Efficacy of CFRP-based techniques for the flexural and shear strengthening of concrete beams

Barros, Joaquim A. O.; Dias, Salvador J. E.; Lima, João L. T.

doi:10.1016/j.cemconcomp.2006.09.001

Cited by 241 publications

(160 citation statements)

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“…Strengthening using externally bonded FRP reinforcement has received by far the largest amount of research [1][2][3][4], but the alternative of near-surface mounted (NSM) FRP reinforcement has also received increasing attention [e.g. [5][6][7][8]. The externally bonded FRP method involves the external bonding of FRP laminates, either formed in-situ via the wet layup process or prefabricated off site generally by pultrusion, to the tension surface of RC members, and the NSM FRP method involves the cutting of grooves in the cover concrete and the embedding of FRP bars in the grooves using an adhesive.…”

Section: Introductionmentioning

confidence: 99%

Strength model for end cover separation failure in RC beams strengthened with near-surface mounted (NSM) FRP strips

Teng

Zhang

Chen

2016

Engineering Structures

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Abstract:As an alternative to externally bonded FRP reinforcement, near-surface mounted (NSM) FRP reinforcement can be used to effectively improve the flexural performance of RC beams. In such FRP-strengthened RC beams, end cover separation failure is one of the common failure modes. This failure mode involves the detachment of the NSM FRP reinforcement together with the concrete cover along the level of the steel tension reinforcement. This paper presents a new analytical strength model for end cover separation failure in RC beams strengthened in flexure with NSM FRP strips (i.e. rectangular FRP bars with a sectional height-to-thickness ratio not less than 5), which was formulated on the basis of extensive numerical results from a parametric study undertaken using an efficient finite element approach. The proposed strength model consists of an approximate analytical equation for the debonding strain of the FRP reinforcement at the critical cracked section and a conventional section analysis to relate this debonding strain to the moment acting on the same section (i.e. the debonding strain). Once the debonding strain is known, the load level at end cover separation of an FRP-strengthened RC beam can be easily determined for a given load distribution. Predictions from the proposed strength model are compared with those of two existing strength models of the same type and available test results, which shows that the proposed strength model is in close agreement with test results and is far more accurate than the existing strength models.

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Section: Introductionmentioning

confidence: 99%

Strength model for end cover separation failure in RC beams strengthened with near-surface mounted (NSM) FRP strips

Teng

Zhang

Chen

2016

Engineering Structures

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“…The effective strain in U-shaped CFRP sheets can be estimated using eqs (2)- (6). A comparison between the maximum measured CFRP strains and the calculated values on the basis of the ACI-440-2008 (ref.…”

Section: Debonding Strainmentioning

confidence: 99%

“…Among the available fibre composites, GFRP and CFRP play a major role in strengthening with respect to their custom in industry. A single layer of CFRP can enhance the shear strength of a beam twice as compared with multiple layered GFRP composites as a result of its higher modulus.A review of FRP application in civil engineering 5 provides a detailed report on the strengthening works done in Indian railways using FRP such as Bata ROB-Kolkata A number of studies have been conducted on strengthening of RC elements using various FRP in the recent past [6][7][8][9][10][11] . The externally bonded FRP composites (EB-FRP) have been successfully used for upgrading the flexural, shear and axial load carrying capacities of RC elements.…”

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confidence: 99%

Influence of End Anchorage on Shear Strengthening of Reinforced Concrete Beams Using CFRP Composites

