Fatigue Damage Modeling for Partially Prestressed Concrete Beams under Repeated Loadings with Variable Amplitude

Introduction Prestressedconcretestructuresfrequentlysub jectedtovariable amplituderepeatedloadingsare widelyusedinbridges,cranebeamsandoffshore structures.Repeatedloadingsmaycausetheprogres siveinternalstructuraldamagedegradingthereliabili tyofstructuresd…     

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城市公共交通发展模式选择问题是我国城市在实施会共交通优先发展战略过程中一个迫切需要解决的问题.文章在分析了当前存在的几种城市主要公共交通模式(常规公交、快速公交系统、轻执和地铁)的技术经济特性的基拙上，结合城市公交发展模式选择问题的特点，建立了城市公共交通发展模式决策矩阵，通过对多属性决策问题的求解来进行城市公共交通发展模式的选择，并定义了城市公共交通模式供求匹配指数来验证所选模式的客流适应性.最后，以西安市为例验证了文章提出的方法的适用性和合理性，提出了西安市城市公共交通建议发展模式.     

Stresses and Shear Fracture Zone of Jinshazhou Tunnel Surrounding Rock in Rich Water Region

Field evidence has shown that large-scale and unstable discontinuous planes in the rock mass surrounding tunnels in rich water region are probably generated after excavation. The tunnel surrounding rock was divided into three zones, including elastic zone, plastic damage zone and shear fracture zone fof assessing the stability of the tunnel surrounding rock. By local hydrogeology, the stresses of surrounding rock of Jinshazhou circular tunnel was analyzed and the stress solutions on the elastic and plastic damage zones were obtained by applying the theories of fluid-solid coupling and elasto-plastic damage mechanics. The shear fracture zone generated by joints was studied and its range was determined by using Mohr-Coulomb strength criterion. Finally, the correctness of the theoretical results was validated by comparing the scopes of shear fracture zones calculated in this paper with those from literature.     

一种新的车辆图像识别分类算法研究

提出了一种在静止背景交通图像序列中运动车辆的检测和分类方法,即基于GVF-Snake模型和惯量椭圆的车辆分类算法。利用混和高斯模型(GMM)、期望最大化(EM)估计算法、改进GVF-Snake模型,从序列交通视频图像中检测出运动车辆;然后,借用刚体惯量椭圆原理,计算运动车辆等效椭圆偏心率,从而建立车长-车投影面积-车的等效椭圆偏心率三参数建立了车辆分类器。该方法的车辆检测与分类都是基于数理统计原理,算法复杂度小,可用数字逻辑编程实现,适合在嵌入式系统中应用。     

交叉口定时信号配时优化设计方法

分析了现行交叉口定时信号配时设计流程中存在的不足,提出了将空间设计和时间设计结合起来的新的信号配时优化设计流程,建立了三目标配时优化模型,并以此模型为基础进行了实例分析,证明该模型优于F.Webster模型,对我国城市信号交叉口的信号配时有一定的指导作用。     

V形支撑结构施工阶段的空间应力分析

采用空间有限元程序ANSYS,对某V形支撑连续梁的V形支撑结构进行施工阶段的空间应力分析,研究V形支撑结构在施工阶段时的应力分布及变化情况,为类似结构的设计提供一定的参考.     

高烈度地震区山岭隧道模型试验研究

以雅泸高速公路高烈度地震区某山岭隧道为背景,对山岭隧道结构地震动力响应进行了大型振动台模型试验研究。试验表明,在隧道洞口段模型土表层裂缝均先从隧道拱顶偏向两侧45°角位置出现,然后斜向向上扩展;在隧道洞身段进出口纵向及斜向裂缝数量较多,大部分裂缝延伸至环向裂缝后终止。在隧道洞身段试验中,拱顶内缘和两侧边墙中部衬砌外缘出现拉裂性裂缝;在仰拱部位出现剪裂性裂缝或压裂性裂缝,并有不同程度的错动,是受地震影响最大的部位。     

温度荷载下沥青路面表面裂缝扩展的数值模拟

文章基于线弹性断裂力学的有限元法,对沥青路面开裂以后的温度应力及裂缝在温度作用下的扩展规律、裂缝尖端的应力强度因子及其与路面温度分布和路面材料特性等参数之间的关系进行了数值分析。结果表明,合理设计沥青面层的厚度和优选温缩性小的路面材料是提高沥青路面抗裂性能的重要方法。     

碎裂岩质高边坡锚杆应力的监测分析

高边坡的现场监测是一个系统工程,文章以西攀高速公路为例,结合高边坡施工期监测锚杆的应力状态和受力原因,建立锚杆应力测值统计模型,分析了开挖、温度、时效变形这三种因素对锚杆应力影响的规律,并对锚固效果和边坡稳定性进行了评价。     

Cooperative traffic control of a mixed network with two urban regions and a freeway

Currently most optimization methods for urban transport networks (i) are suited for networks with simplified dynamics that are far from real-sized networks or (ii) apply decentralized control, which is not appropriate for heterogeneously loaded networks or (iii) investigate good-quality solutions through micro-simulation models and scenario analysis, which make the problem intractable in real time. In principle, traffic management decisions for different sub-systems of a transport network (urban, freeway) are controlled by operational rules that are network specific and independent from one traffic authority to another. In this paper, the macroscopic traffic modeling and control of a large-scale mixed transportation network consisting of a freeway and an urban network is tackled. The urban network is partitioned into two regions, each one with a well-defined Macroscopic Fundamental Diagram (MFD), i.e. a unimodal and low-scatter relationship between region density and outflow. The freeway is regarded as one alternative commuting route which has one on-ramp and one off-ramp within each urban region. The urban and freeway flow dynamics are formulated with the tool of MFD and asymmetric cell transmission model, respectively. Perimeter controllers on the border of the urban regions operating to manipulate the perimeter interflow between the two regions, and controllers at the on-ramps for ramp metering are considered to control the flow distribution in the mixed network. The optimal traffic control problem is solved by a Model Predictive Control (MPC) approach in order to minimize total delay in the entire network. Several control policies with different levels of urban-freeway control coordination are introduced and tested to scrutinize the characteristics of the proposed controllers. Numerical results demonstrate how different levels of coordination improve the performance once compared with independent control for freeway and urban network. The approach presented in this paper can be extended to implement efficient real-world control strategies for large-scale mixed traffic networks.