Dynamic assessment of existing soft catenary systems using modal analysis to explore higher train velocities: a case study of a Norwegian contact line system

Significant advances made on the rolling stock have considerably increased the possibility of higher speeds in existing railways. Thus, it is important to explore higher speeds and potential limiting factors of existing soft catenary systems. The present paper investigates procedures to assess the dynamic behaviour of these systems using response sampling and modal analysis. The assessment evaluates and quantifies dynamic response along the section. To verify the approach, a case study is conducted and the following assessment methods are used: lengthwise track correlation estimating dynamic predictability, power spectral density estimations before and after passage and short-time Fourier transforms and spectrograms. The combination provides detailed information on the dynamic behaviour. The first part introduces necessary considerations for suggested modal analysis. The second part describes an existing Norwegian section. The case study is conducted using a finite element model including a straight and a given section between Oslo-Trondheim, providing detailed evaluations and system limitation detections.     

VBA在Excel水文数据处理中的应用研究

文中在对基于VBA在Excel水文数据处理的基础上,对水文数据的处理过程、成果数据格式及大量报表的合理统计进行了阐述,重点对VBA与Excel的交互、文件与文件数据的交互、数据的流程化管理技术做了探讨。实践表明,VBA在Excel中的开发可以对海量水文数据进行处理,在处理过程中公共参数的设置都可自动化完成,使处理速度大大地提高。     

基于细-宏观数据交互的桥梁水毁数值仿真

为精细化探究桥梁水毁倒塌机理，基于计算流体力学与泥沙动力学数值仿真，得到桥梁冲刷形态演变与波流力时程数据，构建桥梁水毁全过程的连续倒塌数值模型；通过开发细-宏观数据交互接口，将冲刷所致边界条件改变与波流力对桥梁结构作用效应实时传递至结构域桥梁连续倒塌数值模型，高精度连续仿真冲刷发展与波流力作用下桥梁水毁全程力学响应与结构形态演化；最后，通过河源东江大桥倒塌案例分析，验证该仿真方法与数据交互接口的正确性和有效性。结果表明：河源东江大桥连续倒塌可能由冲刷掏空基础后倾斜、拱脚薄弱节点失效以及非制动墩承受不平衡水平推力所致；所提出的仿真方法可实现冲刷仿真、波流力计算与结构倒塌分析的同步交互实施，可为从水文源头探究桥梁水毁失效机理与倒塌模式提供精准高效的分析工具，为桥梁抗水设计、评估以及未来规范修订提供理论基础与技术手段。     

基于M形深度架构的非结构化道路可行驶区域推荐模型

针对边界模糊、路况多变的非结构化道路，为满足智能汽车在正常、应急等复杂行驶工况下对可行驶区域的视觉检测需求，提出一种在M形深度架构下融合多尺度交互策略和双重注意力机制的可行驶区域推荐模型，能够在复杂驾驶场景中精细分割出非结构化道路的强推荐、弱推荐、不推荐行驶区域。首先，在编码器-解码器的骨架基础上，构建倒金字塔式的多尺度分层输入和分层输出结构，以有效融合非结构化道路的浅层形态学特征与深层语义信息，并平衡模型在不同尺度上的预测偏倚，提升复杂驾驶场景下对多尺度与变尺度目标的分割精度；其次，构建集成通道注意力和空间注意力的跳跃连接结构，使模型在实现编码特征与解码特征高效传递的同时，聚焦于学习与道路可行驶性相关的重要特征，进一步强化模型对非结构化道路的检测性能。通过多种途径构建包含城郊、乡村、园区等真实场景的非结构化道路驾驶数据集。试验结果表明：得益于M形深度架构对多尺度交互策略和双注意力机制的融合，提出的模型在多种真实驾驶场景下均能较好地实现强推荐行驶区域、弱推荐行驶区域、不推荐行驶区域和背景区域的精细分割，平均交并比达到92.46%，平均检测速度达到22.7帧·s^-1；与现有其他主流模型相比，提出的模型兼顾了分割精度和时间效率，在非结构化道路可行驶区域检测任务上有明显优势。     

The effect of railway local irregularities on ground vibration

The environmental effects of ground-borne vibrations generated due to localised railway defects is a growing concern in urban areas. Frequency domain modelling approaches are well suited for predicting vibration levels on standard railway lines due to track periodicity. However, when considering individual, non-periodic, localised defects (e.g. a rail joint), frequency domain modelling becomes challenging. Therefore in this study, a previously validated, time domain, three-dimensional ground vibration prediction model is modified to analyse such defects. A range of different local (discontinuous) rail and wheel irregularity are mathematically modelled, including: rail joints, switches, crossings and wheel flats. Each is investigated using a sensitivity analysis, where defect size and vehicle speed is varied. To quantify the effect on railroad ground-borne vibration levels, a variety of exposure–response relationships are analysed, including: peak particle velocity, maximum weighted time-averaged velocity and weighted decibel velocity. It is shown that local irregularities cause a significant increase in vibration in comparison to a smooth track, and that the vibrations can propagate to greater distances from the line. Furthermore, the results show that step-down joints generate the highest levels of vibration, whereas wheel flats generate much lower levels. It is also found that defect size influences vibration levels, and larger defects cause greater vibration. Lastly, it is shown that for different defect types, train speed effects are complex, and may cause either an increase or decrease in vibration levels.     

