STRUCTURE magazine | August 2017 by structuremag

A Joint Publication of NCSEA | CASE | SEI

STRUCTURE

August 2017 Steel/Cold-Formed Steel Inside: John Hancock Building, Chicago

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CONTENTS Columns and Departments EDITORIAL

7 NCSEA Summit 2017 – D.C. Is the Place to Be! By Thomas A. Grogan, P.E., S.E. BUILDING BLOCKS

8 Issues Every Structural Engineer Should Consider When Using Foreign Steel

INSIGHTS

52 Structural Observation By Greg Robinson, S.E., P.E., SECB and Greg Schindler, P.E., S.E. STRUCTURAL LICENSURE

54 Second Order Effects and Structural Licensure By Timothy M. Gilbert, P.E., S.E. SECB

By Richard M. Drake, S.E., Thomas A. Hunt, S.E., and Jennifer A. Memmott, P.E. ENGINEER’S NOTEBOOK

13 Welding Cold-Formed Steel By Roger LaBoube, Ph.D., P.E. STRUCTURAL ANALYSIS

16 Lateral Analysis – Part 2 By Samuel M. Rubenzer, P.E., S.E. PROFESSIONAL ISSUES

21 The Ethics of Procurement By Marc S. Barter, P.E., S.E., SECB STRUCTURAL DESIGN

24 ¼ in 12 Design Slope and Water Drainage – Part 1 By Scott D. Coffman, P.E., SECB

LEGAL PERSPECTIVES

56 A Further Look at Consent to Assignment Agreements By Gail S. Kelley, P.E., Esq. CASE BUSINESS PRACTICES

59 Would You Accept This Indemnification Clause?

61 2017 ASCE Structural and SEI Awards

By Larry Kahaner How is the software industry keeping up with demands from their structural engineering customers for specialty add-ons, increased efficiency, updated code inclusions, information exchange, and more?

STRUCTURAL FORUM

66 When Good Engineering Ideas Go Wrong

41 LONDON FINANCIAL DISTRICT’S FIRST VERTICAL VILLAGE

By Jeremy Herauf

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

By Angie Sommer, S.E. and Nick Sherrow-Groves, P.E.

IN EVERY ISSUE 6 Advertiser Index 14 Noteworthy 57 Resource Guide – Software 62 NCSEA News 64 SEI Structural Columns

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

By John Peronto, S.E., P.E., SECB and Christian DeFazio, P.E. What connects the idea for a one-of-a-kind thrill in Chicago’s Hancock Tower with structural engineers? The ability to make it a reality, of course. Read how engineers were instrumental in creating a fixed-tilt curtain wall that gives visitors a most unusual view of Chicago.

29 SOFTWARE CONTINUES TO EVOLVE

SPOTLIGHT

48 Ross Island Bridge

50 Compensation, Overtime, and the Gender Pay Gap

36 HANCOCK’S TILT

Features

By Ed Schwieter, P.E., S.E.

HISTORIC STRUCTURE

PROFESSIONAL ISSUES

Cover Feature

By Katherine Flesh For this multi-billion-dollar project, structural engineers developed unique solutions for recycling an existing foundation, adjusting column positions to accommodate load transfers in the superstructure, and using innovative technology to enhance the design process.

44 FRP BRIDGE REPAIR

By Greg Schindler, S.E. and Sara Roberts, S.E. For the pedestrian bridge that provides access to a popular beach area on Puget Sound, structural engineers solved unique corrosion problems and construction issues with FRP materials.

August 2017

ADVERTISER INDEX

PLEASE SUPPORT THESE ADVERTISERS

Bentley Systems, Incorporated ............... 12 Bluebeam Software .................................. 4 Canadian Wood Council ....................... 40 Clark Dietrich Building Systems ..... 26, 27 Decon USA Inc ..................................... 39 Design Data .......................................... 23 Dlubal Software, Inc. ............................ 30 Fibergrate Composite Structures............ 47 Hardy Frame ......................................... 15 Independence Tube Corporation ............. 2 Integrated Engineering Software, Inc..... 46 Integrity Software, Inc. ............................ 6 KPFF .................................................... 67 LNA Solutions ...................................... 51

NCSEA ........................................... 34, 35 New Millenium Building Systems ......... 49 Nucor Vulcraft Group ........................... 20 RISA Technologies ................................ 68 SCIA Inc. .............................................. 28 Simpson Strong-Tie............................... 31 Steel Joist Institute................................. 11 Strongwell ............................................. 19 StructurePoint ....................................... 32 Trimble ................................................... 3 USG Corporation ................................. 43 Veit Christoph GmbH .......................... 33 Weyerhaeuser ........................................ 55 Wood Products Council ........................ 60

Erratum The Education Issues article (Okoye et al) in the July 2017 issue of STRUCTURE magazine was based, with permission, on an extended article written for the World Conference of Timber Engineering (2016). The original article is credited as follows: Barnes, C.; Kam-Biron, M.; Okoye, U.; Perkins, B.: Timber engineering education for structural engineers, CD-ROM; Proceedings of the World Conference on Timber Engineering (WCTE 2016), August 22-25, 2016, Vienna, Austria, Eds.: J Eberhardsteiner, W. Winter, A. Fadai, M. Pöll, Publisher: Vienna University of Technology, Austria, ISBN: 978-3-903039-00-1.

STRUCTURE

MARKETING & ADVERTISING SALES sales@STRUCTUREmag.org Joe Murphy jmurphy@STRUCTUREmag.org; Tel: 203-254-9595 Denis O’Malley domalley@STRUCTUREmag.org; Tel: 203-356-9694, ext. 13

EDITORIAL STAFF Executive Editor Alfred Spada aspada@ncsea.com Editor Christine M. Sloat, P.E. publisher@STRUCTUREmag.org Associate Editor Nikki Alger publisher@STRUCTUREmag.org Creative Director Tara Smith graphics@STRUCTUREmag.org

EDITORIAL BOARD Chair Barry K. Arnold, P.E., S.E., SECB ARW Engineers, Ogden, UT chair@structuremag.org Jeremy L. Achter, S.E., LEED AP ARW Engineers, Ogden, UT Erin Conaway, P.E. SidePlate Systems, Phoenix, AZ

Your Opinion Makes a Difference!

On the first of every month, a link to the Editorial Board’s current Issue Survey is posted on the homepage of STRUCTUREmag.org. This survey provides valuable information to the Board on what types of articles readers prefer. Please take 5 minutes to send us your anonymous feedback on the current issue of STRUCTURE!

John A. Dal Pino, S.E. FTF Engineering, Inc., San Francisco, CA Linda M. Kaplan, P.E. TRC, Pittsburgh, PA

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

Dilip Khatri, Ph.D., S.E. Khatri International Inc., Pasadena, CA

Important news for Bentley Users

Jessica Mandrick, P.E., S.E., LEED AP Gilsanz Murray Steficek, LLP, New York, NY Brian W. Miller Davis, CA Emily B. Lorenz, P.E. Chicago, IL Evans Mountzouris, P.E. The DiSalvo Engineering Group, Ridgefield, CT

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STRUCTURE magazine

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August 2017

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 2017, Volume 24, 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 nonmember 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.

Editorial

NCSEA Summit 2017 – D.C. Is the Place to Be! new trends, new techniques and current industry issues By Thomas A. Grogan, Jr., P.E., S.E., F.ASCE, NCSEA President

have exciting news to share with all of you. During the second week of October, from the 11th through the 14th, the structural engineering community will descend upon Washington, D.C., for the 25th annual NCSEA Structural Engineering Summit. This promises to be our best Summit yet, and I hope that you will make time in your busy schedule to join us. Attendees will include the best and brightest our profession has to offer, including our Member Organization Delegates and some of their officers, the NCSEA Board of Directors and staff, an excellent group of presenters, and many of our young members. This is your opportunity to meet and mingle with all of them.

Kevin Moore, Charles Kircher, Steve Kerr, Joseph Kane, John Harris, and Ben Nelson. There will also be several opportunities to meet with vendors on the trade show floor and learn about the many products they offer for our industry. Already this year, we have more than 50 exhibitors, making this our largest trade show ever. Whether it is your first or 25th time, or something in between, there is much to be learned. The evening will conclude with another fantastic CSi event, hosted by Ashraf Habibullah at the National Building Museum. This is one of the most impressive public spaces in our nation’s capital, and the evening will include a great variety of food and drink. This has been one of the Summit’s highlights in recent years, so you will not want to miss it. Friday, October 13, will be another great day at the Summit. It begins with a Delegate Collaboration Session, again hosted by the Communications Committee. After that, there will be two tracks for the remainder of the day. One will be technical in nature and focus on a variety of structural engineering subjects. The other will cover the softer side of our profession, with topics such as networking, engagement, equity, client development, contract negotiations, and accounting/financial systems. Speakers include Jose Busquets, Nick Sherrow-Groves, Angie Sommer, Lori Koch, Cliff Jones, Sarah Appleton, and John Tawresey. Both tracks promise to deliver the best in professional development and leave all attendees better prepared to provide outstanding structural engineering services to their clients. Friday night is the annual banquet to recognize the winners of the Excellence in Structural Engineering Awards, so dress up in style and show D.C. that structural engineers know how to party. On Saturday morning, NCSEA holds its Annual Business Meeting. In the past, this was predominantly intended for the Member Organization Delegates, but this year we are inviting all attendees to participate, especially Member Organization board members. This will give you a bird’s eye view of what is happening within the other Member Organizations, the NCSEA committees, and the NCSEA Board of Directors and staff. In addition to all of the great education sessions, you will leave fully understanding the value that NCSEA and your Member Organizations bring to each of you. When I assumed the office of President last September in Orlando, I mentioned that I would like for us to begin the “drive for five.” I was referring to 500 attendees at the Summit. I sincerely hope that you will consider not only coming yourself but also bringing a friend to help us reach our goal. I look forward to meeting with each of you during our time together in October. For more information on the Structural Engineering Summit, see pages 34 and 35. Or, visit www.ncsea.com/meetings/annualconference for even more information and to register.▪

On Wednesday, October 11, we will have committee meetings all day long. Whether or not you are currently a committee member, please take the time to attend one or several of these meetings to find out how NCSEA committees operate to make our profession better. You might even consider joining one. There will be two private receptions later that day: the Young Member Group Support Committee will host one for all of the young engineers in attendance, and yours truly will host one for the Delegates. In the evening, there will be a formal welcome reception for all attendees. On Thursday, October 12, the day begins with a Delegate Interaction Breakfast hosted by our newly formed Communications Committee. That will be followed by the keynote address presented by Martina Driscoll and Terence Paret from Wiss, Janney, Elstner Associates, Inc. They will be discussing the 2011 seismic event that occurred in Mineral, Virginia, and its effect on the D.C. area. They will specifically address the impacts on the National Cathedral and the Washington Monument. This will provide you with a chance to see seismic solutions, East Coast style. Next will be a panel discussion on how to improve ASCE/SEI 7, Minimum Design Loads and Associated Criteria for Buildings and Other Structures. The discussion will provide you with insight into how the standard is developed and the process for making revisions. Your panelists will be Ron Hamburger, John Hooper, and Don Scott, some of the best minds in our industry. At the conclusion, there will be breakout meetings affording you the opportunity to provide feedback directly to the engineers working on the code. After lunch, we will break into three tracks, one of which has been specifically designed for young engineers. Seismic/wind will be the primary focus of most of the afternoon sessions. Speakers include S. K. Ghosh, STRUCTURE magazine

Thomas A. Grogan, Jr. is Chief Structural Engineer and Director of Quality at The Haskell Company in Jacksonville, FL. He is also the current NCSEA President, member of the NCSEA Licensure Committee and past president of FSEA. Please feel free to reach him via email at thomas.grogan@haskell.com.

August 2017

Building Blocks updates and information on structural materials

he option to use structural steel supplied and fabricated in foreign countries for projects constructed in the United States is a realistic one for many projects in today’s market. Typically, the most obvious factor that is considered by the project team is the economic impact of doing so. However, in addition to economics, project teams must also consider factors that may have a significant impact on the project outcome, including project-specific issues, design requirements, material substitutions, procurement, fabrication, and construction concerns.

Project-Specific Issues When considering foreign-fabricated and foreign material-based steel, the first discussion needs to be with the Client. Some Clients already have experience with foreign products and, as a result, have already developed company policies. Clients

For Structural Steel Buildings (ANSI/AISC 341) and possibly Prequalified Connections For Special And Intermediate Steel Moment Frames For Seismic Applications (ANSI/AISC 358). These American Institute of Steel Construction (AISC) documents include design equations that are based on laboratory testing of standard shapes rolled in accordance with American Society of Testing and Materials International (ASTM) material specifications. Each of these AISC documents requires that steel materials, shapes, bolts, and weld consumables be in conformance with specific listings of ASTM specifications. Although other material specifications may be used, the burden of proof that the alternate materials are equivalent must be determined by the structural Engineer-Of-Record (EOR). Legal approval of alternate materials rests with the local authority having jurisdiction and its building official (See IBC Section 104). Contractually, these materials may also have to be approved by the Client. AISC Shapes

Issues Every Structural Engineer Should Consider When Using Foreign Steel By Richard M. Drake, S.E., Thomas A. Hunt, S.E., and Jennifer A. Memmott, P.E.

Richard M. Drake is a Senior Fellow, Structural Engineering, Fluor Southern California Offices, Aliso Viejo, CA. He can be reached at rick.drake@fluor.com. Thomas A. Hunt is a Technical Director, Structural Engineering, Fluor Southern California Offices, Aliso Viejo, CA. He can be reached at tom.hunt@fluor.com. Jennifer A. Memmott is a Design Engineer, Structural Engineering, Fluor Southern California Offices, Aliso Viejo, CA.

may already have internal procedures and QC/ QA requirements regarding items introduced by sourcing foreign products, such as the procurement of mechanical equipment, vessels, electrical components, and more. In other cases, this may be the Client’s first experience with using foreign-fabricated steel or materials, and detailed discussions, meetings, and presentations may be required. An open dialogue with the Client can help avoid unforeseen roadblocks. For example, depending on the financial arrangements of the project, there could be a “Buy America” clause that prevents the use of foreign-fabricated steel. Jurisdictions Local jurisdictions may not accept foreign grade material and foreign-fabricated steel. Also, if the project is within a Union jurisdiction, some Unions may be reluctant or refuse to erect foreign supplied or foreign-fabricated steel.

Design Requirements United States building codes or Client criteria typically require that the design, fabrication, and erection of structural steel for buildings and structures shall be in accordance with the Specification For Structural Steel Buildings (ANSI/AISC 360). In higher seismic regions, the design and seismic detailing of structural steel for buildings and structures shall be in accordance with the additional requirements of the Seismic Provisions

August 2017

Section 1 of the AISC Steel Construction Manual includes a catalog of dimensions and properties for structural steel shapes. Some foreign suppliers may have a limited number of available shapes. This limitation would also need to be discussed with the Client as alternate shapes available from foreign suppliers may not match the shapes listed as AISC shapes in the Steel Construction Manual. This may be a concern for Clients particularly for future retrofit designs. However, some foreign fabricators do not have problems with obtaining ASTM material and AISC shapes. AISC shapes made in accordance with ASTM materials are now manufactured in many countries throughout the world. This topic should be discussed with each of the proposed foreign bidders. Connection Design Connection design must be considered. In certain areas of the country, connection design is delegated to the structural steel fabricator. If a foreign fabricator does not have access to a U.S. licensed engineer who is familiar with that particular state’s codes, especially in high seismic areas, this may force the EOR to design all of the connections. Another issue that is part of the steel calculations in moderate to high seismic areas, and related to the steel material properties, is the requirement in AISC 341 to use R y and R t when needed to calculate the expected yield stress or expected tensile strength of a member or connection. These values were developed based on an AISC funded study of U.S. domestic supplied mill certificates with detailed analysis to determine the coefficient of variation. The authors are unaware of any similar studies of foreign-based

steel materials and are also unaware of any currently accepted procedures for determining R y and R t of foreign-based materials. Software Commercial CAD and engineering analysis programs typically include databases that contain a limited number of country specific shapes and materials. If a particular set of shapes and materials available from a foreign fabricator are not included in one of the currently available databases, then these would need to be created. Development of a database is time-consuming unless it is available in an electronic format that is compatible with the software platform used for the project.

Material Substitutions The substitution of alternate materials has always been addressed in the U.S. codes. However, to substitute a material may be complicated and the procedure would need to start with the acceptance from the EOR for the specific project. AISC 360, AISC 341, and AISC 358 identify approved materials. The EOR is responsible for accepting alternate materials as adequate substitutes. AISC design requirements are validated by physical testing of standard ASTM materials. Alternate materials may not reflect the ductility, fatigue, and fracture resistance that are indirectly accounted for by the physical testing. Chemical composition limits and Charpy V-Notch test results provide some assurance that the alternate materials will perform as expected. The AISC 360 Commentary outlines an extensive “punch list” of considerations and responsibilities for the EOR if alternate materials are supplied. Note that AISC does not provide acceptance criteria for these items.

AISC design documents also require that welding procedures and welder qualifications shall be in accordance with specific American Welding Society (AWS) specifications. AWS provides several prequalified welding procedures that are based on a list of required items and material properties that a foreign-based material may not meet. Most of the materials are based on ASTM specifications. This may require that structural steel welding procedures be qualified by testing, which can be very time-consuming and expensive. ASTM A Client may not accept foreign steel that doesn’t meet ASTM standards. Alternate material suppliers would have to submit actual testing of all supplied materials. Many foreign material suppliers do not perform all of the equivalent ASTM tests. In addition to the testing documents provided for possible approval, ASTM specifications also require continuous testing of the material and provide very detailed requirements on how often this should occur; i.e., this is not a one-time submittal. For instance, the authors are unaware of any foreign material specification that is equivalent in all respects to ASTM A992. It is not often understood that ASTM materials and AISC shapes are manufactured around the world by many steel producers. With the advent of adjustable rollers, nearly any shape can be made; it is more a matter of quantity required and the local supply and demand conditions. It should therefore not be assumed that only local material and shapes are available to the fabricator. Most structural engineers focus on the strength of the steel materials, yield stress, minimum tensile strength, and modulus of elasticity. In higher seismic regions, structural engineers have the additional concerns of maximum tensile strength, yield stress to tensile strength ratio, and minimum elongation. In cold weather and high seismic regions, structural engineers are concerned with fracture resistance which is intimately related to the chemical composition of the steel materials. Welding engineers are primarily concerned with chemical composition and especially the deliberately added alloys in the material. Some elements added for strength may contribute to “hot cracking” while others may contribute to “cold

STRUCTURE magazine

August 2017

cracking.” If steels contain higher-than-desirable levels of sulfur, phosphorus, lead, or copper, these elements tend to segregate into the center of the solidifying weld bead which may lead to weld cracking. High strength bolts are normally purchased by the fabricator through a third party supplier and shipped directly from the supplier to the job site. Bolts need to go through the same material approval process as structural members. There have been historical problems with counterfeit and out-of-specification fasteners. Because of this issue, some Clients ban the use of foreign manufactured bolts and bolt components.

Procurement All project costs should be captured when evaluating competitive bids. Foreign fabricated steel can attract additional costs and possibly longer schedules than those from local suppliers. Shipping Cost Since a foreign fabricator could be located half way around the world, it is critically important that the bid evaluation includes the cost of shipping. A local U.S. fabricator near the job site may have higher unit rates, but when shipping costs are added, they may become the low bidder. Tariffs In addition to the shipping costs, a study needs to be conducted to see if there are any duties and tariffs on the foreign fabricator’s imported steel. In some cases, there are no duties and tariffs if the project location is in a duty-free zone. If not, the duties and tariffs can be as high as 30 percent. These costs, if any, also need to be added to the pricing summary. Bid Exceptions To make sure that all costs are accounted for, each bid needs to be thoroughly reviewed for exceptions or what might be part of the bidder’s standards. Some foreign bidder’s standards differ from traditional U.S. bidders. For example, some foreign bidder quote fabrication drawings only in metric units, completely exclude the supply of bolts, nuts, and washers, and quote only ASTM A36 plate while the bid documents require ASTM A572 Grade 50 plate. Foreign bidders may also exclude all hollow sections (i.e. HSS and pipe), exclude complete joint penetration (CJP) welds, exclude nondestructive examination (NDE) testing, or exclude the pre-installation of stair treads in the stair stringers. It may be necessary to go back to the bidders to clarify or reject these types of exceptions or fabricator standards.

