Optimal energy dissipation ratio of base-rocking walls

Abstract

Base-rocking walls (BRWs) were excellent in maintaining enhanced post-earthquake serviceability and decreasing repair costs and downtime. However, little research has been aimed at finding the optimal range of energy dissipation ratio for designing BRWs. In this study, an approach was developed first for designing BRWs to obtain an intended level of energy dissipation capacity. Using the proposed approach, fifteen BRWs with different heights (i.e., 16, 25.6, and 38.4 m) and energy dissipation ratios (i.e., 0, 0.25, 0.50, 0.75, and 1.00) were designed and modeled using experimentally validated numerical models. Conducting nonlinear time history analyses using far-field (FF), near-field no-pulse (NFnP), and pulse-like (NFP) ground motions, the walls’ response features (RFs), including residual and transient lateral drifts, story acceleration, energy dissipation capacity, post-tensioning (PT) tendons strain, and structural demand were estimated and compared to the existing criteria. Proposing a desirability index (DI), the extent of criteria exceedance for the walls RFs was investigated to find the optimal range of energy dissipation ratio. The results showed that the walls designed by the developed approach could achieve the pre-assumed energy dissipation capacity. Increasing the energy dissipation ratio increases the lateral residual drift while decreasing the transient lateral drift, PT tendon strain, and wall demand. Increasing the wall height increases dissipated energy, exacerbating the adverse effects of higher modes while decreasing PT tendon strain. The obtained residual and transient drifts and PT tendon strain for NFP records are higher than those for FF and NFnP records. Moreover, the peak moment occurred at the lower wall height for NFP records. The adverse effects of higher modes are more evident in FF records. In general, for designing BRWs, the optimal energy dissipation ratio range was 0.50–0.75.