Structure – Soil – Structure Interaction (SSSI) effects on seismic responses of low-, mid- and high-rise steel moment resisting frame structures

Unknown situations or factors in design of a structure such as underlying soil characteristics and presence of adjacent structures can affect the reliability, and consequently, the cost of the project. Therefore, the effects of soil-structure interaction as well as the simultaneous effects of this interaction in the presence of adjacent structures on the seismic response of 3, 9 and 20-story benchmark steel moment resisting frame structures are investigated, including six different adjacency cases of the structures in three different distances. The effect of soil-structure interaction is considered by using a hybrid method, in which the stiffness matrix of soil system is obtained through analysis of a two-dimensional model in Abaqus considering a plain strain condition. Then, the matrix is added to the nonlinear 2D model of the structure by using a set of pre-defined and a new developed element in OpenSEES. The results obtained from the time history analysis under ten far-field earthquake records show that the effect of soil-structure interaction on the response of a 20-storey high-rise structure is more significant than the other two structures and leads to a maximum increase of 9 percent in the maximum average drift ratio and decrease of 6.99 percent in the average base shear in this structure compared to fixed base. In addition, the presence of high-rise and mid-rise adjacent structures increase the maximum average drift ratio of low-rise structures by 10.44 and 9.36 percent and the average base shear in this structure by 2.87 and 3.93 percent, respectively.