Damage identification and monitoring of bridges using measured natural frequencies

This paper presents an approach for the structural damage identification using only the changes of measured natural frequencies. The structural damage is characterized by a local decrease of stiffness and assumed to be associated with a reduction of a contribution to the element stiffness matrix, equivalent to a scalar reduction of the material modulus. A computational procedure for the direct iteration technique based on the non-linear perturbation theory is proposed to identify structural damage. The presented damage identification method is applied to the footbridge over the Slunjcica River near Slunj to demonstrate the effectiveness of the proposed approach. Using a limited number of measured natural frequencies, reduction in the stiffness of up to 100% at multiple sites is detected.