10.16: Behaviour of high‐strength bolts at elevated temperatures under double‐shear loading

Abstract

ABSTRACTDuring fire events, connections in steel structures may be subjected to large unanticipated deformations and loads. These fire effects can produce failures of connections, including local buckling of the connection zone, rupture of connection plates, shear rupture of bolts, and bolt tear‐out rupture of beam webs. Thus, a key issue in evaluating the response of structural systems to fire effects is the proper representation of material behaviour, including fracture, at elevated temperatures. Temperature‐dependent material behaviour of structural steel plates has been studied by many researchers, both experimentally and numerically. However, the behaviour of structural steel bolts at elevated temperatures, especially under shear loading, is not well established in the literature.This paper presents results from recently conducted tests of high‐strength structural bolts subject to double shear loading at elevated temperatures. The parameters varied between tests included the bolt grade, bolt diameter, and temperature. Bolt grades A325 and A490 were tested. For each bolt grade, three different diameters were tested (19 mm, 22 mm, 25 mm) at five different temperatures (20 °C, 200 °C, 400 °C, 500 °C, and 600 °C). Three tests were conducted for each combination of parameters. Degradation in the mechanical and material properties were characterized. In addition, a new component‐based model for high‐strength bolts was developed based on the experimental data. The component‐based model is shown to accurately account for the temperature‐dependent degradation of bolt shear strength and stiffness, while also providing the capability to model load reversal.