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EDITORIAL BOARD
Chair John A. Dal Pino, S.E. Claremont Engineers Inc., Oakland, CA chair@STRUCTUREmag.org
Kevin Adamson, PE Structural Focus, Gardena, CA
Marshall Carman, PE, SE Schaefer, Cincinnati, Ohio
Erin Conaway, PE AISC, Littleton, CO
Sarah Evans, PE Walter P Moore, Houston, TX
Linda M. Kaplan, PE Pennoni, Pittsburgh, PA
Nicholas Lang, PE Vice President Engineering & Advocacy, Masonry Concrete Masonry and Hardscapes Association (CMHA)
Jessica Mandrick, PE, SE, LEED AP Gilsanz Murray Steficek, LLP, New York, NY
Brian W. Miller
Cast Connex Corporation, Davis, CA
Evans Mountzouris, PE Retired, Milford, CT
Kenneth Ogorzalek, PE, SE KPFF Consulting Engineers, San Francisco, CA (WI)
John “Buddy” Showalter, PE International Code Council, Washington, DC
The Seattle Aquarium’s new Ocean Pavilion proves that virtually any concrete shape can be built when digital tools blend with outside-the-box engineering.
VIADUCT DAMAGE ASSESSMENT AFTER THE 2023 EARTHQUAKE IN TURKEY
By Cenan Ozkaya, Ph.D, Robert K. Dowell, Ph.D, PE, and Faruk Yildiz
26
Five viaducts along the Tarsus-Adana-Gaziantep Highway in southern Turkey were damaged by the 2023 Mw 7.8 earthquake. Damage assessment and the seismic retrofit design for two of those viaducts are shared here in Part 1. The remaining three will be covered in Part 2 in the October issue.
ENGINEERING INNOVATION AND ENVIRONMENTAL LEADERSHIP IN DOWNTOWN HOUSTON
By Connor Brady, Jason Bray, & Fernando Torrealva
32
The Norton Rose Fulbright Tower’s offset core, rotated bays, and forked cantilevered facade were possible through creative structural design solutions.
REBUILDING AFTER THE FIRE: WHAT YOU NEED TO KNOW, AND WHAT
NO ONE TELLS YOU
By Nick Stuart, SE and Eric Kreager, SE
Successful disaster recovery requires planning, collaboration, and communication. 44
Stephanie Slocum,
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Leading Through Uncertainty: Our Profession’s Defining Moment
By Stephanie Slocum, PE
What do you see when you look around your office, your project team, your industry today? I see a profession standing at an inflection point—one where the comfortable certainties of yesterday no longer apply, but where our fundamental purpose has never been more vital.
This year brought substantial challenges: political shifts, continued workforce shortages, and moments that made us collectively wonder, “What can I do about this?” If you’re waiting for the world to return to a simpler, more predictable environment, I have news for you: we are not going back to a non-VUCA world. Volatility, uncertainty, complexity, and ambiguity—what business leaders call a VUCA environment—aren’t temporary disruptions. They’re the new operating conditions for our profession.
Consider the challenges we face: accelerating frequencies and strengths of storms that threaten our communities, a talent pipeline crisis where 55% of structural engineers have considered leaving the profession, the downward trend of structural engineering college graduates compared to other STEM fields, and the urgent need to transform our carbonintensive industry. These are interconnected challenges that require us to lead with an adaptive, systems-viewpoint approach that engages the collective knowledge of those inside and outside our profession.
That’s what I witnessed throughout my year as SEI President: in every challenge, I saw structural engineers determined to lead. I saw structural engineers embracing their role as protectors of both our communities and our profession.
Individual Leadership = Collective Impact
Throughout the year, I was inspired by the over 3,000 active volunteers who power our profession through SEI’s Technical and Professional Communities—people serving on 100-plus committees. I witnessed the 155 firms in the growing SE 2050 movement choosing to lead on carbon reduction, engineers evaluating inefficiencies, and inventing solutions. These professionals proved that we
don’t just react to what’s happening around us; we shape what happens next.
Here’s the uncomfortable truth: if you want to see change in our profession, you’ve got to BE that change. The skill of adaptation becomes THE essential leadership skill in a VUCA world—one that relies on curiosity, a beginner’s mind, and the willingness to learn, qualities that define great engineers at every career stage.
Fifteen years ago, I was frustrated and felt like I no longer belonged in this profession. I wasn’t involved beyond my immediate work. Then I made one choice—I applied to SEI’s Business Practices Committee despite feeling unqualified. That single act of stepping out of my comfort zone connected me with other structural engineers who transformed my career trajectory.
The power to transform our profession begins with our individual choices. You chose to be part of this profession. You face a daily choice to connect or withdraw, to make the profession better or to complain about the status quo. You decide if you’ll build a better future or settle for “this is the way we’ve always done it.”
The Multiplier Effect of Showing Up
Every time you choose to engage by joining a committee, mentoring a colleague, encouraging a struggling coworker, advocating for sustainable design practices, or making a new connection, you’re not just advancing your own career. You’re strengthening the entire structural engineering ecosystem.
Connection across organizations amplifies our impact.
Recent examples of this type of work at SEI include:
• Collaborating with NCSEA and CASE through joint leadership meetings and joint initiatives like the current AI webinar series and the updated Joint Vision for the Future of Structural Engineering (currently under review by our boards).
• Supporting CROSS-US, which helps professionals make structures safer by providing confidential reporting for structural failures.
• Advancing flood resilience in codes and standards with FEMA and ASFPM.
• Co-hosting the Towards Zero Carbon Summit and Symposium with the University of Colorado Boulder.
• Defining the next generation of design via the NIST Forward Looking Codes and Standards Workshop series.
These activities demonstrate SEI’s role as a convening organization, bringing together practitioners, academics, government officials, scientists, and materials organizations (to name a few!). In a VUCA world, this collaborative work positions us to be recognized as both technical problem-solvers and inclusive leaders who are essential to building resilient communities. This vision becomes reality through our individual choice to show up.
Your Moment to Lead
The question isn’t whether you’re qualified to lead. The question is: Will you choose to exercise the power you already have?
Start where you are. Spend 1 minute today to do something that elevates someone else in the profession. Say thank you, make an introduction, or offer an encouraging word to a colleague.
If you’re looking to make a bigger impact, SEI’s technical and professional committees offer direct national pathways, and our local SEI chapters allow you to connect with professionals in your own community. Learn more and join us here: www.asce.org/communities/institutes-and-technical-groups/ structural-engineering-institute.
The future is ours to build, one structure— and one leader—at a time. ■
Stephanie Slocum, PE, recently completed her term as FY25 President of the Structural Engineering Institute and is Founder and CEO of Engineers Rising LLC.
structural INFLUENCER
Kevin Aswegan
When it comes to designing tall buildings, Kevin Aswegan, principal at Magnusson Klemencic Associates (MKA), is up for the challenge. A co-author of the book, for Wind , Aswegan has worked on buildings as tall as 65 stories and as the leader of the firm’s Performance-Based Design Technical Specialist Team. He is also an industry expert on seismicity and a member of MKA’s Earthquake and Wind Technical Specialist Teams. reached out to Aswegan to discuss his structural engi neering career path and focus.
STRUCTURE: In terms of code development, what changes would you like to see in the next 20 years?
Aswegan: More Performance-Based Design. I’ve been lucky to be involved in building code development for my entire career, dating back to my research in graduate school, which included writing code language for the seismic linear response history analysis procedure now in ASCE 7. Unfortunately, code development moves at a glacial pace. Given the abundance of complex issues our society is facing, our building codes need to more explicitly adopt and promote Performance-Based Design approaches to encourage creative solutions to our challenging problems.
STRUCTURE: What unique challenges did you face when undergoing the first application of the ASCE Prestandard for Performance-Based Wind Design for the ATX Tower? Was there a lot of resistance from the city jurisdiction?
Aswegan: There are many challenges inherent to being the first to utilize a new design methodology. Because the Performance-Based Wind Design approach had not yet been “stress tested” on a real project, the challenges for ATX Tower were primarily technical. For example, we built a detailed nonlinear analysis model for the structure and subjected it to five different simulated windstorms. To do this, we needed to understand the real-life behavior of low-seismic coupling beams and shear walls when pushed beyond their elastic range. We also faced computational challenges. Despite using our fastest computers, the analysis for the five records took several weeks to run! Helping us through this effort, we were fortunate to have worked with collaborative building officials within the City of Austin’s Development Services Department, along with a great combination of owner, architect, and peer reviewers.
Committee, Performance-Based Design Committee, ASCE 7, and helping plan the annual Structures Congress. My primary goal across these efforts is to help SEI lead and elevate the profession, such that we attract new, talented young engineers into structural engineering and continue to demonstrate the value of our profession to our clients and the public.
STRUCTURE: You are involved in multiple organizations. Do you have goals you would like to achieve within each of them?
Aswegan: Although I’ve been involved in multiple organizations, my primary focus throughout my career has been with the Structural Engineering Institute (SEI) of the American Society of Civil Engineers (ASCE). This has included SEI’s Tall Buildings
STRUCTURE: In your previous roles leading the PerformanceBased Design Technical Specialist Team (TST) and Earthquake TST within your office, are you getting a lot of participation and excitement from the younger engineers? Can you discuss your role as a mentor or leader for this program?
Aswegan: Absolutely. Our TSTs serve as internal groups for our subject matter experts to meet and stay ahead of industry developments. For example, we have TSTs for Concrete, Steel, and
Timber, which are involved in Building Code development for their respective structural materials, as well as educating our staff on technical topics. We find that this is a great way for younger engineers to develop expertise in an area they find interesting. The TSTs also promote mentoring opportunities across project teams, giving younger engineers and senior leaders opportunities to connect outside of day-to-day work. In my role leading several of the TSTs, I have had the opportunity to personally mentor and see amazing growth from many of my colleagues with whom I would otherwise not have the chance to meaningfully interact.
STRUCTURE: In this post-COVID world, there seems to be a large push for remote work. In conversations, you mention that MKA “believes very strongly in a single office model.” Can you
expand on that idea and discuss MKA’s collaborative office nature?
Aswegan: For MKA’s entire 100-plus-year history, we have resisted the urge to open offices across the world, favoring instead an approach where our expertise is primarily concentrated in one office in Seattle (which is made easier because Seattle happens to be an incredible place to live and work!). This “single office” model has allowed us to attract and retain a pool of very talented engineers who enjoy collaborating in person, while also creating an atmosphere that is much more effective for mentoring and coaching younger engineers. The post-COVID world has reinforced for us the importance of being in person, where we find that we are more social, collaborative, efficient, and productive.
STRUCTURE: You have been working at MKA since 2013 (congratulations!). When did you experience the most growth?
Aswegan: Thank you! The responsibilities for the roles at MKA are generally on a continuum, and we work to continuously grow and get better all the time. For me personally, a point in my career where I grew the most was when I started to manage projects and had to think hard about the big picture in addition to the detailed design. This included considering not only the technical design, but also project schedule, work plans, and communicating with the client.
STRUCTURE: You have buildings in many different places with different jurisdictions. Have you found any place more challenging than the others?
Aswegan: Generally speaking, I have found that the building officials in nearly all jurisdictions are invested in helping projects succeed, and that the best approach is to treat the jurisdiction like a partner and collaborate openly. With that said, the most challenging areas tend to be those with the trickiest combination of environmental hazards, soils, and existing conditions. The Bay Area jumps to mind, given the soil conditions and high seismicity.
STRUCTURE: Graduating from Virginia Tech and then moving/ working in Washington—how was the transition? Did you have any previous experience with the West Coast?
Aswegan: Born and raised in Virginia, I had never been to the West Coast until I started interviewing for jobs during grad school. The transition was relatively seamless (although my family in Virginia might disagree!). I was committed to moving to the West Coast and working for MKA specifically to focus on earthquake engineering and performance-based design. It helped that many of the other engineers at MKA are also transplants, so there is a built-in network of colleagues who are growing together and facing the same life changes.
ATX Tower, the world’s first project designed using Performance-Based Wind Design, under construction in downtown Austin.
STRUCTURE: Throughout your career, who have you relied on as a mentor and/ or advisor? Any words of wisdom that you still hold on to today?
Aswegan: I have had the benefit of many amazing mentors throughout my career, both within and outside of MKA. As it relates to professional organizations and building code development, no one has been more influential than John Hooper. He has provided guidance on my involvement in various professional initiatives and is often the one who has to talk reason into me when I attempt to volunteer for too many things. Other key mentors at MKA have included Sean Clifton and Ron Klemencic, both of whom have taught me the importance of asking “why” and appreciating that to be a successful structural engineer, we must understand the perspectives of everyone else on the project team (developer, architect, contractor, etc.).
STRUCTURE: Do you have any advice for students considering engineering as a profession? What kept you in engineering after so many people seem to be considering leaving?
Aswegan: Structural engineering is not always an easy job, but it is a very rewarding one. In my career, I have worked on projects that have taken me from Toronto to Austin to San Francisco to Shanghai. There is nothing more exciting than seeing a project come to life, and when a TV show or movie shows the skyline of a city I’ve worked in, I will pause and point out my projects to friends and family! Structural engineering is a broad field, and my advice to students considering the profession is to stay open to new opportunities. Early in your career, it may feel like you are drinking from a fire hose, but the knowledge and experience you gain will pay off later.
STRUCTURE: What has been your greatest challenge on a project, and how did you overcome it?
Aswegan: One of my first buildings as a Project Manager was not only a new project type for me, but it also utilized a structural material with which I was relatively unfamiliar. On top of that, it was a large structure on a fast-track schedule. This was a significant challenge for me as a young Project Manager, requiring many hours and sleepless nights. Ultimately, my colleagues at MKA served as a great support mechanism, stepping up to knock out key design tasks and then helping review shop drawings and RFIs. It was a great example of a true team effort. ■
Kevin Aswegan, standing with one of the UCLA coupling beam experimental specimens, tested using a nonlinear wind loading protocol.
New Rules of Thumb for Flat Steel Trusses
Recently published formulas lead to preliminary dimensions for struts, ties, and chords.
By Cesar A. Cruz
In the January 2024 issue of STRUCTURE Magazine, structural engineer Ciro Cuono praised the skills, intuition, and expertise of the individual engineer that result from years of relating calculations to real-world situations, specifically using rules of thumb. As Cuono explained, the value of these abilities have diminished over time as technological innovations and digital tools have continued to put astonishing analytical and design capabilities at our fingertips. This is, of course, a decades-long phenomenon, the kind of historical trend that Cuono points out has put the slide ruler and the slope deflection method in the proverbial junk drawer. Nevertheless, Cuono warns us that continuing to concede more of the hard engineering work to emerging technologies (such as artificial intelligence) without adequate human know-how and supervision can have unintended and unwanted effects. It can dull an engineer’s abilities at interpreting an equation’s results and making informed, evidence-based decisions in the process of structural design. What is there to interpret or explain to the client other than to say, “This is what the computer came up with”?
Previously, rules of thumb for flat steel trusses led only to the height of these trusses. A new set of rules for flat steel trusses (also known as parallel chord trusses) allow an engineer to determine preliminary sizes for a truss’s diagonals, verticals, and top and bottom chords. As such, they fill a valuable gap in our mental toolkit whenever we are working with these lightweight and efficient long-span structures.
Rules of Thumb
The rules of thumb are as follows:
s = l/32 – l/48
h = l/12 – l/ 24
b ≥ s
The first rule of thumb is for a truss diagonal, which yields the sides of a steel square tube, that is, a square hollow structural section (HSS). The side s (in inches) ranges between a maximum size of l/32 and a minimum size of l/48, where l is the nominal length in inches, from node-to-node, of the longest truss diagonal.
Read Online
Visit www.structuremag.org to read the January 2024 STRUCTURE article, “Importance of Hand Calculations and Rules of Thumb in the Artificial Intelligence Age” referenced in this article.
The second rule of thumb is for the top chord of a truss, which yields the height or long side of a rectangular steel tube, that is again, a rectangular HSS. The height h (also in inches) ranges between a maximum size of l/12 and a minimum size of l/24. As in the previous case, l is the nominal length in inches of a segment of a top chord in between two successive nodes. Lastly, the side b of our rectangular HSS must be at least as long as the side of our previously chosen square HSS for our struts and ties. An example will help to explain the uses of these rules.
An Example
Let us begin with an arbitrary truss span L of 175 feet. A longstanding, well-know, and widely published rule of thumb tells us that the height H of a flat steel truss is often equal to one tenth of the span,
H = L/10 = 175 ft/10 = 17.5 ft
Dividing the span into10 equal segments conveniently leads to 10 square panels. Put another way, a flat truss spanning 175 feet can be divided into 10 identical panels, each measuring (nominally) 17.5 feet x 17.5 feet. The truss diagonal is at an angle of 45 degrees and is both nominally and approximately 24.75 feet in length. To apply the two rules of thumb listed previously, it is important to begin with the longest diagonal. This is to safeguard against long compression members, which pose a buckling danger if improperly sized.
• To determine a maximum side dimension for a square HSS that will comprise each truss diagonal, s = l/32 = (24.75 feet)(12 inches/feet) / 32 = 9.28 inches.
• To determine the minimum dimension, s = l/48 = (24.75 feet) (12 inches/feet) / 48 = 6.1875 inches.
• Rounding up to whole numbers, these calculations tell us that we should use a square HSS with sides greater than 6 inches, but no greater than 10 inches. So, we could use an HSS 7 x 7, 8 x 8, 9 x 9, or 10 x 10, which are standard sizes from a readily available table of square HSSs. For the sake of this example, let us select an HSS 8 x 8. Just for the sake of convenience, early on in the design process we will use this size for all truss diagonals and verticals.
• To begin to size the truss’s top chord, switch to the second rule of thumb, h = l/12 – l/24. To determine a maximum height for a rectangular HSS that will comprise the top chord, h = l/12 = (17.5 feet)(12 inches/feet) / 12=17.5 inches.
• For the minimum dimension of h for the top chord, h = l/24 = (17.5 feet)(12 inches/feet) / 24 = 8.75 inches.
• Again, rounding up to whole numbers, the top chord calculations
suggest a rectangular HSS that should be between 9 and 18 inches tall. This would lead us to a rectangular HSS that could be either 9, 10, 12, 14, 16, or 18 inches tall (also standard sizes for rectangular HSSs).
• To ensure a good fit between the top chord and the internal diagonals and verticals, the base b of the top chord should be at least as wide as the side dimension of the square HSSs that we have chosen for the diagonals and verticals. Options include an HSS 10 x 8, 12 x 8, 12 x 10, 14 x 10, 16 x 8, or 18 x 6. One more time, for the sake of the example, an HSS 16 x 8 would work.
• Use the HSS 16 x 8 for both the top and bottom chords. The main concern would be in sizing the top chord, which when supporting mainly gravity loads would be in compression. Again, this is to mitigate against long compression members susceptible to buckling, as mentioned previously with diagonal struts.
• In the final analysis, an HSS 8 x 8 could be selected for all of the diagonals and verticals, and an HSS 16 x 8 for the top and bottom chords.
Rules of thumb may be formula based, or chart or graph based. The charts in Figure 1 simplify the process described previously by relating the rules of thumb in this article directly to a truss’s span. The first chart enables the preliminary sizing of a truss’s diagonal, and the second chart facilitates the preliminary sizing of a truss’s top chord. For each chart, read up from the truss span to the blue line for the minimum size of the desired HSS, and up to the red line for the maximum size of the same HSS.
