Effect of initial deflection shape on the ultimate strength Behavior of welded steel plates under biaxial compressive loads

The shape of weld-induced initial distortion in steel plates bounded by support members is normally very complex. It must be recognized that it is not only the magnitude of initial distortion, but also its shape that can significantly affect the plate collapse behavior. In this paper, some typical plate initial deflection shapes are selected from measurements for merchant ship plating between stiffeners. The influence of such initial deflection shapes on the ultimate strength behavior of steel plates subjected to biaxial compression as well as uniaxial thrust is then investigated applying nonlinear finite element analyses. It is confirmed that an initial deflection shape that approximates the buckling mode, with its maximum amplitude selected to be the same as the measured maximum initial deflection, is a good representation for the purposes of somewhat pessimistic evaluation of the ultimate strength of plating between stiffeners under biaxial compression as well as under uniaxial compression. Also, it appears that the influence of initial deflection shape on the plate collapse behavior under predominantly transverse axial compression or biaxial compression can be quite different from that under predominantly longitudinal axial compression. As another contribution, the ultimate strength interaction relationship of plating under biaxial compressive loads is presented. The results and insights developed from the present study are summarized.