Faculty Publications
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Item Durability studies on glass fiber reinforced concrete(Springer, 2019) George, R.M.; Das, B.B.; Goudar, S.K.In the present experimental study, glass fibers were used in varying dosages of 0.5, 1.0, and 1.5% of cement content (by weight) as partial cement replacement to cement in concrete mix. The effect of different dosage of glass fibers on the bond strength between steel and concrete in reinforced concrete was investigated. As a part of durability study, the combined effect of marine environment and varying levels of pH on the ultimate bond strength retention and compressive strength retention of glass fiber reinforced concrete was also studied. Durability studies were carried out by exposing the 28-day cured cubical specimens into marine environment having different pH levels (1, 4, 7, 10 and 13). The salt solution was simulated in the laboratory by adding 3.5% NaCl to the tap water. Calculated amount of sulphuric acid was added to salt solution to maintain pH of 1 and 4 in marine environment. Similarly, calculated amount of sodium hydroxide was added to salt solution to maintain pH of 10 and 13 in marine environment. The specimens were exposed to aggressive environment for a period of 60 and 90 days. As the fiber dosage increased the workability reduced, and 1.5% fiber dosage had the least slump value. The addition of glass fibers had very minimal influence on compressive strength of glass fiber reinforced concrete. The ultimate bond strength of concrete increased due to the addition of glass fibers. The increase in ultimate bond strength was confirmed through SEM images which shows proper bonding between cement paste and glass fibers. As for as the exposure studies are concerned, 1.0% fiber dosage of glass fiber reinforced concrete had shown better compressive strength and ultimate bond strength retention compared to 0.5 and 1.5% fiber dosage. The pH of the marine environment has a decisive influence on the compressive strength retention and bond strength retention. Exposure to marine environment with pH 1 suffered severe loss in compressive strength and ultimate bond strength with very low strength retention values. However, exposure to marine environment with pH 10 and 13 had minimal strength losses with higher values of compressive strength and ultimate bond strength retention. Increase in exposure period to aggressive media leads to decrease in compressive strength and ultimate bond strength, but the strength retention values for glass fiber reinforced concrete were comparatively better compared to control concrete. © Springer Nature Singapore Pte Ltd. 2019.Item Implementation of Acoustic Emission Testing to Study the Type of Cracking in Reinforced Concrete Beams(Springer Science and Business Media Deutschland GmbH, 2021) Ghosh, S.; Agrawal, R.; Vidya Sagar, R.In this experimental study, crack classification in reinforced concrete (RC) beams was carried out using acoustic emission (AE) testing. Two types of under reinforced RC beams were tested in laboratory subjected to four-point bending, and monotonically increased load was applied. The first type of RC beam had shear reinforcement (steel stirrups), and the second type of RC beam had no shear reinforcement. The generated AE during the fracture process in the tested RC beams were used for the crack classification analysis. Gaussian mixture modeling (GMM) of acoustic emission signals was performed. It was observed that the RC beam without shear reinforcement failed suddenly (brittle nature). However, the RC beam with shear reinforcement failed gradually thereby exhibiting ductile nature. In both the RC beams, considerable AE related to shear cracking appeared at a 20–30% peak load. In the case of the RC beam with shear reinforcement, initially, tensile cracks were developed at the bottom of the beam and slowly started widening upward. Diagonal shear cracks started forming near to the supports when the test specimen reaching to collapse. In the case of the RC beam with no shear stirrups, tensile cracks originated at the bottom of the beam. But in this case, the influence of shear cracks developed near to the supports was more pronounced as it propagated rapidly. By comparing the different AE parameters, a steady increase in the number of hits till failure was observed in the case of the RC beam with shear reinforcement. But on the other hand, an abrupt increase in the number of hits was observed after 50% of peak load in the case of the RC beam with no shear reinforcement. The results are useful to study the sensitivity of AE to the shear reinforcement present in the RC beams. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Numerical investigations on the strength of L-shaped short reinforced concrete columns subjected to combined axial load and bending were undertaken for the purpose of providing design aids for structural engineers. The use of a computer lends itself naturally to the solution of the problem which generally requires an iterative process. Therefore, an attempt has been made in this paper to computerize the analysis procedure for L-shaped sections and in the accompanying paper (part II)‡ for T-shaped column sections. The ACI-318, CP-110 and IS-456 codes presented design aids only for square/rectangular and circular columns. Apparently this study constitutes the first to present the interaction curves for L-shaped and T-shaped column sections with the limit state analysis. © 1992.