【作者】 钱慧；

【导师】 王春生；

【作者基本信息】 长安大学 ， 桥梁与隧道工程， 2008， 硕士

【摘要】 目前,强度、刚度、稳定性控制着钢结构设计的主要方面,然而按照这种指导思想设计的桥梁结构面临较为普遍的疲劳问题。而面外变形疲劳在钢桥的疲劳中相当普遍,钢桥中常见的面外变形疲劳主要有两类,一类是随着极限状态设计法的推广与腹板屈曲后强度的利用,设计上允许结构承受高于其临界屈曲荷载的外荷载作用,这样结构在正常使用状态即出现明显的“呼吸”特征,导致裂纹在腹板边缘焊趾处萌生、扩展,最终疲劳失效,即腹板的呼吸疲劳；另一类是由于结构在运营过程中,相互交错的构件之间发生了在设计阶段未曾预料的相互作用,这种相互作用使得结构的细节,如腹板间隙处于复杂的受力状态,易于发生面外变形,导致桥梁因面外变形产生疲劳破坏。本文参考国内外桥梁钢结构面外变形疲劳评估的文献,利用有限元数值分析方法分析了桥梁结构中典型面外变形疲劳细节的受力行为,并对其主要影响因素进行了参数分析,探究了桥梁结构面外变形的疲劳损伤机理,结合一既有铁路钢桥实测资料,对该桥的面外变形疲劳寿命进行了评估。本文的主要研究工作如下：1.总结了国内外有关桥梁面外变形疲劳问题及其维修策略的研究成果和研究方法。由于影响面外变形疲劳问题的不确定因素较多,一般都采用试验的方法来获得结构在受力过程中所承受的应力,然后结合传统的疲劳分析方法或基于断裂力学的疲劳寿命评估方法,对结构裂纹的扩展及其寿命进行评估。2.建立了三维有限元数值分析模型对桥梁结构中典型面外变形疲劳构造与细节进行分析,对影响面外变形疲劳的主要参数进行了分析,对如何在新建桥梁中避免发生面外变形疲劳提出了建议。3.对几种典型面外变形疲劳问题维修方法通过数值模拟的方法进行了验证分析,确定了其适用条件。4.结合有限元分析结果与现场测量数据,对某既有铁路钢桥面外变形疲劳裂纹形成机理进行了分析,并采用断裂力学方法对其剩余寿命进行了评估,对进一步的维修提出了建议。更多还原

【Abstract】 Recently, strength, rigidity and stability play a key role in steel structure design, but bridge structures constructed following those guiding principles are commonly facing fatigue problems. Out-of-plane distortional fatigue mainly consist web breathing fatigue and web-gap distortional fatigue, which are quite universal in steel bridge structures. The former is caused by using the post-buckling strength of girder webs which may cause the girder behaving evident character of "breathing" and inducing fatigue cracks initiate at the boundaries of the webs. The latter is caused by interaction between conjunction members which were not considered during design state. The interaction made the structure details lay on a complex stress station and is prone to out of plane displacement and lead to structure failure.Reviewd the documents about out-of-plane distortional fatigue in steel bridges at home and abroad, this paper analysed the common fatigue details of out-of-plane distortional fatigue in steel bridges, at the same time, a parametric analysis is developed to study their fatigue mechanisms. Uses the measured data of a railway steel bridge, fatigue life of out-of-plane distortion is evaluated, In this thesis, the following aspects are investigated:1. Research result and method of out-of-plane distortional fatigue at home and abroad. was summarized. Since out-of-plane distortional fatigue was affected by uncertain factors, usually stresses during the loading process was get through tests, and then combined with traditional fatigue analysis method or fracture mechanics approach gave an assessment of crack propagation and remaining life.2. Analysis with 3-D finite element models was developed to investigate the mechanics behaviors of typical out-of-plane fatigue details of bridge structure as well as the factors affecting out-of-plane fatigue, at last, an advice to avoid out-of-plane fatigue for future steel bridges was proposed.3. Verification analysis for several typical out-of-plane fatigue retrofit methods was carried out through numerical method, so their applicable condition was determined.4. Combine the numerical result and in-situ measurements, analysis on formation mechanism of out-of-plane fatigue cracks in the existing railway bridges was developed, assessment of the remaining life use fracture mechanics method was carried out as well. Finally an advice for further maintenance strategy was proposed.更多还原