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.

Steel plate shear walls are lateral load resisting systems consisting of vertical steel plate infills connected to the surrounding beams and columns. One of the parameters affecting the behavior of steel plate shear wall system under lateral load is characteristic of surrounding members. Since there are lots of experimental and analytical studies on steel plate shear walls with I-shaped surrounding members, this research is an experimental study carried out on a one-third scale steel plate shear wall system with box-shaped columns along with further analytical studies. The objectives were to calculate the stiffness, strength and energy dissipation capacity of the specimen and compare them with a very similar system constructed with I-shaped columns. Cyclic loading protocol of ATC-24 was used for test. Obtained experimental results showed a good conformity between box and I-shaped specimens. It is shown that the system can provide good initial stiffness and high ultimate capacity and remain intact under seismic effects. Some analytical studies on failure modes of system with box-shaped columns were also conducted using finite-element software confirming that the columns bottom connections and their flange buckling at that point are one of the most common modes of failure and a triangular reinforcing plate at that point can improve columns connection behavior effectively. KEYWORDSSteel plate shear wall, Box-shaped column, Cyclic behavior, Energy dissipation.