Ultimate torsional strength of flat-bar stiffeners attached to flat plating under axial compression

A parametric study based on numerical analysis using an efficient non-linear finite element method code is presented for the simulation of the interactive flexural-torsional failure behaviour of flat-bar stiffeners in plates under uniform axial compression. The restraining effect of the structural components on one another is investigated by varying the plate and stiffener slenderness. Initial imperfection levels partinent to marine structures have been accounted for. Strength curves for the allowable stress at the top of the stiffener due to elasto-plastic torsional buckling are given for use with approximate design formulas.     

A study of economic indicators in rail freight traffic cycles 1950–76

This paper examines the characteristics of rail freight traffic cycles from 1950 to 1976. Both the NBER's statistical indicator approach and time series approach are used to identify the leading indicators of rail freight traffic cycles from a set of leading economic indicators published by the Department of Commerce. The concepts and empirical results obtained by these two procedures are compared and contrasted. The interesting findings are: (1) the composite index of 12 leading indicators performs very well as a qualitative and quantitative predictor and (2) the empirical results obtained by the NBER approach are, in general, consistent with those obtained by the time series approach.     

The impact of fare and gasoline price changes on monthly transit ridership: Empirical evidence from seven U.S. transit authorities

This paper presents eight empirical models of monthly ridership for seven U.S. Transit Authorities. Within the framework of these models, the impacts upon monthly ridership from changes in the real fare and gasoline prices are examined. Important findings are: (1) the elasticities of monthly transit ridership with respect to the real fare are negative and inelastic, ranging from 0.042 to 0.62; and (2) the elasticities of monthly transit ridership with respect to the real gasoline price are positive and inelastic, ranging from 0.08 to 0.80. Such results have important policy implications for decisions based on the relationships of price, revenue, and ridership; and for assessing the impacts of changing gasoline prices upon urban modal choice.     

Measuring the Cost of Beach Retreat

We estimate the cost over the next 50 years of allowing Delaware's ocean beaches to retreat inland. Since most of the costs are expected to be land and capital loss, especially in housing, we focus our attention on measuring that value. We use a hedonic price regression to estimate the value of land and structures in the region using a data set on recent housing sales. Then, using historical rates of erosion along the coast and an inventory of all housing and commercial structures in the threatened coastal area, we predict the value of the land and capital loss assuming that beaches migrate inland at these historic rates. We purge the losses of any amenity values due to proximity to the coast, because these are merely transferred to properties further inland. If erosion rates remain at historic levels, our estimate of the cost of retreat over the next 50 years in present value terms is about $291 million (2000$). The number rises if we assume higher rates of erosion. We compare these estimates to the current costs of nourishing beaches and conclude that nourishment make economic sense, at least over this time period.     

新型可拆卸开孔钢管连接件抗剪性能

为适用预制钢-混凝土组合桥梁快速装配化施工需求,提出一种新型可拆卸的开孔钢管连接件。通过设计不同钢管壁厚、开孔板条宽度与高度等参数的开孔方钢管连接构造试件,开展水平推出试验,研究其抗剪承载力、抗剪刚度、剪切破坏模式及相对滑移特征。考虑钢材理想弹塑性、混凝土塑性模型及钢-混凝土界面非线性接触,建立可拆卸连接件抗剪分析的高效精细有限元模型,并通过试验结果验证。采用验证的有限元模型,进行与方钢管具有相同用钢量、板厚、开孔形式的圆钢管连接件抗剪性能对比分析。研究结果表明：可拆卸钢管连接件不仅具有开孔板连接件相当的抗剪承载力,而且比焊钉连接件具有更好的延性;增加钢管壁厚能有效提高其抗剪刚度与强度,改变底部开孔形状对连接件的抗剪刚度影响较小,但对强度影响较大;圆管与方管连接件具有相当的剪切屈服强度,但方管连接件的极限抗剪强度更高,而圆管连接件的延性更好;塑性理论推导可拆卸连接件剪切屈服强度计算结果同试验、有限元结果吻合良好,证明该计算式准确、有效;建议荷载作用下,混凝土板不发生开裂和压溃,可拆卸连接件可屈服进入塑性状态,实现混凝土板、钢梁易更换、修复或重复利用。     

A model to assess cost and fuel savings from ride sharing

A model based on geometric probability concepts is developed to assess the performance of carpooling and vanpooling strategies. Fuel consumption and operating cost issues are treated in the paper, and the model can be extended to treat travel time and air quality issues also. It is shown that simple calculations of the fuel saved through carpool programs can overstate the savings by a factor of two. The operating costs of vanpools and carpools are also compared.     