Background of These New Rules of Thumb
These rules of thumb emerged out of a need in a structures classroom in an undergraduate architecture program. An instructor teaching rules of thumb would be fortunate to have on hand an exhaustive set of rules of thumb. Oftentimes, however, instructors find themselves cobbling together rules from various sources— their times as students, on-the-job training, or from this or that textbook. Inevitably, students will ask their instructors, “How do I size [ ]?” So, an instructor is compelled to dig further into the books looking for even more rules of thumb. Surprisingly, the instructor comes to find that nothing is published for the individual components of a truss … at least not in any of the textbooks used to teach architecture students. So then, do you size them like beams? That would seem to be nothing more than an unsubstantiated guess. Thus, one structures professor set upon an engineering analysis in search of these elusive truss rules of thumb.
The engineering analysis centered upon a theoretical roof structure comprised of a simple built-up roof, wide-flange steel beams, and Warren trusses with verticals. The study’s author ran dozens of trials relying on randomly selected truss spans between 100 and 200 feet, and locations across the United States with differing snow and wind loads. The roof dead load was a constant. Factored dead, snow, and wind loads were applied to the steel beams, which then transferred their reactions as point loads onto the steel trusses. A full analysis followed for each truss in our theoretical roof structure, which in each case led to a calculated cross-sectional area for each chord, diagonal, and vertical in our notional trusses. The size of every compression member was further tested and bolstered to guarantee against buckling. Following these calculations, the study’s author compared the length of the worst-case diagonal for each truss (i.e., the diagonal carrying the largest compression force) to the sides of its corresponding square HSS. A similar process
followed for the worst-case top chord segment. After relating the sides of the square HSSs and the top chord heights for rectangular HSSs to their respective lengths, the results were the rules of thumb s = l/32 – l/48, h = l/12 – l/24, and b ≥ s.
The study’s author also conducted test trials on Pratt and Howe trusses with square panels similar to the Warren trusses described previously. Owing to very close geometries across these three types of trusses, the rules of thumb derived from the Howe and Pratt trusses varied slightly from those derived for the Warren truss with verticals. Thus, the rules of thumb listed here worked out best across all of the truss types under consideration.
Key Considerations and Advice
There are three key considerations related to the study’s boundary conditions, as well as some useful advice in the applications of these rules. The first key consideration is the geometries of the trusses in the study. Each truss consisted of a square panel with diagonals at 45 degrees. So, the study that led to these rules of thumb did not include any rectangular panels, or diagonals at 30 or 60 degrees, or any other angles. Second, the study focused on one truss type—the flat steel truss. Thus, the study did not look at triangular, bowstring, scissors, or other novel truss shapes. And third, the study concentrated on two
Figure 1. Rules of thumb charts for truss diagonals (top chart) and a truss top chord (bottom chart).
specific cross sections—square HSSs for diagonals and verticals, and rectangular HSSs for top and bottom chords. Clearly, many other cross sections are useful and plentiful in steel truss designs. The suggested advice for the rules of thumb presented here serve in part to alleviate any concerns behind the study’s boundary conditions mentioned here. To begin with, rules of thumb are suitable for general and preliminary (not final) sizing purposes, and are meant to be flexible in their application. Accordingly, though these rules of thumb were derived for flat steel trusses, they may be applied to truss members in other steel trusses—for example, triangular, bowstring, or sloped trusses in a shed-style roof—with minimal concerns. This is possible because these rules of thumb are not used to approximate truss heights, but rather the cross sections of their individual components. And in that sense, a strut, tie, or chord is an axially loaded part of a truss, whether that truss is flat, triangular, etc. To be sure, further research is called for to generate additional rules of thumb for various steel truss shapes. But for the time being and in the absence of any other guidance, these rules will suffice.
In a similar vein, though these rules of thumb are meant to generate dimensions for square and rectangular HSSs, the dimensions are not strictly limited to those cross sections. The dimensions may be applied towards other cross sections used in similar circumstances, for example, towards wide-flange or round HSS sections used as axially-loaded truss members. If a designer chooses to take this approach, they should do so with one caveat. If translating from a recommended square or rectangular HSS to a different type of cross section, the designer should use the larger dimensions derived from the rule of thumb formulas or charts. This follows from a comparison of recommended cross sections for wide-flange and square HSSs columns contained in the most comprehensive treatment of rules of thumb used by architects
(and architecture students), in Edward Allen’s and Joseph Iano’s The Architecture Studio Companion. In that exhaustive reference book, recommended cross sections for wide-flange columns track closely or slightly larger than their recommended square HSSs. Remember also to use your engineering judgement. To that end, consider the loads and spans for your steel trusses. Settle upon larger sizes for longer spans and/or heavier roof loads, and smaller sizes for shorter spans and/or lighter roof loads. However, if unsure which size to select for a particular strut, tie, or chord, do as one instructor advises his students, “When in doubt, size up” (that is, select the larger option).
Conclusion
The simplicity of rules of thumb belies their utility to anyone working in structural design. The rules presented here narrow an important gap in terms of steel truss design, and hopefully it is a step in the right direction. Further work of this kind would address, for example, the component sizing of space trusses or multistory diagrids. But for now, the rules of thumb in this article are ready for use by engineers, architects, and student designers. ■
Full references are included in the online version of the article at STRUCTUREmag.org
Cesar Cruz is an Assistant Professor of Architecture at Ball State University, in Muncie, Indiana, where he teaches architectural building structures, design, and architectural history. He may be reached at cacruz@bsu.edu.
Machine Learning Model for Wind Load Prediction on Tall Buildings
A large set of wind load time histories can be generated for performance assessment using AI advancements.
By Aniket Panchal, Anastasia Athanasiou, and Nenghui (Chris) Lin
Machine learning is a branch of artificial intelligence that utilizes data and an underlying algorithm to identify patterns and make predictions without programming them explicitly. This is used further to imitate the underlying behavior between the independent and dependent variables. The model iteratively updates the relationship between dependent and independent variables with accuracy improving over time. The last few decades saw the explosion of machine learning applications due to ease of availability of computational resources and the development of complex machine learning models that utilize multi-layered networks to learn from big, complex datasets. Traditional machine learning models cannot often capture the underlying physics of the governing phenomena. Physics-based machine learning models now are being introduced that integrate physical constraints into the learning process, ensuring the model adheres to scientific laws while enhancing predictive accuracy. Traditional machine learning models are deterministic, i.e., they produce
the same output for a given input. In contrast, generative machine learning models, which have gained recent popularity, learn the underlying data distribution and can generate multiple possible outputs for the same input. This enables exploration of a broader range of possible outcomes for the same input. The most popular generative model examples are in the field of image generation (DALL.E, Sora, Midjourney, etc.) and text generation (ChatGPT, Perplexity). Similarly, in civil engineering, historical data and experimental results can be leveraged effectively to train machine learning models aimed at reducing project costs and timelines. This is well summarized by Burton (2021), which entails various applications, such as improving empirical relations proposed by various design standards, surrogate modeling, and information/feature extraction. The field of wind engineering has also seen significant development, offering innovative solutions for analyzing and mitigating wind effects on tall buildings (He et al., 2021; Kareem, 2020; Liu et al., 2023). One such example is about
Fig. 1. Framework for the development of a machine learning model for random wind load histories generation.
the development of a machine model for image processing to identify low velocity areas around a building for the pedestrian-level wind environment. The model was trained on a large dataset of velocity vectors around a building using computational fluid dynamics simulations. Machine learning models have also been extended to predict wind loads on tall buildings (Meddage et al., 2024), where the wind time history over the building surface is predicted given its spatial coordinate as input. Such emerging paradigms of machine learning offer promising opportunities in the field of civil and structural engineering, particularly around the analysis and modeling of complex wind-structure interactions.
Currently, state-of-the-art structural wind engineering revolves around nonlinear response history simulations of tall buildings subjected to recurring winds of increasing intensity (Athanasiou et al., 2022). Performance-based wind engineering, vital for resilient infrastructure, relies heavily on simulating building response to service and design level winds using dynamic wind histories. The wind loads are typically evaluated in dimensionless form through standard atmospheric boundary layer wind tunnel experiments. This test is typically used as the benchmark to generate multiple sets of alongwind, crosswind, and torsional wind load histories, which serve as the input for the nonlinear response history analysis. Monte Carlo simulation, such as from Shinozuka (1972), is generally used to generate the wind time histories while ensuring the consistent energy distribution over frequency (power spectral density) as that of the benchmark case. The generation of reliable wind loadings is crucial for predicting engineering demand parameters. However, Monte Carlo simulations are computationally intensive and require skilled users every time while generating the wind loads.
To mitigate these drawbacks, the article proposes a framework to generate wind load time histories on a rectangular building with the help of generative machine learning models, incorporating the physics of the phenomenon by constraining them to match the power spectral densities of the wind loads. The framework will significantly reduce the computational effort and simplify the process for practicing engineers who require a large set of loading time histories for the performance assessment of such buildings.
Framework
Figure 1 summarizes the major steps involved in developing a machine learning model for generating physically meaningful wind
time histories. These are:
a. Conduct atmospheric boundary layer wind tunnel experiments on wind-sensitive buildings, varying their Height-BreadthDepth (H-B-D) ratios, angles of wind incidence, and atmospheric exposure conditions.
b. Preprocess the wind load histories to train the machine learning models.
c. Develop the base machine learning model to learn the time history patterns of the processed data.
d. Develop the generative machine learning model to generate the wind time histories.
e. Combine the models developed in stages (c) and (d) to generate the wind loading time histories of the required duration.
Atmospheric Boundary Layer Wind Tunnel Database
The atmospheric boundary layer wind tunnel experiment database is a collection of wind-induced pressure measurements on isolated rectangular clad buildings with various geometric configurations under simulated boundary layer wind conditions. This is a standard experimental setup which practitioners are advised to perform for tall buildings/slender structures to obtain reliable wind loading coefficients. Typically, experiments are performed for a range of angles of wind attack (0°-100°) on the buildings examined. A Simultaneous Multi-Pressure System is employed to evaluate the wind pressure forces on each building surface. Tokyo Polytechnic University (TPU) developed an open-access aerodynamic database based on numerous atmospheric boundary layer wind tunnel experiments performed on low- and high-rise buildings in various exposure environments (TPU, https://wind.arch.t-kougei.ac.jp/system/eng/contents/code/tpu). The TPU high-rise building section comprises data from 22 high-rise building models, offering statistical contours of local wind pressure coefficients, graphs of area-averaged wind pressure coefficients on wall surfaces, and time-series data of point wind pressure coefficients for 394 test cases. This data facilitates calculating local and area-averaged wind pressures, as well as wind-induced dynamic responses of high-rise buildings. This dataset is utilized as a benchmark for developing our machine learning model in the present framework. A sample building from the TPU database depicting the pressure tap locations, along with the inlet velocity and turbulent intensity profile, is shown in Figure 2.
Fig. 2.This TPU database experiment arrangement depicts pressure tap distribution along with the inlet velocity and turbulent intensity profile.
Preprocessing of Atmospheric Boundary Layer Wind Tunnel Database
A single atmospheric boundary layer wind tunnel experiment provides wind coefficients at various locations on all the building surfaces (Fig. 2a). This is then used to calculate force coefficient time histories, including alongwind, crosswind, and torsional components. These are calculated by averaging the measured wind coefficients in the respective directions. The power spectral density function of the force coefficients for a sample building having a width-depth-height ratio of 1:1:3 is shown in Figure 3a for a given height (z = 0.75H). Such a high-dimensional dataset is typically complex to train a machine learning model. To overcome this, the dimensionality of the system is reduced to a few dominant modes, using Proper Orthogonal Decomposition (POD - Weiss, 2019). Since the three wind components are independent of each other, separate operations are performed, which helps in reducing the model complexity. For each component, typically two or three modes are sufficient to capture 90% of the energy and are used to train the models. A sample spectral characteristic of the first mode of each of the wind force coefficients is shown in Figure 3b. The spectral shape of the modal component is nearly similar to that of the force coefficient for all three components, thereby verifying that the POD captures the relevant information.
The calculated reduced modes of the time histories are first standardized with their respective mean and standard deviation to ensure equal contribution of each time history during the training of the machine learning model. Then the time histories are further adjusted to remove any trends over time (using successive difference) or any outliers due to measurement errors. Such operations ensure numerical stability as well as faster convergence of the machine learning models. The final processed time histories are utilized to train the machine learning models.
Development of Base Machine Learning Model
The processed wind time histories for each component (alongwind, crosswind, and torsional) are first trained using a traditional machine learning model (referred to as the base model). The objective of the base model is to learn the underlying trends in the time histories and update the model parameters using an iterative process. The most commonly utilized base models for such purposes are Recurrent Neural Network (RNN), Long-Short Term Memory (LSTM), and Transformer models. The LSTM model developed by Hochreiter and Schmidhuber (1997) is used in the present framework due to its effectiveness in capturing longterm dependencies in the time series. The LSTM model is a special type of RNN model that consists of three key components: (1) forget gate, (2) input gate, and (3) output gate, which helps in managing the flow of data through time. The model requires a fixed-length sequence of input
data points (known as “sequence length”) to predict the next output in the time series. This prediction is then recursively used as input for future steps, allowing it to generate the required length of time series.
In addition to the sequence length, other sets of parameters known as hyperparameters are required to define the architecture of the LSTM model. This must be specified before the model training, unlike the model weights and biases, which are learned during training. These hyperparameters need to be tuned to maximize the model’s performance. The model training process typically involves minimizing the mean squared error between the predicted and actual time series, and the model parameters are updated using a gradient descent algorithm. Additionally, physics-based constraints are incorporated by minimizing the mean squared error between the auto-spectral density of the predicted and actual time series. The performance of the model is evaluated not only by comparing the auto-spectral density, but also the coherence between the time series signals.
After training the base model, the initial segment of the time series is given as an input, and the required length of time series is predicted recursively. Once the base machine learning model is developed, a generative model is created to generate random input segments, enabling the generation of random and realistic time histories.
Development of Generative Machine Learning Model
The base model developed operates deterministically, meaning it always produces the same output for a given input segment, which limits the ability to generate diverse or random time history realizations. To address this, a complementary generative model is developed to introduce randomness. This model generates random, physically consistent input sequences, allowing the production of diverse and realistic output sequences.
The most popular generative model is the Generative Adversarial Network (GAN, developed by Goodfellow et al., 2014), which generates realistic data by learning the distribution of the original dataset. GAN consists of two key components: (1) the generator model, and (2) the discriminator model. The GAN model is trained through a min-max game between the generator and discriminator: the generator is trained to minimize the error in creating samples, whereas the discriminator is trained to maximize its ability to distinguish between real and generated data. Similar to the base machine learning model, the generator model also requires a set of hyperparameters, which needs to be specified before the training process. These need to be fine-tuned to maximize the performance of GAN. After training, the performance of the generative machine learning model is evaluated by comparing the distribution of the generated data segment with the real data segment.
Fig. 3. Power spectral density of wind force coefficients.
Combining Models to Generate Random Wind Force Coefficient Time Histories
The random wind time histories can be generated with the help of the machine learning models developed in the previous sections through the following steps:
a. Generate a random input segment of the wind time histories, CpCg(t), using the GAN model.
b. The random input segment from the previous step is then used to predict the CpCg time history recursively, using the LSTM model.
c. Using the back transformation that was used for processing the various modes of the CpCg time history to obtain the original modes.
d. The final wind CpCg time history is then obtained using the same POD process.
The models can be developed for the set of buildings and angles of attack. An overall conditional model will be developed to adjust the model parameters based on the following inputs: building geometry (ratio of building dimensions), terrain roughness, and angle of attack.
Conclusions
The present framework proposes an innovative approach to generate wind load through the application of multiple machine learning models. Until now, most applications in the field of wind engineering are limited to traditional machine learning models, which lack randomness. This is overcome by combining a generative model with a traditional physics-based
machine learning model to generate reliable random outputs. Such an approach highlights the growing potential of such combination models that combine the interpretability of physics-based frameworks with the adaptability of generative machine learning models.
This framework could help practicing engineers reduce the project cost and time by potentially eliminating the need of a standard atmospheric boundary layer wind tunnel experiment to obtain reliable wind force time histories. This also helps in reducing computational efforts and skills required to perform Monte Carlo simulations to generate multiple realistic and random time histories using experimental data.
Future work may focus on the extension of such a framework to include structures of various geometries, improving the interpretability of models, real-time implementation in structural health monitoring, and prediction of climate change. ■
Full references are included in the online version of the article at STRUCTUREmag.org
Aniket Panchal is currently pursuing a Ph.D at Indian Institute of Technology Gandhinagar, India, with a focus on multi-hazard assessment of tall buildings under wind and earthquake excitations.
Anastasia Athanasiou (Ph.D) is an Assistant Professor of Natural Hazards and Structural Resilience at Bauhaus-Universität Weimar, Germany.
Nenghui (Chris) Lin is a Project Engineer at Mott MacDonald and a graduate student at the Department of Computer Science at the University of Texas at Austin. He specializes in end-to-end AI solution design and LLM development.
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structural DESIGN
10Things Every Structural Engineer Should Know
The SE 2050 Resources Working Group developed a list of essential information about embodied carbon as structural engineers approach their work.
By SE 2050 Resources Working Group
The SEI SE 2050 Commitment Program was developed and is managed by a dedicated group of volunteers. Each member of the team brings a unique perspective and level of expertise to SE 2050. The SE 2050 Resources Working Group developed the following list of essential information that every structural engineer should understand about the topic of embodied carbon as they approach their work. This first of the series is general guidance, while material-specific lists will follow in subsequent issues. See http://SE2050.org for a PDF version of this list to learn more about both the commitment program and embodied carbon in general.
1. Embodied carbon and acronyms such as CO2e and GWP are important terminology.
Embodied carbon is the impact of all greenhouse gases emitted into the atmosphere by the production of a material, product, or system (measured in CO2-equivalent or CO2e). CO2e is a unit of measurement quantifying the global warming potential (GWP) of various greenhouse gases compared to an equivalent amount of CO2
2. Embodied carbon is as important to address as operational carbon.
Embodied carbon represents up to 11% of global greenhouse gas emissions and 5% of domestic greenhouse gas emissions. Structural engineers have direct influence over this portion of the climate change challenge. There have been significant advancements in energy codes, mechanical systems, and architectural design that have led to reductions and efficiencies in operational carbon, defined as the greenhouse gas emissions released during the day-to-day use of a building. As these operational emissions get closer to net-zero, embodied carbon will be even more critical to address and reduce.
3. It is important to think about upfront carbon and the time value of carbon when considering the impact of embodied carbon.
Greenhouse gases released during the production of materials and buildings are emitted earlier than carbon released during the operation
of the same projects. This upfront carbon has an immediate impact on the climate and often accounts for the majority of a building’s total carbon footprint for much or most of a building’s life until the annual operational emissions accrue. There is no way to renovate or reduce these emissions once a building has been constructed.
4. It is possible to build a net-zero embodied carbon building using existing technology.
A net-zero embodied carbon or neutral embodied carbon building is when an assessment determines that a project has no net greenhouse gas emissions into the atmosphere from embodied carbon. This is achieved through a combination of emission reductions, the use of carbon sequestering materials (see item 8), and, if necessary, the purchase of verified carbon offsets. Building and material reuse are two effective emission reduction strategies that can set up a project for net zero.
5. A Life Cycle Assessment (LCA) is an environmental impact assessment framework that can be readily applied to building products and systems.
LCA is a method of evaluating the environmental impacts, including the global warming impact, associated with a specific scope. A fully defined scope addresses both the elements and processes being considered and the life cycle stages included. The stages that may be considered when evaluating the embodied carbon of a project include the Product Stage (A1-A3), Construction Process Stage (A4-A5), the Use Stage (B1-B7), the End of Life Stage (C1-C4), and Beyond End of Life (D) (Figure 1). International standards for LCAs include ASTM E2921, EN 15978, ISO 14040, and ISO 14044.
