| Earth-rock dam is a major development dam type at home and abroad for it has some advantages including less investment, shorter construction period and strong adaptability. In recent years earth-rock dam has a great development in China. The dam height is realizing the leap from150m level to300m level. Most of these dams are located in southwest China where strong earthquakes occur frequently therefore, it is very essential to accurately analyze the earthquake resistance of the earth-rock dams.Generally seismic response analysis of earth-rock dam is necessary for seismic design. However, the premise of seismic response analysis is to accurately predict the characteristics of quality, stiffness and damping. However, damping models has great influence to dynamic analysis of earth-rock dams. Damping energy involves many factors.At present research on damping mechanism and damping models of earth-rock dams is relatively less.There is no consistent and determined conclusion of damping value.In the practical engineering application, fundamental frequency of the earth-rock dams is usually used as exciting frequency for simplified calculation.This method will bring disadvantages to anti-seismic design for it will greatly underestimate the earthquake response of the earth-rock dams under building and built completely at present. Therefore, it is very necessary to study the damping models more deeply to reasonably determine the damping value of the earth-rock dams with different height.In this paper,six earth-rock dams with different height are selected as research object. First, static analyse with the method of finite element are carried out to the six models.Then with the help of dynamic finite element, the six models are analyzed with several commonly used damping models.The rationality of these damping models are analyzed and compared by comparing the results of frequency domain calculation and time domain calculation. It gives suggestions to selection of damping models in dynamic analysis of earth-rock dams.Then, dynamic finite element analysis is performed on the aforesaid six earth-rock dams under four seismic waves of great different spectrum characteristics, using a batch of control frequency to determine the damping value.And from this, we can get the peak absolute acceleration at dam top of the earth-rock dams using different control frequency.On this basis, the relation between the spectrum characteristics of seismic wave and vibration mode of earth-rock dams can be analysised.Finally, puts forward a damping calculation method which can comprehensively consider the spectrum characteristics of seismic wave and vibration mode of earth-rock dams. It gives suggestions to selection of damping models and determination of damping coefficient in dynamic analysis of earth-rock dams. |
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