UCLA

Significant structural damages (even collapses) have been observed in past earthquakes. Seismic protective devices and innovative structural systems can be used to improve the responses and post-earthquake serviceability. This study aims to derive the optimal design of protective devices for structures and evaluate the promises of rocking components to effectively improve the structural performance and mitigate the earthquake hazards. First, the hybrid simulation framework is adapted and validated to enable nonlinear structural control of inelastic structures with protective devices. The structure is modeled in OpenSees while the protective devices and control algorithms are modeled in MATLAB. Subsequently, guided by the actively controlled responses, the study provides different optimization procedures to identify the optimal design parameters of equivalent passive protective devices. Demonstrated by an eight-story inelastic building, the equivalent passive design yields much improved structural performance, comparable to actively controlled response. Second, the hybrid simulation scheme is further modified to incorporate multi-support excitations, often observed in bridges due to significant soil-structure interaction effects. The methodology is applied to a benchmark highway bridge where base isolation and supplemental energy dissipation are used. Active control algorithms (either linear or nonlinear) are implemented and optimal parameters for base isolators and damping devices are derived to mimic the actively controlled responses. The robustness of active controls and optimal passive controls is further demonstrated by comparing various control schemes under different bridge systems and motion inputs. Third, rocking components are evaluated as an innovative structural system that can be incorporated along with conventional lateral force resisting systems. Several numerical models are evaluated and improved to account for complex dynamic behavior of rocking components in flexible structures. A probabilistic seismic demand model (PSDM) is also proposed as an alternative way to capture the uncertainties in predicting individual rocking responses. A new finite element-based rocking model is implemented in OpenSees, which consists of a zero-length rocking element with a Dirac-delta type impact model. Finally, a nine-story rocking wall-frame building is designed and analyzed. Nonlinear time history analysis results demonstrated that both strength and deformation demands are reduced, and the structural damage is controlled when rocking motion is activated.