Abstract
Structural health monitoring technique was applied to an aged arch dam, where long-term continuous observation of ambient vibration /seismic motion was performed over a span of three and a half years and where predominant frequency variation along time was detected, variation during ambient vibration/seismic motion. As the result, the following important matters were made clear; 1) Structural health of an aged arch dam can be evaluated through the monitoring of the predominant frequency variation which are detected as the result of the long-term continuous observation of ambient vibration/seismic motion and its data analysis. 2) It was shown objectively by the numerical value of the predominant frequency that the structural health of the observed aged arch dam was maintained even after the main shock of 2011 Off the Pacific Coast of Tohoku Earthquake, and also lots of its large-scale aftershocks. 3) It was confirmed that the structural health of the observed arch dam was maintained and also that the seismic load unchanges through the fact that the predominant frequency of the observed arch dam unchanged before and after the large-scale earthquakes, which shows that the seismic back-check on the observed aged arch dam is unnecessary even after suffering from large-scale earthquakes.
