EXPERIMENTAL STUDY AND THEORETICAL ANALYSIS ON THE RESIDUAL CAPACITIES OF FIRE-DAMAGED CONCRETE CONTINUOUS SLABS

To investigate the effect of traveling fire on the residual capacity of fire-damaged slabs, residual capacity tests of four fire-damaged concrete continuous slabs were conducted. The effects of the parameters, including the traveling fire scenario, reinforcement ratios and reinforcement layout, on the deflection, concrete and steel strains and failure mode of the continuous slabs were studied. In addition, the vertical shear force was considered. The tensile and compressive membrane action regions were proposed to determine the residual capacity of the fire-damaged slabs. For the limit residual capacity of each span in the fire-damaged continuous slabs, a comparative analysis was conducted based on different theories. The results show that several kinds of failure modes often appeared in the fire-damaged slabs, including the mid-span flexural failure, local punching shear failure, punching shear failure near the internal supports and flexural failure near the internal supports. Compared to the traveling fire scenario, the heating time, spalling, reinforcement ratio and reinforcement layout have more important influence on the residual capacities of the fire-damaged slabs. According to the deflection failure criterion, the present method can be used to determine the upper limit loads of fire-damaged slabs.