scholarly journals Degradation Behaviour of Deteriorated RC Beams Strengthened with CFRP under the Compound Effects of Acid-Salt Mist and Carbon Dioxide

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Wei Wang ◽  
Yuan-zhou Wu ◽  
Zhongnian Fang
Keyword(s):  
Carbon Dioxide ◽  
Failure Modes ◽  
Concrete Cover ◽  
Rc Beams ◽  
Acid Salt ◽  
Additional Time ◽  
Degradation Behaviour ◽  
Cfrp Sheets ◽  
Time Period ◽  
Carbon Fibre Reinforced Polymer

The reinforcement effect and durability of carbon fibre-reinforced polymer (CFRP) sheets are important indicators that affect its promotion and application. This study conducted an experimental investigation of the degradation behavior of reinforced concrete (RC) beams strengthened with CFRP. The RC beams were deteriorated under the compound effects of acid-salt mist and carbon dioxide for a time period t1i, then strengthened with one or two layers of CFRP sheets, and placed in the same deterioration environment for an additional time period t2i. The failure modes, load-deflection curves, rigidity, and flexural carrying capacity changes were studied after the deteriorated RC beams were loaded to failure. Three combinations of deterioration periods were considered in this study: different t1i and same t2i, same t1i and different t2i, and same total time (t1i + t2i). This study found that the U-shaped hoops and the side concrete peeled off gradually as the CFRP-strengthened RC beams were deteriorated again with time. Under the ultimate load, the strengthening layer in the tension zone stripped. The strengthened layer, which consisted of CFRP, a binder, and the concrete cover, was stripped from the RC beam during loading. The deflection of the strengthened layer behaved differently from the other part; this disharmony prevented the mobilization of the tensile advantage of CFRP. The mechanism of RC beam’s mechanical behaviour was analyzed in terms of the degrees of deterioration of RC beams and CFRP and their coupled effects. The conclusions of this study can be used as references in the prediction of strength changing and service life of strengthened RC beams.

scholarly journals ANALYTICAL AND EXPERIMENTAL STUDY ON REPAIR EFFECTIVENESS OF CFRP SHEETS FOR RC BEAMS

2013 ◽  
Vol 20 (1) ◽  
pp. 21-31 ◽  
Author(s):  
Moatasem M. Fayyadh ◽  
H. Abdul Razak
Keyword(s):  
Experimental Study ◽  
Failure Modes ◽  
Load Capacity ◽  
Fe Model ◽  
Rc Beams ◽  
Shell Elements ◽  
Cfrp Sheets ◽  
Adhesive Interface ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

This paper presents the results of both analytical and experimental study on the repair effectiveness of Carbon Fibre Reinforced Polymer (CFRP) sheets for RC beams with different levels of pre-repair damage severity. It highlights the effect of fixing CFRP sheets to damaged beams on the load capacity, mid-span deflection, the steel strain and the CFRP strain and failure modes. The analytical study was based on a Finite Element (FE) model of the beam using brick and embedded bar elements for the concrete and steel reinforcement, respectively. The CFRP sheets and adhesive interface were modelled using shell elements with orthotropic material properties and incorporating the ultimate adhesive strain obtained experimentally to define the limit for debonding. In order to validate the analytical model, the FE results were compared with the results obtained from laboratory tests conducted on a control beam and three other beams subjected to different damage loads prior to repair with CFRP sheets. The results obtained showed good agreement, and this study verified the adopted approach of modelling the adhesive interface between the RC beam and the CFRP sheets using the ultimate adhesive strains obtained experimentally.

scholarly journals Flexural strengthening of RC beams with NSM CFRP laminates

2020 ◽  
Vol 323 ◽  
pp. 01010
Author(s):  
Damian Szczech ◽  
Łukasz Krawczyk ◽  
Renata Kotynia
Keyword(s):  
Reference Beam ◽  
Concrete Cover ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Near Surface ◽  
Flexural Strengthening ◽  
Cfrp Laminates ◽  
Carbon Fibre Reinforced Polymer ◽  
Bottom Side ◽  
Cracking Pattern

The paper presents test results of reinforced concrete beams flexurally strengthened with Carbon Fibre Reinforced Polymer (CFRP) laminates using the Near Surface Mounted (NSM) technique. RC beams with a cross section of 200 x 400 mm were tested in four-point bending. Two RC beams were strengthened with one NSM CFRP laminate installed into the concrete cover on the bottom side of the beam. One of the beams was strengthened under the self-weight (B10.1) and the second one under initial preloading equal to 83% of the ultimate load of the reference beam (B10.1o). Failure mechanisms, cracking pattern and flexural behaviour of the beams are described in the paper. All the strengthened beams failed by rupture of the CFRP laminates followed by the internal steel reinforcement yielding. High strengthening efficiency of the NSM strengthening was confirmed by 109% and 130% when compared with the non-strengthened beam, respectively for beams B10.1 and B10.1o.

