An advanced computational method incorporating the stability functions and the distributed plasticity model into the fiber beam-column element is proposed to predict the nonlinear inelastic thermo-mechanical behavior of steel frames subjected to fires. The element stiffness matrix is integrated via the Gauss-Lobatto numerical integration scheme, whereas the geometric nonlinearity of P- and P- effects are considered by using the stability functions and a geometric matrix, respectively. A nonlinear thermal incremental-iterative solution scheme based on the Newton-Raphson algorithm is also developed to address the nonlinear problems due to thermal expansion and material degradation. The reliability and accuracy of the proposed program are verified by comparing the obtained results with results from test data, existing studies, and results obtained from the Abaqus. The obtained results proved that the proposed method is exact and it significantly improves the computational performance. Therefore, it would offer a new tool for the practical design of steel frames under uniform fires.
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