Influence of Brick Masonry Infill Walls on Seismic Response of RC Structures

Abstract

Finite element modelling and analysis of three bays three stories, two-dimensional reinforced concrete (RC) frame are performed to evaluate the seismic performance of structures with infill masonry assuming the structure is in the seismic zone 3, according to the building code of Pakistan.  Masonry RC frames are modelled with two options first with full infill walls (FIF) and second with a soft story at ground floor (SSF). Subsequently, the results are compared with that of the performance of the bare frame (BF) model, considered as reference.  FEMA and ATC 40 guidelines were used to include the effect of masonry walls. The overall performance of all three models were evaluated in terms of the fundamental modal time period, maximum inter-story drift ratio (MIDR), relative displacement (RD), stiffness, and performance points as per ATC 40 capacity spectrum method.  The analysis results confirm that the full masonry infill walls frame model (FIF) was significantly superior to that of bare frame (BF) and soft storey frame (SSF) models. The analysis results also reveal that the single strut model does not capture the real behaviour of the infill wall RC structures therefore it’s recommended to use multi diagonal struts macro modelling techniques.