Strengthening of concrete columns with carbon fibre reinforced polymer wrap

2003 ◽  
Vol 30 (3) ◽  
pp. 543-554 ◽  
Author(s):  
P L Shrive ◽  
A Azarnejad ◽  
G Tadros ◽  
C McWhinnie ◽  
N G Shrive
Keyword(s):  
Carbon Fibre ◽  
Prestressed Concrete ◽  
Concrete Columns ◽  
Element Model ◽  
Maximum Load ◽  
Design Methods ◽  
Reinforced Polymer ◽  
Confining Effect ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

Reinforced and prestressed concrete columns with one or two layers of carbon fibre reinforced polymer (CFRP) wrap were tested to failure in axial compression. When the results were compared with the maximum load predictions of two proposed design methods, the predictions consistently underestimated actual loads. The design methods are thus conservative. A simple analysis for circular columns reveals that the confining effect of the wrap is not engaged until the concrete actually starts failing and dilating. A finite element model of a chamfered square column confirms this analysis, as do strain readings from the tests. It is shown that strength gains are not linearly related to wrap thickness. The failure mechanism suggests that design should not be based on the ultimate strength or strain of the wrap and that strength gains can be expected to reduce with increasing brittleness of the concrete and with increasing eccentricity.Key words: concrete columns, FRP wrap, reinforced, strengthening.

Strengthening precast-prestressed hollow core slabs to resist negative moments using carbon fibre reinforced polymer strips: an experimental investigation and a critical review of Canadian Standards Association S806-02

2006 ◽  
Vol 33 (8) ◽  
pp. 955-967 ◽  
Author(s):  
Abdelhadi Hosny ◽  
Ezzeldin Yazeed Sayed-Ahmed ◽  
Amr Ali Abdelrahman ◽  
Naser Ahmed Alhlaby
Keyword(s):  
Carbon Fibre ◽  
Prestressed Concrete ◽  
Bending Moments ◽  
Hollow Core ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Negative Moment ◽  
Fibre Reinforced Polymer ◽  
Prestressing Strands ◽  
Negative Moments

Behaviour of precast-prestressed hollow core slabs has been extensively studied when these slabs are subjected to positive bending moments, a practical application typical of hollow core slabs. However, in many projects it may be required to have an overhanging part of the roof to act as a cantilever. In doing so, and using precast-prestressed hollow core slabs, the slabs would be subjected to negative moments, atypical for hollow core slabs. In this paper, the behaviour of precast-prestressed hollow core slabs is experimentally investigated when they are subjected to negative bending moments. A proposed strengthening detail to increase the negative moment resistance of hollow core slabs using bonded carbon fibre reinforced polymer (CFRP) strips is presented. The CFRP strips were bonded to the top side of full-scale precast-prestressed hollow core slabs in the negative moment zone in different configurations. In two of the tested slabs the bond between the prestressing strands and the concrete was initially broken (during casting of the slabs) in the negative moment zone. The slabs with the bonded CFRP strips were tested to failure and the load–deflection behaviour was recorded. The results of the tests are presented and the strength enhancement of the hollow core slabs using the proposed technique is reported. The increase in the negative moment resistance of the CFRP-bonded hollow core slabs experimentally determined is also compared with the CSA-S806-02 prediction for the moment resistance of concrete elements with bonded CFRP strips.Key words: carbon fibre reinforced polymer (CFRP) strips, hollow core slab, flexure strengthening, prestressed concrete, precast slabs, prestressing strands.

scholarly journals Prestressing low clinker structural concrete elements by ultra-high modulus carbon fibre reinforced polymer tendons

2021 ◽  
Vol 54 (1) ◽  
Author(s):  
Tobias Dominik Lämmlein ◽  
Janis Justs ◽  
Giovanni Pietro Terrasi ◽  
Pietro Lura
Keyword(s):  
Carbon Fibre ◽  
High Performance ◽  
High Performance Concrete ◽  
Maximum Load ◽  
Image Correlation ◽  
High Modulus ◽  
Transfer Length ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

AbstractThe combination of low clinker high-performance concrete (LCHPC) and ultra-high modulus (UHM) carbon fibre reinforced polymer (CFRP) tendons was recently proposed for prestressed structural elements. The 70% reduction in cement content resulting in limited creep and shrinkage of the LCHPC in comparison to a conventional high-performance concrete (HPC) and the very high UHM-CFRP tendon stiffness (> 509 GPa) were expected to impact the mechanical behaviour of such structures. This study focuses on the behaviour of 3 m-long beam specimens during prestressing, concrete hardening and in 4 point-bending experiments. Fibre optic sensors were implemented inside the CFRP tendons to measure strain during those stages and a digital image correlation system was employed to monitor the 4-point-bending tests. After 28 days, the LCHPC recipe, despite a 70% cement reduction and much smaller environmental footprint, did not show measurable differences in the prestress loss behaviour in comparison to a conventional HPC. The UHM-CFRP prestressing tendons, because of their stiffness, showed both higher prestress losses of around 40% and on average a nearly doubled prestress transfer length. However, they increased the beam`s maximum load-bearing capacity by 21% and showed 47% less deflection at failure in comparison to beams prestressed with the standard modulus (UTS)-CFRP tendons.

