STRUCTURE magazine - January 2020 by structuremag

STRUCTURE JANUARY 2020

NCSEA | CASE | SEI

CONCRETE

INSIDE: Vancouver House

Cutting Prestressed Concrete Framing 8 Anchoring Attachments 12 Adaptive Reuse of Apex Hosiery Building 17

BEFORE IT GOES UP IT HAS TO GO DOWN! Details matter. Don’t put your designs at risk, specify PIERESEARCH for all your rebar and rebar cage alignment projects.

Quick Lo Pier Bo ®ck ot

DURABLE. ECONOMICAL. RELIABLE. PROVEN.

Quick - Lock HD® Pier Wheel

Quick - Lock® Pier Wheel

Quick - Zip Bar Booster®

THE REVOLUTIONARY NEW QUICK-LOCK UNIBAR® CENTRALIZER

Pieresearch provides custom quality alignment products that are critically important to all professionals involved in the structural engineering, geo-design and construction industry. ® Manufacturer of Quality Concrete te Accessories Proudly Made in the USA! EST. 1986

Patent No. 10,151,113

pieresearch.com • stanagee@pieresearch.com 817.277.3738 • 817.275.2335 Fax

ADVERTISER INDEX

Please support these advertisers

STRUCTURE

Aegis Metal Framing ..............................28

Larsen Products .....................................33

American Concrete Institute .....................29

MAPEI Corp .........................................10

sales@STRUCTUREmag.org

Commins Mfg .......................................32

NCEES ...............................................16

CTS ......................................................9

Nucor Vulcraft Group - Redicor ................39

Joe Murphy jmurphy@STRUCTUREmag.org; Tel: 203-254-9595

ENERCALC, INC ....................................3

Pieresearch ............................................2

GeoDesign ..........................................41

RISA ...................................................52

Geopier Foundation Company.................18

Simpson Strong-tie ...........................13, 25

Hohmann & Barnard ..............................20

Structural Engineering Institute ............. 34-35

EDITORIAL STAFF

Integrated Engineering Software ...............51

StructurePoint ..........................................6

Executive Editor Alfred Spada

KPFF .....................................................4

Struware, Inc ........................................31

MARKETING & ADVERTISING SALES

Denis O’Malley domalley@STRUCTUREmag.org; Tel: 203-356-9694, ext. 13 Jerry Preston jpreston@STRUCTUREmag.org; Tel: 602-369-3037

aspada@ncsea.com

Publisher Christine M. Sloat, P.E. csloat@STRUCTUREmag.org

YOUR OPINION MATTERS!

Associate Publisher Nikki Alger nalger@STRUCTUREmag.org

STRUCTURE magazine is always looking for Structural Forum (opinion) articles and Letters to the Editor. We preserve a page at the end of the magazine to print these types of articles, as space permits. Please send your pieces to publisher@structuremag.org. And don’t forget – post questions or comments on the digital versions of articles on the STRUCTURE website. STRUCTURE looks forward to hearing from you!

Creative Director Tara Smith graphics@STRUCTUREmag.org

EDITORIAL BOARD Chair John A. Dal Pino, S.E. FTF Engineering, Inc., San Francisco, CA chair@STRUCTUREmag.org Jeremy L. Achter, S.E., LEED AP ARW Engineers, Ogden, UT

2020 MEDIA KIT

Erin Conaway, P.E. AISC, Littleton, CO

Available Online at STRUCTUREmag.org

Linda M. Kaplan, P.E. Pennoni, Pittsburgh, PA Charles “Chuck” F. King, P.E. Urban Engineers of New York, New York, NY Emily B. Lorenz, P.E. Chicago, IL Jessica Mandrick, P.E., S.E., LEED AP Gilsanz Murray Steficek, LLP, New York, NY

TOGETHER WE BUILD SOLUTIONS

ADVERTISEMENT–For Advertiser Information, visit STRUCTUREmag.org

Jason McCool, P.E. Robbins Engineering Consultants, Little Rock, AR

Excellence in Structural Engineering Campus Kilpatrick • Malibu • CA Seattle Tacoma Lacey Spokane Portland Eugene

4 STRUCTURE magazine

Sacramento San Francisco Los Angeles Long Beach Irvine San Diego

Boise Des Moines St. Louis Chicago Louisville New York

KPFF is an Equal Opportunity Employer www.kpff.com

Brian W. Miller Davis, CA Evans Mountzouris, P.E. The DiSalvo Engineering Group, Danbury, CT John “Buddy” Showalter, P.E. International Code Council, Washington, DC Eytan Solomon, P.E., LEED AP Silman, New York, NY Jeannette M. Torrents, P.E., S.E., LEED AP JVA, Inc., Boulder, CO STRUCTURE ® magazine (ISSN 1536 4283) is published monthly by The National Council of Structural Engineers Associations (a nonprofit Association), 20 N. Wacker Drive, Suite 750, Chicago, IL 60606 312.649.4600. Application to Mail at Periodicals Postage Prices is Pending at Chicago, IL and additional mailing offices. STRUCTURE magazine, Volume 27, Number 1, © 2020 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, 20 N. Wacker Drive, Suite 750, Chicago, IL 60606.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, 20 N. Wacker Drive, Suite 750, Chicago, IL 60606. POSTMASTER: Send Address changes to STRUCTURE magazine, 20 N. Wacker Drive, Suite 750, Chicago, IL 60606. 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 JANUARY 2020

Feature 22 NAPA COUNTY HISTORIC COURTHOUSE – PART 2 By Brett Sheilds, P.E., Luke Wilson, S.E., and Kevin Zucco, S.E.

The 2014 South Napa Earthquake left the Napa County Historic Courthouse heavily damaged. Part 2 of this series describes efforts towards a solution to repair and preserve as much of the historic building as practical while providing improved detailing.

Columns and Departments 7

Editorial The Future of Engineering

By Chris Tokas

Structural Practices Cutting Prestressed Concrete Framing

and Sal A. Capobianco, P.E.

Structural Analysis Analysis of Anchoring Attachments Using Finite Element Modeling By Richard T. Morgan, P.E., and Arif Shahdin

By D. Matthew Stuart, P.E., S.E., P.Eng, SECB

InFocus The Case for

Cover Feature

Data-Supported Project Interviews

26 VANCOUVER HOUSE

By John A. Dal Pino, S.E.

By Geoff Poh, P.Eng

Picture yourself standing at the base of a high-rise tower looking up, with the side of the building being only as wide as you are tall. Above, you see the tower gradually grow out to one side, consecutively with each floor. The playful curve of the Vancouver House tower is turning the heads to all those who walk near it.

Structural Repair Novel Solution for Strengthening Handrail Anchorage By Ali Abu-Yosef, Ph.D., P.E., S.E., Joseph Klein, P.E., Michael Ahern, P.E., et. al

Business Practices Hiring Experienced Structural Engineers By Michael “Batman” Cohen

Spotlight Sarah Mildred Long Bridge By Christopher Burgess, P.E., S.E., P.Eng.,

Structural Rehabilitation Adaptive Reuse of the Apex Hosiery Company Building – Part 2

InSights Cloud-Based Modeling By Michelle McCarthy and Doug Evans

By Michael F. Hughes, P.E., S.E.,

Northridge – 25 Years Later Seismic Safety in California Hospitals

By Stacy Bartoletti, S.E.

Peter Roody, P.E., and Jeffrey Folsom, P.E.

Structural Forum Embodied Carbon By Donald Davies, P.E., S.E., and Kate Simonen, AIA, S.E.

In Every Issue 4 Advertiser Index 41 Resource Guide – Anchor Updates 44 NCSEA News 46 SEI Update 48 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. JANUARY 2020

A Powerful Software Suite for Detailed Analysis & Design of Reinforced Concrete Structures

EDITORIAL The Future of Engineering By Stacy Bartoletti, S.E., Chair CASE Executive Committee

e are all busy taking care of our clients, delivering structural engineering expertise, and running our businesses; we probably do not take much time to sit back and contemplate the future of engineering and, more specifically, the impacts of future changes on structural engineering. Fortunately for all of us, there are organizations and groups of highly engaged professionals considering these questions and developing some interesting material and ideas. I am one of the professionals who believe the engineering profession is heading into a period of rapid change that will ultimately have an impact on all of us and society at large. The American Society of Civil Engineers (ASCE) is investing heavily in analyzing and producing a number of future scenarios through their Future World Vision project. The ASCE work is based on the premise that change is coming rapidly, with trends in smart infrastructure, alternative energy, intelligent transportation, and other areas. These trends are captured in a series of scenarios looking out 50 years and will ultimately be presented in five future worlds. If you have not seen this work, I encourage you to take a look and imagine how these future visions will impact structural engineering and your business. The Structural Engineering Institute (SEI) of ASCE also developed a Vision for the Future of Structural Engineering in 2013 and recently produced a progress report on actions taken to achieve the vision. The SEI Vision was the seed for the three national structural engineering organizations, CASE, NCSEA, and SEI to come together and develop a one-page Vision for the Future of Structural Engineering. Endorsed by all three organizations, the Vision is being used as a guide for future activities in all of the organizations. As the current Chair of CASE and a practicing structural engineer, I am particularly pleased to see the three national SE organizations speaking with a collective voice and actively collaborating to advance our great profession. Beyond these activities, I am personally involved as a member of the steering committee for a more recent initiative and an organization called the Engineering Change Lab USA (ECL). The idea to form ECL came from a small group of people active in the American Council of Engineering Companies (ACEC) and gained early insight from a similar activity in Canada. ECL believes that the world is facing an unprecedented wave of change. Accelerating technological progress, rapidly evolving societal needs, and growing environmental imperatives, including climate change, all present significant challenges and opportunities. Maintaining the status quo is not an option for the engineering community, and, as an uncertain future unfolds, it must serve as stewards of technology, the natural and built environments, and the public health, safety, and welfare. STRUCTURE magazine

The Mission for ECL is to be a catalyst for change within the engineering community, helping it reach its highest potential on behalf of society. To achieve the Mission, the organization convenes stakeholders to explore new knowledge about the role of engineering in an emerging future, complements the work of other organizations, has a goal to be a communications hub, and leads collaborative initiatives designed to transform the engineering community. Over the past two-plus years, ECL has convened seven workshops around different areas of exploration focused on strategic issues impacting the future of engineering. These strategic issues have included public perception of engineers, diversity and inclusion, leadership skills for future engineers, education, public policy, technological forces impacting engineering, engineering ethics, entrepreneurship, new models for licensure, and the future of consulting engineering. Some of these issues have transformed into chartered initiatives, each designed for further experimentation and exploration. The initiatives currently being undertaken by ECL USA, and captured by their future vision statements, include: Education – Imagine if, guided by educators and mentors who understand emerging technologies, every student was prepared and excited to address challenges and problems by applying science and math concepts, using an engineering approach. Future of Consulting Engineering – Imagine if engineering firms are thriving in the future by bringing value to their clients and society as change occurs, leading changes in technology, attracting top talent, and embracing diversity in the profession. New Models for Engineering Licensure – Imagine a future where the practice of engineering is regulated in a simple and transparent manner that enhances public health, safety, and welfare, and technological development for all. Technological Driving Forces Impacting the Engineering Community – Imagine if engineers led the thoughtful embrace and acceptance of integrated technologies to drive business. Public Policy – Imagine if engineers used their knowledge and skills to have a positive impact on society through engagement in public policy. ECL USA has a growing list of stakeholders and is always looking for more people interested in engaging at any level. If you would like to learn more about ECL USA, please check out their website at ecl-usa.org or contact the Executive Director, Mike McMeekin, at mike.mcmeekin@lamprynearson.com.■ Stacy Bartoletti is the CEO and Chair of Degenkolb Engineers in San Francisco, California, and the Chair of the CASE Executive Committee. (sbartoletti@degenkolb.com) J A N U A R Y 2 02 0

structural PRACTICES Cutting Prestressed Concrete Framing Design and Construction Considerations By Michael F. Hughes, P.E., S.E., and Sal A. Capobianco, P.E.

xisting owners often consider repositioning options for their buildings to serve an ever-evolving tenant market,

accommodate new building uses, improve pedestrian circulation and accessibility, increase rentable tenant space, and more. Often, these buildings are served by an abutting above-grade parking structure, which can prevent horizontal expansion unless portions of the garage are removed to accommodate the expansion. Many parking garages are constructed of precast, prestressed concrete (PC) framing members. PC has the favorable characteristics of structural steel framing, such as allowing for â&#x20AC;&#x153;stick-builtâ&#x20AC;? construction and using long, shallow spans. PC also has significantly more durability than conventional mild-reinforced concrete, since it is cast in a controlled environment. Unlike structural steel and mild-reinforced concrete, PC framing is under constant internal stress from the prestressing strands. Partially removing or modifying PC framing elements can appear to be a complicated design and construction challenge, for which there is little published technical guidance as compared to the other traditional building materials that are not under constant internal prestressing. This article examines the structural considerations of modifying existing PC floor elements and provides a case study where these methods were used successfully. The focus is on simply supported tee beams with fully bonded strands. It is important to note that projects and structures are different, and additional considerations may be applicable depending on the specific project.

Design Considerations Internal prestressing is achieved through the bond between the prestressing strands and the concrete. The prestressing strands are located and stressed to create internal flexural stresses in the member that counteract the flexural stresses from externally applied loads. Parking structures commonly use double-tee beams as floor members. In relatively new parking garages, strands are typically straight, whereas older designs utilized a draped strand that varies in height along the length of the beam. If the location and quantity of the strands are unknown, ground-penetrating radar (GPR) can be used to locate the strands and other embedded reinforcement necessary to evaluate the existing PC member. When an existing PC member is shortened, the flexural stresses in the member will change. Flexural stresses from applied loads are lower for the shorter span, assuming the design loads do not change. For PC, the flexural stresses from the prestressing force are not dependent on span length and will not change if the span is reduced. In general, the total stresses under the full design load will be lower for the shortened span. However, in the unloaded condition (i.e., no live load), flexural stresses from the prestressing can overstress the member. 8 STRUCTURE magazine

Figure 1. Plan view of the opening in the existing parking garage.

The flexural stresses in the loaded and unloaded cases must be checked against code-prescribed allowable stresses for the new span length. Stresses can be calculated using standard PC design methods. For PC members with draped strands, flexural stresses from prestressing will be asymmetric; therefore, checks are required at multiple points along the memberâ&#x20AC;&#x2122;s length. Adding dead load (i.e., ballast) could reduce the flexural stresses from the prestressing. PC beams typically contain added shear reinforcement near supports, but not always along the entire length of the beam. When the beam is shortened, the new supported end may have inadequate or no shear reinforcement. Although the shorter span length will reduce the demand shear forces, the shear stress must be checked at the new cut end. ACI-318 requires the concrete shear capacity to be at least twice the demand to have a section without shear reinforcement. The additional shear strength provided by the prestressing can be included. Shear or flexural reinforcement, such as carbon fiber, can be added externally to strengthen the member. Since carbon fiber does not provide the fire resistance required for many structures, an intumescent paint or other fireproofing material may need to be applied over the carbon fiber material. PC beams are designed to have similar cambers between the adjacent members. Differential cambers create tripping hazards and obstruct drainage. Adjacent PC beams of different lengths are designed for

minimal differential camber by adjusting the bond lengths of the New supplemental framing to support the cut end of the PC member prestressing strands prior to concrete placement, but it is impractical will likely need to be installed before demolition. The portion of the to modify the bond length of the strand after concrete placement. member to be removed will likely need to be shored as well. This shorWhen an existing PC member is shortened, the remaining portion of ing can also be configured to act as a debris shield for the demolition the member will deflect upward due to the reduced external load and work. Debris shielding should be designed to support the weight of unchanged internal prestressing force. The approximate amount of the demolished materials plus appropriate construction live loads. anticipated differential camber should be checked against serviceability Shoring should extend down to grade if possible; however, it may and other project-specific criteria. A maximum of a ¼-inch vertical be possible to terminate shoring if there is adequate capacity for the differential is typically allowed by the American Disabilities Act (ADA) shoring loads at a lower level. for pedestrian walkways. If the expected camber exceeds ¼ inch, the It may be possible to use a crane to remove the portion of the member surface can be ground down, or additional dead load could be added. to be demolished. This option might eliminate the need for shoring The perimeters of double-tee (DT) beams typically contain dia- and noisy demolition work near an existing building. However, there phragm reinforcement necessary to transfer the in-plane wind and are significant rigging and logistical challenges that make this option seismic loads to the building’s lateralload-resisting system (LLRS). Typically, chord reinforcement is located at each end, and collector reinforcement is present where the PC element connects to the LLRS. Diaphragm reinforcement bars are usually spaced closely together and located approximately 1 foot from the end of the member. It is common for three to five bars to be provided for the collector or chord reinforcement in moderate seismic areas. When a portion of the PC framing is removed, this reinforcement is lost and needs to be substituted. Additional framing may be required to transfer loads into the LLRS or reinforce the PC framing chords if the diaphragm load path is interrupted. Use for all types of concrete and grout applications, from slabs-on-grade to

Maximize Value and Performance with

SHRINK AGE-COMPENSATING CONCRETE & GROUT SOLUTIONS

Partially demolishing PC is an uncommon demolition task, and a pre-construction meeting with the construction team should cover the special circumstances of partially removing PC. In addition to typical logistic items covered at these meetings, the expected behavior of the PC, cutting procedures, items to monitor, demolition sequence (start at the uppermost level and work down), and identifying stop points in the work to check for distress must be discussed. It is also important to discuss potential behavior for which the Contractor should notify the Engineer. Material stockpiling, equipment that will be used, or any other atypical live loads, such as vehicle barriers, skid steers, trucks, etc., also need to be coordinated. These loads can exceed the design load of the existing framing, and the framing may need to be checked for these loads. A preconstruction inspection should be performed and compared against observations during construction to identify any new distress.

containment tanks, multi-story post-tension structures to bridge decks.

