Browsing by Author "Babu Narayan, K.S."

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Applicability of Meshfree Method in Computational Solid Mechanics
(Springer, 2024) Paul, K.; Babu Narayan, K.S.
Meshfree methods are powerful computational tools that offer several advantages over conventional finite element methods. Based on a cloud of points, meshfree methods are easy to construct and provide great adaptivity. Among these methods, the element free Galerkin (EFG) method is widely used for solving solid mechanics problems. In this study, the influence of nodal density on accuracy and computational time is investigated using the EFG method for an axially loaded 1D bar. The method is also applied to a 2D cantilever beam that is subjected to a point load at the free end, and the essential boundary conditions are enforced using Lagrange multipliers. A MATLAB-based program is used to obtain displacement profiles along the length of the bar. The study evaluates the accuracy and computational cost of the EFG method and reports a good agreement between the obtained results and the exact analytical solution. © 2024, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
Assessment of thermally deteriorated concrete by drilling resistance test and sound level
(Maik Nauka Publishing / Springer SBM compmg@maik.ru, 2017) Kulkarni, K.S.; Yaragal, S.C.; Babu Narayan, K.S.; Vardhan, H.
Concrete being the most versatile and widely used construction material finds application in varied range of structures. Many of these like chimneys, furnaces and reactors have to sustain high temperatures and perhaps all structures have to perform at elevated temperatures in the event of fire accidents. Concrete at elevated temperatures undergoes changes in its physical structure and chemical composition and loses its strength characteristics. Need for quick assessment of fire damaged concrete for strength characteristics, has motivated this work, which explores the potential of drilling resistance test on concrete as a Non Destructive Testing (NDT) tool. Drilling times, penetration depths and sound level measurement while drilling have been recorded and analysed to provide monograms that are handy as reckoners in failure forensics. © 2017, Pleiades Publishing, Ltd.
Bond strength behaviour in reinforced concrete members exposed to corrosive environment - An overview
(2013) Shetty, A.; Venkataramana, K.; Babu Narayan, K.S.; Kimura, Y.
Bond resistance of reinforcing bars, embedded in concrete depends primarily on frictional resistance and mechanical interlock. Corrosion of rebars in concrete is one of the major problems in the durability criteria. Local bond stress slip relationship is generally adopted to determine the mechanical properties of the interface between re-bars and concrete. Therefore the attainment of satisfactory performance in bond is an important, aspect of the design and the detailing of reinforcement in structural components. In this paper an overview of factors affecting specimen geometry of bond strength and Types of bond tests were studied. © 2013 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.
Characteristics of normal strength concrete with and without chemical admixtures at elevated temperatures
(CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2011) Yaragal, S.C.; Warad, S.A.; Babu Narayan, K.S.; Venkataramana, K.
Fire is one of the most destructive powers to which a building structure can be subjected. Behavior of concrete when exposed to fire in cases like nuclear plants, cooling towers or any accidental fire in industrial buildings, is a serious concern, on the strength retention property of concrete. This work reports strength retention studies on compressive and split tensile strength of normal concrete with and without the chemical admixture (Reobuild 918, BASF make) at elevated temperatures. Concrete cubes of size 100 mm have been cast as per prior mix design for M30 grade of concrete, 28 days water cured and tested by destructive method for strength before exposure. Later these specimen were subjected to elevated temperatures of 200°C, 400°C, 600°C and 800°C with a retention period of 2 hours and were allowed cool within the furnace to reach ambient temperature. Later their appearance, colour and cracks were observed and also weight losses were determined. Further, destructive tests were conducted to estimate residual compressive and residual split tensile strengths and prediction equations are proposed to ascertain splitting tensile strengths from compressive strengths. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.
Decision Tree Model for Predicting Exposure Temperature and Retention Period-Dependent Behavior of Blended Concrete
(Springer Science and Business Media Deutschland GmbH, 2023) Kulkarni, K.S.; Babu Narayan, K.S.; Yaragal, S.C.
