桥梁伸缩缝跳车冲击荷载计算方法与模型实验

Numerical methods and model experiment for impact load induced by vehicle bumping at bridge expansion joint

为实测移动车辆对桥梁伸缩缝的冲击荷载,防止桥梁伸缩缝在这种冲击荷载作用下发生早期损坏,制作了缩尺比例为1/30的汽车与桥梁实验模型,进行模型汽车通过模型桥梁的实验研究.针对车轮经过桥梁伸缩缝时,轮胎与路面的接触长度发生改变,提出了两种改进的伸缩缝跳车冲击力计算方法,分别为改进的假设轮底运动轨迹计算方法和改进的分布式弹簧-阻尼单元计算方法.然后,通过数值计算与缩尺模型实验进行了结果比较.最后,基于改进的分布式弹簧-阻尼单元,对三轴载重汽车对单缝式伸缩缝的冲击荷载进行了数值模拟与参数分析.结果表明:改进算法得到的伸缩缝冲击荷载与实测值更为接近,冲击荷载算法有必要考虑轮胎与路面接触长度的改变;车轮荷载的最大冲击系数超过桥梁设计规范的容许值,通过调整伸缩缝的开口宽度可以将其控制在容许范围内.

To measure the impact load of moving vehicles on bridge expansion joint and avoid the early damage of bridge expansion joint under such impact,models of vehicle and bridge were constructed with a scale of 1/30,and the experimental study of the model vehicle passing through the model bridge was carried out.Considering the change of the contact length between the tire and the road when the wheel passes through the bridge expansion joint,two improved calculation methods for the impact load on the expansion joint were proposed,namely improved calculation method with hypothetical trajectory of tire bottom and improved calculation method based on the distributed spring⁃damper element.Then the numerical calculation was compared with the experimental results of the scale model.Finally,based on the improved distributed spring⁃damper element,the numerical simulation and parameter analysis of the impact load induced by three⁃axle heavy vehicle at single⁃gap expansion joint were carried out.Results show that compared with the previous method,the impact load of the expansion joint obtained by the improved calculation methods was closer to the measured value.Therefore,it is necessary to consider the change of the contact length between the tire and the road for the calculation of impact load.The maximum impact factor of the wheel load of heavy vehicle exceeded the allowable value of the bridge design specification,which can be controlled within the allowable range by adjusting the opening width of the expansion joint.