Some aspects of the longitudinal-transverse mode in the elastic thin-walled girder under bending moment

• The Koiter’s asymptotic theory has been used.
• An influence of the longitudinal-transverse mode on interactive buckling were checked.
• The shear lag phenomenon and distortional deformations are taken into account.
• The longitudinal transverse mode from analytical-numerical and FEM were compared.

The present paper deals with an influence of the longitudinal-transverse mode on interactive buckling of the thin-walled composite girder with imperfections subjected to bending moment when the shear lag phenomenon and distortional deformations are taken into account. A plate model (2D) is adopted for the girder. The structure is assumed to be simply supported at the ends. A method of the modal solution to the coupled buckling problem within the first order approximation of Koiter's asymptotic theory, using the transition matrix method and Godunov's orthogonalization, has been used. The calculations have been carried out for square girders.