Flexural behaviour of reinforced or prestressed concrete beams including strengthening with prestressed carbon fibre reinforced polymer sheets: application of a fracture mechanics approach

2007 ◽  
Vol 34 (5) ◽  
pp. 664-677 ◽  
Author(s):  
Yail J Kim ◽  
Mark F Green ◽  
R Gordon Wight
Keyword(s):  
Fracture Mechanics ◽  
Size Effect ◽  
Carbon Fibre ◽  
Prestressed Concrete ◽  
Concrete Beam ◽  
Concrete Beams ◽  
Mechanics Model ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

This paper describes the application of a fracture mechanics model (Hillerborg 1990) to concrete structures, including strengthening with prestressed carbon fibre reinforced polymer (CFRP) sheets. One benefit of the proposed fracture mechanics model, consisting of a unique combined stress–strain response of concrete, is that it includes the size effect of reinforced concrete beams; however, its application and validation have not been fully investigated. The proposed model is reviewed and further developed to cover prestressed concrete beams including a beam strengthened with a prestressed CFRP sheet. To evaluate the model, various approaches such as finite element analysis, a strength-based model, a conventional design method, and experimental results are compared with the fracture mechanics model. The size-dependent parameter (ε1) significantly affects the predicted behaviour of reinforced or prestressed concrete beams, depending on the contribution of reinforcement. Based on the current assessment, ε1 = 0.005 is recommended as an upper limit for normal strength concrete.Key words: carbon fibre reinforced polymer sheet, flexure, fracture mechanics, prestressed concrete beam, reinforced concrete beam, strengthening, size effect.

Accelerated corrosion and repair of reinforced concrete columns using carbon fibre reinforced polymer sheets

2000 ◽  
Vol 27 (5) ◽  
pp. 941-948 ◽  
Author(s):  
C Lee ◽  
J F Bonacci ◽  
M DA Thomas ◽  
M Maalej ◽  
S Khajehpour ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Carbon Fibre ◽  
Concrete Columns ◽  
Corrosion Monitoring ◽  
Reinforced Concrete Columns ◽  
Accelerated Corrosion ◽  
Cfrp Sheets ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

An experimental study on the simulation of corrosion in large-scale reinforced concrete columns and their repair using carbon fibre reinforced polymer (CFRP) sheets is presented. Seven columns were subjected to an accelerated corrosion regime, wrapped using CFRP sheets, then tested to structural failure and (or) subjected to further post-repair accelerated corrosion, monitoring, and testing. Accelerated corrosion was achieved by adding sodium chloride to the mixing water, applying a current to the reinforcement cage, and subjecting the specimens to cyclic wetting and drying. Results showed that the CFRP repair greatly improved the strength of the repaired member and retarded the rate of post-repair corrosion. Moreover, subjecting the repaired column to extensive, post-repair corrosion resulted in no loss of strength or stiffness and only a slight reduction in the ductility of the repaired member.Key words: accelerated corrosion, carbon fibre reinforced polymer, composites, corrosion damage, corrosion rate, external confinement, reinforced concrete columns.

scholarly journals Effect of Carbon Fibre Reinforced Polymer Strengthening on Axial Capacity and Ductility of Non-slender Square Concrete Columns

2020 ◽  
Author(s):  
Muthomi Munyua ◽  
Siphila Mumenya ◽  
John Mwero
Keyword(s):  
Carbon Fibre ◽  
Research Programme ◽  
Concrete Columns ◽  
Steel Reinforcement ◽  
Axial Capacity ◽  
Reinforced Polymer ◽  
Number Of Layers ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Cfrp Confinement

This research investigated the effect of Carbon Fibre Reinforced Polymer (CFRP) strengthening on the axial capacity and ductility of non-slender square concrete columns. There was a problem of buildings collapsing in Kenya. Retrofitting of the buildings vulnerable to collapse was of great importance to ensure the safety of the occupants and to address the housing deficit in the country. An experimental research programme was conducted on 90 non-slender square concrete columns to find out the gain in axial capacity and ductility of the columns strengthened by CFRP. The specimens (150mm x 150mm x 350mm) were made of plain and reinforced concrete. Three different concrete grades: C8/10, C12/15 and C16/20 were used. The specimen had varying configurations of CFRP wrap: partial and full confinement in one and two layers. Four parameters were investigated in this study: concrete grade, steel reinforcement, degree of confinement and the number of layers of CFRP wrap. The specimens were subjected to uniaxial compression up to failure, and the stress-strain curves were plotted. This study found that weaker concrete grades experienced the highest effect due to CFRP strengthening. Presence of reinforcement had a significant effect on the axial capacity and ductility of columns without CFRP strengthening. On the contrary, the presence of steel reinforcement reduced the effectiveness of CFRP strengthening. Partial CFRP confinement offered better material efficiency as compared to full CFRP confinement, and the number of layers had a direct relationship with the increase in strength and ductility.

scholarly journals Prediction of failure in notched carbon-fibre-reinforced-polymer laminates under multi-axial loading

2016 ◽  
Vol 374 (2071) ◽  
pp. 20150273 ◽  
Author(s):  
J. L. Y. Tan ◽  
V. S. Deshpande ◽  
N. A. Fleck
Keyword(s):  
Carbon Fibre ◽  
Damage Evolution ◽  
Structural Integrity ◽  
Axial Loading ◽  
Element Model ◽  
Reinforced Polymer ◽  
Failure Envelopes ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Polymer Laminates

A damage-based finite-element model is used to predict the fracture behaviour of centre-notched quasi-isotropic carbon-fibre-reinforced-polymer laminates under multi-axial loading. Damage within each ply is associated with fibre tension, fibre compression, matrix tension and matrix compression. Inter-ply delamination is modelled by cohesive interfaces using a traction-separation law. Failure envelopes for a notch and a circular hole are predicted for in-plane multi-axial loading and are in good agreement with the observed failure envelopes from a parallel experimental study. The ply-by-ply (and inter-ply) damage evolution and the critical mechanisms of ultimate failure also agree with the observed damage evolution. It is demonstrated that accurate predictions of notched compressive strength are obtained upon employing the band broadening stress for microbuckling, highlighting the importance of this damage mode in compression. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’.

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