Effect of soil-structure interaction and flexibility of base on reduction of shear base by BNWF method

The effects of Soil-Structure Interaction and base flexibility on reduction of base shear has been investigated using BNWF method in this article. Investigating the effects of soil-structure interaction on the seismic behavior of the structure is depended on the soil stiffness, foundation and structure rigidity in a way that increasing or decreasing any of them will affect the base shear directly. The effects of fixed or flexible soil and foundation in changing the base shear has been investigated in this article separately. In this article three concrete moment resisting frames 7,10 and 15 story with 22.2m, 31.8m and 41.8m are investigate that their bay is 5.5m in all of cases. In these models, first the main period, then shear base are calculated. Considering to the period of the structures, the shear base decrease in every model. But the rates of reduction are different. With increasese of base flexibility the rate of reduction of shear base increasesd. To model the flexible foundation, Beam Nonlilear Winkler Foundation (BNWF) method is used. In this method, linear inelastic springs were used in vertical and horizontal directions. In addition, inelastic base with sliding allowed is used to increase the flexibility effect of foundation and to maximaxe the soil-structure interaction effect.