6. Environmental Product Declarations (EPDs) are essential sources of product information.
EPDs are reports measuring the environmental impacts of a product or material from an LCA. The typical life cycle stages measured by
EPDs include the Product Stage only: Raw Materials Supply (A1), Material Transport (A2) and Manufacturing (A3), i.e. “cradle-to-gate”. Most EPDs do not include product installation, operational maintenance, or end of life considerations. The scope and reporting requirements for an EPD are governed by a Product Category Rule (PCR). The international standard for EPDs is ISO 14025.
7. A Whole Building LCA (WBLCA) is the most robust and holistic source of information for quantification of the environmental impacts of a project.
A WBLCA should include as many of the building systems, scope, and life cycle stages as feasible. WBLCAs should address the functional equivalency of options considered, including design loads and functionality. WBLCAs are especially useful for quantifying design strategies, such as material selection and structural configuration, in addition to procurement strategies. WBLCA results should be reported both on a whole-building basis and a per square foot basis.
8. Carbon sequestration, including the concepts of Biogenic Carbon and Concrete Carbonation, are important processes to understand in Life Cycle Assessments.
Wood and other renewable materials (straw, hemp, etc.) inherently have carbon “stored” within the material through photosynthesis, which is often referred to as biogenic carbon. When these materials are used as building materials, this biogenic carbon can be stored during the building’s service life. Once a structure is demolished, a majority of the stored biogenic carbon is released back into the atmosphere through decomposition and burning. Deconstructing rather than demolishing buildings and reusing the reclaimed materials extends the carbon storage benefits. Claiming a reduction in life cycle carbon due to sequestration involves a number of variables, including forest management practices and the end-of-life fate of the material. For this reason, it is common to report LCA results with and without biogenic carbon included.
Concrete sequesters carbon over time through a process known as carbonation. It is estimated that approximately 10% of the emissions associated with the production of the cement and concrete for a structure can be sequestered over the structure’s life, with more carbonation occurring during the end-of-life stage. The industry is working to support accurate accounting of carbon sequestration through carbonation. Consideration of this process reduces the lifecycle impact of concrete emissions.
9. Where and who your construction materials come from matters.
The location of a material or product’s extraction and manufacturing can significantly influence the magnitude of its embodied carbon. Producers, manufacturers, and fabricators who source local raw material, use a larger percentage of recycled material, or obtain electricity from a renewable energy source can greatly reduce the embodied carbon of their material or product. The proximity of a material source to the project site and the means of transportation to the site should also be considered. Always try to obtain and compare EPDs from multiple manufacturers that may supply a project’s material to help inform decision-making and allow for comparison to industry averages.
10. Structural engineers play a crucial role in reducing embodied carbon.
Some strategies structural engineers can use to reduce a project’s embodied carbon are using alternative materials like fly ash and slag in concrete, selecting an efficient structural system for the building type and usage, optimizing structural material usage, conducting whole building life cycle assessments to inform decision making, and increasing the service life of a building. Structural engineers should be engaged early and often in the design process to facilitate these strategies. ■
The SE 2050 Resources Working Group produces, maintains, and publishes resources on the SE 2050 website for structural engineers on the topic of embodied carbon. More information on the SE 2050 Commitment can be found at http://SE2050.org.
Fig. 1. Life cycle stages and modules comprising embodied carbon are illustrated. Source: Carbon Leadership Forum
structural ANALYSIS
Concrete Constructability Resources for Designers
Leaders from the concrete industry are working to provide reliable data and research to help designers reduce inefficiencies and maximize productivity.
By Phil Diekemper, Cary Kopczynski, and Michael L. Tholen
In the September 2024 issue of STRUCTURE, an article highlighted the challenges underlying “The Construction Productivity Problem.” Since then, additional research on the construction productivity decline has been published by respected industry experts, including FMI Corporation’s Construction Labor Productivity: The $20 Billion Opportunity (2023 FMI Labor Productivity Study) and McKinsey Global Institute’s (August 2024 Report) Delivering on Construction Productivity Is No Longer Optional. As an American Concrete Institute (ACI) Center of Excellence for Advancing Productivity, PRO is dedicated to identifying and dismantling the barriers hindering concrete construction productivity. Despite widespread agreement that poor productivity is prevalent, few can articulate what productivity truly means, how it is measured, or how to directly improve it. In many cases, productivity problems are mistakenly attributed solely to the skills of the concrete contractor. While contractor planning and management certainly influence productivity, several factors beyond the contractor’s control play a significant role. PRO intends to identify these factors and present solutions to minimize their impact.
The Challenge of Elusive Knowledge
A key obstacle in improving construction productivity is the lack of accessible knowledge and data. Unlike other sectors, there is no centralized
database for construction productivity metrics. Many contractors consider their productivity data proprietary, leveraging it as a competitive advantage in the design-bid-build model. As a result, productive ways to deal with variables that significantly impact productivity, such as structural design, site conditions, local constraints, and contractor expertise—or even quantify the impact they have are rarely published or shared. This guarded approach has caused a significant gap in industry knowledge. Unlike structural design software, which has made great strides in optimizing material efficiency, few resources are available to help designers integrate productivity-enhancing strategies into their work. Without reliable data or research, designers struggle to maximize the value of their efforts, leading to inefficiencies and missed opportunities for field productivity gains. Thankfully, leading companies from a broad cross section of the industry have joined PRO and are working to offset this guarded approach.
Defining Productivity Gains in Concrete Construction
Traditionally, productivity is defined as value added output divided by resource consumption, such as time and materials. PRO views this issue in a broader sense by looking at:
• Optimizing field labor and construction speed.
• Minimizing concrete conflicts with other trades.
• Increasing overall project value for owners.
• Reducing project RFIs, design changes, and change orders.
The Constructability Imperative
A 2017 report from the McKinsey Global Institute identified several factors contributing to low productivity, including inefficiencies stemming from a lack of standardization and the frequent friction between design and construction. As architectural and structural designs become increasingly complex, these inefficiencies are magnified, and constructability considerations become even more challenging. Although delivery models like Integrated Project Delivery and Design-Build encourage early collaboration among owners, designers, and contractors, these opportunities remain underutilized.
Recognizing this challenge, ACI—the authoritative source for concrete design codes and standards—developed a Constructability Study Course and accompanying certificate program. Offered free to ACI members, this course provides designers with essential constructability knowledge, allowing them to integrate construction expertise in their designs. The goal is to create designs that 1) do not embed barriers to productivity, and 2) allow the productivity potential of modern construction systems to be fully realized.
In alignment with its mission to advance productivity, PRO has launched an initiative to Improve the Constructability of Concrete Structures. This effort advocates for incorporating constructability principles into all designs, either through contractor-designer collaboration or by enhancing designers’ knowledge via the Constructability Certificate Study Course offered through ACI University. Additionally, designers now have access to the Constructability Blueprint, a free PRO document outlining numerous constructability considerations, further supporting efficient project planning and design.
According to the Construction Industry Institute Task Force, implementing constructability practices early in a project can yield a 10:1 return on invested effort—an undeniable advantage for all project stakeholders. By prioritizing constructability principles, projects can realize greater efficiency, fewer delays, and enhanced overall value.
Constructability Blueprint
Improving productivity through constructable design involves a broad set of principles that influence project efficiency and cost-effectiveness.
To support designers and industry professionals, PRO is offering the Constructability Blueprint in a complimentary PDF format, providing easy access to essential constructable design principles.
This resource goes beyond simply recommending constructable actions—it explains the “why” behind each recommendation, helping users gain a deeper understanding of productivity-enhancing strategies. Included in the document are links to supporting research and published articles, allowing users to explore topics in greater detail. The search functionality within the PDF format makes it simple to investigate specific concepts quickly, ensuring efficient access to information.
A key advantage of the digital Constructability Blueprint is the ability to modify and expand it over time. Additional content is already in development, reinforcing PRO’s commitment to advancing concrete constructability knowledge.
The Value of Highly Constructable Projects
Projects designed with embedded constructability and with documents that clearly communicate the design unlock multiple benefits, including:
• Enhanced project planning—Concrete contractors can meticulously plan work in advance.
• Efficient use of modern construction systems—Maximizing labor efficiency and construction speed.
• Predictable outcomes—Reducing uncertainties and ensuring smoother project execution.
• Shorter construction durations—Allowing subsequent trades to begin work sooner.
• Minimized trade tolerance conflicts—Reducing rework and unnecessary delays.
Each of these advantages directly translates into cost savings for project owners, driven by the productivity gains realized through effective constructability practices.
Sampling Constructability Design Principles
In the engineering of concrete structures, optimizing material quantities in the completed structure is often prioritized. While this can reduce a structure’s dead load, embodied carbon, and material costs, it overlooks the primary driver of concrete structural frame costs: construction labor.
Optimizing material efficiency must be balanced with other constructability considerations. Over-emphasizing reductions in materials can unintentionally lead to designs that increase rather than reduce project costs. Since permanent material typically accounts for less than 50% of total concrete structure costs—as demonstrated in Figure 1 from a reference project case study from a high labor cost location—prioritizing labor efficiency is crucial to achieving cost-effective outcomes. Without a clear constructability focus, a structural design can become overly complex if the effort to optimize material is excessive. And an increase in complexity can quickly increase field labor costs.
Overemphasizing material efficiency can also lead to unintended consequences that increase overall construction costs. For example, concrete members sized purely for applied loads may not be large enough to accommodate the required reinforcing steel with sufficient bar spacing to allow satisfactory concrete placement. ACI 318, Building Code Requirements for Structural Concrete, establishes minimum reinforcing bar spacing to allow proper concrete consolidation. It also defines the maximum spacing of bars for crack control. Based
Fig. 1. Material vs. Labor Costs in Concrete Structures
Table 1. Maximum Number of Longitudinal Bars in a Single Layer Permitted Using ACI CODE-318 Requirements
Note:
• Lap splices are not reflected in these quantities.
• Overall bar diameter (in lieu of nominal diameter) is used for longitudinal reinforcement.
• Cover to stirrups = 1.5 in.
• Nominal maximum aggregate size dagg = 3/4 in.
• No. 3 stirrups are used for No. 4, 5, and 6 longitudinal bars, and No. 4 stirrups are used for No. 7 and larger longitudinal bars. While the Table reflects No. 3 stirrups are used for No. 4, 5, and 6 longitudinal bars contractors find #3 stirrups insubstantial and less productive, and No. 4 stirrups are used in the Table for No. 7 and larger longitudinal bars. PRO recommends #4 stirrups as a minimum size
on bar spacing requirements, Table 1 sets out the maximum number of reinforcing bars permitted in a single layer for a given beam width. Concrete formwork benefits from consistency of member size. Contractors seek to maximize formwork reuse to increase field productivity, but formwork is often misunderstood by engineers because it is invisible during design and rarely left behind after construction. Since formwork can be as much as 50% of a concrete structure’s cost, it yields readily to a constructability strategy, the successful implementation of which also reduces the likelihood of field errors due to standardization of components. If structural engineers develop an understanding of formwork logic and visualize the forms and field labor required for various conditions, improved constructability results. Figure 2 illustrates the financial impacts of different formwork scenarios. Complex formwork systems as noted in the graphic include multi-use, high-production systems or self-climbing systems.
Floor framing becomes more economical as formwork reuse increases, provided the design has repetitive elements. Repetitive designs also take advantage of a construction crew’s learning curve (Fig. 3). Design changes cause setbacks to the productivity gains crews realize from repetition. Many formwork systems have significant mobilization, build-up, tear-down, and learning curve costs that are recovered with productivity gain as form reuse increases. Thus, a design that requires single-use formwork is less constructable and more expensive. Structural cost can vary greatly without a significant change in material quantities, primarily due to the degree to which constructability is embedded in the structural design.
Figure 4 illustrates relative costs of three structural elements as a function of building height. Labor costs decrease to an optimum value as workers gain experience and as mobilization costs (including form build-up and tear-down) are amortized over greater form reuse. Thereafter, the unit cost of floor framing remains relatively constant with increasing height. However, after originally decreasing from benefits of repetition, higher loads eventually cause the unit costs of columns, bearing walls, and the lateral force-resisting system to increase with increasing building height. The largest component of the total cost for a concrete building is nearly always the horizontal (floor)
framing, so optimizing floor framing should be a high design priority. This is only a portion of the information available in the PRO Constructability Blueprint. The complete, current 120-page document is available at concreteproductivity.org. PRO envisions the Constructability Blueprint as ever evolving, with new technologies, systems, construction, and design practices added over time. Users of the document who have suggestions for improvement are encouraged to submit them. PRO welcomes all ideas and information that will enhance the value of the material.
Summary
Established by ACI in 2023, PRO: An ACI Center of Excellence for Advancing Productivity serves as a catalyst for overcoming barriers that hinder concrete construction productivity. Leveraging ACI’s global network for the development, dissemination, and adoption of
Fig. 2. Formwork Cost Relative to Reuse
consensus-based standards for concrete design, construction, and materials, PRO is dedicated to driving meaningful improvements in industry efficiency.
The Constructability Blueprint recognizes that perspectives on constructability will vary based on regional, local, and contractorspecific conditions. Many factors influence it, including:
• Weather and environmental constraints.
• Contractor experience and technical expertise.
• Project delivery risks and contract terms.
• Owner payment practices and financial structures.
• Local construction culture and regulatory requirements.
• Availability of skilled labor, materials, and equipment.
While the Constructability Blueprint is not a substitute for early and engaged contractor-designer collaboration, it serves as a valuable reference for designers to enhance construction productivity and efficiency. By providing guidance and insights, the document empowers industry professionals to make informed decisions that drive better project outcomes. ■
Phil Diekemper is the Executive Director of PRO: An ACI Center of Excellence for Advancing Productivity. Cary Kopczynski is the CEO of CKC Structural Engineers and is a past ACI President. He chairs the PRO Board of Directors. Mike Tholen is the Senior Managing Director, Technical Operations at the American Concrete Institute. He is a member of the PRO Board of Directors.
CRSI’s popular design Guides are indispensable resources for structural engineers, educators, students, building officials, and individuals studying for licensing exams.
Seismic Design Guide for Steel Reinforced Concrete Buildings
The purpose of this Design Guide is to assist in the proper application of the earthquake provisions in the 2019 edition of Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19) for cast-in-place concrete buildings with nonprestressed steel reinforcing bars.
Design Guide on the ACI 318 Building Code Requirements for Structural Concrete
With over 140 worked-out examples, this unique Design Guide assists in the proper application of the provisions in the 2019 edition of Building Code Requirements for Structural Concrete (ACI 318-19) for castin-place concrete buildings with nonprestressed reinforcement.
Print and digital versions available!
Design Checklists
Companions to the CRSI Design Guides on ACI 318-19, these Design Checklists are easy-to-use lists of essential items that must be completed when designing and detailing steel reinforced concrete structural members in accordance with the 2019 edition of the ACI 318 Building Code. SAVE 10%* ON ALL DESIGN GUIDES BY USING PROMO CODE: STRUCTURE *Discount applies to print and single digital license (DL1) versions only
Fig. 3. Productivity Relative to Repetition
Fig. 4. Structural Cost Relative to Building Height
Viaduct Damage Assessment After the 2023 Earthquake in Turkey
Five viaducts along the Tarsus-Adana-Gaziantep Highway in southern Turkey were damaged by the 2023 Mw 7.8 earthquake. Damage assessment and the seismic retrofit design for two of those viaducts are shared here in Part 1. The remaining three will be covered in Part 2 in the October issue.
By Cenan Ozkaya, Ph.D, Robert K. Dowell, Ph.D, PE, and Faruk Yildiz
Fourteen viaducts are situated along the Tarsus-AdanaGaziantep (TAG) Highway, which is the main transportation route in Southern Turkey. Three lanes of traffic flow in each direction. Of the 14 viaducts, five were damaged during the 2023 Mw 7.8 earthquake.
Built just before the year 2000, all five viaducts are large and impressive structures set in the low mountains, with interesting designs for earthquake response. Originally designed for a peak ground acceleration (PGA) of 0.4 g (with return period of about 500 years), the damaged bridges were loaded with significantly more ground shaking than they were designed for. Station 2712, the closest free-field strong motion station to all five of these damaged viaducts, recorded a PGA of 0.607 g (see full references with the online article). Other free-field strong motion stations along the fault rupture line showed even larger PGA values (from USGS), but these were not close to the TAG Highway, or any of the damaged bridges (Fig. 1). Hence, based on the available measured data, and how close these five bridges are to each other and to Station 2712, it is reasonable to expect that they were all overloaded by about 50% beyond what they were designed for.
Figure 1 shows how close the USGS-defined fault rupture line for the Mw 7.8 earthquake is to the five damaged bridges, and how the TAG Highway (O-52 in Fig. 1) turns and follows it, in parallel, before turning away again. This proximity to the fault line explains why these five viaducts were damaged, and why the other nine viaducts on the TAG Highway weren’t; for a large earthquake, PGA reduces with normal (perpendicular) distance from the fault rupture line, and
not as the distance from the earthquake epicenter. Also, near-field earthquake conditions existed for these damaged bridges since they were all within 225 meters (738 feet) of the fault line that ruptured.
Two of the five major bridges—the Ataturk and Turgut Ozal Viaducts—are very similar in both scale and seismic design features. As such, their new seismic retrofit schemes were similar as well. Part 2 of this series will appear in the October issue of STRUCTURE and focus on the other three viaducts.
Seismic retrofit designs for the Ataturk and Turgut Ozal Viaducts were done by Cenan Ozkaya, as the engineer of record, working within the PONTEM Engineering Co. The typical seismic retrofit design of a bridge structure is in anticipation of a future large event that will probably never happen, and that the bridge was not originally designed for. This project, however, is the seismic retrofit design for a bridge that has already been subjected to the maximum considered earthquake (MCE). Importantly, these two major bridge structures were damaged but did not collapse, and they were saved for future use by the ongoing seismic retrofitting to larger PGA values than considered in the original design. The high quality of both (1) the original design details and (2) the construction, are important features that helped save the viaducts during the February 2023 Mw 7.8 earthquake.
Retrofitting works are being carried out by the SNH Construction Company, and the owner of the viaducts is the Motorway Division of the General Directorate of State Highways, in the Ministry of Transportation and Infrastructure of the Republic of Turkey.
Fig. 1a (left). The location of the Mw 7.8 earthquake fault rupture line (in red) and the five damaged viaducts along the TAG Highway are shown. Fig. 1b (right). Strong motion stations and PGA are shown at various locations along the fault rupture line (in red), as well as Station 2712, which is close to the five damaged viaducts.
Fig. 2. The view looking down the 130 meter (427 foot) height of the Ataturk Viaduct, which was the tallest viaduct in Turkey when constructed.
Earthquake Information
Just after 4 a.m., local time, on February 6, 2023, a Mw 7.8 earthquake struck Southern Turkey followed by a Mw 7.5 earthquake only six hours later. The first one is the largest earthquake to ever hit Turkey and is consistent with an MCE event in California. When converted to the older Richter scale, it has a magnitude of 8.1, which is the same magnitude as the famous 1906 San Francisco earthquake and the future “big one” in California. Furthermore, the right strike-slip fault mechanism that caused the 2023 Turkey earthquake is the same mechanism for both California earthquakes, past and anticipated future, along the San Andreas fault. Since Turkey closely follows Caltrans seismic bridge design specifications and practices, it is of interest in California to see how Turkey’s major bridges and viaducts performed in this very large earthquake, especially since Caltrans’ infrastructure has not yet been tested like this (the many California bridges were built after the 1906 San Francisco earthquake).