Timing of Fabricator Selection Structural steel calculations are intimately related to the materials and shapes used. Selection of materials and shapes should be made before calculations are begun. If alternate materials and shapes are approved as part of the structural steel procurement process, after the structural calculations have begun, rework may affect both project cost and schedule. Purchase Order/Contract Issues Many items assumed in a standard bid document may not be specifically noted in the contract documents. For example, projects in the U.S. are typically in English and imperial units and, thus, the fabrication drawings are assumed to be in English and Imperial units. This may not be the case if a foreign fabricator’s software defaults to metric units. All the bid documents from foreign fabricators need to be reviewed in detail to identify items that are unacceptable to the project team which may seem standard to the fabricator. Typically, in the U.S., once the steel purchase order is signed, all pricing and contractual agreements are fixed. However, in certain countries, they consider the signing of the purchase order as the beginning of the negotiation for further changes. It must be emphasized to the successful foreign bidder that once they sign the contract, no changes are permitted unless something very significant occurs and is agreed to by the EOR.

Fabrication Shop fabrication drawings are typically reviewed by the EOR. For projects in the U.S., it must be clearly stated in the bid documents that shop drawings are to be in English, use Imperial units, follow AISC detailing practices, and that weld symbols be shown in accordance with AWS A2.4. Shop Certification Clients or project specifications may not accept uncertified fabrication shops. If AISC shop certification is required, then each proposed fabricator should be verified through AISC’s website of qualified shops. It should be noted that many foreign fabricators currently have AISC certification. Note that any steel outsourced by the fabrication shop shall also be AISC certified if required. Welding Procedures AISC design documents require that welding procedures and welder qualifications shall be in accordance with specific AWS specifications, which define prequalified weld procedures

using steel base metal and weld metal materials that are in conformance with specific ASTM material specifications. Weld procedures using alternate materials may have to be qualified by testing, also defined in AWS specifications. It is imperative that all Welding Procedure Specifications (WPS) include a copy of the proposed electrode manufacturer’s data sheet, as it is likely that the WPS reviewer may not be familiar with this locally manufactured product. Welder Qualifications The Client or EOR may require that all welders be AWS qualified. This would need to be verified for all proposed foreign steel fabricators or a procedure developed for accepting foreign welders. Third Party Material Testing Until the EOR has worked with and has confidence with foreign steel fabricators, specifically in their procurement of materials, it is strongly recommended that all foreign supplied steel materials be continuously tested by an independent third party testing agency. Some Clients already have third party testing agencies that they have worked with and can make recommendations. Specific tests for mechanical and chemical testing need to be established, as well as their frequency. Shop Inspection The International Building Code (IBC) requires steel fabrication shops to have a Special Inspector or be acceptable by the local jurisdiction after reviewing the shop’s QA/QC document submittals. Most jurisdictions in the U.S. accept AISC shop certification as meeting this requirement. However, if a foreign fabricator does not have an AISC certification, project schedules can be impacted while they obtain it.

Construction Concerns Due to possible shipping size limitations (i.e. overseas container boxes and skids), the maximum size of members may be restricted. This could result in more column and beam splices. Schedules Fabrication and delivery times to the job site need to be discussed. Many foreign fabricators quote longer delivery times than domestic

STRUCTURE magazine

August 2017

fabricators. The extra time required for shipping, unpacking, and segregating mixed loads needs to be accounted for in the project schedule. Part of the reason for the extended fabrication schedules from the foreign fabricators is that it is common practice for them to buy the majority of their steel directly from the steel mills; whereas, in the U.S., the majority of the steel is available from local steel service centers. If the project cannot accept the extended schedule of the foreign fabricator, then discussions may be necessary for the procurement of steel by means other than from the mill. This will likely increase the steel unit rate costs which will need to be considered by the project team. Field Changes Steel members can be fabricated incorrectly or damaged in shipping. Most U.S. fabricators will immediately resupply the affected members and express ship the new pieces to the job site with little impact to the construction schedule. With a foreign fabricator, resupply will take more time and could impact the construction schedule. Field rework, although not as efficient, may need to be considered in order to have less impact on the schedule.

Conclusion Although there may be economic reasons to purchase structural steel from foreign sources, it may not satisfy the total needs of the project. This article identifies several factors that the project team needs to consider in order to properly assess the impact of the foreign purchase on the total installed cost of the project and when the project may be put in service by the Client.▪

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n cold-formed steel construction, welding is a viable connection method. Prefabrication of trusses, panelization of walls, and hardware components are all ideal applications where welding may be the preferred joining method. Although arc welding or resistance welding may be used to connect thin sheet steel, in building construction the arc welding process is most common. Arc welding is the process of fusing material together by an electric arc, usually with the addition of weld filler metal. Resistance welds are commonly used for connecting thin sheet steels in the automotive or appliance industries. The most common weld types to connect framing members are the fillet weld and the flare groove weld. Arc spot welds, also called puddle welds, are used extensively to attach deck and panels to bar joists or hot-rolled shapes. Groove welds in butt joints are commonly used during the roll-forming process to connect flat sheet of one coil to the next coil. The design of welded connections for coldformed steel construction is governed by the North American Specification for the Design of Cold-Formed Steel Structural Members, AISI S100, and the Structural Welding Code – Sheet Steel, AWS D1.3. AISI S100 and AWS D1.3 documents contain requirements for groove welds, arc spot welds (puddle welds), arc seam welds, fillet welds, flare groove welds, and plug welds. The AWS D1.3 welding code provides requirements for prequalification of WPS (Welding Procedure Specifications), qualification and preparation of WPS, fabrication of a welded connection, and inspection of a weld.

Welding Processes AWS D1.3 defines welding electrodes that appropriately match the strength of the approved base metals. The Welding Code lists the following as approved welding processes: shielded metal arc welding (SMAW), gas metal arc welding (GMAW), flux-cored arc welding (FCAW), gas tungsten arc welding (GTAW), and submerged arc welding (SAW).

objectionable fumes. When welding galvanized sheet, suitable ventilation must be provided. Also, welding of sheet steels shall not be done when the ambient temperature is lower than 0° F, when the surfaces are wet, or when the welder is exposed to inclement weather. The parts to be joined shall be brought into close contact to facilitate complete fusion. The closeness of the two parts cannot be over-emphasized, especially for arc spot welds. If any gap exists between the members prior to spot welding, the strength of the weld may be substantially reduced. Also, to obtain consistently sound welds, the welding current must be controlled.

aids for the structural engineer’s toolbox

Qualification Prequalified Welding Procedure Specifications (WPS), which are exempt from WPS qualification tests, can be established based on the applicable welding code provisions in AWS D1.3. A WPS is a written set of instructions that defines the joint details, welding electrodes, base metals, electrical parameters, and other procedural variables. Any time welding is performed in accordance to AWS D1.3, a written WPS must be used, even for a prequalified WPS. When the welding parameters do not conform to the prequalified status, the welding procedure must be qualified by testing. This happens, for instance, when a base metal other than those given on the approved list is used, or when the joint detail does not match one of the prequalified details. A Procedure Qualification Record (PQR) is used to record the actual values of the welding procedure test. After the welded specimens pass the destructive tests, a qualified Welding Procedure Specification can be written. Welding Procedure Specifications are the responsibility of the manufacturer or the contractor. The required tests, test methods, and required results are prescribed by AWS D1.3. Once a contractor has

Welding Cold-Formed Steel

Fabrication AWS D1.3 stipulates that the surfaces to be welded shall be smooth, uniform, and free of imperfections. Also, surfaces to be welded and surfaces adjacent to a weld shall be free of loose scale, slag, rust, moisture, grease, or other foreign material that would prevent proper welding or produce

EnginEEr’s notEbook

Typical arc spot weld deck to structural connection. Courtesy of Steel Deck Institute.

STRUCTURE magazine

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

Roger LaBoube is Curator’s Distinguished Teaching Professor Emeritus of Civil, Architectural and Environmental Engineering and Director of the Wei-Wen Yu Center for Cold-Formed Steel Structures at the Missouri University of Science and Technology. Roger is active on the American Iron and Steel Institute’s Committee on Specifications and chairs the AISI Committee on Framing Standards. He also served on STRUCTURE’s Editorial Board. Roger can be reached at laboube@mst.edu.

size, and length of a weld, in addition to the bead shape, reinforcement, and undercut. Inspectors are also responsible for confirming that a qualified or prequalified WPS and a qualified welder are used in performing the work.

Design Considerations AISI S100 design provisions apply where the thickness of the thinnest connected part is 3⁄16-inch or less. If the material thickness is greater than 3⁄16-inch, AISC 360, Specification for Structural Steel Buildings, is to be used for weld connection design. The paramount difference between the strength of a welded connection in coldformed steel construction and a welded connection in hot-rolled steel construction is the dominance of sheet tearing as a possible failure mode. Although the design provisions in AISI S100 Chapter E2 provide

Typical fillet welded connections. Courtesy of Don Allen at Super Stud Building Products.

qualified a welding procedure, the procedure can be considered qualified for its use indefinitely.

Inspection AWS D1.3 requires only visual inspection of welded sheet steel joints. The visual inspection shall determine compliance with contract documents. Particular emphasis shall be placed on verifying proper location,

Noteworthy

guidance on the determination of the weld strength, the connection design is often limited by the tearing of the base steel.

Safe Practices Annex F of AWS D1.3 summarizes safe practices for welding. Arc welding is a safe occupation when sufficient measures are taken to protect the welder from potential hazards. When these measures are overlooked or ignored, welders can encounter such dangers as electric shock, over-exposure to radiation, fumes and gases, and fire and explosion; any of these may result in injuries. Everyone associated with the welding operation should be aware of the potential hazards and ensure that safe practices are employed. Infractions should be reported to the appropriate responsible authority. For specific safety precautions refer to ANSI Z49.1, Safety in Welding, Cutting, and Allied Processes. For additional information about the background and application of the AISI S100 equations, refer to Cold-Formed Steel Engineers Institute TN F140-16, www.cfsei.org, and Cold-Formed Steel Design by Yu and LaBoube.▪

news and information

Mike Mota Retires from STRUCTURE’s Editorial Board Mike Mota, Ph.D., P.E., F.ASCE, F.ACI, F.SEI, is stepping down as a member of the STRUCTURE magazine Editorial Board. Mike joined the Board for his second tenure in May of 2015 as a concrete industry representative. Mike is the Vice President of Engineering for the Concrete Reinforcing Steel Institute (CRSI), responsible for the Engineering Department and the development of all technical publications and standards. Mike is an active member of several ACI and ASCE committees, including ACI 318 and 318 sub B and sub R. He is past Chair of ACI Committee 314 and past member of the Board of Directors of the Concrete Industry Board of New York City/ NYC ACI Chapter since 2001. Barry Arnold, P.E., S.E., SECB, Chair of the STRUCTURE magazine Editorial Board, had this to say about Mike’s departure: “Mike has served faithfully on the Editorial Board for many years, working tirelessly on concrete-themed technical and project articles. Mike’s commitment to providing quality articles for STRUCTURE magazine is greatly appreciated. His dedication and commitment to the magazine and the profession are commendable, and he will be missed.” Regarding his tenure on the Board, Mike commented, “I would like to thank the Editorial Board of STRUCTURE and CRSI for the opportunity to represent the concrete industry since 2008. I would also like to thank the readership for making this possible by their outstanding support of STRUCTURE magazine.” STRUCTURE magazine

Emily B. Lorenz, P.E., LEED AP BD+C, will replace Mike Mota as a concrete industry representative. Emily is director of sustainability and publications for the Precast/Prestressed Concrete Institute in Chicago. In this role, Emily oversees the development of all technical manuals and standards for PCI, serves as Associate Editor of ASPIRE magazine, and is Editor-in-Chief of the PCI Journal. She also is active in many technical associations. She serves as Vice Chair of the ASTM E60 committee on sustainability, and is a member of the American Concrete Institute’s (ACI) sustainability committee (130), ACI 550 on precast concrete, the SEI sustainability committee, the fib (International Federation for Structural Concrete) sustainability committee, and is a member of the U.S. TAG to two ISO committees. She has a bachelor’s and master’s degrees in structural engineering from Michigan Technological University in Houghton, Michigan. Barry said this about Ms. Lorenz’s appointment to the Editorial Board: “Emily, with her extensive background in editing technical manuals and standards, brings a plethora of experience and expertise to the Board. She is an experienced editor and has a great passion and enthusiasm for writing and for the structural engineering profession. She was highly recommended by her peers in the concrete industry, so I have no doubt that she will be a productive addition to the STRUCTURE magazine team.” Please join STRUCTURE magazine in congratulating Mike Mota on his service and welcoming Emily Lorenz to the team.▪

August 2017

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THE NEW STANDARD

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

Lateral Analysis Part 2: Right Way, Wrong Way with Software By Samuel M. Rubenzer, P.E., S.E.

Samuel M. Rubenzer is the founder of FORSE. He is a member of ASCE-SEI, on the board of directors and past president of SEA-WI. He has years of experience teaching other structural engineers how to use software programs from many different vendors. He can be reached at sam@forseconsulting.com.

ast month’s article (Structural Analysis, STRUCTURE, July 2017) was devoted entirely to model generation, the critical first step in an accurate analysis and design using the Finite Element Method (FEM). Remember, FEM is broken up into three basic steps: 1) Modeling: A pre-processing step where a user defines elements, connectivity, support conditions, and forces that represent various loading conditions. 2) Analysis: Processing step that requires little user input – the user establishes a few important parameters, and the software solves a vast set of equations based on the model. 3) Validation and Design: Post-processing; the step of interpreting and verifying the results of the analysis and then designing elements based on parameters determined by the material codes one uses. In this article, the modeling is completed by considering loads on the model, followd by a discussion of Steps 2 and 3.

Loading and Load Generators Once the model is created, and the nodes and elements are defined, loads must be imposed on the structure. Self-weight dead load can be automatically generated. Other gravity loads are typically defined by manual input. However, wind and seismic forces can be applied to the model using load generators that are available in many programs. The user simply defines code criteria based on the building’s location and the software determines the load parameters, computes loads, and imposes those on the structure based on the geometric information the program ascertains from the modeled elements. Wind load generators (Table 1) generally use deck (or slab) edge information to determine overall floor dimensions. Together with the story height, the program can determine the area for the wind load to be applied. Programs Wind Load Generator ETABS

are becoming increasingly precise in the method of defining exposure areas by utilizing wall panels (load panels). Wall panels can be used for automatically generated pressures, resulting in a more precise method for applying wind loads. Utilizing wall panels is a practice best used when dealing with semi-rigid diaphragms since pressure can be added to windward walls, leeward walls, side walls, and roofs. Seismic load generators are more complicated, as they can either be based on equivalent lateral force procedures (static load) or dynamic analyses such as response spectrum analysis, time history analysis, or a non-linear dynamic analysis (Table 2). Model stiffness is very important to seismic load determination and dynamic behavior of the model, and it is imperative to model stiffness as accurately as possible. Similarly, the mass of the model is a very important element in determining the dynamic properties, and much care should be used in defining the dynamic mass. It is likely users are conservative and model dead loads are higher than the actual loads on the structure; thus, dead load is not always the same as the mass that should be used in determining dynamic properties. An arbitrarily high mass leads to a lower frequency and a higher building fundamental period; this may result in a lower seismic force coefficient depending on the structural system. Much more can be said about the importance of accurately modeling mass, stiffness, and dynamic characteristics relative to seismic demands. However, that is a broad discussion that will have to be examined in future articles. Whether seismic or wind lateral loads are determined, the applied force from the load generator will either be a single load applied to the entire building diaphragm, or a distributed load applied to the edges of the diaphragm (common for wind) or over the entire area of the diaphragm (common for seismic). Users often have the option of single or distributed forces when generating the loads and must consider the type of diaphragm before making the

Automatic Exposure Area?

User Defined Exposure Area

Combine with User Defined

Parapets be Defined?

yes | yes

walls

yes

areas (sim. to wall panels)

yes

IES VisualAnalysis RAM Structural System

yes | yes

yes

RISA 3D

yes | no

yes

SCIA Engineer

load panels

yes

TEKLA Structural Designer

wall panels

yes

Table 1. Wind generators.

16 August 2017

selection. When using a rigid diaphragm, either option of loading will have the same result. Conversely, when a semi-rigid or no diaphragm is modeled, the only option for loading is distributed loading. For example, a single load on a semi-rigid diaphragm leads to incorrect load distribution to lateral framing members, and diaphragm stresses and deflections that are completely erroneous. Considering all of the above, the most overused feature of software programs today may be the simple load generator that only works effectively for simple models. Features that are common in present-day buildings, such as sloped or stepped floors or roofs, sloped walls, re-entrant corners (floor perimeters that jog in/out), and non-uniform mass loading, can quickly invalidate the generated load. Sometimes these nuances can be accounted for, and the generated loads can be used, but other times users simply need to put away the automatic load-generating features and compute and define loads manually. Look at it this way – you have two options: 1) Manually determine the loads for a structure using software with good element modeling features that accurately represent the real structure, or 2) Automatically generate loads using software having poor element modeling features that are not an accurate representation of the real structure. Most engineers would choose Option 1. Using software that can accurately determine the vertical and lateral load distribution through an indeterminate structure with potentially semi-rigid diaphragms, element stiffness modification factors, and pinned or fixed-end conditions, all the way down to fixed, spring, or pinned supports to represent foundations, are much more valuable. Choose software programs by their ability to create an accurate model and analyze complex sets of equations, not for load generation features that will quickly become invalid with minor complexities of the structure.

Model Analysis – Processing The analysis step of the finite element method is mostly the software “crunching the numbers” and very little is done manually by the user. A user needs to pay attention to a few general setting options that affect the model and are typically located under analysis or processing menus in the program. An example of these settings is auto-meshing, discussed in

Seismic

Static (ELF) Response

Time History

Non-linear Analysis yes

ETABS

yes

IES VisualAnalysis

yes

RAM Structural System

yes

RISA 3D

yes

SCIA Engineer

yes

TEKLA Structural Designer

yes

Table 2. Seismic generators.

Part 1; wherein a finer mesh often provides better accuracy of elastic behavior. Also, plate/ shell elements are more accurate as square shapes, and finer meshes increase the likelihood that the elements are square or nearly square. This is especially true in complex models. However, one should consider the adequate convergence of the solution; that is, if the limited increase in accuracy of the model using a more refined mesh outweighs the processing speed needed to achieve those results. In general, the recommended maximum element mesh size would be the span distance divided by ten and the minimum plate size should be no less than the thickness of the element being modeled. Of course, these are guidelines that must be re-evaluated for unique situations. Other settings to be considered for analysis or processing pertain to P-delta effects. The P-delta effect accounts for the fact that gravity loads increase lateral deformations, increasing element shears and moments, and adds to the overturning moment of the building, becoming an important feature in the overall structural performance, its lateral instability, and in element design. In the first few iterations of the lateral analysis of a building, it is possible that considering P-delta effects will lead to an unstable structure. Therefore, member sizes may need to be refined through an iterative process without the P-delta effect included until reasonable sizes are determined, and a stiffer structure is established. In all cases, the option to consider P-delta in the analysis should be revisited once initial sizes are determined.

