On elastic beams parameter identification using eigenfrequencies changes and the method of added mass

Recently much attention has been focused on the problems of parameter identification based on the measured dynamic response of the structure. Inverse identification can be used either for the reconstruction of missing parameters of the computational analytical model, or as a tool for monitoring the structure during its utilisation. Inverse identification is usually performed with the implementation of the dynamic response of the structure. The method presented in this paper uses measurements of flexural vibration of a beam and of the same beam carrying a known additional concentrated mass to identify the beam’s structural parameters, such as mass and stiffness (i.e. flexural rigidity). From the eigenfrequencies of these two structures and from the analytical solutions of the dynamic response of both structures, the original and the modified, the structural parameters can be determined with satisfactory accuracy. The method is non-destructive and can be applied to many one-dimensional structures for which an analytical description is available. The method only requires measurements of the structural response at a single point, because it does not need information about eigenshapes but only about eigenfrequencies, and measurements performed at several points offer correlated and more reliable results. It is not iterative and therefore demands a modest computational effort, in some special cases it even offers simple expressions. Thus it can be described as a simple and easy-to-handle method having the advantage of performing measurements in situ with a rather simple equipment. One of its main advantages is that after the identification procedure is finished, the added mass is simply removed and the structure remains without negative effects.