钢箱梁斜拉桥等效疲劳车辆荷载模型分析

Equivalent fatigue vehicle load model of steel box girder in cable stayed bridges

为了调查长江中下游地区跨江大桥的车辆荷载运行特性,首先,以某一钢箱梁斜拉桥为例,分析大桥1 a实测交通流特性,得到相关轴型车辆的轴距、车辆质量及轴重分布;其次,基于损伤等效原则计算大桥各轴型车的等效疲劳车辆荷载模型;最后,对我国钢桥规范提供的疲劳荷载模型Ⅲ进行修正,提出适用于同区域类型桥梁的标准疲劳车。研究结果表明:大桥呈现交通流量大、货车载重高及超载现象普遍的特征;等效疲劳车辆荷载模型可简化为6种车型,等效车辆质量大于10 t的疲劳车辆占比高达85.9%,其中6轴车在疲劳损伤中占主导地位;提出的疲劳标准车是1辆质量为64 t的4轴车,单轴重为16 t;国外规范疲劳标准车引起的疲劳损伤均低于本文实际疲劳标准车引起的疲劳损伤;对于顶板U肋连接细节,顶板厚度增加2 mm可至少降低疲劳损伤46.4%。

The study is to investigate the vehicle load operating characteristics of the cross-river bridge in the middle and lower reaches of the Yangtze River.Firstly,based on a steel box girder cable-stayed bridge,the distribution of wheelbase,axle mass,and gross vehicle load of various types was obtained by analyzing the traffic flow characteristics measured on the bridge for one year.Secondly,equivalent fatigue vehicle load models were calculated using the principle of equivalent damage.Finally,the fatigue load model III provided by China's steel bridge code was revised.A standard fatigue vehicle suitable for bridges in the same area was proposed.The results show that the bridge presents the features of heavy traffic flow,heavy truck loads and common overloading.The equivalent fatigue vehicle load model can be simplified to six types of vehicles,and the fatigue vehicles with an equivalent vehicle mass greater than 10 t accounted for 85.9%,of which six-axle vehicles dominate the fatigue damage.The proposed fatigue standard vehicle is a four-axle vehicle with a vehicle load of 64 t and a single-axle load of 16 t.The fatigue damage caused by fatigue standard vehicles from foreign codes is lower than the actual fatigue standard vehicles in this article.For rib-to-deck details,increasing the thickness of decks by 2 mm can reduce fatigue damage by at least 46.4%.