ISSN 0970-0137
Current Issue
February – March 2018 issue, Vol. 44 No. 6

         
44-52

Improvement on axial compressive strength of concrete cylinders using Bfrp composites

M. Ancheeswari and J. Jegan

545

Abstract

The use of Fiber Reinforced Polymer (FRP) materials for repair and strengthening has been worldwide all around. The application of Basalt Fiber Reinforced Polymer (BFRP) as a strengthening material for concrete structures is not popular as of now. In order to enrich and enlarge the knowledge on them, an experimental investigation was under taken to investigate the effectiveness of BFRP confined concrete cylinders. In this experimental work all the concrete cylinders confined with three different layers of BFRP were tested. The lateral confinement provided by the BFRP enhances the load carrying capacity of the cylinder confined with three layers. The externally bonded BFRP enhanced the axial deformation control and ultimate load carrying capacity of the confined cylinders. The external bonded BFRP significantly prevented the Poisson’s effect of the concrete by providing confining pressure. A nonlinear equation available in the literature has been used to determine the theoretical load carrying capacity of the BFRPcylinders. The predicted load carrying capacity was reasonably accurate with minimum error of 1.61%. The test result shows the better confinement efficiency of BFRP as a strengthening material

44-53

Nano-mechanical response of carbon nanotubes – a mechanics based approach incorporating atomistic information

B.S. Sindu,, Saptarshi Sasmal and D. Nishanthi

552

Abstract

Carbon Nanotubes (CNTs) are being widely used in composites to improve their mechanical properties and to further impart smart properties. In order to use CNTs effectively and efficiently in a composite, it is important to understand its behaviour under different loading conditions. The behaviour of CNT is primarily being investigated using molecular level analytical techniques since the experimental techniques are very limited, too expensive and time consuming. Though it is very important to determine the behaviour of CNT before using it in engineering- or building- materials, it is extremely difficult for the engineers to be involved in such molecular level mechanics, whereas usage of conventional structural mechanics approach to understand the behaviour of CNT might be a crude approximation. In order to bridge this gap, structural mechanics approach by incorporating molecular level information has been employed in the present study to evaluate the static (axial and bending behaviour, linear and nonlinear buckling) and dynamic response of CNT. The influence of various geometric parameters like diameter, chirality and aspect ratio on the static and dynamic responses has been studied. The findings will help for easy computational studies on CNT incorporated composites.

44-54

Seismic performance of composite reinforced concrete and steel moment frame structures using pushover analysis

Wei Li, Rui He, Linzhu Sun, Kejia Yang and Junliang Zhao

560

Abstract

In the past decades, many studies have reported the advantages of composite Reinforced Concrete-Steel (RCS) frames, which consist of Reinforced Concrete (RC) columns and Steel (S) beams and thus are better than pure reinforced concrete (RC) and steel frames. This paper evaluates seismic performance of RCS frames based on FEMA-356 and ATC40 with plastic rotations as the acceptance criteria. The effect of joint deformations on overall behavior of RCS frames is studied through nonlinear static analysis (Pushover) in ETABS software. The behavior of three RC frames is compared with that of three RCS frames based on the same columns. The results show a great improvement on the overall behavior of RCS frames using steel beams.

44-55

Experimental study on the behavior of lightweight concrete sandwich panels under axial compression

J. Daniel Ronald Joseph, J. Prabakar and P. Alagusundaramoorthy

568

Abstract

In this paper, results of experimental studies carried out to understand the behavior of prototype lightweight concrete sandwich panels under axial compression are presented and discussed. Four different configurations of the panels with different panel thickness and size of weld mesh used as reinforcement in concrete wythes of 3m height were tested under axial compression till failure. Self-compacting concrete was used for casting concrete wythes and expanded polystyrene (EPS) was used as insulation material. Wire mesh with two different mesh sizes such as 50-mm and 100-mm were considered. Truss-type shear connectors made of wires were used to achieve composite action. Experimental study indicates that stiffening concrete beams near loading and the support regions improved the composite action of the panels and precluded panel failure due to local crushing of concrete wythes. Also, shear connectors were found to be effective in ensuring composite action until failure of the panels. The panels with relatively less thickness failed by buckling at a cross section away from the loading region whereas the panel with higher thickness failed by buckling near the loading region. It is noted that even though mesh size and EPSthickness were varied, the ultimate load of the panels (with stiffening beam) tested are comparable due to same area of concrete wythes

44-56

Experimental study on mechanical properties and durability properties of hybrid fibre reinforced concrete using steel and banana fibres

