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Research Spotlight: Nonlinear Behavior of Global Lateral Buckling of I-Girder Systems

2017 Annual Stability Conference Presentation

Session S1 – Stability of Steel Bridges Wednesday, March 22, 2017 8:30 am

Nonlinear Behavior of Global Lateral Buckling of I-Girder Systems

I-girder systems with relatively long spans and narrow widths are susceptible to a system buckling failure mode that is relatively insensitive to the spacing between cross frame or diaphragm braces. This global buckling mode is of particular concern during deck placement and can compromise the safety and/or constructability of steel bridge systems. This paper presents computational studies on the nonlinear behavior of a variety of steel I-girder systems. A number of geometric factors affecting the nonlinear buckling behavior of I-girder systems such as the shape and distribution of the imperfection along the length as well as the girder curvature were investigated. The process of cross frame installation was simulated to investigate the impact of the installation process of the braces on the resulting behavior. The results demonstrate that the susceptibility of the system mode of buckling to 2nd order amplification is significantly reduced compared to the “critical-shape imperfection”. The initial girder imperfection was significantly altered by fit-up of cross frames and the likely imperfection pattern afterwards. The FEA results demonstrate that the “critical shape” imperfection that has been used for stability bracing of cross frame systems may not be likely to occur in practice. The results of this study provide insight into adequate limits on second-order displacement amplification of I-girder systems under transverse non-composite loading.

Liwei Han and Todd A. Helwig, University of Texas at Austin, Austin, TX

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