Validation and Design Once the modeling is complete and the analysis has been performed, it is then time to turn to the final step of the finite element method – validation and design. With each different material, different design

STRUCTURE magazine

August 2017

codes require checks based on the forces and stresses in the elements of the structure. However, before applying design code rules to the structure, it is first important to have confidence in the results. An important aspect of validation and design is reviewing the data to determine whether modeling and analysis gave expected results. The initial step in this review can be checking the nodal reactions in comparison with the applied loads on the structure. This may seem like an elementary check, but it is very important. Often errors occur when users assume their loads are applied in a manner in which the program is not meant to be used. In addition to load generation errors, another example would be whether self-weight is automatically calculated and applied, and, if it is applied, whether it is applied to dead loads and/or effective mass. Other examples of loading errors can occur when modeling openings in floors and walls of plate/shell elements. When programs perform auto-meshing routines and remove plate/shell elements where the opening occurs, the program also removes the load that would have been applied to that area. This, of course, leads to unconservative results. There are very few programs that account for this missing load automatically, so the user must often address this manually. Another great method to review the validity of the results, which is less quantitative and more qualitative, would be to animate deflection results of the lateral load cases and load combinations. The ability to amplify the results can help in determining whether the structure is behaving as anticipated, or if there is something new that was not expected. At times, the unexpected animation is due to a modeling error that can quickly be observed and repaired. In more complicated structures, however, the modeling approach may need to be changed. When observing the animation, there is an opportunity to understand which element is more critical than expected, how

to improve lateral efficiency, where checks of the projects produced Individual elements – deflected. to increase the stiffness of a single by the office. Unfortunately, element or multiple elements, or these quality assurance meawhether to add a new lateral frame sures are often based mostly or in a particular area of the structure. entirely on manual calculations, Furthermore, it is vital to verify report reviews, and drawing the analysis results before performreviews. Senior engineers need ing code checks. If code checks are to be well versed in the software performed too early, there could be tools to review the models as an over-emphasis on getting the well, so younger engineers are model to simply pass code. During not left alone in the process of Overall structure – deflected. this rush to circumvent the process creating, analyzing, verifying, and not verify analysis results, a critand designing. Also, this responical aspect or underlying problem sibility to understand software with the structure may be missed. may be expanded beyond junior Unfortunately, the results of these and senior engineers to the engiscenarios are all too common. It neering project managers and is important to resist the temptabusiness owners. How can sometion of a combined “analysis and one manage design teams, create design.” Be sure to separate them expectations, define deliverables, into distinct steps in the process. and manage the risks to organizaOnce there is confidence in the tions without understanding the analysis results, then the process tools that are becoming critical of design and code checking may to completing design tasks for begin. Take time to review the many or all of the projects that software’s implementation of the go through engineering firms? code provisions to understand Utilize these software tools for and agree with the design prolateral analysis and continue to cess; only then should the program progress in understanding, maxbe used to design and check the imizing their responsible use. demand (analysis results) versus Remember to always uphold element capacity as defined by the the integrity of structural engicode. As mentioned earlier, this neering by accurately modeling, is the appropriate time to apply analyzing, reviewing results, and conservative measures based on designing with software. As the engineering judgment. author, C.S. Lewis, states, Finally, have the finite element “We all want progress. But progress method checked by a colleague Animate deflected shape for overall and individual elements to confirm results. means getting nearer to the place with strong experience with the where you want to be. And if you method. All of the steps – modeling, analy- of reality to provide a safe, efficient, and effechave taken a wrong turn, then to go forward sis and validation, and design – should be tive design or is it compromising? There was does not get you any nearer. If you are on verified. In today’s structural engineering a time, before finite element methods and the wrong road, progress means doing an firms, a quality review process should be software tools became available, when there about-turn and walking back to the right as focused on the finite element software was little choice but to over-simplify a design road; in that case, the man who turns back programs as it is with the drawings that the problem. Today, however, many software soonest is the most progressive man.” company sends out. tools are readily available, and an FEM soluIt is essential to continue to make progress tion should be considered for all substantial with the use of software. If at any point the structures. When using these tools, ensure profession becomes overly reliant on softConclusion the model accurately represents structures ware for the wrong reasons or realize software It is very important that all engineers in an by examining beyond basic idealized settings. is being used without truly understanding organization truly understand the software There is a point of diminishing returns when both the capabilities and the limitations, then tools used within the company. Recognize more complex modeling yields the same structural engineers may have to go back and the balance between idealized, simple mod- design solution, a good point to approach learn – or re-learn – until what software can eling that saves time (and budget) and more in modeling. do is fully grasped. C.S. Lewis also said, “It is complex modeling that may be a better repAlso, junior engineers are generally the sav- not your business to succeed, but to do right.” resentation of the actual building. This takes a viest with software and are typically the ones Moreover, by doing right, success will follow. thorough understanding of building elements creating the models, analyzing, and designing. Do right and build these models for lateral and more time to implement into the model. They are the doers within most companies. analysis with integrity, by modeling and anaAt each step on the path of modeling, analyz- However, senior engineers – some of whom lyzing structures to represent the real structure ing, and designing, answer the question: does rarely use software products – are the ones accurately, and providing safe and reliable this item provide an accurate representation doing the reviews and the quality control designs for building owners and occupants.▪ STRUCTURE magazine

August 2017

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egardless of your familiarity with have to guard against losing the high ground and Quality Based Selection (QBS), make sure they always hold the truth paramount, there are certain basics of business which means walking away from situations where that all engineers should understand, deception is rewarded. The procurement of our even if you are not in management. Structural services based on a comparison of prices alone, engineering is a professional service business. The rather than in combination with qualifications overwhelming majority of structural engineers are and a defined scope of work, fosters a climate compensated based on the amount of time spent where dishonest behavior can flourish. on a client’s project. If you are a business owner, Dishonesty in the form of excessive self-proyou know that each and every proposal starts out motion, deceptive staffing of the project, both in with the question “How much time will the project number and skill of personnel, the exclusionary take?” Complex projects involve project managers, language in proposals such as overly-limiting site design engineers, and CAD operators, plus others. visits, excessive use of performance specifications, To develop a proposal, hours are estimated and and reducing QA/QC are examples of what can multiplied by billing rates and a total fee is com- occur in competitive bid procurement systems. puted. The more definitive the scope of services, The owner is best served when the structural the greater the accuracy of the fee estimate. engineer provides all of the services necessary to Unfortunately, engineering businesses are being design the structure and observe its construction asked, more and more, to furnish lump-sum fees to the extent the engineer can attest that the intent based on very little information. This in and of of contract documents was generally followed. itself can lead to problems, but combine it with Alabama’s Board of Licensure for Professional the practice of clients requesting proposals from Engineers requires that its licensees respond multiple firms for price comparison, and it is easy only to solicitato see that the more uninformed or unscrupulous tions that employ can often be the more successful. Besides the fact QBS, regardless of that qualified firms that offer fair fees are often whether the client the immediate victims of the process, the long- is a public agency term ramifications of poor structural engineering or a private party. can result in jeopardizing the health, safety, and Engineers are forbidden from participating in welfare of the public, not to mention the grief a bidding process. Radical as it may seem to and headaches that accompany poor construction some, the Federal Government requires the use documents during the construction phase. of QBS through the application of the Brooks Engineering is a thinkAct, realizing that the ing profession. The client best overall value for the Engineers have to guard is purchasing the engipublic is the selection of neer’s ability to solve the the most qualified firm against losing the high problem using the brain. paid a fair and reasonground and make sure Drawings, specifications, able fee. The Alabama and even calculations are Board, together with the they always hold the truth tools of conveyance of Federal Government, paramount, which means what the engineer thinks believes that services and how a solution was that directly deal with walking away from situations developed. Selecting the life and death should not where deception best brains with the most be subject to the same experience will result in procurement rules that is rewarded. the best solution. Does apply to the purchase of it really make sense for pencils or butter. clients to select their engineers based on whether If the public selected their medical professionals the fee for the project is 1% of the construction through bidding for services, health care might be a cost, 0.9%, or even 0.5%? Unfortunately, the few dollars cheaper, but mortuaries would prosper. answer is often “no” if your client is the owner, Imagine you are on trial for a serious crime. Of but” yes” if the client is an architect or an inter- course, you are innocent, and your significant other mediary who sees the structural engineer’s fee brings in your attorney, the low bidder. What kind coming out of his or her pocket. Money can be of chance do you think you have to be home at a powerful motivator that obscures reality and Christmas? No society would want its health or blurs the vision. freedom jeopardized by such an absurd procureEngineers historically have enjoyed a high level ment system as applied to these professions. Well, of trustworthiness, as polled by Gallup, fourth how much sense does it make for the low bidder behind doctors and one position in front of to be the designer of an arena that seats 10,000 dentists. The fundamental canon of every set people, a high-rise building, a long span bridge, of ethics rules for engineers is truth. Engineers or even a child daycare facility or nursing home?

Professional issues issues affecting the structural engineering profession

The Ethics of Procurement

STRUCTURE magazine

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

Marc S. Barter (mbarter@ barterse.com), is the President of Barter & Associates, Inc., a structural engineering consulting firm in Mobile, Alabama. He is a Past President of NCSEA and in his second term as a member of the Alabama Board of Licensure for Professional Engineers and Land Surveyors.

With the exception of If so, the family better like Alabama, licensing boards beans and rice. Isn’t that have been largely mute how the structural engion the subject of procureneer is selected on a large ment in the private sector. number of projects, some Many boards reinforce the rather complex? Given mini-Brooks laws that their that the client may know states have adopted, but are the engineer, understands very cautious in their poswhat the deliverables are, ture on procurement as it and hopes the services prorelates to private transacvided keep everyone out of tions, for a good reason. court, are the services proIn 1978, the United States vided really appropriate or Supreme Court struck just minimal? down the NSPE ethics Ethical practice should rule that prohibited enginot have to be mandated neers from bidding their by licensing boards or services. According to the professional societies. Any United States, the NSPE engineer should understand rule violated the Sherman that prior to providing a fee, Antitrust Act. NSPE, someone has to develop a through its attorneys, scope of services, and if fees unsuccessfully argued that from multiple firms are to the practice of engineering be compared, then every correlated closely with the participating firm should health and safety of the be basing their fee on the public and, therefore, its same scope of services and Engineering is a thinking profession. apparent violation of the assigning similarly qualified The client is purchasing the engineer’s Act should be permitted personnel. Procurement under the Rule of Reason procedures that result in ability to solve the problem using the brain. argument. In a split deciprice comparisons without sion, the court stated, measuring qualifications “Exceptions to the Sherman Antitrust Act to legislators the benefit of QBS, as a rule, and defining the scope of service invite for potentially dangerous goods and services state licensing boards, with one exception, unethical behavior. Even if the licensing law would be tantamount to repeal of the statute. do not opine on the application of QBS does not prohibit participation, the instinct In our complex economy, the number of in private transactions. Alabama’s licensing for self-preservation should dictate caution. items that may cause serious harm is endless board is alone in that regard. Too many times, in these situations, the – automobiles, drugs….” and ruled against In states without specific ethics rules low fee is the wrong fee provided by the NSPE. The Court stated that bidding was addressing procurement, is the practicing wrong firm. not required, but that it was unlawful to structural engineer bound by any ethical It is very difficult in some segments of the reduce competition. duty not to bid engineering services? Why structural engineering business community When viewing QBS through the licens- should it be unethical in some jurisdic- to adhere to QBS without the cover of a ing lens, an important distinction should tions to bid engineering, but not others? legal mandate. In fact, an engineering firm’s be understood. NSPE does not enjoy the What possible good can come from engi- refusal to participate in price comparisons same legal rights as a State. According to neers offering competitive prices without a will likely end any chance of working with the Cornell University Law School, Legal defined scope of work? In exercises where certain clients. The ethical engineer looking Information Institute, “Under the state- structural engineers were asked to provide a to play on a level playing field has a difficult action doctrine elucidated in Parker v. Brown, fee for a project where the only information time but must attempt to shape the process 317 U.S. 341 (1943), state and municipal provided is the location of the building, the such that all participants are treated fairly, authorities are immune from federal anti- size of the building, and cost of the build- including the owner. This may mean walking trust lawsuits for actions taken pursuant to ing, the proposed fees varied by over 200%. away from a project. Ethical behavior can a clearly expressed state policy that, when Is the owner’s interest served in this system; be expensive and good feelings cannot be legislated, had foreseeable anticompetitive if so, how? The client is purchasing a service deposited, but there is an indisputable beneffects. When a state approves and regulates he/she does not understand, in a quantity efit from practicing an honorable profession, certain conduct, even if it is anticompetitive they did not specify, furnished by individu- and an obligation to protect that profession under FTC or DOJ standards, the federal als they do not know anything about. The so that future practitioners are not viewed as government must respect the decision of the only metric that seems to matter is cost. a commodity. Therefore, the next time you state.” Given the litigious nature of society, Would anyone enter a grocery store and bid are asked to compete for a project based on the current attitudes regarding regula- their grocery needs with the only instruc- price, decide if you are offering engineering tion, and the difficulty in demonstrating tions being to feed my family for a week? or just butter.▪ STRUCTURE magazine

August 2017

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Structural DeSign design issues for structural engineers

onstruction Science and Engineering, Inc., an architectural and engineering firm, has investigated several low slope roof applications with water stains, ponding, framing damage on the lower side of the roof span, and structural collapse. Further examination typically reveals a relatively level surface when compared to other roof locations (Figure 1). A similar occurrence is often found in exterior deck applications. (Figure 2). In studying this potentially problematic issue, two building code parameters were identified that contribute to low slope roof and deck serviceability issues. This article examines susceptible bays with respect to the ¼ in 12 design slope and code permitted deflection ratios. Part 2 will identify design and construction practices that contribute to serviceability issues.

Background The 2015 International Building Code (IBC) identifies ponding instability as a design consideration for snow and rain loads. The 2010 edition of the Minimum Design Loads for Buildings and Other Structures (ASCE 7-10),

Building designers routinely stipulate within construction documents the well-known code minimum ¼ in 12 design slope for low slope roofs and exterior deck applications. This practice, on the surface, appears to eliminate the code requirement to investigate a susceptible bay. Additionally, common practice is to specify or accept minimum building code deflection ratios for low slope applications. However, many building designers apparently fail to give due consideration to footnote “e” in IBC Table 1604.3 which states in part; “The above deflections do not ensure against ponding…” A code defined deflection ratio is a function of the span and is therefore not influenced by material characteristics and design load variables. Each deflection ratio defines the deflection limits that are commonly approached as structural members are optimized for cost. Bender and Woeste recognized this relationship and showed a beam member installed to a ¼ in 12 slope that deflects to a code permitted deflection ratio results in an average slope less than ¼ in 12. They also noted the average slope is further reduced when a long-term creep deflection component is introduced. The Bender and Woeste (2011) study validates the author’s field observations for serviceability complaints and water retention associated with low slope roof and deck applications. The deflection curve was approximated using the properties of a circle to verify the average slope was independent of the span and remained unchanged for a specified deflection ratio. Additionally, the lower end of the deflection curve was noted to be relatively flat, which explained potential causes of observed ponding. In the author’s company’s study, surfaces with a design slope of ¼ inch per foot or less should be considered as a susceptible bay. Specifically: 1) The average slope of the deflected member is less than ¼ inch per foot; and, 2) At and near the lower reaction, the deflected member is relatively horizontal or flat.

¼ in 12 Design Slope and Water Drainage Part 1 By Scott D. Coffman, P.E., SECB

Scott Coffman is a Forensic Engineer with Construction Science and Engineering, Inc. in Westminster, SC. He can be reached at scottcoffman@ constructionscience.org.

referenced by the IBC, defines “ponding” as the “retention of water due solely to the deflection of relative flat roofs.” The standard requires “susceptible bays” be investigated to ensure adequate member stiffness is present to prevent progressive deflection. Specifically, “Bays with a roof slope less than ¼ in./ft. …shall be designated as susceptible bays. Roof surfaces with a slope of at least ¼ inch per foot (1.19°) toward points of free drainage need not be considered a susceptible bay.” The phrase “toward points of free drainage” is critical because it gives meaning to what is meant by a slope of ¼ inch per foot. The same principle may be applied to exterior decks, although decks are not specifically identified within ASCE 7-10.

Figure 1. Evidence of ponding on the roof.

24 August 2017

Figure 2. Ponding water on deck.

1/4 Y1

1/4

Average Slope

Y3 Y4

L/2

L/2 SPAN (L)

SPAN (L)

Figure 3. Deflected shape of beam with uniform load.

Figure 3 visually depicts the downward movement of a beam member subject to load and vulnerability to ponding at the low end.

Average Slope Example The average slope for the performance of a member installed to a ¼ in 12 design slope and permitted to deflect to a code permitted L/180 ratio is illustrated by the following example: • Member Span: 25 feet • Roof Total Load Deflection Limit: L/180 • Right Support Datum Elevation: 0.00 inches • Left Support Elevation: 6.25 inches (Y1) • Midpoint Elevation: 3.13 inches (Y2) • Member Total Load Deflection (L/180): 1.67 inches (Y3) • Distance from datum to deflected member: 1.43 inches (Y4) The “average slope” is the slope of a line from the low-end support to the point of maximum deflection for a member. For a simply supported beam member subjected to a uniform load, the average slope is from the center of the span to the low-end support. In this example, the right support is the low end and point of free drainage. Figure 4 shows the original member slope and deflected shape. The distance from a level datum to the deflected member is 17⁄16 inches (Y4); the difference between the member’s original

Figure 4. Average slope of deflected member

position and code permitted deflection ratio at the mid-span. The average slope from the center of the member’s deflected shape to the low-end support is 0.117 inches per foot, a slope less than 1 ⁄8 in 12 or nearly flat. When a member initially installed to a ¼ in 12 design slope deflects and approaches the total load L/180 code permitted deflection ratio, the average slope becomes less than 1⁄8 in 12. The calculated 0.117 in 12 average slope is constant for any span designed to the L/180 deflection ratio. ASCE 7-10 explicitly identifies member stiffness as a means to control progressive deflection of a susceptible bay. Design professionals typically specify a more limiting deflection ratio than required by the building code for the application to achieve a stiffer member. As expected, the average slope approaches the ¼ in 12 design slope for a stiffer member or a higher deflection design ratio. However, a beam element subject to gravity load deflects, and the average slope remains less than the designed ¼ in 12 design slope. Therefore, a beam element installed with ¼ in 12 slope requires a “susceptible bay” analysis based on ASCE 7-10, since all members deflect under load.

Average Slope

L/16 DETAIL "A"

Long-Term Creep Effects and Example Structural materials susceptible to longterm creep intensify the deflection curve. The IBC estimates the creep component of long-term deflection to be half the immediate dead load deflection or a 1.5 factor. The creep deflection component may approach the initial dead load deflection, a 2.0 factor for wood products. The 2014 Truss Plate Institute Standard (TPI) recommends the 2.0 factor where the building designer does not specify adjustment factors for serviceability. The 1.5 building code factor was applied by the author for a “best case” scenario to study the effects of creep deflection. Continuing the previous example, the initial dead load deflection is taken as the difference between the roof ’s total load (L/180) and roof ’s live load (L/240) deflection ratios. This calculates to 0.42 inches (1.67 – 1.25) for a 25-foot span. The long-term creep

The lower end of the deflection curve is also a typical location for ponding, water stains, and damaged framing members (Figure 5). This opinion is based on observations made during

1/4

forensic investigations. The vertical difference between a ¼ in 12 plane and the L/180 deflection curve was calculated for spans of ten feet to forty feet in 2-foot increments. The deflected shape crosses the horizontal datum in the region of L/16, creating negative slope and a “bowl” at the low end. A “bowl” naturally retains water and restricts free drainage or water discharge. Ponding or water retention should be expected toward the low end of a plane designed to a ¼ in 12 slope.

Deflection Curve at the Lower End

1/4

Y3'

Average Slope

Y4'

DETAIL "A"

L/2 L/2

L/2

SPAN (L)

Figure 5. A typical location for ponding.

Figure 6. The average slope of the member with creep.

STRUCTURE magazine

August 2017

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Figure 7. Increased “bowl” is caused by member creep.

Potential solutions to mitigate low slope serviceability issues are limited. ASCE 7-10 indirectly promotes a more stringent deflection ratio to prevent progressive deflection. The ASCE solution is imperfect because stiffer members increase the cost and the average slope remains less than ¼ in 12. A member or plane designed to an “average slope” of ¼ inch per foot is one method to mitigate ponding and resultant material damage. For a simply supported beam member subjected to a uniform load, the average slope line is from the point of maximum deflection at the center of the span to the low-end support. A more practical solution is a combination of increased slope and member stiffness. Design tools currently available afford a quick and efficient means for a designer to calculate the average slope of a member; the “average slope” being the slope of a line from the low-end

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Summary and Conclusions The building code establishes the minimum parameters for building design. A member or system that satisfies each code parameter may create a less than ideal condition when multiple minimum code parameters are combined. The combination of the ¼ inch per foot design slope and a maximum permitted deflection ratio creates such a condition for free drainage. The code, however, does recognize this potential condition in IBC Table 1604.3 footnote “e” and instructs a building designer to investigate applications with insufficient slope or camber for ponding. Building designers, contractors, and perhaps code officials have come to believe a roof or exterior deck surface designed to the ¼ inch per foot slope is satisfactory because it meets building code intent. However, member deflection creates an average slope that limits free drainage and contributes to ponding toward the low end. Members optimized to a code permitted deflection ratio further reduce the average slope and may create a negative slope or a “bowl” at the low end that limits or prevents free drainage. The condition is exacerbated for materials susceptible to creep deflection. Beam elements designed or installed to the ¼ inch per foot slope should be considered a susceptible bay. In the absence of code performance limits for low slope roofs, a building designer should consider implementing a more stringent total load deflection ratio, increase the minimum slope for positive drainage, design to an “average slope” of ¼ in 12, or a combination of each. The practice should also be extended to decks.▪

STRUCTURE magazine

Potential Design Solutions

support to the point of maximum member deflection. A combination of increased member stiffness and design slope that results in a surface with an average slope of at least ¼ inch per foot towards points of free drainage should eliminate susceptible bays.

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component is 0.21 inches (½ * 0.42). The center of the deflected member is 1.25 inches (Y4´) above the right end support (3.13 – 1.67 – 0.21). The average slope from the center of the member deflection curve to the support is 0.10 inches, or essentially no slope, and remains constant for any span (Figure 6, page 25). Although the average slope with a creep deflection component remains positive, albeit small, the low end of the member deflection curve remains of particular interest. The deflected shape crosses the horizontal datum in the region of L/6, creating a larger “bowl” area for ponding (Figure 7). As the dead load becomes a greater percentage of the total load, creep deflection increases and the “bowl” effect becomes more pronounced at the low end. It is imperative that deflection calculations include material long-term creep effects when compared to the ordinary live and total load code permitted deflection ratios.

