C+S January 2021 Vol. 7 Issue 1 (web)

Project Management for AEC Professionals Virtual Seminar


ABOUT THIS VIRTUAL SEMINAR PROJECT MANAGEMENT FOR AEC PROFESSIONALS - VIRTUAL SEMINAR PRICE: $699 THIS VIRTUAL SEMINAR WILL BEGIN ON JANUARY 6, 2021 A new training for project managers led by a panel of three experts backed by a ton of research on how to best train project managers to be more effective and efficient. Each team member brings their own unique experiences and skillset to project teams. Effectively leveraging the talents of your team can optimize team effectiveness. Project Management for AEC Professionals provides people-focused, science-driven practical skills to help project leaders harness the power of their team. By addressing the most important aspects of any project – the people – this course will provide practical tech- niques that can be immediately implemented for a positive impact on any AEC team or business. AEC Professionals are extensively trained on technical skills and less so on how to manage a team. However, with rapidly evolving technology, increasing fee pressure, multi-generational teams, and many other challenges, effective team leadership in project environments has proven to be the key to thriving in the high-pressure AEC environment. These challenges, coupled with the fact that project managers are often left to learn on the job, leaves new and seasoned leaders left to use a trial and error style team leadership that is prone to missteps. Each decision made can impact profit, risk, and client-relationships. This course will take the guesswork out of leading your team and develop project leaders who are equipped with practical, science-backed skills to empower their teams to achieve and surpass their goals. This virtual seminar has SOLD OUT for the last three sessions, so REGISTER NOW! LEARN MORE


PAST ATTENDEE FEEDBACK: • 94% of attendees would recommend this course to other Project Managers. • 97% of attendees state that the skills learned in this course will help them to better lead their team. • 96% of attendees state that the course helped them develop skills to be a more effective Project Manager. • “Probably the best project management course I’ve taken.” • “The single best PM course I’ve taken (and I’ve taken many). It was focused, on-topic, and applicable.”


Zweig Group is an approved provider by the American Institute of Architects (AIA).



THE COVER Holding Their Own – story on page 10

CHANNELS STRUCTURES + BUILDINGS 12 Bradley Plaza Green Alley 14 Hudson Commons: Historic Foundation Meets Modern Engineering in an Innovative Manhattan Overbuild 18 Determining the Right Monitoring System for the Project 20 Stormwater Drainage for Emergency Field Hospital Construction 22 Reopening Buildings After a Shutdown 23 How Retaining Walls Provide A Structural Advantage To Your Project 24 Army Corps helps USMA West Point cadets prepare for what comes next TRANSPORTATION + INFRASTRUCTURE 27 Ready to Roll WATER + STORMWATER 30 Rebuilding of Paradise Counts on HDPE PIPE 32 Land & Water Completes Colchester Hospital Project 34 COVID-19 Presents a Complex Problem for Water Providers 35 The Challenges and Opportunities of Water in Fast Growing Houston BUSINESS NEWS 37 London’s Changing: What does Lower Occupancy Mean for the Future of Commercial Buildings? 38 Increasing Quality and Speed: The Critical Role of Streamlined Submittals in Complex Construction Projects 40 Professional Development During the COVID-19 Pandemic SURVEYING 41 GPR for Utility Locating Offers Safety, Efficiency, and Revenue Benefits 42 Scanning for Property Management


departments 8 Events 40 Reader Index Columns 5 The Structures

Chad Clinehens 6 Combating “Stupidity” and Decentralization Phil Keil



January 2021


VOLUME 7 ISSUE 1 csengineermag.com

publisher Chad Clinehens, P.E. | 479.856.6097 | cclinehens@zweiggroup.com media director Christy Zweig | 479.445.7564 | czweig@zweiggroup.com Production & circulation manager Anna Finley | 479.435.6850 | afinley@zweiggroup.com ART director Maisie Johnson | 417.572.4561 | mjohnson@zweiggroup.com Editor Luke Carothers | lcarothers@zweiggroup.com

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Civil + Structural Engineer (ISSN 23726717) is published monthly by Zweig Group, 1200 North College Avenue, Fayetteville, AR 72703. Telephone: 800.466.6275. Copyright© 2020, Zweig Group. Articles not be reproduced in whole or in part without the written permission of the publisher. Opinions expressed in this publication are not necessarily those of Zweig Group. Unsolicited manuscripts will not be returned unless accompanied by a stamped, self-addressed envelope. Subscriptions: Annual digital subscription is free. To subscribe or update your subscription information, please visit our website www.csengineermag.com/ subscribe/ or call 800.466.6275.

