Effects of elevated temperatures on double shear bolted connections of thin sheet steels

The current design rules of double shear bolted connections in the North American and Australian/New Zealand specifications for cold-formed steel structures are mainly based on the design rules of single shear bolted connections. The design rules may not be applicable for elevated temperature conditions because the design rules of single shear bolted connections were based on tests conducted at ambient temperature. A total of 153 double shear bolted connection specimens were tested, where 102 specimens were tested using a steady-state test method and 51 specimen tests were conducted using a transient-state test method. Three thicknesses of thin sheet steel were used in the investigation. The connection strengths obtained from the tests were compared with the nominal strengths calculated from the North American, Australian/New Zealand, and European specifications for cold-formed steel structures. The current modification factor in the bearing strengths calculation for double shear bolted connections was evaluated at an ambient temperature. The reduced tensile strengths of the thin sheet steels obtained from tensile coupon tests at elevated temperatures were used to calculate the nominal strengths of the connections. It is shown that the strengths of the double shear bolted connections predicted by the three specifications are generally conservative at elevated temperatures. Five failure modes were observed in the tests: bearing, tear-out, net section tension, bolt shear, and material. © 2013 American Society of Civil Engineers.