Punching shear behavior of full-scaled reinforced concrete slab-column connection after cooling from fire-induced elevated temperature

Elevated temperatures caused by fire will deteriorate the behavior of reinforced concrete (RC) structures significantly. In addition, after cooling from elevated temperatures, RC structures will exhibit a significant reduction in load-bearing capacity due to material degradation and internal damage. Understanding the residual behavior of RC structure after fire is crucial for determining whether dismantling and repair strategies. However, limited studies have paid concern on the residual behavior of RC flat slabs after exposure to fire and subsequent cooling. To fill this research gap, a series of full-scale RC slab-column connections were fabricated and tested. The objective of the study was to assess the residual punching shear behavior of RC slab-column connections after cooling from elevated temperatures. The specimens were categorized into two groups based on the flexural reinforcement ratio of the slab: 0.55 % and 0.94 %. The test results show that, after cooling from elevated temperatures, RC slab-column connections with low reinforcement ratio experienced a shift in failure mode from flexural-punching failure to pure punching shear failure, which is quite dangerous in practice design. Furthermore, to improve the prediction of the residual punching shear capacity of RC slab-column connections after cooling from fire exposure, the Critical Shear Crack Theory (CSCT) model was modified by considering the deterioration of the material properties, reducing of the effective slab thickness and widening of the critical shear crack due to high temperature. By comparison of the analytical results with the test one, the proposed model demonstrated high accuracy with less discreteness. • Punching shear capacity of full-scale RC slab-column connection after cooling from elevated temperature was investigated. • Effects of elevated temperature on punching shear resistance of the connection were quantified. • Failure modes of the connections after cooling from elevated temperature were analyzed. • Analytical model to predict punching shear capacity and failure mode of the connection was proposed.