| This thesis investigates topics in soil-structure interaction (SSI) that are of direct concern to performance-based seismic design (PBD) of structures. SSI analysis is an integral part of PBD and the ease of its integration into the design process is linked to the availability of robust and efficient analysis tools. Therefore, the main objective of the study is to develop a beam-on-nonlinear Winkler foundation (BNWF) model that can be easily integrated into commercially-available nonlinear structural analysis software, and can account for various phenomena observed in SSI experimental studies. The thesis focused on: the role of SSI in the PBD procedure; cyclic degradation models for variable-amplitude loading; an analytical Winkler formulation of the monotonic moment-rotation behaviour of rigid foundations; and the development of a BNWF model for analyzing shallow and deep foundations. The developed model accounts for: soil cave-in effects; reduction in radiation damping with increased nonlinearity; and cyclic degradation of stiffness and strength due to variable-amplitude loading.; The BNWF model was used to analyze a wide range of SSI problems including field, centrifuge and laboratory experiments. The model is shown to be versatile, and suitable for applications involving performance-based seismic design of shallow and deep foundations. The predictions of the developed BNWF model were in good agreement with the measured results of the SSI experiments analyzed.; It was found that coupling between the horizontal and rotation-vertical responses of footings significantly influences the development of permanent horizontal displacements. This could be accounted for by employing distributed coupled normal-tangential force BNWF models. In addition, secondary moment (P-delta) effects are critical for problems involving large rotations and should be included in all soil-foundation-structure interaction (SFSI) analyses. It was found that soil cave-in decreased pile maximum moment, moved its point of occurrence closer to ground surface and increased hysteretic in energy dissipation. When plastic hinges develop below ground level, soil cave-in is beneficial as it increases the effective confinement of the plastic hinge, which spreads the curvature demand, and increases the effective length of the plastic hinge. For piles subjected to seismic ground motion, the accurate determination of the input free-field motion for soil-pile-structure interaction (SPSI) problems is more critical than the accurate determination of the BNWF model parameters.; Keywords. Soil-structure interaction, performance-based design, equivalent number of cycles, fatigue damage mechanics, shallow foundations, Winkler model, piles, cyclic, seismic, degradation. |
