An empirical component-based model for high-strength bolts at elevated temperatures

High-strength structural bolts are used in nearly every steel beam-to-column connection in typical steel building construction practice. Thus, accurately modeling the behavior of high-strength bolts at elevated temperatures is crucial for properly evaluating the connection capacity, and is also important in evaluating the strength and stability of steel buildings subjected to fires. This paper uses a component-based modeling approach to empirically derive the ultimate tensile strength and modulus of elasticity for grade A325 and A490 bolt materials based on data from double-shear testing of high-strength 25 mm (1 in.) diameter bolts at elevated temperatures. Using these derived mechanical properties, the component-based model is then shown to accurately account for the temperature-dependent degradation of shear strength and stiffness for bolts of other diameters, while also providing the capability to model load reversal.