Simplified analysis method for catenary action of restrained cellular steel beams at elevated temperature considering strain reversal

A Simplified Analysis Method (SAM) for predicting catenary action of restrained Cellular Steel Beams (CSB) at elevated temperature, as an alternative of finite element method, was proposed in this paper. A finite element model was developed and validated by existing test results and numerical results first. The temperature distribution along the section height was assumed to be linear based on available research results. Then the simplified analysis method was developed based on equilibrium equations, constitutive equations and geometric equations. The approach considered non-uniform temperature, geometric non-linearity, material non-linearity, as well as strain reversal when calculating section stresses. A series of parametric study using verified numerical model were then carried out to assess the accuracy of the proposed method. It was found that the simplified method yielded results which agreed well with those obtained from Finite Element Analysis (FEA). A lower compressive force and catenary tension were predicted when the web at perforated section was not considered. And the ignorance of strain reversal in the SAM would lead to a larger deflection prediction. The simple approach could also be used to predict the behavior of the beam subjected to non-uniform temperature distribution across the section in the latter stage of a fire, which may not always be obtained from FEA due to convergence problem.