Strength criteria for bolted connections at elevated temperature

•The failure mechanism of bolted connections under fire conditions was examined.•The current AISC strength models are evaluated for the usage at elevated temperature.•A 3d end distance is recommended to avoid end tear-out at elevated temperature.•A new model is proposed to determine the bearing strength at elevated temperature.•Reduction factor U for shear lag effect is needed to determine the bearing strength.

Based on the experimental results, this study investigates the feasibility of applying the current AISC strength equations for bolted connection at elevated temperature up 650 °C to prevent the structures from sudden collapses in fire events. Numerical analysis was also carried out to examine the stress distribution characteristic at bolt hole. Based on the results of this study, the connection with 1.5d end distance most likely would fail as tear-out at elevated temperature. Tear-out failure can be prevented by increasing the end distance to 3d. Therefore a minimum end distance of 3d in practical application is strongly recommended. In this study it is also found that the strength determined upon AISC current equations is under estimated at elevated temperatures. While the strength of bolted plate increases linearly with both the end and the edge distances up to certain limit, a new model for bearing strength is proposed with the combined effect of the end and the edge distances. In addition, the reduction factor of the shear lag effect in AISC for tensile fractural strength should be adopted to determine the bearing strength at elevated temperatures.