拉索涡激振动加载和桥面车流共同作用下斜拉桥钢锚箱基于现场监测的疲劳性能研究

Fixing the stay cables to the main girder while transferring tremendous concentrated force, the steel anchorage box is recognized as a complex structure under complicated force action. Stay cables in long-span cable-stayed bridges are prone to large amplitude vortex-induced vibration. Due to highly overloaded traffics on the highway, fatigue performance of steel anchorage box under the coupled loading of vortex-induced vibration of stay cables and traffic flows will be the main concern to guarantee the safety and regular operation of the long-span cable-stayed bridges..After establishing a long-term monitoring system focusing on vortex-induced vibration of stay cables and stress response of steel anchorage box, this project will study the impact of incoming flow condition on the characteristics of vortex-induced vibration of stay cables, and will monitor the stress time histories at the connection details of the steel anchorage box which is under coupled loading of vortex-induced vibration of stay cables and traffic flows. Considering the effects of welding residual stress, fatigue life of the steel anchorage box will be obtained based on the numerical fracture mechanics and finite element analysis(FEA). Based on the stress results of the steel anchorage box obtained from the FEA, and considering the nominal stress approach and the hot-spot stress approach, the fatigue evaluation method for the connection detail on the steel anchorage box, which mainly transfers the shear force, will be determined with its fatigue category and corresponding S-N curve. Consequently, with the monitoring data, the fatigue performance of steel anchorage box under the action of vortex-induced vibration, random traffic loading, as well as the two coupled loading, will be separatively investigated, and the structural safety of the cable-stayed bridge under the vortex-induced vibration of stay cables will also be evaluated. The improvement on structural design of steel anchorage box will also be studied. The present study will provide important theories and engineering guidance for construction of long-span cable-stayed bridges.

斜拉桥钢锚箱连接拉索和主梁并传递巨大集中力，结构和受力复杂，其拉索容易出现较大幅度的涡激振动。由于公路超载严重，在拉索涡激振动加载和桥面随机车流共同加载下钢锚箱的疲劳性能，是大跨度斜拉桥安全和正常运营之关切。.项目将建立拉索涡激振动和钢锚箱构造细节应力的长期监测系统，研究拉索涡激振动特性与来流风特性的关系，监测钢锚箱构造细节在拉索涡激振动加载和桥面随机车流下应力时程。模拟焊接残余应力，基于数值断裂力学和有限元分析获得钢锚箱构造细节疲劳裂纹扩展寿命，根据钢锚箱有限元分析结果并分别结合名义应力法和热点应力法，确定以传递剪力为主的钢锚箱构造细节疲劳评价方法、疲劳等级和对应的S-N曲线。研究拉索涡激振动加载、桥面随机车流加载，以及两种加载同时作用下，现有钢锚箱基于监测数据的疲劳性能，评价拉索涡激振动下钢锚箱的结构安全性，改进现有钢锚箱结构设计。研究成果能为大跨度斜拉桥建设提供重要参考。

斜拉桥钢锚箱连接拉索和主梁并传递巨大集中力，结构和受力复杂，其拉索容易出现较大幅度的涡激振动。由于公路超载严重，在拉索涡激振动加载和桥面随机车流共同加载下钢锚箱的疲劳性能，是大跨度斜拉桥安全和正常运营之关切。.项目研究建立了大桥全桥有限元模型，分析了车道荷载作用下的拉索索力影响线，确定了钢锚箱活载索力幅；建立了上述2个钢锚箱的有限元分析模型，开展了设计索力下的钢锚箱应力响应分析，完成了钢锚箱的应力分布特征和焊缝受力，确定了钢锚箱主要的应力集中位置，明确了钢锚箱构造细节应力车辆的关键构造细节。在实桥上述两个钢锚箱均布设了应变片和数据采集系统。为判断有限元结果的合理性，先根据有限元结果进行了现场应力实测，得到了较为全面的构造细节应力响应水平，并开展了疲劳评价。在此基础上，排除了应力响应较小的构造细节，改进了应变片布置，优化了监测系统传感器布置，通过重点监测应力响应较大的构造细节，降低了监测系统的数据量。.获得了多个月拉索振动、构造细节连续应力时程，分析了不同构造细节的应力水平、单货车通行应力响应特征，构建了构造细节应力谱，计算了等效应力幅，明确了构造细节的疲劳等级和S-N曲线，基于名义应力、热点应力方法研究了构造细节的疲劳性能。研究了作用在锚箱上的拉索振动、温度场和货车通行三种荷载单独和联合加载，构造细节应力的时域和频域特征，分析了不同加载对应力谱的影响和疲劳寿命评价，明确了拉索涡激振动加载的疲劳影响可忽略，从最大应力幅的角度，突出了钢锚箱疲劳分析需要考虑温度作用的结论。.项目主要研究结论，可应用于斜拉桥设计、施工和运维及桥梁规范的完善，也能指导钢锚箱的加工、制造，有重要工程指导意义。