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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
AVRIL Stéphane, VAUTRIN Alain, FERRIER Emmanuel, HAMELIN Patrice,
SURREL Yves
A full-field optical method A full-field optical method for the experimental analysis of for the experimental analysis of
Reinforced-Concrete beams Reinforced-Concrete beams repaired with composite repaired with composite
materialsmaterials
Comp-Test, Châlons en Champagne, 28-30 January, 2003
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Rehabilitation of damaged Reinforced-Concrete infrastructures
Composite sheets are bonded onto concrete.
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Shear and flexural strengthening
Flexural deficiencies: a CFRP plate is bonded onto the bottom of the beam.
Shear deficiencies: GFRP “U-jackets” bonded onto the the lateral surface.
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Efficiency of flexural strengthening
Are vertical cracks bridged by the CFRP plate ?
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Application of the grid method in the area of interest.
Solution: a full field optical method
x
y
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Bridging of shear cracks by the GFRP U-jackets:
Cracks are not visible.
Efficiency of shear strengthening
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
x
y
Solution: still the grid method ?
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
The light intensity reflected by the grid writes:
I = I0 [ 1 + f (]
Principle of the grid method
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
p
U-1(x,y)
Undeformed grid :
(x,y)
Undeformed grid :
Deformedgrid :
Principle of the grid method
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
resolution 5 µm
spatial resolution 2 mm
p = 1 mm
p)y,x(U=)y,x(Δ xπ2φ
Principle of the grid method
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Strain field measurement
resolution 150.10-6,
spatial resolution 10 mm.
25 x 30 strain sensors,
Numerical differentiation by fitting the best plane of 5 x 5 pixels subimages of displacement fields.
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Detection and characterization of cracks
Ux : x
y
Discontinuities
Ux (µm)
Abscissa (pixels)
Crack width
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Example of a crack width investigation
ZOOM
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Application to shear behaviour
x
y
Cracks are detected from displacements fields measured with the grid method.
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Mechanical behavior without composite
Crack openings can be decomposed in two parts:
- mode I,
- mode II.
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Mechanical behavior after strengthening
Strain yy :
Strain xy :
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Modeling of shear cracks
Mode I : Shear strains xy
Mode II : Tensile strains yy Debonded area
Crack under the composite sheet
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Initiation and propagation of peeling failure
Strain xy :
Enlargement of strain concentration areas
6,954,962,980,99
-0,99-2,98-4,96-6,95
xy(x10-3)
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Interest of full-field measurements
The size of strain concentration areas is an indicator for anticipating peeling failure in RC beams strengthened in shear with a GFRP U-jacket.
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Conclusions
The grid technique is a suitable method for evaluating crack bridging in concrete structures repaired with composites:
- crack widths are measured over a whole field area,
- cracks can also be detected under a composite reinforcement bonded onto cracked concrete.
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Perspectives
Application of the grid method to real infrastructures.
Use of other full-field optical techniques which do not need to deposit grids.
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A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites.
Acknowledgements
The authors wish to express their appreciation to the Région
RHÔNE-ALPES for its financial support to the project:
“Rehabilitation of civil engineering structures with composite
materials : modeling of repaired cracked beams”.