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S t r u c t u r a l E n g i n e e r s A x i o m # 7 Structural Engineers Axiom #7

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Get a quote—overnight. Visit: www.fenner-esler.com Click “Need a Quote” Call toll-free: 866-PE-PROTEK (866-737-7683 x. 208) Ask for Tim Esler. Email: tesler@fenner-esler.com im@Insuranc 4Structurals.com ww .insurance4structurals.com Get a quote—overnight. i it: w.insurance4structurals.com Click “Need a Quote” ll toll-free: 866-PE-PROTEK ( 66-737-7683 x.208) Ask for Tim Esler. Email: ti @Insurance4Structurals.com

T H E P RO F E S S I O N A L ’ S C H O I C E S I N C E 1 9 2 3



January 2021

from the publisher

This month we focus on structures and buildings. As we kick off 2021, it is timely to focus on a specific area of this genre, our office buildings. For the majority of us who have spent their careers in an office building, 2020 was an extraordinary year. 2021 may be an even more extraordinary year as many firms will finally have to decide what the long-term office solution looks like. Many firms have spent the majority of 2020 in a variety of work scenarios. Talking with AEC firm leaders, some had 0 percent of their workforce in the office, and others had 100 percent. Firms with multiple office locations had a great deal of variability across offices. Regardless of where you and your firm fell on the spectrum, you are probably facing some decisions in 2021 that will shape what the office of your future will look like long-term. Office space design has evolved since the 18th century, when dedicated office buildings emerged. From open floor plans to walled offices, functionality of offices has changed dramatically over the ages. The development of the elevator and of steel frame construction rapidly evolved office building design and fueled taller buildings that could house multiple companies. Open spaces with modular furniture grew in popularity in the 90s. My first office was in an open space with modular offices made out of plywood. The walls were about 7 feet high in a room with 15 foot ceilings. I thought it was pointless as the height of the walls cut off light from being transmitted while allowing the sounds from the room to be a distraction. The open floor plan of the last 20 years has become much more open with little of any dividers between people. This design was fueled by an interest in increased collaboration. Like any design approach, it had its support- ers and critics. You can find studies on the internet that both prove and dis-prove the merits of about any office design approach. Regardless of what your office design is, the important thing to note is that these spaces are your home away from home. We spent a lot of time in these spaces, or at least we did prior to 2020. So as we put 2020 in the rearview mirror, we have to recognize that we have some decisions in the trunk that we must carry into 2021 and be prepared to handle in the months ahead. Probably the biggest for many firms is, once the virus is no longer an issue, what are the expectations for being in the office that we will apply in a post-COVID world? Most companies are still living in a world of exceptions, where working in the office is optional or even allowed has many office buildings dark. What does a return to the office look like? There are many theories on this – from new space designs that include a return to more walled offices and larger spaces between employees, to a permanent work from home policy for many staff to a “hoteling” system where groups of people cycle in and out of the office. Regardless of how your company chooses to dictate the future of work in your firm, we can all agree that office space and buildings are about to have the biggest shakeup of all time. The “quantum evolution” of flexibility that was forced on us in 2020 has many benefits. As an industry, AEC was behind most other industries in adopting a more flexible work structure. I’ve worked with many leaders who still believe the “butts in seats” is the only way to ensure a productive and efficient workforce. Many of those leaders were proven wrong in 2020 when the pivot to work from home for the majority of their staff affected the firm very little, with many firms actually reporting higher productivity and efficiency. Recent figures from Q3 & Q4 of 2020 show that 67 percent of AEC firms have changed their policies to allow any employee to work remote or telecommute at any time with a median of 70 percent (or av - erage of 63 percent) of a firm’s workforce now working remotely. This survey also found that can firms report up to 90 percent of their workforce (medians) can effectively telecommute / work remotely. Link: https://www. zweiggroup.com/publications/covid-19-response/ Going forward, you are going to have to think very hard about your work environment and what works best for you as an individual and as a firm. Those two may not align. Leaders have a tough job ahead. Figuring out who must work in the office and who doesn’t is one part of it. The other is what the office environment needs to look like, if any different from before. These decisions will affect office space design, property leases, IT investments, recruiting and retention tactics, marketing, business development, project management, and the list goes on. We live in an extraordinary time where we can document the evolution of the office building and space over the past three centuries with future generations seeing a big blip that happened in that crazy year 2020. What the blip looks like will be defined by you and your firm. The future of work in AEC is exciting to me because I hope that we can take this forced flexibility and hold onto it going forward while dreaming big about what the office space of the future can look like.

The structures Chad Clinehens

CHAD CLINEHENS, P.E., is Zweig Group’s president and CEO. Contact him at cclinehens@zweiggroup.com.


January 2021


elicits a larger conversation around organizational theory in which I hope to expand throughout 2021, but in the remaining space I have left in this article, let’s see if I can give you, the reader, a better understanding of the components required. I also welcome debate on the premise as it may not be as self-evident from the events in 2020 and the projected near-term future as I may think. In order for a firm to pursue a decentralization strategy, it needs to be able to do a few things well. I covered one of them already in the training and development of the entire organization— treating everyone as a vital and valuable component of a larger system. Another is teamwork with its fundamental precepts being trust and communication. One person is a simply ill-equipped to succeed compared to a well-functioning team of two. Now think about if that two becomes four. It is simply not a linear expansion of impact and capability, but exponential. Without coordination and cooperation between teams, the organization is doomed to fail. The next, is a clear vision. Your teams need a simple and clear goal that everyone is working towards. It isn’t a how, but a why. Communication is key both up and down the chain of command, so it is important that we focus on the simplicity of the message. The next important component is the ability to prioritize and execute on tasks. A painful lesson that many firms learned this year is that they were focused on too many things and implemented very little of their strategic plans as a result. If a team tries to accomplish too many things at once, they will likely accomplish nothing. Utilizing these key components allows an organization to decentralize in such a way that really makes a firm come to life and accomplish some amazing things. It allows for everyone to step up and become a leader. Ask yourself, if you were CEO of your firm, “What if each division leader clearly knew what your intent was and what you wanted each team to accomplish and they took the initiative to accomplish that intent?” That would make your job as CEO fairly easy. Now, that requires your communication to be simple and clear and simultaneously requires the division leaders to feel empowered enough to make things happen so that they will step up and lead. This has to be imbedded into the culture of your firm. Finally, two additional components are needed to make this strategy work, accountability and balance. Everyone needs to feel ownership, not make excuses, or blame anyone or anything else when problems occur. Leaders also need to be balanced. For example, you can’t talk too much or too little, you also cannot be overly assertive, etc. As I come to a conclusion, I would like to touch on one final thing that many leaders struggle with yet is required for a decentralized structure. That is delegation of authority. Leaders must push tasks and authorities down to their subordinate leaders and so on. It is only when you have delegated all actions that you can truly lead strategically. It is impossible to do so when you are busy trying to manage less significant tasks that could be handled by others. This doesn’t mean you should be trying to do nothing. In fact, from time to time, you should be willing to do the most awful job and get your hands dirty. It will clearly display your humility and increase your team’s respect for you. That is all I have to share to start out the year. Let me know if this reflection is something that resonates with you and how we might help you put these ideas into practice within your own organization.