RETROFIT STEEL CORRODING RC BEAMS USING CFRP COMPOSITES: NLFE ANALYSIS

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
Rami H. Haddad
Keyword(s):  
Bearing Capacity ◽  
Failure Modes ◽  
Concrete Beams ◽  
Load Capacity ◽  
Concrete Cover ◽  
Cfrp Sheets ◽  
Cfrp Composites ◽  
Severe Reduction ◽  
Corrosion Of Steel ◽  
Repair Techniques

Corrosion of steel reinforcement is one of the main durability problems facing reinforced concrete infrastructures worldwide. Steel degradation and/or cracking of concrete both cause severe reduction in bearing capacity, leading ultimately to failure. The potential of repairing corroded concrete beams with two configurations of carbon-fiber reinforced polymeric (CFRP) composites was investigated with a nonlinear finite Element (NLFE) model. CFRP composites were assumed to be either bonded directly to existing concrete or to a new concrete cover; replacing the old one. The data generated showed that the load-bearing capacity and stiffness for concrete beams, as long as corrosion levels were below 10%, can be fully restored. However, the ductility in terms of deflection at failure would be reduced, especially for repair techniques that involved anchoring with CFRP sheets. For corrosion levels greater than 10%, attaching CFRP composites to a new concrete cover contributed to additional improvements in load capacity and stiffness ranging from 10 to 15% of that achieved from similar repairing on existing concrete. The failure modes indicated that debonding failure prevailed, and that the extent of debonding prior to failure depended upon the corrosion level and on whether the concrete cover was replaced or not.

scholarly journals Effect of Stirrups on Plate End Debonding in Reinforced Concrete Beams Strengthened with Fiber Reinforced Polymers

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3322
Author(s):  
Abdulaziz I. Al-Negheimish ◽  
Ahmed K. El-Sayed ◽  
Mohammed A. Al-Saawani ◽  
Abdulrahman M. Alhozaimy
Keyword(s):  
Reinforced Concrete ◽  
Failure Modes ◽  
Failure Load ◽  
Design Guidelines ◽  
Reinforced Concrete Beams ◽  
Fiber Reinforced Polymers ◽  
Rc Beams ◽  
Fiber Reinforced ◽  
Reinforced Polymers ◽  
Cfrp Sheets

Plate end (PE) debonding is one of the critical debonding failure modes that may occur in reinforced concrete (RC) beams strengthened with externally bonded fiber reinforced polymers (FRPs). This study investigated the effect of internal steel stirrups on the PE debonding failure load of FRP-strengthened RC beams. The dimensions of the beams were 3400 × 400 × 200 mm. The beams were strengthened with carbon FRP (CFRP) sheets bonded to the soffit of the beams. The beams were divided into two series based on the distance of the cutoff point of the CFRP sheets from the nearest support. This distance was 50 mm or 300 mm, and the amount of steel stirrups was varied in terms of varying the stirrup diameter and spacing. The beams were simply supported and tested under four-point bending. The test results indicate that the effect of stirrups on the load carrying capacity of the beams was more pronounced for the beams with CFRP sheets extended close to the supports. It was also indicated that beams with larger amounts of stirrups failed in PE debonding by concrete cover separation while beams with lower amounts of stirrups failed in PE by either PE interfacial debonding or critical diagonal crack-induced debonding. The beams were analyzed using several analytical models from design guidelines and the literature. The result of analysis indicates that most of the available models failed to reflect the effect of stirrups in predicting PE debonding failure load of the beams. On the other hand, the models of El-Sayed et al. and Teng and Yao were able to capture such an effect with the best predictions provided by El-Sayed et al. model.

Behavior of Strengthened RC Beams with CFRP Sheets under Combined Bending and Torsion

2020 ◽  
Vol 857 ◽  
pp. 109-119
Author(s):  
Abdul Muttalib I. Said ◽  
Qais H. Al-Shemmari
Keyword(s):  
Experimental Work ◽  
Failure Modes ◽  
Ultimate Load ◽  
Load Capacity ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Loading Conditions ◽  
Pure Bending ◽  
Pure Torsion ◽  
Cfrp Sheets