The major objective of the study is to estimate the behavior of blended concrete at various sustained exposure temperatures and retention times. The study examines the properties of four different types of concrete mixes, including unblended and blended mixes with fly ash and ground granulated blast furnace slag used to partially replace cement at exposure temperatures between 100 °C and 800 °C for varying exposure times of 1, 2, and 3 h. Concrete quality has been evaluated using measurements of density, porosity, and ultrasonic pulse velocity. Residual compressive and splitting tensile strengths have also been determined. The experimental study indicates that blended concrete has better fire-endurance characteristics than unblended concrete. The exposure temperature and retention time dependent behavior of unblended and blended concrete is predicted using classification and regression decision tree techniques. © 2023, The Author(s), under exclusive licence to Shiraz University.
Effect of corrosion on flexural bond strength
(International Association of Physical Chemists, 2014) Shetty, A.; Venkataramana, K.; Babu Narayan, K.S.
Corrosion is one of the main causes affecting durability of structures. Corrosion effects on structures cannot be ignored and replaced. To understand the performance of structures there is a need to study the rate at which different corrosion levels occur. Hence the present investigation has been taken up to study the behaviour of NBS (National Bureau of Standard) beam specimens made up of Ordinary Portland Cement (OPC) and Portland Pozzolona Cement (PPC) concrete matrix were subjected to accelerated corrosion for different corrosion levels of 2.5 % to 10 % at 2.5 % interval. Results are compared with those for control beam specimen. It is observed that bond stress value decreases with the increase in corrosion levels. Also corrosion leads to the decline of load carrying capacity. © 2014 by the authors; licensee IAPC, Zagreb, Croatia.
Effect of recuring on compressive strength of thermally deteriorated concrete cubes
(2011) Prasanth, S.; Yaragal, S.C.; Babu Narayan, K.S.
Concrete is found to undergo degradation when subjected to elevated temperatures during an event such as fire and lose substantial amount of its strength. The loss of strength in concrete is mainly attributed to decomposition of C-S-H and release of chemically bound water, which begins when the exposure temperature exceeds 500°C. When thermally deteriorated concrete is supplied with water there is a substantive gain in strength as a consequence of rehydration of cement that is initiated. This paper presents results of an experimental program carried out to investigate the effect of recuring on strength gain of normal strength concrete specimens subjected to elevated temperatures from 500°C to 800°C, which were subjected to retention time of two hours at the designated temperatures. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.
Experimental and numerical investigation on flexural bond strength behavior of corroded NBS RC beam
(SpringerOpen, 2015) Shetty, A.; Venkataramana, K.; Babu Narayan, K.S.
Corrosion of reinforcing steel is the most detrimental effect endangering the structural performance. Present investigation has been taken up to study the detrimental effect of corrosion on bond behavior. Experimental and numerical investigation has been carried out for four different levels of corrosion—2.5, 5, 7.5 and 10 %. Loss in mass of reinforcement bar has been taken as the basis to fix corrosion levels. Accelerated corrosion technique has been adopted to control corrosion rate by regulating current over predetermined durations. NBS beams have been investigated for performance. Concrete grade M30 and steel Fe-415 have been used. From the experimental investigation, it has been observed that bond strength degradation of 2.6 % at slip initiation and 2.1 % at end of slip have been observed for every percentage increases in corrosion level. Numerical investigation with concrete is modeled as solid 65 element and reinforcement modeled as Link 8 elements. ANSYS has yielded 3 and 2.4 % bond strength degradation values at initiation and end of slip per percentage increase in corrosion levels. © 2015, The Author(s).
Experimental investigation of RC frames using CFRP sheets
(2013) Prashanth, M.H.; Babu Narayan, K.S.; Venkataramana, K.; Sajith, M.
Reinforced Concrete frames are the main load resisting systems used in practice all over the world. These frames will be subjected to sway, due to lateral loading most of the times by either earthquake or wind. Ductility and energy dissipation capacity of the frame are the key parameters for better performance under the action of the sway loading. Retrofitting using the new generation material such as carbon fiber reinforced plastic sheets (CFRP) shows much enhancement in these properties of laterally loaded frames. Frames subjected to lateral loading introduce collapse mechanism due to the formation of the plastic hinges at critical hinge locations. An experimental investigation of partially and fully CFRP wrapped reinforced concrete (RC) frames when compared to conventional(bare) frame has been carried out, to bring out the importance of critical engineered locations to be wrapped. © 2013 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.
