INFLUENCE OF INFILL WALLS ON THE BEHAVIOUR OF RC FRAMES

Abstract

The relation between moment applied to a given frame member and the resulting curvature, through the full range of loading to failure, is important in several contexts. It is basic to the study of member ductility, understanding the development of plastic hinges, and accounting for the redistribution of elastic moments that occurs in most reinforced concrete structures before collapse. A program for moment-curvature analysis of flexural members has been developed in this investigation and its results validated with the help of SAP2000. A parametric study with respect to the influence of tension and compression reinforcement content on the moment-curvature behaviour of flexural members is included. Good sound and heat insulation properties of brick masonry make it the most commonly used infill for interior partitions and the facade of a multi-storied frame building. In the common practice, only mass of masonry infills is considered in design and masonry infills are treated as non-structural members because of their complex behaviour resulting from the frame-infill interaction. The ignorance of the strength and stiffness properties of masonry infills may not always give conservative design. To study the influence of masonry infills on the behaviour of RC frames especially under lateral loads, a non-linear static analysis of a typical symmetric multi-storied RC framed building has been carried out in line with the guidelines of FEMA 356. The required force-deformation properties of the structural hinges for use in the non-linear static analysis have been derived from the FEMA 356. All the inelasticity has been concentrated at the faces of the joints and the elements by the introduction of hinges. A parametric study of the influence of brick masonry (BM) infills on the behaviour of RC buildings is reported in this investigation with respect to a 4, 8 and 12-storied symmetric framed building. The primary infill wall parameter considered is what is defined as the infill wall density for a particular floor, which is assumed to be constant for all floors in a building except for the bare-frame building, which seems as the control structure and the building on stilts. Linear static analysis and design of each bare frame building has been performed as per the provisions of IS-1893 (Part-1):2002 with and without the correction factor mentioned in the clause 7.8.2 of IS-1893 (Part-1):2002. The effect of infill density on the dynamic characteristics, yield patterns, strength and displacement capacities, and storey drift ratio and member forces has been studied using pushover analysis. Relevant conclusions have been drawn with respect to the influence of infills on frame behaviour.