P. Loganathan and G.S.Thirugnanam

577

Abstract

The Fibre Reinforced Concrete (FRC) possesses a high flexural strength, improved ductility and high energy absorption capacity than that of conventional concrete against dynamic loads. When the concrete is reinforced with randomly dispersed fibres it prevents micro cracks form widening1. The combination of various types of fibres results in the formation of hybrid fibre composites. One type of fibre improves the properties of fresh concrete and prevents early shrinkage cracks while the other type of fibre contributes to the improvement of strength and durability of hardened concrete. The scope of the present study is to investigate the influence of different combination of hybrid fibres (steel and banana fibres) on the behavior of Reinforced Concrete (RC) structural elements with hybrid fibres. The laboratory experiments have been conducted with normal plain concrete and fibrous concrete. The mechanical properties such as compressive strength, tensile strength and modulus of elasticity and durability properties such as resistance to chemical attack were investigated in the laboratory test. The RC beams have been designed with M30 grade concrete and reinforced with Fe415 grade steel as main reinforcement and fibres (steel and banana) as secondary reinforcement. Concrete mixes have been prepared with optimum fibre contents and also without adding fibres (normal concrete). The beams were subjected to cyclic loading in order to evaluate the behavior under simulated earth quake loading conditions. Based on the results of the experimental study significant conclusions were arrived at, to show the behavior of Hybrid Fibre Reinforced Concrete (HFRC) beams is relatively better than that of conventional concrete beams in all aspects. Instead of adding a single type of fibre, the combination of different types of fibres (hybrid fibres) increases the ductility and energy absorption capacity substantially. Thus phenomenon is particularly suitable for structures located in seismic areas.

44-42

Prediction of SIFCON compressive strength using neural networks and curve fitting model

Gottapu Santosh Kumar and K. Rajasekhar

450

Abstract

This paper presents the results of experimental investigation conducted to evaluate the possibilities of adopting Levenberg Marquardt (LM) based Artificial Neural Network (ANN) to predict the compressive strength of SIFCON (made with manufactured sand) with different percentage fibre fractions (8%, 10% and 12%) and different curing periods (7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, 91 and 98 days) as input vectors. The network has been trained with experimental data obtained from laboratory experimentation. The Artificial Neural Network learned the relationship for predicting the compressive strength of Slurry Infiltrated Fibrous concrete (SIFCON) in 400 training epochs. The input vector considered for the LM training phase includes curing periods of SIFCON concrete, fibre configuration, number of neurons, learning rate, momentum and activation functions. After successful learning, the LM based ANN models predicted the compressive strength satisfying all the constraints with an accuracy of about 95%. Results of LM algorithm are compared with the polynomial curve fitting method. Research results demonstrate that the proposed LM based ANN model is practical, predicts with high accuracy and beneficial. The various stages involved in the development of Levenberg Marquardt based Neural Network models are enumerated in brief in this paper.

44-57

Rheological properties of smart dynamic concrete containing different supplementary cementitious materials

S.D. Bauchkar, H.S. Chore and S.K. Mukherjee

586

Abstract

An experimental investigation into the rheological behavior of smart dynamic concrete (SDC) is presented in this paper. The investigation was aimed at quantifying the impact of the varying amounts of mineral admixtures on the rheology of SDC containing crushed sand as fine aggregates. Apart from the ordinary Portland cement (OPC), the supplementary cementitious materials such as fly ash (FA), ground granulated blast furnace slag (GGBS) and micro-silica (MS) are used in different percentages keeping the mix paste volume and flow of concrete, constant. The instrument, ICAR (International Center for Aggregate Research) rheometer, employed in the present study for evaluating the rheological behaviour of the SDC is found to detect systematic changes in workability, cementitious materials, successfully. The concrete mix containing OPC and cementitious materials like FA, GGBS, MS demonstrates different rheological behavior. Average viscosity of eleven SDC mixes tested is found to be close to 60 Pa-s. The slump flow, T500, V-funnel, L-box tests can be concurrently used for predicting the flow behaviors of SDC made with different cementitious materials. Traditional test methods of SCC testing such as flow, V-funnel are found to have good relationship with viscosity of mix. fly ash, GGBS and micro silica is observed to help to improve rheology with less stickiness as compared to pure OPC mixes. The fly ash, GGBS and micro silica can be used to reduce the yield stress without resulting in large variation in the plastic viscosity and improved the stability of the mixes.

44-58

Nonlinear finite element analysis of lscc slabs to find effectiveness of three connection schemes

G. Janani, N. Anandavalli, and J. Rajasankar

598

Abstract

The aim of this paper is to compare the structural performance of Laced Steel Concrete Composite (LSCC) slab formed by laterally connecting LSCC units. Performance of three connection schemes are studied based on nonlinear response of the slab for incremental static loads. The analysis is carried out using finite element method. The unique features of LSCC unit responsible for its superior structural performance are described. A brief description of the connection schemes is presented along with the criteria followed for evolving them. Following this, details of the finite element models developed for the slab are presented with emphasis on describing the nonlinear behavior of steel, concrete and the interface conditions. The performance of the connection schemes is evaluated based on the nonlinear response of the slab in terms of peak load, ductility and support rotation. The LSCC slab formed by lateral shifting of the cover plates is found to exhibit far superior performance.

