STUDY OF SOIL-STRUCTURE INTERACTION IN 213/3D BUILDING FRAMES

Abstract

Framed structures are commonly used in the construction of buildings and industrial structures. The conventional practice considers the isolated behaviour of structure during its analysis and design. In reality, however, supporting soil foundation system alters the behaviour of superstructure and hence need for considering the mutual interaction. The phenomenon of soil-structure interaction is more pronounced in multistoreyed building frames especially, when resting on poor soil, due to possibility of large unequal column loads. The term soil-structure interaction is used for the machines of interaction between foundation, soil and superstructure. The phenomenon in which the flexibility of foundation and the compressibility of soil mass alters the superstructure behaviour which in turn alters the foundation deformation pattern, is termed as soil-structure interaction. In present thesis work a typical 3-storeyed framed building structure has been analysed founded on three different types of soil namely loose, medium soil and dense sand by considering typical plane frames in both the direction as well as a three dimensional structure the results of 2D analysis from both the directions are superimposed to ensure full load effect coming onto the coluinns and the results of simplified 2D analysis and 3D analysis have been compared for the three different load cases. • The frame is idealized as an assemblage of column and beam elements resting on spring supports one in each degree of freedom. The analysis yields stress resultants of the superstructure and substructure for design purpose. The dissertatiori work is aimed to find out the affect of soil-structure interaction on member end forces in building frames when the same building frame is founded on iii three different type of soil conditions, hence to estimate the settlement pattern and extent to which the superstructure behaviour is altered by the supporting soil mass underneath, so that frame and footing could be adequately and economically designed. In addition the dynamic response of the test building has also been investigated for a known earthquake acceleration record [Uttarkash Earthquake]. For this purpose damping coefficients have been evaluated for a 2D and 3D analysis for the system for different soil condition. A commercially available software package STAAD-PRO 2001 based on stiffness matrix method has been used. The results of 3D and simplified 2D analysis have been compared for fixed base analysis with those obtained when soil-structure interaction effect has been taken into account. Suitable conclusions have been drawn as a result of the study.