广西三江波里一桥半幅施工方案内力分析

文章针对广西三江波里一桥改建施工的实际情况,提出了桥梁半幅施工方案,并借助不同施工条件下成桥内力计算结果,探讨了桥梁半幅施工方案结构体系转换前后的内力变化情况,对比分析了半幅施工方案和整幅施工方案的成桥内力.分析表明,波里一桥半幅施工方案是可行的.     

南宁大桥水中主墩基础施工方案优化研究

文章针对广西南宁大桥主桥下部结构初步施工方案,结合现场施工条件,因地制宜地提出了大桥主墩基施工的优化方案,并通过与原施工方案对比及安全论证,验证了该优化方案的合理性。     

既有电气化线路增建第二线接触网区间换边拨接施工技术探讨

根据既有电气化线路增建第二线区间换边拨接施工的特点,介绍了接触网拨接施工方案,该施工方案能有效降低停电天窗时间及线路施工方案及其进度等因素对接触网施工的影响,确保接触网拨接施工的安全及其施工进度。     

浅析跨既有线施工方案编制与评审工作

跨越铁路既有线施工是一项难度大、对安全要求高的工作,因此铁路主管部门对施工方案的审查相当严格,从而给施工方案编制和评审工作提出了很高的要求。文章结合工程实践经验,介绍了跨铁路既有线施工方案编制的要点与注意事项,同时阐述了对跨铁路既有线施工方案评审工作的相关认识。     

浅谈钢板桩围堰在浅海区桥梁中的应用

文章以厦门某海湾大桥的钢板桩施工实践为例,对浅海区桥梁下构施工方案进行探讨,对比分析了钢吊箱围堰、钢套箱围堰、钢板桩围堰三个施工方案的经济性与技术性,确定采用钢板桩围堰施工方案,并对其设计要点、施工技术及注意事项进行了介绍。     

跨京九铁路立交桥转体设计与施工探讨

文章以津石高速公路上跨京九铁路立交桥转体施工为例,介绍了转体桥的总体设计和结构设计方案,计算分析了转体结构的力学性能,确定了转体桥施工方案,并对现场施工进行了监控量测。结果表明转体设计及施工方案可行。     

大跨度山区悬索桥钢桁加劲梁施工方案研究

文章以坝陵河大桥为研究对象,建立了全桥施工过程空间非线性分析模型,并采用全刚结法及有铰逐次刚结法两种加劲梁施工方案进行了施工全过程的模拟仿真计算,研究了不同加劲梁方案下大桥结构受力状态及钢桁加劲梁安装阶段临时架设铰的作用,确定了合理的钢桁加劲梁施工方案。     

南充嘉陵江特大桥双壁钢围堰方案比选

文章以兰渝铁路南充嘉陵江特大桥深水基础施工为例,对比分析了先成桩后施工钢围堰和先下钢围堰后施工钻孔桩两种双壁钢围堰施工方案的优缺点,并结合工期、施工季节、河床地质等因素,确定了合理的围堰施工方案。     

钢箱梁在深水区大跨度横梁施工中的创新性运用

本文以佛江高速公路均安水道特大桥主桥下横梁及承台系梁施工为背景,对比了在深水区、大跨度横梁施工中钢管支架、预制梁和钢箱梁支架施工方案的优缺点,简要介绍钢箱梁施工方案,针对施工难点提出了解决措施。     

羊桥坝隧道大型干溶洞处理方案研究

受勘察手段限制,岩溶地区隧道建设过程中可能遭遇大型溶洞,带来施工、运营风险。文章以重庆奉节至巫溪高速公路羊桥坝隧道施工过程中发现的巨型溶洞为例,根据溶洞现状及补充勘察资料,提出了桥梁跨越方案、路基+明洞方案、回填暗挖方案和5种改线方案;通过在地质条件、施工风险、工程造价、工期等方面对诸方案进行综合比较,最终推荐采用新增费用最少、工期最短的左线左偏绕避溶洞方案。由于采用了该方案,在施工中未再遇大型溶洞,达到了规避地质风险、确保施工安全、节约造价、工期可控的效果。     

半填半挖高边坡路段塌方综合养护 处治方案浅析

路基病害养护处治应遵循以防为主、防治结合、力求根治的原则,通过综合技术经济比较,因地制宜,采取合理的处治方案。本文选取了皖南山区某高速公路高边坡路段的塌方综合养护处治案例,从病害成因到处治方案的选择,进行了全面分析和总结,对高边坡路段的养护管理具有较好的借鉴意义。     

A novel permit scheme for managing parking competition and bottleneck congestion

Morning commuters may have to depart from home earlier to secure a parking space when parking supply in the city center is insufficient. Recent studies show that parking reservations can reduce highway congestion and deadweight loss of parking competition simultaneously. This study develops a novel tradable parking permit scheme to realize or implement parking reservations when commuters are either homogeneous or heterogeneous in their values of time. It is found that an expirable parking permit scheme with an infinite number of steps, i.e., the ideal-scheme, is superior to a time-varying pricing scheme in the sense that designing a permit scheme does not require commuters’ value of time information and the performance of the scheme is robust to the variation of commuters’ value of time. Although it is impractical to implement the ideal-scheme with an infinite number of steps, the efficiency loss of a permit scheme with finite steps can be bounded in both cases of homogeneous and heterogeneous commuters. Moreover, considering the permit scheme may lead to an undesirable benefit distribution among commuters, we propose an equal cost-reduction distribution of parking permits where auto commuters with higher value of time will receive fewer permits.     

