Browsing by Author "Ramesh Babu, R."

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Analysis and experimental testing of a built-up composite cross arm in a transmission line tower for mechanical performance
(2013) Selvaraj, M.; Kulkarni, S.; Ramesh Babu, R.
This paper discusses the development of a composite cross arm for a power transmission line tower using FRP pultruded profiles. The mechanical performance of the composite cross arm has been evaluated using experimental testing and an analytical solution as well as a finite element simulation. By using the composite cross arm in place of a steel cross arm with ceramic insulators, considerable reduction of transmission corridor is achieved. © 2012 Elsevier Ltd.
Full scale experiment and finite element modeling of support structures of substation equipment for evaluation of ground motion amplification
(2012) Nandam, S.; Ramesh Babu, R.; Venkataramana, K.
Post earthquake performance of porcelain insulators installed for high voltage substation equipment, in general, revealed their vulnerability to failure, not due to any quality deficiency, but due to failure of their supporting structures. Most of the equipment in standalone state, withstood to tests of induced vibrations conforming to International standards. The same tested equipment, when erected in position over its supporting structure failed to sustain earthquake ground accelerations, as the supporting structure adversely contributed to amplification of the ground seismic motions while traversing to the top of the structure or the base of the insulator. This paper critically examines salutary effects of damping of vibrations on a typical instrument- transformer, using a rubber based elastic damper, with particular reference to the connected porcelain insulators, in partial containment of amplification of earthquake acceleration or in minimizing attendant distress on them. The analytical study carried out is based on experimental studies conducted on the equipment using shake table and then correlating the results obtained using finite element analysis, on the full scale model to draw meaningful conclusions. © 2012 CAFET-INNOVA TECHNICAL SOCIETY.
Influence of masonry infill on fundamental natural frequency of 2D RC frames
(2010) Chethan, K.; Ramesh Babu, R.; Venkataramana, K.; Sharma, A.
Reinforced Concrete (RC) framed structures with Un-Reinforced Masonry (URM) infill panels form a major portion of all the RC framed structures worldwide. The URM panels are considered as non-structural members, which is fairly good assumption under gravity loads, however, it is not the same under lateral forces. Under seismic loads, the stiffness additions due to infill panels modify the dynamic behavior of the structure significantly by altering the frequency of the structure. A research project has been taken up at Earthquake Engineering and Vibration Research Centre (EVRC), Central Power Research Institute (CPRI), Bangalore to investigate the influence of masonry infill on fundamental natural frequency of RC frames. 2D RC frames of one bay and two bay having single storey, double storey and three storeys are cast and tested for bare frame and many combinations of URM infill panels. Tri-axial shake table is used for testing. The details of the numerical analysis and experimentation carried out in the research project are brought out in this paper.
Performance Evaluation of Power Transmission Line Tower Made of Polymer Matrix Composite
(National Institute of Technology Karnataka, Surathkal, 2013) M., Selvaraj; Kulkarni, S. M.; Ramesh Babu, R.
The design of power transmission lines is done to meet multiple constraints – electrical, mechanical and environmental. Thus designers are generous in deciding the margin to meet the above. But presently, with limited space for transmission lines, need for reduction in transmission line space in both horizontal i.e., Right of Way (ROW) and vertical i.e., height of tower has arisen. Several attempts are made to achieve this reduction at the same time reducing the cost. Use of composites for tower and its components is an attempt directed to decrease the space and the cost. Polymer composite materials have emerged as promising engineering materials due to their light weight and non – corrosiveness. The available literature provide few details of polymer matrix composites as alternative materials for tower but a systematic and holistic study on developing and testing of a tower with composites is yet to see the light. Thus, the present work is focused on development of a tower with composite members and test it for meeting mechanical and electrical performances and also achieve reduction in ROW and cost. The work considers two approaches, first is FE analysis and the next is physical building of tower components at different levels and the full tower to test for the performance. As a preliminary step, properties of glassepoxy material processed with pultrusion are determined to assess its suitability in tower applications. Subsequently, various tower members are fabricated with pultrusion process the details of which are provided in Table.1 The tower considered for present work is a 66 kV vertical double circuit lattice type in a line of 200m span operating at a wind speed of 47 m/s. Initially tower and its components are designed as suggested in standard IS: 802 providing all mandatory clearances from the point of electrical insulation. Cross arm which is one of the major components in tower, is modelled in FEM using dimensions determined earlier. The design of cross arm is verified with FE analysis. Subsequently, FE analysis of a portion of the tower body, tower sub assembly, followed by analysis with cross arm mounted is taken up. FE analysis of a full length tower made of composite member is envisaged as an ultimate part of the study.Analysis indicated that stress levels in members far below the permissible ones of a