钢桥面板在温度和车速耦合效应下顶板和纵肋焊缝处疲劳裂纹扩展的数值分析

Numerical analysis of fatigue crack propagation at top plate and longitudinal rib welds under steel bridge decks coupling effect of temperature and vehicle speed

为了研究温度和车辆速度耦合效应下对正交异性钢桥面板疲劳寿命的影响,在不同温度和加载频率下进行沥青材料SMA-13的动态模量试验,并建立加载频率与车速之间的转化关系。根据试验结果,得到温度和车速对沥青铺装层弹性模量的影响。并以安庆长江公路大桥三节标准段为研究对象,建立含有三维疲劳裂纹的有限元模型,对萌生于U肋与顶板连接处焊根与焊趾上疲劳裂纹的扩展进行数值模拟。发现焊根与焊趾处的疲劳裂纹扩展总是偏转一定角度;在裂纹扩展深度相同时,相同车速条件下的I型裂纹累计应变能释放率总值相近,但加载循环次数不同;在相同车速加载下,裂纹扩展寿命随着温度的上升而增大;在相同温度的情况下,温度较低时,行车速度对裂纹扩展寿命的影响不大;温度在20~45℃范围内,行车速度为100 km/h时,裂纹扩展寿命为最小值。

In order to investigate the influence of temperature and vehicle speed coupling on fatigue life of orthotropic steel decks,the dynamic modulus tests of asphalt material SMA-13 were carried out at different temperatures and loading frequencies,and the transformation relationship between loading frequency and vehicle speed was established.According to the test results,the effects of temperature and vehicle speed on the elastic modulus of asphalt pavement were obtained.Using the three standard sections of Anqing Yangtze River Highway Bridge as the research object,a finite element model containing three-dimensional fatigue cracks was established,and the propagation of fatigue cracks on the weld root and weld toe at the connection between U-rib and roof was numerically simulated.It is found that the fatigue crack propagation at the weld root and weld toe always deflects a certain angle;when the crack propagation depth is the same,the total value of cumulative strain energy release rate of Mode I crack under the same vehicle speed is similar,but the number of loading cycles is different;under the same vehicle speed loading,the crack growth life increases with the increase of temperature;at the same temperature,when the temperature is low,the driving speed has little effect on the crack propagation life;when the temperature is in the range of 20℃~45℃and the driving speed is 100km/h,the crack propagation life is the minimum.