Faculty Publications
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Item Shape optimization of steel reinforced concrete beams(Techno Press, 2007) Babu Narayan, K.S.B.; Venkataramana, K.Steel reinforced concrete is perhaps the most versatile and widely used construction material. The versatility is attributed to mouldability of concrete to any conceivable shape. The inherent property of cracking of concrete is the reason for its low tensile strength and hence the design approach of RCC sections in flexure adopts the cracked section theory where in concrete in tension zone is ignored. Means, modes and methods of exploitation of concrete strength by conceiving shapes other than rectangular whereby ineffective concrete in tension zone is reduced and incorporated in compression zone where it is effective needs consideration. Shape optimization of beams is attempted in this analytical investigation employing Sequential Unconstrained Minimization Technique (SUMT). The results clearly show that trapezoidal beams happen to be less costlier than their rectangular counterparts, their usage needs serious reconsideration by the designers.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 Performance of stone columns with circumferential nails(2011) Nayak, S.; Shivashankar, R.; Dheerendra Babu, M.R.D.Stone columns are often used as an effective technique for improving the performance of soft ground. Stone columns derive their load-carrying capacity due to lateral confinement from the surrounding soil. Very soft soils offer very low lateral confinement, leading to large settlements and low load-carrying capacities. In this paper, an alternative method of enhancing the performance of stone columns in soft soils by reinforcing the stone columns with circumferential nails driven vertically is suggested. The method was developed in laboratory-scale model tests and a series of plate load tests were performed in unit cell tanks to investigate the performance of stone columns reinforced with circumferential nails. The investigation was carried out by varying the depth of nails below ground level, the number of nails and the diameter of nails with different diameter stone columns and area ratios (orspacing). It was found that the circumferentially reinforced stone columns have much higher load-carrying capacity with a significant reduction in settlement and less lateral bulging in comparison with plain stone columns.Item Performance enhancement of preloaded RC beams using CFRP sheets(CAFET INNOVA Technical Society cafetinnova@gmail.com 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2012) Prashanth, M.H.; Suraj, K.; Babu Narayan, K.S.; Ravikumar, C.M.Retrofitting concrete structures with Carbon Fiber Reinforced Polymer (CFRP) has grown widely in most parts of the world today. The main reason for the wide spread application of FRP is that it is possible to obtain an effective strengthening with a relative small work effort. Furthermore it is possible to carry out strengthening work without changing the current appearance or dimension of the structure. To strengthen and increase the ductility of the structure, CFRP has become an innovative material in to the field of structural strengthening and rehabilitation. In the present experimental investigation, RC beams were preloaded up to 0 to 50% of the ultimate capacity and were applied with CFRP sheets at the soffit of the beams were compared with control beam. The Load vs deflection, and crack mechanism are studied. The use of CFRP sheets in the soffit of the beam has resulted in enhanced strength and ductility. © 2012 CAFET-INNOVA TECHNICAL SOCIETY.Item Experimental studies on the effects of corrosion on the flexural strength of RC beams(CAFET INNOVA Technical Society cafetinnova@gmail.com 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2014) Pandit, P.; Venkataramana, K.; BabuNarayan, K.S.; Parla, B.; Kimura, Y.RC structures are generally very durable and are capable of withstanding a variety of adverse environmental conditions. However, failures of these structures still occur and reinforcement corrosion is one of the major causes. In the present research, corroded Ordinary Portland Cement (OPC) beams were tested in the laboratory to evaluate their flexural behavior. Accelerated corrosion technique was adopted to corrode the beams. The corrosion was measured using Applied Corrosion Monitoring (ACM) instrument. From the results, it is seen that, as the rate of corrosion increases, the load carrying capacity decreases. The deflection increases initially and then decreases. It is observed that the stiffness of the beams is reduced when rate of corrosion is increased due to changes in the modulus of elasticity of corroded steel. © 2014 CAFET-INNOVA TECHNICAL SOCIETY.Item Flexural bond strength behaviour in OPC concrete of NBS beam for various corrosion levels(Techno-Press, 2014) Shetty, A.; Venkataramana, K.; Babu Naraya, K.S.Corrosion is one of the primary reasons why structures have limited durability. The present investigation is carried out to study the behavior of RC (Reinforced Concrete) structural members subjected to corrosion. Experimental investigations were carried out on National Bureau of Standard (NBS), RC beam specimens made of Ordinary Portland Cement (OPC) concrete. Load versus deflection behaviour was studied for different levels of corrosion i.e., 2.5%, 5%, 7.5% and 10%. It is observed that for every percentage increase in corrosion level, there is about 1.6% decrease in load carrying capacity. Also as the amount of corrosion increases there is a reduction in bond stress. Copyright © 2014 Techno-Press, Ltd.Item Core recovery: a damage diagnosis tool for thermally deteriorated concrete(Emerald Group Holdings Ltd., 2019) Kulkarni, K.S.; Yaragal, S.C.; S.k, B.N.Purpose: This paper aims to study and assess residual strengths of concrete specimen exposed to elevated temperatures by core recovery tests. Design/methodology/approach: The appraisal of concrete structures is typically carried out by means of