Finite Element Analysis of Steel Lap Welded Joint Behavior under Severe Seismic Loading Conditions

The present paper extends the experimental and numerical research presented at the ASCE 2018 conference. The paper is numerical, based on a shell finite element simulation of the welded lap joint subjected to internal pressure and structural loading, which accounts for the bell formation process, the corresponding residual stresses, and the presence of initial (geometric) imperfections of the cylindrical pipes. Previous numerical simulations of the experiments presented in the 2018 conference, have shown a very good comparison between the numerical results and test data. The present paper has the following two purposes: (a) extend the numerical results for the case of axial compression loading, in addition to the case of bending; and (b) examine the effects of pressure on the mechanical response of welded lap joints. Towards the above purposes, two 24-inch nominal diameter pipes with thickness equal to 0.135 in. and 0.25 in. will be considered, similar to those tested in the prior experiments. The pipes contain welded lap joints with single and double weld and are pressurized first to a certain level (up to 50% of yield pressure) and subsequently, they are subjected to either axial compression or bending, well into the plastic regime of the steel material. The numerical results are used for elucidating some interesting issues of welded lap joint behavior under severe axial and bending deformation, allowing for determining the ultimate load deformation capacity of those joints in geohazard and seismic areas, where severe ground-induced actions are expected, towards minimizing the risk of failure.