Yukitada SHIRATA
A Study on Vibration-Based Structural Health Monitoring Techniques of Existing Steel Bridges
Supervisor Masatsugu NAGAI
It is thought that the number of aging bridges in Japan increases rapidly in the near future. Therefore, maintenance of existing bridges becomes important issue.
In particular, since the changes of stiffness or mass of a structure relate to the dynamic characteristics of the structure, vibration-based SHM has been studied extensively in the world.
However, measurement positions and quantities have not been clearly defined in vibration-based SHM. The objective of this study is to clarify measurement positions/quantities and detection limit of damage in vibration-based SHM. The following procedure is taken.
- Finite element model is made based on a drawing.
- The model is updated to reflect present dynamic characteristics identified from vibration measurement.
- Virtual damage is given to each group of members in the model.
- Eigen value analysis is done for the damaged model.
- The change of dynamic characteristics before and after damage is investigated.
The obtained results from this study can be summarized as follows.
¡¦Natural frequencies of local modes of members greatly decrease owing to breaking. This change is larger than that of global modes. Therefore, local modes of members are effective in the damage detection of the bridge.
¡¦There are no changes in natural frequencies when virtual breakings are introduced into a lower chord, a stringer and a floor beam.
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