STRUCTURE magazine - August 2018

A Joint Publication of NCSEA | CASE | SEI

STRUCTURE

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August 2018 Steel/Cold-Formed Steel

Inside: Grant Street Pier, Vancouver, Washington

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LeMessurier Calls on Tekla Structural Designer for Complex Projects Interoperability and Time Saving Tools

Tekla Structural Designer was developed specifically to maximize collaboration with other project parties, including technicians, fabricators and architects. Its unique functionality enables engineers to integrate the physical design model seamlessly with Tekla Structures or Autodesk Revit, and to round-trip without compromising vital design data.

“We’re able to import geometry from Revit, design in Tekla Structural Designer and export that information for import back into Revit. If an architect makes geometry updates or changes a slab edge, we’ll send those changes back into Tekla Structural Designer, rerun the analysis and design, and push updated design information back into Revit.”

Tekla Structural Design at Work: The Hub on Causeway

For over 55 years, LeMessurier has provided structural engineering services to architects, owners, contractors, developers and artists. Led by the example of legendary structural engineer and founder William LeMessurier, LeMessurier provides the expertise for some of the world’s most elegant and sophisticated designs while remaining true to the enduring laws of science and engineering.

Known for pushing the envelope of the latest technologies and even inventing new ones, LeMessurier engineers solutions responsive to their clients’ visions and reflective of their experience.

An early adopter of technology to improve their designs and workflow, LeMessurier put its own talent to work in the eighties to develop a software solution that did not exist commercially at the time. Their early application adopted the concept of Building Information Modeling (BIM) long before it emerged decades later.

While LeMessurier’s proprietary tool had evolved over three decades into a powerhouse of capability, the decision to evaluate commercial structural design tools was predicated on the looming effort required to modernize its software to leverage emerging platforms, support normalized data structure integration and keep up with code changes.

After a lengthy and thorough comparison of commercial tools that would “fill the shoes” and stack up to the company’s proprietary tool, LeMessurier chose Tekla Structural Designer for its rich capabilities that addressed all of their workflow needs. According to Derek Barnes, Associate at LeMessurier, ” Tekla Structural Designer offered the most features and the best integration of all the products we tested. They also offered us the ability to work closely with their development group to ensure we were getting the most out of the software.”

One Model for Structural Analysis & Design

From Schematic Design through Construction Documents, Tekla Structural Designer allows LeMessurier engineers to work from one single model for structural analysis and design, improving efficiency, workflow, and ultimately saving time. “Our engineers are working more efficiently because they don’t need to switch between multiple software packages for concrete and steel design. Tekla Structural Designer offers better integration of multiple materials than we have seen in any other product,” said Barnes.

LeMessurier engineers use Tekla Structural Designer to create physical, information-rich models that contain the intelligence they need to automate the design of significant portions of their structures and efficiently manage project changes.

TRANSFORMING THE WAY THE WORLD WORKS

“Tekla Structural Designer has streamlined our design process,” said Craig Blanchet, P.E., Vice President of LeMessurier. “Because some of our engineers are no longer doubling as software developers, it allows us to focus their talents on leveraging the features of the software to our advantage. Had we not chosen to adopt Tekla Structural Designer, we would have needed to bring on new staff to update and maintain our in-house software. So Tekla Structural Designer is not just saving us time on projects, it is also saving us overhead.

Efficient, Accurate Loading and Analysis

Tekla Structural Designer automatically generates an underlying and highly sophisticated analytical model from the physical model, allowing LeMessurier engineers to focus more on design than on analytical model management. Regardless of a model’s size or complexity, Tekla Structural Designer’s analytical engine accurately computes forces and displacements for use in design and the assessment of building performance.

“Tekla Structural Designer offers better integration of multiple materials than we have seen in any other product.”

Positioning a large scale mixed-use development next to an active arena, a below grade parking garage, and an interstate highway, and bridging it over two active subway tunnels makes planning, phasing and engineering paramount. Currently under construction, The Hub on Causeway Project will be the final piece in the puzzle that is the site of the original Boston Garden.

Despite being new to the software, LeMessurier decided to use Tekla Structural Designer for significant portions of the project. “Relying on a new program for such a big project was obviously a risk for us, but with the potential for time savings and other efficiencies, we jumped right in with Tekla Structural Designer. It forced us to get familiar the software very quickly.”

“Tekla Structural Designer allowed us to design the bulk of Phase 1 in a single model,” said Barnes. The project incorporates both concrete flat slabs and composite concrete and steel floor framing. “Tekla Structural Designer has the ability to calculate effective widths based on the physical model which is a big time saver,” said Barnes. “On this project, the integration with Revit, along with the composite steel design features enabled us to work more efficiently. Adding the ability to do concrete design in the same model was a bonus because we had both construction types in the same building.”

“Tekla Structural Designer helped this project run more efficiently, and in the end it was a positive experience,” said Blanchet.

“Tekla Structural Designer gives us multiple analysis sets to pull from, which gives us lots of control. Most programs don’t have the capability to do FE and grillage chase-down. For the design of beam supported concrete slabs, Tekla Structural Designer allows us to separate the slab stiffness from the beam stiffness, so if we choose to we can design the beams without considering the influence of the slab. In the same model we can use a separate analysis set to review the floor system with the beams and slab engaged,” said Barnes.

Barnes also shared similar benefits with concrete column design. “Tekla Structural Designer does grillage take-downs floor-by-floor, finds the reactions and applies them to the next floor. This allows us to view column results both for the 3-dimensional effects of the structure as a whole and from the more traditional floor-by-floor load take-down point of view.

Doing both has always required significant manual intervention, but Tekla Structural Designer puts it all in one place.” “We reduce the possibility for human error because with Tekla Structural Designer less user input is required,” said Barnes. “Tekla Structural Designer automatically computes many of the design parameters, such as column unbraced lengths. The assumptions made by the software are typically correct, but we can easily review and override them when necessary.”

“Tekla Structural Designer provided the best fit for our workflow compared to other commercially available software.”

Want to Evaluate Tekla Structural Designer? tekla.com/TryTekla

ADVERTISER INDEX

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Adhesives Technology Corp. .....................12 American Concrete Institute ......................2 Anthony Forest Products Co. ...................17 Canadian Wood Council ..........................55 Clark Dietrich Building Systems ..............38 Dayton Superior Corporation ..................24 DEICON.................................................40 Design Data .............................................25 Dlubal Software, Inc. ...............................21 Geo Design, Inc. ......................................51 Hardy Frame ...................................... 10-11 ICC..........................................................53 Independence Tube Corporation ..............37 Integrity Software, Inc. ...............................4

KPFF .......................................................50 Lindapter .................................................44 NCEES ....................................................35 NCSEA .............................................. 32-33 New Millennium Building Systems ..........46 Nucor Vulcraft Group ..............................48 RISA Technologies ...................................64 SEI ...........................................................47 Simpson Strong-Tie............................15, 29 StructurePoint ............................................6 Trimble ......................................................3 USG Corporation ....................................42 Weyerhaeuser ...........................................62

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August 2018

Greg Schindler, P.E., S.E. Sammamish, WA Stephen P. Schneider, Ph.D., P.E., S.E. BergerABAM, Vancouver, WA John “Buddy” Showalter, P.E. American Wood Council, Leesburg, VA

STRUCTURE® magazine (ISSN 1536 4283) is published monthly by The National Council of Structural Engineers Associations (a nonprofit Association), 645 N. Michigan Ave, Suite 540, Chicago, IL 60611 312.649.4600. Application to Mail at Periodicals Postage Prices is Pending at Chicago, IL and additional mailing offices. STRUCTURE magazine, Volume 25, Number 8, C 2018 by The National Council of Structural Engineers Associations, all rights reserved. Subscription services, back issues and subscription information tel: 312-649-4600, or write to STRUCTURE magazine Circulation, 645 N. Michigan Avenue, Suite 540, Chicago, IL 60611. The publication is distributed to members of The National Council of Structural Engineers Associations through a resolution to its bylaws, and to members of CASE and SEI paid by each organization as nominal price subscription for its members as a benefit of their membership. Yearly Subscription in USA $75; $40 For Students; Canada $90; $60 for Canadian Students; Foreign $135, $90 for foreign students. Editorial Office: Send editorial mail to: STRUCTURE magazine, Attn: Editorial, 645 N. Michigan Avenue, Suite 540, Chicago, IL 60611. POSTMASTER: Send Address changes to STRUCTURE magazine, 645 N. Michigan Avenue, Suite 540, Chicago, IL 60611.

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

CONTENTS Cover Feature

39 RECLAIMING THE WATERFRONT

By Michelle Black, P.E., Chris Adams, P.E., and Shane McCormick, P.E., S.E. “The Waterfront” is a new development along the Columbia River with the Grant Street Pier as its centerpiece. The pier’s triangular, post-tensioned concrete deck overhangs the water by 90 feet. A cable system and 80-foot-tall, pipe mast support the deck.

Features 26 EXPANSION OF CONCOURSE A

By Christopher R. Herron, P.E., Christopher H. Garris, A.I.A., and Carlos de Oliveira, P.Eng.

Columns and Departments

STRUCTURAL COMPONENTS

22 Anchorage of Wood Structural Walls

By Greg McCombs, S.E.,

EDITORIAL

7 Efforts toward SE Licensure

and Steven M. Petroff, P.E.

By Susan Jorgensen, P.E., SECB CODE UPDATES

The Expansion of Concourse A at the Charlotte Douglass International Airport includes a wing-like roof that hovers over the concourse.

Exposed V-shaped steel columns support the roof.

Functional AESS connections seamlessly tie the

ENGINEER’S NOTEBOOK

8 Screw Connections Having Other Materials Within the Connection

43 AISI S400-15/S1-16

By Rob Madsen P.E., Helen Chen Ph.D., P.E., and Bonnie Manley P.E.

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

columns together.

30 BEDFORD SQUARE

By Andrew Newland, P.E. For the Bedford Building in Westport, CT, the versatility of conventional cold-formed steel framing was utilized to frame and support

RISK MANAGEMENT STRUCTURAL DESIGN

13 Unanticipated Stresses and the Welded Flange Plate Moment Connection

By Sompandh Wanant, P.E.

an architectural curved brick opening with STRUCTURAL PERFORMANCE

cantilevered roof framing.

16 Seismic Design of Aluminum Structures

34 2017 SETS RECORDS

49 Geotechnical Peer Review

By Theodore von Rosenvinge, P.E.

STRUCTURAL FORUM

63 Education Crisis in America: An Insider’s Perspective

By Dilip Khatri, Ph.D., S.E.

By J. Randolph Kissell, P.E., and Ronald D. Ziemian, Ph.D., P.E.

By Daniel Safarik The Council on Tall Buildings and Urban Habitat provide a worldwide snapshot of the buildings 200 meters in height or taller completed in 2017, a geographically diverse and record-breaking year.

BUILDING BLOCKS

18 Self-Consolidating Concrete

By William S. Phelan

IN EVERY ISSUE 4 Advertiser Index 52 Resource Guide – Software 56 NCSEA News 58 SEI Update 60 CASE in Point

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

STRUCTURE magazine

5

August 2018

Editorial Efforts toward SE Licensure

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

S

tructural Licensure Committee. Structural Engineers Certification Board. Structural Engineering Licensure Coalition. What are these groups? How are they connected? What do they do? Why is it important?

Since its inception, one of the primary goals of the National Council of Structural Engineers Associations (NCSEA) is advocating and supporting structural engineering licensure in each jurisdiction. To work toward achieving this goal, NCSEA created a Structural Licensure Committee to gather information, develop supporting material, and assist state committees working with their licensing boards and legislatures to implement structural engineering licensure. Over the last ten years, the committee has been very successful publishing articles in STRUCTURE magazine, working with NCEES in the development of the 16-hour structural engineering examination, and encouraging consistency among states adopting structural engineering licensure.

In 2006, NCSEA established the Structural Engineering Certification Board (SECB) as an independent organization. The certification process provided an opportunity for those not licensed as structural engineers to be recognized for having met a higher standard. Except for those who signed up under a temporary “grandfathering” option to demonstrate their support for the concept, the requirements for certification include having passed 16 hours of structural licensing examination and meeting rigorous, ongoing continuing education requirements.

SECB is now in the process of taking on some new initiatives to provide more value to its members and encourage more engineers to become certified. These include revising the website and providing a dashboard where members can record licensing information and continuing education of all types. SECB is also focusing more attention on stakeholders like architects, licensing boards, and building officials to make them better aware of the existence and value of the credential.

In some states where structural engineering licensure has been pursued, opponents have claimed that there are four structural engineering organizations, each of which has a different position on licensing. In order to dispel this misconception, NCSEA and SECB joined with the Structural Engineering Institute (SEI) of the American Society of Civil Engineers (ASCE) and the Council of American Structural Engineers (CASE), a coalition of the American Council of Engineering Companies (ACEC), to form the Structural Engineering Licensure Coalition (SELC). Its purpose was and remains “to serve as a united

STRUCTURE magazine

voice for the structural engineering profession for the promotion of structural engineering licensure.” SELC is led by a Steering Committee consisting of two representatives from each organization. The Steering Committee is responsible for coordinating the licensure-related activities of each organization and facilitating joint efforts.

The SELC website (www.selicensure.org) provides articles, case studies, and presentations on the importance of structural engineering licensure and various efforts to bring it about throughout the country.

For example, in Washington, Oregon, and Utah, design by a licensed structural engineer is required only for higher-risk buildings and challenging bridges. A recent initiative of SELC was to develop a list of recommended criteria to define such significant structures. The document is shared with other state committees and licensing boards as a guideline for developing the rules and regulations that would govern structural engineering licensure if it were to be adopted in accordance with such a “partial practice restriction” model.

SELC has been working with the National Society of Professional Engineers (NSPE), traditionally the most vocal opponent of structural engineering licensure, to help its national and state-level leaders and members understand what we are trying to do and why it is important to the entire professional engineering community. SELC has also set up a Structural Caucus at the annual business meeting of the National Council of Examiners for Engineers and Surveyors (NCEES) to educate its members, who are the members of the state licensing boards.

All of these efforts exist for one single reason – to protect the safety, health, and welfare of the public by raising the bar for the practice of structural engineering. Each of the organizations involved has a different role in this quest. More than ten years ago, in my May 2008 editorial in STRUCTURE magazine, I expressed my support of structural engineering licensure in each jurisdiction. That continues to be my goal, and I believe that the efforts of these groups will help the profession eventually achieve it.▪ Susan Jorgensen is the Quality Control Manager for Studio NYL in Boulder, CO, and a Senior Structural Engineer for Integral Engineering Company in Centennial, CO. She was the former Vice President and Managing Principal of the Denver office of Leo A Daly. She is currently the Treasurer on the NCSEA Board of Directors. (susiejorg315@comcast.net)

7

August 2018

engineer’s T NOTEBOOK

he design provisions for the shear strength of steel-to-steel screw connections provided by Section E4.3 of the North American Specification for the Design of Cold-Formed Steel Structural Members, AISI S100-12, are based on testing.

The test specimens were typically steel sheets in contact with each other with no other material or significant gap between the steel components.

However, screw connections are often fabricated such that there is material or a gap within the connection. For example, where continuity of the sheathing is desired, attachment of ledger track to wall studs will have the gypsum wallboard within the connection or attachment of the exterior sheeting to the roof or wall structural members will have insulation material within the connection. Thus, a connection may have an intended or unintended gap between the steel components.

There is minimal test data for screw connections having other materials or intended gaps between the plies of a steel-to-steel connection. Thus, the engineer is often left without clear guidance on how to comply with AISI S240 Section C4.1.2.2, which states that, “Screw fasteners shall penetrate individual components of connections without causing permanent separation between components.”

The objective of this article is to summarize available test data and provide design guidance based on that data.

Screw Connections Having Other Materials Within the Connection

By Roger A. LaBoube, Ph.D., P.E. Roger LaBoube is Curator’s Distinguished Teaching Professor of Civil Engineering and Director of the Wei-Wen Yu Center for ColdFormed Steel Structures at the Missouri University of Science and Technology.

Roger is active in the American Iron and Steel Institute’s Committee on Framing Standards and the Committee on Specifications. He also served on STRUCTURE’s Editorial Board. (laboube@mst.edu)

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

Behavior and Limit States Screw connections that transfer shear forces may fail by three possible limit states – bearing, tiltingtearing, or shear of the screw. The presence of a gap or separation of the steel sheets would likely have little effect on the bearing capacity of a screw connection. However, the presence of a separation may impact the tilting-tearing connection capacity and the screw strength.

Screw Strength Research by Bambach and Rasmussen (2007) developed the following design equation for the

Figure 1. Screw tilting.

nominal shear strength of a screw, Pns, as a function of the separation distance, dsep, Pns = Pss (1 – dsep/2d) Where, d = the nominal screw diameter and Pss = nominal shear strength of the screw as reported by the manufacturer or determined by independent testing. The research is based on the following parameter limits: 0.21≤ nominal screw diameter (in inches) ≤ 0.26, 0.31≤ sheet thickness (in inches) ≤ 0.79, 36 ≤ yield strength (ksi) ≤ 65, and dsep ≤ 0.31 inches. Although the researchers suggest limiting the Pns equation to the test program limits, it is suggested, lacking other data, that the equation may be used for other applications.

Tilting-Tearing Failure Mode The tilting-tearing failure mode results in the fasteners tilting (tipping) when subjected to a shear force, as shown in Figure 1. Also, note that the plies of the connection may separate (Figure 1). Figure 2 also illustrates the tilting effect of the screws and the separation of the steel plies at failure.

As the length of the screw and distance between the connected elements increases, this failure mode becomes more critical. A review of the engineering literature provided test data from three experimental programs. The following is a summary of the three test programs.

A Virginia Tech study by Lease and Easterling (2006) performed 435 tests on single shear screw connections. The focus of the study was to determine the behavior of a screw connection when a blanket of compressed fiberglass insulation was present within the screw connection. The researchers suggested that a 0.85 factor could be applied to the nominal strength equations of AISI S100 Section E4.3 to achieve a better correlation of the test data to nominal strength calculation. However, they went on to conclude that no reduction was needed because the resistance factors fell within the range of the resistance factors of past research on steel-to-steel connections. A review of the data does indicate that, for a gap distance between the plies equal to or less than 0.15 inches, no modification factor may be required.

The International Seismic Application Technology (2009) analyzed data generated by a RAM Tech test program that focused on

Figure 2. Separation of connection components.

STRUCTURE magazine

8

August 2018

the behavior of screw connections in which gypsum wallboard was attached to a 43-mil steel sheet to simulate the attachment to a cold-formed steel wall stud. Tests were performed with either one layer of 5⁄8-inch gypsum or two layers of 5⁄8-inch gypsum to assess the impact of the gypsum wallboard.

The intent was to simulate a one-hour and two-hour fire rated wall application. A ¼-inch-diameter self-drilling screw was used for all tests. A comparison of the test failure load to the AISI S100 Section E4.3 nominal strength, Pn, is summarized in Table 1.

A Steel Framing Alliance (2010) report summarizes the results of a test program that studied the screw connection strength when rigid foam insulation was present within the screw connection. Distances between the plies, ranging from one to four inches, were present in the test specimens. In this case, the distance between the plies was the thickness of the rigid foam insulation. A comparison of the test failure load to the AISI S100 Section E4.3 nominal strength, Pn, is summarized in Table 2.

Table 1. Comparison of test failure load to AISI S100 Section E4.3 (ASAT, 2009).

Distance Stud Screw Between Plies Thickness Diameter

Failure Load

Pn (S100)

Failure/ Pn

(inches)

(inches)

(inches)

(lbs per screw)

(lbs)

One-Hour

0.625

0.043

0.25

682

927

0.74

Two-Hour

1.25

0.043

0.25

599

927

0.65

Table 2. Comparison of test failure load to AISI S100 Section E4.3 (SFA, 2010).

Distance Between Plies

Stud Thickness

Screw Diameter

Failure Load

Pn (S100)

Failure/Pn

(inches)

(inches)

(inches)

(lbs per screw)

(lbs)

1

0.031

0.164

243

447

0.54

4

0.054

0.190

558

1426

0.39

2

0.031

0.164

195

447

0.44

2

0.054

0.190

964

1426

0.68

Table 3. General recommendations for distances between plies (based on test data).

