scholarly journals Stiffness and Crack Behavior of Unbonded Posttensioned Concrete Beam Strengthened with Aluminum Alloy Plate

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Hong Chang ◽  
Wei Zhou
Keyword(s):  
Aluminum Alloy ◽  
Concrete Beams ◽  
Influence Coefficient ◽  
Alloy Plate ◽  
Cracking Behavior ◽  
Crack Behavior ◽  
Unbonded Tendons ◽  
Posttensioned Concrete ◽  
Externally Bonded ◽  
Strengthening Technique

Corrosion resistance of aluminum alloy plates externally bonded by magnesium phosphate cement provides the ability to strengthen inshore infrastructures in harsh environments subject to moisture and humidity. In this study, the aim is to study the stiffness and cracking behavior of concrete beams using this strengthening technique. Six damaged unbonded posttensioned concrete beams were repaired and strengthened and then subjected to monotonic load until failure. This technique improved the stiffness and limited the development of cracks. The formula of elastic-plastic stiffness coefficient related to the comprehensive reinforcement index was established. An influence coefficient δ considering the effect of aluminum alloy plates and unbonded tendons was introduced, and the crack expansion coefficient under short-term load was obtained by statistical analysis. Finally, some simplified methods were proposed to evaluate the stiffness and cracks of unbonded posttensioned concrete beams strengthened with aluminum alloy plates.

scholarly journals Debonding-Related Strain Limits for Externally Bonded FRP Sheets in Flexurally Strengthened Reinforced Concrete Beams

2013 ◽  
Vol 7 (1) ◽  
pp. 58-67 ◽  
Author(s):  
Guibing Li ◽  
Aihui Zhang ◽  
Yugang Guo
Keyword(s):  
Reinforced Concrete ◽  
Tensile Strain ◽  
Concrete Beams ◽  
Experimental Tests ◽  
Critical Issue ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Externally Bonded ◽  
Strengthening Technique ◽  
Code Provisions

Debonding problems of externally bonded fiber reinforced polymer (FRP) sheets in flexurally FRP-strengthened reinforced concrete (RC) beams have been a concern and a research challenge since their application of this strengthening technique. Intermediate crack induced debonding is the most common failure mode which is that the debonding initiates at the critical flexural-shear or flexural cracks and propagates towards the direction of moment decrease. To mitigate debonding failure, most Codes and proposed models take the method by limiting the allowable tensile strain in FRP laminates. This paper presents experimental tests of concrete beams flexurally strengthened with externally bonded CFRP sheets to investigate debonding initiation and tensile strain of FRP laminates. The allowable tensile strain of FRP sheets in flexurally FRP-strengthened RC beams proposed by prevalent Code provisions and models was assessed based on the data obtained from experimental programs. It has beenshown that the allowable tensile strains provided by these provisions and models have a great difference with that of experimental results and exhibit a high level of dispersion. Furthermore, the FRP laminates of most tested RC beams were debonded before reaching the proposed allowable tensile strain. The Code provisions and models are inadequate to effectively prevent intermediate crack induced debonding failure in flexurally FRP-strengthened RC members. This is known to be a critical issue in engineering design and application of RC beams flexurally strengthened by FRP sheets.

Structural Performance and Ductility of Fiber Reinforced Polymer Concrete Bonding System Under Tropical Climates

2013 ◽  
Vol 61 (3) ◽  
Author(s):  
Mohd Hisbany Mohd.Hashim Mohd. Hashim ◽  
Abdul Rahman Mohd. Sam ◽  
Mohd Warid Hussin ◽  
Mohd Fadzil Mohd. Arshad
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Tropical Climate ◽  
Reinforced Concrete Beams ◽  
Structural Performance ◽  
Polymer Concrete ◽  
Cracking Behavior ◽  
Bonding System ◽  
Cfrp Plate ◽  
Externally Bonded

