Browsing by Author "Sitharam, T.G."

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Appraisal of Thanneermukkom bund as a coastal reservoir in Kuttanad, Kerala
(Taylor and Francis Ltd., 2021) Kolathayar, S.; Amala Krishnan, U.S.; Sitharam, T.G.
This paper presents an overview of Thanneermukkom bund with its implications on water security in the region as a freshwater reservoir in the southwest coast of India. The bund was constructed in 1974 to convert southern part of brackish Vembanad Lake into a freshwater reservoir to augment agricultural activities. This paper reviews past studies on the bund and highlights the fact that it is a coastal reservoir though the term coastal reservoir became popular only in the last two decades. The bund divides the Vembanad Lake into a freshwater lake in the south and brackish water lake fed by the ocean in the north. This paper reviews the issues and challenges related to the inefficient operation of the bund and presents possible solutions. The paper proposes to restore this unique coastal reservoir to ensure freshwater supply for drinking and irrigation in the low lands of Kuttanad. © 2021 IAHR and WCCE.
Challenges and opportunities for coastal reservoir development in India
(Elsevier, 2020) Sitharam, T.G.; Kolathayar, S.
In India, presently 320 million people remain in the water-starved parts of the country, and according to the United Nations, 840 million people are expected to be water-starved in India by 2050. Although there has been no significant change in India’s rainfall pattern, the number of areas under drought in India is increasing every year. Increase in population is one of the reasons for water scarcity, but inefficient management of the precipitation received stands as the major cause. Although extreme rainfall events are significantly increasing, there is a spatial nonuniformity in the rainfall events that occur. This makes it difficult to preplan large-scale water storage at different locations. Solution to India’s water problem lies in conserving the abundant monsoon water bounty by storing it in coastal reservoirs for future use. This paper focuses on the challenges and opportunities in India for storing river floodwaters in coastal reservoir. The paper also presents the concept of Sarovar Mala, a chain of coastal reservoirs, an innovative concept that has the potential to ensure water availability to India throughout the year. © 2020 Elsevier Inc.
Deterministic seismic hazard analysis of north and central Himalayas using region-specific ground motion prediction equations
(Springer, 2021) Ramkrishnan, R.; Kolathayar, S.; Sitharam, T.G.
Abstract: A comprehensive deterministic seismic hazard assessment (DSHA) of the north and central Himalayas (NCH) is attempted in the current study using recently developed strong-motion data-based region-specific ground motion prediction equations (GMPEs). Two source models, linear and point sources are used for hazard assessment. An updated seismotectonic map of the NCH is developed by identifying and merging the seismic sources from the Seismotectonic Atlas (SEISAT 2000) developed by the Geological Survey of India and recent literature, and a homogenized, declustered up-to-date earthquake catalogue with events since 250 BC. The NCH is divided into grids of size approximately 5 km × 5 km, and the bedrock level peak ground acceleration (PGA) at the center of each grid point is estimated using a region-specific GMPE considering both source models. The PGA values estimated at these points are exported to a GIS platform to develop a seismic hazard map of the region, separately for different sources, average and maximum of both the sources. It is observed from the current study that the PGA estimated is apparently greater than what is recommended in the codal provisions for seismic zonation and estimation of design horizontal acceleration for the NCH. Research highlights: SHA based on the state of the art DSHA technique has been carried out using various source models and recently developed region-specific GMPEs with an updated homogenized and declustered catalogue.Deterministic Seismic Hazard contour maps have been developed representing the bedrock level horizontal acceleration developed using linear and point sources.The newly developed hazard maps for the North and Central Himalayas shows higher PGA in the range of 0.4g to 0.7g towards the plate boundary region and a decreasing trend towards the peninsular shield region and the southern alluvial plains, except at the National Capital Region.The PGA estimated are comparatively higher than the design horizontal acceleration prescribed for these regions in BIS 1893. © 2021, Indian Academy of Sciences.
Geotechnical considerations for coastal reservoirs
(Elsevier, 2020) Sitharam, T.G.; Kolathayar, S.
Geotechnology and geotechnical schemes have a significant role to play in conserving the water. This chapter highlights the importance of geotechnology in surface and subsurface water storage and in coastal reservoirs. Groundwater hydrology, soil/rock characteristics and permeability are the major factors governing the efficiency of water storage techniques in the ground. The innovative materials for construction of water storage schemes in the ground and for lining are briefly discussed. The chapter further discusses the concept of the subsurface dike or underground dams and its applicability in storing a large amount of water underground and in check seawater intrusion. The role of geotechnology in construction and maintenance of coastal reservoirs is discussed in detail. Different dike construction methods are discussed considering recent developments on techniques and materials. The major geotechnical components in the design and construction of coastal reservoirs are the stability of sea dike and settlement of the soil below the dike. The geotechnical parameters and the concepts of checking the stability factor of safety and settlement calculations are presented in this chapter. The coastal reservoirs must be safe against earthquakes, and deterministic estimation of seismic hazard is introduced briefly at the end. © 2020 Elsevier Inc.