44-59

Investigations on ground rubber tire powder incorporated textile reinforced concrete for flexural strengthening of RC beams

Smitha Gopinath, Irene Bonadies, C. Carfagna, S. Maheswaran, A. Ramachandra Murthy and Nagesh R. Iyer

605

Abstract

This research reports the feasibility of use of rubber tire waste as a component material in textile reinforced concrete. Study mainly focus on arriving at a strengthening system for RC beams using textile reinforced concrete. Basalt and alkali resistant glass textiles are used as reinforcement and ground rubber tire powder incorporated cementitious mortar is used as binder. Experimental investigations are carried out to arrive at the mechanical properties of different percentages of rubber tire powder in a cementitious mortar. Three types of mixes with different rubber contents ranging from 2.5% to 7.5% of partial replacement of cement are used in the concrete mix. Mechanical characterization studies are performed to determine the compressive strength and split tensile strength. The micro structural evaluation is carried by using scanning electron microscopy with energy dispersive X-ray analysis (SEM/EDAX) to correlate the micro structural behaviour with mechanical properties. Further, behaviour of reinforced concrete beams strengthened with ground rubber tire (GRT) powder incorporated textile reinforced concrete is studied in detail. The encouraging results obtained in present study will pave way for extending the application potential of ground rubber tire as an ingredient in textile reinforced concrete for many structural applications in an environmental friendly and cost-effective way.

44-60

Fatigue life prediction of self compacting concrete using S-N-Pf relationship

S. Goel and S.P. Singh

613

Abstract

The paper presents a study on the development of a relationship for Self Compacting Concrete (SCC) beams in terms of fatigue life (N), stress level (S) and failure probability (Pf) to predict its flexural fatigue life. The fatigue life data of SCC was obtained by carrying of flexural fatigue tests on about 50 specimens of size 100 x 100 x 500 mm under four point loading at different stress levels in the range of 0.85 to 0.65. As the estimation of static flexural strength was a desirable pre-requisite for the selection of the maximum and minimum load limits for the fatigue tests, approximately 40 complimentary static flexural tests were also conducted to facilitate fatigue testing. The flexural fatigue tests and static flexural tests were conducted on a 100 kN closed loop servo-controlled actuator. The results have been used to develop a family of S-N-Pf curves graphically to represent the relationship between stress level S, fatigue life N, and probability of failure Pf, thus incorporating probability of failure into the fatigue life data of SCC. The experimental coefficients of the fatigue equation have also been obtained from the fatigue test data to represent the S-N-Pf curves analytically. The two-million cycles fatigue strength of SCC has been observed to be higher than that of Normally Vibrated Concrete (NVC).

44-61

Effect of sulfuric acid environment on fracture parameter of concrete

M.R.L. Sastry, K. Srinivasa Rao and P. Subba Rao

622

Abstract

Fracture tests have been conducted on three plain concrete mixes in normal environment and sulfuric acid environment. Fracture energy GF based on work of fracture method, and fracture energy Gf based on size effect method, have been determined in both of the environments. Effect of sulfuric acid environment is explored by exposing the notched beams of the different concrete mixes to 2, 5 and 8% concentrations of the acid. Relations between the different parameters of investigation such as loss in weight, loss in fracture energy GF and loss in fracture energy Gf are presented. Tests conducted are compressive strength, split tensile strength, modulus of elasticity, impermeability and triple-point bend tests. Results reveal that deterioration of concrete increases as the concentration of acid increases, and decreases as the compressive strength of concrete increases. Percentage loss in weight and percentage loss in fracture energy decrease with increase in compressive strength of concrete. An empirical equation, a function of concentration of acid and time of exposure, to estimate percentage loss of fracture energy against sulfuric acid attack, is calibrated and validated.

44-62

Experimental study on the service load behaviour of the composite space truss

P. Sangeetha and R. Senthil

632

Abstract

Space truss is widely used as roof covering over a large area with or without intermediate support. The space truss with concrete slab with proper shear connector can act as a floor system in industrial and multi-storey buildings for rapid construction. The main challenge of the composite space truss is transfer of shear between steel and concrete. This paper presents an experimental study of the space truss with the concrete slab by introducing steel flat and bolts as shear connector without profile decking sheet. The load carrying capacity of space truss of size 3 m x 2 m x 0.7 m with 50 mm concrete slab on its top was studied under service load condition. From the experimental results, it was observed that the composite action was enhanced by introducing steel flat and bolts with a minimum slip of 0.1 mm under service load.

