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.

Concrete cover separation of reinforced concrete beams strengthened with near-surface mounted method: Mechanics based design approach

2019 ◽  
Vol 22 (7) ◽  
pp. 1739-1754
Author(s):  
Ahmad Azim Shukri ◽  
Zainah Ibrahim ◽  
Huzaifa Hashim
Keyword(s):  
Reinforced Concrete ◽  
Carbon Fibre ◽  
Concrete Cover ◽  
Reinforced Concrete Beams ◽  
Near Surface ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Near Surface Mounted ◽  
Concrete Cover Separation

The primary mode of premature failure for near-surface mounted strengthened beams is the concrete cover separation. Due to its complexity, most of the prediction methods for concrete cover separation tend to be empirical based, which can limit their usage to specific near-surface mounted strengthening configurations. In response to that, this article presents a mechanics-based design which uses the moment-rotation approach and the global energy balance approach which is less reliant on empirical formulations, as the mechanics of reinforced concrete beam such as tension stiffening and propagation of concrete cover separation debonding crack are directly simulated rather than empirically derived. The proposed design procedure was validated against published experimental results of reinforced concrete beams strengthened with near-surface mounted carbon fibre–reinforced polymer bars, near-surface mounted carbon fibre–reinforced polymer strips or side-near-surface mounted carbon fibre–reinforced polymer bars and show good accuracy. As it is less reliant on empirical formulations, the proposed design procedure should be applicable to various near-surface mounted reinforcement configurations and materials.

Design Proposal for Concrete Cover Separation in Beams Strengthened by Externally Bonded Tension Reinforcement

2015 ◽  
Vol 1101 ◽  
pp. 385-389
Author(s):  
Sai Sai Wang
Keyword(s):  
Failure Modes ◽  
Steel Plate ◽  
Concrete Cover ◽  
Premature Failure ◽  
Rc Structures ◽  
Design Load ◽  
External Reinforcement ◽  
Externally Bonded ◽  
Concrete Cover Separation ◽  
Design Proposal

Existing experimental observations have shown that the application of externally bonded reinforcement (steel plate, FRP laminate, overlay, etc.) to strengthen RC structures can lead to brittle failures involving debonding of the external reinforcement before the design load is reached with classical failure modes. The design approach to determine the strengthening material and its area should avoid these premature failures. In this study, an analytical model developed for the overlay strengthening by the authors is firstly proved to be applicable for the steel plate or FRP laminate strengthening by comparing the analytical and experimental failure load as well as the failure mode of the strengthened beams reported in the literature. Then the main parameters involved in the process of concrete cover separation are identified and a simple criterion is proposed for prediction of premature failure.

scholarly journals Flexural capacity of RC beams strengthened with near-surface mounted steel bars

2021 ◽  
Vol 331 ◽  
pp. 05009
Author(s):  
Rendy Thamrin ◽  
Zaidir Zaidir
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Peak Load ◽  
Reinforced Concrete Beams ◽  
Flexural Capacity ◽  
Near Surface ◽  
Steel Bars ◽  
Near Surface Mounted ◽  
Monotonic Loads ◽  
Test Result

An experimental study carried out to observe the flexural capacity of reinforced concrete beams strengthened with Near Surface Mounted (NSM) steel bars is presented. The test was carried out on nine concrete beams. All tested beams were subjected to two-point monotonic loads. The ratio of longitudinal reinforcement (1%, 1.4%, and 2.4%) and NSM bars (1D16 and 2D16) were used as test variables. It was found from the test result that NSM steel bars significantly increase the flexural capacity of reinforced concrete beams. However, the strengthened beams failed in brittle mode, as indicated by a sudden drop of beams capacity. An analytical study was also conducted to obtain the flexural response of the specimens through all ranges of elastic and post-peak load. The prediction of the flexural capacity of the beams compares well with the test result.

scholarly journals Shear strengthening of reinforced concrete beams with near surface mounted steel bars

2019 ◽  
Vol 276 ◽  
pp. 01004 ◽  
Author(s):  
Rendy Thamrin ◽  
Sabril Haris ◽  
Zaidir Haris
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Reinforced Concrete Beams ◽  
Longitudinal Reinforcement ◽  
Shear Forces ◽  
Near Surface ◽  
Installation Angle ◽  
Bending Load ◽  
Steel Bars ◽  
Near Surface Mounted

This paper reports on an experimental study examining reinforced concrete beams without stirrups strengthened with Near Surface Mounted (NSM) steel bars. The beams were simply supported and were subjected to four point bending load. Three beams tested were designed as control specimens and the other six beams were strengthened with NSM steel bars. Three ratios of longitudinal reinforcement (1%, 1.4%, and 2.4%) and two types of installation angle (45 and 90 degree) were used as test variables. The test results in terms of graphs of deflection due to shear forces are presented to demonstrate the ability of different longitudinal reinforcement ratios and installation angle to withstand shear forces. The influence of the test variables on the crack patterns was also observed. It was found that NSM steel bars increase the shear strength of reinforced concrete beams without stirrups significantly. However, in the case of higher longitudinal reinforcement ratios the beams failed in brittle mode as indicated by a sudden drop in the shear force-deflection graphs.

NEAR SURFACE MOUNTED BAMBOO REINFORCEMENT FOR FLEXURAL STRENGTHENING OF REINFORCED CONCRETE BEAMS

2017 ◽  
Vol 79 (6) ◽  
Author(s):  
Yanuar Haryanto ◽  
Buntara Sthenly Gan ◽  
Arnie Widyaningrum ◽  
Agus Maryoto
Keyword(s):  
Reinforced Concrete ◽  
Experimental Tests ◽  
Concrete Cover ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Element Analysis ◽  
Near Surface ◽  
Flexural Strengthening ◽  
Near Surface Mounted ◽  
Nsm Technique

Near Surface Mounted (NSM) is a technique performed for the installation of strengthening material into grooves cut into the concrete cover of reinforced concrete (RC) beams bonded using a bonding agent. This technique is becoming more widely recognized because of its efficiency, effectiveness, and ease of application. We investigated flexural strengthening of RC beams with the NSM technique using bamboo reinforcements, through both experimental tests and a finite element analysis (FEA). The experimental tests were carried out on three RC beams, one consisting of a control beam, and the other two strengthened by the NSM technique with two steel reinforcements, and four bamboo reinforcements. From the experimental tests, we found that the flexural strength of the beam with NSM bamboo reinforcements was increased by 41.7% and the deflection ductility index was reduced by 21.55%. The mode of failure observed in all the strengthened beams was a flexural failure. Finally, the result of FEA behaved similarly to the results of the experimental test.

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.

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