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Software Continues to Evolve NEW OFFERINGS, ADD-ONS, AND UPGRADES ASSIST ENGINEERS IN MEETING TODAY’S CHALLENGES

By Larry Kahaner

ompanies that provide software for the engineering and construction industry are continually updating their offerings to keep pace with what structural engineers want and, most important, to keep up with code changes. At Dlubal Software, Inc. (www.dlubal.com/en-us), CEO Amy Heilig says that the latest addition to their 3D finite element analysis software, RFEM, is the RF-CUTTING-PATTERN add-on module. “We are beyond excited to offer this to engineers who specialize in the design of membrane and tensile structures, as the software market for this type of application is extremely slim. RF-CUTTING-PATTERN generates and organizes cutting patterns for membrane structures taking into account curved geometry, compensations, and overlaps with the minimum energy theory flattening process.” She adds: “This new module can be used in conjunction with RF-FORM-FINDING which determines the membrane’s pre-stressed shape used in the initial state for further static analysis. The supporting structure for the membrane can then undergo a full analysis design per AISC, ACI, NDS, and ADM. A complete structural solution for fabric, cable, and tensile membrane structures can now be achieved with the single design program, RFEM.” A recent company project is the Brock Commons, an 18-story mass timber, hybrid student residence currently under construction at the University of British Columbia in Vancouver, Canada, and designed by Dlubal Customer, Fast + Epp. “When completed in the summer of 2017, it will be the tallest mass timber hybrid building in the world at 174 feet high”, Heilig says. “The structure is comprised of 16 floors of five-ply cross-laminated timber (CLT) floor panels, a concrete transfer slab at level 2, and a steel-framed roof. The structural analysis for the CLT components was completed using Dlubal’s RFEM in conjunction with the RF-LAMINATE add-on module.” As far as trends are concerned, Heilig says that design engineers remain steadily busy which in turn correlates to an increased demand for a high performing structural analysis and design software. “We have seen a surge in cross-laminated timber (CLT) interest, as massive timber continues to be heavily marketed throughout the U.S. and Canada. RFEM remains the top choice for timber engineers for comprehensive CLT analysis and design per the 2015 NDS, in addition to member design per the NDS and CSA. We continue to see steel and concrete design dominate the structural engineering market, and this probably won’t change anytime soon. However, we STRUCTURE magazine

are now seeing an increased demand for unique material and geometric designs as architects and owners are seizing opportunities to stand out with their structures. Dlubal caters to this exact scenario. We provide solutions for the structural engineer who is faced with complex structural geometry or in need of structural design of not only steel and concrete, but also glass, CLT, aluminum, timber, fabrics, and cables.” (See ad on page 30.) Benjamin Follett, U.S. Product & Marketing Manager, for SCIA Inc. (www.scia.net/en), would like SEs to know about SCIA Engineer 17. “For the U.S. market specifically, we updated all the steel codes to the newest versions; that is the 2016 AISC code and 2016 AISI code for cold form steel. The updates include new formulas, new references notations, and terminology.” He adds: “There also are improvements to the design and workflow of composite slabs, such as creating automatic load combinations. We have also added diaphragms. Simplified diaphragms, rigid diaphragms, flexible diaphragms, and semi-rigid diaphragms all have been requested by our users. These users want to simplify a building or perhaps don’t want to go through the full slab design when they are not doing a concrete slab.” Says Follett: “As far as BIM is concerned, we have a new link directly with Revit, so it is support for the newest version SCIA 17 and the newest version of Revit 2018. It was more of a maintenance release for us, a bug-fixing release. “We also improved our interoperability with a cloud BIM tool that we call BIM+. BIM+ is a free online BIM server. The goal of BIM+ for us at the Nemetschek Group is to have all our software utilize this online, cloud-based server to exchange models with other Nemetschek software,” he concludes. “Cold-formed steel design, and especially the AISI North American Specification, can be a little foreign to most engineers,” says Clif Melcher, CFS Product Manager at Simpson Strong-Tie (www.simpson.com). “CFS Designer software by Simpson StrongTie can simplify and automate the design and engineering of CFS structures, and provide great time-saving solutions,” he says. “Many CFS engineers may know CFS Designer by its original name, LGBEAMER. Simpson Strong-Tie has upgraded the software and taken it to the next level. Similar to LGBEAMER, CFS Designer can automate common design components, including wall studs, beams, columns, wall openings, x-braced and sheathed shear walls,

August 2017

floor joists, and rafters. In addition, it includes the latest codes and features a Stacked Wall Design tool that automates the design of up to eight stories of load-bearing CFS stud framing. A new, user-friendly interface as well as organizational and file management tools have been added. The software also has automated the selection of bridging and curtain-wall rigid and slip connectors,” Melcher notes. StructurePoint’s software (www.structurepoint.org) suite includes features which emphasize the solution of intricate scenarios or niche cases in reinforced concrete design, says the company’s Resource Manager, Dana Lee. “Our team routinely posts technical notes on our website to aid users in accessing the full range of capabilities built into the software for specific, frequently-encountered cases. Most recently, we have addressed the effective flexural stiffness for calculation of the critical buckling load of individual columns, as well as concrete type classification based on unit density. These technical notes, among many others, use the latest American (ACI 318-14) concrete codes and provide multiple options for solutions to fit a range of projects. These can be found on the Resources page of our website, along with various technically-focused tools to aid engineers in completing their most demanding projects.” Lee would also like SEs to know that their software manuals for each of the programs within the suite are now easily accessible on their website in multiple formats. “The online versions feature simple headings and easy navigation, including search and filters to efficiently access resources such as methods for a solution and dynamic design examples. The manuals are also available as PDF files.”

StructurePoint is formerly the Engineering Software Group of the Portland Cement Association (PCA), and it continues to develop and enhance the full range of advanced software and engineering services to model, analyze, and design reinforced concrete structures, notes Lee. “Recent focus in the Middle and the Far East, where concrete design software is in high demand, has kept our team busy as we adapt to various business paradigms. StructurePoint has been supporting and growing alongside the global market by meeting the needs of engineers in six continents and over 50 countries. While we provide our products and services as an essential tool to academic institutions and engineering firms internationally, we continue to ensure the stability and growth of our local and national user-base.” Lee concludes: “With the experience and legacy gained over 60 years as PCA’s engineering software group, structural engineers continue to trust StructurePoint to extend knowledgeable support via consulting engineering services. Engineers everywhere value StructurePoint as a gateway to the vast resources and knowledge base of the cement and concrete industry. The promise of rising infrastructure spending in the U.S. economy is creating energy, excitement, and new opportunities for engineering firms to create proposals and feasibility studies. Clients experiencing this trend are tapping into StructurePoint’s concrete industry experience to relieve heavy workloads, augment their staff, and advise on all of their concrete project estimates, preliminary designs, and comparative studies.” (See ad on page 32.) continued on page 33

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STRUCTURE magazine

August 2017

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VCmaster (www.vcmaster.com/en) has been developed with the needs of engineers in mind, according to company officials. They note that the program intelligently combines technical calculations and word processing in one single user interface. Everyday tasks such as calculation, documentation, compilation, as well as the reuse of technical data and calculations, are tackled with their integral concept. Highlights of VCmaster include: • Uniform Documents: VCmaster offers engineers a unique and comprehensive concept. Outputs of all structural analysis or CAD programs can be incorporated into VCmaster, guaranteeing a uniform and consistent layout. • Convenient Revisions: Positions and details are exchanged automatically, and reports are amended and checked by a click of the mouse. All revised pages are then subjectspecifically indexed. • Sustainable Benefit: All digitally compiled VCmaster documents can be easily adjusted, combined, or reused at will. • Interactive Design of Structural Elements: VCmaster automates the design of structural elements. Formulas are presented in standard mathematical notation and calculated automatically. Material or section values are determined from stored databases. • Interactive Design Aids: VCmaster includes numerous predefined design aids for structural analysis. Engineers can create their own design calculations and combine them with existing templates to create design briefs.

This year’s development focus for VCmaster has been on improving the handling of the software and simplifying data entry. VCmaster has been revised in many aspects to achieve this goal. Major improvements include: • Extended options for design and formatting. • Faster data entry due to the new favorites folder, pre-defined input lines, and automated completion of variables. • Easier checking of indices for page numbering and database queries. • VCcopy-technology, an intelligent alternative to the Windows clipboard.▪

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STRUCTURE magazine

August 2017

National Council of Structural Engineers Associations

2017 STRUCTURAL ENGINEERING SUMMIT

OCTOBER 1114, 2017 · WASHINGTON HILTON · WASHINGTON, D.C.

NCSEA invites the best of the structural engineering field to join us in Washington D.C. as we celebrate 25 years of bringing together structural engineers. The 2017 Structural Engineering Summit features education sessions specific to structural engineering, including 3 specialized panels and an entire track dedicated to young engineers. Flip to NCSEA News, pages 62-63, for more information on this year’s Summit! WEDNESDAY, OCTOBER 11 8:00-5:00 NCSEA Committee Meetings 4:30-5:30 Young Member Reception 4:30-5:30 Delegate Reception 5:30-7:00 Welcome Reception THURSDAY, OCTOBER 12

All Attendees Welcome (See the schedule on www.ncsea.com) Young Members & NCSEA Board of Directors Only Delegates & NCSEA Board of Directors Only All Attendees Welcome

12:30-1:30

Delegate Interaction Breakfast Delegates, SEA Leadership & NCSEA Board of Directors Only All Attendee Breakfast Keynote: Shaking Up DC - The Insiders’ Story Martina Driscoll, P.E., Principal & Unit Manager, Wiss, Janney, Elstner Associates and Terrence Paret, Senior Principal, Wiss, Janney, Elstner Associates Break on the Trade Show Floor ASCE Panel on How to Improve ASCE 7 Ron Hamburger, P.E., S.E., SECB; John Hooper, P.E., S.E. and Don Scott, S.E.; ASCE/SEI 7 Committee Leadership Lunch on the Trade Show Floor

1:30–2:30

Concurrent Sessions

Track A

Seismic Design of Diaphragms by the Provisions of ASCE 7-16 S. K. Ghosh, Ph.D., S.K. Ghosh Associates, Inc. NEHRP Recommended Seismic Provisions Kevin Moore, C.E., P.E., S.E., Senior Principal, Simpson Gumpertz & Heger Inc. and Charles A. Kircher, Ph.D., P.E., Kircher & Associates

7:00-9:00 8:00-9:00 9:00-10:00

10:00-10:30 10:30-12:30

Track B

Young Engineer Track Young Member Mentor Roundtable Seth Thomas, P.E., S.E., Chair of the NCSEA Young Member Group Support Committee 2:00-5:00 SEA Executive Director Roundtable SEA Executive Directors & SEA Leadership Welcome 2:30–3:30

Concurrent Sessions

Track A

SEAOC Wind Design Manual - An Overview Emily Guglielmo, P.E., S.E., Martin/Martin, Inc and Steve Kerr, S.E., Josephson, Werdowatz & Associates Solar Photovoltaic Systems in ASCE 7-16 Joseph H. Cain, P.E., Director of Codes & Standards, Solar Energy Industries Association (SEIA)

Track B

Young Engineer Track

3:30-4:00

Wind Design Considerations for Joist/Joist Girder Structures Tim Holtermann, P.E., Canam-Buildings Break

4:00–5:00

Concurrent Sessions

Track A

Assessment of Performance-Based Seismic Design Methods in ASCE 41 for New Steel Buildings John Harris, Ph.D., P.E., S.E., research structural engineer in the National Earthquake Hazards Reduction Program of the Engineering Laboratory (EL), National Institute of Standards and Technology (NIST) You Can’t Just Delegate Everything Away to Others with Deferred Submittals Ben Nelson, P.E., Martin/Martin, Inc.

Track B

STRUCTURE magazine

August 2017

Register now on www.ncsea.com to save $100! Young Engineer Track YMGSC-Basics of Shear Wall Design Moderated by Seth Thomas, P.E., S.E., Chair of the NCSEA Young Member Group Support Committee 5:00 - 6:30

Trade Show Reception Network with the companies providing structural engineering products and software!

7:00

A Celebration of Structural Engineering at the National Building Museum Join CSI for a unique celebration of structural engineering, including dinner, champagne, cocktails, & live music.

FRIDAY, OCTOBER 13 7:00-9:00 8:00-9:50 8:00-9:50

Breakfast on Trade Show Floor All Attendees Welcome Delegate Collaboration Session Delegates, SEA Leadership & NCSEA Board of Directors Only Product Presentations All Attendees Welcome These brief presentations will provide more information on products or software from our exhibitors.

10:00–11:00

Concurrent Sessions

Track A

Cracking Within Existing Concrete Masonry Walls: When Are Calculations Required? Jose Busquets, P.E., Bracken Engineering Structural Engineering Engagement and Equity (SE3) Nick Sherrow-Groves, P.E., ARUP and Angie Sommer, S.E., ZFA Structural Engineers Concurrent Sessions

Track B 11:00–12:00 Track A

12:00-1:00

Tall Wood Buildings in the U.S. – A Codes and Standards Update Lori Koch, P.E., American Wood Council Networking Strategies: Even Introverted Engineers Can Network Effectively! Jennifer Anderson, Career Coach Lunch on the Trade Show Floor

1:00–2:00

Concurrent Sessions

Track A

State of the Practice: Blast Design of Building Facades and Structural Systems Cliff Jones, P.E., S.E., Project Engineer, Protection Engineering Consultants Shhh...It’s No Secret! Ideas to Help Grow Your Firms Clientele and Advance Your Career Jana Monforte, Associate and Director of Marketing/Business Development, Wallace Engineering, and Sarah Appleton, P.E., S.E., Principal, Wallace Engineering Concurrent Sessions

Track B

2:00–3:00 Track A

3:00-3:30

The Structural Innovations of the New Mercedes Benz Stadium Erleen Hatfield, P.E., S.E., AIA, Buro Happold Contract Negotiation as a Tool for Managing Project Risk Gail Kelley, P.E., Esq., LEED AP Break

3:30–4:30

Concurrent Sessions

Track A

Evaluation and Retrofit of Existing Structures for Mitigation of Progressive Collapse Aldo McKay, P.E., Protection Engineering Consultants Applied Business Mechanics Understanding Your Accounting & Financial Systems John Tawresey, S.E., F.TMS, F.SEI, Chief Financial Officer, KPFF Consulting Engineers Awards Banquet Reception Awards Banquet

Track B

Track B 6:00-7:00 7:00-10:00

SATURDAY, OCTOBER 14 8:00-9:00 9:00-12:00

Breakfast Annual Business Meeting

All Attendees Welcome Open to All Attendees

STRUCTURE magazine

August 2017

REVITALIZATION OF THE HANCOCK OBSERVATORY

By John Peronto, S.E., P.E., SECB, LEED AP and Christian DeFazio, P.E., LEED AP

n early 2013, Thornton Tomasetti (TT) partnered with colleagues at Montparnasse 56 (M56), who had recently purchased the 94 th-floor observatory in Chicago’s iconic John Hancock Tower, with a plan to modernize and revitalize the experience for its visitors. The M56 plan involved gutting and modernizing the interior space and installing a unique attraction that would add an adventure element experience for guests. The concept of “tilting” patrons outside the footprint of the tower was pitched by M56 as a way to provide a one-of-a-kind thrill, taking full advantage of the Hancock Tower’s height and spectacular views of Chicago.

Key Challenges Designing and constructing a fixed-tilted exterior curtain wall is no easy task, so taking that concept to the next level and developing an operable exterior wall with the ability to safely hold observatory patrons was a complex challenge. A steel-framed operable wall skeleton was developed to provide a robust and durable system that would be capable of operation 7 days a week. A steel frame provides excellent fatigue resistance and element ductility, as well as a clear load path. Integrated into the steel frame were structural glass components. The powered actuation system was also a direct part of the structure’s load path, so full-scale static load proof testing was done on the actuators to ensure their published load carrying capabilities. Ergonomics and patron experience required evaluation to test the concepts of thrill and comfort. For this challenge, TT fabricated a fullscale mockup of a single bay of the Tilt. This mockup was utilized by surveying the experiences of both a random sampling of TT and M56 staff to evaluate the comfort of the geometry, vertical hand railing, tilt angle, tilt speed, and tilt motion profiles.

HANCOCK’S

TILT STRUCTURE magazine

August 2017

Hancock’s tilt.

The final and very important challenge of maintaining the integrity of the world-famous architecture was also addressed by designing the Tilt structure’s geometry to mimic the existing exterior wall expression.

Wind Tunnel Testing Program

Mechanism and Components The Tilt system is a mechanized steel and glass structure that is comprised of three main components: • 3-Dimensional Steel L-Frame • Rigid Steel Platform at the Base • Overhead Actuation System The 3-D steel frame structure of the Tilt is 27 feet wide and 7 feet tall and can hold eight patrons at a time, one in each module. The geometry of this frame fits in one complete bay of the Hancock Tower and can rotate 30 degrees outward from the face of the tower’s exterior. A 30-degree angle was determined to be a point where the majority of patrons would have their center of gravity outside the exterior face of the tower while maintaining a reasonable clear height for patron modules, as this height is controlled by rotational clearance of the L-frame and the existing structure of the building. Rotational joints are located at three points along the base of the L-frame and are comprised of PTFE spherical bearings with custom machined AISI 4140 quenched and tempered hollow sleeve bolts, each containing an internal ASTM A320 L7 high-strength bolt for redundancy. These three locations serve as the rotational frame’s anchorage to the rigid steel platform at the base. W8 and W6 PTFE rotational joints and redundant pins. wide-flange beam members, STRUCTURE magazine

which were posted down to the existing W18 floor beams, comprise this rigid base platform. Hydraulic actuators, with 4-inch diameter bores and 2.5-inch diameter rods, are located at three locations overhead and are aligned in plan with the three lower L-Frame points of rotation. These actuators are capable of resisting forces over 40,000 pounds and are digitally controlled with the ability to be programmed for different motion profiles and push-pull speeds. A hydraulic pumping system was installed in the mechanical space of the tower core area, which serves to power the Tilt actuation system. Overhead end-stops comprised of steel plates and rubber buffers were mounted to the underside of the existing spandrel beam to prevent over rotation of the L-frame. These stops are engaged by steel armatures, which are welded to the top of the L-frame, contacting them if the frame were to rotate beyond 30 degrees. With the cyclical nature of the Tilt mechanism, a detailed fatigue analysis was conducted utilizing both AISC design approaches and ASME fatigue design approaches like those developed by Shigley. Special detailing and testing requirements for welded connections and their base metals were also developed to be in accordance with AISC’s fracture critical detailing requirements and AWS D1.1 requirements for “cyclically loaded structures.”

At a height of 1030 feet above grade, actual wind loads for the design of Tilt would be much greater than those required by the Chicago

Tilt mockup.

August 2017

Tilt system.

Tilt in use.

Building Code and are greatly influenced by the surrounding tall building topography. The Boundary Layer Wind Tunnel Laboratory at the University of Western Ontario was engaged to address this issue and conduct a High-Frequency Pressure Integration test (HFPI) at a scale of 1:200 of the top of the Hancock Tower, with the Tilt both open and closed. These loads were then utilized for the design of the Tilt structural steel frame, actuation system, and structural glass elements. Wind climate data was also utilized to better understand daily and weekly operational wind speeds, and corresponding wind pressures, that the Tilt would experience regularly.

Structural Glass The glass elements of the Tilt are assemblies of 3⁄8-inch thick fullytempered glass panels with DuPont SentryGlas laminate inner layers. The front elements are comprised of three glass panels and two laminate inner layers, and the side and overhead elements are comprised of two glass panels and one laminate inner layer. The design of these assemblies was based on the results of the wind tunnel test wind pressures, and considering the glass panel assembly as a “Glass Walkway” in accordance with ASTM E2751-11. All panels are continuously supported along their edges and were analyzed in both SJ MEPLA and ABAQUS to evaluate their performance. The finite element analyses indicated that only two 3⁄8-inch thick glass panels with a single SentryGlas inner layer were required for the front main elements; however, the third layer was kept at these locations as a redundant layer for added safety.

connections and implemented by M56. Each quarter, component and member connections are inspected and maintained, as required, to ensure that the Tilt’s condition is in general conformance with the original design intent. All inspections conducted by M56 are performed in conformance with AISC, AWS, and ASTM requirements for cyclically loaded structures.