Case

Distance Between Plies

Reduction to AISI S100 E4.3

Gap Between Sheets

thickness of thinnest ply

No strength reduction required

Fiberglass Insulation

≤ 0.15”

No strength reduction required

Interpretation and Recommendation

Gypsum Wall Board

5/8” 2 x 5/8”

0.74 (33 mil or thicker)

There is a clear trend that, as the distance between the plies increased, the connection strength decreased as illustrated in Figure 3 (although the data is limited). The reduction factor shown in Figure 3 is the ratio of Failure/Pn. Figure 3 indicates a trend; however, because the database is limited, a reduction factor equation is not being proposed. In addition, the strength and stiffness of the material between the plies are also likely an influencing factor for the potential reduction in connection strength. There has been no specific testing for an intended air gap between the plies in the test specimens, although in some cases the test specimens experienced significant deformations or gaps prior to failure as illustrated in Figure 2. Thus, a small gap, for example, equal to the thickness of the thinnest ply, may be deemed acceptable.

It is suggested that, for design, the engineer may be guided by the test results as indicated in Table 3.

Based on available test data, Table 3, along with AISI S100 design equations, offers design guidance for common gap conditions.

This article is based on a Cold-Formed Steel Engineers Institute Tech Note of a similar title (www.cfsei.org).▪

Rigid Foam Insulation

1”

0.54 (33 mil or thicker)

2”

0.44 (33 mil or thicker)

2”

0.68 (54 mil or thicker)

4”

0.39 (54 mil or thicker)

Figure 3. Ratio of failure to Pn.

STRUCTURE magazine

9

August 2018

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n May 2016, the American Institute of Steel Construction (AISC) published ANSI/AISC 358-16, Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications. It has been a significant influence on the research and development of products by government agencies, universities, and engineering research centers. Much of the research was done soon after the failure of steel moment frames during the 1994 Northridge Earthquake.

These Prequalified Connections were developed to establish standards and aid in the design of building structures subjected to seismic loading. There is a total of nine Prequalified Connections, including four proprietary connections (#5, 6, 7 and 8), which are standalone designs and included herein for information only: 1) Reduced Beam Section (RBS) Moment Connection 2) Bolted Unstiffened and Stiffened Extended End-Plate Moment Connections 3) Bolted Flange Plate (BFP) Moment Connection 4) Welded Unreinforced Flange-Welded Web (WUF-W) Moment Connection 5) Kaiser Bolted Bracket (KBB) Moment Connection 6) ConXtech ConXL Moment Connection 7) SidePlate Moment Connection 8) Simpson Strong-Tie Strong Frame Moment Connection 9) Double-Tee Moment Connection

Vertical Beam Shear Distribution Structural engineers have made design assumptions for generations, most of which have been effective and conservative, but some assumptions have yielded less than favorable results. The design assumption we made on the steel moment connection is a prime example; we simply assume the beam shear transfer to the column by the beam web and shear tab or clip angles, and the moment transfer to the column by tensile and compressive forces in the beam flanges.

From Figure 1, we can see that there are three points of contact between the beam and the column, i.e., connections at the top and bottom flanges and the beam web. At each point of contact, a portion of the total beam shear will be distributed to the column in accordance with their relative stiffness. The shear distribution can be determined based on the following equations: d = df + dv = PL3 /12EI + 1.2 PL/GA (Eqn. 1) (Both ends are considered fixed) where d = total deflection, df = deflection due to bending, dv = deflection due to shear deformation, P = applied force, L = distance between both ends, A = cross section area, I = moment of inertia, E = modulus of elasticity, and G = shear modulus. shear modulus, G = E/2(1+µ), where µ = Poisson’s ratio.

For structural steel E = 29 x 106 psi, and µ = 0.30, let P = unit force = 1, and equation (1) becomes d = L3/384I + L/9.3A (Eqn. 2) Since stiffness is the inverse of the deflection, k = 1/d, we can determine the relative stiffness of each connecting element (ktf, kw, and kbf) with respect to the total sum of the stiffness, and thereby obtain the shear distribution at each location.

Are the beam shears distributed to the beam flanges significant? Yes, they are. As an example, a W24x68 beam connects to a column flange by a 7⁄16-inch x 18-inch shear tab, with a CJP weld to the column and slip-critical bolts to the beam web; beam flanges are groove-welded to the column, and the weld access holes conform to the FEMA 350 detail. From Figure 1, let Lw = 3 inches, Ltf = Lbf = 2.63 inches (FEMA 350) and, using the connecting element stiffness deter-

structural

DESIGN

Unanticipated Stresses and the Welded Flange Plate Moment Connection mined from the equations above, the author finds that the portion of the beam shear that goes to the beam web is about 83%, leaving 17% to the beam flanges or 8.5% for each beam flange. This is an average shear on the weld/beam flange rectangular section, and the maximum shear stress at the center would be 50% greater. According to the Hencky-von Mises principal stresses relationship, if we combine this shear stress with the design tensile/compressive stress, we would get an even larger stress (principal stress). This additional stress is significant and should be considered/ included in the design of the connection. It should be noted that the pre-Northridge moment connections had very short weld access holes, thus resulting in very rigid connecting elements between the column and the beam flanges. Therefore, a larger amount of beam shear would be transferred through the beam flanges.

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

Weld Shrinkage Residual Stresses In structural steel construction, a welded connection has some advantages over a bolted connection. It also has many disadvantages, a couple of which are: a) welded joints are highly prone to cracking under fatigue loading, and b) large residual stresses and distortion are developed in welded connections. The magnitude of the residual stresses varies greatly depending upon the joint restraint, geometry, material thermal properties, welding process, and more. If the parts to be joined are free to expand and contract, then the residual stresses would be minimal. However, if one or both parts of

STRUCTURE magazine

13

August 2018

Figure 1. Steel moment connection.

limited number of non-propriety moment connections currently in use. It has not been tested for prequalification but can be used for moment frames subjected to wind load and for structural steel systems not specifically detailed for seismic resistance.

The WFP moment connection is similar to the BFP moment connection; the flange plates are fillet-welded Figure 2. Reprint of Fig. 7.1 (AISC 358-16) bolted flange plate to the beam flanges moment connection. instead of bolted. The the joining members is/are subjected to exter- flange plates and the web shear plate can nal restraints, as in the case of direct welding be made thicker than the beam flange and between beam and column, then a high level the beam web, respectively, to shift the of residual stresses would occur as a result. plastic hinge away from the column. The It should be noted that, in a general welding flange plate shall be welded to the column process, residual stresses are increased when flange with double J or bevel T-joint CJP an increased number of passes are made. This groove weld to minimize weld shrinkage means that the thickness of the beam flange residual stress and distortion. The should be minimized. geometry of the top flange plate is configured such that, when welded to the beam flange, the high tearing Beam to Column stress is minimized. An additional Only Reduced Beam Sections (RBS) and weld between the flange plate and Welded Unreinforced Flange-Welded Web the beam flange may be added in (WUF-W) Moment Connections are direct the high tearing stress area to minibeam-to-column connections. In the actual field mize the tearing stress further. The construction, the beam flange welded joints will depth of the web shear plate should be subjected to weld shrinkage residual stress be made as deep as practically pos(longitudinal and transverse directions). The sible to maximize its stiffness and residual stress in the weld transverse direction thus capture most of the beam shear is substantial due to external restraint during force. Since the WFP connection welding. Neither side of the welded joint is free is very similar to the BFP connecto move, i.e., the beam is restrained by the other tion, the prequalification limit on end connection and other framing. Although the maximum beam depth, weight, both the RBS and WUF-W are prequalified by and flange thickness should be the laboratory testing, the validity of the testing is same, i.e., 36 inches (W36), 150 lbs/ questionable since it did not represent the actual ft and 1 inch respectively. However, building frame construction. In preparing the it is the author’s opinion that the test specimens, there was no external restraint limit should be 30 inches (W30), in the welding of beam-to-column specimens 108 lbs/ft and ¾ inch respectively or the cyclic loading tests. to minimize the residual stress in the The Bolted Flange Plate (BFP) moment welded joint (the thicker the beam connection (Figure 2) employs the flange plates flange, the higher the residual stress). as connecting elements, and the plates are free It should be noted that the cost of to move when welded to the column; therefore, fabrication and erection seems comonly minor residual stress exists at the welded parable to that of the BFP moment joint and may be considered negligible. connection.

WFP Moment Connection

Conclusions

As shown in Figure 3, the author presents Welded Flange Plate (WFP) moment connection design as an alternative to the

• The vertical beam shear distributed to the column through the beam web and top and bottom

STRUCTURE magazine

14

flanges, based on their relative stiffness, should be considered in the design of connections.

• A high level of weld shrinkage residual stress exists when the beam and column are directly welded together; this type of connection should be avoided until the magnitude of the residual stress is better defined, and the testing apparatus and process are made to represent the actual field construction.

• With additional shear and residual stress at the welded joints (with or without flange plates), reduction of the joint moment capacity should be considered.

• The WFP moment connection is a prime candidate for prequalification. If tested and prequalified, it will provide an additional design option for structural engineers.▪ The online version of this article contains references. Please visit www.STRUCTUREmag.org.

Figure 3. Welded flange plate moment connection.

August 2018

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structural

PERFORMANCE

E

arthquakes impose such large and infrequent forces on structures that building codes permit seismic damage if the structures do not collapse. This damage often takes the form of inelastic, permanent deformation of members and connections. The idea is that the occupants can safely exit the building after a significant seismic event; the structure may be a total economic loss when subjected to the maximum considered earthquake, but collapse prevention is the primary goal.

The R-Factor

Seismic Design of Aluminum Structures

By J. Randolph Kissell, P.E., and Ronald D. Ziemian, Ph.D., P.E. J. Randolph Kissell is a Managing Consultant at Trinity Consultants in Durham, NC. He has been active in the development of structural design standards, including the Specification for Aluminum Structures and presently chairs the AWS aluminum structural welding subcommittee. (rkissell@trinityconsultants.com) Ronald D. Ziemian is an Associate Dean and Professor in the College of Engineering at Bucknell University.

His primary area of scholarship is in structural stability, and he currently serves on the AISC, AISI, and Aluminum Association specification committees. (ziemian@bucknell.edu)

In designing for other loads, such as wind and snow, engineers realize that permanent deformations can be expected at strength limit states. But what makes modern seismic design interesting is that this inelasticity is actually advantageous to the performance of the structure during an earthquake. A partially yielded structure has less stiffness and consequently attracts smaller inertia forces – that is, less demand on strength as long as adequate ductility is present. To use elastic analysis for determining internal forces from an earthquake while simultaneously allowing inelastic behavior, building codes permit designers to divide such forces by a seismic response modification factor R. The R-factor is greater than 1, and its value depends on the seismic force resisting system (SFRS) of the structure – such as a braced frame or a moment frame – and the ductility of the structural material and components. For instance, the R-factor for a steel ordinary moment frame is 3.5. The bigger the R-factor, the smaller the seismic forces that must be resisted.

Before the 1994 Northridge earthquake, R-factors were estimated for various structural systems and materials and listed in ASCE 7, Design Loads for Buildings and Other Structures, which is referenced by most building codes. Northridge, however, revealed that some of these estimates were overly optimistic because unexpected fractures occurred.

Consequently, code writers became much more

Aluminum building first dynamic mode shape.

STRUCTURE magazine

16 August 2018

cautious in assigning R-factors and systems that have not been grandfathered into the code now face a considerably higher hurdle to establish their R-factors. Because aluminum seismic force resisting systems did not have R-factors assigned before Northridge, aluminum lateral force resisting systems now fall in the “show me” category.

Part of the reason for this omission is that lateral force resisting systems are rarely designed and constructed of aluminum. In many buildings, the lateral force resisting system is either a steel or reinforced concrete frame, and aluminum and glass are used for the building envelope to transmit the wind pressure on the face of the building to the steel or concrete frame. When the earthquake hits, the aluminum is just along for the ride.

There are exceptions, however, including greenhouses and space frames such as domes.

But it is hard to say today whether aluminum systems do not have R-factors because they are not used as SRFSs, or if aluminum systems are not used as SRFSs because they do not have R-factors.

In the absence of code-defined R-factors, designers either have to estimate a factor and provide justification so that the building official agrees, or set R equal to one, which means not accounting for the beneficial effects of inelasticity that may occur during an earthquake. While conservative, resisting earthquakes elastically is neither efficient nor competitive with other materials, unless, of course, wind loads govern the design of the lateral force resisting system. Wind can often govern the design of aluminum structures because aluminum has a high strength-to-weight ratio, so aluminum structures are light, resulting in less resistance to wind overturning while experiencing less inertial forces in an earthquake.

Aluminum and Steel While it is tempting to think that aluminum SFRSs should have about the same R-factor as equivalent steel SFRSs, that is not necessarily a slam-dunk. Steel and aluminum are both ductile metals, but aluminum has less elongation at rupture than steel. For example, the most commonly used aluminum structural alloy is 6061-T6, which has a minimum strain elongation of 8%, while A992 steel has an elongation of 21%. Also, the ratio of yield to ultimate strength for 6061-T6 is not limited and is 0.92 for minimum strengths, whereas this ratio is limited to 0.85 for A992 steel. Lastly, aluminum strengthened by heat treatment loses that strength when welded, unlike steel.

So where to go from here?

In 2009, the Federal Emergency Management Agency (FEMA) developed a rigorous protocol,

P695 Quantification of Building Seismic Performance Factors, for determining R-factors for building systems. In the P695 procedure, an R-factor is assumed in a structure’s analysis and design. The structure is then subjected to a suite of 44 ground motions and, based on advanced inelastic analyses of the structure for these motions, the probability of collapse is determined. If that probability is below FEMA’s specified threshold, the R-factor assumed at the beginning of the process is good to go. Because there is a significant amount of work involved in inelastically analyzing structures for all those ground motions, you are well advised to pick your initial R-factor wisely.

Studying Differences In 2013, the Aluminum Association, a trade association of aluminum producers, initiated a series of studies conducted by NBM Technologies to investigate aluminum SFRSs. NBM’s work culminated in a paper by Meimand et al. (2016), Incremental Dynamic Analysis and Seismic Performance Evaluation of an Aluminum Framed Building Compared

with Steel. They started by designing a onestory, three-span ordinary moment frame as the lateral force resisting system. This initial system was constructed of 6061-T6 extruded aluminum members in accordance with the Specification for Aluminum Structures, the design code for aluminum structures specified by the International Building Code. The bays of the system were 10 feet in both directions, giving an overall grid of 30 feet by 30 feet, with a 10-foot height. In addition to the dead load, a roof live load of 50 psf was assumed.

Using the FEMA P695 procedure and ABAQUS for the non-linear inelastic analyses, NBM determined a seismic response modification R-factor of 3 for this aluminum frame based on a 10% probability of collapse (see Figure). That alone would have been interesting, but not necessarily conclusive, because the P695 procedure is computational and complicated. To demonstrate the validity of the analysis, NBM next designed a steel frame of the same dimensions, using the AISC Specification for Structural Steel Buildings to size the members. Using the same method of seismic analyses, they found

that the steel structure also satisfied the P695 criteria but with R = 3.5, a very happy outcome since ASCE 7 says that R is 3.5 for such steel SFRSs. Of course, this is good news for the steel design profession too, because it helps to validate the steel seismic factor estimates of the past.

Because codes allow steel SFRSs to be designed without special ductility details for low seismic applications if an R-factor of 3 is used, the study suggests that aluminum SFRSs using an R-factor of 2.5 (3 times 3/3.5) might also not require special ductility details. However, it would be premature to establish this from a limited investigation.

While the study examined only one frame and ignored fracture limit states, the models included local buckling, local-global buckling interaction, and yielding. Perhaps the results are not surprising because aluminum’s ductility is an attribute that contributes to its extensive use, but hindsight rarely fails. Not only aluminum designers, but those working with hot-rolled steel, cold-formed steel, and stainless steel can gain confidence from this study.▪

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building

BLOCKS

S

elf-consolidating concrete (SCC) is increasingly used for reinforced formed-members, architectural concrete, and floors and slabs. It is often the only solution for structural repairs.

SCC is a highly flowable, non-segregating concrete with a slump/flow of 20 to 30 inches. SCC can be easily placed and completely fills forms under its own weight without mechanical vibratory consolidation.

Self-consolidating concrete is achieved by use of the proper dosage of a high-range water reducing admixture and a viscosity-modifying admixture when needed to ensure stability and eliminate bleeding and segregation at the target spread. A high-range water reducer plus a hydration-control admixture may be used. A hydration-control admixture can extend proper plasticity for several hours.

Proposed mixes generally list the target spread as plus/minus 2 inches. The design/contracting team agree on a target spread.

The target spread is the diameter of the concrete after the slump cone is raised.

SCC is defined as concrete with a spread of 20 to 30 inches after the cone is lifted. In heavily reinforced members, the design/contracting team often requires a target spread of 28 inches +/-1 inch. In many tall buildings, the self-consolidating concrete mix used in vertical members is also used in slabs. Having one mix eliminates the required coordination of the switch from the vertical mix to the floor mix.

Proper consolidation of a conventional mix requires two men. One is vibrating, and the other is moving the vibrator from point to point.

Therefore, the SCC mix is more economical. SCC usage means an increase in the volume of daily placements. More concrete can be placed in a typical workday with a smaller crew.

Maximum rental space is the goal in many buildings. Columns and walls are heavily reinforced and are as narrow as possible. SCC is a requirement. Example projects include a 14,000 psi concrete at Tower One at the World Trade Center in New York City. Almost all of New York City’s tall buildings are using 14,000 psi concrete in their vertical members at the lower floors. An 8000 psi SCC mix was pumped blindly into a heavily reinforced elevated slab under the active Number 1 subway line at the World Trade Center. The slab was 50 feet wide.

Every truck had to have a 28-inch spread. A lower spread could have resulted in a blockage, and that would have been disastrous. The Port Authority made a video of the early placements so that the team could see the SCC mix move easily into place.

Architectural concrete is increasingly using SCC. The American Concrete Institute’s ACI 347, Guide to Formwork for Concrete, has included

Self-Consolidating Concrete Specified and Used Regularly for Reinforced Formed Members

By William S. Phelan William S. Phelan is a Concrete Consultant and Technical Advisor and an Honorary Member and Fellow of the American Concrete Institute. (euclidchem@att.net)

10 Hudson Yards, New York.

STRUCTURE magazine

18 August 2018

guidance for determining form pressure. The Eli & Edythe Broad Museum at Michigan State University, Columbia University Medical and Graduate Education Building, and the United States Mission to the United Nations (USUN) are good examples of the use of SCC in successful architectural concrete projects. None of these projects had form pressure problems of significance that required concrete removal and replacement. The architect One World Trade Center. of the Michigan State University, Zaha Hadid, required “no bugholes.”

(Bugholes are small holes or voids in the concrete surface. They are +/- 1⁄8 inch plus/minus in diameter.) The solution was to have the SCC in every truck have a 28-inch spread.

Proper Planning Before the start of each new project, the contractor and design team should conduct a pre-concrete construction meeting to review the proposed mix designs and to discuss the required methods and procedures to achieve the specified concrete construction. The contractor should require responsible representatives from all stakeholders concerned with the concrete work to attend the conference, including but not limited to the following: • Contractor’s Superintendent • Structural Engineer • Ready Mix Concrete Producer • Admixture Manufacturer • Concrete Subcontractor/Finishing Foreman • Concrete Pumping Equipment Manufacturer • Laboratory responsible for field quality control • Independent testing agency responsible for concrete design mixtures The contractor should send a pre-concrete conference agenda to all attendees before the scheduled date of the conference. A typical agenda would include the following: Special SCC Mix Design Requirements • 28 day or 56-day strength.

• High early strength ____ psi @ ___ hours.

• Shrinkage – 0.04% @ 28 days is standard.

0.02% @ 28 days as noted on the drawings (This is the minimum standard if less shrinkage is required and minimal control joints are desired.)

• Freeze-Thaw/Durability • Concrete receiving moisture sensitive floor coverings: -Water Cementitious Ratio < 0.45 -High Range Water Reducing Admixture, Hydration Control Admixture -Fly Ash and/or Slag are required in many mixes (normal set is required for floor mixes). Normal setting concrete will allow the concrete contractor to perform the required finishing operation properly within four to five hours after placement.

The supplementary cementitious content, i.e., fly ash and/or slag, may be lower in floor mixes than in formed members since these supplemental cementitious materials tend to slow down the setting of concrete.

The concrete contractor should state that the proposed mix designs will enable proper placement, pumping, and finishing, and will achieve the concrete quality required by the specifications. The concrete producer should provide a high range water reducer re-dosage chart and a significant quantity of high range water reducing admixture on site to ensure that unexpected delays do not result in a concrete placement with spreads below the agreed upon spread/envelope.

Hydration control admixtures can maintain the proper spread and workability for several hours, which allows the concrete producer to stabilize concrete mixes for long periods without negatively affecting concrete durability.

