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1 I-275 BOB GRAHAM SUNSHINE SKYWAY BRIDGE 4 SENATOR WILLIAM 5 I-295 VARINA- FLORIDA DELAWARE V. ROTH, JR. BRIDGE VVIRGINIAIRGINIA ENON BRIDGE For over 42 years, FIGG companies have been nationally recognized in the bridge industry, creating sustainable designs that blend timeless artistry and engineering. Over 3 billion vehicles have relied on FIGG concrete cable-stayed bridges – over 460,000 vehicles cross every day! FIGG’s major precast concrete cable-stayed A Strong Safety Record bridges are known for: of Sustainability 35 miles of FIGG-designed bridges 1 Longest precast concrete cable-stayed span in the along the Gulf and Atlantic coasts Western Hemisphere when it opened in 1987. have stood strong through record 2 Texas’ first cable-stayed bridge. hurricanes without damage. 3 Largest bridge project in Ohio history when completed in 2007 and fi rst use of FIGG’s Recognizing Excellence innovative cable-stay cradle system™. 422 3 Presidential Awards DESIGN through the National 4 First major concrete cable-stayed bridge AWARDS Endowment for the Arts. in the Northeast. Only 5 of these awards ® 5 In 1993, this cable-stayed bridge Creating Bridges As Art were ever given by the withstood a direct tornado strike across President of the the center of its main span without damage. fi ggbridge.com for bridges. CONTENTS Features Alabama’s Largest Transportation Project 10 Dual 6500-ft-long precast concrete segmental bridges are just one element of the $750 million I-59/I-20 reconstruction 10 in the central business district of Birmingham, Ala. Harlem River Drive Bridge 16 Genesee Avenue Viaduct 20 Departments Editorial 2 Discussion—The Effects of Strand Debonding 3 Concrete Calendar 4 Perspective—Making the Case for Resilient Photo: Volkert Inc. Design 6 Perspective—Checking Our Work: Methods for Verifying Analyses of Structural Designs 8 16 Aesthetics Commentary 12 Concrete Bridge Technology—Shear Assessment of Complex Concrete Pier Caps 24 Concrete Bridge Technology—Epoxy-Coated Prestressing Steel Strand 28 Concrete Bridge Technology—Time-Saving Construction Techniques—I-59/I-20 Bridge Reconstruction 30 Concrete Bridge Technology—Investigating Existing Grouted Tendons 34 Photo: Defoe Corp. Concrete Bridge Technology—Guidelines for Inspection and Acceptance of Epoxy-Coated 20 Reinforcing Steel at the Jobsite 38 FHWA—InfoBridge: Easy Access to the National Bridge Inventory and Much More—Part 2 42 A Professor’s Perspective—Elevating the Role of Materials Science in Bridge Engineering Education 44 Concrete Connections 46 AASHTO LRFD—Structural Design Based on Strut-and-Tie Modeling 48 Perspective—Why Didn’t They Just

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ASPIRE Spring 2020 | 1 EDITORIAL

Editor-in-Chief Our Conversation Continues: Philotimo William N. Nickas • [email protected] Managing Technical Editor Dr. Reid W. Castrodale and the Future of Bridge Engineering Technical Editors Dr. Krista M. Brown Photo: PCI. William N. Nickas, Editor-in-Chief Angela Tremblay Program Manager n the last issue of ASPIRE® (Winter 2020), without a meaning,” behavioral expert John R. “Jack” Nancy Turner • [email protected] we started a difficult conversation about how Schafer, PhD, a professor in the Law Enforcement I Associate Editor our industry can best move forward after a tragic and Justice Administration Department of Western Thomas L. Klemens • [email protected] event. In that issue’s editorial, Gregg Freeby of the Illinois University wrote, “Philotimo encompasses American Segmental Bridge Institute and I shared the concepts of pride in self, pride in family, pride in Copy Editor our thoughts following the release of the final community, and doing the right thing. Philotimo is Elizabeth Nishiura National Transportation Safety Board (NTSB) report1 an all-encompassing concept that gives meaning to Layout Design on the 2018 Florida International University (FIU) life that stretches well beyond ourselves. Elder Paisiou Walter S. Furie pedestrian bridge collapse. In that same issue, Leon aptly defined philotimo as ‘that deep-seated awareness H. Grant, vice president of operations at Coreslab in the heart that motivates the good that a person Editorial Advisory Board Structures (Conn.) Inc., also offered a perspective does. A philotimos person is one who conceives and William N. Nickas, Precast/Prestressed Concrete Institute on how a bridge collapse more than a century enacts eagerly those things good.’”2 To my mind, Dr. Reid W. Castrodale, Castrodale ago inspired an oath of professionalism that every what the retired engineer expressed was a concern Engineering Consultants PC engineering student in Canada takes—and the that professionals in our industry today might lack Gregg Freeby, American Segmental Bridge profound influence that oath has had on his own philotimo. Institute career. Many of you have joined the conversation, and To move forward as a community and industry Pete Fosnough, Epoxy Interest Group of the your comments have given me a lot to think about. that exemplify the values of philotimo, we are going Concrete Reinforcing Steel Institute One person who wrote to me about the last issue of to need to grapple with the implications of mistakes Alpa Swinger, Portland Cement Association ASPIRE was a retired 87-year-old structural engineer we have made, share our points of view, and really Miroslav Vejvoda, Post-Tensioning Institute who wants to know why the bridge construction engage with the perspectives of others. During Cover community seems to have shifted away from the 2020 Transportation Research Board (TRB) Erection of the final segment in the traditional checks and balances. This commenter Construction of Bridges and Structures Committee / elevated bridge worries that we may no longer confidently assume meeting on January 13, 2020, Alan Fisher, chief replacement project in Birmingham, Ala. that (a) materials engineers collect and validate engineer for Cianbro Construction Company, asked Photo: Alabama Department of Transportation. the data used by the construction inspectors; the room full of engineers how many had read the Ad Sales (b) project engineers verify the inspection findings; thoughtful statement by the NTSB vice chairman Jim Oestmann (c) oversight bridge engineers validate field requests (dated October 28, 2019) about what went wrong— Phone: (847) 924-5497 from the owner’s project managers and contractors; and why—in the FIU bridge collapse. Only four Fax: (847) 389-6781 • [email protected] (d) project and field staff are empowered to engage people of the 30-plus in attendance had read the letter, the responsible bridge engineers when they have which could be a sign that we as a community may Reprints concerns; or (e) leadership will escalate issues as not be reckoning with the implications of that event lisa scacco • [email protected] needed. More broadly stated: Do we still cross-check and others like it for our profession. The statement Publisher each other’s data and calculations? And are we is republished in full in this issue (page 51). Precast/Prestressed Concrete Institute prepared to take a pause to do what is right? I encourage you to read it, reflect on it, and discuss it Bob Risser, President That final question reminds me of a concept I with your colleagues. Postmaster: Send address changes to ASPIRE, 200 W. Adams St., Suite 2100, Chicago, IL 60606. Standard postage paid at Chicago, IL, learned when being taught right from wrong in my Also on January 13, Steve DeWitt (formerly the and additional mailing offices. youth. My Greek family often spoke of philotimo. A North Carolina Department of Transportation ASPIRE (Vol. 14, No. 2), ISSN 1935-2093 is published quarterly by the rough English translation might be “love of honor” construction engineer) moderated the TRB panel Precast/Prestressed Concrete Institute. Copyright 2020 Precast/Prestressed Concrete Institute. or “friend of honor,” but neither phrase fully captures discussion on alternative delivery and contract risk If you have a suggestion for a project or topic to be considered for the meaning of the Greek word. In fact, I have sponsored by the TRB Standing Committee on Project ASPIRE, please send an email to [email protected] been told philotimo doesn’t have an exact English Delivery Methods. This discussion suggested to me counterpart. Trying to describe this “Greek word that the balance in public-private partnerships may

American Segmental Bridge Institute Epoxy Interest Group Expanded Shale Clay and Slate Institute

Portland Cement Association Post-Tensioning Institute Wire Reinforcement Institute

2 | ASPIRE Spring 2020 Attention Students & Faculty have shifted too far toward the private sector. This is yet another challenge that we as an industry will need to fold into our ongoing conversations about our future. Based on the comments we received about the editorial and Leon’s perspective in the Winter 2020 issue, we have decided to dedicate space Academic Offer: Chapters on Load, Concrete, and Steel of AASHTO LRFD Academic Version in each issue of ASPIRE to broader engineering topics. In this issue, for Bridge Design Includes Sections 3, 5, and 6 the LRFD Design Specifications, 8th Edition – $60.00 example, Gregg and I offer a perspective on the human dynamics of Specifications closing a bridge or the roadway under a bridge (page 50). AASHTO LRFD Bridge Designs Specifications The bridge community needs to revisit what the NTSB vice chairman Sections 3, 5, and 6: Academic This publication covers loads and load factors and steel and concrete structures for the 8th Edition calls the “safety management system” that should prevent catastrophes. September 2017 purpose of facilitating education in this area. These sections provide steel and concrete We must work to never allow human habits and the time pressures of bridge design requirements to ensure safe, economical bridge information that will assist project delivery to disrupt our bridge engineer’s philotimo. Publication Code: NCBC-8 students growing into future engineers. https://store.transportation/org, search for pub code NCBC-8-UL References FREE Resource for Teaching Concrete Bridge Design 1. National Transportation Safety Board (NTSB). 2019. Pedestrian Bridge Collapse Over SW 8th Street, Miami, Florida, March 15, PCI Bridge Design Manual e-book This comprehensive design manual includes both preliminary and final design 2018. Highway Accident Report NTSB/HAR-19/02 PB2019-101363. information for standard girders and most precast and precast, prestressed concrete https://www.ntsb.gov/investigations/AccidentReports/Reports/ products and systems used for transportation structures. It contains background HAR1902.pdf. information, strategies for economy, fabrication techniques, evaluation of loads, load tables, design theory, and numerous complete design examples. It is designed to 2. Schafer, J.R. 2015 (August 15). “Philotimo: A Greek Word Without explain and amplify the application of LRFD Bridge Design Specifications, 7th edition. Meaning but Very Meaningful” Psychology Today [blog post]. The PCI Bridge Design Manual update is underway. https://www.psychologytoday.com/us/blog/let-their-words-do-the- www.pci.org/MNL-133-11

talking/201508/philotimo-greek-word-without-meaning-very- E-books are fully searchable and references are hyperlinked to online resources. meaningful.

DISCUSSION The Effects of Strand Debonding Author’s response This is a discussion of “The Effects of Strand Debonding” by Dr. Oguzhan The author wishes to thank the discussers for their thoughtful comments. The Bayrak published in the Winter 2020 issue of ASPIRE magazine (pp. 52–53). The points raised by the discussers are addressed in the same order. explanations given by Dr. Bayrak are clear and welcomed. We would like to bring 1. The unnumbered equation in the subject article was provided for the purposes

attention to two items: of clarifying the lower bound for Equation (5.7.3.5-2). The Vs value used in

1. In the paragraph following Eq. (5.7.3.5-2), Dr. Bayrak explains that stirrups this equation cannot be greater than (Vu/φv). Therefore, the interpretation of

in excess of those required to correspond to Vs = (Vu/φv) should not be used the discussers is correct: Adding stirrups can only reduce the demand on the

to artificially reduce the amount of longitudinal tie steel required. This is in longitudinal tie up to a point. Put simply, the definition provided for Vs after accordance with the AASHTO LRFD specifications provision and should be Equation (5.7.3.5-1) in the AASHTO LRFD specifications reads “shear resistance followed. However, the equation given below the paragraph and described provided by transverse reinforcement at the section under investigation as

as the minimum value for the longitudinal tie force can be misleading and given by Eq. 5.7.3.3-4, except Vs shall not be taken as greater than Vu/φv

its use should be clarified. We recommend clarifying that the minimum (kip).” This limit placed on Vs should be taken into account when using requirement for longitudinal tie reinforcement should be the larger of Eq. Equation (5.7.3.5-2). (5.7.3.5-2) and the following equation given in the article: 2. If positive anchorage is provided to debonded strands by extending them into diaphragms and bending them up or by using strand chucks, at the point ⎛ Vu ⎞ A f + A f ≥ 0.5 −V cotθ where this positive anchorage is provided strand can be adequately developed ps ps s y ⎜ φ p ⎟ ⎝ v ⎠ or assumed to be “fixed.” Under additional loads, it is true that the “fixed” or 2. The discussion in the article, and also in the AASHTO LRFD specifications, “positively anchored” debonded strand will pick up some additional strain, indicates that debonded strands may not be used as part of the longitudinal tie and associated stress. This creates an interesting distribution of stress along the reinforcement. We only partially agree with this statement. It is only valid when length of a debonded strand. Additional stresses experienced by the debonded the debonded strands are not anchored after detensioning. Debonded strands portion of a strand anchored at its end due to additional gravity loads acting can be anchored by embedding them into a cast-in-place diaphragm, which on the beam will add to a “zero stress state” and not the effective prestress is a common detail in much of the United States for beams made continuous at the service limit state. So, with this important subtlety acknowledged, the for live load. They can also be anchored by other means, such as using strand author agrees with the discussers’ point on this item. Finally, simply supported chucks and secondary end blocks. If debonded strands are anchored, it would be beams made continuous for live load creates a boundary condition that starts reasonable to assume that they contribute to the longitudinal tie resistance at the deviating from a simply supported beam end such as that depicted in Figure strength limit state. C5.7.3.5-1, where there is no moment reaction at the support.

Dr. Amgad Girgis, Micheal Asaad, and Dr. Maher Tadros Dr. Oguzhan Bayrak e.construct USA LLC University of Texas at Austin Omaha, Nebraska

ASPIRE Spring 2020 | 3 CONCRETE CALENDAR 2020-2021 CONTRIBUTING AUTHORS For links to websites, email addresses, or telephone numbers for these events, go to www.aspirebridge.org and select the Events tab. All dates are subject to change. Dr. Oguzhan Bayrak is a professor at the University of Texas at Austin. Bayrak April 6, 2020 September 13–16, 2020 was inducted into the ASBI Grouting Certification AREMA Annual Conference university’s Academy of Training Course Hilton Anatole Distinguished Teachers in J.J. Pickle Research Campus , Tex. 2014. Austin, Tex. September 23–26, 2020 Gregg A. Freeby is April 22–24, 2020 PCI Committee Days the executive director of DBIA Design-Build for Transportation Loews Chicago O’Hare Hotel the American Segmental & Aviation Conference Rosemont, Ill. Bridge Institute and Hilton Anatole president of the Infrastruc- Dallas, Tex. October 6–9, 2020 ture Advancement PTI Committee Days Institute. April 22–24, 2020 JW Marriott Cancun PTI Level 1 & 2 Multistrand and Cancun, Mexico Grouted PT Specialist Workshop Frederick Gottemoeller is Dallas, Tex. October 25–29, 2020 an engineer and architect ACI Fall 2020 Convention who specializes in the April 25, 2020 Raleigh Convention Center & Raleigh aesthetic aspects of bridges PTI Level 1 & 2 Multistrand and Marriott and highways. He is the Grouted PT Inspector Workshop Raleigh, N.C. author of Bridgescape. Dallas, Tex. October 26–28, 2020 May 3–6, 2020 ASBI 32nd Annual Convention Dr. Thomas Murphy is PTI 2020 Convention & Expo and Committee Meetings vice president, chief Hilton Miami Downtown Hyatt Regency Austin technical officer, and Miami, Fla. Austin, Tex. chairman of Modjeski and Masters Inc. May 27–29, 2020 January 24–28, 2021 PTI Level 1 & 2 Multistrand and 100th Transportation Research Grouted PT Specialist Workshop Board Annual Meeting Gainesville, Fla. Walter E. Washington Convention Dr. Jean A. Nehme is Center team leader of FHWA’s May 30, 2020 Washington, D.C. Long-Term Infrastructure PTI Level 1 & 2 Multistrand and Performance programs and Grouted PT Inspector Workshop February 4–7, 2021 oversees the Long-Term Gainesville, Fla. World of Concrete Pavement Performance and Las Vegas Convention Center Long-Term Bridge June 1–4, 2020 Las Vegas, Nev. Performance programs. AASHTO Committee on Bridges and Structures Annual Meeting February 23–27, 2021 Dr. Kyle A. Riding is an Branson Convention Center PCI Convention with the Precast associate professor of civil Branson, Mo. Show and National Bridge and coastal engineering at Convention the University of Florida. June 8–11, 2020 Ernest N. Morial Convention Center International Bridge Conference , La. David L. Lawrence Convention Center Pittsburgh, Pa. March 28–April 1, 2021 ACI Spring 2021 Convention Miroslav F. Vejvoda is the August 2–6, 2020 Hilton & Marriott Baltimore managing director of AASHTO Committee on Materials Baltimore, Md. engineering and professional and Pavements Annual Meeting development at the InterContinental Hotel Miami April 18–21, 2021 Post-Tensioning Institute Miami, Fla. PTI 2021 Convention & Expo and the editor-in-chief of Westin Indianapolis the PTI Journal. Indianapolis, Ind.

