基于动应变的桥梁动态称重及其优化算法

将桥梁视为“称”对车辆进行动态称重,是一种获取桥面移动车辆行驶速度、轴距、轴重等信息的新方法。本文以桥梁不同截面动应变响应为对象,采用“峰值法”识别车辆速度、轴距,引入最小二乘原理识别车辆各轴重,再结合梯度法对初始识别结果值进行局部优化,最后建立车-桥耦合振动模型模拟桥梁动应变,对桥梁动态称重及优化算法进行数值仿真。结果表明,对已经具备一定精度的动态称重初始结果值进行局部优化能进一步提高精度,满足工程应用要求。     

基于影响线的桥梁移动荷载识别

以桥梁不同截面动应变响应为对象,进行移动荷载识别研究。通过寻找应变曲线峰值点识别车辆行驶速度、轴数、轴距,并采用影响线拟合动应变响应的思路识别车辆各轴轴重。结合车-桥耦合振动模拟计算,对桥梁移动荷载识别问题进行数值仿真分析。     

摆动支承式汽车衡动态称重的缓冲减振研究

为了克服高速公路计重收费系统非正常行车的逃票行为和称重精度不满足连续动态称重的需求,对摆动支承式汽车衡的动态称重过程进行了动力学分析,得到车辆不规范行车状态下的轴重变化。根据柱式负荷传感器的摆动支承振动特性,分别在检定工况和使用工况下对给定参数的双轴刚性车的动态称重过程进行数值仿真,得到车辆轴载的称重误差。考虑电阻应变式负荷传感器的全桥测量特性,针对顶撞式限位的使用缺陷设计了一种缓冲限位减振装置;双轴刚性车在使用工况下的称重误差结果显示,该装置能实现快速稳定秤体、减小冲击、提高称重精度和稳定性。     

桥梁动态称重迭代算法的理论与试验研究

桥梁动态称重(bridge weigh-in-motion,BWIM)能够以桥梁作为载体识别过往车辆的轴重。商用BWIM系统通常基于Moses算法,以桥梁的实测影响线对车桥实测动力响应进行轴重识别。然而,该算法的轴重求解方程是病态方程,在特定情况下轴重识别精度偏低。为解决这一问题,该研究提出桥梁动态称重迭代算法,通过Moses算法和实测影响线算法之间的反复迭代,修正病态的轴重求解方程。该研究介绍了桥梁动态称重迭代算法的原理,并进行了相关公式推导;基于怀化舞水五桥引桥的车桥动力试验,对比分析商用BWIM算法和桥梁动态称重迭代算法的轴重识别精度;并深入探讨影响线的选取对轴重识别精度的影响。研究表明,桥梁动态称重迭代算法能够在一定程度上提高轴重识别的精度,其最佳的基准影响线是实测均值影响线。     

桥梁车辆荷载识别的贝叶斯方法研究

基于贝叶斯推理提出了一种可实现误差模式选择的桥梁车辆荷载识别方法。该方法通过静力影响线构建车辆荷载与实测响应的关系表达式,并建立修正曲面以消除动力效应造成的识别误差。引入与结构响应大小和车速相关的五种误差模式。根据假设的先验分布推导车辆轴重参数的后验分布,以获得车辆荷载的最优估计值和置信区间,并计算各误差模式的后验概率。分别采用简支梁数值算例和某连续梁桥动载试验,对该方法在不同车速工况下的识别精度和可靠性进行了验证。结果表明,修正曲面可以有效消除车辆动力冲击的影响,提高了荷载识别精度;荷载识别结果以置信区间形式呈现,可量化荷载识别结果的不确定性;贝叶斯方法能够识别出最佳误差模式,进一步提升了荷载识别的鲁棒性。     

考虑路面不平顺随机性的汽车过桥动力响应分析

为分析考虑随机路面不平顺情况下的车辆过桥动力响应,建立了随机汽车-桥梁耦合振动模型,路面不平顺采用路面谱进行模拟转换,引入概率密度演化方法对系统的随机响应进行计算,通过2个算例进行了验证:与经典算例进行对比验证模型的可靠性;与蒙特卡洛法对比验证了概率密度演化方法计算随机车-桥系统动力响应的精度及效率。2个算例证明了该随机振动系统模型计算结果可靠,同时概率密度演化方法能够在保证精度的前提下有效提高计算效率。对不同道路不平度、不同车速情况下的车辆、桥梁随机响应进行分析,结果表明:车速对桥梁响应均值的影响不敏感,对车辆响应均值影响较大;桥梁与车辆响应标准差均随车速增大而增大。不同道路等级工况下,桥梁位移与车辆加速度概率最大值总体上都随车速增大而增大;在不同速度工况下,桥梁位移与车辆加速度概率最大值随着道路等级变差而明显增大。     