Tropical climate combines with saltwater exposure may influence the structural performance and durability of FRP–epoxy–concrete system over long period of time. FRP being non–corrodible material has been proven to be efficient materials in rehabilitation jobs compared to steel. Reinforced concrete structures may be required to be strengthened at a later age of their service life to overcome additional loading capacity and deterioration due to environmental effect. The main objective of the current paper is to study flexural behavior of an externally bonded reinforced concrete beams using carbon FRP plate and fabrics due to exposure to natural tropical climate. The research studies the ability of reinforced concrete beams externally bonded with CFRP plate and fabrics to resist numerous environmental conditions such as tropical weather, normal laboratory environment and saltwater solution. The bonded beams are subjected experimental evaluation by performing four points load test until failure to observe the failure loads, deflection, strain, cracking behavior and the patterns of failure. Strengthening of reinforced concrete beams using CFRP plate and fabrics demonstrated significant improvement in the flexural capacity of the beams by 30% and 16%, respectively compare to control specimen without strengthening.

Feasibility and flexural behavior of RC beams prestressed with straight unbonded aluminum alloy tendons

2020 ◽  
pp. 136943322098166
Author(s):  
Zhaoqun Chang ◽  
Guohua Xing ◽  
Jiahua Zhao ◽  
Jiao Huang
Keyword(s):  
Aluminum Alloy ◽  
Failure Modes ◽  
Concrete Beams ◽  
Reference Beam ◽  
Reinforced Concrete Beams ◽  
Flexural Behavior ◽  
Beam Specimen ◽  
Cracking Behavior ◽  
Curvature Distribution ◽  
Prestressed Beams

This paper investigates the feasibility and flexural behavior of reinforced concrete beams internally prestressed with straight unbonded aluminum alloy tendons by testing five partially prestressed beams and one reference beam. For each beam specimen, load-deflection curves, failure modes and cracking behavior, the relationship between load and strains in steel and prestressing aluminum alloy tendons were examined and analyzed. In particular, the effects of effective prestress, combined reinforcement index (CRI), and partial prestressing ratio (PPR) on flexure of concrete beams were discussed. The test results indicated that the spacing and width of concrete cracks of prestressed beams containing the same amount of bonded longitudinal steel reinforcement decreased with the increase of effective prestress, and the combined reinforcement index governs flexural behavior of the prestressed beams. The flexural crack width and displacement ductility exhibited a reduction with the increase of CRI. In addition, an analytical model was established to calculate the flexural strength and corresponding deflection at midspan of the concrete beams internally prestressed with unbonded aluminum alloy tendons by suggesting a new simplified curvature distribution, which is more accordant with the original curvature distribution. The proposed model provides a relatively good estimation of the flexural capacity and midspan deflection of the prestressed beams.

scholarly journals Experimental Characterization of the FRCM-Concrete Interface Bond Behavior Assisted by Digital Image Correlation

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1154
Author(s):  
Dario De Domenico ◽  
Antonino Quattrocchi ◽  
Damiano Alizzio ◽  
Roberto Montanini ◽  
Santi Urso ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Mechanical Tests ◽  
Image Correlation ◽  
Front Face ◽  
Full Field ◽  
Bond Behavior ◽  
Externally Bonded ◽  
Strengthening Technique ◽  
Concrete Interface

Digital Image Correlation (DIC) provides measurements without disturbing the specimen, which is a major advantage over contact methods. Additionally, DIC techniques provide full-field maps of response quantities like strains and displacements, unlike traditional methods that are limited to a local investigation. In this work, an experimental application of DIC is presented to investigate a problem of relevant interest in the civil engineering field, namely the interface behavior between externally bonded fabric reinforced cementitious mortar (FRCM) sheets and concrete substrate. This represents a widespread strengthening technique of existing reinforced concrete structures, but its effectiveness is strongly related to the bond behavior between composite fabric and underlying concrete. To investigate this phenomenon, a set of notched concrete beams are realized, reinforced with FRCM sheets on the bottom face, subsequently cured in different environmental conditions (humidity and temperature) and finally tested up to failure under three-point bending. Mechanical tests are carried out vis-à-vis DIC measurements using two distinct cameras simultaneously, one focused on the concrete front face and another focused on the FRCM-concrete interface. This experimental setup makes it possible to interpret the mechanical behavior and failure mode of the specimens not only from a traditional macroscopic viewpoint but also under a local perspective concerning the evolution of the strain distribution at the FRCM-concrete interface obtained by DIC in the pre- and postcracking phase.

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