Influence of Outrigger System in RC Structures for Different Seismic Zones

construction of tall buildings has laid more challenges for engineers to meet the requirements with respect to the demand growth. In the recent trend of tall buildings, lateral loads due to wind or seismic action are resisted by a arrangement of coupled shear walls. But when the structure increases in height, the stiffness of the structure becomes more important and introduction of outrigger beams between the shear walls and exterior columns is more commonly used to give sufficient lateral stiffness to the structure. The outrigger system is one of the most commonly used lateral load resisting structural system as to mitigate the excessive drift due to lateral load in an effective manner. The analysis has been carried out to study the effect and performance of outrigger system in 30 story building. The outrigger system is provided at different levels along the height of the building by varying the relative stiffness. Loads are considered as per Indian Standards IS: 875(Part1)-1987 and IS: 1893(Part-1) - 2002. The analysis is done with Equivalent static method for different seismic zones. The modeling and analysis were performed using finite element software ETABS 9.7.4.It is infer that, with the increase in relative stiffness of the outrigger system, there is a decrease in lateral displacement and inter-story drift. Further there is increase in base shear of the structure with higher relative stiffness in all seismic zones.