Finite-Element Reliability Analysis of Structures Subjected to Fire

A reliability-based design methodology is urgently needed in the fire resistant design of structures to ensure adequate reliability in the face of uncertainty. This paper presents the application of the analytical reliability methods, namely the first-order reliability method (FORM) and second-order reliability method (SORM), to the design of structures subjected to fire. In particular, the FORM and SORM algorithms are implemented in a sequentially coupled thermal-structural finite-element model. A protected steel column exposed to natural fire is presented as an example. In comparison to Latin hypercube sampling (LHS), the analytical reliability method yields sufficient accuracy and provides a significant saving in computational expense. Discrepancies between the analytical methods and LHS are analyzed in depth, and it is shown that the parametric fire model produces a response surface that is highly nonlinear. Despite differences between the FORM and LHS solutions, the utilization of FORM is recommended for the rapid estimation of the reliability of structures threatened by fire. (C) 2014 American Society of Civil Engineers.