Seismic behavior of slender reinforced concrete walls

Abstract

Residential reinforced concrete buildings performed well during the 2010 Mw 8.8 Maule, Chile earthquake.However, brittle damage was observed in reinforced concrete structural walls. The most frequentobserved damage in such walls was crushing of concrete due to flexural-compressive interaction,buckling and fracture of longitudinal reinforcement, and opening of the horizontal reinforcement. Themain objective of this study is to understand the observed damage in slender walls after 2010 Mauleearthquake and to reproduce and analyze experimentally the seismic behavior of such walls. The secondobjective is to provide recommendations to estimate the lateral displacement and the effective stiffnessof slender walls. To achieve these objectives, six ½-scale slender reinforced concrete walls were testedusing a conventional quasi-static cyclic incremental lateral displacement test protocol with a constantaxial load. The test results are compared to a reference wall tested previously in the same researchproject. The variables analyzed in this study are: wall thickness, wall aspect ratio, use of uniformly distributedvertical reinforcement, detailing of 135-degree hooks for the horizontal reinforcement, additionof closed stirrups in the wall boundaries, and addition of transverse cross-ties. The observed damage inthe tested walls was similar to that observed in walls of buildings damaged during the 2010 Maule earthquake.The behavior of the tested walls was dominated by bending due to their relatively large aspectratio. The failure, determined by the loss of ability to carry axial load, occurred suddenly as a compressionfailure along the entire cross section at the base of the tested walls. Test results showed that a 25%reduction in wall thickness reduced the ultimate displacement capacity, ductility, and energy dissipationability of the wall. Closed stirrups and cross-ties were effective in increasing displacement capacity andductility, and closed stirrups were effective in preventing out-of-plane buckling of the wall after compressionfailure. The average effective stiffness ratio of the tested walls was 0.39, which is slightly largerthan the ACI 318 suggestion of 0.35.