partially destructive tests such as tests on concrete cores taken from the structure and non-destructive testing. Findings: This paper presents results associated with determination of residual compressive strengths of plain and reinforced concrete elements exposed to elevated temperatures by core recovery test. Physical observations and results of compressive strengths of cores extracted from plain cement concrete, as well as from reinforced concrete beam elements exposed to elevated temperatures, have been presented. Originality/value: The empirical relations have been proposed between standard cube and core extracted for compressive strength of concretes exposed to elevated temperatures are useful for damage diagnosis. © 2019, Emerald Publishing Limited.Item Role of longitudinal reinforcement on the behavior of under reinforced concrete beams subjected to fatigue loading(Elsevier Ltd, 2019) Prashanth, M.H.; Singh, P.; Chandra Kishen, J.M.C.In this work, the role of steel reinforcement in under reinforced concrete beams when subjected to flexural fatigue loading is studied using the acoustic emission (AE) technique. Three-point bend notched beams of three different sizes and with varying reinforcement ratios are subjected to step-wise increasing variable amplitude fatigue loading. The crack mouth opening displacement (CMOD) and AE parameters are analyzed to study the evolution of damage, load carrying and failure mechanisms in under reinforced concrete beams. It is concluded that the presence of reinforcement substantially increases the fatigue life. Further, the CMOD could be used as a criterion for failure in reinforced concrete beams under fatigue loading. © 2019 Elsevier LtdItem Time-dependent safety performance of reinforced concrete structures(Emerald Group Holdings Ltd., 2020) Worabo Woju, U.W.; Balu, A.S.Purpose: Performance of the structure depends on design, construction, environment, utilization and reliability aspects. Other factors can be controlled by adopting proper design and construction techniques, but the environmental factors are difficult to control. Hence, mostly in practice, the environmental factors are not considered in the analysis and design appropriately; however, their impact on the performance of the structures is significant along with the design life. It is in this light that this paper aims to perform the time-dependent performance analysis of reinforced concrete structures majorly considering environmental factors. Design/methodology/approach: To achieve the intended objective, a simply supported reinforced concrete beam was designed and detailed as per the Euro Code (EC2). The time-dependent design parameters, corrosion parameters, creep and shrinkage were identified through thorough literature review. The common empirical equations were modified to consider the identified parameters, and finally, the time-dependent performance of reinforced concrete beam was performed. Findings: Findings indicate that attention has to be paid to appropriate consideration of the environmental effect on reinforced concrete structures. In that, the time-dependent performance of reinforced concrete beam significantly decreases with time due to corrosion of reinforcement steel, creep and shrinkage. Originality/value: However, the Euro code, Ethiopian code and Indian code threat the exposure condition of reinforced concrete by providing corresponding concrete cover that retards the corrosion initiation time but does not eliminate environmental effects. The results of this study clearly indicate that the capacity of reinforced concrete structure degrades with time due to corrosion and creep, whereas the action on the structure due to shrinkage increases. Therefore, appropriate remedial measures have to be taken to control the defects of structures due to the environmental factors to overcome the early failure of the structure. © 2020, Emerald Publishing Limited.Item Fuzzy uncertainty and its applications in reinforced concrete structures(Emerald Group Holdings Ltd., 2020) Worabo Woju, U.W.; Balu, A.S.Purpose: The aim of this paper is mainly to handle the fuzzy uncertainties present in structures appropriately. In general, uncertainties of variables are classified as aleatory and epistemic. The different sources of uncertainties in reinforced concrete structures include the randomness, mathematical models, physical models, environmental factors and gross errors. The effects of imprecise data in reinforced concrete structures are studied here by using fuzzy concepts. The aim of this paper is mainly to handle the uncertainties of variables with unclear boundaries. Design/methodology/approach: To achieve the intended objective, the reinforced concrete beam subjected to flexure and shear was designed as per Euro Code (EC2). Then, different design parameters such as corrosion parameters, material properties and empirical expressions of time-dependent material properties were identified through a thorough literature review. Findings: The fuzziness of variables was identified, and their membership functions were generated by using the heuristic method and drawn by MATLAB R2018a software. In addition to the identification of fuzziness of variables, the study further extended to design optimization of reinforced concrete structure by using fuzzy relation and fuzzy composition. Originality/value: In the design codes of the concrete structure, the concrete grades such as C16/20, C20/25, C25/30, C30/37 and so on are provided and being adopted for design in which the intermediate grades are not considered, but using fuzzy concepts the intermediate grades of concrete can be recognized by their respective degree of membership. In the design of reinforced concrete structure using fuzzy relation and composition methods, the optimum design is considered when the degree of membership tends to unity. In addition to design optimization, the level of structural performance evaluation can also be carried out by using fuzzy concepts. © 2020, Emerald Publishing Limited.