PhD Oral Exam - Armin Farahbakhshtooli, 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 in low- to high-rise buildings as the lateral load resisting system. Most commonly used SPSWs in multi-storey buildings are unstiffened, stiffened, and composite SPSWs. Unlike unstiffened SPSWs, very little research has been conducted to assess the seismic performance of stiffened and composite SPSWs. The stiffened and composite SPSWs have been proved to provide higher level of ductility due to the fact that they can prevent the buckling of thin infill plate, while increasing the initial stiffness and energy absorbance capacity of the whole system. The objective of current study is to assess the seismic performance and collapse capacity of stiffened and composite SPSWs. In the current research work, two types of composite SPSWs (traditional and innovative) are considered. In innovative composite SPSW, there is a small gap between reinforced concrete (RC) panel and surrounding boundary members, while in traditional one, RC panel is in direct contact with surrounding boundary members. In the first step, a reliable macro-modelling approach was developed for each type of SPSWs considered in this study. The validity of the proposed macro models was then investigated against available experimental data. Several multi-storey stiffened and composite SPSWs were designed according to CSA S16-14 and NBC 2015. To estimate the seismic response parameters (i.e., ductility-related force modification factor and overstrength-related force modification factor) for designing stiffened and composite SPSWs, nonlinear static pushover analysis and incremental dynamic analysis (IDA) have been performed on all archetypes using OpenSees following the procedure presented in FEMA P695. Quantification of seismic parameters of stiffened and composite SPSWs, including period-based ductility, overstrength, and collapse margin ratio has been conducted to better understand the seismic response and collapse capacity of the SPSW system. The results showed that all archetypes provide significant safety margin against collapse (large collapse margin ratio values) and satisfy the requirements of FEMA P695. Seismic response sensitivity of traditional composite SPSWs to the variation of post-yielding parameters (i.e., ductility capacity and post-cap stiffness ratio) in infill plate and variation of post-cracking parameters (i.e., shear strain correspond to maximum shear stress, yielding shear strain, and residual stress) in shear behavior adopted for RC panel are further investigated. The study showed that the capacity of composite SPSW is more sensitive to the variation of post-yielding parameters of the infill plate, while the variation of post-cracking parameters of the concrete panel has a minor effect on overall performance of the composite SPSW system.

Steel plate shear wall with regularly spaced circular perforations has recently been developed. While the current edition of AISC 341-16 and CSA S16-14 have adopted perforated SPSW in their design standards, no simple numerical model is currently available for this SPSW system. In this study, a reliable macro-modelling approach was developed for regularly spaced circular perforation and was validated against available experimental results. Nonlinear seismic response of perforated SPSWs was studied through conducting a series of time history and incremental dynamic analysis to better understand the overall performance of the system when subjected to strong ground motions.