Global Lateral - Torsional Buckling of I-Girder Systems in Cantilever

Global lateral – torsional buckling (GLTB) is a failure mechanism that may compromise the structural stability of a system of girders connected with cross-frames or diaphragms, during construction stages. This limit state may occur at load levels lower than those required to cause lateral – torsional buckling of individual girders between bracing points; especially, in bridges with relatively long spans and short widths. Closed form solutions are available to determine the GLTB resistance of single span girder systems with simple supports and subject to various loading cases. This paper presents the results of research conducted to determine the susceptibility to GLTB of I-girder systems in cantilever, in particular, in bridges erected with the incremental launching method (ILM). The results obtained from refined finite element models show that structures constructed with the ILM may be vulnerable to GLTB as the girder group cantilevers out from the support. Recommendations are provided to conduct the GLTB strength checks of I-girder systems in cantilever using available equations.

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