ADVANTAGES ¡ Maximize joint spacing (up to 300 ft, L/W 3:1)

¡ Enhance compressive and flexural strengths

¡ Prevent shrinkage cracking and curling

¡ Eliminate pour/delay strips

¡ Thinner slabs and walls viable

¡ Reduce long-term relaxation of P/T tendons and shear wall stresses

¡ Reduce reinforcement requirements ¡ Improve durability and lower permeability ¡ Increase abrasion resistance 30-40%

¡ Minimize creep and moment ¡ Minimize waterstops

ADVERTISEMENT–For Advertiser Information, visit STRUCTUREmag.org

Construction Considerations

by CTS Cement Manufacturing Corp.

impractical for most applications. In other words, extreme care must cutting should start at the joint between the section to remain and the be taken when cranes are employed for partial demolition of PC. section to be removed so that the remaining portion is not affected When the existing member is cut, it will camber upward or move by the segmental demolition of the adjacent PC. Saw cutting should differentially from the adjacent existing construction. Therefore, begin in the tension zone, to prevent binding the saw blade. After the existing member must be disconnected from adjacent struc- cutting the joint between the portion to remain and the portion to be tural elements, including beam-to-beam connections and chord and demolished, it is advantageous to remove mild-reinforced portions of diaphragm splices, to avoid damaging the connections or adjacent the PC first, such as the flanges of the tee beam. This will reduce the INFO SPECS elements. These elements will need to be reattached after the work dead load and increase upward camber, further reducing the potential File Name: 19-1670_Ad_1/2Island Structure_July_Bridge Repair SolutionsWOC tag Page Size: 5w" x 7.5h"the bleed is complete. Nonstructural elements, such as partition walls, should for binding saw blade. Job#: 19-1670 PR#: N/A Number of Pages: 1 be temporarily disconnected and modified if the expected amount of During saw cutting, some “popping” noises may be heard as the strands Artist: Georgina Email: gmorra@mapei.com Bleed: are Yes cut. Amount: .125" E . N e w p o upward r t C e n t emovement r Dr. exceeds theirMorra deformation capacity. The Contractor should inform the Engineer if this occurs. ield Beach, FL 33442 Date: December 16, 2019 4:45 PM Colors: CMYK Process, 4/0 The PC to be demolished will likely be removed in sections. The Frequent popping sounds may indicate that the strands are debonding, O L O R S V I E W E D O N - S C R E E N A R E I N T E N D E D F O R V I S U A L R E F E R E N C E O N L Y A N D M A Y N O T M A T C H T H E F I N A L P R I N T E D P R O D U C T. size of each section will depend on the construction logistics. Saw which will require immediate review. Horizontal concrete cracking along the strand typically indicates strand debonding. It is essential to look for any unexpected cracking in the PC that is to remain, such as shear cracking at the support, horizontal cracking along the strand, or tension cracking at midspan. Work should be stopped until unexpected cracking issue or consistent strand popping are understood and resolved.

ADVERTISEMENT–For Advertiser Information, visit STRUCTUREmag.org

MAPEI bridges the gap with concrete repair solutions

Carroll Avenue Bridge Takoma Park, MD

Case Study

Corrosion protection Bear Cut Bridge Key Biscayne, FL

Concrete repair mortars

JEA Northside Generating Station Jackonville, FL

Visit us at Booth #S11127

10 STRUCTURE magazine

I-80 Verdi Bridge Verdi, NV

Products for structural strengthening

In 2018, the Owner of a four-story office building was exploring opportunities with a potential new tenant; however, the existing building elevator configuration and capacity did not suit the tenant’s needs. Adding another elevator inside the building was not possible as it would be too disruptive, so the Project Team explored adding an exterior elevator. The Richmond Group (TRG) was the Design-Builder for the project, and Simpson Gumpertz & Heger Inc. (SGH) was the Structural Engineer of Record. Three sides of the building abutted a street, a parking lot, and conservation land. The fourth side of the building abutted an existing, six-level parking garage. The project team decided to “notch” a portion of the existing parking garage and install a new building elevator in the garage to service the building. The elevator required a new vestibule at each floor, and new storage rooms were added at each floor above the first-floor machine room, which increased the rentable area on the second, third, and fourth floors. To complicate matters, the floors of the garage and the office building did not align on the upper levels. The elevator would service the building levels only and would only align with the garage on the ground floor. The existing parking garage consisted of a steel-framed superstructure with braced frames in the short direction and moment frames in the long direction.

Figure 2. Steel support framing installed prior to demolition. Figure 3. Supplemental horizontal steel bracing to the Shoring towers for the portion of the PC framing to be restore diaphragm connection to LLRS. demolished can be seen in the background.

PC DT beams spanned approximately 60 feet between steel girders to form the parking deck. The DTs were approximately 11 feet wide and 30 inches deep. The new elevator hoistway required an opening approximately 14 feet by 30 feet to provide new vestibule and storage room floors that aligned with the office levels. This cut required completely removing 30 feet of the DT closest to the building and notching the flange of the next adjacent DT up to the stem. Figure 1 (page 8) shows the plan layout of the new garage opening. The remaining portion of the DTs would still be used for garage parking. Structural drawings were not available, and the reinforcement and strand profile of the DTs was unknown. SGH used GPR to determine the location and quantity of the strands and their profiles. There were seven straight profile strands in the DT stem. GPR also showed three collector reinforcement bars along the long edge of the DT flange that connected to a braced frame and three-chord reinforcement bars along the short edge of the DT flange. Test pits showed that the existing garage was founded on shallow spread footings. The portion of DT to remain was supported on a new steel frame (Figure 2). The new steel columns were founded on new shallow foundations and laterally attached to the DT at each level for frame stability. The bottom of the new foundations was set at the same elevation as the existing garage and building foundations to avoid surcharging those foundations. The existing diaphragm connection of the DT to the braced frame would also be removed as part of the demolition; therefore, new horizontal steel bracing was added to connect the remaining diaphragm to the LLRS (Figure 3). The strand diameters were initially estimated based on the as-designed DT length and code-required live loads and were confirmed via a small opening at the end of the DT stem at the start of construction. The analysis showed that the flexural stresses in the DT to remain were within ACI limits in the loaded and unloaded conditions. The additional upward camber increase was estimated to be only 1⁄8 inch; therefore, differential camber was within tolerance. Shear strength at the cut location was a significant consideration. The DT did not contain any shear reinforcement at the cut location. The concrete strength and compression from the prestressing provided the required shear strength. It was determined that the shear strength

Figure 4. Top 3 levels of PC DT framing demolition immediately after removal at Level 4. Courtesy of The Richmond Group.

of the existing portion of DT that remained was at least twice the required shear demand. Therefore, additional shear reinforcement was not required. TRG installed the steel frame by cutting localized openings in the flanges for the columns to pass through and then installing the beams under the DT stems before removing the DTs. The full portion of the DT was removed in sections at night, and the garage remained operational during the day. The DT was shored using standard shoring frames, aluminum beams, and plywood to create a combined shoring platform and debris shield at each level, and was supported on grade. Demolition started at Level 6 (roof ) and proceeded downward. Five levels of DTs were cut and removed. Figure 4 shows the demolition progress at Level 4. The Contractor reported that they did not hear any popping sounds consistent with strand slip and no new distress was observed. Once demolition began, it took the TRG approximately three days to remove the portion of the DT at each level. The demolition work went smoothly and was considered a success by all parties.

Conclusion Projects requiring modifications to existing PC framing have a unique set of design and construction challenges that differ from those of traditional building materials. Consideration must be given to changes in flexural stresses, shear resistance, camber, and relative displacements. Demolition and construction means and methods require close coordination and communication between the design and construction teams to ensure that all parties understand the unique behavior of PC. In conclusion, existing PC members can be successfully modified in place by carefully reviewing and addressing all of the unique design and construction challenges associated with the work.■ Michael F. Hughes is a Senior Project Manager at Simpson Gumpertz & Heger’s office located in Waltham, MA. (mfhughes@sgh.com) Sal A. Capobianco is a Senior Principal at Simpson Gumpertz & Heger’s office located in Waltham, MA. (sacapobianco@sgh.com) JANUARY 2020

structural ANALYSIS Analysis of Anchoring Attachments Using Finite Element Modeling By Richard T. Morgan, P.E., and Arif Shahdin

nchoring-to-concrete provisions in the American

Concrete Institute’s Building Code Requirements for Structural Concrete (ACI 318) are used to calculate anchor design strengths that consider possible anchor failure modes. These design strengths are checked

Figure 1. Rigid fixture strain compatibility relationships.

against calculated factored loads acting on anchors. ACI 318 anchoring-to-concrete parameters for calculating anchor design strengths are derived from testing and analysis that includes the use of a rigid fixture to apply tension load to anchors. Therefore, ACI 318 provisions for anchor design can be considered relevant if the fixture being attached can be considered “rigid.” A rigid fixture is assumed to have a cross-section that remains plane under loading and does not undergo deformation from bending. However, for some anchoring-to-concrete applications, a rigid fixture assumption may not be valid, thereby precluding the use of ACI 318 anchoring-to-concrete provisions to design the anchorage. Finite Element Modeling (FEM) provides a means to assess whether a rigid or non-rigid fixture assumption is valid. This article explains how finite element modeling can be used to analyze a fixture and how the results of this analysis can be interpreted for the design of a concrete anchorage.

Why Finite Element Modeling? Structural and nonstructural components are attached to a concrete member using cast-in-place or post-installed anchors. Tension load, shear load, and moments acting on the component are transferred into the anchors through a plate or other fixture. Determining the tension load distribution on the anchors from the loads acting on the component is necessary to design the concrete anchorage. If the fixture being attached is assumed to be rigid, the tension load distribution on the anchors can be calculated using strain compatibility relationships (PL/AE) and basic statics (Σ forces and Σ moments). Figure 1 illustrates how strain compatibility relationships can be utilized in conjunction with a rigid fixture assumption to define the tension load distribution on a group of anchors. Assuming the fixture is rigid permits the stress/strain distribution to be defined as linear, which allows for the use of similar triangles to define the tension load distribution on the anchors and the compression stress in the concrete beneath the fixture. 12 STRUCTURE magazine

The linear stress/strain distribution assumed for a rigid fixture permits a simplified approach for calculating tension loads on anchors. It is important to keep in mind that ACI 318 anchoring-to-concrete provisions are predicated on a rigid fixture assumption. Tension loads acting on anchors must be checked against the calculated anchor design strengths for each relevant anchor failure mode. The magnitude of anchor tension loads calculated using a rigid fixture analysis will typically be less than the magnitude of anchor tension loads calculated using a non-rigid analysis. A rigid fixture analysis assumes the stress in the fixture resulting from the tension loads acting on it is less than the fixture yield stress. Prying action causes a non-rigid fixture to bend and possibly yield, resulting in the displacement of the fixture and tension load re-distribution among the anchors. The stress/strain distribution for a non-rigid fixture subjected to prying action will be non-linear, and the analysis to determine tension loads acting on the anchors becomes more complex. ACI 318 anchoring-to-concrete provisions include parameters to account for the resultant tension load acting on an anchorage being eccentric with respect to the centroid of the anchors in tension. The parameter Ψec,N is used to calculate nominal concrete breakout strength in tension, and the parameter Ψec,Na is used to calculate nominal bond strength. Ψec,N and Ψec,Na include a parameter for eccentricity (eŃ) that corresponds to the distance of the resultant tension load from the centroid of the anchors in tension. The equations to define Ψec,N and Ψec,Na, as well as the analysis to determine eŃ, are predicated on anchor attachment with a rigid fixture. Therefore, calculating eŃ using a fixture that exhibits non-rigid behavior could lead to unconservative calculation results for Ψec,N and Ψec,Na. When one is unsure if a rigid or non-rigid fixture assumption is valid, FEM can be used to ascertain the following:

You’ve got cracks. We’ve got you covered.

A complete line of structural epoxy repair products. From viscosity, to cure time, to pot life, to temperature, to class — the Simpson Strong-Tie® family of crack repair products has a solution for almost every job. And we’ve got the dispensing tools and injection systems that help make application fast, easy and clean. Our epoxies are tested to the latest standards, so you can be sure that repairs are strong, and that your structures are safer. To learn more about our versatile set of crack repair solutions, visit go.strongtie.com/crackrepair or call (800) 999-5099.

Strong-Tie Company Inc. WSV19

Component-Based Finite Element Modeling

Figure 2. Discretization using finite element modeling.

• The stress magnitude in the fixture • The strain magnitude in the fixture • Does the fixture undergo prying action? • Anchor tension loads for rigid versus non-rigid behavior Non-rigid fixture behavior cannot be analyzed using algebra, but it can be analyzed with software that performs FEM. “Discretization” is the critical FEM parameter. Consider a plate with a uniformly distributed load acting on it, as shown in Figure 2. The reactions at the fixed boundary can be determined using FEM. “Discretization” means “dividing into elements.” The uniform load in Figure 2 is transferred to the fixed boundary by square elements that are connected via “nodes.” Load transfer only occurs at nodes. Reactions at the fixed boundary are obtained in terms of stress and strain. The accuracy of the calculated reactions will increase the more the plate is discretized. A structure can be discretized using different types of elements. One-dimensional elements are typically used for load analysis (based on stiffness) in most structural analysis software. FEM for anchoring applications uses two-dimensional elements modeled as a plate/shell. Three-dimensional elements are used for complex applications such as machine design. FEM provides a realistic analysis of a material’s engineering and mechanical properties by considering stiffness. The ability of a material to transfer load can be accounted for via its stiffness. FEM utilizes a matrix algebra equation {F} = [k] {d}; where “k” corresponds to a stiffness matrix, and “d” corresponds to the displacement matrix that results from forces “F” created within the element. Displacements correspond to the degrees of freedom modeled at each node.

Figure 3. Component-based finite element modeling. Courtesy of IDEA StatiCa.

14 STRUCTURE magazine

Typically, structural analysis software that uses FEM models loadcarrying members such as beams and columns as a one-dimensional element. Load must be transferred from one member to another via a connection. Typically, connections must be designed separately, either in a spreadsheet or as a separate FEM application. Component-Based Finite Element Modeling (CBFEM) software permits calculation of all relevant component loads without separate analysis. CBFEM models steel components, such as a base plate or column, as a plate/shell element. This material behavior can be depicted by Von Mises yield criterion, which assumes the element behaves elastically before yielding. The green bi-linear stress/strain curve in Figure 3 illustrates this material behavior. Strain hardening (plastic strain), defined by the horizontal portion of the green curve, occurs after yielding. Consider a steel column anchorage modeled using CBFEM. The column and base plate are modeled as two-dimensional shell/plate elements. Anchors are modeled as a tension-only “spring,” as illustrated in Figure 4a. Under tensile or bending load, the base plate deforms due to the force distribution resulting from the stiffness of the shell/plate elements. This base plate deformation causes the “spring” to elongate by an amount (d). Anchor stiffness (k) is associated with the spring elongation. The product of anchor stiffness (k) and displacement (d) is used to calculate the tension force (F) transferred to the anchor per the matrix algebra equation {F} = [k] {d}. CBFEM uses a Winkler-Pasternak subsoil model to represent concrete deformation numerically. This permits the concrete interface to be defined as two-dimensional compression-only springs (Figure 4b). Concrete stiffness is determined using the concrete modulus of elasticity (Ec). Welds between the column profile and base plate are modeled as load deformation constraints, defined by special plate elements, that simulate load transfer through the weld (Figure 4c). The model defines the weld as a connection between two plate/shell elements: one element on the column profile and one element on the base plate. The element nodes are not directly connected. A midline surface of the connection between two plate/shell elements is modeled with an offset, which represents the weld geometry. If fillet welds are used, weld stresses are calculated in the throat.

Rigid Versus Non-Rigid Analysis CBFEM can be utilized to determine if a fixture exhibits rigid or nonrigid behavior; however, using CBFEM to obtain a design solution must also be considered. Steel design codes, such as those published by the American Institute of Steel Construction (AISC), only include provisions for rigid base plate analysis to determine anchor loads. However, AISC publications do not preclude non-rigid base plate analysis to determine anchor loads. Anchor design strengths calculated per ACI 318 anchoringto-concrete provisions are predicated on the attachment of a rigid fixture, which can be assumed to act as

Figure 4. Component based finite element modeling of a steel column anchorage. Courtesy of IDEA StatiCa.

illustrated in Figure 5a and Figure 5c. If the anchor loads are calculated assuming non-rigid fixture behavior, as illustrated in Figure 5b and Figure 5d, ACI 318 anchor design strengths checked against these loads could result in a misinterpretation of ACI 318 code provisions. Consider a column subjected to pure tension load. A non-rigid base plate will tend to deform, as shown in Figure 5b. This deformation induces “prying” forces in the plate, which create increased tension load on the anchors. Now consider the column with a moment acting on it. If the plate is rigid, it will rotate, but its cross-section does not deform (Figure 5c). A triangular stress distribution is assumed to occur beneath the plate, where it is in contact with the concrete. The moment arm (z) corresponds to the distance between the anchors that are in tension and the centroid of the triangular stress distribution. If the plate is non-rigid (Figure 5d), it will rotate and deform. The moment arm (zred) corresponds to the distance between the anchors that are in tension and the centroid of the compression stress distribution beneath the deformed part of the plate, where it is in contact with the concrete. zred (Figure 5d ) is less than z (Figure 5c) because the non-rigid plate deformation causes the compression stress distribution to shift from a location close to the edge of the plate to a location closer to the perimeter of the column profile. If forces and moments are summed to calculate tension load on the anchors, the smaller lever arm zred will result in higher tension forces on the anchors, illustrating how the magnitude of anchor tension loads calculated using a non-rigid fixture analysis will typically be greater than the loads calculated using a rigid analysis.

Parameters for CBFEM Plastic strain, as depicted by the horizontal portion of the green bi-linear stress/strain curve in Figure 3, is initiated at yielding. A limiting plastic strain can be expressed as a strain percentage beyond the strain at yielding. Steel design codes in the United States do not have provisions to limit the amount of plastic strain. The Eurocode recommends limiting the amount of plastic strain beyond yielding to

a value of 5%. Therefore, setting a limit on the “permissible” amount of plastic strain beyond yielding (for example 5%) can be a CBFEM fixture design parameter. Anchor parameters to be considered in CBFEM include the anchor type and the anchor stiffness when subjected to tension loading. Castin-place and post-installed anchors have specific material properties and performance characteristics. Cast-in-place anchors include headed bolts and headed studs. Post-installed anchors include mechanical anchors (for example expansion or undercut anchors) and adhesive (bonded) anchor systems. Cast-in-place anchor stiffness values can be calculated. Post-installed anchor stiffness values can be established through testing.

