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Experimental and numerical investigations of ductile slender reinforced masonry shear walls subjected to in-plane seismic loads Robazza, Brook Raymond

Abstract

Ductile slender reinforced masonry shear walls (DSRMSWs), defined here as ductile walls with height-to-thickness (hu/tw) ratios greater than 20 and height-to-length (hu/Lw) ratios greater than 1.5, that are designed and detailed with modern seismic design provisions are often used as the seismic-force-resisting system (SFRS) for contemporary buildings. The in-plane seismic performance of these walls is however relatively poorly understood compared to other types of SFRS shear walls, particularly with regards to their lateral stability during in-plane seismic loading. This is partially because the majority of recent experimental testing on reinforced masonry shear walls (RMSWs) has been conducted using wall specimens that are either non-slender, with design parameters that do not reflect walls typically used in current Canadian masonry construction practice, or that do not experience any form of lateral instability. Moreover, as the Canadian Standards Association standards transition to performance-based design provisions, there becomes a need for practical and reliable numerical models that have been developed and validated using experimental results, which are limited at this time. This dissertation presents experimental and analytical studies examining the in-plane performance of DSRMSWs undergoing simulated seismic effects. The experimental phase involved the testing of eight full-scale DSRMSWs (two of which were tested during the author’s M.A.Sc. thesis work) composed of fully-grouted concrete block masonry units with varying hu/Lw and hu/tw ratios, amount and distribution of reinforcement, cross-sectional shape, axial stress level, and type of cyclic loading protocol. The analytical phase first analyzed the results of the experimental phase to classify and improve the understanding of the failure modes affecting DSRMSWs, as well as to compare current design provisions of several international masonry design codes. The analytical phase also employed a nonlinear multiple-vertical-line-element (MVLE) model that was calibrated using the numerical results of the specimens tested in the experimental phase. It was demonstrated that the model was able to reproduce the observed in-plane lateral load-displacement responses of both the experimental phase specimens as well as those of another study by others, with reasonable accuracy. The proposed MVLE model may be used as a useful tool for practicing engineers following performance-based design provisions for DSRMSWs.

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