Experimental Evaluation of Inelastic Higher-Mode Effects on the Seismic Behavior of RC Structural Walls

Abstract

Most midrise and high-rise reinforced concrete (RC) buildings rely on RC structural walls as their seismic force resisting system. The contribution of higher lateral modes to the elastic response of RC structural walls produces base shear forces significantly larger than those resulting from the static code procedure. The relative contribution of higher lateral modes increases due to an additional dynamic effect occurring while the RC wall is yielding at the base. Accordingly, the first-mode contribution saturates and reduces as its corresponding period elongates and higher modes assume a more relative contribution. This paper describes an original pseudodynamic hybrid test that has been used to experimentally measure the shear amplification during an earthquake excitation of a model shear wall structure. The experimental results show that the shear amplification factor due to nonlinear higher modes effects can be larger than 1.5. Additionally, the test results indicate that the modern structural codes appear to be conservative in calculating the shear force resistance of RC structural walls.