Making Sense of it All Tension load on anchors must be checked against calculated anchor design strengths. Since ACI 318 anchoring-to-concrete provisions assume the fixture being attached is rigid, the tension loads acting on the anchors must be relevant to rigid fixture behavior. If CBFEM indicates non-rigid fixture behavior, the anchor tension loads derived from this analysis should not automatically be considered relevant to designing the anchorage using ACI 318 anchoring-to-concrete provisions, but they could be considered relevant. Experienced engineers may elect to utilize non-rigid CBFEM tension load results for ACI 318 anchorage design based on their engineering judgment, but a more conservative alternative would be to re-design the fixture to conform to rigid behavior. Software capable of performing CBFEM can be utilized to ascertain if a fixture exhibits rigid or non-rigid behavior. Examples of “non-rigid” fixture behavior can be defined as CBFEM results that indicate high stresses and strains in the fixture and significant fixture displacement resulting from prying action. Following are suggestions for interpreting FEM results that indicate “non-rigid” fixture behavior. • “Force” the fixture to be “rigid” by modeling its steel modulus of elasticity (Es) as infinite (for example let Es equal

Figure 5. Rigid and non-rigid plate behavior. JANUARY 2020

100,000,000 psi). Compare the anchor tension loads calculated for non-rigid behavior versus the anchor tension loads calculated for the “forced” rigid behavior. If the difference between the loads calculated for each behavior can be considered insignificant, it would be reasonable to use the fixture geometry/properties and anchor tension loads determined from the non-rigid analysis to design the anchorage with ACI 318 anchoring-to-concrete provisions. • A plastic strain limit beyond the strain at yielding can be set for the fixture by using engineering judgment. U.S. steel codes do not address a plastic strain limit for steel design, but the Eurocode recommends a limit of 5% beyond the strain at yielding. CBFEM-calculated plastic strain values greater than a set limit could be considered unacceptable for designing the anchorage with ACI 318 anchoring-to-concrete provisions. Conversely, plastic strain values less than or equal to a set limit could be considered acceptable for designing the anchorage with ACI 318 anchoring-to-concrete provisions. CBFEM-calculated values for deformation of the fixture and anchor displacement can also be considered in conjunction with the plastic strain parameters for the fixture.

CBFEM. Similarly, anchorage of pipes, equipment, and storage tanks are all examples of applications for which the applied loads could cause the fixture anchoring the component to exhibit nonrigid behavior. This methodology for evaluating an anchorage with CBFEM software helps ensure that the component being anchored, the fixture, and the anchors act in harmony. Let the software do the hard work!

Conclusion Component-Based Finite Element Modeling is a means to assess whether a fixture exhibits rigid or non-rigid behavior. Assuming rigid fixture behavior when the behavior is actually non-rigid could lead to unconservative results if using ACI 318 anchoring-to-concrete provisions to design the fixture anchorage. This article explained how CBFEM can be used to analyze a fixture and how the results can be interpreted for anchor design.■ Richard T. Morgan is the Manager for Software and Literature in the Technical Marketing Department of Hilti North America. He is responsible for PROFIS Engineering and PROFIS Rebar. (richard.morgan@hilti.com)

When is CBFEM a Good Idea?

Arif Shahdin is a Steel Design Expert at HILTI in the Software Department

CBFEM can be utilized to ascertain if a fixture exhibits rigid or non-rigid behavior. For example, thin fixtures and/or fixtures with a widely-spaced anchor configuration could be analyzed using

Engineering and also manages PROFIS Installation and HILTI’s content in

where he is responsible for the Baseplate Design Module for PROFIS Smart3D and AVEVA E3D/PDMS. (arif.shahdin@hilti.com)

ADVERTISEMENT–For Advertiser Information, visit STRUCTUREmag.org

RECORDS “An NCEES Record makes it fast, easy, and convenient to apply for additional P.E. licenses in other states.” Alexander Zuendt, P.E. Zuendt Engineering Record holder since 2011

National Council of Examiners for Engineering and Surveying® P.O. Box 1686, Clemson, S.C. 29633 864.654.6824

16 STRUCTURE magazine

Build your NCEES Record today. ncees.org/records

structural REHABILITATION Adaptive Reuse of the Apex Hosiery Company Building Part 2: SMI Concrete Flat Plate and Site Safety Demolition Plan Peer Review By D. Matthew Stuart, P.E., S.E., P.Eng, F.ASCE, F.SEI, A.NAFE, SECB

his four-part series (Part 1, STRUCTURE, November 19) discusses how the collapse of a building during a demolition operation in Philadelphia in 2013, which resulted in several fatalities, led to the enactment of a City Ordinance to prevent similar future calamities. As a result of the Ordinance, the author became involved with the structural investigation, review of the Site Safety Demolition Plan, and Demolition Special Inspections associated with the adaptive reuse of the Apex Hosiery Company Building located in Philadelphia.

SMI System The SMI System (Smulski Method) of designing and constructing reinforced concrete flat plate slabs was developed prior to the 1920s by Edward Smulski, a consulting engineer from New York City. The system was unique in that the primary flexural reinforcement consisted of concentric rings of smooth reinforcing bars supplemented with diagonal and orthogonal trussed bars placed between the supporting columns, and radial hairpin bars located at the columns as shown in Figure 7. The rings consisted of smooth bars which were lapped at the ends to develop their full strength. The laps of the concentric rings were also staggered to avoid adjacent laps from occurring at the same radial location within each group of concentric reinforcing. The concentric rings of the SMI System were located in the top of the slab directly above the columns, in the bottom of the slab at the mid-span of what is now referred to as a column strip, and in the

Figure 8. The slab was separated into three independent sections as a part of the structural design.

Figure 7. The primary flexural reinforcement for the unique SMI system.

bottom of the slab at the mid-span of what is now referred to as a middle strip, centered in the bay formed by the column grids. There was no top reinforcing provided in the middle strip at the intersection with the column strips, as is now required by the building codes. The concentric rings of bottom reinforcement also overlapped at the interface zones while the top reinforcement above the column overlapped the bottom bars below. The theory behind the design of the SMI System was based on the same flexural theory of reinforced concrete used by other methods of analysis at the time, in that bending moments were resisted by internal stresses in the concrete, compressive on one side of the neutral axis of the section and tension resisted by reinforcing on the other. The primary difference with the SMI System is that the tensile stresses in the structure are offset by the concentric rings of reinforcing bars, which resisted the tendency of the concrete within the ring to deform and elongate due to the tensile bending forces. So, in other words, the rings were subjected to hoop stresses in which axial tensile forces were induced in the rebar via the perpendicular radial forces of the concrete tension. The slab was separated into three independent sections as a part of the design of the system, as shown in Figure 8. The column head was analyzed as if it were a circular cantilever fixed at the column and loaded uniformly around its circumference. The orthogonal and diagonal slab clear spans between the columns were analyzed for positive bending moments only. The hoop reinforcing for all of the sections was calculated as indicated in Table 1 (page 18). Comments by one of the authors of the 4th Edition of Plain and Reinforced Concrete, Volume 1, published in 1925, indicates that the SMI System required 20 to 24% less reinforcing than comparable two-way and four-way flat slab systems that were constructed during the same time period. Load tests of the SMI System were conducted at Purdue University prior to 1920 with the results published in the 1918 ACI Journal Proceedings. Stresses within the reinforcing rings were measured using an “extensometer” developed by Professor Claude Berry of the University of Pennsylvania. The 41-by 36.5-foot, 2x2 bay test frame, with cantilevers on three sides and an upturned spandrel beam on the fourth, was loaded using bricks stacked in such a way to prevent arching action of the masonry units. The center-to-center spacing of the columns was 16 feet. All columns included a capital. The slab thickness was 5½ inches. J A N U A R Y 2 02 0

The test frame was loaded from 150 psf Table 1. Calculated hoop reinforcing for all three slab sections. to 950 psf until failure occurred. The principals of circumferential and radial bending moment analysis were also being researched at the University of Wisconsin in the early 1900s. A discussion of the methods of analysis can be found in the Principals of Reinforced Concrete Construction, 3rd Edition, published in 1919. Also, before the development of the SMI system, another similar rein- concentrically positioned bars in overlapping top and bottom layers. In forced flat slab method of framing was patented in 1911 by Claude addition, based on the challenges associated with the renovation of the Turner. Mr. Turner, who referred to his method of design as the Apex building, the SMI system was more susceptible to the introduction “Mushroom” flat slab system, developed the method of construction of new mechanical and utility openings required in the framed floor in Minneapolis, Minnesota. slab than the southern, conventionally reinforced two-way flat slab. The available literature that deals directly with the SMI Systems indicates that Edward Smulski patented the method of construction. Peer Review of Site Safety However, a cursory search through the U.S. Patent Office indicates Demolition Plan (SSDP) that there were only two patents granted to Smulski, one for a castin-place counterfort system for retaining, reservoir, and dam walls and Structural analysis of the existing building was completed as a part one for a two-way, orthogonal reinforced slab system that included of the peer review of the SSDP and to determine the feasibility of encased steel beams. It is also not clear how prevalent the use of the the proposed adaptive reuse of the building. For the peer review, a SMI System was during both the early 1900s and later in the century. separate analysis of the structure, in addition to what had previously The author is only aware of one other SMI structure in Philadelphia, been completed as a part of the original SSDP, was required for three and the number of structures that were constructed or currently remain primary reasons: that were built using this system is unknown. 1) The engineer reviewing the SSDP had assumed that the entire In the author’s opinion, it is not likely that this system was used to existing building was constructed with only a conventionally a large degree or was very popular because of the assumed difficulty reinforced two-way slab and was not aware of the presence of the associated with properly fabricating and placing perfectly round and SMI system on the north side of the building. ADVERTISEMENT–For Advertiser Information, visit STRUCTUREmag.org

GEOPIER GROUND IMPROVEMENT CONTROLS STRUCTURE SETTLEMENT GIVE YOUR STRUCTURE STABILITY Work with Geopier’s geotechnical engineers to solve your ground improvement challenges. Submit your project specifications to receive a customized feasibility assessment and preliminary cost estimate at geopier.com/feasibilityrequest.

GEOPIER IS GROUND IMPROVEMENT® 18 STRUCTURE magazine

800-371-7470 • geopier.com info@geopier.com

Figure 9. Example of an incorrect method of flat slab FEM via pinned supports at the column that was used in the SSDP.

2) The analysis had only considered the weight of the mechanized demolition equipment and not the anticipated piles of debris. 3) The analysis/modeling of the two-way conventionally reinforced slab had not been performed correctly. The peer-review analysis involved determining if the existing two-way concrete slab could simultaneously support the proposed mechanized demolition equipment and piles of debris created during the demolition operation. Also, the results of the analysis were used to assess the proposed sequence of demolition to determine if the remaining portions of the structure would continue to be stable as adjacent bays of framing and columns were removed. The methods of analyzing the existing structure used by Pennoni for the proposed approach to demolishing the upper levels of the building

were also the same as what will be described for the feasibility study analysis included in Part 3 of this article. However, the method of analysis used by the original SSDP engineer involved a finite element model (FEM) of three bays of a typical framed level in both directions. Unfortunately, the model did not 1) Include the existing column capitals or drop panels 2) Use accurate bay dimensions 3) Assume the correct slab thickness In addition, the column support locations were modeled as a cluster of four closely spaced pinned connections associated with the location of the FEM mesh. Figure 9 illustrates an example of this incorrect method of modeling a flat slab via pinned supports at the column that was used in the SSDP, while Figure 10 shows the correct method that also engages the column supports in the story above and below the slab. As a result of modeling an individual column as a group of four pinned supports in the FEM, an exaggeration of the magnitude of negative moments that could be transferred to the columns occurs. This is because the pinned supports, at any one column location, result in a point of fixity that does not accurately represent the interaction between the slab and the flexible, story-high column stiffnesses above and below the slab. As a result, the SSDP model underestimated the positive moment at the column and middle strips by approximately 24%, as illustrated by a comparison of the outputs shown in Figures 11a and 11b. Also, Figure 10. Correct FEM method that engages column supports in the story above and below the slab. the SSDP engineer did not include an analysis of the punching shear effects around the column supports, as required by the ACI 318, Building Code Requirements for Structural Concrete and Commentary.

Conclusion The Site Safety Demolition Plan review associated with the adaptive reuse of the Apex Hosiery Company Building located in Philadelphia involved an analysis of the unique SMI system of reinforced concrete flat plate slabs and a review of the SSDP FEA of other areas of the building. Part 3 of the series will provide an overview of the feasibility analysis for the slab retrofit.â&#x2013; Figure 11a. The SSDP FEM underestimated positive moments at column and middle strips by approximately 24%.

Figure 11b. The properly modeled FEM results in correct positive moments at the column and middle strips.

Matthew Stuart is the Senior Structural Engineer at Pennoni Associates Inc. in Philadelphia, PA. (mstuart@ennoni.com) J A N U A R Y 2 02 0

CRACK FIX KIT by HOHMANN

& BARNARD

Specifically formulated as a two-component, lowviscosity, fast-curing epoxy sealing system for repairs to cracks in concrete and solid masonry. The injection resin conforms to ASTM C-881: Grade 1, Class C, Types I, II. + Fast curing + As strong as concrete + Cartridges fit standard applicators

www.h-b.com/crackfixkit

INFOCUS The Case for Data-Supported Project Interviews By John A. Dal Pino, S.E.

enjoy reading The Journal of Light The July 2018 issue of STRUCTURE This would include providing alternative Construction (JLC) to learn about expert included an InSights piece titled Marketing structural systems (for gravity, wind, or seistechniques used on residential projects. In Services in an Amazon World by Michael mic) so that clients can see what they get their June 2019 issue, I read two articles; Bernard. Bernard argued that when faced for the price of each system. Where our Defining Efficiency Goals – A process for selling with the low-bid, pick-from-three-choices industry falls short, compared to, say, energy performance in new homes by Indigo Ruth- dilemma, the best approach is to market using usage (see Ruth-Davis), is that we have difDavis and As Best I Can by Mark Luzio. The the tried and true relationship model and ficulty accurately predicting the benefit our Ruth-Davis article addressed how to sell to develop a strong personal bond that will work provides to the client, as measured by high performing environmental designs for increase loyalty and trust, and make your firm damage avoided relative to the cost. Trying homes in Vermont by providing alternative the go-to choice. I agree. to predict the actual damage and downtime designs with estimated construction to a building exposed to a major costs and annual energy costs. The event due to wind, I urge engineers to make a face-to-face design-basis Luzio article focused on providing earthquake, or flood is difficult, quality construction and working interview a required part of their proposal if not impossible. The recent picwith clients. Luzio describes always tures from the July 2019 Ridgecrest so their clients get the best information California earthquakes (backdoing the best he could, noting that he and his best clients know that to-back 6.4 and 7.1 magnitude they can before making a decision. everything is not perfect (“a fool’s events) show minimal structural errand” to quote), but that his work damage and plenty of structures was not a low bid job either. But, in addition, I urge engineers to make a standing or undamaged that most engineers These two articles made me think about how face-to-face interview a required part of their would have predicted to be otherwise using to more successfully sell structural engineering proposal so their clients get the best informa- our current tools. Faced with this reality, it is services in a marketplace that frustratingly is tion they can before making a decision. My hard to sell quality, well-conceived structural continuing the trend toward commoditization, suggestion is not intended to inflate fees or fix systems, and high-performance alternatives, lack of personal contact, and selection decisions the market, but to make sure clients hire the summarized succinctly by Luzio as doing As based on initial fee (the Amazon effect). best engineer for their project. If your client Best I Can. The lowest price seems to be the It must be written in stone somewhere that only builds one dream project in their life, right choice. Ouch! sophisticated and unsophisticated clients they need to get it right, or as right as they can. As you can see, I am more than a little frusalike, be they architects, developers, or homeTo be honest, project interviews have never trated by the current marketplace for structural owners, must solicit three proposals before been my favorite part of marketing. It takes engineering services. It is impossible for any selecting their structural engineer. Proposal a lot of time to put together a team, prepare one person to turn the clock back, but I think text, scope, and qualifications seem unimport- the presentation, rehearse, re-configure the our clients would benefit greatly if we, as proant; just scroll down to the price and hourly presentation, re-rehearse, and then perform fessionals, advocated for qualification-based rates and pick, since any building that meets well. But interviews are really the only good selections that include face-to-face interviews the code must be the same as any other build- opportunity to develop a bond with the client where hard information can be exchanged, ing that does too, right? My experience has and show how valuable you can be. Face expectations and goals discussed, and a level demonstrated that price is almost always the to face, you can engage in the many subtle of confidence developed. We can show how basis of selection, even though clients have aspects of your design approach and discuss good we are too! Continuing to participate in reassured me that it is not. Even long-term, the value of regularity, uniformity, configura- the Amazon selection process will not turn out repeat clients make selections this way. So tion, detailing, state-of-the-art practices, etc. well for anyone. Classical theory on perfectly much for loyalty and trust. Clients have also I almost always feel complete after the competitive markets, in which work products reassured me that they always get proposals interview. If my team is selected, I know we are not easily differentiated, tells us that. The from three “essentially equal” engineers, so were the best; if we are not selected, at least low price always wins, and lots of the costlier, there is no need for the decision-maker to I learned what to do better the next time, full service firms go bankrupt and engineers speak with the structural engineering candi- other than lower my fee. In contrast, I feel lose their jobs. This might not be obvious to dates on the telephone, or have a face-to-face empty writing proposals and waiting weeks or everyone today because the demand interview to discuss design approach, per- months for the decision to be handed down. for engineering services is high, but formance goals, schedule, cost, quality, and But to develop a winning interview markets are cyclical.■ communications (see Luzio). Given the mon- approach, engineers need to develop data John A. Dal Pino is a Principal with FTF etary risk associated with making a decision and metrics (see Ruth-Davis). With a little Engineering located in San Francisco, California. based on little data, when not chosen, my last effort, engineers should be able to develop He serves as the Chair of the STRUCTURE thought is always, “I hope they get lucky and cost and material quantities to demonstrate Editorial Board. (jdalpino@ftfengineering.com) it all works out for them.” that they can provide economical designs. STRUCTURE magazine

‘‘

JANUARY 2020

Napa County HISTORIC

Courthouse PART 2

By Brett Shields, P.E., Luke Wilson, S.E., and Kevin Zucco, S.E. Figure 1. Entry showing damage taken the morning of the earthquake.

n August 24, 2014, the South Napa Earthquake left the Napa County Historic Courthouse heavily damaged with partially collapsed walls, ceilings, and extensive wall cracking (Figure 1). The City of Napa red-tagged the courthouse as un-occupiable, which began the extensive damage documentation effort outlined in the December 2019 edition of STRUCTURE. After documenting and assessing damage, the design team refocused efforts towards a solution to repair and preserve as much of the historic building as practical while providing improved detailing.

