横风下车辆-轨道耦合动力学性能

应用多体系统动力学理论, 建立了车辆-轨道耦合动力学模型, 利用新型显式积分法求解动力学方程组, 利用赫兹非线性弹性接触理论计算轮轨法向力, 利用沈氏理论计算轮轨蠕滑力, 编写了车辆-轨道耦合动力学计算程序, 研究了轨道结构对高速列车动力学性能的影响, 分析了不同横风环境下高速列车动力学性能和列车姿态。研究结果表明: 当列车运行速度为350 km·h^-1, 横风速度为15 m·s^-1时, 车体最大横向加速度为0.45 m·s^-2, 车体最大垂向位移为24.5 mm, 车体向背风侧横移80.0 mm, 车体最大侧滚角为2.23°; 一位轮对的最大轮重减载率接近0.80, 二、四位轮对均向背风侧横移, 背风侧车轮易发生爬轨现象, 二位轮对的横向位移最大, 为7.4 mm。在横风下, 高速列车的运行安全性指标变差, 车体振动加速度变化不明显, 车体向背风侧横移。在所有轮对中, 二位轮对最危险。     

城市道路改造工程设计的几点体会

随着城市建设的不断发展,需改造的城市道路越来越多。道路改造工程因其功能不同,所处环境不同,设计思路和解决手段也千差万别。该文通过几个设计实例,对设计的一些难点及应对措施进行了简单的分析和介绍。     

Flexing service schedules: Assessing the potential for demand-adaptive hybrid transit via a stated preference approach

This paper assesses the demand for a flexible, demand-adaptive transit service, using the Chicago region as an example. We designed and implemented a stated-preference survey in order to (1) identify potential users of flexible transit, and (2) inform the service design of the flexible transit mode. Multinomial logit, mixed-logit, and panel mixed-logit choice models were estimated using the data obtained from the survey. The survey instrument employed a d_p-efficient design and the Google Maps API to capture precise origins and destinations in order to create realistic choice scenarios. The stated-preference experiments offered respondents a choice between traditional transit, car, and a hypothetical flexible transit mode. Wait time, access time, travel time, service frequency, cost, and number of transfers varied across the choice scenarios. The choice model results indicate mode-specific values of in-vehicle travel time ranging between $16.3 per hour (car) and $21.1 per hour (flexible transit). The estimated value of walking time to transit is $25.9 per hour. The estimated value of waiting time at one’s point of origin for a flexible transit vehicle is $11.3 per hour; this value is significantly lower than the disutility typically associated with waiting at a transit stop/station indicating that the ‘at-home’ pick-up option of flexible transit is a highly desirable feature. The choice model results also indicate that respondents who use active-transport modes or public transit for their current commute trip, or are bikeshare members, were significantly more likely to choose flexible and traditional transit than car commuters in the choice experiments. The implications of these and other relevant model results for the design and delivery of flexible, technology-enabled services are discussed.     

大同南中环快速化改造工程总体设计

快速化改造后的南中环是未来大同市东西向流量最大的交通走廊,其将新老城区及铁路航空交通枢纽有效串联.对南中环快速化改造总体设计进行了详细描述,结合现状道路断面及交通需求分析,进行了断面优化设计.通过对现状横向路网的梳理以及重要节点立交的设置,对快速路系统匝道设置提出了具体方案.针对道路现状过河桥梁及立交的问题,借用现状地...     

交叉梁法在现浇混凝土空腹楼盖结构分析中的应用

现浇混凝土空腹楼盖是在楼板内按照一定的规则布置一定数量的薄壁箱体形成网格状的空腔,以得到较低的结构自重和较高承载力的组合结构体系.这种楼盖空隙率大,施工方便、快捷,特别适用于大柱网、重荷载的楼盖结构体系中.本文在真型试验的基础上研究其受力分析,并提出了一些处理建议.     

暗挖地铁车站空间交叉结构施工对邻近扩大基础桥梁影响分析

北京地铁12号线安贞桥站采用暗挖分离结构形式侧穿安贞东桥,桥梁下部结构形式为斜腿刚构,下接扩大基础。在安贞东桥南北两侧,车站的施工横通道和车站主体结构的相交部位形成空间交叉结构,其施工将对桥梁安全造成威胁。为减小交叉部位施工对桥梁的影响,提出"超前深孔注浆"和"超前深孔注浆和地表隔离桩联合使用"两种保护措施,并采用数值模拟方法对两种保护方案的实施效果进行计算分析。结果表明:仅采取超前深孔注浆加固措施,桥梁扩大基础沉降超出指标要求,采用"超前深孔注浆和地表隔离桩联合使用"的保护措施可有效控制基础沉降,因此确定后者为对安贞东桥的保护措施。最后分析了目前施工阶段桥梁下部结构和扩大基础沉降监测数据较大的原因,探讨了后续的施工对策。     

