A.Vijayakumar, Dr.D.L.Venkatesh babu, R. Jayaprakash / International Journal of       Engineering Research and Application...
A.Vijayakumar, Dr.D.L.Venkatesh babu, R. Jayaprakash / International Journal of       Engineering Research and Application...
A.Vijayakumar, Dr.D.L.Venkatesh babu, R. Jayaprakash / International Journal of       Engineering Research and Application...
A.Vijayakumar, Dr.D.L.Venkatesh babu, R. Jayaprakash / International Journal of       Engineering Research and Application...
A.Vijayakumar, Dr.D.L.Venkatesh babu, R. Jayaprakash / International Journal of       Engineering Research and Application...
A.Vijayakumar, Dr.D.L.Venkatesh babu, R. Jayaprakash / International Journal of       Engineering Research and Application...
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Cy25593598

  1. 1. A.Vijayakumar, Dr.D.L.Venkatesh babu, R. Jayaprakash / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.593-598 Analytical Study on Various Types of FRP Beams by using AVSYS *A.Vijayakumar, **Dr.D.L.Venkatesh babu, ***R. Jayaprakash *(Assistant Professor, Department of Civil Engineering, Jansons Institute of Technology, Coimbatore, Tamilnadu, India) ** (Principal, United Institute of Technology, Coimbatore, Tamilnadu, India)*** (PG student, Department of Civil Engineering, Tamilnadu College of Engineering, Coimbatore, Tamilnadu, India)ABSTRACT Fibre reinforced polymer (FRP) is one of 1. Introductionthe best retrofitting materials for strengthening The maintenance, rehabilitation anddue to a number of advantages, such as excellent upgrading of structural members, are perhaps one ofstrength to self-weight ratio, large fatigue the most crucial problems in civil engineeringresistance capacity, etc. Presently, many different applications. Moreover, a large number of structurestypes of FRP models are used in analysis, thereby constructed in the past using the older design codes increating erroneous analytical results. Reinforced different parts of the world are structurally unsafeconcrete (RC) beams with carbon and glass fibre- according to the new design codes. Sincereinforced polymer (CFRP and GFRP) composites replacement of such deficient elements of structuresoffer an attractive solution to enhance the incurs a huge amount of public money and time,behaviour of concrete in terms of strength and strengthening has become the acceptable way ofductility, as well as altering the mode of rupture of improving their load carrying capacity and extendingsuch structural members. However, very little is their service lives. Infrastructure decay caused byknown about their performance. Thus, this paper premature deterioration of buildings and structurespresents to investigate the behaviour of FRP has lead to the investigation of several processes forbeams. In order to calculate the bending moment, repairing or strengthening purposes. One of thethe model considers an exponential function in the challenges in strengthening of concrete structures isstress–strain diagram of RC in both tension and selection of a strengthening method that will enhancecompression parallel to the fibres. A four-point the strength and serviceability of the structure whilebending test configuration was conducted as addressing limitations such as constructability,short-term experiments to determine the load– building operations, and budget. Structuraldisplacement relationships of RC beams with strengthening may be required due to many differentCFRP and GFRP sheets/plates adhered to the situations.tensile side. Therefore, this study is carried out toassess and to compare a comprehensive finite Investigation of the behaviour of FRPelement analytical model of FRP that can properly retrofitted reinforced concrete structures has in theconsider the properties of FRP as a retrofit last decade become a very important research field.material. After reviewing available FRP models In terms of experimental application several studiescurrently used by researchers in the field, two were performed to study the behaviour of retrofittedanalytical FRP models are selected to assess the beams and how various parameters influence thebehaviour of FRP sheet /plate to concrete behaviour.structure; using the selected FRP models, noiseanalysis of FRP sheet and FRP is carried out to The effect of number of layers of CFRP onconfirm mesh sensitivity for convergence. In the behaviour of a strengthened RC beam wasaddition, finite element analysis of FRP RC beam investigated [1]. They tested simply supported beamsis under performed to select the most appropriate with different numbers of CFRP layers. TheFRP model and to validate the analysis technique. specimens were subjected to a four-point bendingAll of the analysis results for four selected FRP test. The results showed that the load carryingmodels are compared to verify and select the capacity increases with an increased number of layersoptimum model. Finally, a discussion about of carbon fibre sheets.the study results with respect to code responsecriteria is presented. Investigation of the effect of internal reinforcement ratio on the behaviour of strengthenedKey words: Bending moment, Ductility, Fibre beams has been performed [2]. Specimens withreinforced polymer, Retrofitting, Strength. different internal steel ratio were strengthened in flexure by CFRP sheets. The authors reported that the 593 | P a g e
