混凝土重力坝的耐震时程损伤指标分析方法

Analysis method of endurance time damage factors for concrete gravity dam

为了获得混凝土重力坝在强地震动作用下的损伤情况,基于耐震时程法提出了一种损伤指标分析方法.耐震时程分析(ETA)法表征了耐震时程与峰值加速度的线性增长关系,可以获得坝体在不同峰值加速度下的动力响应.依据耐震时程分析法的基本理论,合成了一组耐震时程加速度曲线;建立KOYNA混凝土重力坝有限元模型,以耐震时程加速度曲线作为坝体基底输入,通过谐响应分析方法得到了KOYNA混凝土重力坝在ETA激励下响应随峰值加速度变化的频谱曲线;采用坝体顶部中点和下游折坡点作为主要特征点,分析主要特征点的不同指标(位移、应变、加速度响应、固有周期)与耗散能、损伤体积的拟合关系,提出了可以宏观刻画坝体损伤扩展情况的损伤指标--响应频谱差面积.研究结果表明,坝体顶部中点位移频谱差面积和一阶频率的固有周期可以很好地表征坝体的损伤情况,且具有良好的精度,为工程设计提供了可靠的依据.

In this paper,the damage factor analysis method based on endurance time analysis(ETA)method is proposed to acquire concrete gravity dam′s damage condition under the strong ground motions.Endurance time analysis method aims to character how the ground motions increase with time,which can simulate the dam′s dynamic responses in the different peak accelerations.According to the theory of endurance time analysis method,agroup of endurance time accelerations are synthesized.The finite element model of KOYNA concrete gravity dam is established,and the endurance time accelerations are used as the input of the dam base,and the evolutionary process of different damage factors of KOYNA concrete gravity dam along with the peak acceleration under ETA motions are acquired by harmonic response analysis.The top midpoint and slope of the downstream of the dam is taken as the main feature points which aims to analyze the relationship between the different indexes(displacement,strain,acceleration response and natural period)and the dissipation energy and damage volume to obtain the damage factor,i.e.the response spectrum non-overlap area(RSNA),which can depict the historic extension of the dam factor macroscopically.The results show that the RSNA for the horizontal displacement at the top midpoint of the dam and the natural period are good factors to characterize the damage of the dam,which also manifest good accuracy.These factors provide the reliable basis of engineering practice.