Shear Strength of Partially Grouted (PG) Masonry Shear Walls:  Experimental and Analytical Studies
Creators: Ba Rahim, Amr Abubaker
Publisher: name: University of Alberta Library
Year: 2023

<p>When subjected to in-plane loads, the shear behaviour of partially grouted (PG) masonry shear walls is complex due to the heterogeneous and anisotropic nature of the masonry materials and the nonlinear interactions among their constituents. For instance, insufficient shear strength will lead to a brittle failure mechanism, causing sudden failure and significant loss of life and property. Compared to the other wall systems, experimental studies aimed to investigate the resistance of PG walls against in-plane loads are limited, with some studies lacking features that are important when attempting a generalization of results (such as full-scale test specimens or realistic boundary conditions).  Due to this lack of data, equations in North American codes (CSA.S304-14 2014; TMS 2016) for the shear strength prediction in PG walls are largely based on results obtained in fully grouted (FG) masonry walls, even when the nature and behaviour of two types of construction are fundamentally different. In consequence, arbitrary, semi-empirical strength reduction modifiers are required to fit the PG experimental data to the theory developed for FG walls.  Unfortunately, it has been shown by Hassanli et al. (2014), Hung (2018), and Izquierdo (2021) that the current provisions in CSA S304 and TMS 402 for PG walls may result in uneconomical and/or unsafe designs in some circumstances.In an attempt to advance the knowledge regarding PG wall construction, in this study, the in-plane strength of four full-scale PG walls is investigated through experimental and analytical studies.  In a departure from some existing literature on the topic, these PG walls were designed and built to simulate and reproduce actual masonry construction practices, including wall geometry, reinforcement distribution, boundary conditions, and loading scenarios. All the walls were subjected to a combination of constant vertical load and reverse in-plane lateral cyclic load that mimics conditions that may be found in actual walls.  The variable design parameters investigated in this study were the aspect ratio and horizontal reinforcement type (bond beams or bed-joint reinforcement). The response of these walls and the role of the variable design parameters were evaluated in terms of hysteretic response, peak strength, energy dissipation, displacement ductility, and damage progression. The experimental peak strength of the specimens was compared to the predictions of North American code-based equations for walls that failed in diagonal shear and the general flexural analysis method for walls that failed in flexure.The analytical component of the study consisted of the simulation of PG wall behaviour via an analysis model based on the finite element method.  After validation with the experimental results obtained in this study and representative cases from the literature, a parametric study was conducted to investigate the role of the horizontal reinforcement types and their interaction with the aspect ratio, axial stress, vertical reinforcement, and compressive strength of masonry on the shear strength of PG walls. Finally, a stepwise regression analysis was performed on the parametric study results to propose an equation that resembles the CSA S304 equation to predict the diagonal shear strength of PG walls. The experimental results revealed that the bed-joint reinforcement demonstrated to be a feasible economic option as a horizontal reinforcement in terms of energy dissipation, ductility, and crack size control when compared to the classical bond beam reinforcement, particularly in areas with low seismic hazard risk. In addition, the peak lateral load capacity attained by walls with similar aspect ratios had no significant difference regardless of the reinforcement type used in terms of peak load.  On the other hand, the lower the aspect ratio, the higher the peak strength. Regarding the analytical study, there was an acceptable agreement between the experimental and analytical results in terms of initial stiffness, peak load and its associated displacement. Based on the parametric study, the compressive strength of masonry and axial stress were found to significantly influence the shear capacity of PG walls. At the same time, there was a negligible effect of horizontal and vertical reinforcement amounts on shear strength.  The proposed coefficients to the CSA S304 equation improved the precision and accuracy of the equation by 59% and 99%, respectively.</p>