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by Evan Reis, U.S. Resiliency Council

My hometown, Half Moon Bay, Calif., is an unassuming and quaint hamlet south of San Francisco. People know it as the center of Prohibition era “rum running” on the northern California coast, and it claims to be the pumpkin capital of the world. Although many tourists and residents cross the Pilarcitos Creek Bridge as they drive or walk to Half Moon Bay’s charming downtown, they likely do not comprehend the structure’s historical significance. Built in 1900, it was the first reinforced concrete bridge erected in San Mateo County—and a very early attempt at prestressing, too. Functioning continuously for more than 100 years, the bridge remained in operation after the 1906 earthquake and following several flood events in which the creek overflowed its banks. To me, the bridge defines resilience! Measuring Resilience Built in 1900, the Pilarcitos Creek Bridge in Half Moon Bay, Calif., was the first reinforced concrete bridge erected in San Mateo County. Photo: Burnell G. West. When we think of what makes a community resilient after a natural or bridge collapses caused by flooding sustainability is about more than just disaster, the measure is how quickly and landslides in Cedar Rapids, Iowa, eliminating carbon. the services that a city provides to its in 2009, and Big Sur, Calif., in 2017, residents (housing, employment, goods to see that the performance of bridges As the USRC has developed its and services, emergency care, etc.) is an essential link in the chain that building rating systems for describing can be restored. Three components of allows a community to function during the expected impacts of earthquakes, the built environment are essential to and after a natural or human-caused hurricanes, wildfires, and floods on a recovery: the buildings in which these disaster (see Fig. 1). building, it has used leading engineering services are provided, the utilities that and scientific research on performance- allow these buildings to function, and USRC Mission and Goals based design to quantify performance the transportation infrastructure that The U.S. Resiliency Council (USRC) not only in terms of safety but also in permits people to get to and from was founded in 2011 as a nonprofit terms of repair costs and recovery time. places where they live, work, and organization with the goal of “improving The latter two metrics allow owners, conduct business. community resilience, one building at a government agencies, lenders, and time.” Its mission, however, is broader insurers to calculate the return on Transportation infrastructure (roads, than just looking at building structures. investment of building more resiliently. bridges, airports, and railways) is often Resiliency must be the focus of every taken for granted. However, when component of community infrastructure, The USRC is aware that considerable the 2010 and 2011 earthquakes hit including transportation. As we have research on the performance of bridge Christchurch, New Zealand, residents seen in disasters within the United States structures has been done and is ongoing. throughout the earthquake-affected just since , a mere 15 Quantifying the long-term performance region suffered as transportation years ago, true sustainability cannot be of bridges will help define the benefits of routes were shut down because of measured only by our impact on the building more resiliently. These benefits infrastructure damage. In the United environment; we must also consider the can be turned into incentives to cities States, we only have to look to the impact the environment has on us. In and builders to use concrete technologies River Bridge other words, resilience is different than and other means to create durable, high- collapse in Minneapolis, Minn., in 2007, and complements green design, and performing systems.

6 | ASPIRE Spring 2020 Announcing The First Edition of Natural Residential Healthcare resources Report Building stock recovery performance

Critical Recommended Practice infrastructure for Lateral Stability of EmergEmergencyency Precast, Prestressed Concrete Bridge Girders FEMA services Transportation recovery functionalityfunctionality planning Financial recovery CB-02-16-E CCommunityommunity Business cohesivenessohesiveness Community recovery Emergency insurance planning ratings First Edition © USRC, 2018

This is a new comprehensive method- Figure 1. The central importance of transportation in resiliency. Figure: Evan Reis, U.S. ology to analyze the lateral stability of Resiliency Council (www.usrc.org). long slender bridge girders. Technol- ogy has enabled the manufacture of I worked as a consultant on a project based design can be employed by the increasingly longer girders. Slender for the renovation of a major freeway bridge industry to promote the benefits girders present a lateral stability con- corridor in southern California that of precast/prestressed concrete design. cern. Each stage of a girder’s transi- included the structural risk modeling tion from the casting bed to its final of more than a dozen overpasses and Conclusion location in the bridge is considered. bridges. My efforts were used by the As a structural engineer, I know that the These conditions include when han- contractor to obtain proper construction people who work or live in the buildings dling from the top with embedded or term insurance against the potential for I design are unlikely to reflect on how attached devices and supported from earthquakes or flooding. The evaluation the structures are constructed to keep below during storage, transit, or in var- of resilience of the many concrete bridge them safe and protect their livelihoods. ious conditions on the bridge during structures had a direct impact on the Bridge engineers also understand that construction. These recommendations amount of insurance that the builder was their work, although essential, is not are the result of ground-breaking re- required to obtain, a cost shared in part widely appreciated. Most of the folks search conducted by Robert Mast in the by the transportation authority. This was that visit Half Moon Bay or do their 1990s. In 2007, the PCI Committee on a “concrete” example (forgive the pun) grocery shopping in town and cross Bridges clearly saw the need to address of how the resilience and durability of a the Pilarcitos Creek Bridge probably girder stability. They selected a spe- specific structural system translated into do not think about the engineers who cialized team to develop these recom- cost savings. designed it. And that’s okay. But those mendations. The producer members of of us responsible for making sure the team have contributed substantial The USRC encourages the bridge buildings don’t collapse in an earthquake practical field experience. Together and transportation industries to and bridges aren’t swept away in a with a large number of designer prac- invest in research that quantifies the flood must consider the long-term titioners, the team has developed an performance of bridge structures performance of structures and weigh the industry consensus recommended subject to natural hazards. It is the costs and benefits of resilient design. practice that provides methods to cal- first necessary step to make the case culate the factors of safety during each that using resilient materials such as of several stages of a girder’s life. This is concrete is a worthwhile investment EDITOR’S NOTE a must-have publication for all stake- that more than pays for itself in the holders in bridge design, fabrication, short and long term by reducing the See the Perspective article on and construction. social and economic impacts of natural quantitative assessments of hazards on communities. The USRC resilience and sustainability in the This ePublication is available on ® would like to expand its rating system Spring 2019 Issue of ASPIRE . line at www.pci.org/epubs to include infrastructure and to make ______the strongest case for resilience as an essential component of sustainable Evan Reis is a structural engineer licensed design. In future articles, I will examine in California and executive director of the how the detailed process of resilience- U.S. Resiliency Council. PERSPECTIVE Checking Our Work: Methods for Verifying Analyses of Structural Designs

by Dr. Thomas Murphy, Modjeski and Masters Inc.

For designers, there is often a strong analytical model (see photo). attempt to resolve any differences in incentive to keep things simple. Fortunately, our profession now has the results. There will almost always Construction cost, design effort the tools to analyze and design virtually be differences between any two required, and the possibility of any structural system, no matter how analyses due to differing assumptions unforeseen problems push us to choose complex. The challenge is making and approaches, but this does not uncomplicated, easily understandable sure the analysis method and the necessarily mean that one analysis is structural models for our designs. There corresponding results are adequately incorrect, or that a design based on are, however, other factors influencing checked. This can be a daunting task, the results of either would be deficient. design that can lead to more complex but there are methods that engineers The challenge for the designer in this structural systems and behaviors. can use to give them confidence that situation is twofold: ensuring that the Aesthetics, geometric constraints, and the complex behavior has been correctly base assumptions made in both analyses the need to minimize material quantities captured in the results of the analysis. are valid (that is, the same error was not are just some of the factors that can made in both analyses), and resolving lead designers to select systems that The most direct approach is to perform any differences in results until they are are more difficult to analyze and more an independent analysis and compare acceptably small. challenging to understand. The Bronco the results of the analyses. This can be Bridge in Denver, Colo., is an example time-consuming because you essentially The method of comparing analyses of a structure that required a complex perform the analysis twice and then will vary depending on the details of

Designed to optimize the use of precast concrete, the Bronco Bridge in Denver, Colo., features a totally precast concrete rigid frame and is one example of a structural design that required a complex analytical model. Photo: Modjeski and Masters Inc. the models (see “Element Modeling Moments and Reactions for Rectangular Options” for more information). If only Plates,3 or texts such as Roark’s Formulas Element Modeling Options beam- and frame-type elements are for Stress and Strain.4 Concepts such as used, a comparison of deflections and the elastic center method, historically Engineers have many different choices key forces will likely suffice. However, used to simplify hand calculation of for how to model a structure. Simpler if shell or solid elements are included, frames and arches, and the associated structures can be modeled using beam or there is typically an additional step to column analogy method of determining frame elements, which idealize behavior as go from the model output, typically the location of the elastic center can one-way bending, whereas more complex stresses, to design values, typically still prove extremely useful in fashioning structures require elements that can forces and moments, with many simpler models of complex behavior capture bending in two directions, such as opportunities for errors to creep into that can verify the solutions derived plate elements. Curved plate elements are the process. A comparison of the final, from far more involved and complicated sometimes referred to as shells. integrated force and moment values numerical models. would then be in order. There are few references that a bridge one hand, the engineers with the When performing an independent designer can consult to address the least experience may have the most analysis, it is sometimes useful to issue of verification of the results of expertise with finite element software intentionally vary the analytical complex models. One exception to packages and complex engineering approach from the base analysis as this is the recently published Federal issues. On the other hand, the an additional check. For example, if Highway Administration Manual for engineers with the least numerical the base analysis uses shell or solid Refined Analysis in Bridge Design and modeling expertise may be the elements, an independent analysis Evaluation.5 While primarily focused most familiar with the shortcuts and that uses beam elements can provide on typical structure types, the manual approximate approaches that can be so further assurances that the overall provides some guidance on the valuable in providing a critical check on results are reasonable, even if the verification and validation of refined analytical results. localized results may be less accurate analyses, along with examples of how due to the lower-order elements in the relatively complex models were verified References independent analysis. by various methods. 1. Pucher, A. 1977. Einflussfelder elastischer Platten/Influence Surfaces When time and budget allow, the of Elastic Plates, 5th ed. Vienna, independent replication of results by a The bridge design Austria: SpringerVerlag Wien. separate analysis is probably the best profession consists of 2. Homberg, H., and W. Ropers. 1965. practice. However, it is not always Fahrbahnplatten mit verändlicher appropriate, and other methods can multiple engineering Dicke,1st ed. Berlin, Germany: be successfully and more efficiently generations with widely Springer-Verlag Berlin Heidelberg applied. GmbH. differing attitudes 3. Moody, W.T. 1990. Moments Moving away from a full replication of toward analysis. and Reactions for Rectangular the analysis, approximate methods of Plates. Engineering Monograph analysis can be used to provide what Currently, the bridge design profession No. 27. Washington, DC: U.S. is often termed a “sanity check” on consists of multiple engineering Department of the Interior Bureau of higher-order analytical results. Here, generations with widely differing Reclamation. https://www.usbr.gov/ what is desired is a general check on the attitudes toward analysis. In a design tsc/techreferences/hydraulics_lab/ overall results without an independent office today, you might encounter pubs/EM/EM27.pdf. evaluation of detailed results. In these engineers for whom a finite element 4. Young, W., G. Budynas, and A. cases, designers can take advantage of analysis is considered something Sadegh. 2012. Roark’s Formulas for the rich library of approximate analysis exotic, only to be used in the most Stress and Strain, 8th ed. New York, techniques that were developed before extreme circumstances, as well as NY: McGraw-Hill. the advent of the digital tools we heavily engineers who would create a shell 5. Adams, A., N. Galindez, T. Hopper, rely on today. There are many and varied element model to find the axial load in T. Murphy, P. Ritchie, V. Storlie, J. examples of these techniques, including a member of a statically determinate Weisman. 2019. Manual for Pucher1 and Homberg2 charts used to truss. When developing an approach Refined Analysis in Bridge Design determine moments in box-girder top for the verification and validation of and Evaluation. Federal Highway flanges created by local loads and similar analytical models of complex structural Administration Report FHWA- tables of moments in plates for a variety behavior, it is often important to HIF-18-046. McLean, VA: FHWA. of fixity conditions from old U.S. Bureau include multiple designers with a mix https://www.fhwa.dot.gov/bridge/ of Reclamation publications, such as of engineering backgrounds. On the pubs/hif18046.pdf.

ASPIRE Spring 2020 | 9 PROJECT Alabama’s Largest Transportation Project Renews Birmingham’s CentralBusinessDistricCentral Business Districtt

by Lloyd Pitts, Volkert Inc., Eric Johnson, Corven Engineering Inc., and William (Tim) Colquett, AAlabama Department of Transportation

Aerial view of the Phase III segmental bridge site, shown here in magenta. Five miles of segmental box girders with a total of 2316 segments were erected in only 217 days, and the bridges reopened to traffic ahead of schedule. Figure: Volkert Inc. For nearly 50 years, millions of motorists elevated structures were designed for or no shoulders. Three of these ramps have traveled the Interstate 59/,000 vehicles per day. Current traffic were considered outdated and forced 20 (I-59/I-20) from Meridian, Miss., to exceeds 160,000 vehicles per day, and motorists to make unanticipated and Birmingham, Ala. Once the interstates traffic forecasting suggests that this unsafe lane crossings, sometimes reach Birmingham, a city with a route may be subject to over 225,000 resulting in accidents that forced traffic legacy built on steel and iron, they are vehicles per day by 2035. slowdowns or stoppages (see the State now supported by elevated concrete article on Alabama in the Spring 2019 structures over the downtown area. As a result of the age and heavy use of issue of ASPIRE®). the facility, the bridge decks had begun Serving Birmingham’s central business to deteriorate, often requiring costly Rebuilding the Bridges district (CBD), this artery has the repairs that resulted in lane closures. Considering the safety concerns, traffic highest rate of traffic flow in the state The original bridges featured left-lane congestion, and maintenance issues, the of Alabama. Built in 1973, the original entrance and exit ramps, with minimal Alabama Department of Transportation

INTERSTATE 59/INTERSTATE 20 BIRMINGHAM CENTRAL BUSINESS DISTRICT profile BRIDGES / BIRMINGHAM, ALABAMA BRIDGE DESIGN ENGINEERS: Volkert Inc., Mobile, Ala. (prime consultant, substructure and foundations); Corven Engineering Inc., Tallahassee, Fla. (segmental superstructure) CONTRACTOR’S CONSTRUCTION ENGINEERS: McNary-Bergeron & Associates, Broomfield, Colo.; Infrastructure Consulting & Engineering, Columbia, S.C. PRIME CONTRACTORS: Johnson Bros. Corp., a Southland Company, and Oscar Renda Contracting Inc. Joint Venture, Roanoke, Tex.

10 | ASPIRE Spring 2020 (ALDOT) deemed this infrastructure functionally obsolete and determined that immediate action was required. Multiple options were considered, including burying the interstates, rerouting the corridor, or simply redecking the existing bridges. Some of these options were projected to take 20 years and billions of dollars to complete, and yet they would not adequately solve the corridor’s problems.

ALDOT determined that the best course of action would be to replace some CBD bridges and widen others, with the interstates completely shut down during construction. Compared to long-term construction phasing, this plan required the shortest turnaround time and thus would cause the least disruption to the traveling public. A typical span after erection of the four lines of box-girder segments. A longitudinal ALDOT engaged a single consulting firm closure pour about 3 ft 6 in. in width was used to join the segments for each of the two team to provide the engineering design bridges. The completed eastbound and westbound structures are separated by a 6 in. and construction inspection services gap. Photo: Volkert Inc. for the $710 million megaproject. The project, with 36 bridge sites for either new bridges or widening of existing bridges, was separated into four bid packages—Phases A, I, II, and III. The concrete bridges for the project totaled 14.3 miles of precast, prestressed concrete girders and 5 miles of segmental box girders. The $440 million Phase III project included the segmental box girder bridges.

Work on the Phase III CBD bridge replacement project was performed in concert with many other improvements in the CBD region to improve traffic movements, replace or modernize existing facilities, and revitalize the downtown experience for the citizens and visitors of Birmingham. Substructure Challenges and Solutions To minimize the impact of the project on downtown Birmingham, a diverse Falsework towers were used to support segments during erection. Photo: Volkert Inc.

ALABAMA DEPARTMENT OF TRANSPORTATION, OWNER

POST-TENSIONING CONTRACTOR: Structural Technologies, Columbia, Md. CASTING MACHINES AND ERECTION SYSTEM: Structural Technologies, Columbia, Md. BRIDGE DESCRIPTION: 6500-ft-long precast concrete segmental box-girder bridges with 2316 segments total STRUCTURAL COMPONENTS: Five miles of precast concrete segmental box girders, 172 spans, and 2316 segments, precast concrete piers SEGMENTAL BRIDGE CONSTRUCTION COST: $195 million

ASPIRE Spring 2020 | 11 business hub with a bustling food and art scene, only 14 months of full interstate closure were allowed for construction; also, access to certain CBD public venues was required throughout the project. Additional challenges included limited right-of-way, utility conflicts, varying geotechnical conditions along the project corridor, and limited vertical clearance under the existing structures to perform foundation work before the interstates were closed.

Aesthetics were a priority for ALDOT, so the design team decided to use single- column piers under each segmental girder line. The piers are accented with vertical fluted lines in the near and far faces, and the pier caps flare out at the top to complement the sloping lines of the segmental girders. The contractor elected to precast the piers as two separate pieces, columns and caps, for faster construction. The reinforcement for the pier sections was made continuous with grouted couplers. This allowed the piers to be constructed efficiently once the demolition and removal operations for the existing structures were completed.

The first two-thirds of the project had A precast concrete pier cap with fluted aesthetic detailing is erected on a column sound rock for foundation design. element. Segments are connected using grouted couplers. Photo: Volkert Inc. Near 22nd Street North, there was a

thinness of the Birmingham piers keeps the long views open, and the “room” inviting. The piers’ only architectural details are the closely spaced vertical grooves that visually reinforce their thin appearance. Faced with a request for a viaduct that would “revi- at once, so that it can be organized for uses The concrete box girders also keep the longitudinal talize the downtown experience for the citizens beyond parking, such as farmers markets and art views simple. The sight lines are not blocked by and visitors of Birmingham,” the project’s design- fairs, and so that there are few opportunities for transverse pier caps, and there are no braces or ers thought creatively about the appearance of concealment. The concrete box girders contribute diaphragms to catch the eye. The wide spacing the space below the structure. Such spaces are to this goal by minimizing the number of pier between box webs means that light can reach often dark and uninviting, filled with haphazardly legs both longitudinally (by allowing relatively to the underside of the deck slab, and the whole parked cars and drifting waste paper, depressing long spans) and transversely (by requiring only underside of the bridge stays bright. Finally, a the activities around them. Improving the appear- four pier legs per pier line). The thin piers also reflective white coating on the underside of the ance of such a space requires conceiving of it as avoid a problem that sometimes results when structure keeps light bouncing around the “room,” a huge outdoor “room,” with the superstructure designers are asked to provide a structure with meaning the space is brighter during the day and as its ceiling and the bridge piers articulating the architectural grandeur: They attempt to do so easier to light at night. room-like impression. with physical mass and “architectural” detail. The result can be an agglomeration of massive It is heartening to see this high level of aesthetic The attractiveness of this “room” depends, first piers with nonstructural decorative details. Thus, quality achieved within the discipline of acceler- of all, on long, uninterrupted sight lines in both an individual looking along the bridge sees ated bridge construction. Birmingham has met its the transverse and longitudinal directions, so the piers line up one behind the other, visually schedule while achieving an “aesthetically pleas- that the whole area can be seen and understood filling the “room” with concrete. In contrast, the ing area for public events”—all at the same time.

