The need for a journal in India, devoted exclusively to activities in the field of structural engineering with special emphasis on research and development had been felt since long. To meet this demand and to provide a medium for structural engineers in India and abroad and to document, discuss and debate current trends in design, research, and development relating to all areas of structural engineering, SERC decided to undertake the publication of a quarterly journal entitled Journal of Structural Engineering (JoSE). The first publication came out in April 1973. From 1993 onwards, the first issue in each Volume has been dedicated to a special topic of current R&D interest. From the year 2005 onwards, the JoSE has been converted in to a bi-monthly Journal to meet the enhanced responses received from the prospective authors, nationally and internationally.
CSIR-Structural Engineering Research Centre
Experimental and numerical studies on GGBS based fibrous geopolymer concrete beams
This paper presents the investigations carried out on Ground Granulated Blast furnace Slags (GGBS) based geopolymer concrete beams with and without glass fibres. The main ingredients considered for the study include constant GGBS, varying proportions of fly ash, silica fume and metakaolin. Beams were tested under four point bending and various responses such as first crack load, ultimate load, deflection corresponding to ultimate load and crack pattern were studied. From the experimental investigations, it was observed that the behaviour of the beams are similar to RC beams. Nonlinear finite element analysis (FE) has been carried out on RC flexural members made up of GGBS with and without considering glass fibres. The non linear properties of concrete and steel are considered for simulation. The widely used concrete damage model available in ABAQUS has been employed to represent the nonlinear behavior of concrete. The integrity of all the elements i.e. concrete and steel has been ensured by applying the appropriate constraint conditions. Static nonlinear analysis has been conducted and the responses such as peak load and the deformations are compared with the corresponding experimental observations. It is observed that the responses obtained from FE analysis are in close agreement with the corresponding experimental values.
GGBS; glass fibres; geopolymer concrete; displacement; finite element analysis; RC beams.
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Investigation of geopolymer mortar using M-sand and dredged marine sand under ambient curing conditions
Influence of damage in steel rebars with different yield strengths and compressive strength of concrete on longevity and ductility of RC beams under fatigue loading
Influence of depth of induced damage in steel reinforcement bars with different yield strengths and compressive strength of concrete on longevity and ductility of RC beams under fatigue loading is reported. RC beams fabricated with four concretes of compressive strengths of 25, 35, 45 and 55 MPa combined with three types of steel reinforcement with yield strengths of 250, 415 and 500 were studied. The reinforcement bars were damaged with varying crack depths of 5.0, 5.5, 6.0 and 8.0 mm. The modes of failure and life of RC beams under fatigue loading established in terms of number of cycles (N) vs. mid-span deflection; load vs. mid-span deflection; normal strain vs. number of cycles; stiffness vs. number of cycles and crack lengths vs. number of cycles have been discussed. The magnitude of induced damage in rebars significantly influences the load carrying capacity and life of RC beams under fatigue loading, leading to conservative prediction of fatigue life. The fatigue life of RC beams with induced damage in RC beams with low yield strength steel reinforcement is greater than that of the High Yield Strength Deformed bars (HYSD ). Further, the fatigue performance of RC beams decreases with increase in the strength of concrete. Hence, the longevity and ductility of RC beams with low strength concrete and low yield strength reinforcement has been observed to be significantly improved.
Partial damage; fatigue life; reinforced concrete; compressive strength; yield strength.
Binder index as criteria for assessing the strength of geopolymer concrete
Geopolymer is being developed as new the binder, instead of cement paste, to produce concrete. The geopolymer paste binds with coarse aggregates, fine aggregates together to form the Geopolymer Concrete (GPC). Several investigators used the industrial bye products such as Fly Ash (FA), Ground Granulated Blast Furnace Slag (GGBS) in combination with alkaline activator solutions in producing the Geopolymer binders. The published literature has revealed several variables that are affecting the strength of GPC. This paper presents a new parameter called ‘Binder Index’ which combines the effect of different parameters and it may be considered as unique parameter influencing the compressive strength of GPC and thereby help in development of binder index based criteria for mix design of GPC.
Binder index; geopolymer concrete; GGBS, fly ash; alkaline activator.
