Seismic Analysis of High Rise Steel Structure with Outrigger Braced System

Abstract

Urbanization, increase in population and lack of living space in urban areas lead to development of the high rise structures and this situation is unavoidable in the twenty-first century. The constant evolution of high rise structures is very essential for the development of developing nations like India. However, designing and construction of high rise building is a challenging one because as the height of the structure increases the structural stiffness and resistance of building against lateral loads become the crucial considerations. For high rise structures, the major dominating lateral forces are wind loads and seismic loads. Therefore, minimizing the lateral displacement and inter-storey drift of high rise structures is a demanding factor. There are many lateral load resisting systems available for high rise structures such as shear walls, diagrids, braced frames and outriggers are used in recent decades. In this study, the effectiveness of outrigger system at various locations along the height of the high rise structures in resisting lateral loads is discussed. Time history analysis is carried out on three models of 20 storey steel frame structures for this study such as (1) model with outrigger at 0.3 H and at top floor, (2) model with outrigger at 0.45 H and at top floor and (3) model with outrigger at 0.6 H and at top floor. It is found that the proper location of outrigger especially at 0.6 H and at top floor enhances the seismic performance of the high rise structures.