Investigation on improving the shear behavior of columns in masonry infilled RC frames under lateral loads

Abstract

Presence of infills in reinforced concrete (RC) frames enhances the lateral load behavior of the bare frame system, but makes the columns vulnerable to shear failure under strong ground motions. This local adverse effect of infill is more pronounced in exterior ground storey columns where strong and stiff infills are present on one-side of the columns. Some of the current seismic standards address the local adverse effect of infill using variety of recommendations but their application is limited. Therefore, it is of primary importance to develop methods to counteract the adverse effect of infill. To prevent or delay the shear failure of columns, three methods (increasing the dimensions of the columns taking care of the effect of infill, using weak and soft masonry to reduce the effect of infill on columns, and decreasing the frame-interaction using collector beams in infills) were adopted in the present experimental study. From the results, it was observed that the methods not only enhanced the lateral load behavior, but also delayed the shear failure of columns without compromising the other functional requirements. The three methods can be efficiently used in both existing and new constructions to reduce the seismic vulnerability of masonry infilled RC frame buildings.