Seismic Performance of Outrigger-Braced System Based on Finite Element and Component-Mode Synthesis Methods

Abstract

Determining the optimum location of outrigger-belt truss system is of the most important challenges in tall structures. In this paper, two numerical methods, finite element method (FEM) and component-mode synthesis (CMS), are evaluated to determine the seismic performance of two buildings with different heights: one with 20 stories and the other with 30 stories. To find the optimum location of the outrigger, seismic performance of 2D outrigger-braced buildings in terms of inter-story drift ratio, roof displacement, base shear, and base moment is investigated. It is concluded that CMS as a model reduction method is very effective and useful in reducing the required analysis time as well as having good concordance with FEM results. The seismic responses of the two buildings change significantly as the outrigger location changes from the first to the last story. The accuracy of the results is verified through the OpenSees program. Results show that the component-mode synthesis method is able to reduce the analysis time significantly, and also the efficiency and impotence of this method are more obvious as degrees of freedom are increased. In addition, placing the outrigger system at 0.6H to 0.8H of the total height of the building improves the seismic performance of the structure.