Chen, Teng et al. (2010) suggested that beams retrofitted with U-wrap or side- bonded CFRP material usually failed by premature debonding. This type of brittle failure limits the critical crack width such that not all steel stirrups intersected by this crack reach yielding strain. Consequently, the stirrups in this case contribute less than what was predicted by guidelines and codes. Based on their proposed model, they assume that not all steel stirrups yielded; hence, the full contribution of steel stirrups can not be obtained. Mofidi and Chaallal (2014) conducted a series of tests on beams with and without transverse steel. Specimens with transverse steel consisted of heavily reinforcedbeams (stirrups at d/2) and moderately reinforcedbeams (stirrups at 3d/4). They observed that all transverse steel yielded before failure, and the addition of the CFRP did not affect the strain in the transverse steel. This observation was in contrast to what had been proposed in Chen, Teng et al. (2010). In that study, they concluded that the full contribution of transverse steel cannot be utilized.
There are several options available for retrofitting the structural members of existing reinforcedconcrete (RC) structures. Bonding thin steel plates is one of the common methods of retrofitting. Though the technique is successful in practice, the added steel plates are susceptible to corrosion, which leads to an increase in future maintenance costs. Therefore, attention has shifted to the use of carbonfiberreinforcedpolymer (CFRP) as alternative material. Based on previous studies, bonding CFRP sheets to the damaged members helps increase load carrying capacity, ductility, and stiffness of the damaged structure. Such a technique is an effective way to improve the flexural and shear performance of the RC damaged structure. In this experimental study, CFRP materials were used for structural strengthening. CFRP materials do not corrode because they are a combination of carbon fibers and an epoxy resin matrix. Moreover, they have very high strength and rigidity in the fiber direction.
3. Sherif H. Al-Tersawy. (2013), examined the performance of reinforcedconcrete (RC) beams strengthened in shear. Experimental investigation was carried out on nine RC beams of three different sets, as-built beams (unstrengthen), beams strengthened with vertical CarbonFiber-ReinforcedPolymer (CFRP) wraps, and beams strengthened with inclined CarbonFiber-ReinforcedPolymer (CFRP) wraps. The main parameters investigated were concrete strength, CarbonFiber-ReinforcedPolymer (CFRP) thickness and wraps orientations (900 & 450). The results of the experimental work indicated that externally bonded CFRP wraps enhanced the shear strength of beams significantly and that inclined CarbonFiber-ReinforcedPolymer (CFRP) configuration is more effective than vertical ones. 4. Firmo J et al, (2015) This paper presents experimental and numerical investigations about the fire resistance behavior
(2001) recommends anchorage for shearstrengthening of RC beams with FRP strips using simple mechanical anchors or by bonding the ends of the strips into core holes through the flange of a T-beam. Schuman (2004) used a GFRP/steel anchorage system in an FRP- concrete double-shear bond test series. Mofidi (2008) successfully explored the possibility of using an unbonded CFRP U-jacket anchorage system to strengthen RC T-beams in shear. In this method, dry CFRP sheets were wrapped around and bonded to two steel rods. The steel rods were anchored to the corners of the web-flange intersection of the T-beam with mechanical bolts. Eshwar et al. (2008) investigated the performance of spike anchors and near-surface mounted (NSM) end-anchorage systems in a series of FRP-concreteshear bond tests. A spike anchor consists of a bundle of carbon or glass fibres. One end of the fibers takes the form of a fan which is sandwiched between the two FRP sheets to be anchored. The other end of the bundle is fully bonded and inserted into a hole through the RC beam. In a research study by Eshwar et al. (2008), many of the spike anchors failed prematurely and did not add to the FRP-concrete bond resistance. The NSM end-anchorage system used by Eshwar et al. (2008) was similar to one proposed by Khalifa and Nanni (2000) and had been successfully tested in FRP-concreteshear bond tests. Ceroni et al. (2008) compared the effectiveness of different anchorage systems in a series of double-tension tests on CFRP sheets epoxy-bonded to T-shaped concrete specimens. Among the different anchorage systems considered in their research study, EB FRP laminates, EB steel plates, and NSM FRP end-anchorage systems showed superior performance. Based on the research studies described above and on recommendations from various guidelines, the use of end-anchorage systems for shearstrengthening of RC beams using EB FRP methods can result in a greater FRP contribution to shear resistance. Several end-anchorage systems have been proposed by researchers, but their effectiveness has not yet been well documented. In addition, few experimental research studies comparing different anchorage systems under similar test conditions exist in the literature (Ceroni et al. 2008).
Improved the shear capacity of RC T-beams using unidirectional CFRP composites and compared between the experimental and analytical used ACI Committee report. He tested six beams of sizes; 120mm width 360mm depth 1750mm length and 75mm flange thickness. Two of these beams were control specimen and four beams were strengthened with different configurations of CFRPstrips, all these beams were tested under cyclic loading. These beams had longitudinal reinforcement and no stirrups for beams except one of the control beam.
