中文摘要：

为研究货运繁重公路上某正交异性钢桥面弧形切口开裂现象,基于动态称重系统（WIM）得到了疲劳车模型,并建立了钢箱梁节段模型和桥面板子模型,开展了该钢桥弧形切口应力响应分析和疲劳寿命评估。研究表明：横隔板弧形切口的应力局部效应非常明显,其横桥向应力影响线长度在2个纵肋范围左右,纵桥向应力影响线长度在2个横隔板范围左右;弧形切口仅能分辨轴组,而不能分辨轴组内单轴,因而1辆疲劳车加载可以在弧形切口产生2个大应力幅,分别对应中间双联轴和后面的三联轴;弧形切口在最小净截面处存在显著应力集中,周围存在明显的应力梯度,越靠近弧形切口边缘,应力梯度越明显,其最大主应力方向与实桥开裂形态相符;面内应力显著主导弧形切口应力响应,横隔板存在一定的面外变形,适当增加横隔板的厚度,可有效降低弧形切口应力水平;考虑轮载横桥向分布,纵肋R18和R19之间的弧形切口疲劳寿命为6~13年,这与实桥弧形切口疲劳开裂时间和位置均比较吻合;货车通行比例高、通行量大和超载严重是导致该桥过早出现疲劳开裂的主要原因;提出的实测疲劳车模型能为货运繁重公路上的钢桥,特别是正交异性钢桥面板疲劳设计和评价提供重要的参考。

英文摘要：

In order to investigate the floorbeam cutout cracks of orthotropic steel bridge on heavy freight transportation highway,the fatigue truck model based on Weight in Motion（WIM）system,as well as the girder sectional model of steel box and sub-model of bridge deck were carried out to investigate the stress response and fatigue life of floorbeam cutout detail.The results show that the stress local effect of floorbeam cutout detail is evident,that is,its stress influence line in bridge transverse direction is in about 2-rib range,and that along longitudinal direction is about 2-floorbeam range.The axles group rather than individual axle can be identified by floorbeam cutout,thus the fatigue truck model loading can produce 2large stress cycles at floorbeam cutout,corresponding to the mid 2-axles group and the rear 3-axles group respectively.The cutout detail presents obvious stress concentration at the floorbeam critical section,andobvious stress gradient around it.The closer to the cutout free edge,the more obvious stress gradient is,and the maximum principal stress direction fits with the direction of cracks.The stress response of floorbeam cutout is controlled by in-plane stress and a certain degree of out-ofplane distortion exists at the floorbeam,so stress at cutout decreases effectively by increasing the thickness of floorbeam.Considering the transverse variation of wheel loading,the fatigue life at cutout details between R18 and R19are 6to 13 years,in accordance with the actual bridge cracking time and cracking location.It＇s demonstrated that the main causes of the bridge premature fatigue cracking include the large number of average daily truck passage,as well as the high fraction of the trucks with overweight.The fatigue truck model presented in this paper will be an important reference for fatigue design and evaluation of steel bridges,especially the orthotropic steel bridge decks on heavy freight transportation highway.