Early detection of defects in concrete structures, such as bridges or dams, is essential to optimize the maintenance of
civil engineering facilities. Optical methods constitute non-destructive means of control and measurement but they are
generally confined in laboratories where both the setup and environnement are controlled. The method of shearography
is especially well adapted to detect damages due to both its capacity to distinctly visualize strain concentration zones and
its robustness. The experimental set-up is relatively compact, which enables to examine an extensive surface area by
simply moving the shearographic head.
In this paper, the application of this methodology for the detection of cracks is presented on concrete samples and
circulated outside concrete structures. Due to its sensitivity to strain concentration, shearography is able to detect
structural cracks, even when they were not through-cracks.
Operational implementation is made on two circulated structures with experts in manual cracks detection. No stimulation
device is used. In the first structure, cracks are detected on the bridge deck and on the bridge abutment. In the second
structure, cracks on the intrados of the bridge deck are detected and also beginning of cracks which have not been
detected by the visual inspection. Different areas are scanned and the results are in agreement with the visual inspection.
This technique enables detecting cracks on structures subjected to traffic load. The natural loading of an engineering
structure, i.e. the rolling traffic it bears, proves well suited for cracks detection by means of shearography, provided
traffic patterns are regular enough.