Characterization of combined longitudinal and transverse FRPs for strengthening concrete columns

2020 ◽  
Vol 47 (6) ◽  
pp. 718-728
Author(s):  
Pedram Sadeghian ◽  
Brandon Fillmore
Keyword(s):  
Bending Moment ◽  
Concrete Columns ◽  
Fiber Reinforced Polymer ◽  
Near Surface ◽  
Strain Behavior ◽  
Reinforced Polymer ◽  
Concrete Cylinders ◽  
Near Surface Mounted ◽  
Glass Frp

This paper presents the results of a study on the characterization of combined longitudinal near-surface-mounted (NSM) fiber-reinforced polymer (FRP) bars and transverse FRP wraps for strengthening concrete columns. A total of 21 concrete cylinders were prepared, strengthened, and tested to characterize the performance of the strengthening system. Three arrangements of glass FRP (GFRP) bars were mounted in surface grooves, and unidirectional basalt FRP (BFRP) composite was used to wrap the specimens. It was shown that the wrapping system effectively prevented premature failures of the NSM bars and extended the contribution of the bars from a mean of 17.5% in the NSM specimens to a mean of 27.7% in the specimens strengthened with the combined NSM and transverse FRPs. An analytical model was also presented to predict the load–strain behavior and the effect of combined axial load and bending moment.

Retrofitting of reinforced concrete columns using near-surface-mounted steel rebars and fiber-reinforced polymer straps under eccentric loading

2019 ◽  
Vol 23 (4) ◽  
pp. 687-701 ◽  
Author(s):  
Sayed Behzad Talaeitaba ◽  
Ehsan Barati ◽  
Abolfazl Eslami
Keyword(s):  
Reinforced Concrete ◽  
Concrete Columns ◽  
Fiber Reinforced Polymer ◽  
Small Scale ◽  
Fiber Reinforced ◽  
Reinforced Concrete Columns ◽  
Near Surface ◽  
Reinforced Polymer ◽  
Near Surface Mounted ◽  
Steel Rebars

This experimental study focuses on the retrofitting of reinforced concrete columns subjected to axial compression loading with different eccentricities. The proposed hybrid retrofitting technique incorporates two components: near-surface-mounted longitudinal steel rebars and transverse carbon-fiber-reinforced polymer straps. The latter was implemented to preclude buckling of the near-surface-mounted steel rebars under compression, to postpone debonding of near-surface-mounted steel rebars, to increase shear capacity of columns, and to improve the confinement level of concrete. The efficiency of the adopted retrofitting technique was evaluated through experimental testing of undamaged and damaged columns. Toward this, a total of 20 small-scale reinforced concrete circular columns including 5 control, 5 repaired, and 10 strengthened specimens were tested. All specimens were built to be identical with a diameter of 150 mm and a height of 500 mm. The specimens were tested under pure compression, combined axial–flexural (with eccentricities of 30, 60, and 90 mm), and four-point flexural loadings. Comparison of the results showed the efficacy of the proposed retrofitting strategy in enhancing the structural performance of both the undamaged and damaged columns in terms of loading capacity, ultimate displacement, and ductility factor. Finally, the axial load–bending moment interaction curves were discussed for all the tested columns.

scholarly journals Behavior of concrete beams reinforced with FRP during bending

2021 ◽  
Vol 263 ◽  
pp. 02052
Author(s):  
Igor Gorbunov ◽  
Vladimir Kakusha
Keyword(s):  
Crack Formation ◽  
Concrete Beams ◽  
Bending Moment ◽  
Bending Stiffness ◽  
Fiber Reinforced Polymer ◽  
Strain Behavior ◽  
Linear Elastic ◽  
Reinforced Polymer ◽  
Glass Frp ◽  
Frp Bars

