土石坝动力反应分析的阻尼模型及计算频率

Damping models and calculated frequencies of earth-rock dams

土石坝动力计算中,通常采用基频作为控制频率的Rayleigh阻尼模型。这样处理对50m左右的低坝是基本合适的;而对300m级的高坝,会高估高阶振型的阻尼比,低估坝体的地震反应,使设计偏不安全。研究了Rayleigh阻尼模型2个控制频率的不同取法以及不同特征周期的规范谱人工地震波对坝体地震反应的影响,认为阻尼控制频率的选取应综合考虑坝体动力特性及地震波的频谱特性。

Rayleigh damping model was adopted commonly in seismic response analysis of earth-rock dam. It is appropriate for lower dams that the height is about 50 m; and the modal damping ratios are overrated and the seismic responses are underrated for 300 m high dam. In this paper, the seismic responses of earth- rock dams have been studied by Rayleigh damping models and 2 frequencies spectrum seismic wave. The calculation results shows that the calculated frequency of damping model is affected by dam dynamic character and frequency spectrum of input seismic wave.