  2. 2. A.Vijayakumar, Dr.D.L.Venkatesh babu, R. Jayaprakash / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.593-598flexural strength and stiffness of the strengthened portions towards one of the ends of the plate. It isbeams increased compared to the control specimens. believed to be the result of high interfacial shear andWith a large reinforcing ratio, they also found that normal stresses concentrated at a crack along thefailure of the strengthened beams occurred in either beam. Also mid span debonding may take concreteinterfacial debonding induced by a flexural shear cover with it.crack or interfacial debonding induced by a flexuralcrack. A test programme on retrofitted beams withshear deficiencies was done [3]. The experimentalresults indicated that the contribution of externallybonded CFRP to the shear capacity of continuous RCbeams is significant. There are three main categories of failure inconcrete structures retrofitted with FRP that havebeen observed experimentally [4 - 6]. The first andsecond type consist of failure modes where thecomposite action between concrete and FRP ismaintained. Typically, in the first failure mode, the steelreinforcement yields, followed by rupture of CFRP asshown in Fig 1(a). In the second type there is failurein the concrete. This type occurs either due tocrushing of concrete before or after yielding oftensile steel without any damage to the FRP laminate,Fig 1(b), or due to an inclined shear crack at the endof the plate, Fig 1(c). In the third type, the failure Figure 1: Failure modes in beam retrofitted inmodes involving loss of composite action are flexure.included. The most recognized failure modes withinthis group are debonding modes. In such a case, the Researchers have observed new types ofexternal reinforcement plates no longer contribute to failures that can reduce the performance of CFRPthe beam strength, leading to a brittle failure if no when used in retrofitting structures [7]. These failuresstress redistribution from the laminate to the interior are often brittle, and include debonding of concretesteel reinforcement occurs. layers, delamination of CFRP and shear collapse. Brittle debonding has particularly been observed at Fig 1(d)-(g) show failure modes of the third laminate ends, due to high concentration of sheartype for RC beams retrofitted with FRP. In Fig 1(d), stresses at discontinuities, where shear cracks in thethe failure starts at the end of the plate due to the concrete are likely to develop [8]. Thus, it isstress concentration and ends up with debonding necessary to study and understand the behaviour ofpropagation inwards. Stresses at this location are CFRP strengthened reinforced concrete members,essentially shear stress but due to small but non-zero including those failures. Several researchers havebending stiffness of the laminate, normal stress can simulated the behaviour of the concrete– CFRParise. interface through using a very fine mesh to simulate the adhesive layer defined as a linear elastic material Fig 1(e) the entire concrete cover is [9]. However, they have not used any failure criterionseparated. This failure mode usually results from the for the adhesive layer. Most researchers who haveformation of a crack at or near the end of the plate, studied the behaviour of retrofitted structures have,due to the interfacial shear and normal stress however, not considered the effect of the interfacialconcentrations. Once a crack occurs in the concrete behaviour at all [10].near the plate end, the crack will propagate to thelevel of tensile reinforcement and extend horizontally The selection of the most suitable methodalong the bottom of the tension steel reinforcement. for strengthening requires careful Consideration ofWith increasing external load, the horizontal crack many factors including the following engineeringmay propagate to cause the concrete cover to separate issues:with the FRP plate. In Fig 1(f) and (g) the failure is  Magnitude of strength increase;caused by crack propagation in the concrete parallel  Effect of changes in relative memberto the bonded plate and adjacent to the adhesive to stiffness;concrete interface, starting from the critically stressed 594 | P a g e
