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Journal ArticleDOI

Improving shear capacity of existing rc t-section beams using cfrp composites

01 Jun 2000-Cement & Concrete Composites (Elsevier)-Vol. 22, Iss: 3, pp 165-174
TL;DR: In this article, different configurations of externally bonded carbon fiber reinforced polymer (CFRP) sheets were used to strengthen the specimens in shear, and the results indicated that the most effective configuration was the U-wrap with end anchorage.
Abstract: This paper presents the shear performance of reinforced concrete (RC) beams with Tsection. Different configurations of externally bonded carbon fiber reinforced polymer (CFRP) sheets were used to strengthen the specimens in shear. The experimental program consisted of six full-scale, simply supported beams. One beam was used as a bench mark and five beams were strengthened using different configurations of CFRP. The parameters investigated in this study included wrapping schemes, CFRP amount, 90 0 /0 0 ply combination, and CFRP end anchorage. The experimental results show that externally bonded CFRP can increase the shear capacity of the beam significantly. In addition, the results indicated that the most effective configuration was the U-wrap with end anchorage. Design algorithms in ACI Code format as well as Eurocode format are proposed to predict the capacity of referred members. Results showed that the proposed design approach is conservative and acceptable.
Citations
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Journal ArticleDOI
TL;DR: In this paper, a simple, accurate and rational design proposal for the shear capacity of FRP-strengthened reinforced concrete (RC) beams which fail by FRP debonding is presented.

448 citations

Journal ArticleDOI
01 Jan 2003
TL;DR: In this paper, the authors provide a concise review of existing research on the behaviour and strength of FRP-strengthened reinforced concrete (RC) structures, with a strong focus on those studies which contribute directly to the development of strength models.
Abstract: Extensive research has been carried out in recent years on the use of fibre-reinforced polymer (FRP) composites in the strengthening of reinforced concrete (RC) structures. This paper provides a concise review of existing research on the behaviour and strength of FRP-strengthened RC structures, with a strong focus on those studies which contribute directly to the development of strength models. Topics covered include flexural and shear strengthening of beams, flexural strengthening of slabs, and strengthening of columns subject to both static and seismic loads. For each of the topics covered, the methods of strengthening are first explained, followed by a description of the common failure modes. Available strength models are then summarised and discussed.

258 citations

Journal ArticleDOI
TL;DR: In this paper, a simple, accurate, and rational design proposal for the shear capacity of FRP-strengthened reinforced concrete beams which fail by FRP rupture is presented.
Abstract: A recent innovation in shear strengthening of reinforced concrete beams is to externally bond fiber-reinforced polymer (FRP) composites. Many studies have been undertaken on this strengthening technique. These studies have established clearly that such strengthened beams fail in shear mainly in one of the two modes: FRP rupture and FRP debonding, and have led to preliminary design proposals. This paper is concerned with the development of a simple, accurate, and rational design proposal for the shear capacity of FRP-strengthened beams which fail by FRP rupture. To this end, existing design proposals are reviewed, and their efficiencies highlighted. A new strength model is then developed, which recognizes the fundamental characteristics of FRP. The model is validated against experimental data collected from the existing literature. Finally, a new design proposal is presented.

236 citations

Journal ArticleDOI
TL;DR: In this paper, the authors developed a mechanics-based model of the shear capacity of reinforced concrete beams, strengthened with externally bonded fiber reinforced polymers (FRP), which is obtained through the following steps, with due consideration of the underlying physical mechanisms: (a) the generalised constitutive law of an FRP layer bonded to concrete is defined first, then, the compatibility imposed by a shear crack opening and the appropriate boundary conditions, which depend on the strengthening configuration (either side bonding, U-jacketing or wrapping) are included in the formulation, and,

172 citations

Journal ArticleDOI
TL;DR: In this paper, an extensive experimental investigation on reinforced concrete T-beams retrofitted in shear with externally bonded carbon fiber-reinforced polymer (CFRP) is presented.
Abstract: The results of an extensive experimental investigation on reinforced concrete T-beams retrofitted in shear with externally bonded carbon fiber-reinforced polymer (CFRP) are presented. The authors researched the CFRP ratio, the internal shear steel reinforcement ratio and the shear length to the beam's depth ratio. By studying the aforementioned parameters, the behavior of reinforced concrete T-beams strengthened in shear with externally applied CFRP was analyzed. It appears that the contribution of CFRP to shear resistance depends on if a strengthened beam is reinforced in shear with internal transverse steel reinforcement, and not on the CFRP stiffness provided. It seems that the American Concrete Institute and the Canadian Standards Association guidelines fail to incorporate the presence of the transverse resistance and overestimates the shear resistance for high fiber reinforced polymer thickness.

