A STUDY FOR THE OPTIMUM LOCATION OF OUTRIGGERS FOR HIGH-RISE CONCRETE BUILDINGS

Tall building development has been rapidly increasing worldwide introducing new challenges that need to be met through engineering judgment. In modern tall buildings, lateral loads induced by wind or earthquake are often resisted by a system of coupled shear walls. But when the building increases in height, the stiffness of the structure becomes more important and introduction of outrigger beams between the shear walls and external columns is often used to provide sufficient lateral stiffness to the structure. The outrigger and belt truss system is commonly used as one of the structural system to effectively control the excessive drift due to lateral load, so that, during small or medium lateral load due to either wind or earthquake load, the risk of structural and non-structural damage can be minimized. For high-rise buildings, particularly in seismic active zone or wind load dominant, this system can be chosen as an appropriate structure. The objective of this thesis is to study the behavior of outrigger and belt truss, outrigger location optimization and the efficiency of each outrigger when two outriggers are used in the structure. In Nine 30−storey three dimensional models of outrigger and belt truss system are subjected to wind and earthquake load, analyzed and compared to find the lateral displacement reduction related to the outrigger and belt system location. For 30−storey model, 23% maximum displacement reduction can be achieved by providing first outrigger at the top and second outrigger at the middle of the structure height. The difference in behaviour of outrigger with belt truss proven to be more effective when compare to the outrigger without belt truss. The influence of second outrigger system is studied and important results are tabulated and drawn.