12 | ASPIRE Spring 2020 Erection of a precast concrete box-girder segment on temporary support towers for the first span of the central business district bridges. Photo: Volkert Inc. geological shift, and the last one-third concrete segmental superstructure for into three groups: 33 ft 6 in. wide for of the project had karst limestone Phase III of the project. the four-lane configuration; 39 ft 6 in. conditions. In areas with sound rock, wide for the five-lane configuration; the footings used either drilled shafts Because of the limited right-of-way and 45 ft 6 in. wide for the six-lane or micropiles. In karst conditions, the and the need to preserve existing configuration. Individual box girders were foundations used steel H-piles with buildings along the project corridor, the joined with a longitudinal deck closure driving shoes. The span layouts for the replacement bridges were built within the strip approximately 3 ft 6 in. wide to make project considered existing foundation same footprint as the original bridges. up the total deck width for one bridge. To locations and minimized conflicts for the The eastbound and westbound structures facilitate the precasting operations, all box new substructure locations. are each approximately 6500 ft in length girders used a constant core dimension and are separated by a 6 in. gap. with only the wing lengths varying. Prior to the closure of I-59/I-20, the contractor built as many of the Each bridge comprises twin precast The top slab of each box-girder segment footings as possible. Because of the concrete segmental box girders, and every was transversely post-tensioned with limited vertical clearance, low-overhead mainline bridge includes entrance and four-strand tendons that anchor at equipment was used to install the drilled exit ramps. Along the transition regions the end of each segment wing. To shafts, micropiles, and steel H-piles. The for these ramps, the mainline structures accommodate the variation in the width footings were then covered with fill to comprise three segmental box girders. of the top slab, two transverse post- protect them during the demolition of tensioning spacings were used: four the existing overhead structures. With a total deck area of over 1 million tendons per segment for box-girder square feet, the bridges are composed widths of 39 ft 6 in. or less, and five Creating the Superstructure of 172 spans, with nominal lengths of tendons per segment for box-girder When ALDOT decided to allow 165 ft. There are 2316 precast concrete widths greater than 39 ft 6 in. I-59/I-20 to be closed for 14 months segments, with typical segment lengths of construction, the designers had to between 11 ft 6 in. and 12 ft 6 in. The The longitudinal post-tensioning in each find a design solution that could be overall box-girder segment depth is box-girder span consists of external achieved within this tight schedule. The 9 ft, with an additional ½ in. of draped tendons. Eight permanent contractor was allowed to fully close sacrificial deck surface that was milled tendons (four per web) were anchored the interstates for 14 months without to achieve a smooth deck surface after at the ends of the spans in the pier penalty, and would be awarded bonuses segment erection. segment or expansion-joint segment of $250,000 per day for finishing early, diaphragms. The longitudinal post- with total bonuses capped at $15 The lane configurations for the bridges tensioning tendon sizes vary depending million. However, at the end of the vary along the project corridor from four on demand, with hardware sized to 14-month window, penalties would be to six lanes, resulting in a variation of out- accommodate a maximum of 22 strands assessed at a rate of $250,000 per day, to-out bridge width. To accommodate per tendon. Wider sections with longer with no cap. These time constraints led this variation in overall bridge width, the span lengths feature one additional the design team to choose a precast individual box girders were categorized 12-strand tendon per web, anchored

ASPIRE Spring 2020 | 13 The area beneath the completed mainline spans after painting. City officials intend to use this area for public events. Photo: Johnson Bros. at the deviation diaphragms. Each span construction site for placement. This The Finish Line also includes hardware to accommodate expedited the construction process The challenges and time constraints two 12-strand future post-tensioning compared to the traditional methods of this project proved how beneficial tendons. Project-specific specifications for building bridges. By the time the precast concrete segmental bridge for the installation and grouting of interstates were closed to traffic, design and construction can be. The the post-tensioning tendons included approximately 1000 of the 2316 I-59/I-20 CBD bridges reopened to many aspects of the PTI/ASBI M50.3-12 segments were already cast and ready traffic ahead of schedule on January 17, Guide Specification for Grouted Post- for erection. 2020, with a closure of only 12 months Tensioning.1 (A newer version of this compared with the 14 months allowed specification is now available—see the Segment Erection in the contract. Concrete Bridge Technology article in The original design assumed a traditional the Summer 2019 issue of ASPIRE.) span-by-span erection method, with all Reference precast concrete segments supported 1. Post-Tensioning Institute (PTI) Advantages of the Precast by longitudinal erection trusses. The and American Segmental Bridge Concrete Segmental Design contractor elected to use a unique Institute (ASBI). 2012. PTI/ASBI The precast concrete segmental bridge technique, for which the design was M50.3-12: Guide Specification design was chosen for several reasons verified, erecting each precast concrete for Grouted Post-Tensioning. stemming from ALDOT’s decision to segment within a span on individual Farmington Hills, MI: PTI. completely shut down I-59/I-20 during shoring towers. This erection technique ______construction. In particular, the selected meant the contractor could work on as design minimized the time of interstate many as eight spans at any given time Lloyd Pitts is vice president and chief closure by using off-site fabrication and and facilitated nonlinear construction. bridge engineer with Volkert Inc. in rapid construction methods. The method proved to be successful, Mobile, Ala., Eric Johnson is a bridge with all 2316 segments (172 spans) engineer with Corven Engineering Inc. The casting yard was located erected in only 217 days. (For more in Tallahassee, Fla., and William (Tim) approximately 4 miles from the project, details on this technique, see the Colquett is the state bridge engineer which allowed efficient transport of Concrete Bridge Technology article on for the Alabama Department of the precast concrete segments to the page 30 of this issue of ASPIRE.) Transportation in Montgomery.

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ASPIRE Spring 2020 | 15 PROJECT Harlem River Drive Bridge over East 127th Street

by Silvio Garcia, Hardesty & Hanover LLC

Harlem River Drive is a limited-access passenger vehicle highway adjacent to the Harlem River in the New York City borough of Manhattan. The section of Harlem River Drive included in this project extends south to north from the Willis Avenue Bridge to the Park Avenue entrance ramp, a total length of approximately 4500 ft. As part of this project, the 676-ft-long Harlem River Drive Bridge over East 127th Street was reconstructed to improve the operation of this segment of highway and address deficiencies of a structure that carries mainline traffic over the East 127th Street on- and off- ramps. A Perilous Stretch of Highway Aerial view of project limits. The yellow area indicates the project limits, which The existing bridge carried three lanes extended beyond the bridge replacement to accommodate the updated vertical profile of southbound traffic and two lanes and safe traffic patterns during the staged construction. The red areas indicate on- and of northbound traffic plus a wide, off-ramps that were impacted by the project and therefore included in the project striped shoulder on the northbound limits. Photo: Google / Hardesty & Hanover. side. The 11-span structure consisted of seven steel multigirder spans plus This section of Harlem River Drive with the addition of a left lane exit to two concrete cellular-type spans at was categorized as one of the worst Second Avenue, thereby eliminating the each end. The seven main spans were segments of highway in New York state, weaving condition, and modifications supported by steel columns on concrete based on the high traffic accident rates to the vertical profile on the bridge and footings and founded on concrete- and severe congestion, particularly in approaches to increase the stopping filled steel pipe piles socketed in rock. the southbound direction. The causes sight distance. The cellular spans were composed of of traffic accidents in this area included a structural reinforced concrete slab a weaving condition on southbound New Southbound and supported by reinforced concrete girders Harlem River Drive at the exit to Second Northbound Bridges and retaining walls in the longitudinal Avenue, and substandard stopping The single existing structure was direction founded on steel H-piles driven sight distance on the bridge. The new replaced with two adjacent bridges, to bedrock. bridge addresses these deficiencies one for southbound traffic and one

HARLEM RIVER DRIVE OVER EAST 127TH STREET / NEW YORK, NEW YORK profile BRIDGE DESIGN ENGINEER: Hardesty & Hanover LLC, New York, N.Y. PRIME CONTRACTOR: Defoe Corporation, Mount Vernon, N.Y. PRECASTER: Coastal Precast Systems, Chesapeake, Va.—a PCI-certified producer

16 | ASPIRE Spring 2020 (a) (b)

Typical cross sections of the new (a) southbound bridge and (b) northbound bridge over an on-ramp. Figure: Hardesty & Hanover. for northbound traffic. Each bridge is The alignment for the southbound 3% inflation rate was used. Periodic approximately 990 ft long. Two bridges bridge is on a compound horizontal steel painting, joint replacement, and were required to accommodate the curve with radii of 1885 and 2828 ft bearing replacement were considered. A new left-hand exit from southbound followed by a tangent. The northbound full bridge rehabilitation including deck Harlem River Drive to Second Avenue. alignment is on a compound horizontal replacement was assumed after 45 years The southbound bridge carries four curve with radii of 2920 and 1937 of service. lanes of traffic, and the northbound ft followed by a tangent. The bridge bridge carries two lanes of traffic. profiles have a 5% maximum grade The proposed bridges would be Both bridges include wide shoulders and the decks are superelevated, with located adjacent to an existing park that ease congestion in the case of the cross slopes varying from 2.00% to that includes a large mural, “Crack emergencies. 4.52%. Is Wack,” painted by the artist Keith Haring, as well as the planned Harlem The new southbound and northbound Why Precast Concrete Bulb River Waterfront Park; therefore, it bridges consist of nine and ten spans, Tees? was important to provide a structure respectively; and the spans range in A structure justification study was that blended into its surroundings. length from 65 to 132 ft. The bridges performed during the preliminary design Accessibility for future painting of the are composed of prestressed concrete to determine the best superstructure/ bridges would have been problematic bulb-tee beams (PCEF-63). The beams substructure combination for the given their location. Because the are composite with a 9.5-in.-thick replacement bridges. The study prestressed concrete superstructures reinforced concrete deck and are considered both steel and concrete would not require painting, both supported on multicolumn concrete alternatives, including several maintenance costs and potential for piers founded on 4- and 5-ft-diameter prestressed concrete girder shapes, and future park disruptions were minimized. drilled shafts. The prestressed concrete evaluated them for future maintenance beams have a design concrete requirements, construction duration, Prestressed concrete bulb tees, compressive strength of 10 ksi with construction cost, life-cycle cost, specifically the PCEF-63, were found 270-ksi, 0.6-in.-diameter low-relaxation geometry needs, staging needs, and to be the best alternative for the strands. The piers and drilled shafts other parameters. superstructure because they provided have a design concrete compressive the lowest life-cycle cost of all the strength of 4 ksi. All elements, including The life-cycle cost analysis assumed a superstructure types analyzed, eliminated the beams, use 60-ksi epoxy-coated 4% discount rate and a 75-year service the need for painting, and offered a reinforcing bars. life. For the estimated future costs, a neutral, nonintrusive appearance. Also,

NEW YORK CITY DEPARTMENT OF TRANSPORTATION, OWNER BRIDGE DESCRIPTION: Twin 990-ft-long bridges on a horizontally curved alignment with precast, prestressed concrete bulb-tee beams placed on chords, a cast-in-place 9.5-in.-thick concrete deck, and multicolumn concrete piers supported on 4- and 5-ft-diameter drilled shafts STRUCTURAL COMPONENTS: 139 PCEF-63 bulb-tee beams, 9.5-in.-thick cast-in-place concrete deck, cast-in-place concrete pier caps, columns, and drilled shafts BRIDGE CONSTRUCTION COST: $126.9 million AWARD: 2020 Diamond ACEC New York Engineering Excellence Award

ASPIRE Spring 2020 | 17 Aerial view of the completed project showing the northbound bridge in the foreground. Plans to develop the waterfront area into parkland have been initiated and will be completed under a future contract. Photo: Defoe Corp. the bulb-tee shape best accommodated Edison, which supply electricity to In stage 2 of the project, a portion of the construction staging and vertical Manhattan’s East Side. To minimize southbound bridge was constructed. The clearance requirements. the risk of damaging the lines, the close proximity of the new construction following requirements were placed (left) to the existing structure (right) Substructure Selection on the contractor for all shaft and required extensive coordination and For any project in an urban substructure excavation work adjacent surveying throughout the project. Photo: environment, utilities play a large role to these high-voltage facilities: Hardesty & Hanover. in the selection of the substructure • Con Edison needed to locate the and foundation. For the Harlem River facilities prior to any substructure Construction in a High- Drive project, multicolumn concrete work. This entailed hand digging Traffic Urban Environment piers supported on drilled shafts or test pitting to verify the location Northbound and southbound lanes of were the preferred substructure/ of shallow buried facilities and a Harlem River Drive have annual average foundation option due to the numerous gyroscope survey for the submarine daily traffic in excess of 28,000 and underground utilities that needed to cable river crossing. The survey 68,000 vehicles, respectively. Because of be maintained and protected during established the limits of the zones the high traffic volumes and the highway’s construction. Underground utilities in which no drilled shafts or driven importance as a main route into and within the project limits included piles could be installed. through Manhattan, all traffic lanes and electrical lines, intelligent traffic system • Vibration velocity was limited to the major on- and off-ramps needed to be lines, communications lines, water less than 0.5 ft/s and was to be maintained throughout construction. mains, and stormwater systems. monitored via vibration monitoring. • Outage time was restricted, with no The space limitations imposed by a Among the underground utilities summer outages permitted. dense urban environment and the need within the project limits are • Minimum clearance of 11 ft was to maintain all lanes required that the approximately fifteen 270-kV electrical required between drilled shafts and project be built in five stages, from submarine cables, owned by Con submarine cables. west to east.

In stage 3 of the project, construction of the southbound bridge The new southbound bridge was initially opened for traffic continued, while northbound traffic was maintained on the at-grade in both directions, with its shoulders used as temporary lanes. temporary roadway. Note that the prestressed concrete bulb tees are The temporary roadway along the river was removed and the set on chords of the horizontal curves. Photo: Defoe Corp. northbound bridge was constructed. Photo: Defoe Corp. The prestressed concrete bulb tees were transported by barge from the producer to the The cross section of the 63-in.-deep site and lifted directly from the barge onto the new piers. Photo: Defoe Corp. prestressed concrete bulb tee (PCEF-63) from New York State Department of During stage 1, a temporary at-grade between active traffic on the new Transportation (NYSDOT) standards.1 Based roadway was constructed adjacent southbound bridge and the temporary on a justification study, the PCEF-63 was to the river. Northbound traffic was roadway carrying northbound traffic the best alternative and was used for all moved to the temporary roadway along the river. The prestressed concrete spans. Span lengths ranged from 65 to 132 and the southbound traffic shifted to bulb tees were transported by barge ft. Figure: NYSDOT. the east side of the existing structure. from the producer to the site and erected This accommodated the demolition of directly from the barge onto the new during construction. In stage 4, the the first half of the existing bridge and piers. Intermittent night closures of temporary roadway was removed, and construction of approximately two-thirds northbound traffic lanes were approved the northbound bridge was constructed. of the new southbound bridge (stage 2). by local authorities to allow the bulb tees During the fifth and final stage, tie-ins and to be lifted from the barge, over the approaches at each end were completed. In stage 3, southbound traffic was temporary roadway, and into place. moved onto the new structure. The Conclusion remainder of the southbound bridge was Once stage 3 was completed, all traffic The project was substantially complete built during this stage, which required was shifted to the new southbound and open to traffic in May 2019. additional coordination and safety bridge, with the wide shoulders used Continuous communication and precautions as construction occurred to accommodate temporary lanes coordination among all parties ensured the success of this project, which provides Drilled shafts were strategically placed outside the required minimum 11 ft clearance limit a safer facility with minimal required from each of the Con Edison submarine high-voltage cables. Figure: Hardesty & Hanover. maintenance of the new bridges. The new structures will provide at-grade access to the new waterfront park and a HIGH VOLTAGE direct connection between the Robert F. ELECTRICAL CABLES (TYP.) Kennedy Bridge and northbound Harlem River Drive via a ramp currently being constructed by the Triborough Bridge and Tunnel Authority.

11 FOOT MIN. NEW CLEARANCE SOUTHBOUND (TYP.) STRUCTURE Reference 1. New York State Department of Transportation. 2017. “Prestressed DRILLED SHAFTS Concrete PCEF and AASHTO I-Beam (TYP.) Typical Sections.” https://www. dot.ny.gov/main/business-center/ NEW NORTHBOUND engineering/cadd-info/bridge-details- STRUCTURE sheets-repostitory-usc/BD-PC14E.pdf. Accessed January 11, 2020. ______N Silvio Garcia is a senior associate with Hardesty & Hanover LLC in New York, N.Y.

ASPIRE Spring 2020 | 19 PROJECT GENESEE AVENUE VIADVIADUCTUCT The First Curved Precast Concrete Spliced U-Girder Light-Rail Transit Viaduct in California

by Ali Seyedmadani and Pooya Haddadi, WSP

The Mid-Coast Corridor Transit Project driving forces during delivery of the is a 10.8-mile-long, $2.2 billion light-rail Mid-Coast Transit Project. When it was transit (LRT) link connecting downtown being planned, the owner, San Diego San Diego, Calif., to the La Jolla, Calif., Association of Governments (SANDAG), business center on Genesee Avenue. This was executing and overseeing the transit line uses the existing Los Angeles– delivery of several transit projects San Diego–San Luis Obispo (LOSSAN) rail simultaneously, and the association corridor in the southern portion of the decided that the construction manager/ line. It crosses over the San Diego River in general contractor (CM/GC) alternative parallel with (I-5), then crosses delivery method would be the right over I-5 in the vicinity of the San Diego VA approach for this large, complex project. Medical Center, runs near the University of California San Diego (UCSD) campus, Project Delivery crosses over I-5 again, and terminates When SANDAG selected the CM/ in the median of Genesee Avenue near GC for the project, a review of Westfield UTC mall in La Jolla. the project schedule and cost was undertaken. Through this process, The entire Mid-Coast Corridor Transit it was determined that changing two Project includes 12 bridges, four bridges from the preliminary design of aerial stations with side platforms, cast-in-place (CIP) post-tensioned (PT) three viaducts (each over 1 mile long), box-girder designs to precast concrete and more than 70 retaining walls of girder structures would save time and various types. As the project navigates minimize construction impact on the through heavily urbanized and less- communities. The 1758-ft-long Rose urban areas, there are also significant Creek LRT Overhead Bridge that crosses changes in elevations. Soil conditions the alignment from the east side of the vary, and there may be perched water existing LOSSAN track to the west side tables within foundation footprints. In and the 5726-ft-long Genesee Avenue addition, because Southern California Viaduct were identified for redesign as is in a high-seismic zone and project precast concrete girder bridges. alignment crosses over a seismic fault, special bridge design elements were Genesee Avenue is the business, required for potential ground movement shopping, and office center of La Jolla due to fault rupture. and a major arterial street. For the Genesee Avenue Viaduct, the contractor Mid-Coast Transit Corridor alignment Project cost (guaranteed maximum concluded that a precast concrete girder near the San Diego VA Medical Center. price) and schedule were the major bridge would eliminate several months Photo: Mid-Coast Transit Constructors.

