【作者】 陈一馨；

【导师】 吕彭民；

【作者基本信息】 长安大学 ， 机械设计及理论， 2013， 博士

【摘要】 钢桥的日常维护、安全评估等是桥梁管理部门非常关心的问题，很多钢桥的损毁大多数是由于桥梁关键部位构件的疲劳破坏引起的。桥梁结构的安全性和耐久性主要由其关键部位构件的疲劳状态决定，故疲劳分析对桥梁的安全运营有着重要的意义。本文以某长江公路大桥主跨钢箱梁结构为研究对象，对其细部结构的疲劳性能进行了系统研究。针对该公路大桥主跨正交异性钢桥面板构造和受力特点，对桥面板与U形肋、桥面板与横隔板和U形肋、横隔板与U形肋等焊接细部构造进行疲劳试验研究，得到失效概率分别为50%及2.3%的Δσ-N曲线，并参照BS5400规范、EC.3规定，将疲劳试验所得到的S-N曲线延长至长寿命区，提出了适合该公路大桥的车辆随机载荷作用下的特定细节处的疲劳设计曲线及寿命计算公式。同时，进行了该桥钢-混凝土结合梁段剪力连接件推出试验和恒幅载荷疲劳试验，研究了静载破坏与疲劳破坏的形式，得到了该结构剪力钉的极限剪切强度和载荷-滑移曲线及可用于疲劳寿命计算的S-N曲线。对大桥进行了实际车流状况调查，得到用于钢桥疲劳累积损伤计算的18种代表车辆类型及比例，并经过等效轴重和平均轴距，形成了由7类典型车辆组成的载荷谱，计算得到各构造细节关注点的名义应力谱，结合疲劳寿命计算公式，对该公路大桥正交异性钢桥面板各关注点的疲劳强度进行了验算，并详细研究超载量对桥梁造成的损伤。同时对点焊定位点的存在及试样表面质量对焊接构造细节的疲劳寿命的影响进行了详细研究，并阐述了焊接质量、组装错边量及横隔板与U肋安装偏转对疲劳寿命的影响。为充分考虑各种车重对大桥的疲劳风险，根据实际调查的车流数据，整理得到由18类典型车辆组成的车重分布频值谱，依次加载得到各构造细节对应的应力谱，并用应力谱进行疲劳累计分析，分别计算了不考虑车流增长和考虑车流增长两种情况下，可靠度分别为50%和97.7%时，各关注点疲劳寿命；并计算了综合考虑均匀腐蚀作用时，车流增长和不增长两种工况下，可靠度分别为50%和97.7%时各焊接构造细节的疲劳寿命。对桥梁需要养护部位进行了详细的阐述和分析，研究并制订基于S-N曲线钢桥焊接细部构造各关注点疲劳累计损伤值，分不考虑车流增长和考虑车流增长两种情况，可靠度为97.7%时的各关注点养护及维修计划。同时，结合线弹性断裂力学理论方法提出了钢桥面板与U肋焊接细部构造疲劳可靠度评估方法，采用Paris方程建立疲劳断裂的极限状态方程；选择合理的参数对桥面板与U肋焊接细部构造进行疲劳可靠度评估并制订详细的维修计划。更多还原

【Abstract】 The maintenance and safety evaluation of the steel bridge are the issues of concern bythe bridge management department. Much damage of steel bridge is caused by the fatiguedamage of the bridge key components. The safety and durability of the bridge are mainlydetermined by the fatigue status of the key components, so the fatigue analysis on the safetyof the bridge operation is important. To study the fatigue performance of the orthotropic steelbridge deck weld structure, a steel box girder of a highway bridge on the Yangtze River waschosen as the research object.According to the orthotropic steel bridge deck construction and mechanicalcharacteristics, the weld structure of U-rib with cover, U-rib with diaphragm plate and coverand diaphragm plate with U-rib of the orthotropic steel bridge deck was chosen as researchobjects. The Δσ-N curves of the weld structure were obtained by the fatigue test, which failureprobabilities were50%and2.3%, respectively. The fatigue curves were extended to thelong-life span, and adequate fatigue design curves and calculation equation were proposed forthe weld structure following the specification of BS5400and EC.3. Meanwhile, According tothe steel-concrete bridge composite structure, the steel-concrete test samples were designedto test the ultimate shearing strength and the fatigue performance. The mechanical propertiessuch as ultimate shearing strength, load-sliding curve and the S-N curves of the shear studswere all obtained.The traffic flow was investigated on the bridge and18types of typical vehicles andproportions were gotten. Based on the equivalent axle load and average wheelbase, the typicalvehicle spectrum composed by7types typical vehicles were proposed to calculate thenominal stress spectrum of the focus points of the welding structures. With the nominal stressspectrum and calculation equations, the cumulative fatigue damage of the welding structureswas calculated, and the fatigue damage of the bridge that caused by overloaded vehicles wasdiscussed. The effects on the fatigue life that caused by the spot welding, the surface qualityof the samples, the welding quality, the assembled error and the value of the deflection error of U-rib and diaphragm plate were also discussed.In order to get full consideration to the fatigue risk of the bridge caused by the weight ofthe vehicles, the vehicle load distribution spectrum composed by18kinds of the typicalvehicles were obtained based on the actual survey traffic flow data. The stress-time curvesand the nominal stress spectrum were calculated by using the vehicle load distributionspectrum. Based on two cases with or without considering the traffic growth, the cumulativefatigue damage of welding structures were calculated by using the nominal stress spectrumand the calculation equations, in which the reliabilitys were50%and97.7%, respectively.Combined with considering the uniform corrosion, the fatigue life of the welding structureswas calculated by using the same method, in which the reliability was also the same.The components of the bridge which need maintenance and repair are mainly introduced.In the above two cases with or without considering the traffic growth, the maintenance plansof the welding structures were suggested based on the cumulative fatigue damage of thewelding structures, in which the reliability was97.7%. Meanwhile, according to the linearelastic fracture mechanics theory, the fatigue reliability assessment method was developed forsteel bridge cover and U-rib welding structure. The limit state function was established byusing the Paris equation, and reasonable parameters were chosen to do the fatigue reliabilityassessment and put forward the specific maintenance plans.更多还原