Faculty Publications
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Item 3D soil–structure interaction analyses of annular raft foundation of tall RC chimneys under wind load(Springer, 2014) Jisha, S.V.; Jayalekshmi, B.R.; Shivashankar, R.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.Item Soil–Structure Interaction Effect on Seismic Force Evaluation of RC Framed Buildings with Various Shapes of Shear Wall: As Per IS 1893 and IBC(Springer India sanjiv.goswami@springer.co.in, 2015) Jayalekshmi, B.R.; Chinmayi, H.K.Behaviour of a structure is altered by the interaction amid the structure, foundation and the soil medium below the foundation. This mutual dependent behaviour of structure and soil is called as soil–structure interaction (SSI). Hence, it is not realistic to analyse a structure as per conventional structural design practice which considers the base to be fixed. Comparative study on seismic provisions of Indian seismic code, IS 1893:2002 (IS) and International building code IBC:2006 (IBC) is carried out in present study to look into the effect of soil flexibility on variation in natural period, spectral acceleration coefficient, base shear and storey shear. Multi-storey reinforced concrete framed buildings of varying height with various shapes of shear walls over raft foundation were considered. Analysis of 3D SSI models with three different shear wall shapes founded on four different soil types which are classified based on shear wave velocity has been carried out using finite element software LS DYNA. Study shows the significant effects of SSI in altering the seismic response of structure. It also shows that the base shear obtained as per IBC are higher than the IS values and the corrugated shape of shear wall experience the lowest base shear compared to cylindrical and rectangular shape shear walls for buildings with aspect ratio below 3. © 2014, Indian Geotechnical Society.Item Dynamic soil-structure interaction analysis of RC framed building with various positions of shear walls(CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2016) Chinmayi, H.K.; Jayalekshmi, B.R.In the present study, a three-dimensional dynamic soil-structure interaction analysis of symmetric buildings in time domain is performed using IS spectrum ground motion record corresponding to zone III to evaluate the dynamic response of structure-foundation-soil system. Three types of shear wall buildings of aspect ratio 1, 1.5, 2, 3 and 4 categorized based on the shear wall locations were considered in conjunction with four types of soil of shear wave velocities ranging from 150m/s to 1200 m/s, symbolizing soil classes B, C, D and E of FEMA-356: 2000. Integrated structure-foundation-soil systems were analyzed using commercial finite element software LSDYNA, based on direct method of soil-structure interaction (SSI) assuming linear elastic behavior. The study shows considerable variation in dynamic characteristics and structural seismic response of the structure due to the incorporation of the effect of flexibility of soil and position of shear walls. Tall buildings with shear walls placed at the exterior corners experience the least base shear. © 2016 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Effect of Coir Reinforced Soil on the Seismic Response of RC Framed Buildings(Springer, 2022) Sreya, M.V.; Jayalekshmi, B.R.; Venkataramana, K.This study examines the effectiveness of reinforcing the soil with coir mat, a natural material, to act as a seismic soil-isolation medium. A 3D finite element simulation has been carried out on models of five-storey buildings resting on raft foundations in soft and stiff soil with and without the soil-isolation mechanism. The optimum values of the parameters such as the depth of embedment, width, and thickness of the coir mat have been analyzed. The isolated soil-structure system was exposed to two different earthquake motions, such as El Centro (1940) and simulated seismic excitation corresponds to the elastic design spectrum for Zone III as per the Indian Standard code (IS 1893 (Part 1): 2016). The optimum value for the depth of embedment, width, and thickness of the coir mat was identified as B/18, B/0.45 and B/36. The proposed study also deals with the coir (C) mat composited with other isolation materials such as polyethylene (PE) foam, rubber (RU) mat and geomembrane (G) to form C-PE, C-RU and C-G mats. These composites were proposed to increase the durability of the coir mat. The reinforcement of the C-PE mat shows a maximum of about 30% reduction in roof acceleration and 68% reduction in contact pressure. A pore water pressure analysis of soil bed also has been carried out to study the efficacy of these materials to reduce the excess pore water pressure generated in soil under earthquake loading. For that, a simple soft soil is modelled in Cyclic 1D software with and without the soil-isolation mechanism. The soil bed was exposed to El Centro (1940) and Northridge (1994) input motions. C-PE mat significantly reduces the excess pore water pressure by almost 93% and 88% in soil under El Centro and Northridge input motions, respectively. © 2022, Indian Geotechnical Society.Item Integrating soil-nailed walls with RC building for seismic stability in space-constrained sites(Springer Science and Business Media Deutschland GmbH, 2024) Amrita; Jayalekshmi, B.R.; Shivashankar, R.In urban environments, space constraints necessitate innovative construction methods. Due to rising demand for infrastructures and scarcity of plane ground, structures are built on sloping or irregular ground. To make use of available land, vertical cuts or excavations are made in the natural soil stratum which can be effectively retained using the soil nailing technique. However, if the area adjacent to the nailed vertical cut is utilised for constructing a multi-storeyed building, the behaviour of the nailed structure may vary. This study examines the impact of the presence of multi-storeyed RC buildings on the response of soil-nailed structures in their proximity during earthquake ground motion. The seismic response of a soil-nailed structure is evaluated in the presence of various heights of medium-rise multi-storeyed buildings. Three-dimensional multi-storeyed buildings and soil-nailed structures are analysed with various arrangements and connectivities between them, taking into account different soil profiles at the site. Dynamic finite element analyses of integrated soil-nailed wall-building systems have been performed using time history data of ground motion. The findings suggest that the integration between the two structures enhances the seismic stability of both the structures under dynamic load as evident in the reduced deformation and acceleration of the structures. It restricts the lateral movement of the nailed wall and reduces its displacement by about 40%. This integration can be implemented in space-constrained sites for optimum utilisation of available space. © The Author(s) 2024.