(Computer aided analysis of reinforced concrete columns subjected to axial compression and bending-I L-shaped sections) Mallikarjuna; Mahadevappa, P.1992Item Load-moment interaction envelopes for design of tall stacks - A limit state approach(2007) Babu Narayan, K.S.B.; Yaragal, S.C.Chimneys act as an indirect and effective means of air pollution control and have been popular from time immemorial. Environmental protection agencies have been forced to frame, implement and monitor stringent pollution control policies. With control regulations becoming more stringent, chimneys of heights over 400 m are being erected and used. Design of reinforced concrete tall stacks for load and wind induced moments by trial and error technique involves rigorous computational efforts. Availability of interaction envelopes help reduce computational time. This paper presents such design aids for tall stacks.Item Performance enhancement of RC frames using welded wire fabrics - An experimental investigation(2010) Prashanth, M.H.; Chinnagiri Gowda, H.C.; Babu Narayan, K.S.; Ramana, K.V.The paper presents the performance enhancement of RC frames using welded wire fabrics to appraise beneficial effects of welded wire fabrics as lateral reinforcement in Reinforced Concrete elements. The RC frames subjected to lateral loading have been simulated to rhombus frame with vertical loading. The experimental investigation has been done on rhombus frame with vertical loading. Experimental program involved details of test specimens, test set-up and instrumentation. Comparison of conventional bare frames has been done for frame with welded wire fabrics as lateral reinforcement at discrete zone and frame with welded wire fabrics as lateral reinforcement throughout the length for the same volume fraction. Results of Experimental investigation have been reported from which the discussions and conclusions had been drawn. © 2010 Cafet-Innova Technical Society.Item 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.Item 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.Item Performance appraisal of RC beams using welded wire fabrics as lateral reinforcement in seismic zones(CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2011) Gowda, H.C.C.; Babu Narayan, K.S.; Venkataramana, K.Ductility is the key to design earthquake resistant structures. More rigid the structure or the element, more it attracts inertia forces. Structures and elements of infinite rigidity are out of question. Codes of practice also advocate design philosophies wherein effects of small earthquakes are to be absorbed with little or no damage, medium with damage to such extents that rehabilitation is possible and large earthquake effects to be catered without collapse. To absorb the tremendous energies that are input to structures and elements unless ductility is ensured, performance levels proposed by codes and standard practices cannot be attained. Lateral ties hold longitudinal reinforcement of R.C.elements in place and also confine the concrete. The basis of the present work is the usage of welded wire fabrics as lateral reinforcement in RC beams. A series of beams were tested with lateral ties and welded wire fabric at discrete locations and welded wire fabric alone throughout the beam with different mesh opening sizes. This paper presents the encouraging results with marginal increase in strength and considerable improvement in ductility in addition to reduced crack widths as observed for specimens having welded wire fabric with smaller mesh openings as lateral reinforcement by confining concrete. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Flexural fatigue analysis of steel fibre reinforced concrete(2012) Girish, M.G.; Chandrashekar, A.; Ravi Shankar, A.U.This paper presents the experimental investigation carried on Steel Fiber Reinforced Concrete (SFRC) subjected to repeated loading. The SFRC beam specimen of size 500mm × 100mm × 100mm containing mixed steel fibers of size 50mm × 2mm × 0.6mm and 0.5mm?× 30mm in different proportions were tested under two point flexural fatigue load at a frequency of 2Hz at various stress levels. The readings obtained from the flexural fatigue test were used to plot S-N diagram and also to perform statistical analysis using two parameter Weibull distributions. © 2012 CAFET-INNOVA TECHNICAL SOCIETY.Item Effect of soil-foundation-structure interaction on fundamental frequency of rc chimneys(2013) Jayalekshmi, B.R.; Menon, D.The construction of tall reinforced concrete chimneys has been increasing, worldwide, in recent times due to industrialization. These tall and slender structures are usually wind-sensitive, requiring a dynamic analysis, to account for a proper assessment of responses under along-wind and across-wind directions and also under seismic loading. The modelling is usually carried out assuming the base (usually raft foundation supported on soil) as fixed. However, in reality, the base is compliant, due to compressibility of the soil, and this can significantly alter the dynamic characteristics of the chimney. This paper presents a comprehensive assessment of modification in the fundamental natural frequency of tapered RC chimneys in the height range of 100m to 400m due to the effect of soil-foundation-structure interaction (SFSI) through a parametric study. The parameters considered for the investigation are the height to mean base diameter ratio of the chimney, rigidity of raft foundation and the flexibility of soil. The flexibility of the supporting soil is represented by a series of Winkler springs, attached to the bottom of the raft foundation, corresponding to soft, medium and hard soils. The results of modal analysis of the three dimensional finite element model of the integrated soil-raft foundation-chimney system are compared with that of a chimney with fixed base.