基于虚拟简支梁法的桥梁动态称重研究

Moses算法是桥梁动态称重(BWIM)技术中最可靠的算法之一,是目前各商业BWIM系统的基础。然而,受影响线标定的约束,当前的商用BWIM系统仅适用于短跨径桥梁。针对这一情况,提出了虚拟简支梁法。该方法利用桥梁上的某一区段的隔离应变计算车辆的轴重和总重,不受桥梁跨径的限制。建立了跨径为20 m和40 m的简支T梁桥有限元模型,基于车桥耦合振动理论模拟获得桥梁响应,并利用提出的新方法识别了车辆的轴重和总重。分析了路面平整度、车辆行驶速度等因素对识别精度的影响。结果表明:对于较短跨径的20 m T梁桥,常见三轴车的总重识别误差平均值在2%左右,五轴车的总重识别误差平均值低于1%,精度都稍优于传统Moses算法;而对于传统Moses算法不适用的40 m T梁桥,该方法识别车辆总重的误差平均值仍可控制在3%以内,表明该方法不受桥梁跨径的限制,具有更广的应用前景。     

桥上移动车辆车轴识别小波变换方法

通过连续小波变换对车辆过桥产生的桥梁动应变响应进行分析,提取特定尺度下小波系数,能够凸显与车轴信息对应的峰值点,弥补传统局部峰值提取法在识别短轴距问题的不足。车-桥耦合振动模型数值分析表明,结合小波变换的车轴信息识别方法对于行驶速度高、路面平顺性差的工况仍具有较高精度。选取与车辆激振频率相对应的尺度系数,准确提取原始信号中有用信息的同时有效减小干扰信号影响。     

基于贝叶斯后验估计的桥梁动态称重算法理论与试验研究

桥梁动态称重(bridge weigh-in-motion, BWIM)利用过桥车辆对桥梁产生的动力响应快速识别车辆轴质量。由于实测的动力响应包含测量误差,在一定程度上降低了传统BWIM算法的轴质量识别精度。为了解决这一问题,提出基于贝叶斯后验估计的桥梁动态称重算法。该算法考虑了测量误差对轴质量识别精度的影响,假设测量误差和轴质量服从高斯分布,利用测量误差的标准差和轴质量标准差得到能抑制测量误差的约束因子,推导出新的轴质量求解方程。基于数值仿真和实桥试验,分别得到传统BWIM算法和贝叶斯算法的轴质量识别精度,并进行对比分析。试验结果表明：相比于传统BWIM算法,贝叶斯算法能够有效抑制测量误差的影响,明显改善轴质量识别精度。     

基于斜拉桥索力监测的在线车速车重识别

为充分发挥监测系统的应有作用,实现大型桥梁车辆荷载识别,将桥梁动态称重(B-WIM)技术与健康监测系统(HMS)相结合,研究基于HMS的B-WIM的相关理论与方法。依托斜拉桥及其HMS实际工程,选取被监测的运营索力为观测参数,通过索力时程特征分析和神经网络方法识别车速和车重;首先采用小波和EMD分解方法对运营索力进行处理和解析,将索力的车辆响应分量与恒载、温度响应以及随机干扰部分分离,进而通过单索力车辆响应峰值锐度对车速预估,再通过多索力车辆响应峰值的匹配解算车速;然后,面向多索力响应构建车重识别的BP网络模型,基于相似公路车速车重联合分布模型构建车队样本进行车桥耦合分析,提取索力响应建立了2 916组数据样本用于网络的训练和检验,实现了较高精度的车重识别网络训练;最后,采用实际斜拉桥连续24 h索力监测数据,将上述车速车重识别方法在实际工程进行了应用和检验,共识别出车重50 kN以上的车辆463辆。通过对识别结果的统计分析表明,识别的车速、车重分布以及二者的联合分布较好的符合实际。斜拉索具有全桥空间广泛分布的特点,索力也是监测系统的必测响应并对车辆具有良好的敏感性,以索力为观测参数实现车重车速的识别是可行的,并该方法的数据处理与车辆识别过程易于实现在线和自动化。     

基于逆有限元法的形状还原传感阵列及桥梁挠度监测试验

桥梁挠度是桥梁工程从设计阶段到运维阶段的重要控制指标,对其进行实时监测对桥梁工程的性能评估至关重要。该文提出一种形状还原传感阵列,该传感阵列基于逆有限元方法,仅通过有限点的实测应变数据即可实时、准确地还原出桥梁挠曲线。详细阐述了逆有限元法基本原理与形状还原传感阵列装置,将该项技术应用于混凝土自锚式悬索桥梁模型进行挠度监测试验研究,分别对桥梁模型进行静态加载与动态加载,通过水准仪与激光位移计对还原得到的挠曲线形状与精度进行验证。结果表明:形状还原传感阵列对于桥梁挠度的监测具有易于安装、数据准确、实时性好的优点,不仅可以准确还原出桥梁挠度,而且可以实时反演出桥梁挠曲线形状,能够有效地评估桥梁工程性能质量。     

