AN ENERGY METHOD FOR CALCULATION THE LOAD-CARRYING CAPACITY OF TWO-WAY SLABS WITH TWO EDGES SIMPLY SUPPORTED AND TWO EDGES CLAMPED IN FIRE

Fire-resistant experiments were conducted on two full-scale reinforced concrete two-way slabs with two edges simply supported and two edges clamped. This paper presents the design of the furnace and specimens, the test plan, the measuring contents and methods. The test phenomena, cracking and failure characteristics of the tested reinforced concrete two-way slabs were described. The temperature distribution along the depth of the slab, vertical deflection and horizontal displacement have been studied. Internal force redistribution of the clamped edges has been analyzed. The results indicated that the cracks on the unfired side of the slab formed a semielliptical pattern. Based on the experimental results, a new energy method for the limit load-carrying capacity calculate of concrete slabs with two edges simply supported and two edges clamped in fire conditions was presented. The model assumed that the tensile membrane effect of the slabs showed only after the formation of plastic hinge lines, and was caused by the plastic work done by the reinforcement elongation at the yield line section. Comparison between the developed model and test results showed good correlation, while the classical energy method based on the yield line theory gave a conservative value.