基于健康监测系统的钢箱梁桥疲劳可靠性及车流量优化管理研究

Fatigue cracking in steel box girders has been one of the difficult issues in bridge engineering. At present fatigue assessment based on strain monitoring data has become a research hotspot for in-service steel box girder bridges. But due to structural complexity and limited strain sensors, the strain monitoring data from limited strain sensors is still unable to meet the needs of fatigue assessment. So in this project both the strain data and vehicle loading data collected by structural health monitoring system will be utilized for fatigue reliability assessment and optimization management of vehicle flow for steel box girder bridges. The main content of this project is as following. (1) The stress field distribution around the welds will be investigated for the classic welded components of steel box girder. The relation between stress measured by strain sensors and nominal stress of welds will be analyzed. Accordingly, the spatial adjustment factor between measured stress and nominal stress will be calculated and the method to determine the fatigue stress of weld details will be presented. (2) The probability model of vehicle loads will be established based on Weigh-in-Motion system, which is usually installed as a part of the structural health monitoring system. Then the probability model of vehicle loads will be updated and validated using the measured strain data. Then the random simulation method of fatigue load effects will be presented. (3) The influence mechanism of vehicle loads on the fatigue reliability of welded details will be analyzed in depth. And the correlation model will be established between fatigue reliability and vehicle flow. At last the optimization method of vehicle flow for overweight vehicles will be explored on the basis of fatigue reliability . The research results of this project are expected to provide new ideals for the in-depth application of bridge structural health monitoring data.

钢箱梁桥焊缝的疲劳开裂是工程中较难解决的问题之一。利用应变监测数据开展在役钢箱梁桥疲劳评估已成为国内外的研究热点，但由于结构自身的复杂性及应变测点数量的限制，有限的应变监测数据难以满足实际需要。 本项目综合运用应变和桥址车辆荷载的监测数据，开展在役钢箱梁桥的疲劳可靠性评估及车流量优化管理研究，研究内容包括：（1）研究钢箱梁典型焊接构件焊缝周围应力场的分布规律，分析应变传感器测点应力与焊缝名义应力的关系，获取两者之间的空间调整系数，提出焊缝疲劳应力确定方法；（2）依据动态称重系统监测数据建立车载概率模型，并采用应变监测数据对车载概率模型进行修正和验证，在此基础上提出焊缝细节疲劳荷载效应的随机模拟方法；（3）揭示车辆荷载对焊缝细节疲劳可靠度的影响机理，建立疲劳可靠度与车流量的相关性模型，探索基于疲劳可靠度的超重车流量优化管理方法。研究成果可为桥梁结构健康监测数据的工程应用提供新的思路。

钢箱梁桥焊缝的疲劳开裂是工程中较难解决的问题之一。本项目利用结构健康监测系统的焊缝疲劳应变和车辆荷载监测数据，系统地建立了运营状态下钢箱梁桥疲劳可靠性评估方法，分析了车辆荷载对钢箱梁桥疲劳可靠度的影响规律。主要研究内容包括：（1）基于名义应力概念的钢箱梁桥应变监测数据分析与疲劳评估方法；（2）钢箱梁多尺度有限元建模方法及局部构造对其焊缝疲劳行为的影响；（3）基于桥址动态称重系统的随机车流建模方法；（4）钢箱梁桥疲劳荷载效应监测数据概率建模与疲劳可靠性分析方法；（5）随机车流作用下钢箱梁焊接构件疲劳可靠度的多尺度有限元分析方法；（6）车流量增长、车辆超载等因素对桥梁疲劳性能的影响规律。研究发现：（1）钢箱梁焊缝的疲劳荷载效应及损伤极易受车辆荷载随机性的影响，采用短期应变监测数据将很难给出准确的疲劳评估结果；（2）由于纵向加强桁架极大地增大了其附近区域正交异性钢桥面的局部刚度，从而使得有纵向加强桁架的关键焊缝的疲劳应力范围和损伤要远小于相同位置的无纵向加强桁架关键焊缝；（3）考虑随时间呈规律性变化的行车参数和行车道车流量横向分布特征，使随机车流更符合实际车辆运营状态；（4）高斯混合模型能很好地描述疲劳荷载效应实测数据的多峰分布特征；（5）交通量和运营期的增长使钢箱梁细节疲劳可靠指标显著下降，在运营期应通过实测车流数据对交通量进行控制，以确保桥梁的疲劳可靠性；（6）建立了车辆超载率概率模型，并将超载率与桥梁疲劳损伤的关系应用于桥梁疲劳寿命评估中。项目研究成果成功应用于南溪长江大桥，也可为同类型桥梁的运营疲劳评估提供参考。