Performance of beams reinforced with PSWC-bars and other rebars
Compared to concrete constructions of earlier periods, constructions of recent decades have suffered early decay and distress. In most cases, this early decay and distress in concrete structures is due to higher rates of corrosion in today’s reinforcing bars of high strength steel. This higher and accelerated rate of corrosion can be attributed to the provision and presence of ribs on the surface of rebars. In the absence of ribs or any other surface feature, PSWC-bars, characterized by their plain surface and gentle wave-type configurations, will be naturally much less susceptible to corrosion than ribbed bars are. Consequently, the use of PSWC-bars will remove the principal causes of early distress in today’s reinforced concrete constructions, ushering in therewith many attendant benefits. Twenty four beams with eight different rebar varieties were tested for their load-carrying capacities. The tests confirmed earlier findings by others that, as in the case of compression elements, the use of well-proportioned PSWC-bars, among different types of rebars, would lead to the highest load-carrying capacities of concrete flexural elements.
Beam; corrosion; deformed bar; durability; rebar; reinforced concrete; reinforcement; reinforcing bar.
Performance of exterior precast beam column connection under seismic effects - a review
The connections of precast beam and column elements plays a major role in implementation of this technology in seismic regions through which the lateral stability and structural integrity will be maintained. So far the review papers published on precast beam-column connections concisely outlines the concepts, development and suitability of different form of connections in seismic regions. However review works related to seismic behaviour of different precast beamcolumn connections with analyses and discussion compared to their monolithic connection in a single platform were limited. Hence, this paper presents the overall review of the precast beam-column connection’s experimental results by correlation with their monolithic connections in terms of the load carrying capacity, ductility, energy dissipation capacity, stiffness degradation and the failure mode. The different forms of connections were grouped under wet and dry connections (post-tension and mechanical device). The performances of various connection systems are analysed and compared based on the connection construction detail and seismic behaviour. Overall, the seismic performance of wet connection and post-tension connection are acceptable with some major construction drawbacks. Despite of the poor seismic performances, the mechanical device connections may be implemented in construction field with the benefit of economy and simplicity in construction. However, certain innovative ideas and or modification are to be performed to the existing systems to suit the regions of high seismicity.
Precast beam-column connection; seismic behaviour; wet connection; dry connection; monolithic connection; post-tension connection; mechanical device connection.
Experimental study on mechanical properties of hybrid fiber quaternary concrete with supplementary cementitious materials subjected to extended curing period
The present study investigated the effect of Supplementary Cementitious Materials (SCMs) on mechanical properties of quaternary blended hybrid fiber cement concrete subjected to longer curing periods. Cement was partially replaced with SCMs like fly ash, rice husk ash and lime stone powder concrete was reinforced with steel, carbon and fibrillated polypropylene fibers in different proportions. Steel fibers were added at volume fraction of 0.5%, 1% and 1.5 % while carbon and fibrillated polypropylene fibers at weight fraction of 0.25% and 0.5% in the concrete mix. Carbon fibers were added in mono form and in hybrid form with steel and polypropylene fibers. Compressive strength, split tensile strength, flexural strength and impact resistance of all the mixes were investigated at 56 and 90 days. The tests results revealed that steel-carbon and steel-carbon-polypropylene hybrid fiber reinforced concrete performed better in compressive, split tensile, flexural strength properties and impact resistance than control and mono carbon fiber reinforced concrete. The results also revealed that substitution of cement with SCMs greatly influenced the mechanical properties of the fiber reinforced concrete at the later ages.
Quaternary; steel fiber; carbon fiber; polypropylene fiber; post crack resistance.
An innovative mix proportioning with recycled concrete coarse aggregate
Strength and behavior of cold-formed steel built-up battened columns: tests and numerical validation
Field demonstration of continuous monitoring of a steel railway bridge
Many railway bridges in India are aged requiring an analysis on their current health. Appropriate instrumentation is necessary to determine the health of the bridges. This paper explains the instrumentation philosophy followed and its implementation in the field for continuous monitoring of a railway bridge. The bridge considered for this study is a single span steel plate girder bridge. Using a wired data acquisition system the bridge was monitored for 125 days. Also, an economical wireless data acquisition system developed in-house was validated using this wired data acquisition system. Finally, the collected strain time histories are summarized in the form of count versus strain range, as determined from the rainflow count algorithm. Thus, a viable methodology for continuous monitoring of railway bridges is demonstrated which may be used to assess the health of the bridge and arrive at rational design loads for railway bridges.