几种典型车辆在斜拉桥桥面行使的临界风速研究

研究强侧风作用下三种典型汽车在斜拉桥桥面行驶时的临界风速和车速。分析汽车运动方程的随动坐标特性和桥梁的侧向抖振对汽车相对桥面侧偏的影响,得到侧偏位移及速率的计算式,在以往基础上,研究了考虑车辆侧偏和驾驶员行为的风-车-桥空间耦合振动系统,完善了仿真分析程序的功能。以某斜拉桥为实例,分析三种典型车辆在桥面行使的临界风速。分析结果表明：采用控制重心还是前轮侧滑的驾驶员模型不显著影响桥面汽车临界风速的大小;不同类型汽车的事故原因可能不同,对于箱式货车,侧滑事故起控制作用,对于桑塔纳和一汽佳宝,车速高时,侧倾事故起控制作用,低车速时,侧滑事故起控制作用。     

Evaluation of fiber optic sensors for remote health monitoring of bridge structures

Health monitoring of civil infrastructure systems has recently emerged as a powerful tool for condition assessment of structural performance. With the widespread use of modern telecommunication technologies, structures could be monitored periodically from a central station located several miles away from the field. Sensors are placed at several critical locations along the structure, and send structural information to the central station. This remote capability allows immediate damage detection, so that necessary actions that ensure public safety are taken. The goal of this research work is to evaluate the use of Fiber Optic sensing technology as a tool for structural health monitoring. To perform this task, a case study involving installation of Fiber Optic Sensors on a selected bridge structure during its construction phase was conducted. The bridge is located in the state of Florida, USA and is considered the first smart structure in this state. Static and Dynamic testing of the bridge were performed using loaded SU4 trucks. A 3-dimensional analytical finite element model of the bridge was developed and its results were compared to the test data. The study confirmed the accuracy of the sensors in estimating the bridge behavior under heavy truck loads. In addition, the sensors were connected to a data acquisition system permanently installed on-site. The acquisition system could be accessed through remote communication, which permits the evaluation of the bridge behavior under live traffic loads. Currently, live structural data under traffic loading is being transmitted continuously to the central maintenance office. The study revealed that the proposed health monitoring technology will enable practical, cost-effective, and reliable maintenance of bridge structures.     

A general solution to the identification of moving vehicle forces on a bridge

Bridge weigh‐in‐motion systems measure bridge strain caused by the passing of a truck to estimate static axle weights. For this calculation, they commonly use a static algorithm that takes the bridge influence line as reference. Such a technique relies on adequate filtering to remove bridge dynamics and noise. However, filtering can lead to the loss of a significant component of the underlying signal in bridges where the vibration does not have time to complete sufficient number of cycles and in cases of closely spaced axles traveling at high vehicle speeds. In order to overcome these limitations and also to provide additional information on the dynamics of the applied forces, this paper presents an algorithm based on first‐order Tikhonov regularization and dynamic programming. First, strain measurements are simulated using an elaborate three‐dimensional vehicle and orthotropic bridge interaction system. Then, strain is contaminated with noise and input into the moving force identification algorithm. The procedure to implement the algorithm and to derive the applied forces from the simulated strain record is described. Vehicle axle forces are shown to be accurately predicted for smooth and rough road profiles and a range of speeds. Copyright © 2008 John Wiley & Sons, Ltd.     

Balancing techniques for strain gauge bridges

Four common methods of adjusting the resistive balance of a strain gauge bridge installation are described and compared. Effects on gauge factor and temperature stability are discussed and formulae are presented for the calculation of possible errors.     

