Lateral buckling of bridge steel girders (AGB2008/004)

Lateral torsional buckling (LTB) is the important object of research in particular for the steel rolled beams used in building. The models for the LTB verifications of structural safety of these beams are based on many research studies. For the slender girders made up of plates, used in the construction of steel and composite bridges, the same verification models are used, however with a very large conservatism. No intensive theoretical and experimental study exists to validate these models for plate girders used in steel bridges construction.

In the field of the steel bridges, the parameters which play a role in LTB are very numerous and their influence cannot be evaluated with simple investigation methods. Indeed, plate girders of bridges belong to a structure of the space whose behaviour is influenced by their connections with the other elements of the structure and nature of the actions acting on the bridge. In addition plate girders have manufacturing defects, initial deformations and are the seat of residual stresses, completely different from the one of the rolled beams.

The suggested research wants to analyze in an exhaustive and thorough way the resistance to LTB of the plate girders and to propose models to evaluate their resistance to LTB which correspond better to the reality of the behaviour of steel bridges. These models could advantageously be used for better dimensioning steel bridges but also to evaluate in a more realistic way resistance to LTB of existing bridges.