4. RESULTS AND DISCUSSIONS
A study of three dimensional 200 m chimney structure models with different slenderness ratio, with different raft thickness of annular raft and resting on three types of soils ranging from vary soft to stiff has been carried out. The structure is subjected to acceleration time history of Bhuj earthquake ground motion. Here, the soil is idealized as an elastic model and the prescribed ground motion is used for SSI analysis. The variation of natural frequency, deflection of raft and structural response for various parameters like tangential and radial moments of annular raft on different types of soil is studied. Comparisons are made with those obtained from the analysis of conventional method (IS 11089: 1984).