Faculty Publications

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    Seismic Response of Buildings Resting on Geosynthetics Reinforced Sand Bed
    (Springer Science and Business Media Deutschland GmbH, 2023) Sreya, M.V.; Jayalekshmi, B.R.; Venkataramana, K.
    An earthquake is a significant disaster that destroys structures all over the world. The structure must be designed to resist the impacts of the earthquake. The present study analyzes the efficacy of an Ultra-High Molecular Weight Polyethylene (UHMWPE) liner to lower the amount of seismic energy conveyed and the dynamic response of buildings. Finite element simulation of the transient response of an integrated soil isolation-building system in which buildings are resting on a raft in medium dense sand beds, with and without a soil-seismic isolation system, has been performed with the help of a recorded accelerogram of the El Centro (1940) earthquake. Two sets of space frame building models (two and three storey) of single bay reinforced concrete frames have been considered to estimate seismic response. UHMWPE thickness has been varied from 0.0064 m to 0.15 m to investigate its impact on peak acceleration at building roof levels. The analysis results indicate that earthquake vibration energy transmission to the superstructure is limited by the use of a UHMWPE liner, as a soil isolation medium and the thickness of the soil isolation liner significantly influences the building response during an earthquake ground motion. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.
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    Numerical Modelling of 2D Geogrid Reinforced Sand Bed
    (Springer Science and Business Media Deutschland GmbH, 2020) Sreya, M.V.; Makkar, F.M.; Sankar, N.; Chandrakaran, S.
    The use of continuous geosynthetic inclusions is involved in traditional soil reinforcing techniques such as geotextiles or geogrids, which are strong in tensile resistance. They protect the environment and promote a stronger planet by conserving energy and the earth’s resources through the production of durable and sustainable structures. In the present investigation, a numerical analysis is performed to understand the behavior of a square footing resting on geogrid reinforced soil. The numerical simulations were carried out using a three-dimensional FEM software, PLAXIS 3D. The numerical model was systematically validated with the results obtained from experimental studies. The effect of various factors such as embedment depth of first layer, spacing between consecutive layers and the multi-layers of the reinforcing elements are studied. It is observed that, four numbers of geogrid elements give the maximum bearing capacity ratio of 3.51 for an optimum depth of first layer and the spacing of 0.25B. © 2020, Springer Nature Singapore Pte Ltd.
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    Seismic Response of Buildings Resting on Raft Foundation with EPS Geofoam Buffer
    (Springer Science and Business Media Deutschland GmbH, 2021) Sreya, M.V.; Jayalekshmi, B.R.; Venkataramana, K.
    Seismic isolation is a technique that has been used around the world to protect building structures, non-structural components and content from the damaging effects of earthquake ground shaking. The present study deals with analysing the efficiency of Epoxy Polystyrene (EPS) geofoam buffer as a soil isolation medium to reduce the seismic energy transferred, thereby reducing the dynamic response of building under earthquake loads. The behaviour of an integrated soil isolation-building system has been investigated analytically, by using recorded accelerogram of El Centro earthquake. Finite element simulation of transient response has been carried out on three-dimensional field-scale models of one-storey, two-storey, three-storey and four-storey buildings resting on raft foundation in sand beds of different stiffnesses, with and without soil isolation mechanism. Four sets of three-dimensional buildings of single bay moment resisting concrete frames with 4 m bay length in either directions and 3 m storey height have been considered for the estimation of seismic response. EPS geofoam buffer of thicknesses 0.05, 0.10, 0.15 and 0.20 m and stiffnesses 22, 16, 10 and 5 MPa are placed at a depth of 0.15 m below the raft foundation of dimension 5 m × 5 m × 0.5 m. Different soil stiffnesses are considered to study its effects on the seismic response of building. Size of the soil stratum considered is 55 m × 55 m with a depth of 20 m. Absorbent boundaries have been used to eliminate the problem of reflection of the waves back into the soil from lateral boundaries. The interface between the underneath soil and EPS geofoam is formulated with a coefficient of friction 0.3. The results under field-scale conditions indicate that soil isolation provided by the EPS geofoam buffer substantially reduces the earthquake energy transmission to the superstructure during a strong earthquake. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    A Comparative Study on Dynamic Response of Buildings Resting on Coir and Rubber mat Reinforced Soil Bed
    (Institute of Physics, 2023) Sreya, M.V.; Jayalekshmi, B.R.; Venkataramana, K.
    Geotechnical seismic isolation has emerged as an efficient technique for mitigating the severe effects of earthquakes by providing smooth synthetic liners beneath foundations or between soil layers for dissipating seismic energy through sliding. This study investigates the efficacy of using a rubber mat and a natural coir mat as reinforcement materials within the soil to act as a seismic soil-isolation medium. A three-dimensional finite element simulation of five-storey buildings resting on raft foundations in soft soil with and without the soil-isolation mechanism has been performed. The reinforced soil-structure system was exposed to two different earthquake motions, such as the ground motions corresponding to the elastic design spectrum for Zone III as per the Indian standard code (IS 1893 (Part 1): 2016) and the Northridge earthquake (1994). The proposed study deals with the analysis of dynamic responses of buildings when the soil is reinforced with a coir mat and rubber mat under earthquake motions. The findings show that the seismic responses of low-rise buildings are significantly reduced by a novel technique proposed in this work to reinforce the soil with isolation materials in their mat form to reduce the seismic responses under earthquake loads. © Published under licence by IOP Publishing Ltd.
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    3-dimensional numerical modelling of sand bed reinforced with 3D geogrids of triangular form
    (Australian Geomechanics Society, 2019) Makkar, F.M.; Sreya, M.V.; Chandrakaran, S.; Sankar, N.