Combating “Stupidity” and Decentralization Phil Keil

As we wrap up 2020 and enter into the new year, it is often a time of reflection and contemplation. I always encourage others to take this time when things are usually slower to look back on the lessons that have been learned and look forward towards the triumphs that are yet to be won. There is much to celebrate even while the year has been a difficult one. We’ve learned that our organizations need to be more agile and adaptable, our vision clearer. We need everyone to understand the purpose we are building towards, and that everyone is valuable. We’ve also learned that there is never a better time to develop ourselves and our people than now. It can be difficult to look at ourselves and our firms clearly and admit that change needs to occur. Therefore, as we enter this new year with much hope and anticipation, let us empower those around us and work towards a more decentralized structure within our workplace. Admittedly, I have at least one thing to get off of my chest before entering the new year. It is something I hope that we leave behind. I’ve had too many discussions with leaders that feel like their people cannot understand certain concepts and ideas. It is certainly phrased in a myriad of ways, but the bottom line essentially boils down to two things. Either “my people are too stupid to understand”, or “they are not ready.” It makes me want to simply say, “stop treating people like they are stupid.” Now, I submit that everything has a time and place, but the mentality being so pervasive within our space is troubling. I doubt, that when pressed, any leader would truly say this is how they feel, but if this is the takeaway I have, you can be certain that the people they lead feel the same implication. Exposure to advanced concepts, principals, and ideas in the way our business operates, how things fit together, and what we are building towards is long to be understood to be beneficial to an individual’s career. It is also been shown that the higher the average intelligence (business, emotional, etc.) of the people whose summation comprises an organization, the more successful that entity is. The reticence in sharing information or concepts simply astounds me given these precepts. So, without elaborating any further, I’d like to leave this negativity behind us in 2020, as you reflect on your performance this past year, let’s recognize that we can do a better job moving forward. I encourage you to take those moments in your career or while mentoring others to simply find the opportunity to learn/teach the more advanced concepts that we all know would make us more successful. Even if you or your people cannot put everything into practice at a particular moment, allow the time for growth and a recognition of concepts that we must be aware of. It will allow the performance of the firm to be elevated substantially. Now onto the second premise, which the first helps us to facilitate. That is the decentralization of structure within our firm to allow for a more agile, adaptable, and counterintuitively unified organization. This certainly

PHIL KEIL is director of Strategy Consulting, Zweig Group. Contact him at pkeil@zweiggroup.com.



January 2021

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events + virtual Events

january 2021

lines. The design parameters are applicable to guyed and self-supporting structures using a variety of foundations, including concrete caissons, steel piling, and direct embedment. https://collaborate.asce.org/integratedstructures/sei-standards The Collaborative Network for Engineering and Computing Diversity (C o NECD) january 24-28 The vision of the CoNECD (pronounced, “connected”) Conference is to provide a forum for exploring current research and practices to enhance diversity and inclusion of all underrepresented populations in the engineering and computing professions including gender identity and expression, race and ethnicity, disability, veterans, LGBTQ+, 1st generation, and socio-economic status. https://sites.google.com/a/vt.edu/conecd/home?authuser=0 ASCE values the involvement and ideas of early career professionals and sees its younger members as the future of the Society. Younger Members help shape the profession at all levels. As members and leaders of Sections, Branches and Younger Member groups they support one another by providing individual and group resources; opportunities for professional and leadership development; community service and advocacy; and social and professional networking. If you are a student, we have a section for you too. https://www.asce.org/younger_members/ Mobile connectivity is a key enabler for drone operations including BVLOS flights over people, night flights and more. This session will explore technology solutions that are advancing UTM and enabling the future of new applications while ensuring the safe integration of drones in the NAS. Speakers: Tom Brittingham, Sales Engineer - Skyward, A Verizon company Greg Belaus - Network Infrastructure, Elevate, Uber Eszter Kovacs - Acting Secretary General of GUTMA Registration: Registration is free for all attendees. https://www.auvsi.org/events/webinars/5g-wireless-connectivity- unmanned-systems younger member week 2021 january 25-29 5G Wireless Connectivity for Unmanned Systems january 27 ICCAE2021: InternationalConferenceonCivilSocietyandArchitectural Engineering january 28-29 – New york, Ny International Conference on Civil Society andArchitectural Engineering aims to bring together leading academic scientists, researchers, and research scholars to exchange and share their experiences and research results on all aspects of Civil Society and Architectural Engineering. It also provides a premier interdisciplinary platform for researchers, practitioners and educators to present and discuss the most recent innovations, trends, and concerns as well as practical challenges encountered and solutions adopted in the fields of Civil Society and Architectural Engineering.

