Influence of polygonal wear of railway wheels on the wheel set axle stress

The coupled vehicle/track dynamic model with the flexible wheel set was developed to investigate the effects of polygonal wear on the dynamic stresses of the wheel set axle. In the model, the railway vehicle was modelled by the rigid multibody dynamics. The wheel set was established by the finite element method to analyse the high-frequency oscillation and dynamic stress of wheel set axle induced by the polygonal wear based on the modal stress recovery method. The slab track model was taken into account in which the rail was described by the Timoshenko beam and the three-dimensional solid finite element was employed to establish the concrete slab. Furthermore, the modal superposition method was adopted to calculate the dynamic response of the track. The wheel/rail normal forces and the tangent forces were, respectively, determined by the Hertz nonlinear contact theory and the Shen–Hedrick–Elkins model. Using the coupled vehicle/track dynamic model, the dynamic stresses of wheel set axle with consideration of the ideal polygonal wear and measured polygonal wear were investigated. The results show that the amplitude of wheel/rail normal forces and the dynamic stress of wheel set axle increase as the vehicle speeds rise. Moreover, the impact loads induced by the polygonal wear could excite the resonance of wheel set axle. In the resonance region, the amplitude of the dynamic stress for the wheel set axle would increase considerably comparing with the normal conditions.     

Activity patterns,time use,and travel of millennials: a generation in transition?

Millennials, defined in this study as those born between 1979 and 2000, became the largest population segment in the United States in 2015. Compared to recent previous generations, they have been found to travel less, own fewer cars, have lower driver’s licensure rates, and use alternative modes more. But to what extent will these differences in behaviour persist as millennials move through various phases of the lifecycle? To address this question, this paper presents the results of a longitudinal analysis of the 2003–2013 American Time Use Survey data series. In early adulthood, younger millennials (born 1988–1994) are found to spend significantly more time in-home than older millennials (born 1979–1985), which indicates that there are substantial differences in activity-time use patterns across generations in early adulthood. Older millennials are, however, showing activity-time use patterns similar to their prior generation counterparts as they age, although some differences – particularly in time spent as a car driver – persist. Millennials appear to exhibit a lag in adopting the activity patterns of predecessor generations due to delayed lifecycle milestones (e.g. completing their education, getting jobs, marrying, and having children) and lingering effects of the economic recession, suggesting that travel demand will resume growth in the future.     

Can Coastal Management Programs Protect and Promote Water-Dependent Uses?

Anecdotal evidence indicates that commercial and recreational water-dependent uses have been under development pressure in recent years, and in some cases have been converted to other uses. The conversion of water-dependent uses, which range from commercial shipyards to recreational marinas, may have many public costs, including the loss of access to public trust waters, the loss of jobs and associated economic activity, and the loss of traditional working waterfronts. This two-part study investigated the role of five coastal management programs in the northeastern United States in managing, monitoring, and protecting water-dependent uses. First, coastal managers in Massachusetts, Rhode Island, Connecticut, New York and New Jersey were interviewed to assess the conversion problem. Second, in collaboration with New York City-based Regional Plan Association, follow-up interviews were conducted with coastal managers and local planners in Connecticut, New York, and New Jersey to gain greater insight into the role of coastal management programs and local governments in managing and promoting water-dependent uses. This article presents select findings from this study and discusses recommendations for improving the capacity of coastal management programs and local governments to manage water-dependent uses for the benefit of the public.     

综合管廊有偿使用收费方式及其适用性探究

采用理论研究和案例分析法针对城市地下综合管廊有偿使用收费方式进行了详细的探讨，并依托成都市IT大道地下综合管廊工程，同时借鉴了日月大道、成洛大道、成渝高速入城段等试点管廊的相关参数测算综合管廊有偿使用费，其中入廊费和日常维护费分别采用直埋成本法和空间比例法进行计算，建立了成都市地下综合管廊入廊费和日常维护费收费标准。研究结果表明采用该方法测算得到的成都市管线入廊费和日常维护收费标准较适应管线现状实际建设和运维情况，更易让各管线单位接受。     

城市道路沥青路面结构力学响应分析

针对济南市城市道路常用的三种主要沥青路面结构形式,半刚性基层、复合式基层及柔性基层路面结构,该文采用壳牌设计软件BISAR 3.0计算三种结构沥青路面的应力、应变响应,对各自受力不利形式及空间位置进行对比分析.通过比较,证明:从力学角度分析,复合式基层沥青路面在各项力学性能均优于半刚性基层沥青路面及柔性基层沥青路面,推...     

交通拥堵反思

通过对交通拥堵进行反思,认为交通拥堵是充满活力的成功城市的伴生品,应从不同角度考虑拥堵问题.提出了十项有别于传统观点的提议,主要包括:机动性至关重要,交通拥堵是社会、经济活力的象征;道路扩容效果短暂,并会诱发潜在需求,但仍可带来一定的社会、经济效益;土地使用对出行行为的改变需要长期的努力;紧凑型发展会加剧交通拥堵;降低...     

城市土地利用特征对居民出行方式的影响——以深圳市为例

为缓解日益严重的城市交通问题、优化居民出行方式,有必要研究城市土地利用与交通系统的协调问题.以深圳市为例,应用多元Logit模型(MNL模型),纳入城市土地利用变量与出行者的家庭、社会、经济等变量,分析其对居民工作与非工作出行方式的影响.研究结果表明,出行起点的城市区位是影响居民出行方式的重要因素之一.相对于组团中心和...     

柔性拱钢性梁桥设计

合肥铁路枢纽南环线跨合宁高速特大桥是一座铁路上跨高速公路的特大桥,该桥采用(114.75+229.5+114.75)m柔性拱刚性梁,主跨跨度在国内同类型桥梁中居于首位.介绍了该桥的总体设计、结构构造及总体施工方法.     

The development of the TIGRIS XL model: A bottom-up approach to transport, land-use and the economy

The project appraisal method in the Netherlands distinguishes direct effects, indirect distribution effects and indirect generative effects. Transport models are generally available for calculating the benefits of transport projects to travellers as part of the direct effects. The TIGRIS XL model, a Land-Use and Transport Interaction model, adds indirect distribution effects for the housing and labour market, by modelling changes in the spatial distribution of jobs and residents. This paper describes the current TIGRIS XL model and how it can be applied in the evaluation of transport projects. It refers to work done with the TIGRIS XL model to improve the calculation of the direct benefits by applying the so-called ‘logsum’ method. Finally it discusses ideas on how to extend the TIGRIS XL model to address indirect generative effects as well.The current TIGRIS XL model, its integration with the National Model System (the standard tool for the Dutch government to analyse the effects on passenger transport) and basic design principles are the starting point of such an exploration. These design principles include:

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an emphasis on detail, both spatial as well as in socio-economic segments, to account for differences in the availability of choice alternatives and in choice behaviour, and to provide impacts by region and socio-economic group;

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the requirement that the relationships used rest on an empirical foundation.

The post-processing methods proposed on this paper for the calculation of the direct benefits and indirect generative effects are consistent with these design principles. To calculate the indirect generative effects, a post-processing module is proposed which transforms changes in travel times and land-use into agglomeration effects. These agglomeration effects combine several of the generative effects, like scale economies, an increasing variety of products, labour market matches and knowledge spill-over. The effects of changes in the agglomeration indicator on productivity can be estimated with existing data sources, as was demonstrated in the UK (Graham, 2005).