具有无序排列管片环结构的地铁盾构隧道数字模型智能重建北大核心CSCD

运营地铁隧道的管理、健康监测及维护正逐渐趋向于数字化、智能化;但常因地铁盾构隧道管理和检测单位缺少隧道数字模型,限制了地铁隧道智能维护和管理系统的应用和发展。文章针对地铁盾构隧道中无序排列的管片环结构,提出了一种基于深度学习和机器视觉的地铁盾构隧道数字模型智能重建方法,利用检测车获取的隧道衬砌内表面高清图片,对管片特征物(螺栓孔)进行智能识别与自动分类,再根据螺栓孔群的分布特点自动推断隧道管片环的排版规律,从而结合隧道实际线路实现隧道数字模型快速重建。某地铁隧道的实例应用结果表明,该方法适用于管片无规律性错缝拼装的情况,能以100%的准确率实现地铁盾构隧道数字模型的智能重建。     

Low-cycle fatigue assessment of offshore mooring chains under service loading

The integrity of mooring chains is essential to the safety of a range of offshore platforms. However, mooring line failures are occurring earlier than their design lives, with a high number of these failures occurring due to fatigue. Early in the fatigue life of the component fatigue initiation processes occur, where the fatigue hotspot is sensitive to the mean load and there is plastic strain accumulation from the multiaxial stress-strain responses of the material, leading to cyclic plastic damage accumulation. The traditional SN approach suggested by mooring standards does not consider these effects, and it is proposed that this lack of consideration under low-cycle fatigue conditions is the reason for the current non-conservative fatigue assessments of mooring chains. This paper aims to develop a fatigue approach based on a critical plane multiaxial fatigue criterion for mooring chains that can consider the damage-induced by the cyclic plasticity and the mean load effect, to investigate the importance of incorporating low-cycle fatigue into the mooring chain life prediction. To develop the critical plane approach, the multiaxial stress-strain states are extracted for the critical plane at the fatigue hotspot from a finite element model of a mooring chain. This is then correlated with a fatigue life prediction provided by conventional fatigue design data. It uses a simulation of an FPSO as a case study to demonstrate the importance of low cycle fatigue, which shows that the mean load effect is significant in reducing the fatigue life for mooring chain applications, while the effect of fatigue damage-induced cyclic plasticity is limited. The fatigue damage accumulation predicted by the critical plane approach is significantly higher than that of the traditional SN approach and should be accounted for in mooring line design.     

气垫船导管组合结构设计初探

随着气垫船向大型化发展,作为气垫船结构设计重要组成部分的导管组合结构设计越来越受到重视。文中结合国内已有的典型大中小型导管组合结构的设计参数,从导管组合结构的材料、结构型式以及传力方式等方面进行分析,总结其设计特点,并结合相关规范要求,对导管组合结构设计载荷进行分析。     

重载交通对公路路面使用寿命的影响

目前,车辆超载超限运输现象相当普遍,对公路的破坏相当严重,主要表现为大大降低了道路的服务水平、缩短了道路的使用寿命。从标准轴载的当量作用次数入手,通过对公路车辆超载问题的研究,可知超载是引起路面使用寿命缩短的主要原因。     

Simplified analysis for estimation of the behavior of a submerged floating tunnel in waves and experimental verification

To achieve rational design in waves for a submerged floating tunnel which has emerged as a new offshore transportation infrastructure, it's necessary to understand its hydrodynamic behavior. For simple but accurate estimation of hydrodynamic forces, a theoretical method is proposed and the tests with physical models in a wave flume were carried out for verification. Morison's equation was used to estimate wave loads composed of inertia force and drag force. Forces calculated by applying the linear wave theory to Morison's equation coincided well with those measured by the tests. The test results showed that mooring systems played a significant role in the movement of the submerged floating tunnel in waves. A pendulum model could be used to describe the motion of the submerged floating tunnel with a single vertical mooring. Based on the verified relations, a simple slack condition which causes the submerged floating tunnel to be unstable was also proposed. The simplified approach proposed by this study proved to be useful in designing the submerged floating tunnel in the initial stage.     

