Abstract
This article describes the experimental and analytical results of tests on two medium-scale steel frames to investigate the collapse behavior of a heated interior column in steel-framed structures and the fire-induced collapse mechanism of the structures. Because the heated column in the structure was under realistic inelastic end constraints (inelastic effects from the surrounding cool structures) as opposed to an idealized column in a furnace, the tests were designed to investigate the effect of inelastic end constraints and different load ratios. The interior column subjected to fire in the first story was connected with a force-measuring bearing, which was developed to measure the axial force in the heated column. This article presents the observations and analysis results of structural fire behavior, including the temperature distribution of the column, the development of deflection and axial forces, and the column failure modes. The results show that the effect of realistic inelastic end constraint is not significant for the column behavior during the pre-buckling stage, compared with the elastic constraint, but it is significant during the post-buckling stage. An analytical model was adopted to analyze the behavior of the column with inelastic end constraint under fire. Comparison of the theoretical and experimental results shows that the simplified analytical model can be used to predict the collapse behavior of the interior column in steel-framed structures under fire.
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