横风中高速列车以及桥梁的气动特性研究

运用通用的流体动力学软件FLUENT,利用二维定常不可压缩Navier-Stokes方程、SST湍流模型,采用有限体积法分析计算了车辆断面、32 m箱型简支梁桥断面以及两者组合体在15 m/s横风作用下受到的阻力、升力和倾覆力矩系数。数值分析结果表明,在横向风的作用下,发现车辆在简支梁桥上时,车辆受到的升力系数大于车辆单体的情况,倾覆力距系数明显小于车辆单体情况,而此时简支梁桥的升力系数明显小于简支梁桥单体情况。     

Some LCP Decompositions of Multistage Interconnection Networks

IntroductionIn a multiprocessor system,multistage inter-connection networks(MINs)with different inter-connection patterns had been proposed for differentapplications.Let N=2n.In an MIN of size N×N,communications between the N inputs and the Noutputs can be described by a permutation on thesetN={0,1,…,N-1}.Routing a permutation isto find N edge-disjoint paths in the network,eachconnecting an input/output pair.For a parallel sys-tem,rearrangeable MINs are preferable as they arecapable …     

Application of analytical model in the prediction of dynamic responses and fatigue damage of flexible risers: Part I – Improvement of analytical model considering shear deformation and varying tension effects

Flexible risers have been widely utilized for the transfer of oil and gas products from a well to production units. The components of flexible risers, unlike steel risers, experience complex contact phenomena during bending. The contact between helical wires and adjacent layers especially causes a significant level of bending nonlinearity, making it hard to estimate the structural responses. Accordingly, a large-scale dynamic analysis of flexible risers usually involves an analytical model that predicts the bending moment and axial stress of helical wires based on theoretical approaches. The analytical model consists of an axis-symmetrical model and a bending model. Among them, the bending model plays a critical role in the prediction of the bending responses of flexible risers. The conventional bending models usually neglect the shear deformation of internal layers and continuity of sliding force, which leads to a significant error of analysis. Furthermore, the previous bending models assume that the contact pressure on helical wires is constant during bending. In real operating conditions, however, most flexible risers experience a considerable change of tension that governs the slip of helical wires. Hence, the current study presents a new dynamic analysis method for flexible risers. The suggested analytical model improves the bending model based on an accurate estimation of the internal strain field considering the shear deformation and continuous sliding force. Also, this study proposes a stiffness update method to reflect the effect of varying tension in the dynamic analysis. The presented method updates the bending property of flexible risers considering the continuous change of the contact pressure from varying tension. For the validation of suggested method, the current study carries out numerical simulations with a pure bending and varying tension for the internal diameter 7 inches flexible risers. It is identified that the suggested analytical model provides accurate analysis results. Moreover, it is found that the effect of varying tension gives a significant impact on the bending behavior of flexible risers by changing the slip condition of helical wires. Part I of this series of papers describes the detailed formulation method for the analytical model and with some verification examples. The suggested analytical model is expanded to the large-scale dynamic analysis in Part II for the investigation of the effect of shear deformation and varying tension.     

基于市民生活行为学的交通行为研究综述

对交通行为的研究应该打破传统研究方法，转向基于市民生活行为学(狭义：生活导向型方法论)的研究方法。市民生活行为学侧重于考量生活选择之间的相互依存关系，不仅主张交通行为是各种生活选择的结果，也主张生活选择受交通行为的影响。这些主张既有理论基础也有实证依据，因此，涉及市民生活的各种决策需要不同部门的沟通与合作，这种沟通与合作需要有共同语言。市民生活行为学既为跨部门交通规划与管理提供全新的理论，也是服务于跨部门城市与区域政策(公共政策)的全新理论。市民生活行为学作为跨学科的理论体系，有望成为支持跨部门决策的通用语言。本文首先介绍市民生活行为学及其在交通行为研究的应用。其次，针对生活方式、汽车依赖、家庭能源消耗、信息通信技术与生活、健康与生活选择、旅游行为、老年人出行、年轻人风险行为、自然灾害应对及生涯流动在内的10个与交通行为密不可分的热点话题，介绍了基于市民生活行为学的交通行为研究进展。最后，提出基于市民生活行为学的交通行为研究的挑战与展望。