Making sense of high dimensional concrete data - A statistical approach
(Institute of Physics Publishing helen.craven@iop.org, 2019) Manoj, A.; Babu Narayan, K.S.
Performance of concrete is dependent on a number of factors. It is difficult to understand the influence and interrelationship among these variables, when there are many. Dimensionality reduction techniques can yield the best possible data interpretation based on the variance in data, without loss of much of original information. This paper presents the application of dimensionality reduction technique for analysis of data and decision making in the field of Concrete Technology. Â© Published under licence by IOP Publishing Ltd.
Meshfree Methods in Computational Mechanicsâ€”State of the Art
(Springer Science and Business Media Deutschland GmbH, 2024) Paul, K.; Babu Narayan, K.S.
The finite element method (FEM) has widespread use in solving problems in computational mechanics and applied sciences. However, researchers continue to develop and implement new numerical methods to solve problems that involve complex geometry, material non-linearity, and fracture mechanisms, including crack formation and propagation with moving and discontinuous boundaries. Meshfree methods have seen a significant increase in their application to solve partial differential equations (PDE). These methods involve modelling and solving procedures that depends on a cloud of nodes or points for geometry representation and discretization. In the field of computational fracture mechanics, the meshfree nature of meshfree methods has gained considerable attention for modelling two-dimensional and three-dimensional crack growth. While FEM uses interpolation methods to formulate shape functions, meshfree approaches use approximation methods. This review aims to examine the developments, utility, limitations, and potential for refinements of meshfree techniques. Â© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.
Multi-criteria optimization of fly ash and iron ore tailing based concretes subjected to elevated temperatures
(Associated Cement Companies Ltd., 2019) Yaragal, S.C.; Babu Narayan, K.S.; Kumar, B.; Francis, J.G.
Due to the rapid increase in concrete utilization all over the world, there is increased consumption of Ordinary Portland Cement (OPC), natural fine aggregate (NFA), and natural coarse aggregates. Increased use of OPC, is posing a serious threat due to excess CO2 emissions, and its production is highly energy intensive. On the other hand, extraction and processing stone-based fine and coarse aggregates too, is energy intensive, and the virgin resources are fast depleting. Therefore, for sustainable development, efforts are on all over the world to look for alternative materials in place of conventional ones. In this study, it is attempted to partly replace OPC with fly ash (FA) and partly replace NFA by iron ore tailings (IOT) in concretes. The performance of such concretes at ambient and elevated temperatures is also presented. Full factorial design of experiments was adopted with two control factors under three levels of replacement, i.e., FA (0, 15, and 30% by weight of OPC) and IOT (0, 50, and 100% by volume of NFA). Total nine concrete mixes were prepared and tested for their compressive strengths at room temperature, and residual compressive strengths when subjected to various levels of elevated temperatures (200, 400, 600, and 800°C), and cost of these concretes has also been analyzed. Further, three traditional multi–criteria optimization methods, i.e., grey relational analysis (GRA), technique for order of preference by similarity to ideal solution (TOPSIS), and desirability function approach (DFA) were used to optimize concrete mixes. Results showed that TOPSIS based optimization method is more significant when compared to other two methods. Further, FA-based concrete mixes showed improved performance under multi-criteria optimization. © 2019, Associated Cement Companies Ltd. All rights reserved.
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.
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.
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.
Profiled sheets - the optimum vs the oft used
(Techno-Press, 2010) Babu Narayan, K.S.
Profiled sheets are used extensively in roofing, cladding, sheet piling and containments. Profile development is increasingly rapidly owing to advancement in materials and construction technology. The resistance to longitudinal bending is proportional to the depth and thickness and depends greatly on the profile itself. The strength of the profiled sheet in longitudinal bending is proportional to the depth of corrugation, thickness and on the profile itself. More often than not profiles are repetitive and most popular being of the sine wave form. Hence it may be assumed that if a quarter of the best form is determined, the most optimum profile is known. It is calculated that the strength/unit length of the most widely used sine wave form is in agreement with the best profile suggested by the calculus of variations.