material. Thus design of tower and its components is verified. Table 1. Details of GE pultruded cross arm and tower members Sl. No Member Dimensions of member cross section Reinforcement Matrix 1 Solid rectangle section 20 mm x 70 mm E- Glass continuous fibres ( 70 - 75 % ) Epoxy (20-25%) Lapox L-12 Hardener K-6 2 Solid angle section 50x50x6mm 76.2 x 76.2x6.35 - do- - do- 3 Solid circular section Ø30 mm, Ø33 mm - do- - do- 4 Hollow sections 101.6x101.6x9.525 101.6x101.6x6.35 - do- - doIn order to reinforce the feasibility of tower with composite material, physical construction and testing of its components and in the end full tower is taken up. All tests are carried out at station in Central Power Research Institute (CPRI), Bangalore. Initially cross arm is constructed and loads as suggested in standard IS: 802 are applied on the cross arm. The deflection measured at the tip of cross arm is only about 44 mm also strains in members of the cross arm are found to be not vey excessive. Prototype testing is extended to a tower sub assembly without cross arm and with cross arm mounted successfully. Later a full length tower with all cross arms mounted in place is constructed and tested. The tower with composite member performed satisfactorily without any visible damage at 100 % full load suggested in standard. The maximum deflection of tower is found to be only 1.4 % of tower height and is within permissible limit of 5 %. The tower with composite member successfully withstood even 300 % full load without any visible signs of failure suggesting a Factor of safety 3.0.Tests for electrical performance of cross arm and tower with composite members are carried out. Table.2 provides the results of electrical test wherein it can be observed that the test parameters determined are higher than the suggested minimum values. Thus the cross arm and tower satisfactorily meet the electrical requirements. Table 2. Results of electrical testing Electrical Performance test Suggested minimum values in IS:2165 Experimentally determined values Cross arm with tower sub-assembly Full tower Power frequency ( kV ) 140 150 143 Impulse voltage ( kV ) 325 328 328 From the study it could be inferred that the tower with composite members satisfied both mechanical and electrical requirements. Since the tower is without insulator strings and the associated problems of their swing, the ROW for the line is less and a saving of about 17 % is achieved in ROW. The height of the proposed tower is only 15 m as against 18 m for metallic tower suggested by Indian standard IS: 5613. Thus a saving of about 18 % is achieved. Consequently on account of this lesser height and lower weight of composite members, the saving in total weight of the tower against a metallic tower is about 33 %. Thus with savings and benefits mentioned above, the proposed tower could be most suitable for earthquake prone zones and for Emergency Restoration Systems (ERS).
Seismic base isolation for structures using river sand
(Techno Press technop2@chollian.net, 2016) Patil, S.J.; Reddy, G.R.; Shivshankar, R.; Ramesh Babu, R.; Jayalekshmi, B.R.; Kumar, B.
Generally seismic isolation is achieved by supporting the structure on laminated rubber bearings, friction pendulum bearings, roller bearings etc. Very little work has been performed using soil as a base isolation media. Experiments and analytical work has been performed on a structural model with isolated footing and found encouraging results. Details of this work are presented in this paper. © 2016 Techno-Press, Ltd.
Seismic Response Of Substation Equipment with Porcelain Components Seismic Response of Substation Equipment with Porcelain Components
(National Institute of Technology Karnataka, Surathkal, 2013) Srujana, N.; Ramesh Babu, R.; Venkataramana, Katta
The performance of equipment and structures during earthquake depends on their configuration, strength of construction, ductility and their dynamic properties. Lightly damped structures having one or more natural modes of oscillation within the frequency band of ground excitation may experience considerable amplification of forces, component stresses and deflections. Substation equipment comes under this category. The satisfactory operation of substation during and after an earthquake depends on the survival, without malfunction, of many diverse type of equipment. Individual equipment needs to be properly engineered. In addition, their anchorages and interconnections need to be well designed.Porcelain components are identified as most vulnerable parts against earthquake vibrations than any other components of the substation. In this research, substation equipment are divided into three categories based on the length of porcelain cylinders/components and bushings. i.e., short, medium and long porcelain insulator components. Electrical equipment are mounted on support structure or on Transformer tanks. Support structure and Transformer tank amplify the ground acceleration at the base of porcelain components.Dynamic characteristics of substation equipment are calculated by carrying out shake table experiments and finite element analysis. Assumptions are introducedin finite element modeling of equipment with respect to internal components like coil windings, metering equipment, insulating oil etc., are appropriately lumped at respective nodes to reduce the complexity involved in modelling non structural components. Basic validation of finite element models of substation components have been done with shake table experiments. Results of shake table experiments and finite element analyses are compared well with the less difference. The research concentrated towards identifyingexact earthquake ground motion amplification at the base of the porcelain components. At the same time discussions are presented on ground motion amplification of equipment with respect to recommendations available in International standards like IEEE-693-2005.
