Optimal Location of Energy Dissipation Outrigger in High-rise Building Considering Nonlinear Soil-structure Interaction Effects

Buckling-restrained braces (BRBs) emerged to improve the seismic performance of high-rise structures as compared to the ordinary diagonal bracing. In this paper, the seismic performance of braced buildings with the BRB outrigger system is investigated to determine the optimal configuration of BRB outrigger, considering the nonlinear SSI effect. For this purpose, the nonlinear dynamic analysis is carried out on four braced buildings with a BRB outrigger system placed on three different soil types. The outrigger configuration changes from first to the top story to capture the seismic performance of different locations of BRB outrigger. It is observed that the outrigger location affects the seismic performance, which is measured in terms of inter-story drift ratio, story displacement, story shear, and energy dissipation capacity. The results are compared to the fixed base condition buildings, which proves considering SSI, shifts the optimal location to the upper story of the structure. Moreover, the effect of soil’s stiffness on the seismic responses of structures and the optimal BRB outrigger location is investigated. Finally, the merits of BRB outrigger are shown by comparing its seismic performance that of the conventional outrigger, under frequent, basic, and rare earthquakes. The results show that the optimal locations of different 2-D buildings rested on the dense soil, medium soil, and soft clay are obtained at 0.6, 0.65, and 0.7 of the building’s height (H), respectively. Also, the results show that the optimum location of the BRB outrigger system based on the energy dissipation criteria is 0.45H to 0.65H.