Damage evaluation in reinforced concrete using damping measurements

Damping measurements have been performed on a reinforced concrete beam, at increasing levels of damage. The aim was to investigate if these data, which were obtained in a nondestructive way, could be used as indicators for the crack damage of the concrete. The increase of friction associated with the initiation and propagation of cracks should indeed cause an increase of the modal damping ratios of the test structure. It was found that the measured damping values are very sensitive to the vibration amplitude, as a result of the nonlinear behaviour of reinforced concrete. Using an experimental technique that allows us to measure the damping ratios of specific eigenmodes as function of vibration amplitude revealed that the nonlinearity of the damping is more sensitive to crack damage than the damping itself.