Structural Failure of Reinforced Concrete Bearing Walls under Fire: A Full-Scale Experimental Investigation

Abstract

This paper describes the structural damage and failure observed during a full-scale experimental investigation on the out-of-plane behavior of seven planar reinforced concrete (RC) bearing walls under fire. The specimens were heated on one surface over half of the wall height through the ASTM E119 standard fire time-temperature curve, while simultaneously being subjected to a constant axial load at the top. The walls were fixed at the base and free to displace vertically and rotate at the top. In the out-of-plane lateral direction, the top of four specimens was restrained (representing a rigid floor slab), the top of one specimen was free (representing a compromised floor slab), and the top of two specimens was subjected to a step-wise increasing lateral load (to investigate the change in wall lateral stiffness during the fire). Catastrophic out-ofplane buckling failures of two walls occurred at fire durations much shorter than the resistance rating per Section 2.1 of ACI 216. The walls that did not fail during fire were subjected to slow-rate reversed-cyclic out-of-plane lateral displacements immediately after fire and after natural cooling. There were significant losses in the out-of-plane lateral strength of the walls during the fire, with additional losses occurring during natural cooling as well. It was also observed that through-thickness diagonal cracking from fire can result in shear-dominated out-of-plane lateral behavior and failure of otherwise slender walls. Implications of these results for current RC building design codes are discussed