基于软土路面的越野车辆平顺性研究

研究不同路面上行驶越野车平顺性问题,针对软土路面振动特性,为了准确的仿真和预测越野车在软土路面上的平顺性,通过基于载荷沉陷理论开发出用于计算弹性轮胎-软土路面接触力的ADAMS用户子程序,在某越野车整车虚拟样机模型中实现了弹性轮胎与软土路面之间非线性接触仿真,再改变子程序中软土路面相关参数对越野车进行随机输入行驶试验仿真,仿真结果表明,随着路面变形的增大,轮胎动载荷,悬架动挠度均有较大变化,车身的振幅有显著增大,说明适应于硬地面的悬架不适应于软土路面.通过模型能够较准确地仿真由于路面变形对整车平顺性的影响,为设计提供了科学依据.     

车-简支梁桥耦合振动系统中全局最大动力响应研究

本文采用四分之一车辆模型和等截面简支梁模型,建立了车-桥耦合振动计算模型,分析了车辆匀速驶过桥梁时,桥梁动挠度、动弯矩、动剪力的全局最大值及发生的位置.进一步分析计算了车速、车距和桥梁模态截断阶数对桥梁动挠度、动弯矩、动剪力全局最大值的影响.结果表明,车速对桥梁动挠度、动弯矩、动剪力全局最大值影响较大,全局最大动挠度和全局最大动弯矩均出现在跨中附近,车速不同位置也不同,而全局最大动剪力均出现在车辆下桥的梁端;两车同时上桥时,前后车车距越大,桥梁动挠度、动弯矩、动剪力全局最大值越小,当达到一定车距时三者不再减小且与单车情况相同;为提高桥梁动挠度、动弯矩、动剪力全局最大值计算精度,桥梁模态截断阶数宜分别大于3阶、6阶、7阶.     

基于轮胎与三维路面接触分析的车辆半主动控制研究

轮胎与路面的接触关系的模拟影响着车辆悬架响应和控制的精度.在运用分形理论构建的三维路面模型基础上,建立了轮胎与路面的三维动态接触关系.针对1/4车辆悬架模型,分别搭建了被动悬架、模糊PID控制和天棚阻尼控制算法,在两种接触条件下对比了被动悬架和两种控制算法的车辆悬架垂向加速度、悬架动挠度及轮胎力的时域和频域响应情况.计算结果表明,采用模糊PID控制算法在车辆平顺性方面优于被动悬架和天棚阻尼控制算法;车辆在考虑轮胎和路面三维接触时,在面接触工况下,车身加速度、悬架动挠度及轮胎力响应的峰值都低于点接触工况.     

大跨钢桁架拱桥地震响应有限元分析

采用ANSYS建立某大跨钢桁架拱桥有限元模型,对其进行模态分析;采用瑞利阻尼理论,通过拱桥前2阶圆频率计算质量阻尼和刚度阻尼;采用动力时程分析法对拱桥进行地震响应有限元分析.结果表明:横向位移的最大峰值由水平地震波载荷沿横桥向输入决定,纵向位移的最大峰值由水平地震波载荷沿纵桥向输入决定,竖向位移的最大峰值由重力载荷工况决定.     

水平单调载荷作用下的桩基桥墩滞回特性

为研究桩基桥墩-地基系统的非线性性能,根据模型与原型的物理相似关系制作1∶5比例的桩基桥墩模型. 采用力-位移混合控制加载的拟静力试验方法,通过在墩顶施加水平单调增加载荷,得到墩顶水平载荷下桩基桥墩的载荷-位移滞回曲线、骨架曲线和滞回特性. 用非线性弹簧单元模拟土体、用梁单元模拟桩和桥墩,建立模型桥墩的计算模型. 计算模型的骨架曲线与试验模型的骨架曲线吻合较好,表明采用非线性弹簧单元和梁单元分别模拟土体和桩是可行的,可以为考虑土-结构相互作用时的桥梁抗震分析提供参考依据.     

