Symmetrical Signal Method and Its Application in Structural Damage Detection

Abstract eng:
It is well known that a baseline is necessary in most cases for structural health diagnosis, and it is very difficult to obtain a proper baseline for a given structure. But for some special types of structure, such as truss, cable-stayed and suspension bridges, there are a lot of pairs of elements, which are symmetrical both for geometry and boundary conditions. The vibration signal of these elements should also be symmetrical under symmetrical excitation; the Symmetrical Signal Method (SSM) is based on this idea. With respect to structures composed of slim elements, it is assumed that the same damage occurring simultaneously in the symmetric pairs is an event with small probability. Therefore, transversal flexible vibration of each pair if elements is easy to measure, and a frequency difference between symmetrical components indicates that there may be some problem with the one which has a lower frequency. Detailed inspection can be employed for the suspicious element. Analytical and truss model tests results show that SSM is very effective for detecting local damage in structures composed of pairs of slim elements.

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