Fire resistance of stainless steel single shear bolted connections

This paper presents a numerical investigation on single shear bolted connections of cold-formed stainless steel (CFSS) at elevated temperatures. A finite element model (FEM) is developed and verified against the existing single shear bolted connection tests. It is shown that the FEM is able to predict the test strengths and failure modes of the bolted connections. Therefore, the verified FEM was used to perform a parametric study of 225 CFSS single shear bolted connections at 5 different temperature levels. Based on both the test and numerical results, two sets of bearing factors are proposed for the bearing strengths of CFSS single shear bolted connections at elevated temperatures by considering the equivalent plastic strains in the bolt hole and the bolt hole deformation. The connection bearing strengths obtained from the tests and numerical analyses were compared with the nominal strengths calculated using the current international stainless steel specifications. In this study, modified design rules are proposed. In calculating the nominal strengths of the bolted connections, the reduced material properties of CFSS were used due to the effects of elevated temperatures. It is shown that the predictions provided by the modified design rules are more accurate than the predictions provided by the current design rules for bearing strengths of CFSS single shear bolted connections at elevated temperatures. Reliability analysis was also performed to assess the reliability of the current and modified design rule.