粘弹性沥青路面车辆动力响应仿真分析研究

不同载重车体对粘弹性沥青路面的应力反映波动性极为复杂,路面的响应规律,车辆的车速、负载等瞬态信息很难与应力反应建立稳定的规范模型.传统方法将移动的车辆荷载假定为作用在固定位置的静载荷;采用线弹性材料模型来仿真实际沥青路面材料;与实际的路面受力状况有所差别,造成结果失真.为解决上述问题,提出一种粘弹沥青性路面的三维瞬态有限元分析模型;计算行车荷载作用下路面动力响应规律,比较车速变化,载荷变化,不同载荷作用位置以及不同深度对动力响应的影响.实验结果表明:模型可以很好得到应力响应,在应力响应有明显的波动性的情况下;准确计算载荷横向作用位置对动力响应的影响,与真实结果比较吻合.     

基于有限元的轮胎自激振动时频分析

研究汽车轮胎减少磨损,延长使用寿命的问题,轮胎多边形磨损与胎面质量块的侧向自激振动密切相关.了解产生自激振动的速度区间以及胎面与地面的摩擦状态就显得十分重要.因此建立了轮胎一地面系统的理论模型,引入符合轮胎橡胶摩擦规律的摩擦曲线.运用有限元软件,建立子轮胎与地面有限元模型,导入上述摩擦曲线,分析了位移时间历程和位移速度相平面图,发现了容易产生自激振动的速度区间.选择三种特征车速进行仿真.结果证明通过研究可以减少轮胎的磨损量,延长寿命,为今后轮胎多边形磨损正确建模有参考价值.     

高速动态车辆称重研究

针对动态车辆超重检测,建立了一种新型的高速动态车辆称重方法。桥梁采用简支梁模型,车／桥相互作用模型化为两个具有固定间距点力匀速通过桥面。利用安装在桥梁下面的应变传感器测量车辆经过桥面引起的桥梁应变,通过积分运算消除车辆振动对计算结果的影响,进而获得动态车辆的载重值。试验结果表明该方法可以较准确地进行高速动态车辆载重的测量。     

大跨钢箱梁悬索桥地震响应有限元分析

根据某大跨钢箱梁悬索桥的设计图纸,采用ANSYS建立其有限元模型,采用壳单元对主梁进行模拟.通过不断调试找出最佳的主缆初始应力,完成悬索桥的初始找形分析.对悬索桥进行预应力模态分析,采用瑞利阻尼理论,通过悬索桥有限元模型的前2阶圆频率计算模型的质量阻尼和刚度阻尼.采用动力时程分析法对悬索桥进行地震响应有限元分析.结果表明:横桥向位移的最大峰值由横桥向地震波输入决定,纵桥向位移的最大峰值以及竖桥向位移的最大峰值主要由重力载荷工况决定,地震载荷工况对其贡献非常小.     

里程仪测距纵坡度及加减速模型研究

针对轮式车辆导航特点,综合车辆载荷转移和轮胎滑动两方面,提出了计算半径的概念,建立能同时补偿路面纵坡度和车辆加速度对里程仪测距影响的误差模型,跑车试验表明:纵坡度角每增加1°里程仪计算刻度系数约减小1.0762×10-3mm,加速度每增加1 m/s2里程仪计算刻度系数约减小6.295×10-3mm,经过路面纵坡度和车辆...     

Dynamic response of highway girder bridges

The objective of the paper is to investigate the variation of dynamic loading of girder bridges with different girder number and span length due to several vehicles moving across rough bridge decks. Nine girder bridges with girder number ranging from four to eight and span length changing from 40 to 120 ft are designed based on the AASHTO standard highway bridges and modeled as grillage beam systems. The vehicle is simulated as a nonlinear vehicle model with 11 d.f. according to the HS20-44 truck design loading contained in the AASHTO specifications. Four types of road surface roughness generated from power spectral density function for very good, good, average and poor roads in accordance with International Organization for Standardization (ISO) specifications are used in this study. The maximum impact factors of different girders of bridges are obtained for different number of loading trucks (side by side), road surface roughnesses, transverse loading positions and the vehicle speeds changing from 15 to 75 mph. The conclusions reached in this study are useful in the further study of the impact of highway bridges and for practical bridge design engineers.     

