Nonlinear dynamic buckling of thin‐walled beam‐columns under ground excitations

A new analysis technique has been developed to study the non-linear elastic mode interaction in thin-walled beam columns under ground excitation. The technique is capable of handling arbitrary cross-sectional shapes and end conditions. In the analysis of P - Δ effects in the building frames, the technique incorporates the instantaneous loss of stiffness due to local buckling of the individual plates in a rational and convenient manner. The latter is achieved via use of the finite-strip technique which is found to be extremely efficient in the local and post-local buckling analysis of prismatic plate structures. The overall behaviour is modelled by a one-dimensional finite element in which the effects of local buckling are appropriately incorporated. It is observed that moment frames lose stability at an axial load significantly lower than the static buckling load, even for moderate levels of earthquake.