GENESEE AVENUE VIADUCT / LA JOLLA, CALIFORNIA profile BRIDGE DESIGN ENGINEER: WSP, Orange and Sacramento, Calif. CONSTRUCTION ENGINEER: PGH WONG Consulting Engineers/Kleinfelder, San Diego, Calif. PRIME CONTRACTOR: Stacy and Witbeck/Herzog/Skanska–Mid-Coast Transit Constructors (MCTC), San Diego, Calif. PRECASTER: Oldcastle Infrastructure, Perris, Calif.—a PCI-certified producer POST-TENSIONING CONTRACTOR: DYWIDAG Systems International (DSI), Long Beach, Calif.

20 | ASPIRE Spring 2020 Typical Genessee Avenue Viaduct section (top), and typical section at stations (bottom). Figure: WSP. begun, and the early construction concrete spliced girder segments per package was underway. Therefore, span per girder line, integral at the the superstructure span layout was bents. The second type is a hybrid somewhat set when the design was of precast concrete spliced girders changed to a precast concrete U-girder and CIP hammerhead pier tables to system. extend the typical 180-ft-long spans Genesee Avenue Viaduct alignment to accommodate the crossing over the near the University of California San However, the precast concrete girder La Jolla Village Drive intersection. The Diego campus. Photo: Mid-Coast Transit layout for the 5726-ft-long bridge third type is a traditional CIP PT concrete Constructors. eliminated one span from the CIP box girder; this was used for the two of nighttime construction, reducing the configuration, resulting in 35 spans aerial stations with side platforms. project’s impact on surrounding hotels, divided into 12 frames (units). Eleven There are five in-span internal hinges businesses, residences, and the traveling frames have three spans and one frame on the viaduct, one at each end of public without compromising aesthetic has two spans. The longest frame is 590 the two station units and one at the appearance. ft and the longest span is 225 ft; most interface with the UCSD Viaduct. These spans are 180 ft long and have three in-span hinges will isolate the seismic Viaduct Configuration 60-ft-long girder segments. The radius displacement of the CIP frames from the The preliminary design of the Genesee of the curved viaduct is at least 990 ft, remaining frames of the viaduct during Avenue Viaduct using CIP PT box girders except in one section where the radius extreme seismic events. had identified column and foundation is 500 ft. locations along the median of the arterial The Genesee Avenue Viaduct’s typical and had set the span arrangement based There are three types of frames on two U-girder-line section is 32 ft 1 in. on critical intersections and driveway the viaduct. The first type is a precast wide, except at the stations, where crossings. Early utility relocation had concrete frame with three precast sections are widened to 57 ft 5 in. The

SAN DIEGO ASSOCIATION OF GOVERNMENTS, OWNER OTHER MATERIAL SUPPLIERS: Cosmic Inc., Athens, Tex. (spherical bearings); GERDAU, San Diego, Calif. (reinforcing steel fabricator) BRIDGE DESCRIPTION: 5726-ft-long light-rail transit bridge consisting of 35 spans in 12 frames with two lines of straight or curved precast concrete spliced girders STRUCTURAL COMPONENTS: One hundred forty modified PCI U-96 precast concrete girders (48 were curved), maximum of 60 ft in length and 100 tons maximum haul weight, supported on cast-in-place pier caps, 7- to 9-ft-diameter columns, and 9- to 10-ft-diameter drilled shafts BRIDGE CONSTRUCTION COST: $60 million ($320/ft2), including station platforms

ASPIRE Spring 2020 | 21 Typical precast concrete straight U-girder segment. Photo: WSP. The precast producer used two straight and one adjustable-curve PCI U-96 girder forms. Photo: WSP. curved precast concrete section is the were 6000 psi at transfer and 8500 psi substructure stiffness in each frame. In same size as the typical section and uses at 28 days. addition, it required that adjacent frames PCI U-96 girders with 10 in. webs and have a similar fundamental period of a 9-in.-thick bottom slab. To control Girder hauling costs in Southern vibration in the longitudinal direction. torsional forces induced in the curved, California increase significantly when Therefore, the designers had to adjust open-section girders, 4¼-in.-thick CIP lid segment weight is over 100 tons. column and drilled-shaft sizes as column slabs were constructed in the fabrication This weight includes any temporary height and span length varied. plant to close the top of the U-girders. stiffening braces or lid slabs in curved 13 There are four 3 ⁄16-in.-diameter ducts sections of bridge segments. Lid slabs The viaduct substructure consists of with nineteen 0.6-in.-diameter strands are used to stiffen the open U-girder pier caps supported by single columns in each web; four ducts were used section during the hauling and erection with a drilled-shaft foundation. The for splicing, and four ducts were used operations and to serve as a stay-in- column sizes vary from 7 to 9 ft in for PT continuity. There are also four place form for the deck. diameter, and the drilled shafts are 9 1 3 ⁄8-in.-diameter ducts with twelve to 10 ft in diameter. The pier caps are 0.6-in.-diameter strands at the curved On the Genesee Avenue Viaduct 7 to 9 ft in the longitudinal direction, section in the bottom slab of the project, one strategy used to keep the approximately 22 ft wide, and vary in girder for self-weight post-tensioning; haul weight of segments below the depth from 4 ft at the outside edge to pretensioned strand was used for the 100-ton limit was to not include the 8.5 ft at the column face. The shape straight girder sections. post-tensioning anchorage hardware of the piers mimicked the shape of the and concrete section at the girder other CIP box-girder viaduct piers except Each precast concrete U-girder was end diaphragm. This resulted in the the top of the pier was enlarged to designed to carry one LRT track loading construction of a CIP closure section of accommodate a seat for the U-girders. in addition to dead loads. The LRT about 7 to 9 ft prior to post-tensioning. loading is approximately 50% heavier The CIP section also provided tolerance The superstructure/substructure than the standard highway truck for forming the tendon deviators and connection is a pin at the interior loading. Because this viaduct is close girder flares in the end zone. pier caps and an expansion joint at to the ocean, designers chose to have the exterior pier caps of each frame. no tension in the girders to improve Substructure Configuration There are two types of pins at the pier the structure’s durability and service life. The seismic design of the Genesee caps. One type was designed using The minimum concrete design strengths Avenue Viaduct required similar reinforcing bars to engage during service and post-tensioning operations; Girder segment with blockout for closure pour and post-tensioning anchorage the second type has much larger pins hardware. This photo also shows both pins in the pier cap. Photo: WSP. and sockets that are designed to remain elastic during major seismic events, allowing the superstructure to rotate. All pier caps with seismic pins include transverse high-strength threaded rods at the top of the pier cap within the pin support area. These rods increase confinement and improve shear capacity of the pier caps during a seismic event.

The drilled shafts were detailed assuming wet ground conditions during construction. Cross-hole sonic testing was performed to ensure quality of the placed Erection over the La Jolla Village Drive intersection. For the longest span crossing over Rendering of the completed Genesee the La Jolla Village Drive intersection, hammerhead pier tables were constructed on Avenue Viaduct. Source: WSP. falsework. The two main span U-girders were spliced on the ground in the staging area testing of the concrete mixture to check and then erected on the falsework tower at the ends of the pier tables. The back-span strength development and concrete girders were erected on falsework towers and then spliced together. Photo: Mid-Coast temperature during curing, the proposal Transit Constructors. was approved. With the approval, the concrete. All longitudinal reinforcing with diaphragms and the CIP deck contractor was able to form, place, cure, steel in the columns and drilled shafts is were constructed and the remaining and achieve required concrete strength continuous with no lap splices. two ducts in each web were used for of the closure pours in two days. Then, continuity post-tensioning of the full the first-stage post-tensioning could be Girder Erection Sequence frame (stage 2 post-tensioning). completed and the intersection opened The design plans had three basic to traffic within six days. This approach methods for U-girder erection. The first The third erection method shown in reduced night work, shortened the method was used for frames that do not the design plans was a hybrid method schedule, and reduced risk. cross over any intersection or driveway and was used to construct the longest wider than 60 ft. This method involved frame crossing over the La Jolla Village As of this writing, the contractor erection of individual girder segments Drive intersection. Hammerhead pier had completed the viaduct and was that are about 60 ft or shorter, weighing tables were constructed on falsework. attaching direct fixation rails and utilities less than 100 tons, on temporary towers. The two main-span U-girders were to the bridge. Then, the closure pours, diaphragms, spliced on the ground in the staging and CIP deck were constructed, followed area and then erected on the falsework The use of a precast concrete U-girder by post-tensioning the full frame in one tower at the ends of the hammerheads. bridge for this viaduct reduced the operation (single stage). The back-span girders were erected total construction duration and on falsework towers and spliced significantly reduced night construction. The second method was designed for together. To complete the construction, These time savings greatly benefited frames that cross over an intersection the diaphragms and CIP deck were the nearby residences, businesses, wider than 60 ft. For this method, constructed and continuity post- and travelers along this major arterial girders were erected on falsework tensioning was applied to the full frame. street. The precaster’s initial investment towers at all locations except the in U-girder forms helps provide future intersection. Then, after closure pour As the contractor gained experience and opportunities to design concrete bridges construction, the erected U-girders were confidence in the girder erection, closure with more complex, longer spans and spliced using two ducts in each web pours, and post-tensioning operations, aesthetically pleasing features, with (stage 1 post-tensioning). The U-girder they proposed using a quick-set, high- fewer construction impacts, in Southern segments for the intersection were early-strength concrete mixture with no California. spliced on the ground in the staging fly ash. It was hoped that use of this ______area, and then erected on falsework mixture would eliminate the need for a Ali Seyedmadani is vice president towers, allowing the intersection to staging-area splicing operation and lifting and technical director with WSP in remain open. Then, the closure pours of already spliced girders. After mock-up Sacramento, Calif., and Pooya Haddadi is lead bridge engineer, also with WSP, in Splicing operations for two U-girder segments crossing the Esplanade Court intersection. Orange, Calif. The contractor closed the intersection and used a quick-set, high-early-strength concrete mixture. This span terminates at the in-span hinge of the cast-in-place (CIP) box station frame in the foreground. The falsework is for the hinge and the CIP box frame. Photo: EDITOR’S NOTE Mid-Coast Transit Constructors.

The PCI U-girder sections mentioned in this article were developed by PCI Zone 6. The full set of drawings is available at www.pci.org/PCI_Docs /Design_Resources/Transportation_ Resources/PCI%20Zone6%20 Curved%20Spliced%20Girders.pdf.

ASPIRE Spring 2020 | 23 CONCRETE BRIDGE TECHNOLOGY Shear Assessment of Complex Concrete Pier Caps by Daniel J. Baxter, Emily Thomson, and Dr. Francesco M. Russo, Michael Baker International, and Jessica Wahl Duncan, Minnesota Department of Transportation

The Lake Avenue Bridge over Interstate To perform a load rating of the box-girder The evaluation team load rated the bridge 35 (I-35) in Duluth, Minn., is a stylish, web lines and tributary flange widths, for the HL-93 loading at the inventory cast-in-place reinforced concrete box- the MBI evaluation team used output and operating levels, and the standard girder bridge, which was constructed in forces from this model in conjunction Minnesota legal and permit vehicle 1982. Supporting a single-point urban with spreadsheets that tracked the many loadings. The nearly 40-year-old bridge is (SPUI), the bridge connects reinforcement transitions along the in good condition, and the superstructure downtown Duluth to the tourist hotspot length of the bridge units. Following the and corbel joints had passing load of Canal Park along Lake Superior and project scope of work, the team also used ratings for all legal vehicles and nearly is one of the primary means of access the demands output from the model to all permit vehicles. However, the integral to downtown and Canal Park from I-35. conduct load ratings using strut-and-tie cap beams did not have adequate shear Every June, the structure is a focal point modeling (STM) of the internal integral capacity for some current legal loads for the thousands of runners who pass cap beams over the piers (Fig. 2) and when analyzed with STM or when using a under it just before making the final of the bridge’s corbel joints between sectional model approach, as would have turn to the Canal Park finish line of superstructure units (Fig. 3). been used during their initial design. The Grandma’s Marathon. problematic cap beam regions were nearly The intent of the technical approach all located within a distance extending The Lake Avenue Bridge consists of was to rigorously apply the American horizontally outward from the face of the multiple concrete box-girder units with Association of State Highway and piers equal to the effective shear depth dv. complex geometry to fit the SPUI and Transportation Officials (AASHTO) Within these regions, the existing vertical the ramps to I-35. When the Minnesota Manual for Bridge Evaluation (MBE);2 reinforcing steel area in the integral cap Department of Transportation (MnDOT) however, the evaluation team understood beams was not enough to provide the required a load rating for this structure, and expected that various elements of the shear reinforcement contribution capacity it retained Michael Baker International piers would not meet current AASHTO Vs required to produce passing load (MBI) to prepare a load and resistance design and detailing requirements. In the ratings using sectional analysis, or the factor rating (LRFR). MBI developed eighth edition of the AASHTO LRFD required reinforcing steel area to satisfy a three-dimensional (3D) finite-element Bridge Design Specifications,3 Articles the vertical tie demands from STM for model of the structure (Fig. 1) using 5.1 and 5.5.1.2 establish a clear path the same applied loads. midas Civil software, following the that leads to the conclusion that STM is grillage analysis methods specified for the only appropriate design approach for AASHTO LRFD specifications require horizontally curved concrete box-girder new structures with disturbed regions. that the shear capacity within a distance bridges in Design Specifications and But when faced with evaluating existing extending dv from the face of the support Commentary for Horizontally Curved structures designed and detailed using a be evaluated if concentrated loads are Concrete Box-Girder Highway Bridges, different standard, the solutions are not located within this distance. On the Lake published by the National Cooperative always as clear (see the FHWA article in Avenue Bridge, most of the integral cap Highway Research Program.1 the Fall 2019 issue of ASPIRE®). beams support box-girder web lines within

Lake Avenue Bridge looking north on Interstate 35. Photo: Minnesota Department of Transportation. Figure 1. Rendering of the three-dimensional finite-element model of Lake Avenue Bridge. Figure: Figure 2. Cross section of the three-dimensional Michael Baker International. finite-element model showing the cast-in-place reinforced concrete box-girder unit, pier column, this distance; the evaluation team initially distance and poor rating results using an and integral pier cap beam for a Lake Avenue treated these as concentrated loads, with all-sectional or all-STM approach, the Bridge ramp structure. Figure: Michael Baker the critical section being taken at the observed fair performance of the integral International. face of support. The team also considered cap beams needed to be reconciled with taking the critical section at a distance the poor results of multiple calculation in AASHTO LRFD specifications), the of dv from the face of the support if a models that indicated more extensive hybrid analysis ensures there is a load path detailed bridge inspection found no signs shear cracking with wider crack widths to couple the B- and D-regions together of shear cracking in the dv region. They should be present. The evaluation team and carry the demand to the columns. reasoned that if an inspection of these had to either resolve these discrepancies regions found no shear cracks after nearly or use the results of the models to load In the STM for the example cap beam

40 years of service, the performance of post the bridge, which would potentially shown in Fig. 5, forces VA and VB each the bridge would be demonstrating that be followed by costly retrofit repairs. equal one-half of the total shear demand the loads from the webs and integral Vu at a distance dv from the left face of flanges were effectively acting more like The analysis team obtained higher load- the column. This analysis causes vertical distributed loads, for which AASHTO rating results that better reflected the good tie AB in the model to only carry half of

LRFD specifications permit the critical condition of the cap beams by using a the total shear demand Vu. The other half section for shear to be taken at dv from hybrid analysis method incorporating both of the total shear demand Vu is applied the support face for a sectional analysis. sectional analysis and STM. They used to top node A and transferred by the MnDOT’s District 1 bridge inspection staff STM to evaluate the integral cap beams diagonal strut AD and other struts and performed a supplementary inspection of within dv from the face of the column, ties into model supports D and F (which multiple cells of the bridge adjacent to the and applied the sectional method in the represent the pier), without creating integral cap beams, which revealed narrow, span beyond dv from the column face demand in tie AB. diagonal cracking in the cap beams near because that method discretely considers the support faces, as shown in Fig. 4. the concrete and shear reinforcement If the entire cap beam had been modeled

contributions to shear, Vc and Vs, both of using STM, vertical tie AB would be Given the multiple, fine shear cracks which appear to be intact. At the interface required to carry the entire shear demand in the integral cap beams within the dv between the B- and D-regions (as described at distance dv from the face of the Figure 3. Lake Avenue Bridge corbel joint showing the primary reinforcement and strut-and-tie models used for evaluation. Note: Solid and dashed lines represent tension ties and compression struts, respectively. Figure: Michael Baker International.