The 2023 Mw 7.8 earthquake, in Turkey, occurred due to sudden slip along the Eastern Anatolia Fault Zone (EAFZ), which is the second most active fault system in Turkey and is the most significant for the two major viaducts considered in this article. It is a right strike-slip fault system that is 550 km (342 miles) long and separates the Anatolian and Arabian tectonic plates. These two plates move relative to each other at a rate of about 10 to 12 mm (0.394 to 0.472 inches) per year. Using the maximum measured relative displacement of 40 feet from the 2023 earthquake, and the upper value of the relative rate of plate motion, this translates to a return period for such a large earthquake of 40(12)/(0.472) = 1,017 years. Therefore, a large earthquake is expected along this region about every 1,000 years, which is consistent with the historical record going back just over 2000 years, to 30 BC. A large earthquake happened in 30 BC, then again in 1114 AD, and the most recent earthquake was in 2023. The average time between these three historical records is 1,027 years, which agrees with the approximate time of 1,000 years between big events. Knowing that the last large earthquake in this region was in 1114 AD, one could have predicted this latest large earthquake to occur where it did in about 2114, with perhaps a 150-year window in either direction to allow for natural variations in soil/ rock strength. So, it would have been expected anytime between 1964 and
2264, for example. Now that the slip has occurred along this fault, the strain energy that had built up for 1,000 years is released, and it will take another 1,000 years or so before enough strain energy builds up to suddenly fracture the rocks at the tectonic plate interface and produce a large earthquake again.
Ataturk Viaduct
At a height of over 130 m (427 feet), the Ataturk Viaduct was the tallest viaduct in Turkey when it was built, and is the tallest bridge anywhere in the world to be subjected to an earthquake of this magnitude (to be hit by its MCE). As shown in Figures 2-5, the bridge is so tall that clouds and mist often form below the superstructure.
The viaduct is supported by hollow rectangular reinforced concrete columns with 9 m x 6 m (29.5 feet x 19.7 feet) main core (without ears/protrusions) cross-section dimensions at the column top and a wall thickness of 0.60 m (1.97 feet). Column flares linearly increase these cross-section dimensions from the top to the bottom of the column, with primary vertical rebar following these flared regions to increase the internal moment arm and, hence, moment capacity of the column toward its base, where the moment demand is largest. As with the three damaged bridges in the companion article, the columns have primary vertical rebar cutoffs but with no adverse effects for this viaduct. The largest reinforced concrete foundations have dimensions of 22 m x 34 m in plan and are 6 m thick (72.2 feet x 112 feet x 19.7 feet). This eight-span viaduct has a total length of 802 m (2,630 feet; about half a mile), with span lengths that range from 70.7 m (232 feet) to 110 m (361 feet) and is on a 1,200 m (3,937 feet) horizontal curve, with 3% longitudinal slope. Column heights range from 130 m (427 feet) to 9.62 m (31.6 feet). Expansion joints are provided at the ends of the bridge.
Side-by-side superstructures consist of weathering steel U girders, with width of 9 m (29.5 feet) and depth of 4.9 m (16.1 feet), are 17.5 m (57.4 feet) wide, and have a 4.5 m (14.8 feet) clear space (gap) between them. Girders were placed by incremental launching and have a cast-in-place (CIP), reinforced concrete topping slab that is 39.5 cm (15.6 inches) thick, as well as an asphalt concrete overlay for the driving surface. The
Fig. 3. The Ataturk Viaduct is so tall, clouds and mist often form below the superstructure.
Fig. 4. The Ataturk Viaduct is the tallest bridge in the world to be subjected to an earthquake of the magnitude of the 2023 event.
steel girders are supported by a prestressed concrete transverse beam and reinforced concrete single-column-bents (Fig. 5). Hence, the reinforced concrete columns act as cantilevers in both the longitudinal and transverse directions, with large reinforced concrete footings at their bases, and micropiles below the footings to prevent overturning; as well as to eliminate problems arising from karstic cavities present along all the viaducts in the Nurdag district. The tallest columns at Bents 5, 6 and 7 have caisson foundations.
The original seismic design included multiple shock-absorbing bumpers added to the expansion joints at both ends of the bridge, and at Bents 2, 3, 4, 5 and 8, which takes the longitudinal force, with steel beams and slider pot bearings not allowing longitudinal movement at the other bents. These unique, elastic, high-force-capacity bumpers act in tension and compression and were intended to provide a self-centering behavior to the viaduct after an earthquake. Tall columns at Bents 6 and 7 are longitudinally guided by using a custom steel connection detail by the contractor. However, since the seismic ground shaking was significantly larger than the viaduct was designed for, the bumpers and expansion joints failed, with the bumpers no longer functioning after the earthquake (Fig. 6). Sliding surfaces of the bearings were also damaged and are no longer functional. In the transverse direction, the bridge was restrained from movement by steel seismic braces.
The force-displacement response of the bumpers is initially linear but with increasing slope as the displacements increase; hence, a stiffening spring. The steel superstructure, columns, footings, and bent cap were not damaged in the earthquake. Both approaches to the viaduct settled, and trees adjacent to the bridge moved downhill in the soil. The concrete slab was locally damaged at the expansion joints due to impact forces, while the asphalt concrete overlay buckled, and many potholes, bumps, and undulations are now on the driving surface, significantly affecting traffic.
Since these elastic bumpers are no longer made, and due to the extreme difficulty of retrofitting the large, hollow rectangular reinforced concrete columns and large reinforced concrete footings, it was decided to reduce any
future seismic forces on the substructure by incorporating seismic isolation at the tops of all the columns. This lengthened the longitudinal period of the structure from 2.6 seconds to 3.45 seconds, reducing maximum structural accelerations and, hence, the seismic substructure forces. It also ensured that the shorter, stiffer, columns wouldn’t get more seismic load than the taller and more flexible columns. In the transverse direction, the structure period increased only slightly from 4.06 seconds to 4.20 seconds. Viscous dampers were also added in the bridge longitudinal direction. The final seismic retrofit design was validated using nonlinear time-history analyses (NTHA), showing that the superstructure, bent caps, columns and footings remain linear-elastic from a design maximum considered earthquake event. This viaduct was 75 m (246 feet) from the fault rupture line.
Turgut Ozal Viaduct
The Turgut Ozal Viaduct (Fig. 7) is very similar to the Ataturk Viaduct, with the same use of elastic, high-force-capacity bumpers at the end expansion joints, as well as at the bents with shorter columns, Bents 2 and 5. It is also a very large structure with two side-by-side steel superstructures of the same dimensions as the Ataturk Viaduct, with reinforced concrete topping slab and asphalt concrete overlay for the driving surface. Likewise, the superstructure of the Turgut Ozal Viaduct is supported by a prestressed concrete bent cap, and hollow rectangular reinforced concrete columns that act as cantilevers, in both the longitudinal and transverse directions. However, unlike the Ataturk Viaduct, there are no column flares and no vertical rebar cutoffs. It is on a horizontal curve with 2,600 m (8,530 feet) radius, and 3% longitudinal slope. While the reinforced concrete column cross-section details are the same as the Ataturk Viaduct, the tallest column of the Turgut Ozal Viaduct is 76 m (249 feet), which is significantly shorter than the 130 m (427 feet) column height of the Ataturk Viaduct. Also, the total length of 424 m (1,391 feet) for the Turgut Ozal Viaduct is much less
Fig. 5. Steel girders are supported by a concrete transverse beam (pictured) and reinforced concrete single-column bents at the Ataturk Viaduct.
Fig. 6. Elastic high-force-capacity bumpers at the Ataturk Viaduct failed from the seismic ground-shaking.
than the 802 m (2,630 feet) length of the Ataturk Viaduct. Pot bearings with sliding surfaces were used at interior bents and abutments. These sliding surfaces had a displacement capacity which was consistent with the displacement capacity of the high-force-capacity elastic bumpers, demonstrating a good design. Longitudinal movement of the tall columns, at Bents 3 and 4, was restrained by steel beams. Hence, in the earthquake, all of the bents did not share the longitudinal load equally. Damage occurred to the elastic impact bumpers and expansion joints, as well as all sliding surfaces, which are no longer functional. As with the Ataturk Viaduct, the seismic retrofit design consisted of providing seismic isolation to the tops of the columns and adding viscous dampers in the bridge longitudinal direction, which lengthened the period of the structure, reducing substructure forces, and resulting in linearelastic superstructure, bent cap, column and footing responses from a future maximum considered earthquake event. Thus, no retrofit of the substructure was required. This viaduct was 225 m (738 feet) to the fault rupture line. Micropiles of 25 m (82 feet) length were provided under the foundations.
NTHA showed that a combination of seismic isolation at the tops of the columns and added viscous dampers allows the viaduct to survive a future maximum considered earthquake event (about a 2,500-year return period) based on the Turkish National Earthquake Design Code. PGA of 0.983 g was used for the base motions. Vertical accelerations were also included in this NTHA. The program Larsa 4D was used for static
and dynamic analyses, with the XTRACT program utilized for section moment-curvature analyses. Although the axial force for any given column is constant along its length from dead load of the bridge superstructure and bent cap, the total axial force in the column varies over its height due to the added weight of the big column, requiring various moment-curvature analyses up the column height. For typical, smaller, bridge structures, the changing axial load along the column length from the weight of the column often can be ignored, allowing a single moment-curvature analysis to represent the whole column height, so long as the cross-section and/ or rebar details don’t change over the column length.
The detailed analysis demonstrates that with this seismic retrofit, the steel superstructure, prestressed concrete bent caps, reinforced concrete columns and foundations remain linear-elastic from a maximum considered earthquake event. Therefore, no strengthening was required for these members. With spherical sliding (curved surface slider-friction pendulum) bearings provided at the tops of all the columns as the seismic isolation scheme, longitudinal forces from a future earthquake will be almost the same at all the bents. Displacement capacity had to be ensured, since the isolation system reduces forces but increases displacements. A total of 14 time-history analyses were conducted. Rotational mass inertia of the superstructure was included in the dynamic analyses, which was shown to be important in a study by Robert K. Dowell for single-column-bent structures.
Material tests indicated the concrete and steel had strengths that were
Fig. 7. The Turgut Ozal Viaduct has two side-by-side steel superstructures the same size as the Ataturk Viaduct. It is on a horizontal curve with a 8,530-feet radius and 3% longitudinal slope.
consistent (or higher) with the values given in the original design plans. For both the Ataturk and Turgut Ozal Viaducts, the friction pendulum bearings (used as the seismic isolation system) had a dynamic friction coefficient of 0.07 and radius of 5 m (16.4 feet). For the Ataturk Viaduct, at some bents and at the abutments, supplemental elastomeric bearings were added, working in the longitudinal bridge direction to control the bridge’s natural period. At both viaducts, to save the shorter columns from high earthquake forces, transverse seismic movement is now allowed by removing shear bracing that would, otherwise, restrain these transverse movements.
Summary
Five of the 14 viaducts on the TAG Highway in Southern Turkey were damaged in the 2023 Mw 7.8 earthquake, which was the strongest earthquake to ever hit Turkey. Each viaduct was designed for a PGA of 0.4 g, which is much smaller than the closest measured PGA to all five of these bridges of 0.607 g. Importantly, all damaged viaducts were very close to the fault rupture line—225 m (738 ft) or closer—while the remaining, undamaged, viaducts on the TAG Highway were further away from the fault that ruptured.
The Ataturk and Turgut Ozal Viaducts are major bridge structures with similar superstructure, column and footing details, and dimensions. They both have impressive reinforced concrete columns of hollow rectangular cross-section, as well as very advanced and innovative original seismic designs and details, that would probably have worked well if the earthquake had been about 50%, or maybe even 75%, of the size that it was. Hence, the seismic retrofit strategy for both of these viaducts was the same, to provide seismic isolation at the top of each column by use of friction pendulum sliding bearings and added viscous dampers. This lengthened the period of the two bridges and reduced the substructure seismic forces so that the columns and footings did not need any work done, since detailed NTHA showed that they remain linear-elastic in this modified design.
Importantly, these two major viaducts on the TAG Highway didn’t collapse and were saved for future use by the ongoing seismic retrofitting, with no closure to vehicles. It is expected that under a future large earthquake of similar size to the 2023 earthquake, these two retrofitted bridge structures would not be damaged. However, it is unlikely that an earthquake of this magnitude would hit these structures again within their remaining service life. ■
Cenan Ozkaya got his B.S., M.S. and Ph.D degrees from the Civil Engineering Department of Middle East Technical University-Turkey. He is working as Technical Manager in the PONTEM Engineering Company.
Robert K. Dowell received his B.S. degree in Civil Engineering from San Diego State Univeristy (SDSU), and his M.S. and Ph.D degrees in Structural Engineering from the University of California at San Diego (UCSD). He is a licensed Civil Engineer (PE) and a Professor of Structural Engineering at SDSU.
Faruk Yildiz got his B.S. degree from the Civil Engineering Department of Yildiz Technical University-Turkey, and is working at the Motorway Division of the General Directorate of State Highways-Turkey.
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Engineering Innovation and Environmental Leadership in Downtown Houston
The Norton Rose Fulbright Tower’s offset core, rotated bays, and forked cantilevered facade were possible through creative structural design solutions.
Rather than view the irregular site geometry as a limitation, the design team leveraged its form to create a cohesive and efficient layout. Key planning strategies included:
An offset concrete shear wall core, strategically placed to maximize views of the park and enhance daylight penetration, resulting in high-value, uninterrupted leasable floor space.
Standardized 60-foot-wide floor plates, providing optimal tenant flexibility and planning efficiency across all office
A segmented, modular facade system with purposefully located vertical notches to follow the site’s curvature without requiring custom
curved glazing.
• A side-mounted, spiral ramp system providing access to below-gra de parking while preserving above-ground functionality and minimizing the required footprint.
• Providing simple stepped massing along the facade to create building setbacks and integrating accessible terrace amenities.
• A basement and foundation configuration coordinated with the adjacent hotel’s foundation including special considerations taken to ensure excavation sequencing and construction would limit differential pressures and maintain existing stability of the hotel.
Basement and Foundation Design
In early design stages, multiple strategies for foundation design were evaluated. The three main frontrunners were as follows:
1. A no basement solution with deep foundations.
2. A single-level basement solution with a stepped mat foundation that aligned with the adjacent hotel foundation.
3. A two-level basement solution with a continuous mat foundation.
Option 1 offered key advantages: Deep foundations would have eliminated the need for complex, sequential excavation and significantly reduced the risk of destabilizing the adjacent hotel. However, the associated cost and schedule implications to drill and install the foundations coupled with the loss of valuable below ground parking levels made this option impractical, leading to its dismissal.
Option 2 presented a different opportunity. Excavation for a single basement level (approximately 17-feet of soil) would reduce the overburden pressure on the soil layer at the base of the proposed mat foundation, enabling the soil to better support the new tower’s loads—a common strategy with mat foundations in Houston. The primary challenge was the complex interface between the existing hotel foundations and the new structure. Careful
Fig. 1. Level 01 Site plan at grade illustrates the constrained footprint for Norton Rose Fulbright Tower. (Photo Credit: Skanska USA Commercial Development, Inc.)
coordination was needed to prevent either building from imposing loads on the other's foundation. This constraint led to deeper-thannecessary foundations in some areas, and ultimately, it was more efficient from a cost and planning point of view to add the second basement level, carrying a deeper foundation design across the entire project. This addition of an extra below-grade parking level without increasing the overall building height above grade benefited project efficiency and enhanced the overall ability to appeal to future tenants of the building.
The final solution featured a mat foundation bearing at 35 feet below street level, matching the bearing elevation of the neighboring hotel’s mat. To mitigate lateral soil pressures and prevent undermining of the adjacent structure during both construction and in the final condition, the mat was designed as three separate segments. This approach enabled a staggered excavation and pour sequence: the soil for the central section was removed and the concrete was placed first while the soil for adjacent sections was left undisturbed. Only when the central section had cured did excavation begin on the adjacent mat sections, allowing the central mat section to prohibit sliding of the existing hotel mat foundation.
In total, approximately 8,200 cubic yards of 6,000 psi concrete were used across all mat pours. The mix design used for the mats limited the maximum cement content to 300 lb/cy and implemented a 55% Class C flyash cement replacement to reduce heat of hydration. Thermocouples were embedded to monitor temperature gradients and ensure temperatures met project mass concrete placement requirements of ACI 301 Specifications for Structural Concrete.
Excavation Retention and Shoring Systems
The retention system selected for the project consisted of permanent,
30-inch-diameter drilled slurry retention piers spaced at 3 feet, 9 inches and extending 45 feet deep, tied back with a single row of anchors (Fig. 2). The closely spaced slurry retention piers, also known as soldier piers, were faced with a 9-inch cast-in-place concrete wall to provide a clean finish for the interior basement levels. In zones where tiebacks were infeasible—specifically adjacent to the existing hotel—larger soldier piers were used and internally braced during the excavation phase.
At one critical grid intersection, a pair of 42-inch-diameter piers extending 100 feet deep served as direct supports for a vertical building column, with the cap beam embedded into the excavation shoring system.
Foundation Settlement Evaluation
Working in collaboration with the geotechnical engineer, the structural team conducted a comprehensive foundation analysis. The mat foundation, ranging from 5 feet to 8 feet thick depending on tributary loading, was evaluated through an iterative soil-structure interaction model in CSI SAFE. Subgrade reaction modulus values ranged from 14 to 60 pci. Predicted settlements were within acceptable thresholds—ranging from ½ inch at the lightly loaded northwest end to a maximum of 4 inches beneath the offset core.
Rotating Bays and Forking Cantilevers
A defining architectural feature of this Houston high-rise was the use of an offset concrete shear wall core—a deliberate deviation from the conventional centrally located core typically favored for structural lateral efficiency and elevator access. Adding further complexity to the project was the tower’s distinctive massing. Its curved and stepped profile is made up of six vertical segments—or “towers”—each offset by 9 degrees and with facade
Fig. 2. As illustrated in this layout of retention system elements, the system consisted of 30-inch-diameter drilled slurry retention piers spaced at 3 feet, 9 inches and extending 45 feet deep, tied back with a single row of anchors.
Fig. 3. This mat pressure coordination document between Walter P Moore and Ulrich Engineers shows maximum soil pressures at the underside of the mat.
Fig. 4. This rendering developed by Walter P Moore shows a forked cantilever solution.
setbacks at different elevations. This geometry not only generates a dynamic skyline presence but also creates elevated terraces that serve as highly desirable outdoor amenities. Nevertheless, the building’s articulated form presented challenges for framing and constructability.
The rotation and stepping of the tower segments required precise beam alignment and load path continuity, particularly through the moment frames and interior girders. To address this, the structural team implemented a 21-inch-deep wide module panformed normal weight concrete framing system with a 4 5/8-inch thick concrete slab, designed to repeat across rotated bays. This approach allowed for the standardization of formwork—a key cost and schedule advantage within the Houston market—while preserving architectural consistency across the varied elevations.
A signature structural element used to create the tower’s unique profile was a “forked” cantilevered, post-tensioned concrete beam. This innovative beam relied on a single continuous back-span to support the desired horizontal layout. Both its analysis and detailing were critical, requiring careful attention to constructability and serviceability.
Walter P Moore developed a standardized detailing approach that clearly established reinforcing steel hierarchy and placement unique to each beam configuration. This clarity streamlined shop drawing review, field
installation, and trade coordination. The layout also allowed for straightforward anchoring and stressing of the post-tensioning tendons—eliminating conflicts with mild reinforcement and contributing to a predictable, efficient construction process.
Lateral Force Resisting System
The implementation of the offset core meant that an eccentricity was introduced intentionally in the lateral force resisting system. To address this, Walter P Moore supplemented the lateral system by using concrete moment frames. The most noteworthy of these were two additional lines of circumferential moment frames wrapping the perimeter that were used to effectively collect and transfer lat eral loads back to the offset core while providing the stiffness and torsional resistance needed for overall stability. This integrated system allowed the structure to align with the building’s unique architectural aspirations without compromising performance.