Construction Documents The 140-year-old building is constructed with unreinforced brick, an â&#x20AC;&#x153;archaicâ&#x20AC;? structural system. After considering the California Building Code (CBC) or American Society of Civil Engineers Standard for Seismic Evaluation and Retrofit of Existing Buildings (ASCE 41), ZFA Structural Engineers decided the California Historic Building Code (CHBC) was the appropriate design code for the project because it would allow reuse of the historic brick walls.

Traditional Repair Methodology Traditional repair methods, such as repointing mortar beds and grout injecting cracks, were used where observed damage was less extensive and cracking was limited to discrete locations. This was primarily concentrated on the first floor and the west end of the second floor that experienced smaller deformations. Grout injecting was determined to be preferable for the repair of distinct larger cracks, but an alternative repair solution was needed in areas of numerous cracks prevalent throughout the second floor.

Fabric Reinforced Cementitious Matrix Overlay Early in the repair design, the design team considered using traditional Fiber Reinforced Polymer (FRP) overlay on brick walls demonstrating extensive cracking. Due to surface preparation requirements and material incompatibilities of FRP (epoxy resin vs clay and mortar), the team turned to a new overlay product uniquely suited for brick masonry construction called Fabric Reinforced Cementitious Matrix (FRCM) used extensively in Europe. FRCM was used to repair brick

Repair Approach An overarching goal of the repair was to save the historic brick structure in its original state utilizing the original construction, where possible, and providing modern construction techniques with ductile detailing where rebuilding or strengthening the damaged condition was required. Because of the historical materials and construction techniques, 140 years of use and modification, and the wide range of damage throughout, a single repair option was not appropriate. Repair details were approached with continuity, resilient detailing, and construction tolerances in mind. During documentation, the high level of historic brick masonry craftsmanship became apparent, particularly at the exterior of the building (Figure 2). Therefore, repair work was kept on the inside face of the building to preserve hand-shaped decorative brick features and trim adorning the exterior of the structure. In areas of new wall construction, these features were recreated with modern appendages and plaster to preserve the historic appearance. Additionally, the historic interior wood trim and wall wainscot were salvaged and reinstalled throughout the building. 22 STRUCTURE magazine

Figure 2. Historic exterior wall brick construction and dental cornice.

Figure 3. Analysis model showing original brick, CMU, and CMU with control joints.

masonry walls with significant cracking but minimal permanent deformations, and to provide continuity through floors, walls, and around corners. As a new product being brought to the United States by manufacturers, including Simpson Strong-Tie, FRCM presented several challenges and opportunities from design through construction. These will be discussed in a future Part 3 article in STRUCTURE.

Figure 4. CMU reconstruction of damaged 2nd-floor walls.

Reinforced CMU construction was used in place of brick to reconstruct areas where significant damage and permanent seismic deformations required walls to be rebuilt. These areas were primarily concentrated at the east end of the second floor. Special design consideration was taken to avoid concentrating lateral and overturning loads from relatively stiff new CMU above to the remaining historic brick below. Analytical models were created using tested in-situ historic brick material properties to determine approximate stiffnesses of existing wall piers to be replaced. The same piers were then modeled with multiple CMU construction options, including partially grouted CMU, adjusted specified compression strength of masonry (fÂ´m) using different grout, different block and mortar properties, and alternate block layouts to compare stiffnesses and strengths. These adjustments did not provide the desired reduction in stiffness; therefore, strategically located control joints were added to further reduce the stiffness of the areas rebuilt with CMU (Figure 3). The

final design included a stacked bond, in lieu of a traditional running bond and control joints located above and below windows, at reentrant corners, and regular vertical spacings in long rebuilt walls. The final layup more closely matched the stiffness of the original brick walls such that new walls work in unison with existing walls, and lateral loads are not concentrated in any one area. Additionally, many of the exterior reentrant corners, whose stiffness concentrated seismic load and deformations, were reconstructed out of CMU with control joints in the corners to decouple perpendicular walls. Combining the CMU rebuild with existing historic brick construction presented dimensional obstacles that were addressed in detailing. The brick arches at the 1st and 2nd-floor windows of rebuilt walls were recreated with precast concrete elements to adjoin rectangular CMU with curved historic windows. CMU was aligned at the exterior face of brick to minimize furring and plasterwork on the visible historic exterior and aid in providing a flush plaster joint with the existing plaster finish. At interior walls, CMU was detailed to be centered on the brick below to limit the dimensional offset from the brick below each side for installation of FRCM continuity laps. Transitions of CMU to unreinforced brick were dowelled with alternating embedment lengths to tie the walls together and avoid creating a defined weak plane in the brick similar to those observed at the 2003 concrete shear wall interface. The unique condition of anchoring new CMU walls to existing inplace ceiling framing allowed for cast-in-place anchorage to be located

Figure 5. Detail of CMU interface with historic brick arch.

Figure 6. CMU and precast lintel construction above the original brick wall.

CMU Design

JANUARY 2020

accurately, avoiding the traditional difficulties associated with locating cast-in-place anchorage. Connections employed slotted holes, post-installed anchorage, acceptable dimensional ranges, shims, and acceptable offsets to allow for as much existing variability as possible, maximizing construction tolerances.

Construction

rebuilding a new â&#x20AC;&#x153;straightâ&#x20AC;? wall between two existing points (Figure 4, page 23) while still supporting the floor and ceiling. This condition was resolved through shimming of ledgers at small gaps and providing bearing angles at larger offsets. While CMU has some adjustability to accommodate small existing dimensional offsets, the number of intricate interface conditions to existing construction was a challenge. CMU had to interface with historic brick arches (Figure 5, page 23), existing floors and ceilings, adjacent precast concrete lintels (Figure 6 , page 23), uneven base levels, wall anchorage, and existing penetrations while adjusting to match existing walls. The result was a number of details, both planned and unforeseen, requiring a level of mason care and ability beyond that of typical construction.

As is typical for working within an existing building, multiple unforeseen conditions were discovered during construction. This included uncovering additional damage to brick walls, unknown wall voids or changes in wall thickness, minor areas of dry rot, and incomplete or changed configuration of work shown in the 1977 retrofit Figure 7. Example of damage documentation drawings. documents. Damage documentation was largely completed by observing cracking in the finished plaster to assess Conclusions overall damage before requiring expensive removal and reapplication of plaster. Localized areas were selected for removal to verify From the beginning of the damage documentation phase in early that plaster cracking correlated to a crack in the brick substrate. 2016 to completion of construction, the overarching goal was to Removing plaster during construction often revealed that numerous preserve the historic fabric of the building while providing improved small patterned cracks observed in the plaster typically resulted from resiliency, with modern structural design and detailing techniques fewer large cracks in the brick ultimately requiring grout injection. woven into the project. Even in areas receiving FRCM overlay, larger, open cracks were grout Due to the archaic materials, the age of the building, and the architecinjected to provide a cohesive substrate for the FRCM. The process tural layout of rooms, the extent of damage from a brief walkthrough of injection uncovered a handful of unforeseen wall voids and chases could be easily underestimated. Extensive documentation utilizing that required grout filling before crack injection. new technologies and proven methods to create a 3-D BIM model, In addition to material similarities, CMU was used in the project for clearly and effectively documenting the as-built/damaged building, its adjustability to accommodate small dimensional variations in the allowed all stakeholders to witness the entire building as affected existing structure. Modern construction procedures and metrics focus on by the earthquake (Figure 7 ). While time-consuming, this detailed installing materials straight, true, and plumb rather than matching exist- process was critical to the success of the project in supporting a steping conditions. The roof and second floor experienced small permanent by-step agreement process in the scope of work and extent of repairs displacements, which were compounded with plan dimension variations with all stakeholders. along the length and height of each wall. This created a challenge in A combination of repair strategies was used, including repointing, grout injection, localized rebuild of brick, FRCM overlay, and reconstruction of walls with CMU. Reconstructed CMU walls provided at areas of permanent deformations were designed and detailed to perform similarly to the original construction, allowing the first floor walls to remain with minimal alterations. Additionally, the CMU thicknesses closely matched the original building configuration, maintaining the architectural layout and maximizing reuse of historic trim and wainscot. While there were challenges and unforeseen conditions along the way, the building has successfully reopened and provides the County with services in a uniquely rich environment (Figure 8). The design, construction, and lessons learned of the Fabric Reinforced Cementitious Matrix overlay system will be covered in a future STRUCTURE article.â&#x2013; All authors are with ZFA Structural Engineers in Santa Rosa, California. Brett Shields is an Engineer. (bretts@zfa.com) Luke Wilson is an Associate Principal. (lukew@zfa.com) Figure 8. Grand opening on January 22, 2019.

24 STRUCTURE magazine

Kevin Zucco is an Executive Principal. (kevinz@zfa.com)

Easy design. Total control.

Yield-Link® Software

Streamline structural steel connections with Yield-Link® technology tools from Simpson Strong-Tie. Our Yield-Link software plugins and design support services provide the functionality and technical expertise to help you quickly develop, model and document complete designs matched to your project’s unique specifications — all while keeping you on time and within budget. Download the right tools for your structural steel project by visiting go.strongtie.com/ylplugineng or call us at (800) 999-5099 to learn more.

Available plugins: SAP2000® and ETABS®, Autodesk® Revit and our Microsoft® Excel Connection Design spreadsheet.

Vancouver House By Geoff Poh, P.Eng

icture yourself standing at the base of a 515-foot-tall high-rise tower looking up to the sky with the side of the building being only as wide as you are tall. Looking up, you see the tower gradually grow out to one side above you, consecutively with each floor, seemingly without any columns supporting the tower as the floor plate expands in width by 16 times and doubles in area. This was the challenge faced by the design team on the Vancouver House project in Vancouver, British Columbia, Canada. Now toppedoff and nearing occupancy, the playful curve of the tower is causing a stir and turning the heads to all those who walk near it.

Spatial Limitations without Compromise Vancouver House is a unique building that required unique solutions from all disciplines. The design philosophy originates from the airspace clearance requirements surrounding the Granville Street Bridge. Needing to maintain at least a 98-foot (30-meter) safety offset from the bridge, the design architects at Bjarke Ingels Group sculpted the outline of the tower around these constraints without compromising the usage of the space, taking the shape of what Bjarke Ingels describes as a curtain being drawn aside.

Geometric Induced Structural Demands The top of the building is rectangular, standing at nearly 100 feet wide (30.5 meters) and 13,200 square feet (1,226 square meters) in area. As you descend the building, the floors narrow and transform at the north end of the tower to a triangular shape nearly half the size of the roof at only 6 feet (1.8 meters) in width at the north end and 7,800 square feet (725 square meters) in area at the north end. Post-tensioned reinforced concrete flat slabs stack the tower at each of the 60 floors above ground. Supporting concrete columns to each of the floor slabs walk along the curved silhouette of the building following the northeast edge. The Vancouver House model views. Core only offset nature of the col(top left); Full structure (top right); Full structure exploded section view (bottom). umns shifting each floor 26 STRUCTURE magazine

Topped-out Vancouver House tower north view (left) and south view (right).

pulls the tower floor slabs towards the bridge (eastward), collecting the vertical gravity load of the concrete structural system and the superimposed loading. As the vertical columns gradually walk down the height of the building, they merge together. As the north tip of the building tapers to the width of a single column at the base of the tower, they push against the floor slab in the opposing direction (westward). Overlaying the rectangular floor onto the triangular shape below, the elevator-and-stair core â&#x20AC;&#x201C; the consistent vertical layout of the building â&#x20AC;&#x201C; is located off-center, pushed southwest from the center of the rectangular building above. With both principles of the walking columns and the offset core, the tower is subject to sustained lateral and torsional forces under its own gravity loading, resulting in a permanent elastic lateral displacement up the height of the tower.

Gravity-Induced Lateral Design in a High Seismicity Region Adding to the complexity of the structural design, the high-seismicity of the west coast of North America compounded the challenge for

the structural engineers at Glotman Simpson Consulting Engineers. The summation of both gravity and seismic forces onto the system necessitated a rigid vertical spine that is both flexurally and torsionally robust to stabilize the building. Vancouver House employs a reinforced concrete core utilizing innovative systems that have never been used in the local residential high-rise construction industry. At the entrance to the elevator lobby, heavy wideflange beams embed 5 feet into the concrete walls at both ends directly above as you enter and exit the core, connecting the two ‘C’ shapes of the core and closing it into a torsionally-strong box section. Rather than traditional yielding link beams, these heavy steel sections remain elastic under gravity and cyclic seismic loading. Wing walls outrigger from northwest and southwest corners of the offset core, staggering their openings between the two walls on every floor. At the extreme ends of the wing walls and the furthest location from the core stand 11 posttensioned high-strength DYWIDAG threaded rods counteracting the primarily unidirectional loading of the tower, pulling the building back to near verticality.

Limiting Cracks and Ensuring Performance

challenges, the coordination of the building façade and all other services around a moving structure in construction was a tall order for the executive architects at DIALOG. Mechanical and electrical services supporting the daily use of the building were required to do similar gymnastics up its height. Centralized in one single location just north of the concrete core at the base of the tower, the services branching out to the outer extremities of the building were like the branches of a tree. The cumulative stresses onto the post-tensioned reinforced concrete slabs meant significant limitations on the allowable concrete embedded services. The mechanical HVAC and electrical services were removed from within the depth of the flat slabs – moving to coordinated ceiling drops – leaving only a handful of special lighting features and mechanical lines at each floor to be meticulously coordinated into the structure. An industry built around static structures under gravity required a new approach to coordination leading up to the construction of the building. All secondary components completing the architectural aesthetic of the tower were designed with additional movement tolerance and adjustability to move with the building’s lean and twist for years to come.

Construction Monitoring

Concrete cracks are a result of the inherent nature Proving Performance of the material as it cures and is stressed. While shrinkage and flexural cracks quite commonly If constructed using traditional methods, at the occur on reinforced concrete buildings, it is much point of structure top-off, the elastic movement at more important to fully understand the perforthe upper height of the tower would have displaced mance and sensitivity of a tower with this level nearly 10 inches towards the east relative to the base. of complexity and scrutiny. Glotman Simpson’s To bring the tower design back to near verticality expertise in non-linear performance-based design and account for long-term creep, Vancouver House in high-rise concrete structures along the west coast was deliberately constructed vertically out of plumb of North America was invaluable in assessing the (tower cambering) at each floor following directly requirements for the Vancouver House structure. opposite to the final displaced shape of the tower. Models of the structure with post-yield strucThe upper floors of the tower were cambered to tural element properties were created using offset the slopes formed by building rotation and PERFORM3D and run against selected ground column shortening. motions tailored to the project site (1.0x Maximum The engineers at Glotman Simpson worked diliCredible Earthquake – or MCE). Strain compatgently with the construction team from ICON Floor plans and lateral loading. ibility and stresses of critical elements were checked West Construction, both in the planning leading under this level and then increased to 2.0x MCE. up to construction and for the duration of conIt is essential to understand the cumulative crack widths at the core struction activities, to monitor the verticality of the tower through walls and post-tensioned concrete flat slab diaphragms, the sum of each floor construction sequence. Movement surveys of the tower at which will propagate the lateral displacement of the tower. The design every second floor were performed for the duration of construction of the system followed the analysis to limit the cracks at these critical up to one year after topping off the building. Survey data collected elements. Ultimately, the residual set of the structure was analyzed followed closely with the calculated movement of the tower during to confirm near elastic performance under 1.0x MCE and vertical and after construction; there was no better way to confirm the stability and safety under 2.0x MCE. Both service level gravity and calculated performance of the building well into the long lifespan seismic load cases were also evaluated. of this world-class tower.

Success in Design Coordination and Planning

An Icon for the West Coast of North America

“Every unit is custom-designed.” This aspect of the project was genuine and not just a marketing tactic. Easily as complex as the structural

Creativity, innovation, and meticulous design and coordination led to the success of this project. Performance-based-design with the use JANUARY 2020

Wide-flange coupling beams in construction.

Vertical post-tensioned high-strength DYWIDAG threaded rods in construction.

of the latest technology in non-linear analysis developed the possibility for a tower like this to exist. Collaborative work to develop construction staging and sequence analysis turned the tower from paper to reality. The level of scrutiny placed on this project made it essential for efforts above and beyond any other project to develop a practical, constructible design. Vancouver House topped off in July 2018 and will always be a catalyst for creative architects and engineers.â&#x2013; Geoff Poh is a Project Engineer at Glotman Simpson Consulting Engineers in Vancouver, British Columbia, Canada. He is the Project Manager and one of the structural design engineers for the Vancouver House project.

Vancouver House in construction.

Project Team Developer: Westbank Corp. Design Architect: BIG (Bjarke Ingels Group) Executive Architect: DIALOG Structural Engineering Consultant: Glotman Simpson Consulting Engineers Landscape Architect: PFS Studio Mechanical Engineering Consultant: Integral Group Electrical Engineering Consultant: Nemetz (S/A) & Associates Ltd. Building Envelope Consultant: Morrison Hershfield General Contractor: ICON West Construction

ADVERTISEMENTâ&#x20AC;&#x201C;For Advertiser Information, visit STRUCTUREmag.org

Aegis developed Ultra-Span trusses with a proprietary shape that brings your building the strongest Cold-Formed Steel on the market. ÂŽ

â&#x20AC;˘ 100% non-combustible Prime Steel â&#x20AC;˘ Does not warp, shrink, split or twist with age â&#x20AC;˘ Resistant to insects, mold and rot â&#x20AC;˘ Wide variety of sizes and configurations â&#x20AC;˘ Industry leading estimating and design software

www .aeg

isme

ROOF 28 STRUCTURE magazine

â&#x20AC;˘

WALL

â&#x20AC;˘

FLOOR

talfra

ming

.com

WHY JOIN ACI? American Concrete Institute is a leading authority for the development, distribution, and adoption of consensus-based standards, technical resources, educational programs, and proven expertise for those committed to pursuing the best use of concrete. We are always advancing!