ICBC 2021 : International Conference on Building Cracks january 7-8 – tokyo, Japan International Conference on Building Cracks aims to bring together leading academic scientists, researchers, and research scholars to exchange and share their experiences and research results on all aspects of Building Cracks. It also provides a premier interdisciplinary platform for researchers, practitioners and educators to present and discuss the most recent innovations, trends, and concerns as well as practical challenges encountered and solutions adopted in the fields of Building Cracks. https://panel.waset.org/events/2021/01/tokyo/ICBC International Conference on Analysis and Design of Protective Structures january 11-12 – singapore International Conference on Analysis and Design of Protective Structures aims to bring together leading academic scientists, researchers and research scholars to exchange and share their experiences and research results on all aspects of Analysis and Design of Protective Structures. It also provides a premier interdisciplinary platform for researchers, practitioners, and educators to present and discuss the most recent innovations, trends, and concerns as well as practical challenges encountered and solutions adopted in the fields of Analysis and Design of Protective Structures. https://waset.org/analysis-and-design-of-protective-structures- conference-in-january-2021-in-singapore USING INERTIAL AND POSITION MEASUREMENTS IN TESTING AND SURVEY PROJECTS – BRIDGING THE GAP BETWEEN AUTONOMOUS VEHICLE DEVELOPMENT OxTS Inertial Navigation Systems are used throughout the world to provide autonomous vehicle testing engineers and surveyors with highly accurate, absolute position and orientation measurements. These measurements help users realize cm-level surveying and testing accuracy, while at the same time increasing repeatability. But how do these two industries dovetail when it comes to using this information? Join NavtechGPS and OxTS as we discuss “Using inertial measurements in testing and survey projects – bridging the INS gap between autonomous vehicle development and survey.” Speakers: Paris Austin, Business Manager, Survey & Mapping, OxTS Franck Boynton, VP and CTO, NavtechGPS. https://www.auvsi.org/events/webinars/using-inertial-and-position- measurements-testing-and-survey-projects-%E2%80%93-bridging-gap ASCE/SEI 48 – Design of Steel Transmission Pole Structures january 21 The primary reference for structural engineers and construction managers involved in designing and building electrical transmission lines — provides a uniform basis for the design, detailing, fabrication, testing, assembly, and erection of steel tubular structures for electrical transmission poles. These guidelines apply to cold-formed single- and multi-pole tubular steel structures that support overhead transmission AND SURVEY january 14



January 2021

september 2021 Commercial UAV Expo Americas september 7-9 – las vegas, nv

https://waset.org/civil-society-and-architectural-engineering- conference-in-january-2021-in-new-york March 2021

Commercial UAV Expo Americas 2021 is where the commercial drone community gathers to learn, connect, and drive the industry forward. In addition to content about new opportunities and challenges the industry is facing due to COVID-19, industries covered include Construction; Drone Delivery; Energy & Utilities; Forestry & Agriculture; Infrastructure & Transportation; Mining & Aggregates; Public Safety & Emergency Services; Security; and Surveying & Mapping. It is presented by Commercial UAV News and organized by Diversified Communications. https://www.expouav.com/ on demand Chasing specific business applications to solve a unique challenge used to be the answer to one problem, except as the technology stack grows, so does the disjointedness. This problem introduces more data and workflow challenges to be solved. As the construction technology landscape continues to evolve, one solution will not be the answer to today’s complex file sharing and storage challenges. Join Newforma, Autodesk, and Schmidt Architects to learn how the construction technology space is progressing towards more unity and the benefits of working in a connected environment. Discover how Newforma’s integration with Autodesk BIM 360 further streamlines collaboration to provide increased flexibility to view, search, and manage project files to improve project delivery. https://csengineermag.com/newforma-autodesk-bim360/ Newforma & Autodesk BIM 360 – Working Together 1 pdh Composite steel construction has been recognized for a number of years as one of the most economical systems for constructing building floors. This webinar will focus on information contained within SJI’s “2nd Edition CJ-Series Composite Joists,” which includes the standard specifications, weight tables, bridging tables and code of standard practice; share how one can utilize SJI’s Floor Bay Tool for estimating the cost of CJ-Series joists; and describe recent projects where CJ-Series composite joists have been utilized. https://csengineermag.com/economic-floor-systems-with-composite- steel-joists/ Economic Floor Systems with Composite Steel Joists 1 pdh

structures congress 2021 march 10-13 – seattle, wa

As a structural engineering professional, you can find the latest information, innovation, products, and technology at Structures Congress. Learn best practices to push the boundaries of structural design, and bring back new ideas to improve your practice, help clients problem-solve, and be more innovative. Join us to experience all that SEI/ASCE offers to lead and innovate in Structural Engineering. Interact with and learn from the experts on Blast, Bridges, Buildings, and more, and earn Professional Development Hours (PDHs). https://www.structurescongress.org/ april 2021 The concept of living buildings has recently emerged as the new ideal for sustainable building design and construction. Defined as a building that generates all of its own energy with renewable, non-toxic resources, captures and treats all of its water, and operates efficiently with an uncompromising aesthetic, living buildings represent a new species of buildings that blends boundaries between the built environment and the natural world and necessitates creative, integrative engineering and architecture solutions to meet rigorous design challenges. https://www.aei-conference.org/ May 2021 aei conference april 7-9

