桥梁基桩的屈曲及其可靠度分析方法研究

【作者】 丁加明；

【导师】 赵明华； 刘代全；

【作者基本信息】 湖南大学 ， 建筑与土木工程， 2002， 硕士

【摘要】 随着我国大跨度桥梁的高速发展，超长、超高的桥梁基桩在工程建设中应用日益广泛，因此桥梁基桩的屈曲分析也日益受到应有的重视。基桩的屈曲分析是一个相当复杂而又具有实际工程意义的课题，其影响因素繁多。尽管国内外学者上世纪就已有相应的探讨，取得了许多研究成果，但大多局限于对基桩本身的屈曲研究，而未考虑基桩本身的初始弯曲、施工缺陷和土体分层等诸多特殊情况的影响。结构可靠度设计是近年来才提出的基于概率论的设计方法，由于桩土共同工作，桩基的结构体系和设计计算体系十分复杂，各种土性的取值因为样本空间的非常庞大而难以准确确定，因此离实际应用尚存在一定问题，而对基桩屈曲的可靠度分析目前似尚未见文献报道。通过对桥梁基桩屈曲破坏机理的深入分析，客观地评价了国内外基桩屈曲的各种分析方法，讨论了诸如桩身初始倾斜、初始弯曲、初始倾斜以及分层地基等特殊环境对基桩屈曲的影响；给出了多种边界条件下基桩屈曲分析的能量法解答及其幂级数解的思路，提出了基桩屈曲分析的非线性有限元方法，并利用大型有限元结构分析软件ANSYS实现了桥梁基桩屈曲分析的非线性分析；完成了对桥梁基桩在初始倾斜、初始弯曲、初始缺陷及分层地基情况下的非线性屈曲分析，得出一些可用于指导工程实践的重要结论；提出了基桩屈曲的可靠度分析思想，采用贝叶斯方法对基桩屈曲极限荷载的概率分布进行修正，引用模糊随机可靠度的验算点法计算基桩的屈曲可靠度，利用蒙特卡洛模拟求解基桩屈曲极限荷载随机变量的统计特征值，提出了几种计算基桩屈曲可靠度指标的方法，从而实现了基桩屈曲的可靠度分析；将本文方法用于已有模型实测资料及大型现场实桩实测资料的分析，其表明本文方法计算结果与实测值吻合良好。更多还原

【Abstract】 With the great development of brides with large-scale span in China, the application of superlong and superhigh bridge pile in construction is increasingly popular, so that the bridge-pile buckling analysis (hereafter abbreviated as BPB Analysis) gradually receives its due importance. Being a practically significant topic on project, the BPB Analysis influenced by many factors is rather complicate. Though scholars at home and abroad had made corresponding research during the last century and at the same time they had made great achievements, most of them confine themselves to the research on perfect pile buckling, not considering the influence of many special situations such as the initial bend, the defects in construction and the layered soil, etc...The reliability design has not been advanced according to the design method of probability theory until recent years. For the cooperation of pile-soil, the complicacy of the structure system and the design and calculation system of the pile foundation, and further more for it’s difficult to determine the properties of various kinds of soil due to the large scope of samples, there are still some problems in real applications. By the way it seems there is no document or report about the reliability analysis of pile bucking at present. After deeply analyzing the destructive mechanism of BPB Analysis, the author objectively appraises different analytical means of pile buckling at home and abroad, and discusses the influence on pile buckling under special conditions, e.g. the initial inclination and bend of the pile, the layered soil, etc. By doing so, the author puts forward some practical analytical means. Firstly, under different boundary conditions, the author advances a solution to BPB Analysis through the principle of potential energy and the power series solution to BPB Analysis. Secondly, the author puts forward non-linear FEM and has realized the non-linear analysis of BPB by adopting ANSYS. Thirdly, the author has accomplished the non-linear BPB Analysis under the conditions of initial inclination, initial bend and defect, and layeredsoil. Also the author has drawn some valuable conclusions applying to project practice. Fourthly, the author puts forward to analyzing the pile buckling reliability, revising the probability distribution of limited loads of pile buckling by adopting the Bayes’ theorem, calculating the pile buckling reliability by applying to the design point method for random fuzzy reliability, stimulating to find the statistically characteristic value of the random variant of limited loads of pile buckling by adopting the method Monts -Carlo, and meanwhile the author raises several calculating methods for the influential factors of pile buckling reliability. Additionally, the author has applied these analytical means to some ready materials of survey models or large-scale spot pile survey and finds that the results are identical with the real survey values.更多还原