Pull-out tests on bond behavior between timber and near-surface-mounted steel bars

Nowadays, the use of near surface mounted (NSM) technique strengthening reinforced concrete (RC) structural members is going very popular. The failure modes of NSM strengthened reinforced concrete (RC) beams have been shown to be largely due to premature failure such as concrete cover separation. In this study, CFRP U-wrap end anchorage with CFRP fabrics was used to eliminate the concrete cover separation failure. A total of eight RC rectangular beam specimens of 125 mm width, 250 mm depth, and 2300 mm length were tested. One specimen was kept unstrengthened as a reference; three specimens were strengthened with NSM steel bars and the remaining four specimens were strengthened with NSM steel bars together with the U-wrap end anchorage. The experimental results showed that wrapped strengthened beams had higher flexural strength and superior ductility performance. The results also show that these beams had less deflection, strain, crack width, and spacing.

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Bond behavior of Near Surface Mounted Carbon Fiber Reinforced Polymer rod under temperature cycles

Resources, Environment and Engineering II ◽

10.1201/b19136-33 ◽

2015 ◽

pp. 215-220

Keyword(s):

Carbon Fiber ◽

Fiber Reinforced Polymer ◽

Carbon Fiber Reinforced Polymer ◽

Fiber Reinforced ◽

Near Surface ◽

Bond Behavior ◽

Temperature Cycles ◽

Reinforced Polymer ◽

Near Surface Mounted ◽

Carbon Fiber Reinforced

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Near-surface-mounted retrofitting of damaged/undamaged adobe walls using steel bars: Analytical evaluation of experimental results

Structures ◽

10.1016/j.istruc.2020.10.020 ◽

2020 ◽

Vol 28 ◽

pp. 2111-2121

Author(s):

Hosein Mirabi Banadaki ◽

Abolfazl Eslami ◽

Hamid Ronagh

Keyword(s):

Experimental Results ◽

Analytical Evaluation ◽

Near Surface ◽

Steel Bars ◽

Near Surface Mounted

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Characterization and Simulation of the Bond Response of NSM FRP Reinforcement in Concrete

Materials ◽

10.3390/ma13071770 ◽

2020 ◽

Vol 13 (7) ◽

pp. 1770 ◽

Cited By ~ 3

Author(s):

Javier Gómez ◽

Lluís Torres ◽

Cristina Barris

Keyword(s):

Load Capacity ◽

Numerical Procedure ◽

Fiber Reinforced Polymer ◽

Near Surface ◽

Bond Slip ◽

Pull Out ◽

Reinforced Polymer ◽

Frp Reinforcement ◽

Near Surface Mounted ◽

Shear Stress And Strain

The near-surface mounted (NSM) technique with fiber reinforced polymer (FRP) reinforcement as strengthening system for concrete structures has been broadly studied during the last years. The efficiency of the NSM FRP-to-concrete joint highly depends on the bond between both materials, which is characterized by a local bond–slip law. This paper studies the effect of the shape of the local bond–slip law and its parameters on the global response of the NSM FRP joint in terms of load capacity, effective bond length, slip, shear stress, and strain distribution along the bonded length, which are essential parameters on the strengthening design. A numerical procedure based on the finite difference method to solve the governing equations of the FRP-to-concrete joint is developed. Pull-out single shear specimens are tested in order to experimentally validate the numerical results. Finally, a parametric study is performed. The effect of the bond–shear strength slip at the bond strength, maximum slip, and friction branch on the parameters previously described is presented and discussed.

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Numerical simulation of the debonding process in pull-out tests of near-surface mounted FRP rod in concrete

Engineering Computations ◽

10.1108/ec-01-2019-0032 ◽

2019 ◽

Vol 37 (3) ◽

pp. 1109-1130

Author(s):

Tie-Lin Chen ◽

Wenbin Tao ◽

Wenjun Zhu ◽

Mozhen Zhou

Keyword(s):

Three Dimensional ◽

Crack Model ◽

Bond Failure ◽

Near Surface ◽

Content Type ◽

Rc Structures ◽

Pull Out ◽

Smeared Crack ◽

Near Surface Mounted ◽

Debonding Process

Purpose Near-surface mounted (NSM) fiber-reinforced polymer (FRP) rod is extensively applied in reinforced concrete (RC) structures. The mechanical performances of NSM FRP-strengthened RC structures depend on the bond behavior between NSM reinforcement and concrete. This behavior is typically studied by performing pull-out tests; however, the failure behavior, which is crucial to the local debonding process, is not yet sufficiently understood. Design/methodology/approach In this study, a three-dimensional meso-scale finite element method considering the cohesion and adhesion failures is presented to model the debonding failure process in pull-out tests of NSM FRP rod in concrete. The smeared crack model is used to capture the cohesion failures in the adhesive or concrete. The interfacial constitutive model is applied to simulate the adhesion failures on the FRP-adhesive and concrete-adhesive contact interfaces. Findings The present method is first validated by two simple examples and then applied to a practical NSM FRP system. This work studied in detail the debonding process, the bond failure types, the location of peak bond stress, the transmitting deformation in adhesive and the morphology of contact zone. The developed method provides a practical and convenient tool applicable for further investigations on the debonding mechanism for the NSM FRP rod in concrete. Originality/value A three-dimensional meso-scale finite element method considering the cohesion and adhesion failures is presented to model the debonding failure in NSM FRP-strengthened RC structures. The smeared crack model and the interfacial constitutive model are introduced to develop a convenient approach to analyze the failures in adhesive, concrete and related interfaces. The developed numerical method is applicable for studying the debonding process, the bond failure types, the location of peak bond stress, the transmitting deformation in adhesive and the morphology of contact zone in detail.

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