Faculty Publications
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Item Seismic response analysis of reinforced concrete frames including soil flexibility(Techno-Press, 2013) Jayalekshmi, B.R.; Deepthi Poojary, V.G.; Venkataramana, K.; Shivashankar, R.The seismic response of RC space frame structures with isolated footing resting on a shallow soil stratum on rock is presented in this paper. Homogeneous soil stratum of different stiffness in the very soft to stiff range is considered. Soil, footing and super structure are considered to be the parts of an integral system. A finite element model of the integrated system is developed and subjected to scaled acceleration time histories recorded during two different real earthquakes. Dynamic analysis is performed using mode superposition method of transient analysis. A parametric study is conducted to investigate the effect of flexibility of soil in the dynamic behaviour of low-rise building frames. The time histories and Fourier spectra of roof displacement, base shear and structural response quantities of the space frame on compliant base are presented and compared with the fixed base condition. Results indicate that the incorporation of soil flexibility is required for the realistic estimate of structural seismic response especially for single storey structures resting on very soft soil. Copyright © 2013 Techno-Press, Ltd.Item Seismic force evaluation of RC shear wall buildings as per international codes(Techno Press technop2@chollian.net, 2016) Jayalekshmi, B.R.; Chinmayi, H.K.Seismic codes are the best available guidance on how structures should be designed and constructed to ensure adequate resistance to seismic forces during earthquakes. Seismic provisions of Indian standard code, International building code and European code are applied for buildings with ordinary moment resisting frames and reinforced shear walls at various locations considering the effect of site soil conditions. The study investigates the differences in spectral acceleration coefficient (Sa/g), base shear and storey shear obtained following the seismic provisions in different codes in the analysis of these buildings. Study shows that the provision of shear walls at core in low rise buildings and at all the four corners in high rise buildings gives the least value of base shear. © 2016 Techno-Press, 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 Influence of Earthquake Characteristics on Pervious Concrete Column Improved Ground(Springer Science and Business Media Deutschland GmbH, 2022) Rashma, R.S.V.; Jayalekshmi, B.R.; Shivashankar, R.In this paper, the influence of earthquake characteristics on the seismic performance of ground improved with pervious concrete columns in place of conventional stone columns is presented. Two scaled earthquake ground motions with different seismic characteristics are applied to the finite element models of ground with and without column inclusions. Total stress analysis is also conducted and compared with effective stress analysis on maximum response profile along the depth of column improved ground. The study is further extended to sandwiched liquefiable soil deposits of varying thickness. It is noted that the average lateral displacement reduction of the pervious concrete column improved ground is 90% when compared to unimproved sand strata when subjected to two different earthquake excitations. It is found that the generation of excess pore pressure reaches near zero values when the permeability of pervious concrete column is greater than 0.3 m/s irrespective of the characteristics of the earthquake events. From total stress analysis and effective stress analysis, it is observed that for column improved ground, in addition to pore pressure build-up, the maximum response profile is highly influenced by significant duration and frequency of seismic excitation. The pervious concrete column performed better in homogeneous sand deposit as well as sandwiched liquefiable soil of varying thickness when subjected to different seismic excitations with different characteristics. © 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 Numerical investigation of a novel flow damping device for mitigating liquid sloshing under bi-directional excitation(Springer Science and Business Media B.V., 2024) Jogi, P.; Jayalekshmi, B.R.Sloshing in liquid storage tanks (LSTs) poses a significant challenge, especially during the seismic events and necessitating the implementation of effective mitigation strategies. This study proposes a novel technique by introducing a flow-damping device (FDD) made up of singly curved cylindrical plates connected to a cylindrical stem. The FDD is designed to be placed inside the LSTs to dissipate seismic energy, thereby reducing sloshing effects. Numerical analysis was conducted using the Arbitrary Lagrangian and Eulerian formulations in ABAQUS to assess the efficiency of various FDD configurations in reducing sloshing displacements in LSTs. The liquid storage tank with and without FDDs, were subjected to uni and bi-directional ground motion records of Imperial valley and Northridge earthquakes with a scaled peak ground acceleration. The study revealed that the FDD configuration consisting of eight plates evenly distributed around the stem with two plates oriented towards each other is the most effective FDD in reducing the seismic response parameters. When the FDD is connected to the tank base and placed centrally inside the tank at a distance of one-sixth of the tank’s length from both ends of the tank wall achieved a maximum reduction of 52.64% in sloshing displacements and 47.99% in impulsive hydrodynamic pressures. These results emphasize the substantial effectiveness of the proposed FDD design in reducing sloshing and hydrodynamic effects in LSTs during seismic events. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.Item Dynamic response assessment of RC buildings featuring basement storeys integrated with soil-nailed structures(Elsevier Ltd, 2025) Amrita; Jayalekshmi, B.R.; Shivashankar, R.The rising demand for high-rise buildings and infrastructure has led to construction on hilly and sloping terrains, necessitating their stabilisation. The area adjacent to a vertical cut, stabilised through the soil nailing technique, presents opportunities for constructing multi-storey buildings. Incorporating basement levels in buildings is also a common practice to maximise the utility of space. This study evaluates the seismic performance of integrated soil-nailed wall-building systems, where the multi-storey building is connected to the soil-nailed structure through a shear wall, termed the Shear wall (SW) system. The effect of providing two basement levels on the seismic response of the integrated SW system is analysed in soft soil conditions, denoted as the SWB system (Shear wall system with basement floors). Finite element analysis of three-dimensional models of these integrated systems is conducted in PLAXIS software. The influence of the frequency content of dynamic excitations on the responses of these structures is assessed using time history data of three different earthquakes, considering various heights of the building. Results indicate that the SWB system provides substantial benefits, including a 35.17 % reduction in seismic building deformation, a 19.23 % reduction in soil-nailed wall acceleration, an 81.66 % reduction in axial nail force and a 54.77 % reduction in inter-storey drift. However, these improvements come with increased lateral earth pressure on the soil-nailed wall, necessitating careful design to ensure optimal seismic performance. These integrated configurations are recommended as suitable for optimum space utilisation in space-constrained urban sites while ensuring structural stability under seismic loading. © 2025 Elsevier LtdItem Numerical study on reinforced vertical cuts integrated with RC buildings under the effects of ground motion(Institute of Engineering Mechanics (IEM), 2025) Amrita; Jayalekshmi, B.R.; Shivashankar, R.Soil nailing is an effective method used for stabilizing excavations and natural ground slopes. In situations with space constraints due to rapid urbanization, the available space near the soil-nailed vertical cuts can be utilized to construct multi-storied buildings. However, the presence of a building in proximity to the retained soil mass may alter the seismic response of a nailed structure. The building can be either constructed at a distance, connected or attached to the soil-nailed structure depending on the space availability. This study evaluates the behavior of such an integrated soil-nailed, wall-building system under seismic excitations by employing finite element analysis. The seismic response of a nailed wall supporting a vertical cut of a height of 6m under different connectivity conditions with an adjacent multi-story RC building is analyzed. Parametric studies are conducted with various heights of a building and under different frequency content of seismic excitations. The performance of the integrated system is evaluated regarding displacement and the acceleration response of the soil-nailed wall, as well as tensile force mobilized in nails. The innovative concept of integration between the two structures yields better seismic stability of the nailed structure, as well as for optimum use of land in space-constrained grounds with vertical cuts. © Institute of Engineering Mechanics, China Earthquake Administration 2025.Item Sloshing mitigation in liquid storage tanks using vertical floating wooden baffles(Springer, 2025) Jogi, P.; Jyothish, S.S.; Jayalekshmi, B.R.Liquid storage tanks (LSTs) are essential infrastructure but susceptible to failure due to liquid sloshing during seismic events. This sloshing generates additional hydrodynamic forces, which can impose pressure on the tank walls. Conventional methods to mitigate sloshing often rely on rigid internal structures, which can be expensive and inflexible. To overcome these challenges, the present study investigates the effects of lightweight floating wooden baffles that adapt to the liquid level within the tanks, offering a more flexible and cost-effective solution. This research aims to assess the performance of vertical floating wooden baffles in mitigating sloshing within liquid storage tanks. Numerical analysis was conducted on 3D ground-supported rectangular tanks with seven different baffle configurations, including both solid and porous designs, using the arbitrary Lagrangian–Eulerian (ALE) approach in ABAQUS. The models were subjected to horizontal seismic ground motion records from the Imperial Valley and Northridge earthquakes. Critical parameters such as sloshing wave height, hydrodynamic pressures and kinetic energy in the LST were analysed. The findings reveal that porous wooden baffles positioned near the tank walls are particularly effective in reducing sloshing and the associated hydrodynamic forces, offering a cost-efficient solution to enhance the safety of LSTs during seismic events. © Indian Academy of Sciences 2025.