Continuous monitoring; steel plate girder; railway bridge; wireless acquisition; strain; thermocouple.
Fatigue behaviour of latex modified reinforced concrete beams
The slow cyclic fatigue behaviour under flexural loading of Latex Modified Reinforced Concrete (LMRC) beams containing 10 and 15 percent latex made of M30 grade has been investigated. The beams were tested in such a manner that in some cases the maximum load level was kept below the permissible load level (peak of stability point as obtained under cyclic tests) to confirm the permissible load level while in other cases the maximum load level was kept above the permissible load such that the accumulation of strains to failure occur due to the repetition of load cycles. The envelope curve, stability point curve and load capacity of LMRC beams obtained from load-deflection plots under flexural fatigue tests were compared with that of cyclic tests. The results obtained are in close proximity with that observed under cyclic tests.
Cyclic-fatigue; strain-accumulation; load-ratio; crack-pattern; common-point and stability-point.
Flexural fatigue analysis of plain and glass fibre reinforced polymer concrete composites
Results of an investigation conducted to study the flexural fatigue of epoxy resin based Polymer Concrete Composites (PCC) and Glass Fibre Reinforced Polymer Concrete Composites (GFRPCC) are reported. Three point flexural fatigue tests were conducted on PCC and GFRPCC specimens using MTS servo controlled cyclic load test setup to obtain the fatigue lives at different stress levels. One hundred and sixty four specimens of size 40 × 40 × 160 mm were tested in flexural fatigue. Sixty eight static flexural tests were also conducted to facilitate fatigue testing. As a pre-requisite to the analysis reported in this paper, it has been shown that the fatigue life of PCC and GFRPCC, at any stress level, can be modeled by the two-parameter Weibull distribution. The fatigue strength prediction models, representing S-N relationships have been examined and the material coefficients have been obtained for PCC and GFRPCC containing 0.5%, 1.0% and 2.0% glass fibres. Further, using Weibull distribution probability of failure has been incorporated into the fatigue life data of PCC and GFRPCC to develop S-N-Pf relationships, both graphically and analytically. The two million cycle endurance limits for PCC and GFRPCC containing different amount of glass fibres have also been estimated.
Endurance limit; fatigue life; polymer concrete; weibull distribution; probability of failure.
Assessment of interlaminar shear in fiber reinforced composite materials
Behaviour of cold-formed steel built-up columns: tests and numerical simulation
This paper describes a test program on cold-formed steel built-up columns composed of two-lipped channels placed back to back. In this study, 14 specimens were tested between pins with the warping restrained end condition. The overall initial geometric imperfections are measured. The compression resistance, load-axial shortening response and deformed shapes are presented. A nonlinear finite element models were developed, and numerical analysis that includes material nonlinearity, geometric nonlinearity, contact nonlinearity and geometric imperfections was performed. The FE and the experimental results were found in good agreement in terms of ultimate compression resistance, deformed shapes and load-axial shortening curves. The Direct Strength Method (DSM) and Effective Width Method (EWM) for cold-formed steel were evaluated against the obtained test results. It is concluded that the design strengths predicted by design codes are provided conservative strength predictions for the built-up columns, and these design rules are also assessed by the reliability analysis.
Built-up column; cold-formed steel; direct strength method; effective width method; experiments; finite element analysis; lipped channel.
Specific fracture energy for normal strength concrete, high strength concrete and fibre reinforced concrete - three approaches
For the analysis of cracked concrete structures, advanced mechanical properties, such as fracture energy and the corresponding tension softening relation are essential. Although significant studies have been reported on evaluation of specific fracture energy, still, there is no clarity and applicability of the approach for various concretes. This paper examines the determination of fracture energy by using (i) RILEM work of fracture with tail correction to loaddisplacement plot (ii) boundary effect model of Hu and Wittmann and (iii) energy release rate approach for various concrete mixes. Several concrete mixes, whose compressive strength ranges from about 20 to 90 MPa comprising of normal strength concrete, high strength concrete and fibre reinforced concrete have been considered in the present study to evaluate the specific fracture energy. From the study, it is observed that the specific fracture energy obtained by the above methods are in close agreement with each other and designer can employ either of the methods for analysis and design of concrete structures and also for safety evaluation of sensitive structures.
