半直立式圆筒护岸地基现场加载试验及变形分析

半直立式圆筒护岸是一种新式港口工程结构,结合其在大连某水工护岸工程中的应用,进行了半直立式圆筒护岸地基的加载试验,通过实测土压力、沉降、水平位移及孔隙水压力,分析了半直立式圆筒护岸地基的沉降及水平位移变化特点,并进一步研究了其不均匀沉降的发展过程。试验结果表明：半直立式圆筒护岸沉降及水平位移对护岸荷载分级、每级荷载加载量、加载历时及两级荷载之间的间隔时间较为敏感,其中护岸后方最后一级不对称加载对圆筒结构的不均匀沉降影响最大,孔隙水压力变化主要受每级加载量、加载历时及潮汐作用影响,而圆筒安装及第一级荷载施加后,孔隙水压力产生较大的波动。     

塑料套管混凝土桩加固公路软土地基现场试验研究

根据某一高速公路塑料套管混凝土桩加固软土地基工程实例,对桩土应力、地表沉降、横向位移、不同深度孔隙水压力进行观测,讨论了塑料套管混凝土桩桩承式路堤的工作机理。结果表明：塑料套管桩加筋路堤的临界高度约为1.26倍桩净距,观测期末,荷载分担比接近89%;桩帽和桩间土最大差异沉降为30 mm左右,且应力集中比随着差异沉降的增大而线性增大;路堤堤脚附近不同深处横向位移随着路堤填筑高度的增加而增加,施工结束时,地表以下2.5 m处横向位移最大,为12.86 mm;横向位移-沉降比和横向位移增加率随着路堤填筑高度的增加逐步减小并趋于稳定,塑料套管混凝土桩加筋路堤系统能够有效防止路堤横向位移的发展和改善路堤的整体稳定性。     

Numerical evaluation on shell buckling of empty thin-walled steel tanks under wind load according to current American and European design codes

Liquid storage steel tanks are vertical above-ground cylindrical shells and as typical thin-walled structures, they are very sensitive to buckling under wind loads, especially when they are empty or at low liquid level. Previous studies revealed discrepancies in buckling resistance of empty tanks between the design method proposed by the American Standard API 650 and the analytical formulas recommended by the European Standard EN1993-1-6 and EN1993-4-2. This study presents a comparison between the provisions of current design codes by performing all types of numerical buckling analyses recommended by Eurocodes (i.e. LBA-linear elastic bifurcation analysis, GNA-geometrically nonlinear elastic analysis of the perfect tank and GNIA-geometrically nonlinear elastic analysis of the imperfect tank). Such analyses are performed in order to evaluate the buckling resistance of two existing thin-walled steel tanks, with large diameters and variable wall thickness. In addition, a discussion is unfolded about the differences between computational and analytical methods and the conservatism that the latter method imposes. An influence study on the geometric imperfections and the boundary conditions is also conducted. Investigation on the boundary conditions at the foot of the tank highlights the sensitivity to the fixation of the vertical translational degree of freedom. Further, it is indicated that the imperfection magnitude recommended by the EN1993-1-6 is extremely unfavorable when applied to large diameter tanks. Comments and conclusions achieved could be helpful in order to evaluate the safety of the current design codes and shed more light towards the most accurate one.     

Knowledge-based system for safety control of damaged ship

The maritime casualties cause serious consequences such as loss of life, property and maritime pollution. Therefore, the large-scaled casualties will be derived from loss of structural strength and stability due to the progressive flooding and enlargement of damage by the effect of wave and wind. The improvement of damage survivability is very important in maritime safety. In this paper, the knowledge-based system which could improve the safety level of stability and longitudinal strength through posture control of a damaged ship is studied. The system has been incorporated to interface with user to develop an ‘operationally practical’ action list based on ballasting to improve the ship's structural safety and stability status.     

