Fire behavior and resistance of partially encased and slim-floor composite beams

In this study, fire behavior and resistance of unprotected H-section, partially encased (PE), and slim-floor (SF) composite beams were experimentally and numerically investigated under standard fire condition. Experimental results of this study showed that unreinforced or reinforced PE beams and reinforced SF beams can achieve the standard fire resistance of 2 hours or more up to the load ratio of about 0.30. The use of fire reinforcements in SF composite beams was shown to be very effective in increasing the fire resistance time. It was again confirmed that the maximum and average temperature criteria can significantly underestimate or overestimate the realistic fire resistance of PE and SF composite beams. The test-validated coupled thermal-stress analysis indicated that the fire resistance predicted by the bending moment capacity criterion alone can be unconservative for the types of composite beams of this study. It is emphasized that the deflection-related criteria should be considered for the rational fire resistance rating of PE and SF composite beams.