Experimental studies on continuous reinforced concrete slabs under single and multi-compartment fires with cooling phase

Abstract

This paper experimentally investigates the effect of number and position of heated compartments on the fire behaviour of continuous reinforced concrete slabs. A total of five continuous three-span slabs are tested under single compartment fire, two-compartment fires and three-compartment fires. The measurements involve furnace temperatures, slabs’ temperature, displacements, restraint forces, cracks and failure modes. The results show that the cracking pattern, displacement and reaction force of continuous slabs greatly depend on the furnace temperature, the position and number of heated compartments. Transverse cracks and short cracks appear on the top and bottom surfaces of the heated compartments, respectively, and the number of cracks increases with increasing heated compartments. The heated middle compartment or the unheated edge compartments may experience upward or downward deflections. Explosive concrete spalling is observed in the tests, which affects the failure mode of slabs and water evaporation from the unexposed surface. The selection of the worst fire scenario depends on the furnace temperature, the layout of heated compartments and concrete spalling. The conventional failure criteria (temperature or deflection failure criteria) can result in conservative or unconservative predictions of fire resistance of continuous slabs, which should be improved to include the favourable effect of structural continuity.