SEISMIC EVALUATION OF RETROFITTED RC FRAME BUILDING USING SHEAR WALL AND STEEL BRACES

Abstract

Many existing buildings lack the seismic strength and detailing requirements of IS1893:2002 and IS 13920:1993, because they were designed for only gravity loads or built prior to the implementation of these codes. In present study two buildings 8 and 12 storey are considered. They are designed for only gravity loads according to 15 456:2000 without ductile detailing. Seismic evaluation of these buildings is carried out with nonlinear static pushover analysis using SAP 2000 software. Moreover, the performance points and performance levels of existing and retrofitting cases were determined by capacity spectrum methods from SAP 2000. Both the buildings were found in LS-CP range for DBE condition. Then various retrofitting schemes viz. Steel X braces, inverted V braces, shear wall are employed. For retrofit of the buildings, requirement of immediate occupancy (I0) under design basis earthquake (DBE) is aimed at. The evaluation of structural overstrength, the global ductility, behavior factor of retrofitted buildings was extracted from pushover curve. Idealized force-displacement capacity curve was evaluated based on the method recommended by FEMA-356 provisions. The results were compared based on performance point, yield strength, lateral stiffness, overstrength and ductility parameters. The results show that there is no unique solution and several different schemes can be provided to give adequate performance. Most increase in the lateral strength and stiffness is related to using steel X braces and shear wall respectively