PhD Oral Exam - Mahmoud Abdelrahman, 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

Dry-stacked interlocking masonry (DSIM), also referred to as mortarless masonry, is an innovative construction system that replaces conventional mortar joints with mechanical interlocking shear keys between adjacent concrete masonry units. By eliminating mortar, DSIM reduces construction time, labour requirements, and material consumption, making it an attractive solution for low-rise buildings and rapid post-disaster reconstruction. However, the absence of mortar introduces unique structural challenges, including initial seating deformation caused by gaps between adjacent units, stress concentrations, and reduced stiffness and strength compared with conventional masonry. Furthermore, the structural behaviour of DSIM under compression, monotonic in-plane shear, and cyclic loading has not been comprehensively quantified, and no Canadian design provisions currently permit its use as a structural load-bearing system. This thesis presents an integrated experimental and numerical investigation of the structural behaviour of the Sparlock DSIM system. It evaluates its suitability as an alternative to conventional concrete masonry for small buildings. The study comprises three parts. The first investigates the compressive behaviour of DSIM through experimental testing and validated three-dimensional finite element modelling, leading to the development of strength correlations, height correction factors, idealized stress–strain relationships, and recommended compressive design values. The second quantifies the in-plane shear behaviour of DSIM under monotonic and cyclic loading, evaluates the applicability of existing masonry design provisions, and proposes a new shear strength equation. The final part compares the structural performance of DSIM with conventional concrete masonry under comparable testing conditions. Conventional masonry exhibited higher strength and stiffness, whereas DSIM provided greater ductility and energy dissipation. However, increasing the grouting and reinforcement levels significantly enhanced the structural performance of DSIM. Overall, this research establishes a comprehensive experimental and numerical framework for the structural design of Sparlock DSIM and provides recommendations that support its future codification and practical implementation as a sustainable alternative to conventional masonry construction for low rise buildings.