The Studies On Structural Damage Detection Based On The Change Of Modal Strain Energy Ratio

This paper clarifies the significance of structural damage detection and summarizes the research actuality of damage detection technique. Different kinds of damage detection methods are described in detail as well as their advantages and disadvantages. We go deep into discussing the studies on structural damage detection based on modal strain energy, and propose a new damage detection index based on the change of modal strain energy ratio.Modal parameters which identified under ambient excitation are different from that obtained from analytical models in respect that: the mode shapes can not be mass-normalized; the structural rotational degree of freedoms can not be measured in dynamic tests and higher modal parameters are difficult to be excited under operational conditions etc. To avoid these limitations of the factors mentioned above, this paper studies damage detection methods based on modal strain energy and summarizes the present situation of the methods in both home and abroad. Then a new damage method to detect complex structural damage is proposed on the basis of the change of modal strain energy ratio. The new method does not require the mass-normalized mode shapes and the number of damage members, only using measured mode shapes excluding information of rotational degrees of freedom. Firstly, numerical studies of three-dimensional frame structure and benchmark structure finite element models are performed to testify the validity of the new method. Then in order to further improve the feasibility of the proposed method for damage detection, an offshore platform physical model was chosen for damage detection testing. The results indicate the proposed method can effectively locate the damage in different damage scenarios. The damage detection method based on the change of modal strain energy ratio have wider prospect to put into practice.Though people have made much progress in developing damage detection methods based on dynamic characters, many problems still remain when the methods putting into practice, such as influence of measured noise, accuracy of finite element model. Thus, further studies are still required.