Given the building’s unusual form and low seismicity require ments, wind behavior was a critical consideration. Initial lateral analyses used ASCE 7-10 code-based Main Wind Force Resisting System (MWFRS) loading and an ultimate wind speed of 139 mph across multiple directions to identify critical load cases. As the design progressed into Design Development, CPP
Fig. 5. Shown is a simplified version of Walter P Moore typical forked cantilever reinforcement hierarchy detail.
Fig. 6. A forked cantilever created a unique facade for the Norton Rose Fulbright Tower. (Photo Credit: Skanska USA Commercial Development, Inc.)
Fig. 7. Wind tunnel testing aided the design team in refining pressure assumptions and reducing uncertainty. (Photo Credit: CPP Wind Engineering Consultants)
Fig. 8. A coordinate system for the base reactions provided by the wind tunnel consultant aided in forming the final lateral design. (Photo Credit: CPP Wind Engineering Consultants)
Wind Engineering Consultants conducted a wind tunnel study to refine pressure assumptions and reduce uncertainty (Fig. 7). Using 36 synchronized pressure tap measurements and local climate data, the team captured wind behavior from all directions. These pressures were converted into equivalent static frame loads using the tower’s dynamic modal properties. The resulting data provided statistically reliable wind loads for both 700-year and 10-year return periods, forming the basis for the final lateral design (Fig. 8-9).
Serviceability and Drift Studies
The building is clad primarily in a glazed curtain wall system supplied by Arrowall Co., requiring strict control of inter-story drift
to prevent damage to the cladding joints and interior partitions. Although inter-story drift limits for wind loading are not explicitly defined by code, industry practice for buildings of this scale typically limits drift to H/400 under 10-year mean recurrence interval (MRI) wind events.
To quantify potential distortion, Walter P Moore modeled null area elements representing the curtain wall within the lateral system and calculated a Drift Measurement Index (DMI) for each panel. This index captured the average in-plane shear distortion across elements. Higher DMI values indicated greater potential for cladding or partition damage.
These values were then compared to Drift Damage Index (DDI) thresholds, defined as the maximum acceptable level of distortion before material
damage occurs—based on racking test data from comparable materials given in “Serviceability Limit States Under Wind Loads” by Lawrence G. Griffis (AISC Q1,1993).
The following serviceability condition was enforced across the facade system:
Drift Measurement Index (DMI) ≤ Drift Damage Index (DDI)
This analytical approach provided a quantitative and materials-based framework for evaluating serviceability limit states under wind loading.
Quantifying Sustainability
Skanska, the project’s developer, has a strong focus on reducing
the carbon footprint of all their projects and has set an ambitious goal of achieving net-zero emissions across their operations and value chain by 2045. Walter P Moore shares this commitment to sustainability by supporting the net-zero goals outlined by SE2050, aligning with the broader industry shift toward low-carbon, climate-resilient design practices.
To benchmark sustainability goals on the project, the design team used the Embodied Carbon in Construction Calculator (“EC3”) tool co-developed by Skanska. EC3 is an opensource platform that allows users to assess embodied carbon in building materials including steel, concrete and architectural finishes. The team used EC3 to evaluate and compare the carbon impact of various concrete mix
Fig. 9. Structure base overturning reactions for 700-year MRI for all wind directions, were provided by the wind tunnel consultant. (Photo Credit: CPP Wind Engineering Consultants)
Fig. 10. An overlay of Autodesk Revit 3D view on an overall building photo highlights where different concrete mix designs were utilized throughout the building height.
1550 on the Green
options, with the goal of reducing embodied carbon emissions by 20% from a benchmark building.
From the outset, the Walter P Moore project team adopted a data-driven approach by performing a Whole Building Life Cycle Assessment (WBLCA) during early design phases. This allowed the team to identify major contributors to embodied carbon, especially in the foundation and floor systems, and informed the structural design process. The insights from this assessment were crucial in setting performance targets for low-carbon concrete and achieving compliance with the LEED v4.1 Building Life Cycle Impact Reduction credit.
To support the use of low-carbon concrete, Walter P Moore included specific requirements in the construction documents for each mix, such as maximum cement content and limits on Global Warming Potential (GWP). Strength requirements for foundation and column elements were specified at 90 days rather than the conventional 28 days, allowing for lowercement mixes with higher cement replacement and slower strength gain to be utilized. To
maintain construction pace, Walter P Moore collaborated with the contractor by permitting maturity meter testing on all elevated floor framing, ensuring early strength targets required for post-tensioning operations were met without relying on the higher-cement mixes that are traditionally used. These combined strategies reduced cement content while maintaining structural integrity and meeting the project schedule.
In addition, Walter P Moore required the ready-mix supplier submit Environmental Product Declarations (EPDs) during construction for acceptance by the design team to ensure project goals related to sustainability were achieved. This was the first project in the Houston market with mix-specific EPDs.
As a result of these efforts, Norton Rose Fulbright Tower achieved an approximate 45% reduction in embodied carbon overall compared to standard baselines and achieved LEED Platinum V4 certification. This was made possible not only by the strategic selection of materials but also by requiring environmental criteria in the concrete
specifications—something that structural engineers have growing influence over.
The tower demonstrates that even in markets where EPD infrastructure is still emerging, it’s possible to set meaningful carbon goals, engage with suppliers, and use tools like EC3 to make datainformed decisions. For engineers looking to design more sustainable structures, this project highlights the critical role they play in shaping both environmental outcomes and industry expectations.
Conclusion
The Norton Rose Fulbright Tower stands as a landmark
project in Houston—one that demonstrates the power of integrated design to overcome site constraints, architectural ambition, and environmental imperatives. Through a combination of structural innovation, material transparency, and collaborative execution, the project sets a new standard for what is possible in high-rise office construction. From its offset core and rotated bays to its forked cantilevered facade and low-carbon concrete mixes, every design decision was both intentional and performancedriven. The building not only enriches the urban fabric of downtown Houston but also charts a path forward for sustainable, resilient urban development. ■
Jason Bray, PE, SE, is Principal and Design Manager with Walter P Moore. He has over 20 years of experience in diversified aspects of structural engineering analysis and design. He has been an integral part of the delivery of performing arts venues, office buildings and healthcare projects.
Fernando G. Torrealva, PE, is a Principal and Senior Project Manager with Walter P Moore with 19 years of experience in the design and analysis of high-rise buildings and complex infrastructure projects. He received his Master’s degree from the University of Texas at Austin and is licensed in Texas and California.
Connor Brady, PE, is a Senior Engineer I with Walter P Moore with 9 years of experience and brings structural engineering expertise across various market sectors, including commercial, healthcare, and sports.
Fig. 11. Material GWP reductions from regional baselines for different structural elements.
Elevated Floor
Mat Foundation Columns
Elevated Floor
Slab on Grade Columns
Elevated
Foundation Walls
A Structural Habitat in Seismic Seattle
The Seattle Aquarium’s new Ocean Pavilion proves that virtually any concrete shape can be built when digital tools blend with outside-the-box engineering.
By Hannah (Bonotto) Walters, PE, SE
To meet the complex design requirements of the newest addition to the Seattle Aquarium campus, a twostory, 50,000-square-foot “Ocean Pavilion,” structural engineers at Magnusson Klemencic Associates (MKA) designed a massive concrete marine habitat at the heart of the project that sets new benchmarks for what is possible in concrete design.
An Aquarium Unlike Any Other
The new Reef habitat at Seattle Aquarium’s Ocean Pavilion (SAOP) contains nearly
500,000 gallons of water in a 3D shape optimized for animal welfare. Unlike aquariums with straight walls or smooth curves, the mathematically generated yet free-form geometry dreamed up by LMN Architects and Thinc Design considered the individual hideaway preferences and swimming heights and radii of each species. When it comes to SAOP, form follows function—not the other way around.
The Seattle Aquarium’s addition is more than an exhibit within a building—the marine habitat is the building. Human-occupied floor spaces hang from the main Reef habitat, enveloping it like a wrapper. The building also includes an additional seismically isolated concrete “Archipelago” habitat, various “jewel”
habitats, interactive exhibits, circular seating for educational programming, and the Aquarium staff’s animal care and water quality lab. The structural design utilizes the tank’s walls as the building’s primary lateral-force-resisting system during earthquakes or high-wind events—critical in seismic Seattle—resisting the sloshing force of four million pounds of saltwater inside. In an earthquake, the weight and stiffness of the tank provide safety for the entire building. Seismic design considered the tank’s unique geometry, evaluating potential earthquakes from 12 directions—every 30 degrees of compass headings.
The tank’s walls were extended higher to support the roof, eliminating the need for a separate structural system and avoiding myriad
unsightly columns that would have extended from the floor to the roof, thereby obstructing public access outside and throughout the exhibit space. Saltwater corrodes metal, so prestressed hollow-core concrete planks were used over the habitat where it connects to the roof, instead of conventional metal decking, which would have been costly due to the vast amount of high-performance coating required. Eleven specially shaped roof beams, each 40 inches deep and up to 80 feet long, support the public rooftop park above the tank. MKA customized these beams to shape the public tiered seating, so the beams served double duty, capping the building and eliminating the added structure (and weight) that would have been needed to form the tiered seating.
Inside, the Reef features five viewing windows, including a massive, two-story-tall, 30-footwide window that resists 1.1 million pounds of water pressure and a dramatic, 50-foot cantilever that stretches over SAOP’s south entrance. This cantilever features an 18-foot-diameter oculus viewing window, allowing passersby to look up and see the marine creatures swimming within. More than 2,000 tons of concrete, steel, and saltwater are supported above the heads of pedestrians, allowing the building to occupy a smaller footprint and preserve valuable waterfront public space.
While SAOP was designed to awe visitors, the multi-function scope of the concrete Reef habitat added an order of magnitude to the difficulty of execution.
Above: The concrete “Archipelago” habitat is seismically isolated from the Reef structure, as seen in this central atrium space. (Photo by Lara Swimmer, Esto)
Opposite page: The Ocean Pavilion’s main tank structure doubles as the building’s primary lateral and gravity system, supports the rooftop plaza, and sets new benchmarks in concrete design. (Photo by Adam Hunter, LMN Architects)
Project Team
Design
Structural Engineer
Magnusson Klemencic Associates
Landscape Architect
Field Operations
Civil Engineer
Magnusson Klemencic Associates
Geotechnical Engineer
Shannon & Wilson
MEP Engineer
PAE Consulting Engineers
Contractor
Turner Construction Company
Site and Weight
Seattle’s Central waterfront has long been the bustling center of one of North America’s major ports, home to mills, wharves, piers, docks, and feats of waterfront engineering. SAOP is adjacent to the 48-year-old existing Seattle Aquarium and at the intersection of the new Seattle Waterfront Park to the south, the Olympic Sculpture Park to the north, and the famous Pike Place Market to the east. As the centerpiece of these projects, SAOP makes possible the ADA connection
linking Seattle’s iconic Pike Place Market to the Puget Sound waterfront for the first time in the Market’s history. This connection provides a multi-modal, ADA-accessible public pedestrian pathway as it descends the 110-foot-high bluff to the waterfront, spanning the landscaped SAOP roof and offering breathtaking views of Puget Sound. However, poorly consolidated, earthquake-liquefiable soils pocked by century-old fill materials and buried remnants of old piers and railroad tracks, a high water table, and space limitations due to constraints from other projects on all sides make it the “absolutely wrong location” to build a highly
The Reef habitat supports the entire south and southwest sides of the building, eliminating the need for additional columns.
(Image by Magnusson Klemencic Associates)
Completed in August 2024, SAOP is a striking example of architectural engineering integrated with urban planning and rightfully takes its place alongside Seattle’s list of iconic landmarks. The Ocean Pavilion’s public rooftop and elevator act as the final puzzle piece in the ADA-accessible connection between Pike Place Market and the waterfront.
(Photo by Hero Creative)
settlement-sensitive concrete habitat.
Differential settlement due to poor soil can lead to cracking of the tank and issues with waterproofing. To address this, MKA, alongside Turner Construction, departed from typical, expensive pile foundations, instead opting for 1,000 Deep-Soil-Mixed (DSM) columns that use augers to mix grout with soil to create underground “columns” down to solid bearing layers, improving the stiffness and strength of the existing soil to support the building and meeting all functional and cost requirements. The concrete for the 22- to 28-foot-long underground DSM columns was mixed at a batch plant on site.
MKA collaborated with geotechnical engi neers at Shannon & Wilson to prepare for subsurface debris during the installation of the DSM columns. The excavation uncovered rem nants of docks—even a railroad trestle three or four tracks wide—requiring the relocation of many planned DSM columns to avoid the existing wood piles, which were impenetrable by standard equipment. The DSM installa tion was a collaborative process that quickly mitigated the challenging subgrade condi tions through the strategic relocation of DSM columns. MKA’s tank design met restrictive cri teria for differential foundation movement (less
The dramatic 50-foot cantilevered Reef habitat includes an oculus window poised above visitors’ heads at the aquarium’s entrance—its position above public space means glimpses into the habitat are free and accessible for all.
The main Reef habitat required 355 tons of rebar— more than three times the quantity of rebar per cubic yard of concrete than in the typical core of a high-rise building in Seattle.
Where most habitats have planar and singly curved walls, the Reef also includes doubly curved walls that integrate into the overall shape.
Photo by Lara Swimmer, Esto
Photo by Magnusson Klemencic Associates
Photo by Magnusson Klemencic Associates
than 1/8 inch over 20 feet) due to the liquefiable soils on which the habitat is built and relied on tighter bar spacing requirements to minimize cracking. The reinforcement typically consisted of two bundled #6 bars at 4-1/2-inch spacing each way on each face, with increased clear cover on the water side.
Meanwhile, fitting SAOP’s 50,000 square feet of structure onto a 38,000-square-foot site in the public right-of-way required an optimized design capitalizing on efficiencies. MKA designed the structure to minimize the number of points of support at ground level. The
tank’s role as both the lateral and gravity systems eliminated the need for secondary structures, and a dramatic 50-foot cantilever extends the tank-supported building to open up more site. More than 100 feet of SAOP’s south face is artfully balanced using the weight of the tank.
Form Follows Function
Using LMN’s 3D geometry model, MKA created its structural analytical model to analyze and design the concrete shear walls. At all stages,
the habitat was built from a 3D model—not 2D drawings. Pushing the boundaries of virtual design and construction, the project team’s 3D model was imported into SketchUp to design the custom formwork and create instructions for machining foam inserts into the required shapes.
The main Reef habitat used built-to-curve formwork created by a maker of ship hulls. Typical plywood or other reusable straight panel formwork was impossible for SAOP since the form shape needed to be custom-made for the tank’s unique geometry. Instead, formwork was created using data-controlled 3D milling machines to cut the unique shape.
A Seattle fabricator that makes parts, tools, and molds for airplanes, boats, wind turbines, and ship hulls created foam inserts to produce the shape for the formwork based on the architectural model, sized up to 20 feet by 8 feet, and no two alike. Expanded polystyrene panels made up of large blocks of foam inserts were glued together, secured to the traditional formwork structure, sculpted to shape, and inscribed with easy-to-read piece numbers assigning them to their unique spots, creating the shape for the final geometry of the habitat.
Turner Construction used the same 3D model to establish the amount of concrete required in each portion of the structure, allowing workers to know how much concrete had been placed at any time and ensuring that the formwork pressure was within acceptable limits.
Rebar Remedies
Where most aquarium habitats have planar and singly curved walls, the Reef habitat also includes doubly curved walls that seamlessly integrate into the overall shape, requiring a complex latticework of rebar.
The Reef, functioning as SAOP’s main lateral force-resisting system with constantly varying curvature, required 355 tons of rebar—more than three times the quantity of rebar per cubic yard of concrete than in the typical core of a high-rise building in earthquake-prone Seattle. No two pieces of reinforcement are fabricated
The Ocean Pavilion is shoehorned into a right-of-way with no contractor staging or lay-down space. (Photo by Adam Hunter, LMN Architects)
Every piece of rebar was bent on a prescribed curvature to fit the formwork and hand-threaded—one bar at a time—to create the dense latticework required to strengthen the 41-foot-tall main Reef habitat. (Photo by Magnusson Klemencic Associates)
With the constantly changing geometry, the contractor elected to computer model every single piece of rebar. (Image by Turner Construction Company)
to the same length due to the challenging curvature of the structure. Every piece was bent on a prescribed curvature to fit the formwork and hand-threaded—one bar at a time—to create the dense latticework required to strengthen the 41-foot-tall main Reef habitat. The curving nature of the tank did not allow for rebar cages to be dropped in. Rebar was installed from the dry face and built inward.
Working with the contractor, Turner Construction, smaller diameter, more easily field-bendable bars were bundled and spaced— in lieu of larger diameter bars that could only be shop bent—in order to meet design requirements. Small bars were required for bendability, as spacing would have been too tight for individual bars. MKA’s design also allowed the rebar installation to be tilted in any direction, provided that, in the rebar grid, the vertical bars remained perpendicular to their cross bars, giving Turner the flexibility to orient bars to better suit construction sequencing and preferences. With the constantly changing geometry, the contractor elected to computer model every single piece of rebar.
The tank’s structure, eight layers of rebar deep in some locations, was needed to support the main tank’s hydrostatic, earthquake, wind, and gravity forces. The tank’s unique geometry showcases how complex concrete shapes can be used as structural shear walls in high-seismic zones.
The Pour
A special concrete mix with small aggregate and specialized admixtures was developed to ensure that concrete could be properly consolidated, meet required high strength criteria, and provide some corrosion resistance (resistance to chloride ions). To avoid construction joints that could compromise integrity, 680 cubic yards were placed continuously over 23 hours.
Seismic Separation
The Archipelago habitat is seismically separated from the rest of the building. Due to its central location in the building, MKA’s initial computer analysis showed that the tank’s walls attracted a significant portion of the earthquake force, meaning they needed to be made much thicker—and more unsightly. MKA isolated the Archipelago to restrict the seismic forces of the surrounding floors from being resisted by the Archipelago walls. While this required slide bearing connections at the incoming steel beams, the added complexity at the connections paid dividends in achieving the architect’s vision. To
Expanded polystyrene panels made up of large blocks of foam inserts were glued together, secured to the traditional formwork structure, sculpted to shape, and inscribed with easy-to-read piece numbers assigning them to their unique spots, creating the shape for the final geometry of the habitat. (Image by Turner Construction Company)
achieve the curved shape, the contractor elected to shotcrete the 14-inch-thick walls.
Raising the (Concrete) Bar
In 2019, the elevated, double-deck Alaskan Way Viaduct was demolished. Today, 20 acres of new public space and a new multi-modal, ADAaccessible pedestrian pathway on the Ocean Pavilion’s roof enable easy movement between Pike Place Market, the new Overlook Walk, and the new waterfront park—complete with ramps and a public elevator—for the first time.
Conquering immense sequencing/phasing challenges, SAOP celebrated its grand opening in August 2024 as a masterful accompanying puzzle piece in the city’s complex urban planning efforts, successfully completing Seattle’s
waterfront redevelopment vision. The innovative tank structure that made SAOP possible does more than anchor a waterfront redevelopment plan decades in the making—it redefines the future of aquariums and concrete design for generations to come.
Seattle Aquarium’s Ocean Pavilion proves that virtually any concrete shape can be built using digital tools and collaborating with capable contractors and that complex concrete geometry can be used to build structural concrete shear walls in high-seismic locations. These special concrete shear walls set new benchmarks for what’s possible in concrete design. ■
Hannah (Bonotto) Walters, PE, SE, is a Senior Associate at Magnusson Klemencic Associates.
