Faculty Publications
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Item Textbook of Seismic Design(2019) Reddy, G.R.; Muruva, Hari Prasad; Verma, Ajit KmarItem On Structural Rehabilitation and Retrofitting for Risk Reduction(Springer Science and Business Media Deutschland GmbH, 2022) Reddy, G.R.Structures which resist the normal as well as accidental loads due to natural hazards or manmade hazards have major role on risk. Risk may be synonym of loss of life or economy. In this script, qualitatively, it is referred as low risk and high risk and is a function of hazard levels and structural vulnerability and exposure time. In this paper, structures are referred to civil engineering buildings, equipment and piping systems. Every structural system will contribute to the risk. The risk levels are function of type of structural systems such as residential structures, office buildings, Industrial structures and lifeline structures. The risk level in industrial structures handling poisonous gases and liquids is high. Lifelines such as transport related structures, hospitals, water supply piping systems, evacuation centers including schools have to be treated exclusively/specially since these will contribute to the risk during and also after hazards especially natural one. For brevity, qualitative description is made on hazards and risk reduction targeting clear vision. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Dynamic Behaviour of Bridge Pier Due to Direct Vehicle Collision(Springer Science and Business Media Deutschland GmbH, 2022) Rahman, P.A.; Reddy, G.R.; Venkataramana, K.Bridge is the structure that is expected several normal and postulated dynamic loads. Vehicle collision with the bridge pier is one of the postulated dynamic loads considered in the design provisions. The Indian code IRC-6 consider the vehicle collision load as equivalent static load, whereas European standards EN 1991-1-7 gives provisions for both static and dynamic analysis. However the both codes don’t give a simplified mathematical model for the dynamic analysis. The Finite element analysis (FEA) is the popular method used for analysis of pier subjected to the collision load. However, the finite element analysis requires a combination of vehicle and concrete structure modeling which is a tedious process. This analytical study includes calculation of dynamic load on the bridge pier as per Eurocode EN 1991-1-7 and its dynamic responses, due to the direct vehicle collision with pier. In this article a simplified model the pier is discussed. Since majority of mass located at the top of the pier and the collision load is acting at bottom part of the pier, pier is modelled as a Two Degrees of Freedom System and the Lumped mass approach is adopted. The dynamic responses of the pier are calculated by Newmark’s Beta Linear Acceleration Method. The dynamic analysis of vehicle collision load also gives the load transferred to the superstructure and its components like bearings. Comparison study of the effect of the impact of the vehicle having 30 tonnes mass and 300 kN/m stiffness with speed 130, 90, 70 and 50 km/h as per EN 1991-1-7: 2006, shows that there is no significant difference in response of the pier for hard impact when vehicle speed varies from 50 to 130 km/h. This may be due to the peak intensities of dynamic actions affect the structure over such a short time in which the structure cannot properly respond to them. However, acceleration response is significantly high when the velocity of impact increases. And vehicle impact load never fails to induce a considerable amount of base shear in the column which is more than the equivalent static loading suggested IRC-6. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.Item Dynamic Behaviour of Road Bridge Deck When a Truck Moves Along the Irregularities of the Road Profiles(Springer Science and Business Media Deutschland GmbH, 2022) Rahman, P.A.; Reddy, G.R.; Venkataramana, K.Bridge is the structure that is seen several dynamic loads unlike other structures. Ministry of Road Transport and Highways (MORTH) said that 10,876 people were killed due to potholes in the year 2015, which denotes the lack of proper maintenance of road pavements. When a vehicle moves along these surface irregularities, it not only causes uncomfortable to the passenger but also causes dynamic loads on the components like deck slab, bearings. Since the road surface irregularities like unevenness, potholes, etc., are unavoidable, we should understand the dynamic effect on the structure due to such undulations. IRC-6, standard to find the loads and load combinations on the road bridges, doesn’t talk about the dynamic load induced by surface irregularities with respect to the different classes of road profile as per ISO: 8608. On the other hand, IRC-6 only gives provisions of static analysis in the case of the vertical dynamic effect produced by moving vehicles. This study aims to generate road profiles having different degrees of unevenness as per ISO: 8608 and to propose a conservative method to find the vertical dynamic load on the bridge deck and its vertical response. A bridge deck is modeled as a Single Degree of Freedom system and the vertical dynamic responses of the bridge deck are found by Newmark’s Beta Linear Acceleration Method. It is found that the dynamic response, almost doubles when road profile quality changes from one class to the very next class. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.Item 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.Item 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.Item Studies on concrete cylinders subjected to elevated temperatures(2010) Babu Narayan, K.S.; Anil Kumar, G.; Chandrakala, C.; Shashikumar, H.M.; Venkataramana, K.; Yaragal, S.C.; Chinnagiri Gowda, H.C.; Reddy, G.R.; Sharma, A.Concrete is a poor conductor of heat, but can suffer considerable damage when exposed to fire. Concrete in structures is likely to be exposed to high temperatures during fire. The relative properties of concrete after such an exposure are of great importance in terms of the serviceability of buildings. Unraveling the heating history of concrete is important to forensic research or to determine whether a fire exposed concrete structures and its components are still structurally sound or not. Assessment of fire damage concrete structures usually starts with visual observation of color change, cracking and spalling. On heating, a change in color from normal to pink is often observed and this is useful since it coincides with the onset of significant loss of concrete strength. This work reports the characteristics of concrete at elevated temperatures. Popular normal strength grades (M20, M25, M30, M35, M40 and M45) produced by Ready Mix Concrete (RMC) India, Mangalore have been used in production of test specimens (150 mm diameter and 300mm height cylinders) to obtain more meaningful and realistic data. In the preliminary phase 150 mm diameter and 300mm height cylinders were cast, cured and tested by destructive method for gathering data on strength characteristics. Later these test samples were subjected to elevated temperatures ranging from 100°C to 800°C, in steps of 100°C with a retention period of 2 hours. After exposure, weight losses were determined and then again destructive tests were conducted to estimate the residual split tensile strength. Test results indicated that weight and strength significantly reduces with an increase in temperature. © 2010 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Strength retention characteristics of concrete cubes subjected to elevated temperatures(2010) Yaragal, S.C.; Clarke, K.S.; Mahesh Babu, K.; Ashokumar, S.; Venkataramana, K.; Babu Narayan, K.S.; Chinnagiri Gowda, H.C.; Reddy, G.R.; Sharma, A.Concrete in structures is likely to be exposed to high temperatures during fire. The relative properties of concrete after such an exposure are of great importance in terms of the serviceability of buildings. The probability of its exposure to elevated temperatures is high due to natural hazards, accidents and sabotages. Therefore, the performance of concrete during and after exposure to elevated temperature is a subject of great interest to the designer. Physical changes like cracking, colour change, spalling and chemical changes like decomposition of Ca(OH)2 and the C-S-H gel take place when subjected to elevated temperatures. This work reports the characteristics of concrete at elevated temperatures. Popular normal strength grades (M20, M25, M30, M35, M40 and M45) produced by Ready Mix Concrete (RMC) India, Mangalore have been used in production of test specimens (150 mm cubes) to obtain more meaningful and realistic data. In the preliminary phase 150 mm cubes were cast, cured and tested by destructive method for gathering data on strength characteristics. Later these test samples were subjected to elevated temperatures ranging from 100°C to 800°C, in steps of 100°C with a retention period of 2 hours. After exposure, weight losses were determined and then again destructive tests were conducted to estimate the residual compressive strength. Test results indicated that weight and strength significantly reduces with an increase in temperature. © 2010 CAFET-INNOVA TECHNICAL SOCIETY.Item Studies on normal strength concrete cubes subjected to elevated temperatures(2010) Yaragal, S.C.; Babu Narayan, K.S.; Venkataramana, K.; Kulkarni, K.S.; Gowda, H.C.C.; Reddy, G.R.; Sharma, A.Concrete in structures is likely to be exposed to high temperatures during fire. The probability of its exposure to elevated temperatures is high due to natural hazards, accidents and sabotages. Therefore, the performance of concrete during and after exposure to elevated temperature is a subject of great importance and interest to the designer. Popular normal strength grades of concrete produced by Ready Mix Concrete (RMC) India, Mangalore have been used in production of test specimens (150 mm cubes), cured and tested by destructive method for gathering data on strength characteristics. Later, these test samples were subjected to elevated temperatures ranging from 100 C to 800 C, in steps of 100 C with a retention period of 2 hours. After exposure, weight losses and the residual compressive strength retention characteristics are studied. Test results indicated that weight and strength significantly reduces with an increase in temperature. Residual compressive strength prediction equations are proposed for normal strength concretes subjected to elevated temperatures.Item 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.