Shear Behavior of Superior High-Performance Steel Bolted Connections at Elevated Temperatures

With the maturity of production technology, a new type of superior high-performance (SHP) steel which combines high-strength, high-ductility, fire- and corrosion-resistance has been developed. However, there is no reliable design method for the typical bolted connections of this type of steel, which limits the further application in engineering. An experimental study on the shear behavior of 11 SHP steel bolted connections at elevated temperatures is carried out in this paper, considering the influence of different friction surface treatment methods. The test temperatures range from 20°C to 900°C, and the trend of slip load, ultimate load and failure mode with temperature is obtained. Based on test results and finite element simulation, a three-stage shear mechanism model for such bolted connections at elevated temperatures is proposed, and the bolt pretension and antislip coefficient at elevated temperatures is quantitatively modeled. Finally, a design method for this type of SHP steel bolted connections at elevated temperatures is proposed. The SHP bolted connection can be designed as a slip-critical type below 350°C but suggested to be designed as a bearing type due to the significantly decrease of pretension after the temperature exceeds 350°C. The existing formulas for bearing type capacities at room temperature are extended to elevated temperatures, and some configuration details and matching criteria are proposed to ensure an appropriate failure mode. The research in this paper is significant for improving fire design and optimizing material research and development.