Dynamic airspace sectorisation for flight-centric operations

Today’s air traffic operations follow the paradigm of ‘flow follows structure’, which already limits the operational efficiency and punctuality of current air traffic movements. Therefore, we introduce the dynamic airspace sectorisation and consequently change this paradigm to the more appropriate approach of ‘structure follows flow’. The dynamic airspace sectorisation allows an efficient allocation of scarce resources considering operational, economic and ecological constraints in both nominal and variable air traffic conditions. Our approach clusters traffic patterns and uses evolutionary algorithms for optimisation of the airspace, focusing on high capacity utilisation through flexible use of airspace, appropriate distribution of task load for air traffic controllers and fast adaptation to changed operational constraints. We thereby offer a solution for handling non-convex airspace boundaries and provide a proof of concept using current operational airspace structures and enabling a flight-centric air traffic management. We are confident that our developed dynamic airspace sectorisation significantly contributes to the challenges of future airspace by providing appropriate structures for future 4D aircraft trajectories taking into account various operational aspects of air traffic such as temporally restricted areas, limited capacities, zones of convective weather or urban air mobility. Dynamic sectorisation is a key enabling technology in the achievement of the ambitious goals of Single European Sky and Flightpath 2050 through a reduction in coordination efforts, efficient resource allocation, reduced aircraft emissions, fewer detours, and minimisation of air traffic delays.     

高速公路路堤基底承载力计算方法分析

基于高速公路路基基底应力的三种计算方法，即比例荷载法、等效荷载法、三维数值分析软件FLAC3D，对高速公路路堤基底承载边进行计算。通过计算结果的对比分析，归纳了路基基底应力随着路堤高度和基底软土厚度变化的分布规律，并提出了路基基底应力的计算公式，可作为路基基底承载力或软基清淤的量化评定，避免人为地判断地基处理合格性。     

现浇箱梁桥桥面板受力分析

为了研究现浇预应力混凝土城市桥梁桥面板的受力、 构造及配筋， 以天水市藉口镇藉河大桥工程的3～35 m现浇预应力混凝土梁为例， 采用Midas Civil程序进行桥面板结构计算， 在此基础上提出常规现浇箱梁桥面板的倒角尺寸。计算结果表明: 城市桥梁车辆荷载轴重较大， 且由于新桥涵通规基本组合对车辆荷载分项系数的提高， 以往的小尺寸倒角桥面板在腹板根部抗剪承载力已显不足， 需增大倒角尺寸以满足桥面板抗剪承载力要求。     

时速200km城际铁路双线圆端形空心墩受力性能分析

结合时速200 km城际铁路双线圆端形空心墩设计实例,阐述铁路空心墩在非温差工况和温差荷载工况作用下的受力分析思路,总结出空心墩的受力特点和配筋原则。结论为:非温差工况作用下,墩身应力水平较低,仅需配置构造钢筋,按混凝土构件对墩身进行检算;温差工况作用下,部分墩身截面应力已超出混凝土的容许应力,需按计算配置钢筋,按钢筋混凝土构件对墩身进行检算;实体和空心交界处存在明显固端干扰效应,需局部加强钢筋布置。     

关于辐流式二沉池设计计算方法的探讨

针对辐流式二沉池设计资料中存在的相关问题,从平面设计要点和竖向设计要点两方面分别对辐流式二沉池中设计流量的选定、沉淀池表面积计算、进出水口、污泥区容积计算,以及有效水深、池边水深和总池高计算等进行了探讨,并对刮(吸)泥设备和配水井的设计要点进行了相关说明.同时结合工程实践,优化平面设计参数和竖向设计参数,合理选择刮(吸)泥设备和配水井等辅助设施,能为相关技术人员提供一定的参考和借鉴意义.