153 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the authors deal with the application of fiber reinforced polymer (FRP) laminates or fabrics as shear strengthening materials for reinforced concrete beams and develop an analytical model for the design of such members within the framework of modern code formats.
Abstract: The paper deals with the application of fiber reinforced polymer (FRP) laminates or fabrics as shear strengthening materials for reinforced concrete beams. The study aims at increasing the experimental database on shear strengthening of concrete using composites and, most importantly, developing an analytical model for the design of such members within the framework of modern code formats, based on ultimate limit states. The experimental part of the study involved testing of eleven concrete beams, strengthened in shear with carbon FRP at various area fractions and fiber configurations, while the analytical part resulted in a model for the contribution of FRP to shear capacity in analogy with steel stirrups, with an effective FRP strain that decreases with increasing FRP axial rigidity. It is shown that the effectiveness of the technique increases almost linearly with the FRP axial rigidity and reaches a maximum, beyond which it varies very little.

618 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a review of the current research on shear strengthening with FRP and propose design algorithms to compute the contribution of FRP to the shear capacity of RC flexural members.
Abstract: Fiber reinforced polymer (FRP) materials are continuing to show great promise for use in strengthening reinforced concrete (RC) structures. These materials are an excellent option for use as external reinforcing because of their light weight, resistance to corrosion, and high strength. Externally bonded FRP sheets have been used to increase moment capacity of flexural members and to improve confinement in compression members. Investigations into the use of externally bonded FRP sheets for use in shear strengthening have also been conducted and have shown this to be a viable strengthening method. The objective of this study is to review the current research on shear strengthening with FRP and propose design algorithms to compute the contribution of FRP to the shear capacity of RC flexural members. Methods for computing the shear capacity based on the stress level to cause tensile fracture of the FRP sheet (which may be less than ultimate due to stress concentrations) and based on delamination of the sheet from the concrete surface are presented. Areas which have the potential for further development are also discussed.

570 citations

Journal ArticleDOI
TL;DR: In this paper, a study of 12 under-reinforced concrete T-beams that were tested to determine the effectiveness of using externally applied composite fabrics as a method of increasing a beams's shear capacity.
Abstract: This paper describes a study of 12 under-reinforced concrete T-beams that were tested to determine the effectiveness of using externally applied composite fabrics as a method of increasing a beams's shear capacity. Woven composite fabrics made of aramid, E-glass, and graphite fibers were bonded to the web of the T-beams using a two-component epoxy. The three different fabrics were chosen to allow various fabric stiffnesses and strengths to be studied. The beams were tested in flexure, and the performance of eight beams with external shear reinforcement was compared to results of four control beams with no external reinforcement. All the beams failed in shear and those with composite reinforcement displayed excellent bond characteristics. For the beams with external reinforcement, increases in ultimate strength of 60 to 150 percent were achieved.

317 citations

Journal ArticleDOI
TL;DR: In this article, a study on strengthening of reinforced concrete beams having deficient shear strength and showing major diagonal tension cracks is presented, where different shear repair schemes using fiberglass plate bonding (FGPB) techniques were used to upgrade beams' shear capacity.
Abstract: Reinforced concrete structures often exhibit structural and nonstructural cracking due to a variety of reasons. Major cracks are signs of distress and require immediate attention. Results from a study on strengthening of reinforced concrete beams having deficient shear strength and showing major diagonal tension cracks are presented in this paper. The beams with deficient shear strength were damaged to a predetermined level (the appearance of the first shear crack) and then repaired by fiberglass plate bonding (FGPB) techniques. Different shear repair schemes using FGPB to upgrade beams' shear capacity were used: FGPB repair by shear strips, by shear wings, and by U-jackets in the shear span of the beams. Experimental data on strength, stiffness, steel strain, deflection, and mode of failure of the repaired beams were obtained, and comparisons between the different shear repair schemes and the unrepaired control beams were made. Shear repair by FGPB is shown to increase shear capacity and restore the degraded stiffness of the beams. The study results also show that the increase in shear capacity by FGPB was almost identical for both strip and wing shear repairs. However, this increase was not adequate to cause beams repaired by these two schemes to fail in flexure. On the other hand, the enhanced shear capacity by U-jacket was sufficient that flexural failure occurred for these beams.

193 citations

Journal Article
TL;DR: The U-anchor as mentioned in this paper is based on the idea of embedding a bent portion of the end (or near the end) of the fiber reinforced polymer (FRP) reinforcement into a preformed groove in the concrete/masonry.
Abstract: This paper presents a novel anchor system called U-anchor that can be used to significantly improve the performance of surface mounted reinforcement for concrete/masonry made of fiber reinforced polymer (FRP) composites. In applications where bond and/or development length of FRP are critical, the U-anchor prevents debonding of the reinforcement. The anchor is based on the idea of embedding a bent portion of the end (or near the end) of the FRP reinforcement into a preformed groove in the concrete/masonry. The groove is filled with a viscous paste and may or may not include an FRP bar. The U-anchor is compatible with any external FRP strengthening system and avoids high stress concentration and durability concerns. It can be used with sheets and pre-cured laminates that are unbonded or fully bonded to concrete. Laboratory testing confirms the excellent performance of the U-anchor system.

82 citations