Behavior of Reinforced Concrete Frame with Masonry infill Walls having Opening Subjected to Lateral Loading

Abstract

Reinforced Concrete frames having masonry infill have been widely used in building system. The ground floor is generally open for car parking or other facilities in this type of building. It is a common practice in conventional structural design of buildings often to ignore the interaction of masonry infill with the frame. But observations of past research have revealed that the actual behavior of infill frame with open ground floor due to lateral loading is significantly different to that of bare frame. Therefore, an extensive experimental analysis in the laboratory and computational analysis in software have been performed to study the behavior of masonry infill Reinforced Concrete frames having opening keeping open ground floor subjected to lateral loading. In the experimental work, three different types of specimen such as two storied single bay RC bare frame, infill frames having door and window opening have been constructed and tested under in-plane lateral loading. A total of 36 numbers of building frames without infill and with infill having opening of door and window have been analyzed in STAAD.Pro software for parametric study considering variation in number of floor and beam-column aspect ratios by Equivalent Static Analysis (ESA) and Response Spectrum Analysis (RSA). The masonry infill has been modeled as equivalent diagonal strut and the size, shape and other properties have been calculated using different published equations of literature. Bangladesh National Building Code has been followed for earthquake load in the analysis and base shear, sway, inter story drift, bending moment, and shear in ESA and RSA of these frames are evaluated and compared. It has been observed from experimental analysis that the strength and stiffness have been increased and displacement is reduced for RC infill frame having opening than bare frame. First crack is observed as flexure crack at ground floor beam for bare frame and stair crack at the infill for infill frame having opening. From parametric study it is noticed that the presence of infill walls in upper stories make those floors much stiffer compared to ground floor resulting major deflection at ground floor level. The bending moment and shear force are also concentrated at ground floor level where infill walls are absent in both ESA and RSA. The maximum moment and shear in RC infill frame having opening is decreasing significantly in RSA compared to ESA due to interaction of infill to the frame. Thus Equivalent Static Analysis showed conservative results compared to Response Spectrum Analysis for conventional design of buildings as bare frame.