44-63

Numerical study on composite CCSTRCS frame structures under cyclic loading

Wei Li, Kejia Yang, Lingjie Wu, Xiaoniu Yu and Lianmeng Chen

637

Abstract

This paper presents finite-element (FE) modeling and nonlinear analysis of moment frames consisting of reinforced concrete columns and steel (composite) beams (RCS) subjected to cyclic loading. A three-dimensional FE model is developed to carry out the nonlinear analysis. Modeling details of the RCS frame structures, composite moment frames consisting of continuous compound spiral hoop reinforced concrete (CCSTRC) column and composite steel beam with novel beam-column joint and the associated constitutive relationships for cyclic loading are presented. Appropriate experimental data available from the literature are utilised to verify the model. Load-displacement responses, cumulative dissipated energy, and damage mechanisms from the numerical simulation are compared to the experimental results. The comparison shows that the numerical model accurately predicts the trend of the response as well as the possible damage mechanisms. The procedure proposed here can be adopted in future studies by researchers and also engineers to assess the seismic performance of composite frame with various dimensions and construction details, especially where test data are not available.

44-64

Impact resistance of fibre reinforced concrete containing lime sludge based composite cements

V.R. Ramkumar,, K. Chinnaraju and G. Murali

649

Abstract

The development of composite cements using supplementary cementitious materials is considered to be state of art in cement production. This paper presents the results of an experimental impact test conducted using drop weight hammer on fibre reinforced concrete (FRC) with 0.32 and 0.40 water/binder ratio made with binary and quaternary composite lime sludge cements. For this purpose, 34 concrete mixes containing hooked end steel fibres with aspect ratios of 50 at dosage of 0.5%, 1.0% and 1.5% were prepared with binary and quaternary cementitious systems. The binary systems were designed with various proportions of lime sludge ranging from 5%, 10% and 15%, while the quaternary systems were designed with various proportions of lime sludge combined with 15% of flyash and 10% of silica fume as partial substitute of cement. Further, a six regression models were constructed and validated for the assessment of effectiveness in determining the impact energy at first crack and failure. The results depict that replacement of 10% lime sludge in quaternary cementitious systems with this proportion is very effective in increasing the compressive strength and impact strength in concrete.

44-65

Seismic performance of multi-storey RC SMRF and OMRF buildings

A.K. Mapari, and Y.M. Ghugal

663p>

Abstract

Reinforced concrete moment resisting frames are one of the widely used lateral load resisting systems. Special moment resisting frames (SMRFs) are known for its enhanced ductility capacity and used for the same in high seismic risk zones. In this study, performance assessment of multi-storey RC special moment resisting frames (SMRFs) and ordinary moment resisting frames (OMRFs) is presented to compare the base shear capacity and ductility of the buildings using SAP2000 software. The nonlinear static analysis i.e. pushover analysis is adopted for studying the behaviour of SMRFs and OMRFs. The effect of infill walls are also taken into account in terms of base shear and roof displacement. The buildings response reduction factors are obtained from the capacity curves obtained for each modelled building by studying its behaviour parameters such as overstrength factor and ductility reduction factor. The FEMA P695 methodology is used to calculate response reduction factors.

44-66/td>

Investigations on the wind uplift behaviour of standing seam cold formed steel roofing sheets

Mini Koshy and S. Arul Jayachandran

673

Abstract

There is a steady rise in the usage of cold formed sheets made as standing seam panels in the roofs of pre-engineered buildings. Nevertheless, there are also reports of failure of these roof panels while in service. The behaviour of these panels cannot be captured analytically. A literature study is carried out on the testing and design methods of the cold formed steel (CFS) metal roof system. It is seen from literature survey that none of the international codes of practice specifies the procedure for the calculation of structural capacity of a standing seam roof system unless supported by experimental evidence. In view of that, the structural performance of a standing seam CFSmetal roof system under wind uplift is tested in a vacuum chamber as per ASTM E1592. The objective of the presented work is the study of the behaviour and failure modes of the rigid purlin-sheeting system with standing seam CFSpanel under uplift. The paper presents the details of an experimental investigation to achieve this objective. This study and the experimental infrastructure is first of its kind in India. The paper also presents various limit states of sheeting – purlin interaction failure based on experimental evidences. It is concluded that in order to treat the sheet-purlin dual load resisting behaviour, the disengagement of the sheet with purlin through the halter must be avoided. One of the main conclusions of the work is the concept of adjustable halter length in regions of high pressure in the roofs.

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