AUVSI XPONENTIAL may 3-6 – atlanta, ga & virtual

At the world’s largest (virtual) event for unmanned and autonomous systems, you’ll find your momentum, that something extra that gives you a competitive edge – your X factor. https://www.xponential.org/xponential2020/public/Content. aspx?ID=3662&sortMenu=107001

AUVSI XPONENTIAL may 26-27 – ExCel, London

Drones are transforming the processes of many sectors and improving safety. More and more companies are using drones for different purposes. At the DroneX Trade Show & Conference you can reimagine the possibilities of unmanned vertical flight, and take a first-hand look into the latest technological advancements. https://www.dronexpo.co.uk/


January 2021


Regardless of the industry, nobody is a stranger to maintenance. From equipment to vehicles to facilities, these capital investments will likely need to be maintained. However, the level of required maintenance can vary greatly depending on the solution involved. A common engineering solution for building users in markets such as government, aviation, recreation, commodity storage, and more is to utilize tension fabric structures. Fabric buildings have typically been chosen because of their quicker installation schedules and overall cost- effectiveness. Thanks to better engineering and improved materials, many of today’s fabric structures are practically maintenance-free as well, to the point where there’s almost zero upkeep actually needed for The biggest advancement for modern fabric buildings came several years ago when Legacy Building Solutions took the step of marry- ing together a tension fabric membrane with a structural steel I-beam frame, essentially bringing a conventional construction look to the fabric building industry. Historically, fabric structures used a tubular web truss frame, charac- terized by a “hoop” shape with curved sidewalls. The appearance of a hoop structure wasn’t the issue. The main problem arose from the inconsistent engineering of truss designs. Different engineers often came to different subjective conclusions about the integrity of a given web truss framing system. A building collapsing due to an unidentified failure point was a real possibility. a quality fabric building. Rigid Steel Framing By shifting toward rigid-frame, tapered I-beam design that was known and proven in the engineering community, newer fabric buildings re- moved any lingering question marks about the strength and longevity of the frame. This also opened up many possibilities for fabric build- ing users, who could now have their structures customized to exact dimensions and other parameters, thanks to the design flexibility that is Beyond shear strength, structural steel I-beams have the advantage of being completely solid steel and, therefore, better suited to surviving high-humidity environments or just the basic long-term effects of cor- rosive elements over a building’s life cycle. By contrast, many tension fabric structures in the industry use hollow-tube frames that are vulner- able to corrosion originating inside the tube. In effect, truss frames can experience corrosive damage long before anyone can see it. inherent with a rigid-frame approach. Preventive Corrosion Protection Although fabric liners are available to provide a finished building in- terior in certain applications, in many industries the steel beams are Holding Their Own Today’s fabric buildings are engineered to keep maintenance to an absolute minimum By Eric Donnay

left exposed inside a fabric building. A variety of treatment options are available as a preventive maintenance measure against corrosion for the frame and other steel components. Hot dip galvanizing has been among the most popular techniques. There is, however, a significant difference between galvanizing protec- tion for solid beams and hollow tube frames. Tube frames are inline galvanized, meaning they’ve already been galvanized at the factory. The building supplier then welds the frames later, which diminishes the value of the galvanization where new heat is applied. With rigid I-beams, galvanizing occurs post-production, so the beams are already welded together before receiving topical treatments. The same holds true for a recently introduced corrosion barrier offering for rigid frames – epoxy paint. Epoxy coating creates an actual barrier between corrosion and the steel beam, where galvanizing only slows down the corrosion process by sacrificing itself, allowing a thin zinc coating to be eaten away over time. Epoxy paint is quickly becoming recognized as a worthwhile investment to help extend the life cycle of buildings and equipment. Fabric Longevity One area where corrosion is definitely not a factor is with the fabric cladding material itself. Whether using polyvinyl chloride (PVC) or polyethylene (PE), architectural fabrics are not susceptible to corroding. Tension fabric has long been known to provide a variety of opera- tional benefits. Its translucency allows for natural daylighting inside a building. Unlike metal sheeting, fabric has thermally non-conductive properties, helping to keep building interiors warmer in the winter and cooler in the summer. However, like any single-layer material, if it’s necessary to eliminate condensation or provide heating or cooling, insulation and a fabric liner are definitely needed to provide superior results and meet energy code requirements. Fabric’s benefits can be enjoyed for many years, but the type of fabric used can have a big impact on the roof’s overall longevity. PE fabric is the most widely used material in the industry, while PVC has been commonly reserved for higher end projects due to its price point. How- ever, owners have realized that PVC’s long-term benefits and increased lifespan effectively offset the initial investment.



