scholarly journals Activated Ductile CFRP NSMR Strengthening

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2821
Author(s):  
Jacob Wittrup Schmidt ◽  
Christian Overgaard Christensen ◽  
Per Goltermann ◽  
José Sena-Cruz
Keyword(s):  
Failure Modes ◽  
Elastic Response ◽  
Applied Theory ◽  
Strengthening Effect ◽  
The Novel ◽  
Near Surface ◽  
Linear Elastic ◽  
Near Surface Mounted ◽  
High Elongation ◽  
Strengthened Beam

Significant strengthening of concrete structures can be obtained when using adhesively-bonded carbon fiber-reinforced polymer (CFRP) systems. Challenges related to such strengthening methods are; however, the brittle concrete delamination failure, reduced warning, and the consequent inefficient use of the CFRP. A novel ductile near-surface mounted reinforcement (NSMR) CFRP strengthening system with a high CFRP utilization is introduced in this paper. It is hypothesized that the tailored ductile enclosure wedge (EW) end anchors, in combination with low E-modulus and high elongation adhesive, can provide significant strengthening and ductility control. Five concrete T-beams were strengthened using the novel system with a CFRP rod activation stress of approximately 980 MPa. The beam responses were compared to identical epoxy-bonded NSMR strengthened and un-strengthened beams. The linear elastic response was identical to the epoxy-bonded NSMR strengthened beam. In addition, the average deflection and yielding regimes were improved by 220% and 300% (average values), respectively, with an ultimate capacity comparable to the epoxy-bonded NSMR strengthened beam. Reproducible and predictable strengthening effect seems obtainable, where a good correlation between the results and applied theory was reached. The brittle failure modes were prevented, where concrete compression failure and frontal overload anchor failure were experienced when failure was initiated.

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.

scholarly journals Experimental and Numerical Study of Behaviour of Reinforced Masonry Walls with NSM CFRP Strips Subjected to Combined Loads

Buildings ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 103
Author(s):  
Houria Hernoune ◽  
Benchaa Benabed ◽  
Antonios Kanellopoulos ◽  
Alaa Hussein Al-Zuhairi ◽  
Abdelhamid Guettala
Keyword(s):  
Failure Modes ◽  
Numerical Study ◽  
Masonry Wall ◽  
Brick Masonry ◽  
Masonry Walls ◽  
Near Surface ◽  
Combined Loads ◽  
Reinforced Masonry ◽  
Brick And Mortar ◽  
Near Surface Mounted

Near surface mounted (NSM) carbon fibers reinforced polymer (CFRP) reinforcement is one of the techniques for reinforcing masonry structures and is considered to provide significant advantages. This paper is composed of two parts. The first part presents the experimental study of brick masonry walls reinforced with NSM CFRP strips under combined shear-compression loads. Masonry walls have been tested under vertical compression, with different bed joint orientations 90° and 45° relative to the loading direction. Different reinforcement orientations were used including vertical, horizontal, and a combination of both sides of the wall. The second part of this paper comprises a numerical analysis of unreinforced brick masonry (URM) walls using the detailed micro-modelling approach (DMM) by means of ABAQUS software. In this analysis, the non-linearity behavior of brick and mortar was simulated using the concrete damaged plasticity (CDP) constitutive laws. The results proved that the application of the NSM-CFRP strips on the masonry wall influences significantly strength, ductility, and post-peak behavior, as well as changing the failure modes. The adopted DMM model provides a good interface to predict the post peak behavior and failure mode of unreinforced brick masonry walls.