The Tilt Experience The Tilt system is an understandable, robust, and regularly maintained structural steel and glass mechanism that has been offering Chicagoans, and its visitors, a safe but unique and exhilarating experience in the much loved John Hancock Tower.▪

Inspection and Maintenance Program As the Tilt is a machine in addition to being a structure, a required regular Quarterly Inspection Program was developed for the steel

Actuation system and overhead end-stops.

John Peronto, S.E., P.E., SECB, LEED AP, is an Associate Principal with Thornton Tomasetti. John designed the mechanized Tilt structure, for which he is a Patent Inventor. He can be reached at JPeronto@ThorntonTomasetti.com. Christian DeFazio, P.E., LEED AP, is a Senior Project Engineer with Thornton Tomasetti and served as the Project Manager of Tilt through construction. He can be reached at CDeFazio@ ThorntonTomasetti.com.

Project Team Owner: Montparnasse 56 USA Structural Engineer: Thornton Tomasetti Contractor: Cupples

BLWTL HFPI test model.

STRUCTURE magazine

August 2017

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LONDON FINANCIAL DISTRICT’S

FIRST VERTICAL VILLAGE

Use of Innovative Software Helps Reduce Costs and Project Delivery Time By Katherine Flesh

et to be the United Kingdom’s second tallest building next to the Shard skyscraper, 22 Bishopsgate is a 62-story, 912foot (278-meter) glass-clad tower that will sit at the center of a cluster of high rises in London’s Financial District. PLP Architecture conceptually designed the building, featuring 120,000 square meters (nearly 1.3 million square feet) of office space, retail shops, fitness centers, educational facilities, restaurants, and an open viewing terrace and observatory, in a bid to create the city’s first vertical village. WSP Parsons Brinckerhoff (WSP) was retained to manage the structural modeling and design, as well as provide multi-discipline engineering services to ensure sustainability, achieve a BREEAM excellent rating, and be the first in London to adopt the WELL Building Standard promoting the health and well-being of the building’s 12,000 occupants. The £1.5 Billion (approximately $1.9 Billion US) project required that 22 Bishopsgate be built on the site of a previously unfinished building, the Pinnacle, where the foundation, basement, and partially constructed core (called the “stump”) of this structure remained. The new tower needed to incorporate the former Pinnacle’s foundation and three stories of basement structures. In addition to the site constraints amid several high-rise buildings, a tight timeline, and budget requirements, “The challenge was to marry the superstructure, which did not correspond to where the foundations were,” explained WSP structural engineer Diego Padilla Philipps. The project team used Bentley Systems’ RAM Structural System and RAM Concept to provide WSP an integrated BIM solution to structurally design an efficient building that would be larger than, and completely different from, the Pinnacle design.

Recycling the Foundation Working cooperatively with local structural specialists, WSP chose to demolish the seven-story Pinnacle stump and analyze the interaction between the new design and the existing basement and foundation structural elements to determine what could be salvaged. Said Philipps, “We used RAM Concept to analyze the complicated geometry and export the spring reactions for the piles from the geotechnical analysis, and tried to make them compatible and interpret how the foundation was going to work.” Since the core footprint of 22 Bishopsgate is larger than the Pinnacle, the team determined that if they added new raft and pile caps to adapt the existing supports to transfer the structure’s weight, they could establish the additional foundation capacity for the bigger building while still using 100 percent of the former Pinnacle’s foundation. Saving and reusing the existing foundation not only reduced costs but also minimized impact to the environment on this multi-use tower project.

Innovative Solutions Because the footprints for the two buildings did not match, the team decided that the basement was the best place for the substructure load transfer structures. Using RAM Concept, WSP STRUCTURE magazine

analyzed and modeled the three basement floors to determine how to build around and through them to optimize the transfers. On the north side of the structure, the project team designed three columns to support the 62 stories. WSP designed a raft to spread the loads for the three columns into the existing foundations. However, the raft could not support the loads, so the project team used A-frames to distribute the weight appropriately. Due to the waste management strategy implementation on the south side of the structure, the team could not use a vertical column going down to the foundation. WSP needed to incorporate an inclined column on this side of the structure, with high-strength cables to tie the column to the core. Similar to the basement transfers, the superstructure also required some elements to be transferred using inclined columns. However, while the basement’s inclined column was tied to the core, the superstructure did not lend itself to this type of support because the high-strength cables would interfere with the services running through the openings at these levels. To resist the lateral forces generated by an inclination spanning 50 stories high, WSP used RAM Structural System to analyze 22 Bishopsgate Tower. and design a horizontal transfer system where the “The technology allowed floor plates behaved horizontally. for an efficient building Having columns at different positions throughout design. We achieved 100 the superstructure, without corresponding foundapercent re-use of existing tions in the substructure, required WSP to design foundations, 50 percent concrete walls all the way around to transfer the re-use of the existing loads. The integrated software solution WSP used basement, and 30 percent resulted in an innovative design solution that salmore building space than vaged the existing basement structure. the previous scheme.” — Andrew Woodward, BIM Advancements Director, WSP Parsons Brinckerhoff To design the floors and determine the optimal shape of the overall structure, WSP linked “22 Bishopsgate is one of RAM Structural System with Fabsec and Revit. those rare projects that truly Stated Philipps, “At some point in the design of the project, it was requested that we transfer all showcases the ingenuity the elements to Fabsec... so we integrated RAM of the engineers to deal with Fabsec.” The team used RAM Structural with difficult site conditions System to analyze the steel frame for the floors and demanding program and exported all the elements to Fabsec for requirements to develop design. Linking the two technologies allowed a truly innovative solution. for the integrated design of the steel-plated floor Using innovative technology enabled WSP to consider over 50 alternate designs, and address complex 3D geometric irregularities and construction conditions to meet the demands of this amazing project.” — Raoul Karp, Vice President, Analytical Modeling Product Development, Bentley Systems New A frame. STRUCTURE magazine

August 2017

beams, and facilitated seamless collaboration and information mobility with the client to meet the project’s changing demands. Furthermore, the team conducted up to 70 iterations to achieve the required design. With each iteration taking one or two engineers a week to model, WSP used Revit integrated with RAM, through Bentley’s Integrated Structural Modeler, to produce drawings and models simultaneously. This integrated approach accelerated the structural design process, reducing engineering and modeling time from 70 to 43 weeks, a reduction of nearly 40 percent.

Interoperable Technology Drives Design Using Bentley’s interoperable applications for schematics through to construction design provided efficient and economical solutions within the tight time frame, as well as ensured strict compliance with European regulatory codes. The final design for 22 Bishopsgate was a structural steel frame that was 15 percent lighter than the Pinnacle design, with an efficient shape housing 30 percent more floor space and designed to achieve an excellent BREEAM rating and promote the health and wellbeing of its occupants.

Fast Facts • 22 Bishopsgate is set to be London Financial District’s tallest building and the city’s first vertical village designed to promote the health and well-being of its occupants. • WSP used RAM to design the structural system of the multi-use tower, incorporating existing structural elements from the previous Pinnacle building. • The final design was 15 percent lighter and 30 percent larger than the original Pinnacle design.▪ Katherine Flesh is the Director of Analytical Modeling that leads the marketing strategy and positioning for Bentley’s Bridge, Offshore, Pipe Stress, Site Optimization and Structural products. She can be reached at katherine.flesh@bentley.com.

Horizontal trusses to resist push and pull.

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erched on a bluff along the shore of Puget Sound, Howarth Park is a heavily wooded and frequently used public park in Everett, Washington. With its spectacular views of the Sound and small beach at the water’s edge, the park is very popular. However, like most of the eastern shore of Puget Sound north of Seattle, the actual beachfront is cut off from the uplands by the Burlington Northern Santa Fe (BNSF) railroad line. The public must cross a pedestrian bridge over the railroad tracks and descend down to the beach level on a wooden stair tower to access the beach.

The Existing Bridge The existing pedestrian bridge is a nine-foot tall, eight-foot wide, two-span steel box truss structure that spans 49 feet from the hillside abutment to its center steel support tower, and then 80 feet across the BNSF tracks. This bridge, built in 1987 to replace an earlier timber bridge, was constructed entirely of weathering steel tubular sections. It was designed and built by a large national bridge design-build firm and was constructed economically, with small, thin-walled hollow structural sections (HSS). Many of the HSS truss members were 1⁄8or 3⁄16-thick. It is likely that weathering steel was chosen for its natural weather protection and low maintenance attributes.

About the time that this bridge was built, weathering steel was very popular for bridges and other structures throughout the country. However, some issues were starting to come to light and, in 1989, the Federal Highway Administration (FHWA) published a Technical Advisory, Uncoated Weathering Steel in Structures, which presented guidelines for the proper use of weathering steel. This document outlines several situations in which weathering steel is not recommended. Unfortunately, several of these situations could exactly describe the Howarth Park pedestrian bridge. FHWA guidelines include: 1) weathering steel should not be used where the atmosphere is wet for long periods of time; 2), weathering steel should not be used in a marine environment; and 3) weathering steel should not be used where site conditions don’t allow rapid drying, or where detailing may cause trapping of water on the steel surface. All of these conditions exist at the site of this structure, located on a bluff overlooking the Puget Sound.

The Existing Conditions

The owner was concerned about the condition of the bridge, as some excessive corrosion of the truss members had been observed near the hillside abutment. That end of the bridge is shielded from the drying action of the wind by surrounding trees and vegetation as well as the abutment itself. KPFF was requested to perform an assessment of the integrity Weathering Steel of the existing bridge. It Weathering steel is often was decided that a survey referred to by the trade name of remaining steel thickof Cor-Ten, or Corten as ness should be conducted originally produced by the on representative members By Greg Schindler, S.E. and Sara Roberts, S.E. US Steel Corp. It is available throughout the structure. in various ASTM standards, Bridge walkway with new FRP decking. This was based on visual including A588 and A847 observation of the members (for pipe and tubes shapes), and has a special chemical makeup that and the knowledge that the original thickness of the steel members causes the surface to develop a protective oxide patina that can reduce was thin. Mayes Testing Engineers conducted ultrasonic testing of or eliminate the need for a protective coating. Initially, this patina the HSS section thicknesses of selected members of all parts of the develops similarly to corrosion of normal carbon steel. However, once bridge structure. the patina stabilizes, it forms a dense barrier between the base metal The primary members of the box truss – the chords, diagonals, and and the external elements. Some additional corrosion continues over cross beams – all were found to have minimal loss of section. The the life of the structure but at a very slow rate. Thus, the patina protects protective patina seemed to be performing as intended. The walkthe steel from the atmosphere. The successful use of weathering steel ing surface of the bridge consisted of 3x12 timbers laid across three depends on several factors, but key among them is one crucial design HSS 4x3x1⁄8-inch longitudinal stringers, which in turn rested on HSS concept – the steel must be allowed to dry fully between wettings. If 5x3x3⁄16 cross beams at the truss bottom chord panel points. When the steel is used in conditions that cause it to stay wet for long periods some of the timbers were removed to test the HSS stringer members, of time, the oxidation process continues beyond the protective patina it was discovered that many had corroded so badly that large holes stage, and detrimental corrosion will develop. were present on the top faces. This was the result of a design detail STRUCTURE magazine

August 2017

Bridge during repair.

New FRP deck framing.

that allowed the wood members to prohibit drying of the steel surface. Also, the timbers were bolted to the stringers with bolts tapped into the steel tubes. This allowed water to make its way into the tubes, corroding them from the inside. In addition, there was a lot of sand trapped in the joints between the timber walking surface members. The foot traffic from the beach delivered a continuous supply of chloride-laden beach sand to the steel surface. As a result of this discovery, the bridge was immediately closed to the public and a design commenced to replace the degraded members.

Several types of decking were investigated as options to replace the timbers, and it was determined that Fiberglass Reinforced Plastic (FRP) T-bar pultruded grating would provide the best alternative as it is weather resistant, non-corroding, and lightweight. The open cross-section allows unrestricted air flow to the steel truss members. Initially, the repair design intended to replace the corroded stringers with new weathering steel HSS sections. During discussions with the FRP grating supplier, Fibergrate Composite Structures, it became apparent that a better long-term solution would be to use FRP structural members for the stringers. The three HSS 4x3 deck stringers were replaced with four stringers of 6-inch by 3⁄8-inch double FRP C-shapes, also provided by Fibergrate. New weathering steel tabs were

welded to the tops of the existing cross beams and the FRP C’s were bolted to these. The only members of the existing primary steel box truss that were replaced with new weathering steel were a few lower chord diagonals and cross beams near the abutment end of the pedestrian bridge. These members, as well as strategic portions of the existing steel structure where there was a possibility of continuous wet conditions, were coated with a high-performance paint system. In keeping with current common practice, the overall approach was to paint weathering steel in portions of the bridge where excessive moisture or inadequate air flow was likely. The chosen FRP decking has a T section with small spaces at the walking surface. This shape is often used near pools and other places where people walk barefoot. It was chosen for the Howarth Park project to minimize the possibility of pedestrians dropping small items through the cracks onto the active railroad lines below. Also, to minimize the buildup of sand on the remaining steel cross beams and diagonals below the deck, flat sheets of ¼-inch FRP were installed above those members as sloped “sand shields” to shed the sand that falls through the grating. Another benefit of using FRP members to replace existing members is that FRP is lightweight, an important factor for an existing structure with little reserve capacity. The repair approach decreased the weight imposed on the structure, as well as the seismic mass.

View from below – before.

View from below – after.

Repair Design

STRUCTURE magazine

continued on page 47

August 2017

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Design that Addresses Construction Constraints An additional consideration in choosing light weight FRP members to replace existing ones is that the Howarth Park pedestrian bridge is in a remote location, with limited access. The remote site meant that the contractor, Forma Construction, was required to hand-carry all construction materials and equipment to the site. Very little field welding was required in the new design, and the FRP members were connected with stainless Typical corrosion in steel steel bolts or self-tapping screws. The stringers. sand shields were connected with stainless steel gauge metal clips normally used for wood construction. The entire project was accomplished with hand tools. The FRP supplier produced shop drawings for the members, similar to steel fabrication drawings. Once construction started, the process went smoothly. The biggest challenge on the project turned out to be the lengthy process of getting approvals from the railroad to work over a highly trafficked, active railway.

Completed project.

Conclusion Over the course of its 30 years, a majority of the Howarth Park pedestrian bridge weathering steel members performed as intended with regard to corrosion, despite being located in a marine environment. Only where detailing or natural shielding of the bridge prevented adequate drying of the steel did the steel corrosion continue to a dangerous state. With weathering steel, proper design and detailing to allow air circulation and thus drying cycles is essential. The choice to replace some weathering steel members with FRP members allowed for efficient design and construction. Typically, FRP is used in caustic environments such as chemical plants or proximity to salt water, but the use of FRP structural members for this pedestrian KNOW FRP. bridge repair enabled the work to be completed effi ciently with corro∙ Fiberglass Reinforced Plastic sion-resistant materials. The bridge ∙ Corrosion resistant is now re-opened to the ∙ Lightweight public and will provide many years of additional ∙ Low maintenance service.▪

Project Team Owner: City of Everett Parks and Recreation Structural Engineer: KPFF Consulting Engineers, Seattle, WA Testing Agency: Mayes Testing Engineers, Inc., a Terracon Company, Lynnwood, WA Contractor: Forma Construction, Olympia and Seattle, WA FRP Structural Sections: Fibergrate Composite Structures

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Greg Schindler, S.E., is an Associate at KPFF, Seattle. He is also a Past President of NCSEA and is a member of the STRUCTURE magazine Editorial Board. Greg can be contacted at greg.schindler@kpff.com.

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Historic structures significant structures of the past

Ross Island Bridge By Frank Griggs, Jr., Dist. M.ASCE, D.Eng., P.E., P.L.S.

Dr. Frank Griggs, Jr. specializes in the restoration of historic bridges, having restored many 19th Century cast and wrought iron bridges. He was formerly Director of Historic Bridge Programs for Clough, Harbour & Associates LLP in Albany, NY, and is now an Independent Consulting Engineer. Dr. Griggs can be reached at fgriggsjr@verizon.net.

ustav Lindenthal, a leading proponent of continuous bridges, finished his Sciotoville Bridge (STRUCTURE, May 2017) in August 1917. In late 1922, a call went out to the largest and best-known engineers of the country to design three bridges (the Burnside, Ross Island, and Sellwood) across the Willamette River in Portland, Oregon. A group consisting of Ira Hedrick and Robert Kremers (Kremers was the local connection and had previously worked as an Engineer for the City) was awarded the contract to design the three bridges. Hedrick had been in partnership with J. A. Ross Island Bridge. Courtesy of HAER. L. Waddell up to 1907 when he went on his own. When announced, the local newspaper in the Engineering News-Record, to which the wrote, under the headline Good Team to Build Strong & McNaughton Trust Co. had called Bridges, “By awarding the contract for engineer- my attention in their telegrams, I thought the ing on the Burnside and Ross Island bridges to matter important enough to assist you with any Hedrick and Kremers, the county commissioners professional advice I could give. The telegrams have lived up to their pledge to cover all that needs to be said at present in a employ a local engineer and business way.” at the same time have secured Hedrick’s design for the Ross Island Bridge was the services of an engineer of for “six reinforced concrete arches of 267 feet span wide experience with large rising to 135 feet above the river, joined on each structures of the kind proposed side by approaches of the girder and post type and of high reputation.” and with a total length of 4,122 feet, including By early 1924, Hedrick and Kremers had a fill 400 feet long.” designed concrete bridges for Ross Island and Lindenthal’s report came out on July 7, 1924, Burnside, and planned to reuse parts of the exist- with the Oregonian headline, Dr. G. Lindenthal ing Burnside Bridge to build the Sellwood Bridge. to Build Bridges, County Board Ousts Hedrick Bids were called for in March for the Ross Island. and Kremers from Job, Change in plans urged, Three bids were received with the Pacific Bridge Revised Structures for Sellwood and Ross Island Are Company coming in low at $414,000, well below Considered by Engineer. The paper then printed the second bidder, the Missouri Valley Bridge excerpts from Lindenthal’s report, calling him & Company. On the Ross Island Bridge, only “the world’s greatest engineer.” After indicating one bid came within the estimate. Hedrick and that Hedrick and Kremers would receive another Kremers recommended that the bids should be $25,000 for their work, it reported Lindenthal rejected and the work re-advertised. had been awarded a contract for a major redesign The Commission voted to accept the tainted of the Ross Island Bridge as well as the other two bids, which resulted in political turmoil. A bridges. His contract was for $119,000 for the recall election was held, and three members three designs and supervision of construction, and of the County Commission were removed was signed on July 11, 1924. On November 4, from office for gross irregularities in the bid- 1924, the County voters approved an additional ding on the bridge. A new board was elected. $500,000 for the bridges. This new Board had little trust in the team of In his report, Lindenthal told the board that Hedrick and Kremers and began looking for an there were four conditions to ensure a bridge was engineer of national reputation to advise them appropriate and adequate. They were “Location, on the designs of the bridges. They contacted Traffic Capacity, Structural Character, and, for Lindenthal, who initially did not want to get a city bridge, the Architectural Features, in the involved in what was becoming a political free order named.” Lindenthal stated, regarding the for all. He eventually relented and wrote, “Just Ross Island Bridge, “I recommend that the plans for the record, I beg to enclose copies of tele- for this bridge be entirely redesigned for the folgrams received and sent in the matter of the lowing reasons: proposed examination of plans for the three 1) It is doubtful whether the bridge on the bridges named therein. I confess that I first present plans could be built within the felt disinclined to undertake this long trip in amount appropriated for it. the midst of pressing engagements, but after 2) The borings in the river bottom indicate reading the account of your bridge situation an irregular stratification of sand and

48 August 2017

gravel which, in my judgment, does not offer sufficient security against the uneven settlement of the pier foundations proposed to be sunk by the air process. A slight settlement which would not endanger a low structure may be enough to seriously endanger high piers and high concrete arches which require a greater degree of safety for their foundation. No chances should be taken with the foundations for high concrete arches. 3) The axis of the bridge should, if possible, be on a straight line and for better appearance, the hump in the roadway over the river hold be taken out. For that purpose, the clear height over the channel should be reduced 135 feet to about 80 feet… I am informed that an act of Congress authorizing such lowered height will be necessary, but that it can be obtained without much delay when desired by the people.” A notice to contractors on the completely redesigned Ross Island Bridge went out on April 25, 1925, and bids were due back by May 18, 1925.

