EFFECT OF INFILL WALLS ON THE SEISMIC PERFORMANCE OF MULTI-STOREY BUILDINGS

Abstract

Reinforced concrete frames with masonry infill walls are extensively used as interior partitions and exterior walls in many parts of the world. Infill walls are typically not considered structural elements in structural design because they are primarily employed for insulation and partitioning rather than structural objectives. However, these infills assist the structure in responding to an earthquake, and the behavior of infilled-frame buildings differs from what is predicted for bare-frame structures. For the comparison investigation, models of G+4 and G+8 RC-framed structures located in seismic zone IV were taken into consideration. The models account for the equivalent diagonal strut by FEMA-356 and IS 1893 (Part 1) : 2016, masonry walls stiffness. According to IS 1893 (Part 1) : 2016, linear dynamic analysis and response Spectrum Analysis have been performed. The impact of infills on dynamic features, yield patterns, and seismic performance has been studied using nonlinear static pushover analysis. At performance points for each model taken into consideration, the results are compared for various parameters including natural period, storey drift, displacement, and hinge status. The non-linear dynamic analysis is performed using 11 ground motion sets on 2 RC frame buildings located in seismic zone IV of IS 1893 (Part I) : 2016. The effects of infills on the inter-story drift ratios of buildings are also presented in this study. This study also assesses the seismic performance of RC frame structures with URM infills by performing NLTH analysis and also probabilistic predictions of the risk of collapse of structures. Collapse is predicted through Incremental dynamic analysis in which the structures are subjected to ground motions which are scaled each time by increasing the scale factor until the collapse of the structure. The fragility curves are developed using the incremental dynamic analysis using 11 sets of ground motions. It has been found that the presence of infills significantly changes the collapse mechanism of the structure. The probability of collapse of a bare frame is found to be higher than the uniformly infilled structures.