库水模拟对拱坝动力特性的影响分析

Effects of reservoir water on simulations of arch dam dynamic characteristics

库水可压缩性和库水-坝体动力相互作用是影响坝面动水压力以及拱坝动力特性的重要因素。本文以拉西瓦拱坝为例,建立拱坝-地基-库水系统有限元模型,研究库水模拟对拱坝动力特性的影响。采用Westergaard附加质量与流固耦合两种不同的库水模拟方法,分别考虑附加质量、流固耦合的不可压缩库水、流固耦合的可压缩库水等三种情况,对比分析了拉西瓦拱坝的动力特性。分析结果表明,库水的存在会导致拱坝系统的各阶自振频率减小;考虑库水可压缩性导致拱坝的各阶自振频率进一步减小,且各阶振型发生变化。分析结果可以为高拱坝真实工作性态研究和地震反应分析提供参考依据。

Water compressibility and dam-water dynamic interaction are important factors that affect the hydrodynamic pressure on dam surface and the dynamic characteristics of an arch dam. This study develops a finite element model of the arch dam-foundation-reservoir water system to evaluate the effects of reservoir water on arch dam dynamic characteristics through a case study of the Laxiwa arch dam. In analysis, we use two reservoir water models, a Westergaard added mass model and a fluid-structure coupling model;three conditions are examined of Westergaard added mass, structure coupling with incompressible water, and structure coupling with compressible water. Results show that water storage behind an arch dam reduces its natural frequencies;compressibility of the water reduces them further, thereby changing its vibration modes. The results help improve the accuracy of high arch dam analysis and seismic response analysis.