Joint Time Frequency Analysis Based Synthesis of Acceleration-Time History and Response Spectra for Japanese Earthquakes
(Springer Science and Business Media Deutschland GmbH, 2022) Ramkrishnan, R.; Devaraj, D.; Kolathayar, S.; Sitharam, T.G.
Timeâ€“Frequency Analysis (TFA) techniques help to obtain the ideal time and frequency occurrence characteristics of earthquake motion confined in a seismic recorded signal. Time-histories from recording stations in Japan has been adopted in the present analysis, considering a large number of available data. The seismograms were transformed using Gabor transform, a Linear Joint TFA method, to assess their frequency content by generating their Gabor coefficients. Average Gabor coefficients were estimated for recorded seismograms within a magnitude range of 5.5â€“6.0 and hypocentral distances ranging from 0 to 50Â km. The estimated average Gabor coefficients were used to synthesize a generalized acceleration-time history for the specific distance and magnitude ranges using Gabor Expansion, without compromising the frequency content of the waves. Additionally, it is demonstrated that the response spectra of the synthesized signal and the original signal match very well. These response spectra will be valuable for the nonlinear investigation of structures in this region. Â© 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
Performance Evaluation of Premium Services in Bangalore Metropolitan Transport Corporation (BMTC)
(2016) Hanumappa, D.; Ramachandran, P.; Sitharam, T.G.; Lakshamana, S.; Mulangi, R.H.
In this paper we are measuring the performance of Bangalore Metropolitan Transport Corporation (BMTC) specifically aiming at premium bus services of BMTC operating in Bangalore city. The performance measurement of premium bus services is done using two different approaches. Ratios were computed considering different operational and financial indicators and these ratios are benchmarked by considering the best performing units as the target to compare the bus depots performance. Further we studied the performance of bus depots using data envelopment analysis (DEA). Our analysis indicated that most of the depots are efficient where as depot 13 have significant opportunities for improvements. � 2016 The Authors.
Performance Evaluation of Premium Services in Bangalore Metropolitan Transport Corporation (BMTC)
(Elsevier B.V., 2016) Hanumappa, D.; Ramachandran, P.; Sitharam, T.G.; Lakshamana, S.; Mulangi, R.H.
In this paper we are measuring the performance of Bangalore Metropolitan Transport Corporation (BMTC) specifically aiming at premium bus services of BMTC operating in Bangalore city. The performance measurement of premium bus services is done using two different approaches. Ratios were computed considering different operational and financial indicators and these ratios are benchmarked by considering the best performing units as the target to compare the bus depots performance. Further we studied the performance of bus depots using data envelopment analysis (DEA). Our analysis indicated that most of the depots are efficient where as depot 13 have significant opportunities for improvements. Â© 2016 The Authors.
Performance of Footing on Clay Bed Reinforced with Coir Cell Networks
(American Society of Civil Engineers (ASCE) onlinejls@asce.org 1801 Alexander Bell DriveGEO Reston VA 20191 Alabama, 2020) Kolathayar, S.; Narasimhan, S.; Kamaludeen, R.; Sitharam, T.G.
Geocells are three-dimensional polymeric hexagonal pockets that provide lateral confinement to the soil, thereby increasing the bearing capacity of the soil bed. This paper briefly reviews past studies on geocell reinforcement of soil and presents a new product, cells made out of natural coir fiber, as an alternative to commercially available high-density polyethylene (HDPE) geocells. A series of model plate load tests were conducted on unreinforced soil and on soil reinforced with coir geocells to understand the soil reinforcement mechanism. It was observed that with the introduction of coir geocells, the load-bearing capacity of the soil bed increased up to three times and a significant reduction in the settlement was observed in the underlying weak soil bed. The study also presents a comparative performance evaluation of the natural coir cell-reinforced soil with conventional HDPE geocell-reinforced soil. Further, this paper analytically demonstrates the influence of the lateral resistance effect and vertical load dispersion effect incorporated by coir cells in strengthening the soil bed. © 2020 American Society of Civil Engineers.
Probabilistic seismic hazard analysis of North and Central Himalayas using regional ground motion prediction equations
(Springer Science and Business Media Deutschland GmbH, 2021) Ramkrishnan, R.; Kolathayar, S.; Sitharam, T.G.