ASPIRE Spring 2020 | 25 VA

HA A G C E column, assuming no concentrated loads Vu M are applied at nodes A or B. Flexural demands were similarly addressed but are not shown for clarity. VB D F H Horizontal forces H and H are obtained B A B HB from the moment M at the interface between the sectional and strut-and- d tie models. These forces are equal and v dv opposite, and are equal to the moment M divided by the vertical distance between nodes A and B. The forces are applied in Figure 5. Strut-and-tie model of the hybrid analysis of the integral cap beam. V and V each equal one- the direction needed to induce tensile and A B half of the total shear demand V . Note: Solid and dashed lines represent tension ties and compression compressive axial forces in the horizontal u struts, respectively. Strut-and-tie modeling was used in the D-region of the cap beam (shaded gray). The chords of the strut-and-tie model that sectional model was used in the B-region of cap beam (not shaded). Figure: Michael Baker International. are of the same sense as the top and bottom flexural stresses induced by the vertical and align with the existing References moment M at the interface. For the Lake reinforcement layout. 1. National Cooperative Highway Avenue Bridge integral pier caps, this Research Program (NCHRP). 2008. procedure resulted in the top chords of All portions of the integral cap beams that Design Specifications and Commentary the strut-and-tie models being in tension did not have passing legal load ratings for Horizontally Curved Concrete Box- over the piers, and the bottom chords in using the original sectional method checks Girder Bridges: Final Report. NHCRP compression. were evaluated using the hybrid approach. Project 12-71. Washington, DC: The evaluation team’s 3D finite-element Transportation Research Board. http:// This hybrid analysis approach recognizes model was used to generate concurrent onlinepubs.trb.org/onlinepubs/archive/ the contribution of concrete to shear live-load forces for use in the hybrid notesdocs/nchrp12-71_fr.pdf strength by not requiring that vertical tie method to evaluate capacity. 2. American Association of State Highway

AB transfer the entire shear demand Vu and Transportation Officials (AASHTO). up to node A, as would be needed for the Using this hybrid analysis method produced 2018. Manual for Bridge Evaluation, STM of the entire cap. The existing vertical passing ratings for Minnesota legal loads 3rd ed. Washington, DC: AASHTO. reinforcing steel area in the cap beams was and permit loads for all the Lake Avenue 3. AASHTO. 2017. AASHTO LRFD sufficient to satisfy the vertical tension Bridge integral pier cap beams. These Bridge Design Specifications, 8th ed. demand in tie AB obtained using the results conform with the condition observed Washington, DC: AASHTO. hybrid approach. The overlapping diagonals in these regions of the bridge and avoid the ______CF and DE in the example model of Fig. 5 need for load posting or structure retrofits. Daniel J. Baxter is a senior bridge engineer were analyzed as compression-only truss The Lake Avenue Bridge should provide and bridge department manager with Michael elements, which effectively removes one of many more decades of service to Duluth’s Baker International in Minneapolis, Minn.; the two diagonals for different unbalanced citizens and visitors, and will continue to Emily Thomson is a bridge engineer with live-loading patterns. This technique serve as a landmark for weary marathon Michael Baker International in Indianapolis, ensures that all ties are horizontal or runners nearing the finish line. Ind.; Dr. Francesco M. Russo is vice president and technical director, bridge engineering Figure 4. Diagonal cracking (dashed lines) noted during inspection of an integral cap beam of the Lake with Michael Baker International in Avenue Bridge. Cap beam is on the left, and girder web is on the right. Photo: Minnesota Department of Philadelphia, Pa.; and Jessica Wahl Duncan Transportation. is existing structure evaluation and design manager with the Minnesota Department of Transportation in Oakdale, Minn.

EDITOR’S NOTE

This is the first part of a two-part Concrete Bridge Technology article series on strut-and-tie modeling (STM) by these authors. The second article will discuss how to use STM for portions of new design that are more challenging than what is typically shown in example problems, as well as some of the techniques Michael Baker International uses for complex designs. Structural Welded Wire Reinforcement - A Best Kept Secret

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ASPIRE Spring 2020 | 27 CONCRETE BRIDGE TECHNOLOGY Epoxy-Coated Prestressing Steel Strand Three types of surface finish are available for by Jon Cornelius and Jeff Feitler, Sumiden Wire Products Corporation epoxy-coated strands (from left): smooth, for unbonded applications; fine grit; and coarse grit. The latter two are for bonded applications. Prestressed concrete was introduced in example, when the coating was initially Note individual coating of each wire. Photo: the 1950s and is now widely recognized developed for bonded applications, sand Sumiden Wire Products Corporation. as a durable and superior construction was impregnated on the epoxy coating method for many structural applications, to enhance the bond performance. This shot-blast process to remove the mill including bridges of all sizes and types, coarse-grit finish was effective at scale remaining after the steel hot-rolling wind towers, and single-story and high-rise developing bond, but it proved to be manufacturing process, a subsequent buildings. To further increase the service problematic for thin members because cleaning and removal of the shot blast life of prestressed concrete structures, resulting transfer lengths were very media and related debris, and a heating owners, design engineers, and contractors short. The coarse grit (sand) epoxy-coated process at ~450°F; then, the epoxy want cost-effective and reliable methods strand was also abrasive to handle and coating is applied. to prevent premature corrosion of the caused unwanted wear when it rubbed reinforcing steel. Carbon fiber, stainless against tooling, as it would when passing For epoxy-coated strand, the mill scale steel, and epoxy coatings have all been through the holes in prestressing form is removed from the hot-rolled wire rod successfully used to help eliminate or bulkheads. To address these issues, fine- before the production of the individual significantly reduce the risk of premature grit epoxy-coated strand was developed wires. Next, the descaled wire rod is cold- reinforcing steel corrosion. This article using aluminum oxide impregnated on the drawn through a series of dies, which focuses on the development and success of epoxy surface. The fine-grit finish on the ensures the wire surface is uniform and epoxy-coated prestressing steel strand (as epoxy-coated strand resolved the handling free of any loose debris. During the specified in ASTM A882). and wear concerns associated with the stranding process, the individual wires coarse-grit finish, and its transfer length are stranded and then heated to over History is similar to bare strand. Currently, three 700°F, burning off a large portion of any Epoxy-coated strand was first developed types of surface finish are available: remaining surface contaminants. This in the early 1980s by Florida Wire and smooth, for unbonded applications; fine heated strand is rapidly cooled in a water Cable with the help of a grant from the grit; and coarse grit–the latter are both bath, which also acts as another cleaning Federal Highway Administration. When for bonded applications. Epoxy-coated process. Prior to epoxy coating, the bare the product was initially developed, prestressing strands are available in the strand is passed through an acid-cleaning the epoxy coating was only applied same diameter ranges as uncoated steel operation, a subsequent water rinse, and to the outside of the strand. Field strands. a heating process at ~400°F. After all of experience with this first-generation these processing and cleaning steps, the 15- epoxy-coated product soon proved this Distinctive Characteristics coating practice had a serious flaw: Although epoxy-coated prestressing Bite-through wedges, which have longer teeth, water could enter the strand from the steel strand has been available in the must be used when tensioning epoxy-coated exposed ends and migrate through the U.S. market since the 1980s, many in prestressing steel strand. Coated strand at left unfilled interstitial spaces between the the prestressed concrete community are shows how the teeth have penetrated the coating wires. When this was recognized, the not familiar with this product. When to engage the surface of the strand. Photo: epoxy-coating process was redesigned first hearing about epoxy-coated strand, Sumiden Wire Products Corporation. to remove this vulnerability by filling many people may associate this product the interstitial spaces with the epoxy- with its distant cousin, epoxy-coated coating material in addition to applying reinforcing bars. While this association the coating on the outside of the strand. is understandable, there are significant differences between the two products. In the following years, the technology for making epoxy-coated strand was One of the primary differences between further refined and improved, with the two products is the surface advancements made in the uniformity of preparation prior to epoxy coating. coating thickness, coating adhesion, and Surface preparation for an epoxy-coated other characteristics of the product. For reinforcing bar primarily consists of a

28 | ASPIRE Spring 2020 Coating thickness @ crown of wire: All internal voids 15 mils – 45 mils completely filled with (380 µm – 1,140 µm) epoxy

to 45-mil epoxy coating is finally applied. coated prestressing steel strand in bridge Each wire individually When epoxy-coated prestressing steel construction for applications such as coated with strand is coated, each individual wire external tendons for segmental bridges, epoxy is coated as well as the overall strand transverse tendons, internal tendons, and surface. The strand is untwisted and extradosed/stay cable tendons. Epoxy- then retwisted during the epoxy coating coated strand has also been used for process to ensure that all surfaces of ground anchors and mine roof bolts. Pinhole-free coating Strong adhesion between (100% inline inspection) the epoxy and steel surface the wires are covered and the interstitial In the United States, epoxy-coated spaces are filled. As a result, if the strand has been successfully used in Cross section of an epoxy-coated strand showing coating is damaged in the field, only the pretensioned concrete girders, piling, and the complete coating of each wire. Photo: wires with damage have been exposed deck panels; post-tensioned stay cables; Sumiden Wire Products Corporation. to potential corrosion. Additionally, ground anchors; and several other because of the superior adhesion of the specialty applications. Owners are now demanding 100-year- coating, corrosion does not migrate or plus service lives for many of their key travel along the strand if the epoxy is One of the largest U.S. pretensioned infrastructure projects. Epoxy-coated damaged and bare steel wire is exposed. concrete projects using epoxy-coated prestressing steel strand provides a Only the exposed surfaces can corrode, strand was the widening of the San viable and cost-effective option to meet and the adjacent epoxy coating does Mateo Bridge, crossing San Francisco this challenging durability standard. not blister or soften. This remarkable Bay between Hayward and Foster City, ______adhesion property has been confirmed in Calif. The total length of this section of Jon Cornelius is the executive vice president 3000-hour salt fog tests with the strand the San Mateo Bridge is 4.9 miles and and general manager of the PC strand tensioned at 70% of its guaranteed consists of 2160 bulb-tee girders, 826 division in Dickson, Tenn., and Jeff Feitler ultimate tensile strength. piles, and 18,293 deck panels (see article is the vice president of sales and marketing in the January-February 2005 issue of in Stockton, Calif., both with Sumiden Wire The tensioning properties of epoxy-coated the PCI Journal). Epoxy-coated strand Products Corporation. strand are essentially the same as those was selected for all prestressed concrete of traditional bare strand, but there are elements because this structure is very slight differences in handling and care. close to the water level with all elements EDITOR’S NOTE For example, bite-through wedges must within the marine splash zone and the be used when tensioning the epoxy-coated owner set the objective of achieving a ASTM A882 is listed as “Withdrawn” strand, unless the user elects to strip off 125-year service life. The bridge was by ASTM as of this writing. This the epoxy in the gripping sections. Also, completed in 2002, within budget and on standard is in the process of being the epoxy-coated strand is delivered on schedule, and has performed as designed revised and will become active wooden spools, whereas conventional bare without any corrosion concerns. again once it passes the ASTM prestressing steel strand is delivered with balloting process. reel-less packaging; therefore, a different The U.S. prestressed concrete industry payout device must be used when working has used epoxy-coated strand in a variety When the San Mateo Bridge was widened, with epoxy-coated strand. of pretensioned applications, including epoxy-coated strand was used in the prestressed bridge decks, piling, and girders. Precast concrete of its 2160 bulb-tee girders, 826 piles, The epoxy coating on epoxy-coated strand concrete H-columns for highway sound and 18,293 deck panels. Photo: Balfour Beatty is both durable and ductile. If the coating walls are a new pretensioned concrete Construction. were to become damaged, a two-part application in areas where deicing epoxy-patching compound is available for salts are frequently used. Another repairs of any size. The patching process market application is ground anchors can be easily performed in the field with and tiebacks where corrosion can be a a small applicator and heat gun. The significant concern. resultant patch has the same adhesion and elongation properties as the original To date, the most prominent application epoxy coating. The coating material is for epoxy-coated prestressing steel strand also specially engineered to exceed the in the United States has been cable- elongation demands needed in both the stayed bridges. Two iconic cable-stayed longitudinal direction and when bending bridges using epoxy-coated strand are the strand in radii as tight as 32 times the the Penobscot Narrows Bridge near nominal strand diameter. Bucksport, Maine, and the Veterans Glass City Skyway Bridge in Toledo, Ohio. Two Applications for Bridges additional signature cable-stayed bridges and Other Transportation currently under construction are using Structures a combined total of over 5000 tons of Since the early 1990s, over 700 projects epoxy-coated strand: the Harbor Bridge in Asia, primarily in Japan and South in Corpus Christi, Tex., and the Houston Korea, have successfully used epoxy- Ship Channel Bridge in Houston, Tex. CONCRETE BRIDGE TECHNOLOGY Time-Saving Construction Techniques—I-59/I-20 Bridge Reconstruction

By Robert W. Sward, Structural Technologies LLC

Since the 1970s, precast concrete segmental bridge construction has been used throughout the United States and many other parts of the world. Precast concrete segmental bridges are highly durable structures and may have predicted service lives greater than 100 years. As with most other forms of precast concrete construction, precast concrete segmental bridges can be constructed relatively quickly and allow the contractor to take advantage of innovative construction techniques. The recently completed Interstate 59/ Interstate 20 (I-59/I-20) elevated bridge replacement project in Birmingham, Ala., showcases the benefits of precast concrete segmental construction (see the Project article on page 10 of this issue of ASPIRE®). This replacement project is one part of the $750 million Alabama Precast concrete column in form with core form being extracted. Photo: Johnson Bros. Department of Transportation (ALDOT) reconstruction program for the I-59/I-20 minimize schedule risk, Johnson Bros. Use of Custom Shoring Towers in corridor. implemented the following strategies. Precast Concrete Segment Erection In the original design, the use of Strategies to Achieve an Advance Work Beneath the Existing longitudinal erection trusses was assumed. Aggressive Timeline Bridge This is a linear method of segmental To minimize the impact of construction The contractor decided to complete many construction in which the erection on the community, ALDOT opted to of the new foundations and footings truss is launched to the next span only shut down the corridor to complete the prior to shutting down the interstates after one span is fully erected. To meet replacement of the elevated structures for demolition. They used a combination an incentive-maximizing 12-month in one phase. The maximum construction of driven H-piles and drilled shafts and, construction schedule using this method, duration established in the contract was where there was limited head room, Johnson Bros. would have needed a 14 months, but the contractor could implemented micropiles to install the minimum of six launching trusses working maximize early-completion incentives new foundations around and beneath the concurrently. This linear method of by completing construction in 12 existing elevated roadway. erection would have been risky because months. Constructing the replacement if the erection of a particular span could in multiple phases would have extended Precasting the Concrete not progress in sequence, the contractor the project duration for several years. Substructures lacked the flexibility to quickly move the In May 2017, ALDOT awarded Johnson By precasting 160 pier cap and column erection equipment to another work area. Bros. Corporation the $474.7 million substructure elements, the contractor was contract for the I-59/I-20 bridge able to benefit from the nearby casting Working with Structural Technologies/ replacement project. This contract yard and minimize critical path activities. VSL, Johnson Bros. elected to use custom included a substantial bonus for early Delivering and assembling precast shoring towers to support the precast completion and unlimited liquidated concrete elements proved to be much concrete segments during segment damage penalties for late completion. faster than conventionally forming and erection in lieu of longitudinal erection To successfully complete this project and pouring variable-height piers in place. trusses. This method reduced schedule risk

30 | ASPIRE Spring 2020 Precast concrete column segments in storage. Note the extended column reinforcement and grout Reinforcing bar cage with transverse tendons sleeves that are visible on the ends of the segments. Photo: Johnson Bros. being installed into forms. Photo: Johnson Bros. by providing the contractor the flexibility on up to eight fronts at one time. To segments to cast, store, transport, and to deploy erection crews and equipment ensure that underground utilities near erect by about 400 segments. The team as needed to maintain the construction the towers would not be damaged by had to account for subsequent increases schedule, while allowing the use of more the construction loads imparted by the in segment weights and ensure that limits traditional construction equipment shoring towers, a foundation load analysis would not be exceeded for cranes, shoring, (cranes) for erection of the segments. If was performed. and hauling. one particular span could not be erected in series, the crew and erection equipment Three-Dimensional Modeling Dedicated Batch Plant could be redeployed to another area of During the bid phase, a virtual three- A project-dedicated batch plant was the project. This method also allowed dimensional model of the entire project installed in the casting yard, including a flexibility in sequencing the work. was developed. Using this model, each quality-control lab. The dedicated batch bridge span was studied to confirm that plant ensured consistent delivery and The shoring towers supplied were custom it could be erected using the proposed quality of concrete as needed for both the designed and fabricated for this project. shoring method. The study revealed that jobsite (approximately 4 miles away) and Shoring towers were preassembled at several spans would require special the precast yard. the fabricator’s facility to ensure proper portal frames and/or sliding of the fit-up. The tower bases were fitted with segments due to crane access limitations Maximizing Ef ciency in the screw jacks for vertical adjustments, and and ground conflicts, such as railroad Casting Yard the tops were telescopic and fitted with tracks and streets that could not be The casting yard for the 2316 box-girder jacking boxes. The main elements of the closed. segments included 12 casting cells for the shoring towers were color-coded to be segments—eight for typical segments, easily identified by field crews for their Minimizing the Number of Segments two for pier segments, and two for proper locations. Approximately 127 The length of typical and deviator expansion-joint segments. There were also individual shoring towers were provided, segments was increased from 10 ft to 20 reinforcing bar jigs. In addition to the which allowed the contractor to work 12 ft, which reduced the number of box-girder segments, 160 pier-cap and column elements were cast. Casting cells for precast concrete box-girder segments with protective covers. Photo: Johnson Bros. Casting cells and reinforcing bar jigs were organized to allow a single crawler crane to service four casting cells. The casting cells were fitted with movable shelters to protect both the segments and workers from the weather. To ensure reinforcement was ready when the forms were ready, each cell typically had two reinforcing bar jigs.

