Structural parameter identification by use of additional known masses and its experimental application

Abstract

SUMMARY In this study, a structural parameter identification method for damped structures is proposed. Modal identification is performed under several mass-modified conditions and structural parameters consistent with the identified modal parameters are determined. Its advantages as compared to other parameter identification methods are as follows. Initial guess of the system's structural parameters is unnecessary. Computational cost is low due to the algorithm's non-iterative calculation scheme. Furthermore, the proposed algorithm can detect not only a single damage, but also multiple damages without compromising the identification accuracy. First, the identification algorithm is theoretically developed. Modal parameter identification of a structure before and after the introduction of additional masses is conducted. By considering the relationship between the additional masses and modal properties before and after mass modification, structural parameters of a damped system, i.e. mass, stiffness and damping coefficient, are inversely identified from these modal parameters. The algorithm is subsequently validated through both numerical simulation and experiments on scale-models. The algorithm gives stable identification of structural parameters, provided all degrees of freedom of the system are observable. A mode selection indicator is also proposed. The effectiveness of this empirical indicator and the use of various mass-modified conditions in improving the robustness of the identification method are also numerically and experimentally confirmed. Finally, the proposed algorithm is extended to identify stiffness of beam models without utilizing rotational elements in mode shapes. Numerical simulation on a damaged beam model is performed, and its stiffness is identified. Copyright © 2011 John Wiley & Sons, Ltd.