基于五自由度车辆模型的桥头搭板容许纵坡变化值研究

桥头搭板纵坡变化值是桥头跳车严重与否的决定因素,但迄今为止其容许值多据行车调查确定,本文对其进行理论研究。采用折线形状的路桥过渡段模型和五自由度车辆模型,考虑上桥和下桥两个方向,认为车辆通过路桥过渡段做一定初始条件下的强迫振动,并将其全过程分为首尾相连的四个阶段,而且将前一阶段末车辆的振动状态经修正后作为后一阶段振动的初始条件,用拉普拉斯变换法对人-车-路系统的相互作用进行了动力响应分析,得到了人的加速度及路面对车的作用力随时间的变化曲线、人的加速度最大瞬态振动值和路面对车的最大作用力。最后,考虑汽车行驶的舒适性和安全性,以加速度最大瞬态振动值作为行驶舒适性指标,提出了搭板容许纵坡变化值的确定方法和步骤。

A STUDY ON THE ALLOWABLE DIFFERENTIAL SLOPE OF THE APPROACH SLAB WITH FIVE-DEGREE-FREEDOM VEHICLE MODEL

It is the differential slope of the approach slab that determines whether a vehicle bump is serious or not.In view of that there only empirical information about the allowable differential slope,a theoretical study is conducted while the bridge approach is simplified as broken lines,and the vehicle is simplified as a five-degree-freedom system.The vehicle passing the bridge approach is considered as experiencing forced vibration,the whole vibration process is divided into four consecutive phases,and the end of one phase is regarded as the initial condition of the next phase. The dynamic response of Man-Vehicle-Road system when the vehicle is approaching or leaving the bridge is analyzed by means of Laplace transform,to obtain the curve of ManBF]'BFQ]s acceleration versus time,the vertical force between the vehicle and the road versus time,the maximum transient vibration value of the ManBF]'BFQ]s acceleration and the maximum force between the vehicle and road. Finally, taking into account the comfort and safety of the passengers,using the maximum transient vibration value of the acceleration as the comfort index,a method and procedure is provided to determine the allowable differential slope of the approach slab.