Frederick¹,

Sharma²,

Gupta³

2017

Current Science

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The article presents an experimental study on the influence of various end anchorage systems on the shear strengthening of reinforced concrete (RC) T-beams using externally bonded fibre reinforced polymer (EB-FRP) composites. Two different end anchorage techniques namely self-end anchorage (SEA) and sandwich anchorage (SWA) were used. This study mainly focussed on evaluating the effectiveness of these anchorages to eliminate the conventional fibre reinforced polymer (FRP) debonding failure. A total of twelve R.C. T-beams with different strengthening techniques using CFRP including control beams were used. The test results show improved shear strength and better energy dissipation over conventional technique; this authenticates the influence of end anchorage and its effectiveness in improving shear resistance. Also, the enhanced FRP strain at failure proves that the anchorage employed improves the efficacy of FRP strengthening in terms of ductility and damage tolerance.Keywords: CFRP strengthening, external bonded FRP, end anchorage, shear behaviour.MANY existing reinforced concrete (RC) structures in the world need reconstruction or strengthening because of ageing, lack of maintenance and up-gradation in code recommendations. Though conventional strengthening techniques such as RC jacketing, steel plate jacketing, ferrocement and fibre reinforced concrete strengthening [1][2][3][4] have been used, fibre reinforced polymer (FRP) wrapping has emerged as the most successful technique in recent years due to its ease and efficiency in construction practice. Strengthening of structural systems in India could be traced back from 1990s. Different types of fibre composites are available and the mechanical property of each material is unique as shown in Figure 1. Among the available fibre composites, GFRP and CFRP play a major role in strengthening with respect to their custom in industry. A single layer of CFRP can enhance the shear strength of a beam twice as compared with multiple layered GFRP composites as a result of its higher modulus.A review of FRP application in civil engineering 5 provides a detailed report on the strengthening works done in Indian railways using FRP such as Bata ROB-Kolkata A number of studies have been conducted on strengthening of RC elements using various FRP in the recent past [6][7][8][9][10][11] . The externally bonded FRP composites (EB-FRP) have been successfully used for upgrading the flexural, shear and axial load carrying capacities of RC elements. Many studies have focussed on the effect on shear strengthening of reinforced concrete (RC) elements [12][13][14][15][16] . Most of these studies [17][18][19][20][21] reported premature FRP debonding failure limiting the application of FRP on shear strengthening. In order to address this debonding failure many investigations have been done on different end anchorage systems using steel rod, steel plate and steel bolts as anchorage for FRP [22][23][24][25][26] . But these anchorage materials are prone to corrosion and not durable under seve...

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“…The debonding loads would also increase for concretes with higher compressive strengths. Testing specimens with different amounts of NSM FRP, Barros et al (2007) reported that strengthening efficacy, a measure of improved flexural strength, has an inverse relation with the FRP reinforcement ratio (ρ f ). Analyzing the available research data, they also reported that the ratio of the maximum to ultimate strains in FRP (ε max /ε u ), increased with decreasing ρ f and increasing d g and d e .…”

Section: Generalmentioning

confidence: 99%

“…FE model was further verified using Specimen S1-NSM of Barros et al (2007). Figure 4.24 Model Validation for Specimen S1-NSM (Barros et al 2007) Considering the case of bond model with springs the error predicting the peak load, displacement at the peak load and post-cracking stiffness were 4%, 24% and 1%, respectively.…”

Section: Generic Model Descriptionmentioning

confidence: 99%

Development of Surface Flaw Thresholds for Pre-Cured Fiber Reinforced Polymer and Groove Size Tolerance for Near Surface Mounted Fiber Reinforced Polymer Retrofit Systems

Kalayci¹

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Since the introduction of fiber reinforced polymers (FRP) for the repair and retrofit of concrete structures in the 1980's, considerable research has been devoted to the feasibility of their application and predictive modeling of their performance. However, the effects of flaws present in the constitutive components and the practices in substrate preparation and treatment have not yet been thoroughly studied.This research aims at investigating the effect of surface preparation and treatment for the pre-cured FRP systems and the groove size tolerance for near surface mounted (NSM) FRP systems; and to set thresholds for guaranteed system performance. This study was Test results, confirmed by further analyses, indicated that contrary to the general belief in the industry, the impact of surface roughness on the global performance of precured FRP systems was negligible. The study also verified that threshold limits set for wet lay-up FRP systems can be extended to pre-cured systems. The study showed that larger surface voids and cracks (cuts) can adversely impact both the strength and ductility of pre-cured FRP systems. On the other hand, frequency (or spacing) of surface cracks (cuts) may only affect system ductility rather than its strength. Finally, within the range studied, groove size tolerance of +1/8 in. does not appear to have an adverse effect on the performance of NSM FRP systems.

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Efficacy of CFRP-based techniques for the flexural and shear strengthening of concrete beams

Cited by 241 publications

References 4 publications

Strength model for end cover separation failure in RC beams strengthened with near-surface mounted (NSM) FRP strips

Strength model for end cover separation failure in RC beams strengthened with near-surface mounted (NSM) FRP strips

Influence of End Anchorage on Shear Strengthening of Reinforced Concrete Beams Using CFRP Composites

Development of Surface Flaw Thresholds for Pre-Cured Fiber Reinforced Polymer and Groove Size Tolerance for Near Surface Mounted Fiber Reinforced Polymer Retrofit Systems

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