Seismic response analysis of reinforced masonry core walls with boundary elements

Abstract

The seismic design of mid- and high-rise reinforced masonry (RM) structures necessitates a reliable seismic force resisting system (SFRS) that provides adequate capacity and ductility. Core walls are commonly used as the SFRS for counterpart reinforced concrete buildings due to the convenience of locating the elevators and staircases inside it. This study introduces reinforced masonry core walls with boundary elements (RMCW+BEs) as a potential SFRS alternative to rectangular reinforced masonry shear walls (RMSWs) with and without boundary elements given their enhanced structural and architectural characteristics in typical RM buildings. A macroscale nonlinear numerical model was developed using the Extreme Loading for Structures software (ELS) to evaluate the seismic performance of RMCW+BEs. A nonlinear time history analysis (NLTHA) was carried out for three archetype RM buildings with 10-, 15-, and 20-story heights designed according to the CSA S304-14 and located in a North American moderate seismic zone. The results showed that utilizing RMCW+BEs as the main SFRS system adequately controlled the seismic demands on RM buildings subjected to typical North American ground motions. However, the 20-story building showed a shear demand exceeding the nominal flexural resistance of the core wall at the plastic hinge region at the base, which was attributed to the adverse effect of the higher modes of vibration effects on the seismic demand parameters. Therefore, the three buildings were redesigned using a dual plastic hinge (DPH) design approach. The numerical results demonstrated that using the DPH reduced the shear demand and mitigated the effect of the higher modes of vibration on the seismic response of the core walls. The findings of this study highlight the need to integrate a new shear demand magnification factor to account for the higher mode effects in estimating the seismic demand of ductile RMSWs in the next generation of the North American design standards for masonry structures.