  3. 3. A.Vijayakumar, Dr.D.L.Venkatesh babu, R. Jayaprakash / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.593-598  Size of project (methods involving special point loads have been analyzed using ANSYS materials and methods may be less cost- software and the results so obtained have been effective on small projects); compared to available GFRP/CFRP sheets and plates  Dimensional/clearance constraints (section result from the work done. Finally, comparison enlargement might be limited by the degree between the analytical results and experimental to which the enlargement can encroach on results the salient conclusion and recommendations surrounding clear space); of the present study.  Environmental conditions (methods using adhesives might be unsuitable for 2. Finite Element Modelling applications in high-temperature The basic concept of FEM modelling is the environments, external steel methods may subdivision of the mathematical model into disjoint not be suitable in corrosive environments); (non-overlapping) components of simple geometry.  In-place concrete strength and substrate The response of each element is expressed in terms of integrity (the effectiveness of methods a finite number of degrees of freedom characterized relying on bond to the existing concrete can as the value of an unknown function, or functions or be significantly limited by low concrete at a set of nodal points. The response of the strength) mathematical model is then considered to be the  Accessibility discrete model obtained by connecting or assembling  Operational constraints (methods requiring the collection of all elements as shown in Figure 2. longer construction time might be less desirable for applications in which building operations must be shut down during construction)  Availability of materials, equipment, and qualified contractors  Construction cost, maintenance costs, and life-cycle costs; and  Load testing to verify existing capacity or evaluate new techniques and materials.1.2 Objective and Scope of the present work The purpose of this paper is to provideanalytical data on the response of RC beamsstrengthened in shear using GFRP sheets/plates andCFRP sheets/plates. The analytical program aimed atraising the strength of the shear deficient beams tothat of the fully strengthened by GFRP sheets/platesand CFRP sheets/plates to provide single layerwrapping for beams. The analysis aimed atunderstanding the best wrapping style for retrofittingthe deficient beams. The objective of thisinvestigation is to study the effectiveness of CFRPsheets/plates and GFRP sheets/plates supplied byFibre Reinforced Systems (FRS) in increasing theflexural strength of concrete beams. The objective is achieved by conducting thefollowing tasks: (i) Flexural testing of concretebeams strengthened with single layers of GFRPsheets/plates and CFRP sheets/plates. (ii) Calculatingthe effect of single layers of GFRP sheets/plates andCFRP sheets/plates on the flexural strength. (iii)Evaluating the failure modes (iv) Developing ananalytical procedure to calculate the flexural strengthof concrete beams strengthened with FRP composites(v) comparing the two different experimental andanalytical results. CFRP-Sheet GFRP-Sheet CFRP-Plate GFRP-Plate In the scope of the present study to FEMmodelling of the control RCC beam under the static Figure 2 Various Configuration of the beam elements 595 | P a g e
  4. 4. A.Vijayakumar, Dr.D.L.Venkatesh babu, R. Jayaprakash / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.593-5982.1 Material Models behaviour in tension and compression. In this study; The program system ANSYS offers a the GFRP/CFRP material modelling used forvariety of material models for different materials and retrofitted RCC beams.purposes. The most important material models inANSYS for RCC structure are concrete and 2.2 Material Propertiesreinforcement. These advanced models take intoaccount all the important aspects of real materialDESCRIPTION GFRP GFRP CFRP CFRP ADHESSIVE CONCRETE SHEET PLATE SHEET PLATE EPOXY RESINTHICKNESS/ 4mm 12mm 4mm 12mm 2mm 150mm xSIZE 230mmDENSITY 2000 kg/m3 1600 1900 1300 1050 kg/m3 2400 kg/m3 3 3 3 kg/m kg/m kg/mYOUNG’S 70 GPa 50 GPa 200 GPa 100 GPa 3 GPa 23 GPaMODULUSPOISSON’S 0.26 0.28 0.22 0.26 0.35 0.2RATIO However, in the present study the steel reinforcing2.3 Concrete Modelling was connected between nodes of each adjacent Solid65 element was used to model the concrete solid element, so the two materials sharedconcrete. This element has eight nodes with three the same nodes. The same approach was adopted fordegrees of freedom at each node – translations in the FRP composites.nodal x, y, and z directions. This element is capableof plastic deformation, cracking in three orthogonaldirections, and crushing. A schematic of the elementis shown in Figure3. Same cracking approach hasbeen used in modelling the concrete in the presentstudy. Figure 4 Link8 element geometry.Figure 3 Solid65 element geometry2.4 Reinforcement Modelling Modelling of reinforcing steel in finiteelements is much simpler than the modelling ofconcrete. A Link8 element was used to model steelreinforcement. This element is a 3D spar element andit has two nodes with three degrees of freedom –translations in the nodal x, y, and z directions. Thiselement is also capable of plastic deformation. Thiselement is shown in Figure4. A perfect bond between Figure 5 Geometry of the reinforcementthe concrete and steel reinforcement considered. 596 | P a g e
