Numerical modeling of reinforced masonry walls under lateral loading at the component level response as opposed to system level response

Abstract

Many experimental and analytical investigations were carried out on fully-grouted reinforced masonry shear walls types (rectangular, flanged or end-confined) to investigate their behavior under lateral loads. These studies mainly focused on evaluating the seismic response parameters for reinforced masonry shear walls (RMSW) such as ductility capacity, energy dissipation, stiffness degradation and strength. Yet, most of the research was conducted on studying each wall individually (component level response) and quite few investigations were carried out considering the system level response when different wall types are combined in a single building/system. In this paper, a simple numerical macro finite element model for walls is verified and used to simulate the in-plane response of a structure composed of ten RMSW having different ductility capacities but designed to have the same ultimate strength. The model was initially verified against available experimental data in the literature, then a parametric study was introduced to represent the effect of reinforcement ratio and axial compression on wall behavior prior to modeling structures composed of several walls. The current investigation intended to introduce how the structure ductility is affected when walls, having different ductility capacity, are interacting within one lateral load resisting system in the structure. Three methods were proposed to measure the yield displacement of the entire system to determine the value of displacement ductility for the structure and compared it to that of the individual walls within the system. Finally, a set of fragility curves were represented to illustrate the enhancement of seismic performance of masonry structures through adding end confined and flanged walls inside the structure. The results of this study showed that the displacement ductility of a structure could be significantly improved when flanged and end-confined boundary walls are included in the system as opposed to that constructed using only rectangular walls. The effect of adding end-confined masonry walls in improving structure displacement ductility is found to be more significant compared to adding flanged ones. Using fragility curves, the effect of end confined and flanged wall in the enhancement of the structure performance and delaying the damage state appears clearly in third and fourth damage states but did not have any contribution in enhancement of the first and second damage states. Keywords: Finite element, Nonlinear models, Reinforced masonry, Shear wall, Numerical analysis