基于加固寿命周期成本最小的桥梁维修决策

提出了桥梁维修加固应该像新建桥一样进行寿命周期成本分析,同时提出了加固桥梁的加固寿命周期成本的概念,为加固决策提供了一种决策方法。应用年值成本概念对寿命周期不一样的方案进行比较。     

Influences on bicycle use

A stated preference experiment was performed in Edmonton in Canada to both examine the nature of various influences on bicycle use and obtain ratios among parameter values to be used in the development of a larger simulation of household travel behaviour. A total of 1128 questionnaires were completed and returned by current cyclists. Each questionnaire presented a pair of possible bicycle use alternatives and asked which was preferred for travel to a hypothetical all-day meeting or gathering (business or social). Alternatives were described by specifying the amounts of time spent on three different types of cycling facility and whether or not showers and/or secure bicycle parking were available at the destination. Indications of socio-economic character and levels of experience and comfort regarding cycling were also collected. The observations thus obtained were used to estimate the parameter values for a range of different utility functions in logit models representing this choice behaviour. The results indicate, among other things, that time spent cycling in mixed traffic is more onerous than time spent cycling on bike lanes or bike paths; that secure parking is more important than showers at the destination; and that cycling times on roadways tend to become less onerous as level of experience increases. Some of these results are novel and others are consistent with findings regarding bicycle use in work done by others, which is seen to add credence to this work. A review of previous findings concerning influences on cycling behaviour is also included.     

紫坪埔隧道小净距段施工方案模型试验研究

为节约工程造价,董家山隧道汶川端设计为渐变小净距隧道与整幅修建的泯江大桥相接。该端隧道洞口段左、右线间距较小,围岩较差。为保证隧道的安全施工,利用模型试验对洞口小净距段岩墙的加固措施、开挖方式及支护体系等施工方案进行了研究,提出了该段合理的施工方法和岩墙加固措施的建议,为董家山隧道小净距段的顺利施工提供指导。     

车辆超载对新疆地区干线公路沥青路面的损伤影响分析

目前新疆地区主要干线等级公路的车辆超载现象十分严重,从而对沥青路面造成很大的损伤和破坏,使其正常使用寿命大大降低。以新疆某干线公路典型的半刚性路面结构为例,针对车辆超载情况并考虑到超载时轮胎接地压力为非均匀分布的特点,运用三维有限元方法分析了路面弯沉、轴载及基层模量之间的关系以及超载对路面使用寿命的影响。     

Numerical modelling of fish eggs dispersion at the Patos Lagoon estuary — Brazil

The Patos Lagoon estuary is the most important nursery ground for commercially relevant species of fish and crustaceans in the South of Brazil, maintaining fisheries that sustain 3500 fisher families throughout the Rio Grande do Sul State coastline. Around 80% of the interior estuarine area is very shallow (< 2 m), and recruitment of fish eggs and larvae to the inner parts of the Patos Lagoon estuary is directly related to the circulation pattern in the area, which is controlled by local and non-local wind effects and freshwater discharge. The objective of this study is to investigate the processes controlling the transport of estuarine dependent fish eggs between the Atlantic Ocean and the Patos Lagoon estuary.An integrated numerical system based on a bi-dimensional hydrodynamic model and a Lagrangean transport model of passive particles is applied to a selection of scenarios representing the passage of weather fronts over the area. At this stage, fish eggs are represented as buoyant passive particles. Modelling results are compared against field data for the period under investigation (September/October 1999) and historical records. Short term results are analysed in terms of the meteorological conditions (wind direction, intensity and duration) controlling the transport of eggs to the inner parts of the estuary and the extension of their excursion. This experiment is the first attempt to couple biological and physical information to study fish eggs transport, and to enhance the current knowledge about recruitment of important fisheries resources in southern Brazil.     

基于过程控制的机车状态修管理系统

建立基于过程控制的机车状态修管理系统,采用过程控制与机车状态修工作的有机结合,使机车状态修的整个工作过程成为完整有机的整体,通过强化过程控制来实现铁路运输的安全。     

Comparing whole-link travel time models

In a model commonly used in dynamic traffic assignment the link travel time for a vehicle entering a link at time t is taken as a function of the number of vehicles on the link at time t. In an alternative recently introduced model, the travel time for a vehicle entering a link at time t is taken as a function of an estimate of the flow in the immediate neighbourhood of the vehicle, averaged over the time the vehicle is traversing the link. Here we compare the solutions obtained from these two models when applied to various inflow profiles. We also divide the link into segments, apply each model sequentially to the segments and again compare the results. As the number of segments is increased, the discretisation refined to the continuous limit, the solutions from the two models converge to the same solution, which is the solution of the Lighthill, Whitham, Richards (LWR) model for traffic flow. We illustrate the results for different travel time functions and patterns of inflows to the link. In the numerical examples the solutions from the second of the two models are closer to the limit solutions. We also show that the models converge even when the link segments are not homogeneous, and introduce a correction scheme in the second model to compensate for an approximation error, hence improving the approximation to the LWR model.     

An Alternative to the Roll Axis for Use in Commercial Vehicle Simulation

Vehicle dynamicists have frequently assumed that the roll motions of the sprung mass take place about a roll axis. Equations of motion based on this assumption must be expected to exhibit dynamic coupling, a significant complication in the case of digital computer simulations of multi-unit vehicles.

Digital simulations have been developed which, while preserving the physical character of the roll axis formulation, use further approximations to avoid the dynamic coupling. Validation exercises have been performed which demonstrate the accuracy of this methodology.     

A note on trip matrix estimation from link traffic count data

In this note, a simple network equilibrium based approach for estimating a trip matrix using link traffic count data is proposed. In essence a combined distribution and assignment model is formulated in which the link flow data serve to furnish an estimate for the sum of the integrals of the link cost functions. A comparison of this model with others proposed previously is made.