The segments included transverse post- tensioning (PT) tendons in the deck with four 0.6-in.-diameter, 270-ksi strands that were installed, tensioned, and

ASPIRE Spring 2020 | 31 Erect PS(a) Erect PS(b) and Erect S1 Erect S2 and connect to PS(a) connect to S1

Reset jacksjacks Reposition jacksjacks under S1 under S1 and S2

Figure 1. Typical segment erection sequence of a span. Note: PS indicates pier segment and S indicates span segment. Figure: Structural Technologies.

grouted in the casting yard. The 9386 Typical Span Erection bridge typically had four parallel lines four-strand PT transverse tendons were The shoring method for segment erection of box girders, towers could be moved prefabricated and individually placed provided an additional benefit by reducing transversely from one girder line to the in the reinforcing bar cage. To minimize the time it took to erect segments. With next or set in position using a crane. the number of transverse tendon pockets a truss-supported method, the truss Once the shoring towers were positioned, that would need patching, the dead-end must be loaded with all segments before the typical span erection progressed by anchorages of the four-strand transverse the segments can be joined together; placing the leading edge pier segments, tendons were cast into the deck. this requires handling and moving the followed by the span segments (Fig. 1). segments several times during the span The PT tendons were then installed and Once a segment was moved off the erection cycle. In contrast, the shoring tensioned to an initial force. Closure joints match-cast station, it was placed on a method does not require as much were placed and the tendons tensioned to finishing stand where any blemishes were handling and moving of segments. full force once the closure pour concrete patched, and transverse tendons were achieved the minimum required strength. tensioned. Segments were then moved The span erection cycle began with the At this point, the shores were released and and double-stacked in the storage area placement of shoring towers. Because the moved to the next span. An advantage of where transverse tendons were grouted. Using a three-dimensional model, engineers determined that several spans would require portal frames. With eight different erection fronts, Here, two portal frames support segments over an existing bridge. Photo: Structural Technologies. management of segment storage was critical to ensure that proper segments were delivered to the correct span and in the correct sequence.

Heavy segment haulers were used to transport the segments to the different erection fronts. During segment transit, the haulers were escorted by local police.

Multiple Work Fronts During segment erection, the jobsite was organized into eight work fronts. Each had its own dedicated superintendent, crews, and erection equipment. Using multiple work fronts fostered a competitive environment that motivated crews to adhere to quality, schedule, and safety goals.

32 | ASPIRE Spring 2020 The erection of the first span was completed on March 11, 2019. The main elements of the shoring towers were color coded to be easily identified by field crews for their proper locations. Approximately 127 individual shoring towers were provided, which allowed concurrent work on up to eight fronts. Photo: The erection of a split-pier segment. Photo: Structural Technologies. Structural Technologies. this shoring method was that the segments existing structure in 41 days, precast 160 could be placed and aligned in the same pier caps and columns as well as 2316 operation, reducing the number of times box-girder segments in 18 months, and the segments needed to be handled during erected the 172 spans of the new bridge span erection. in just over 7 months. This replacement structure opened in mid-January 2020 Conclusion and will serve the people of Birmingham In the I-59/I-20 project, the project team and the traveling public for years to leveraged precast concrete segmental come. bridge construction to deliver a durable ______structure efficiently and maximize an Robert W. Sward is a vice president with early completion incentive. The strategy Structural Technologies LLC in Fort Worth, Tex. of using custom-designed shoring towers to allow nonlinear construction, using longer but fewer segments, and the use of EDITOR’S NOTE Sliding shoring tower. The custom shoring precast concrete substructure elements towers could be moved transversely for erection all served to enhance constructability Visit aspirebridge.org for additional of an adjacent girder line. Photo: Johnson Bros. and reduce the contractor's risks. The information about and photos of project team demolished 180 spans of this and other projects.

technical knowledge New in Guide Specification for Grouted Post-Tensioning

Specification for Grouting2 of0 PT Structures19 certification

ASPIRE Spring 2020 | 33 CONCRETE BRIDGE TECHNOLOGY Investigating Existing Grouted Tendons by Miroslav Vejvoda, Post-Tensioning Institute

Post-tensioning (PT) tendons enable which the industry has been striving to designers to build large, economical address. First, owners want to be assured concrete bridges with low maintenance that quality grouting can be consistently costs. PT tendons are the primary achieved. Great progress has been made reinforcement relied on for the bridge’s in this direction (see the Concrete Bridge structural integrity. Tendons are typically Technology articles in the Winter 2017 Cover of the July issue of 2019 PTI Journal, grouted for two reasons: the grout issue of ASPIRE®). The fourth edition which featured grouted post-tensioning for protects the strand against corrosion, of PTI M55.1-19: Specification for bridges. All Photos and Figures: PTI Journal. and it provides the bond with the Grouting of Post-Tensioned Structures,1 surrounding concrete that achieves strain was issued in 2019. This document duct is fully grouted, the compression compatibility in design. includes requirements for the design, wave velocity generated and recorded testing, and installation of grout, along by the impact-echo system remains Owners’ Concerns with detailed grouting procedures. When constant. When voids or soft grout exist Given the significance of the grouted the specification is followed in its entirety, in the tendon, the resonant frequency is tendons, we need to ensure adequate good results are achieved. Also, the PT significantly lower or not measurable, durability to satisfy the design industry has moved to prepackaged grout indicating anomalies along the wave path. expectations. Although the vast majority mixtures that achieve consistent results of grouted tendons perform as designed, when mixed and handled properly. There are limits to the effectiveness of there have been limited cases of tendon these testing methods related to the corrosion due to grout defects or entry of Second, owners want to know how thickness of the concrete member. Most contaminants. The observed grout defects to detect grout defects in an already of the time, these limitations are not an included voids in the tendons and soft installed tendon. To address this concern, issue when evaluating a typical thin- grout. Both can lead to reduced protection three papers on the subject have been walled segmental or box-girder bridge. of the strands as well as local corrosion recently published in the PTI Journal. The However, GPR and impact-echo methods that can lead to strand breakage or, in articles are available for download on the have limited accuracy in thicker areas, extreme cases, tendon failure. Post-Tensioning Institute website using such as tendon high points. Even with the the links provided in the references. limitations, the impact-echo system is a The owners of major PT bridges have two promising method that can help identify main concerns about grouted tendons, Nondestructive Tests to Detect issues in existing tendons. Defects The most recent of the three PTI Journal The second article is “NDT Investigation articles is “Nondestructive Testing for of PT Ducts,” by David Corbett.3 This Voided and Soft Grout in Internal Post- December 2018 article also describes how Tensioning Ducts,” by Paul Fisk and GPR is used to locate tendons; once they Benson Armitage.2 This July 2019 article are located, potential grouting defects investigates the use of two nondestructive are identified through an ultrasonic pulse Sensor Array testing methods that can be used in and echo (UPE) method. Objects in detecting grout defects in tendons. The concrete are detected through reflections ground-penetrating radar (GPR) method that occur at the boundary between is used to accurately locate the internal two materials with different properties. ducts to a precision of ½ in. Then, sonic/ GPR works with reflections occurring ultrasonic impact-echo testing can be used when the two materials have different to detect voids or soft grout. Once a defect dielectric properties, whereas UPE location is identified, workers can drill into works with reflections occurring when the duct and use a borescope to document the two materials have differing acoustic Projectile Energy the tendon condition. The impact-echo impedance. GPR waves are totally Source system uses a projectile impact-energy reflected at a concrete-steel boundary source, a sensor array, and a computer and partially reflected at an air or Impact-echo testing. See Reference 2. to achieve quality display of data. If a plastic boundary. UPE waves are totally

34 | ASPIRE Spring 2020 Sonic/ultrasonic impact-echo testing identified potential voids and soft grout areas. See Reference 4. These three PTI Journal articles highlight together, tendon grouting deficiencies can how GPR can be used for locating be largely avoided. Pulse echo instrumentation includes a transducer tendons and the impact-echo method can and an indicating device (upper photo). The be used to locate tendons in congested References lower photo shows the transducer directly above areas and to detect potential voids or soft 1. Post-Tensioning Institute (PTI). 2019. a duct. See Reference 3. grout in ducts. Together, these methods PTI M55.1-19: Specification for reflected at a concrete-air boundary and have been used to successfully identify Grouting of Post-Tensioned Structures. partially reflected at a steel or plastic grouting deficiencies, typically voids but Farmington Hills, MI: PTI. boundary. Because of that, UPE enables sometimes also soft grout. Subsequent 2. Fisk, P., and B. Armitage. 2019. PT duct detection through reinforcing bar drilling into the ducts of those areas “Nondestructive Testing for Voided configurations that would limit GPR. More and the use of a borescope gives the and Soft Grout in Internal Post- significantly, the total reflection from air investigators sufficient information to Tensioning Ducts.” PTI Journal may make detection of voids in the duct devise an effective repair. 15 (1): 31–35. https://www. possible. A comprehensive evaluation post-tensioning.org/Portals/13/ using the amplitude and phase analysis Conclusion Files/PDFs/Publications/Reprints/ techniques of the pulse-echo technology is As always, the best defense against PTIJOURNALFisk-Armitage.pdf. now possible as three-dimensional imaging corrosion of the tendons is to do the job 3. Corbett, D. 2018. “NDT Investigation is available in commercial equipment used right the first time. This starts with the of PT Ducts.” PTI Journal 14 on site. owner and the designer using the state- (2): 31–34. https://www.post- of-the-art specifications PTI/ASBI tensioning.org/Portals/13/Files/ The third article of note is “Grouted M50.3-19: Specification for Multistrand PDFs/Publications/Reprints/ Post-Tensioning Tendon Evaluation,” and Grouted Post-Tensioning5 and PTI PTIJOURNALCorbett.pdf. by Liao Haixue.4 This December 2017 M55.1-19: Specification for Grouting 4. Haixue, L. 2017. “Grouted Post- article discusses the causes of corrosion of Post-Tensioned Structures1 (see the Tensioning Tendon Evaluation.” in tendons and describes evaluation Summer 2019 issue of ASPIRE for an PTI Journal 13 (2): 23–27. https:// techniques (GPR for locating tendons and article discussing these specifications). www.post-tensioning.org/Portals/13/ sonic/ultrasonic impact echo for detecting These specifications are intended to Files/PDFs/Publications/Reprints/ grout voids or soft grout). Additionally, be used together and should both be PTIJOURNALHaixue.pdf. the paper discusses a case study of a referenced in their entirety in the project 5. PTI and American Segmental Bridge bridge evaluation in British Columbia. specifications. Doing the job right the Institute (ASBI). 2019. PTI/ASBI Two possible voids, approximately 25 to first time also means specifying and M50.3-19: Specification for Multistrand 30 ft long, were identified using GPR enforcing the field personnel certification and Grouted Post-Tensioning. Farmington and the impact-echo method. Subsequent requirements as outlined in the M50.3 Hills, MI: PTI. drilling into the duct and borescope specification. A properly trained investigation confirmed the voids to be workforce is much less likely to make EDITOR’S NOTE 28 to 33 ft in length, demonstrating errors in the installation and grouting that the nondestructive testing method processes. The grouting plan, as required The editors thank the Post- identified the voids with good accuracy. in the M55.1 specification, should be Tensioning Institute for making Once the issues are located and evaluated, followed from the beginning to the end, links available for the three articles corrosion mitigation and repair solutions including any contingencies that are discussed so that readers can obtain can be designed. part of the plan. With all parties pulling them at no charge.

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Pictured: PHX Sky Train Project, Phoenix AZ CONCRETE BRIDGE TECHNOLOGY Guidelines for Inspection and Acceptance of Epoxy-Coated Reinforcing Steel at the Jobsite

by Pete Fosnough, The Epoxy Interest Group

Inspection of epoxy-coated reinforcing steel prior to concrete placement is critical to ensure that optimum corrosion protection is provided to the structure. In particular, repair of coating damage on the reinforcing bars prior to concrete placement and the use of plastic-headed vibrators should be addressed. This article presents information on the inspection of epoxy-coated reinforcing steel and may be used to supplement state or other agency requirements for epoxy-coated reinforcement. Handling Just like any material used on a jobsite, epoxy-coated reinforcing steel requires appropriate handling. These steps are aimed at reducing damage to the coating that could reduce its corrosion- protection performance. Handling and storage requirements for epoxy-coated Epoxy-coated reinforcing steel placed on epoxy-coated wire and plastic bar supports. All Photos: EIG. reinforcing steel may be included in contract documents or individual agency steel should be stored on suitable coated or plastic bar supports, and these specifications by reference to many material, such as timber cribbing. At should meet Class 1A requirements, as different sources including ASTM A775, no time should reinforcing steel be defined in the CRSI Manual of Standard A934, A1055, A1078, and D3963,1–5 stored directly on the ground. Practice.7 Bars should be tied using as well as ACI 301.6 The following • If the epoxy-coated reinforcing steel coated tie wire. This wire is typically summarizes the main requirements found is to be exposed outdoors for more 16.5 gauge or heavier and black in these specifications: than 30 days, it should be covered annealed. When used with epoxy-coated • Epoxy-coated reinforcing steel with a suitable opaque material reinforcing bars, tie wire is typically should be lifted using a spreader bar that blocks ultraviolet light and coated with polyvinyl chloride (PVC). or strongback with multiple pickup minimizes condensation. Coated bars may be cut using power points to minimize sag. During • Epoxy-coated reinforcing steel and shears, chop saws, or bandsaws; the cut sagging, steel reinforcing bars may uncoated steel should be stored ends should be patched using a two- rub against each other, causing separately. part epoxy. Bars must not be flame cut. damage to the coating. Bars may be bent at the jobsite, but • At no time should epoxy-coated Placement only with the permission of the engineer reinforcing steel be dragged. To protect epoxy-coated reinforcing responsible for the project, and this • Nylon or padded slings should be from oil contamination, steel forms should be documented. If bending is used, and at no time should bare should be oiled prior to placement of to be conducted on site, it should be chains or cables be permitted. the reinforcing bars. Bars should not be conducted at ambient temperatures. • Epoxy-coated reinforcing steel dragged or placed directly on the forms, should be unloaded as close as as this may result in oil contamination of Coating Damage possible to the point of concrete the bar surface. Bars should be placed If the epoxy-coated reinforcing steel has placement to minimize rehandling. on supports coated with or made of more than 2% of its area damaged in any • Bundles of epoxy-coated reinforcing nonconductive material, such as epoxy- given 1 ft section of coated reinforcement,

38 | ASPIRE Spring 2020 With proper inspection and handling, epoxy-coated reinforcing steel effectively protects against corrosion in reinforced concrete applications such as this bottom mat of reinforcement for a bridge approach slab. it may be rejected. ASTM D39635 further • Bar spacing, size, and type: Bars on supports coated with or made requires that the total bar surface area should be placed in accordance of nonconductive material, such as covered by patching material shall not with the structural drawings for the epoxy-coated or plastic bar supports. exceed 5% in any given 1 ft section of particular project, and conformance • Tie wire: Epoxy-coated reinforcing coated reinforcement. These limits on to the required specifications steel should be tied using a coated damaged and repaired areas do not should be documented. Current tie wire. include sheared or cut ends. practice often uses photographic • Bar samples: Some agencies require documentation for recording mill and inspectors to collect coated steel Coating Repair bar strength information, which is samples from the jobsite. These All damage to epoxy-coated steel stamped onto the bar. Information samples should be clearly identified reinforcement should be repaired to obtained from the mill and fabrication prior to submittal to the appropriate ensure maximum corrosion-protection reports may also be obtained. laboratory for testing. performance. The areas to be repaired • Bends: The coating at bends • Welding: Welding should only occur should be prepared for patching by using should not exhibit any cracking or with the permission of the engineer. a wire brush to remove any rust or other fractures. Particular care should Any welded surfaces should be contaminants. It is recommended for all be taken to inspect the condition cleaned and repaired with patch epoxy repairs to use a two-part patch of the coating in these regions material. material that has been recommended by because damage may occur during the powder-coating manufacturer. This fabrication. Protection of Coated material should be mixed according to • Lap lengths: Lap lengths approved Reinforcement Before, During, the manufacturer’s recommendations by the structural engineer should be and After Concrete Placement and should be used within the specified measured and documented. Laps are A meeting with the concrete contractor pot life. Patch repair materials should only permitted at locations approved prior to concrete placement may be be provided enough time to cure prior by the structural engineer. beneficial to discuss precautions that to concrete placement, which may be • Mechanical splices: Where should be taken to protect coated up to 8 hours for some patch materials. mechanical splices are used, they reinforcement. After placement of epoxy- All repairs should be conducted in should be epoxy-coated. Any damage coated reinforcing steel, minimize traffic strict accordance with the written to the coating after the bars are over it. At no time should stands or rails instructions furnished by the patch connected should be repaired. used for concrete placement machines be material manufacturer. For epoxy-coated • Tolerances and clear cover: welded to the epoxy-coated reinforcing reinforcing steel to comply with ASTM Concrete cover should be measured. steel. Care should be used to ensure that A775,1 the patch material must meet Additional information on placing activities during the concrete placement all of the requirements in Annex A2 of tolerances is provided by ACI do not result in damage to the epoxy- ASTM A775. Committee 1178 and CRSI.7 If coated reinforcing steel. Avoid placing concrete cover on the reinforcing concrete hoses on installed reinforcing Inspection steel is inadequate, force is steel; they may damage the coating as Inspection prior to concrete placement is sometimes used to move the they are moved. Care should also be taken critical as this is the final opportunity to reinforcement. When such methods to ensure that items such as unprotected document that the coated reinforcing steel are employed, damage to the couplers for concrete delivery hoses is installed according to the structural coatings must be avoided. are not dragged across the steel; these design and that the coating will provide • Repair of all damage: All damage actions may result in coating damage. optimum durability. Prior to concrete should be repaired. Consider a runway if necessary. Concrete placement, the following should be • Bar supports: Epoxy-coated pumps should be fitted with an “S” inspected and appropriately documented: reinforcing steel should be placed bend to prevent free fall of concrete

ASPIRE Spring 2020 | 39 directly onto the coating. Plastic-headed Bars. West Conshohocken, PA: About the Epoxy Interest vibrators should be used to consolidate ASTM International. Group concrete; steel vibrators may cause 3. ASTM International. 2016. ASTM coating damage. Bars that are partially A1055/A1055M-16 Standard The Epoxy Interest Group (EIG) of the cast in concrete and then exposed for Specification for Zinc and Epoxy Concrete Reinforcing Steel Institute extended periods, should be protected Dual-Coated Steel Reinforcing Bars. (CRSI) is a not-for-profit trade association against exposure to ultraviolet light, salts, West Conshohocken, PA: ASTM providing an authoritative resource for and condensation. Wrapping bars with International. information related to the use of epoxy- plastic or individual tubing is suitable for 4. ASTM International. 2019. ASTM coated reinforcing steel in reinforced providing long-term protection. A1078/A1078M-19 Standard concrete applications. Epoxy-coated Specification for Epoxy-Coated reinforcing steel is also known as epoxy- Conclusion Steel Dowels for Concrete Pavement. coated rebar (ECR), as well as fusion- Epoxy-coated reinforcing steel has been West Conshohocken, PA: ASTM bonded epoxy-coated rebar (FBECR). successfully applied to concrete bridge International. construction since the 1970s. As materials 5. ASTM International. 2015. ASTM The association serves the needs of and processes have been improved D3963/D3963-15 Standard specifiers, engineers, architects, fabricators, through the years, bridges using epoxy- Specification for Fabrication and end users with the most recent coated reinforcement have consistently and Jobsite Handling of Epoxy- information about how and where epoxy- demonstrated good field performance. Coated Steel Reinforcing Bars. coated reinforcing steel is used, as well Following the recommendations in this West Conshohocken, PA: ASTM as recent technical changes, educational article helps ensure that the highest quality International. seminars, and promotional activities. of corrosion resistance is provided for 6. American Concrete Institute EIG serves the construction market in the every project. (ACI) Committee 301. 2016. United States, Canada, and Mexico. Specifications for Structural References Concrete (ACI 301-16). Farmington 1. ASTM International. 2019. ASTM Hills, MI: ACI. Our Mission A775/A775M-19 Standard 7. Concrete Reinforcing Steel Institute The mission of the EIG is to promote the Specification for Epoxy-Coated (CRSI). 2018. Manual of Standard use and advance the quality of epoxy- Steel Reinforcing Bars. West Practice, 29th ed. Schaumburg, IL: coated reinforcing steel. Epoxy-coated Conshohocken, PA: ASTM CRSI. reinforcing steel is used instead of International. 8. A C I . 2 0 1 0 . Specification conventional reinforcing bars to strengthen 2. ASTM International. 2019. ASTM for Tolerances for Concrete the concrete and protect against corrosion. A934/A934M-19 Standard Construction and Materials (ACI The epoxy coating is applied to the steel in Specification for Epoxy-Coated 117-10). Farmington Hills, MI: a factory prior to shipping. Prefabricated Steel Reinforcing ACI.

