Date of Award
9-12-2024
Publication Type
Dissertation
Degree Name
Ph.D.
Department
Civil and Environmental Engineering
Keywords
Effective compression zone width;Effective stiffness;Flexural performance;Reinforced masonry wall;Running bond;Stack pattern
Supervisor
Sreekanta Das
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Abstract
Loadbearing masonry is widely used in North America, offering architects various unit patterns, including running bond (RB) and stack pattern (SP), for both architectural and loadbearing purposes. However, stack pattern masonry in loadbearing walls faces additional design restrictions compared to running bond. Many prefer stack pattern for its aesthetics but are often unaware of the structural limitations. These constraints originate from the lack of unit overlap and resulting continuous vertical head joints contained in the masonry. Thus, stack pattern walls are believed to be significantly weaker in flexure than running bond pattern walls based on design provisions. Hence, the primary focus of this study is to investigate the structural behaviour of running bond, stack pattern, and stack pattern with bond beams (SP BB) tall partially reinforced concrete masonry walls under constant axial and varying out-of-plane loading. The study found that the out-of-plane flexural capacity of stack pattern and running bond pattern walls is similar. Additionally, stack pattern walls with bond beams performed the same as, or slightly better than, walls with running bond construction, and incorporating bond beams into stack pattern walls improves the flexural capacity of the wall by up to 19%. Flexural failure mode dominated the walls, which is associated with openings of horizontal bed joints at the mid-height. The crack formation and patterns were similar for running bond and stack pattern walls, but different crack formation was observed for stack pattern walls with bond beams due to the presence of bond beams acting as crack distributors along the wall height. The displacement ductility decreased with an increase in vertical reinforcement spacing, while stack pattern walls with bond beams and walls with rebar spaced at 400 mm exhibited better performance. The findings from this study show that the provisions of the CSA S304-19 standard for effective compression zone width are not applicable for stack pattern walls with largely spaced vertical reinforcements. Also, the CSA S304 formula for effective stiffness was not valid for higher lateral loads or bending moments. Thus, this study advocates that the CSA S304-19 standard should adopt the provisions made by the TMS 402/602-22 standard, as it aligns more closely with the behaviours observed from the tests. This study concludes with a recommendation to cap the effective stiffness at 33% of the gross uncracked section stiffness (0.33EIo) for masonry walls. The structural performance of finite element (FE) wall models was in good agreement with the experimental results. The parametric study revealed that larger vertical rebar sizes enhanced tensile reinforcement, thereby improving the overall flexural strength and out-of-plane load resistance of the FE wall models. Furthermore, the outcome of this study confirms that SP and SP BB walls are adequate as loadbearing elements in buildings and recommends design changes to enhance structural integrity.
Recommended Citation
Ehikhuenmen, Samuel Onosedeba, "STRUCTURAL BEHAVIOUR OF STACK PATTERN AND RUNNING BOND MASONRY WALLS" (2024). Electronic Theses and Dissertations. 9394.
https://scholar.uwindsor.ca/etd/9394