1/22 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 for the experimental analysis of Reinforced-Concrete beams repaired with composite materials Comp-Test, Châlons en Champagne, January, 2003

2/22 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.

3/22 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.

4/22 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 ?

5/22 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

6/22 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

7/22 A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites. x y Solution: still the grid method ?

8/22 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 = I 0 [ 1 +  f (  ] Principle of the grid method

9/22 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 : Deformed grid : Principle of the grid method

10/22 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 Principle of the grid method

11/22 A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites. Strain field measurement resolution  , 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.

12/22 A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites. Detection and characterization of cracks U x : x y Discontinuities U x (µm) Abscissa (pixels) Crack width

13/22 A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites. Example of a crack width investigation ZOOM

14/22 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.

15/22 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.

16/22 A full-field optical method for the experimental analysis of Reinforced-Concrete beams repaired with composites. Mechanical behavior after strengthening Strain  yy : Strain  xy :

17/22 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

18/22 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 6,95 4,96 2,98 0,99 -0,99 -2,98 -4,96 -6,95  xy (x10 -3 )

19/22 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.

20/22 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.

21/22 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.

22/22 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”.