Faculty Publications
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Item Liquefaction hazard mapping of Chennai, India using SPT data(2011) Anbazhagan, P.; Basavaraj, S.; Premalatha, K.V.Liquefaction hazard is one of the major concerns for earthquake geotechnical engineering. In this paper an attempt has been made to assess liquefaction potential of Chennai city using SPT N values. Chennai is located between 12.75° to 13.25° N and 80.0° to 80.5° E on the southeast coast of India and in the northeast corner of Tamil Nadu. To understand the liquefaction possibility of Chennai city, about 650 Borelogs have been collected from different geotechnical agencies and used for the analysis. These boreholes were drilled for different projects in Chennai, most of them were drilled up to hard stratum and a minimum depth of 10m. SPT borehole data contains information about depth of water table, the classification of soil and the field observed 'N' values, index properties, rock depth. These borehole information are used to prepare N corrected table by applying the universally followed correction factors for liquefaction study. These corrected N values are further used to estimate the factor of safety against liquefaction of soil layer. Based on the factor of safety, the regional liquefaction hazard maps have been developed for depths of 1.5m, 3.0m, 6.0m and 10.0m. To represent the worst scenario, least factor of safety has been identified for each borehole location and mapped. Further the estimated factor of safety against liquefaction is used to estimate liquefaction potential index by considering depth of layer. These results are analyzed and compared in this paper. © 2011 CAFET-INNOVA technical society. All right reserved.Item Experimental investigation of RC frames using CFRP sheets(2013) Prashanth, M.H.; Babu Narayan, K.S.; Venkataramana, K.; Sajith, M.Reinforced Concrete frames are the main load resisting systems used in practice all over the world. These frames will be subjected to sway, due to lateral loading most of the times by either earthquake or wind. Ductility and energy dissipation capacity of the frame are the key parameters for better performance under the action of the sway loading. Retrofitting using the new generation material such as carbon fiber reinforced plastic sheets (CFRP) shows much enhancement in these properties of laterally loaded frames. Frames subjected to lateral loading introduce collapse mechanism due to the formation of the plastic hinges at critical hinge locations. An experimental investigation of partially and fully CFRP wrapped reinforced concrete (RC) frames when compared to conventional(bare) frame has been carried out, to bring out the importance of critical engineered locations to be wrapped. © 2013 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 COMPARATIVE ANALYSIS OF STRENGTH BEHAVIOURS ON CONCRETE FRAMES UNDER SEVERE EARTHQUAKE LOADS(Scibulcom Ltd., 2023) Balasubramanian, S.; Palanisamy, T.; Senthil Kumar, S.The increase in the development of constructions and infrastructures to compensate the growing population of the world had led to the tremendous demand for concrete. Concrete has been revolutionised by Romans and its use resulted as the finest building material on earth. But as the concrete strength improves, the brittleness increases and as a result the potential for deformation decreases, thus restricting the use of concrete in seismically active areas. Hence, this paper does the experimental research and study of the strength behaviour of reinforcement concrete (RC) and high strength concrete (HSC) effectively. The main aim of this study is to improve the properties of the frame and to withstand the burdens arising from earthquake charges against seismic behaviour. The research analysis includes the design and manufacture with casting and examination of frame speci-mens. The experimental data is checked with empirical results, and the average error percentage is 4.86. The study result showed that HSC infilled frame’s overall load-bearing capability is 4.27 times higher than RC infilled frame, and also 4.48 times higher for HSC bare frame than the RC bare frame. © 2023, Scibulcom Ltd. All rights reserved.Item Influence of Separation Layer Properties on Seismic Response of Modified Piled Raft Foundations(Springer, 2025) Amalu, P.A.; Jayalekshmi, B.R.Conventional piled raft foundations, with the raft and piles interconnected, severely restrict lateral movement, especially during seismic events. These constraints result in substantial stresses at the connection, posing a risk of potential breakage. Therefore, in seismic-prone areas, where transient lateral loadings of larger magnitudes are expected, conventional piled raft foundations are not feasible. Providing a separation layer between the raft and pile foundations is a viable solution to improve the performance of conventional piled raft foundations. The performance of such a modified piled raft system depends largely on the properties of the separation layer introduced. However, limited studies have been conducted to evaluate the seismic performance of these separation layers by considering the effect of soil–structure interactions. The present study thus aims to investigate the performance of modified piled raft systems by comparing them with their conventional counterpart. The existing conventional piled raft foundation of the Treptower building has been chosen as the prototype and is numerically analysed for static and dynamic loading conditions. Further, a separation layer has been introduced between the pile and raft, and the performance of the modified piled raft foundation is analysed under similar loadings. The results of these analyses are comprehensively compared to ascertain the performance of modified piled rafts under seismic excitation. It is found that the modified piled raft foundation with PE foam in the separation layer is advantageous in damping the propagation of seismic waves to the superstructure, reducing settlement and lateral displacements, and thereby decreasing the potential risk of failure of superstructures in seismic-prone areas. © The Author(s), under exclusive licence to Indian Geotechnical Society 2024.