2026 Dennis & Leslie Drag Distinguished Lecture

The Role of Structural Failures and Field Problems in Directing Research and Specification Design Provisions

A Presentation by Todd Helwig, Ph.D., P.E.
David Allen Cockrell Chair in Engineering
University of Texas at Austin

Tuesday, April 14, 2026

Problems frequently arise in structural systems that can range from field problems that complicate construction to a total structural collapse. In some cases, the problems arise as a result of design or construction errors, while in others the problems shed light on a lack of understanding in the structural behavior. This lecture begins with an overview of the collapse of the Marcy Pedestrian Bridge in 2002 and is further highlighted with an overview of related field problems in other bridges. While the collapse of the Marcy Pedestrian Bridge was caused by a design error, the failure initiated deeper investigations on the stability behavior of girder systems that demonstrated a lack of understanding of the fundamental behavior during construction. Subsequent studies led to the recognition of a limit state now referred to as the system-buckling mode that often controls the design and construction of narrow girder systems. The focus of the subsequent investigations targeted improving the fundamental understanding of girder stability during construction as well as the development of comprehensive design solutions to ensure stable behavior during construction. The investigations resulted in the development comprehensive guidelines for the design of bracing systems for both I-shaped girder systems as well as partial-bracing of steel tub girders that have been incorporated into the AASHTO Bridge Design Specifications to provide efficient and safe steel bridge systems.

Speaker Bio

Todd Helwig, Ph.D., P.E. has had a 31-year career teaching and conducting research in the field of structural engineering. He holds the David Allen Cockrell Chair in Engineering at the University of Texas at Austin. His primary area of interest is the design and behavior of steel structures with an emphasis in full-scale testing, field monitoring, structural stability, fatigue, and stability bracing requirements.

He is a member of several technical committees within the American Institute of Steel Construction (AISC), the AASHTO/National Steel Bridge Alliance Collaboration (NSBA), the Design Advisory Group and Steel Bridge Task Force for AASHTO, and the Structural Stability Research Council (SSRC). He is a member of the AISC Committee on Specifications. He served on the Executive Committee for SSRC from 2002-2019 and served as Chair from 2016-2019.

He has developed and taught numerous short courses on the design and behavior of steel buildings and bridges on behalf of AISC, SSRC, and the National Highway Institute. More than 5000 engineers have attended his short courses in person with thousands more attending webinars.

His research has been recognized with several awards including the 2025 SSRC Lynn S. Beedle Award, the 2025 SSRC Distinguished Member Award, the 2025 Wilbur Schoeller Award from the Structural Engineers Association of Texas, the 2023 George Richardson Medal presented at the International Bridge Conference, 2022 Richard S. Fountain Award given by AASHTO/ AISI/NSBA, the 2022 AISC Lifetime Achievement Award, the 2017 AISC T. R. Higgins Lectureship Award, the AISC Special Achievement Award, the ASCE Collingwood Research Prize, the ASCE Moisseiff Award, and the ASCE Shortridge Hardesty Award. He was recognized in 2025 with the Joe King Professional Achievement Award from the University of Texas College of Engineering.