单跨斜箱梁桥设计计算研究

随着国家路网的不断发展,出现了各式各样的斜交桥梁。对于单跨密肋密支座整体斜箱梁桥,斜交角度大于20°时斜桥效应将非常明显,因此按照正交桥设计会留下很大的安全隐患。该文通过大量计算分析对比,提出计算斜桥的有效方法(梁格法)的同时,总结出一些能够缓解斜桥效应的有效途径,并对可能出现的斜桥病害提出可行有效的预防方法。     

ADS-B空管监视系统误差分析与研究

在空中交通管制中,利用监视设备提供的航空器飞行动态,管制员就可以为航空器配备飞行间隔,防止航空器与航空器相撞.监视设备存在的误差会对飞行间隔产生较大的影响.对比二次雷达系统,基于ADS-B的侧向间隔研究是当前的重点.文中通过分析监视系统信号处理流程,得出ADS-B监视误差主要有GPS接收机误差、数据链误差和系统延时误差组成,并阐述了各部分对于侧向间隔的影响.     

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在城市交通网络中,每个交通小区的交通发生量以及吸引量与其经济发展水平、土地利用、人口数量等因素密切相关,通常能够较为准确的预测,而小区之间的交通需求很难准确的预测. 本文假定所有起讫点的交通发生量和吸引量是确定的,而OD需求不确定且属于一个有界区间,利用鲁棒优化的方法建立OD需求不确定环境下考虑用户均衡约束的交通网络设计极小极大模型,并提出了灵敏度分析结合相继平均法(MSA)的求解算法. 数值算例表明,利用鲁棒优化方法得到的网络设计方案较传统的确定性网络设计方案具有更高的可靠性.     

基于行驶轨迹的双车道公路弯道路段交通安全特性研究

针对双车道公路曲线路段碰撞事故高发的特点,选取某双车道公路5个简单平曲线,实测弯道路段车辆行驶轨迹,分析大货车、大客车、小货车和小客车等主要车型在上行、下行方向的轨迹中线偏移量,研究不同车型的行驶轨迹偏移特性.通过测定不同车型在不同半径平曲线行驶的轨迹交叉面积,建立车型、平曲线半径与行驶轨迹交叉面积关系模型,为双车道公...     

自钻式旁压仪测定黏性土原位水平应力和K_0值

根据剑桥自钻式旁压仪的工作原理,分别按确定原位水平应力的观察法、迭代法、拟合法对天津市滨海新区黏性土的旁压曲线进行分析,并剖析算得的初始压力P0的物理意义,提出以观察法为基础的相关公式,用以确定原位水平应力。将试验数据按相关公式、迭代法、拟合法得到的P0计算K0,并与经验公式进行对比,认为K0值与土性和分析方法的基本假设有关。分析结果表明,用观察法的相关公式确定原位水平应力及K0值是一种适用于工程实践的有效方法。     

基于分阶段粒子群优化算法的船舶横向运动水动力参数辨识

提出了一种基于分阶段粒子群优化算法的船舶横向运动参数辨识问题。针对船舶横向水动力参数多、参数之间耦合度高的特点,提出了一种计算参数敏感性系数的方法,并依据敏感性系数对参数进行了分类,采用分阶段粒子群优化算法对参数进行辨识。对船舶横向运动参数辨识问题的求解结果表明,该算法能够快速地辨识出满足精度要求的船舶横向运动参数,验证了算法的有效性。     

桥梁施工过程的仿真分析研究

桥梁的精确分析必须与其施工方法,施工过程紧密联系。在施工过程中,结构的自重和施工荷载都是在各施工阶段逐级施加的,而且每一阶段伴随着徐变、收缩,预应力的张拉,边界约束的增减和体系转换等因素。所以导致通用的结构分析程序应用于桥梁结构分析存在一定的局限性。对此,该文阐述了有关桥梁施工过程的仿真分析研究。基于Visual Basic6.0开发了桥梁分析程序系统,以解决对桥梁进行精确分析的问题。实践证明该程序使用方便,结果可靠。     

强夯置换法加固地基现场试验研究

为评估强夯置换施工对周边油气管道的影响,结合大亚湾石化区强夯置换加固路基工程,在试验路段(周边无油气管)布置了位移边桩、测斜管和强夯振动监测点。利用全站仪测量了地表变形情况;数字测斜仪测量了土体内部的侧向变形情况;振动测试仪记录了强夯施工时地表监测点的振动曲线。试验结果表明:深层侧向位移在2～4 m深度范围内衰减较快,5 m以下深层侧向位移基本为零;强夯置换振动的影响范围为25～30 m。对位移和振动的监测数据的分析,可知在5 000 kN.m的夯击能时:强夯置换施工的影响范围为25～30 m。     

The stability and mechanical characteristics of heavy haul couplers with restoring bumpstop

To investigate the stability and mechanical characteristics of a type of heavy haul coupler with restoring bumpstop, the geometry and force states of couplers were analysed at different yaw angles and the longitudinal forces. The structural characteristics of this coupler were summarised. To aid in the investigation, a multi-body dynamics model with four heavy haul locomotives and three detailed couplers was established to simulate the process of emergency braking. In addition, the coupler yaw instability and lateral forces were tested in order to investigate the effect of relevant parameters on the locomotive's wheelset lateral forces. The results show that only when the bumpstop force exceeds half of the coupler longitudinal compression force, can the follower be rotated and the yaw angle of the coupler increase. The bumpstop preload is the most important stabilising factor. The coupler lateral force is constant when the coupler longitudinal force is smaller than the critical values of 2000, 1400 and 1150 kN at coupler free angles of 7°, 8° and 9°, respectively, for operation on straight track. The coupler free angle and the locomotive's lateral clearance of the secondary stopper are important in decreasing the wheelset lateral forces of the locomotive. It is advised that a smaller locomotive's secondary lateral suspension stiffness, a free clearance of 35 mm and an elastic clearance of 15 mm from the secondary lateral stopper be selected. If the coupler's free angle is less than the self-stabilising angle which is 5.5° for operation on straight track, the coupler is stable no matter how great the longitudinal force is. The wheelset lateral forces are allowed at the coupler longitudinal force of 2500 kN when the free angle is 6°. These studies establish meaningful improvements for the stability of couplers and match the heavy haul locomotive with its suspension parameters.     

A curving ACC system with coordination control of longitudinal car-following and lateral stability

The paper presents a curving adaptive cruise control (ACC) system that is coordinated with a direct yaw-moment control (DYC) system and gives consideration to both longitudinal car-following capability and lateral stability on curved roads. A model including vehicle longitudinal and lateral dynamics is built first, which is as discrete as the predictive model of the system controller. Then, a cost function is determined to reflect the contradictions between vehicle longitudinal and lateral dynamics. Meanwhile, some I/O constraints are formulated with a driver permissible longitudinal car-following range and the road adhesion condition. After that, desired longitudinal acceleration and desired yaw moment are obtained by a linear matrix inequality based robust constrained state feedback method. Finally, driver-in-the-loop tests on a driving simulator are conducted and the results show that the developed control system provides significant benefits in weakening the impact of DYC on ACC longitudinal car-following capability while also improving lateral stability.