考虑斜入射的重力坝耐震时程法抗震性能评估

Seismic performance assessment of gravity dams based on endurance time analysis method considering oblique incidences

为明晰不同入射角度对基于性能的高坝抗震设计的影响,采用耐震时程分析(ETA)法同时考虑空间斜入射,分析大坝抗震性能变化情况。基于ETA法原理合成了3条耐震加速度时程曲线,建立Koyna重力坝-地基三维有限元模型,将耐震时程以不同角度输入地基进行地震动力分析。以裂缝贯穿时间、坝基损伤指标DBI、结构损伤耗能、坝顶顺河向相对位移为性能指标,进行重力坝抗震性能评估研究。结果表明:在耐震时程以不同角度入射时,大坝地震动力响应的差异显著,因此有必要在采用ETA法时考虑斜入射的影响。综合分析,60°入射下坝体损伤最剧烈、损伤耗能最高、坝顶顺河向相对位移最大。

To clarify the effect of different incident angles on the performance-based seismic design of high dams,the endurance time analysis(ETA)method is used to evaluate the variation in the seismic performance of a dam while considering spatial oblique incidences.First,three endurance acceleration time curves are synthesized based on this method;then a three-dimensional finite element model is constructed for the Koyna gravity dam-foundation,and the time curves are taken as inputs for simulations of the foundation at different angles.Finally,the dam’s seismic performance is evaluated using four performance indicators-crack penetration time,dam foundation damage index DBI,structural damage energy dissipation,and dam crest relative downstream displacement.The results show that significant differences occur in the dam’s seismic dynamic response when different incidences are input through the time curves,and this suggests the ETA method should consider oblique incidences.Generally,a seismic input at 60°incidences gives the most severe damage,highest damage energy dissipation,and largest dam crest relative downstream displacement.