Daniel Baggio (2014) et al. investigated the shear performance of eight reinforcedconcretebeams strengthened with Carbon FRP, Glass FRP & FiberReinforced Cementitious Matrix sheets and FRP anchors and one control specimen. Total nine shear deficient slender RCC beam were casted. Beams were tested in four point bending using a closed-loop hydraulic MTS actuator with a 500 kN capacity in a MTS 322 test frame. The beams were simply supported with a clear span of 2200 mm with 400 mm spacing between the two loading points and a shear span of 900 mm. Finally they found that beams strengthened with GFRP full depth and partial depth showed 50% and 36% increase in ultimate load then control specimen whereas beams strengthened with CFRP and FRCM showed 34% and 75% increase in ultimate load over control specimen. Authors also found that when the available bonded length is limited then the installation of FRP as a viable option to prevent a brittle shear failure mode due to FRP debonding.
of cross section height larger than the cover thickness requires that the bottom arm of the steel stirrups be cut. This work aims to assess the influence, in terms of shear resistance, of cutting the bottom arm of steel stirrups to install NSM strips for the flexural strengthening of RC beams. The obtained results showed that, for monotonic loading, cutting the bottom arm of steel stirrups led to a decrease of the beam’s load carrying capacity of less than 10%. Due to the high effectiveness of the adopted NSM flexural strengthening systems, shear can be a predominant failure mode for these beams. To avoid this type of failure mode, strips of wet lay-up CFRP sheets with U configuration were used, resulting in effective strengthening solutions for RC beams. In the present paper the experimental program is described, and the obtained results are presented and discussed
investigation four beams were strengthened by bonding CFRP plates to their tension flange. Immediately after application of the strengthening, during curing of the adhesive, three of the beams were subjected to cyclic loading conditions. The fourth beam was allowed to fully cure and was tested as a control beam. In the second investigation, five pairs of beams were strengthened simultaneously. One of the beams in each pair was subjected to cyclic loading during curing of the adhesive while the other was allowed to cure undisturbed. The stiffness of the beams was evaluated by conducting periodic static tests throughout the duration of the cyclic loading. The testing confirmed the gradual increase in the stiffness of the adhesive with time. Beams subjected to higher loads during curing did not develop the full stiffness of the adhesive. It was recommended that the shear stress in the adhesive be limited to 1 MPa prior to full curing of the adhesive. Subsequent tests to failure of the same beams demonstrated that cyclic loading at higher load levels also reduced the ultimate capacity of the strengthened beams (Moy and Nikoukar, 2002). The loss in stiffness and strength of the beams was attributed to the loss in stiffness of the adhesive caused by the cyclic loading which resulted in a shear lag affect. Measured strain profiles which were reported at different load levels were linear through the section and through the adhesive joint.
The importance of the study in the strengthening of the beam using CFRP laminate in the strengthening system provides an economical and versatile solution for extending the service life of reinforcedconcrete structures. From the literature, it is evident that epoxy resin is favoured in strengthening and also the end of anchorage was used to eliminate the debonding failure. Future research is needed for a complete awareness for strengtheningreinforcedconcretebeams with FRP, with the aim to efficiently contribute in the concrete structures repair tasks as well as, to decrease the dimensional stability of the structure. A working knowledge of how material properties change as a function of climate, time and loading will also be of great value to the engineering and design communities. Moreover, FRP in concrete allows engineers to increase or decrease margins of safety depending on environmental and stress conditions, generic FRP type and required design life.
Flexural and shear failures are the main critical failure patterns of the RC members. Flexural failure of under-reinforced sections is ductile and develops progressively with significant cracking and displacements, which show a warning of failure. On the contrary, shear failure is extremely brittle and does not allow significant redistribution of shear forces; therefore, shear failure develops without warning and is usually disastrous. Shear-deficient beam failed in shear prior to achieving the full flexural capacity. Thus, RC structures should have sufficiently more margin with regards shear capacity when compared with flexural capacity. Therefore, retrofitting and repairing of the reinforcedconcrete members could be required to improve the shear capacity of the reinforcedconcrete structures. Structures that are deficient in shear can be strengthened or repaired by using FRP composites (Bellamkonda, 2013). Many experimental and theoretical studies have been conducted regarding the shearstrengthening of normal weight reinforcedconcrete (NWRC) structures retrofitted externally with FRP. Limited studies were found in the literature review for FRP strengthening of lightweight reinforcedconcrete (LWRC) structures tested for shear failure, in spite of the shear capacity of lightweight concrete (LWC) being lower than normal weight concrete (NWC).
