Crack detection in prestressed concrete structures by measuring their natural frequencies

When inspecting the health of a civil structure, it is important to have efficient techniques to detect the possible presence of structural damage. This work deals with the detection of damage in prestressed concrete structures, which are widely used in road bridges and long span slabs, among others. Concrete structures can be affected by different pathologies, with the transverse cracks beingone of the most dangerous damages, since they involve a localized reduction of the flexural rigidity of the structure. Such cracks change both the static and dynamic behavior of the structure. In this paper, an inverse method of damage detection is applied on two experimental beams built in the laboratory, from the measurement of the first three natural frequencies of vibration. An algorithm for solving the system of equations has been developed by the authors. Explicit equations were obtained to calculate both the crack position and its depth. The predicted damages by the algorithm have been in good agreement with the real damages of the experimental models. An important aspect of this methodology for crack detection is the simplicity of its experimental implementation.