| To evaluate seismic performance of dams against large earthquakes, it is necessary to select physical properties of each dam and its foundation appropriately so that their actual dynamic behaviors during earthquakes are accurately estimated. Focusing on vibration characteristics such as natural frequencies obtained from analysis results of earthquake motion records observed at each dam are one of the most popular and practical way to identify values of various properties such as the elastic modulus of dam body. The values estimated in this way, however, may be affected by fluctuations of the reservoir water level and the temperature. The vibration characteristics, that reflect the stiffness of a dam, may also provide an effective barometer to monitor the structural soundness of the dam body. But the factors effecting the vibration characteristics, such as reservoir water level should be adequately considered to detect the sign of deterioration of the dam due to aging. In this paper, the effect of reservoir water level and temperature on the vibration characteristics of a dam body such as natural frequency is investigated by analyzing seismic motion records including those obtained at the time of a large-scale earthquake and microtremor measurement result at a concrete gravity dam. As a result, it is revealed that the natural frequencies of the dam are obviously affected by fluctuation of not only the reservoir water level but also the temperature. In addition, the reason for these behaviors is discussed based on analysis of displacement measurement data of transversal joints of a dam and numerical analysis of a model dam considering transversal joints. |
