Damage assessment of structures using modal test data

System health monitoring of structures is important not only for conducting safe operation but also maintaining system performance. In this paper, two identification algorithms for assessing structural damages using the modal test data have been developed. An important characteristic in the present approaches is that the employment of the global numerical models (e.g. FEM model) and some important information (e.g. Young's modulus) of structures are avoided to a great extent. As the first step of the damage identification, two algorithms for the detection of damage location are proposed, which are similar in concept to the subspace rotation algorithm or best achievable eigenvector technique. Furthermore, a quadratic programming model is set up for the two approaches to predict the damage extent. To demonstrate the capability of the proposed approaches, an example of a 10-bay planar truss structure is employed for checking the present approaches numerically. Furthermore, the experimental data from the vibration test of a beam with two fixed ends are used directly in the present approaches. The final results show that the present techniques perform quite well in spite of the little structural information and measurement inaccuracies.