    In this paper, the bearing capacity improvement of a square footing resting on sand bed reinforced with 3D geogrids of triangular form is numerically studied with the help of Plaxis 3D software. The performance of 3D geogrid reinforced sand is also compared with planar geogrid reinforced sand to understand its effectiveness. In the numerical modelling, the soil behaviour is simulated by linear elastic-perfectly plastic Mohr-Coulomb model. The 3Dgeogrid and planar geogrid is modelled using geogrid structural elements available in the software. The model was validated with the experimental results and found to be in fairly good agreement with each other. The effect of various parameters on the behaviour of reinforced soil system was also investigated. It was found that the bearing capacity of multilayered planar geogrid reinforced sand bed improved by 3.68 times, while, the 3D geogrid reinforced sand bed shows 6.8 times improvement compared to the unreinforced sand bed. © 2019 Australian Geomechanics Society. All rights reserved.
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    Seismic Response of Buildings Resting on Soil Isolated With EPS Geofoam Buffer
    (IGI Global, 2022) Sreya, M.V.; Jayalekshmi, B.R.; Venkataramana, K.
    The present study deals with analyzing the efficacy of EPS (epoxy polystyrene) geofoam buffer as a soil-isolation medium to reduce the seismic energy transferred and thereby to reduce the dynamic response of buildings under earthquake-induced loads. Finite element simulation of the transient response of an integrated soil isolation-building system in which buildings resting on raft foundation in medium dense sand beds with and without soil-isolation mechanism has been carried out using a recorded accelerogram of El Centro earthquake. Four sets of three-dimensional buildings (one, two, three, and four story) of single bay moment resisting concrete frames have been considered for the analysis. The EPS geofoam buffer of various thicknesses was placed at different depths below the raft foundation. The results under field-scale conditions indicate that soil isolation provided by the EPS geofoam buffer substantially reduces the earthquake energy transmission to the superstructure during a strong earthquake. © 2022 IGI Global. All rights reserved.
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    Pore Water Pressure Analysis in Coir Mat-Reinforced Soil Incorporating Soil-Structure Interaction
    (Springer Science and Business Media Deutschland GmbH, 2022) Sreya, M.V.; Jayalekshmi, B.R.; Venkataramana, K.
    The proposed study investigates the effectiveness of reinforcing the soft soil by a coir mat, a natural material, to act as a seismic soil-isolation medium. A 3D finite element simulation in PLAXIS 3D software has been carried out on models of five-storey buildings resting on raft foundations in soft soil with and without the soil-isolation mechanism. This study also deals with the coir composites, coir–polyethylene and coir–rubber were proposed to increase the durability of the coir mat. The isolated soil-structure system was exposed to four different earthquake motions, such as the ground motions corresponding to the elastic design spectrum for Zone III as per the Indian standard code (IS 1893 (Part 1): 2016), the scaled Northridge earthquake (1994), El Centro earthquake (1940) and Chi-Chi earthquake (1999). A pore water pressure analysis of soil bed has been carried out to study the efficacy of these materials to reduce the excess pore water pressure generated in soil under earthquake loading. The other parameters, such as shear strain mobilized shear strength, effective stress in soil, and roof acceleration, in the building were analyzed. Isolation efficiencies of reinforcement materials to reduce the excess pore water pressure generated in soil under different earthquake motions obtained are 75–82%, 71–80% and 67–72% with coir, coir–polyethylene and coir–rubber, respectively. The resulting shear strain in soil reinforced by isolation mats is lower than that in unreinforced soil because the isolation mats strengthen the soil. Compared to the unreinforced soil, the mobilized shear strength and effective stress in the soil are increased when it is reinforced with coir and coir composites. The roof acceleration and bottom acceleration in the building got reduced by the isolation mechanism. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.
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    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.
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    Seismic response analysis of RC framed buildings on geo-reinforced soil
    (Springer Science and Business Media Deutschland GmbH, 2023) Sreya, M.V.; Jayalekshmi, B.R.; Venkataramana, K.
    Geotechnical seismic isolation is a recently emerged isolation technique to prevent the damaging effects of the earthquake on the building structures and nonstructural components. The study analyzes the effectiveness of different materials such as epoxy polystyrene, polyethylene foam, coir mat, rubber mat, and coir composites as a soil isolation medium to reduce the seismic energy transferred, thereby reducing the dynamic response of buildings under earthquake loads. Finite element analysis was carried out to evaluate the soil–structure interaction (SSI) effect in low-rise reinforced concrete structures with raft foundations subjected to various earthquake motions. Two kinds of soil, namely soft and stiff soil, were considered based on their flexibility to study dynamic soil–structure interaction effects. Roof acceleration and base shear of the building and contact pressure distribution and settlement at raft foundation–soil interface were the parameters evaluated for the different soil properties. The linear elastic behavior was assumed for the integrated building–foundation–soil system. This system was exposed to ground motions corresponding to scaled El Centro (1940) earthquake and simulated seismic excitation, which corresponds to the elastic design spectrum for Zone III as per the Indian standard code (IS 1893 (Part 1): 2016). The results indicate that the soil isolation provided by the high stiff polyethylene foam and coir mat substantially reduced the earthquake energy transmission to the superstructure. It is also observed that the seismic response of the buildings and raft is dependent on the flexibility of underlying soil. Seismic responses increase as the soil flexibility increases. Compared to stiff soil, the reinforced materials are very efficient in reducing seismic responses in soft soil. © 2023, Springer Nature Switzerland AG.