基于长期结构健康监测数据的大跨公铁两用桥梁交通荷载模型研究

Highway and railway loadings are the main live loads long-span road-rail bridges suffer in the service life, and they are the primary cause of bridge fatigue. Therefore, they should be correctly understood and fully considered in the design stage of the bridge. However, there is still no accurate grasp of the highway loading for long-span bridges because of the complexity and randomness of the traffic flow. Besides, since adequate monitoring data of vehicle loads and structural responses are absent, the fatigue vehicle models also remain to be demonstrated. Based on the long-term structural health monitoring (SHM) data collected from a typical long-span road-rail bridge, and the finite element model (FEM) of the bridge as well as the structural analysis theory, this project investigates the static highway loading for long span bridges, and the fatigue loadings of both highway and railway traffic. In addition to WIM data and video recordings of typical traffic conditions, strain data are also incorporated into the study of static highway loading model, which quantifies the model corresponding to the structural response. As for the fatigue vehicle models, their accuracy is greatly improved by the stress spectra obtained from strain data and the FEM calibrated by measured data. Taking the studied bridge as a benchmark, traffic load models in bridge codes worldwide will be compared and evaluated. This project will provide valuable reference of traffic load models for the design and assessment of long-span road-railway bridges in our country.

汽车和列车荷载是大跨公铁两用桥梁服役中承受的主要活载，是导致桥梁疲劳劣化的最主要原因，在桥梁设计之初就要对其有准确把握。然而，由于大跨桥梁交通流复杂、随机性大，目前仍难以准确把握公路交通荷载；疲劳车辆荷载模型由于缺乏足够真实可靠的车辆荷载和结构响应数据也仍有待论证。本项目基于一座典型大跨公铁两用桥梁上测得的长期健康监测数据，借助有限元模型和结构分析理论，对以下几个方面进行深入研究。(1) 大跨桥梁公路交通静力荷载模型。除了长期WIM数据、典型交通监控录像，应变数据也将纳入研究体系，使荷载模型对应结构响应得以量化。(2) 公、铁路交通疲劳荷载模型。基于结构部件实测的长期应力时程直接得到应力谱，借助经监测数据校准后的有限元模型反算代表疲劳车辆模型荷载，可大大提高模型精度。(3) 国内外桥规交通荷载模型在本项目所研究桥梁基准上的比较。该项目为我国大跨公铁两用桥的设计和评估提供交通荷载依据。

汽车和列车荷载是大跨公铁两用桥梁服役中承受的主要活荷载，是桥梁承载力计算、刚度校核、可靠性评估及寿命预测等需考虑的重要因素，涉及到设计、运营及保养维护的各个阶段。为了保证桥梁全寿命期的正常运营及结构安全，在桥梁设计之初就要对其有准确把握。然而，大跨桥梁交通流复杂、随机性大，目前仍难以对这两种活荷载有较全面的认识。本项目基于一座典型大跨公铁两用桥梁上测得的长期结构健康监测（SHM）数据，借助有限元模型和结构分析理论，研究了大跨公铁两用桥梁的公铁交通静力荷载模型和疲劳荷载模型。本项目充分利用了实际桥梁上获取的长期SHM数据，除了WIM数据和典型交通监控录像，还通过结构响应数据，即应变和位移，量化交通荷载模型对应的结构响应，反推交通荷载模型相关参数。均布荷载由长期WIM数据、桥面典型交通监控录像和桥面系的竖向位移数据（整体响应）确定，利用各车道上估计出的车道荷载数值得出多车道横向折减系数。集中荷载和列车荷载借助桥梁有限元模型以典型构件（局部响应）一定重现期水平的应力极值为目标反推。为研究交通疲劳荷载模型，本项目先由WIM数据得桥上所有的公路交通车辆类型以及各类型车辆的总重、轴数、轴距、轴重信息，用数理统计方法得到汽车疲劳荷载频值谱、轴重频值谱。类似的，由铁轨底部的应变数据反推出的列车总重、转向架数、转向架间距、轴重信息，统计出列车疲劳荷载频值谱、轴重频值谱。然后，按照疲劳车辆荷载频值谱、轴重频值谱，找出典型车辆，进而精简典型车。最后基于长期动应变时程得出公铁交通分别引起的疲劳损伤因子，根据Miner线性积伤率和等效疲劳损伤原理，推出代表疲劳车辆模型。本项目旨在为我国大跨公铁两用桥的设计和评估提供交通荷载参考，研究具有理论意义和工程实用价值。