Analysis of Structural Members under Elevated Temperature Conditions

Abstract

This paper presents a general numerical method to calculate the nonlinear behavior of load-bearing members under elevated temperature conditions. The method, although similar in concept to earlier approaches, differs with respect to both solution procedure and capability. The governing equations are formulated in a succinct format and an innovative iteration procedure is used to obtain the solution. The method can take into account the combined actions of axial force and biaxial bending, external restraints, temperature variation over the cross section and along the member, material nonlinearity, geometric nonlinearity, unloading and reloading, residual or initial stresses, and initial “out-of-straightness” of the member. It applies to members of any cross-sectional shape and with any elevated temperature stress-strain relationship for the material, including one with zero or negative slope. The application of the method is illustrated using a practical design example in which the fire resistance of an unprotected steel column of large cross-sectional area was evaluated.