Recently developed region-specific GMPEs are used for a comprehensive seismic hazard analysis (SHA) of the North and Central Himalayas (NCH) using a probabilistic approach considering two source models. Vulnerable seismic sources in the areas are identified based on the Seismotectonic Atlas (Dasgupta et al. 2000), published by the Geological Survey of India. An up to date, homogenized and declustered earthquake catalogue is compiled from various sources, with earthquake data since 250 BC, to create a new digitized seismotectonic representation of the region. Regional seismic zones having similar seismicity are recognized based on the Gutenberg-Richter (GR) parameters and the region is delineated into 5 seismic zones. The study area is divided into grids of size 0.05° × 0.05° and the hazard in terms of Peak Ground Acceleration (PGA) at the centre of each grid point is estimated and presented as hazard maps for individual seismic sources, maximum of all sources, and average of both sources. From the current study, it could be concluded that the PGA estimated in the regions is comparatively higher than what is reported in the codal provisions for seismic zonation and estimation of design horizontal acceleration for the region. © 2021, Springer-Verlag GmbH Germany, part of Springer Nature.
RECENT DEVELOPMENTS IN SYNTHESIS OF EARTHQUAKE MOTIONS USING LINEAR JOINT TIME FREQUENCY ANALYSIS TECHNIQUES
(International Association for Earthquake Engineering, 2021) Ramkrishnan, R.; Devaraj, D.; Kolathayar, S.; Sitharam, T.G.
Temporal distribution of the frequency contents of a multi-component signal like seismic motions are not captured and well-represented in Fourier Transform (FT) techniques. Linear Joint Time-Frequency Analysis (LJTFA) addresses this issue and can transform and represent a signal in not only time domain and frequency domain, but in time-frequency domain simultaneously. Considering the better resolution and less spectral spillage when compared to Short Time Fourier Transform (STFT) and less complexity when compared to Wavelet Transform (WT), Gabor Transform (GT) is adopted in the current study. Actual recorded time-histories from recording stations in Japan had been considered for a LJTFA based synthesis of earthquake motions in this study considering the high seismicity of the area and large number of data available. Recorded time-histories of 23 earthquakes throughout Japan has been collected from K-Net and Kik-Net Strong Motion Seismograph Network of Japan and is categorized according to various Magnitude and hypocentral distances. Events of magnitude ranging from 5 to 5.5 and hypocentral distances 0 to 100km is sorted and GT is applied to transform the signals to their time-frequency domain and estimate their Gabor amplitude coefficients. Mean Gabor amplitude coefficients are estimated for different Magnitude (Mx) and Distance (Dy) combinations like M5D0-25, M5D25-50, M5-5.5D0- 25, and M5-5.5D25-50. Using an inverse GT process; Gabor Expansion (GE), the mean transformed Gabor amplitude coefficients are used to reconstruct and synthesize a time-history which doesn’t compromise on the quality of their spectral and frequency contents, thus yielding reliable synthetic seismic motions. Response spectra is developed from the actual and synthesized time-histories and are compared. A statistically good fit in terms of the coefficient of determination factor, R2 is observed between the actual and synthetic response spectrum developed. © 2021, International Association for Earthquake Engineering. All rights reserved.
Seismic Hazard Assessment of Nuclear Power Plant Site in Jaitapur: Deterministic and Probabilistic Approaches
(Springer Science and Business Media Deutschland GmbH, 2021) Kolathayar, S.; Sitharam, T.G.
This paper presents the seismic hazard analysis of Jaitapur region on the west coast of India, where a nuclear power plant is being planned to locate. A homogenized earthquake catalog in unified moment magnitude scale for the region has been prepared compiling updated data from different agencies. The seismicity parameters were estimated for Jaitapur region, and the hazard evaluation has been performed using different methodologies with different source models and attenuation relations. The deterministic and probabilistic seismic hazard analyses were performed with currently available data and their best possible scientific interpretation by considering alternative models (source models, maximum magnitude, and attenuation relationships). The hazard maps have been produced for horizontal ground motion on the bedrock level using both deterministic and probabilistic methods. The value of Peak Horizontal Acceleration (PHA) for the study region estimated probabilistically for 475Â year return period varies from 0.05 to 0.2Â g, whereas with deterministic approach, PHA reaches value as high as 0.3Â g. Â© 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
Site Characterization Using Satellite Data and Estimation of Seismic Hazard at Ground Surface
(Springer Science and Business Media Deutschland GmbH, 2021) James, N.; Kolathayar, S.; Sitharam, T.G.
