Component-based models of beam-column joints exposed to fire in steel framed structures against progressive collapse

This paper is supplementary research following the previous experimental and numerical studies on the progressive collapse behaviors of beam-column substructures with different joint configurations under middlecolumn removal scenarios induced by fire. The component-based models (CBMs) of beam-column joints exposed to fire, which include the welded web-welded flange (WW) joint, as well as the bolted web-welded flange (BW) joint, were proposed based on refined FE models established in previous studies. Subsequently, the proposed CBMs with detailed spring arrangements and constitutive parameters were incorporated into the ABAQUS software to validate the collapse responses of beam-column joints obtained from both test results and refined solid FE models. A comparison investigation with experimental data indicates that the proposed CBMs can accurately reflect the nonlinear collapse behaviors of different fire-exposed beam-column joints with relatively high computational efficiency. Moreover, the validated CBMs are further incorporated into the collapse analysis of a multi-story planar steel framed structure exposed to fire, by compiling the VUSDFLD subroutine, to realize the component deletion process. The parameter effects of fire location, joint configurations, and loading ratios on collapse behaviors and force redistributions of framed structures exposed to fire were investigated. Based on analysis results, it is shown that the component failure temperature is quite sensitive to whether the specific joint configurations are considered in the analysis of fire-resistant progressive collapse in planar framed structures, which should be paid sufficient attention to in the performance evaluation of collapse resistance. For those planar framed structures with larger loading ratios, it is recommended to increase the section of the frame column or carry out fire protection to prevent the progressive collapse of the structure.