The experimental investigations were carried out to study the behavior of reinforced concrete beams strengthened by CFRP sheets under different loading conditions (pure bending, combined bending and torsion and pure torsion). The experimental work included testing twenty RC beams of the rectangular cross-section of dimensions of 160×240 mm and of 2600 mm length with an area of the ordinary reinforcement being kept constant for all beams. Two parameters were taken into consideration (Twisting to bending moment ratio (T/M) and CFRP strengthening pattern). The tested beams are divided into five groups. Each group consists of four beams; the first beam is without CFRP strengthening, the other three are strengthened with CFRP sheets of different arrangements (U-stirrups, U-stirrups and longitudinal CFRP sheets in the bottom and Full U- stirrups wrapping). Each beam is loaded to a different loading conditions (pure bending, T/M = 0.5, T/M = 1.0, T/M = 2.0 and pure torsion). The CFRP sheets were attached externally to the beam. Test results were analyzed based on the influence of CFRP on the ultimate load, vertical mid-span deflection and failure modes. In the experimental work, it was found that all strengthening patterns of CFRP sheets exhibited a significant increase in ultimate strength. This increase reached up to 78.9% for tested beams, when the beam strengthened in the form of full U- stirrups wrapping pattern for T/M = 0.5. In this study, it is observed that the use of external CFRP sheets attached to the tension sides of beams (U-stirrups and longitudinal CFRP in the bottom) could enhance the ultimate load capacity by 32.7% over the capacity of the unstrengthen control beam for T/M = 1.0.

Experimental Study on RC Beams Strengthened with CFRP Sheets

2011 ◽  
Vol 213 ◽  
pp. 548-552 ◽  
Author(s):  
Jiang Feng Dong ◽  
Qing Yuan Wang ◽  
Ci Chang Qiu ◽  
Dong He
Keyword(s):  
Reinforced Concrete ◽  
Concrete Cover ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Flexural Capacity ◽  
Control Beam ◽  
Cfrp Sheets ◽  
Four Point Bending ◽  
Cfrp Sheet ◽  
Cover Thickness

This paper presents the flexural performance of reinforced concrete (RC) beams with rectangular section. Seven RC beams strengthened using carbon fiber reinforced polymer (CFRP) sheets were subjected to four-point bending to investigate the effect of fiber reinforcement on the beams strengthened. The main experimental parameters included in the study are the pre-cracked width, CFRP sheet layers, the longitudinal tensile reinforcement ratio, the shear span ratio, and the concrete cover thickness. In total, seven beams were cast, one beam without any reinforcement as a control beam, two beams strengthened by CFRP sheets without making pre-cracks on the beam and four pre-cracked beams repaired with one layer or two layers CFRP sheets. Test results show the effectiveness and flexural capacity of the CFRP strengthened beams. The flexure enhancement of the CFRP strengthened beams varied between 41.7% and 124.1% over the control beam. This study confirms that the CFRP reinforcing technique significantly enhances the flexural capacity of reinforced concrete beams.

Experimental Study on Precracked RC Beams Strengthened with Externally Bonded CFRP Sheets

2010 ◽  
Vol 150-151 ◽  
pp. 842-846 ◽  
Author(s):  
Jiang Feng Dong ◽  
Qing Yuan Wang ◽  
Yan Mei Zhu
Keyword(s):  
Reinforced Concrete ◽  
Research Work ◽  
Concrete Cover ◽  
Reinforcement Ratio ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Flexural Capacity ◽  
Control Beam ◽  
Cfrp Sheets ◽  
Modes Of Failure

This paper presents the results of an experimental research work designed to study the flexural strengthening capacity and the modes of failure of Reinforced Concrete (RC) rectangular beams which are strengthened with external bonding of carbon fiber reinforced polymer (CFRP) composite materials to the tensile face of the RC beams. In total, seven beams were cast, one beam was preserved as control beam, two beams were strengthened without the application of preloading and the four beams were precracked and repaired with CFRP sheets. The main experimental parameters include the original damaged degree of RC beams, the amount of CFRP sheets, the longitudinal tensile reinforcement ratio, shear span to effective depth ratio, and the concrete cover thickness. All beams were tested in four-point bending over a span of 1500mm. Test results in the current study indicate that the effectiveness and flexural capacity of the CFRP strengthened beams. The flexure enhancement of the CFRP strengthened beams varied between 41% and 125% over the control beam. This study confirms that the CFRP sheets technique significantly enhances the flexural capacity of reinforced concrete beams. Finally, the contribution of CFRP sheets on the flexural capacity and rigidity of precracked and non-precracked RC beams is significant for the more longitudinal tensile reinforcement ratio.

scholarly journals Inclusion of CFRP-Epoxy Composite for End Anchorage in NSM-Epoxy Strengthened Beams

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Md. Akter Hosen ◽  
Mohd Zamin Jumaat ◽  
A. B. M. Saiful Islam
Keyword(s):  
Reinforced Concrete ◽  
Failure Modes ◽  
Concrete Cover ◽  
Structural Members ◽  
Premature Failure ◽  
Near Surface ◽  
Steel Bars ◽  
Near Surface Mounted ◽  
Separation Failure ◽  
Concrete Cover Separation

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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