Stability Analysis in a Curved Road Traffic Flow Model Based on Control Theory

In the paper, a novel traffic flow model is proposed to describe the behavior of vehicles moving on a curved road with a slope. We investigate the related influences on uniform traffic jam analytically and numerically. Based on control theory, the condition for no traffic jam is obtained analytically. Finally, simulations are carried out to verify the new traffic flow model. The theoretical and numerical results show that the related factors including the friction coefficient, radius of curvature, slope of the curved road and the parameter λ have major effects on the stability of traffic flow respectively.     

Reality of virtual damage identification based on neural networks and vibration analysis of a damaged bridge under a moving vehicle

Presented here is a reality of virtual damage detection and vibration behaviour study of a discrete beam-like bridge with one or several non-propagating edge cracks subjected to a moving vehicle. In this model, the simply supported beam elements are replaced by a range of rigid bars, which are connected by transverse and rotational springs, while the mass and rotational moment of inertia may be lumped at various points along the beam. The adopted vehicle model here is a four degrees-of-freedom, two axes half-vehicle model with tires flexibility and linear suspensions. Damage can be modelled by altering the spring stiffness equation at the crack position according to predictions, which allows the inclusion of simple or complex damage. To simplify, damage is represented here by an open crack, and stiffness of a given element with damage is calculated by fracture mechanics. Both the discrete element and finite element methods are used to investigate vibration analysis of a discrete beam model subjected to a moving vehicle to confirm model feasibility in vibration analysis under a moving vehicle. Besides, some dynamic response laws are obtained. Considering an irregular road profile, the effects of the moving vehicle velocity, the moving vehicle mass, the crack location and the crack depth on dynamic response of a beam-like bridge are analysed by a numerical example, combining a vehicle–bridge coupled vibration MATLAB program with ANSYS. In addition, the neural network is used to identify the damage of the structure. Numerical results of the numerical model predictions, compared with those obtained from the continuous elements beam, support the accuracy of the discrete elements beam model in both cases of undamaged beam and damaged one. The evidence for condition assessment and damage identification of bridge is obtained from this simulation as obtaining the vibrational characteristics of the damaged beam structure subjected to a moving vehicle. And the inversion results show that the neural network method can identify the injury location and injury size of the structure accurately.

     

双车道公路弯道驾驶员轨迹决策行为研究

车辆行驶轨迹是道路路线安全性和舒适性评价的重要指标之一。采用计算机仿真技术,模拟驾驶员操纵车辆行驶时的轨迹决策行为,研究在自由流交通状态下,道路几何线形对车辆行驶轨迹的影响规律。为此,在郭孔辉院士提出的预瞄最优曲率模型的基础上,引入了SK道路几何模型,建立了实际道路条件输入的驾驶员方向控制模型。得到以下主要研究结论：当驾驶员轨迹决策行为只受道路本身条件影响时,且车辆在进入曲线段时,行驶轨迹存在着朝曲线内侧偏移的运动趋势;在出曲线段时,车辆行驶轨迹趋向朝曲线外侧偏移。平曲线半径大小对驾驶员轨迹决策行为有着显著的影响,圆曲线半径越大,行车轨迹侧向偏移量越小,反之越大。     

Influence surfaces by boundary element/least square methods coupling

This work presents a new application for calculating the influence surfaces of transverse displacements, directional derivatives and bending moments for generic bridge decks. A plate bending boundary element method formulation is coupled with the application of a continuous field surface derived by the least square procedure. This original BE formulation permits calculating influence surfaces of plates with polygonal, curved or circular geometry, and several transverse load conditions. The proposal allows future analysis of building floors and single and continuous bridge trusses connected to longitudinal and transversal girders. Numerical examples are presented to demonstrate the potential of the present formulation and the results are compared with analytical values and with usual vehicular loads.     

