ABSTRACT- the older design codes in different parts

ABSTRACT- This paper presents the use of fiber reinforced plastic wraps, laminates and sheets in the repair and strengthening of reinforced concrete members. Fiber-reinforced polymer (GFRP) application is a very effective way to repair and strengthened structures that have become structurally weak over their life span. Experimental investigations on the flexural and shear behavior of RC beams strengthened using continuous glass fiber reinforced polymer (GFRP) sheets are carried out. Externally reinforced concrete beams with epoxy-bonded GFRP sheets were tested to failure using a symmetrical two point concentrated static loading system, experimental data on load, deflection and failure modes of each of the beams were obtained. The detail procedure and application of GFRP sheets for strengthening of RC beams is also included. The effect of number of GFRP layers and its orientation on ultimate load carrying capacity and failure mode of the beams are investigated.Keywords: GFRP, Wrapping Techniques.I INTRODUCTIONThe maintenance, rehabilitation and upgrading of structural members, is perhaps one of the most crucial problems in civil engineering applications. 5 Moreover, a large number of structures constructed in the past using the older design codes in different parts of the world are structurally unsafe according to the new design codes. Since replacement 3 of such deficient elements of structures incurs a huge amount of public money and time, strengthening has become the acceptable way of improving their load carrying capacity and extending their service lives. Infrastructure 2 decay caused by premature deterioration of buildings and structures has led to the investigation of several processes for repairing or strengthening purposes.One of the challenges in strengthening of concrete structures is selection of a strengthening method that will enhance the strength and serviceability of the structure while addressing limitations such as constructability, building operations, and budget. Structural strengthening may be required due to many different situations.Additional strength may be needed to allow for higher loads to be placed on the structure. This is often required when the use of structure changes and a higher load carrying capacity is needed. This can also occur if additional mechanical equipment, filing system, planters, or other items are being added to a structure.Strengthening may be needed to allow the structure to resist loads that were not anticipated in the original design. This may be encountered when structural strengthening is required for loads resulting from wind and seismic forces or to improve resistance to blast loading.Additional strength may be needed due to a deficiency in the structure’s ability to carry the original design loads. Deficiencies may be the result of deterioration (Eg., Corrosion of steel reinforcement and loss of concrete section), structural damage (eg,. Vehicular impact, excessive wear, excessive loading and fire), or error in the original design or construction (eg., misplaced or missing reinforcing steel and inadequate concrete strength).When dealing with such circumstances, each project has its own set of restriction and demands. Whether addressing space restrictions, constructability restrictions, durability demands, or any number of other issues, each project requires a great deal of creativity in arriving at a strengthening solution.II STRENGTHENING USING GFRP COMPOSITESOnly a few years ago, the construction market started to use FRP for structural reinforcement, generally in combination with other construction materials such as wood, steel, and concrete. FRPs exhibit several improved properties, such as high strength-weight ratio, high stiffness-weight ratio, flexibility in design, non-corrosiveness, high fatigue strength and ease of application. The use of FRP sheets or plates bonded to concrete beams has been studied by several researchers. Strengthening with adhesive bonded fiber reinforced polymers has been established as an effective methodJournal of Current Research in En gineering and Science Page 2applicable to many types of concrete structures such as columns, beams, slabs, and walls. Because the FRP materials are non- corrosive, non-magnetic, and resistant to various types of chemicals, they are increasingly being used for external reinforcement of existing concrete structures. From the past studies conducted it has been shown that externally bonded glass fiber-reinforced polymers (GFRP) can be used to enhance the flexural, the flexible glass fiber sheets are found to be highly effective for strengthening of RC beams.III MATERIALSA. Fiber SystemThe fiber system used in an FRP pultruded part can consist of different types and architectures of fiber materials. The raw fiber is processed and supplied either in strand form on a spool and known as roving or tow, or in broad goods form on a roll and known as mat, fabric, veil, or tissue. Two