The central span was 535 feet with the two 321-foot flanking spans on each side. Simple girder deck spans formed the long approach viaducts on each side of the river. The central three spans were continuous over four supports. The outer flanking spans were simply supported trusses, 321 feet long. The total length of the bridge was 3,649 feet with a deck width of 43 feet. The fixed bearing was on the right side of the central span with the others being expansion bearings. The bridge was on a vertical curve with the grade on the approach spans on each side being 2.5%. The four flanking spans were built on falsework. Each half of the long center span was built out as a cantilever and connected at the center by a pin. Under dead and full live load, they acted as two determinate cantilevers, similar to the Queensboro Bridge. In fact, some commentators called this an inverted Queensboro as it also didn’t have a suspended span. Under unbalanced live load, the bridge acted as a fully continuous bridge, and the member loading was determined using elastic methods. The steel was fabricated by the American Bridge Company and was erected by Booth and

Pomeroy, Inc. It opened December 1, 1926, at the cost of just less than $2,000,000. It was completely rehabbed in 2002 at the cost of $12,500,000. A cable-stayed bridge just upstream, the Tilikum Bridge, was opened in 2015. Lindenthal’s Sellwood bridge, built at the same time, was a continuous bridge over four spans. The two interior spans were 300 feet long, and the flanking spans were 246 feet long. It carried two lanes plus a sidewalk over the Willamette River. Its cost was $541,000. It was replaced in 2016. These two bridges, plus the Burnside Bridge (a bascule span) were the last bridges Lindenthal worked on, even though he continued to promote his Hudson River Bridge until his death in 1935. In the July 1932 issue of Civil Engineering Magazine, Lindenthal wrote an article entitled, Bridges with Continuous Girders, Reviewing Half a Century of Experience in American Practice. In it, he gave a summary of his efforts over the years to promote continuous truss bridges. He was 82 years old at that time and still contributing to the literature of bridge building. Lindenthal was rightfully called the Dean of American Bridge Builders.▪

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STRUCTURE magazine

August 2017

4/28/17 9:21 AM

Professional issues

issues affecting the structural engineering profession

Compensation, Overtime, and the Gender Pay Gap Structural Engineering Engagement and Equity (SE3) Committee Survey Results By Angie Sommer, S.E. and Nick Sherrow-Groves, P.E.

n Part 1 of this series (STRUCTURE, April 2017), the results of the 2016 SE3 Study focused on overall career satisfaction, development, and advancement. This article highlights survey findings regarding compensation, overtime, and the gender pay gap. A full report that includes findings on work-life balance, flexibility benefits, and caregiving can be found at SE3project.org/full-report.

Compensation Respondents overall indicated that pay and compensation were the top reasons that they had considered leaving the structural engineering profession or leading reasons why they had left the profession. When asked to rate their satisfaction with pay/compensation, 20% of the respondents reported being “unsatisfied” or “very unsatisfied.” The average income of all respondents currently practicing structural engineering is $106,800 per year. Pay data were received from 1,955 respondents. Because nearly half of the respondents were from California, where the cost of living is higher than in most other parts of the country, income data for this group is noted separately. The average income of all of the respondents from California is $117,600 per year. As a snapshot of income during the careers of respondents, the average income of a structural engineer with five years of experience is $78,900 per year (in California, the average is $89,000). The average income of a structural engineer with 15 years of experience is $110,600 per year (in California, the average is $118,700). Pay data of the survey respondents is also shown in Figures 1 and 2. For this survey, “income” is defined as gross annual income, including bonuses. Note that the data includes part-time employees who work fewer than 40 hours per week, which accounted for 110 respondents (6%). Considering only full-time employees residing in metropolitan cities, respondents in California reported income 21% higher than those living outside California. However, when income is normalized to cost of living data (as reported by the Council for Community and Economic Research, http://coli.org), respondents in California make 7% less than those outside California.

Figure 1. Average income vs. years of experience (all respondents).

For comparison, nationwide data, collected by the U.S. Bureau of Labor Statistics (BLS) in 2015, show that the mean annual wage for a civil engineer in the “architecture, engineering, and related services” category was $88,820 (in California, the mean annual wage was $100,980) (BLS, 2016b). The BLS calculates “annual wages” by multiplying the hourly mean wage by a “year-round, full-time” figure of 2,080 hours. For those occupations where there is not an hourly wage published, the annual wage is directly calculated from the reported survey data. The BLS does not report information on structural engineers specifically. In comparison with the average income of all practicing survey respondents to the “mean annual wages” reported by the BLS, SE3 survey respondents reported approximately 20% higher income than the BLS data, some of which is likely due to the inclusion of bonuses in the SE3 survey responses. Additionally, SE3 data may be more highly weighted by California responses than BLS data. A 2013 Structural Engineering Institute (SEI) survey reported the average salary of respondents to be $85,500 per year, based on 728 responses from throughout the United States (Leong et al., 2013). This average salary also excluded bonuses and is therefore noted to be a similar finding to BLS data, especially considering inflation.

Figure 3. Compensation for overtime.

Figure 2. Average income by position title.

STRUCTURE magazine

August 2017

Gender Pay Gap

Figure 4. Income vs. years of experience (full-time only).

A significant pay gap was reported between genders. Out of 1,401 men and 553 women who provided pay data, women reported making $27,500 per year less than men, on average, which amounts to women making approximately 75% of the salaries of their male colleagues. When controlling for years of experience and full-time employment, men still reported making significantly more money than women. For example, for full-time employees, men with 14-17 years of experience made $7,900 per year more than women, and men with 18-20 years of experience made $41,200 per year more than women, as shown in Figure 4. When broken down by position, a similar trend persisted, though the gender pay gap widened significantly starting at the senior engineer/project manager level. A $9,000 pay gap was present for senior engineers/project managers, a $12,000 pay gap was present for associates/shareholders, and a $52,000 pay gap was present for principals/ owners, as shown in Figure 5. Further analyses were performed based on a variety of factors (location, position, full-time employment, firm size, with/without children), and in all cases, the gender pay gap was found to exist. Additionally, because nearly half of respondents were from California, the gender pay gap within this state was also reviewed. The pay gap was found to be less pronounced in California as compared to the overall data set, but it was still present. The 2013 SEI survey found that the average annual salary for women was 78% of that reported by men. Similar to the SE3 data, the pay gap widened as the number of years of experience increased.▪ Angie Sommer is an associate at ZFA Structural Engineers in San Francisco, California. She is the primary author of the 2016 SEAONC SE3 Survey Report and is the 2016-17 co-chair of the SEAONC SE3 Committee. She can be reached at angies@zfa.com.

Figure 5. Average income by title and gender.

Hours Worked and Overtime

Nick Sherrow-Groves is a senior engineer at the San Francisco office of Employees who work extra hours are more likely to consider leaving Arup. He is the 2016-17 co-chair of the SEAONC SE3 Committee the profession. For each additional hour worked per week over 40, the and can be reached at nick.sherrow-groves@arup.com. odds of an employee considering leaving the profession were found to be 4% higher. This points to a tendency for people to “burn out” when their workload is consistently over 40 hours per week. Additionally, satisfaction with pay and benefits was found to decrease as the number of hours worked each week increased. • Full line of high-strength, corrosion-resistant fasteners Conversely, being compensated for over• Ideal for secondary steel connections and in-plant equipment time is correlated with significantly higher • Easy to install or adjust on site satisfaction with pay/compensation. Of • Will not weaken existing steel or harm protective coatings the 1,629 respondents who responded • Guaranteed Safe Working Loads to this question, 46% indicated that they receive pay for overtime and compensatory time for hours worked over 40 in one week, as shown in Figure 3. This group was 20% more likely to report being “satisfied” or “very satisfied” with their pay/ BoxBolt® for HSS blind FastFit universal kits compensation than those who are not connections. ICC-ES for faster, easier steel compensated for overtime. certified. connections. Interestingly, those who reported being compensated for overtime also reported working an average of two fewer hours per week than those who are not paid for For a catalog and pricing, call toll-free 1-888-724-2323 overtime. Reasons for this were beyond A K E E S A F E T Y C O M PA N Y or visit www.LNAsolutions.com/BC-2 the scope of the survey.

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STRUCTURE magazine

InSIghtS new trends, new techniques and current industry issues

here are three aspects of field Quality Assurance for construction projects: Inspection by the Building Official, Special Inspection by the owner’s special inspection agency, and Structural Observation performed by the Engineer of Record (EOR) or his/her designee. All three of these functions are important and non-redundant. As the scale and complexity of a project increases, the more important it becomes that all three functions are provided. By definition, the Building Official is charged with the administration and enforcement of the building code. As part of their responsibility, they will make various inspections related to foundations, floor slabs, and framing (usually wood) in addition to other non-structural inspections as defined in Chapter 1 Section 110 of the International Building Code (IBC). The Building Official’s inspections are not for the purpose of counting reinforcing bars or confirming weld sizes, but rather are more concerned about the overall compliance of the work with, and as required by, the Building Code. Many Building Officials delegate or rely on other professionals (the EOR) and inspectors (the Special Inspector) to provide confirmation that the completed structure is in compliance with the building code and approved construction drawings. Special Inspection is a detailed inspection of individual members, components, and framing systems assembled by the contractor using the approved construction drawings as a reference. The Special Inspector is a qualified person who has knowledge and expertise that will ensure that the constructed items conform to the construction drawings. The Special Inspector is limited to interpreting the drawings and is testing and inspecting only those items specified in the Statement of Special Inspections. Further, the Special Inspector provides detailed verification of the quality, quantity, and placement of critical structural elements such as structural materials, fasteners, reinforcement, welds, and more. Structural Observation is defined in the IBC as the visual observation of the structural system by a Registered Design Professional (the EOR) for general conformance with the construction documents. More importantly, this is the opportunity for the EOR to determine

Structural Observation Confirming Your Intentions and the Interpretation by Others By Greg Robinson, S.E., P.E., SECB and Greg Schindler, P.E., S.E.

Greg Robinson is a Principal with LBYD, Inc. in Birmingham, AL. He is the Chair of the NCSEA Code Advisory Subcommittee on Special Inspections and Quality Assurance and is a Past President of NCSEA. Greg can be contacted at grobinson@lbyd.com. Greg Schindler is an Associate with KPFF Consulting Engineers in Seattle, WA. He is a member of the NCSEA Code Advisory Subcommittee on Special Inspections and Quality Assurance, is also a Past President of NCSEA, and serves on the Editorial Board of STRUCTURE magazine. Greg can be contacted at greg.schindler@kpff.com.

52 August 2017

the conformance of the construction with the structural design intent, bridging the gap left between the Building Official’s responsibility for conformance with the building code and the Special Inspectors more focused attention on the elements of the structure. The structural observer would be looking for continuity of load path, conformance to structural details, appropriate usage of typical details, and arrangement of reinforcing, anchors, and connections, all with the benefit of the understanding of the engineering behind the design. The requirement for situational structural observation has been in the IBC from its inception, as well as in the previous model building codes. Section 1704.6 of the 2015 IBC code requires a registered design professional, typically the EOR or an appropriate designee, to perform structural observation only in high wind or seismic loading situations. Structural observation is not mandated by code for any other conditions regardless of structure size, height, use, or occupancy. For example, a high-rise building in New York City does not require structural observation, while it would be required for a two-story office building in San Francisco. Many engineers believe that structural observation is warranted in many structures beyond those in high seismic or wind situations. Having the engineer who is familiar with the structural design look at the construction, in addition to the special inspectors, is beneficial for any structure, especially large, tall, high occupancy, or other important facilities. Many reputable engineering firms realize that it is in their best interest, as well as the owner’s, to have a larger presence at the construction site. They promote the observation of the structure by their staff, regardless of the code requirements. The engineer who designed the structure can often find issues that may not be recognized by the contractor or the inspectors. In 2016, the Structural Engineers Association of Northern California published Guidelines for

Special Inspection and Structural Observation in Accordance with the 2013 California Building Code. This document provides an excellent overview of both inspection and observation, and includes the following explanation: Structural Observation focuses on the building’s structural system, rather than on the use of particular materials or processes. It is typically performed by the engineer-of-record, is non-continuous, and uses visual means only to determine if the construction is in general conformance with the intent of the plans and specifications. In contrast, special inspections are comprehensive, systematic, and detailed, with a focus on materials, workmanship, and processes. During the current code update cycle for the 2018 IBC, the Special Inspection and Quality Assurance Subcommittee of the Code Advisory Committee of NCSEA proposed a change to the Structural Observation requirements that would expand the types of projects that would require Structural Observation. The anticipated IBC 2018 code language is as follows: 1704.6.1 Structural observations for structures. Structural observations shall be provided for those structures where one or more the following conditions exist:

1) The structure is classified as Risk Category IV. 2) The structure is a high-rise building. 3) When so designated by the registered design professional responsible for the structural design. 4) When such observation is specifically required by the building official. 1704.6.2 Structural observations for seismic resistance. Structural observations shall be provided for those structures assigned to Seismic Design Category D, E, or F where one or more of the following conditions exist: 1) The structure is classified as Risk Category III. 2) The structure is assigned to Seismic Design Category E, is classified as Risk Category I or II, and is greater than two stories above the grade plane. 1704.6.3 Structural observations for wind resistance. Structural observations shall be provided for those structures sited where Vult is 130 mph or greater and where the structure is classified as Risk Category III. The key differences are as follows: • Structural Observation was only required for high wind or seismic areas. Now all high-rise and Risk Category IV structures are required

2017

to have Structural Observations anywhere in the country. Highrise buildings are defined as those buildings taller than 75 feet. • Both the EOR and Building Official have the option to specify when Structural Observations are required. The last point is significant. Previously, the EOR had limited control over when Structural Observations were required on a project. NCSEA worked with several Building Officials at the recent code hearings. Those individuals in the discussion agreed that the option for either the EOR or Building Official to specify Structural Observation was a good and necessary code provision. The structural panel at the code hearing agreed. Structural Observations bridge an important gap between what the Building Official and the Special Inspector review. Even the best drawings can be misinterpreted and may not convey the importance or critical nature of a portion of the design. Structural Observations provide an opportunity for the EOR to confirm their design intentions and proper interpretations of the drawings. The EOR, using their best judgment, can now specify when to require Structural Observations.▪

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STRUCTURE magazine

August 2017

Structural licenSure

issues related to the regulation of structural engineering practice

Second Order Effects and Structural Licensure By Timothy M. Gilbert, P.E., S.E. SECB

he NCSEA Structural Licensure Committee, like many of us, occasionally “takes stock” to reflect and make resolutions for the future. Over the past few years, the Committee has advocated for structural licensure in various ways: articles, newsletters, member surveys, presentations, and communication with other organizations. Though structural licensure has yet to be established in many jurisdictions, NCSEA continues to believe its implementation would offer better protection to the public and ultimately save lives. These reflections led to the conclusion that the second order effects of the Committee’s actions are worth the investment of our time and, in the coming years, continual support of the mission: The Licensing Committee works with the Member Organizations to influence states to adopt consistent licensing laws and rules in the interest of public safety, especially relating to licensure of structural engineers. Second-order effects are a typical consideration in structural analysis. It recognizes that, as structures deflect under loads, deformations can cause the initial loads to induce further stresses into the structure. These induced stresses are the second order forces and moments arising from the structure’s initial response to first order loads. In a stable structure, the second order effects are self-limiting – the second order deflections are small enough that they do not continue to amplify. Unstable structures exhibit a different behavior; second order deflections are large enough to induce even larger forces, leading to greater and greater deflections and ultimately to collapse. Second order effects are not merely a structural concern. These effects arise in a wide variety of endeavors. In a simple example, a decision to save money for vacation has first order effects leading to less disposable income. Having less disposable income, a person or family might choose to go for walks in the evening rather than out to dinner, leading to the second order effect of losing weight. Similarly, legislation can also have second-order effects that stretch beyond the law’s strict wording. It is commonly noted by legislators and economists

that tax changes can influence behavior, not merely affect revenue. If structural licensure provisions are passed in a jurisdiction, the effects will extend beyond limiting who may perform structural engineering – and this is why the NCSEA Structural Licensure Committee supports its implementation. Saving lives is the most significant second order effect of structural licensure. By establishing a standard specifically developed for structural engineering, the practice, as related to significant structures, would be limited to individuals who have demonstrated the requisite qualifications. Increasing complexity of both current designs and building codes combine to compound their effects, yielding circumstances where the testing protocols to obtain an engineering license do not align with structural engineering practice as applied to complex design. Partly in recognition of this discrepancy, NCEES created the 16-hour Structural Exam. In the instances where a structural design has the potential for significant impact on the public, the Committee favors a requirement that the engineer has demonstrated sufficient proficiency in structural engineering. Structural licensure would provide a means for engineers to demonstrate proficiency in the subject to the public. One might ask what evidence supports this assertion. In a recent incident, one worker was killed and 20 were injured when a Jacksonville, Florida parking garage collapsed while it was under construction. Investigations revealed that the design was inadequate. Some columns did not have sufficient strength to support the dead weight of the structure alone, without any live or environmental loads. OSHA has a thorough discussion of the investigation available for review (http://goo.gl/IvNUoI). The Florida Board of Professional Engineers determined that the structural engineer of record bears a significant responsibility for the accident (http://goo.gl/iIv07j). Had structural licensure been established there, it is much less likely that this tragedy would have taken place. Saving lives is a second order effect with positive results. Some opponents of

STRUCTURE magazine

August 2017

structural licensure are concerned with other potential second order effects. The potential for increased fees, a possible limited availability of service providers, and a reduction in the number seeking to practice are sometimes cited as reasons for opposing structural licensure. These conceptual second order effects center around the idea that structural licensure is an obstruction to business practices. This contention parallels debate held decades ago about the establishment of licensure for engineers. Research has shown that the passage of licensure for engineers did not result in these adverse effects (http://goo.gl/rNzgL9). The NCSEA Structural Licensure Committee contends that, like engineering licensure, structural licensure would not have these adverse effects. Those who practice capably and responsibly are likely to have few concerns with attaining structural licensure and would contribute to a competitive marketplace. To further allay concerns, the Committee advocates for a robust “grandfathering” provision that would allow currently qualified structural engineers to continue practicing while providing a path forward for younger engineers based on the NCEES 16 hour Structural Exam. The rationale for such a transition mechanism has been well reviewed in past editions of STRUCTURE magazine. As with structural analysis, a careful consideration of second order effects is prudent in many endeavors. In the case of structural licensure, we believe that the lives saved by second order effects are why it deserves the profession’s support as well.▪ Timothy M. Gilbert is a Project Specialist for TimkenSteel in Canton, OH. He is also the current Past-President for SEAoO and chairs its Structural Licensure Committee. He may be reached at tgilbert.pe@gmail.com. This is an update to an article, by the same author, that originally appeared in the February 2015 SEAoO Newsletter.

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LegaL PersPectives

discussion of legal issues of interest to structural engineers

A Further Look at Consent to Assignment Agreements By Gail S. Kelley, P.E., Esq.

onsent to Assignment for engineers, also referred to as an Acknowledgement and Consent or a “will-serve letter,” is usually drafted by the bank providing construction financing for a project. A typical consent requires the engineer to agree that the bank can exercise the rights it has acquired through an assignment from the owner; among these rights will be the right to assume the design agreement if the owner defaults on the construction loan. Prior articles (June and July 2017, STRUCTURE magazine) looked at key concerns with respect to consent agreements, specifically whether the lender is required to pay outstanding amounts due to the engineer, whether the lender has the right to use the plans and specifications if it does not assume the design agreement, and what information or certifications the lender is entitled to. This article looks at some of the other provisions commonly found in these agreements.

The Assignment When the owner is a public or quasi-public entity such as a city or a water district, the document that the engineer is asked to sign may include the actual assignment. In such cases, the form may start with an introductory paragraph such as: THIS ASSIGNMENT OF ENGINEER’S CONTRACT AND ENGINEER’S AGREEMENT AND CONSENT TO ASSIGNMENT (this “Assignment”) is made as of _____ by and between _____ (“Borrower”) and _____ (“Engineer”) for the benefit of _____ (“Lender”). In such cases, the document creates obligations for both the owner (the borrower) and the engineer, so both parties must sign it. Typically, however, if the owner is a private entity, the engineer will not be provided with the assignment; it is simply asked to acknowledge that the assignment must occur before the loan is closed. In most cases, the lender will require that the contractor, the architect, and other key consultants also agree that their contracts can be assigned and may list all of the contracts to be assigned in a single document. The consent may then include wording such as: The undersigned, as Engineer under the agreement dated _____ (the “Agreement”) between _____ (“Borrower”) and the undersigned,

which is one of the contracts referred to in the Assignment of Agreements, Licenses, Permits and Contracts (the “Assignment”) between Borrower and _____ (“Lender”), hereby acknowledges and consents to the terms of the Assignment. If, as is usual, the engineer does not know the terms of the Assignment, it is not reasonable to expect the engineer to sign a document stating that it agrees to the terms. The engineer is agreeing to the assignment of the design agreement; the above provision should be edited as follows: hereby acknowledges and consents to assignment of the design agreement.

