Buckling behaviour of large steel cylinders with patterned welds

Steel silos and tanks are commonly constructed by welding together a large number of curved steel panels. The panels are first connected with short meridional welds to form circular strakes (or courses), which are then connected by continuous circumferential welds to form the entire shell wall. Associated with the large number of welds are welding-induced shrinkage deformations and residual stresses, both of which may have a significant effect on the buckling strength of the shell wall. In this paper, a simple method for the simulation of the weld depressions and associated residual stresses is first introduced. The results of a series of finite element buckling analyses of a typical steel cylinder with such simulated welding effects are next presented and discussed, leading to a number of significant conclusions. One of these conclusions is that a weld depression pattern produced using the present weld simulation method can offer a suitable equivalent imperfection form for use in the non-linear analysis of shells for stability design, as it leads to buckling loads in close agreement with predictions by the new European code for steel shell structures.