This paper presents the seismic site characterization carried out for Karnataka (state level) as well as for India (country level) using topographic slope map derived from Digital Elevation Model (DEM) data. Two DEM data, SRTM, and ASTER were used to derive the slope maps. For Karnataka (state level), the slope map was generated from ASTER DEM considering a grid size of 5 Ã— 5Â km and for India (country level), the slope map was generated from SRTM DEM considering the grid size of 10 Ã— 10Â km. Based on the slope value, every grid point was characterized into various NEHRP site classes, and spatial variation of average shear wave velocity for top 30Â m (Vs30) value throughout the study areas is presented in this paper. Peak horizontal acceleration (PHA) at bedrock level was evaluated for the same grid points using deterministic as well as probabilistic methodologies. The amplification factor for every grid point was obtained from the site coefficients corresponding to NEHRP site class. The surface level peak horizontal acceleration (PHA) was then evaluated for every grid point by multiplying bedrock level PHA with the corresponding amplification factor. Spatial variation of seismic hazard at the surface for the state of Karnataka as well as for entire India is presented in this paper. Â© 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
Strong Motion Data Based Regional Ground Motion Prediction Equations for North East India Based on Non-Linear Regression Models
(Taylor and Francis Ltd., 2022) Ramkrishnan, R.; Kolathayar, S.; Sitharam, T.G.
Existing Ground Motion Prediction Equations (GMPE) in practice for North East India have been developed using limited or simulated datasets of recorded ground motions. The current study presents the development of a new GMPE based on a well-established model considering actual recorded ground motion data comprising of acceleration, magnitude, and hypocentral distances. A larger dataset with magnitudes ranging from 4.2 to 6.9 and up to 640 kms, with a total of 204 recordings is used in non-linear multiple-regression. The newly developed GMPE could predict ground acceleration realistically over larger ranges of distance and magnitudes, compared to existing GMPEs. © 2020 Taylor & Francis Group, LLC.
Sustainable Water Resource Development Using Coastal Reservoirs
(Elsevier, 2020) Sitharam, T.G.; Yang, S.-Q.; Falconer, R.A.; Sivakumar, M.; Jones, B.G.; Kolathayar, S.; Lim, S.P.
Coastal reservoirs are viewed in many regions of the world as an emerging concept of storing fresh water when the river basin is in flood. Similar reservoirs (or impoundments) can be used to generate tidal renewable energy and/or provide the catalysis for urban regeneration. Constructed near the coast in natural river basins, these reservoirs have a smaller environmental footprint and are less obstructive than inland dams. Written by an international group of Civil, Environmental, and Geotechnical Engineers, Sustainable Water Resource Development using Coastal Reservoirs discusses the latest research and breakthroughs in their use, while offering expert advice into their sustainable design and construction. The perfect reference for researchers exploring the feasibility of this emerging technology or experienced professionals who wish to implement this technology as a water scarcity solution or a tidal renewable energy source or for urban regeneration, Sustainable Water Resource Development using Coastal Reservoirs provides an expert resource to the design, construction and use of coastal reservoirs. The reference begins with a brief but readable examination of water quantity, quality design and geotechnical considerations. The book includes international case studies to clearly illustrate the various uses, design, planning, construction, and operation methods. These case studies include projects such as: Afsluitdijk in the IJsselmeer, (Netherlands), Zuiderzee (Netherlands), Thanneermukkom Bund (India), Sihwa (South Korea), Saemangeum, (South Korea), Chenhang (China), Plover Cove (China), and Marina Barrage (Singapore). Â© 2020 Elsevier Inc.
Synthesis of Linear JTFA-Based Response Spectra for Structural Response and Seismic Reduction Measures for North-East India
(World Scientific, 2020) Devaraj, D.; Ramkrishnan, R.; Prabu, T.; Kolathayar, S.; Sitharam, T.G.
North-East India (NEI) has a long history of devastating earthquakes due to the complicated tectonic setting of the region. A shortage of sufficient recorded time-histories from the region calls for a synthesis of accelerograms for dynamic analyses. In this study, a novel Joint Time-Frequency Analysis (JTFA) technique is adopted for the synthesis of accelerograms, considering the non-stationary behavior of earthquake waves. JTFA is used for analyzing the signals in a joint time and frequency domain to better understand its characteristics and synthesize signals without compromising its inherent characteristics like frequency content and amplitude. Synthetic accelerograms are developed using JTFA techniques for different magnitude and distance ranges between 5 to 6.8 and 0-480km and response spectra are developed. Synthesized generalized accelerograms and their response spectra are compared with actual signals in the same magnitude-distance ranges and were found to match. A comparison of the frequency contents of actual and synthetic signals was also carried out using Fourier Transforms and spectrograms (SPs) and was found to be in good agreement. Further, a comparative study of various earthquake reduction measures for NEI is carried out for a scenario earthquake using the synthesized data, and the best suitable structural input for the region is recommended. © 2020 World Scientific Publishing Company.