NETWORKING Networking with our powerful community of over 30,000 concrete professionals

INFLUENCE

EXPERTISE BE

NEFIT

Shape concrete knowledge through ACI committee participation

MBER E M Receive free access to ACIâ&#x20AC;&#x2122;s 200+ guides and reports

Gain a competitive edge with access to our continuing education resources including ACIU

LEARNING

248.848.3800 | www.concrete.org/membership

JOIN ACI

structural REPAIR Novel Solution for Strengthening Handrail Anchorage By Ali Abu-Yosef, Ph.D., P.E., S.E., Joseph Klein, P.E., Michael Ahern, P.E., and Randall Poston, Ph.D., P.E., S.E., NAE

esign and detailing of handrail anchorages in concrete structures must consider both structural performance

and susceptibility to corrosion. Without these dual considerations, handrail anchorages are more likely to fail. For decades, premature corrosion of handrail anchorage components was prevalent in the concrete industry. Deterioration of the anchor embedments due to galvanic corrosion, direct exposure of aluminum to concrete, or insufficient concrete cover resulted in costly repairs. While improvements in structural detailing and material selection to mitigate corrosion have been successfully implemented and are now common practice, the structural design and installation of handrail anchorages remains a minefield. A primary cause of continued handrail anchorage issues is the lack of clear delineation of design responsibilities and detailed coordination between the architect, handrail system manufacturers, the engineer of record, and the contractor. As a result, inappropriate assumptions and poor communication remain a source of deficient handrail installations. Repair of structurally deficient rail-post anchors is both challenging and costly. Rail-post anchorage repairs often must maneuver tight geometries, a concrete substrate congested with steel reinforcement, numerous forms of potential corrosion cells, and elevated access limitations. This article presents a novel repair solution that was used to address structurally deficient handrail anchorages in a high-rise building. The repair approach presented herein uses inert materials that are not susceptible to corrosion due to environmental exposure.

Figure 1. Free body diagram for the anchor reaction forces produced by handrail loading. Adapted from Raths 1974.

analytical methods can be used to provide rational estimates of the reaction forces that develop within the anchorage assembly due to externally applied shear and moment forces. The free-body diagram shown in Figure 1 is based on the findings reported by Raths (1974) for steel embedments in concrete at the ultimate state. The externally applied handrail forces are resisted by a shear couple (CF and CB) that develops within the embedded depth of the anchorage assembly. The free-body diagram can be used to calculate the breakout shear demand (CF). It should be noted that Figure 1 does not include wind loading for simplicity, but the demands due to wind loading can be included similarly. In addition, a load reversal is possible but results in smaller concrete breakout stresses due to the relative magnitudes of CF and CB per the equation, (CF = VU + CB).

Handrail Anchorage Assemblies â&#x20AC;&#x201C; The Basics The International Building Code (IBC) specifies the minimum applied live loads on balcony railings. The effects of live and wind loads need to be considered when designing handrail components. The selected anchorage system should resist the effects produced by a 200-pound concentrated live load or a 50 lb/ft linear live load applied directly at the handrail, as well as location- and elevation-specific wind loading. The applied loads are transmitted from the railing posts into the anchorage assembly and the concrete slab. The post anchorage should be designed to resist the effects of the externally applied shear force and moment couple, without causing breakout failure of the concrete slab. Calculating the force that is developed within the anchor is not straightforward. This is particularly true for anchorages embedded into the concrete slab. Several published 30 STRUCTURE magazine

Figure 2. Concrete removal along a slab edge exposed grout pockets with missing hairpin anchor reinforcement.

Handrail anchorage assemblies in concrete elements are designed following the requirements of Chapter 17 of ACI 318-19, Building Code Requirements for Structural Concrete. According to ACI requirements, the breakout shear force can be resisted by either the shear breakout resistance of the concrete material at the slab edge or anchor reinforcement. Unlike one-way beam shear strength requirements, the contribution of the concrete resistance and the anchor reinforcement cannot be added when calculating the breakout shear strength. The concrete shear breakout strength is proportional to the distance separating the anchorage embedment and the slab edge and is calculated using the formulas in Section 17.5.2 of ACI 318-19. In typical balcony installations, the edge distance is minimized to increase usable balcony space. As a result, the concrete breakout strength is marginal and often insufficient to resist the applied design forces. Hence, anchor reinforcement, commonly steel hairpins (U-shaped reinforcement with legs extending back into the slab), are used to reinforce typical anchorage assemblies in concrete balconies. Article 17.5.2.9 of ACI 318-19 permits the use of properly developed hairpin anchor reinforcement to resist the applied breakout forces. Because the concrete breakout strength is marginal, failure to provide anchor reinforcement around handrail posts due to improper design or installation can lead to anchor failures. The following discussion examines a case study of deficient handrail anchorages and the repairs performed to ensure adequate structural performance.

A Hidden Deficiency Figure 3. Details for typical NSM GFRP hairpin repair.

with building code requirements. Due to the limited edge distance between the grout pocket and the slab edge, the post anchorages were susceptible to breakout if design-level, or even service-level, loads were applied. Hence, structural repairs to strengthen the deficient anchorages were necessary.

A Novel Repair Approach Given that the existing and repaired slab edges did not have sufficient breakout strength to resist the design loads, it was evident that mechanical strengthening using post-installed reinforcement was needed. However, the use of drilled-in, post-installed steel anchor reinforcement was not a feasible option. To adequately develop a post-installed anchor reinforcing bar beyond the breakout failure plane, minimum 12-inch-deep holes had to be drilled into the slab

Demos at www.struware.com Wind, Seismic, Snow, etc. Struwareâ&#x20AC;&#x2122;s Code Search program calculates these and other loadings for all codes based on the IBC or ASCE7 in just minutes (see online video). Also calculates wind loads on rooftop equipment, signs, walls, chimneys, trussed towers, tanks and more. ($250.00). CMU or Tilt-up Concrete Walls Analyze solid walls for out of plane loading and panel legs next to or between openings by automatically calculating loads to the wall leg from vertical and horizontal loads at the opening. ($75.00 ea) Floor Vibration Program to analyze floors with steel beams and/or steel joist. Compare up to 4 systems side by side ($75.00). Concrete beam/slab Program to provide bending, shear and/or torsional reinforcing. Quick and easy to use ($45.00).

ADVERTISEMENTâ&#x20AC;&#x201C;For Advertiser Information, visit www.STRUCTUREmag.org

Rail-post anchorage deficiencies were discovered during slab-edge repairs on an 8-year-old high-rise condominium. The slab edge repairs were performed to address the widespread corrosion of steel reinforcement. The premature corrosion was the result of improper placement of reinforcing bars along the post-tensioned (PT) slab edges in the 54-story building and mostly unrelated to the rail-posts anchorages. The repairs included removal and replacement of more than 1.5 linear miles of slab edges directly exposed to weather. To mitigate future corrosion problems, the repairs utilized glass-fiber-reinforced polymer (GFRP) bars to reinforce and anchor the newly cast slab edges. The balcony railing system at the building consists of an aluminum frame with glass panels. The railing posts are embedded into 4-inchdeep grout pockets that were blocked out during placement of the 5.5-inch-thick PT slabs. The blockouts were later filled by no-shrink, high-strength mortar after the railing posts were secured in place. The original design called for No. 5 steel hairpin reinforcement to be placed around the grout pockets with a top concrete cover of 1 inch. The diameter of the grout pockets is approximately 4 inches, with the centerline of the pockets located 3 to 6 inches from the slab edge. As a result, the distance between the outer edge of the grout pocket and the slab edge ranged between 1 and 4 inches. The rail post-block-out position and depth contributed to congestion and low reinforcement cover in the vicinity. During the early stages of repair construction, the contractor exposed railing post anchorages that did not have the No. 5 hairpin anchor reinforcement as specified in the original design (Figure 2). The issue of missing anchor reinforcement was only observed at the bottom four stories of the residential tower. A review of the original construction documents suggested that the culprit for the missing anchor reinforcement was likely miscommunication between the structural engineer, the railing system manufacturer, and the contractor. As constructed, the railing anchorages with missing anchor reinforcement were structurally deficient and did not comply

JANUARY 2020

substrate. Due to steel congestion near the slab edge and the presence of PT tendons and anchor components, the risk of accidentally damaging existing reinforcement and PT tendons during drilling was substantial. The steel congestion near the slab edge mitigated the use of non-destructive testing methods to reliably locate embedded PT components before drilling. The repair team also considered using externally applied carbonfiber-reinforced polymer (CFRP) sheets to strengthen the slab edges around the post anchorages. However, due to the slab edge geometry and the presence of a drip edge along the slab soffit, the CFRP sheets could not be adequately developed. Furthermore, the repaired slab edges were to remain exposed, with only a thin layer of elastomeric coating. Hence, the surface applied CFRP sheet fibers would have visibly affected the aesthetics of the repair. Given the numerous project restraints, the repair team determined that near-surface mounted (NSM) reinforcement was an ideal solution. NSM reinforcing bars are embedded within purposely prepared surface grooves using epoxy. Stresses are transmitted from the reinforcing bar to the epoxy and then to the Figure 4. GFRP hairpin installed around a railing post grout pocket. concrete substrate through mechanical bond. Because the NSM grooves do not extend more than 1.0-inch-deep into the slab, the the NSM reinforcement solution has little to no impact on the repair risk of damaging existing reinforcement or rupturing PT tendons aesthetics and effectively resists the design forces. is mitigated. The epoxy-filled NSM grooves can be leveled with the If poorly detailed or constructed, the use of steel reinforcement in top concrete surface, which is eventually coated with an elastomeric NSM repairs can lead to premature corrosion. To mitigate corrosion waterproofing membrane. Also, a top surface placement is most effec- risk, the design team opted to use GFRP hairpin reinforcement for the tive in resisting the moment resulting from applied forces. Hence, handrail anchorage repairs. GFRP bars are electrochemically inert and are not susceptible to corrosion, regardless of the exposure conditions. ACI 440.2R-08, Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures, provides ® design provisions and construction guidelines for NSM systems with FRP bars. The size of the GFRP bar is first determined by evaluating the tensile capacity of the bar. The tensile strength of GFRP reinforcement must be reduced to account for environmental BETTER PERFORMANCE exposure effects. Also, the tensile strength of GFRP reinforcement with bends (for example, hairpins) is further reduced to account for the stress concentrations that can occur within the bend region. ACI Committee 440 provides guidelines for minimum allowable GFRP bend radii to alleviate the stress concentrations at the bend locations. The repair specifications in this project also restricted the allowable amount of cross-sectional distortion of the bends to reduce the effect of manufacturing discrepancies on stress concentrations. Based on the calculated demands, the analysis determined that a No. 3 GFRP hairpin was sufficient to provide anchor reinforcement for each handrail post. The length of the hairpin legs was determined based on the bond strength criteria provided in Section 13.3 of ACI 440.2R. For the selected bar dimensions and load demands, a development length of 12 inches was needed. The surface groove dimensions were detailed based on the ACI 440 guidelines. The minimum specified depth and width of the surface grooves (¾ inch) were greater than 1.5 times the GFRP bar diameter. Also, the groove surfaces had to be roughened and cleaned before installation of the epoxy adhesive and the GFRP bar. Because slab edge repairs were in progress immediately adjacent to the rail posts, measures had to be developed to reliably incorporate the NSM repairs into the newly cast slab edges. To this end, the repair engineer provided two alternatives for the contractor. The first ZERO LOOSENESS alternative allowed for placing a blockout over the newly cast slab edge to form the needed NSM groove. This option was ideal if the PH: (360) 378-9484 – WWW.COMMINSMFG.COM slab edge repairs at a given location needed to be performed before

AutoTight

ADVERTISEMENT–For Advertiser Information, visit STRUCTUREmag.org

TIGHTER CONNECTIONS

32 STRUCTURE magazine

the NSM installation. The blockout is then removed, and the groove surfaces are prepped and cleaned before the GFRP hairpin installation. If the NSM installation could be performed before the slab edge was cast, the contractor was allowed to embed the curved portion of the hairpin into the repair concrete. Because the thermal expansion properties of concrete and GFRP are different, the design specified an increased concrete cover over the portion of the GFRP hairpin embedded in concrete and not epoxy. Shallow concrete cover over GFRP bars can result in cracking due to a thermally-induced strain differential between the concrete and the GFRP material. As such, while a clear cover of ⅛ inch was sufficient for portions of the GFRP bars covered with epoxy, a more significant cover was needed for portions embedded in concrete. Per ACI 440 guidelines, the portions of the GFRP hairpin that were embedded in concrete had a vertical cover of at least ½ inch. This was achieved during construction by gradually increasing the depth of the NSM groove as the distance to the slab edge decreased. Figure 3 (page 31) schematically shows the repair details, and Figure 4 shows a GFRP hairpin soon after installation. The repair contractor was able to perform the repairs without removing the railing components, which further reduced the cost of the repairs. The groove edges were created using shallow saw cuts, and then 15-pound chipping hammers were used to remove the concrete within the sawcut boundaries. The groove surfaces were roughened per ACI 440 requirements to improve the bond between the epoxy and concrete substrate. The epoxy adhesive selected for the NSM repair was chosen based on reported past performance and recommendations of the GFRP bar manufacturer. During NSM repair

execution, the railing system in each of the affected balconies was temporarily supported in the out-of-plane direction, and public access to balconies was restricted to prevent failure of the handrail system during repair execution.

Conclusion The use of fiber-reinforced-polymer bars in concrete construction has increased rapidly over the last few decades. Due to their inherently inert characteristics, GFRP bars provide an attractive solution for structures in corrosive environments. As demonstrated here, GFRP reinforcing bars are a viable solution for use in repair projects. The limitations and challenges encountered in this project were not unique or isolated, and this repair option provided an effective means of avoiding the traditional pitfalls of conventional rail post anchorage repairs.■ The online version of this article contains references. Please visit www.STRUCTUREmag.org. All authors are employed by Pivot Engineers, PLLC in Austin, Texas. Ali Abu-Yosef is a Senior Engineer. (yosef@pivotengineers.com) Joseph Klein is a Project Engineer. (klein@pivotengineers.com) Michael Ahern is a Principal. (ahern@pivotengineers.com) Randall Poston is a Senior Principal and the President of the American Concrete Institute. (poston@pivotengineers.com)

ADVERTISEMENT–For Advertiser Information, visit STRUCTUREmag.org

Weld-Crete®—The pale blue bonding agent with over 60 years of superior performance in the field.

Simply brush, roll or spray Weld-Crete® on to concrete or any structurally sound surface. Then come back hours, days or a week later and finish with new concrete, stucco, tile, terrazzo, other cement mixes or portland cement plaster. Plus Weld-Crete’s® low VOC content significantly reduces airborne pollutants that affect health and the environment.

Originators of leading chemical bonding agents… worldwide since 1952

800.633.6668 www.larsenproducts.com

JANUARY 2020

STRUCTURAL ENGINEERING INSTITUTE

STRUCTURES CONGRESS 2020

APRIL 5-8, 2020 | St. Louis, Missouri

KEY:

BUILDINGS

BRIDGES

BLAST

FORENSIC

CAREER DEVELOPMENT/BUSINESS/PROFESSIONAL PRACTICE NON BUILDING/SPECIAL STRUCTURES

NATURAL DISASTERS EDUCATION/RESEARCH

NON STRUCTURAL

View interactive technical session detail, keynotes, and events, and plan your schedule: www.structurescongress.org IES sessions — presenters showcase their work in a very short presentation and then have time to interact directly with attendees. Monday, April 6 9:30 -10:30 a.m.

 Climate Change and Our Structural Systems: SE 2050 Initiative

 Evolution of Stadium Designs – Structural Expression and Aesthetics

 Structural Collapse Investigation  Accelerated Bridge Construction  How to Verify SE Software  Coming Soon to ASCE7-22: Coupled Analysis of Nonbuilding Structures

 Classroom to the Boardroom: Transitioning to an Entry-Level Engineer

 Concrete Research in Bridges (IES)  Data-Driven Models and Physics-Based Models: Friends or Foes?

 Tornado Loads – Coming in ASCE 7-22! 11:00 -12:30 p.m.

 Impact of New Snow Load Research on ASCE-7  Negotiation Strategies That Benefit Your Career  Multi-Threat Environments and Integration of Protection Technology

 Management, Inspection and Rehabilitation of ABC Bridges  VR for Structural Engineers – An Interactive Presentation  FIU Pedestrian Bridge Collapse  The Iconic Gateway Arch: Design, Rehabilitation and Future  Diaphragms and Load Paths: Structural Systems Working Together (IES)

 Novel Building and Bridge Design with Structural Optimization

 Life-Cycle of Structures & Infrastructures Under Climate Change

 Finite Element Modeling for Concrete Anchorages 1:30 - 3:00 p.m.

 Rain Loads – The Forgotten Natural Hazard  When Engineer's Make Mistakes: Peer Review, Company Culture and the Peter Principle

 Existing Masonry: Assessment and Repair  Advanced Inspection and Monitoring of Bridges  Business of BIM: Perspective on State of the Practice/ Common BIM Pain Points

 Autonomous Transportation Structures Inspection and Maintenance

 Tall Buildings in Timber – Achieving Sustainable Urban Density  Hostile Vehicle Mitigation and Evolution of Space It is Applied To (IES)  Machine Learning for Structural Engineers: A Critical Examination Advances in Performance-Based Wind Engineering  Advances in Performance-Based Wind Engineering

SPECIAL SESSIONS 3:30 - 5:00 p.m.

 Millennium Tower – The Story

Tuesday, April 7 9:30 -10:30 a.m.

 Cold-Formed Steel Connections to Other Materials  Creating Custom Tools for your Firm's Analytical Software and the Benefits of Sharing

 Overview – Structural Design for Physical Security Manual of Practice

 Nonbuilding and Special Structures Case Studies  Expanding Engagement – Working for Equity in the AEC Workplace by Leading Cultural Change

 Impact of Climate Change on Infrastructure  Recycle Me! Reusing and Repairing Buildings  Computational Imaging and Machine Vision for Civil Engineering (IES)

 Cultivating 21st Century Traits in UG Engineering Students

 Vintage is In: Retrofitting for Today's World (IES)  Computational Research  Trends in Onshore Heavy Industrial Modularization  Seismic Renovation of the Robert A. Young Federal Building 1:30 - 3:00 p.m.

 ASCE 7-16 Learn from the Experts – Wind Design Examples  Claim – Share: Full Disclosure  Practice in Shock Loads and Protection Against Close In Explosives

 Bridge Loading and Rating  Engineer to Entrepreneur  Iconic Bridges of St. Louis City  Exemplar Guidance: Advancing Structural Fire Engineering in the U.S.

 Building Envelopes: A Critical Factor in a

 Structural Testing Research (IES)  Design and Analysis of Nonstructural Components  Vision for the Future: HPC and AI in Structural Engineering

Building’s Resistance to Natural Hazards.

11:00 -12:30 p.m.