振动对光纤陀螺线形测量系统影响分析

在使用光纤陀螺测量系统对桥梁线形进行测量的过程中,由于线形测量结果是通过积分算法得到的,所以来自汽车发动机和路面不平的振动影响会给测量结果带来巨大的误差,并且这类误差会随着测量时间和距离的增加变得越来越大,呈现出发散的特性;为了减小这些振动给测量结果带来的误差,可以使用时频分析的手段,通过时间信息和运动速度得到位置和路况信息,进而得到不同路况下的频域特点;选择路面完好的路段进行实验,点状减速带代表路面不平,使用Morlet小波对光纤陀螺采集到的信号进行时频分析,发现了不同工况下带来的振动噪声信号的频域特点,并且确定了27 Hz以上均为振动带来的噪声信号;在实际对某跨江大桥的线形测量中,使用切比雪夫滤波器去除光纤陀螺所采集到27 Hz以上的噪声信号,相比没有使用低通滤波处理的线形,测量精度提高了50%。     

Speed and Accuracy Tradeoff for LiDAR Data Based Road Boundary Detection

Road boundary detection is essential for autonomous vehicle localization and decision-making, especially under GPS signal loss and lane discontinuities. For road boundary detection in structural environments, obstacle occlusions and large road curvature are two significant challenges. However, an effective and fast solution for these problems has remained elusive. To solve these problems, a speed and accuracy tradeoff method for LiDAR-based road boundary detection in structured environments is proposed. The proposed method consists of three main stages: 1) a multi-feature based method is applied to extract feature points; 2) a road-segmentation-line-based method is proposed for classifying left and right feature points; 3) an iterative Gaussian Process Regression (GPR) is employed for filtering out false points and extracting boundary points. To demonstrate the effectiveness of the proposed method, KITTI datasets is used for comprehensive experiments, and the performance of our approach is tested under different road conditions. Comprehensive experiments show the road-segmentation-line-based method can classify left, and right feature points on structured curved roads, and the proposed iterative Gaussian Process Regression can extract road boundary points on varied road shapes and traffic conditions. Meanwhile, the proposed road boundary detection method can achieve real-time performance with an average of 70.5 ms per frame.      

Analysis of distortional stress in curved I girder bridges

A simplified means of determining more accurately the stress distribution in a curved girder system considering web distortion is presented. The distortional response of a single span curved plate girder bridge is determined utilizing a finite difference procedure. The analysis finds the maximum bending, warping and distortional stresses along each girder.

A UNIVAC 1108 computer was used in the development of the simplified equations which relate the bending and warping stresses to the induced distortional stress. The program written in FORTRAN V, calculates the stresses developed in a four plate girder system having any number of diaphragms along its span.     

基于板单元形函数的公路桥梁车桥耦合振动分析方法研究

为研究公路多片式梁桥的车桥耦合振动问题,提出一种基于矩形薄板形函数的车桥耦合振动分析方法.该方法以车轮与桥面接触点为界,将车桥耦合系统分为汽车与桥梁2个子系统,分别采用虚功原理与有限元法建立各自的运动方程,并通过车轮与桥面接触处的位移协调条件及车桥相互作用力的平衡关系相耦合,采用矩形薄板形函数实现车桥接触点位移与桥梁节点位移的联系以及车桥相互作用力的分配,通过迭代求解汽车和桥梁的运动方程得到其动力响应.根据分析方法的计算流程,编制了汽车 桥梁耦合系统的动力分析程序,并通过算例分析验证其可行性.研究结果表明,使用基于矩形薄板形函数的公路桥梁车桥耦合振动分析方法得到的车桥动力响应具有较好的精度,该方法具有广泛的适用性,可为多片式梁桥的车桥耦合振动分析提供一种新思路.