primary types of fiber systems are used when the hand-layup method is used for FRP strengthening: unidirectional tow sheets and unit-or multidirectional woven or stitched fabrics system.B. Fiber RovingIndividual continuous fiber filaments are bundled, generally without a twist, into multifilament strands known as roving that are used in the pultrusion process either as is or in fabrics produced from roving. In the United States, roving quantity is traditionally measured in units of yield (yd/lb). Roving is produced in yields of 56, 62, 113, 225,250, 450, 495, 650, and 675. Not all producers manufacture all yields. The number of filaments in an individual roving with a specific yield depends on the fiber diameter of the filament. The most common roving used in pultruded parts is a 113 yield roving, which has approximately 4000 filaments, usually having a diameter of 24 fm (93 X 10-3 in.) each. Figure 2.1 shows a spool of 113 yield glass fiber roving.C. Fiber MatsContinuous filament mat (CFM) also referred to in the United States as continuous strand mat, is the second most widely employed glass fiber product used in the pultrusion industry. CFM is used to provide crosswise (CW) or transverse strength and stiffness in plate like parts or portions’ of parts (e.g., the flange of a wide-flange profile)Fig. 1 woven glass roving combination fabricA. FiberglassFiberglass is a type of fiber reinforced plastic where the reinforcement fiber is specifically glass fiber. The glass fiber may be randomly arranged but is commonly woven into a mat. The plastic matrix may be a thermosetting plastic- most often epoxy. The glass fibers are made of various types of glass depending upon the fiberglass use. These glasses all contain silica or silicate, with varying amounts of oxides of calcium, magnesium, and sometimes boron. To be used in fiberglass, glass fibers are made with very low levels of defects.Fiberglass is a strong lightweight material and is used for many products. Although it is not as strong and stiff as composites based on carbon fiber, it is less brittle and its raw materials are much cheaper. Its bulk strength and weight are also better than many metals, and it can be more readily molded into complex shapes. Applications of fiberglass include aircraft, boats, automobiles, bath tubs and enclosures, hot tubs, septic tanks, water tanks, roofing, pipes, cladding, casts, surfboards, and external door skins.Journal of Current Research in En gineering and Science Page 3IV EXPERIMENTALWORKA. Experimental workTwo sets of beams were casted for this experimental test program. In set of first three beams weak in flexure were casted using same grade of concrete and reinforcement detailing. In set of second three beams weak in shear were casted as same grade of concrete and reinforcement detailing. The dimensions of all the specimens are identical. The cross sectional dimensions of both set of beams is 200mm by 100mm and length is 1500mm. in SET first beams 2,8mm dia bar are provided as the reinforcement and 6 mm dia bar as stirrups at the spacing of 150 mm C/C, set of second beams as identical and stirrups at the spacing of 250 mm C/C.B. Casting of BeamsTwo sets of beams are identical. Reinforcement detail of beam and section is shown in Fig 3.1& 3.2respectively.C. Materials used for Casting1. CementOrdinary Portland cement was used for the investigation. It was tested for its physical properties in accordance with Indian Standard specifications.Fig. 2 Reinforcement Details of beamsFig. 3 Section of beams2. Fine aggregateThe fine aggregate clear from all sorts of organic impurities was used in this experimental program. The fine aggregate was passing through 4.75mm sieve and had a specific gravity of 2.65. The grading Zone of fine aggregate was Zone III as per Indian Standard specifications.3. Coarse aggregateThe coarse aggregates used were two grades available in local quarry. One grade contained aggregates passing through 4.75mm sieve and retained on 10mm size sieve. Another grade contained aggregates passing through 10mm size but retained on 20mm sieve.4. WaterOrdinary tap water used for concrete mix in all mix.5. Form WorkPly is used to prepare formwork for beam of size 100mm x 200mm and 1500mm long. The form work is thoroughly cleaned and all the corners and junctions were properly sealed to avoid leakage ofJournal of Current Research in En gineering and Science Page 4concrete through small openings. Shuttering oil was then applied to the inner face of the form work. The reinforcement cage is then placed in position inside the form work carefully keeping in view a clear cover of 20 mm for the top and bottom bars as shown in Fig 3.3Fig. 4 Casting of BeamsV EXPERIMENTAL SETUPThe SET of I beams (F1,F2,F3,F4) are strengthening with flexural and SET II beams (S1,S2,S3,S4) are strengthening with shear. F1 and S1 are control beams. All the specimens were tested in the loading frame of concrete lab in Bharath University. The testing procedure for the entire specimen