Masonry Infills, which generally have high stiffness and strength, play a crucial role in reinforced concrete frame buildings during earthquakes but these are normally considered as non-structural elements and their stiffness contributions are generally ignored in practice, such an approach can lead to an unsafe design. The Masonry infill (MI) though constructed as secondary elements behaves as a constituent part of the structural system and determines the overall behaviour of the structure especially when it is subjected to seismic loads. The proportions of opening in MI play a major role in the seismic analysis of RC frames. In this seismic analysis, 3D RC frames by varying the number of store’s, proportions of opening in MI and soft storey is considered. The MI is represented by equivalent diagonal strut and the proposed openings are considered with aspect ratio of the opening to that of the infill. Finite Element Analysis is adopted in modeling, equivalent static and response spectrum analyses are used. The results such as natural time period, mode shapes, base shear for static and dynamic loading, storey displacement and storey drift are presented.
