Experimental and numerical studies on flat slab-column joint exposed to fire considering slab boundary conditions

Abstract

Reinforced concrete flat slab-column structures have been widely applied in building construction. However, this type of structure has been reported to exhibit high vulnerabilities under fire conditions. This study investigated the fire resistance of flat slab-column structures through experimental and numerical studies, considering the effect of slab boundary conditions. Two full-scale slab-column joint specimens were designed to conduct a fire resistance test and a full process fire test. Large reinforced concrete beams surrounding the slab were constructed to apply a fixed constraint to the edges of the slab, mimicking the slab boundary in practice. Water evaporation, crack development, and concrete spalling were recorded to facilitate the exploration of the failure mechanism. Detailed analysis of the thermal and mechanical responses revealed that adding the slab boundary, specifically axial restraint, would cause severe concrete spalling and significantly reduce fire resistance. Post-fire tests showed that 50% of the load-carrying capacity had been lost, even though the slab was only exposed to fire for half an hour. Finite element models considering the concrete spalling observed in the fire tests were established. The simulation results, including the temperature, deflection, and load-carrying capacity, coincided with the test results.