Numerical simulation and effect of curling on bolted connections in cold-formed stainless steel

Finite element (FE) model with three-dimensional solid elements is established for investigating the structural performance of bolted connections loaded in static shear with cold-formed stainless steel (austenitic steel; SUS304) plate, based on the existing test data performed by Kuwamura et al. for calibration. From the experimental results, modifications of current Japanese steel design standards for calculating the ultimate strength to account for the mechanical properties of stainless steel and thin-walled steel plates were made. However, curling, i.e., out of plane deformation in connection plate ends with a long edge distance was observed, and led to the strength reduction of bolted connections. In this study, non-linear material and non-geometric analysis are carried out in order to predict the load-displacement curves of bolted connections. Therefore, finite element analysis results are compared with previous experimental results, failure modes and ultimate strengths predicted by recommended procedures of FE method show a good agreement with those of experimental results and it can be also found that curling which occurred in test specimens is also observed in FE model. Failure criterion, which predicts failure mode of bolted connections and curling criterion are proposed considering the stress distribution at the region where initial crack may occur. In addition, influence of curling on the strength reduction is estimated quantitatively and change of in-plane stress of connection plate is investigated according to the advancement of curling.