软土地区大型船坞底板优化设计

采用PLAIXS软件分析了船坞开挖卸荷和坞墙侧限对底板承载力的影响,结果表明,目前底板设计没有考虑土体开挖的卸荷效应和坞墙的侧限效应显得过于保守。考虑桩土共同作用,用理论的方法分析了船坞底板的受力特性,得到了不同土层分布对底板沉降和土体荷载分担的影响。计算结果与有限元计算值进行对比分析,验证了该方法的正确性。     

Boussinesq方程的研究进展

从Boussinesq方程的导出出发,总结了方程的特点,对方程的频散性和非线性、考虑复杂地形、波浪破碎、与水流的相互作用等方面的改进工作进行总结和评述,并对方程的求解方法和应用情况进行系统的归纳总结,以期对本领域的发展有一定的参考价值.     

桩土相互作用分析模型比较

地震作用下桩-土-结构动力相互作用是当前岩土工程和地震工程领域中研究的热点和难点,也是桥梁抗震设计中面临的重要课题。     

夹层板在舰艇冲击防护中的研究进展

为了提高舰艇抗冲击能力,已发展了各种舰艇冲击防护方法。传统的冲击防护手段会使舰艇的重量大幅增加,影响舰艇总体性能。夹层板的出现给舰艇冲击防护提供了另外一条途径,成为近期国内外相关研究的热点。文中以舰艇冲击防护为背景,从夹层板的冲击变形模式、微惯量效应、应变率效应、几何非线性效应、流固耦合效应、以及均匀化和模拟试验方法等方面,回顾了近期国内外相关研究进展。     

考虑多维动态特征交互的高速公路实时事故风险建模

为探究天气和道路等特征,以及交通流、天气、道路及时间等多维动态特征之间的交互作用对实时事故风险预测模型精度的影响,本文基于京哈高速公路北京段的事故数据,以及匹配的交通传感器数据、天气数据和道路特征等,构建4个数据集,分别为只包含交通流变量,包含交通流变量、天气及时间特征变量,包含交通流变量、道路及时间特征变量,包含交通流变量、天气、道路及时间特征变量。从考虑多维动态特征的交互效应出发,基于深度交叉网络,提出一种新的实时事故风险预测模型。结果显示,本文所构建的深度交叉网络模型比其他几种实时事故风险预 测方法显示出更高的精度。模型的AUC值(Area Under Curve)可达0.8562,在0.2的概率阈值下, 可以正确分类84.26%的非事故数据和77.55%事故数据。结论表明,本文采用的多维动态特征交互样本条件下的深度交叉网络模型能够有效地预测高速公路交通事故,可为我国高速公路安全管理部门提供理论与技术支持。     

The social context of informal commuting: Slugs, strangers and structuration

Despite considerable interest in the role of social interactions and social context on transportation, there have been very few attempts to explore specific cases of social interaction influencing transportation systems. This paper explores the social practice of slugging, an informal system of carpooling in the Washington, DC area. Slugging emerged in response to the establishment of Virginia’s High Occupancy Vehicle (HOV) lanes in the early 1970s, as single drivers picked up riders alongside the road (slugs) in order to meet the requirements for driving in the less congested HOV lanes. Drawing on the work of sociologist Anthony Giddens, as well as the sociological insights of Georg Simmel and Stanley Milgram, we suggest that the practice of slugging highlights the processes of institutionalization and structuration. This paper details how the region’s mass transportation policies and urban culture have combined to result in an institutionalized practice with particular norms and logics of behavior. We conclude that looking at specific cases where social context has affected transportation, like slugging, could provide useful insights on the impact of social context on transportation policies and systems.     

Vibration control in train–bridge–track systems

To study the problems associated with vibration control of train–bridge–track systems a mathematical model with the capability of representing supplementary vibrational control devices is proposed. The train system is assumed as rigid bodies supported on double-deck suspension mechanism with semi-active features. The bridge system is modeled using the modal approach. Vibration control for bridge responses is provided by tuned mass dampers. A non-classical incremental Eigen analysis is proposed to trace the system characteristics across the time. In an example, the capability of the proposed model in investigating the vibration control prospects of a bridge–train system is shown. The results indicate the effectiveness of active suspension mechanism in reducing train's body movements, particularly the pitching angle and the vertical accelerations. Accordingly, the results also verify the potential of TMD devices in reducing the bridge responses at resonance motions.     

水平荷载作用下钢管支架的弹塑性极限承载力分析

通过考虑桩土相互作用以及材料和几何非线形，对钢管支架在水平荷栽作用下的极限承载力及其影响因素进行了分析，从而对钢管支架的安全度作出合理的评价。     

Influence of uneven rail irregularities on the dynamic response of the railway track using a three-dimensional model of the vehicle–track system

A mathematical model of the vehicle–track interaction is developed to investigate the coupled behaviour of vehicle–track system, in the presence of uneven irregularities at left/right rails. The railway vehicle is simplified as a 3D multi-rigid-body model, and the track is treated as the two parallel beams on a layered discrete support system. Besides the car-body, the bogies and the wheel sets, the sleepers are assumed to have roll degree of freedom, in order to simulate the in-plane rotation of the components. The wheel–rail interface is treated using a nonlinear Hertzian contact model, coupling the mathematical equations of the vehicle–track systems. The dynamic interaction of the entire system is numerically studied in time domain, employing Newmark's integration method. The track irregularity spectra of both the left/right rails are taken into account, as the inputs of dynamic excitations. The dynamic responses of the track system induced by such irregularities are obtained, particularly in terms of the vertical (bounce) and roll displacements. The numerical model of the present research is validated using several benchmark models reported in the literature, for both the smooth and unsmooth track conditions. Four sample profiles of the measured rail irregularities are considered as the case studies of excitation sources, examining their influences on the dynamic behaviour of the coupled system. The results of numerical simulations demonstrate that the motion of track system is significantly influenced by the presence of uneven irregularities in left/right rails. Dynamic response of the sleepers in the roll direction becomes more sensitive to the rail irregularities, as the unevenness severity of the parallel profiles (quantitative difference between left and right rail spectra) is increased. The severe geometric deformation of the track in the bounce–pitch–roll directions is mainly related to such profile unevenness (cross-level) in left/right rails.     

Influence of some vehicle and track parameters on the environmental vibrations induced by railway traffic

A study is performed on the influence of some typical railway vehicle and track parameters on the level of ground vibrations induced in the neighbourhood. The results are obtained from a previously validated simulation framework considering in a first step the vehicle/track subsystem and, in a second step, the response of the soil to the forces resulting from the first analysis. The vehicle is reduced to a simple vertical 3-dof model, corresponding to the superposition of the wheelset, the bogie and the car body. The rail is modelled as a succession of beam elements elastically supported by the sleepers, lying themselves on a flexible foundation representing the ballast and the subgrade. The connection between the wheels and the rails is realised through a non-linear Hertzian contact. The soil motion is obtained from a finite/infinite element model. The investigated vehicle parameters are its type (urban, high speed, freight, etc.) and its speed. For the track, the rail flexural stiffness, the railpad stiffness, the spacing between sleepers and the rail and sleeper masses are considered. In all cases, the parameter value range is defined from a bibliographic browsing. At the end, the paper proposes a table summarising the influence of each studied parameter on three indicators: the vehicle acceleration, the rail velocity and the soil velocity. It namely turns out that the vehicle has a serious influence on the vibration level and should be considered in prediction models.