Pradeep Kumar Dammala
Bio: Pradeep Kumar Dammala is an academic researcher from Indian Institute of Technology Guwahati. The author has contributed to research in topics: Pile & Liquefaction. The author has an hindex of 6, co-authored 15 publications receiving 103 citations. Previous affiliations of Pradeep Kumar Dammala include University of Surrey & Indian Institute of Technology, Jodhpur.
TL;DR: In this article, the stiffness and damping properties of two naturally occurring sandy soils collected from a river bed in a highly active seismic zone in the Himalayan belt were analyzed using a series of resonant column tests.
Abstract: Stiffness and damping properties of soil are essential parameters for any dynamic soil structure interaction analysis. Often the required stiffness and damping properties are obtained from the empirical curves. This paper presents the stiffness and damping properties of two naturally occurring sandy soils collected from a river bed in a highly active seismic zone in the Himalayan belt. A series of resonant column tests are performed on the soil specimens with relative densities representative of the field and with varying confining pressures. The results are compared with the available empirical curves. Furthermore, a ground response analysis study is also carried out for a bridge site in the region using both empirical curves and experimentally obtained curves. It has been observed that the application of empirical modulus and damping curves in ground response prediction often leads to underestimation of the seismic demands on the structures.
TL;DR: In this article, a comprehensive study of dynamic soil properties and pore water pressure parameters of a river bed sand (Brahmaputra sand), sampled from a highly active seismic region (northeast India), is presented.
Abstract: This article presents a comprehensive study of dynamic soil properties [namely, initial shear modulus-Gmax; normalized shear modulus reduction (G/Gmax); and damping ratio (D) variation curves] and pore water pressure parameters of a river bed sand (Brahmaputra sand), sampled from a highly active seismic region (northeast India). Two independent high quality apparatus (resonant column-RC and cyclic triaxial-CTX) are adopted in the study. Resonant column apparatus was used to obtain the small strain properties (up to 0.1%) while CTX equipment was adopted to obtain the high strain properties along with the pore water pressure parameters. The results obtained from both the equipment are combined to provide a comprehensive data of dynamic soil properties over wide range of strains. A modified hyperbolic formulation was suggested for efficient simulation of G/Gmax and D variations with shear strain. Based on the CTX results, a pore water pressure generation model is presented. Furthermore, a nonlinear effective stress ground response study incorporating the pore water pressure generation, is performed using the recorded earthquake motions of varying peak bed rock acceleration (PBRA) in the region, to demonstrate the applicability of proposed dynamic soil properties and pore pressure parameters. High amplification for low PBRA ground motions (˂ 0.10 g) was observed and attenuation of seismic waves was witnessed beyond a PBRA of 0.10 g near the surficial stratum due to the induced high strains and the resulting high hysteretic damping of the soil. Also, increased excess pore pressure generation with increased PBRA of the input motion was observed and the considered soil stratum is expected to liquefy beyond a PBRA of 0.1 g. The established properties can be handy to the design engineers during seismic design of structures in the northeast Indian region.
TL;DR: In this article, a facile solvothermal method using ethylene glycol (EG) as solvent in three different ways maintaining the pH of the solution at either 3 or 9 followed by calcination at 700 °C.
Abstract: Zn2SnO4/SnO2 and ZnO/SnO2 biphasic nanocatalysts have been synthesized by a facile solvothermal method using ethylene glycol (EG) as solvent in three different ways maintaining the pH of the solution at either 3 or 9 followed by calcination at 700 °C. The nanocatalysts are characterized by different techniques to investigate their structure, composition, morphology and optical properties. The XRD results indicate the formation of pristine biphasic composites. The UV-absorbance and photoluminescence spectra confirms the formation of biphasic composites as well as presence of large number of defects in the prepared nanocatalysts. The biphasic nanocomposites possess better photocatalytic activity towards the degradation of Acid Red-183 (AR-183) dye than pristine SnO2 and ZnO nanoparticles. This is mainly due to better charge separation, minimal recombination rate of charge carriers and defect-riched structures of nanocatalysts.
TL;DR: In this paper, the role of polyols such as diethylene glycol (DEG), and polyethylene glycols (PEG, Mw = 400 and 1000) on the formation of ZnO nanostructures with anisotropic in morphology was investigated.
Abstract: Metal oxides nanomaterials are widely investigated for electrode materials of supercapacitor. However, the performance of supercapacitor strongly correlated to the variable oxidation state of metallic ions in metal oxides as well as morphology (shape and size) and porosity of the nanomaterials. Here, we have investigated the role of polyols such as ethylene glycol (EG), diethylene glycol (DEG) and polyethylene glycols (PEG, Mw = 400 and 1000) on the formation of ZnO nanostructures with anisotropicity in morphology. The phase of ZnO and coating with polyol was confirmed by X-ray diffraction and thermogravimetric (TG) analysis. FESEM image reveals nanosphere, nanoassemblies, nanorod, and hexagonal (cup shaped and rigid shaped) morphology of ZnO particles in different dimensions. The specific capacitance of the nanomaterials was measured by cyclic voltammetry method in a three electrodes system with 1 M KCl solution as electrolyte. Hexagonal rigid shaped ZnO gives better capacitance value of (6.42 F/g) followed by hexagonal cup shaped (6.4 F/g), nanoassemblies (5.75 F/g), nanorod (4.03 F/g), and nanosphere (3.67 F/g) at 10 mV/s. Further hexagonal shaped zinc oxide was made composite with reduced graphene oxide (rGO) and interestingly, the composite with 1:2 wt% of rGO to ZnO exhibits excellent specific capacitance of 251.16 F/g at 2 mV/s. Chronopotentiometry analysis indicated good charging and discharging behavior of the composite whereas electrochemical impedance spectroscopy revealed a good charge transfer characteristic.
