UC San Diego

To date, experimental studies have illustrated that foundation rocking can advantageously provide an isolation mechanism, dissipating energy, and re-centering of building-foundation systems. It is hypothesized that by balancing the beneficial attributes of foundation rocking and inelastic structural behavior (structural fuse), a building-foundation system's seismic performance can be significantly improved. This dissertation validates this hypothesis from three distinct, yet complementary aspects. The first two involve a pair of system-level experiments focused on low-rise moment-resisting frame and frame-wall structural systems at centrifuge scale, while the last is completed via numerical analyses. For each of the test programs, three fundamental model configurations were constructed considering the strength difference between the rocking foundation and the structural fuse, namely; Structural Hinging Dominated (SHD), Foundation Rocking Dominated (FRD), and Balanced Design (BD) models. All model specimens were subjected to a sequence of earthquake loading. Experimental results indicate that the SHD models consistently observe the largest building residual drifts and peak roof accelerations, while the FRD models consistently observe the largest footing settlement. The BD models, however, are able to recover and report negligible residual displacements. Importantly, dissipated energy is well distributed amongst the structural fuses and the rocking footings in the BD systems. The frame-wall system test also highlights the significant impacts of seismic-induced axial load variation and building asymmetry on seismic performance. With the rocking wall placed at the far end of the lateral load resisting path, loading towards the strong (wall) direction dramatically reduces axial load on the interior rocking footing. This reduction leads to a highly asymmetric footing moment- rotation hysteresis with a "bend-over" behavior. Moreover, system-level load-carrying capacity varies significantly between the weak and strong directions. In the final phase of this research, two parameters, defined as the energy dissipation ratio (R/ED) and the re-centering ratio (R/RC), are proposed to quantify the ability of an inelastic system to dissipate hysteretic energy and to recover from large amplitude transient displacements, respectively. The relation between the R/ED and R/RC is investigated by numerically studying a variety of simplified inelastic systems under cyclic loading. Results of these analyses indicate that balancing the strength between the rocking foundation and the structural fuse allows the hybrid system to benefit from the positive attributes of each inelastic mechanism, further substantiating findings from the test programs