 ASCE 7-16 Learn from the Experts – Seismic Design Examples  Software  Recent Advances in Disproportionate Collapse  Bridge Rehabilitation  Career Advancement Bootcamp for the Young  Structural Engineer Structural Health Monitoring for Bridges  Updating ASCE 49: Wind Tunnel Testing for Buildings and Structures

SPECIAL SESSIONS 3:30 - 5:00 p.m.

  Conceptual Design of Bridges and Buildings – The Sequel  Don’t Touch That Dial! Professional Liability Case Study Marathon (CASE)

 Confidential Reporting of Structural Safety in the United States

Wednesday, April 8 9:00 -10:00 a.m.

 Design by the Book: When Old Codes Learn New Tricks  Engineering Ethics and Teamwork  Foundation Issues – Nonbuilding and Special Structures  Long Span Bridges Case Studies  Leading and Leveraging Conflict to Achieve Innovation  Emerging Trends in Inspection Robotics  Make Mine a Tall: Overcoming Challenges in Tall Building Design

 Active Shooter Mitigation: Ballistic Hardening and Other Ideas (IES)

 Materials Research  Effect of Building Code Changes on Community Recovery and Resilience

10:15 - 11:15 a.m.

 Precast Concrete and Disproportionate Collapse  Technical Summit on AI in Structural Engineering Innovative Materials and Techniques

 Composite Materials in Bridges  Famous Structures in St. Louis  Seismic Research in Bridges  Diverging from Disposable Buildings  Infrastructure Life-Cycle Analysis: Frameworks and Applications (IES)

 Restoration, Repair and Structural Health Monitoring (SHM) Research

 Effect of Policy Changes on Community Recovery and Resilience

NORTHRIDGE

25 YEARS LATER

Seismic Safety in California Hospitals By Chris Tokas

Performance of all Buildings at 23 Hospital Sites with One or More Yellow or Red Tagged Buildings

he performance of existing buildings in earthquakes provides many lessons. Most of them – building system

specific – have been very eloquently articulated in the preceding articles published in STRUCTURE (Northridge – 25 Years Later series). However, as the discussion about creating resilient communities continues, other lessons learned are factors to consider before drafting policies intended to reduce

Number (%) of Buildings Type of Damage

Pre Act

Post Act

Structural Damage Red tagged

12 (24%)

0 (0%)

Yellow tagged

17 (33%)

1 (3%)

Green tagged

22 (43%)

30 (97%)

Major

31 (61%)

7 (23%)

Minor

20 (39%)

24 (77%)

Nonstructural Damage

Total Buildings

the risks associated with Natural Hazard Events (NHE).

Figure 1. Northridge Earthquake – hospital performance.

The Hospital Seismic Retrofit Program, known as SB 1953, provides an exceptional opportunity to study a large-scale program designed to enhance seismic safety in existing buildings. Mazmanian and Sabatier (1989) studied and wrote extensively about public policy and stated that implementation runs typically through a number of stages: beginning with the passage of a statute or law, followed by policy inputs made by implementing agencies or regulations, compliance by target groups with those inputs (decisions), assessment of the actual impacts (both intended and unintended), perceived impacts of agency decisions, and, finally, important revisions or attempted revisions in the basic statute. The case of California Senate Bill (SB) 1953 provides excellent lessons in policymaking.

Safety Act in 1972. The act required buildings to have special seismic detailing to resist earthquake forces with limited damage. Since March 7, 1973, the design, construction, and maintenance of California's hospitals have been governed by individual statutes, regulations, and design standards aimed at assuring hospital functionality following a major earthquake. The standards are intended to ensure that vulnerable patients are safe in an earthquake, and the facilities remain functional to care for injured persons in the community after such a disaster. These standards are implemented by California’s Office of Statewide Health Planning and Development (OSHPD) and include stringent seismic design requirements, thorough plan review, approval of all designs, continuous construction inspection, materials testing, and strict monitoring of all construction projects. However, the 1972 HSSA only applied to new hospital buildings and the alterations or remodeling of existing structures. OSHPD had no authority to require upgrading of pre-HSSA structures to meet the mandated standards for new construction. When the Act became law, it was envisioned that these pre-1973 Act or nonconforming buildings would be replaced with new conforming buildings through attrition. However, years later, a significant number of nonconforming hospital buildings with questionable earthquake performance were still in use.

Legislative History

The law that established the hospital seismic retrofit program did not develop in a vacuum. Its origins lie deep within California’s concerns about earthquake safety, and it emerged from a long series of events. To truly appreciate the California Hospital Seismic Retrofit Program as a whole, it is essential to look back to the genesis of the program. Following the 1971 San Fernando Earthquake in which several hospitals sustained substantial damage or collapsed, government officials, design professionals, and health care providers came to the realization that functioning hospitals after a major earthquake are critically important. While emergency field hospitals, medical tents, and air-lifts to available facilities are often used to supplement when hospitals are damaged, these will never provide a sufficient substitute. Only modern health care facilities, located within the damaged region and capable of functioning at full capacity, can adequately provide the needed medical assistance. As a result, the Legislature passed the landmark Hospital Seismic Figure 2. California hospital seismic safety definitions. 36 STRUCTURE magazine

The Impact of the Northridge Earthquake The performance of these newer hospitals in the 1994 Northridge Earthquake proved that the HSSA was responsible for dramatically improving the performance of hospital buildings (Figure 1). While no buildings constructed after the HSSA were red-tagged, 24% of the pre-HSSA hospital buildings were red-tagged, meaning the buildings had to be evacuated because of structural damage. Another 33% of the

Seismic evaluations and Improvements pre-HSSA buildings were “yellow-tagged,” meaning SB 1953 Enacted plans for compliance to allow the buildings had restricted use and access. Extensions submitted to OSHPD Evacuation Alfred E. Alquist The effects of the Northridge Earthquake on hospitals (NPC-2) HSSA Enacted provided the additional incentive needed to advance leg2013 2018 2025 2008 2015 2020 2030 islation addressing the concern about hospital buildings built before 1973. The bill, SB 1953, was introduced 1973 1994 2001 2002 into the California Senate only five weeks after the 15 years Northridge Earthquake. 36 years The basic strategy incorporated into the SB 1953 21 years 19 years program was first to evaluate each hospital building 57 years and place it into a specific seismic performance category Prevent collapse (Figure 2). and loss of life (SPC-2 or higher) The seismic compliance portion of the law was based All buildings capable of continued on a two-step approach: operation (SPC-3 or higher) –1971 Sylmar, 1989 Loma Prieta, and 1994 Northridge EQs • Buildings that provided acute care services and Figure 3. California hospital seismic compliance program major milestones. posed a significant risk of collapse during an earthquake (SPC-1 Buildings) had to be removed from service by 2008 or strengthened to SPC-2 level (LS level). RAND (2019) corporation, in a recent report, stated: “In recent years, • By January 1, 2030, all acute care hospital buildings must be OSHPD has worked closely with hospitals to maintain compliance with capable of not only surviving a major earthquake but also must legislative requirements of SB 1953 while pursuing opportunities to be capable of providing on-going services after an earthquake. address common barriers to compliance. Such collaborative relationships Very rarely are public policies implemented without unanticipated, between OSHPD and hospitals enable ongoing deliberation regarding often adverse side effects, and SB1953 had its share of adverse side effects. the reasonableness of seismic requirements. This deliberation enhances The high percentage of SPC 1 buildings and a healthcare industry in the likelihood of identifying policy innovations that reduce the burden, turmoil because of financial problems, especially after the passage of and therefore increase the likelihood of compliance.” the Affordable Care Act, sparked several legislative efforts to modify The following are some examples of when interventions by the the original compliance deadline, which had already been extended to implementing agency (OSHPD) was very instrumental in realigning 2013 (Figure 3). The lesson here is that significant changes in design the program and facilitating compliance. practice concerning existing buildings of varying ages on complicated The “Safer Sooner” Concept sites take a much longer time to implement than anyone could foresee. Eventually, the 2008 compliance deadline was moved to 2025. Why spend good money on outdated/obsolete buildings and extend However, the compliance date of 2030 for all California hospitals life for only a few more years? In 2007, California enacted SB 306 required to meet the “functionality” performance level has remained to permit a delay in compliance for SPC-1 buildings if the hospitals unchanged thus far. demonstrated they lacked the financial capacity to remove SPC-1 buildings from service by 2013 and if the hospital agreed to replace the SPC-1 building by 2020. Twenty-four hospitals were granted Re-examine, Re-align, Repeat… SB 306 extensions. As was learned, the implementation of public policy is not a linear The “Worst Buildings First” Concept process. The seismic evaluation of the existing hospital buildings yielded a surprisingly large number of buildings that required either Not all buildings “posing threat to life” (SPC-1 buildings) pose the retrofit or replacement, and which constituted a large proportion of all same risk. In 2005, after careful evaluation, OSHPD selected the acute care hospital buildings in California. OSHPD had to develop, HAZUS (Hazards US) earthquake loss estimation methodology as in conjunction with the Hospital Building Safety Board, innovative a tool to re-examine and assess the seismic risk for each SPC-1 hossolutions to this dilemma; “How to keep pital building (Tokas et al., 2008, 2009). existing hospitals functioning at the same Utilizing the HAZUS AEBM methodoltime ensuring compliance with the Law?” ogy, SPC-1 buildings were ranked based OSHPD, keenly aware of the cost of reton their relative risk, thereby enabling the rofitting, attempted to require only the policymakers to implement “Worst First.” absolute minimum and gave as much flex“The Public has the Right ibility as possible for compliance. OSHPD to Know.” has looked for ways to lessen the impact of the seismic retrofit program without In 2009, the California legislature enacted jeopardizing safety. That has been achieved SB 499, which requires hospitals to report by continually re-examining the program their compliance progress. This motivated and realigning it by adopting policies to hospitals. provide flexibility in its implementation, Compliance Time vs. Risk or by looking forward at the national level to adopt state of the art seismic retrofit In 2011, the California legislature enacted standards to provide hospitals with options SB 90, which authorized OSHPD to grant on how to meet seismic standards. The hospitals an extension of up to seven years Figure 4. Compliance time vs. risk. JANUARY 2020

beyond the 2013 deadline to retrofit or replace SPC-1 hospital buildings. The length of the extension was determined by OSHPD on a case-by-case basis using the following criteria: 1) structural integrity of the building risk (Figure 4, page 37 ); 2) community access to care if the hospital building was to close; and 3) financial capacity of the hospital to complete the construction projection. However, the law specifically required that such extension shall not exceed the time necessary to reasonably complete the strengthening to at least a life safety performance level (SPC-2).

The Need for SPC-4D Model codes have changed, making upgrading of pre-1973 hospital buildings to the immediate occupancy performance level costprohibitive to meet the 2030 functionality requirements. Rural and other hospitals in underserved areas have limited resources to upgrade to these requirements. Furthermore, the SPC-2 buildings may be landlocked by higher SPC buildings such that removing the SPC-2 building from service could make the hospital inoperable, or the hospital may not have property on which to build a replacement building. As such, OSHPD instituted a new Seismic Performance Category, SPC-4D, which allows hospitals to comply with a building code edition that meets the level of performance of many SPC-4 buildings (Figure 5), but which is less than complying with current code (SPC-5) as had previously been required. Strengthening to SPC-4D is intended to control damage to permit return-tofunction similar to post-1973 compliant buildings (SPC-3 or 4) but not as quickly as SPC-5 (IO level) buildings. Hospitals are using this option to strategize their master plan and explore various cost-effective options.

Policy Implementation The extent that policies are implemented is affected by events that occur even before the policy is adopted. The need to mitigate against the likely consequences of NHE takes public regulation of private behavior to protect the public interest. Assumptions that organizations outside the policymakers will automatically comply with directives and regulations imposed on them cannot be made. Alesch, Arendt, and Petak (2012) suggest several questions to consider before drafting a policy intended to reduce risks associated with NHE: What are the primary obstacles to implementing public regulatory policies? How do â&#x20AC;&#x153;Organizationsâ&#x20AC;? make choices of how much to spend on mitigating the likely consequences of rare but potentially catastrophic events? What characteristics of public policies increase the likelihood of successful implementation? The relative long-term success of public policy design and implementation depends on the entire context within which the process takes place. As the context changes, the policy needs to change. Rigidity in policymaking and implementation limits the capacity of the affected system to achieve the initially desired outcomes in the face of dynamic contextual change. Following the OSHPD model, and being cognizant of the damage and disruption a major earthquake can cause for big cities and large populated areas, San Francisco and Los Angeles have led the charge in the development and successful passage of mandatory ordinances to improve the vulnerability of the building stock. Earlier voluntary retrofit programs were less effective in achieving the desired level of

38 STRUCTURE magazine

Figure 5. Seismic performance of SPC-4D hospital buildings.

safety for the city. The window of discourse (otherwise known as an Overton window), which defines the range of thinking by the public on what is acceptable, sensible, or popular in terms of public safety, has shifted in public opinion and policy to make some of the voluntary retrofit programs mandatory as opinions and minds have changed over time. To achieve this required years of effort, planning, and communication with elected officials, stakeholders, and the public at large.

The Results Following the Northridge earthquake, California hospitals have made great strides towards building and community resilience that is both practical and cost-effective. Recognizing that it is extremely costly to bring existing buildings up to the fully functional level of modern codes, OSHPD, in consultation with the Hospital Building Safety Board, has established reasonable and achievable seismic performance categories and standards for existing hospital buildings and has adapted as necessary. A majority of hospital owners have embraced the seismic safety standards and are on a path towards seismic compliance with the Hospital Seismic Safety Act. While it may appear that some of the building seismic safety standards such as SPC-4D and NPC-4D are lower than what model code dictates as the standard of performance for critical facilities, the proper enforcement of the standard compensates for it. Plan review oversight, construction observation, and continuous inspection significantly improve the reliability of hospital buildings in a damaging seismic event, which translates to re-occupancy in a very short period. California is overdue for its next big earthquake. The resiliency preparedness of the hospitals will soon be tested, and OSHPD will confirm or revise the standards based on lessons learned. Retrofitting or upgrading a building before a damaging event is always better than post-event recovery.â&#x2013; The online version of this article contains references. Please visit www.STRUCTUREmag.org. Chris Tokas is the Deputy Division Chief, Facilities Development Division (Sacramento) at the Office of Statewide Health Planning and Development (OSHPD).

Are You Redi?

REDICOR SIMPLIFIES AND ACCELERATES THE CONSTRUCTION OF REINFORCED CONCRETE CORES. Conventional cast-in-place, pre-cast and masonry methods of constructing reinforced concrete shear cores often require long and expensive Pre-engineered load- schedules bearing structural before connections enable structural framing to begin framing can immediately. begin.

Now there’s a better way. RediCor is a pre-fabricated, ready-to-set modular steel form system that simplifies and accelerates concrete core construction. Our load-bearing modules are ready to set once on-site, and structural framing can be installed simultaneously – saving time, energy and money. Are you Redi? VISIT US AT REDICOR.COM FOR THE REDICOR STORY.

V U LC R A F T/ V E R C O

Powerful Partnerships. Powerful Results.

INSIGHTS Cloud-Based Modeling

Why It’s Catching On and What You Need to Know By Michelle McCarthy and Doug Evans

“The original idea of the web was that it should be a collaborative space where you can communicate through sharing information.” –Tim Berners Lee, inventor of the world wide web

oday, cloud-based modeling for construction is an example of Lee’s original thought. Companies employing these methods are reaping real, recognizable benefits from cloud-based modeling. The technology required to support cloud-based modeling can be challenging to sift through, but understanding and harnessing its power can pay off in both time savings and productivity increases.

What is Cloud-Based Modeling Cloud-based modeling, in its broadest interpretation, means that the Building Information Model (BIM) you are designing and contributing data to is accessed via the internet and hosted on a cloud computing service. Technology companies have differing philosophies when it comes to cloud-based modeling tools. Some technologies enable you to do the processing on a local computer, pulling and pushing data to a central model that is hosted in the cloud. At the same time, other tech tools offer the ability to login to the cloud-hosted model where all modeling and processing is done live in the cloud, either via online software tools or virtualized networks. Cloud computing services can be broken down into Infrastructure as a Service (IaaS) and Software as a Service (SaaS). IaaS refers to services that offer servers, virtual machines, networks, and storage on a rent basis. SaaS, in turn, requires that users connect to the applications through the internet on a subscription basis. There is not just one way to accomplish cloud-based modeling. (https://bit.ly/2m4ZHc3)

The Advantages Why are so many companies introducing this technology? First, it takes geographic location out of the equation as a limitation and broadens the available talent pool when it comes to manpower. Now, a perfect hire does not have to relocate to be a valuable resource on your team. Also, the accessibility to the model in the 40 STRUCTURE magazine

cloud means your team can be spread across multiples states, countries, or continents, and all they need is an internet connection. For smaller companies or even single-person operations, cloud-based modeling offers scalability in being able to team up with others for collaboration on a project. The ability to share the model via the cloud makes it far easier to collaborate with outside companies. In a “follow the sun” workflow, teams are dispersed globally but working on the same project and passing it from team to team at the end of the workday; cloud-based modeling significantly reduces file management tasks as all data is accessed in a single location. Also, for work performed in countries where power outages occur with some frequency, cloudbased modeling provides a distinct advantage when hosted on a virtualized network. While the power may go out locally, it will likely not have gone out at the hosted site. Cloud-based modeling can provide a significant impact on a project basis as well. The In-Model Review process, which allows engineers of record to use the fabrication model as an added data point for the submittal and review process, can be moved to the cloud – meaning that notes, revisions, and change orders are immediately accessible by the fabricator and detailers and can be addressed sooner, shaving days off turnaround times. Access to the cloud-based model extends its benefits beyond just engineers to many of the partners on the project; whether it is General Contractor or a tradesman like an erector or a plumber. Using the model as the center of communication gives visual feedback to high priority RFIs, change orders, revisions, and members on hold. Dealing with that information through the model is significantly easier than sifting through emails. The data in the BIM has value to all involved in the project. For IaaS cloud-based modeling that is accomplished on a virtualized network, there are other benefits to consider, such as the user’s technology infrastructure. When operating on a virtualized network, local machines are just a portal to the virtual network. High-level

processing power is done in the virtualized network rather than locally, reducing the cost of upgrading local machines to maintain the processing power required when working on data-rich BIMs. Cloud hosting providers continually upgrade their servers to keep up with the demands of current software so that users do not have to. Also, backups are generally a part of the cloud-hosting providers’ services, taking another worry off the user’s plate.

