Seismic effects on outrigger-braced high-rise buildings

Abstract

Outrigger-braced structural system, for their effectiveness and efficiency in resisting lateral loads, has been widely adopted in high-rise buildings around the world. However, due to the stiffness mutation induced by outrigger, this kind of structure is vulnerable to damage when subject to severe earthquake. Hence, an in-depth research on improving the seismic-resistant capacity of the outrigger-braced tall buildings is needed. With the use of the advanced nonlinear finite element program ATENA 3D, numerical modeling that aiming to have more insightful study of the behavior of outrigger region is conducted. In this paper, the overall nonlinear structural behavior, in terms of progressive failure patterns is introduced; then the critical concerns, covering the abrupt changes of stresses at outrigger region, as well as the global and local deformations of the structure is discussed; lastly, the internal load path between the reinforced concrete shear wall and steel outrigger truss, the local stress concentration at the outrigger truss-wall joint, as well as the influence of the wall openings is presented. With a better understanding of the structural behavior of outrigger-braced structures, some useful recommendations for the design of shear wall at outrigger level, the appropriate numerical analysis and optimum design for the embedded outrigger truss are proposed.