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ASPIRE Spring 2020 | 41 FHWA

InfoBridge: Easy Access to the National Bridge Inventory and Much More—Part 2

by Dr. Jean A. Nehme, Federal Highway Administration

In January 2019, the Federal Highway Ad- user may customize and export. InfoBridge also Figure 2. An InfoBridge two-variable ministration (FHWA) released the inaugural displays the results on a map, which may be chart displaying the correlation between version of the Long-Term Bridge Performance exported and used in reports or presentations bridge age and bridge condition. (LTBP) InfoBridge—a user-friendly, centralized (Fig. 1). portal for e cient access to bridge performance- related data and information (https://infobridge. New to the second version of InfoBridge is fhwa.dot.gov). InfoBridge includes tools to fa- the ability to query on geographical boundar- cilitate bridge data analytics and provides for ies of metropolitan planning organizations storage, retrieval, dissemination, analysis, and (MPOs) and political districts such as U.S. visualization of data collected through state, congressional districts, state senate districts, national, and LTBP program e orts. In January and state house districts. In addition to MPOs 2020, the second version of the web portal was and political districts, this latest version of released.  is article, the second of two about InfoBridge allows querying based on special InfoBridge, discusses enhancements implement- projects. Currently, data from three FHWA ed in the new release and describes some of the research projects are included: ultra-high-per- portal’s advanced features (see the Winter 2020 formance concrete, timber bridges, and weath- issue of ASPIRE® for part 1). ering steel. More projects will be added in the future. Advanced Querying of Bridge Data Historical Changes to InfoBridge users are presented with an intui- Bridge Speci cations tive interface that enables querying on almost InfoBridge allows the user to explore changes all data  elds available within the portal. For to national bridge speci cations over the years. example, the user could query the database  is is a crucial feature for researchers investigat- for all bridges that have prestressed concrete ing the performance of bridge assets.  is tool as their main span material, have a structure lists speci cation changes chronologically and length between 150 and 500 ft, and are in poor allows for searches based on a single keyword or Data Analytics and condition as de ned in Chapter 23 of the Code on combinations of keywords. It also lists all per- Visualization of Federal Regulations (23 CFR 490.409).  e tinent references to each speci cation. It has been said that a picture is worth a thou- query generates a table of results, which the sand words; therefore, InfoBridge contains mul- Currently, the following types of speci ca- Figure 1. Queries can be made to tiple tools to transform data and information tions are included: form subsets of bridge data based on into graphs, charts, contour plots, dashboards, • Reinforcing steel almost any attribute stored within and maps. All analytics and visualization tools • Loads—braking force, centrifugal force, InfoBridge. All Figures: Federal Highway are available on the selection of bridges that re- earth pressure, earthquake load, ice load, pe- Administration. sults from a user’s query. An example of a two- destrian live load, temperature load, vehicu- variable chart is provided in Fig. 2. lar live load, water load, wind load • Load combinations Models for Bridge Deck Condition Forecasting In the future, the following types of speci ca- InfoBridge now includes three newly devel- tions will be added: oped models to forecast bridge deck conditions: • Minimum and maximum reinforcement (1) time in condition, (2) deep learning, and • Shear design of concrete (3) proportional hazards deterioration models • Prestressed concrete design (Fig. 3). All three models use historical National • Lightweight concrete Bridge Inventory data in addition to data from • Load rating other sources, such as the National Aeronautics • Approximate methods of analysis and Space Administration Modern-Era Retro- • Steel bridge design spective Analysis for Research and Applications,

42 | ASPIRE Spring 2020 Figure 3. Three new models are now available to forecast bridge deck conditions. Version 2 climatic data, to forecast bridge deck on bridge performance. Currently, the tables are bridges with multiple rounds of NDE assess- conditions. being restructured to enable more consistent ments. querying and improve the accuracy of research ese models are intended to be used for conclusions drawn from InfoBridge design and research. Improvements are being planned to construction data. A stand-alone interface is be- EDITOR’S NOTE increase their forecasting accuracy and will be ing designed to facilitate the inclusion of addi- included in future releases of InfoBridge. Doc- tional data by bridge owners. InfoBridge is intended for research, umentation for the models is published in the but its data and tools can also be Library module of InfoBridge. Technical papers Nondestructive Evaluation useful to bridge designers. To access describing the models are currently being pre- Data InfoBridge, visit https://infobridge. pared for publication in peer-reviewed journals. InfoBridge has a tabular interface that pro- fhwa.dot.gov. For more information vides access to downloadable  les containing on the portal and the LTBP Design and Construction nondestructive evaluation (NDE) bridge data program, visit https://highways. Data and metadata. In addition, tools for NDE data dot.gov/long-term-infrastructure- As-built plans for 1600 bridges have been visualization are included under the Bridge In- performance/ltbp/long-term-bridge- transposed into searchable data tables (Fig. 4). formation/Graph tab (Fig. 5). Future versions performance, or contact Jean is e ort aims to help users better understand of InfoBridge will include a tool to display the Nehme at (202) 493-3042 or jean. the impacts of design and construction practices progression of bridge deck deterioration for [email protected].

Figure 4. Bridge design and construction Figure 5. Nondestructive evaluation contour plots with dynamic value ranges enable data for a project in the LTBP database. users to adjust the ranges and instantly display the resulting change in values.

ASPIRE Spring 2020 | 43 A PROFESSOR'S PERSPECTIVE Elevating the Role of Materials Science in Bridge Engineering Education

by Dr. Kyle A. Riding, University of Florida

s a new decade begins, we are inclined to reflect on progress we Chicago and Walnut Lane Gemert Cyclist Bridge: A Memorial Bridge: Three-Dimensional- Alton Railroad Buffalo Creek Brooklyn Bridge: have already made and plan and project Bridge Over Precast, Post- Bridge: Fiber- Printed Prestressed The Iron Steel-Cable Missouri River: Tensioned Concrete Reinforced Polymer Concrete Bridge in the our efforts going forward. For those Bridge: Cast Suspension Steel Bridge in Bridge in Reinforcing Bars in Netherlands Iron Bridge Bridge in New of us working in education, this is also Missouri Pennsylvania West Virginia in England York an opportune time to assess how we can best prepare our students and new engineers for future success. 1780 1800 1820 1840 1860 1880 1900 1920 1940 1960 1980 2000 2020

Alvord Lake Bridge: Oued Fodda Bridge: Pedestrian Bridge in Akashi Kaikyo Reinforced Prestressed Concrete Sherbrooke, A Century of Progress Suspension Bridge in Concrete Bridge in Canada: Ultra-High- Bridge in Algeria Japan: Self- In the bridge community, I think it California Performance Consolidating is especially useful to highlight the Concrete Bridge Balduinstein Bridge: Prestressed Concrete Used in enormous progress we have made over Concrete Segmental Bridge in Anchor Blocks the last century or more. The timeline in Germany Constructed Using Balanced-Cantilever Method Fig. 1 shows a few bridges that I view as technological pioneers. While there are Figure 1. Timeline showing the year of construction for bridges that introduced many important and noteworthy bridges innovative technologies. All Figures and Photos: Dr. Kyle A. Riding. in communities around the world, I selected these bridges to highlight fibers in concrete mixtures. Going performance concrete (UHPC) proved because they represent early examples forward, bridge construction can be to be so economical and successful in a of technologies that have made bridges semiautomated by leveraging three- four-span, 361-ft-long segmental, post- faster to construct, lighter, more cost- dimensional printing, machine learning, tensioned pedestrian bridge constructed effective, more durable, and—most and concrete with tailored flow and in 2017 in Medellín, that a second importantly—safer. strength-gain properties. UHPC segmental, post-tensioned bridge, two spans and 98 ft long, was built in These bridges also have something else Pioneering engineers make progress by Manizales in 2018.3 in common. Each was constructed using combining a solid grasp of fundamental new structural engineering designs engineering mechanics, new knowledge Preparing Engineers enabled by the development of new in materials science, and practical to Build the Bridges of materials. For example, the Chicago and construction in their designs. One such Tomorrow Alton Railroad Bridge over the Missouri pioneer was Eugène Freyssinet. While As bridge technologies have become River and the Brooklyn Bridge in New other researchers had previously tried increasingly sophisticated, engineers have York City took advantage of cheap and to embed tensioned wires into concrete needed greater knowledge and control plentiful steel made possible by the to introduce prestressing, Freyssinet over their materials. Structural engineers new Bessemer steel process. The Oued successfully designed modern, functional in the United States are now called Fodda Bridge in Algeria, the Balduinstein prestressed concrete members for upon to evaluate material options and Bridge in Germany, and Walnut Lane the Oued Fodda Bridge project. He submittals and to be the final word on Memorial Bridge in Philadelphia, Pa., accomplished this by using high-strength their suitability to meet the performance were showcases for the benefits of steel and concrete and by calculating expectations of owners. prestressing concrete in bridge structures. concrete creep and shrinkage losses.1 While the concept of prestressing had He also pioneered long-line prestressing However, even as the need for been theorized for several decades, beds still used by many precast, knowledge of materials has increased, higher strength concrete and steel made prestressed concrete plants to cost civil engineering programs have come it practical for these bridges.1 effectively fabricate bridge members.2 under pressure by state legislatures and university administrations to reduce credit In recent history, bridge designers When pioneering technology is shown hour requirements.4 For example, in have focused on simpler construction to work well and be economical, it 2018 the University of Florida reduced and greater durability by using high- can soon become commonplace. the number of credit hours required to performance materials, including For example, in Columbia, ultra-high- obtain a bachelor of science degree in

44 | ASPIRE Spring 2020 My final suggestion is to encourage new hires to use free web-based resources. For example, free lectures by world-renowned professors and engineers have been posted on YouTube. Also, ACI offers free videos of excellent presentations on a variety of new materials and structural concepts, including recent technology developments at https://concrete. org/education/freewebsessions/ completelisting.aspx. Conclusion This segmental, post-tensioned pedestrian bridge in Medellín, constructed in 2017, is Bridge engineering has come a long the first ultra-high-performance concrete bridge in Colombia. way in the past century. Much of this progress was steered by clever engineers civil engineering from 131 to 128; many materials, pavements, and structures using materials science to enable new other universities in the United States cosponsored by the American Concrete bridge load-support systems. Materials have made similar reductions. Institute (ACI) Foundation and the science will continue to yield great Portland Cement Association (PCA) advancements in bridge design and Today, undergraduates majoring in civil Education Foundation is an excellent durability and should be an integral part engineering typically take only one place to start. of the formal and continuing education course on materials, with a couple of of bridge engineers. weeks at most dedicated to each civil A second way to increase materials engineering material. Engineers certainly science knowledge is by using References need a deeper knowledge base than professional development hour (PDH) 1. Sanabra-Loewe, M., and J. Capellà- that to make critical decisions about requirements as an opportunity to Llovera. 2014. “The Four Ages of Early material performance in bridges and learn. Peers and new hires should also Prestressed Concrete Structures.” PCI to make breakthroughs in new bridge be encouraged to participate. Excellent Journal 59 (4): 93–121. technologies. So how do we elevate the materials science courses are offered by 2. Freyssinet, E., and J. Seailles. 1930. level of materials science knowledge in several organizations. Here are some France Patent No. 680547. the structural engineering community? prominent offerings: 3. Núñez, A., J. Patiño, S. Arango, Here are a few suggestions. • The PCA course Design and Control and W. Echeverri. 2019. Review of Concrete Mixtures is offered on First Structural Applications First, structural engineering master’s regularly. For more information, of UHPC in Colombia. Second programs should include a materials visit https://www.cement.org/Learn/ International Interactive Symposium science course as a core competency. education/design-and-control-of- on UHPC, 1–10. https://www. Partly as a response to dwindling credit concrete-mixtures-course. extension.iastate.edu/registration/ hour requirements at the undergraduate • The National Ready-Mixed Concrete events/2019UHPCPapers/UHPC_ level, master’s degrees have become the Association (NRMCA) offers a series ID118.pdf. de facto entry-level degree for many of courses on concrete technology 4. Myers, J.J. 2018. “Developing structural engineering firms. Adoption with different levels of certification a Greater Feel for Structural of a materials science course as a as a concrete technologist. NRMCA Engineering.” ASPIRE 12 (2): 36–38. master’s requirement could help raise the courses on concrete fundamentals, knowledge level of engineers responsible concrete durability, and other topics for specifications, acceptance, and are offered around North America. design . I believe that a concrete materials For more information about the or composite materials course would give program, schedule, and locations of EDITOR’S NOTE structural engineering students a good courses, visit https://www.nrmca.org/ foundation for future learning on the products/conferences.asp. Technical institutes play a vital topic. If your university does not offer a • The ACI University has a wide role in promoting continuing graduate course in structural materials, it range of web-based courses with education opportunities for new may be possible to take an online course continuing education credits. To learn and experienced engineers. PCI through another university's distance about ACI courses on a variety of offers eLearning modules on many education program and transfer the concrete topics, visit https://concrete. transportation topics, including credits to your university. org/education/aciuniversity.aspx. “Materials and Manufacturing of • Local ACI chapters often host Precast, Prestressed Concrete.” See Universities looking to train faculty to speakers at events that include a page 41 of the Winter 2020 issue of teach a graduate concrete materials dinner or other activity. To find your ASPIRE® for additional information course will find that the annual local chapter, visit https://concrete. and a sampling of other course professors’ workshop on concrete org/chapters/findachapter.aspx. options.

ASPIRE Spring 2020 | 45 PCI Offers eLearning Modules Courses on Design and Fabrication of Precast, Prestressed Concrete Bridge Beams

The PCI eLearning Center is offering a new set of courses that will help an experienced bridge designer become more pro cient with advanced design Start with PCI eLearning Series T100 Courses methods for precast, prestressed concrete  exural members. There is no cost to enroll in and complete any of these new bridge courses. The courses are based Preliminary Precast, Prestressed Concrete Design (T110) on the content of the 1600-page PCI Bridge Design Manual, now available for free Materials and Manufacturing of Precast, Prestressed after registering with a valid email. While the courses are designed for an engineer with 5 or more years’ experience, a less experienced engineer will nd the content Concrete (T115) very helpful for understanding concepts and methodologies. Design Loads and Load Distribution (T120) Where applicable, the material is presented as part of a “real world” design Additional courses are available at www.pci.org/eLearning of a complete superstructure example so that the student can see how actual calculations are completed according to the AASHTO LRFD speci cations. This web-based training course was developed by the Precast/ All Transportation courses on the PCI eLearning Center are completely FREE and Prestressed Concrete Institute (PCI) for the Federal Highway include PDHs or other continuing education credits. Administration (FHWA) through a contract with the American Association of State Highway and Transportation Of cials (AASHTO).

CONCRETE CONNECTIONS Concrete Connections is an annotated list of websites where information is available about concrete bridges. Links and other information are provided at www.aspirebridge.org. IN THIS ISSUE https://www.ntsb.gov/investigations/AccidentReports/ district. The bridges are featured in the Project article on page Reports/HAR1902.pdf 10 and the Concrete Bridge Technology article on page 30. This is a link to the National Transportation Safety Board https://www.pci.org/PCI_Docs/Design_Resources/ (NTSB) Highway Accident Report for the 2018 pedestrian About_Precast/PCI%20Zone6%20Curved%20 bridge collapse in Miami, Fla., which is referenced in the Spliced%20Girders.pdf Editorial on page 2 and the Perspective article on page 50. This is a link to information on PCI curved and straight https://www.ntsb.gov/news/events/Pages/2019- precast concrete U-girders Curved U-girders are mentioned in HWY18MH009-BMG.aspx the Project article on page 20 and the AASHTO LRFD article This is a link to information presented at the NTSB meeting on page 48. on October 22, 2019, to determine the probable cause of https://www.youtube.com/watch?v=Hmk6W27r92w&f the 2018 pedestrian bridge collapse in Miami, Fla., which eature=youtu.be is referenced in the Editorial on page 2 and the Perspective This is a link to a video and renderings of the Mid-Coast article on page 50. Corridor Transit Project, a light-rail transit project in Southern https://www.fhwa.dot.gov/bridge/pubs/hif18046.pdf California. A Project article on the Genesee Avenue Viaduct, This is a link to FHWA’s Manual for Refined Analysis in Bridge which is part of this project, begins on page 20. Design and Evaluation, which is mentioned in a Perspective https://www.fhwa.dot.gov/bridge/loadrating/pubs/ article on page 8. hif18061.pdf https://www.al.com/news/2020/01/alabama-your-700- This is a link to the Federal Highway Administration (FHWA) million-i-5920-bridge-through-birmingham-is-ready.html report Concrete Bridge Shear Load Rating Synthesis Report. This is a link to photos and a video of the Interstate 59/ Shear load rating of an existing bridge is the focus of a Interstate 20 bridges through Birmingham’s central business Concrete Bridge Technology article on page 24.

