PhD Oral Exam - Omar Elmeligy, 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

Partially grouted reinforced masonry shear walls (PG-RMSWs) have emerged as an efficient and economic seismic force-resisting system (SFRS) in North America. In PG-RMSWs, grout is only placed in cells with vertical reinforcement and horizontally reinforced bond beams. Despite the economic benefits of PG-RMSW systems in low-rise buildings, using such a system in mid- and high-rise buildings is still questionable. This research aims to evaluate and quantify the in-plane cyclic response of slender rectangular and flanged PG-RMSWs failing in flexure. This includes re-evaluating the TMS 402/602-22 and CSA S304-14 seismic design provisions for such types of walls and recommending changes to relevant standards’ clauses. In addition, methods to enhance the behavior of PG-RMSWs failing in flexure are recommended.

Accordingly, this research is divided into two main phases. Phase I, titled “Enhancement of the behavior of slender PG-RMSWs failing in flexure,” involves conducting a detailed numerical sensitivity analysis for a group of rectangular PG-RMSWs failing in flexure and subjected to quasi-static lateral cyclic displacement and constant axial load. This sensitivity analysis was conducted employing a validated simplified micro-model using VecTor2 software. This sensitivity analysis acts as a step towards acknowledging the most influential parameters that can be enhanced to obtain a better seismic response of PG-RMSWs. Afterward, experimental characterization of the compression and shear behavior of masonry constructed with polyvinyl alcohol (PVA) fiber-reinforced mortar and grout was conducted. This aims at improving the mechanical properties of masonry, which shall result in improving the PG-RMSWs' seismic behavior. Phase II, titled “Experimental and numerical investigation of North American Standards for the design of slender rectangular and flanged PG-RMSWs failing in flexure,” involves experimental investigation of the in-plane cyclic response of flanged PG-RMSWs failing in flexure by testing two walls with different shear span-to-depth ratios under constant axial stress and quasi-static cyclic loading. In addition, a new simplified micro-model was developed to simulate the quasi-static cyclic behavior of PG-RMSWs, using Extreme Loading for Structures (ELS) software. This model was then employed to conduct a comprehensive numerical assessment of the seismic design provisions of TMS 402/602-22 and CSA S304-14 for slender rectangular and flanged PG-RMSWs failing in flexure.

According to the work done in Phase I, the numerical sensitivity analysis revealed that ungrouted masonry properties are the most influential parameters on the behavior of the investigated PG-RMSWs. This effect is more evident for short walls and walls with large reinforcement spacings. This also concludes that the seismic behavior of PG-RMSWs can be enhanced by improving the grouted and ungrouted masonry properties. Afterward, the experimental investigation of PVA-reinforced masonry revealed that using PVA fibers in mortar and grout can be a promising approach to enhance masonry properties. Accordingly, PVA-reinforced masonry can be utilized to enhance the seismic behavior of PG-RMSWs.

The experimental work performed in Phase II reveals that increasing the shear span-to-depth ratio enhances the behavior of slender flanged PG-RMSWs failing in flexure. This shall participate in the supporting evidence that PG-RMSWs can perform well in mid- and high-rise masonry buildings. In addition, the numerical work performed in Phase II shows that CSA S304-14 and TMS 402/602-22 can be safely used to design slender PG-RMSWs only when using the proposed provisions for each standard. For CSA S304-14, the possibility of updating clause 16.8.5.2 is concluded, allowing the use of PG-RMSWs without limitations. New R values were proposed for TMS 402/602-22 to design slender rectangular and flanged PG-RMSWs.

This research acts as a step forward to prove the applicability of using PG-RMSWs in mid- and high-rise reinforced masonry buildings. In addition, the research proposes modifying some seismic design provisions to allow for more economical and safe usage of such a system.