Development of a Macro-Model for concrete masonry infilled frames

Abstract

Masonry walls, when built to infill a frame structure, have been shown to have a significant effect on the strength, stiffness, and seismic properties of the frame structure. The accurate consideration of this effect is crucial in lateral behavior analysis of the infilled frame structures, especially under the seismic loading condition. This study proposes a new macro-model in an effort to developing a practical and rational approach for evaluating the masonry infill contribution in the design of masonry infilled frames. This model accounts for the compressive and shear behavior of the masonry infill as well as the infill effect on the bounding frame. Compressive behavior was represented through compressive struts located in the diagonal direction connecting loaded corners of the infill. Two sets of three struts were used to replace the top and bottom half of the masonry infill. The shear behavior of the infill was captured through a shear spring connecting the two sets of struts at the center of the infill. The struts and shear spring were configured in a serial manner such that both compressive and shear sliding failure can be predicted. The constitutive laws assigned to the struts and spring were based on consideration of orthotropic properties of masonry and experimental observations. This model was verified against the test results of masonry infilled masonry frames obtained in this study and of masonry infilled RC frames reported in the literature. Both monotonic pushover and quasi-static cyclic analyses were considered in the model verification. The results showed that the proposed model is capable of simulating the in-plane response of infilled frames of both materials and in both loading conditions adequately.