高功率激光焊接船板的组织性能

采用高功率激光进行船板材料的焊接实验。实验条件为:10 kW快轴流CO2激光器和5轴数控机床;船用St370-2低碳钢板;SG填充焊丝;Y型坡口。采用光学显微镜(OM)、扫描电子显微镜(SEM)和X射线衍射仪(XRD)研究了激光焊缝组织和结晶特性,讨论了抑制裂纹生长因素,并进行了焊缝强度实验、硬度实验和X光探伤实验。结果表明,在8～10 kW激光功率和焊速1 m/min参数下,在12 mm厚船板上获得了无裂纹的良好焊缝,实现单面焊双面一次成形。与常规埋弧焊(SAW)焊接相比,激光焊接变形很小,激光焊缝宽度窄(最宽处5 mm),热影响区小(0.3 mm)。焊缝组织为细小板条马氏体加少量残余奥氏体,硬度HV350,抗拉强度536 N/mm2,经180°冷弯不断裂,具有良好的综合力学强韧性能。     

Moving-body simulations using overset framework with rigid body dynamics

The simulation of flow past bodies in relative motion is a challenging task due to the presence of complex flow features, moving grids, and rigid body movements under the action of external forces and moments. A generalized grid-based overset framework is presented for the simulation of this class of problems. The equations that govern the fluid flows are cast in an integral form and are solved using a cell-centered finite volume upwind scheme. The rigid body dynamics equations are formulated using quaternion and are solved using fourth-order Runge–Kutta (RK) time integration. The overset framework and the six degree of freedom (6-DOF) rigid body dynamics simulators are developed in a library form for easy incorporation into existing flow solvers. The details of the flow solver, the 6-DOF library, and the overset framework are presented in this paper along with the validation results of the developed system.     

“奋威”轮沉船海域水动力条件数学模型研究

通过建立波浪潮流数学模型,对"奋威"轮沉船坐浅期间海域水动力条件进行模拟计算。结果表明:(1)沉船仅对局部海域的流态有影响,总体影响不大,沉船附近涨落急时流速为1 m/s左右;(2)沉船坐浅期间,沉船附近最大波高可以达到2.63 m左右,大风情况下的巨浪可能对沉船的稳定性造成影响。模拟结果为沉船沉降计算提供水动力条件。     

遮帘桩工作性状影响因素分析

遮帘桩作为挡土桩在深水建港、深基坑开挖及护岸工程中应用越来越广泛.为了研究开挖过程中遮帘桩的工作性状,运用大型有限元软件建立三维有限元的遮帘桩结构模型,模拟某板桩码头港池开挖.分析港池开挖后遮帘桩的刚度、桩长、桩间距及遮帘桩与板桩墙距等对板桩墙结构的影响,从而提出控制板桩墙结构变形、保持港池开挖后稳定的遮帘桩布置方法.研究结果表明,增加遮帘桩桩长和刚度能有效减小板桩墙的变形、陆侧主动土压力和弯矩,而遮帘桩间距和墙桩距的变化对遮帘桩挡土效果的影响不明显.     

动床阻力研究与应用

动床阻力随床面形态的变化而变化,而床面形态又是水流强度的函数,Simons将两者关系分为三个流区,即低水流区、过渡区和高水流区.不同流区阻力特性和规律是不相同的,正确和合理地判别流区是正确确定阻力关系的先决条件.此文在Browline研究的基础上,进一步分析了影响床面形态的基本要素,提出了在第一时间判别流区的方法,建立了各区阻力关系式,并利用长江和黄河实测资料和水槽试验资料进行了预报计算,其精度优于其它同类公式.     

闸墩冰荷载及过冰能力的模型试验研究

本文针对我国东北地区某航电枢纽设计中泄洪闸闸墩的冰荷载以及流冰期排冰的问题进行了对应的物理模拟试验。通过孤立闸墩和双闸墩的冰荷载试验，证实了边界条件对冰荷载的影响，获得了边界影响系数.同冰速的试验也证明，冰速对于冰力具有明显的影响。文中将试验结果与理论公式计算进行了比较并提出了作者的看法，可供工程设计人员参考。根据现场实测资料，进行了三种江面冰排不同分布和密度的闸墩过冰能力的定性物理模拟试验，阐述了现有工况下闸墩间流冰通过的可能性。