Collateral Assignment Often, the consent will state that the design agreement is being used as collateral for the loan. There may, for example, be a provision stating: As a condition to Lender making the Loan to Borrower, Lender has required that Borrower collaterally assign the Contract to Lender pursuant to the Assignment of Contracts made by Borrower for the benefit of Lender (the “Assignment”). The assignment may, in fact, be called a “Collateral Assignment.” This does not create an obligation on the engineer or affect the engineer’s rights, however. Even when the assignment is not specifically referred to as a Collateral Assignment, it is likely that the lender is considering the design agreement as collateral. Lenders generally want a security interest in all of the project assets as collateral for the financing; this includes not just the physical assets of the project but also the design agreements, construction contracts, supply agreements, and easements. The Assignment itself will generally contain wording such as: FOR VALUE RECEIVED, and as additional security for the Loan, Borrower hereby transfers, assigns and grants a security interest in favor of Lender, in all of the rights of Borrower in its contract with _____ (Engineer) dated _____.

Design Agreement Since each lender has its own form, an engineer is typically not asked to sign a Consent

STRUCTURE magazine

August 2017

to Assignment until the owner is arranging the construction loan; this may be weeks or even months after the design agreement was signed. However, some design agreements contain a simple, one-paragraph statement of consent, using language such as: Engineer agrees that if Developer defaults under the provisions of this Agreement, Engineer shall, if requested, continue to perform its obligations under this Agreement for Lender. Lender shall agree in writing to perform all obligations of Developer after the date Lender succeeds to Developer’s rights and obligations. As written, the above provision only requires the lender to pay the engineer for services provided after the lender assumes the agreement; the lender has no obligation to pay any outstanding amounts owed to the engineer. At a minimum, the above provision should be edited as follows: ...Lender shall agree in writing to perform all obligations of Developer including payment of all outstanding amounts due to Engineer. The language in AIA B101 can also be used as a guide. Before 1987, the AIA owner-architect agreements prohibited assignment of the agreement without the consent of the other party. However, the 1987 and subsequent versions of these agreements have included an exception for assignments to the lender, in recognition of the fact that such assignments are common. Section 10.3 of AIA B101-2017 states: ...Neither the Owner nor the Architect shall assign this Agreement without the written consent of the other, except that the Owner may assign this Agreement to a lender providing financing for the Project if the lender agrees to assume the Owner’s rights and obligations under this Agreement, including any payments due to the Architect by the Owner prior to the assignment. Thus, the owner can assign the agreement to its lender without obtaining the A/E’s consent, provided the lender assumes all of the owner’s obligations, including outstanding payments. If the lender requires the A/E to execute (sign) a consent agreement, §10.4 of B101 includes the further provision: If the Owner requests the Architect to execute consents reasonably required to facilitate assignment to a lender, the Architect shall execute all such consents that are consistent

with this Agreement, provided the proposed consent is submitted to the Architect for review at least 14 days prior to execution. Section 10.4 makes it clear that the A/E is not required to execute a consent that would require the A/E to do more than what is required under the design agreement.

Conclusion A Consent to Assignment will often state that the engineer’s consent is a condition to the loan. The typical wording is: Engineer acknowledges that Lender is relying on this Consent as a condition of extending the Loan. If the owner defaults on the loan, this statement could theoretically allow the lender

to argue that it has relied on the consent to its detriment, thus giving it rights against the engineer that it would not otherwise have. However, the language is standard in consent agreements and is generally considered to be just an acknowledgment that the engineer’s consent is a condition of the loan. In contrast, the engineer should not agree to provisions that suggest the consent is being signed as an inducement to the lender, as the word “induce” provides the lender a much stronger basis to argue that it has relied on the consent to its detriment. Provisions such as the following should be deleted: Engineer is executing this Consent of Engineer to induce Lender to advance funds under the Loan Agreement.

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

The consent is being signed as a courtesy to the engineer’s client, not as an inducement to the lender.▪ Disclaimer: The information in this article is for educational purposes only and is not legal advice. Readers should not act or refrain from acting based on this article without seeking appropriate legal or other professional advice as to their particular circumstances. Gail S. Kelley is a LEED AP as well as a professional engineer and licensed attorney in Maryland and the District of Columbia. She is the author of “Construction Law: An Introduction for Engineers, Architects, and Contractors,” published by Wiley & Sons. Ms. Kelley can be reached at Gail. Kelley. Esq@gmail.com.

sOFtWare gUiDe

ADAPT Corporation

Autodesk®, Inc.

Design Data

Phone: 650-218-0008 Email: florian@adaptsoft.com Web: www.adaptsoft.com Product: ADAPT-PTRC Description: An indispensable production tool for the fast and easy design of concrete slabs of any form, beams, and beam frames. Uses equivalent frame method to design post-tensioned or conventionally reinforced projects. Easily switch between PT and RC modes. Updated with ACI 318-14 / IBC 2015.

Phone: 844-262-9170 Web: www.autodesk.com Product: Autodesk Steel Connections for Revit® Description: Provides access to a variety of parametric steel connections, enabling connections to be modeled with a higher level of detail. Includes a built-in steel connection design engine based on U.S. and European codes. Take advantage of model-based collaboration to create better coordinated designs and documentation that extends to fabrication.

Phone: 402-441-4000 Email: sales@sds2.com Web: www.sds2.com Product: SDS/2 Concrete Description: The newest solution oﬀered by SDS/2 includes connection design to concrete walls, providing full design calculations. Automatically recognizes framing situations to determine the type of connection and embed plate conﬁguration to be used; the software also includes tools for automated placement of rebar in a 3D model.

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

Applied Science International, LLC Phone: 919-645-4090 Email: support@appliedscienceint.com Web: www.extremeloading.com Product: Extreme Loading for Structures Description: A new, advanced level of nonlinear dynamic structural analysis. Allows users to study structural failure from any number of actual or possible extreme events such as blast, seismic, and progressive collapse. Users can easily model structures composed of reinforced concrete, steel composite, and other structures with all as-built and as-damaged details.

CADRE Analytic Phone: 425-392-4309 Email: cadresales@cadreanalytic.com Web: www.cadreanalytic.com Product: CADRE Pro Description: Finite element structural analysis. Loading conditions include discrete, pressure, hydrostatic, seismic, and dynamic response. Features for presenting, displaying, plotting, and tabulating extreme loads and stresses across the structure and across multiple load cases simultaneously. Basic code checking for steel, wood, and aluminum. Free fully functioning evaluation version available.

Concrete Masonry Association of California & Nevada Phone: 916-722-1700 Email: info@cmacn.org Web: cmacn.org Product: CMD15 Design Tool for Masonry Description: Structural design of reinforced concrete and clay hollow unit masonry elements for design in accordance with provisions of Ch. 21 2010 through 2016 CBC or 2009 through 2015 IBC and 2008 through 2013 Building Code Requirements for Masonry Structures (TMS 402/ ACI 530/ASCE 5).

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Dlubal Software, Inc. Phone: 267-702-2815 Email: info-us@dlubal.com Web: www.dlubal.com Product: RFEM Description: Non-linear FEA complete with USA/ International Standards for steel, concrete, timber, CLT, glass, aluminum, and membrane/cable structures. Direct interfaces with Revit, Tekla, AutoCAD, MS Excel, and more. Incorporates seamless and bidirectional data exchange. Created by engineers for engineers, RFEM’s interface and modeling workﬂow are highly intuitive and easy to learn.

ENERCALC, Inc. Phone: 800-424-2252 Email: info@enercalc.com Web: https://enercalc.com Product: Structural Engineering Library (SEL) Description: SEL has been a useful tool for structural engineers and architects for 30+ years. Our new cloud-based system, ENERCALC SE, includes the same loads, forces, analysis, and design modules as the installed SEL software (no learning curve!) – plus retaining wall (“EARTH”) and ENERCALC 3D modules.

continued on next page

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

Hexagon PPM

RISA Technologies

Struware, LLC

Phone: 214-448-9462 Email: geoffrey.blumber@hexagon.com Web: www.coade.com/products/gtstrudl Product: GT STRUDL® Description: Intergraph’s structural analysis and design modeling software; a market leader in its field for nonlinear and linear dynamic and static analysis. A strategic database approach to all model data and analysis results. And fast, high-quality results.

Phone: 949-951-5815 Email: info@risa.com Web: www.risa.com Product: RISA-3D, RISAFloor ES, RISAFoundation Description: RISA offers everything you need for concrete design. For concrete floors, including beams and two way slabs, nothing beats RISAFloor ES for ease of use and versatility. The design of columns and shear walls with RISA-3D offers total flexibility. Integration between RISA-3D and RISAFloor ES provides a complete building design.

Phone: 904-302-6724 Email: email@struware.com Web: www.struware.com Product: Structural Engineering Software Description: Struware provides easy to use structural engineering software. So quick and easy, the software pays for itself the first time you use it. Programs include a wind, seismic, snow, dead & live loadings, CMU walls, tilt-up concrete walls, steel floor vibration, and concrete beams. Demos at website.

Simpson Strong-Tie®

Trimble

Phone: 800-925-5099 Email: web@strongtie.com Web: www.strongtie.com Product: Strong-Wall® Shearwall Selector Description: The Strong-Wall Shearwall Selector web app is designed to help Designers select the appropriate shearwall solution for a given application in accordance with the latest code requirements.

Phone: 770-426-5105 Email: kristine.plemmons@trimble.com Web: www.tekla.com Product: Tekla Structural Designer Description: Revolutionary! Gives engineers the power to analyze and design buildings efficiently and profitably. Fully automated and packed with 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, Tekla Structural Designer can transform your business.

IES, Inc. Phone: 800-707-0816 Email: info@iesweb.com Web: www.iesweb.com Product: VisualAnalysis Description: IES VisualAnalysis has the features you need for structural analysis and design. It is easy to learn. IES offers great pricing, licensing flexibility, and lower lifetime costs. Find out for yourself why VisualAnalysis powers successful engineers.

Losch Software Ltd Phone: 323-592-3299 Email: loschinfo@gmail.com Web: www.LoschSoft.com Product: LECWall Description: The industry standard for precast concrete sandwich wall design handles multi-story columns as well. Analyze prestressed and/or mild reinforced wall panels with zero to 100 percent composite action. Flat, hollow-core or double tee configurations are supported. Complete handling analysis is also included.

MKT Fastening, LLC Phone: 800-336-1640 Email: sales@mktfastening.com Web: www.mktfastening.com Product: MKT Website Design Software Description: New Anchor Design software now available to assist with calculations meeting ACI 318 and IBC design requirements. It runs on Windows operating systems; calculates in metric or imperial units for mechanical or adhesive anchoring systems. Visit the website to download your copy.

RedBuilt

Phone: 866-859-6757 Email: info@redbuilt.com 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.

Product: CFS Designer™ V 2.0.2 Software Description: With the CFS Designer, you can design CFS beam-column members according to AISI specifications and analyze complex beam loading and span conditions. Intuitive design tools automate common CFS systems such as wall openings, shearwalls, floor joists, and, with the newest software update, up to eight stories of load-bearing studs.

StrucSoft Solutions Phone: 514-538-6862 Email: a.gordon-stewart@strucsoftsolutions.com Web: strucsoftsolutions.com Product: MWF Description: A template-based and rule-driven extension to Autodesk® Revit® for framing. It empowers users to automate the modeling, clash detection and manufacturing of light gauge steel and wood framing, including shop drawings, cut lists, BOM, CNC output & more.

StructurePoint

Phone: 847-966-4357 Email: info@structurepoint.org Web: structurepoint.org Product: spBundle Description: Recently upgraded to include ACI 318-14 and CSA A23.3-14, the remaining programs in our software bundle (spSlab, spBeam, spWall, spMats, spFrame) compliment spColumn for complete reinforced concrete building design including floor systems, beams, cast-in-place walls, tilt-up walls, commercial building foundations, pile caps, and slabs on grade. Product: spColumn Description: Featuring a flexible graphical interface in the new spSection module for creating and modifying irregular sections, spColumn is used for design and investigation of columns, shear walls, bridge piers, and typical framing elements in buildings and other structures subject to combined axial and flexural loads.

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August 2017

Product: Tekla Structures Description: Create and transfer constructible models throughout a design. 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 architects, consultants, fabricators, and contractors.

Veit Christoph GmbH Phone: +49 711 518573-30 Email: melanie.engel@vcmaster.com Web: www.vcmaster.com/en Product: VCmaster - Intelligent Engineering Software Description: A comprehensive, affordable, user-friendly software solution for compiling professional structural design calculations. Offers a unique combination of reliable calculation capacity and extensive text processing features. Includes numerous predefined design calculations according to AISC and ACI. With VCmaster, engineers can work efficiently while making fewer mistakes.

Yrtechnosoft Phone: 581-235-8710 Email: yves.rossignol@yrtechnosoft.com Web: www.yrtechnosoft.com Product: Weld Design Description: Software for calculating welding beads according to permissible stresses and the Blodgett method. 14 different forms of cord and the flows are calculated in 3 locations. The cdn price includes updates for one year. English, French, 32 and 64 bit version as well as student version available.

business issues

CASE BuSinESS PrACtiCES

Would You Accept This Indemnification Clause? By Ed Schwieter, P.E., S.E.

ndemnification clauses are the number one source of problems in contracts for professional services. Structural engineers are frequently presented with very one-sided contracts drafted by their Client’s attorney, who may not understand contracting for design professional services or merely wishes to maximize the contractual benefits for the Client. These contracts may contain an indemnification clause like this (real) one: To the fullest extent permitted by law, Consultant shall indemnify, defend, and hold harmless Client (including its owners, affiliates and subsidiaries), its officers, directors, agents, shareholders, successors and employees (the “Indemnitees”) from and against any and all claims, liability, actions, causes of actions, complaints, costs, expenses (including prejudgment interest), and demands whatsoever, in law or in equity, including without limitation those for bodily injury, personal injury, sickness, disease, death or property damage (including but not limited to the Construction Work itself), arising out of, or alleged to arise out of, or as a result of, or alleged to be the result of the performance of the Services. Consultant, at Consultant’s sole expense, shall promptly dispose of all such claims, defend all lawsuits filed against Client on the account thereof, pay all judgments rendered against Client in such lawsuits (including any prejudgment interest assessed against any Indemnitee), and reimburse Client in cash upon demand for all reasonable expenses incurred by Client on the account thereof including, but not limited to, attorney fees, expert witness fees, and court costs. Consultant shall indemnify Client and hold Client harmless from the above-referenced claims regardless of whether such claim is caused or alleged to be caused in part by any joint or concurrent negligent act (either active or passive) or omission by an Indemnitee; provided however, that Consultant shall not be obligated to indemnify for those claims to the extent that the same is proximately caused by the sole negligence or willful misconduct of Client or Client’s agents, servants or, independent contractors who are directly responsible to Client, excluding Consultant. Notwithstanding anything to the contrary contained herein, Client at its option shall have the right to participate in the defense of any claims asserted against it, approve the selection of counsel and approve the terms of any settlements made in its name or on its behalf. Would you sign the contract offered with this clause? I would not and you should not! The Client may tell you that the contract clause is “non-negotiable,” or “everyone else accepts it,”

or “if you do not sign this, your competitor will.” However, do Clients expect engineers to pay as little attention to engineering services as they expect engineers to pay toward onerous and inappropriate contract language? Engineers should be just as conversant with contract provisions as they are with design criteria and engineering analysis. The problem phrases in the indemnification clause are many, including: 1) An expansive duty to defend. The duty to defend against third party claims is not required under common law. The duty to defend can only arise through contractually assumed obligations and, therefore, third party claims defense costs are not covered by professional liability insurance. 2) Extreme language like “any and all” and “without limitation.” Extreme language is considered to be too broad and open-ended to be included in fair and balanced contracts. These extreme words may expand the indemnification to include other damages that might otherwise be excluded. 3) Does not require liability to be established. The words “alleged to arise out of ” expands the indemnification clause to include situations where liability has not been established. 4) Does not limit liability to the extent the Consultant is responsible. The indemnification should be limited to losses “to the extent arising out of ” negligent performance of the services. This establishes the proportionality of liability for claims since often several parties are negligent to varying degrees. 5) Requires immediate reimbursement of attorney fees. The cost of defending starts well before mediations or trial and any determination of fault. The immediate reimbursement required under the duty to defend requires paying attorney fees in advance, even when liability is not eventually established. 6) Requires indemnification of Client even if they are negligent. The indemnification clause as written obligates indemnification except when the Client’s “sole negligence” is established. What if the Client is partially liable? If the consultant’s actions contributed 1% to the damages, the client would not be solely negligent, and yet the indemnification clause would require the Client to be held entirely harmless. The indemnification clause would be insurable, fairer, and far simpler and easy to

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understand if it included a reciprocal indemnification and read: Each party to this Agreement shall indemnify and hold harmless, but without duty to defend, the other party (including its owners, affiliates and subsidiaries), its officers, directors, shareholders, successors, and employees (the “Indemnitees”) from and against liability, actions, causes of actions, complaints, costs, and expenses, including those for bodily injury, personal injury, sickness, disease, death, or property damage, to the extent arising out of or as a result of the negligent performance of their duties. Neither party shall be obligated to indemnify the other party in any manner whatsoever for the other party’s own negligence. Assistance with contract review and negotiation are available through professional liability insurance brokers, your professional liability insurance carriers, and the engineer’s attorney. There are many other resources available, including books written by attorneys on design professional contracts and by professional liability insurance carriers and brokers on their websites. Good resources include: • Contract Guide for Design Professionals written by J. Kent Holland, Jr. and published by Zurich (available for free download at http://bit.ly/2tpQFYl • DPIC Companies’ Guide to Better Contracts (out of print) Another option is to counter the Client’s contract with one written by an industry association, which are typically written from a more balanced perspective. Such contracts are offered by CASE, EJCDC, AIA, ConsensusDOCS, and DBIA. The contracts from CASE, EJCDC, and AIA tend to be best suited for structural engineers and require the least amount of changes and additional negotiations as they are fair and balanced. Some engineers “just sign” the uninsurable and unreasonable contract offered by the Client. This is a disservice to themselves and the engineering industry, and sets a bad precedent that other engineers have to work hard to change and overcome. Don’t ignore the contractual terms offered in client-written contracts.▪ Ed Schwieter is Vice President at Schaefer Structural Engineers, Cincinnati, Ohio. He can be reached at ed.schwieter@ schaefer-inc.com.

award winners and outstanding projects

Spotlight

2017 ASCE Structural and SEI Awards

he Structural Engineering Institute (SEI) is proud to congratulate the winners of the 2017 ASCE Structural and SEI Awards:

STRUCTURAL ENGINEERING INSTITUTE AWARDS

2017 Chapter of the Year Award The 2017 SEI Chapter of the Year Award was given to the SEI Illinois Chapter. The SEI Illinois Chapter has focused on creating professional development activities and networking opportunities for structural engineers in the ASCE Illinois Section. They offer a Biennial Lecture Series bringing national speakers to the Chicagoland audience. Chapter dinner meetings often highlight local projects. 2017 Graduate Student Chapter of the Year SEI presented the 2017 Graduate Student Chapter award to the University of Texas, Arlington Graduate Student Chapter. The chapter offers software training sessions, structural workshops, and site tours of existing structures and buildings under construction. The chapter’s activities help students broaden their educational experience and prepare for the transition to a professional career in structural engineering. W. Gene Corley Award The 2017 W. Gene Corley Award was given to Donald Dusenberry, P.E., SECB, F.SEI, F.ASCE, for his many years of service to the Institute and the profession of structural engineering in nearly every possible capacity. He is a former President of the SEI Board of Governors, served on numerous SEI standards, technical and administrative committees, and was key to the development of the Vision for the Future of Structural Engineering: A Case for Change, which laid out a bold set of strategic initiatives to transform the profession. Gene Wilhoite Innovations in Transmission Line Engineering Award The 2017 Gene Wilhoite Award was presented to Ronald J. Carrington, P.E., M.ASCE. Mr. Carrington is an industry expert with over 30 years of experience in the engineering of power delivery projects and has worked extensively with SEI committees that have developed publications and information for transmission line engineers.

