Out-of-Plane Behavior of Reinforced Concrete Bearing Walls after One-Sided Fire

摘要

This paper discusses measured out-of-plane lateral behavior of five full-scale planar reinforced concrete (RC) bearing wall specimens immediately after one-sided ASTM Ell 9 fire exposure as well as lateral behavior after unrestrained natural cooling. The specimens were fixed at the base and free to displace vertically and rotate at the top. A near-constant axial load representing tributary service-level gravity loading was applied at the top of each wall. The walls were subjected to slow-rate reversed-cyclic out-of-plane lateral displacements immediately after fire as well as after complete natural cooling. The tests immediately after fire revealed significant losses (as compared to ambient conditions) in the out-of-plane lateral strength of the walls both in the direction with the heated surface in compression and in the direction with the heated surface in tension. As the walls cooled, the heated regions contracted, resulting in a significant bow in the deflected shape-concave toward the furnace. The post-cooling lateral behavior with the heated surface in tension showed a considerable strength regain. Conversely, the post-cooling behavior with the heated surface in compression had further strength loss and increased bow in the out-of-plane deflected shape, which indicate that fire-induced out-of-plane instability of RC bearing walls can become more critical during and after cooling. It was also observed that through-thickness diagonal cracking from fire can result in shear-dominated out-of-plane lateral behavior of slender walls. Implications of these results for current RC building design are discussed.