Shake table tests to investigate the effi cacy of geomembranes for soil isolation in a space frame with isolated footing
(2011) Jayalekshmi, B.R.; Shivashankar, R.; Venkataramana, K.; Ramesh Babu, R.; Reddy, G.R.; Parulekar, Y.M.; Patil, S.J.; Gundlapalli, P.
Generally a base isolator shifts the natural period of the building away from that of the predominant period of the most probable earthquakes and provides additional damping to absorb the energy. The present study focuses on the effi cacy of soil, geofi bre reinforced soil and a layer of smooth geosynthetic membrane placed in soil in reducing the seismic response of a structure. Shake table tests are carried out in a tri-axial shaker system on a 1/3rd scaled model of a single storey, single bay RC space frame. A steel tank fi xed to the shake table is used as a container for soil and reinforced soil. The structure with different base conditions is subjected to sine sweep tests and the motion corresponding to the response spectrum of Zone III as per IS 1893(Part1):2002. Analysis of results shows that smooth geomembrane in sand can be effectively used to reduce the seismic response of the structure.
Significance of modeling techniques in pushover analysis of RC buildings
(2010) Thapa, M.; BabuNarayan, K.S.; Halemane, K.P.; Venkataramana, K.; Yaragal, S.C.; Ramesh Babu, R.; Sharma, A.; Reddy, G.R.
The study presented here focuses on the effectiveness of the models adopted for the nonlinear static pushover (NSP) analysis and providing the best model that can predict the nonlinear response of RC buildings with sufficient accuracy with respect to the experimentally obtained results. NSP analysis considers material nonlinearity and is an effective tool to evaluate the performance of the structure under lateral seismic loads. However, the actual test data in order to verify the results of NSP analysis are very rare for RC structures, which are analytically sensitive to the models and procedure adopted by the analyzer. Under the present work three cases of geometric models; a) Frame with beamcolumn elements, b) Frame with beam-column elements and slabs modelled as a rigid diaphragm and c) Frame with beam-column elements and slabs modelled as shell element considering concrete as confined and unconfined were analyzed. Comparision of analytical curve with the experimental pushover curve, clearly suggests that frame modelled as confined beam-column elements and slabs modelled as a rigid diaphragm gives closer results. © 2010 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.
Studies on the dynamic characteristics of monolithic RC wall panels
(2013) Amitha, S.B.; Chethan, K.; Bhavanishankar, S.; Annapurna, B.P.; Venkataramana, K.; Ramesh Babu, R.
Monolithically built RC wall panels permits for the industrialized construction of a group of integrated buildings using mechanized, rationalized and mass-production procedure. This is a unique, fast and economical technique. Most of the national and international codes comprise of a brief design procedure of this type of construction. Lot of research is being carried out worldwide about the effect of dynamic loads on these structures. In this paper, FE analysis is done on a designed typical monolithic RC wall panel structure for all zones as per Indian code and the results are compared with different international codal provisions and the formulae presented by Saheb & Desayi and Doh & Fragomeni. This paper consists of background, design and construction of monolithic RC wall panel, FE analysis and comparison of results. © 2013 CAFET-INNOVA TECHNICAL SOCIETY.
Studies on the influence of infill on dynamic characteristics of reinforced concrete frames
(CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2011) Chethan, K.; Ramesh Babu, R.; Venkataramana, K.; Sharma, A.
The basic investigation under dynamic loads starts with the estimation of the natural frequencies of the structure or system under consideration. This is an important parameter under dynamic analysis. Hence a detailed study has been carried out on the influence of masonry infill (MI) on fundamental natural frequency of RC frames. MI though considered as non-structural element largely affect the strength, stiffness and ductility of the framed structure during the application of lateral forces such as wind and earthquake loads. Experimental and Numerical studies are carried out on RC frames under different configurations of MI in addition to bare frames. The RC frames are designed and detailed as per the relevant Indian standard codes. A simple numerical method has been formulated to obtain the natural frequencies of RC frames with MI using FE analysis. Tri-axial shake table is used for the determination of natural frequencies experimentally. This is a part of the collaborative project between BARC, Mumbai and CPRI, Bangalore focusing on the Response evaluation of RC frames under dynamic loading. This paper consists of numerical formulation, FE analysis, Shake table tests and comparison of results. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.