  5. 5. A.Vijayakumar, Dr.D.L.Venkatesh babu, R. Jayaprakash / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.593-5982.5 FRP Plate FRP plates were added at support andloading locations in the finite element models (as inthe actual beams) in order to avoid stressconcentration problems. An elastic modulus equal to50,000 N/mm2 to 100,000 N/mm2 and Poisson’s ratioof 0.28 were used for the plates. The steel plates wereassumed to be linear elastic materials. A Solid 45element was used to model steel plates.2.6 FRP Laminates FRP composites are materials that consist oftwo constituents. The constituents are combined at amacroscopic level and are not soluble in each other.One constituent is the reinforcement, which isembedded in the second constituent, a continuouspolymer called the matrix. The reinforcing material is Fig.7.(a) CFRP-Sheet Fig.7.(b) CFRP-Sheet Fig.7.(c)CFRP-in the form of fibres, i.e., carbon and glass, which are heet Deflection Strain Stresstypically stiffer and stronger than the matrix. TheFRP composites are orthotropic materials; that is,their properties are not the same in all directions.3. Numerical Analysis In order to validate the numericalrepresentation of the reinforced concrete beamsstrengthening with fibre reinforced polymercomposites, the finite elements representation usingANSYS program has been applied to practicalsections and the results will be compared with theexperimental results reported by previous researches. Numerical analysis is performed using theANSYS finite element program to predict thedeflection of rectangular reinforced concrete beamstrengthened by fibre reinforced plastics applied atthe bottom of the beam. In the numerical analyses, Fig.8.(a) GFRP-Plate Fig.8.(b) GFRP-Plate Fig.8.(c) GFRP-simply supported reinforced concrete beam is Plate Deflection Strain Stressconsidered. Three-dimensional finite element modelwas developed to examine the structural behaviour ofthe strengthened beam. A quarter of the full beamwas used for modelling by taking advantage of thesymmetry of the beam and loadings. See Figure 6 to9. Fig.9.(a) GFRP-Sheet Fig.9.(b) GFRP-Sheet Fig.9.(c) GFRP- Sheet Deflection Strain StressFig.6.(a) CFRP-Plate Fig.6.(b) CFRP-Plate Fig.6.(c) CFRP-PlateDeflection Strain Stress 597 | P a g e
  6. 6. A.Vijayakumar, Dr.D.L.Venkatesh babu, R. Jayaprakash / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.593-5984. Discussion of Results REFERENCES4.1 Load Deflection Curve 1. Esfahani, M., Kianoush, M., & Tajari, A. The experimental and numerical load- Flexural behaviour of reinforced concretedeflection curves obtained for the beams are beams strengthened by CFRP sheets.illustrated in Figure 10 and 11. The curves show Engineering Structures 2007; 29: 2428-good agreement in finite element analysis with the 2444.experimental results throughout the entire range of 2. Pham, H., & Al- Mahaidi, R. Experimentalbehaviour and failure mode, for all beams the finite investigation into flextural retrofitting ofelement model is stiffer than the actual beam in the reinforced concrete bridge beams using FRPlinear range. Several factors may cause the higher compoistes. Composite Structures 2004; 66:stiffness in the finite element models. 617-625. 3. Camata, G., Spacone, E., & Zarnic, R. Experimental and nonlinear finite element studies of RC beams strengthened with FRP plates. Composites: Part B 2007; 38: 277- 288. 4. Coronado, C. A., & Lopez, M. M. Sensitivity analysis of reinforced concrete beams strengthened with FRP laminates. Cement and Concrete Composites 2006; 28: 102-114. 5. Ebead, U., & Marzouk, H. Tension - stiffening model for FRP strengthend RC concrete two-way slab. Materials and Structures 2004; 193-200. 6. Lundquist, J., Nordin, H., Täljsten, B., &Fig.10. Deflection Curve for GFRP/CFRP-Plate Olafsson, T. Numerical analyis of concretebonded Beams beams sterengthened with CFRP- A Study of anchorage lengths. In: FRP in Construction, Proceeding of The International Symposium of Bond Behaviour of FRP in Structures. 2005; 247- 254. 7. Esfahani M, Kianoush M, Tajari A. Flexural behaviour of reinforced concrete beams strengthened by CFRP sheets. Eng Struct 2007; 29:2428–44. 8. Teng JG, Smith ST, Yao J, Chen JF. Intermediate crack-introduced debonding in beams and slabs. Construct Build Mater J 2003;17(6–7):447–62.Fig.11. Deflection Curve for GFRP/CFRP- Sheet 9. Hu H-T, Lin F-M, Jan Y-Y. Nonlinear finiteWrapped Beams. element analysis of reinforced concrete beams strengthened by fibre-reinforced5. Conclusions plastic. Compos Struct J 2004; 63:271–81. The numerical solution was adopted to 10. Lundquist J, Nordin H, Täljsten B, Olafssonevaluate the ultimate shear strength of the reinforced T. Numerical analysis of concrete beamsconcrete beams reinforced with FRP laminates in strengthened with CFRP – a study ofsimple, cheap and rapid way compared with anchorage lengths. In: FRP in construction,experimental full scale test. The general behaviours Proceeding of the international symposiumof the finite element models show good agreement of bond behaviour ofFRP in structures;with observations and data from the experimental 2005. p. 247–54.full-scale beam tests. The addition of FRPreinforcement to the control beam shifts thebehaviour of the control beams from shear failurenear the ends of the beam to flexure failure at the midspan. The results obtained demonstrate that carbonfibre polymer is efficient more than glass fibrepolymer in strengthening the reinforced concretebeams for shear. 598 | P a g e

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