摘要
采用无质量地基模型和弹簧–阻尼边界模型研究了在不同频谱地震荷载、不同基岩与混凝土弹性模量比值条件下重力坝的地震反应。基于大量计算分析,提出等效结构阻尼的理念与近似方法,使无质量地基模型计算坝体反应与考虑辐射阻尼效应的结果相接近。结果表明:弹簧–阻尼边界对重力坝的影响与不考虑辐射阻尼的无质量地基相比,位移和应力反应减小,降幅范围为10%~65%;随着基岩与混凝土弹性模量比值的增加,降幅总体减小。采用等效结构阻尼无质量地基模型的重力坝反应与使用弹簧–阻尼边界以计入辐射阻尼效应的结果接近,位移误差在7%以内。
Different earthquake input models, i.e. massless foundation and viscous-spring boundary models, are employed to analyze the seismic response of gravity dams. The effects of different spectral earthquakes, different ratios of modulus of foundation rock to dam concrete and different dam heights are taken into account. A concept of increased equivalent structural damping used in massless foundation model for approximately considering the effects of radiation damping is presented based on case studies. The results demonstrate that the crest displacements and the maximum tensile stresses in dams are reduced using the viscous-spring boundary model compared with those obtained by the massless foundation model. The reduction amplitude of the response ranges between 10% and 65%, and it decreases with the increasing modulus of foundation rock. It is concluded that the structural response using the massless foundation model with increased equivalent structural damping is close to that obtained from the viscous-spring boundary model with an error of 7%.
引文
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