PhD Oral Exam - Abdelrahman Abdallah, 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

Reinforced masonry shear walls (RMSWs) are vital for lateral stability of reinforced masonry (RM) structures, especially in seismic-prone regions. These walls are classified as fully grouted (FG), partially grouted (PG). While fully grouted reinforced masonry shear walls (FG-RMSWs) offer high strength and stiffness, making them ideal for high-seismic zones, partially grouted reinforced masonry shear walls (PG-RMSWs) present a cost-effective alternative that balances performance and economy, by reducing the number of grouted cells in RMSWs. However, PG-RMSWs are primarily used in low-rise RM buildings due to limited research about their seismic behavior in mid- and high-rise RM structures. This research aims at investigating the in-plane quasi-static and dynamic responses of flexure-dominated RMSWs, including the effects of grouting (PG vs FG), cross-sectional configurations (rectangular and with boundary elements (BEs)) and shear reinforcement configurations (bond beam reinforcement (BBR) vs bed joint reinforcement (BJR)), with the goal of optimizing the CSA S304 seismic design provisions and extending the application of RMSWs in mid- and high-rise RM buildings.

The research is divided into two phases. Phase I, “Shear and Flexural Behavior Enhancement of RMSWs,” focuses on experimental testing of flexural-dominated PG-RMSWs under quasi-static cyclic loading, as well as testing of masonry wallets (assemblages) under diagonal tension (shear) loading. Two PG-RMSWs having the same aspect ratios, axial stresses, and flexural capacities, but with different cross-sectional configurations (rectangular and with BEs). In addition, 34 masonry assemblages and 40 masonry prisms with different mortar and grout strengths and reinforcement configurations were tested to evaluate the effect of the test parameters on the shear and compressive behavior of concrete masonry. The results show that PG-RMSWs with bed joint reinforcement exhibited ductile behavior, a significant energy dissipation, and an improved shear strength and ductility. These findings underscore the potential of using PG-RMSWs in mid-rise RM buildings and could inform updates to the seismic design provisions in the Canadian Standards for Design of Masonry Structures (CSA S304).

Phase II involves two numerical studies, focusing on the investigation of the lateral cyclic response of RMSWs subjected to quasistatic and dynamic Loadings. The numerical models of FG- and PG-RMSWs were developed using the Applied Element Method (AEM) adopted in the Extreme Loading for Structures (ELS) software to simulate and analyze the behavior of the studied walls under dynamic and quasistatic loading conditions. FG-RMSWs with boundary elements were analyzed using Eastern Canada earthquake records to assess stiffness, ductility, and seismic force modification factors (R_d and R_o). Moreover, a comparison of PG-RMSWs with BBR or BJR and FG-RMSWs with various cross-section configurations, aspect ratios and axial stress levels were also conducted. The numerical results reveal that PG-RMSWs exhibited comparable ductility and drift capacities to FG-RMSWs, achieving up to 41% material savings for rectangular walls.

The experimental and numerical results of this research highlight the necessity of revisiting the partial grouting seismic design provisions as well as the shear strength equation of FG and PG masonry in CSA S304. This research represents a significant step toward a more economical use of PG-RMSWs in mid- and high-rise RM buildings, thereby encouraging their wider adoption in performance-based seismic design of structures.