Numerical Study of Structure-Soil-Structure Interaction Effects on Deflection Amplification Factor and Correction for Special Steel Moment Frames

Considering the importance of the deflection amplification factor ,Cd, in the structural design and the lack of consideration of the structure-soil-structure interaction effects on structural response, this paper has investigated the effects of the most important parameters affecting this factor in the structure-soil-structure systems. Key parameters are period of main (T1) and adjacent (T2) structures, distance between the structures (d) and type of soil. The purpose of this study is to correct the Cd coefficient in steel moment frames under the influence of structural-soil-structure interaction effect. For this aim, 6 structures of 2 to 15 story based on two types of clay soil in a three distances of zero, 10 and 25 meters using direct method is modelled and analyzed with nonlinear time history method. According to the results, most of the story drifts is concentrated at the first story due to soft base. The minimum ratio of first story drift with respect to the fix-base, is 1. 1 and the maximum is 3.61. Increasing T1 And T2, the value of this ratio is increased. For the main structures with T1 in the range of 0.7 to 1.5 times the soil period, the structural drift is intensified. Finally, using the results of this study and regression analysis, a correlation coefficient for the Cd is presented based on the spectral response of the structural drift. Based on the obtained relationship, story drifts, especially at first story, should be increased for the design of the structures .