January 2021

includes standard 18-inch overhangs, along with gutters and downspouts to assist with water mitigation. By contrast, buildings with curved side- walls have no ability to control rain runoff; water simply runs down the side of the building, potentially causing damage to the foundations or even pooling and seeping inside the structure at the base. Movement of air reduces any maintenance problems from humidity or moisture. Passive ventilation systems, using ridge and soffit vents, rely on the simple movement of warm air; and this passive ventila- tion is a standard feature for some rigid-frame building manufacturers. Additional mechanical ventilation can easily be added to the building frames if necessary. Another benefit from a rigid-frame structure is the ability to handle hanging or live loads. From overhead cranes to fire suppression sys- tems to conveyors, loads can be easily incorporated into the design from the beginning of the project. The I-beams are simply modified in the early engineering stages to account for the intended collateral or point loads. The steel frame and attached fabric can also be designed to handle the environmental factors in a given location, such as wind loads, snow loads, and seismic codes. This is particularly important for buildings located in wide open areas or extreme climates with higher exposure to the wind and other elements. Leading fabric building manufacturers have achieved a number of applicable certifications related to weather, such as Florida Product Approval for high-velocity hurricane zones. The derecho storm that whipped across Iowa and Illinois in August 2020 unleashed winds gusting up to 100 mph over an area 250 miles long. Users of two Legacy rigid-frame buildings in the storm’s path reported that their structures sustained no damage. Trusted Construction Fabric buildings can also be engineered, manufactured and installed faster in the first place. Furthermore, while engineered to be perma- nent, most fabric structures are also designed to be portable if the need arises to move the building later. In some cases, the whole project can be contracted through a single entity. Certain companies in the industry have their own manufacturing facilities on-site to produce everything from fabric panels to I-beams and components. They employ the engineers who work with the cus- tomer to design the building from the very beginning. Additionally, they employ their own in-house professional installation crews, ensur- ing the final construction job is done by those with the proper expertise. By acting as a one-stop full-service shop, these suppliers are able to guarantee quality and workmanship at every step of the process. Ultimately, solid framing materials and better fabric technology wind up contributing to the equivalent of a robust long-term preventive maintenance program. With proven engineering leading the way, purchasers can procure fabric buildings that eliminate traditional head- aches and maintenance, allowing users to focus on the primary aspects of their business.

Legacy offers ExxoTec™ PVC, which features a high-strength woven fabric with additional primer and lacquer layers to provide more du- rability, and an improved warranty to match. This fabric is designed to retain more than double the tensile strength of a standard PE fab- ric and carries a longer life expectancy. These benefits have actually challenged building suppliers to think differently about the uses of the material and expanded the possibilities of fabric building design. Fabric Performance The natural properties of fabric and the way it’s manufactured help to deliver additional performance advantages that reduce building maintenance. Fabric provides a surface area that is leak-proof, ensur- ing superior protection of the interior environment. Users can consider washing down the interior side of the fabric if they want, but otherwise the occasional rainfall will take care of basic exterior cleaning. Just like different fabrics can offer differing life expectancies, the method of installing and tensioning fabric can contribute to differ- ent long-term outcomes and maintenance needs. Older style hoop buildings often had mono-cover designs that involved stretching one piece of fabric over the entire structure. This design makes it difficult to properly tension the fabric and leaves it susceptible to additional movement from wind and snow. This will lead to premature wear, as well as potentially point-loading the structure in ways that it was not designed to resist. Years ago, Legacy developed a fabric attachment system that uses half- inch bolts to secure a keder rail to the top flange of each structural steel frame instead of the industry-standard tek screw method. This method ensures fabric is properly attached and less likely to fail from improper screw installation. The biggest advantage of the system was that it allowed for individual fabric panels – typically 20-feet wide – to be properly tensioned. Each and every section of the roof is horizontally and vertically tensioned in the correct order, which eliminates billowing of the fabric and ensures it remains taut throughout its lifespan. Environmental Concerns Rigid frame tension fabric buildings are ideally suited to reduce main- tenance concerns in other ways as well. Their conventional architecture


January 2021


With a population of over 80,000 people, the City of Pacoima is one of the oldest neighborhoods in the San Fernando valley of Los Angeles, California. The closing of factories around Pacoima in the early 1990s started an economic decline, and Pacoima has become one of the most underserved communities in the Los Angeles area. Pacoima’s park-poor status and its highly permeable soils, together with the rise of the grassroots environmental justice organization, Pacoima Beautiful, has recently led the City to become a focal point for innovative groundwater recharge and community pilot projects. A recent street vacation project at Bradley Ave created a small commu- nity space (Bradley Ave Plaza). However, the success of this project was impacted by the alley that bisects this space, which was run down and not well utilized due to safety concerns, especially at night. As a standalone project, the space was under-utilized and offered limited The Bradley Plaza Green Alley pilot project is both an innovative stormwater and community project that reimagines how alleys func- tion in the Los Angeles area. The project team, which is comprised of The City of Los Angeles, The Trust for Public Land and Pacoima Beautiful as the client team, and Arup as the lead Designer and Engi- neer of Record, were driven to design and construct a project that not only managed stormwater effectively, but created a community space with which people could interact safely. From the start, the community was involved in the design process. Initially, a community design char- rette was held at the project site so that the community could have a say on three concepts that the team had developed. In addition to stormwater management, which was part of the project’s grant funding requirements, the community wanted better lighting and more shade, value to the community. Reimagining Pacoima Bradley Plaza Green Alley By Tony Kirby and Vanessa Thompson

landscaping, and interactive play and exercise elements along the alley. The community also voted to incorporate the Bradley Ave Plaza into the alley project so the alley and plaza could be designed as a single project, increasing the opportunity for community amenities and mak- ing the plaza, which is at the midpoint of the alley and closed to traffic, the focal point of the project. Breaking Down Barriers The project moved into formal design with the preferred elements of