Proper mix designs and successful test placements onsite to verify proper workability, pumpability, setting time, and finishing are required on all highperformance concrete projects. Setting times and spread targets are adjusted as necessary for the change of seasons. When the planning and preparation are thorough, and appropriate Quality Assurance/Quality Control (OA/QC) procedures are followed, a very successful project is the result.

SCC Usage Today SCC is also more economical because the crew requires two fewer people. The spread of placement and optimum crew size are of great concern for the concrete contractor. Many concrete contractors now know that the SCC cost-in-place for reinforced formed concrete is lower and the end product is superior compared to continuously placed and vibrated concrete. Early strength gain is essential on most projects to conform to an agreed upon rapid cycle schedule.

The Federal Highway Administration (FHWA) continues to work with the states, researchers, concrete industry, admixture suppliers, and other partners in advancing SCC technology through research development, deployment, and construction projects. Many Eli & Edythe Broad Museum at Michigan State University. states are using SCC in beams and girders, bridge piers and pile caps, slump. At the Freedom Tower, the water savcolumns, walls, and drilled shafts. SCC is also ings was 70 lbs/cy for 40,000 cubic yards of used in the repair of concrete members with concrete = 280,000 pounds of water saved limited access for conventional placement (33,533 gallons). and vibration techniques.

SCC results in a stronger, more durable SCC has many technical, economic, and concrete in place. Its use ensures easier and environmental advantages. It can help solve better consolidation, which results in a some difficult and costly field problems and longer lasting concrete. The elimination of should be given consideration when the con- vibration provides a safer workplace with crete involves: less noise and less damage to the hands and • Intricate and complex formwork arms of the workers vibrating the concrete.

• Congested steel reinforcement • Architectural features Successful SCC Projects • Pre-Cast elements • Need for quality, speed, and high The Table gives a summary of five recent sucproductivity cessful SCC projects. These proposed mix • Limited access for proper vibration designs were confirmed by successful trial The use of SCC in North America is placements onsite for architectural concrete increasing at a steady rate. It is similar to the and heavily reinforced members. automatic transmission in a car. Very few 1) Tower One at the World Trade Center people choose a stick shift car or choose con(WTC): 14,000 psi @ 56 days was crete mix for reinforced formed members that required for the shear walls from the requires vibration. foundations to the 30th floor.

SCC benefits include speed of job site pro2) No. 1 Subway Line: Another challengduction, ease and speed of placement, faster ing SCC was the new 3-foot-thick slab turnaround time of concrete trucks, elimiunder the No. 1 subway line, which nation of vibration and noise, lower water runs through the World Trade Center. content, and results in high performance and A very heavily reinforced slab, 50-feetlong-lasting structures. wide, was required. The SCC mix was For sustainability, SCC is the optimal consuccessfully pumped into this location crete mixture. SCC mixes tend to be more blindly. Cameras were installed to efficient because of the higher rate of cementiobserve the complete filling of the new tious efficiency (psi/lb. of cementitious). It slab. benefits from the use of significant quanti3) Columbia University Medical and ties of supplementary cementitious materials Graduate Education Building, New such as fly ash, slag, and silica fume. Cement York: SCC in use – Sloping Columns. content can be lowered. The water content 4) The Eli & Edythe Broad Museum is lower. Conserving water is a priority all at Michigan State University: This over the world. was another challenging architectural As an example, for the 1,776-foot-tall concrete project because of inclined Freedom Tower, the cement content of the forms. ACI 347 has included guid14,000 psi @ 56 days was 300 lbs/cy. (Total ance for determining form pressure. cementitious content was 873 lbs/cy). The Kamal H. Khayat and David Lange addressed the form pressure subject in water content was 220 lbs/cy. The project their presentation at the International averaged 16,160 psi at 56 days.

Workshop Conference, SelfTypical concrete, i.e., 3000 psi or 4000 psi Compacting Concrete, June 1st, 2012, concrete, with ¾-inch aggregate requires 290 pounds of water/cubic yard for a 3-inch in Stockholm, Sweden. Both Kamal

STRUCTURE magazine

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August 2018

Khayat and David Lange are world renowned authors and experts on SCC. (See the online version of this article at www.STRUCTUREmag.org for detailed references.)

5) 10 Hudson Yards, New York (52 Stories): New York City Concrete Industry Broad Grand Award Winner 2016.

requirements. In fact, the goal in North America is to have SCC become 15% of all ready-mixed concrete. This goal, set by the Industry Critical Technology Committee (ICT is part of the Strategic Development Council (SDC), a council of the ACI Foundation), is being achieved in more cities because of use in tall buildings. All major design firms today specify SCC for architectural concrete and heavily reinforced members. The benefits of SCC are recognized by many owners, designers, and concrete producers throughout the country. A leading repair contractor in the United States will not form and pour without SCC. A prominent concrete contractor in the Carolinas is using SCC regularly in wall placements to ensure a uniform finish and economy and speed of placement. Most structural engineering firms today include SCC in their master specifications.▪

Conclusion Many specifications require a maximum shrinkage of 0.04% at 28 days. SCC mixes can be designed for very low shrinkage (0.02% at 28 days) by adding a shrinkage reducing admixture. That very low shrinkage is often specified for exposed slabs and toppings and concrete below the waterline.

The goal is to reduce joints and cracks.

SCC dramatically expands the possibilities of successful high-performance concrete placements with difficult and demanding

Columbia University Medical and Graduation Education Building.

Table of successful SCC project examples.

Tower One at the World Trade Center (WTC)

No. 1 Subway Line New York

Columbia University Architectural Concrete

Eli & Edythe Broad Museum at Michigan State Univ.

10 Hudson Yards Tower (52 Stories)

Cement

300 lbs.

200 lbs.

350 lbs.

560 lbs.

425 lbs.

Microsilica

25 lbs.

---

---

---

40 lbs.

Fly Ash Class F

65 lbs. (Class C)

100 lbs.

200 lbs.

240 lbs.

---

Slag (Grade 120)

483 lbs.

550 lbs.

350 lbs.

---

575 lbs.

Sand

1160 lbs.

1260 lbs.

1320 lbs.

1312 lbs.

1000 lbs.

Coarse Aggregate

1646 lbs. (#67 & #8)

1380 lbs.(3⁄8”)

1020 lbs. (3⁄4”) 520 lbs. (3⁄8”)

1525 lbs. (3⁄4”)

1450 lbs. (#67) 450 lbs. (#8)

Water

220 lbs.

340 lbs.

300 lbs.

272 lbs.

262 lbs.

High Range Water Reducing Admixture (HRWR)

65 oz.

10 oz.

95 oz.

52 oz.

135 oz.

---

8 oz.

2 oz.

---

Viscosity Modifier Admixture --Hydration Control Admixture ---

68 oz.

25 oz.

---

---

Designed Water/Cementitious 0.25 Ratio

0.40

0.33

0.34

0.25

Designed Air Content

< 2%

---

---

< 2%

< 2%

FINAL RESULTS Air Content

1.75%

2.1%

< 2%

3% - 6%

< 2%

Slump Flow

25”

28” on every truck

28” +/- 1”

28” on every truck

25” +/- 1”

Water/Cementitious Ratio (Microwave)

0.29

0.40

0.33

0.34

0.27

16160 @ 56 days (14,000 psi Specified)

7174 @ 7 days 11044 @ 28 days 1178 @ 56 days (8000 psi Specified)

10.000 @ 56 days

11,000 @ 56 days

12,000 @ 56 days (Specified) 15,150 @ 56 days (Average)

153.9

---

---

---

---

7.8 x 10

---

---

---

---

18.5

13.9

---

13.75

14.57

Compressive Strength, f´c, psi (Actual)

Unit Weight, lb/cf.

Modulus of Elasticity @ 90 days, psi Cementitious Efficiency, psi/lb.

6

STRUCTURE magazine

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August 2018

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structural

COMPONENTS

T

he scope of the American Society of Civil The typical method of framing a multi-story Engineers ASCE 7-16 (ASCE 7) is to provide wood building is to use either the platform framminimum loads, hazard levels, associated criteria, ing method or the balloon framing method. In and intended performance goals for structures. addition to traditional framing, there is a method One of the performance goals of ASCE 7 is to being used where the top plates extend to the bottom provide General Structural Integrity (GSI). The side of the floor sheathing (Figures 1 and 2). In these GSI requirement for anchorage of structural walls cases, the WSW out-of-plane forces are anchored by is specified in Section 1.4.4.; “The anchorage shall the diaphragm sheathing. This puts the diaphragm provide a direct connection between the walls sheathing in direct tension and compression. and the roof or floor construction.” There are ASCE 7 Commentary Section C1.4, under the additional requirements for seismic out-of-plane guidelines for the provision of general structural wall anchorage in Section 12.11. integrity, specifies: ASCE 7, the 2015 International Building Code Generally, connections between structural com(IBC), and the American Wood Council’s (AWC) ponents should be ductile and have a capacity for Special Design Provisions for Wind & Seismic, 2015 relatively large deformations and energy absorption edition (SDPWS), are vague when it comes to under the effect of abnormal conditions. Details the specific requirements for anchoring wood that are appropriate for resistance to moderate stud walls (WSW) for out-of-plane forces. The wind loads and seismic loads often provide sufrequirements for ficient ductility. anchoring concrete How can ductility be provided in the out-of-plane and masonry walls wall anchorage of a WSW to a wood diaphragm to are better defined. meet the requirements for GSI, as well as provide When a structural ductility and redundancy in a wood structure engineer designs a structure, it is important, when relying on the wood sheathing alone? requirements are vague, to remember ductility, Figure 1 and Figure 2 can be constructed to meet redundancy, and GSI. the intent, material standards, and specifications The goal of this article is to clarify the wall anchorage of WSW’s to wood diaphragms for out-of-plane forces to meet the GSI requirement. Keeping the intent and performance goals of the code in mind, please consider the following question.

Is it appropriate to rely on the wood sheathing alone to provide ductility, redundancy, and GSI of WSWs out-of-plane anchorage forces? Major sources of ductility in wood structures are provided in FEMA P-751.

GSI is not only important for earthquake-resistant design, but also for resisting loads from wind, floods, explosion, progressive failure, and even such ordinary hazards as foundation settlement. It is essential to consider the requirements of the ASCE 7 section being used, as well as to consider the intent of Figure 1. Framing of wall parallel to floor joist.

ASCE 7 for GSI as a whole. Consider the purpose of Section 11.1.1 which clarifies that the detailing requirements and limitations prescribed in Chapter 11, and referenced standards, are required even when the design load combinations involved include forces other than seismic such as wind loading. ASCE 7 Section C11.1.1 specifies that “This detailing is required so that the structure resists, in a ductile manner, potential seismic loads in excess of the prescribed wind loads.”

ASCE 7 Commentary Section C12.1.3 has some clarifying language, “Good… engineering practice is to provide as much ductility and redundancy as possible.”

Figure 2. Framing of wall perpendicular to floor joist.

Anchorage of Wood Structural Walls

By Greg McCombs, S.E., and Steven M. Petroff, P.E. Greg McCombs is currently retired, having worked as an engineer in California for 18 years and another 5 years in Utah. Greg currently volunteers his time as a member of the Seismic Com-mittee of SEAU. (spideygsm24@icloud.com) Steven M. Petroff is a Project Engineer at ARW Engineers in Ogden, Utah, and serves on the Seismic Committee and Resilience Committee of SEAU. (stevenp@arwengineers.com)

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in ASCE 7. In Figure 3 and Figure 4, anchors are utilized to connect the joists and blocking to the wall, putting the diaphragm nailing in shear for the seismic out-of-plane WSW anchorage force. If the joists or blocking are not anchored to the WSW, the diaphragm sheathing is in tension or compression.

Without anchoring the joists and blocking to the wall, the joists and blocking may slip.

Ductility and redundancy are not provided by the wood diaphragm sheathing in direct tension or compression. The ductility is provided by the diaphragm nailing, in shear, to the joists and blocks as well as the metal anchors and straps.

Section 12.14.7.5 of ASCE 7 directly instructs that, “Structural walls shall be anchored to all floors, roofs, and members that provide out-of-plane lateral support for the wall…” This section continues with an explanation that the anchorage is selected to have the strength to resist the out-ofplane force. From this, it seems the intent of ASCE 7 is to utilize an anchor for out-ofplane force transfer from the wall into the supporting element, whether it be a floor, roof, or another structural element.

ASCE 7-16 Section 12.11.2.2 provides additional anchorage requirements for concrete and masonry walls to the diaphragm.

In ASCE 7-10, this same section applies to all structural walls, not just concrete or masonry.

The disparity between code cycles introduces confusion. What is the intent of this section?

Does this additional anchorage requirement also apply to WSWs? What is the intent of the codes regarding wood sheathing to resist forces in tension or compression?

ASCE 7 Commentary Section C12.11.2.2.3 specifies that the, Material standards for wood structural panel diaphragms permit sheathing to resist shear forces only; use of diaphragm sheathing to resist direct tension or compression forces is not permitted.

This is also consistent with ASCE 7 Commentary Section C11.2 which, under the sub-section Shear-Controlled Diaphragm, explains that wood-sheathed diaphragms are “diaphragms that are intended to yield in shear rather than flexure” (flexure results in tension and compression in the diaphragm).

Per the SPDWS Section 4.2.6.1 Framing Requirements: Diaphragm boundary elements shall be provided to transmit the design tension, compression, and shear forces. Diaphragm sheathing shall not be used to splice boundary elements.

Diaphragm chord members are used to resist the tension and compression forces at the

boundaries. This is also consistent AWC SPDWS Section 4.1.4 for Boundary Elements: Shear wall and diaphragm boundary elements shall be provided to transfer the design tension and compression forces.

Diaphragm and shear wall sheathing shall not be used to splice boundary elements.

The purpose of commenting on diaphragms and boundary members is to reinforce the intent that wood sheathing is not to be used to resist tension or compression forces in any manner.

Figure 3. Modification of Figure 1 to meet the intent of building codes.

To illustrate, consider the following calculations to adequately detail Figures 3 and 4.

For the purposes of the calculations, the following design information is assumed. The structure is a multi-story wood structure with a 10-foot floorto-floor height. Seismic design criteria is provided as Ss = 1.5, S1 = 0.5, Fa = 1.0, Fv = 1.8, Ie = 1.0. Wind design criteria is provided as V = 120 mph, Exposure C, h = 30 feet, Kd = 0.85, Kzt = 1.0, and Ke = Figure 4. Modification of Figure 2 to meet the intent of building codes.

1.0. The architectural finish of the wall uses 4-inch face-brick veneer. 7-16. Listed there is Exterior Stud Walls with The distance between vertical elements that Brick Veneer at 48psf. With all the values provide lateral support to the diaphragm determined, calculate Fp. L f = 50 feet. With the design criteria for wind and seismic determined, it is now Fp = 0.4 * 1.0 * 1.5 * 1.0 * 48psf = 28.8 psf possible to calculate the out-of-plane forces for seismic and wind.

Wind forces are determined per ASCE 7-16, Seismic forces are determined per ASCE 7-16, Section 27.3 Section 12.11.2.1, Wall Anchorage Forces. p = qGCp ‒ qi (GCpi ) (Eqn. 27.3-1) Fp = 0.4SDS kaIeWp > 0.2kaIeWp (Eqn. 12.11-1) Note that q is determined at the mean roof L 50 =1.5 where ka = 1.0 + 100 = 1.0 + 100 height, h, for walls and roofs of enclosed (Eqn. 12.11-2) buildings and that qi is evaluated at the highest opening that could affect the positive internal where Wp = the weight of the wall tributary pressure; for simplicity and conservatism, this to the anchor. Note that the minimum is taken as qh. The gust effect factor G is deterrequirement for Fp, the right side of the mined per Section 26.11.1 and taken as 0.85 for inequality, controls whenever SDS is less this example. The internal pressure coefficient, than 0.50. The design earthquake response GCpi, is determined from Table 26.13.1 and acceleration parameter at short periods, SDS, taken as ±0.18. The external pressure coefficient, is per Section 11.4.5 Cp, is determined from Figures 27.3-1, 27.3-2, and 27.3-3, where only Figure 27.3-1 is used SDS = 23 SMS = 23 Fa Ss = 23 * 1.0 * 1.5 = 1.0 for this example. A simplification of Equation (Eqn. 11.4-1 and 11.4-3) 27.3-1 is possible considering that q and qi are both evaluated as qh.

To determine the weight of the wall assembly, refer to Table C3.1-1a of ASCE p = qh (0.85Cp ‒ (±0.18))

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qz = qh = 0.00256KzKztKdKeV 2 (Eqn. 26.10-1) Per Table 26.10-1, Kz at 30 feet for Exposure C is 0.98. Therefore, solving Equation 26.10-1 provides: qz = qh = 0.00256KzKztKdKeV 2 = 0.00256 * 0.98 * 1.0 * 0.85 * 1.0 * 1202 = 30.7 psf

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Consider that, per Table 27.3-1, only the wall pressure coefficients are of interest for this example. Recall that, per Section 26.4.1, positive pressure acts toward the surface and negative pressure acts away from the surface.

Worst case compression forces would be at the windward wall, Cp = 0.8, and worst-case tension forces would be at the leeward wall, Cp = -0.7. Solving the simplified version of Equation 27.3-1 provides: pcompression = 30.7psf (0.85 * 0.8  (±0.18)) = 26.4 psf ptension = 30.7psf (0.85 * (-0.7)  (±0.18)) = ‒23.8 psf The allowable stress design load coefficients for seismic and wind are 0.7 and 0.6, respectively, per Section 2.4.1. Seismic and wind out-ofplane forces can be summarized as follows.

FpASD = ±0.7 * 28.8 = ±20.2 psf pcompressionASD = 0.6 * 26.4psf = 15.8 psf ptensionASD = 0.6 * ‒23.8psf = 14.3 psf

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Therefore, seismic controls both the tension and the compression force for this example.

Consider out-of-plane anchors installed at 4 feet on-center (o.c.) along the length of the wall. This produces a tributary area of 40 square feet, (4 x 10). The engineer should consider that, when the anchor spacing exceeds 4 feet o.c. per Section 12.11.2.1, the structural wall is to be designed to resist bending between the anchors. As the anchor spacing of this example does not exceed 4 feet o.c., this design check is not required. The ASD level forces for compression and tension are: FpASD = 40ft 2 * ±20.2psf = 808 lb Using this force, the SE would then select an anchor with a minimum of 808-pound tension capacity. The SE is also to consider the requirement of Section 12.11.2.2.2 to increase the out-of-plane force by 1.4 for specific steel elements. An additional step is to determine the length that blocking must be extended into the diaphragm to resolve the tension and compression force. For this example, use a diaphragm composed of 19⁄32-inch sheathing on 2x material

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with 10d nails spaced at 6 inches at the boundaries and edges. Per SDPWS-2015, the nominal unit shear capacity, Table 4.2A, is 640 plf. The ASD design unit shear capacity per Section 4.2.3 of SDPWS-2015 is 320 plf. The length, or drag, into the diaphragm is at least: LDIA =

808lb = 2.53 ft = 30.4 in 320plf

If joists are spaced at 16 inches o.c., this would require a minimum of two (2) joist spacings. As joist layouts are undetermined until framing is underway, it is unknown what the spacing between the wall and the first joist is. Depending on the joist layout, this spacing may be less than 16 inches. It is recommended to specify a minimum distance in addition to a minimum number of joists spaces to account for this condition.

For this example, the authors would use three (3) joist spacings with a minimum of 36 inches. The increase in force to select an anchor per Section 12.11.2.2.2 is not required to determine the development length into the diaphragm.

Note that Figure 4 has additional tie straps over the joist, as the joist interrupts the continual length of the blocking. These continuous tension straps are to be considered at each joist intersecting the drag length into the diaphragm to ensure adequate tension transfer. An alternate approach is to use a continuous strap.

For the condition presented in Figure 3, the approach to determine the out-of-plane tension and compression force would be the same. The main deviation between the approach presented for Figure 4 is that no blocking is required, as the out-of-plane force can be transferred from the wall into the joist via the wall anchor. This anchor is to be designed to the same out-of-plane force as determined above. The engineer may consider specifying boundary nailing along the top of the joist for the length into the diaphragm required to develop the anchorage force.

