Stiffness Irregularity in RC High-rise Building

Abstract The present study aims at analyzing the effect of vertical stiffness irregularities in a high-rise reinforced concrete building through analytical investigation. Vertical stiffness irregularity refers to uneven distribution of story stiffness. The study focuses on vertical stiffness irregularity induced due to variation in floor-to-floor height. The study of various design codes and review of recent literature is done and subsequent comparison is presented. Further, a detailed analysis of high-rise building by using software is carried out for varied degree of stiffness at various locations of building. The findings of the study like top story displacement, story drift ratio and ductility factor are presented. The efforts have been made to co-relate the degree of irregularity and its impact on top story displacement, story drift ratio and fundamental time period of building. The top story displacement and story drift ratio found higher in buildings with vertical stiffness irregularity. Further, the nonlinear static analysis is done to assess the effect of vertical stiffness irregularity in high-rise RC building by obtaining ductility factor. It was found that vertical stiffness irregularity reduces the ductility of building, especially when present at base of building. Reduction in ductility increases the seismic vulnerability of building which may leads to structural damage or failure in some cases. This aspect must be taken into consideration while designing a building with vertical stiffness irregularity.