Conference Papers
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Item Evaluation of the effect of soil-structure interaction on the raft of tall reinforced concrete chimneys under across wind load(Research Publishing Services editorial@rpsonline.com.sg, 2013) Jisha, S.V.; Jayalekshmi, B.R.; Shivashankar, R.A three dimensional soil-structure interaction (SSI) analysis of tall reinforced concrete chimneys with piled annular raft and un-piled annular raft subjected to across wind load is carried out in the present study. Effects of SSI were evaluated using four different soil types and three different ratios of external diameter to thickness of the annular raft. The across wind load was computed according to IS:4998 (Part 1)-1992. The integrated chimney-foundation-soil system was analysed by finite element 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 un-piled raft and (II) chimney with piled raft. The responses in raft were evaluated for both the cases and compared to that from conventional method of analysis. It is found that due to the addition of piles, there is considerable reduction in the responses in the raft when compared to that in the un-piled raft especially for loose sand and medium sand. © © 2013 APCWE-VIII. All rights reserved. Published by Research Publishing, Singapore.Item Dynamic soil-structure interaction analysis of 300m tall industrial reinforced concrete chimneys on piled raft foundations(Earthquake Engineering Research Institute, 2014) Jisha, S.V.; Jayalekshmi, B.R.; Shivashankar, R.Soil-structure interaction (SSI) analysis of 300m tall slender industrial reinforced concrete chimneys with piled raft foundation subjected to Elcentro (1940) ground motion is carried out in the present study. The transient analysis of three dimensional chimney-piled raft-soil system was conducted based on direct method of SSI using finite element method. Linear elastic material behaviour was assumed for the chimney, piled raft and soil. Parametric studies were conducted by considering different thickness of raft of piled raft foundation and different soil types to understand the significance of SSI. The time history analysis of the integrated chimney-foundation-soil was carried out with ground motion corresponding to the Imperial Valley earthquake at Elcentro (1940) with a magnitude of 7.0 and peak ground acceleration of 0.319g. The time history of acceleration was applied in the global X direction of the entire soil-structure model. The responses in terms of tangential and radial bending moments in raft, settlement of raft and tip deflection of chimney were investigated. The bending moments in raft of piled raft foundation obtained from SSI analysis were compared with that obtained from conventional analysis. It is found that the response in chimney and raft is considerably high for chimney-piled raft system resting on loose sand and it depends on the characteristics of ground motion also.Item Analysis of foundation of tall RC chimney with 3D finite element method(American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2014) Jisha, S.V.; Jayalekshmi, B.R.; Shivashankar, R.3D finite element (FE) analyses were carried out for 100-m and 400-m-high RC chimneys having piled annular raft and annular raft foundations considering the flexibility of soil subjected to across-wind load. Stiffness of supporting soil and foundation were varied to evaluate the significance of SSI. The integrated chimney-foundation-soil system was analysed by finite element software ANSYS based on direct method of SSI assuming linear elastic material behaviour. FE analyses were carried out for two cases of SSI, namely: (1) chimney with annular raft foundation, and (2) chimney with piled annular raft foundation. The responses in raft, such as bending moments and settlements, were evaluated for both cases and compared to those obtained from the conventional method of analysis of annular raft foundation. It is found that the responses in raft depend on the stiffness of the underlying soil and the stiffness of foundation. © ASCE 2014.Item Response of tall chimneys with piled raft and annular raft foundation under wind loads considering SSI(Taylor and Francis - Balkema pub.nl@tandf.co.uk, 2015) Jayalekshmi, B.R.; Jisha, S.V.; Shivashankar, R.The effect of Soil-Structure Interaction (SSI) was studied for tall industrial Reinforced Concrete (RC) chimneys with annular raft and piled raft under along-wind load. Effects of SSI were evaluated using three different soil types and three different thickness of the annular raft.The along-wind loadwas computed according to IS:4998 (Part 1)-1992.The integrated chimney-foundation- soil systemwas analysed by finite element software ANSYS based on direct method of SSI assuming linear elastic behaviour. FE analysis was carried out for two cases of SSI; (I) chimney with annular raft and (II) chimney with piled raft. The responses in chimney and raft were evaluated for both the cases and compared to that from conventional method. It is found that due to the addition of piles, the radial bending moment and settlement of raft are significantly reduced by more than 40%, especially for very tall chimney resting on loose sand. © 2015 Taylor & Francis Group, London.Item Seismic analysis of piled raft foundations of tall chimneys considering the effect of SSI(Taylor and Francis - Balkema pub.nl@tandf.co.uk, 2015) Jayalekshmi, B.R.; Jisha, S.V.; Shivashankar, R.A direct method of Soil-Structure Interaction (SSI) analysis of 300m and 400m tall slender Reinforced Concrete (RC) chimneys with piled raft foundation subjected to Elcentro (1940) ground motion is carried out in the present study. The parametric studies have been conducted by taking different geometrical properties of raft of piled raft foundation and different material properties of soil stratum to understand the significance of SSI. Different responses in chimney, raft and pile are evaluated. The bending moments in raft and base moment of chimney with and without considering the SSI effect are compared. The maximum radial moment in raft of the chimney-foundation system resting on loose sand is more than that obtained from the conventional analysis whereas a reduction in tangential moment is seen when the piled raft foundation with rigid raft interacts with loose sand. © 2015 Taylor & Francis Group, London.