Relationships between interfacial shear stresses and moment capacities of RC beams strengthened with various types of FRP sheets

Kim, Naeun; Shin, Yooleemi; Choi, Eunsoo; Kim, Hee Sun

doi:10.1016/j.conbuildmat.2015.05.007

Cited by 13 publications

(4 citation statements)

References 21 publications

(23 reference statements)

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“…In brief, these results were consistent with the previous literature regarding the influential factors on debonding failure, which is significantly affected by the maximum interfacial stress [ 40 , 56 , 57 ] but insensitive to changes in fracture energy and mixed-mode failure criteria [ 53 ]. However, disagreement can also be observed once the global response of the strengthened slab with a hybrid retrofit system was found to be impacted by changing the criteria of the stiffness of interface elements and damage initiation.…”

Section: Resultssupporting

confidence: 91%

The Effects of Bond–Slip Laws on the Debonding Failure and Behavior of Flexural Strengthened RC Slabs in Hybrid FRP Retrofit Systems

Nguyen

Nguyen²,

Lee³

et al. 2022

Materials

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The hybrid retrofit system using FRP and concrete overlay applied on the top of slabs has proven effective in strengthening and overcoming logistical constraints, compared with conventional strengthening techniques using externally bonded composite materials to the underside of the slabs. Nevertheless, the performance of retrofitted slabs is governed by debonding failure due to the low bond strength between CFRP and concrete overlay. Thus, this study investigates the behavior of flexural strengthened slabs with FRP retrofit systems and the effect of bond–slip laws on debonding failure. Firstly, two full-scale RC slabs with and without a retrofit system were tested in a four-point bending setup as the control specimens. Then, the same retrofitted slab was simulated by utilizing the commercial program ABAQUS. A sensitivity analysis was conducted to consider the influence of bond–slip laws to predict the failure mechanism of the retrofitted slabs based on load–deflection relationships. The results showed that the strengthened slab enhanced the load-carrying capacity by 59%, stiffness by 111%, and toughness by 29%. The initial stiffness of 0.1K0 and maximum shear stress of 0.13τmax, compared with the corresponding values of Neubauer’s and Rostasy’s bond–slip law, can be used to simulate the global response of the retrofitted slab validated by experiment results.

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Section: Resultssupporting

confidence: 91%

The Effects of Bond–Slip Laws on the Debonding Failure and Behavior of Flexural Strengthened RC Slabs in Hybrid FRP Retrofit Systems

Nguyen

Nguyen²,

Lee³

et al. 2022

Materials

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“…Many studies on FRP-strengthened flexural members have demonstrated that both their strength and stiffness increase significantly after strengthening. However, the strengthening effectiveness and mechanical behaviour of the strengthened beam or slab are greatly affected by the interfacial bond performance (Achillopoulou et al, 2016; Gao et al, 2007; Kim et al, 2015; Sayin and Manisali, 2010; Tounsi and Benyoucef, 2007; Xie et al, 2017). When the interfacial principal stress exceeds the bond strength of the FRP/concrete interface, premature brittle debonding failure may occur unless reliable additional anchoring measures (Oller et al, 2011; Smith and Teng, 2002; Teng and Chen, 2008; Zhou et al, 2017a, 2017b) are provided.…”

Section: Introductionmentioning

confidence: 99%

Interfacial stresses in reinforced concrete cantilever members strengthened with fibre-reinforced polymer laminates

Zhou

Wang

2019

Advances in Structural Engineering

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Fibre-reinforced polymers have been increasingly used to strengthen reinforced concrete structures. However, premature brittle debonding failures may occur at the ends of externally bonded fibre-reinforced polymer laminates due to interfacial stress concentrations caused by stiffness imbalances. Although many studies exist on fibre-reinforced polymer-strengthened simply supported beams and slabs, the interfacial stress distributions in fibre-reinforced polymer-strengthened cantilever members are very different from those in simply supported members. Based on the assumptions of linear elasticity, deformation compatibility and static equilibrium conditions, the interfacial stresses in fibre-reinforced polymer-strengthened reinforced concrete cantilever members under arbitrary linear distributed loads were analysed. In particular, closed-form solutions were obtained to calculate the interfacial stresses under either a uniformly distributed load or a single concentrated load located at the overhanging end of the cantilever member. Existing test results on cantilever slabs strengthened by carbon fibre–reinforced polymer sheets were used to verify the model. According to the parametric analysis, the maximum interfacial stresses can be reduced by decreasing the fibre-reinforced polymer thickness, increasing the fibre-reinforced polymer bonding length and increasing the adhesive layer thickness, and by using less rigid fibre-reinforced polymer laminates with high tensile strengths. These results are useful for engineers seeking to optimize strengthening design parameters and implement reliable debonding prevention measures.

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“…Nevertheless, one of the primary reasons retrofitted slabs failed to achieve their ultimate carrying capacity was a premature debonding failure between CFRP and overlay interface [ 18 ]. A specialized adhesive layer permits interfacial stress to be transferred from slab to CFRP or vice versa more effectively than from CFRP to overlay concrete, resulting in a higher potential debonding failure between overlay and CFRP [ 19 , 20 ]. Moon et al [ 21 ] also suggested using shear connectors to enhance the bond strength and flexural carrying capacity of retrofitted slabs.…”

Section: Introductionmentioning

confidence: 99%

A Design Process for Preventing Brittle Failure in Strengthening RC Slabs with Hybrid FRP-HPC Retrofit Systems

et al. 2023

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The retrofitting of existing RC slabs with an innovative system comprising FRP and HPC has been demonstrated to be effective in strengthening and overcoming the logistical challenges of installation. Nonetheless, the excessive improvement of flexural strength over shear strength would cause the sudden failure of rehabilitated flexural members. The literature has previously recommended failure limits to determine the additional moment strength compared with the shear strength to prevent brittle shear failure of strengthened, continuous RC slabs. This study suggests a design process for preventing shear failure and inducing the ductile-failure mode to improve the safety and applicability of retrofitted RC slabs based on the proposed failure limits. The effectiveness of the procedure in brittle-failure prevention for the end and interior spans of retrofitted RC slabs is illustrated via a case study. The outcomes showed that the retrofit system with 0.53-mm-thick-CFRP prevented brittle failure and significantly enhanced the design-factored load and ultimate failure load by up to 2.07 times and 2.13 times, respectively.

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Relationships between interfacial shear stresses and moment capacities of RC beams strengthened with various types of FRP sheets

Cited by 13 publications

References 21 publications

The Effects of Bond–Slip Laws on the Debonding Failure and Behavior of Flexural Strengthened RC Slabs in Hybrid FRP Retrofit Systems

The Effects of Bond–Slip Laws on the Debonding Failure and Behavior of Flexural Strengthened RC Slabs in Hybrid FRP Retrofit Systems

Interfacial stresses in reinforced concrete cantilever members strengthened with fibre-reinforced polymer laminates

A Design Process for Preventing Brittle Failure in Strengthening RC Slabs with Hybrid FRP-HPC Retrofit Systems

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