Article describes methods and results of experimental research for strain behavior, crack formation and fracture of concrete beams reinforced with fiber reinforced polymer (FRP) bars during bending moment action. 18 beams (3+3 series) reinforced with glass FRP (GFRP) and basalt (BFRP) 6, 10 and 14 mm in diameter were tested. Deflection in the middle of the beam, concrete and bars strain and ultrasonic transmission time for 4 routes were measured during tests besides visual inspection. Main crack formation occurred at 8-20% of the ultimate load for all beams. Crack formation was transition border to linear (elastic) straining at low bending stiffness. More than 15 times decrease in bending stiffness was seen for beam reinforced with two types of bars 6 mm in diameter compared to initial values. Existence of main cracks and major deflections is not allowed during design of bending elements. However small bending stiffness at linear elastic straining is a positive factor in case of «hard» loading and impact (pulsed) loading. It is possible to prevent structures collapse and people deaths at impact loading and cyclic «hard» loading by permitting crack formation in load bearing structures.

scholarly journals Strengthening of Bent LVL Beams with Near-Surface Mounted (NSM) FRP Reinforcement

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2350 ◽  
Author(s):  
Michał Marcin Bakalarz ◽  
Paweł Grzegorz Kossakowski ◽  
Paweł Tworzewski
Keyword(s):  
Bending Moment ◽  
Experimental Tests ◽  
Fiber Reinforced Polymer ◽  
Wood Structures ◽  
Near Surface ◽  
Bending Tests ◽  
Laminated Veneer Lumber ◽  
Reinforced Polymer ◽  
Frp Reinforcement ◽  
Near Surface Mounted

The topic of the article is the analysis of the static work of unreinforced and reinforced with composite material timber beams under bending tests. The results of the experimental tests and a brief outline of the characteristics of the internal reinforcement of wood structures are presented. Experimental tests were performed on full-scale beams made of laminated veneer lumber (LVL) with nominal dimensions of 45 × 200 × 3400 mm. Two strips of carbon fiber-reinforced polymer (CFRP) reinforcement were glued into rectangular grooves in the component bottom with two-component epoxy resin (0.62% reinforcement percentage). The reinforcement mainly affected the enhancement of the maximum bending moment values evaluated at the points of application as having concentrated forces of 32% and 24% in comparison to the unreinforced elements. Increases of 11% and 7% in the global modulus of elasticity in the bending and stiffness coefficients were achieved, respectively. The failure of the reference beams was caused by exceeding the tensile strength of the LVL. The reinforced elements were characterized by a greater variation in failure mode, resulting from tension, compression or lateral torsional buckling. The strain profile reading showed a higher utilization of the compression characteristic of veneer in specimens reinforced with carbon laminates.

scholarly journals Numerical Analysis of the Flexural Response of Rc Beams Strengthened with NSM-CFRP

2018 ◽  
Vol 28 (3) ◽  
pp. 90-102
Author(s):  
Ahmed Khene ◽  
Habib Abdelhak Mesbah ◽  
Nasr-Eddine Chikh
Keyword(s):  
Parametric Study ◽  
Reinforced Concrete Beams ◽  
Fiber Reinforced Polymer ◽  
Near Surface ◽  
Flexural Response ◽  
Reinforced Polymer ◽  
Near Surface Mounted ◽  
Concrete Coating ◽  
A New Technique ◽  
Nsm Technique

Abstract In this study, we have chosen to use a new technique of reinforcement with composite materials, namely the near surface mounted technique (NSM). The NSM technique consists in inserting strips of carbon fiber reinforced polymer (CFRP) laminate into slits made beforehand at the level of the concrete coating of the elements to be reinforced. A numerical investigation was conducted on rectangular reinforced concrete beams reinforced with NSM-CFRP using the ATENA finite element code. A parametric study was also carried out in this research. The numerical results were compared with the experimental results of the beams tested by other researchers with the same reinforcement configurations. Overall, numerical behavior laws are rather well-suited to those obtained experimentally and the parametric study has also yielded interesting results.

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

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1770 ◽  
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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