Analysis of static response of RC beams with NSM CFRP/GFRP rods

In this paper experimental results of investigation on reinforced concrete (RC) beams strengthened with the near surface method (NSM) are analyzed considering the response under bending tests on two beams. One of the RC beams was damaged by bending until the yield of reinforcement and successively strengthened with carbon fiber polymer (CFRP) rod, while the second beam was strengthened with glass-FRP rod. Both the beams have been subjected to bending tests until failure. Experimental diagrams and discussion on static response are presented in the paper. It also places a particular emphasis on the non-linear response of RC sections strengthened with CFRP and GFRP rods under bending moment beyond the first elastic behavior.

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Torsional Strengthening of RC Beams with Near-Surface Mounted Steel Bars

Advances in Materials Science and Engineering ◽

10.1155/2020/1492980 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Nasih Habeeb Askandar ◽

Abdulkareem Darweesh Mahmood

Keyword(s):

Twist Angle ◽

Bending Moment ◽

Rc Beams ◽

Near Surface ◽

Concrete Members ◽

Epoxy Adhesives ◽

Steel Bars ◽

Externally Bonded ◽

Near Surface Mounted ◽

Combined Actions

The strength of reinforced concrete members can be enhanced by using the externally bonded reinforcement (EBR) and near-surface mounted (NSM) methods. However, very few studies have adopted the NSM method for torsional strengthening. Although previous studies have reported the efficacy of using epoxy-resin-bonded NSM steel bars in increasing the flexural and shear strength of RC beams, no study has examined the use of steel bars and epoxy adhesives for torsional strengthening. Therefore, this study investigates the behaviour of RC beams subjected to the combined actions of torsion and bending moment when they are strengthened with NSM steel bars (Ø10 mm) in different configurations. The practical part of this investigation consisted of seven cast and tested beams of 150 × 250 × 2000 mm dimensions. One beam was reference, which is not strengthened; meanwhile, all the other beams were strengthened with two U-shape-welded NSM steel bars. During the testing process, the twist angle at the torque intervals, first cracking torque, ultimate torque, and ultimate twist angle of the conventional beam were compared with those of the strengthened beams. The torsional performance of the RC beams was significantly improved by using NSM steel bars, whereas in various NSM configurations, the 90° NSM beams outperformed the 45° NSM beams.

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Comparative Investigation on Torsional Behaviour of RC Beam Strengthened with CFRP Fabric Wrapping and Near-Surface Mounted (NSM) Steel Bar

Advances in Civil Engineering ◽

10.1155/2019/9061703 ◽

2019 ◽

Vol 2019 ◽

pp. 1-15 ◽

Cited By ~ 4

Author(s):

Nasih Askandar ◽

Abdulkareem Mahmood

Keyword(s):

Twist Angle ◽

Bending Moment ◽

Comparative Investigation ◽

Rc Beams ◽

Near Surface ◽

Reinforced Polymer ◽

Steel Bar ◽

Fibre Reinforced Polymer ◽

Near Surface Mounted ◽

Cfrp Wrapping

Many researchers worldwide have extensively used fibre-reinforced polymer (FRP) strengthening materials and near-surface mounted (NSM) to enhance the shear and flexural strengths of reinforced concrete (RC) beams. However, studies on torsional strengthening are limited. Although a few studies have focused on torsional strengthening, none of them simultaneously investigated torsion with shear and/or bending moment. This study aims at demonstrating the behaviour of RC beams strengthened with FRP sheets (strips) with different configurations and NSM steel bars with different spacing that was subjected to combined actions of torsion and bending moment and making a comparison between them. Seven beams with a dimension of 15 × 25 × 200 cm were casted. One of the beams was not strengthened; three of them were strengthened with carbon FRP, and the others were strengthened with NSM steel bar. The angle of twist at torque intervals, first cracking torque, ultimate torque, and ultimate twist angle of the conventional and strengthened beams during the testing process are compared. Results show a significant improvement in the torsional performance of RC beams using carbon FRP and NSM steel bar. The test beams that were strengthened with CFRP wrapping showed better enhancement in the ultimate torsional moment as opposed to the beams that were strengthened with NSM steel bar.