Specific fracture energy; normal strength concrete; high strength concrete; fibre reinforced concrete; rilem work of fracture; boundary effect method; energy release rate.
Experimental study on flexural behavior of NSM and external bonded FRP strengthened pretensioned precast hollow core slabs
Prestressed Precast Hollow Core (PPHC) slabs are floor/roof elements which have longitudinal cores along the span. Strengthening of these slabs may be required for several reasons. The objective of this study is to understand the flexure and flexure-shear behavior, failure mechanisms of PPHC slabs with and without Fiber-Reinforced Polymer (FRP) strengthening. Experimental variables include (i) different FRP strengthening techniques, namely External Bonding (EB) and near-surface mounting (NSM), (ii) strengthening reinforcement ratios and (iii) shear span to depth (a/d) ratios. Test results revealed that the FRP strengthening is very effective in increasing the ultimate strength of slabs and strengthening changed the failure modes of the slabs. Experimental results show that the flexural load carrying capacity of PPHC slabs increased in the range of 14% to 36% depending on the strengthening scheme used. It was found that Near Surface Mounted (NSM) flexural strengthening ratio should be carefully selected to avoid unfavorable brittle shear failure. Interesting transition from flexure to the flexure-shear failure of the slabs was noted in the behavior as the FRP strengthening ratio was increased.
Hollow core slab; prestress; GFRP; strengthening; NSM technique; external bonding.
Evaluation of dynamic characteristics of RC overhead tanks
Spacing and orientation of stud shear connectors in steel – concrete composite constructions
In steel concrete composite constructions, the behavior of mechanical shear connectors plays a vital role in establishing composite action. The behavior of mechanical shear connectors can be well studied by push – out tests. A modified push out test as developed by Cem Topkaya, et al.,, is adopted in this study after a small modification. Headed stud connectors are the most frequently used connectors which is categorized as flexible type shear connectors. In most of the real construction mainly in bridges and multistoried structures the 19mm dia headed shear connectors were extensively used. In this paper an attempt has been made to study the spacing pattern and orientation of 19mm dia stud for the composite member. Experimental investigations were made to identify the impact of orientation and spacing of stud in resisting horizontal shear. Numerical modelling using Abaqus 6.13 was developed in this study to validate the obtained experimental results. The stud behavior which was observed in various spacing and orientations in the experiments is also modelled in the numerical simulations.
Composite beams; stud shear connectors; modified push – out tests; load – slip curves; headed studs; stud spacing; flexible connectors; finite element method.
Behaviour of steel fibre reinforced self compacting concrete beams in flexure
The addition of steel fibre to Self Compacting Concrete (SCC) imparts superior mechanical properties to concrete. The workability and strength performance in fresh and hardened state of SCC containing steel fibres having aspect ratio 55 and volume fractions 0%, 0.5%, 1.0% and 1.5% of M30 grade were taken to study the effect of fibre content. Fly ash has been used as partial replacement of cement by a constant 18% for all mixes. In addition, eight nos. of steel reinforced beams having size 125 × 150 × 1100 mm have also been cast, cured normally and then tested under two point loading for flexural strength. The workability results of Steel Fibre Reinforced Self Compacting Concrete (SFRSCC) satisfy all properties of self compaction as per EFNARC specifications. It is observed that a marginally higher compressive strength, split-tensile strength and flexural strength has been found with 1% volume of steel fibres as compared to 0.5% and 1.5% of steel fibre content. Maximum values of ductility factor, energy absorption capacity and toughness index were found to be 2.86, 194.20 kN-mm and 5.05 respectively for SFRSCC beams with 1% steel fibres. Also, the toughness index, ductility factor and energy absorption of SFRSCC beam increased with increase in fibre content upto 1% beyond which it decreased marginally for 1.5% steel fibre content.