基于监测数据的钢箱梁U肋细节疲劳可靠性分析

针对某悬索桥钢箱梁疲劳开裂严重,基于WIM动态称重系统采集的数据,对该桥通行车辆的车型、轴距、轴重、总重、是否超载进行了统计,明确了该桥交通荷载特征及各车道随机车流差异性,依据实桥动应变监测数据,运用雨流计数法及Palmgren-Miner线性损伤累积理论,获得了运营状态下各车道的疲劳应力谱,基于均匀设计-径向基神经网络-重要蒙特卡罗法（UD-RBF-IMC）相结合的算法,运用线弹性断裂力学对U肋对接焊缝疲劳可靠性进行了评估,研究了交通量及轴重增长对疲劳可靠度的影响规律。研究结果表明:该桥疲劳车型可简化为V2~V10共9类,左、右幅V2车型的总重均为单峰偏态分布,超载率不到4%,V3~V10车型的总重均为多峰分布,超载率大于30%,最高达69%;重车道V2~V10车型的比例明显高于其他车道;温度日变化对疲劳应力谱的影响较小,采样频率对应力谱的影响较为显著,不宜小于50 Hz;结合UD、RBF、IMC算法各自的优点,有效提高了基于监测数据的钢箱梁细节疲劳可靠度指标的求解精度和效率;轴重增长系数对疲劳可靠度的影响明显大于交通量增长系数,在运营期间除控制交通量外,还需重点控制重车比例和超载率;当交通量增长系数为3%,轴重增长系数为0.6%时,1#测点疲劳寿命仅为74年;超车道重载卡车数量较少,高水平应力循环较少,疲劳寿命较长,而快车道和重车道重载卡车较多,高水平应力循环较多,存在疲劳开裂风险,需重点关注。     

基于ANSYS的多轴汽车振动响应分析

为了高效预测路面不平度输入下多轴汽车悬挂质量某一位置处的振动响应特性,依据多体动力学理论,利用ANSYS仿真工具建立多轴汽车的七自由度动力学仿真模型。在整车发动机定转速的试验基础上,运用理论分析、仿真计算相结合的方法,根据建立的模型对整车进行仿真分析与研究。结果表明仿真计算结果与试验结果基本一致,可见,所提出的动力学模型和分析方法具有较好的可信度。仿真结果表明：在路面不平度输入下,影响悬挂质量[-]6 m～[-]4 m处的加速度响应以第1阶固有频率为主;而在[-]2 m～4 m处以第2阶固有频率为主,尤其是在悬挂质量的后端;第2阶固有频率是影响多轴汽车加速度振动响应特性的最主要的因素,改善该多轴汽车的平顺性需把研究重点放在多轴汽车的第三四车轴的悬架系统上。     

A case study on the fracture of sinter machine pallet axles

A sinter machine produces sinter at 1200–1400 °C to supply raw materials for blast furnace ironmaking. The sinter machine is composed of a series of pallet cars which are constrained on rails. Each pallet car has four axles which connect the pallet car and four running rollers. In sinter production, the pallet axles experience periodic thermal expansion and periodic load changes under high temperature, high moisture, corrosive atmosphere and heavy dust. After serving for about seven years, pallet axles of one of ArcelorMittal sinter machines started breaking, causing unscheduled production delay. The fracture of the axles is in the orientation of top and bottom, and the cracks are deeper in upper portions than in lower portions of axle cross sections. The axles have been studied through chemical analysis, strength analysis, stress analysis, lifetime analysis via deterministic mechanics and lifetime distribution analysis. It has been found that the axles are breaking in fatigue-crack mechanism. The fatigue cracks are resulted from effect of thermal expansion on net tensile stress of the axles. Considering harsh working environment and dynamic loading, lifetime analysis, using deterministic mechanics, indicates that originally installed pallet axles are approaching the end of their lifetime. Weibull distribution function can very well describe lifetime distribution of pallet axles. Accordingly, about 50% of originally installed axles will be gone before next two and half years, and more than 90% of them will break before next six and half years. An intelligent replacement strategy is recommended. In a scheduled maintenance time, carefully inspect all axles using ultrasonic crack detectors, and replace those axles whose expected lifetime is shorter than next scheduled maintenance date. To replace steel SAE 1045 with steel SAE 4040 for fabricating new pallet axles may significantly increase lifetime of the new pallet axles.     

涵道式无人机的悬停姿态控制与运动稳定性分析

进行了涵道式无人机的运动稳定性分析,指出无人机在悬停状态下受近地空间、气流颠簸和荷兰滚的影响,导致系统极易出现抖动甚至失控,而优化飞行器的结构参数对于提高飞行器运动稳定性具有重要意义.基于这种分析,从机械结构设计出发,通过Lyapunov指数方法建立飞行器结构参数与系统运动稳定性之间的量化关系,以此指导系统的机械结构设计及控制系统优化,为提高系统执行飞行任务的可靠性和稳定性奠定理论基础.该方法与Lyapunov直接法相比最大的优点是其可构建性,从而为分析其他机器人等非线性系统的运动稳定性提供了一种简单有效的工具.     

轨道不平顺检测中数字补偿滤波器的设计及仿真

轨道不平顺是影响列车安全舒适的主要因素，轨检车可实时准确的检测出轨道不平顺状态；但车速的变化会使传感器信号发生畸变和衰减，使分析数据失真。为了消除车速的影响，分析了轨检系统中数字补偿滤波器的理论及设计方法，最后进行了CCS5000仿真验证。结果表明，数字补偿滤波器能够消除前端有用信号的衰减，且可达到较高的精度。