What You Need to Know A critical concern for cloud hosting BIM data is that there can be legal issues when it comes to where the data is hosted – or where the cloud hosting provider’s servers are located. Laws differ from the U.S. to the EU when it comes to data privacy, so be sure to investigate what laws apply to your project and your company, and what your options are when it comes to locations of your cloud hosting service. Finally, cloud-based modeling requires an internet connection, and the user is reliant on the quality, consistency, and availability of that connection. This will impact choices for cloud-based modeling. The availability and affordability of cloud hosting services will continue to come more within reach. While there are some perceived cons that might scare some away, the efficiencies gained and savings made by companies who implement cloud computing push it into common practice, just as Building Information Modeling and Integrated Project Delivery did ten years ago. This final quote from Tim Berners Lee is an excellent summary for the future of cloud-based modeling, “The Web as I envisaged it, we have not seen it yet. The future is still so much bigger than the past.”■ Michelle McCarthy is Director of Sales Operations at SDS/2, a Nemetschek Company. Doug Evans is the Vice President of North America Sales for SDS/2.

JANUARY 2020

ANCHOR updates Adhesives Technologies Corporation

Phone: 800-892-1880 Email: jklaus@atcepoxy.com Web: www.atcepoxy.com Product: ULTRABOND® HS-1CC Description: A leading manufacturer of nextgeneration adhesives including epoxies, urethanes, acrylics, ester blends, and polyureas for use in construction and infrastructure projects. The company offers dozens of products under well-known brands ULTRABOND®, CRACKBOND®, and MIRACLE BOND®, with made in USA, ICC certified product available in bulk and cartridge forms.

IES, Inc. Phone: 800-707-0816 Email: info@iesweb.com Web: www.iesweb.com Product: VAConnect Description: Design base plates by AISC Design Guide #1 and anchorage calculations for ACI 318. Both of these, independently, are difficult by hand! With VAConnect you will get the job done quickly and accurately. Works alone or with IES VisualAnalysis.

American Wood Council

Phone: 202-463-2766 Email: info@awc.org Web: www.awc.org Product: Connection Calculator Description: Provides users with a web-based approach to calculating capacities for single bolts, nails, lag screws. and wood screws per the 2015 NDS. Both lateral (single and double shear) and withdrawal capacities can be determined. Wood-to-wood, wood-toconcrete, and wood-to-steel connections are possible.

ASDIP Structural Software

Phone: 407-284-9202 Email: support@asdipsoft.com Web: www.asdipsoft.com Product: ASDIP STEEL Description: An advanced software for the quick and efficient design of base plates, anchor rods, and shear lugs per the latest ACI anchorage provisions. See graphic results immediately with every change. Focus your attention on engineering and let ASDIP take care of the calculations.

ENERCALC, Inc.

ENERCALC

Not listed? All 2020 Resource Guide forms are now available on our website.

Phone: 847-966-4357 Email: software@structurepoint.org Web: www.structurepoint.org Product: spMats Description: Widely used for analysis, design, and investigation of concrete mat foundations, footings, and slabs on grade. spMats is equipped with the American (ACI 318-14) and Canadian (CSA A23.3-14) concrete codes. spMats is utilized by engineers worldwide to optimize complicated foundation design and improve analysis of soil structure interaction. Product: spLearn Description: StructurePoint licensed structural engineers have decades of experience with reinforced concrete design. As such, we have multiple resources on our website for the structural engineer's benefit, including: detailed design examples, technical articles, video tutorials, webinars, and more. Visit our website to learn more and request a webinar or consultation.

Phone: 678-737-7379 Email: jodi.hendrixson@trimble.com Web: www.tekla.com/us Product: Tekla Tedds Description: Automating your everyday structural designs, the Tekla Tedds’ library includes anchor bolt design per ACI 318 Appendix D. The calculation includes comprehensive checks for tensile and shear failure of anchors and is available as part of a free trial by visiting the website. Product: Tekla Structural Designer Description: Revolutionary software that gives engineers the power to analyze and design steel and concrete buildings efficiently and profitably. Physical, information-rich models contain all the intelligence needed to fully automate the design and document your project, including all end force reactions communicated with two-way BIM integration, comprehensive reports, and drawings. Product: Tekla Structures Description: An Open BIM modeling software that can model all types of anchors required to create a 100% constructible 3-D model. Anchors can either be created inside the software or imported directly from vendors that have 3-D CAD files of their products.

Wej-It High-Performance Anchors Phone: 203-523-5833 Email: julien@toggler.com Web: www.wejit.com Product: POWER-Skru Large Diameter Concrete Screw Description: A high-strength screw anchor with self-tapping threads that offers a unique undercutting design for anchoring into concrete and masonry. No secondary setting is needed. The POWER-Skru Large Diameter Concrete Screw provides high-strength performance with low installation torque. A heavyduty mechanically-galvanized finish is available to enhance corrosion resistance.

ADVERTISEMENT–For Advertiser Information, visit STRUCTUREmag.org

Phone: 800-424-2252 Email: info@enercalc.com Web: https://enercalc.com Product: Structural Engineering Library, ENERCALC SE Cloud, ENERCALC 3D, RetainPro Description: Design of anchors and anchor bolts requires a thorough development of applied loads and analysis of full structures or connected components. ENERCALC’s Structural Engineering Library helps determine loads and perform analyses via loads and forces modules and analysis and design modules. Clear, succinct reports represent your work well.

StructurePoint

Trimble

STRUCTUREmag.org. J A N U A R Y 2 02 0

business PRACTICES Hiring Experienced Structural Engineers By Michael “Batman” Cohen

TEM jobs (Science, Technology, Engineering, and Math) are on the rise, and STEM degree programs and graduates are on the rise too. So, why are Structural Engineers so hard to find, particularly midlevel engineers with a few years of experience? Several reasons are essential to understand if we are going to create strategies to find and attract that elusive talent. Finding entry-level engineers is not a problem for most firms but a mid-to-senior level? Incredibly challenging. Here’s why: 1) Structural Engineering (SE) projects last longer and are more complex than many other STEM professions. Unlike most other non-research-based STEM jobs, the project lifecycle for an SE is much longer, which leads to higher job loyalty and retention for the employer. 2) There are less drastic changes in the SE space than other STEM fields, and most clients have SE firms sign NDAs limiting the ability to talk about your exciting or unique projects. 3) In an industry that is not considered a hotbed for recruiting and hiring, many of the best practices, tooling, and cutting-edge approaches have been missed. There are three ways to overcome each of these obstacles: 1) Lengthy and Complex Projects (most last 6 – 24 months) a) Reach out to candidates when they have been at their current firm for three to six months. By this time, they have been integrated into their teams/ organizations and started working on their first project(s). This is the time when candidates are getting over the honeymoon phase and are starting to assess if this company/role makes sense for them and their careers. A great time to get on their radar. b) The next opportune time to reach out is in the 18 to 24-month range. They will have finished or be finishing their first or second project, and it could be a great time to touch base with a more exciting opportunity/project. c) The other best times to reach out are at anniversaries and birthdays – these are two times when people are naturally thinking about change. They, like New Years Day, are a time where 42 STRUCTURE magazine

people reflect on their future, ask questions of themselves, and make new goals/strategies. 2) Selling Your Organization a) Unlike other STEM fields, technology is not as rapidly advancing for SEs, so other details have to be taken into account when reaching out to sell a candidate on working for you. Remember, “Everyone is working on exciting projects with cool clients,” – so be SPECIFIC! Share details they cannot easily find on their own. b) Overcoming NDA’s can be tough, and, if not thought out ahead of time, reaching out to hire top talent can be a difficult challenge. Try having an internal conversation with the business team about getting some flexibility with your firm’s NDA – perhaps being able to list and share certain details about the project (location, structure type, length of project, and other interesting details) that could help sell the project to potential candidates. c) Find better specifics to use to reach out – Universities or past companies shared with hiring managers or team members, personal interests of hiring managers shared with candidates (found in LinkedIn Groups, Meetup Groups, etc.), or any other interesting similarities that may not just be based on what they do and what you are hiring for someone to do. 3) Best Recruiting Practices in the STEM Field a) Finding Candidates – Use Natural Language Processing (NLP) in your search to find relevant people. This means searching using words/phrases the same way a candidate would use them in their profile. Example: “Bridge Design” OR “Designed Bridge” OR “Designed Bridges” OR “Responsible for Designing” OR “Responsible for the design of” OR “Managed Bridge Design” OR “Designing Bridges.” The capitalized word “OR” is a Boolean Operator used as a conjunction to combine keywords in a search, resulting in more focused and productive results. b) Messaging Candidates – Subject line less than 38 characters. This parameter allows the subject to show up on cell

phones. Communicate in short oneto two-sentence paragraphs. Include relevant links (projects, coworkers, managers, etc.). It is okay to be funny and be yourself. Authenticity comes through in an email. If you want to test your authenticity, read your email aloud (to yourself or a colleague) – does it sound very natural and reflect how you usually communicate? c) Qualifying/Screening Candidates – An important thing to remember for the phone screening is to have a predetermined list of information you want to gather every time. Our best practices consist of using an acronym to help remember it every time as a makeshift “checklist,” so we do not end the call until we have all the data we need. Conversely, it is important to be conversational, do not be an ordertaker! If you want to see how much of an order-taker you are (we all have it in us), try the following easy exercise (I encourage EVERYONE to try this – it is very revealing, both professionally and personally). Go through a qualification call with a coworker or friend. Notice what your “filler word(s)” is/ are. This is the word you say after a candidate answers a question and you want to move to the next one. Typical examples: “Cool,” “Awesome,” “Got it,” etc. The fewer of these filler words you use, the less of an order-taker you are! Practice makes perfect. All companies are struggling to find top talent – it is the nature of having a low unemployment rate and a boom in STEM industries. Every company has a “great reason for candidates to work there.” But the company who will have the most hiring success and, as such, the most growth and market share increase will be the one who adopts these best practices and modernization of the recruiting organizations. After all, the companies that can hire enough people and hire the best people will always be the most successful.■ Mike “Batman” Cohen is the Founder of Wayne Technologies and Paired Talent, recruiting solutions providers that offer recruitment training and deliverables-based recruitment, respectively. Mike is a nationally recognized key-note speaker, contributing author, webinar host, and industry thought leader. JANUARY 2020

SPOTLIGHT Sarah Mildred Long Bridge

Between Kittery, Maine and Portsmouth, New Hampshire By Christopher Burgess, P.E., S.E., P.Eng., Peter Roody, P.E., and Jeffrey Folsom, P.E.

he new Sarah Mildred Long Bridge carries the US Route 1 Bypass and a heavy rail line that serves the Portsmouth Naval Shipyard over the Piscataqua River. Coined “three bridges in one,” the crossing consists of vehicular approach bridges stacked over railroad approach bridges leading to a vertical lift span over the navigation channel. The moveable span lifts from the normal roadway position to allow passage of tall vessels underneath and lowers to railroad track level, allowing trains to pass on the rail in the roadway median of the lift span. With a 56-foot vertical clearance in the “resting” position at the vehicular level, there are 68% fewer bridge openings compared to the previous bridge.

The lift span is a multi-box steel girder system with a composite steel plate and concrete deck. The 300-foot-long span is supported at each end by steel lifting girders that transfer loads to the substructure through wire rope attachments on each end and multiple sets of bearings mounted to the underside of the girder. The total load to lift, including all permanent loads from the girder span and lifting girders, is four million pounds. The 200-foottall precast concrete lift towers fully encase

STRUCTURE magazine

the counterweights and related lift mechanisms. The 2,434-foot-long segmental vehicular bridge provides two 12-foot lanes with 5-foot shoulders and tall bridge railings for cyclists. The new bridge has long open spans of up to 320 feet and 11 fewer piers than the previous FIGG and Hardesty & Hanover were Award Winners for the bridge, providing enhanced vistas Sarah Mildred Long Bridge project in the 2019 Annual Excellence for residents and motorists while in Structural Engineering Awards Program in the Category – New minimizing impacts to the river Bridge and Transportation Structures. Photos courtesy of FIGG. and the surrounding environment. The 1,437-foot-long segmental railroad The precast concrete superstructure segments bridge is 19 feet wide with spans up to 160 were erected using the balanced cantilever feet long. The heavy rail live loads were quite construction method. The precast segmental different than the live loads used to design design allowed for segments to be erected at multiple locations simultaneously with both land-based cranes and a barge-mounted ringer crane. Erecting the railroad bridge first provided access and support for the construction of the vehicular bridge directly above. The project team provided an enhanced alignment for the new bridge, which improved navigation by reducing the bridge skew from 25 to 15 degrees and allowed larger ships to access the Port and Portsmouth Naval Shipyard. The span layout enabled the new bridge to cross Market Street without a pier in the median and serve as a gateway entrance into historic downtown Portsmouth. The new Sarah Mildred Long Bridge opened to traffic on March 30, 2018, and has a design life of over 100 years.■

the vehicular bridge due to the Cooper E80 and Alternate Navy Load requirements. For efficiency, the single shaft reinforced concrete railroad piers were spaced approximately onehalf that of the vehicular bridge piers to keep the railroad and vehicular bridge superstructure elements nearly the same depth. There are three shared piers where the railroad bridge is supported at the footing between two vertical columns that are integrated into the vehicular bridge superstructure above.

Christopher Burgess is a Principal Bridge Engineer with FIGG. Peter Roody is a Principal Associate with Hardesty & Hanover. Jeffrey Folsom is the Assistant Bridge Program Manager for the Maine Department of Transportation.

Project Team Owners: Maine Department of Transportation and New Hampshire Department of Transportation Designer: FIGG/Hardesty & Hanover Joint Venture

JANUARY 2020

NCSEA NCSEA News

National Council of Structural Engineers Associations

The Structural Engineering Summit Drew Record Attendance…Again NCSEA's Summit broke records once again in 2019. This year’s event hosted more than 800 total attendees, beating last year’s record by almost 200. The Summit has been steadily growing over the last four years as NCSEA has been able to offer more educational and networking opportunities to more and more attendees and exhibitors. The 2019 event featured over 45 education sessions for the practicing structural engineer, several networking and awards events (including NCSEA’s newly revamped Awards Celebration), and a trade show with 70 exhibitors. This year’s expert-led education sessions were met with high ratings from attendees. Only the highest-quality abstracts were selected to offer top-notch education that is for practicing structural engineers by structural engineers; this included the five keynote addresses that were presented throughout the week.

Attendees during Stacy Bartoletti's Keynote address.

• Wednesday started off with Stacy Bartoletti, Degenkolb Engineers, who spoke on the future of the profession and what it may look like in coming years. • Melissa Marshall, Present Your Science, spoke later on Wednesday, motivating attendees on the importance communication has to the success and advancement of technical work. • Avery Bang, the President and CEO of Bridges to Prosperity, started off day two of the Summit, speaking on the positive effects of connecting rural populations. • Lucy Jones, Dr. Lucy Jones Center for Science and Society, spoke on what needs to be done to protect the economy during inevitable future earthquakes. • The final keynote of the week was Ashraf Habibullah, Computers & Structures, Inc., who emphasized the importance of developing interpersonal skills that will help engineers to inspire themselves and each other. NCSEA partnered with the local member organization, the Structural Engineers Association of California (SEAOC), to host a one-of-a-kind Welcome to California event that highlighted California’s contributions to the profession, as well as its diverse regions. The event featured an earthquake simulator, sponsored by the California Earthquake Authority, that mimicked the experience of a 3.0 to 7.0 magnitude earthquake, and a surf simulator! In addition, the event paid homage to wine country, the Golden Gate Bridge, and, of course, Disneyland. The 2019 Summit introduced a revamped Awards Celebration. This event annually highlights the NCSEA Special Awards, honoring NCSEA members who have provided outstanding service and commitment to the association and to the structural engineering field, as well as the Excellence in Structural Engineering Awards, showcasing some of the best examples of structural engineering ingenuity throughout the world. The Awards Celebration began with a short networking reception that moved into an “Oscars-style” awards presentation that shined a spotlight on the night’s winners, and then attendees shifted to an outdoor gala with dinner, live music, and more networking.

Representatives from SSG Structural Engineers, LLP posing with their project poster. Their project Epoch Estate Wines, Tasting Room was one of the winners of the Forensic/Renovation/ Retrofit/Rehabilitation Structures < $20 Million Category of NCSEA's Excellence in Structural Engineering Awards.

This year’s Special Awards were presented to:

• NCSEA Service Award to Ben Nelson, P.E., for the work he has put toward the betterment of NCSEA that is beyond the norm of volunteerism. • James M. Delahay Award to Kelly E. Cobeen, S.E., for her outstanding contributions toward the development of building codes and standards. • Robert Cornforth Award to Thomas A. DiBlasi, P.E., SECB for his exceptional dedication and exemplary service to an NCSEA Member Organization and to the profession. • Susan M. Frey NCSEA Educator Award to S.K. Ghosh, Ph.D., for his genuine interest in, and extraordinary talent for, effective instruction to practicing structural engineers. For more information on these awards, visit www.ncsea.com/awards/specialawards. NCSEA also introduced some new events into this year’s Summit. The National Chapter of the Structural Engineering Engagement and Equity (SE3) Committee hosted the first ever national symposium, with topics focusing on various aspects of engagement, retention, diversity, and inclusion within the structural engineering profession. NCSEA also held the first ever national Timber-Strong Design Buildsm Competition, which challenged student teams from across the country to build a two-story playhouse in just 90 minutes. 44 STRUCTURE magazine

News from the National Council of Structural Engineers Associations The winning schools in the Timber-Strong Competition were: 1st – California Polytechnic State University, San Luis Obispo 2nd – University of California, Los Angeles 3rd – University of Kentucky The winners of the first MO Public Outreach Challenge were also announced. This Challenge was led by NCSEA’s Communication Committee to involve the NCSEA Member Organizations in outreach via news articles, blog posts, videos, and a variety of other media channels, while educating the public and other industries about structural engineering. The winners of the very first MO Public Outreach Challenge were:

Winning team of the Timber-Strong Design Build s m Competition, California Polytechnic State University, San Luis Obispo

1st – Structural Engineers Association of California (SEAOC) 2nd – Structural Engineers Association of Illinois (SEAOI) 3rd – Structural Engineers Association of Oregon (SEAO) In the past, the Summit has marked the transition of the NCSEA Board of Directors. During the NCSEA Board Meeting at this year’s Summit, the Board of Directors approved a change in NCSEA’s fiscal year and, with that, a new transition year for board members. The outgoing and incoming members were announced, but positions will not be active until January 2020. Williston "Bill" Warren IV, P.E., S.E., will complete his term as Past President and will retire from the board, and Stephanie Young, P.E., will step down at the end of this year. The incoming Board of Directors for 2020–2021 is as follows:

Team UCLA during construction of their 2-story playhouse at the Timber Strong Design Build Competition.

