承台-群桩结构波浪力理论分析

目前桥梁基础的波浪力计算大多采用数值模拟的方式进行研究,但数值模拟存在计算成本高、耗时长等缺点。因此基于线性势流理论首次推导了承台-群桩结构的波浪绕射作用计算公式,求解得到了承台波浪力的半解析解。首先将承台-群桩结构简化为上层穿出水面、下层嵌入水底的双层多柱体结构,其中上层单柱体代表承台,下层多柱体代表群桩。然后将计算域划分为承台外侧和下侧2个子域,子域间的交界面函数通过傅里叶级数处理,通过匹配特征函数展开法对每一个子域的速度势函数进行求解,最终得到承台表面波浪力。在进行解的收敛性分析和与边界元软件进行大量的对比验证后,分析了桩半径和承台高度对承台表面波浪力的影响。研究发现：在小波数范围内,承台表面的量纲一的波浪力会随着群桩的存在而增大,并随着桩半径的增加而进一步增大;同时承台高度的增加会首先对波浪力的增加有促进作用,但在承台高度达到某一临界值后,承台量纲一的波浪力将会减小。首次基于势流理论推导的双层多柱体波浪作用的理论公式,为承台-群桩结构表面波浪力的求解提出了一种新的半解析方法,相较于数值模拟,其能在保证结果准确性的同时,也能使得计算更加方便快捷、成本低廉,为之后波浪作用理论的进一步完善提供有力支撑。     

融合卡尔曼滤波的高速公路状态估计误差界限分析

为分析高速公路交通流检测数据质量,本文构建平方流量误差界(Squared Flow Error Bound, SFEB)和扩展卡尔曼滤波(Extended Kalman Filter, EKF)的决策级融合模型SFEB-EKF,在检测器空间覆盖不足情况下,计算检测路段和无检测器路段的交通状态估计误差界限。与SFEB 算法相比,融合模型利用EKF交通状态估计模型估计全路段交通状态,基于得到的估计样本计算全路段交通状态估计误差下界。同时,采用最近邻法(Nearest Neighbor Method, NNM)计算全路段交通状态估计误差上界。应用开源高速公路数据集测试模型,结果表明,与需要输入真实样本的SFEB算法相比,融合模型SFEB-EKF在缺少真实样本情况下,能取得相似的结果且误差保持 在5%以内,不同检测器覆盖率实验下模型表现出良好的稳定性。本文模型通过给出无检测器路段交通状态估计界限,为高速公路交通检测器布设方案提供参考。     

城市快速公交专用道道路线形设计分析

以汽车的动力特性和通过特性为理论依据,根据目前快速公交专用车辆大都采用低地板大型铰接底地板车辆的现状,结合其容量比一般普通公交大得多的特点,对快速公交专用道的道路线形设计进行分析,提出设计方法。     

A competing Markov model for cracking prediction on civil structures

Cracks on the surface of civil structures (e.g. pavement sections, concrete structures) progress in several formations and under different deterioration mechanisms. In monitoring practice, it is often that cracking type with its worst damage level is selected as a representative condition state, while other cracking types and their damage levels are neglected in records, remaining as hidden information. Therefore, the practice in monitoring has a potential to conceal with a bias selection process, which possibly result in not optimal intervention strategies. In overcoming these problems, our paper presents a non-homogeneous Markov hazard model, with competing hazard rates. Cracking condition states are classified in three types (longitudinal crack, horizontal crack, and alligator crack), with three respective damage levels. The dynamic selection of cracking condition states are undergone a competing process of cracking types and damage levels. We apply a numerical solution using Bayesian estimation and Markov Chain Monte Carlo method to solve the problem of high-order integration of complete likelihood function. An empirical study on a data-set of Japanese pavement system is presented to demonstrate the applicability and contribution of the model.     

Suspension system state estimation using adaptive Kalman filtering based on road classification

This paper provides a new method to solve the problem of suspension system state estimation using a Kalman Filter (KF) under various road conditions. Due to the fact that practical road conditions are complex and uncertain, the influence of the system process noise variance and measurement noise covariance on the estimation accuracy of the KF is first analysed. To accurately estimate the road condition, a new road classification method through the vertical acceleration of sprung mass is proposed, and different road process variances are obtained to tune the system’s variance for the application of the KF. Then, road classification and KF are combined to form an Adaptive Kalman Filter (AKF) that takes into account the relationship of different road process noise variances and measurement noise covariances under various road conditions. Simulation results show that the proposed AKF algorithm can obtain a high accuracy of state estimation for a suspension system under varying International Standards Organisation road excitation levels.     

Adhesion estimation at the wheel–rail interface using advanced model-based filtering

The railway industry in the UK is currently expanding the use of condition monitoring of railway vehicles. These systems can be used to improve maintenance procedures or could potentially be used to monitor current vehicle running conditions without the use of cost prohibitive sensors. This paper looks at a novel method for the online detection of areas of low adhesion in the wheel/rail contact that cause significant disruption to the running of a network, particularly in the autumn season. The proposed method uses a Kalman–Bucy filter to estimate the creep forces in the wheel–rail contact area; post-processing is then applied to provide information indicative of the actual adhesion level. The algorithm uses data that, in practice, would be available from a set of modest cost inertial sensors mounted on the vehicle bogie and wheel-sets. The efficacy of the approach is demonstrated using simulation data from a nonlinear dynamic model of the vehicle and its track interface.     

Contents Index Volume 35 and 36

Active safety systems would benefit from tyre force and friction potential information. Different sensor concepts, including, among others, the EU–funded Apollo–project developed tyre sensor based on optical position detection, are being studied. The sensor can measure tyre carcass deflections with respect to the rim. The carcass deflections can be used to calculate tyre forces and they may be exploited in the estimation of friction potential. The waveforms of the sensor signal are illustrated. The vertical and lateral force estimations are presented with unavoidable compensation parts. The tyre sensor measurements were compared to the measurement–vehicle results and good correlations achieved. Continuing activities are concerned with the estimation of friction potential and the detection of aquaplaning.     

Dynamic demand estimation and microscopic traffic simulation of a university campus transportation network

Abstract

This article documents the authors' experience with the modeling, simulation, and analysis of a university transportation system, using the TRansportation ANalysis and SIMulation System (TRANSIMS). The processes of data preparation and network coding are described, followed by the algorithm developed to estimate the dynamic 24-hour demand, which includes a procedure for estimating the ‘desirability’ of the different parking lots from readily available data. The dynamic demand estimation algorithm is validated by comparing estimated and observed parking lot occupancies, where it is shown that the algorithm is capable of replicating observed results. Finally, an example is included to demonstrate how the developed model can be used in campus transportation planning. Besides serving as a first case study for using TRANSIMS to model a university campus, the study's contributions include the development of a procedure for parking lot desirability ranking and a practical procedure for estimating dynamic demand on university campuses.     

基于应力松弛试验用有限元预估车辙

为了使车辙预估变得更为简便,提出一种基于应力松弛试验的改进的有限元车辙预估方法。研究结果表明：不仅从粘弹性力学的角度分析,应力松弛试验在理论上与Maxwell模型具有一致性,而且实例计算结果也验证了此方法的可行性。该方法便于不熟悉本构理论的工程人员进行车辙预估。     

基于卡尔曼滤波算法的电机转速精确估计

从无刷直流电机入手建立数学模型，利用卡尔曼Kalman（EKF）滤波原理算法，对无刷直流电机的转速进行精确估计，然后在Matlab环境下仿真，验证卡尔曼滤波算法对电机转速估计的精确性。