Influence of Openings in Masonry Walls in the Modelling of Masonry Infilled Reinforced Concrete Frames

Reinforced concrete buildings with masonry infill walls are one of the most commonly constructed type of buildings. Previous studies based on post-earthquake damage surveys have stated the obvious and significant effects of the presence of infill in an RC building. In the design of RC buildings, mostly the weight of the infills is considered without the consideration of its contribution to stiffness of the building. Addition of infill walls, enhance the in-plane strength and stiffness of the RC buildings in the event of an earthquake. However, after the failure of the walls, the entire force initially resisted by the walls is transferred to the surrounding RC frames. Although masonry infill walls are considered as a non-structural element, it clearly interacts with the structure in contact. The openings in the infill walls are another significant parameter that cannot be avoided. Various kinds of opening corresponding to architectural need, aesthetic appearance, or any other functional requirements, such as doors and windows can exist in the infill walls. The presence of openings and their location can alter the global capacity of the structure entirely. These openings also vary in shape and size. There are existing provisions under seismic design guidelines to replace the infill in a fully infill frame by calculating the width of an equivalent diagonal compression member which provides the same magnitude of stiffness as an infill. Also, there are a few existing studies which inculcate the reduction in stiffness of the equivalent diagonal strut according to the size of the opening. The present study considers a mid-height building (three bay–four storeys) with openings in masonry infill walls. Influence of the location, size, and the aspect ratio of the openings in infills are also checked on the overall behaviour of the building frame.