Pushover analysis - Result borders due to hinge formation orders
(Techno Press technop2@chollian.net, 2018) Kulkarni, S.R.; Babu Narayan, K.S.
Performance evaluation of RC frame building by nonlinear static pushover analysis that accounts for elastic and post elastic behavior is becoming very popular as a valid decision making tool in seismic hazard resistant designs. Available literature suggests great amount of interest has shown by researchers in suggesting refinements to geometric and material modelling to bridge the gap between analytical predictions and observed performances. Notwithstanding the attempts gaps still exists. Sequence of plastic hinge formation which has great influence on pushover analysis results is an area less investigated. This paper attempts to highlight the importance of hinge sequence considerations to make analysis results more meaningful. Variation in analysis results due to different hinge sequences have been quantified, compared and bounds on analysis results have been presented. © 2018 Techno-Press, Ltd.
Recuring studies on concretes subjected to elevated temperatures and suddenly cooled by water quenching
(Multi-Science Publishing Co. Ltd, 2015) Yaragal, S.C.; Kittur, M.M.; Babu Narayan, K.S.
Concrete is found to undergo degradation when subjected to elevated temperatures during an accidental event, such as fire and lose substantial amount of its original strength. The loss of strength in concrete is mainly attributed to the decomposition of Calcium Silicate Hydrate (C-S-H) and release of chemically bound water, which begins when the exposure temperature exceeds 500°C. When such a concrete is supplied with water and allowed to recure, it is found to recover substantial amount of its lost strength. This work is carried out to investigate the effect of recuring on strength recovery of un-blended and blended concrete specimen (100 mm cubes) subjected to elevated temperatures from 400°C to 700°C, in steps of 100°C, for a retention period of two hours at the designated temperatures. The concrete cubes immediately after exposure were subjected to thermal shock by quenching them in water, and then temperature of thermally shocked concrete is allowed to cool to room temperature. The cooled specimen were then recured in water for 1, 3, 7, 14, 21, 28, 56 days and tested for compressive strength recovery. These studies were carried out for Portland Cement (PC) based concrete and Portland & Granulated Blast Furnace Slag (70% PC + 30% GGBS) based concrete (blended concrete), and some interesting results are presented and discussed in this paper. © 2015, Multi-Science Publishing Co. Ltd. All rights reserved.
Sensitivity of Pushover Curve to Material and Geometric Modelling-An Analytical Investigation
(Elsevier Ltd, 2015) Panandikar, N.; Babu Narayan, K.S.
Nonlinear static analysis or pushover analysis developed over the last two decades and became the preferred procedure for design and seismic performance evaluation, as this procedure is relatively simple and considers post-elastic behaviour. It provides information on seismic demands imposed by the design ground motion on the structural system and its components. Generation of pushover curve from analysis for reinforced concrete structure involves tremendous amount of computational efforts as the input data for analysis itself is quite exhaustive. The analysis results are very sensitive to the techniques employed in geometric and material modelling. This paper envisages presenting the sensitivity of pushover analysis results to geometric and material modelling parameters by comparing the analysis results with that of experimental investigations. Attempt has been made to understand the sensitivity of parameters like variation in material properties, inaccuracies in placement of reinforcement, effect of confinement of concrete and modelling techniques for elements and plastic hinges. SAP-2000 has been utilised in the current investigation and results have been highlighted suggesting strategies to enhance pushover analysis capabilities. © 2015 Elsevier B.V.
Shape optimization and assessment of wind induced stresses in domes
(2009) Babu Narayan, K.S.; Yaragal, S.C.; Tamura, Y.
Domes are popularly used for column free areas. They are employed as covers to reservoirs and treatment units and also as containment in nuclear reactors. Inverted domes are popular as foundations. This paper demonstrates the need and scope for optimization of domes by formulating and solving the problem by use of calculus. A simple but elegant method is suggested for determination of wind stresses by statics which compares very well with that obtained by rigorous method.