Transport emissions and travel behaviour: A critical review of recent European Union and UK policy initiatives

There are clear signs of a shift in the UK transport policy in response to concerns about the environmental impacts of road transport and anxieties about the implications of the projected future growth in demand.Much of the framework of UK transport policy is now determined at the overall European Union level. To date most European legislation and policy proposals have been concerned with reducing the specific externalities associated with the transport sector, with none of the measures involved likely to have more than a marginal impact on the growth in demand. The emerging research evidence suggests however that the private costs of car use in Europe may fall substantially short of its total social costs and there is an important emerging policy debate about how this gap might be closed.The UK has introduced a policy package designed to reduce the growth of car travel and its environmental impact, within which land-use planning measures feature prominently. The land-use policies, which to some extent represent a reassertion of many traditional UK planning policies, include: an emphasis on focussing new development in urban areas, increasing residential densities, strengthening the role of existing centres and improving provision for walking and cycling.A number of factors will constrain the effectiveness of the package in practice. There are also concerns about its impact on key environmental objectives, including air quality. There are important questions too about the welfare effects of increasing densities and about the wider impacts of the package on economic efficiency.     

The usefulness of the Sequence Alignment Methods in validating rule-based activity-based forecasting models

This research paper aims at achieving a better understanding of rule-based activity-based models, by proposing a new level of validation at the process model level in the A Learning-based Transportation Oriented Simulation System (ALBATROSS) model. To that effect, the work activity process model, which includes six decision steps, has been investigated. Each decision step is evaluated during the prediction of the individuals?? schedules. There are specific decision steps that affect the execution pattern of the work activity process model. So, the comportment of execution in the process model contains activation dependency. This branches the execution and evaluation of each agent under examination. Sequence Alignment Methods (SAM) can be used to evaluate how similar/dissimilar the predicted and observed decision sequences are on an agent level. The original Chi-squared Automatic Interaction Detector decision trees at each decision step utilized in ALBATROSS are compared with other well known induction methods chosen to appraise the purpose of the analyses. The models are validated at four levels: the classifier or decision step level whereby confusion matrix statistics are used; The work activity trips Origin?CDestination matrix level; the time of day work activity start time level, using a correlation coefficient; and the process model level, using SAM. The results of validation on the proposed process model level show conformity to all validation levels. In addition, the results provide additional information in better understanding the process model??s behavior. Hence, introducing a new level of validation incur new knowledge and assess the predictive performance of rule-based activity-based models. And assist in identifying critical decision steps in the work activity process model.     

沥青路面的全厚式再生暨泡沫沥青稳定

大功率的道路现场回收机械在过去一、二十年得以开发并不断改进。并配备有现代化的计算机控制的外加剂添加装置。这使得全厚式再生技术成为快速发展的技术之一,也成为各国路面工程师优先采用的路面修复技术之一。与传统的翻修相比,全厚式再生技术充分保护利用道路初建时的旧材料,降低大修费用,大幅度减少施工时间。现场再生技术被分类为现场冷再生、现场热再生和全厚式再生。本文在指出它们之间的区别后,重点介绍全厚式再生技术的施工工艺过程,候选路面的评估和修复设计,外加剂的选择和施工中的质量控制和质量保证措施。本文最后给出笔者的一个用泡沫沥青稳定的全厚式再生的工程项目实例。     

Is Somali piracy a random phenomenon?

This paper investigates whether Somali piracy is a random phenomenon. The investigation takes place in two distinct parts. Its statistical analysis spans over a period of 11 years, from 2000 until 2011 for the first part (flags), and 5 years, from 2007 until 2011 for the second one (crews). The reason is that although prior to 2007 there have been a substantial number of attacks (parameter used in the first part of the research), very few ships were practically pirated (parameter used in the second part) within the same period. Firstly, it is widely believed that Somali pirates select their targets at random and the decision on attacking a vessel registered under a particular flag is unrelated to the participation of the flag state in any of the naval forces operating around the Horn of Africa. The enquiry attempts to assess whether these two common beliefs are supported by historical data and to what extent. Secondly, this paper asks whether there are certain nationalities of crews which are for ethnic and/or cultural reasons more (or less) vulnerable to fall victims of pirates off Somalia. Such groups (if there are any) would in effect indirectly ‘support’ Somali piracy, and for this reason, they could be considered as ‘passively supportive crews’. The analysis focuses on the crew composition of the attacked vessels with special interest cast upon those ships (meaning the crews) which eventually succumbed to Somali pirates and were in the end seajacked.