How Fire Resistance and Progressive Collapse Shape the Steel Industry and Beyond

Peer Perspective: Dr. Spencer Quiel, Associate Professor of Structural Engineering at Lehigh University

When designing structures, there are plenty of design criteria to take into account. Fire, blast and progressive collapse are where Dr. Spencer Quiel’s expertise lies. From government-sponsored projects to advising graduate student work, let’s hear more about Dr. Quiel’s experience, professional resource recommendations and more.

Q: Can you introduce yourself and tell us more about your current professional role?

A: My name is Spencer Quiel. I’m an associate professor of structural engineering at Lehigh University. I’m associated with the Department of Civil and Environmental Engineering and the ATLSS Engineering Research Center here at Lehigh.

Q: Can you tell us about your general background, including involvement in student and professional organizations?

A: I am actively involved in technical efforts with the American Society of Civil Engineers (ASCE), American Institute of Steel Construction (AISC), and Precast/Prestressed Concrete Institute (PCI). Before Lehigh, I spent four years in professional practice, and I’m a licensed engineer in Pennsylvania and Virginia. At Lehigh, I have been the faculty liaison to the Structural Engineering Institute Lehigh Valley chapter for the better part of eight years. I’ve advised a number of undergraduate groups like the Steel Bridge Club, which participates in the national ASCE-AISC Student Steel Bridge competition every year. I’ve served as an academic advisor to two undergraduate cohorts in the civil engineering major. I’ve also worked with several of our professional master’s students on side projects as well.

Q: Your area of research and expertise is on the resistance of buildings, tunnels, bridges and other structures to loads like fire, blast and progressive collapse. What drew you to study this topic? Are there any subtopics within your research that you take a particular interest in?

A: Structural fire engineering was the focus of my graduate work at Princeton with my advisor and mentor, Professor Maria Garlock. The opportunity to work on that topic was an exciting part of the offer to go to Princeton.

But really, one of the reasons I became interested in this topic was because I was a sophomore in college when 9/11 occurred. The impact of the fire on the Twin Towers, and all the other surrounding structures, was something that was very motivating to me as a structural engineer. How can we understand the thermomechanical causes of the collapse, and how can we prevent them in the future? Structural fire engineering is a field that’s rapidly evolving. I’ve been able to serve on a couple of technical and national committees that have been involved in writing new language for design standards and guidelines. In particular, I was a contributor to a new ASCE manual of practice that has helped move this field forward.

Dr. Quiel worked for Hinman Consulting Engineers for four years before arriving at Lehigh University. At Hinman, he helped cultivate structural fire engineering services and market opportunities but was also interested in the work they did for protective design against blast and progressive collapse. His position at Hinman Consulting Engineers opened up significant learning opportunities, leading to new research avenues when he started at Lehigh.

Q: Can you talk a bit about your experience with steel design, especially HSS if applicable, and fire protection design?

A: One of my primary projects focuses on composite floors in steel-framed buildings under fire. We’re just finishing this project up now, but it was funded by AISC as part of their Milek Fellowship program. Two graduate students and I conducted five large-scale experimental tests in our modular structural testing furnace facility at the ATLSS laboratory under high-intensity heating, which was intended to resemble a compartment fire in a building.

Because the floor is horizontal, the fire underneath it will induce material weakening, thermal expansion and deflection. This creates unintended forces as the heated floor members expand and push, then sag and pull. The columns and lateral systems are affected by their interaction with the floor, which can increase the risk of severe damage.

Dr. Quiel explains that bridge fires are more of a problem than people think. When annualizing the data, the number of bridges lost to fire is comparable to the number of bridges lost to seismic activity. Right now, Dr. Quiel is working with the Federal Highway Administration on a project to develop guidance for how to design bridges for fire loads.

Q: With steel and HSS in mind, can you share some notable projects you’ve worked on or studied?

A: In terms of research projects, the AISC-funded work on steel-framed buildings and composite floor systems has been a really big part of my work over the past several years during my time at Lehigh. I’ve also completed several projects looking at steel girders and steel cables in both short-span and long-span bridges. I haven’t had a chance yet to pursue an HSS-focused project, but concrete filled HSS columns are widely studied for their fire resistance. I would be excited to pursue some of the work on that topic in the future.

Q: Some fire-focused design references such as AISC Design Guide 19 are aging, and there is not much information available for some types of structures such as bridges. Are there other good sources for available information pertaining to HSS members?

A: Absolutely. Even doing a search in a place like Google Scholar, there are research papers that have been published about concrete filled tubes under fire. Numerous tests have been performed in Europe, Canada, China and elsewhere around the world. Because these construction methods are gaining traction, the industry has been increasingly interested in determining an actual performance expectation when they are exposed to fire. The last 20 years of testing, combined with additional research and simulation have significantly improved our understanding of structural fire resistance.

