洪水环境下群桩基础桥梁易损性分析与评估

发布时间：2018-08-05 15:53

【摘要】：桥梁作为交通生命线系统中的重要枢纽,在社会日常生活中起着至关重要的作用。对于跨越河流的桥梁,洪水是造成桥梁倒塌破坏的主因之一。洪水出现的频率远高于地震,通常会带来大规模的河流冲刷,从而引起剧烈的河床变化。尽管冲刷并不能对桥梁结构形成直接的作用荷载,但它却对桥梁的安全构成了潜在威胁,将使桥梁在遭遇洪水、泥石流、地震等灾害下更易于损毁。因此,洪水环境下桥梁结构的安全性研究是十分有必要的。易损性分析作为一种评估结构安全性能的方法,广泛应用在结构的抗震分析上,取得了丰富的成果,然而,将该分析手段应用在洪水环境下桥梁的易损性分析与评估却鲜有引起关注。因此,本文将尝试将易损性分析用于评价桥梁在洪水环境下的安全性,针对洪水环境下典型群桩基础桥梁的易损性分析与评估进行初步探索。本文首先回顾了国内外学者在洪水灾害、冲刷以及易损性相关领域的研究现状,接着叙述了易损性分析的基本理论和结构损伤指标的选取,提出了适用于桥梁抗洪性能研究的改进的混合易损性分析方法。以台湾双圆大桥为工程实例,借助Opensees有限元分析平台建立了其下部结构计算模型进行展开讨论分析。文中第三章重点介绍了Opensees中的单元算法、非线性有限元分析理论以及双圆大桥计算模型建立过程中的关键参数和需要注意的问题,包括桩工作用的处理、群桩效应的简化以及洪水荷载的施加等。在第四章中引入了洪水位高度和桩基冲刷深度的不确定性,运用随机pushover分析方法,结合多变量随机函数统计矩的点估计法求得了结构在不同洪水位高度、不同冲刷深度下的抗洪能力概率分布情况。第五章则考虑了洪水位高度、冲刷深度以及洪水荷载的不确定性,运用有限元可靠度分析方法中的一次二阶矩法(FORM)得到了 96种情况下的结构抗洪需求概率分布。第六章结合前两章的计算结果运用本文第二章提出的改进的混合易损性分析方法拟合并绘制了四种洪水位,三种洪水流速共12种情况下的易损性曲线,并以此评估该桥的安全性能,分析结果可作为决策的重要参考依据。本文得到的主要结论有:1)本文的计算结果与2009年台湾双圆大桥遭洪水冲毁的事故案例相吻合,也表明将易损性的分析思路用于结构的抗洪安全性能评估是可行的,并能根据具体的研究对象给出定性的判断和定量的参数分析,计算结果可作为决策参考依据,具有一定的工程意义。2)同一洪水流速不同洪水位高度的易损性曲线具有相近的统计参数,表现出相似的规律,因而可以得出在洪水位未淹至梁底之前,结构的抗洪安全性能受洪水位高度变化影响不大。3)随着冲刷深度的增加,结构发生各损伤等级的概率将迅速增大;且各损伤等级的超越概率对洪水流速较为敏感,也即随着洪水流速增加,发生对应损伤等级所需要的冲刷深度将明显减小;对应同一冲刷深度,发生某一损伤等级的超越概率将显著加大,这也意味着结构更易损伤甚至损毁。4)结构的安全性能与洪水流速以及冲刷深度较为密切。对于桥梁的管养而言,对下部结构进行补强加固,采取相关措施减缓冲刷侵蚀的发生,将是提高结构在洪水环境下的安全性能的重要手段。
[Abstract]:As an important hub in the transportation lifeline system, bridge plays an important role in the daily life of the society. For bridges across the river, flood is one of the main causes of bridge collapse and damage. The frequency of the flood is far higher than the earthquake, which usually brings large scale river flow scour, thus causing severe river bed changes. Scour can not produce direct action load on bridge structure, but it poses a potential threat to the safety of bridge, which will make the bridge more easily damaged under flood, debris flow, earthquake and so on. Therefore, it is necessary to study the safety of bridge structure under flood environment. Vulnerability analysis is a kind of evaluation structure safety. The method of performance has been widely used in the seismic analysis of the structure, and has made great achievements. However, it is rarely concerned about the analysis and evaluation of the vulnerability of bridges under flood environment. Therefore, this paper will try to use the vulnerability analysis to evaluate the safety of bridges under flood environment and to the allusion to the flood environment. This paper first reviews the research status of scholars at home and abroad in the fields of flood disaster, scour and vulnerability, and then describes the basic theory of vulnerability analysis and the selection of structural damage indexes, and puts forward the improvement of the study on the performance of bridge flood resistance. Mixed vulnerability analysis method. Taking the Taiwan double circle bridge as an example, the calculation model of its substructure is established by the Opensees finite element analysis platform. The third chapters in this paper mainly introduce the unit algorithm in Opensees, the nonlinear finite element analysis theory and the closing of the double circle bridge calculation model. The key parameters and problems to be paid attention to, including the treatment of pile working, the simplification of pile group effect and the application of flood load, are introduced in the fourth chapter. In the fourth chapter, the uncertainty of the flood water level and the depth of the scour of the pile foundation is introduced. The random pushover analysis method is used to calculate the structure of the multi variable random function. The flood level height, the probability distribution of flood resistance under different scour depth. The fifth chapter considers the flood water level, the scour depth and the uncertainty of the flood load, and uses the first time moment method (FORM) in the finite element reliability analysis method to obtain the probability distribution of the structural flood resistance in 96 cases. The sixth chapter is combined with the former two. In the second chapter, the result of the improved mixed vulnerability analysis method proposed in this paper is to draw up the vulnerability curve of four flood water levels and three flood flow velocities in all 12 cases, and to evaluate the safety performance of the bridge. The analysis results can be used as an important reference for the decision. The main conclusions obtained in this paper are: 1) this paper The result of the calculation coincides with the case of the 2009 Taiwan double round bridge which has been destroyed by the flood. It also shows that it is feasible to use the analysis idea of vulnerability to evaluate the safety performance of the structure. The qualitative judgment and quantitative parameter analysis can be given according to the specific research object. The calculation results can be used as a reference basis for decision making, and the results can be used as a reference for the decision. .2) the vulnerability curve of the same flood water level at the same flood water level has similar statistical parameters, showing a similar law. Therefore, it can be concluded that the safety performance of the structure is less affected by the height of the flood water level before the flood level is not flooded to the bottom of the beam. With the increase of the depth of the scour, the structure has various damage. The probability of the grade will increase rapidly, and the transcendental probability of each damage grade is more sensitive to the flood flow velocity, that is, the scour depth required for the damage level will be significantly reduced with the increase of the flood flow velocity, and the transcendental probability of a certain damage level will be significantly increased with the same scour depth, which also means that the structure is more vulnerable. The safety performance of the structure is more closely related to the flood flow velocity and the scour depth. For the pipe raising of the bridge, it is an important means to improve the safety performance of the structure in the flood environment by strengthening and strengthening the substructure and taking relevant measures to mitigate the occurrence of erosion erosion.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U443.15

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