In conclusion, it appears ASCE 7 intends that the wood diaphragm sheathing alone should not be used to provide the out-ofplane wall anchorage of any structural wall. To answer the question previously posed, using wood diaphragm sheathing alone to resist tension or compression forces to brace WSWs for out-of-plane anchorage is not consistent with the intent of the building codes. The out-of-plane WSW anchorage forces must be developed a sufficient distance into the diaphragm by use of framing members, anchors, blocking, etc. Detailing with adequate attention to anchor load paths meets the intended performance goals of ASCE 7 for GSI.▪

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EXPANSION OF CONCOURSE A Charlotte Douglas International Airport

By Christopher R. Herron, P.E., Christopher H. Garris, A.I.A., LEED AP, and Carlos de Oliveira, M.A.Sc., P.Eng. Erection of arched steel trusses spanning the width of concourse over the elevated concrete slab.

A

primary feature of Destination CLT, the Charlotte Douglas International Airport (CLT) in Charlotte, NC, the expansion of the airport’s Concourse A is now under construction.

The overall goal of the Concourse A Explansion - Phase I (Phase I Expansion) is to enhance the arrival and departure experience of regional and connecting travelers while providing new gates to accommodate existing and future growth at CLT, ranked among the nation’s 10 busiest airports.

This multiphase project will ultimately provide up to 27 new gates, with 9 new gates completed under Phase 1 now under construction.

The new concourse is connected to the main terminal with a 750-foot corridor which will provide areas for services and be energized with art both inside and outside.

The Phase I Expansion is sited along the main entry drive to the airport terminal. The new concourse and connector’s location and signature architectural expression will go far in providing a new “gateway” to the airport.

The Team of Perkins+Will and CDesign, with Stewart Engineering providing structural design services, designed a simple yet dynamic structure composed of an arched roof which is asymmetrical to the north to allow for maximum daylight into the concourse. The structure for the large overhanging roof is enclosed between metal roof panels and a slightly reflective interior ceiling. The overall result is a wing-like roof that hovers over the concourse spaces below.

Exposed V-shaped steel columns support the roof, which reflects the asymmetrical geometry of the concourse, and change from the south to the north to accentuate the sense of motion implied within the structure. By use of both standardized and custom-designed steel castings, the design team was able to achieve functional, architecturally exposed structural steel (AESS) connections that seamlessly tie the columns together and elevate the exposed structure into something spectacular.

movers, and service features below for storage, mechanical, tugs, and luggage circulation.

The roof structure used arched steel trusses, which span the 105foot concourse width. The trusses were relatively shallow, at a depth of 8 feet to stay within the arching ceiling space, and were spaced at 15 feet on-center to support the long span steel decking. The spacing resulted in every other truss framing into the columns with the remaining trusses supported on transfer beams. The trusses consist of arched wide flange top and bottom chords with wide flange web members. The truss members are connected with bolted plate connections. The trusses cantilever 17 feet past the supporting columns

Challenges The expansion posed several structural challenges in the concourse and connector areas. These issues included a long span roof with a high arched roof structure, a low clearance between the tarmac and the first elevated floor, expansive glass walls throughout the entire concourse and a very long connector area, which includes people STRUCTURE magazine

Completed cantilevered truss ends, arched decking, and wind girt system at the sloping exterior wall with the “V” columns.

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as they taper to form a “wing” point on the edge of the roof.

Initial Concepts The roof was cantilevered in all four directions resulting in a particular challenge at the corners due to the cantilevered roof framing extending in both directions.

The low clearance below the elevated first floor required a shallow structure to maximize the open space below for operations. The design team determined that the most economical system that met clearance and vibration requirements was a two-way concrete 12-inch slab system supported on concrete columns. The team designed the space below to allow a conventional 30-foot by 30-foot grid. The concrete slab system also facilitated a seamless support for the recessed walkways which extended the full length of the connector. The concrete structure also provided the needed rigidity to resist seismic and wind loads. Due to the open floor plan and building function, vibration was an important design constraint best Collaborative Design Evolution addressed by the concrete structure.

Conceptual design development of custom cast steel bases.

The V-shaped hollow structural steel columns were located on either side of the concourse. The columns supported the CONC FILLING PORT TO roof trusses and the wind girt structure of the glass walls. The BE LOCATED ON HSS COLUMN exposed wind girt structure consisted of hollow structural steel members spanning vertically with the window mullions. The angle of the “V” columns supported the sloped glass wall, REVEAL HSS20 which leaned outward over the full height of the structure.

HSS20 The lateral system of the building had high demands due to the 55-foot tall clear-story roof, the tall walls, and the AESS HSS16 90 MPH wind speed with a wind exposure C at the airport CUSTOM DESIGNED site. The lateral system also needed to support the required CAST CONNEX STEEL COLUMN BASE NODES blast loading on the structure. The steel portion of the lateral (3)#5 BARS STACKED system utilized the steel trusses on round hollow structural EACH SIDE steel columns as moment frames. Each of the round columns (3)#5 HAIRPINS @ANCHOR BOLTS (3)#5 BARS consisted of two columns connected at the base and extending STACKED EACH SIDE apart forming the “V.” The lateral system along the length of the concourse consisted of moment frames using steel beams, which spanned between the HSS columns along with the (3)#5 HAIRPINS (3) ADDITIONAL addition of steel lateral trusses within the wind girt systems @ANCHOR BOLTS TIES @ ANCHORS PROVIDE SS CAPS OVER along the perimeter. The building contained a steel framed ANCHOR ROD NUTS (3) ADDITIONAL TIES @ TOP OF (3) ADDITIONAL TIES mezzanine for a portion of the concourse, which also assisted COLUMN @ ANCHORS with the lateral support of the building. The concrete lower (3) ADDITIONAL TIES @ TOP OF COLUMN level of the building used reinforced concrete shear walls.

(5)ADDITIONAL EMBEDDED ANCHOR RODS The long-span, tall-truss moment frame resulted in signifiTIES @ANCHOR HEADS (5)ADDITIONAL TIES cant vertical and horizontal loads and overturning demand at @ANCHOR HEADS #4 "U" BAR AT EACH ANCHOR its base. The peak reaction forces at the underside of the cast #4 "U" BAR AT GROUP EACH ANCHOR node were in the range of 840 kip-ft and 260 kip-ft in the inplane and out-of-plane directions, respectively; 460 kip peak Custom designed cast steel column base node details as shown in the structural set. compression; 10 kip net uplift; and 100 kip shear at the base.

These loads had to be transferred to the concrete columns below, through the elevated concrete slab. It was not possible to recess above the baseplate were also undesirable and were unsafe with people the column connection below the slab due to the required connections walking throughout the area. between the concrete slab and the concrete columns below. This meant Consequently, the design team was excited to explore the benefits of the connection had to be located above the slab level where they would the casting process. Key features of the base design included: be exposed. The connection also needed to accommodate the two • Integrate dual column for structural support and bracing into a columns framing into a single point to form the “V.” single sculptural base • Fire-resistance rating for steel casting required concrete fill to prevent the need for intumescent paint coating on the castings Custom Castings • High-performance coating on the base to transition to Intumescent Initially, a standard steel connection was designed to transfer the loads at paint above the casting datum line the column. This consisted of a series of welded vertical and horizontal The resulting nodes are over four feet tall and have an oviform four-foot plates with large anchor bolts. Due to the geometry and the significant by three-foot base with expressive counterbores to accommodate field loads, the connection became very large and was not aesthetically installation and anchorage to the reinforced concrete base. At a weight pleasing for an exposed condition. The exposed anchor bolts projecting of over 4,000-pounds, the castings are designed to be filled with concrete STRUCTURE magazine

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supplier and the steel fabricator, and c) outlined structural performance and aesthetic requirements (structural loading and surface finish requirements, for example) for the castings. Cast Connex did not charge any upfront consulting fee for the support provided during the design phase of the project; however, Cast Connex was the specified manufacturer of the specialty design-built elements. As procuring and incorporating the castings into the structural steel framework was left within the scope of the steel fabricator, Cast Connex provided their design and manufacturing proposal to all steel fabricators bidding on the project.

Post-Tender Casting Engineering and Construction

Finite element stress analysis result.

after being set, thereby negating the need for fire coatings. Finally, a purposeful reveal was designed into the casting to provide a clean transition between the high-performance coating system on the castings and the intumescent coating required on the HSS columns above.

Cast Connex provided support to Perkins+Will, CDesign, and Stewart Engineering during the design phase to facilitate the specification of structural steel castings as a delegated design item in the contract documents. Discussions with a specialized casting design-builder during a project’s design phase ensures that the resulting component is not only architecturally appropriate and structurally adequate but also that the design is economically castable and best leverages the advantages of casting manufacturing to the benefit of the project.

The collaborative design process commenced with the development of four initial concepts by the casting design-builder, followed by successive iterations of input by the design team and remodeling to address aesthetic preferences and functional needs. Augmented reality visualization – where 1-to-1 scale, 3-dimensional design models were superimposed over the user’s view of the real world – was employed to study and convey the design concepts for consideration through the process. This technology, quickly becoming mainstream, was a valuable tool for exploration and decision-making.

As noted above, the need for a 2-hour fire resistance and the desire for the base to be painted with a high-performance coating rather than intumescent also drove the design. Ultimately, fire resistance requirements drove the design away from a pin-connected inclined column to a welded connection at the base. The wall thickness and concrete fill volume of the cast node were then proportioned to achieve the 2-hour fire resistance as confirmed via 2-dimensional heat transfer analysis conducted by The Fire Consultants of Apex, NC. Once the conceptual design of the base was finalized, structural and architectural drawings were updated to show the cast steel components diagrammatically. When so doing, it is important to provide the overall dimensions of the casting, its general configuration, and its relationship and connectivity to other structural elements.

Also, the casting design-builder provided a template performance specification for the castings. This formed the basis for a subsection of the division 05 specification on the steel castings. The specification a) delegated structural design responsibility to the casting supplier, b) clearly defined the roles and responsibilities of both the steel casting STRUCTURE magazine

Cast Connex analyzed the cast steel bases by using a sophisticated finite element analysis model that included coupling constraints, contact boundary conditions, and non-linear material models to sufficiently capture the interaction between the steel columns, cast steel base, anchor rods, and reinforced concrete structure below the base. Stress and strain states from over 1,000 unique load combinations were analyzed to ensure the structural adequacy of the casting.

The casting design-builder created detailed casting and machining shop drawings, clearly differentiating as-cast features versus those which would be machined. They also coordinated and stipulated manufacturing tolerances, casting non-destructive examination criteria, material chemistry and heat treatment, and all other production parameters necessary to ensure the manufacture of castings that are fit for purpose.

Finally, Cast Connex provided support to CMC Structural on all aspects of fabricating with steel castings, including providing technical support related to the development and qualification of welding procedure specifications (WPS) via procedure qualification records (PQR) and testing for welds to be applied between the various cast and rolled steel products.

Conclusion The design of the Concourse A Expansion - Phase I will provide a new “threshold” experience for CLT and will accommodate future growth and flexibility for change. The architectural expression works well with the existing architecture of the main terminal but provides a new “spin” on the way structure and architecture are realized. By concealing the roof trusses and expressing the structural columns, the team seized the opportunity to articulate the column bases where passengers will have a direct, visual connection. The proportion, finish, and required code ratings all worked to drive a solution that was achieved by leveraging the benefits of steel casting.

The cast bases and frame connections serve as a functional solution and provide dramatic sculptural and artful detail intrinsically valued by the architectural team. The final product is one that is both beautiful and functional, something that will be enjoyed by travelers for years to come.▪

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Christopher R. Herron, P.E., is the Director of Charlotte Operations for Stewart Engineering located in North Carolina.

Christopher H. Garris, A.I.A., LEED AP, is a Design Principal with Perkins+Will.

Carlos de Oliveira, M.A.Sc., P.Eng., is a Co-founder and President and CEO of Cast Connex Corporation.

August 2018

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Bedford Square Conventional Cold-Formed Steel Framing Solves Unconventional Problems

D

Overall Bedford Square view.

Courtesy of Centerbrook Architects and Planners.

esign challenges often present themselves where a readymade solution is not available, and a unique solution using standard products must be designed. Various manufacturers in the cold-formed steel industry have developed a wide range of products, including unique clips and curved members. These products may have been designed to solve specific problems but, as new challenges are presented, a solution using standard products may be required. Such was the case on a renovation project in Westport, CT, where the versatility of conventional cold-formed steel framing was utilized to frame and support an architectural curved brick opening with cantilevered roof framing.

Project Summary Bedford Square is a new mixed-use community in Westport which combines a renovated/converted historical Firehouse and 1920s-era Bedford Buildings with multiple new buildings ranging from two to four stories. The new, planned community will combine residential living with amenities such as public spaces, retail, and restaurants. The new additions, the Main and Gunn buildings, set out to match the historical architectural features of the original construction. In August of 2015, ADTEK Engineers began performing delegated design for the Bedford Square project for its client, Manganaro Northeast LLC, a drywall subcontractor in the New England area.

The Bedford Square project utilized a mixture of structural systems. Cold-formed steel framing was used throughout in a range of applications including non-load bearing and load bearing systems.

Cold-formed steel framing was also used in various buildings as floor joists and roof rafters, for exterior skylight support, exterior concrete stair support framing with integrated planters, and exterior raised platforms. Additionally, plywood sheathed cold-formed steel shear walls were used as the lateral force resisting system for the new buildings.

This project had many unique architectural features, including a complex roof geometry with hips and valleys of varying slopes and curves, and several curved architectural openings and canoEyebrow opening. Courtesy of Derek Hayn/ Centerbrook Architects and Planners. pies. To support roof STRUCTURE magazine

By Andrew Newland, P.E.

framing within the complex geometry, ADTEK relied heavily on proprietary clips and joist hangers from Simpson Strong-Tie and The Steel Network. The availability of design information, as well as the availability of manufacturer representatives, aided in the design of connections using the proprietary products. Specifying multiple manufacturers made it possible to use the correct clip or hanger for the correct application.

Using products from these manufacturers solved many problems; however, these products do have their limitations and may not be appropriate or provide a feasible solution for all applications.

Understanding these limitations is critical to solving design issues.

The architect and engineer of record relied on the versatility of cold-formed steel framing to create curved framing that would support gravity and lateral wind loading. Various features were curved in either vertical or horizontal directions and with large radii, many times without supplementary structural support.

In most areas, ADTEK was able to design curved openings using straight headers with rigid framing. Where straight headers and rigid framing were not feasible, and a continuously curved header was required, ADTEK specified Radius Track at the curved headers.

Design Challenges There were several design challenges that emerged due to the complex geometry and various specific features. One particular wall design challenge was a large brick “eyebrow” which was included as one of the balcony features in what is considered the Main building of Bedford Square. This opening created several challenges because it required an extremely large radius and the opening framing had to support the roof rafters.

This “eyebrow” opening was specifically challenging because the apex of the curved opening was higher than the roof rafters bearing on either side. The geometry of the opening and roof framing prevented a single straight header with rigid framing from being installed, so proprietary curved framing was investigated. Also challenging, as shown in the rendering, was the large radius originating at the floor level. The large length and radius necessitated the need for large heavy-gauge cold-formed steel members. Realizing the limitations of proprietary members, it was determined that they would not be feasible.

Solutions To solve the design challenges, a series of headers and posts were used. As shown in the elevation, one high header, which supports the roof framing at the apex, and two low headers, which support

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CFS eyebrow wall sections.

CFS eyebrow detail elevation.

the high header and the remaining roof framing, were provided. achieve the complex geometry required at Bedford Square while The low headers are supported by two cold-formed steel posts, one still using proprietary clips. of which acts as the jamb stud to transfer lateral wind load to the Knowing the limitations of these products allows for creativity roof diaphragm and the floor system. The low header cantilevers and highlights the versatility of conventional cold-formed steel past the post/jamb member over a portion of the opening which framing. In this instance, a proprietary curved member was not allows the framing to provide support for the high header posts at feasible or desired by the client. Additionally, the complexity of the ends of the cantilever. the detail eliminated standard design methods and also eliminated The lack of continuous framing around the opening created the issue the need for a curved structural steel member to be installed by of transferring lateral load from the feature back to the structure. another trade.

The lower headers were located at or near the roof so that the lateral ADTEK was awarded 1st place for Cold-Formed Steel Engineers load could be transferred from the full height wall studs adjacent to Institute (CFSEI) Design Excellence Category Award for its the opening, the post/jamb studs, and a portion of the opening to unique detailing and solution to this problem at the CFSEI the roof diaphragm. Similarly, the ends of the upper header were Expo in Fort Worth, TX, in May of 2017.â&#x2013;Ş located at the roofline to transfer the lateral load from the opening Andrew Newland is the Team Leader of ADTEK Engineers, Inc. into the diaphragm.

Specialty Department in Fairfax, VA. He is an Executive Committee Once the transferring of the lateral load was solved, various aspects Member of the CFSEI, Mid-Atlantic Steel Framing Alliance, and ASCE-SEI of the architectural features needed to be met. Stud infill framing Committee on Cold-Formed Structures. (anewland@adtekengineers.com) and track members were used to partially make the curves of the opening. This supplemental framing was tied back to the beams and posts. Additionally, wood blocking was installed and connected back to the cold-formed steel framing to complete the curve.

Solving this design challenge emphasizes the importance of understanding various manufacturersâ&#x20AC;&#x2122; limitations as well as proper detailing of unique conditions by the architect and engineer of record. Proprietary cold-formed steel products such as Radius Track, Simpson Strong-Tie, and The Steel Network can solve CFS eyebrow details. numerous design issues, but they also have their limitations. Radius Track made many of the curved openings and canopies on this project possible without requiring specialized details. Simpson Strong-Tie and The Steel Network provided clips and hangers that made designing connections to concrete, masonry, structural steel, and cold-formed steel much easier in many cases. Simpson Strong-Tie also provided assistance in hanger specification for numerous connections which required sloped and/or skewed geometries to achieve architectural features. Despite the versatility of both Simpson Strong-Tie and The Steel Network clips, there were still numerous areas which required specialized detailing to be able to Church Street view. Courtesy of Derek Hayn/Centerbrook Architects & Planners.

STRUCTURE magazine

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August 2018

2018 NCSEA STRUCTURAL ENGINEERING SUMMIT Rates increase on September 7th, register today to save! Visit www.ncsea.com/register

Wednesday, October 24, 2018 7:30 - 6:00 8:00 - 4:00 12:00-1:00 12:15-3:30 4:00-5:00

Registration Committee Meetings Committee Lunch Atlas Tube Plant Tour YMG Reception

7:00 - 6:00 7:30-9:00 8:00-9:00 8:00-6:30

Registration Delegate Interaction Breakfast Attendee Breakfast on Trade Show Floor Trade Show Floor Open

9:00-10:30

Always Striving for Better Ron Klemencic, P.E., S.E., MKA

4:00-5:30 5:00-6:30 6:00-7:30 8:30-10:00

Thursday, October 25, 2018

Advances in material science, construction methods, analytical tools, and design methodologies continue to provide opportunities for improving on what has been accomplished in the past. This presentation will review how some of the most impactful innovations were developed and speculate as to what areas are ripe for the next wave.

10:30-12:00

Influence Redefined…Be the Leader you Were Meant to Be, Monday to Monday Stacey Hanke

Are you as good – or bad as you think you are when you communicate with influence? This presentation will help you persuade, sell, influence, and communicate face-to-face with a clear message.

12:00-1:00

2:15-3:15

3:45-4:45

Wind Design Beyond the Code

Patrick Ragan, S.E., WSP, and Brian Greve, P.E., S.E., Wiss, Janney, Elstner Associates

2:15-3:15

Wrigley Field Renovations and Chicago’s First Tied Arch Bridge Bill Bast, P.E., S.E., SECB, Thornton Tomasetti, and Soliman Khudeira, P.E., S.E., CDOT

3:45-4:45

Chicago Riverwalk and Apple Store Matt Johnson, P.E., Simpson, Gumpertz & Heger; Andrian Parkinson, P.E., S.E., Foster & Partners; Terry McDonnell, P.E., S.E., Simpson, Gumpertz & Heger

TRACK 4 1:00-2:00 2:15-3:15

Standard of Care: in Theory and in Practice

Jerry Maly, P.E., Wiss, Janney, Elstner Associates

Picture. Plan. Perform... Ideas for Successful Business Development Brad Thurman, P.E., Wallace Engineering, and Dana Birkes, Crossland Construction

Risk Management Claim Studies

John Tawresey, S.E., F.SEI

TRACK 5: Young Engineer Education

Design and Inspection Responsibilities for a Project Utilizing a Metal Building

1:00-2:00

Greg Robinson, P.E., S.E., SECB, LBYD; Dustin Cole, P.E., S.E., Chief Buildings; W. Lee Shoemaker, P.E., Ph.D., MBMA

2:15-3:15

Lessons Learned from Safety Evaluation of Buildings after Windstorms

Three Tools for More Efficient Seismic Design Rafael Sabelli, S.E., Walter P Moore

Update of ATC-20 Post-Earthquake Safety Evaluation of Buildings – Session 1

Ayse Hortacsu, S.E., Applied Technology Council

3:45-4:45

Zurich NA Headquarters and Marina City Renovations

Emily Guglielmo, S.E., Martin/Martin, Inc.

