The influence of circumferential weld-induced imperfections on the buckling of silos and tanks

Abstract The load carrying behaviour of cylindrical thin-walled shell structures under axial load is strongly dependent on imperfections invariably caused by various manufacturing processes. Axisymmetric imperfections have been known to result in particularly severe reductions in strength. Imperfections in the vicinity of circumferential welds in steel silos and tanks fall into this category and therefore deserve special attention. A detailed bifurcation and post-buckling finite element analysis was performed on imperfect cylindrical shells. Special care was taken to model the weld-induced circumferential imperfection. The geometry was calibrated against data gained from measuring such imperfections on existing silos and residual stresses were taken into account. Interaction between neighbouring weld imperfections and the role of the strake height in this interaction was investigated. Weld-induced residual stresses were found to have a small strengthening influence on the buckling load. Interaction between neighbouring imperfections was found to reduce the buckling strength of the structures. A post-buckling analysis was undertaken and an explanation of the load-carrying behaviour of the structure after initial bifurcation was given.