城市桥梁下部结构抗重型车辆撞击的数值仿真分析

为研究城市道路桥梁结构在重型车辆撞击下的抗撞性能,建立了车桥碰撞的精细化有限元模型.桥梁模型具有两跨上部结构和双柱墩支撑的下部结构,上部结构采用梁和壳单元,下部结构采用实体单元模型.同时构建了具有不同吨位和长度的重型车辆模型.通过考察碰撞过程的能量平衡曲线以及与碰撞事故后的桥墩破坏形式的对比,验证了车桥碰撞有限元模型的合理性.计算给出了不同吨位车辆的碰撞力时变曲线,讨论了碰撞力作用位置和幅值的变化规律,探讨了车桥碰撞中桥梁损伤等级的划分.模拟结果表明,车速不变情况下,碰撞力峰值随车重增加而增加,重车碰撞力峰值发生的时刻有后延的趋势、碰撞力作用中心也以车辆前部首次接触区域为主,而车身较短的重车有可能出现后部车厢对桥墩的二次碰撞.

Numerical Simulation of Urban Bridge Substructures Impacted by Heavy Vehicles

In order to investigate the crashworthiness of unban bridge piers impacted by heavy vehicles, a refined finite element model of the bridge in conjunction with vehicle was developed. The bridge model has two spans of superstructures and one bent supported by two piers. Beam and shell elements are adopted for the superstructures, while solid elements are used for the substructure. Additionally, a modified heavy vehicle model with various lengths and weights was developed. The proposed bridge model in conjunction with the vehicles was verified against the actual damage modes reported in vehicle-impacting-bridge accidents. The validity of the proposed model was also evaluated by the energy balance curve of the impacting process. Time history impact load due to the heavy vehicle with various weights was then presented. The development trend for the magnitude and location of impact load was also discussed. Numerical results show that at a fixed impact velocity the peak impact force increases with the increase of the vehicle weight. A lagging tendency of the peak crash force occurs in the heavier vehicle, and the collision center is mainly concentrated near the first contact point. A secondary collision at the rear compartment may take place for the shorter and heavier vehicle.