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广东省英德市北江四桥大站镇岸跨堤引桥为单跨102 m超高性能混凝土(UHPC)简支箱梁桥,桥面总宽37 m, UHPC等级为R120。结合目前UHPC制备及浇筑工艺水平,主梁采用预制节段拼装箱梁结构,预制标准节段长4 m,梁高4 m,重约70 t;采用4 m标准间距密集横隔板,以减少薄壁箱梁的翘曲、畸变和剪力滞效应;横向设4片大箱梁,单片预制箱梁宽8.825 m,箱梁间设0.6 m宽桥面湿接缝;主梁采用短悬臂的同时将桥面板横肋间距加密至2 m。主梁采用全体外预应力体系,以适应薄壁箱梁构造;采用“三人孔横隔板”构造与转向块共同承担体外索转向力,降低了转向块应力水平;梁端采用整体式锚垫板,有效分散了体外索集中锚固力。 相似文献
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As Global Positioning System (GPS) technology advances, it has been increasingly used to supplement traditional self-reported travel surveys due to its promising features in capturing travel data with better accuracy and reliability. Realizing the limitations of diary-based surveys, this paper presents a study that directly accounts for trip misreporting behavior in trip generation models. Travel data were obtained from prompted-recall assisted GPS survey along with a diary-based survey. Negative Binomial models for count data were developed to accommodate misreporting behavior by introducing interaction effects of the sample-indicator variable with various personal and household variables. The interaction effects indicate how the impacts of the socioeconomic and demographic variables on trip-making vary across the two samples. Assuming that the GPS sample represents the ground truth, the interaction effects actually capture the likelihood and the extent of trip misreporting by detailed personal and household characteristics. The model results reveal significant interaction effects of several personal and household variables, indicating misreporting behavior associated with these attributes. The addition of interaction coefficients to the main effect model represents the real impacts of the independent variables, after compensating for trip misreporting behavior, if any. 相似文献
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Singfat Chu 《Transportation》2018,45(5):1419-1432
Singapore’s Vehicle Quota System, implemented in 1990, uses uniform-price auctions to allocate Certificates of Entitlement (COE) or registration rights in five categories presently. Four of these are restricted to small and big cars, commercial vehicles and motorcycles. The fifth one is unrestricted as it allows successful bidders to register a vehicle in any restricted category of their choice. Owners are incentivised via another policy to deregister their vehicle by the tenth year expiry of the COE instead of revalidating it. Each deregistration results in a new COE. Currently, 10% of the COEs from each restricted category is channelled to the unrestricted category. However, hardly any of the expensive COEs in the unrestricted category has been used to register motorcycles. The sharp decline in the number of motorcycle COEs since 2014 has led to a surge in auction premiums at about twice the price of an entry-level motorcycle. The auction process before 2014 is shown to be exemplary with the COE premium driven by its inertia and a host of exogenous factors. After 2014 however, it appears to be unresponsive to the historically low quota levels. This undesirable auction trait needs to be remedied by a reformulation of the COE quota in order to help those most in need of a motorcycle to earn a living. Measures announced in the February 2017 Singapore Budget trudge in that direction. 相似文献
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为了保证大型船舶安全、经济地靠离码头,驾引人员应当对所需拖船协助力心中有数。国内外研究人员已在理论和实验方面做了大量的工作,但实用的计算方法仍不多见,且存在着一些问题。提高大型船舶横向靠离码头所需拖船协助力估算精度的关键是横流阻力系数C(wy)的估算。该文根据12条船模试验数据用逐步回归分析法获得了可以表达C(wy)与船型及水深之间关系的近似公式;同时依据大型船舶横向离码头实际是加减速运动这一事实,考虑了加速运动对C(wy)系数的影响;此外还分析了岸壁对船舶横向运动的影响。该文所提供的计算方法是实用和可靠的,可供船舶驾引人员使用,亦可供船舶操纵运动数学模型研究人员参考。 相似文献
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评标是工程项目招标程序中极为重要的环节。本文基于邓聚龙灰关联分析法理论,研究了灰关联熵分析法用于工程项目评标的原理和步骤,建立了灰关联熵分析法的评标模型。从而在一定程度上消除了以往评标工作中由于专家的主观性、随意性和倾向性所带的偏差。并通过实例对该模型进行了实证研究,表明了该方法的有效性。 相似文献
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