The Ocean Pavilion is seamlessly integrated into Seattle’s waterfront redevelopment effort, designed and constructed concurrently with two adjacent/adjoining projects, including Seattle’s new Overlook Walk. (Photo by Hero Creative)
Rebuilding After the Fire: What You Need to Know, and What No One Tells You
Successful disaster recovery requires planning, collaboration, and communication.
By Nick Stuart, SE and Eric Kreager, SE
When a wildfire disaster strikes, it doesn't just destroy homes; it upends lives and changes your future. For those facing recovery, rebuilding can feel like stepping into a second storm, but this one is full of building code restrictions, tough decisions, and financial hardships. Whether you’re a homeowner, a contractor, or a community official, there’s one truth we all need to embrace: recovery is a marathon, not a sprint.
This article will review critical phases of recovery after a major fire, based on lessons learned in Sonoma and Napa County from 20172020. These experiences need to be shared, as knowledge backed by experience makes all the difference. As an example, the initial phases of recovery for the Sonoma and Napa County fires involved case-studies
and hands-on experience from previous fire disasters such as the 1991 Oakland Hills fire and 2005 fires in San Diego County.
Insurance: Not All Policies Are Created Equal—The Good, The Bad, and The Ugly
In the wake of disaster, the first thing most people turn to is their insurance policies. And while some policies seem “good,” pay quickly and without issue, many homeowners are shocked when policies turn “bad” and further payments related to the rebuild are reduced or outright denied. Then to rub salt on an open wound, they later become “ugly” and are not renewed after project completion. We have even
This Pacific Palisades neighborhood was left in ruins by the January 2025 wildfires.
witnessed some insurance companies “dig in their heels” and stall on approving payments, often leaving people in limbo for months or years.
The lesson? Insurance companies are doing business under increas ingly intense scrutiny and need to minimize disbursements on a given claim. Your persistence, documentation, and outside professional help are your best allies. Attorneys, contractors well-versed in insurance work, or other experts in the realm of insurance are often necessary to navigate this process in order to fund your rebuild project.
Debris Removal and the Pitfalls of Over-excavation
After the flames are out, the land itself becomes a challenge. The Federal Emergency Management Agency (FEMA) and the California Office of Emergency Services (CalOES) offers a debris removal pro gram that may seem like a no-brainer, but it’s not always the best fit for everyone or every lot. Private clean-up options can sometimes be faster or more tailored, but they also come with their own risks and potentially higher costs.
One of the biggest concerns with debris removal is over-excavation. Removing too much soil changes the natural site topography that later must be addressed using taller retaining walls or deeper foot ings that must be established into native soil. New footings are not usually established into fill brought in after debris removal. At times, FEMA and CalOES brought in clean fill to address over-excavated sites where complaints were heard. However, the backfill was not documented by the Geotechnical Engineer hired by the Owner in
Widespread destruction in Santa Rosa during the 2017 wildfires made a severe impact on homes and structures.
The Stonefield neighborhood in Santa Rosa’s Fountaingrove area is a higher-density neighborhood rebuilt after 10 units were destroyed during the 2017 Tubbs Fire.
most cases and therefore was not as useful to rebuild upon, since it was essentially undocumented fill. In this scenario, footings were still required to extend through the fill into the native soil. All this increases both foundation rebuild cost and site design costs that can delay rebuilding even further.
Existing foundations should be reviewed by a contractor, and a geotechnical or structural engineer. Some foundations are salvageable, even if they appear scorched, and some can be left in place unused without compromising the rebuild project. Existing foundations can provide slope stability to the exposed former building site in the months prior to the start of construction—in many ways that is what they were originally intended to do.
Rebuilding from Archives
People don’t just lose homes and personal belongings in fires; they lose their records and building plans. Contact your local building departments, architects, structural engineers, and even your neighbors. They all can become crucial resources in piecing together lost building documents. A saved PDF or a scanned plan set could be priceless, and you never know what could be valuable for the re-building efforts.
Governments Need to Show Up-Fast
From local building departments to FEMA and CalOES, government entities play an important role in recovery. Progress happens when temporary permitting offices are set up close to impacted areas, are supported by FEMA funding, and staffed by individuals who understand and are dedicated to the urgency of recovery.
If you are a public official: get proactive. People need answers, and they need them fast. If you are a homeowner, be your own advocate and demand transparency and support, you deserve it.
The Human Toll: Grief, Loss, and Urgency
Homeowners recovering from the disaster are grieving survivors. They have suffered a huge loss and can be confused as to how to move forward. Nobody is excited or wants to go through this process. Often homeowners feel pressure to rebuild as quickly as possible or be left
Wildfire heat compromised the original structural integrity of the steel and burned away wood decking of a vehicular bridge in Sonoma County.
Rebuilding on an Existing Foundation
behind by all the other families that need to rebuild. But labor and resources are limited for everyone to rebuild at the same time. Speed isn’t always the right choice, and recovery can come in waves. It’s okay to wait, gather strength, and proceed with a proper and wellconceived plan. Not everyone will (or should) rebuild immediately. Even still, those who have homes that remain standing amongst the damage suffer a different kind of grief—the loss of neighborhoods, neighbors, property value, and other intangible elements of a neighborhood and region. Many may choose to sell their properties that
are undamaged or partially damaged in a fire zone as real disruption will occur for the coming years. Polluted air for weeks and smoke damage lingers in existing homes and can be hazardous to continue living in the area. Even those who complete a rebuild in a given fire zone quickly have similar issues, or suffer psychological issues for years to come, and even have trouble sleeping in the rebuilt house on windy nights, leading to the sale of their newly rebuilt home. All these issues are items to consider before embarking upon a rebuild project as the original homeowner.
Post-fire, October 2017
Post-demo, early 2018
Retrofit, early 2018
Tie Dowels, early 2018
Pool, April 2018
May 2018
Summer 2018
Infrastructure Before Homes
Even the most eager builder will have issues placing a new concrete slab if the road is gone or the water is toxic. Community recovery must prioritize:
• Power and Communications.
• Road and Bridge Repairs.
• Water Systems (potentially contaminated with Benzene, a PVC byproduct).
• Septic Systems vs. New Leach Lines.
These are invisible barriers that often hold up rebuilding longer than waiting for the design plans from an architect or engineer.
The Realities of Rebuilding
Rebuilding costs generally surge as demand outpaces both available labor as well as materials. From previous experience, labor tends to be in more scarce supply than materials, and even more populated cities see bottlenecks in available labor. Value those willing to help.
Expect these areas to be greatly affected during rebuilding:
• Labor (qualified tradespeople get booked fast).
• Construction Professional Services (the limited number of architects and structural engineers will quickly be overwhelmed).
• Materials (concrete, steel, and even basic lumber).
Despite an increased interest in fire safe alternatives like steel or concrete construction, most people still rebuild using wood framing. It is a matter of economics and affordability. The most important thing you can do is rebuild using the latest fire-resistant standards and choose design professionals that have this knowledge.
Choosing the Right Team
Whether you are a builder or a homeowner, your success depends on your team.
• Homeowners: Ask for references from your design professionals and contractors.
• Builders: Work with experienced design professionals.
• Architects/Designers: You are essential to the entire process and are advocates for all your clients that lost their home or building to a fire. Architects provide professional advice on building to Wildland-Urban Interface (WUI) standards and lead teams in rebuilding entire neighborhoods.
Originally, subdivision-style neighborhoods may have a common theme or set of design guidelines set forth by the original developer and the City, but when these types of neighborhoods are destroyed in a wildfire scenario, during recovery each individual owner tends not to be subjected to the same types of design restrictions that were put on the original developer. After a few years of rebuilding, these new independent designs occurring all at once can lead to neighborhoods that appear mis-matched or out of character with the neighborhood, if proper architectural design is not considered.
Geotechnical Review Considerations
The ground is just not the same after the fire. The soil is contaminated, and debris needs to be removed. Heat and erosion change soil content and structure. Every site should be re-evaluated, and a geotechnical report should be considered. In addition, verify that
the Geotechnical Engineer can be available for construction support during initial phases of foundation construction.
Terrain Trouble
In rugged areas, terrain becomes a critical variable. Fires often expose poor planning, homes built on unstable slopes, footings that are shallow without confinement, or building sites without proper drainage or driveway access.
Post-fire, expect:
• Winter mudslides.
• Steep site challenges.
• Retaining wall failures.
• Roadway slip outs and burned-out access bridges. Get creative with site stabilization and new building pad construction, which are the keys to a successful rebuild. A grading plan prepared by a Civil Engineer is often a necessary step to a successful foundation design that can be implemented directly by a contractor. Do not shy away from the site design. A stable site and proper foundation are critical building blocks for your rebuild.
Recovery Takes a Team and Time
As recovery accelerates, referrals become lifelines. Builders, architects, engineers and consultants should develop a network. Referrals help everyone and are not just good business, it’s community support in action. Disaster recovery reshapes communities, not just in how they look, but in how they function and can bring a community closer together. For a few years after the event, construction may pivot almost entirely toward rebuilds. In the end, the folks who recover best are those who plan, collaborate, and communicate. Resilience isn’t just a buzzword, it’s a way of working, living, rebuilding, and eventually, recovering as best as we all can. ■
Eric Kreager, SE, Senior Principal and Owner of MKM & Associates Structural Engineering, brings deep expertise in Bay Area building codes, advanced structural engineering, and the complex challenges of wildfire recovery. His hands-on experience in post-disaster rebuilding has made him a trusted leader in restoring resilient communities.
Nick Stuart, SE, Engineering Project Manager at MKM & Associates Structural Engineering, oversees high-end residential and public works projects, guiding both engineering execution and business strategy. His leadership ensures precision, innovation, and lasting quality in every project the firm undertakes.
One of 43 newly rebuilt homes in Santa Rosa’s Berry Brook neighborhood, where no original structures survived the wildfire’s devastation.
Barriers to Design Optimization: Concrete in the Built Environment
Key insights from an American Cement Association workshop highlight both challenges and pathways for concrete design, construction, and reuse.
By Aubrey Smading
Concrete remains a resilient and dependable building material; however, the production and manufacturing of this material is one of the largest contributors to CO2 emissions in the built environment. The American Cement Association (ACA, formerly the Portland Cement Association) published its Roadmap to Carbon Neutrality in 2021, with the goal of carbon neutrality for the cement and concrete industry by 2050 (available for download at www.cement.org). While reductions at the cement plant are underway, further opportunities for carbon reduction exist across the value chain, including optimized structural design to reduce the material use. By intentionally minimizing the volume of concrete used in a project’s design, significant carbon reductions are possible and have been achieved at the project level.
Despite growing momentum, the construction industry is slow to adopt change. The ACA hosted a workshop in June 2025, bringing together structural engineers, architects, general contractors, concrete contractors, and academics. The event featured a series of presentations showcasing the state of the art of optimized design, cutting-edge research, and case studies, followed by collaborative discussions on barriers to implementing structural optimization, and identification of a path forward.
Research and Innovation: Insights from the Workshop
Shape and Structural Optimization
Presented by Caitlin Mueller, MIT Professor Caitlin Mueller emphasized that “shape matters” when designing with concrete. At MIT’s Digital Structures research group, Mueller’s team combines code-based analytical equations with numerical optimization to generate efficient designs that can be built today. For example, her research demonstrates that ribbed slab geometries— optimized using analytical equations and numerical modeling—can reduce material mass, cost, and carbon by 60–80% compared to flat slabs. Recent research suggests that structural optimization can bring reinforced concrete buildings to minimal embodied carbon levels as compared to other structural systems.
Mueller’s team has also developed automated tools to simulate concrete behavior and evaluate designs in real time. Their Beam Shape Explorer, an open-source tool, integrates with design tools such as Rhino and Grasshopper, allowing designers to evaluate constraints like ductility, deflection, and geometric form concurrently during early-stage design.
One standout case study featured the Pixelframe system—a reusable, reconfigurable precast concrete system that maintains structural performance across multiple building lifecycles. The system’s first-life carbon efficiency outperforms typical construction, and through reuse, total carbon can be reduced by more than half.
Voided Post-Tensioned Slabs and Systems-Level Analysis
Presented by Jonathan Broyles (MIT) and Michael Hopper (LERA) Broyles and Hopper presented the embodied carbon performance of post-tensioned voided slabs: flat soffit systems that combine prestressing with internal void formers. These systems achieved 50–60% reductions in concrete volume relative to conventional slabs.
The team advocated for expanding the concept of optimization to incorporate fire rating, acoustic insulation, and structural performance. Their research found that while ribbed systems appear most efficient structurally, voided flat slabs often outperform ribbed systems when considering a holistic analysis—evaluating the trade-offs across multiple building performance goals.
A case study highlighted how an optimized reinforced concrete design was abandoned before the construction phase due to concerns about cost, perceptions of risk, and project politics—underscoring the disconnect between capability and real-world adoption.
The Pixelframe system utilized precast concrete optimized for reuse. (Photo courtesy Caitlin Mueller)
Extending Service Life Through Preservation
Presented by David Whitmore, P+Ex / Vector Corrosion Technologies Representing the Center of Excellence for Preservation and Service Life Extension (P+Ex), David Whitmore presented a compelling case from Toronto’s Gardiner Expressway, where maintaining over 70,000 cubic yards of concrete avoided 35,000 tons of CO₂ emissions.
P+Ex called for a cultural shift toward valuing repair, preservation, and reuse alongside durability in new construction. Their strategic goals include developing tools and guidelines to embed service-life extension into routine design practice, enabling circularity by keeping structures in use longer.
Contractor Insights on Slab Optimization
Presented by Rian Meyers and Tom Vance, Lithko Contracting
Lithko Contracting shared a contractor’s perspective, highlighting the value of early collaboration among the project team. In the case study presented, Lithko worked with all project stakeholders to develop a slab design that saved 7,400 cubic yards of concrete and 15,000 labor hours in rebar installation—all while meeting the stringent requirements of the owner for a perishable goods distribution center.
The team credited their success to proactive design-assist services, optimized concrete mixtures, and strategic preconstruction coordination. They emphasized that practical optimization often depends more on project communication than on technical capability.
Industry-Wide Frameworks and Policy Levers
Presented by Scott Shell, ClimateWorks
Scott Shell connected design-level decisions with systemic policy trends. He highlighted three high-impact levers:
1. Procurement policies that reward low-carbon design.
2. Development of net-zero-ready cement and concrete products.
3. Codification of efficient design through updates to building standards.
Shell’s framing emphasized the need for clear performance targets and trust-based collaboration across disciplines. He noted that structural overdesign often stems from institutional risk aversion rather than technical necessity.
Emerging Tools and Perception Barriers
Presented by Josephine Carstensen, MIT
Professor Carstensen highlighted how topology optimization can reduce material use while maintaining structural performance. For example, her team evaluated a topology optimized beam design that used 25% less concrete while maintaining elastic performance that was validated through structural testing.
Yet barriers remain. A survey of practicing structural engineers revealed limited familiarity with computational design tools and a widespread perception that architects or cost concerns control key decisions. Even when aware of embodied carbon, many engineers cited lack of tools, budget, or insufficient influence as reasons why optimization strategies are not implemented in practice.
Workshop Outcomes: Perspectives from Practice
Following the presentations, participants engaged in discussion groups focused on four core topics:
1. Slab and Member Shape Optimization
Participants discussed a range of strategies—from one-way pan systems to machine-learning-based parametric models, participants shared a diverse array of design strategies. Key enablers included:
• Structural demand-based shape and topology optimization.
• Post-tensioning, prestressing, and voided slabs systems.
• Innovative forming methods, such as 3D-printed and fabric molds.
• Grid and span coordination with programmatic layouts.
• Parametric design tools for evaluating cost, carbon, and constructability.
The consensus was that optimization must be initiated early and be cross-disciplinary. Many cited missed opportunities when decisions were made before mechanical layouts or budgets were defined. A clear call was made for the development of design guides and published case studies to aid the industry in mainstreaming these practices.
2. Deconstruction and Reuse
Reusing concrete structures or components is feasible, but still a rare practice in many areas of the United States. Participants identified several critical shifts for scaling reuse:
• Design for disassembly, including reversible connections and service-life planning.
Workshop participants Eric Giannini and Anne Ellis discuss slab design optimization.
This optimized slab design resulted in a 35% embodied carbon savings for the project. (Photo courtesy of LERA)
• Policy incentives, such as landfill penalties or reuse incentives.
• Case studies and guidelines of best practices.
• Digital inventories or “material passports” to track components.
• Public and private investment in modular systems and circular economies.
Many participants noted the current use of recycled concrete as aggregate or base, while there is a clear desire to move beyond the current practice and begin reuse of whole concrete elements. Cultural perceptions also play a role. Attendees noted the need to “make reuse desirable” through storytelling, showcasing durability, or emphasizing heritage.
3. Derisking Innovation
Concrete optimization often stalls not because ideas lack merit, but because they feel risky. Participants outlined ways to derisk:
• Pilot projects, mockups, and demonstration sites to test innovations.
• Grant funding or cost-sharing to offset early-stage costs.
• Performance-based specifications that accommodate new approaches.
• Early involvement of code officials and inspectors.
• Centralized databases for test data, construction lessons, and performance history.
Trust and transparency were recurring themes. Early and honest communication about proven—but unfamiliar—methods can help owners and teams move toward accepting novel solutions.
4. Stakeholder Communication
Across all topics, communication emerged as a central success factor. Key recommendations included:
Automated RC Column Design & Schedule
• Integrated kickoff meetings during schematic design.
• Templates for charrettes, decision logs, and meeting minutes.
• Contracts that incentivize collective problem-solving at all phases of a project.
• Shared language and guidelines to align teams across sectors.
Participants emphasized the need to educate owners, who often default to conventional systems out of caution. Providing clear carbon and cost tradeoffs can unlock flexibility.
Conclusion: From Ideas to Action
The ACA Workshop revealed a clear consensus: the tools and strategies to optimize concrete design already exist—and have been proven at scale. Research has shown that shape optimization, service-life extension, and smarter structural systems can dramatically reduce concrete’s carbon footprint, often with cost savings.
Now, we look to widespread adoption. To bring them into everyday practice, the industry must bridge gaps in education, incentive alignment, and cross-disciplinary engagement. By aligning policies, practices, and project teams around shared goals, the concrete industry can help lead the transformation to a more sustainable built environment.
Aubrey Smading, PE, is the Director of Concrete Design and Technology at the American Cement Association and works to advance ACA’s Roadmap to Carbon Neutrality. Aubrey leverages her experience as a structural design and forensics engineer to support decarbonization of the industry’s value chain.
historic STRUCTURES
Muscatine, Iowa Bridge 1891
19th
Century Mississippi River Bridges
By Dr. Frank Griggs, Dist. M. ASCE
Muscatine, Iowa, is located approximately 30 miles down-river from Davenport and 50 miles upstream from Burlington, the sites of two earlier bridges across the Mississippi. Pressure for a bridge at Muscatine started as early as 1872, but a bill in Congress to permit a bridge was not passed until July 16, 1888, as “CHAP. 628.-An act to authorize the construction of a railroad, wagon, and foot passenger bridge across the Mississippi River at or near Muscatine, Iowa.” Section 2 stated in part,
That any bridge built under the provisions of this act may, at the option of the company building the same, be built as a drawbridge or with unbroken and continuous spans: Provided, That if the said bridge shall be made with unbroken and continuous spans, it shall have one or more channel spans, each having not less than three hundred and fifty feet clear channel-way, and not less than fifty-five feet clear head-room above high-water mark, and the clear head-room under other than channel-spans may be less than fifty five feet…
The clearance widths and heights are once again, for no apparent reasons, different than earlier laws governing these factors in the past. The bill allowed a bridge for railroads, carriages, pedestrians, etc. A Private Company the Muscatine Bridge Company, composed of resident merchants and businessmen, was formed to build a bridge to provide wagon traffic across the river to the rich agricultural region in Illinois. It chose a high-level bridge over a low-level swing bridge with the possibility of in the future adding a low-level bridge for railroad traffic with a swing span. It would be financed by stock issues and bonds. Failing in raising the necessary funds a proposition to assist in the funding by a 3% tax on residents was proposed and passed by a large margin providing approximately 1/3 of the cost of the bridge. It would be the third bridge across the Mississippi for wagon and carriage traffic and the third at a high level.
