土石坝地震可靠度分析

发布时间：2018-04-23 09:33

本文选题：地震可靠度 + 响应极值　；参考：《大连理工大学》2014年硕士论文

【摘要】：20世纪50年代以来,国内外在强地震区建造的土石坝日渐增多。今后几十年,特别是在中国,将有更多的土石坝在强地震区兴建,从而使这一工程的抗震技术日益受到关注。土石坝的抗震设计存在大量的不确定性,包括土性参数的不确定性、计算模型参数的不确定性、模型尺寸的不确定性以及地震荷载的不确定性等等,以往的设计中,工程设计人员常常把实际工程中的这些不确定性归结为一个确定性的安全系数上,对于静力计算通常会预留出较富裕的安全储备,但对于随机性很强的地震作用,安全系数很高的土石坝可能因为一次地震作用就出现永久性的破坏,这与地震动的峰值加速度、卓越周期以及持时都有很大关系。本文基于传统定值设计法的不足,考虑地震动的随机性,用可靠度指标评价土石坝的安全程度。同时,文中对比了多种传统可靠度计算方法,认为以往的可靠度分析方法主要分为静力和动力两类,静力可靠度方法多用来解决材料参数以及方法本身的不确定性,对于地震动的随机性,往往不能独立使用；动力可靠度方法主要是基于随机振动首次超越概率理论提出的可靠度计算公式,这种方法应用理论多、难度大、成果较少且计算过程复杂。鉴此,本文引用了一种解决土石坝地震可靠度的简便思路—响应极值分布法,通过考察土石坝地震响应极值的概率分布,给出了土石坝在一系列符合某场地地震统计特性的地震动作用下结构直观的失效概率和可靠度指标。在此思路基础上,本文做了以下几项工作： (1)通过时域和频域内双重非平稳性的地震动模型,人工合成了大量峰值加速度满足某种分布规律的随机地震波,考察了某些土石坝地震响应(坝顶加速度反应、加速度放大倍数、坝坡安全系数、坝体竖向永久变形)的概率分布,分析了地震参数(震级、震中距)对这些响应分布的影响情况。 (2)将坝坡最小安全系数的分布拟合为概率密度函数,计算了土石坝坝坡地震作用下的失效概率和可靠度指标,列出了最小安全系数不同的临界值下土石坝的失效概率参考值。 (3)将土石坝坝顶竖向永久变形量的分布拟合为概率密度函数,计算了土石坝由于震陷而导致的失效概率和可靠度指标,用《水利水电工程结构可靠度设计统-标准》中可靠度指标的参考值,对土石坝给出危险性评价。
[Abstract]:Since the 1950s, more earth-rock dams have been built in the strong earthquake area at home and abroad. In the next few decades, especially in China, more earth-rock dams will be built in strong earthquake areas, which makes the seismic technology of this project receive more and more attention. There are a lot of uncertainties in seismic design of earth-rock dam, including uncertainty of soil parameter, uncertainty of calculation model parameter, uncertainty of model size and uncertainty of seismic load, etc. Engineering designers often attribute these uncertainties to a deterministic factor of safety. For static calculations, they usually reserve a richer safety reserve, but for highly random earthquakes, A high safety factor earth-rock dam may be permanently destroyed by an earthquake, which is closely related to the peak acceleration of the ground motion, the excellent period and the duration of the earthquake. Considering the randomness of ground motion, the reliability index is used to evaluate the safety of earth-rock dam. At the same time, compared with many traditional reliability calculation methods, the former reliability analysis methods are mainly divided into static and dynamic methods, and static reliability methods are used to solve the uncertainty of material parameters and the method itself. The dynamic reliability method is mainly based on the reliability calculation formula proposed by random vibration first transcendence probability theory. The results are less and the calculation process is complicated. In this paper, a simple method to solve the seismic reliability of earth-rock dams, the response extremum distribution method, is introduced, and the probability distribution of seismic response extremum of earth-rock dams is investigated. The structural failure probability and reliability index of earth-rock dam under a series of ground motions which accord with the seismic statistical characteristics of a certain site are given. On the basis of this idea, this paper has done the following work: In this paper, a large number of random seismic waves with peak acceleration satisfying a certain distribution law are synthesized by using the time-domain and frequency-domain double nonstationary ground motion models. The seismic response of some earth-rock dams (the acceleration response of the dam top) is investigated. The probability distribution of acceleration magnification, safety factor of dam slope and vertical permanent deformation of dam body is analyzed. The influence of seismic parameters (magnitude, epicentral distance) on these response distributions is analyzed. (2) the distribution of minimum safety factor of dam slope is fitted as probability density function, the failure probability and reliability index of earth-rock dam slope under earthquake action are calculated, and the reference values of failure probability of earth-rock dam under different critical values of minimum safety factor are listed. The distribution of vertical permanent deformation at the top of earth-rock dam is fitted as probability density function, and the failure probability and reliability index of earth-rock dam due to earthquake subsidence are calculated. Based on the reference value of reliability index in structural reliability design of water conservancy and hydropower engineering, the risk assessment of earth-rock dam is given.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV641;TV312

【参考文献】