DYNAMIC PROPERTIES OF A LARGE ARCH DAM AFTER FORTY-FOUR YEARS OF COMPLETION

摘要

To evaluate seismic safety of an aged concrete arch dam, present dynamic properties have been continuously measured by ambient vibration test for more than one year, which are employed for calibrating a finite element model of the dam-foundation rock-reservoir water interaction system, as well as for collecting the fundamental data about vibration test based structural health monitoring. Hitotsuse arch dam, treated in this paper, was completed in 1963 (aged 44 years), and its height is 130m. To obtain the present dynamic properties, two kinds of ambient vibration test are conducted: one is the high-density vibration array test to obtain mode shapes of the dam. The other is the long-term continuous vibration-measuring test to evaluate the seasonal changes of the natural frequencies. In this paper, we mainly show test results on identification of the lowest three mode shapes, and seasonal changes of the natural frequencies, and discuss on the seasonal changes of the natural frequencies mainly ruled by the reservoir water level, and the comparison between the results from the present ambient vibration test and past forced vibration test and earthquake records.