The Chief Engineer was George F. Baker. Baker was an Iowa native who attended Cornell University graduating in 1879 and worked on several railroads in the Midwest. He would go on to also design bridges across the Mississippi River at Clinton, Iowa, and Winona, Minnesota. He later became involved in politics serving as Mayor of Davenport and was on an Emergency Railroad Board appointed by President Calvin Coolidge.
The Milwaukee Bridge Company, a well-known regional bridge builder,
received the contract to build the bridge in July 1889 with completion date of July 1890. The plan consisted of, beginning from the Iowa end of bridge, Length of span in feet
Earth embankment. 30 (Iowa End)
Six bents, iron trestle work. 120
Three iron girders 158 (45’, 58’, 55’)
Two 160 feet spans 320
One 361 feet span 361 Anchor Span
One 442 feet span 442 Main Span
One 361 feet span 361 Anchor Span
One 240 feet span 240
Four 160 feet spans 640
Pile trestle work. 260
Earth embankment. 170 (Illinois end)
Total length 3,101
The approach grades were 3.65%. The wooden deck width was only 18 feet which was sufficient for slow moving wagons but narrow for future faster moving automobiles and trucks. In addition, it carried one 4-foot sidewalk on the downstream side.
This was the second time a cantilever bridge was built across the Mississippi. The first was the Fort Snelling Bridge. Several cantilevers had been built in the East including one over the Niagara River by C. C. Schneider and the Poughkeepsie Bridge over the Hudson River that opened in early 1889. The 361-feet anchor spans were longer than on
Three styles of piers can be seen in this view of the Muscatine Bridge looking west towards Illinois.
Here you can see the Muscatine Bridge’s cylinder piles on 160-feet spans with a collapsed span in 1899. Note all three style piers shown.
the typical cantilever, the cantilever arms shorter than usual and the suspended span longer than usual. The total length of the cantilever arms and suspended span was 422 feet, giving a horizontal clearance of greater than the required 350 feet. The rest of the iron trusses were single intersection Pratt trusses with curved upper chord. Originally each foundation for the piers was to be of masonry resting on wood piles and a wooden mat of 12 inches by 12 inches timbers of a sufficient thickness to reach within 1 foot of the low water level. To cut costs, three piers were replaced with iron cylinders, with diameters of 5 feet, 5 feet 6 inches and 6 feet, filled with concrete. The piers above the masonry foundations were a variety of iron bents with one of masonry. The original plan was likely to have them all masonry, but to cut costs, the rest were iron.
Work was started in July 1889 and the bridge opened on May 8, 1891, to a grand celebration. The Muscatine Journal wrote it was, “constructed of the best material and on the latest improved plan. It is one of the
most handsome bridges on the river.” The final cost of the bridge was $149,000 with $52,600 of stock, $60,000 of bonds and the rest by the 3% property tax. The tolls for crossing were 15 cents for each team and 5 cents for each person.
As noted, one span collapsed in 1899 when ice pushed one of the iron cylinders out of plumb and the span slipped off its support. A second failure occurred in 1956 when a vehicle collided with one of the trusses causing a span to collapse. The span was replaced, and the bridge continued service until its successor, the Norbert Beckey Bridge, was opened On December 2, 1972. The only remaining remnant of the old bridge is the masonry pier. ■
Dr. Frank Griggs, Dist.M. ASCE, specializes in the restoration of historic bridges, having restored many 19th Century cast and wrought iron bridges. He is now an Independent Consulting Engineer (fgriggsjr@verizon.net).
This view of the Muscatine, Iowa, bridge shows its cantilever portion.
New renderings revealed as Concourse D at O’Hare International Airport breaks ground
The City of Chicago and Chicago Department of Aviation (CDA) broke ground on Concourse D at O’Hare International Airport. Designed by Skidmore, Owings & Merrill (SOM) in collaboration with Ross Barney Architects, Juan Gabriel Moreno Architects (JGMA), and Arup, the first new building in O’Hare’s transformative ORDNext expansion has been underway since the team was selected in 2019 through an international design competition.
Concourse D marks the first new building in ORDNext, the centerpiece of the airport’s Terminal Area Plan that will construct two new concourses, a new global terminal, and a tunnel connecting the facilities. This $1.3 billion Concourse D represents the first major milestone of the program, reimagining the passenger experience from curbside arrival to aircraft gate. It will be one of the country’s first domestic-international codeshare concourses, built to accommodate a wide range of aircraft types and improve operational flow for passengers landing or laying over in Chicago. New renderings reveal the architectural vision for the concourse’s signature public spaces, offering a first glimpse into their dynamic, passengercentric design.
“Our vision for the new Concourse D considers the entire passenger journey from curb to gate,” said SOM Design Partner Scott Duncan. “From skylit spaces to orchardinspired columns, every element contributes to a bright, easy-to-navigate environment designed to elevate the travel experience and leave a lasting impression of O’Hare.”
At the center of the concourse is a multi-level
space marked by an oculus that directs daylight into the levels below. As the primary arrival point for passengers entering from the Concourse C bridge or a new underground tunnel linking to the upcoming O’Hare Global Terminal, this node serves as a welcoming threshold to the concourse experience, helping orient travelers to their destinations.
The layout is shaped by soft, curved lines inspired by the oxbow bends of Midwestern rivers, defining zones for rest, dining, retail, and play. Landscaped areas further organize the space into distinct amenity zones, using a palette of colors, textures, and plantings drawn from the native beauty of Midwestern landscapes. An airline club lounge positioned on the upper floor offers elevated views of the connecting gates.
The concourse integrates a structural system
that minimizes vertical supports, with branching columns inspired by the orchards that once gave the airport its name. The design improves sightlines and opens up views across the concourse. Tuned to the Midwest climate, the roof’s contours and overhangs help regulate temperature, while the minimized structure reduces embodied carbon.
At the southern terminus of the concourse, a bright, open area framed by a double-height glazed wall offers expansive views across the airfield and toward the distant Chicago skyline. Conceived as a calm, light-filled retreat, the space is flanked by six gate lounges and includes two concession zones—one at its center and another at the far end—giving passengers options to unwind, socialize, or focus before boarding. Among large, planted areas, varied seating with integrated charging stations provides a range of settings: larger benches accommodate groups, café-style tables invite travelers to enjoy coffee or a quick meal, and raised seating with counters offering a comfortable workspace.
Concourse D is being delivered through a close partnership between the SOM-led design team, the City of Chicago, and the construction manager at risk, AECOM Hunt Clayco Bowa, appointed in 2024. That collaboration has kept the project on schedule and within budget, with completion expected in late 2028. Planning work is also underway for Concourse E, the second satellite facility designed by the same team. ■
Photo courtesy City of Chicago
APA Research Center offers industry-leading testing capabilities
Built in 1969, APA–The Engineered Wood Association’s 42,000-square-foot facility—has long been recognized as one of North America’s top engineered wood research centers. In 2019, the Association made significant upgrades to the research and testing capabilities at its Tacoma, Washington, laboratory.
The upgrades ensure that it maintains that reputation while continuing to serve the industry as a leader in supporting the innovative design, development and end-use of code-compliant, energy-efficient structures built with engineered wood, mass timber and wood structural panels.
The lab expansion was built as an engineered wood showcase, with laminated veneer lumber purlins and studs, and glulam columns supporting a roof framed with long-span curved glulam beams. The glulam columns are also designed as dual function to support crane rails. The wall and roof diaphragm are sheathed with wood structural panels, while OSB lap siding makes up the exterior cladding.
The significant lab enhancements provide numerous benefits for the engineered wood industry, according to Eric Gu, vice president of APA’s Technical Services Division.
“The expansion of APA’s Tacoma laboratory represents a transformative moment for the Association and the engineered wood industry as a whole,” Gu said. “With cutting-edge capabilities for full-scale structural testing and performance evaluation, we are empowering
innovation in timber product development and design. These upgrades underscore APA’s leadership in advancing resilient, sustainable building systems that meet the demands of modern codes and construction practices.”
Extensive Renovations
As part of the renovations, a section of the laboratory’s existing ceiling was raised from 24 feet to 40 feet in height. The near doubling in height enables APA staff to leverage the strong wall to test taller specimens and vertical assemblies.
“This update allows for full-size structure testing,” Gu said. “It provides a state-of-the-art research facility that supports structural testing from small-scale all the way to whole-house
testing.” Results of these tests provide insight for APA staff to understand the performance of engineered wood products at the element, assembly and system levels.
The laboratory has a 4-foot-thick reinforced strong floor, which provides a precision-level surface for reaction support and instrumentation mounting. The floor is reinforced with 28 tons of rebar. It’s made of 830 tons of concrete with 868 anchors at 2 feet on center. Each anchor has a 100,000-pound-force capacity, which means staff can coordinate tests simultaneously if needed.
“The strong floor is 70 by 75, for a total of 5,250 square feet. The large format of the strong floor, coupled with dual overhead cranes, improves our lab testing efficiency,” Gu said.
“And we have the versatility of coordinating multiple tests at the same time in the same area—thanks to its large size,” he added.
APA’s lab also has 10 strong wall blocks with anchors. Gu said that was another improvement made possible by the near doubling of the ceiling height to almost 40 feet.
The lab is equipped with two 5-ton overhead cranes. These cranes make moving, lifting and maneuvering test objects much safer and more efficient, facilitating full-scale structural assembly testing.
The lab’s hydraulic actuator was upgraded from 55,000 pound-force to 220,000 poundforce. Gu said it’s another way APA expanded its testing capability for the industry.
One aspect of the lab that hasn’t changed: It’s staff comprised of highly educated engineered wood experts. Among the APA lab employees are PEs, doctorates in timber engineering, master’s in wood science and Ph.Ds in civil engineering. Their collective knowledge brings tremendous value to Association members and the greater engineered wood products industry. ■
Photo courtesy
City of Chicago
IN BRIEF
Walter
P Moore grows Southwest footprint
Walter P Moore has expanded into Phoenix, Arizona, enhancing its ability to deliver innovative engineering solutions in one of the nation’s fastest-growing regions.
Bryan Salt joins the firm as Managing Director for the Structures Group in Phoenix. He brings over 30 years of experience delivering complex projects across sectors including healthcare, life sciences, advanced manufacturing, education, government, sports, and aviation. The Phoenix office also welcomes Christopher Pfeiff as Practice Area Director for Construction Services. Pfeiff brings 25 years of experience delivering innovative construction solutions to complex projects as an executive in the construction industry. .
NRMCA publishes report on fire testing study for exterior walls constructed of ICFs
The National Ready Mixed Concrete Association (NRMCA) and the Insulating Concrete Forms Manufacturers Association (ICFMA) have published a June 2025 report, Investigating ICF Wall Construction Meeting the Requirements of NFPA 285, that determines National Fire Protection Association (NFPA) 285 compliance for exterior walls constructed of Insulated Concrete Forms (ICFs).
The report is authored by Arthur J. Parker, PE and Daniel A. Martin, PE, CFEI, CVFI of Jensen Hughes. NFPA 285 is a consensus-developed fire test standard developed by NFPA that is referenced in building codes to evaluate the surface burning characteristics of exterior wall assemblies containing combustible materials such as water-resistive barrier materials, foam plastic insulations and combustible cladding materials.
With support from NEx (An ACI Center of Excellence for Nonmetallic Materials), the American Concrete Institute (ACI) Foundation and the Concrete Advancement Foundation, the project included fire testing of ICF walls within various exterior wall constructions to determine wall assemblies which meet the performance criteria of NFPA 285 and the development of window opening construction details. Following the fire testing, an engineering analysis was conducted to demonstrate other ICF wall assemblies with similar but different components, including a broad range of claddings that can be recognized as meeting the performance requirements of NFPA 285.
The report is available for download from NRMCA’s website at https://www.nrmca.org/association-resources/ codes-and-standards/.
Case Engineering expands structural team with four new hires
Case Engineering has expanded its Structural team to include recent new hires Adam Griffin and Nate Massey as
Structural Engineers and Brennan Wille and John Sommer as Structural Designers.
Griffin recently graduated from Missouri University of Science and Technology in Rolla with Bachelors of Science in Civil Engineering and Architectural Engineering. His experience includes a four-month Civil Structural Engineering Internship at CDS Engineering Company in Fenton, MO. He has passed the Fundamentals of Engineering Exam and is a licensed Engineering Intern.
Massey has six years of engineering experience as a Structural Design Engineer for BrandSafway. He has a Bachelor of Science in Civil Engineering from the University of Missouri-Columbia and a Bachelor of Science in Economics & Finance from Southern Illinois University Edwardsville. Outside of work, he volunteers as a House Captain with Rebuilding Together.
Wille is a cross-discipline designer with experience in architecture, interior design, visual merchandising, and photo/ video. His prior experience includes Visual Merchandising Specialist at IKEA in St. Louis, and architectural internships at Pennsylvania-based Gannett Fleming and Chris Dawson Architect, and Helen & Hard in Oslo, Norway. He has a Bachelor of Arts in Architecture from Washington University in St. Louis and studied architecture abroad at the Santa Reparata International School of Art in Florence, Italy.
Prior to college, Sommer worked in both residential and commercial construction. He graduated from State Technical College of Missouri with an Associate of Applied Science Degree in Drafting Design Technology. He has nine years of experience as a Structural Steel Joist and Deck Detailer at Canam Steel Corporation.
AISC Education Foundation awards $235,000 in scholarships
The AISC Education Foundation is helping 58 students across the U.S. make their higher education dreams a reality, funding $235,000 in scholarships for the 2025-2026 academic year. These scholarships support juniors, seniors, and master’slevel students in civil engineering, architectural engineering, construction engineering, materials/metallurgical engineering, construction management, and architecture programs in the U.S.
“Thanks to the generosity of the industry and the AEC community, we were able to distribute roughly $35,000 more than last year--and we’re providing support for three more students,” said AISC Director of Foundation Programs Maria Mnookin. “But these students are more than numbers, and the impact of our donors goes far beyond dollar signs. This generation will make a difference in the world, and it’s always an honor to help them get started.”
Visit aisc.org/giving to learn more about the Foundation and how to help support students and educators.■
New report reveals valuable building safety industry insights
The International Code Council released the State of the Building Safety Industry Report: Envisioning the Future, summarizing responses from a diverse range of building safety professionals across different generations, trade specialties, geographic locations, and income levels. It covers compensation, work environment, career satisfaction, workplace challenges, future opportunities, and more.
Respondents rated the value of continuing education assistance, flexible work schedules, work-life balance, benefits, and time off. Answers provided averages that will help employers and individuals benchmark themselves against others in the industry.
“This new report gives us an in-depth understanding of what lies ahead for the industry, especially since 56 percent of
respondents plan to retire in the next ten years,” said Code Council Board of Directors President David Spencer, CBO. “Among other benefits, our members gain critical insight into the most pressing challenges shaping the building safety industry including the increased cost of materials and complexity of modern construction.” The report is available now to ICC members. ■
New committee report for transmission lines released
Deep Foundations Institute (DFI) and the Electric Power Systems Foundations Committee have released a new committee report, Design and Construction of Deep Foundations to Support Electric System Transmission Lines State of the Practice. This state-of-practice report gathers into a single document the diverse deep foundation investigation, design, and construction practices the power industry uses in North America, according to Peter Kandaris, P.E., Gannett Fleming (retired) and co-chair of
DFI’s Electric Power Systems Foundations Committee. “The committee brought together experts with a deep level of experience to create a shared repository of good practices. The report establishes the need for consistent and uniform foundation design and construction practice across a wide variety of subsurface conditions, geographic locals and climates, presenting the basis for future guideline documents, practices manuals and codes.”
One of the primary reasons the committee started working on the document was the
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inconsistent and disjointed approaches to designing and constructing foundations for electric systems transmission lines, explains Matthew Glisson, P.E., DFI director of technical activities. “They recognized that the first step in developing a consistent practice was to document the current state of the practice. I am thrilled for the committee members to reach this milestone and look forward to continuing to work with them on the next steps in developing consistent practice across this industry.”
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SEI Update
The Results Are In: Welcome the 2025-2026 SEI Board of Governors
As we approach the start of another fiscal year, SEI is proud to introduce the 2025-2026 SEI Board of Governors. Their leadership is key as we build on our strong foundation and continue to enhance SEI’s effectiveness in a rapidly evolving industry. With their expertise, we are prepared to tackle new challenges and seize emerging opportunities. We extend our sincerest thanks to all members who participated in the recent SEI Board Election. Your votes have elected Chad Schrand, PE, F.SEI, M. ASCE as SEI President-Elect, John Duntemann P.E., S.E., F.SEI, M.ASCE as SEI At-Large Governor, and Ishwarya Srikanth, Ph.D, PE, M.ASCE as SEI Young Professional Governor. Please join us in warmly welcoming our newly elected Board members as we work together to shape a dynamic and impactful future. Our appreciation for their service and leadership to Board members who finish their terms September 30:
• Jerome F. Hajjar, Ph.D, PE, F.SEI, F.ASCE, SEI Past President.
• Elaina J. Sutley, Ph.D, PE, M.ASCE.
• James P. Wacker, PE, M.ASCE.
Save the Date for SEI’s 30th Anniversary at Structures Congress
SEI is turning 30—and the celebration is set to take center stage at Structures Congress 2026 in Boston. This year’s Congress will be a milestone moment, packed with forward-thinking sessions, high-impact keynotes, and immersive experiences like the SE 2050 Summit and behind-the-scenes technical tours. Special anniversary events and social gatherings will honor SEI’s journey while sparking new connections and ideas for the future.
Three decades in, SEI is still leading the way. Join the celebration in Boston and be part of what’s next. Learn more: structurescongress.org.
Edwin T. Huston, PE, SE, F.SEI, M.ASCE SEI President
Chad M. Schrand, PE, F.SEI, M.ASCE SEI President-elect
Stephanie L. Slocum, PE, M.ASCE SEI Past President
Hamid R. Adib, Ph.D, PE, F.SEI, F.ASCE SEI Treasurer
Jennifer L. Goupil, PE, F.SEI, F.ASCE SEI Secretary
Michael J. Bolduc, PE, SE, M.ASCE
John Duntemann PE, SE, F.SEI, M.ASCE
Maria M. Garlock, Ph.D, PE, F.SEI, M.ASCE
Robin A. Kemper, PE, LEED AP, ENV SP, F.SEI, Pres.19.ASCE
Kenneth L. Sharpless, PE, F.SEI, F.ASCE
Ishwarya Srikanth, Ph.D, PE, M.ASCE
Shuxian (Susanne) Wassenius, PE, F.SEI, M.ASCE
Jennifer Zabik, PE, F.SEI, M.ASCE
Call for Applications: SEI Fellow Recognition
If you’ve made a meaningful impact on structural engineering, this is your opportunity to be recognized at the highest level. SEI is now accepting applications for advancement to SEI Fellow. SEI Fellows are celebrated for their leadership, mentorship, and enduring contributions to structural engineering through service, practice, and engagement within the Institute.
Eligible applicants must be current SEI members in good standing, licensed Professional Engineers (PE) or Structural Engineers (SE), actively involved in SEI chapters or committees, and have held responsible charge in the field for at least ten years.
