In the concept of conventional structural design, the general assumption is that the structure is fixed at its base, while the fact is that the supporting soil medium allows for some general motions of the foundation due to its flexibility. Regardless of stiffness of structure's frames, this phenomenon results in a subsequent increase in natural period of the system and alters the overall expected response. Moreover, considering soil-structure interaction (SSI) in dynamic analysis of a building structure may result in producing an additional motion of the structure due to rocking motion of the building. The main purpose of the current study is to explain how the mechanism of the effect of rocking motion on the behavior of a steel plate shear wall (SPSW) structure. In this order, the SSI phenomenon is studied and explained in a typical mid-rise steel plate shear wall frame resting on shallow foundation. The SSI effects on the inelastic responses of such a frame due to El Centro 1940 earthquake were examined in detail using a direct method, and also, the results were compared to those for the fixed base frame. Then, a procedure is presented to clarify how SPSW behavior could be influenced by rocking component. Here, two site conditions were considered (typical stiff and soft soil deposits). The results indicated that the SSI greatly affects the seismic performance of the SPSW structure in terms of the seismic story shear forces, displacements and story drifts.