TL;DR: In this article, the authors developed a simplified methodology to carry out scenario based seismic requalification of major river bridges supported on caisson foundations (aslo known as Well Foundation), and an example problem of Saraighat Bridge located in high Himalayan seismic zone is considered to demonstrate the application of the methodology.
Abstract: Many major river bridges were constructed in highgly active seismic areas of India much before the seismic code development. Bridges are lifelines infrastructure and as a result, it is necessary to requalify/reasses these structures in the light of the new and improved understanding of seismic resistant design philosophies. The aim of the paper is to develop a simplified methodology to carry out scenario based seismic requalification of major river bridges supported on caisson foundations (aslo known as Well Foundation). An example problem of Saraighat Bridge located in high Himalayan seismic zone is considered to demonstrate the application of the methodology. Field investigation and advanced laboratory tests on soil samples from the bridge site were carried out. The test results reveal that the soil is susceptible to liquefaction and as a result, soil structure interaction analyses are carried out. It is shown that good performance of these type of bridges depend on the displacement response of the pier head so as not to cause unseating of the decks. It is concluded, owing to the large stiffness of the foundations, bridges supported on caisson foundations may not adversely affected by liquefaction induced effects.
31 Oct 2001
TL;DR: The American Society for Testing and Materials (ASTM) as mentioned in this paper is an independent organization devoted to the development of standards for testing and materials, and is a member of IEEE 802.11.
Abstract: The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.
TL;DR: In this paper, the authors compared the results of simple shear test data with those of more approximate triaxial test procedures and concluded that the liquefaction characteristics observed in the two types of tests are qualitatively similar.
Abstract: Test data to compare the resulting behavior with that observed under cyclic loading triaxial test conditions are presented. It is concluded that the liquefaction characteristics observed in the two types of tests are qualitatively similar. However, under cyclic simple shear conditions, which provide a close simulation of the stresses induced under field conditions, the cyclic shear stresses required to cause liquefaction were only about 35% of those determined by more approximate triaxial test procedures. It is suggested, however, that limitations of the simple shear test procedure induce liquefaction at stress levels perhaps 40% to 50% lower than those corresponding to actual field conditions, and that a correction factor of this order of magnitude should be applied to laboratory simple shear test data intended for use in the analyses of field problems. The test program also showed that frequency effects, within the range from 1/6 cps to 4 cps, are small.
TL;DR: In this article, the authors introduced six typical transition metal oxides (TMOs) for supercapacitor electrodes, including RuO 2, Co3O4, MnO2, ZnO, XCo2O4 (X = Mn, Cu, Ni), and AMoO 4 (A = Co, Mn, Ni, Zns).
Abstract: In the past decades, the energy consumption of nonrenewable fossil fuels has been increasing, which severely threatens human life. Thus, it is very urgent to develop renewable and reliable energy storage devices with features of environmental harmlessness and low cost. High power density, excellent cycle stability, and a fast charge/discharge process make supercapacitors a promising energy device. However, the energy density of supercapacitors is still less than that of ordinary batteries. As is known to all, the electrochemical performance of supercapacitors is largely dependent on electrode materials. In this review, we firstly introduced six typical transition metal oxides (TMOs) for supercapacitor electrodes, including RuO2, Co3O4, MnO2, ZnO, XCo2O4 (X = Mn, Cu, Ni), and AMoO4 (A = Co, Mn, Ni, Zn). Secondly, the problems of these TMOs in practical application are presented and the corresponding feasible solutions are clarified. Then, we summarize the latest developments of the six TMOs for supercapacitor electrodes. Finally, we discuss the developing trend of supercapacitors and give some recommendations for the future of supercapacitors.
15 Jun 1980
TL;DR: In this article, a review of various types of supercapacitors, such as electrochemical double-layer capacitors, hybrid supercapACs, and pseudo-supercapacitor, is presented.
Abstract: Supercapacitors (SCs) have received much interest due to their enhanced electrochemical performance, superior cycling life, excellent specific power, and fast charging–discharging rate. The energy density of SCs is comparable to batteries; however, their power density and cyclability are higher by several orders of magnitude relative to batteries, making them a flexible and compromising energy storage alternative, provided a proper design and efficient materials are used. This review emphasizes various types of SCs, such as electrochemical double-layer capacitors, hybrid supercapacitors, and pseudo-supercapacitors. Furthermore, various synthesis strategies, including sol-gel, electro-polymerization, hydrothermal, co-precipitation, chemical vapor deposition, direct coating, vacuum filtration, de-alloying, microwave auxiliary, in situ polymerization, electro-spinning, silar, carbonization, dipping, and drying methods, are discussed. Furthermore, various functionalizations of SC electrode materials are summarized. In addition to their potential applications, brief insights into the recent advances and associated problems are provided, along with conclusions. This review is a noteworthy addition because of its simplicity and conciseness with regard to SCs, which can be helpful for researchers who are not directly involved in electrochemical energy storage.