An augmented Lagrangian origin‐based algorithm for link‐capacitated traffic assignment problem

The origin‐based algorithm is embedded into the augmented Lagrangian method for the link‐capacitated traffic assignment problem. In order to solve the “nonexistence” problem due to the second partial derivatives of the augmented Lagrangian function at some specific points, the approximate expressions of the second partial derivatives are amended in the origin‐based algorithm. The graph of last common nodes is developed on the basis of the restricted single‐origin network. A method is proposed for finding n–1 last common nodes of the restricted single‐origin network, resulting in computational complexity of O(n²) in finding last common nodes. Numerical analysis on the Sioux Falls network and Chicago Sketch network demonstrated the effectiveness and characteristics of the proposed algorithm. Copyright © 2014 John Wiley & Sons, Ltd.     

任意截面P-M曲线绘制原理及其在强度验算中的应用

《公路钢筋混凝土及预应力混凝土桥涵设计规范(JTG 3362-2018)》中关于偏压构件承载能力的计算仅适用矩形、T型等规则截面。本文根据《混凝土结构设计规范(GB 50010-20100)》附录E相关内容讨论异性桥墩的偏压构件验算方法,并据此提出任意截面P-M曲线的绘制原理及其在强度验算中的应用。     

加强灌注桩结构水平承载力方法探讨

针对港口工程中现场灌注桩承台结构的水平向结构分析和设计问题,结合港口工程的特点讨论了几种加强结构水平承载力的方法。     

波浪和潮流共同作用下的输沙问题

基于紊流中的泥沙受紊动支撑才得以悬浮的基本认识,从能量平衡原理出发,导出了潮流、波浪以及波、流共同作用下的悬移质挟沙能力及输沙率公式.野外和室内资料验证表明了公式的合理性,进而表明了公式所依据的基本理论的普适性。     

航空货运多航段多阶段模型

在航空货运运力分配中需要解决两个问题:一是选择哪条航段来运输货物,二是在满足货物运输的前提下,选择哪个时期运输货物.本文使用数学规划方法建立了航空货运多航段多阶段模型,以解决航空货运运力分配中的两个问题.通过实例数值仿真,证明了该模型的有效性,并揭示了飞机的承载能力、航段的收益水平和货物的利润水平对舱位分配策略影响较大.     

Platoons of connected vehicles can double throughput in urban roads

Intersections are the bottlenecks of the urban road system because an intersection’s capacity is only a fraction of the maximum flows that the roads connecting to the intersection can carry. This capacity can be increased if vehicles cross the intersections in platoons rather than one by one as they do today. Platoon formation is enabled by connected vehicle technology. This paper assesses the potential mobility benefits of platooning. It argues that saturation flow rates, and hence intersection capacity, can be doubled or tripled by platooning. The argument is supported by the analysis of three queuing models and by the simulation of a road network with 16 intersections and 73 links. The queuing analysis and the simulations reveal that a signalized network with fixed time control will support an increase in demand by a factor of (say) two or three if all saturation flows are increased by the same factor, with no change in the control. Furthermore, despite the increased demand vehicles will experience the same delay and travel time. The same scaling improvement is achieved when the fixed time control is replaced by the max pressure adaptive control. Part of the capacity increase can alternatively be used to reduce queue lengths and the associated queuing delay by decreasing the cycle time. Impediments to the control of connected vehicles to achieve platooning at intersections appear to be small.     

Prohibited–permitted right-turn phasing strategy based on capacity analysis of right-turn movements