Rasuk kekotak, dengan kekuatan kilasan tinggi, ringan dan rintangan struktur yang besar, amat popular digunakan dalam struktur jambatan. Walau bagaimanapun, rasuk kotak mungkin gagal dengan tiba-tiba disebabkan oleh jumlah dan beban trafik meningkat dan kapasiti berkurang akibat dan pada kemerosotan. Teknik pengukuhan polimer bertetulang gentian (FRP) telah dikaji dan digunakan dalam struktur untuk meningkatkan keupayaan lenturan dan ricih rasuk. Namun, sangat sedikit perhatian ditumpukan kepada rasuk kotak konkrit bertetulang (RC) dari segi ricih, kilasan, mahupun gabungan ricih-kilasan. Oleh itu dalam kajian ini, tiga set ujikaji ke atas rasuk kotak RC diperkukuhkan dengan polimer karbon-bertetulang gentian (CFRP) dalam ricih, kilasan tulen, dan gabungan ricih-kilasan telah dijalankan. Berdasarkan eksperimen, matlamat utama adalah untuk: (a) meramal sumbangan ricih CFRP; (b) menilai keberkesanan pengukuhan dan meramalkan sumbangan CFRP kepada kilasan; (c) menyiasat kelakuan rasuk kotak dengan pengukuhan tertakluk kepada gabungan ricih-kilasan dan membangun persamaan matematik untuk meramal kekuatan. Model
All the Fifteen beams are tested under simply supported end conditions. Single point loading is adopted for testing and spacing between single concentrated loads is so selected that l/d ratio for the beam to be failing in combined shear and flexure. The testing of beams is done with the help of hydraulically operated machine connected to load cell. The load is applied to the beam with the help of universal testing machine and the data is recorded from the data acquisition system, which is attached with the load cell. Out of these 10 beams of each grade (M15,M25,M35) 2 are control beam, which were tested after 28 days of curing to find out the safe load which is taken as load corresponding to deflection of L/250 i.e. 3 mm. Four each of the remaining 8 beams are stressed up to 60% and 90% of the safe load.
Through the comparisons of the shear stress–strain behavior and the local opening and slip behavior between the NP1F0 specimen without steel ﬁbers and the other specimens with steel ﬁbers, the behavioral difference by the ﬁber reinforcement can be clearly observed. The shear strain of the NP1F0 specimen increased abruptly immediately after diagonal cracks appeared (Fig. 5). At this point when the shear strain was approximately 0.0005 (Figs. 10a and 11a), the slopes of the opening and slip also rapidly changed. Then, the opening and slip displacements increased at a constant rate without a signiﬁcant change in the slope until the maximum load was reached. Because the tensile resis- tance of concrete in the direction perpendicular to the diagonal crack disappeared immediately after diagonal cracking, the angle of principal strain was changed, and consequently the slope of openings and slips was changed. Since then, however, there was no change in the resistance mechanisms, and little change therefore occurred in the slope of the openings and slips until after the maximum load was reached. On the other hand, the other specimens, which were reinforced with steel ﬁbers (i.e., HP0F1, HP1F1, NP2F1, and HP2F1), showed no signiﬁcant change in their shear stiff- ness when shear cracks occurred (Fig. 5). Instead, the shear strains increased after a signiﬁcant increase in loads or even near their maximum loads. This can also be observed in Figs. 10b to 10e, in which the slopes of the opening and slip changed signiﬁcantly in accordance with the rapid increase in shear strains a long time after diagonal cracking. The reason for no signiﬁcant change in their shear stiffness as well as the slopes of slips and openings soon after diagonal cracking is that the steel ﬁbers replaced the tensile resistance of the concrete that was lost at diagonal cracking. The steel ﬁbers at the crack surface continuously resisted until they reached their bond strengths. Some ﬁbers started to be pulled out at the crack opening of approximately 0.5–1.0 mm as
It can be also used for repair and damage structure it is called as retrofitting  . There may be reason for deterioration of structure such as error in design and construction, environmental, corrosion in steel, earthquake, accidental event or it may be error caused due to time of construction  . So for this purpose the strengthening technique has developed to get strength requirement. There are various FRP materials available in market such as CFRP, GFRP and Aramid etc  .The FRP material is widely used but more research is required to be carried out for strengthening  . From IS-456 2000 clause 29.simply supported beam consider as deep beam if the ratio to effective span i.e. L/D is less than 2.0 and for continuous beam the ratio to effective span i.e. L/D is less than 2.5 If we consider a normal beam with steel stirrups it has more width of crack and has less avg.ultimate load.So in this paper we exactly solve how to increase a load capacity on it so that it can carry shear. In this paper we are going to increase the shear strength with CFRP fabric strips of 10mm and 20mm with various wrapping pattern.