was same. After the curing period of 28 days was over the beam as washed and its surface was cleaned for clear visibility of cracks. The most commonly used load arrangement for testing of beams will consist of two points loading. This has the advantages of substantial region of nearly uniform moment coupled with very small shears. The load will normally be concentrated at a suitable shorter distance from a support.Two points loading can be conveniently provided by the arrangement shown in figure. The load is transmitted through a load cell and spherical seating on a beam. This beam bears on rollers scatted on steel plates bedded on the test member with mortar, high strength plaster or some similar material.The loading frame must be capable of carrying the expected test loads without significant distortion. Ease of access to the middle third for crack observations, deflection readings and possibly strain measurements as important consideration as is safety when failure occurs. The specimen was placed over the two steel rollers bearing leaving ends of the beam. Two point loading arrangement was done as shown in the figure 5. Two number of dial gauges were used for recording the deflection of the beams. One dial gauge was placed just below the center of the beam and the remaining dial gauges were placed just below the point loads to measure deflections.After setting and reading all gauges the load was increased incrementally up to the calculated working load, with loads and deflections recorded at each stage, loads will then normally be increased again in similar increments upto failure, with deflection at this stage will usually be large and easily measured from a distance. Similarly cracking and manual strain observations must be suspended as failure approaches unless special safety are taken. If it is essential that precise deflection readings are taken upto collapse. Cracking and failure mode was checked visually and a load was prepared.Fig.5 Experimental SetupJournal of Current Research in En gineering and Science Page 5VI DISCUSSIONS ON EXPERIMENTAL RESULTSA. GeneralIn this chapter, discussion is made on the effect of strengthening on the reinforced concrete beams by using different glass fiber with that of control beams, such as deflection and load carrying capacity.Fig.6 wrapping techniquesB. Testing ProcedureBefore testing the member was checked dimensionally and detail visual inspection made with all information carefully recorded. After setting all, the load was increased up to the failure of beam and deflection was recorded at each stage, and a load/deflection plot was prepared.C. Failure ModeFailure modes have been observed in the experiments of RC beams strengthened by GFRP. The GFRP strengthened beams and the control beams are tested to find out their ultimate load carrying capacity. The SET of I beams (F1,F2,F3,F4) are strengthening with flexural and SET II beams (S1,S2,S3,S4) are strengthening with shear. F1 and S1 are control beams. After setting and reading all gauges the load was increased incrementally up to the calculated working load, with loads and deflections recorded at each stage. A number of failure modes have been observed in the experiments of RC beams strengthened in flexure and shear by GFRPs. These include flexure failure, shear failure due to GFRP rupture and crushing of concrete at the top. Cover delamination or FRP bonding can occur if the force in the FRP cannot be sustained. The GFRP strengthened beam and the control beams were tested to find out their ultimate load carrying capacity. It was found that the control beams were failed. In set of three beams are failure in flexure and other set of three beams are failure in shear.D. With Respect to Load and DeflectionFrom the load of deflection of data of SET I beams F1, F2, F3 and F4, load vs deflection is plotted for all the four beams. From this load Vs deflection curve it is clear that beam F1 has lower ultimate load carrying capacity compared to beams F2, F3 andF4.Bottom side wrappingGraph 1 Load Vs Deflection Curve for beam F1,F2, F3& F46543210F4F3F2F13.83.63.43.9ton4.44.244.5ton4.64.63tonBeamF1BeamF2BeamF3 BeamF40 2 4 6load in TonDeflection in mmJournal of Current Research in En gineering and Science Page 6Deflection of beam for bottom side GFRP wrap.1. The beam with bottom side single mat wrap is having the more deflection than that of double mat wrap and woven roving wrap.2. The beam with bottom side double mat wrap is having the minimum deflection than that of single mat wrap.3. Similarly, the beam with bottom side woven roving wrap is having the minimum deflection than that of single mat wrap and double mat wrap.E. Both sides wrappingFrom the load of deflection of data of SET II beams S1, S2, S3 and S4, load vs deflection is plotted for all the four beams. From this load Vs deflection curve it is clear that beam S1 has lower ultimate load carrying capacity compared to beams S2, S3 andS4.Graph 2 Load Vs Deflection Curve for beam S1, S2, S3& S4Deflection