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

The load carrying behaviour of cylindrical thin-walled shell structures und er axial load is strongly dependent on imperfections invariably caused by v arious manufacturing processes. Axisymmetric imperfections have been known to result in particularly severe reductions in strength, Imperfections in t he vicinity of circumferential welds in steel silos and tanks fall into thi s category and therefore deserve special attention. A detailed bifurcation and post buckling finite element analysis was performed on imperfect cylind rical shells. Special care was taken to model the weld-induced circumferent ial imperfection. The geometry was calibrated against data gained from meas uring 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-induc ed 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 analysi s was undertaken and an explanation of the load-carrying behaviour of the s tructure after initial bifurcation was given, (C) 2001 Elsevier Science Ltd . All rights reserved.