A Study on the Soil Structure Interaction of a 15 Storey 2 × 3 Bay Building Subjected to Lateral Load (Earthquake Load)

Abstract

The consequences of interaction between a structure and the supporting soils in a structural model including the stiffness and strength of the geotechnical (soil) components of the foundation are essential in analyzing a structure. The basic method followed by placing the structural model on a rigid base or fixed-base is not the appropriate method of analysis as it is necessary to model the structural and geotechnical (soil) components of the foundation which results in the response of the overall structural system including deformations (elastic and inelastic) in the structural and geotechnical parts of the foundation system which helps for better design. Compared with the fixed-base modeling approach, the soil structure interaction predicts period change, the distribution of forces which changes for various elements, the sequence of inelastic change and the modes of inelastic behavior. All of these result in more realistic evaluation of the structural behavior and performance. In the current study, “3D model 15 stories having [2 × 3] bay moment- resisting RC frame with Isolated and Raft foundation resting on different types of soil is analyzed. Comparison is carried out between soil flexibility (Interacting analysis) with fixed base (Non interacting analysis) for RSM method of analysis. The investigation is carried out in zone- V of seismic zones of India as per IS 1893 (part 1):2002, considering loads (dead, live and seismic loads) and their seismic load combinations”. The soil is idealized by Two [2] forms of soil models i.e. Modified Winkler model and Continuum soil model. Totally 12 models are analyzed, for each approach 6 models are analyzed by RSM method for 3 types of soil conditions and 2 types of foundations. The models chosen for analysis are 1] Basic moment resisting RC frame with isolated footing and raft foundation - Modified Winkler model 2] Bare frame with isolated and raft footing - Continuum model. The results obtained analytically are precisely studied for higher values of period, base reaction, axial force, bending moment and displacement. The result suggests which soil condition requires SSI effect to be considered for analysis and also specifies which method of soil idealization gives realistic results.