公路工程项目组合施工进度风险防范策略

为了降低公路工程施工进度风险，考虑风险事件的交互关系提出了公路工程项目组合施工进度风险防范策略。首先，通过公路工程建设文献资料梳理和专家筛选补充，构建了公路工程项目组合施工进度风险三级指标体系。然后，利用网络层次分析法解析了公路工程项目组合施工进度风险指标间的交互关系，运用Super Decisions软件确定了各级风险指标的权重。最后，通过系统动力学建立了公路工程项目组合施工进度风险水平评估模型，在验证模型的有效性后运用Vensim软件对施工进度风险水平进行模拟。在此基础上，为降低公路工程施工进度风险，综合考虑风险破坏和交互程度改进传统“概率-损失”风险矩阵，对不同风险防范策略实施后的管控效果进行仿真模拟，进而提出了相应的风险防范策略集。研究结果表明：风险间交互关系致使公路工程项目组合施工进度风险在整个施工阶段呈上升趋势，且施工阶段中后期风险上升趋势明显升高，有必要对风险进行控制；采取单一风险防范策略后总体施工进度风险降低[0.13%，10.12%]，下降程度并不显著；采取组合风险防范策略后总体施工进度风险下降[10.45%，17.42%]，显著度明显提高。该结果厘清了公路工程项目组合施工进度风险的交互关系，验证了风险防范策略的科学有效性，为解决公路工程项目组合施工进度的风险防范问题提供了依据。     

Dynamic response of the train–track–bridge system subjected to derailment impacts

Derailments on bridges, although not frequent, when occurs due to a complex dynamic interaction of the train–track–bridge structural system, are very severe. Furthermore, the forced vibration induced by the post-derailment impacts can toss out the derailed wagons from the bridge deck with severe consequences to the traffic underneath and the safety of the occupants of the wagons. This paper presents a study of the train–track–bridge interaction during a heavy freight train crossing a concrete box girder bridge from a normal operation to a derailed state. A numerical model that considers the bridge vibration, train–track interaction and the train post-derailment behaviour is formulated based on a coupled finite-element – multi-body dynamics (FE-MBD) theory. The model is applied to predict the post-derailment behaviour of a freight train composed of one locomotive and several wagons, as well as the dynamic response of a straight single-span simply supported bridge containing ballast track subjected to derailment impacts. For this purpose, a typical derailment scenario of a heavy freight train passing over a severe track geometry defect is introduced. The dynamic derailment behaviour of the heavy freight train and the dynamic responses of the rail bridge are illustrated through numerical examples. The results exhibit the potential for tossing out of the derailed trains from the unstable increase in the yaw angle signature and a lower rate of increase of the bridge deck bending moment compared to the increase in the static axle load of the derailed wheelset.     

A linear complementarity method for the solution of vertical vehicle–track interaction

A new method is proposed for the solution of the vertical vehicle–track interaction including a separation between wheel and rail. The vehicle is modelled as a multi-body system using rigid bodies, and the track is treated as a three-layer beam model in which the rail is considered as an Euler-Bernoulli beam and both the sleepers and the ballast are represented by lumped masses. A linear complementarity formulation is directly established using a combination of the wheel–rail normal contact condition and the generalised-α method. This linear complementarity problem is solved using the Lemke algorithm, and the wheel–rail contact force can be obtained. Then the dynamic responses of the vehicle and the track are solved without iteration based on the generalised-α method. The same equations of motion for the vehicle and track are adopted at the different wheel–rail contact situations. This method can remove some restrictions, that is, time-dependent mass, damping and stiffness matrices of the coupled system, multiple equations of motion for the different contact situations and the effect of the contact stiffness. Numerical results demonstrate that the proposed method is effective for simulating the vehicle–track interaction including a separation between wheel and rail.     

海洋非金属管道在位稳性数值模拟

文章研究了在波流水动力荷载作用下海洋非金属管道管土接触的在位稳性。通过嵌入UWAVE子程序的ABAQUS施加考虑升力的水动力荷载,编写基于Zhang理论弹塑性模型自定义管土接触单元,对管道进行动态分析。结果发现管道的应力应变处于较低水平,在位状态失效不是由强度破坏造成的;不考虑升力将使管道陷深增大,侧向位移受到约束。最后做了参数分析,包括管道安装过程中的集中荷载效应、海床土壤类型及考虑海床不平整造成的悬跨段长度。     

基于流固耦合的螺旋桨水动力性能数值仿真

根据螺旋桨理论,将基于粘流理论的计算流体动力学方法与结构有限元分析方法相结合,构建螺旋桨的流固耦合数值仿真方法。运用该方法对螺旋桨进行计算分析,并与试验结果进行对比,两者吻合较好。证明了利用构建的FSI方法与传统的CFD方法计算同一金属材料螺旋桨时,在低进速下计算所得结果较传统CFD方法更为准确。从多角度阐明所建立的流固耦合数值方法在复合材料螺旋桨研究方面的独特优势,为复合材料螺旋桨性能分析提供了必要的工具。