January 2021

all three concepts being incorporated from the community design char- rette. The design team of Arup and Landscape Architect RIOS had a larger palette to express the design after the plaza was incorporated into the project by the client team. The design team strategized to combine the planting, shade and stormwater elements into the project corridor and challenged the conventional design of Los Angeles’ alleys. The existing sidewalk was removed, the central v-gutter (a City standard) was also challenged, and the alley sloped in one direction to a series of stormwater planters on the south side to provide initial filtrations. A subsurface infiltration trench and dry well system was designed to drain the planters and infiltrate the runoff along the alley to replenish the aquifer. The project treats stormwater from a 4.5-acre watershed far exceeding any City requirements. Agreements were made between the City (Department of Sanitation) and a low-income housing authority which abuts the south side of the alley to locate stormwater best management practices (BMPs). This in- cluded many of the stormwater planters, within their right-of-way but with a commitment from the Sanitation Department to maintain them. Shared street signage and traffic controls were incorporated along the alley to avoid the need for large speed tables and promote the European shared surface concept, a first for the City of Los Angeles. The plaza was totally transformed with the project team taking the op- portunity to utilize this area for community gatherings, performances, and a nature classroom to promote outdoor learning. A large shade structure and “social stacks'' for community seating are the centerpiece of this space and provide what the community demanded: a safe and shaded area for gathering, performance and meeting. A wall along the alley has also been given over to local artists for a large mural, which is part of Pacoima’s recent heritage and community with a passion for art and expression. Looking Forward but Remembering the Past The project is groundbreaking in several ways and provides a new tem- plate for transforming Los Angeles’ 900+ miles of alleys. However, the heritage of Pacoima was not forgotten, and as a gesture to the indig- enous Tataviam Band of Mission Indians that put Pacoima on the map,

Tataviam symbols were designed and incorporated into the custom salvaged timber amenity elements throughout the project. The alley’s bonded asphalt surfacing and pattern provide a further link back to the City’s heritage through its depiction of running water as large streams of water used to flow through the area from the surrounding mountain canyons. These refer to this project as a stormwater mitigation project at heart but also so much more in its finished form. The project has transformed a standard and downtrodden service alley into a Place for People and, over time, will help reconnect the community to this space and the heritage of the City. As structural engineers, we have a unique opportunity to contribute to the improvement of resiliency in our cities. Without being restricted by the minimum building code requirements, having clear communica- tion on project specific seismic performance objectives with our clients at the onset of a project would allow us to deliver resilient buildings that would remain functional even after rare earthquake events. This, in conjunction with making digital investments in the industry, will help us achieve resiliency in our communities.


January 2021


What began in 1962 as a functional-but-unassuming eight-story ware- house on Manhattan’s West Side has become the foundation of one of the most unexpected and fascinating projects in New York City today – the 26-floor Hudson Commons building. Over the years, the cast-in-place concrete building at 441 Ninth Av- enue has been reimagined; notably in the 1980s when it was converted into an office building that retained most of the architectural character from its original era. But it never experienced anything quite like its most recent transformation. When Cove Property Group acquired the commercial property in 2016, they envisioned a vertical expansion of the site to capitalize on the 2005 rezoning of Manhattan’s west side. That left the developer with a decision to make on the fate of the former warehouse: Would they demolish the old building and rebuild from a clean slate, or would they find a way to reposition the existing structure to meet their needs? Early site investigations showed that the robust structure was in good structural condition making it suitable for reuse. Thus, after weighing their options, Cove selected the most cost-efficient solution that would achieve the maximum rentable area: the rehabilitation, retrofitting and reuse of the existing structure. The existing building would add 17 floors and 300,000 square feet of commercial space, creating a sleek new steel and concrete office tower. Now that its transformation is complete, Hudson Commons emerges as a 26-floor, LEED Platinum Class A property that provides 700,000 square feet of rentable office space, topping out at 421 feet. The architect of the renovation and addition is Kohn Pederson Fox As - sociates (KPF), with WSP USA serving as the engineer of record. Mue - ser Rutledge Consulting Engineers (MRCE) served as the geotechnical consultant. The construction manager is Pavarini McGovern (PMG). Best of Both Worlds For the project to succeed, several challenges had to be addressed, from precise demolition procedures without the use of interior shoring, and retrofitting of the existing columns, slabs and foundation systems; to the articulation of the new building core. Hudson Commons: Historic Foundation Meets Modern Engineering in an Innovative Manhattan Overbuild By Joseph Provenza, AIA, P.E., LEED AP BD+C; Jeffrey Smilow, P.E., F. ASCE; Yujia Zhai, P.E., Motaz Elfahal, Ph.D., P.E.; and Gerardo Aguilar, Ph.D.

