Elevated temperature performance of restrained stainless steel beams

This paper reports the results of a numerical investigation into the response of axially restrained austenitic stainless steel beams in fire, where in addition to the degradation of strength and stiffness at elevated temperatures, the influence of thermally induced stresses, are also included. The finite element (FE) programme ABAQUS has been used to model austenitic stainless steel welded I-section beams of different axial end restraint stiffness subjected to fire. The FE models are firstly validated against a selection of literature test data, which are shown to accurately capture the effects of restrained thermal deformations with a high degree of accuracy, and then used to perform parametric studies to further explore the structural behaviour in fire. A simplified analytical model for predicting the restraint axial force-temperature response is presented and validated against the numerically obtained results. The numerical models and the simplified analytical model allow the influence of frame continuity to be explicitly considered in design of stainless steel members in fire to quantify the required strength and ductility demands on connections for catenary action to develop. Comparisons with carbon steel beams demonstrate that while austenitic stainless steel beams show similar stages of behaviour in fire, they are capable of withstanding higher temperatures prior to the onset of catenary action, while developing similar levels of maximum tensile catenary force to carbon steel beams, despite the higher thermal expansion of the material.