Risk-neutral second best toll pricing

We propose a risk-neutral second best toll pricing (SBTP) scheme to account for the possible nonuniqueness of user equilibrium solutions. The scheme is designed to optimize for the expected objective value as the UE solution varies within the solution set. We show that such a risk-neutral scheme can be formulated as a stochastic program, which complements the traditional risk-prone SBTP approach and the risk-averse SBTP approach we developed recently. The proposed model can be solved by a simulation-based optimization algorithm that contains three major steps: characterization of the UE solution set, random sampling over the solution set, and a two-phase simulation optimization step. Numerical results illustrate that the proposed risk-neutral design scheme is less aggressive than the risk-prone scheme and less conservative than the risk-averse scheme, and may thus be more preferable from a toll designer’s point of view.     

瓮马铁路南北延伸线引入都匀地区方案研究

通过分析都匀地区既有铁路现状及规划铁路,结合瓮马铁路货物流向,提出了瓮马铁路南延线引入黔桂线的必要性。结合都匀地区地形、城市规划和自然保护区范围,研究了瓮马铁路在黔桂线的前方站(都匀北站)或黔桂线绿荫湖站设置交接场引入都匀地区的方案,考虑到运营管理分解划分明确,减少折角运输,一次性建成南北直通通道,吸引国铁直通车流等因素,宜采用设置都匀北站交接场的方案。根据线路引入既有黔桂线接轨点的不同,对双线区间接轨方案、新都匀站站房同侧引入方案和新都匀站站房对侧引入方案进行分析,从工程量、工程投资、运输组织、施工难度及风险、投资建设模式等方面比较,得出双线区间接轨引入都匀地区方案最优。     

Sensor location problems in path-differentiated congestion pricing

Path-differentiated congestion pricing is a tolling scheme that imposes tolls on paths instead of individual links. One way to implement this scheme is to deploy automated vehicle identification sensors, such as toll tag readers or license plate scanners, on roads in a network. These sensors collect vehicles’ location information to identify their paths and charge them accordingly. In this paper, we investigate how to optimally locate these sensors for the purpose of implementing path-differentiated pricing. We consider three relevant problems. The first is to locate a minimum number of sensors to implement a given path-differentiated scheme. The second is to design an optimal path-differentiated pricing scheme for a given set of sensors. The last problem is to find a path differentiated scheme to induce a given target link-flow distribution while requiring a minimum number of sensors.     

Distributional impacts of road pricing: The truth behind the myth

This paper shows that road pricing can be regressive, progressive or neutral, and refutes the generalised idea that road pricing is always regressive. The potential distributional impacts of a road pricing scheme are assessed in three English towns. It is found that impacts are town specific and depend on where people live, where people work and what mode of transport they use to go to work. Initial impacts may be progressive even before any compensation scheme for losers is taken into account. When the situation before the scheme is implemented is such that majority of drivers entering the area where the scheme would operate come from households with incomes above the average, it can be expected that, once the scheme is implemented, these drivers coming from rich households will continue to cross the cordon and will be prepared to pay the charge. In such a case the overall effect will be that on average, rich people will pay the toll and poor people will not.     

Structural Optimization and Strength Analysis of the Lifting Arm of a Wet Shotcrete Spraying Unit北大核心CSCD

Wet shotcrete spraying units are widely used in underground engineering, for railways, highways, water conservancy and hydropower stations, municipal works, mining and military and other industries. Structural analysis and mechanical behavior optimization are conducted regarding the lifting arm of a TKJ series shotcrete spraying unit, and optimization of the hinge point position and working scope of the lifting arm is realized. The optimal layout scheme for the hinge force is given based on the Monte Carlo method, the hinge force of the lifting arm is improved for the mean and maximum values, and the maximum and average hinge force of the lifting cylinder decrease by 23.14% and 7.70%, respectively, compared with that of the original scheme. The static strength is checked using Ansys-Workbench for the optimized scheme, and the results show that the optimized scheme has a larger safety re-serve and that the structural design is more reasonable than the original scheme. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

A traffic congestion detection and information dissemination scheme for urban expressways using vehicular networks

The cooperative vehicle-infrastructure technologies have enabled vehicles to collect and exchange traffic information in real time. Therefore, it is possible to use Vehicular Ad-hoc NETworks (VANETs) for detecting traffic congestion on urban expressways. However, because of the special topology of urban expressways (consisting of both major and auxiliary roadways), the existing traffic congestion detection methods using VANETs do not work very well. In addition, the existing dissemination methods of congestion information lack the necessary control mechanism, so the information may be disseminated to irrelevant geographical areas. This paper proposes a congestion detection and notification scheme using VANETs for urban expressways. The scheme adopts a simplified Doppler frequency shift method to estimate and differentiate traffic conditions for major and auxiliary roadways. Vehicular cooperation and human cognition are introduced to improve the estimation accuracy and to describe the overall traffic conditions. Additionally, the scheme develops a spatial–temporal effectiveness model based on the potential energy theory to control the dissemination area and survival time of the congestion information. Meanwhile, the proposed scheme uses several broadcast control mechanisms to alleviate vehicular network congestion. Simulations through TransModeler indicate that our scheme ensures the accuracy of the estimation of congestion degree. Consequently, the scheme can provide effective references for driving decision-making and path-planning.     

基于信号配时的路网交通流分析及优化研究

文章以南宁市四条主干道上七个交叉口组成的闭合路网为优化对象,通过交叉口交通流量分析,利用R.Kimber饱和流量计算法和F.Webster交叉口信号配时理论,初步拟定车辆延误最小的信号配时方案,然后使用遗传算法优化配时方案,最后利用VISSIM进行交通仿真,验算服务水平指标的变化,验证该优化方案。