Buildings are subjected to lateral loads caused by wind, blasting and earthquakes. The high stresses developed by these loads literally tear the building components apart, which are in general designed for gravity loads. To resist these lateral forces, shear walls can be introduced in buildings. Present study aims to determine the apt shear wall position which attracts the least earthquake forces in symmetric plan multi-storey buildings. Dynamic response of a structure is significantly influenced by the underlying soil due to its natural ability to deform. Three dimensional finite element soil-structure interaction analyses of reinforced concrete shear wall buildings with shear walls placed at various locations is carried out in time domain using scaled down Elcentro ground motion to determine the seismic response variation in the structure due to the effect of stiffness of soil. Four different soil types based on shear wave velocity and six varying shear wall positions in multi-storey buildings up to 16 storeys are considered to determine the effect of soil-structure interaction. From the study, it is found that structural response as per conventional fixed base condition is very conservative. For buildings founded on soil with V s B 300 m/s, providing the shear walls at the core is advantageous whereas for soil with V s [ 300 m/s, the shear walls placed at exterior corners of the building attracts the least earthquake force.
A three-dimensional (3D) soil-structure interaction (SSI) analysis of 300 m high reinforced concrete chimneys having piled annular raft and annular raft foundations subjected to along-wind load is carried out in the present study. To understand the significance of SSI, four types of soils were considered based on their flexibility. The effect of stiffness of the raft was evaluated using three different ratios of external diameter to thickness of the annular raft. The along-wind load was computed according to IS:4998 (Part 1)-1992. The integrated chimney-foundation-soil system was analysed by commercial finite element (FE) software ANSYS, based on direct method of SSI assuming linear elastic behaviour. FE analyses were carried out for two cases of SSI (I) chimney with annular raft foundation and (II) chimney with piled raft foundation. The responses in chimney such as tip deflection, bending moments, and base moment and responses in raft such as bending moments and settlements were evaluated for both cases and compared to that obtained from the conventional method of analysis. It is found that the responses in chimney and raft depend on the flexibility of the underlying soil and thickness of the raft.
Soil-structure interaction (SSI) analysis was carried out for tall reinforced concrete chimneys with piled raft foundation subjected to wind loads. To understand the significance of SSI, four types of soil were considered based on different material properties. Chimneys of different elevations and different ratios of height to base diameter of chimney were selected for the parametric study. The thickness of raft of piled raft foundation was also varied based on different ratios of outer diameter to thickness of raft. The chimneys were assumed to be located in open terrain and subjected to a maximum wind speed of 50 m/s. The along-wind and across-wind loads were computed according to IS: 4998 (Part 1)-1992 and applied along the height of the chimney. The analysis was carried out using three-dimensional finite element technique based on the direct method of SSI. The linear elastic material behaviour was assumed for the integrated chimney-foundation-soil system. The radial and tangential moments, lateral deflection and base moment of chimney were evaluated through SSI analysis and compared with the response obtained from chimney with fixed base. The base moment of chimney considerably reduces due to the effect of SSI. It is found that the variation of different responses in chimney due to the effect of SSI depends significantly on the geometrical properties of chimney and foundations.The response variation at base for a distance of 1/40th of the height of chimney should be considered for a safe design.
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