Self compacting concrete; beams; steel fibres; workability; flexural strength.
Flexural behavior of concrete beams reinforced with innovative FRP wrapped steel bars
Corrosion is the main problem in the use of steel for reinforcing concrete structures. Steel rebars after corrosing causes strength and stiffness degradation of the concrete structures. To prevent the corrosion of steel, in this paper an innovative hybrid rebar produced by wrapping Fiber Reinforced Polymer (FRP) around a steel core is proposed. The FRP wrapping would prevent direct exposure of steel surface to the contaminating environment and hence would improve the life of the reinforcement and the concrete structures. Results of the experimental and analytical studies carried out to understand the behavior of the concrete beams reinforced with hybrid rebars are presented in this paper. Type of fibers (glass or carbon fibers), wrapping length of the FRP and shear stirrups spacing are the primary variables considered in the experimental program. Test results indicate that the type of fibers and the FRP wrapping length affect the failure modes, ultimate load, and the load-deflection behavior of the beams. The volume fraction of the fibers and the strength of the fibers used in the hybrid rebars affect the flexural behavior of the beams and it is found that there is large scope for using hybrid rebars with carbon fiber wrapping as reinforcement in the concrete structures. The predicted ultimate flexural loads of the beams reinforced using hybrid rebars with carbon fibers are in good agreement with the test results.
Hybrid reinforcement; GFRP; CFRP; reinforced concrete; beams; corrosion.
Mechanical properties of fiber reinforced concrete using copper slag as a fine aggregate
In this paper, results and discussions of the experimental study carried out to determine the properties of steel Fiber Reinforced Concrete (FRC) consisting of graded Copper Slag (CS) as fine aggregates are presented and discussed. The properties of the concrete evaluated from the experimental study are workability, compressive strength, flexural strength, split-tensile strength, stress-strain curve under compression and bond strength. The test variables are volume content (0.5, 1.0, 1.5 and 2.0%) and length (30 and 60mm) of the fibers. Test results indicated that addition of steel fibers decreased the workability of the concrete. It is observed from the test results that the strength of the concrete containing graded CS without fibers is lower than that of the control concrete containing conventional fine aggregates. However, addition of crimped steel fibers up to an optimum volume content improved the strength of the concrete. It is concluded from the experimental study that the concrete with properties better than that of the control concrete could be achieved by using graded copper slag as fine aggregates and crimped steel fibers together in the manufacturing of concrete.
Copper slag; crimped steel fibers; fiber reinforced concrete; sustainable concrete; gradation.
Behaviour of reactive powder concrete under direct tension and flexure
Reactive Powder Concrete (RPC) is a high strength new generation concrete, formed from a special combination of constituent materials. The composition of RPC includes cement (Ordinary Portland cement) fine sand, mineral and chemical admixtures with high strength micro steel fibres. The evaluation of the tensile stress-strain characteristics is of considerable interest in the analysis of RPC structural applications. The present study focuses on the behavior of RPC under direct tension and flexural tension. The study also focuses on the effect of various dosages and aspect ratio of fibers. Among the several RPC mixes evaluated, the RPC mix with a combination of 13mm and 6mm length fibers showed the highest tensile strength under direct tension. The specimens with mixed fiber ratio (13mm+6mm) exhibited both tension stiffening and tension softening. Residual flexural tensile strength, fracture energy and toughness indices of different types of RPC beams also evaluated. The results reveal that the RPC has enhanced tensile properties and the ductility increases with respect to the addition of fibres.
Reactive powder concrete; direct tension; tensile strength; residual strength.
Prediction of fresh properties of various SCC mixes using support vector machine
This paper presents the methodologies developed for prediction of fresh properties of Self Compacting Concrete (SCC) by using Support Vector Machine (SVM) which is an advanced statistical model. The fresh properties include L-box, slump flow, slump flow time and V-funnel. The experimental data of fresh properties of various SCC mixes has been consolidated by considering the effect of water cement ratio, water binder ratio and steel fibres. In support vector machine, Support Vector Regression (SVR) is based on the computation of a linear regression function in a high dimensional feature space where in the input data are mapped through a nonlinear function. Four models were developed to predict various fresh properties of SCC. Models were developed by using MATLAB software for training and prediction. About 75% of the data was employed for development of model and about 25% of the data is used for validation. The predicted flow properties for SCC mixes are found to be in very good agreement with those of the corresponding experimental observations available in the literature. The analysis indicates that the proposed SVM model serves as an alternative method for prediction of fresh properties of SCC.