Q: Do you use computer modeling for performance-based design? If so, could you describe that approach and how it can help design processes?

A: Yes, we use a number of different methods ranging from generalized finite element (FE) analysis packages to simple analytical semiempirical expressions. On a lot of our higher-end projects, we’ll use generalized FE packages like Abaqus, Ansys or a specialized package called SAFIR, which is more streamlined for thermomechanical analysis and has a lot of unique capabilities for modeling the response of structures to fire.

For modeling the fire itself, we often use the Fire Dynamics Simulator (FDS), which is developed at the National Institute of Standards and Technology, in addition to simpler fast-running tools that we develop in-house. Semiempirical approximations for modeling fire include those published by the U.S. Nuclear Regulatory Commission. We use these models quite often for bridge analyses since fire hazards near these structures tend to be open-air. We’ve also adapted some of that work for tunnels.

As with any high-fidelity analysis, Dr. Quiel reiterates that FE users should exercise caution when selecting input data for these thermomechanical analyses and to be mindful that the outcome can be sensitive to boundary conditions, material properties, etc. As elements cool after being exposed to fire, they have permanent deformations that can introduce new forces, especially on connections.

Q: In your extensive research on fire protection and progressive collapse, are there any insights or design tips you would like to offer designers for steel design? Do you have any fire protection tips specific to HSS?

A: From a fire perspective, the Manual of Practice 138 from ASCE is a great reference. The more visibility a document like that gets, the better because it’ll introduce information and help practitioners formulate questions and look for new research results that they can benefit from. These documents can help point people in the right direction to go digging for solutions. Things constantly evolve on the research front through the various national technical committees.

Q: What resources would you suggest the engineer of record or architect use when designing for fire protection with performance-based design?

A: I recommend Appendix E in ASCE 7-22 for buildings, which focuses on fire loads. Also, I recommend the companion for that appendix, Manual of Practice 138, for structural fire engineering. For composite floor systems in steel buildings, I recommend a report that ASCE recently commissioned, which offers several examples that were published by teams made up of professional firms paired with academic experts. I would encourage organizations to try and engage with academics to find solutions or distill research results for practical use. These types of efforts, when you have those partnerships to develop guidance, are invaluable.

Q: Similarly, what resources do you recommend for the engineer of record when designing for progressive collapse in steel structures?

A: UFC 4-023-03 is one of the most widely used progressive collapse resistance documents in U.S. practice. It describes in detail several recommended approaches for performing analyses and how to represent plasticity in structures to resist collapse. ASCEhas also been producing more resources on progressive and disproportionate collapse. These materials are relatively generalized but can give designers more breadth on this topic. System-specific guidance is also available from organizations such as AISC and PCI.

Q: From your perspective as an educator, what are some challenges young engineers face when entering the field?

A: For most engineers, it comes down to finding the work that interests and excites you. Namely, you’re doing things that you feel matter, are interesting and challenge you. Also, working with good people who value your contributions. One thing I stress to my students entering the workforce is to provide value to their organizations. Provide good work, curiosity and insight, but also receive value from your organization. Do you have mentors? Are you compensated well? Do you feel your work is assigned a high level of value from what you provide? That type of value proposition drives job satisfaction. People feel good when they feel they provide value and are being valued in return. The challenge is to find those jobs where you can advance and receive mentorship along the way.

Dr. Quiel says discovering your place in the grand scheme of engineering is important for students finding their footing. Young engineers may sometimes need to try a few experiences and should not be afraid to make a change in order to find what they like and where they thrive. What a student does now and 10 years from now should still feel rewarding and valuable.

Q: In what ways do you hope to see the steel and design industries grow?

A: Though “performance-based design” has become a bit of a buzzword, I think that the more aware structural engineers can become of new innovations and where they themselves fit into that development, the further we can go as an industry. We can enhance not only hazard resistance but also lifecycle and sustainability of structures to make our overall built environment more resilient. The longer we can make things last, the fewer resources we need to build, rebuild and maintain them.

Q: Is there anything else you’d like to share with our readers?

A: I encourage structural engineer practitioners to explore the opportunities offered by a performance-based design mindset. A lot of people assume that performance-based methods have to be complex and complicated, but they really don’t have to be. Sometimes a complex method is appropriate, but there are ways we can be elegant in our approach and lean into efficiency. There are certain projects that just won’t fit within the budget for doing really complex, high-fidelity numerical analyses. You can still do something quickly and provide high value beyond the code-based minimum.

How people view the structural engineering profession is often not commensurate with the value we provide to society. I think a lot of people take for granted what we do. We need to educate clients and the public about what we do and why it’s valuable. Often, we’re only noticed when things go sideways. But those instances are rare. The vast majority of the things we design and build work well and continue to work well on a daily basis because of the people, research, standards, codes and guidelines that make these things happen.