Abstract
To evaluate present dynamic properties of two aged large arch dams, the ambient vibration has been continuously measured for more than four years. These measuring tests results are employed for calibrating the earthquake response analysis models (FEM models) to evaluate the seismic safety of each dam, as well as for collecting fundamental data about vibration test-based structural monitoring. To obtain the present dynamic properties, two kinds of ambient vibration test are conducted. One is the high-density vibration array test to obtain the mode shapes of each dam. The other is long-term continuous vibration measuring test to evaluate the seasonal changes in the natural frequencies. In this paper, we show the results on identification of the some lower mode shapes, and seasonal changes in the natural frequencies due to reservoir water level and temperature. And we show the comparisons between the results from the present ambient vibration test and past forced vibration test just after the completion, and also show the comparisons between the natural frequency estimated from the ambient vibration records and the one estimated from the recent earthquake observation records.