Qualified candidates are required to submit a complete application package by November 1 to be considered for induction in the following calendar year.
Learn more about the submission process: go.asce.org/seifellowinfo. Apply: go.asce.org/seifellowapplication.
Call for Content for ASCE2027: A New Era for SEI
In 2027, Structures Congress will be integrated into ASCE2027:
The Infrastructure and Engineering Experience, ASCE’s premier conference. SEI members who have attended past Structures Congresses can expect a rich and relevant experience within the ASCE2027 framework.
The conference will feature deep technical content and forwardlooking sessions that reflect the evolving needs of structural engineers, including topics like AI-driven design, cyber resilience, future materials, and advanced structural-design methods. SEI members will have many opportunities to connect with peers, industry leaders, and collaborators across disciplines.
The Call for Content opens in October 2025, inviting abstracts across seven themes, 21 technical areas, and 230 topic options. The seven themes are:
• Autonomous & Smart Tech Frontiers.
• Engineering at the Edge.
• AI-Driven Design & Cyber-Resilience.
• Future Materials & Construction Methods.
• Rethinking Infrastructure Finance & Policy.
• The Future Workforce & Practice.
• Deep Technical Dive.
Explore the themes and prepare to shape the future of structural engineering at ASCE2027. go.asce.org/asce2027.
2026 ASCE/SEI Awards Call for Nominations—Celebrate Excellence in Civil Engineering
Recognize the remarkable achievements of your peers by submitting nominations for the prestigious ASCE and SEI awards. Awards span technical innovation, scholarly research, and contributions to professional practice.
Apply Now – October Awards Deadline
• Arthur M. Wellington Prize—Honors transportation-related papers published in ASCE journals.
• ASCE State-of-the-Art of Civil Engineering Award—Recognizes leading publications reviewing advancements in civil engineering.
• J. James R. Croes Medal—Presented for notable contributions to engineering science in ASCE publications.
• Norman Medal—ASCE’s highest technical paper award for significant practical impact.
• Walter L. Huber Civil Engineering Research Prize—Celebrates mid-career researchers driving progress in civil engineering.
Apply Now – November Awards Deadline
• Walter P. Moore Jr. Award—Recognizes leadership in developing structural codes and standards.
• Dan M. Frangopol Medal for Life-Cycle Engineering of Civil Structures—Honors achievements in life-cycle performance and resilience.
• Alfredo Ang Award on Risk Analysis—Awarded for advancing probabilistic risk and reliability methods in infrastructure design.
• James A. Rossberg Award for Collaboration—In memory of the SEI Founder Jim Rossberg this award will honors collaboration that strengthens structural engineering.
• David P. Billington Award—Recognizes transformative impact in structural engineering education and practice
• Gene Wilhoite Innovations in transmission line Engineering Award—Celebrates innovation and integrity in transmission line engineering.
• O.H.Ammann Research Fellowship in Structural Engineering— Awarded to fuel new ideas and discoveries in structural design and building methods.
Learn more about awards and apply today: go.asce.org/seiawards.
ASCE is hosting a two-day short course in Reston September 25th-26th on Structural Engineering of a 4-Story Combined Material Building as part of ASCE Seminar Week. Attend in person or via livestream, earn PDHs/CEUs, and take home practical skills you can apply immediately. Visit www.asceweek.org.
NCSEA News
NCSEA Foundation Collaborates on ‘CURE’ to Reduce Embodied Carbon
The National Council of Structural Engineers Associations (NCSEA) Foundation is proud to announce the launch of CURE—Code Updates for Reduction of Embodied-Carbon—a bold new initiative aimed at significantly reducing embodied carbon through updates to structural engineering codes and standards.
Structural engineers influence nearly 15% of global CO₂ emissions through their specification of materials. Even a modest 1% reduction in material use would equal the environmental benefit of removing 10 million gasoline-powered vehicles from the road for a year. CURE is designed to seize that opportunity through smarter, more efficient design standards.
“CURE is about rethinking the assumptions built into our structural codes and unlocking meaningful reductions in carbon emissions at scale,” said Ron Klemencic, P.E., S.E., Hon. AIA, and Secretary of the NCSEA Foundation Board of Directors, who is leading the effort. “We have a responsibility, and a real opportunity, to modernize the codes that guide our profession.”
CURE is a collaboration among leaders in structural engineering and sustainability, including ASCE/SEI, AISC, ACI, the Charles Pankow Foundation, the University of Colorado Boulder, and the MKA Foundation. The initiative focuses on identifying and recommending targeted updates to widely used standards such as ASCE 7, ACI 318, and AISC provisions, with the goal of reducing embodied carbon across the built environment.
In addition to Klemencic’s leadership, Kelly Roberts, P.E., S.E., LEED AP BD+C, represents the NCSEA Foundation on the
CURE Advisory Panel, and Emily Guglielmo, P.E., S.E., serves on the Embodied Carbon Code Review Committee. Their technical expertise and advocacy ensure that the voice of the structural engineering community is central to the initiative.
How To Get Involved
The CURE committee officially launched its work at the 2025 Towards Zero Carbon Summit and will provide quarterly progress updates, with final recommendations expected by June 2026.
Firms can support the initiative with a minimum gift of $1,000, joining a coalition of sustainability-minded organizations helping shape the next generation of building codes. Donors will receive early access to draft findings and the opportunity to provide feedback that informs national standards.
To learn more or make a donation, visit www.ncsea.com/cure. ■
AI Grant Team Joins National Conversation on Structural Sustainability
The NCSEA Foundation’s AI Grant Team participated in the Towards Zero Carbon 2025: Summit & Symposium, hosted by SEI and the University of Colorado Boulder. The event on June 26 to 27 brought together structural engineers, researchers, and academics focused on driving progress toward a zero-carbon future.
Sheng Zheng, P.E. (Martin/Martin), a member of the NCSEA AI Grant Team, joined a panel discussion titled “Structural Design –Visions for the Future,” alongside Laura Karnath (Walter P Moore) and Ian McFarlane (Magnusson Klemencic Associates). While other sessions focused on innovative materials and low-carbon products, this panel explored how technology — particularly artificial intelligence — could transform design workflows and decision-making. AI presents exciting opportunities to efficiently explore a broader range of design alternatives, though its use in practice remains limited. While these tools will need to evolve to meet the profession’s needs, engineers can play a proactive role by rethinking data strategies — positioning the profession to better leverage emerging technologies as they mature. The discussion sparked important conversations around how achieving low-carbon outcomes may require both cultural and technological shifts, including greater collaboration, improved data practices, and the integration of new tools into daily workflows. It also reinforces
the NCSEA Foundation’s commitment to supporting the structural engineering profession as it explores AI’s potential to drive scalable, sustainable design. Through initiatives like the AI Grant Program, NCSEA continues to foster innovation, share actionable strategies, and promote leadership toward a more sustainable built environment. ■
NCSEA Launches Mastering Masonry Webinar Series
Join NCSEA for Mastering Masonry: Designing, Constructing, and Sustaining Resilient Masonry Structures, a four-part webinar series designed to sharpen your masonry expertise. Each 90-minute session (1.5 PDHs) will focus on practical strategies and design insights:
• September 2: Concrete Masonry Construction with Adam Hutchinson
• September 9: Masonry Wall Design: Out-of-Plane Loading with Phil Ledent
• September 16: Retrofit and Repair of Existing Masonry Walls with Donald Harvey
• September 23: Masonry Detailing for Seismic Resistance with John Hochwalt
The full series provides six hours of education and access to recordings for one year. Registration is $495 for NCSEA members ($795 nonmembers), or sessions can be purchased individually. To register, visit www.ncsea.com/webinar-calendar. ■
SEAMASS Young Members
Group Supports Its Community
The Structural Engineers Association of Massachusetts (SEAMASS) Young Members Group continues to show a strong commitment to community engagement through a range of volunteer efforts.
Among their ongoing initiatives, SEAMASS YMG regularly participates in Habitat for Humanity build days, offering hands-on support to help create safe, affordable housing. Earlier this year, the group also partnered with the Neponset River Watershed Association for its annual Earth Day River Cleanup, dedicating their time to environmental stewardship and local conservation efforts.
SEAMASS YMG’s dedication to service reflects the values of the broader structural engineering community—building not just structures, but stronger, more connected communities. ■
Countdown to the 2025 NCSEA Structural Engineering Summit in New York City
Structural engineers from across the country will convene in New York City this fall for the 2025 NCSEA Structural Engineering Summit, taking place October 14–17 at the Midtown Hilton. The Summit is the profession’s premier event, offering a unique blend of technical education, networking, and celebrations that highlight the critical role of structural engineers in shaping resilient and innovative communities.
The four-day program is packed with opportunities: a robust lineup of education sessions, an industry-leading Exhibit Hall, social events like the Welcome to New York Party, the annual SEE Awards Celebration, and guided tours showcasing some of New York’s most iconic structures.
This year’s Summit features three keynote sessions designed to inspire and challenge attendees:
• “One Vanderbilt Structure: The Interplay Between Engineering and Architecture in Midtown’s Tallest Office Building” by James von Klemperer, FAIA, RIBA
• “Mastering the Moment” by Kevin Hekmat
• “Small Teams with Big Impacts: Taking the Next Steps with AI Adoption” by Jesse Light, S.E., P.E., Ayush Singhania, P.E., and Sheng Zheng, P.E.
In addition, a preconference workshop on October 14 will dive into practical applications of artificial intelligence for structural engineers, offering two tracks—Consumer and Developer—for professionals at different levels of expertise.
With a balance of technical content, professional development, and networking, the NCSEA Summit continues to be the must-attend event for structural engineers. To learn more and register, visit /www. ncseasummit.com. ■
CASE in Point
ACEC Fall Conference, Coalitions Winter Summit, and a New Chapter for CASE Coalition members
The American Council of Engineering Companies (ACEC) will host its Fall Conference October 5–8, 2025, at the Marriott Marquis San Diego Marina. Alongside the keynote sessions and national networking, this year’s agenda delivers real-world, highimpact content that structural engineers can apply immediately in their firms and projects.
Highlights for Structural Engineers:
• ACEC Research Institute: Workforce Study from the Firm of the Future—With competition for engineering talent at record levels, understanding workforce dynamics is critical to firm growth. This session will deliver data on hiring trends, retention strategies, and emerging skills, insights that CASE members can use to plan for the next generation of structural engineering talent.
• Climate Risk & Liability: What Every Engineering Firm Needs to Know—Climate change is already influencing building codes, design standards, and liability exposure. For structural engineers, this session will explore how evolving risk profiles affect project contracts, insurance considerations, and professional responsibility.
• From Drones to Digital Twins: Real-World AI in Infrastructure Inspections—Technology is transforming how structural assessments are performed. Learn how firms are integrating drones,
photogrammetry, and AI-driven modeling to streamline inspections, improve safety, and reduce costs, tools that can reshape how SEs deliver value to clients.
In addition, the Fall Conference will host a joint roundtable for Structural Engineers and MEP professionals, offering a forum to share lessons learned, discuss design coordination challenges, and identify new opportunities for collaboration.
Register Now for the ACEC Fall Conference
October 5–8, 2025 Marriott Marquis San Diego Marina conference.acec.org
ACEC Coalition Membership: Broader Access, More Flexibility for CASE Members
ACEC has launched a new model for its Coalitions program, removing membership fees for all coalitions except the Design Professionals Coalition.* For the Coalition of American Structural Engineers (CASE), this means ACEC member firms and their employees can now participate in CASE activities without a separate dues payment.
Under this structure, CASE members will have access to a mix of free and fee-based events, education, publications, and other resources developed specifically for structural engineering firms. These include
CASE’s widely used contract documents, risk management tools, and business practice guidelines.
The change is designed to broaden access, simplify participation, and allow more structural engineers to connect with CASE’s network, resources, and expertise. ACEC and your Member Organization will provide updates in the coming weeks on how to take advantage of CASE offerings under the new model.
*Design Professionals Coalition (DPC) is not impacted by this change and will continue with its current membership structure.
CASE Publications and Committee Participation
CASE produces contract documents, guidelines, and risk management tools to support structural engineering firms. Its work is driven by four committees:
• Toolkit – Tools based on the Ten Foundations of Risk Management.
• Programs & Communications – Sessions, articles, and industry collaboration on risk reduction.
• Guidelines – Business practice guidance on legal, financial, and client relations.
• Contracts – Contract templates and commentary for risk education.
For more information or to express interest in joining a subcommittee, contact Michelle Kroeger at mkroeger@acec.org. A complete list of CASE publications is available at www.acec.org/member-center/get-involved/coalitions/case/resources/case-publications/.
News of the Coalition of American Structural Engineers
Save the Date: Coalitions Winter Summit 2026
The Coalitions Winter Summit, held February 26-27, 2026, in Houston, Texas, is where ACEC members come together across disciplines to exchange ideas, tackle shared challenges, and explore innovative solutions. In 2026, the program expands to offer dedicated education tracks and peer roundtables for:
• Mechanical, Electrical, and Plumbing (MEP) Engineers
• Structural Engineers
• Geoprofessionals
• Professional Surveyors
• Land Developers
Over a day and a half, attendees will take part in targeted education, in-depth discussions, and cross-discipline exchanges that encourage practical takeaways and professional connections. This event is open to all industry professionals, including those who are not ACEC members. Firms are encouraged to send both
senior leaders and emerging professionals, ensuring that multiple perspectives and experience levels contribute to the dialogue.
Call for Presenters, Exhibitors, and Sponsors
Individuals interested in presenting an education session at the Summit should contact Senior Director Michelle Kroeger at mkroeger@acec.org.
The Winter Summit also offers opportunities for exhibitors and sponsors to engage with attendees in a program format that fosters sustained, meaningful conversations. Those interested in participating as an exhibitor or sponsor can request details on available options.
Contact Erin Wander at mwander@acec.org.
CASE Coalition Meets in Philadelphia, Tours AERO Aggregates
The CASE Coalition held its Summer Meeting in Philadelphia on August 14–15, and one of the highlights was a tour of AERO Aggregates, a company transforming recycled glass into an innovative lightweight aggregate.
AERO’s process converts post-consumer glass into ultra-light foam aggregate, which has become a go-to solution in geotechnical projects where weight and stability are critical. During the tour, CASE mem bers were impressed not only by the sustainability of the process, but also by its potential niche applications including lightweight concrete and grout mixes that could prove valuable to structural engineers. That innovation was on display in Philadelphia two years ago, when AERO Aggregates’ product was used in the emergency reconstruction of the I-95 bridge collapse. The lightweight aggregate helped crews move quickly, stabilizing the site and allowing the highway to reopen in record time. The project drew national attention as an example of engineering resilience and public–private collaboration in action. By seeing the production process firsthand, CASE attendees came away with a deeper understanding of how recycled materials can be repurposed into high-performance building products. For structural engineering firms looking ahead, AERO’s work highlights both the immediate impact innovative materials can have on urgent infra structure projects and the longer-term opportunities for expanding applications across the industry.
The Case Coalition toured AERO Aggregates, which transforms recycled glass into a lightweight aggregate.
in SIGHTS
Navigating Fast-Tracked Industrial Projects
By adopting a collaborative approach, structural engineers can meet the increasing demands of fast-track projects, ensuring timely and cost-effective delivery while maintaining high standards of design and coordination.
By Sheikhameed Sikkandhar, SE, PE, and Heath Chesnut, PE
Fast-tracked industrial projects face unique challenges, including the need to release structural packages early and to manage continuous changes amid overlapping design and construction phases.
Design Challenges
Key challenges include:
1. Incomplete Layouts and Selections: Developing design criteria is difficult when process layouts, mechanical equipment, architectural layouts, and floor/roof openings are not yet finalized. Early design packages must balance cost-effectiveness with the risk of over-designing or under-designing, which can lead to increased project costs or the need for structural modifications. Examples include tentative stair and elevator locations, undecided mechanical equipment locations, and premature decisions on associated ducts and piping.
2. Client Requirements and Technological Changes: Clients may alter manufacturing processes due to technological advances, budget constraints, or value engineering initiatives even during detailed design or after construction starts. Budget limitations, policy shifts, or updates to the owner’s process can drive such changes.
3. Overlapping Phases: Fast-tracked projects often overlap detailed design and construction administration. Early steel mill orders and foundation packages help maintain schedules but require added planning and resources. Concurrent activities mean shop drawing reviews and RFIs may occur before detailed design is complete, heightening resource demands.
4. Coordination With Other Trades: Structural packages often precede those of other trades, increasing the chance of field modifications and rework. Securing agreement from other disciplines before early package release is vital, as early structural deliverables can limit the design flexibility of others. For example, moving a stair or door after the superstructure is set presents significant challenges.
Leveraging Technology
Meeting the demands of fast-tracked industrial projects requires a rapid, adaptive approach to design and engineering. Unlike traditional project timelines, these projects often demand early release of foundation drawings and steel tonnage for procurement, since steel is a major long-lead item. Advanced technology plays a crucial role in accelerating the design process and supporting the timely delivery of project packages. The rise of AI and automation has become essential for structural engineers aiming to maximize efficiency and keep pace with compressed schedules. Structural engineers and technology team are implementing digital workflows and data-driven strategies that streamline every phase of a project from analysis and design to documentation, fabrication, and construction modeling. Examples include improving interoperability between analysis software and BIM platforms, automating data transfer from calculations to drawings, and using parametric tools to optimize framing system layouts.
In-model reviews, which replace traditional PDF-based shop drawing reviews, further expedite the process. By consolidating all drawing information into a single 3D environment, engineers can review shop drawings
more accurately and efficiently, eliminating the need to cross-reference multiple documents. This significantly reduces cycle times and supports better coordination.
References such as AISC’s “Model Review and Approval for Structural Steel” provide valuable guidance on in-model review benefits and implementation. Integrating early connected models into the review process streamlines design-to-fabrication workflows, allowing for upfront creation of connection details and shop drawings. This approach reduces rework, improves cost estimation, and enhances project profitability.
By strategically leveraging technology from advanced digital workflows to in-model reviews and early connected models structural engineers are better equipped to meet the challenges of fast-track projects, delivering on time while maintaining quality and efficiency.
Collaboration, Communication, and Risk Management
The early release of structural packages for procurement, steel detailing, and foundations, driven by continuous technological advancements, leads to frequent process changes, complicating design criteria and increasing the risk of rework.
To mitigate these challenges, it is essential to establish clear and open lines of communication with the overall design team, construction team, and client. This helps identify risks and unknown information early, preventing significant construction rework later. Documenting these communications is crucial to ensure that identified risks are acknowledged by the client before construction begins. Project execution using cutting-edge project management strategies and techniques such as lean design or lean operating strategies is very effective in fast-paced projects. Engaging the fabrication and construction team as early as possible in a design-assist role is also vital. This collaboration helps identify the flow of information, explore options and alternatives, and create efficiency gains while mitigating risks.
Determining loads that cover uncertainties without driving up material costs is another critical aspect of risk management. Structural engineers must balance cost-effectiveness with the need to avoid over-designing or under-designing, which can lead to increased project costs or the need for structural modifications. Early coordination with other trades is essential to understand their needs, loading criteria, and any special requirements, such as vibrations for sensitive equipment and processes. This collaboration helps develop a reasonable uniform live load that accommodates the needs of other trades. Identifying zones for special loadings, such as pipe racks and electrical substations, and developing separate uniform live loads for these zones is crucial. Additionally, careful consideration of serviceability checks using sound engineering judgment is necessary to minimize the possibilities of excessive deflections and differential movements, given the unknown exact heavy loading layouts and locations. ■
Sheikhameed Sikkandhar, SE, PE, and Heath Chesnut, PE, are both Senior Associates at SSOE Group Inc. They specialize in leading large-scale, high-tech advanced facilities projects and have served as Engineers of Record.