TRACK 2

2:15-3:15

1:00-2:00

3:45-4:45

Ed Huston, P.E., S.E., Smith & Huston, Inc

1:00-2:00

TRACK 3: Chicago Project Highlights

Lunch on the Trade Show Floor

TRACK 1 1:00-2:00

Delegate Reception Welcome Reception on Trade Show Floor Structural Engineering River Cruise 1 Structural Engineering River Cruise 2

Update of ATC-20 Post-Earthquake Safety Evaluation of Buildings – Session 2

Ayse Hortacsu, S.E., Applied Technology Council

The Devil’s in the Details: Connection Design Andrew Murray, P.E., S.E., Thornton Tomasetti

How to be an (Effective) Project Manager

Howard Birnberg, Assoc. for Project Managers

3:45-4:45 4:45-6:30

Mentor Roundtable: NCSEA Leaders Cocktails on the Trade Show Floor

7:00-11:00

A Celebration of Structural Engineering, hosted by Computers & Structures, Inc.

OCTOBER 2427, 2018 · SHERATON GRAND CHICAGO Friday, October 26, 2018 7:00 - 4:00 7:30-10:30 7:30-8:00 7:30-12:00 8:00-10:10

Registration Delegate Collaboration Breakfast Attendee Breakfast on Trade Show Floor Trade Show Floor Open Exhibitor Presentations:

TRACK 1 8:00-8:25 8:35-9:00 9:10-9:35 9:45-10:10

Trimble Sky Civ Lindapter ASCE

TRACK 2 8:00-8:25 8:35-9:00 9:10-9:35 9:45-10:10

Giza Steel Freyssinet MiTek LaFargeHolcim

TRACK 3 8:00-8:25 8:35-9:00 9:10-9:35 9:45-10:10

RISA MeadowBurke Bekaert AZZ Galvanizing

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Dlubal Peikko Fyfe CHANCE

11:00-12:00

12:00-1:15

Chicago and the Skyscraper – A Look at Chicago’s Role in the History and Future of Structural Engineering of the Skyscraper Bill Baker, P.E., S.E., and John Zils, S.E., Skidmore, Owings and Merrill LLP Lunch with Keynote Inspiring the Next Generation of Structural Engineers to Lead, Influence, and Inspire Ashraf Habibullah, S.E.,CSi, Inc.

The presentation will discuss how the structural engineer’s education and role must change if our profession is to triumph and flourish in these rapidly-changing times.

TRACK 1 1:15-2:15

PCI Design Handbook – 8th Edition Content and Updates Jared Brewe, Ph.D., P.E., S.E., Simpson Gumpertz & Heger

2:30-3:30

Force Transfer Around Openings for Wood Framed Shear Walls

Jared Hensley, P.E., APA

3:45-4:45

2018 NDS for Wood Construction – Significant Changes Michelle Kam-Biron, P.E., S.E., SECB, American Wood Council

TRACK 2 1:15-2:15 2:30-3:30

ICC / NCSEA Disaster Response Programs

Colby Baker, P.E., SEA, Limited

Special Inspections and Observations: “Power Tools” for Modern Engineers

Mariola Sullivan, P.E., City of Austin

3:45-4:45

Design and Testing of Facade Access Equipment

Gwenyth Searer, P.E., S.E.; Jonathan Lewis, S.E.; and Kurt Holloway, P.E., S.E., Wiss, Janney, Elstner Associates

TRACK 3 1:15-2:15 2:30-3:30

Structural Engineering Licensure

Alan Kirkpatrick, P.E., KFC Engineering

Snow Drift Loading – Current Provisions and Future Direction Michael O’Rourke, Ph.D., P.E., Renssalaer

3:45-4:45

Structural Engineering Engagement and Equity (SE3): 2018 Survey Results

Nick Sherrow-Groves, P.E., Arup, and Angie Sommer, P.E., ZFA Structural Engineers

TRACK 4 1:15-2:15

It’s Not Just Paperwork – Effective Onboarding and Training

Carrie Johnson, P.E., Wallace Engineering, Structural Consultants, Inc.

2:30-3:30

What Really Matters for Success in Your Career

3:45-4:45

Structural Engineering Ethics: Doing the Right Thing and Knowing Why

Ben Nelson, P.E., Martin/Martin, Inc.

Kevin Sido, J.D., and Elyse Ryan, J.D., Hinshaw & Culbertson, LLP

6:00-7:00

Awards Reception

7:00-10:00

NCSEA Awards Banquet

This banquet features the presentation of the NCSEA Excellence in Structural Engineering Awards, honoring the best examples of structural engineering ingenuity throughout the world, as well as the presentation of the NCSEA Special Awards, given to NCSEA members who have provided outstanding service and commitment to the association and to the structural engineering field.

Saturday, October 27, 2018 8:00 - 8:30

All Attendee Breakfast

8:30-12:00

Annual Business Meeting All attendees are invited to attend.

Rates increase on September 7th, register today to save! Visit www.ncsea.com/register

2017 ETS RECORD S S for Geographical Diversity, Number, and Height of Skyscrapers

By Daniel Safarik

Tallest completed during 2017: Ping An Finance Center, Shenzhen, 599 meters. Courtesy of Tim Griffith for KPF.

M

ore buildings of 200 meters (656 feet) in height or taller Key Worldwide Market Snapshots of 2017 were completed in 2017 than in any other year, with a total of 144 completions, marking the fourth consecutive Asia (Not including the Middle East) record-breaking year. This was an increase of 95 percent from 2013 when only 74 buildings of 200 meters or more were While 2017 may have been the most geographically diverse year completed. The total number of 200-meter buildings in the world for 200-meter-plus building completions, Asia retained its status as is 1,319, an increase of 12.3 percent from 2016 the world’s skyscraper epicenter, completing 109 and a 402 percent increase from 2000 when only buildings of at least 200 meters in height. The top 263 existed. two cities, Shenzhen and Nanning, are in China, Notably, 2017 was also the most geographically with Jakarta (Indonesia) and Chengdu (China) diverse year regarding the number of cities and tied for third place with five completions each. countries that completed 200-meter-plus buildSurprisingly, Pyongyang, North Korea, tied for ings, with 69 cities across 23 countries represented sixth place with four buildings of 200 meters or in the data, up from 54 cities across 18 countries in greater completed in 2017. Seoul, South Korea, 2016. High-rise construction is no longer confined completed three 200-meter-plus buildings, to a select few financial and business centers, but including Lotte World Tower, a 555-meter (1,821instead is becoming the accepted global model for foot) mixed-use building. densification, as more than one million people on Mumbai completed its new tallest building (as our planet urbanize each week. Thirteen cities saw well as India’s), One Avighna Park, at 266 meters their first 200-meter-plus high-rise completion in (873 feet). Two other 200-meter-plus buildings 2017, in addition to the 28 cities and eight countries were completed in the coastal city in 2017. Sri that saw their tallest building completed this year.

Lanka also completed its new tallest building, Once again, for the tenth time in a row, China the Grand Hyatt Colombo, which rises to 230 completed the greatest number of 200-meter-plus meters (755 feet). buildings in 2017, with 76 completions for 53 perThe Middle East and Africa cent of the total. Although this is a slight decrease from 2016, when China completed 83 such buildThe Middle East had nine completions of ings or 65 percent of the global total, China is still 200-meter-plus buildings in 2017. Dubai saw three by far the world leader in skyscraper construction. In completions in 2017, and all were supertall – the fact, the city with the most 200-meter-plus building tallest of which, Marina 101, now holds the title of completions, Shenzhen, China, finished 12 buildthe 18th tallest building in the world at 425 meters ings or 8.3 percent of the year’s global completions (1,394 feet). Israel and Saudi Arabia tied with two – that is more than any other country, let alone city, 200-meter-plus completions, with Qatar marking except China itself. The United States completed the Second tallest completed in 2017, one. Africa completed its second 200-meter-plus second-greatest number of 200-meter-plus buildings Lotte World Tower, Seoul, 554 meters. building, Britam Tower, which is both Kenya’s and of any country, with 10 buildings finished in 2017. Courtesy of Tim Griffith for KPF. its capital Nairobi’s first.

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August 2018

North America (includes Central America)

Australia and Oceania

North America more than doubled its 2016 record with 15 tall building completions in 2017. This was reflected both in the United States, which saw 10 completions in 2017, and Canada, which completed five buildings of more than 200 meters in height. Toronto alone notably represented 80 percent of Canada’s tall building completions this year, as the city experiences an ongoing boom in high-rise construction.

While not yet completed, Toronto’s first supertall – named The One – broke ground in late 2017.

In the United States, New York completed four 200-meter-plus buildings while two were completed in Chicago. Los Angeles completed one building of 200-plus-meters, the Wilshire Grand Center, which is now the city’s tallest at 335 meters (1,099 feet).

Mexico completed its tallest building, Torre KOI, a 279-meter (915-foot) mixed-use tower in San Pedro Garza Garcia. This marks the second year in a row that Mexico has crowned a new tallest building. Meanwhile, Panama City added two completions to its disproportionately large collection of high-rises, about 65 percent of which are residential.

Two tall buildings of 200 meters or greater were completed in this region in 2017. Both were in Melbourne, Australia, and both were residential.

Australia is amidst a building boom and is rapidly becoming one of the world’s most urbanized nations.

South America Only one tall building of 200 meters or greater was completed in 2017 in South America – the Hotel Estelar Bocagrande in Cartagena, Colombia, at 202 meters (663 feet).

Europe Europe doubled its 2016 output with four buildings of at least 200 meters in height, all of which were in Turkey – three in Istanbul and one in Izmir. Skyland Towers, at 284 meters (932 feet), became Istanbul’s tallest and Europe’s seventh-tallest buildings.

Completions by Function The functional share of tall buildings in 2017 proved to be among the most interesting discoveries in the study, as the data showed a significant shift from all-office and mixed-used function to all-residential towers. Buildings with all-residential th function spiked to 49 completions, or 10 tallest completed in 2017, Zhuhai St. Regis Hotel & Office 34 percent of the total, up from just 19, Tower, Zhuhai, 322 meters. or 15 percent of the total last year. At the Courtesy of Jason Leung. same time, all-office building completions fell to 56, or 39 percent of the total, compared to 67, or 52 percent of completions in 2016. Of all the pure-office buildings completed, 44 (78.6 percent) were in China.

Completions by Material Of the 144 buildings of 200 meters or greater height completed in 2017, 74, or 51 percent, used concrete as the primary structural material;

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August 2018

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64, or 44 percent, used a composite of steel and concrete. The significant use of concrete can be attributed to a combination of concrete’s relative ubiquity and lower cost in many regions, as well as its comparative simplicity in construction, which would increase its appeal in regions with lower-skilled labor pools.

In 2017, two buildings had all-steel construction, consistent with the 2016 figure. As of this writing, there were only seventeen 200-meterplus buildings currently under construction that employed all-steel structural systems.

“Supertall” Completions A total of 15 supertalls (buildings of 300 meters (984 feet) or higher) were completed in 2017, tying with 2015, the first year to break this record. The total number of supertall buildings worldwide is now 126, up from 111 in 2016. This fact is even more extraordinary, considering that much of the activity has been in the past few years.

The 2017 figure represents a 66 percent increase in just four years. In 2013, there were 76 buildings 300 meters or higher; in 2000, only 26.

The World’s 100 Tallest Buildings Of the 100 World’s Tallest Buildings in 2017, 54 were in Asia, a figure unchanged from 2016. Twenty-six were in the Middle East, up from 24 the previous year. North America has 15 of the buildings on the list. Europe’s figure dropped from five in 2016 to four in 2017.

Mixed-use continues to dominate the functional mix of the tallest 100 buildings with 46 buildings, an increase from 41 in 2016. Meanwhile, office functions take a slightly lower share in 2017, with 38 buildings, down from 40 in 2016 and equal to the 2015 figure. Residential and hotel functions have shrunk as a proportion once again, with 11 and five buildings, respectively, down from 12 and seven in 2016.

Composite construction, in which a combination of steel and concrete components is used in the main structural elements, represents the majority of structural approaches to the 100 Tallest list, with 51 of the buildings being of composite construction, the same as in 2016.

All-concrete buildings decreased by one to 34 from 35 in 2016. The number of all-steel buildings in the 100 Tallest list remains at 10 in 2017, as it was in 2016. Those buildings reported as being of “mixed” construction, in which distinctive sections of the buildings are predominantly steel or concrete, increased to five in 2017 from four in 2016.

Two new additions were also added to the list of the World’s 10 Tallest Buildings in 2017 – the fourth and fifth tallest, Ping An Finance Center in Shenzhen and Lotte World Tower in Seoul, respectively. Ping An Finance Center rises 599 meters (1,965 feet), while Lotte World Tower reaches a pinnacle of 555 meters (1,821 feet). The completion of these two towers resulted in Petronas Twin Towers being removed from the World’s 10 Tallest Buildings list.

year’s total increasing by 350 percent over the past decade. While the total number of tall building completions is an important metric to watch, the data on the rapid geographic diversification of 200-meter-plus building completions in 69 cities across 23 countries is perhaps the most telling result. In 2007, only 20 cities across the globe completed 200-meter-plus buildings – the highest number on record at the time. A decade later, the number of cities represented in this report has more than tripled. A record 28 of those cities completed their tallest building in 2017. th China still leads the world in 200-meter- 35 tallest completed in 2017, Raffles City Hangzhou Tower 1, plus building completions, but the region Hangzhou, 254 meters. may start to lose its dramatic lead as Courtesy of Hufton+Crow. other regions, such as India, accelerate economic and population growth. North America, which for much of the 20th century completed the majority of 200-meter-plus buildings in the world, is also beginning to see a resurgence in tall building construction. In addition, new technologies and increased international capital flows are facilitating the creation of ever-taller skyscrapers.

The data from 2017 shows a continuation of the trend towards a higher global proliferation of skyscraper construction. Most of the prevailing trends of the past few years – the preponderance of construction taking place in Asia and, in particular, China, and the predominance of composite construction being used to achieve greater heights and more complex designs – have held steady.

However, a few discoveries this year are notable, if not wildly divergent.

The increase in geographic diversity, such that 69 cities had at least one 200-meter building completion, up from 54 in 2016 – and 28 cities got a new tallest building – invites further scrutiny. Of these, 34 were in China.

While not entirely surprising, nevertheless it is clear that, in addition to powerhouses like Shenzhen, there are also some smaller regional cities joining the list, such as Baoji in Shaanxi province; Yantai, in Shandong province; Lianyungang, in Jiangsu; and Yinchuan, in Ningxia. Although, in many cases, each of these cities has more than one million people and each has erected only a single building of 200 meters or more in 2017.

The term “smaller regional city” is relative in China, which seems to be executing on its plan to create impressive skylines and more evenly distribute people in its campaign of mass urbanization.

Outside China, some infrequently-seen city names include Giv’atayim, Israel (near Tel Aviv); Izmir, Turkey; Nairobi, Kenya; and Pyongyang, North Korea. The reasons for this are likely as diverse as these countries are from each other; the functions span office, residential, and mixed-use.

The resurgence of all-residential tall buildings, against what had been an increasing trend towards a mix of functions, is also of interest. In the past, the Council on Tall Buildings and Urban Habitat (CTBUH) has credited the prevalence of the mixed-use function in buildings at the upper end of the height range to a developers’ hedging strategy.

The greater the number of functions in the building, the less likely it is that economic weakness in one sector could delay or halt the project, or result in it being unsold or unrented for prolonged periods.▪

Analysis 62 nd tallest completed in 2017, Madison Square Park Tower, New York City, 237 meters. Courtesy of Lester Ali.

Research by Shawn Ursini & Marshall Gerometta, CTBUH

Overall, 2017 was a record-breaking year for skyscraper completions on a variety of fronts.

We are once again witnessing an all-time-high for 200-meter-plus building completions, with this STRUCTURE magazine

36

Daniel Safarik is overall Editor at CTBUH. He has co-authored or co-edited several of the Council’s recent technical publications and served as the Director of the China Office of CTBUH. (dsafarik@ctbuh.org)

August 2018

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RECLAIMING the Waterfront

By Michelle Black, P.E., C.E., Chris Adams, P.E., and Shane McCormick, P.E., S.E.

T

he City of Vancouver, Washington, has a new development along the Columbia River with the Grant Street Pier as its centerpiece. The site, formerly home to a local paper mill, is now home to hotels, restaurants, and a boardwalk. As the focal point for this up-and-coming area known as “The Waterfront,” the pier has an iconic form that is sure to attract visitors. The pier’s triangular, post-tensioned concrete deck overhangs the water by 90 feet and provides an expansive view of the river. A cable system and 80-foottall mast support the deck. Though the structure itself is unique, the reasons behind the form and shape are just as impressive. Developed by an artist and designed to meet environmental concerns, this is not a typical pier.

Master Plan The master plan for The Waterfront included a gathering area for sightseeing and special events. The City of Vancouver originally planned a platform extending over the Columbia River supported directly on permanent piling. After initial plans were developed, it was discovered that using permanent structures in the river negatively impacted native fish migration. The city needed to create a platform without permanent piling in the river and a structure that was airy enough to allow sufficient light to reach the river to ensure fish migration was not affected.

The city decided to produce a signature structure without permanent piling and respective of the fish migration issue. They contacted Larry Kirkland, international public artist, to design the piece. Kirkland’s design included a thin, cable-supported platform. The cables were supported by a structural element resembling a ship’s mast, paying homage to the sailing vessels that navigated the Columbia River in earlier eras. Kirkland also created an A-shaped platform that would STRUCTURE magazine

Pier cantilevering over the Columbia River. Courtesy of the City of Vancouver.

permit enough light into the river and inherently generate pedestrian circulation. Kirkland also specified white surfaces on the piece, further contributing to its signature design. With this new concept, every design feature, including cable and mast connections, required elegant and creative structural detailing.

Design Concerns The structure’s durability was a primary concern as it would cantilever over the Columbia River. The design team investigated structural steel and post-tensioned concrete deck options, weighing the pros and cons of each system. The structural steel option incorporated a high-performance paint system capable of providing the required durability. The benefits of this system were a lightweight structure with ease of construction; however, maintaining the painted surface over the river was a concern due to regulations and cost. The posttensioned concrete option inherently gets its durability from a properly designed concrete mix. The benefit of this system is the significantly reduced maintenance cost. Challenges included a heavier structure, an expensive white concrete mixture consisting of white cement and white aggregate, and a complex construction sequence. The city studied these options and chose a post-tensioned concrete deck system because maintaining a painted steel system over the river was too expensive.

The proposed concrete design utilized a bonded, multi-strand posttensioned system, further addressing durability. Post-tensioning tendons would run inside plastic corrugated ducts cast into the concrete structure.

Once the tendons were stressed, the spaces between the tendons and corrugated plastic ducts would be filled with flowable grout to add an additional level of corrosion protection for the tendons. Figure 1 shows the typical deck section with three post-tensioned beams and hollow areas between. Voids would be placed between the beams, both to rid

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August 2018

the structure of unnecessary weight and to provide an area for vibration mitigation equipment to be housed.

Analyses Once the structural system had been selected, the design team requested a wind report to understand the structure’s performance during varying wind speed events.

Structural modal information and Figure 1. Typical deck section. cable tension values were sent to RWDI Consulting Engineers and Scientists (RWDI) for dynamic analysis. They found the structure to be globally stable and not excitable over a wide variety of wind speeds. RWDI also reported that the cables had sufficient sustained tension load to resist wind excitation and would not require additional dampers to help reduce fatigue loading on their associated connections. Globally, the final structure was designed for an ultimate wind speed of 145 miles per hour with an Exposure Category D. Adjacent to the west coast, the site is prone to severe seismic events.

Mapped spectral response accelerations SS and S1 of 94%g and 41%g, respectively, resulted in Seismic Design Category D classification.

Because the A-shaped deck inherently had a significant amount of lateral load resisting capability, the design team decided to design the structure elastically using a seismic response modification factor equal to one. This resulted in a base shear equal to nearly 600 kips, and the structure was found to be able to resist this load magnitude without the need for special structural detailing. Shoreside, the soil

is prone to liquefaction and lateral spreading during a seismic event.

