3D soil structure interaction analyses of annular raft foundation of tall RC chimneys under wind load

Abstract

Three dimensional soil structure interaction (SSI) analyses of tall reinforced concrete chimneys with annular raft foundation subjected to wind loads are presented in this paper. Different ranges of height and slenderness ratios of the chimneys and different ratios of external diameter to thickness of the annular raft were selected for the parametric study. To understand the significance of SSI, four types of soils were considered based on the stiffness. The chimneys were assumed to be located in terrain category two and subjected to a maximum wind speed of 50 m/s as per IS:875 (Part 3)-1987. The alongwind and across-wind loads were computed according to IS:4998 (Part 1)-1992. The linear elastic behavior was assumed for the integrated chimney-foundation-soil system and it was analysed using finite element software ANSYS based on direct method of SSI. The radial and tangential moments and settlement of annular raft foundation were evaluated through SSI analysis and compared with that obtained from conventional method of analysis as per IS:11089-1984, assuming foundation system is rigid. From the analysis, it is concluded that the SSI analysis results in higher radial moments and lesser tangential moments as compared to conventional method. All these variations depend on the geometric properties of chimney and annular raft foundations. Indian Geotechnical Society 2013.