A non destructive method for damage detection in steel-concrete composite structures based on finite eigendata

This paper proposes a non-destructive method for damage detection in steel-concrete beams based on finite spectral data associated to a given set of boundary conditions. The inverse problem consists in determining two stiffness coefficients of the connection between the steel beam and the concrete beam. The inverse problem is transformed to a variational problem for a cost function which includes eigenvalue data and transversal displacements of eigenfunctions. A projected gradient method which uses the analytical expressions of the first partial derivatives of the eigenvalues and eigenfunctions is proposed for identifying the unknown coefficients. The results of an extended series of numerical simulations on real steel-concrete beams are presented and discussed.