Ultimate bearing shear strength of cold-formed steel members using bolted connections at elevated temperatures

The external columns of frames are usually protected against fire, the design requirement being, after failure of the joints or beams, that the columns must remain upright to prevent spread of fire to an adjacent building or compartment. To prevent collapse of the columns, the bolt-group must be designed to have sufficient shear strength to resist the tensile forces that result from the ensuing catenary action. Whilst experimental investigations at ambient temperature into the ultimate shear strength of cold-formed steel members using bolted connections have been described in the literature, no consideration has been given to the behaviour of such connections at elevated temperatures. This paper describes non-linear elasto-plastic finite element parametric studies into the effects of elevated temperatures on the shear strength bolted connections between cold-formed steel members. The numerical results illustrate how the shear strength of the bolt-holes is affected by elevated temperatures, from which design recommendations for the bearing shear strength of the bolt-hole at elevated temperatures are proposed.