The bulkhead walls separating the shore and Columbia River, designed

by BergerABAM, Inc., were designed for additional lateral loading to resist these phenomena. See STRUCTURE magazine’s December 2017 issue for a discussion of the pier’s foundation system.

Other unique design loadings included flood loading and impact loading from a passing ship.

The final concrete deck elevation was below the 500-year flood event, so the deck structure was designed for a 50 psf lateral stream load on each surface expected to be submerged. While unlikely, the deck structure was also designed for impact load from Figure 2. Superstructure and foundations. a small passing vessel.

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August 2018

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Figure 3. Pier with construction substantially complete. Courtesy of the City of Vancouver.

Figure 4. Cable backstay abutment. Courtesy of the City of Vancouver.

Since the pier is intended for special events such as weddings, a substantial finite element vibrational analysis was performed to understand how the structure reacts to a variety of dynamic loading scenarios. The structure’s low fundamental frequency (1.2 Hz) combined with low damping made it prone to movements that may not be acceptable for human comfort. As a result, a pair of tuned-mass dampers were installed in voids in the concrete deck. With these dampers installed and tuned appropriately, the structure’s response will meet standard industry acceleration guidelines over a variety of loading scenarios.

Another complex design feature was the sloping concrete on the top surface of the pier. Environmental concerns do not allow water falling on the pier surface to drain into the river; all water must be guided back to drains at the shore. To accommodate this, the pier slopes at one percent from the tip back to shore and has a slightly V-shaped top surface. Though this solved the drainage concern, it made the decking on top of the concrete surface more difficult to install. Composite lumber sleepers were tapered to fit the sloping top of concrete and provide a flat surface for the decking. This wood decking provides a finished walking surface on the top of the pier continuous with the connecting park boardwalks while providing visual contrast to the white concrete and the steel of the mast.

are each attached to 2-inch-thick continuous fins protruding from the 24-inch-diameter, schedule 160 pipe mast. Given the cables are under tension, the unstiffened pipe was studied using a finite element model to understand how the prying forces distorted the pipe. The schedule 160 pipe thickness was chosen to withstand the applied forces.

To oppose the force in the eight forestay cables, two pairs of four backstay cables extend from the mast and are anchored at the shore. Each set of backstay cables meets at a common point at the shore, connecting to a large, built-up gusset plate assembly located approximately seven feet off the ground (Figure 4 ). This gusset plate assembly is anchored to a rectangular concrete abutment with ten 1¾-inch-diameter prestressed threaded rods extending below grade into an even larger pile cap. Each threaded rod was prestressed to counteract elastic deformation and to keep the concrete abutment in compression to reduce cracking.

Though the design of the structural elements was challenging, fitting individual elements together in a cohesive construction sequence was perhaps a more significant challenge. Piles were installed in the river to support the weight of the pier under construction, but the piles eventually needed to be removed. The design team developed the following sequence: 1) install temporary formwork and piles in the river, 2) pour and posttension the concrete deck, 3) set the mast and cables in place, 4) tension the cables to values that caused the tip of the pier to lift off the formwork, and 5) remove the formwork and piles from beneath the pier. The cables were tensioned in stages, with the contractor adding tension to each of the 16 cables in a calculated manner. As the tensioning progressed, the tip of the pier slowly lifted off the formwork. Final cable tension values were within two percent of the design cable tensions.

Unique design criteria including environmental factors, proximity to the river, vibration concerns, and seismic site conditions challenged the design team. Aesthetics provided a second and welcomed set of challenges. Working with an artist focused attention on how to make the structure efficient, yet graceful. In the end, the blending of art and engineering makes a striking product. The Grant Street Pier now stands over the banks of the Columbia, waiting for visitors to come and see The Waterfront.▪

Mast Design As the mast is the visual focal point of the structure, extra attention was paid to the appearance of the cable connections. Eight forestay cables, with four splaying to each side of the deck, meet at discrete locations along the mast. The 2½-inch-diameter, full-locked, galvanized cables are sized for stiffness to limit pier tip deflection. The cable end clevises

The authors are with Martin/Martin, Inc., in Lakewood, CO. Michelle Black is a Professional Engineer. (mblack@martinmartin.com) Chris Adams is a Project Engineer.(cadams@martinmartin.com) Shane McCormick is a Principal (smccormick@martinmartin.com)

Project Team Owner: City of Vancouver, Washington Superstructure EOR: Martin/Martin, Inc. Foundations EOR: BergerABAM, Inc. Contractor: Rotschy, Inc. Landscape Architect: PWL Partnership Landscape Architects, Inc.

Temporary piles and formwork.

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I

n 2015 and early 2016, the American Iron and Steel Institute (AISI) published AISI S40015/S1-16, North American Standard for Seismic Design of Cold-Formed Steel Structural Systems with Supplement 1. This first edition of AISI S400 represents a merging of the following previously published standards: • AISI S213, North American Standard for Cold-Formed Steel Framing-Lateral Design, a standard for the design of cold-formed steel frame shear walls, strap-braced walls, and diaphragms; and • AISI S110, Standard for Seismic Design of ColdFormed Steel Structural Systems – Special Bolted Moment Frames, a standard for the design of cold-formed steel special-bolted moment frames.

This consolidated seismic design standard brings together all North American cold-formed steel seismic-force-resisting systems (SFRS) into one standard, adding a consistent capacity-based design philosophy to each. It provides U.S.-based requirements for buildings located in Seismic Design Categories D and E, and for buildings located in Seismic Design Categories B and C when the chosen seismic response modification factor, R, as specified in ASCE 7-16, is taken as other than 3.

The standard also provides Canadian seismic design provisions where the seismic force modification factors, RdRo, are taken as greater than or equal to 1.56, or the design spectral response acceleration S(0.2), as specified in the National Building Code of Canada (NBCC), is greater than 0.12.

Chapter A, Scope and Applicability

specifies both the expected yield stress and the expected tensile strength as: Expected yield stress: Fy_expected = RyFy Expected tensile strength: Fu_expected = RtFu Ry and Rt are provided in AISI S400 Table A3.2-1.

Unique to cold-formed steel, an additional yield stress increase must be considered due to the cold work of forming and inelastic reserve capacity: • The modification coefficient for strength increase due to cold work of forming is determined as: Rcf = Fya/Fy ≥ 1.1 Fya = average yield stress considering corner strength increase Fya can be determined using AISI S100 • The modification coefficient for inelastic reserve capacity for the fully effective section in bending is calculated as: Rre = Mn/My For λ < 0.673 (Eqn. A3.2.3) Rre = 1 For λ ≥ 0.673 where Mn and My = nominal moment capacity considering inelastic reserve capacity and yield moment, respectively, determined in accordance with AISI S100.

Chapter B This chapter, General Design Requirements, outlines fundamental seismic design requirements.

Specifically, the available strength of the SFRS must be greater than or equal to the required strength determined from the applicable load combinations to ensure adequate performance in a design-level seismic-event. The required strength for structural members and connections in the lateral-force-resisting system, which is not part of the designated energy-dissipating mechanism, is determined from the expected strength of the SFRS; however, it does not need to exceed the seismic load effects determined in accordance with the applicable building

This standard focuses on the design and construction of cold-formed steel members and connections in seismic-force-resisting systems (SFRS) and diaphragms in buildings and other AISI S400-15 Table A3.2-1 structures. It is intended to be used Ry and Rt Values for Various Product Types in conjunction with AISI S100, AISI S240, and the applicable building code.

Steel Ry Rt In the absence of an applicable buildPlates and bars: A36/A36M, A283/A283M 1.3 1.2 ing code, the design requirements must follow accepted engineering practice A242/A242M, A529/A529M, A572/A572M, 1.1 1.2 for the location under consideration, A588/A588M as specified by ASCE 7-16. The standard is not applicable in Seismic Design Hollow Structural Sections: Category (SDC) A; or, SDC B or C A500 Grade B 1.4 1.3 when the chosen seismic response A500 Grade C 1.3 1.2 modification coefficient, R, equals 3.

A1085 1.25 1.15 Chapter A also provides the provisions Sheet and strip (A606, A653/A653M, A792/ for determining the material expected A792M, A875, A1003/A1003M, A1008/ strength for steel. Expected strength is A1008M, A1011/A1011M): used to estimate the maximum forces 1.2 Fy< 37 ksi (255 MPa) 1.5 the SFRS is anticipated to resist prior to dissipating energy through yield1.4 1.1 37ksi (255MPa) ≤ Fy< 40 ksi (275 MPa) ing. In earlier standards, this concept 1.3 1.1 40ksi (275MPa) ≤ Fy<50 ksi (340 MPa) was described as the “maximum force 1.1 Fy ≥ 50 ksi(340 MPa) 1.1 the system can deliver.” The standard STRUCTURE magazine

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CODE

updates

AISI S400-15/S1-16

By Rob Madsen P.E., Helen Chen Ph.D., P.E., LEED AP BD+C, and Bonnie Manley P.E., F.SEI Rob Madsen is a Senior Engineer at Devco Engineering, Inc. in Enterprise, Oregon. He has been active in the development of cold-formed steel related codes and standards since 1994. He presently chairs the AISI Committee on Framing Standards Lateral Subcommittee.

Helen Chen is Manager of the Construction Standards Development of the American Iron and Steel Institute. She is directly involved in the development and update of AISI construction standards. (hchen@steel.org) Bonnie Manley is a Regional Director for the American Iron and Steel Institute. She has been active in building code and standard development on behalf of the steel industry for over ten years. (bmanley@steel.org)

with the applicable building code and AISI S100. Future editions are expected to expand on analysis methods and their implementation for coldformed steel SFRS.

Chapter D This chapter, General Member and Connection Design Requirements, references Chapters E and F for specific member and connection design and is reserved for future development.

Figure 1. Shear wall sheathed with wood structural panels.

code, where the seismic load effects include overstrength (Ωo).

The designated energy dissipating mechanism and methods for determining the expected strength of the various SFRS are included in Chapter E, as discussed below.

Chapter C This chapter, Analysis, prescribes that the structural analysis should be done in accordance

Chapter E

In this chapter, Seismic Force-Resisting Systems, U.S. design provisions for the following coldformed steel SFRS are provided: (a) Cold-formed steel light frame shear walls sheathed with wood structural panels SFRS (Figure 1 ): Seismic energy is dissipated in wood structural panel shear walls through titling and bearing deformation in the screw connections between the wood structural panel sheathing and the cold-formed steel structural

members, and in the wood structural panels themselves. Two types of shear walls are included within the section: Type I shear walls (Figure 2a) are fully sheathed and require hold-downs and anchorage at each end of the shear wall. If an opening exists, details must be provided for load transfer around the opening. The nominal shear strength for 15⁄32-inch structural 1 sheathing and for 7⁄16 OSB shear walls with a variety of fastener spacings and framing thickness are tabulated. Aspect ratio (shear wall height, h, divided by length, w) limits for the various assemblies are also provided.

Type II shear walls (Figure 2b) permit openings in the wall without specific design for force transfer around the openings. The nominal shear strength, Vn, can be determined: Vn = CavnΣLi (AISI S400 Eqn. E1.3.1.2-1) where vn = nominal shear strength per unit length; Ca = shear wall adjustment factor; Li = the total length of Type II shear wall segments that are sheathed full height. The nominal shear strength per unit length, vn, is based on the values

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Wall Pier Width

Sheathing

Window Door

Sheathing

Wall Pier Height

Sheathing

Wall Pier Width

Window Door

(a) Hold-Downs and Anchorage

Wall Pier Width

Sheathing

Wall Pier Height

(b) Hold-Downs and Anchorage

Hold-Down and Anchorage

Hold-Down and Anchorage

Figure 2. Sheathed shear wall analysis models. a) Type I shear walls (without detailing for force transfer around openings); b) Typical Type II shear wall.

for Type I shear walls and Ca is tabulated the seismic energy, while other limit in the standard for a variety of shear wall states (such as fracture at the strap geometries. ends and buckling of the chord studs) The expected strength of the SFRS, are avoided. The shear wall strength is capped by the seismic load effects includdetermined by the nominal strength of ing overstrength, is to be used to design the strap as follows: other components in the SFRS that are not part of the designated energyVn = Tnw/â&#x2C6;&#x161;h2 + w2 dissipating mechanism, including any (AISI S400 Eqn. E3.3.1-1) collectors. For this SFRS, the expected Tn = nominal strength of the strap strength equals 1.8 times the nominal braced wall in yielding; strength of the SFRS. w and h are as defined in Section (a) To ensure the shear wall performs as intended, additional system requireThe expected strength of the strap ments must be met as further detailed equals the expected yield strength of the in AISI S400, Section E1. strap times its gross area. The expected (b) Cold-formed steel light frame shear walls strength of the SFRS can be derived by with steel sheet sheathing SFRS: Seismic simple mechanics based on the strap energy is dissipated through the conexpected strength. nections between the steel sheet and the Additional system requirements must cold-formed steel structural members. be met as further detailed in Section E3.

Yielding also occurs in the tension fields For instance, provisions must be made to across the steel sheet. The nominal shear guard against loose strap bracing either strength, Vn, can be determined using the same equations provided in Section (a) except that values for vn and Ca are tabulated separately in the standard. In addition, a new effective strip method has been introduced in this edition, which can be used to determine the nominal shear strength of the shear wall analytically.

The expected strength of steelsheet sheathed shear walls is specified as 1.8 times the nominal strength of the SFRS. To ensure the shear wall performs as intended, additional system requirements must be met as further detailed in AISI S400, Section E2. (c) Cold-formed steel light frame strap braced wall systems SFRS: To perform as intended in a design level seismic event, this common SFRS must be designed and detailed to ensure that the diagonal tension strap yields first, thus dissipating Figure 3. Cold-formed steel special bolted moment frame.

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by pre-tensioning the straps or through other similar methods of installing the tension-only strap bracing. (d) Cold-formed steel special bolted moment frames SFRS: This system is formed by cold-formed channel beams and HSS columns with bolted moment connections, as detailed in Figure 3. Seismic energy is dissipated through sliding and bearing deformations in the bolted connections between the beams and columns. The beams and columns, therefore, need to be designed to resist the expected moment (Me) and shear (Ve) at the bolted connections defined as: Ve = (VS + VB) (AISI S400 Eqn. E4.3.3-1) Me = h(VS + RtVB) (AISI S400-C Eqn. C-E4.3.3-1) VS = column shear corresponding to the slip strength of the bolt group;

VB = connection bearing component of column shear corresponding to the displacement ∆ (design story drift) h = height from column base to the centerline of the beam R t = ratio of expected tensile strength to specified minimum tensile strength Detailed guidance on how to determine the expected strength is provided in the standard.

Currently, this SFRS has a number of limitations that are further detailed in AISI S400, Section E4. For instance, it is limited to single story structures no higher than 35 feet. (e) Cold-formed light frame shear walls with gypsum board or fiberboard panel sheathing SFRS: This SFRS has a similar designated energy dissipating mechanism as described in Section (a). The system is designed as Type I shear walls with h/w ≤ 2, and walllength ≥ 24 inches. The nominal shear strength and detailed requirements are provided in Section E6 of the standard.

The expected strength of this SFRS equals 1.5 times the nominal strength.

Chapter F This chapter outlines requirements for Diaphragms. Acting to collect and distribute seismic forces to the SFRS, diaphragms must be designed to resist the forces specified by the applicable building code. The diaphragm stiffness needs to be taken into consideration in determining the required strengths of both the SFRS and the diaphragm itself since the stiffness directly affects the force distribution. This standard currently provides the design provisions for cold-formed steel-framed diaphragms sheathed with wood structural panels. Future editions may be extended to include other common diaphragm systems.

Chapter G This chapter discusses Quality Control and Quality Assurance. The cold-formed steel shear walls and strap-braced walls follow the QC and QA provisions provided in AISI S240, Chapter D, which includes requirements for lateral force resisting systems. For CFS special bolted moment frames, the QC and

QA requirements are provided in AISI S400, Section G4.

Chapter H This chapter, Use of Substitute Components and Connections in Seismic Force-Resisting Systems, permits the substitution of components or connections in any of the SFRS specified in Chapter E as long as they follow the applicable building code requirements and are approved by the authority having jurisdiction. This is intended to dovetail with ASCE 7-16 Chapter 12, which provides general guidance on this topic.

In Conclusion AISI S400 and all AISI published design standards can be downloaded from the website www.aisistandards.org. A design guide for the seismic design of cold-formed steel framing will be published in 2018.▪ The online version of this article contains a Design Example and references.

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Risk ManageMent Geotechnical Peer Review Adding Value, Reducing Risk

By Theodore von Rosenvinge, P.E., D.GE

G

eotechnical peer review is not new, but it is not common industry practice.

Today, however, there is a trend by public agencies in the United States to require it for tall buildings. What is geotechnical peer review, what is this trend, and what is its role in the design and construction industry for buildings and civil works?

News Flash!

August 21, 2017. The City of San Jose Office of the City Auditor issued a 52-page report to the City Council titled Audit of Residential High-Rises: Considerations for a City with a Growing Number of Tall Buildings. San Jose is the third largest city in California both in population and land area. Included in the report is the statement, “The City should consider additional safeguards to protect against geotechnical risk as taller buildings are developed.”

November 7, 2017. The City and County of San Francisco released Interim Guidelines and Procedures for Structural, Geotechnical, and Seismic Hazard Engineering Design Review for New Tall Buildings, where the “Structural Design Team shall include at least one Geotechnical Engineer” in all future projects.

January 2018. In New York City, discussions about geotechnical peer review begin with the New York City Department of Buildings and the American Council of Engineering Companies (ACEC) Metro Structural Codes Committee.

In the words of the song “For What It’s Worth” (written by Stephen Stills and first recorded by Buffalo Springfield in1967 ), “there’s something happening here.” Is it one recent event or the culmination of issues? Population growth, seismic safety, concerns about effects of dewatering, and concerns about the settlement of buildings appear to have converged into a developing focus on geotechnical issues and geotechnical peer review.

Geotechnical Peer Review Geotechnical peer review is not a new practice, but it is not the common practice.

However, owners and designers are discovering the benefit of proactive peer review and

Tall buildings generating agency driven geotechnical peer review. Courtesy of Sergio Ruiz.

the added value of managing risks to all parties associated with underground construction.

There are several published examples of voluntary geotechnical peer review for some of the world’s tallest buildings.

Structural peer review is required by some building codes. For instance, it is well established in some jurisdictions including in New York City, Chicago, Los Angeles, Florida, Massachusetts, and Connecticut.

Requirements (e.g., tall buildings or highrisk occupancy use) vary for when reviews are required. However, the geotechnical peer review component in these structural peer review requirements is generally absent.

The New York City (NYC) Building Code requires the structural peer reviewer to review the geotechnical report and confirm that the design incorporates the recommendations of the geotechnical investigation. The 2014 NYC Building Code Section 1617.5.1 states, “Review geotechnical and other engineering investigations that are related to the foundation and structural design and confirm that the design properly incorporates the results and recommendations of the investigations.”

However, the NYC Building Code does not require an independent geotechnical engineer to review the geotechnical report, nor does it require the reviewer to confirm the validity of the recommendations in the report.

Are the San Jose recommendations and San Francisco directive the beginning of a national or perhaps a worldwide trend?

Agency Driven Cities and states supplement adopted national building codes (e.g., International Building

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Code – IBC) with amendments and procedures to address local conditions, especially for tall buildings.

For tall buildings (240+ feet), the San Francisco Department of Building Inspection implemented amendments to its building code to include a geotechnical engineer as a member of the structural peer review team.

The city auditor of the City Council of San Jose seeks to adopt similar guidelines in response to an increasing number of proposed tall buildings. Some excerpts from the auditor’s guidelines report include: • San Jose may also adopt similar guidelines to the city’s building code to include peer reviews of geotechnical reports and designs.

• The city should consider additional protections to safeguard against geotechnical risk as taller buildings are developed.

• Typically, the Building Division does not critically review the validity of the report itself when reviewing geotechnical reports.

• The additional review can help insure[sic] that there are no major engineering mistakes and that the appropriate effort has been made to develop a safe and cost-effective foundation design.

• A second opinion on soil conditions and foundations designs could help catch errors that could result in structural issues with building. However, this additional layer of review would add to project costs.

Some jurisdictions have introduced voluntary peer-review programs. Effective January 2018, the City of Chicago, Illinois, has implemented an internal Structural peer review program through its Department of Buildings. continued on next page

The Process In the author’s experience, requests for geotechnical peer reviews often come in one or more of these contexts: • “We would just like to double-check the solutions being presented.”

• “This is an unusual project.”

• “We have not done this type of project or used this technology before.”

