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AVRIL Stéphane , VAUTRIN Alain, FERRIER Emmanuel, HAMELIN Patrice, SURREL Yves

Comp-Test, Châlons en Champagne, 28-30 January, 2003. A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composite materials. AVRIL Stéphane , VAUTRIN Alain, FERRIER Emmanuel, HAMELIN Patrice, SURREL Yves.

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AVRIL Stéphane , VAUTRIN Alain, FERRIER Emmanuel, HAMELIN Patrice, SURREL Yves

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  1. Comp-Test, Châlons en Champagne, 28-30 January, 2003 A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composite materials AVRIL Stéphane, VAUTRIN Alain, FERRIER Emmanuel, HAMELIN Patrice, SURREL Yves

  2. Rehabilitation of damaged Reinforced-Concrete infrastructures Composite sheets are bonded onto concrete.

  3. 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.

  4. Efficiency of flexural strengthening Are vertical cracks bridged by the CFRP plate ?

  5. Solution: a full field optical method Application of the grid method in the area of interest. y x

  6. Efficiency of shear strengthening Bridging of shear cracks by the GFRP U-jackets: Cracks are not visible.

  7. Solution: still the grid method ? y x

  8. Principle of the grid method The light intensity reflected by the grid writes: I = I0 [ 1 + g f (j ) ]

  9. Undeformed grid : Deformed grid : p (x,y) Principle of the grid method Undeformed grid : U-1(x,y)

  10. p = 1 mm resolution  5 µm spatial resolution  2 mm Principle of the grid method

  11. Strain field measurement Numerical differentiation by fitting the best plane of 5 x 5 pixels subimages of displacement fields. 25 x 30 strain sensors, resolution  150.10-6, spatial resolution  10 mm.

  12. Detection and characterization of cracks Ux (µm) y x Crack width Abscissa (pixels) Ux : Discontinuities

  13. Example of a crack width investigation ZOOM

  14. Application to shear behaviour Cracks are detected from displacements fields measured with the grid method. y x

  15. Mechanical behavior without composite • Crack openings can be decomposed in two parts: • mode I, • mode II.

  16. Mechanical behavior after strengthening Strain eyy : Strain exy :

  17. Modeling of shear cracks Mode I :  Shear strains exy Mode II :  Tensile strains eyy Debonded area Crack under the composite sheet

  18. Initiation and propagation of peeling failure Strain exy : Enlargement of strain concentration areas exy(x10-3) 6,95 4,96 2,98 0,99 -0,99 -2,98 -4,96 -6,95

  19. 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.

  20. 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.

  21. Perspectives Application of the grid method to real infrastructures. Use of other full-field optical techniques which do not need to deposit grids.

  22. 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”.

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