Resilient self-centering steel plate shear walls
Dowden, Daniel Mal Bok
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Conventional lateral force resisting systems (LFRS) that comply with current building codes typically are designed for collapse prevention for a design level earthquake. Accordingly, significant structural damage is expected, leading to large residual drifts where yielded elements are difficult to repair or replace. Consequently, after a design level earthquake, demolition of the building may be required due to severe structural damage. An innovative self-centering steel plate shear wall (SC-SPSW) is proposed. The objective is to offer enhanced structural performance beyond conventional lateral systems by providing frame recentering and also to minimize structural damage of gravity frame components of the LFRS. The SC-SPSW combines the advantages of high initial stiffness and substantial energy dissipation provided by SPSW infill web plates, provides frame self-centering capability through the use of post-tensioned (PT) rocking frame joint connections, and concentrates hysteretic energy dissipation to replaceable infill web plates. In doing so, the SC-SPSW is intended to recover to its near pre-earthquake condition, after a moderate to significant earthquake, decreasing life-cycle costs. To investigate and validate the behavior of the SC-SPSW system, an experimental program of one-third scaled single-bay three-story frames was developed and conducted, consisting of quasi-static cyclic and dynamic shake-table testing. SC-SPSWs detailed with three different beam-to-column rocking joints were investigated. A final complementary test was performed at the National Center for Earthquake Engineering in Taiwan, where a full scale single-bay two-story specimen was subjected to an earthquake excitation loading using the pseudo-dynamic testing method. The experimental results show that SC-SPSWs systems can be a viable LFRS appropriate for buildings in regions of high seismicity. Furthermore, to assist in the design of SC-SPSWs, fundamental knowledge on the kinematics of SC-SPSWs through detailed free body diagrams are established, from which validated closed-form equations describing beam strength demands, tensile strain demands on the infill web plate, and unrestrained PT boundary frame expansion (aka beam-growth) of frames with PT rocking connections are provided in a form suitable for use as design tools.