Buckling of thin-walled beams under concentrated transverse loading

The transversely loaded thin-walled beam under a non-uniform bending moment forms an example of the detrimental influence that a local effect may have on the overall behaviour. The local effect is the plate buckling in the region of maximum bending moment. The overall behaviour is the lateral-torsional buckling of the beam as a whole. If the local buckling load is smaller than the overall buckling load, the overall mode may be triggered in the post-buckling region even if the individual buckling loads are well separated. This interaction problem is being investigated both experimentally, and by analysis by means of a simple discrete model as well as by means of a spline finite strip computer program. A special feature of this program is the use of splines instead of Fourier series, so that strongly non-periodic buckling modes, such as occur in the afore mentioned problem, can be handled.

Preliminary results show a qualitative agreement between the experiments and the discrete model. Moreover, the numerical model describes the shape of the non-periodic local buckle very well.