Shoring can be costly, so it was important to the owner that the project included a plan for shoring-free demolition of a 125- by 25-foot area throughout the existing building to accommodate the new core. In lieu of shoring, the existing slabs were reinforced with a combination of temporary and permanent steel members that provided the required support of the structure. The original structure is comprised of two-way concrete slabs on a 24- by 28-foot grid with drop panels, “mushroom” capitals, and a ma- sonry core providing lateral stability. The low-rise, massive building is representative of the 1960s. The addition takes the form of a sleek modern office tower, which speaks to the 14-acre Hudson Yards megaproject development rising to the west of Hudson Commons. By contrast, the subtle renovation of the original building, which reuses the existing wrap-around brick façade while upgrading the structure to meet current design and construction codes, will keep the project grounded in the context of the neighbor- hood and its 1960s roots. WSP faced several unprecedented challenges that demanded highly in- novative structural solutions if the vision developed by Cove and KPF was to be realized. The existing cast-in-place columns and footings required sizeable retrofits for the gravity loads imposed by the new tower above, and the existing roof slab required extensive retrofitting to accommodate a heavily landscaped amenity space. The most invasive feature, however, was the addition of a new re - inforced concrete core linking existing and new construction that would provide the required lateral stability and stiffness for the new taller building. A Solid Foundation Although the existing structure was bearing on the good-quality sub- strate typical of Midtown Manhattan, the geotechnical composition The addition of a 17-story tower to the original building has resulted in Hudson Commons emerging as a 26-floor building with 700,000 square feet of rentable office space in Manhattan. Photo: ©2017 NEOSCAPE, INC.



January 2021

were available, core samples were extracted from various locations to determine the in-situ compressive strength of concrete. WSP provided 3D laser scanning services for the entire structure, yielding an accurate representation of as-built column dimensions and locations, the latter being critical to tie in the column grid of the tower above. To minimize potential compatibility problems, concrete compressive strength for the retrofitting jackets matched the one determined through the coring campaign (approximately 5,000 psi). Furthermore, to minimize the increase in column size, large diameter high-strength rebar was used. Reinforcement continuity was critical to maintaining a consistent load path. Ground Penetrating Radar scanning was performed around each column, allowing WSP to map and coordinate locations for holes to be drilled for reinforcement to pass through the existing slabs. Large diameter (#14 bars) and high-strength (Gr 75) reinforcement were used to maintain jacket thicknesses under 12 inches, resulting in 60-inch-maximum-diameter columns. Column capitals were removed to achieve the desired reinforcement continuity and full column bear- ing but were rebuilt during the cast operation to maintain the original aesthetic, which was important to KPF’s vision. The forming and casting of circular columns in the building’s con - strained environment presented a potentially costly and troublesome prospect, so shotcrete was used for columns and capitals. Concrete was placed, compacted and consolidated all at the same time due to the design pressure with which the shotcrete was sprayed. The final layer of concrete was applied by a skilled technician using a hand trowel, an aesthetic treatment that left the final appearance indistin - guishable from traditional methods. This application by the construction team was a genuinely innovative feature of Hudson Commons. Lateral-Load Performance To provide stability to both the existing structure and the new tower, a full upgrade of the Hudson Commons lateral force resisting system was required. WSP collaborated closely with KPF on an architectural design that included a new circulation and mechanical core eccentri- cally placed along the north side of the property that would maximize the building’s rentable area. One notable feature of the building’s core is its prominence in the ar- chitectural expression of Hudson Commons as it rises above the exist - ing building. The new spine of the building uses exposed architectural concrete as a tribute to the historic architecture of the neighborhood. The new reinforced concrete core runs from foundation to the top of the building and is comprised of 10,000-psi concrete shear walls ranging from 12 to 24 inches in thickness. WSP envisioned a box-like configuration wrapping the entire mechanical and circulation program that would counteract the torsional effects associated with an eccentric core. In this closed-box layout, the core is placed along existing col - umn lines, and the existing columns create breaks in the shear walls analyzed by considering individual piers at the base building.

Hudson Commons now tops out at 421 feet. Photo: ©WSP USA

of the site and its existing foundation elements presented a significant engineering challenge. The bearing capacity of the structure ranged from 20 to 40 ton/ft2, and there was a steep drop-off throughout the site. In addition, the con - straints of working within the confines of an existing structure were immediately evident, particularly for the use of deep foundation ele- ments and the equipment required for their construction. The reinforced concrete core is supported by a new 48- to 72-inch-thick mat foundation bearing directly on sound bedrock. With the core walls in-line with existing columns, consideration of existing column founda- tions added another layer of complexity. While some column foundations were narrow piers reaching the bedrock, a few columns were supported by larger pile caps. The latter were treated as local interruptions in an otherwise continuous mat foundation with cold joints only. The small footprint of the new core in combination with its eccentric lo - cation translated to large overturning moments, which were addressed by providing 45 600-kip anchors socketed 45 feet into rock. MRCE specified 450-ton micropiles socketed 15 feet into sound bedrock to achieve the required load demand. From these constraints emerged the development of three types of foundation retrofits: • piers-to-rock encapsulating and tied into existing piers-to-rock, • new caisson caps encompassing existing piers-to-rock, and • enlarged caisson caps articulating existing pile caps. Concrete Jackets One major challenge was the original building columns insufficient capacity to accommodate 17 additional floors. To achieve expansive column-free areas, large spans in the office tower – some reaching 48 feet – amplified the demands at the base of the building where higher loads go to fewer columns. Conversely, a smaller number of original columns required retrofitting for the project. The solution implemented by WSP was the retrofitting of existing con - crete columns employing new reinforced concrete jackets. The first task was the assessment of existing conditions and the study of available construction documents. Although some original drawings


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