractual Risk: Mastering Indemnity, Insurance, and the Standard of Care Speakers: Ryan Kohler, Collins, Collins, Muir + Stewart 2:00 pm Developing a Risk Management Plan for Your Firm Diane Mika, Berkeley Design Professional Underwriters 3:45 pm Balancing Project Risk and Reward: Lessons Learned from Current Professional Liability Claims Robert Hughes, Ames & Gough; Sam Muir, Collins, Collins, Muir + Stewart 5:00 pm ACEC / Coalition Meet and Greet

CASE in Point

ACEC Fall Conference Features CASE Risk Management Convocation and More!

STRUcTURAl FORUm

opinions on topics of current importance to structural engineers

A Personal Call to Regain Seismic Design Code Simplicity By David W. Anderson, P.E., SECB

he March 2016 edition of STRUCTURE magazine just happened to contain a pair of articles which, when considered together, seem to indicate that our structural engineering profession is facing a sort of dichotomy in our seismic design methodologies. In this column, I examine certain statements from those two articles and relate them to my experience as a structural engineer. I also reflect on how our seismic design methodologies have become exponentially more complex over the years. From that realization, I entreat structural engineers nationwide to acknowledge that there is a real need for a much-simplified method of designing the vast majority of our seismic force resisting systems. In his article, Seismic Design Value Maps, Ronald O. Hamburger states that “… the [seismic design values] maps portray precision in the design values that is inappropriate, given the substantial uncertainty in the values portrayed.” He then goes on to say that the USGS/BSSC Project 17 group will address this issue (among others) by providing “… mapped value stability”, and addressing the “… portrayal of inappropriate levels of precision.” I want to speak to those Project 17 goals, and relate them to the companion article in that very same STRUCTURE magazine issue, Alternative Diaphragm Seismic Design Force Level of ASCE 7-16, by S. K. Ghosh. As an every day practicing structural engineer, I have watched, as have many, as the seismic design procedures for buildings and structures have grown ever more complex (and to my purposes, ever more confusing). As the implied precision of the seismic design maps attests, all of this growing design complexity appears to be based on a house-of-cards foundation constructed from the idea that ever-increasing precision of calculations and modeling equals better built, and safer structures. I, for one, applaud the efforts of the Project 17 group to try and add some simplicity back into the mix, and maybe begin reversing the complicating trend of the past 25 years. To gain some perspective on the subject of simplicity, the ASCE 7-10 seismic

provisions now run to something like 180 pages. I do acknowledge that these provisions cover a multitude of specific design subjects. Compare that, however, with the ASCE 7-88 (only 28 years ago!). The earthquake design section then was only 9 pages long! Moreover, it, too, covered multiple subjects. Following immediately after Mr. Hamburger’s article, Dr. Ghosh’s article on diaphragm design forces indicates that an additional, alternative procedure for calculating these forces will be included in Section 12.10 of the soon to be released edition of ASCE 7-16. In that section, the calculation of seismic forces will once again be taken to a more complex, and precise, level of scrutiny. For designs of extraordinary, complex, or critical structures located in high-seismic areas, this type of additional complexity might well be justified. Though, for the remainder of the structures located in the rest of the US, that level of precision seems to me like overkill. The author himself appears to imply as much with his statement “… [the] empirical approach has been generally satisfactory”. Given the overall, decent, historical seismic performance of the majority of the structures located in much of the U.S., I believe that it is now time to simplify life a bit (at least, the life of the ordinary structural design engineer). I think that the time has come for a much-simplified, complete seismic design methodology to be included in the ASCE 7 Code, based on aspects of empirical designs of yore which still serve us well – though informed by a more modern, applicable, physical understanding.

This alternative, simplified methodology would apply to much of the country, and be usable within its stated restrictive assumptions, in a similar fashion to the simplified wind provisions which were introduced into recent ASCE 7 editions. Maybe a target of 8 to 10 total code pages might be a good goal? I have become increasingly aware, as have many of my colleagues with whom I have discussed this subject, that our design codes have been trending toward a much more academically-driven level of precision and complexity that doesn’t necessarily help the majority of us to design buildings that are intrinsically any safer. The outcome of good research and good academe should be to take complex phenomena and make them simple, and understandable – and in our case, more usable. As R. Buckminster Fuller once said, “… if the solution is not beautiful, I know it is wrong.” Beautiful answers are quite often the simplest. In the case of seismic design codes, I believe the simplest answers are, reflectively, the beautiful ones – and the most useful. As Tenet 1 of the ASCE Code of Ethics proclaims, let’s continue to “…hold paramount the safety, health and welfare of the public…” by simplifying life where we can, and especially where it counts: for us engineers, and by extension, for our clients and their wallets.▪ Dave Anderson (davida@integdes.net) is the company principal engineer for Integrity Design Services, Inc., in Trinity, Alabama. He is a member of ASCE/SEI, SECB, and SEAoAL.

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

August 2016

STRUCTURE magazine | August 2016

Articles inside

STRUCTURAL FORUM

SPOTLIGHT

STRUCTURAL DESIGN

STRUCTURAL FAILURES

STRUCTURAL ANALYSIS

ENGINEER’S NOTEBOOK

PRACTICAL SOLUTIONS