Energy savings due to land transportation management in Singapore

Singapore has been actively engaged in implementing various land transportation policies and traffic management schemes since the early 1970s to reduce traffic congestion. This paper examines the benefits in energy savings arising from the following five major schemes: (a) the Area Licensing Scheme, (b) the computerised Area Traffic control System, (c) the adaptive traffic control system, (d) the exclusive bus lane scheme, and (e) the island-wide expressway system. The analyses are made based on the findings of a two-year study that developed vehicle fuel consumption models for Singapore traffic. The Area Licensing Scheme that restricts traffic flow into the Central Business District (CBD) is found to have the greatest energy impact, followed by the island-wide expressway system and the traffic-signals control systems within the CBD.     

Pollution history of a tropical estuary revealed by combined hydrodynamic modelling and sediment geochemistry

Hydrodynamic modelling of water movement in Hunts Bay, a protected part of Kingston Harbour, Jamaica, shows that depth averaged tidal flows are very low. In the northeast corner of Hunts Bay, water is essentially stagnant. Even under high flow conditions, much of the Bay bottom water is ‘bypassed' by buoyant, lower salinity surface flows. The muddy sediments of Hunts Bay reflect these sluggish to stagnant conditions; sediment cores from the northeast corner of the Bay contain progressively higher amounts of organic matter in their upper parts (last 15–20 years sedimentation). Combined C/N ratios and stable carbon isotope compositions of this organic matter imply a sewage origin. Both lead and chromium metal concentrations and enrichment factors relative to average crustal shales show geographically related patterns that reflect hydrodynamic circulation predicted by modelling. In particular, metal concentrations and enrichment factors are highest at the northern end of the bay, especially in the northeast corner. Modelling confirms that stagnant conditions would occur in the northeast part of the bay even without the presence of a major causeway. The causeway may contribute to low flow conditions, but is not the principal cause of organic contamination, which is simply an excessive input of sewage.     

上软下硬地层大直径土压平衡盾构下穿民房建筑群沉降控制北大核心CSCD

依托广州地铁18号线盾构施工,针对其地层分布复杂、软硬差异大及穿越密集民房建筑群等特点,通过注浆加固、现场动态监测、优化掘进参数等一系列主动措施,解决实际工程中掘进参数合理取值与地表建筑沉降变形控制两大难题。研究结果表明:(1)在该类软硬地层中掘进时,刀盘在通过不同岩层断面分界线时扭矩、推力等参数波动较大,总推力与扭矩有良好的相关性,各掘进参数宜控制为:推力30000~35000 kN、扭矩4500~6000 kN·m、推进速度35~45 mm/min;(2)提出的多段式封孔洞内超前注浆工艺可使刀盘前18 m范围内的地表上抬3~5 mm,最大上抬值能达9.02 mm,同时能缓解土体在盾构下穿时及后续固结稳定的沉降趋势;(3)因刀具磨损、掘进参数波动大、螺旋机卡死等引起的临时停机会造成地表建筑日沉降速率超过3 mm/d,在预设停机点位置前采取洞内超前注浆和克泥效工法能有效缓解沉降趋势,在带压开舱期间日沉降速率控制在2 mm/d以下;(4)左右隧道轴线附近的地表建筑沉降基本可分为“微小隆起—沉降较大—逐渐稳定”三个阶段,测点最大沉降值最终稳定在-21.38 mm、-22.49 mm,均小于控制值。     

BFRP加固损伤混凝土梁挠度计算方法

为了准确计算玄武岩纤维增强复合材料(BFRP) 加固损伤混凝土梁的挠度, 为BFRP加固损伤混凝土梁的设计与施工提供理论依据, 按照配筋率不同设计了11片试验梁进行试验, 每组试验梁设置不同的BFRP布加固量与加载方法。计算了各试验梁的荷载-挠度曲线, 分析了未加固梁、1层BFRP布加固梁、2层BFRP布加固梁在不同初始荷载下的挠度变化规律。给出了BFRP加固损伤混凝土梁跨中挠度的计算公式, 对比了挠度计算值与实测值。分析结果表明: BFRP加固混凝土梁的挠度受初始荷载和加固量的影响, 有初始荷载的加固梁挠度较无初始荷载的加固梁挠度增大30%~4%, 2层BFRP布加固梁的挠度较1层加固梁的挠度增大19%~2%, 计算挠度时需考虑BFRP布滞后应变的影响; 挠度计算值与实测值的最大差值平均为7.26 mm, 初始荷载小与配筋率高的试验梁挠度计算值与实测值较为接近, 可以用于实际工程计算。     

Proposal for Testing and Rating of Traction and Stability Control Systems

Function and object of existing control systems for traction and stability are described. The problem of rating and objective evaluation of the influence of such slip control systems on vehicle dynamics is demonstrated. Closed-loop manoeuvres with subjective assessment and open-loop tests with measured data are shown. Analysis of correlation results in characteristic values which allow assessment of dynamic performance of slip control systems. Tests on natural and synthetic μ-low road surface with two passenger cars, equipped with different slip control systems, demonstrate the objective test method and show their results.     

Theoretical Comparison Between Different Configurations of Radial and Conventional Bogies

This article compares the dynamic behaviour of different configurations of radial and conventional two-axle bogies. In general, the design parameters for a better curve negotiation are not compatible with those for good stability. As the main target of this article is to compare the curving performances of different bogies under the same design basis, several bogie configurations with the same level of stability, obtained by choosing proper primary suspension stiffnesses, have been used. The comparison includes a conventional bogie and three radial bogies with differing self-steering and forced-steering principles in three different passenger services: High Speed, Regional and Mass Transit. The analysis has been concentrated on parameters such as stability, lateral wheel-track forces in curve and wheel wear indices. The results show that the radial bogie configurations studied do not make significant contributions in general applications with regard to a conventional bogie. It is only under specific running conditions and types of service that some radial bogie configurations provide advantages with respect to the conventional bogie.     

PACDIN statement of methods

PAntograph–Catenary Dynamic Interaction (PACDIN) is a code developed by the vehicle technology research centre (CITV) of the Universitat Politècnica de València in collaboration with the railway company Talgo S.L. The model of the catenary is a finite element model using absolute nodal coordinates. It is based on a general formulation that can be applied for analysing a wide range of catenary configurations, including stitch wire, transitions or non-straight path tracks. The formulation is fully non-linear and includes large deformations, dropper slackening and contact interaction. The model is linearised when deformations are small, as in the case of the benchmark dynamic analysis. The results of the PACDIN code show a good agreement with the average results of other benchmark codes.     

Lateral Dynamics of Commercial Vehicle Combinations A Literature Survey

This paper presents a review of theoretical and experimental works relative to the handling performance of commercial vehicle combinations. A commercial vehicle combination (road train) is defined as a tractor unit and an arbitrary number of trailers. The review contains literature corresponding the most widely used types of trains: tractor-semitrailer, truck-trailer and tractor-semitrailer-semitrailer (doubles). The vehicle dynamic performance has been investigated taking into consideration the following features: directional performance, roll dynamics, braking performance and combined braking and directional performance. With the aim of evaluating the present state of research activities in the field of lateral dynamics of articulated commercial vehicles, the author has compiled some 250 references.