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RC beams damaged by cracking and strengthened with NSM CFRP/GFRP rods

Frattura ed Integrità Strutturale ◽

10.3221/igf-esis.58.28 ◽

2021 ◽

Vol 15 (58) ◽

pp. 386-401

Author(s):

Roberto Capozucca ◽

Erica Magagnini ◽

Maria Vittoria Vecchietti ◽

Samir Khatir

Keyword(s):

Loading Path ◽

Beam Model ◽

Rc Beam ◽

Rc Beams ◽

Near Surface ◽

Damage Level ◽

Near Surface Mounted ◽

Vibration Tests ◽

Glass Frp ◽

Non Destructive

The near surface mounted (NSM) method of inserting fiber reinforced polymer (FRP) elements (rods or lamina) into notches has been shown to be a good way for restoring reinforced concrete (RC) elements. The knowledge about the use of Glass-FRP rod following the NSM to reinforce RC beams is limited. This paper deals with the analysis of static and dynamic behaviour of RC beams with and without strengthening. The response of RC beams was assessed at different concrete’s damage level by non-destructive vibration tests. First, a couple of beams have been analysed: one RC beam subjected to bending and under vibration tests; another one beam, damaged by bending and strengthened with NSM Carbon-FRP rods tested again under vibration. Further, one RC beam damage was analysed under bending and vibration tests without strengthening; successively, the beam model with NSM GFRP rod has been tested following the same loading path. Below experimental results are shown and commented; in particular, changes in frequency values are related to the evolution of damage level affected RC beams with NSM CFRP and GFRP rods.

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

Materials ◽

10.3390/ma13102350 ◽

2020 ◽

Vol 13 (10) ◽

pp. 2350 ◽

Cited By ~ 1

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.

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Characterization of combined longitudinal and transverse FRPs for strengthening concrete columns

Canadian Journal of Civil Engineering ◽

10.1139/cjce-2018-0813 ◽

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.

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Stressing State Analysis of Reinforced Concrete Beam Strengthened by CFRP Sheet with Anchoring Device

Materials ◽

10.3390/ma14030576 ◽

2021 ◽

Vol 14 (3) ◽

pp. 576

Author(s):

Liang Luo ◽

Jie Lai ◽

Jun Shi ◽

Guorui Sun ◽

Jie Huang ◽

...

Keyword(s):

Carbon Fiber ◽

Strain Distribution ◽

Carbon Fiber Reinforced Plastic ◽

Rc Beams ◽

Fiber Reinforced ◽

Strain Distribution Pattern ◽

Fiber Reinforced Plastic ◽

Reinforced Plastic ◽

Cfrp Sheet ◽

Carbon Fiber Reinforced

This paper investigates the working performance of reinforcement concrete (RC) beams strengthened by Carbon-Fiber-Reinforced Plastic (CFRP) with different anchoring under bending moment, based on the structural stressing state theory. The measured strain values of concrete and Carbon-Fiber-Reinforced Plastic (CFRP) sheet are modeled as generalized strain energy density (GSED), to characterize the RC beams’ stressing state. Then the Mann–Kendall (M–K) criterion is applied to distinguish the characteristic loads of structural stressing state from the curve, updating the definition of structural failure load. In addition, for tested specimens with middle anchorage and end anchorage, the torsion applied on the anchoring device and the deformation width of anchoring device are respectively set parameters to analyze their effects on the reinforcement performance of CFRP sheet through comparing the strain distribution pattern of CFRP. Finally, in order to further explore the strain distribution of the cross-section and analyze the stressing-state characteristics of the RC beam, the numerical shape function (NSF) method is proposed to reasonably expand the limited strain data. The research results provide a new angle of view to conduct structural analysis and a reference to the improvement of reinforcement effect of CFRP.

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Near-Surface Mounted Reinforcement of Sawn Timber Beams-FEM Approach

Materials ◽

10.3390/ma14112780 ◽

2021 ◽

Vol 14 (11) ◽

pp. 2780

Author(s):

Izabela Burawska-Kupniewska ◽

Piotr Beer

Keyword(s):

European Standard ◽

Near Surface ◽

Bending Tests ◽

Starting Point ◽

Structural Applications ◽

Bending Stresses ◽

Complex Models ◽

Near Surface Mounted ◽

Sawn Timber ◽

Timber Beams

The demand for timber has increased significantly in recent years. Therefore, reliable tools are needed to predict the mechanical properties of sawn timber, especially for structural applications. Very complex models require a lot of input data for analysis, which cannot always be guaranteed, especially in industrial practice. Thus, a simplified model for material description was developed and assessed with experiments (static bending tests carried out in accordance with the guidelines suggested in the European standard EN 408) and an analytical approach (gamma method according to the guidelines given in the European standard EN 1995). The effective stiffness was calculated as a major parameter, which has an influence on the elements’ behavior. The model included a near-surface mounted (NSM) local reinforcement technique, with CFRP strips of Scots pine timber beams being subjected to bending stresses. It is anticipated that the developed model can be a starting point for the repair engineering field, contributing to decision-making regarding conservation technique selection and range. Next, improvements of the model will provide more and more realistic results for numerical analysis in terms of the obtained failure mechanisms for sawn timber elements.

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