46 | ASPIRE Spring 2020 NEW CHAMPLAINNEW BRIDGE

WE MAKE INFRASTRUCTURE SAFER, STRONGER, AND SMARTER. AASHTO LRFD Structural Design Based on Strut-and-Tie Modeling

by Dr. Oguzhan Bayrak, University of Texas at Austin

tructural design and detailing of It must be emphasized that the to-straddle-cap connection must Sreinforced and prestressed concrete detailing of the end of the U-beam must accommodate the assumed load transfer members and structures requires a be consistent with the assumed transfer mechanism, which is hard to accomplish thorough understanding of load transfer of loads into the cap, as noted in the with standard details that involve mechanisms. Since its introduction in following discussion. anchorage of U-beam reinforcement into the late 19th and early 20th centuries,1,2 the straddle cap and continuity post- strut-and-tie modeling (STM) has Option 1—Reaction Applied at tensioning passing through the cap, enabled structural designers to Nodes A and B in addition to providing a substantial appropriately visualize the transfer of The reaction for beam 2 is divided amount of hanger reinforcement within loads from their points of application in half and applied at nodes A and B. the U-beams. The required detailing down to structural foundations. This Because no loads are being applied at renders this option impractical in most explicit visualization then helps guide nodes C and D, the demand for the situations, and the effectiveness of such a the associated structural detailing based hanger reinforcement (ties AE and BF) load transfer mechanism is questionable. on key load transfer mechanisms. In the is zero. This load transfer mechanism United States, the American Association calls for the U-beam design and detailing Option 2—Reaction Applied at of State Highway and Transportation to be consistent with the assumed Nodes C and D Officials’ AASHTO LRFD Bridge Design load application to the straddle cap. For this option, the reaction for beam Specifications has included STM design Therefore, a substantial quantity of 2 is again divided in half but is applied provisions since 1994. To illustrate the hanger reinforcement must be provided at nodes C and D. This concept for load power of STM, this article discusses an within the prestressed concrete U-beam application assumes that the inclined integral superstructure and substructure at or within the immediate vicinity of its webs of beam 2 are supported directly connection and how STM provides connection to the straddle cap. Picking beneath the bottom flange; therefore, the insights on load transfer. up the entire reaction with stirrups support reaction introduces compression placed within the U-beam webs at the into the webs of the U-beam. This Options for Modeling Load face of the cap presents a substantial assumption is overly conservative in Transfer challenge for detailing because the most common structural connection Figure 1 shows three lines of hanger reinforcement provided must be details. Hanger reinforcement prestressed concrete U-beams rigidly centered on the vertical tie envisioned sufficient to transfer 100% of the beam connected to an integral straddle bent. within the end region of the U-beam. reaction must be provided within the For the sake of simplicity, let us assume Structural detailing of the U-beam- cap where the superstructure meets symmetrical loading in forward and Figure 1. Strut-and-tie modeling (STM) for integral superstructure-to-substructure back spans that frame into the straddle connection for U-beams framing into a straddle cap. Figure: Dr. Oguzhan Bayrak. cap and all loads are vertical. Live and dead loadings on the deck result in substantial beam reactions that need to be transferred to the cap and through the cap to the columns. Where beam lines 1, 2, and 3 frame into the straddle cap, the loads (U-beam reactions) need to be transferred to the cap in a realistic manner. To envision this transfer of vertical loads to the cap at beam line 2, the designer has three options: Option 1: Apply beam reaction at nodes A and B Option 2: Apply beam reaction at nodes C and D Option 3: Apply beam reaction at nodes A, B, C, and D

48 | ASPIRE Spring 2020 the substructure. Furthermore, the of those bars into the cap, along with We must reconcile how loads reinforcement needs to be centered on the roughened surfaces of the webs are transferred from their points ties AE and BF. To resist the two forces of the precast concrete U-beam, all of application into the concrete from the beam reaction (notably, in this help justify dividing the beam reaction component, then from one element case, the beam reaction is presumed to among the four nodes. In my view, to the next, and eventually to the be significant), a substantial quantity and in most structural details I have foundations. In my view, the fact that of hanger reinforcement must be seen to date, this balanced approach STM stimulates structural designers to provided in the cap where the bottoms constitutes a good structural think through the load path is the most of the slanted webs of the U-beam engineering solution. important attribute of this technique. intersect the straddle cap. Although As we aspire to design concrete bridges this assumption is conservative, it may Once the load transfer model for the to last no less than a century, STM result in an excessive amount of hanger U-beam-to-straddle-cap connection plays a role in the design of unique reinforcement in the cap; detailing is selected for beam 2, this model can structures, critical bridge components, of this reinforcement may present be repeated for the other U-beam-to- and the bridge infrastructure that will constructability challenges. straddle-cap connections. The complete serve our communities. truss visualized in the straddle cap can Option 3—Reaction Applied at then be used to transfer the loads into References Nodes A, B, C, and D the columns and subsequently into the 1. Ritter, W. 1899. “Die Bauweise For this option, the reaction for foundations. Hennebique” (The Hennebique System). beam 2 is divided into four equal Schweizerische Bauzeitung 33 (7). vertical loads and applied at nodes A, Conclusion 2. Mörsch, E. 1902. Der Eisenbetonbau, B, C, and D. With this assumed load The superstructure-to-substructure seine Theorie und Anwendung (Reinforced application, 25% of the beam reaction connection discussed in this article Concrete: Theory and Application). would transfer to each of the diagonal illustrates the decision-making process Stuttgart, Germany: K. Witter. compression struts framing into nodes in STM. As can be observed in the A and B, with the remaining vertical example, STM drives a designer to 3. American Association of State Highway load going into struts CE and DF. consider the implications of model and Transportation Officials (AASHTO). A compression strut is also required selection, construction methods, and 2017. AASHTO LRFD Bridge Design between C and D. The vertical details. In structural engineering, we Specifications, 8th ed. Washington, DC: components of the forces in struts do not get something for nothing. AASHTO. CE and DF need to be picked up by ties AE and BF. Option 3 results in a more practical quantity of hanger reinforcement that is easier to detail and construct than either of the other options with half the force in the tie reinforcement in the U-beam as for Option 1. It is also worth noting that the compressive forces in struts CE and DF influence the tie-force distribution along the length of the longitudinal tie at the bottom of the cap. With respect to U-beam design, one-fourth of the total beam reaction must be carried by the stirrups within each web of the U-beam, such that load application at the top nodes A and B can be justified. As required in the AASHTO LRFD specifications, the sectional shear design of the U-beams must be done using provisions based on simplified Modified Compression Field Theory (MCFT) (AASHTO LRFD specifications article 5.7.3).3 The quantity of stirrups required in the U-beam, on the basis of MCFT design, is typically sufficient to satisfy the application of one-half of the beam’s reaction to the top nodes (A and B). Furthermore, the skin reinforcing bar detailing of the webs and extension

ASPIRE Spring 2020 | 49 PERSPECTIVE Why Didn’t They Just Close the Road?

by Gregg Freeby, American Segmental Bridge Institute, and William Nickas, Precast/Prestressed Concrete Institute

After the release of the National ensure public safety, health, and welfare • How is the insurance coverage Transportation Safety Board (NTSB) were maintained. When you are in that addressed? report on the Florida International type of situation, bridge technical staff • How is the performance bond University (FIU) pedestrian bridge gather data and calculate scenarios: addressed? collapse,1 many have asked, “Why • Let’s look at what changed since • If this is a design-build job: Do we didn’t they just close the road?” While the last inspection. need to wait for others to propose this article will not attempt to answer • Let’s look at the plans and details. the fix? this event-specific question, we will • Let’s look at the existing • If we do not own this problem yet, provide the perspective of two former calculations. can we let their insurance carrier state bridge engineers (the authors) • Let’s make some new calculations. sort this out? about their decision-making process • Let’s use our manuals of practice when faced with similar challenges to reevaluate the damage or Sometimes, the engineers involved will regarding whether to recommend deterioration. conclude with complete certainty that closure of a roadway. • Have we looked at the distress the bridge needs to be closed because and quantified the accumulated the engineering calculations and data Our Preeminent damage to the member(s)? clearly support that decision. Still, Responsibility • What is the consequence of load putting that decision into action isn’t As engineers, our first responsibility is exceedance? always as easy as it sounds. to protect the public safety, health, and • Is there public access on or below welfare. This is spelled out in most states’ this bridge? Pushback authorizing legislation that regulates the • Who owns the road on and/or When making a recommendation to practice of engineering as well as in most below the bridge? close a bridge, state bridge engineers engineering codes of ethics. • Can the structural support system inevitably hear the following types of be changed—for example, by objections from those around or above In 1914, the American Society of Civil installing temporary supports—to them: Engineers (ASCE) adopted its first code of mitigate the concern? • We can’t close that road—10,000 ethics to be used as a model for conduct • Can traffic be shifted or loads vehicles per day use that facility. for ASCE members. In the current version reduced by a truck detour to • That’s the only route to the school. of this code, the first point under Canon temporarily mitigate the risk? • That will create an hours-long 1 is the following statement:2 detour. When you are in that same type of • Closing the bridge will make us Engineers shall recognize that situation during construction, procurement look like we don’t know what we the lives, safety, health and managers and governmental legal counsel are doing. welfare of the general public are gather different types of data: • Commissioner So-and-so isn’t dependent upon engineering • Who has the contract authority to going to be happy—that road is on judgments, decisions and practices stop the construction? his way home. incorporated into structures, • Was the contractor proceeding at • We’re likely to endanger more machines, products, processes and their own risk? people with the traffic detour. devices. • Can we suggest that the contractor close the project? These objections are often followed by Assessing a Potential • Are you questioning the second-guessing: Closure Situation contractor’s means and methods? • Aren’t your capacity calculations As state bridge engineers, we both • What is the standard of care always on the conservative side? faced situations that required making defined in the procurement Isn’t there always more capacity the recommendation to close a given document? than what we predict? roadway or bridge due to findings • Who owns this problem? • Are we really going to see the from an in-service or construction • Is the bridge fit for service, and can live loads you used in your inspection, or some other event, to it meet its intended purpose? computations?

50 | ASPIRE Spring 2020 • Hasn’t the structure been this way Elected officials are often sensitive to Conclusion for several days, months, or years? how their constituents will react when As the recommendation for closure Why close it now? their usual commute home from work is escalated, the individual with the • We’ve had problems like this in the gets disrupted by an unexpected ultimate legal authority may be on the past and nothing bad happened. transportation asset closure. DOT frontlines of a media firestorm when the Why would we expect this to be leadership can also be sensitive to the closure is announced and implemented. any different? general message a specific closure sends To withstand this public scrutiny, the to the traveling public: If this bridge had individual in charge requires not only In his October 28, 2019, concurring to be closed, what about other ones like courage but also complete confidence statement about the FIU bridge it? These pressures are felt by everyone in the recommendation being brought collapse (see the statement following involved in these decisions. Ultimately, to them by the state bridge engineer. this article), NTSB vice chairman Bruce it is be better to be asked why you took While it may be a simple thing to say, Landsberg rightfully identified that the preemptive action that might not have “Just close the bridge,” implementation recommendation to close the roadway been needed, rather than trying to explain of this decision can often be a would have been an “unpopular after a tragedy why you didn’t; however, challenge. Again, you only get to go to step.” Indeed, “unpopular” is probably in the decision-making moment, this that well so many times. an understatement at a time when sentiment is of little consolation. most motorists expect to be able to References go anywhere at any time with few Who Makes the Call? 1. National Transportation Safety impediments. In recent years, crashes State bridge engineers typically do not Board (NTSB). 2019. Pedestrian involving 50 to 60 cars at a time have the direct authority to close any Bridge Collapse Over SW 8th during inclement winter weather and all bridges in the state. The DOT Street, Miami, Florida, March illustrate this point. may also lack the legal authority to close 15, 2018. Highway Accident a bridge. Instead, this authority often Report NTSB/HAR-19/02 PB2019- For a state bridge engineer, advising lies with local law enforcement, local 101363. https://www.ntsb.gov/ the department of transportation governments, or owners of the bridge. investigations/AccidentReports/ (DOT) leadership that a major in-service In these instances, the DOT must rely Reports/HAR1902.pdf. roadway or bridge needs to be on these local officials or owners to take 2. American Society of Civil Engineers closed may even have career-limiting appropriate action. (ASCE). 2017. Code of Ethics. https:// repercussions. That may be unfair, www.asce.org/code-of-ethics. but the reality is you only get to go Sometimes, convincing local officials of to that well so many times before you the urgency of the recommendations is EDITOR’S NOTE lose credibility. The traveling public challenged by their complacency or lack and elected officials expect that the of understanding—“I drove over that The entire text of the concurring transportation owner will do everything bridge yesterday. What could possibly statement by NTSB vice chairman in its power to keep traffic moving. be wrong?” Instances like this call for Bruce Landsberg (see pp. 106–107 of Closing a bridge or roadway or shutting strong leadership from not only the state Reference 1) is reproduced below. down a construction project is counter bridge engineer but also those above the The text has been reformatted from to that expectation. engineer in the chain of command. the report to fit the page.

National Transportation Safety Board (NTSB) Member Statement Vice Chairman Landsberg filed the following concurring statement on October 28, 2019. Concurring Statement of Vice Chairman Bruce Landsberg re Miami Pedestrian Bridge Collapse A bridge-building disaster should be incomprehensible in today’s technical world. We have been building bridges in this country for over two hundred years, and long before that in other parts of the world. The science should be well sorted out by now—and for the most part, it is. The investigation clearly high- lighted basic design flaws and a complete lack of oversight by every single party that had responsibility to either identify the design errors or stop work and call for a safety stand-down, once it was clear that there was a massive internal failure. The “what” is very clear but the “why” is more elusive. Despite the public’s anger, distress, and disappointment, none of the responsible organizations had any intent for this tragic event to occur or to cause any injury or loss of life. Sadly, good intentions do not suffice for competence and diligence. Engineering schools will use this as a landmark case study for years—and they should. The Engineer of Record (EOR) employed by FIGG Bridge Engineers, Inc., was experienced, but his calculations were erroneous. Reflection on this event should go far beyond merely a technical review. The checks and balances that were required by the Florida Department of Transportation (FDOT) and American Association of State Highway and Transportation Officials guidance and incumbent upon Louis Berger (LB), the peer-reviewing organization, were completely lacking. LB lowered their bid to review the project by 43 percent in order

ASPIRE Spring 2020 | 51 to get the business, but also reduced the scope of the review. The reason given was there wasn’t enough money in the project to cover their efforts. That’s both disingenuous and unconscionable. It also was in violation of FDOT’s requirement that there be an independent second set of eyes to review everything—not just what was economically convenient. It is likewise incomprehensible and unethical that LB would even bid on a job for which they lacked the requisite qualifications. That FDOT, which was supposed to review the plans, did not know, or think to ask, about their qualifications is more than just an oversight. It’s just plain sloppy. Ditto for FIGG. FDOT claimed a technical error on the FDOT website and then, after the collapse, fabricated a disclaimer that they are not responsible for the data that they post. That’s unac- ceptable in my view—either ensure the information is accurate or don’t post it. The bridge was not properly designed, and there was no qualified oversight on that design. When the inevitable began to happen—a creeping, catastrophic mate- rial failure, nobody did anything, despite what NTSB Chairman Sumwalt accurately described as the “bridge screaming at everyone that it was failing.” Why? Once the cracking became evident, not one of the organizations involved was willing to take the essential and unpopular step to call a halt and close the road. This is similar to the circumstances of the space shuttle Challenger disaster where the decision was made to launch in extremely cold weather. The engineers recommended against it because the O-Rings that were critical to fuel system integrity would be operating outside their design parameters. Rationalization, optimism, and schedule pressure contributed to what has been described in management training circles as “Group Think.” Strong and confident personalities persuade everyone that everything will be OK. Despite misgivings and technical expertise that advise against such action, the team moves forward as a group. It appears that the same mindset was in play here, in every organization: FIGG, LB, MCM (the construction company), Bolton Perez (the engineering firm over- seeing the bridge construction), FDOT, and finally, Florida International University. It also appears that every organization absolved themselves of responsibility by rationalizing that if the EOR says it’s OK, it must be OK, and if anything bad happens—it’s on him. That is not the intent of peer review or safety oversight, and certainly fails the system of checks and balances in place to prevent catastrophes like these. We’ve learned this the hard way too many times in transportation modes. The NTSB’s stated role is not to lay blame, but some would say that’s exactly what we do when we apportion causation. The human failing that affects all of us is complacency. It is not a term the NTSB uses often, but in my opinion, it is present in nearly every accident and crash. We are creatures of habit, and when we become comfortable through long repetitive experience, the guard often comes down—periodically with disastrous results. This is precisely what safety management systems are designed to prevent—to trap errors in process before they become catastrophes. While disasters may be perfectly clear in hindsight, the best organizations take proactive measures—constantly. Schedule pressure, economics, overconfidence, and complacency all work to counter good intentions and too often create tragedy. It is my fervent hope that the organizations involved will take the NTSB recommendations seriously and quickly implement them. The lives lost and the families disrupted deserve at least that much.

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