Faculty Publications
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Item 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.Item 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.Item 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.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 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.