• “We would like another opinion.”

• “We would like to review constructability.”

• “Are there other solutions available.”

The peer review process can help all parties better understand, address, and ultimately reduce project risk. Naturally, the “reviewee” engineer or team can feel slightly uncomfortable by the prospect of an outside review.

However, this can be mitigated with a positive attitude and a respectful, collaborative approach on the part of the reviewing engineer.

The best reviews actively and positively engage the design team to the benefit of all involved. Good peer reviewers possess both the required technical expertise (or know when, where, and how to bring it in), and strong communication and team-work skills.

Most peer reviews should take place during the design phase and start early, although a

need for peer review can also develop from an unexpected construction issue. The review process may include inquiries about design procedures, analytical methods and results, and whether alternative solutions were considered. Commercial bid-ability and constructability may also be central topics.

The true purpose of a review is not to find fault or redo the work but to review the big picture and the processes, procedures, and rationale used during analysis and design.

While the situation may dictate “audit level” technical or computational checking, the key is asking the right questions.

Questions may include: • What are the geotechnical risks?

• How will the project be built?

• Have other solutions been evaluated along with relative merit and risks?

• Have intermediate loading cases (e.g., construction staging) been considered?

• What range of settlement is expected?

What confidence level? What happens if it is more?

• What is the impact of the work on adjacent facilities and utilities?

• What could go wrong during construction of the design?

• What actions and contingency plans may be appropriate to address risks?

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Qualifications A geotechnical peer reviewer should: • Be a qualified, experienced geotechnical engineer • Possess mature analytical and problem-solving skills • Possess both technical and good communication skills • Know when to bring in highly specialized experts • Seek to reveal opportunities to reduce risk, time, and cost • Be a team player

Geotechnical Peer Review Examples

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31-story building in Boston, MA, used geotechnical peer review for an innovative foundation system.

Courtesy of Kohn Pedersen Fox.

Seattle Tacoma Lacey

San Francisco Los Angeles Long Beach

Portland Eugene Sacramento

Irvine San Diego Boise

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St. Louis Chicago Louisville New York

August 2018

The author has been involved with voluntary peer reviews as both the reviewer and the reviewee. A few brief examples are provided below: • 101 Federal Street, 31 Story Building, Boston, MA: This office building is where drilled shaft foundations installed with a slurry method was first used in Boston. At the time (the mid-1980s), the technique had been used for slurry walls in Boston but not for drilled shafts. Noted drilled shaft expert Clyde N. Baker, P.E., S.E., of Chicago, provided the peer review and exhibited the desirable qualities of a peer reviewer (much appreciated by the young project engineer and author of this article whose work was reviewed!).

The review gave the team comfort to proceed with an innovative process to the benefit of the owner.

• The purpose of a geotechnical peer review is to check for compliance with minimum code standards, completeness, to note obvious factual errors, consistency of data with conclusions, and standards of geotechnical practice, as well as to identify areas where the proposed design may lead to future significant problems.

• The geotechnical reviewer should recognize that geotechnical engineering is characterized by diverse opinions among the various geotechnical professionals. If the professional opinion of the geotechnical consultant of record is supported by a sufficient level of data and geologic and engineering analyses, and professional experience indicates that the recommendations will provide satisfactory performance, the opinion of the consultant of record should be accepted.

Often times, no singular valid opinion or interpretation is possible given the diversity of experience and background of the professionals involved.

• All parties should recognize that the geotechnical reviewer is not a part of the design or study team. As such, the reviewers should have limited involvement in the design.

CGEA should be applauded for their proactive development and publication of these guidelines. Agencies cited above do not yet reference such guidelines. As is often the case, if the geotechnical profession is not proactive in developing such guidelines, others may. Institutional peer review requirements are continuing to evolve for both structural and geotechnical peer reviews and, as geotechnical peer review is closely related to structural engineering peer review processes

The Future Beyond guidelines presented in this article, published geotechnical peer review guidelines could be beneficial.

However, each project is different and no cookbook can be developed to cover experience and engineering judgment.

In 2004, the California Geotechnical Engineers Association (CGEA) published Recommended Practice, Peer Review Guidelines. This two-page document provides thoughtful guidance and key characteristics of a geotechnical peer review. Highlights include: STRUCTURE magazine

Geotechnical peer-reviewed design-build bridge, Martin’s Point Bridge Portland-Falmouth, ME. Courtesy of Dave Cleaveland, Maine Imaging.

already established in some venues, professional geotechnical organizations should take this opportunity to develop and disseminate such guidelines for practice.

In the meantime, owners, engineers, and agencies should embrace the trend towards geotechnical peer review. Appropriately used, a nominal investment in geotechnical peer review will add value and reduce risk for all parties.▪ Theodore von Rosenvinge is President of the geotechnical consulting firm, GeoDesign, Inc. (NY/NJ/CT/VT). He may be reached at ted.von@geodesign.net.

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• Governors Island, New York, NY: A man-made reinforced steep earth hill over filled land, up to 70 feet high, required extensive analysis of slope stability, settlement, and detailed design of slope stabilization. This was a very complex, high visibility, one-of-akind project. Geotechnical peer review challenged the design team to use threedimensional geotechnical modeling for settlement and stability analysis and to optimize the design.

• Martin’s Point Bridge, Portland, ME: This was a design-build bridge replacement on large-diameter driven pipe piles and approach fills over compressible soils.

This was MaineDOT’s first multi-integral pier project, and the geotechnical investigation was highly scrutinized.

According to Steven M. Hodgdon, P.E., VHB Designer-of-Record, the geotechnical peer review helped “ensure that we got it right!”

• Commercial Building, Teton Village, WY: Subgrade instability was encountered during construction for two basement level excavations below the water table.

Geotechnical peer reviews with the design and construction team helped to solve the problem.

• Manufacturing Facility Warehouse, Fairfield, CT: This was a peer review of foundation recommendations to address slab and foundation settlement. Prior to the geotechnical peer review, the owner was facing the cost of $1 million to implement previously recommended underpinning of the slab and foundation with drilled-in piles. Through peer review, future settlements were better understood and it was determined that the building could tolerate additional settlement without expenditure for underpinning and without loss of functionality.

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August 2018

Software Guide ADAPT Corporation

CADRE ANALYTIC

ENERCALC, Inc.

Phone: 650-306-2400 Email: florian@adaptsoft.com Web: www.adaptsoft.com Product: ADAPT-PTRC Description: Software for the design, analysis, and investigation of reinforced (nonprestressed) and post-tensioned concrete beams, frames, slabs, and floor systems. The industry standard and choice of consulting engineers that want an easy-to-use, efficient, and reliable production tool. Now with rebar scheduling feature.

Phone: 425-392-4309 Email: cadresales@cadreanalytic.com Web: www.cadreanalytic.com Product: CADRE PRO 6.9 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.

Phone: 800-424-2252 Email: info@enercalc.com Web: www.enercalc.com Product: Structural Engineering Library/Retain Pro/ ENERCALC SE Cloud Description: New for 2018: 3D component sketches in Structural Engineering Library make your reports stand out. New functionality and performance improvements to ENERCALC SE cloud-based application platform. ENERCALC SE Cloud combines Structural Engineering Library, RetainPro (earth retention structure design), and 3D Finite Element analysis and design application: ENERCALC 3D.

Product: ADAPT-Builder Wall Designer Description: Includes option of integrated wall design. Check shear walls for code compliance or automatically design based on a variety of loads.

Design output presented graphically or in concise XLS tables. Combine with Builder’s column, slab, and foundation design for an efficient overall design workflow for your concrete projects.

American Wood Council Phone: 202-463-2766 Email: info@awc.org Web: www.awc.org Product: Connections 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.steelsmartsystem.com Product: SteelSmart Framer Description: Provides designers with a powerful new tool to better design, estimate, and communicate light steel framing on projects using Autodesk® Revit™ Building Information Modeling (BIM) software.

Product: SteelSmart System Description: Provides structural engineers with a structural design software tool engineered for optimal design and detailing of light steel framing studs, joists, shear walls, and connectors.

Bluebeam, Inc. Phone: 866-496-2140 Email: sales@bluebeam.com Web: bluebeam.com Product: Bluebeam Revu Description: Bluebeam develops innovative, cloudbased editing, markup, and collaboration solutions that set the standard for workflow efficiency for +1 million design and construction professionals worldwide, delivering enhanced PDF-based takeoff and workflow automation tools that span the entire project lifecycle and give you the competitive edge.

ClarkDietrich Building Systems Phone: 513-857-4406 Email: jenny.hull@clarkdietrich.com Web: www.clarkdietrich.com Product: ClarkDietrich iTools Description: Gives contractors and architects access to a broad range of data including cost-saving calculators, design tools, ClipExpress Navigation, LEED request forms, and product literature directly from their mobile devices.

Concrete Masonry Associate of California and 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 of masonry elements 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).

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, wood, cross-laminated timber, glass, aluminum, and membrane/cable structures. Direct interfaces with Revit™, Tekla, AutoCAD, and many more incorporate seamless and bi-directional data exchange. Software created by engineers for engineers; RFEM’s interface and modeling workflow are highly intuitive and easy to learn.

Hexagon PPM Phone: 281-671-1528 Email: sales.cas.ppm@hexagon.com Web: www.coade.com/products/gtstrudl Product: GT STRUDL Description: Supports your modeling, analysis, and design requirements for comprehensive steel and concrete designs. Take advantage of powerful documentation and intuitive design tools for 3D visualization. Complementary modeling environments offer essential tools for fast and productive system analysis. Boost accuracy by eliminating component design and manual drawing.

Integrity Software, Inc. Phone: 512-372-8991 Email: sales@softwaremetering.com Web: www.softwaremetering.com Product: SofTrack Description: Save money on monthly, quarterly, and annual Bentley® license fees! Automatic control to prevent over-usage of Bentley licenses. Ensure licensed applications are used within your license limits. Includes support for all Bentley licensing policies. Automatically block usage of products you do not own. Ask about enhanced Autodesk and ArcMAP reporting.

Losch Software Ltd 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. LECWall can analyze prestressed and/or mild reinforced wall panels with zero to 100 percent composite action. Flat, hollow-core, and stemmed configurations are supported. Complete handling analysis is also included.

Not listed? All 2018 Resource Guide forms,

including the 2018 Trade Show in PrinT, are available on our website. www.STRUCTUREmag.org

STRUCTURE magazine

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August 2018

People Helping People Build a Safer World

MKT Fastening, LLC

2 New Tools for Structural Design Gain expert insight on hot topics impacting structural engineering

Wind Design Manual: Based on the 2018 IBC® and ASCE/SEI 7-16, Examples for Wind Forces on Buildings and Solar Photovoltaic Systems

POSTEN Engineering Systems

RISA Inc Phone: 949-951-5815 Email: info@risa.com Web: risa.com Product: RISAFoundation Description: Designs retaining walls, two-way mat slabs, spread footings, grade beams and pile caps all within an open modeling environment. With synchronized load transfer from RISA-3D and RISAFloor models, foundation design has never been easier. Punching shear checks, rebar design, and international codes make it the smart choice for engineers.

Product: RISAFloor Description: Designs and optimizes building systems constructed of steel (composite and noncomposite), concrete, wood and CFS, as well as combinations of materials. Automatic live load reduction, additive or exclusive floor area loads, vibration calculations and more make RISAFloor the first choice for the design of all types of building systems.

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

continued on next page

Offers examples on wind force design that illustrate the practical requirements of provisions in ASCE/SEI 7-16. Practicing structural engineers, trained designers, building department engineers, other plan review agencies, professors and students, can all learn from these examples of code-compliant designs engineered to achieve good performance under wind loading.

Developed by a SEAOC task group with the expertise of authors from across the U.S., the Manual contains example problems that apply to a variety of geographic areas: · 7 Solar PV systems examples · 4 General topics examples

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

Phone: 510-275-4750 Email: sales@postensoft.com Web: www.postensoft.com Product: POSTEN X Description: Simply the fastest, most comprehensive, most efficient and easy to use post-tensioned concrete software. No guessing and fiddling with drapes and prestress, POSTEN takes you to the most efficient designs automatically. What takes you days with other software happens in minutes with POSTEN Capabilities Like No Other.

· 3 Buildings examples · 2 Special topics examples

SOFT COVER #9000S18 | PDF DOWNLOAD #8026P18

A Guide to the 2018 IRC® Wood Wall Bracing Provisions Wall bracing is a common source of confusion and misapplication. This full-color illustrative guide was developed by ICC and APA – The Engineered Wood Association to help code users apply the lateral bracing requirements of the 2018 IRC. Topics include: · Understanding wind and seismic forces on a house · Bracing options available to the builder/designer · Determining how much bracing is required with adjustments and variations

· Connection details for bracing units · Cripple walls and foundations · Special bracing provisions for stone and masonry veneer · Whole house considerations

SOFT COVER #7102S18 | PDF DOWNLOAD #8799P18

Get your new design resources today!

1-800-786-4452 | shop.iccsafe.org

STRUCTURE magazine

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August 2018

18-15705

Phone: 800-336-1640 Email: charley@mktfastening.com Web: www.mktfastening.com Product: MKT Anchor Design Software Description: MKT Fastening launches new Anchor Design software – an MKT anchor design program 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.

®

S-FRAME Software

StructurePoint

Phone: 604-273-7737 Email: info@s-frame.com Web: s-frame.com Product: S-FRAME Analysis Description: Faster. Better. More Advanced. Model, analyze, and design structures regardless of geometric complexity, material type, loading conditions, nonlinear effects, or seismic loading. Integrated concrete, foundation, and steel design maximizes productivity. Our continued investment in R&D and client support gives you the latest analysis advantages with dedicated technical backing.

Phone: 847-966-4357 Email: info@structurepoint.org Web: structurepoint.org 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.

Product: S-STEEL Description: Code check and auto design steel members for both strength and serviceability.

S-STEEL supports many steel design codes and has a wide range of optimization criteria and constraints to accommodate your design and performance assessment process from preliminary to final design stages to ensure structural safety and economy.

Phone: 770-426-5105 Email: kristine.plemmons@trimble.com Web: www.tekla.com Product: Tekla Tedds Description: Automates repetitive and error prone structural and civil calculations, allowing engineers to perform 2D frame analysis, access a large range of automated structural and civil calculations to U.S. codes, and speed up daily structural calculations.

Product: S-CONCRETE Description: Code check and auto design steel members for both strength and serviceability.

S-STEEL supports many steel design codes and has a wide range of optimization criteria and constraints to accommodate your design and performance assessment process from preliminary to final design stages to ensure structural safety and economy.

Simpson Strong-Tie® Phone: 800-925-5099 Email: web@strongtie.com Web: www.strongtie.com Product: Strong-Wall® Bracing Selector Web App Description: Selecting pre-engineered shearwall alternatives for code-prescribed braced wall panels just got easier. New app updates provide more design flexibility and bracing solutions. Quickly determine the number of Strong-Wall panels needed to meet wall-bracing-length requirements. Based on job specific requirements, the app provides the narrowest bracing solutions possible.

Product: Adhesive Cartridge Estimator Web App Description: This App makes it easy to estimate how much adhesive you need for your project. Input the size and number of adhesive anchors to get the amount of adhesive cartridges needed for the job.

Choose between six types of adhesive, including our new SET-3G™ high-strength epoxy adhesive.

Trimble

2018 ANNUAL

TRADE SHOW IN PRINT

Product: Tekla Structural Designer Description: Fully automated and packed with unique features for optimized concrete and steel design, Tekla Structural Designer helps engineering businesses win more projects and maximize profits.

From quick comparison of alternative design schemes through cost-effective change management and seamless BIM collaboration, Tekla Structural Designer can transform your business.

Product: Tekla Structures Description: Create and transfer constructible models throughout the design life cycle, from concept to completion. With Tekla Structures, accurate and information-rich models reduce RFIs, leverage models for drawing production, material take offs and collaboration with architects, consultants, fabricators, and contractors.

Visicon Inc. Phone: 650-306-2400 Email: sales@visicon.com Web: www.visicon.com Product: Visicon BIM Model Manager Description: A versatile tool for your daily interaction with BIM models. It facilitates easy data extraction, markups, 3D measurements, coordination of issues, clash detection, quantity takeoffs, and change management. It extracts Revit models in one click of a button and opens IFC, ETABS, ADAPT, and other model file formats.

WoodWorks Software

Phone: 540-239-6355 Email: floorvibe@gmail.com Web: FloorVibe.com Product: FloorVibe v3.0 Description: New release. Provides calculations and advice for the floor vibration prediction procedures in the new AISC Design Guide 11 2nd Ed. Vibrations of Steel-Framed Structural Systems Due to Human Activity. Floors supporting residences, offices, sensitive equipment, and rhythmic activities are easily evaluated, as well as linear stairs and footbridges.

Phone: 800-844-1275 Email: sales@woodworks-software.com Web: www.woodworks-software.com Product: Design Office Suite Description: Conforms to IBC 2015, ASCE7-10, NDS 2015, SDPWS 2015. SHEARWALLS: designs perforated and segmented shearwalls; generates loads; rigid and flexible diaphragm distribution methods. SIZER: designs beams, columns, studs, joists up to 6 stories; automatic load patterning.

CONNECTIONS: Wood to: wood, steel or concrete.

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STRUCTURE magazine

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News form the National Council of Structural Engineers Associations

2018 Summit is Drawing Near – Register Now Before Rates Increase on September 7th The Summit is the best and biggest it has been and has tons to offer: • Attendance has increased by more than 100% in the last 3 years • Educational offerings have been increased for more choices – Over 25 presentations led by SE and business experts; 5 education tracks on Thursday, 4 on Friday, plus 4 general sessions, including the Opening Keynote by Ron Klemencic; Leadership Plenary by Stacy Hanke; and the Luncheon Keynote by Ashraf Habibullah.

• The Trade Show has expanded by more than 30%. This year’s Trade Show will be the largest in NCSEA history!

• Several can’t-miss events every single day!

– Some events have limited space available. Register now to guarantee your spot!

Atlas Tube Plant Tour – Wednesday, October 24

Take part in a tour of the Atlas Tube manufacturing mill to see how Hollow Structural Sections are made. Atlas Tube, a division of Zekelman Industries, manufactures a wide range of steel tubular products and is the leading provider of hollow structural sections (HSS) in North America. This tour has been NCSEA Diamond Review-approved for 1 continuing education hour.

Structural Engineering Cruise on the Chicago River – Wednesday, October 24

This one-of-a-kind event, sponsored by Atlas Tube and brought to you by NCSEA and SEAOI, will offer a river’s-eye view of the structural engineering and architectural marvels along the Chicago River. The cruise will feature special presentations about the architecture surrounding the river delivered by Chicago Engineers and SEAOI Members, our personal docents of the evening. Food and cocktails will also be available on the fully enclosed, climate-controlled boat.

A Celebration of Structural Engineering at Navy Pier – Thursday, October 25

Hosted by Computers & Structures, Inc., and held at one of Chicago’s top attractions, Navy Pier. This extravagant event includes dinner, champagne, and live music that will be enjoyed with extraordinary views of the lake and Chicago’s magnificent skyline. Come celebrate the immeasurable contributions of the structural engineering profession and the ways in which structural engineers are essential to the progress of society while experiencing the architecturally stunning environment that showcases the vitality of Chicago.

NCSEA Awards Banquet and Reception – Friday, October 26

This banquet features the presentation of the NCSEA Excellence in Structural Engineering Awards, honoring the best examples of structural engineering ingenuity throughout the world, and the NCSEA Special Awards, given to NCSEA members who have provided outstanding service and commitment to the association and to the structural engineering field.

NCSEA News

Register now to guarantee your spot at the Summit! www.ncsea.com/register

Thank You 2018 Summit Sponsors Platinum Sponsors Computers & Structures, Inc. www.csiamerica.com Atlas Tube www.atlastube.com Gold Sponsors DrJ Engineering, LLC www.DrJcertification.org Hilti www.hilti.com Silver Sponsors ICC ES www.icc-es.org Nucor Corporation www.nucor.com Bronze Sponsors Freyssinet www.freyssinetusa.com Hexagon PPM www.hexagonppm.com MiTek www.mitek-us.com STRUCTURE magazine

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August 2018

The Structural Engineers Association of Illinois (SEAOI) is pleased to announce the Eighth Annual Structures Symposium. SEAOI’s Structures Symposium is an event that provides a forum for engineers to share analysis, design, and construction information from recent projects with unique and/or distinguishing characteristics. The attendance at each symposium represents a diverse cross-section of all aspects of the structural engineering profession, including: design, construction management, material suppliers, academia, general contracting, and owners’ representatives.

