ABSTRACT
Two qualitatively different approaches which may be applied to determine the stiffness of a steel beam-to-column joint subjected to thermal influence induced by direct fire action are compared in this paper. The first of these approaches is based on the appropriately generalized algorithm of the classical component method, while the second one is based on the numerical simulation of a three stage load application sequence. At the first stage of such simulation only the prestressing and gravitational loads are applied to the joint. In the subsequent step the joint is uniformly heated to the predetermined temperature value to simulate the fire action, while at the third and last stage the monotonously increasing statical load is applied to the heated joint until its destruction. A set of M – ϕ curves representing the relationship between the bending moment applied to the joint in fire conditions and the increase in the relative rotation angle between the column flange and the beam end-plate is obtained as the final result of both juxtaposed computational approaches and presented in enclosed figures.
