基于碰撞仿真的F型混凝土护栏路侧安全分析

Roadside Safety Analysis on F-shaped Concrete Barrier Based on Impact Simulation

为解决路侧安全设计中选取护栏等级的问题,采用显式有限元软件LS-DYNA 3D建立了F型混凝土护栏和中型单体货车碰撞模型,碰撞速度为40~80 km/h。选用经实车碰撞试验修正后的车辆有限元模型单体卡车Ford F800,提高了模型可信度。研究碰撞速度、混凝土护栏等级与车辆侵入路侧区域的关系,通过Ford F800模型模拟货车碰撞混凝土护栏过程中车辆姿态变化与护栏碰撞力,分析了碰撞过程中车辆运动稳定性与护栏受力情况。以车辆最大动态外倾当量值量化评价了混凝土护栏对路侧障碍物防护的有效性,得到了护栏迎撞面到路侧障碍物的最小安全距离,比较了护栏碰撞力计算中规范公式和50 ms平均侧向碰撞力的关系。结果表明:当护栏等级为3~6级,设计速度为60 km/h的道路,护栏与路侧障碍物的最小安全距离为1.8~1.2 m;设计速度为80 km/h的道路,护栏最小安全距离为3.0~1.7 m;同等级别的护栏中,带阻挡坎的加强型护栏能降低货车最大动态外倾当量值至少5%,使车辆导向运动过程更稳定;货车车厢与护栏的50 ms平均碰撞力接近规范公式的计算结果;在同样的碰撞条件下,提高护栏等级能有效减少车辆外倾距离,由于车厢更可能与护栏发生碰撞,护栏受到的碰撞力将大幅增加。

In order to select the barrier grade in the roadside safety design,the models of single unit truck collisions with F-shaped concrete barrier are established by adopting explicit finite element software LS-DYNA 3D,and the impact speed is between 40 km/h and 80 km/h.The vehicle finite element model single truck Ford F800 modified by full-scale impact test is selected to improve the credibility of the simulation model.The relations among impact speed,level of concrete barriers and the amount of vehicle overhang beyond the barrier are studied,the Ford F800 model is used to simulate the vehicle attitude change and barrier collision force during the truck collision with the concrete barrier.The vehicle motion stability and barrier force during the collision process are analyzed,the effectiveness of concrete barriers shielding roadside obstacles is quantitatively evaluated by using VIn,the minimum safe distance from the traffic side of barriers to roadside obstacles is obtained,and the relationship between China’s specification method and the 50 ms mean lateral impact force in the calculation of barrier impact force is compared.The result shows that(1)when the barrier grade is grade 3 to grade 6 and the design speed is 60 km/h for roads,the minimum safe distance between barriers and roadside obstacles is 1.8 m to 1.2 m;(2)for roads with the design speed of 80 km/h,the minimum safety distance between barriers and roadside obstacles is 3.0 m to 1.7 m;(3)the single unit truck VIn of enhanced barrier is 5%at least lower than F-shaped concrete barrier at the same grade,that leads the single unit truck in a more stable manner;(4)the 50 ms mean lateral impact force between the cargo and the barrier is close to China’s specification method;(5)under the same impact condition,higher level of barrier can lower VIn significantly,however,the impact force of barrier increases greatly since the cargo more likely to collide with barrier.