Seismic Response Analysis of Lightly Reinforced Concrete Block Masonry Shear Walls Based on Shake Table Tests

Abstract

This paper presents detailed analyses of experimental shake table test results with the goal of providing a better understanding of the seismic performance of lightly reinforced fully grouted masonry shear walls. The paper first gives a brief summary of the experimental program followed by detailed analyses of the inelastic behavior characteristics of the walls. This includes quantifying the walls’ displacement ductility levels, extent of plastic hinge zones, and equivalent plastic hinge lengths based on the experimental results. Separation of the various energy components of the system, including those of the shake table, the walls, and the external mass support system, based on the experimental results, is also carried out. Utilizing the evaluated energy components, the characteristics of the system, including the change of input energy levels with time and the contributions of the different energy dissipation mechanisms (e.g., hysteretic, viscous damping, and coulomb friction damping), are quantified. In general, the results from this study demonstrate that the displacement ductility capacity of the reinforced masonry (RM) walls and their capability to dissipate energy through plastic hinging are higher than what is currently recognized by the National Building Code of Canada. In addition, the effective dynamic properties of the walls including the effective secant stiffness, period, and equivalent viscous damping are quantified, and their variations at different response levels are characterized. A single-degree-of-freedom (SDOF) substitute structure model, based on the aforementioned properties, is subsequently used to predict the experimental base shear demands of the walls. The study forms a part of the ongoing efforts to quantify the seismic performance parameters of RM wall systems to facilitate their adoption in the next generation of seismic codes in North America.