Experimental Study on Flexural Behavior of Damaged Concrete Beams Strengthened with NSM-CFRP Strips

2012 ◽  
Vol 256-259 ◽  
pp. 1012-1016
Author(s):  
Gu Sheng Tong ◽  
Yong Xiang Wang ◽  
Qiu Lan Wu ◽  
Yong Sheng Liu
Keyword(s):  
Failure Modes ◽  
Fiber Reinforced Polymer ◽  
Flexural Behavior ◽  
Rc Beams ◽  
Near Surface ◽  
Damage Level ◽  
Reinforced Polymer ◽  
Near Surface Mounted ◽  
Strengthen Effect ◽  
Capacity Loading

In order to investigate the strengthen effect of different embedment lengths of the NSM strip on different damage levels. A series of tests were conducted on damaged reinforced concrete (RC) beams in flexure strengthened with near surface mounted (NSM) carbon- fiber-reinforced polymer (CFRP) strips, and initial cracking load, ultimate capacity, loading-deflection curves, and failure modes are examined and analyzed in the paper. The results showed that not only the initial cracking loads and ultimate capacities of the beams are significantly increased，but also the flexural stiffness of the beams in the yield and ultimate behavior stages are improved by using NSM-CFRP strips. The strengthen effect on lower damage level RC beams has no obvious difference with that on non-damaged RC beams. Anchoring of the strip end can increase the ultimate load capacities and decrease the ductility of RC beams. Debonding was found to be the primary failure mode in all cases.

scholarly journals Experimental Study of Behaviour of Reactive Powder Concrete Strengthening by NSM-CFRP Corbels

2018 ◽  
Vol 4 (5) ◽  
pp. 980 ◽  
Author(s):  
Abdul Kareem Qasim Mohammad ◽  
Mushriq Fuad Kadhim Al-Shamaa
Keyword(s):  
Carbon Fiber ◽  
Failure Modes ◽  
Load Capacity ◽  
Reactive Powder Concrete ◽  
Near Surface ◽  
Near Surface Mounted ◽  
Effective Depth ◽  
Group B ◽  
Cracking Pattern ◽  
Reactive Powder

The research contain an experimental examination for the behaviour of reactive powder concrete corbels, strengthened with  varying orientation of  Near Surface Mounted Carbon Fiber Reinforcement Polymers (CFRP) strips. Six reactive powder concrete corbels were tested. Divided into two groups, each group contain three specimens, one of them without strengthening takes as control corbel specimen, two corbels in each group strengthened by inclined and horizontal near surface mounted carbon fiber reinforced polymer (NSM-CFRP) stripes, other variable was the shear span to the effective depth ratio (a/d) to study the influences of those variables on the ultimate strength carrying capacity, cracking pattern, cracking load, vertical deflection, failure modes. The results showed an important improvement in the behaviour and load capacity of strengthened reinforced RPC corbels in addition to enhancing the stiffness of corbels. For group A where a/d =0.65, the percentages of increase in load failure were about (10.3% - 15.45%) for inclined and horizontal strengthening respectively, and for group B where  a/d =0.4, the percentages of  increase in load failure were about  (7.1% - 14.6%) for inclined and horizontal strengthening respectively.

Mechanical Behavior for RC Beams Strengthened with Near-Surface-Mounted Bars Considering Effect of Secondary Loading

2014 ◽  
Vol 638-640 ◽  
pp. 1360-1364
Author(s):  
Hai Xia Zhang ◽  
Jia Wei Pei ◽  
Lu Yuan He
Keyword(s):  
Failure Modes ◽  
Concrete Beams ◽  
Load Level ◽  
Rc Beams ◽  
Near Surface ◽  
Initial Load ◽  
Bond Property ◽  
Near Surface Mounted ◽  
Frp Bars ◽  
Strengthening Method

Compared with other strengthening methods, NSM FRP bars strengthening method has obvious advantages in bond property and fire prevention performance. In accordance with current experimental study and the theory of concrete beams strengthened in bending with FRP are introduced, and the effect of FRP bars strengthening quantity on failure modes of reinforcement beams and the initial load level influence on the ultimate bearing capacity are analyzed. It provides a basis for further research and application in China.