In traffic-crowded metropolitan areas, such as Shanghai and Beijing in China, right-turn vehicles that operate with a permitted phase at signalized intersections are normally permitted to filter through large numbers of pedestrians and bicycles. To alleviate such conflicts and improve safety, traffic engineers in Shanghai introduced a prohibited–permitted right-turn operation, adding a subphase to the permitted phase in which right-turns are prohibited. Unfortunately, the prohibited subphase would reduce the capacity of right-turn movements when it prohibits right turns even if there are few pedestrians and bicycles crossing the street. This paper aims at quantifying the impact of both non-vehicular flows and the prohibited subphase on the right-turn capacity, and then proposes a strategy to determine appropriate prohibited–permitted right-turn operation that minimizes the capacity reduction caused by the prohibited subphase. To achieve this goal, we improved the pedestrian and bicycle adjustment factor described in the Highway Capacity Manual by taking into account: (1) the variety in space competition between pedestrians and bicycles, and (2) the effect of two conflict zones in each phase on right-turn operation. In addition, we revised the capacity estimation model in the Highway Capacity Manual, and developed a model based on bicycle/pedestrian volume fluctuation to describe the capacity reduction due to both non-vehicular flows and the prohibited subphase. Furthermore, we proposed a timing strategy for the onset and duration of appropriate prohibited subphase. When bicycle and pedestrian volumes are low, the actuated strategy turns to the permitted phase. When these volumes are moderate, the strategy turns to the prohibited–permitted operation. With the volumes increasing, the prohibited subphase onset advances and duration increases. In these two scenarios, the new strategy has higher right-turn capacity than the current pretimed prohibited–permitted operation. Unfortunately, when bicycle and pedestrian volumes are high, the strategy yields similar right-turn capacity. However, the new prohibited subphase has less potential vehicle–bicycle and vehicle–pedestrian conflicts.     

Optimal timetable development for community shuttle network with metro stations

This paper investigates an issue for optimizing synchronized timetable for community shuttles linked with metro service. Considering a passenger arrival distribution, the problem is formulated to optimize timetables for multiple community shuttle routes, with the objective of minimizing passenger’s schedule delay cost and transfer cost. Two constraints, i.e., vehicle capacity and fleet size, are modeled in this paper. The first constraint is treated as soft, and the latter one is handled by a proposed timetable generating method. Two algorithms are employed to solve the problem, i.e., a genetic algorithm (GA) and a Frank–Wolfe algorithm combined with a heuristic algorithm of shifting departure times (FW-SDT). FW-SDT is an algorithm specially designed for this problem. The simulated and real-life examples confirm the feasibility of the two algorithms, and demonstrate that FW-SDT outperforms GA in both accuracy and effectiveness.     

船体结构加筋板极限强度的影响因素

为了探究邮轮异型甲板结构的强度底数,针对邮轮剧院布置使用的非常规阶梯甲板进行极限承载力研究。

基于ABAQUS准静态方法计算阶梯甲板的极限承载力,确定结构的薄弱位置,并与常规甲板失效模式进行对比,同时探究甲板、纵骨、纵桁腹板以及纵桁面板厚度变化对结构极限承载力的影响,提出支柱加强和纵桁加强两种结构优化方法。

结果表明：阶梯甲板的失效主要发生在高度差最大的层交界处,极限承载力较常规甲板大幅下降,对应的压缩位移和塌陷深度明显增大;极限承载力会随甲板、纵骨、纵桁腹板以及纵桁面板厚度的增大而增大,其中纵桁腹板厚度变化的提升效果最显著;在结构薄弱位置增设支柱,或增大该处纵桁腹板高度能有效提高结构的极限承载力。

所做研究对指导现代邮轮特殊甲板的设计和优化具有重要意义。

     

环境约束下中国交通运输业产能利用测算

测度交通运输业产能利用可帮助交通行业应对产能优化和节能减排的双重挑战,实现高质量发展。研究旨在环境约束视角下,构建一个普适性的产能利用(CU)评价框架,并用于交通运输业产能利用测度研究。将交通运输业能源消耗量和CO2排放量纳入产能利用评价框架,采用改进的基于数据包络分析的差分法,测度2011～2017年中国交通运输业产能利用。研究结果表明:①2011～2017年间中国交通运输业平均CU值为0.026 0,并以2014年为临界点,呈现先降后增的趋势,这表明中国交通运输业确实存在产能利用不足的问题,且2015～2017年非常严重;②交通运输业产能利用水平区域差异化显著,研究期内与中国其他地区的CU水平相比,西南地区产能利用不足问题最严重;③与原始差分法的测度结果进行对比,所提出的改进方法更具合理性和先进性;④推动交通技术创新发展和合理规划交通资源是产能利用水平提升的关键途径。该研究为制定交通运输业产能利用提升的政策提供科学依据,对建立完善的交通运输业产能利用监测体系具有实际指导意义,有利于实现中国交通运输业产能利用水平整体的提升。