地基土体对货车与波形梁护栏碰撞效应的影响

公路上正常行驶的车辆一旦操纵失控，安装在路侧的护栏就显得极为重要，可避免车辆直接冲出道路发生致命危险。波形梁护栏是最常见的一种被动防护装置，可有效抵御车辆施加的碰撞荷载。依据常规的设计思路，这种护栏可以利用波形梁板、防阻块和立柱的变形来吸收汽车碰撞所产生的能量。但与实际情况不同的是，在这一过程中忽略了地基土体对碰撞过程可能产生的影响。本文通过分别建立不考虑和考虑地基约束作用的碰撞计算模型来研究土体的贡献。在模拟过程中，分别观测货车的运行轨迹、护栏的变形和土体的变形。此外，也分析了不同部件对碰撞能量的吸收比率。与立柱接触区毗邻的土体因受冲击荷载影响，可能发生剪切失效。整个护栏系统中超过10%的系统能量实际上是由土体吸收的，常用的简化固定基模型跟实际情况有一定的出入。

Influence of soils upon the impact effects of a truck on the W-beam guard rail

Once a driver loses control of an operating vehicle on the highway, the guard rail installed as a protection will be im-portant to eliminate the risk of fatal accidents during offroad crashes and collisions with hazardous roadside objects. The W-beam guard rail is one of the widely used passive safety devices designed to absorb loads applied by impacting vehicles. It can absorb the impact energy from large vehicles through the deformation of beams, blockouts and posts according to the traditional design method. Нowever, contributions from the soils which the posts are rammed into are neglected. To this purpose, two computing models with and without soil bodies were considered, respectively. The trajectory of the truck, the deformation of the guard rail and the soil were observed dur-ing crash simulations. Moreover, the energy-absorbed ratios of different components in the guard rail system were also analyzed. A comparison between the two models indicates that the soil bodies adjacent to the post beneath the ground may become instable under shock loading, and more than 10% of the total impact energy is dissipated by the soil bodies. Consequently, the general fixed-base model cannot describe the real situation accurately enough.