Flexural Behavior and Ductility of Concrete Beams Strengthened with Near-Surface Mounted GFRP Bars

2010 ◽  
Vol 163-167 ◽  
pp. 3610-3614 ◽  
Author(s):  
Hai Xia Zhang ◽  
Ling Wang ◽  
Guo Rui Liu
Keyword(s):  
Cross Section ◽  
Ultimate Load ◽  
Rectangular Cross Section ◽  
Reinforced Concrete Beam ◽  
Flexural Behavior ◽  
Near Surface ◽  
Displacement Ductility ◽  
Gfrp Bars ◽  
Near Surface Mounted ◽  
Strengthened Beam

The objective of this study is to investigate the flexural behaviors and ductility of reinforced concrete beam with near-surface mounted (NSM) GFRP bars. A total of 5, simply supported rectangular cross-section beams strengthened with NSM GFRP bars and two control beams are tested in this paper. The mode of failure, load-deflection relationship, strain distributions along the height of the beam on mid-span cross-section, and ductility of the beams are analyzed. The studies indicate that the yield and ultimate load have a significant increase compared with the control specimen. Especially, the ultimate load has a more measurable improvement than the yield load. The strain distribution along the height of specimen shows a clear nonlinear characteristic as a result of the crack propagating and steel yield. Also, the studies show that GFRP bars has played an important role in the flexural capacity of the strengthened beam during the stage from the yield to the failure of the beam. Besides, the strengthened beam is considered to be ductile using the displacement ductility index.

Research on Rc Beams Strengthened with near-Surface Mounted Helical Rib Bar

2011 ◽  
Vol 90-93 ◽  
pp. 1757-1760
Author(s):  
Zhen Hua Ren ◽  
Xian Tao Zeng ◽  
Han Long Liu
Keyword(s):  
Crack Resistance ◽  
Bearing Capacity ◽  
Concrete Beams ◽  
Concrete Cover ◽  
Experimental Results ◽  
Rc Beams ◽  
Near Surface ◽  
Near Surface Mounted ◽  
Strengthened Beam

Four concrete beams were cast with normal reinforcement bars. According to different the amount of mounted strengthening, grooves are opened in the concrete cover of tensile region in the concrete beams. Helical Rib Bar（HRB）is inserted in the grooves that is filled with resin. Flexural experimental results indicate that the limit bearing capacity, rigidity and crack resistance of beams strengthened with HRB are all improved obviously. With the increase in the amount of mounted strengthening, the limit bearing capacity of the strengthened beam is improved obviously. In comparison with the contrastive beam, the limit bearing capacity of the beam strengthened with one near-surface mounted HRB is increased by 20.91%, and that of the beam strengthened with two near-surface mounted HRB is increased by 54.55%，and that of the beam strengthened with three near-surface mounted HRB is increased by 90.91%.

scholarly journals Experimental Evaluation of PSC Structures from FRP with a Prestressing Strengthening Method

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1265
Author(s):  
Tae-Kyun Kim ◽  
Sang-Hyun Kim ◽  
Jong-Sup Park ◽  
Hee-Beom Park
Keyword(s):  
Prestressed Concrete ◽  
Strengthening Effect ◽  
Fiber Reinforced ◽  
Prestress Loss ◽  
Near Surface ◽  
Reinforced Plastics ◽  
Near Surface Mounted ◽  
Fiber Reinforced Plastics ◽  
Flexural Tests ◽  
Strengthening Method

A prestressed concrete (PSC) structure is subject to prestress losses in the long and short terms, and the structure ages over time. The structure is susceptible to corrosion from exposure to environmental factors such as moisture, chloride, and carbonation, thus causing prestress loss. Therefore, strengthening the structure is needed to address this problem. Here, the near surface mounted (NSM) method and the external prestressing (EP) method were selected because they are capable of applying additional prestressing. Further, we used fiber-reinforced plastics or polymers, or carbon fiber-reinforced plastics or polymers because of their high tensile strength and noncorrosive properties. For EP tests, prestressed strands were used. Accordingly, this study performs four-point flexural tests and evaluations for 12 types of specimens fabricated with different PSC methods. All specimens fabricated with the NSM (prestressing, no prestressing) and EP methods achieved stiffness that was 50–60% higher than that of the control PSC specimen. It was observed that the EP method in conjunction with prestressing yielded the best strengthening effect. It is expected that the results of this study will be applied to real structures for strengthening them and improving their performances.

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