FiberReinforcedPolymer (FRP) is a relatively new class of composite material manufactured from fibers and resins and has proven efficient and economical for the development and repair of new and deteriorating structures in civil engineering. FRP composite materials possess superior mechanical properties. It includes impact resistance, strength, stiffness, flexibility and ability to carry loads. To meet up the requirements of advanced infrastructure, new innovative materials/ technologies in construction industry has started to make its way. Any technology or material has its limitations. To meet the new requirements, new technologies have to be invented and put to use. With structures becoming old and the increasing bar corrosion, old buildings have started to demand additional retrofits to increase their durability and life. Use of FRP for confinement has proved to be effective retrofitting and strengthening application.
The versatility of concrete with respect to control on strength and conformability to any shape makes it one of the most common and popular construction materials for building structures around the world. However, concrete, being weak and brittle in tension, is prone to sudden shear failure. The most commonly adopted solution against such a failure is the provision of transverse reinforcement (shear stirrups) in concretebeams. However, past research has revealed that it is not always as effective as expected [1-3]. The use of high reinforcement ratios can also increase construction time and cost and make it difficult to work with such concrete. Furthermore, this may adversely affect the mechanical properties of concrete.
Empirical equations have been developed and validated through experimental programs. Narayanan and Darwish  developed Eq. (17) for the ultimate shear strength by testing SFRC beams with different crimped fiber contents and fiber aspect ratios of 100 and 133, with variable a/d ratio and concrete compressive strengths from 36 to 75 MPa. A similar experimental program  with two different compressive strengths (31 and 65 MPa) and hooked-end steel fibers with an aspect ratio of 62.5 was used to develop Equation (19). Moreover, Shin et al developed Eq. (20) by testing 22 reinforcedconcretebeams with and without steel fibers and with a concrete compressive strength of 80 MPa. The main variables in this program were the fiber content, a/d ratio, amount of longitudinal reinforcement, and amount of shear reinforcement. All of the proposed equations consider three shear-resisting mechanisms: 1) the fiber contribution represented by the splitting cylinder strength f sp , 2) dowel action provided by the longitudinal reinforcement and taking into account the influence
Reinforcedconcrete structures can be strengthened with CFRP reinforcement. Such method is quite widely applied and is supposed to be efficient and convenient for the purpose of strengthening (Lamanna et al. 2004; Bank, Arora 2007; Li et al. 2008; Skuturna et al. 2008; Valivonis, Skuturna 2007; David et al. 2003; Bulavs et al. 2005; Duthinh, Starnes 2004; Chahrour, Soudki 2005; Ekenel et al. 2006; Ferrier, Hamelin 2002; Fayyadh, Razak 2012; Ceroni, Pecce 2007; Trapko, Trapko 2012; Buyukozturk et al. 2004; Yail et al. 2013; Smith, Teng 2002a; Smith, Teng 2002b; Hajsadeghi et al. 2011; Heffernan, Erki 2004; Xie, Hu 2013; Thomsen et al. 2004; Hsu et al. 2003; Harries et al. 2007). This strengthening technique, due to such excellent qualities of CFRP as high tensile strength, resistance to aggressive environment, and low weight, has a lot of advantages in comparison to other commonly applied techniques.
which the matrix is metal or a ceramic. For the most part, these are still in a development stage, with problems of high manufacturing costs yet to be overcome. Furthermore, in these composites the reason for adding the fibers are often rather complex; fir examples, improvements may be sought in creep, wear, fracture toughness, thermal stability, etc.… . Fiberreinforcedpolymer (FRP) are composites used in almost in every type of advanced engineering structure, with their usage ranging aircraft, helicopter and spacecraft through to boats, ships and offshore platforms and to automobiles, sports, goods, chemicals processing equipment and civil infrastructure such as bridges and buildings. The usage of FRP composites continues to grow at an impressive rate as these materials are used more in their existing markets and become established in relatively new markets such as biomedical devices and civil structures. A key factor driving the increased applications of composites over the recent years is the development of advanced forms of FRP materials. This includes development in high performance resign systems and new style of reinforcement, such as carbon nano tubes and nano particles. This paper provides an up-to-date account of the fabrication. Mechanical properties, delimitation resistance, impact tolerance and application of 3 D FRP composites.
Asghari et al. (2013), presented an experimental investigation on shear strength enhancement of reinforcedconcrete lightweight deep beams externally reinforced with vertical CFRP sheets. The shear span/depth ratio was taken equal to 1, and the percentage of shear strength improving by strengthening was 30%. Khudair and Atea (2015), studied the shear behavior of self-compacting concrete deep beams strengthened with CFRP sheets. The experimental work includes testing of reinforcedconcrete self-compacting concrete (SCC) deep beams with shear span/depth ratio of 2. The tested results show that the specimens strengthened by vertical CFRP sheets provided enhancement in ultimate loads reached 30%.