Support vector machine; self compacting concrete; fresh properties; variance.
Empirical period - height relationship for shear wall system buildings in India
Researchers all over the world are continuously working towards development of latest techniques for improving earthquake safety of tall buildings. The period – height relationships are very essential in determining the seismic demands of the structure. It is revealed that, although the code formulas provide periods of vibration that are generally shorter than measured periods of vibration, these formulas can be improved to provide better correlation with the measured data. Therefore, a relationship is sought that will give precise prediction of period of vibration for structural assessment of Indian reinforced concrete shear wall buildings. Many researchers have attempted to revise these code specified formulae. In this study 19 existing reinforced concrete shear wall buildings in India, with varying length, width and height are considered. The fundamental time periods of all the selected buildings were calculated using finite element method and IS 1893(Part 1) : 2002 based empirical formula. On the basis of fundamental period of vibration of an Indian Reinforced Concrete Shear Wall (RCSW) building, obtained by finite element analysis, new equation has been proposed. The comparison of proposed equation with Indian code shows that finite element analysis yielded 97.64% higher periods as compared to the code approach.
Fundamental period; height; empirical formula; reinforced concrete; shear wall.
Comparative study on properties of self compacting concrete using artificial neural network and regression analysis
Analytical models are developed by using Artificial Neural Network (ANN) and Multiple Regression Analysis (MRA) for predicting the Slump Flow Diameter (SFD), L-box Ratio (LR), V-funnel Flow Time (VFT) and Compressive Strength (CS) at 28 days of Self Compacting Concrete (SCC). In this work, 60 Mix proportions were prepared for different grades of SCC containing 20%, 30% and 40% of fly ash as partial replacement of cement. The fresh and strength properties of SCC which are arrived through experimental investigations are utilized for developing the analytical models. The mix constituents such as Cement (C), Fly ash (F), Fine Aggregate (FA), Coarse Aggregate (CA), Super plasticizer dosage (SP) and Water-Binder ratio (W/B) were fed as input parameter to achieve the four output parameters as targets. Four models were developed using both ANN and MRA and their results were evaluated and compared. ANN models demonstrated more accuracy and had higher correlation.
Artificial neural network; analytical model; compressive strength; multiple regression analysis; self-compacting concrete.
Fatigue ratcheting studies on pressurised stainless steel straight pipes under cyclic bending
Ratcheting is a phenomenon which leads to reduction in fatigue life of a structural component by loss of ductility due to cycle by cycle accumulation of plastic strain. Ratcheting occurs in a structure subjected to a combination of steady and cyclic loads such that the material response is inelastic. Fatigue ratcheting studies were carried out on five numbers of SA 312 Type 304LN stainless steel straight pipes of 168 mm outer diameter under four point cyclic bending. The nominal thickness of the pipe specimens was 14.5 mm and inner diameter was 139 mm. Out of the five pipe specimens, four specimens were tested under combined internal pressure and cyclic bending and the remaining one specimen was tested under cyclic bending without internal pressure. Cyclic bending load was applied on the pipe specimens by subjecting them to different levels of load-line displacement applied at the centre (axis of the actuator piston). Loadline displacement is the vertical distance by which the actuator piston moves; the same was measured from the in-built LVDT in the actuator. Number of cycles corresponding to through-thickness crack and final failure of the component were recorded. During the tests, load, load-line displacement and deflections (measured at the bottom of the pipe specimen) at four locations were continuously monitored. Local bulging and ovalization of the pipe cross-section and consequent reduction of the pipe wall thickness were observed due to fatigue ratcheting. The pipe specimens subjected to combined internal pressure and applied cyclic displacement failed either by occurrence of through-wall crack accompanied by simultaneous ratchet swelling (ballooning) or occurrence of through-wall crack accompanied by simultaneous ratchet swelling (ballooning) and bursting.
