Experimental investigation of post-fire seismic behavior of reinforced high-strength concrete shear walls

Abstract

Reinforced high-strength concrete shear walls (RHSCSWs) are widely used for lateral load-resisting systems in tall buildings. Due to the high possibility of explosive spalling of high-strength concrete under high temperature, the structural performance of high-strength concrete shear wall may be greatly reduced after fire, which should be paid attention to by the engineering community. In this study, the post-fire seismic performance of RHSCSWs was investigated. Twelve RHSCSW specimens were fabricated and tested under an ISO-834 standard fire. Thereafter, 10 of these specimens were subjected to an in-plane cyclic load to evaluate their post-fire seismic performance. The remaining two specimens were subjected to concentric axial loads because they were severely damaged by explosive concrete spalling in the fire. The investigated parameters of the specimens included the concrete strength, fire exposure condition (one-side or four sides), fire duration, aspect ratio, axial load ratio, surface mortar layer, and strengthening technique (i.e., whether an X-shaped steel brace was installed). Their fire and post-fire structural performances were carefully assessed. The concrete walls with a cube compressive strength of 75.8 MPa were prone to explosive spalling in fire, whereas the concrete walls with a cube compressive strength of 60.3 MPa were not. Moreover, concrete shear walls with surface mortar layers were more likely to experience explosive spalling in fire than walls without such layers. With increasing axial load ratio, the horizontal load-bearing capacities of the shear walls after the fire first increased and then decreased, with the critical value being in the range 0.2–0.25. The specimens damaged by explosive spalling retained considerable axial load-bearing capacities (i.e., 69 % of the sectional concrete compression-bearing capacity of the unfired wall).