Susan Jorgensen, P.E., SECB, F.SEI, F.ASCE | President

Richard Boggs, P.E., SECB, LEED AP | Director

Emily Guglielmo, S.E., P.E. | Vice President

Eli B. Gottlieb, P.E. | Director

David Horos, P.E., S.E., LEED AP | Secretary

Ryan A. Kersting, S.E. | Director

Ed Quesenberry, S.E. | Treasurer

Jon Schmidt, P.E., SECB | Past President

Paul J. Rielly, P.E., S.E., SECB | Director Next year’s Structural Engineering Summit will be held November 3-6 at the MGM Grand in Las Vegas, NV. Information on attending and exhibiting will be available soon at www.ncsea.com.

NCSEA Webinars

January 9, 2020

Serviceability Design for the Practicing Engineer

February 4, 2020 SpeedCore: Rainier Square – A Project Case Study

Emily Guglielmo, S.E.

Brian Morgen

January 14, 2020 The Use of Geotechnical Reports by the Structural Engineer

February 20, 2020 Basics of Strut and Tie Modeling Royce Floyd, Ph.D., S.E.

Mark Gilligan, S.E.

January 30, 2020 Efficient Design of Long-Span Composite Steel Deck-Slabs Vitaliy Degtyarev, Ph.D., P.E., S.E.

Courses award 1.5 hours of continuing education after the completion of a quiz. Diamond Review approved in all 50 states. JANUARY 2020

SEI Update All the best from SEI/ASCE for a happy, healthy, and prosperous 2020! What’s on your to-do list for the New Year? Connect with your local SEI Chapter for technical/professional networking and learning. www.asce.org/SEILocal

You Are Invited

On behalf of the SEI St. Louis local planning committee, we are excited to invite you to Structures Congress, April 5-8 in St. Louis, where you will not only experience technical content offered by the preeminent event in structural engineering but be able to enjoy it in a downtown location which has experienced over eight billion dollars in recent and current construction. This construction includes work at the conference headquarters, St. Louis Union Station, which has recently been transformed into the St. Louis Aquarium along with a 200-foot observation wheel and several other familyfriendly amenities. Add in the new Major League Soccer stadium to be constructed across the street, the Ballpark Village development down the block, and the recently renovated Arch grounds, and it is an exciting time to visit St. Louis.

The Structures Congress program presents the latest in cutting edge engineering knowledge, including tracks with the latest on new standards, building and bridge design, forensic engineering, natural disasters, education, and professional practice. While you are taking in the conference, your family and friends can enjoy the world-class Saint Louis Zoo, City Museum, and the newly renovated Gateway Arch Grounds, among many other attractions the city has to offer. We hope to see you (and your family) in St. Louis for Structures Congress 2020, and look forward to sharing this magnificent city with you and over 1,200 other structural engineers at the premier event in structural engineering. Structures Congress Co-Chairs Heather Neri, P.E., S.E., M.ASCE, and Chad Schrand, P.E., S.E., F.SEI, M.ASCE

STRUCTURES CONGRESS 2020 St. Louis, Missouri

Closing Keynote:

April 5 –8

NEW Group Discount for 5+ full registrants from an organization

The Premier Event in Structural Engineering

Museum of the Future: Trends & Technologies Shaping the Future of Structural Engineering, with Christopher Wodzicki, P.E., BuroHappold Engineering Michael Gustafson, P.E., Autodesk

View full program of sessions, keynotes, and events and plan your schedule.

46 STRUCTURE magazine

For the best rate, register by February 4  www.structurescongress.org

News of the Structural Engineering Institute of ASCE

Leadership Changes ASCE/SEI Committee of Electrical Transmission Structures Wesley J. (Wes) Oliphant, P.E., has accepted an appointment as Chair of the ASCE/SEI Committee of Electrical Transmission Structures. He succeeds Mr. Ron Carrington, P.E., who will remain on the committee as the immediate past Chair of the Committee. Otto Lynch has also been appointed and accepted a new opportunity to serve as Vice-Chair during this new term. The important purpose of the ASCE/SEI Committee of Electrical Transmission Structures is to organize and foster development of continuing education programs, as well as develop important technical publications needed to continue to advance the available body of knowledge for Civil/Structural Engineers working in the electric utility industry. These include Engineering Standards, Manuals of Practice, Guides, Reports, White Papers, and more. Why is this work important? It has been said that the electric power grid in the USA is “the largest, most complex machine ever designed by man.” Few can argue that every critical infrastructure system essential to minimizing societal and economic disruption and allowing modern society to efficiently function is dependent on a reliable, cost-effective supply of electrical power. In supporting this critical infrastructure work, the ASCE/SEI Committee of Electrical Transmission Structures plays a vital role among the many Civil/Structural Engineers working in the Utility Industry while also supporting and overlapping with several other technical communities both inside and outside of ASCE/ SEI. The Committee also has an occasional role providing technical background information that may be needed for various inquiries relevant to the Industry and the Public. Whether new to this industry, or a long-termer, this is a great time to think about volunteering your time, enthusiasm, and experience to add to the body of knowledge on which this technical community depends. Within the next 12-18 months, several task committees within the Committee of Electrical Transmission Structures (CETS) will be nearing completion of their work. Opportunities will be available to join new task committee activities to continue technical

improvements and updates to these important efforts. New task committee activities are also in the works. So, please provide any suggestions and stay tuned when announcements will be made for signup for these opportunities. The giving of your knowledge and expertise through participation on a CETS Task Committee is one of the most satisfying and best ways to become more valuable to your organizations, all the while providing the industry with an essential technical foundation from which more reliable Transmission, Distribution, and Substation structures can be designed, constructed, and maintained. For more information contact either, Wes or Otto at the email address below. Wesley J. (Wes) Oliphant, P.E., is a Principal and the Chief Technical Officer of Exo Group, LLC, an infrastructure asset inspection and remediation firm near Houston, Texas. In 2010, Wes was the recipient ASCE/SEI’s Gene Wilhoite Award for his contributions and body of work related to the design of electric transmission line structures. He is a Life Member and Fellow of ASCE, and a charter member and Fellow of the SEI. He is also a member of the IEEE and a representative of that organization on Subcommittee 5 (Strengths & Loadings) of the National Electrical Safety Code (NESC). Wes can be reached at woliphant@exoinc.com. Otto J. Lynch, P.E., is President and CEO of Power Line Systems, the developers of the Industry Standard overhead line design software PLS-CADD based in Madison, Wisconsin. Otto is a Fellow of ASCE and a Fellow of the SEI. He was honored to receive ASCE/ SEI’s Gene Wilhoite Innovations in Transmission Engineering Award in 2012. He is a member of numerous ASCE, IEEE, and ANSI committees involving overhead line design and analysis. He is a voting member of the National Electrical Safety Code (NESC) Subcommittee 5 (Strengths & Loadings) as well as the Main Committee. Otto can be reached at otto@powline.com.

SEI Online

View Best of SEI Youtube Playlist, including:

• Vision for the Future of SE by SEI President Glenn Bell and conversations at Northeastern University • ASCE 7-16 Overview by Greg Soules made possible by SEI Futures Fund • 2019 SEI Annual meeting and Awards video https://bit.ly/2DLyl01

SEI News SEI on Twitter

Errata

Read the latest at www.asce.org/SEINews

Standards SEI on Facebook SEI Visit www.asce.org/SEIStandards Follow us: @SEIofASCE

to View ASCE 7 development cycle

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. J A N U A R Y 2 02 0

CASE in Point Did you know? CASE has tools and practice guidelines to help firms deal with a wide variety of business scenarios that structural engineering firms face daily. Whether your firm needs to establish a new Quality Assurance Program, update its risk management program, keep track of the skills young engineers are learning at each level of experience, or need a sample contract document – CASE has the tools you need! CASE has several tools available for firms to use for managing projects and training staff: Tool 3-2 Tool 3-4 Tool 3-5 Tool 4-1

Staffing and Revenue Projection Project Work Plan Templates Staffing Schedule Suite Status Report Template

Tool 4-2 Tool 4-5 Tool 4-6 Tool 5-5

Project Kick-off Meeting Agenda Project Communications Matrix Project Team Coordination Project Management Training Guide

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

CASE Practice Guidelines Currently Available CASE 962 – National Practice Guidelines for the Structural Engineer of Record

CASE 962-B – National Practice Guidelines for Specialty Structural Engineers

The purpose of this document is to give firms and their employees a guide for establishing Consulting Structural Engineering Services and to provide a basis for dealing with Clients, generally, and negotiating Contracts in particular. Since the Structural Engineer of Record (SER) is usually a member of a multi-discipline design team, this document describes the relationships that customarily exist between the SER and the other team members, especially the team leader. Further, this Guideline promotes an enhanced Quality of Professional Consulting Structural Engineering Services while also providing a basis for negotiating fair and reasonable compensation. Additionally, it provides a basis for Clients to better understand and determine the Scope of Services that the Structural Engineer of Record should be retained to provide.

This document has been prepared to supplement CASE’s National Practice Guidelines for the Structural Engineer of Record by defining the concept of a specialty structural engineer and the interrelation between the specialty structural engineer and the Structural Engineer of Record. CASE encourages the concept of one Structural Engineer of Record for an entire project. However, for many, if not most projects, there may be portions of the project that will be designed by different specialty structural engineers. The primary purpose of this document is to better define the relationships between the SER and the SSE and to outline the usual duties and responsibilities related to specific trades. This is done for the benefit of the owners, the PDP, the SER, the SSE, and the other members of the construction team. The goal is to help create positive coordination and cooperation among the various parties.

CASE 962-A – National Practice Guidelines for the Preparation of Structural Engineering Reports for Buildings

CASE 962-C – Guidelines for International Building CodeMandated Special Inspections

The purpose of this document is to provide the structural engineer a guide for not only conducting conditional surveys, code reviews, special purpose investigations, and related reports for buildings but includes descriptions of the services to aid with the client risk management communication issues. This Guideline is intended to promote and enhance the quality of engineering reports. A section of this Guideline deals specifically with outlines for various reports. While it is not intended to establish a specific format for reports, it is believed there may be certain minimal information that might be contained in a report. The Appendix includes disclaimer language, which identifies statements one might consider, clarifying the depth of responsibility accepted by the report writer.

The CASE Guidelines Committee has developed three distinct versions of the Guidelines for International Building Code-Mandated Special Inspections covering the following IBC Code Updates: 2012, 2015, 2018. The Guidelines describe the roles and responsibilities of the parties involved in special inspection and testing processes, how to prepare a special inspection and testing program, the necessary qualifications of the special inspectors, how to conduct the program, and who should pay for the special inspections and test program. The Appendix contains sample forms for specifying special inspections and tests, and sample letters to be filed with code-enforcement agencies after the program is completed.

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

Follow ACEC Coalitions on Twitter – @ACECCoalitions.

48 STRUCTURE magazine

News of the Council of American Structural Engineers Donate to the CASE Scholarship Fund! The ACEC Council of American Structural Engineers (CASE) is currently seeking contributions to help make the structural engineering scholarship program a success. The CASE scholarship, administered by the ACEC College of Fellows, is awarded to a student seeking a bachelor’s degree, at minimum, in an ABET-accredited engineering program. Since 2009, the CASE Scholarship program has given $32,000 to help engineering students pave their way to a bright future in structural engineering. We have all witnessed the stiff competition from other disciplines and professions eager to obtain the best and brightest young talent from a dwindling pool of engineering graduates. One way to enhance the ability of students to pursue their dreams to become professional engineers is to offer incentives in educational support. Your monetary support is vital in helping CASE and ACEC increase scholarships to those students who are the future of our industry. All donations toward the program may be eligible for a tax deduction, and you do not have to be an ACEC member to donate! Contact Heather Talbert at htalbert@acec.org to donate.

CASE Winter Member Meeting February 27-28, 2020

The 2020 CASE Winter Member Meeting is scheduled for February 27-28, 2020, in New Orleans. The agenda for the meeting includes:

Thursday – February 27 1:30 pm to 5:30 pm 6:15 pm to 7:30 pm

CASE ExCom Meeting CASE Project Speaker

Friday – February 28 7:30 am to 8:30 am 8:30 am to 10:00 pm 10:00 am to 10:30 am 10:30 am to 12:00 pm 12:00 pm to 1:15 pm 1:30 pm to 5:30 pm

Shared Breakfast CASE Roundtable – Stacy Bartoletti, Moderator Shared Morning Break Technology Panel Discussion – Kevin Peterson, Moderator Shared Lunch CASE Breakout Sessions

Registration can be found at www.acec.org/coalitions/upcoming-coalition-events. Questions? Contact Heather Talbert at htalbert@acec.org.

Two Essential Courses that Build Project Management Expertise Week by Week Successful, profitable project delivery starts with superior management. Project management training designed specifically for engineering firms? That’s a great start! Designed to help new project managers gain the skills and confidence to fit your firm’s unique internal systems and workflow specifications, this two-part training, Project Management 101 & 201, combines the scheduling ease of video learning and the immediacy and intensity of a live classroom – with little or no disruption to billable staff time. The first 9-module interactive class begins on January 13 and is limited to 25 registrants. 18+ PDHs are offered. Help your rising stars develop into confident, forward-thinking PMs with a flexible, step-by-step course that adapts to their current workload while motivating them to grow. For more information and to register, visit https://programs.acec.org/pm-2020.

JANUARY 2020

structural FORUM Embodied Carbon

Challenges and Opportunities for Structural Engineers By Donald Davies, P.E., S.E., and Kate Simonen, AIA, S.E.

rchitecture 2030 (architecture2030.org) reports that, between now and 2060, growth in the world’s population will require a doubling in the amount of building floorspace, equivalent to building an entire New York City every month for 40 years. Much of the carbon footprint of these new buildings will take the form of embodied carbon – the carbon emissions associated with building construction, including extracting, transporting, and manufacturing materials. As a result, owners, designers, engineers, and contractors are turning their attention to building materials and seeking information on these products so they can make more environmentally informed and smarter choices. Structural engineers have an essential role to play in understanding and reducing embodied carbon. By mass and carbon footprint,

‘‘

progress towards that vision. Much like the Architecture 2030 Challenge does for operational energy in buildings, this SE 2050 Challenge asks structural engineers to meet embodied carbon benchmarks and increasingly higher reduction targets in a race towards the most carbon-efficient buildings as we approach the year 2050. The SE 2050 Challenge includes guidelines on best practices and an opportunity for individuals and firms to sign on in support. As of September, twelve major structural engineering firms and over fifty individual engineers have signed in support of the challenge. The EC3 tool was created with input from a diverse coalition of more than 50 forward-

‘‘

The goal of the challenge is to inspire structural engineers to contribute towards the global vision of Zero Carbon buildings by 2050, and to provide measurements of progress towards that vision. structural materials are a dominant percentage of a building. Additionally, making structural materials, such as concrete, steel, or the harvesting and processing of wood, results in emissions. These emissions come from resource extraction, transportation, powering factories, and even the chemical reactions that take place during the manufacturing process. Structural engineers are experts at balancing performance criteria such as stiffness, strength, depth, and quantities. Adding in the assessment of embodied carbon is a natural fit for our profession. Two initiatives of the Carbon Leadership Forum provide opportunities for industry leadership in this area: the SE 2050 Challenge and the recently announced Embodied Carbon in Construction Calculator tool (EC3), a tool to help evaluate embodied carbon impacts. The Carbon Leadership Forum issued the Structural Engineers 2050 Challenge (SE 2050 Challenge), stating, “All structural engineers shall understand, reduce, and ultimately eliminate embodied carbon in their projects by 2050.” The goal of the challenge is to inspire structural engineers to contribute towards the global vision of Zero Carbon buildings by 2050, and to provide measurements of 50 STRUCTURE magazine

looking and innovative building industry leaders including owners, architects, engineers, contractors, manufacturers, and industry organizations. A public beta of the EC3 tool was launched November 19, 2019, and initially focuses on: • Structure: concrete, steel, timber • Enclosure: aluminum, glass, insulation • Finishes: carpet, ceiling tiles, gypsum wallboard The EC3 tool enables the building industry to access and view material carbon emissions data easily. It also enables making this data actionable for more informed decision-making at different parts of the design process, and most importantly, at the time that structural material suppliers are brought on board for a project’s construction. This is when double bottom-line decision making can best occur and be influential, when dollars are about to be committed. This free and open-source software will help users select materials based on embodied carbon. It will also help integrate material quantities and embodied carbon estimates together to create a whole building, embodied carbon “budget” to evaluate options during design, procurement, and construction. Users are able to

evaluate “cradle-to-gate” emissions, those that take place before and during manufacturing up to when the product leaves the “gate” of the factory. We all have a stake in improving how we move our industry toward a lower carbon footprint. Knowing project quantities, their embodied carbon impacts, and managing to a budget are best practice design principles and ways the structural engineer can help the client meet their project goals. Bringing both the SE2050 Challenge into your work and integrating the EC3 Tool into your project’s design, specification, and procurement efforts build upon these principles and provide opportunities for demonstrating structural engineering leadership. To learn more about embodied carbon, these initiatives, and the Carbon Leadership Forum, visit www.carbonleadershipforum.org. Learn more about the SE250 Challenge at https://bit.ly/2Lk7bS2. To register for access to the EC3 tool visit www.buildingtransparency.org.■ Donald Davies is President of Magnusson Klemencic Associates (MKA), headquartered in Seattle. He is a leader in promoting urban density and low carbon construction. He frequently lectures on Embodied Carbon Life Cycle Analysis and is a founding member of the Carbon Leadership Forum, an academic and industry collaboration hosted at the University of Washington. Kate Simonen is the Founding Director of the Carbon Leadership Forum at the University of Washington. Kate directs the research of the Carbon Leadership Forum and leads collaborative initiatives such as the Embodied Carbon Network, the Embodied Carbon in Construction Calculator (the EC3 tool), and the Structural Engineers 2050 Challenge.

JANUARY 2020

model.iesweb.com

Easy-to-use structural software. Get a free trial in 2 minutes. Promo code: SM20A