Dennis L. Tewksbury Award The 2017 Tewksbury Award was presented to Robert E. Bachman, P.E., S.E., F.SEI, M.ASCE. Mr. Bachman has been one of the most effective liaisons among the many civil engineering professional organizations. He was chair of the SEI Codes and Standards Activities Division Executive Committee and served on the SEI Board of Governors. Walter P. Moore, Jr. Award The 2017 Walter P. Moore, Jr. Award was given to Andrew S. Whittaker, Ph.D., P.E., S.E., F.SEI, F.ASCE. Dr. Whittaker has made fundamental contributions in earthquake and blast engineering of buildings, bridges, and mission critical infrastructure. A hallmark of his work is quickly moving research results into design practice through codes, standards, and guidelines. SEI President’s Award The 2017 SEI President’s Award was given to Ashraf Habibullah, P.E., M.ASCE, for his many contributions to SEI and the profession. Mr. Habibullah is being honored primarily for his passionate advocacy in promoting the Vision for the Future of Structural Engineering: A Case for Change. Mr. Habibullah has been a strong advocate for strategic initiatives through the SEI Futures Fund and exemplifies the Structural Engineer’s role as Leader and Innovator. AMERICAN SOCIETY OF CIVIL ENGINEERING STRUCTURAL AWARDS Jack E. Cermak Award The 2017 Jack E. Cermak Award was given to Xinzhong Chen, Ph.D., M.ASCE. Dr. Chen is one of the leading authorities in bridge and building aerodynamics. His research interests include modeling and simulation of wind load effects on dynamically sensitive structures, nonlinear aerodynamics and nonstationary wind load effects, reliability- and performance-based design of structures to extreme wind loading, probabilistic fatigue, and extreme response of large wind turbines. Shortridge Hardesty Award The 2017 Shortridge Hardesty Award was given to W. Samuel Easterling, Ph.D., P.E., F.SEI, M.ASCE, for his outstanding contributions to the field of steel and composite steel/concrete structures. His primary field of study is the development, testing, analysis,

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August 2017

and design of composite steel/concrete floor and roof systems in steel building structures. Ernest E. Howard Award The 2017 Ernest E. Howard Award was given to John W. van de Lindt, Ph.D., F.ASCE. Dr. van de Lindt is a globally recognized expert in wood engineering. His research over the past decade has pushed the boundary of performance-based engineering for wood frame structures. He has greatly advanced the engineering community’s understanding of wood building system performance to extreme natural hazards. Moisseiff Award The 2017 Moisseiff Award was presented to Daniel M. Dowden, Ph.D., P.E., S.E., M.ASCE; Patricia Clayton, Ph.D., A.M.ASCE; Chao-Hsien Li; Jeffrey Berman, Ph.D., A.M.ASCE; Michel Bruneau, Ph.D., P.Eng., P.E., F.ASCE; Laura N. Lowes, Ph.D., A.M.ASCE; and Keh-Chyuan Tsai, Ph.D., for the paper titled “Full-Scale Pseudodynamic Testing of Self-Centering Steel Plate Shear Walls,” published in the January 2016 issue of the Journal of Structural Engineering. Nathan M. Newmark Medal The 2017 Nathan M. Newmark Medal was awarded to Xilin Lu, Ph.D., M.ASCE. Dr. Lu has made numerous significant contributions to structural engineering, particularly focusing on earthquake resistant design and testing of structures. Through shake table tests and theoretical analysis, his research results and devices have been successfully applied in many major projects. Raymond C. Reese Research Prize The 2017 Raymond C. Reese Prize was presented to Yongchao Yang, Ph.D., A.M.ASCE; Shunlong Li, Ph.D., Aff.M.ASCE; Satish Nagarajaiah, Ph.D., F.SEI, M.ASCE; Hui Li, Ph.D., Aff.M.ASCE; and Peng Zhou, for their paper titled “Real-time OutputOnly Identification of Time-Varying Cable Tension from Accelerations via Complexity Pursuit,” published in the January 2016 issue of the Journal of Structural Engineering. ▪

Visit the SEI website at www.asce.org/ structural-engineering/structuralengineering-awards to submit a nomination for the 2018 awards.

2017 STRUCTURAL ENGINEERING SUMMIT

NCSEA News

News form the National Council of Structural Engineers Associations

October 11-14, 2017 | Washington Hilton | Washington, D.C. The 2017 Structural Engineering Summit is only two months away! And there’s only one month left to save $100 on your registration (fees increase on September 7th). Designed by structural engineers for practicing structural engineers, the Summit hosts all you need to advance your career and the profession. An array of educational sessions are available each day along with several social & networking events, and the NCSEA Committee and Annual Business Meetings. The complete schedule for the NCSEA Committee meetings will be available on www.ncsea.com. For an overview of the full schedule for the Structural Engineering Summit, see pages 34 and 35. We’re also glad to announce that this year we’re hosting the largest Trade Show in NCSEA history! Over 50 exhibitors will be lining the aisles featuring their products and software; make sure to visit their booths during the several events happening on the Trade Show floor. In addition to the Trade Show, several of our exhibitors will be holding brief educational sessions on their products. These Product Presentations run on Friday, October 13th from 8–9:50am. The Summit serves as a vehicle to educate not only everyday Structural Engineers, but it also serves to educate leadership within the organization. Along with sessions on manuals, seismic provisions, codes, and improving your business, the Summit also offers dedicated sessions for SEA Delegates, Executives Directors, and other SEA leadership. These sessions are meant to bring SEA leadership together to promote a sense of community and to provide the opportunity to learn from others in the same position. This year’s Host hotel is the Washington Hilton. Located in the epicenter of vibrant neighborhoods and only blocks from the Dupont Circle Metro, it is convenient for those who wish to explore in their free time. The NCSEA Summit rate starts at $239 per night and the block is selling quickly! Visit www.ncsea.com to reserve your room before it is too late!

2017 STRUCTURAL ENGINEERING SUMMIT SPONSORS P LATINUM

A Celebration of Structural Engineering at the National Building Museum

Join Computers and Structures, Inc. on Thursday evening at the National Building Museum for a unique celebration of the structural engineering profession, including full dinner, champagne, finely crafted cocktails, and live music. Come celebrate the immeasurable contributions of the structural engineering profession to all generations, and the ways in which structural engineers are essential to the progress of humanity! Come mingle and unwind with your fellow conference attendees as you take in the stunning architecture of America’s leading cultural institution devoted to interpreting the history of architecture, engineering, and design.

S ILVER

B RONZE Interested in becoming an exhibitor or sponsor for the 2017 Summit? Visit www.ncsea.com for more infomation! STRUCTURE magazine

August 2017

Panel on How to Improve ASCE 7

Brand new to the 2017 Structural Engineering Summit, this Thursday afternoon track is dedicated to educating Young Engineers.

Following the keynote on Thursday, October 12, representatives from the ASCE/SEI 7 Committee will conduct a workshop with a goal to collect constructive feedback on how to make the loading standard more effective and efficient to use. Led by Ron Hamburger, P.E., S.E., SECB; John Hooper, P.E., S.E., and Don Scott, S.E., these presentations will discuss the standard’s development and adoption processes; the mission of the standard; and, the new digital platform format that will be available for the 2016 edition. Ideas and suggestions from participants will be reported back during the workshop conclusion.

• Young Member Mentor Roundtable This session, restricted to Young Engineer attendees, will facilitate interaction between young engineers and leaders in the field in a highly interactive “speed-dating” format. • Wind Design Considerations for Joist/ Joist Girder Structures This session highlights key updates to Technical Digest No 6, Design of Steel Joist Roofs to Resist Uplift Loads, and will explain how to communicate the design requirements of the ASCE/SEI 7-10 wind provisions for open web steel joists and joist girders.

Join the NCSEA Board at the Young Member Reception on Wednesday, October 11; all attendees under 35 are welcome!

2017 Summit Keynote:

Shaking Up DC – The Insiders’ Story Martina Driscoll, P.E., Principal & Unit Manager, Wiss, Janney, Elstner Associates Terrence Paret, Senior Principal, Wiss, Janney, Elstner Associates

Upcoming NCSEA Webinars August 29, 2017 Wind Loads on Non-Building Structures for the Practicing Engineer Emily Guglielmo, P.E., S.E. This session will focus on wind loads on non-building structures, including equipment, walls, signs, and towers. The session will discuss ASCE 7 wind load provisions for non-building structures and how to correctly apply them through examples. An in-depth exploration for engineering commonly encountered situations that are not directly addressed in the code will follow. September 12, 2017 ASCE 7-16 Wind: How it Affects the Practicing Engineer Donald R. Scott, S.E., F.SEI, F.ASCE ASCE 7-16 will include several significant changes to the wind loading provisions which will impact the practicing engineer. This session will provide an in-depth discussion of the most important changes and discuss the impacts to a structural engineer’s design. October 24, 2017 Understanding and Interpreting Geotechnical Reports Trent Parkhill, P.E. The goal of this webinar is to help structural engineers better understand geotechnical reports, focusing on recommendations that can be misunderstood. Areas covered will include topics such as what is the “right” exploration program, lateral earth pressures, uncertainty in settlement estimates, the relationship between bearing pressures, and more. Two exclusive annual plans are available to NCSEA corporate members & SEA members only. The Live & Recorded Webinar Subscription Plan with access to all live webinars and the entire recorded webinar library, hosting over 180 webinars, or the Live Webinar Subscription Plan. Visit www.ncsea.com to purchase your subscription today! Visit www.ncsea.com to register and read the full description of each webinar. 1.5 hours of continuing education. Approved for CE credit in all 50 states. STRUCTURE magazine

August 2017

News from the National Council of Structural Engineers Associations

• YMGSC – Basics of Shear Wall Design Most young engineers graduate with minimal education in material-specific design with masonry, wood, and lateral systems, which can take years of experience to understand. This session will help to tackle shear wall design addressing multiple materials and the coinciding codes.

NCSEA News

New! Young Engineers Track

Structural Columns

The Newsletter of the Structural Engineering Institute of ASCE

Top 5 Reasons to Attend 1) Expand your knowledge at technical sessions on transmission line and substation structures and foundations. 2) Earn professional development hours (PDH’s) by attending technical sessions and workshops. 3) Network with global leaders and colleagues working with high-voltage transmission structures around the world. 4) Connect with exhibitors showcasing state-of-the-art products, services, and solutions for your transmission line and substation projects. 5) Discover Southern hospitality and enjoy over 100+ live entertainment venues.

ELECTRICAL TRANSMISSION & SUBSTATION STRUCTURES CONFERENCE 2018 Atlanta, Georgia November 4–8 Dedicated to Strengthening our Critical Infrastructure

Electrical Transmission & Substation Structures Conference 2018

Exhibits & Sponsorships

Call for Abstracts and Sessions

The State-of-the-Industry Forum for Transmission and Substation Engineers • Discover Technical Knowledge • Hear Project Case Studies • Find Real-World Solutions • Visit Vendors and Learn about their Products and Services The SEI/ASCE Electrical Transmission & Substation Structures Conference is recognized as the must-attend conference that focuses specifically on transmission line and substation structure and foundation construction issues. This event – for utilities, suppliers, contractors, and consultants – offers an ideal setting for learning and networking.

Increase your company’s visibility and reach hundreds of industry professionals at this important specialty conference. Contact Bob Nickerson at renicker@flash.net or 817-319-8779, or Sean Scully at sscully@asce.org or 703-295-6154, for exhibiting and sponsorship opportunities. Questions? Contact Debbie Smith dsmith@asce.org or 703-295-6095. Submit your sessions at www.etsconference.org.

Dedicated to Strengthening our Critical Infrastructure Abstracts & Session Proposals due September 12, 2017

Call for New Members Minimum Design Load Standard – ASCE 7 The revision cycle for ASCE 7-16 Minimum Design Loads and Associated Criteria for Buildings and Other Structures is starting in September 2017. The committee will be seeking new members in the summer of 2017 to begin work on the next edition of the standard. Ronald O. Hamburger, S.E., P.E., SECB, F.SEI, Senior Principal at Simpson Gumpertz Heger will chair the 2022 cycle. In this next cycle, the chair will pursue practical means to simplify the standard from the user’s perspective, while assuring that it remains a stateof-art design loading standard. He will also hope to engage the profession at large in the standards development process, including many younger engineers. Young professional interested in serving on ASCE 7 committees may apply to participate in the SEI CSAD-YP program, a funded opportunity. In addition to younger professionals, anyone with a strong desire to contribute to further development of the ASCE 7 standard is welcome to apply for membership on the STRUCTURE magazine

committee. Practicing engineers, researchers, building officials, contractors, and construction product representatives are all needed and welcome. Individuals with broad knowledge of structural engineering or limited focus on a particular practice area or expertise such as hydrology, climate, or seismology can make significant contributions. If you are interested in applying for the committee, please submit an application at www.asce.org/codes-and-standards/ standards-committee-application-form by Sept. 30, 2017. On the online form, select “SEI” from Institute drop down and then “Minimum Design Loads (ASCE/SEI 7)”. Carefully indicate the category of membership for which you are applying (Voting or Associate) for each of the main or subcommittees. Associate members can be accepted until balloting begins. Eligible regulatory members can qualify for travel reimbursement per ASCE Travel Policy. Contact Jennifer Goupil at jgoupil@asce.org or 571-421-3998 with questions. August 2017

Free BETA access thru 8/31/17

The ASCE 7 Hazard Tool provides a single destination for the quick, reliable lookup of key design parameters specified in ASCE 7-10 and 7-16. Easy-to-use mapping features allow instant retrieval of hazard data for a specific location including seismic, wind, rain, flood, snow, ice, and tsunami. Generate and download design load PDF reports to include in engineering proposals. Individual and Corporate subscriptions will be available. Get started today and try the ASCE 7 Hazard Tool at http://asce7hazardtool.online. For more information, contact asce7tools@asce.org or learn about other ASCE 7 products at www.asce.org/asce7.

2018 Ammann Fellowship Call for Nominations

ASCE Week – Las Vegas

ASCE Week will be held September 24 – 29, 2017, at the Green Valley Ranch Resort Spa & Casino in Las Vegas. Register and save up to $1,100 when you register for two seminars or save up to $450 when you register for one seminar. Earn up to 42 PDHs in one week. Choose from 11 seminars and be part of a private Hoover Dam tour, all while earning the PDHs you need for license renewal. View the schedule and register at www.asce.org/event/2017/asce-week.

SEI Local Activities Oregon State University Graduate Student Chapter Welcome to the new SEI Grad Student Chapter (GSC) at Oregon State University chaired by Cody Beairsto, with Faculty Advisor Dr. Thomas Miller. Their mission is to promote structural engineering and SEI/ASCE to OSU students and connect them with industry and professional structural engineers. For more information, contact the chair at beairstc@oregonstate.edu.

Get Involved in Local SEI Activities 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 Chapters serve member technical and professional needs. SEI GSCs prepare students for a successful career transition. SEI supports Chapters with opportunities to learn about new initiatives and best practices, and network with other leaders – including annual funded SEI Local Leader Conference, technical tour, and training. SEI Chapters receive Chapter logo/branding, complimentary webinar, and more.

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.

STRUCTURE magazine

August 2017

The Newsletter of the Structural Engineering Institute of ASCE

The O. H. Ammann Research Fellowship in Structural Engineering is awarded annually to a member or members of ASCE or SEI for the purpose of encouraging the creation of new knowledge in the field of structural design and construction. All members or applicants for membership are eligible. Applicants will submit a description of their research, an essay about why they chose to become a structural engineer and their academic transcripts. This fellowship award is at least $5,000 and can be up to $10,000. The deadline for 2018 Ammann applications is November 1, 2017. For more information and to fill out the on-line application visit the SEI website at www.asce.org/structural-engineering/ ammann-research-fellowship.

Structural Columns

ASCE 7 Hazard Tool

Structural Forum

opinions on topics of current importance to structural engineers

When Good Engineering Ideas Go Wrong By Jeremy Herauf

or centuries, engineers have come up with great new ideas and leveraged them to build stronger, better, lighter, longer, taller, and more beautiful bridges. Throughout history, some design and procedural innovations have gone wrong, leading to serious structural problems, failures, collapses, and even deaths. Many bridges that seemed like great ideas on the drawing board and in the planning process failed during construction or soon thereafter. This article examines engineering and design concepts, and construction procedures, that led to these problems.

Tacoma Narrows Bridge The first bridge across the Puget Sound in Washington was proposed in 1889 when the Northern Pacific Railway was looking for ways to speed travel from Tacoma to the Kitsap Peninsula. A simple trestle bridge was considered but never built because engineers determined that it would not hold up to the extreme winds and tides it would have to endure. Also, they could not find an engineering solution to span the extreme distance across the sound.

It took almost 50 years – and a costly study – to finally design a span that engineers felt confident about. Designer Leon Moisseiff came up with a plan for a solid, rigid suspension bridge that many believed was ideally suited for the challenging location. Despite all the great engineering minds that reviewed the bridge plan, they failed to see that all the factors that made the bridge strong and stable also made it too rigid to withstand the extreme winds that would batter it day after day. While under construction, workers noticed that the bridge shook in unprecedented ways whenever the wind blew. It was so extreme, they nicknamed the bridge “Galloping Gertie.” Surprisingly, Moisseiff and the on-site engineers dismissed the shaking, assuming the issue would resolve itself once construction was complete. Work continued, and the bridge opened on July 1, 1940. Just over five months later, on November 7, the bridge collapsed under 42 mile-per-hour winds, due to aeroelastic flutter. It took ten years for a lighter, more flexible bridge to be completed. The replacement structure still stands today and serves as the westbound lanes of the current pair of bridges that cross the Puget Sound.

Nipigon River Bridge The Nipigon River Bridge is an integral part of the Trans-Canada Highway, a critical roadway that moves traffic, including vital deliveries, across the continent. The first vehicular bridge at the location was opened in 1937, replacing an earlier railroad bridge. It was replaced in 1974 and again in 2013 when higher traffic volume necessitated it. The 2013 replacement is a pair of innovative cable-stayed structures, novel because they were the first bridges of this type constructed in a cold-weather climate. The first of the twin bridges opened in late November 2015. It was forced to close less than two months later when an expansion joint shifted more than two feet after a winter storm. The closure led to a major failure in the Canadian roadway system. It forced traffic to detour hundreds of miles south into the United States, leading to a state of emergency. The bridge was partially re-opened to traffic using a temporary fix several days later. However, it took until September of that year for officials to determine the cause of the fissure. The immediate reason for the break was attributed to a simple failure of the bolts that connected the bearings to the bridge girders. The bigger issue was that the shoe plates, which connected the two components, were too flexible. When stressed by extreme cold, the plates twisted and pried out the bolts. Also, bearings that should have been flexible and mitigated this issue failed and were unable to rotate. To fix the problem, a new linkage system was designed and implemented that allowed for greater flexibility during periods of thermal expansion and contraction. In the end, a bridge design that was effective in more temperate climates was not adequate for the cold of an extreme Canadian winter.

Quebec Bridge The Quebec Bridge failed not once, but twice, during construction because of engineering and construction errors on the breakthrough bridge designs.

Tacoma Narrows Bridge collapse, 1940.

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 2017

Pont de Québec Bridge collapse, 1907.

management are necessary when developing record-breaking structures. Just because something works on a small scale does not mean it will work on a larger one.

Conclusion Innovative bridge design and engineering are constantly improving the capacity and function of critical structures. The biggest lesson designers and engineers can learn from the bridge failures outlined here is that it is important to be cautious and pay attention to signs something could be wrong with a cutting-edge structure or building technique. Numbers, measurements, and physical clues often indicate something is wrong. Paying attention to them allows for innovation to continue while keeping workers and the general population safe.▪ Jeremy Herauf is the President of Bridge Masters, Inc., a company with over 40 years of experience installing and repairing bridge utilities. He can be reached at info@bridgemastersinc.com.

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The first time anyone thought of connecting Lévis on the south shore of the St. Lawrence River to Quebec City on the north was back in 1852, but no one came up with a solution to bridging the chasm. Options were explored in 1867, 1882 and 1884. Finally, near the turn of the 20th century, a record-length cantilever bridge structure was decided on for the site. Edward Hoare was selected as the chief engineer for the project even though he had never worked on a similar type of bridge on such a large scale. Several people assisted in engineering this ambitious project. The design and construction phases were chaotic because no one on the team could agree on the correct load calculations to support the span. In the end, the recommendations of the engineering team were overruled by a government agency. Work on the structure continued. As early as 1904, when the bridge was almost half completed, engineers confirmed that the bridge itself weighed far more than its carrying capacity. They apparently ignored this, as construction kept going through 1907. In the summer of that year, the team began noticing stretching and contorting of important structural elements. Some engineers claimed that they were installed in this condition and the issues were once again ignored. Soon after, the southern and central sections of the bridge suffered a catastrophic collapse, tumbling into the river in less than 15 seconds. Of the 86 workers on the bridge at the time, 75 were killed and the rest seriously injured. It is the world’s worst bridge construction disaster and was officially blamed on engineers not closely

monitoring and managing the development of this novel design. Once the investigation into the collapse was completed, work began on a replacement bridge. The new design would be an even more massive cantilever structure with a broad center span. Once again, engineers raised concerns, this time over the weight and size of the center span that was to be raised into place by a new type of hoisting device. The novel technique was used to speed construction. Sure enough, the hoists failed, and the span fell into the river, killing 13 workers. It still sits at the bottom of the St. Lawrence River today. Another center span had to be built, which was difficult because it was hard to source steel during World War I. The bridge finally opened in 1919, and remains the longest cantilevered bridge in the world. This innovative structure brought home the fact that careful calculations and project

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