The 2018 Symposium will take place Thursday, October 11, at 150 N Riverside Plaza, Chicago, IL. The event offers 7 hours of CE credit. More information can be found on the SEAOI website, www.seaoi.org.

Abstracts for the 2018 Structures Symposium are being accepted until August 13; to submit your abstract visit http://bit.ly/SEAOIabstracts2018.

Follow NCSEA on Facebook and Twitter! @NCSEA

Subscribe to Knowledge with NCSEA’s Webinar Subscription

NCSEA News

SEAOI Announces 2018 Structures Symposium

Enhanced Benefits. Expert Speakers. Unlimited Attendees.

Sign up for your Yearly Live & Recorded Webinar Subscription now! www.ncsea.com

NCSEA Webinars August 23, 2018 Changes to the 2018 National Design Specification (NDS) for Wood Construction Lori Koch, P.E. This presentation will provide an overview of the significant changes for wood design per AWC’s National Design Specification® (NDS) for Wood Construction.

September 13, 2018 ICC Storm Shelter Design: Code Criteria & Project Challenges John Funk, P.E. The speaker will discuss the current IBC and ICC code provisions, how it can apply to locating the shelter in a project, and material selection to design a storm shelter.

September 20, 2018 Overview of Changes & Additions in ACI 318-14 Royce Floyd, Ph.D., S.E. This webinar will provide a general overview of the reorganization of the ACI 318 Building Code Requirements for Structural Concrete and Commentary for the 2014 edition.

September 27, 2018 Designing Wood-Frame Structures for High Winds Ricky McLain, P.E., S.E. This presentation will cover the design of a building’s wind-resisting system, including wind load calculations, diaphragms, shear walls, and collectors. Load path continuity will be discussed, as will unique design considerations for designing wood-frame structures to resist uplift, in-plane, and out-of-plane wind loads.

Register at www.ncsea.com. Courses award 1.5 hours of continuing education after the completion of a quiz.

Diamond Review approved in all 50 States.

STRUCTURE magazine

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August 2018

News from the National Council of Structural Engineers Associations

NCSEA’s newly enhanced Yearly Webinar Subscription is the most user- and wallet-friendly plan to date! This Live and Recorded Webinar Subscription offers all the same benefits as before, but now includes even more. With this annual plan, you get: • 20+ live webinars a year featuring the highest-quality speakers available. View the upcoming schedule at www.ncsea.com.

• New! Receive an unlimited number of free CE certificates for each webinar – no more $30 fee – so multiple viewers at the same location can receive credit for every live webinar with no additional costs.

• Unlimited 24/7/365 access to NCSEA’s Recorded Webinar Library – more than 100 relevant and high-quality webinars.

• New! A brand new and enhanced education website. NCSEA’s Education Portal provides easy access to all of your education content, including: • Purchase history • Earned Certificates to track your PDHs with ease

Learning / Networking

NEW SEI/ASCE Live Webinars — Learn from the Experts August 3 August 10 August 13 August 17 August 20 August 22 August 24

The News of the Structural Engineering Institute of ASCE

August 31

Significant Changes to Tensile Membrane Structures, ASCE 55-16 Calculating and Applying Design Wind Loads on Buildings Using the Envelope Procedure of ASCE 7-16 – UPDATED Flood Design for a Changing Climate Engineering Judgment - Structural Renovation of a 100-Year-old Historic Barn Seismic Base Isolation: State of the Art and Practice Seismic Screening of Buildings Using ASCE 41-17 – UPDATED Practical Application of Fiber Reinforced Polymer (FRP) in Strengthening Existing Concrete and Masonry Structures Elimination of Deck Expansion Joints on Existing Bridges

Register at Mylearning.asce.org for these and much more.

SEI Local Leaders Conference

Local SEI Chapter Chairs: Save the date, October 5-6 at ASCE, for best practices and leadership training to serve member technical and professional needs locally.

If you are a local SEI Chapter Chair and are not on the local SEI leaders email list, contact Suzanne Fisher sfisher@asce.org. Connect with your local SEI professional or Grad Student Chapter at www.asce.org/SEILocal.

Learn more and register at www.etsconference.org #ETSC18 Free access to ETS 2015 papers through August 14 for registered users and subscribers at ascelibrary.org/page/etss18.

Save the date for inspiring speakers, dynamic learning, networking, collaboration with partners, and fun social events. www.structurescongress.org #Structures19 Learn about scholarship opportunities for young professionals at www.asce.org/SEIYoungProfessionals.

SEI Online

NEW ASCE Manual of Practice No. 135 Monitoring Dam Performance: Instrumentation and Measurements

Presents the fundamentals and current state of practice, balancing visual surveillance and instrumental measurements to accurately understand how well a dam is performing.

SEI Update

Your Invitation to Get Involved • Do your summer plans include visiting ASCE Landmarks, inspiring new structures, bridges…? Share your favorite photos and/or links to summer reading on Twitter and tag @ASCE_SEI. Or send to sei@asce.org to post and share with colleagues.

• Community Engineering Corps (CECorps), an alliance with Engineers Without Borders USA and the American Water Works Association (AWWA). Lend your technical expertise, mentor student groups, or form/join a project team through you ASCE Section, Branch or SEI Chapter. www.asce.org/community_engineering_corps.

• ASCE Bridge Photo Contest: Viewer’s Choice Vote for your favorite bridge photo today! www.ascebridgephotos.org.

SEI News

Follow SEI on Twitter

View the latest SEI news and opportunities at www.asce.org/SEI.

Errata

@ASCE_SEI

SEI Standards Supplements and Errata including ASCE 7. See www.asce.org/SEI-Errata.

If you would like to submit errata, contact Jon Esslinger at jesslinger@asce.org.

STRUCTURE magazine

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August 2018

Congratulations…

To recently elected ASCE President-Elect Elect (2018-2019) Kancheepuram (Guna) N. Gunalan, Ph.D., P.E., D.GE., F.ASCE, and ASCE Region Directors-Elect (2018-2021) including Technical Region Director David J. Odeh, P.E., S.E., SECB, F.SEI, F.ASCE. View full election results at www.asce.org/elections.

Join or Renew SEI/ASCE

SEI Standards

For innovative solutions and learning, to connect with leaders and colleagues, and enjoy member benefits such as SEI Member Update monthly e-news opportunities and resources – visit www.asce.org/myprofile or call ASCE Customer Service at 800-548-ASCE (2723). Follow @ASCE_SEI

Visit www.asce.org/SEIStandards to: • View ASCE 7-22 Committee Meeting schedule and archive • Submit proposals to revise ASCE 7

Reach more than 30,000 SEI members year-round with SEI Sustaining Organization Membership. Show your support for SEI to advance and serve the structural engineering profession. Learn more and join today at www.asce.org/SEI-Sustaining-Org-Membership.

SEI Elite Sustaining Organization Members

Advancing the Profession

Help Bring dream BIG to More Communities Every child should Dream Big. Together, we can make that possible.

The acclaimed giant-screen documentary Dream Big: Engineering Our World has inspired audiences in museums around the world, surpassing one million viewers in just six months.

Now with generous support from the United Engineering Foundation, join us to put a copy of the Dream Big film and educational toolkit in every public school in America.

Give $5 to place a toolkit in the school of your choice at www.engineersdreambig.org.

Ethics and Engineering The practice of engineering entails an enormous number of professional responsibilities – responsibilities to clients; to employers, staff, and colleagues; to government regulators; and to the public at large. As illustrated in the ethical codes adopted by the profession, these obligations include the duty to provide faithful and competent service, to comply with legal obligations and the applicable standard of care, and to protect above all the public health, safety, and welfare. Fortunately, most engineers have a solid understanding of these responsibilities and share a genuine commitment to avoid circumstances in which their professionalism or integrity may be questioned.

In return for the profession’s diligence in meeting these lofty ethical principles, the engineering profession enjoys an overall stellar reputation among members of the general public, who consistently rank engineers as among the most trusted and esteemed professions.

Yet it is not uncommon for an engineer to encounter situations that might best be described as an ethical “gray area” – cases in which the engineer is unsure of his/her precise legal or ethical obligations, or might question whether a good result justifies a dubious choice. What are a departing employee’s obligations to his/her employer? What should an engineer do when overruled STRUCTURE magazine

by a supervisor on a matter of ethics? When is it acceptable to accept gifts from a business connection? When the ethical line is unclear, it is often helpful to seek guidance from written case studies and advisory opinions published by engineering societies like ASCE. For example, a column recently published in ASCE News discusses five “gray areas” that an engineer may encounter: https://bit.ly/2KUactB. Another potential ethical challenge lies in the complexities of navigating the modern workplace. Today’s workforce, like no other before, features tremendous diversity in terms of age, gender, race, national origin, and other characteristics; and it brings with it tremendous expectations in terms of accommodating different work, life, and family needs. While these issues have traditionally been addressed in the United States by employment laws and regulations, many members of the engineering profession feel that “fair treatment of others” is not only a legal obligation but an ethical one as well. A recent article by the ASCE Executive Director discusses the importance of diversity in the engineering profession and introduces the new provision in the ASCE Code of Ethics that addresses this issue: https://bit.ly/2L2aLy3.

See ASCE Ethics Resources at www.asce.org/ethics.

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August 2018

The News of the Structural Engineering Institute of ASCE

SEI Sustaining Organization Membership

SEI Update

Membership

CASE in Point

The News of the Council of American Structural Engineers

CASE Summer Planning Meeting Update The CASE Committees continue to support and create various industry initiatives and practice guidelines which are critical to building competitive successes for our member firms. We continue to investigate new ways of connecting creative business solutions to common problems while helping member firms reduce the severity of claims and project/firm risk. Over 30 CASE committee members and guests were in attendance at the recent CASE Summer Planning Meeting on June 6-7 in Anaheim, CA. During the meeting, break-out sessions were held by the Contracts, Guidelines, Membership, Toolkit, and Programs & Communications Committees.

CASE needs your help to keep up with the fast-paced changes that are moving our industry forward. If you have an interest in getting involved in one of the areas listed below, please contact the chair for more information or contact Heather Talbert, htalbert@acec.org or 202-682-4377.

The next planning meeting will take place at the beginning of February 2019.

1) Contracts Committee – Brent Wright (brent@wrighteng.net) • Updating contract matrix to include definitions of each contract for ease of use • Preparing all CASE Contracts for next legal review in 2018-2019 o Updating all contract documents to include “must have” terms and conditions; scope provisions; certificate of merit sections 2) Guidelines Committee – Kirk Haverland (khaverland@larsonengr.com) • Be the point committee to review documents from the joint SEI/CASE BIM Committee when released: Fall 2018 Level of Development (LOD) and BIM Execution Plan (BXP) • Revising the following current Practice Guideline Documents: o 962: National Practice Guidelines for the Structural Engineer of Record o 962-D: A Guideline Addressing Coordination and Completeness of Structural Construction Documents

• Working on the following new documents: o Commentary on ASCE-7 Wind Design Provisions o Commentary on ASCE-7 Seismic Design Provisions o Geotech guideline document • Future publications: o Guideline to Projects within Flood Plains o Discussing creation of a practice guideline around Design-Build o Reviewing the new AISC COSP and updating the CASE Commentary document with new information 3) Programs and Communications Committee – Nils Ericson (nericson@m2structural.com) • Discussed options for sessions at the 2018 ACEC Fall Conference • Discussed options for sessions at the 2019 ACEC Annual Convention • Discussed options for the 2019 Business of Structural Engineering o Instead of Workshop, will be changing the format of the winter/summer meetings to become a dinner meeting option for local ACEC/SEA organizations to try and increase visibility among member organizations for ACEC and SEAs 4) Toolkit Committee – Brent White (brentw@arwengineers.com) • Revising the following current documents: o Tool 3-3: Website Resource Tool o Tool 4-3: Sample Correspondence Letters o Updating current Contract Document pertaining to RFIs into a regular tool • Working on the following new documents: o Tool 8-2: Contract Review o Tool 3-5: Short-term Staffing • Future Tools/Activities: o Will updated the tool that links the CASE 962-D Guideline – A Guideline Addressing Coordination and Completeness of Structural Construction Documents as the Guidelines Committee updates it o Continue to review current tools for possible updates.

Prepare Your Top Talent for Executive Leadership Pathways to Executive Leadership is ACEC’s leadership development program for early-career high-achievers and exceptional mid-career professionals with approximately 9 to 12 years of experience in the engineering consulting industry. Pathways Class III kicks-off at ACEC’s 2018 Fall Conference with sessions on sustaining lifetime client relationships, advancing along the career leadership pipeline, and forecasting new markets for firm growth.

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Follow ACEC Coalitions on Twitter – @ACECCoalitions.

STRUCTURE magazine

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August 2018

When you’re packing for summer travel – think light for business insights!

CASE Risk Management Tools Available Foundation 5: Education – Educate all of the Players in the Process • Educate management, staff, and clients • Have established education and training policies and procedures • Coaching and mentoring is an essential part of the education process Tool 5-1: A Guide to the Practice of Structural Engineering Intended to teach structural engineers the business of being a consulting structural engineer and things they may not have learned in college. While the target audience for this tool is the young engineer with up to 3 years of experience, it also serves as a useful reminder for engineers of any age or experience.

The Guide also contains a test at the end of the document to measure how much was learned and retained. Other sections deal with getting and starting projects, schematic design, design development, construction documents, third-party review, contractor selection/project pricing/delivery methods, construction administration, project accounting and billing, and professional ethics.

Tool 5-2: Milestone Checklist for Young Engineer The tool will help your engineers understand what engineering and leadership skills are required to become a competent engineer. It will also provide managers with a tool to evaluate engineering staff.

Tool 5-3: Managing the Use of Computers and Software in the Structural Engineering Office Computers and engineering software are used in every structural engineering office. It is often a struggle to manage and STRUCTURE magazine

supervise these tools. Software availability is in constant flux, software packages are continually updated and revised, and few software packages fully meet the needs of any office. This tool is intended to assist the structural engineering office in the task of managing computers and software.

Tool 5-4: Negotiation Talking Points This tool provides an outline of items for your consideration when you are in a situation in which you are pressured to agree to lower fees. The text is subdivided into situations that are commonly experienced in our profession. This document is purely advisory and designed to assist you in your negotiations and business practices.

Foundation 6: Scope – Develop and Manage a Clearly Defined Scope of Services A well-developed scope of services: • Avoids later misunderstandings • Provides clarity for future additional services • Clarifies the work effort and fee • Establishes many contract terms • Functions as a guide for your staff • Helps to mitigate claims Tool 6-2: Scope of Work for Engaging Sub-Consultants This tool should be used when a structural engineer is asked by the prime consultant or owner to provide input on sub-consultant selection and scope of work, or when the structural engineer is required to retain the sub-consultant directly.

You can purchase these and the other Risk Management Tools at www.acec.org/bookstore.

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August 2018

CASE is a part of the American Council of Engineering Companies

With a range of topics from proposal writing to project delivery, these digital resources are a perfect addition to your business library – instantly available in PDF, MOBI, or E-PUB – at a great price. Download one or all!

• Can I Borrow Your Watch? A Beginner’s Guide to Succeeding in a Professional Consulting Organization • 33 Proven Secrets to Writing Successful Client-Centered Proposals • Construction Management at Risk, Second Edition • Project Delivery Systems Owner’s Manual, Second Edition • Winning Strategies for A/E/C Firms: An Executive’s Guide to Maximizing Growth and Profitability, Third Edition • Win More Work: How to Write Winning A/E/C Proposals To purchase these and other resources, go to https://programs.acec.org/digitalsummer.

CASE in Point

Catch Up on Your Summer Reading!

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Structural Forum Education Crisis in America: An Insider’s Perspective

By Dilip Khatri, Ph.D., S.E.

I

n this competitive international economy, Head Coaches, with pay packages exceeding to his father’s support and desire that he not fall the demand for educated talent is growing. $3 Million/year. Professors in Health Science into the student loan trap. His Chemistry and As such, it makes sense that the United are not too far behind, with total compensation Physics classes were over 400 students/class; States should strive to reduce the expense of packages exceeding $1.8 Million/year. Most of his instructors were mostly part-time lecturers education. However, the current trend reflects these compensation packages are derived from and graduate students. Some full-time and skyrocketing costs. “other pay” which is linked to revenue genera- fully-tenured faculty taught his upper division In 1983, the author graduated from tion from research grants (for Health Science engineering courses. Why are there not more California State University Los Angeles faculty) and sports revenue (for the coaches). full-time faculty teaching courses? The reason is (CSULA) with a Bachelor of Science Degree From the perspective of a business leader and that Universities have become “profit centers.” in Civil Engineering in 3 years (12 quarters), pro-capitalist, there is no problem with coaches Where are the students in all of this? Nowhere. and the total tuition cost was approxThey are expected to take loans to imately $1,200 plus books ($100/ Today, based on the author’s research, a graduate fund a system only concerned with quarter). Overall, including books with a college degree has over $80,000 of student its own interests. and miscellaneous expenses, the In contrast, we have some of the debt at the start of their life and doesn’t even own a estimated total degree expense was best higher education institutions car, let alone a house. about $3,000. Adjusted for inflation, in the world. Their focus at the that would be about $6,000 in 2018.

Master’s and Doctorate levels are At CSULA today, the cost for the same making $3 Million/year. BUT – if the univer- the best because these are research-based uni4-year degree is approximately $68,000 sity is deriving revenue from this resource, then versities; whereas undergraduates are viewed ($17,000/year excluding living cost). At a they should also pay their workers (i.e., athletes) only as an income source and part-time University of California (UC) Campus, the who bear the risk of play, break their bones, nuisance. However, the costs are outstripcost is approximately $104,000 ($26,000/year and suffer long-term effects of brain damage ping the American Family Budget and are excluding living cost). At the University of from concussions. Student-athletes are paid not sustainable. Today, based on the author’s Southern California, a private college, the cost zero. It is easy to make money when you do research, a graduate with a college degree is $240,000 ($60,000/year). These estimates not have employee costs. The entire college has over $80,000 of student debt at the start assume someone will graduate in 4 years, which sports system, run by the NCAA, is operating of their life and doesn’t even own a car, let is highly questionable because of the availability under this questionable shadow of profit taking alone a house. of courses and student overcrowding. (Note without expenses.

Where do we go from here? Some politicians – readers are encouraged to verify exact tuition Current educational priorities are a problem have suggested that we find a way to fund numbers with the universities.) nationally but, in the author’s experience tuition for students so that a college education In America, the expectation is that life will – which is based in the California higher is available for everyone. However, how do get “better” for our children; that they will education system – there are three priorities we pay for it? There is no simple answer to have the same opportunity to pursue higher that public and private universities expect that question. It seems that, as the wealthiest education and that our present generation from new faculty: nation on earth, it would be possible to find a will contribute to the prosperity of future 1) Publish anything anywhere way to make college accessible for ALL who generations. So, what happened?

2) Bring external, Publicly Funded Research wish to pursue a degree. As a start, universities The author has been on several sides of 3) Bring external, Privately Funded Research need to separate out profit incentives such as this debate, having been a Faculty Member Note that student education and their welfare sports, research funding, and other extraneous in the Civil Engineering Department for 9 is nowhere to be found on this priority list. activities that are not part of Education. If years at California State University, Pomona International students have also become a universities want to pursue these revenue(CalPoly Pomona). In 1997, the author left significant market for campuses nationwide. generating activities, then they should set academia to start his own firm in the pri- In California, foreign tuition rates are up separate, private corporations that should vate sector. In addition, he also worked for approximately double that for local students; for be taxed and regulated as part of the private NASA- JPL/CALTECH for 3 years early U.C. Berkeley, this is over $50,000/year for an sector. Let education be where it should be – a in his career, so he has worked in both the international student. This results in universities non-profit venture for the benefit of students.▪ public and private sectors over the past 34 increasing foreign student populations while Dilip Khatri is the Principal of Khatri International years and brings a unique perspective on the ignoring local students. The math is simple; Inc, Civil and Structural Engineers, based in issue of Education in America. if they are going to collect twice as much per Las Vegas, NV, and Pasadena, CA. He was a Firstly, for public universities, there is a serious student, then those students get higher priority.

Professor of Civil Engineering at Cal Poly Pomona problem with costs and educational priorities.

So, what are the results of this system? The for 10 years. He served as a member of the The top 4 positions in the State of California author’s son attended a California University STRUCTURE Editorial Board. (dkhatri@gmail.com) with the highest paid compensation are all for 4 years and graduated without any debt, due 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, the Publisher, or the STRUCTURE® magazine Editorial Board.

STRUCTURE magazine

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August 2018

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