PhD Oral Exam - Mahtabsadat Razavi, Civil Engineering

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Steel plate shear walls (SPSWs) are commonly used as the lateral load resisting system in buildings in seismically active regions. In a conventional SPSW, the infill plate acts as the designated fuse, and yielding and tearing of the plate are irreversible, so residual interstorey drift remains after an earthquake. Self-centering and controlled rocking systems, which provide a restoring force and concentrate damage in replaceable components, have been proposed to address this limitation.

The objective of the current study is to assess the seismic performance, collapse capacity, and economic performance of self-centering and rocking SPSWs in which the lateral strength, energy dissipation, and restoring force are provided by separate components. Three configurations are considered: post-tensioned beam-to-column connections with perforated infill plates; a base-rocking wall with mid-bay post-tensioning and friction devices; and a low-damage wall with post-tensioning within the vertical boundary elements and elastic plates, confining inelastic demand to replaceable friction devices.

Macro models were developed in OpenSees and validated against available experimental data. A performance-based design procedure was developed for the rocking systems, and several multi-storey archetypes were designed according to CSA S16-19 and NBC 2020. Nonlinear static, nonlinear time history, incremental dynamic, and mainshock–aftershock analyses were performed following FEMA P695, and loss assessment was carried out following FEMA P58.

The results showed that all archetypes satisfy the requirements of FEMA P695. Post-tensioned beam-to-column connections reduced residual drift and demolition losses but lowered the peak strength and the collapse capacity. Relocating the rocking interface to the base removed this penalty, giving collapse capacities comparable to those of conventional walls together with a substantial reduction in residual drift. In the low-damage configuration, no yielding of the beams, columns, or infill plates was observed, and a response modification factor as high as 12 satisfied the FEMA P695 criteria. The study demonstrates that the seismic performance of steel plate shear walls is improved most effectively by relocating the inelastic mechanism out of the infill plate rather than by increasing system strength.