*Co-chairs of the subcommittee that prepared this document. Note: The committee acknowledges the contribution of associate member Paul Kelley. ACI encourages the development and appropriate use of new and emerging technologies through the publication of the Emerging Technology Series. This series presents information and recommendations based on available test data, technical reports, limited experience with field applications, and the opinions of committee members. The presented information and recommendations, and their basis, may be less fully developed and tested than those for more mature technologies. This report identifies areas in which information is believed to be less fully developed, and describes research needs. The professional using this document should understand the limitations of this document and exercise judgment as to the appropriate application of this emerging technology.

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Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures

External bonding of steel plates has been used to strengthen deficient reinforced-concrete structures since the 1960s. In recent years, fiber-reinforced polymer (FRP) plates have been increasingly used to replace steel plates due to their superior properties. A key issue in the design of an effective retrofitting solution using externally bonded plates is the end anchorage strength. This paper first presents a review of current anchorage strength models for both FRP-to-concrete and steel-to-concrete bonded joints under shear. These models are then assessed with experimental data collected from the literature, revealing the deficiencies of all existing models. Finally, a new simple and rational model is proposed based on an existing fracture mechanics analysis and experimental observations. This new model not only matches experimental observations of bond strength closely, but also correctly predicts the effective bond length. The new model is thus suitable for practical application in the design of FRP-to-concrete as well as steel-to-concrete bonded joints.

Anchorage strength models for FRP and steel plates bonded to concrete

Bond-slip models for FRP sheets/plates bonded to concrete

Externally bonded FRP reinforcement for RC structures

Full-range behavior of FRP-to-concrete bonded joints

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.

Contribution of Externally Bonded FRP to Shear Capacity of RC Flexural Members

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.

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

Rehabilitation of rectangular simply supported RC beams with shear deficiencies using CFRP composites

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.

http://acerestoration.net/news/anchorage.pdf

Anchorage of Surface Mounted FRP Reinforcement

The near surface mounted (NSM) fiber reinforced polymer (FRP) reinforcement is emerging as a promising alternative strengthening technique to externally bonded reinforcement (EBR) for increasing the load carrying capacity of reinforced concrete (RC) members. NSM FRP technique has several advantages, in comparison with the EBR method, such as reducing the risk of debonding, and a better protection from the external sources of damage. In this research, the performance and effectiveness of the NSM and EBR techniques for the flexural strengthening of RC beams are compared. In order to achieve this objective, six full-scale, RC beams were strengthened with different carbon FRP (CFRP) schemes and tested. Such beams were designed to fail in a flexural mode. Test results indicated that if the same amount of CFRP is used, beams strengthened with NSM strips achieved higher ultimate load than those strengthened with EBR. Such increase in the ultimate load ratio ranged between 12% and 18%. Furthermore, a design approach for computing the moment capacity of RC flexural members strengthened with NSM CFRP strips is developed and presented in this paper.

https://cyberleninka.org/article/n/590464.pdf

Ahmed Khalifa

Papers

Contribution of Externally Bonded FRP to Shear Capacity of RC Flexural Members

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

Rehabilitation of rectangular simply supported RC beams with shear deficiencies using CFRP composites

Anchorage of Surface Mounted FRP Reinforcement

Flexural performance of RC beams strengthened with near surface mounted CFRP strips