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文章基于宁夏灵武黄河特大桥桥墩托盘的裂缝调查情况,利用有限元模型从力学角度分析了托盘裂缝产生的原因,提出了预应力筋、碳纤维布、预应力筋+碳纤维布三种加固方案,并对比分析了各方案的加固效果。 相似文献
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Given a road network, a fundamental object of interest is the matrix of origin destination (OD) flows. Estimation of this matrix involves at least three sub-problems: (i) determining a suitable set of traffic analysis zones, (ii) the formulation of an optimisation problem to determine the OD matrix, and (iii) a means of evaluating a candidate estimate of the OD matrix. This paper describes a means of addressing each of these concerns. We propose to automatically uncover a suitable set of traffic analysis zones based on observed link flows. We then employ regularisation to encourage the estimation of a sparse OD matrix. We finally propose to evaluate a candidate OD matrix based on its predictive power on held out link flows. Analysis of our approach on a real-world transport network reveals that it discovers automated zones that accurately capture regions of interest in the network, and a corresponding OD matrix that accurately predicts observed link flows. 相似文献
396.
This paper concerns the development of a new decision support framework for the appraisal of transport infrastructure projects. In such appraisals there will often be a need for including both conventional transport impacts as well as criteria of a more strategic and/or sustainable character. The proposed framework is based on the use of cost-benefit analysis featuring feasibility risk assessment in combination with multi-criteria decision analysis and is supported by the concept of decision conferencing. The framework is applied for a transport related case study dealing with the complex decision problem of determining the most attractive alternative for a new fixed link between Denmark and Sweden – the so-called HH-connection. Applying the framework to the case study made it possible to address the decision problem from an economic, a strategic, and a sustainable point of view simultaneously. The outcome of the case study demonstrates the decision making framework as a valuable decision support system (DSS), and it is concluded that appraisals of transport projects can be effectively supported by the use of the DSS. Finally, perspectives of the future modelling work are given. 相似文献
397.
The LAX North Airfield Safety Study was undertaken by an Academic Panel consisting of the present authors, and was based in large part on a simulation that was conducted at FutureFlight Central at NASA Ames Research Center. The primary aim of the study was “to estimate as specifically as possible the level of future safety associated with several geometrical configurations of the LAX North Airfield.” This paper describes the study, and how it combined information from human-in-the-loop simulations at NASA with historical data from LAX and other US airports about runway incursions and collisions. The analysis indicated that, even under its existing physical layout, LAX North would experience very low risk of runway collisions at traffic levels projected for 2020. That risk could be reduced by about half if the North Airfield runways were reconfigured, and some reconfigurations would also add appreciably to the operational efficiency of the airport. But because the “baseline” level of risk is so low, the Study concluded that “it would be difficult to construct a compelling case on safety grounds alone for reconfiguring the North Airfield.” 相似文献
398.
This study describes a methodology to quantify and characterize the vehicular emissions of functionally interdependent roundabouts at a corridor level. Corridor segments include those upstream of each roundabout, the circulating area, downstream of the roundabout as well as midblock sub-segments between adjacent roundabouts. The main purpose of the study is to identify the locations along the corridors where emissions tend to be consistently high. These locations are termed “Emission Hotspots”. The methodology is applied to four existing roundabout corridors in San Diego (California) and Avon (Colorado) in the United States, and in Mealhada and Chaves (Portugal). An extensive sample of second-by-second speed traces is available for these four corridors with roundabouts.The analysis shows that when roundabouts are fairly spaced and have similar geometric design features, no significant differences are observed between emissions of roundabouts located in the corridor. In such cases, the downstream sub-segments are the emission hotspots both in absolute terms (overall contribution on total emissions is higher than 34%) and per unit distance (22% higher than the average corridor value). When roundabouts are unequally spaced the highest emissions hotspots (more than 9% above the average corridor value) are found at the circulating area sub-segments. The results also demonstrate that the entry deflection angle has a slight impact on the spatial distribution of emissions especially in the case of closely spaced roundabouts. 相似文献
399.
Transportation is a major cause for environmental degradation via exhaust emissions. For many transit-oriented metropolitan areas, bus trips often constitute a sizeable mode share. Managing the bus fleet, in particular updating buses to comply with the newer emissions standards, therefore, can have a substantial impact on transportation-induced air quality. This paper presents the approach of remaining life additional benefit–cost (RLABC) analysis for maximising the total net benefit by either early-retiring or retrofitting the current bus fleet within their lifespans. By referring to the net benefits for different bus types estimated by RLABC analysis, the most beneficial management scheme for the current bus fleet can be identified. Optimal bus fleet management (BFM) models based on the RLABC analysis for the operator and the government are developed. Then a government subsidy plan is produced to achieve win–win solutions, which will offer efficient and flexible management schemes. To illustrate the approach, the largest bus company in Hong Kong, which carries more than 23% of the total trips in Hong Kong, is taken as a case study example. Instead of adopting a fixed retirement plan, such as replacing buses at the age of 17 as is currently practised, the proposed method develops an optimal BFM scheme that progressively phases out buses or retrofits them. This study produces promising results to demonstrate the large benefit of this approach for optimal bus fleet management. 相似文献
400.
泡沫沥青冷再生施工作为一种路面废旧材料再生利用新型冷再生技术,其混合料除了具有良好的路用性能,施工中还可以起到明显的节能减排作用,是发展循环经济、创建环境友好节约型社会的重要举措,目前已开始得到应用和推广;通过对泡沫沥青冷再生施工技术节能效益分析,了解其节约资源、保护环境、减少污染、降低造价等优点。 相似文献