SOIL STRUCTURE INTERACTION IN NONLINEAR PUSHOVER ANALYSIS OF SHEAR WALL FRAME RC STRUCTURES NONHOMOGENEOUS SOIL CONDITION

Determining the real displacement demand and seismic force resisting capacity of structures get importance to obtain performance level of structures when considering soil-structure interaction. Pushover analysis, a method of nonlinear static analysis, is generally used in assessment of existing buildings. Pushover analysis gives more accurate results when compared to linear analysis methods to evaluate seismic performance level of structures. In the study, three-dimensional soil structure interaction problem stemming from soil inhomogeneity is carried out with nonlinear pushover analysis. In this analysis, an investigation of effect of story number on performance level of five and eight-story reinforced concrete (RC) structures designed as shear wall-frame systems is performed. Inhomogeneity of soil is considered by impedance functions, which represent static stiffness of foundations for elastic soil behavior. These functions are calculated by considering shear wave velocity, shear modulus, depth of soil and poisson ratio for saturated normally and slightly over consolidated clays for spread foundation. For each foundation horizontal and vertical translations, and rocking stiffness are calculated with these impedance functions. Analysis results are compared in terms of target displacements, story drifts, plastic hinge mechanisms and rotations obtained from pushover analysis of superstructure. According to the results, displacement demand and plastic hinge rotations increase if soil inhomogeneity is considered. In other words, if impedance functions are employed in the analysis, plastic deformations can be observed in elastic deformation regions due to soil-structure interaction.