of beam for both side GFRP wrap.1. The beam with both side single mat wrap is having the more deflection than that of double mat wrap and woven roving wrap.2. The beam with both side double mat wrap is having the minimum deflection than that of single mat wrap.1. Load at Initial CrackLoad at Initial Crack of SET I BeamsGraph 3 Load at Initial Crack of SET I BeamsTwo points loading was done on both SETI and SETII beams and at the each load and deflection and crack development were observed. The load at initial crack of all beams was observed, recorded and is shown in graph 3 and 4.4.63ton4.64.5ton4.44.243.9ton3.83.63.4F1F2F3F4Journal of Current Research in En gineering and Science Page 7Load at Initial Crack of SET II BeamsGraph.4 Loads at Initial Crack of SET II Beams2. Ultimate Load Carrying CapacityThe load carrying capacity of the controls beams and the strengthen beams were found out. The control beams were loaded up to their ultimate load. The strengthen beams F2, F3,F4 and S2,S3,S4 are had the higher load carrying capacity compared to the controlled beam F1 and S1. An important character to be noticed about the usage of GFRP sheets is high ductile behavior of the beams.Graph 5 Ultimate Load of SET I BeamsThe shear failure being sudden can lead to huge can give us damage to the structure. But theBehavior obtained by the use of GFRP can give us enough warning before the failure.Graph 6.6 Ultimate Load of SET II BeamsVII CONCLUSIONSIn this experimental investigation the flexural and shear behavior of reinforced concrete beam strengthened by GFRP sheets are studied. Two sets of reinforced concrete beams, inset I four beams one is control beam and other three are weak in flexural and SET II beams one is control beam and other three were in weak in shear were casted and tested. From the test results and calculated strength values the following conclusions are drawn.SET Beams (F1, F2, F3 andF4)1) Initial flexural cracks appear at a load by strengthening the beam. The ultimate load carrying capacity of the strengthen beam F2 is 7% more than the controlled beamF1.2) Load at initial cracks is further increased by strengthening of beam .the ultimate load carrying capacity of strengthen beam F3 is 7% more than the controlled beamF1.765432105.9ton4.6ton5ton3.7tonS1 S2 S3 S4Ultimate load (Tones)108.8957.187.63 7.63Ultimateload(Tones)0F1 F2 F3 F4Ultimate load (Tones)7.576.565.57.09 7.16.96.3Ultimateload(Tones)S1 S2 S3 S4Journal of Current Research in En gineering and Science Page 83) Load at initial cracks is further increased by strengthening of beam .the ultimate load carrying capacity of strengthen beam F4 is 24% more than the controlled beamF1.4) When the beam is not strengthen it failed in flexure but after strengthening the beam is flexural, the flexural failure of the beam as it does not give much warning before failure. Therefore it is recommended to check the shear strength of the beam and carry out shear strengthening along with flexural strengthening if required.5) Flexural strengthening up to the neutral axis of the beam increase the ultimate load carrying capacity but the cracks developed.6) By strengthening up to the neutral axis of the beam increase in the ultimate load carrying capacity of the beam and cost involvement is almost three times compared to the beam strengthen by GFRP.SET II Beams (S1, S2, S3 andS4)1) The control beam S1 failed in shear it was made weak in shear.2) The initial crack in the strengthen beams S2 and S3 appears at higher load compared to the control beamS1.3) After strengthening the shear zone of the beam the initial cracks appears at the flexural zone of the beams and the crack is widen. The final failure is shear in the beam and the ultimate load capacity of the beam S2 is13% more than the controlled beamS1.4) When the beam is both sides wrapping in the shear zone the ultimate load carrying capacity of all beams.5) The beam S3 having the 13% ultimate load carrying capacity.6) The bonding between GFRP sheets and the concrete is in act up to the failure of the beam which clearly indicates the composite action due to GFRP sheet.7) Restoring or upgrading the shear strength of beam using GFRP sheet can result in increased shear strength and stiffness with highly shear strength of beam using is a highly effective techniques.REFERENCES1Alferni .M.B.S, Abdul Samad A.A (2013) Uses of carbon fiber reinforced polymer laminates for strengthening reinforced concrete beams in shear.(International Reference Journal of engineering and science)(IRJES).2Ancy Joseph, JayasreeRamanujan (2011) Linear behavior of carbon fiber reinforced polymer plate bonded beam.(International Conference on Emerging Technology)(ICETT).3GoaBo,Chirstroper.K,Dong.G(2007)Failure diagrams of FRP strengthened RC beams of composite structures.(International Conference of Civil Engineering)4 N.Kishi, H.Mikami, T.Ando (2002) Impact behavior of shear-failure type of RC-beams of strengthened materials. 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