基于坝肩失稳破坏模式的高拱坝地基体系地震易损性分析

Seismic fragility analysis of a high arch dam foundation system based on dam abutment instability failure mode

为了开展高拱坝-地基体系整体稳定地震易损性分析,从坝肩潜在滑块滑动失稳破坏模式出发,综合考虑了地震动和材料参数的不确定性,采用增量动力分析方法(Incremental Dynamic Analysis,IDA),开展了基于概率统计框架的1000次非线性动力响应分析。分别采用特征点残余滑动位移和滑动面积比作为评价结构响应的性能指标,以地震动峰值加速度(peak ground acceleration,PGA)为地震动强度指标,定量的划分了高拱坝-地基体系的不同性能水平,绘制了地震易损性曲线,并对不同极限状态下的地震易损性进行了评估和分析。结果表明,基于特征点残余滑动位移的IDA曲线可以将高拱坝-地基体系分别划分为局部滑动破坏和整体滑动失稳破坏两个破坏等级;基于滑动面积比的IDA曲线可以划分为轻微滑动破坏、中等滑动破坏和整体滑动失稳破坏三个破坏等级;从而根据高拱坝-地基体系的实际地震需求从概率意义上评判结构所处的破坏状态,为高拱坝的抗震优化设计、加固和维修决策提供科学依据。

In order to carry out the seismic fragility analysis of the overall stability of a high arch dam-foundation system,1000 times nonlinear dynamic response analysis taking into account ground motions and material parameters uncertainty by incremental dynamic analysis method(IDA)is performed based on probabilistic and statistical framework from the perspective of seismic instability failure mode of potential sliding block of dam abutment.Residual sliding displacement and sliding area ratio of the bottom sliding surface are taken as seismic sliding stability performance indexes.The peak ground acceleration(PGA)is adopted as intensity measure.Then,different limit states are quantitatively divided and fragility curves are obtained.A comparative analysis and evaluation are performed to discuss seismic fragility under different limit states.The results show that IDA curves based on residual sliding displacement can be divided into two levels,local sliding damage and overall sliding instability,respectively.Three limit states are divided according to sliding area ratio-based IDA curves,local sliding damage,moderate sliding damage,and overall sliding instability.Thus,this provides a scientific basis for seismic optimization design,reinforcement,and maintenance decision of a high arch dam by evaluating damage levels of the arch dam in a probabilistic framework based on actual seismic demand of a high arch dam-foundation system.