Seismic Design of Outriggered Tall Building

A damped outrigger system is an effective structural scheme that has been realized in Canadian construction in the past decade for resisting seismic and wind loads. These outriggers increase the stiffness of concrete core walls, reduce the moment demand within the walls, and add additional energy dissipation. Essentially, the outrigger system acts as a rotational spring, providing additional moment resistance and rotational stiffness, which leads to lower drifts and displacements. Although the outrigger systems demonstrate desirable seismic performance, no seismic design procedures exist within Canadian building codes.

In this study, a comprehensive parametric analysis would be conducted, providing empirical relations for the dynamic response of outrigger buildings. These parameter studies are used to develop a practical seismic design guideline for outrigger systems. Prototype outrigger-wall buildings are designed with the proposed methods. These prototype buildings are located in a high seismicity region of Canada (Vancouver). Detailed finite element models are developed in OpenSees software to assess the seismic performance of the prototype buildings via the nonlinear time history analysis. The result shows that the outriggers are an efficient method to increase the seismic performance of Canadian high-rises.



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