Performance Level of RC Structure Considering Soil-Structure Interaction for Nonhomogeneous Soil Condition

Abstract eng:
Determining the real displacement demand and seismic force resisting capacity of structures get more important to obtain performance level of structures when considering soil-structure interaction. Pushover analysis, one method of nonlinear static analysis, is generally used in the assessment of existing buildings. Pushover analysis gives more realistic results when compared to linear analysis methods to achieve seismic performance level of structures. In this study, three-dimensional soil structure interaction due to the soil inhomogeneity problem is carried out with nonlinear pushover analysis to determine the effect of story number on the performance level of RC structures which are designed as frame and shear wall-frame structural systems with five and eight stories. Inhomogeneity of soil is taken account into with impedance functions, which represent static stiffness of foundations for elastic soil behavior. These functions are calculated by taking shear wave velocity, shear modulus, depth of soil and poisson ration for a soil type can be given as saturated normally and slightly over consolidated clays for spread foundation. At each foundation horizontal translation, vertical translation and rocking stiffness is calculated with these impedance functions. Shear wall are modeled with mid-pier frame approach. These are connected to the structural system with infinite rigid beams. Sap2000 finite element software package is employed in all the numerical analysis. Target displacements, story drifts, plastic hinge mechanisms and rotations obtained from pushover analysis of superstructure are compared according to the analysis results. All these results from rigid soil behavior are compared with those obtained from five and eight story and nonhomogeneous soil conditions. Displacement demand and the plastic hinge rotations increase when soil inhomogeneity considered. The difference between rigid and nonhomogeneous soil conditions is more apparent when the number of story increases. In other words, an elastic deformation in the structure can change into a plastic deformation when impedance functions are employed in the analysis.

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