Fatigue ratcheting; Type 304LN stainless steel; straight pipe; internal pressure; cyclic bending; ratcheting strain; through-thickness crack; ballooning; ovalization.
Investigations on one-way flexural behaviour of biaxial voided slab with cuboid shape void formers
Biaxial voided slab system is an innovative slab system which is being developed and adopted all over the world. It is used as an alternate for the solid slab and reduces the self-weight up to 50 % in comparison with solid slabs without significant change in its structural performance. This type of voided slab systems consist of void formers with various shapes like spherical, donut, cuboid, etc. Experimental and numerical investigations were carried out to study the behaviour of two-way cuboid voided slab under one-way flexure. Voided slab specimens were prepared and tested with commercially available cuboid shape void former. Experimental study carried out by four-point bending test and numerical study has been carried out in finite element software DIANA 10.2. Comparison of experimental and numerical studies showed that the ultimate load carrying capacity of cuboid voided slabs were 91 % of solid slab. The reduction in flexural stiffness corresponding to yield stage was observed to be 14 % of the solid slab. Ultimately, it is found that the cuboid shape voided slabs can be used as the alternate for conventional solid slab with necessary correction for loss of cross-section caused by voids.
Biaxial voided slab; cuboid shape void; one-way flexure; four-point bending test; finite element analysis.
An artificial neural network approach for corrosion assessment of structures exposed to marine atmosphere
The aim of this paper is to demonstrate the use of Artificial Neural Network (ANN) to assess the relative corrosion state of steel rebar in three different cementation materials (i.e. Ordinary Portland cement (OPC), Portland Pozzolona Cement (PPC) and Portland Slag Cement (PSC)). Steel rebar is embedded in M30 and M40 mix design with the cover thickness of 25 and 40 mm and exposed in corrosive marine environment for the accurate representation of real conditions. Open Circuit Potential (OCP) measurements were used for the analysis and model development through ANN. Comparison of measured and predicted OCP is done. It is very clear that the results obtained using ANN has high accuracy. Further, assessing the relative performance using ANN assures confidence in future predictability and is practical and beneficial.
ANN; performance; blended cements; marine environment; pozzolans; corrosion inhibitor.
Tension stiffening and cracking behaviour of hybrid fibre reinforced ternary blend geopolymer concrete
This paper describes an experimental investigation on the effect of mono and hybrid fibres on the tension stiffening effect and cracking behaviour of ternary blend geopolymer concrete (TGPC). A total number of 45 prismatic tension members, axially reinforced with 10 mm diameter High Yield Strength Deformed (HYSD) bar were tested under uniaxial tension. The grade of concrete considered was M55. The main variables considered in this work were the volume fraction of fibres, viz. steel fibres (0%, 0.5% and 1%) and polypropylene fibres (0%, 0.1%, 0.15%, 0.2% and 0.2%). Test results reveal that the addition of hybrid fibres enhances the tension stiffening effect and reduces the cracks spacing and width in TGPC. A method to predict the crack width of hybrid fibre reinforced TGPC was proposed, and the estimated values were found convincing with the test results.
Bond stress; crack width; geopolymer concrete; hybrid fibre reinforced concrete; tension stiffening; ternary blend.
Influence of water fill condition on the seismic response of ground supported circular water tanks
The dynamic behaviour of cylindrical ground supported concrete water tanks with different aspect ratios is investigated by performing coupled acoustic structural Finite Element (FE) analysis. The influence of water fill condition on the natural impulsive frequency of tanks with different aspect ratio from FE analysis is compared with the values obtained from standard codes. The parametric study on tanks of aspect ratio varying from 0.2 to 2.0 necessitates to incorporate the water fill condition for the determination of impulsive frequency. Time history analyses for full fill and half fill conditions are carried out for tanks with different aspect ratio in response to past three major earthquakes of varying frequency content. The responses of the tank such as hoop stress, normal stress and radial displacement to seismic loading depend not only on the frequency content of earthquake, but also on the tank dimensions and its water fill conditions.
Ground supported cylindrical water tank; fluid – structure interaction; aspect ratio; modal analysis; water fill condition; time history analysis.