Fracture behavior of high-strength bolts and connections in the whole process of fire

Abstract

High-strength bolts have been widely used in steel bolted connections, and fire-induced high temperatures will affect its basic mechanical properties and fracture behavior, leading to failure of the connection and even collapse of the overall structure. Tensile experiments are conducted on Grade 10.9 high-strength bolts to investigate the effect of stress triaxiality and heating history on their mechanical and fracture properties in the whole process of fire. The true stress-strain curves are obtained to determine the material properties. The SMCS fracture model is calibrated based on test results, and parametric studies are conducted on fracture performance of T-stub connections in fire. The experimental results show that the SMCS model can effectively predict the fracture behavior of Grade 10.9 high-strength bolts for a stress triaxiality range of 0.3 to 1.2. There are three failure modes of T-stub connections under different temperature histories: yield fracture of flange plate, simultaneous yield fracture of flange plate and bolt, and yield fracture of bolt.</p