Reaction of infill walls and its impacts on rcc framed structures

In tall buildings, occurrence of vertical loads do not cause much problem in the analysis and design, but the horizontal forces due to wind, earthquake or blast loads are the matter of great concern and need very careful consideration. The reinforced concrete moment resisting frame with in-filled walls is a common structural system widely used for multi-storey building construction. Such composite structures formed through the combination of a moment resisting plane frame and infill wall is termed as ‘In-filled frames’. The rationale behind neglecting infill walls in the design process is partly attributed to incomplete knowledge of the behavior of quasi-brittle materials such as unreinforced masonry (URM), of the composite behavior of the frame and the infill, as well as due to the lack of conclusive experimental and analytical results to substantiate a reliable design procedure for these type of structures, despite the extensive experimental efforts and analytical investigation over the past decades. Infill has been found to be sometimes beneficial and other times detrimental to the seismic performance of frames. This type of failure is basically due to stiffening effect of infill panels that changes the basic behavior of buildings during earthquakes and creates a new failure mechanism. To avoid this type of failure, either interaction of infill wall with frame should be considered in the design or a movable joint (Adaptive interface) between infill and frame should be provided. In this Journal, the Structural behaviour of diagonally loaded masonry in filled RC frames with different infill and interface properties under static reversed cyclic loading was investigated. Based on the test outcomes, the following conclusions can be drawn. All the specimen failed in a ductile manner due to the occurrence of plastic hinges at the ends of beams and columns. The addition of infill walls increases the stiffness of the bare frame. The initial stiffness of all in filled frame is about 10 times greater than that of the bare frame. The addition of infill walls increases the strength of the bare frame also. The initial cracking load of all in filled frames is about 5 times greater than that of bare frame. The ultimate load of all in filled frame is about 2 times greater than that of bare frame. In filled frame structures will be the better option to prefer in the seismic region, as in the case of bare frame, ultimate load is very less than the other in-filled frames, which may cause the early collapse of the frames during the strong earth quake shaking.