Numerical analysis of simply supported two-way reinforced concrete slabs under fire

The response mechanism of simply supported two-way reinforced concrete (RC) slabs under fire was numerically studied from the view of stress redistribution using the finite element software ABAQUS. Results show that: (1) Simply supported two-way RC slabs undergo intense stress redistribution, and their responses show four stages, namely elastic, elasticplastic, plastic and tensile membrane stages. There is no cracking in the fire area of the slabs until the tensile membrane stage. (2) The inverted arch effect and tensile membrane effect improve the fire resistance of the two-way slabs. When the deflection is L/20, the slab is in an inverted arch effect state, and the slab still has a good deflection reserve. The deformation rate of the slab in the tensile membrane stage is smaller than that in the elastic-plastic and plastic stages. (3) Fire resistance of square slabs is better than that of rectangular slabs. Besides, increasing the reinforcement ratio or slab thickness improves the fire resistance of the slabs. However, an increase of cover thickness has little effect on the fire resistance of two-way slabs. (4) Compared with one-way slabs, the time for two-way slabs to enter the plastic and tensile cracking stage is postponed, and the deformation rate in the plastic and tensile cracking stage is also slowed down. (5) The simply supported two-way RC slabs can satisfy with the requirements of a class I fire resistance rating of 90 min without additional fire protection.