海底溢油输移扩散的可视化数值模拟系统

为直观研究溢油在复杂水下环境中的动态行为,设计和开发一套海底溢油可视化数值模拟系统(SIMPACT-SOS).系统由数值模型、数据库和图形界面构成,具有地理信息系统(GIS)应用平台、数值建模分析、溢油数值模拟等专业功能.应用算例表明,SIMPACT-SOS系统可为海底沉船溢油、海底输油管道泄漏、海洋石油钻井井喷等水下污染事故的风险评估、应急决策及损害评估提供理论和技术支持.     

长短桩复合地基桩土荷载分担比研究

对长短桩复合地基在竖向荷载作用下的力学性状进行了研究,揭示了长短桩复合地基在不同桩土刚度比条件下桩土相互作用、荷载分担比、桩土应力比及荷载传递方面的变化规律。试验结果表明,此类复合地基能使刚性桩、柔性桩以及土体协调变形,合理发挥它们各自的承载能力,为今后的设计和推广应用提供了依据。     

Geometric stress distribution along the weld toe of the outer brace in two-planar tubular DKT-joints: Parametric study and deriving the SCF design equations

Regarding the research efforts expended so far on the calculation of stress concentration factors (SCFs) in tubular joints, two major shortcomings can be noted: (a) significant effort has been devoted to the study of SCFs in various uni-planar connections. Nevertheless, for multi-planar joints which cover the majority of practical applications, very few investigations have been reported due to the complexity and high cost involved; (b) majority of these research works focused on the study of SCFs at certain positions such as the saddle, crown toe, and crown heel, and they have ignored the hot-spot stress (HSS) at other positions along the weld toe. In the present paper, effects of dimensionless geometrical parameters on the SCF distribution along the weld toe of main (outer) braces in the axially loaded right-angle two-planar tubular DKT-joints are investigated. In order to study the multi-planar effect, SCF distribution in two-planar joints is compared with the distribution in a uni-planar joint having the same geometrical properties. A complete set of SCF database is constructed based on the two-planar DKT-joint Finite element models which are verified against experimental results and the predictions of Lloyd’s Register (LR) equations. The FE models cover a wide range of geometrical parameters. Six new SCF parametric formulae are developed through nonlinear regression analyses for the accurate and reliable fatigue design of two-planar DKT-joints under axial loads. An assessment study of these equations is conducted against the experimental data, the original FEM database and the acceptance criteria recommended by the UK Department of Energy.     

氯盐腐蚀环境下混凝土结构时变可靠度计算

基于Fick扩散定律,建立了氯离子在混凝土中扩散的多因素修正模型,给出了模型中参数的取值。依据可靠性理论,考虑氯离子侵蚀深度的不同分布特征,利用建立的扩散模型,说明了氯盐侵蚀环境下考虑时变效应的混凝土结构可靠度计算方法。最后给出了实际工程算例,算例结果说明,假定氯离子侵蚀深度服从正态分布带来的计算偏差并不大,却可大大简化计算过程。     

毛羽山隧道高地应力软岩大变形施工控制技术

兰渝铁路毛羽山隧道出口段穿越薄层状碳质板岩地层,区域原岩应力较大且以水平构造应力为主,隧道开挖过程中出现严重的大变形情况。通过分析,认为高地应力、最大水平主应力与隧道轴线呈大角度相交是大变形的主要因素。隧道施工过程中,通过采取提高支护体系刚度、合理预留变形量,以及采用长锚杆、多重支护和超短台阶法等常规措施控制了围岩变形;基于对围岩动态演化机制的认识,提出了高地应力隧道超前导洞法应力控制释放技术,开展了大型工程试验。阶段性试验成果表明,采用超前导洞有效地降低了正洞施工时的变形速率,对上中台阶影响尤为显著。通过对应力控制释放技术研究的进一步深化,有望探索出安全、高效的高地应力软岩施工新技术。     

上下重叠盾构隧道设计施工关键技术

文章结合深圳地铁2号线大剧院站至湖贝站上下重叠小净距盾构区间隧道工程实例,针对重叠盾构隧道的施工关键问题,进行了受力分析,提出下洞采取钢管支撑的施工技术措施,并通过实测进行了验证,为后续项目提供了经验。     

Lagrangian modelling of plankton motion: From deceptively simple random walks to Fokker–Planck and back again

The movement of plankton, either by turbulent mixing or their own inherent motility, can be simulated in a Lagrangian framework as a random walk. Validation of random walk simulations is essential. There is a continuum of mathematically valid stochastic integration schemes upon which random walk simulations depend, each of which lead to radically different macro-scale dynamics as expressed in their corresponding Fokker–Planck equations. In addition, diffusivity is not a unique parameter describing a random walk and its corresponding Fokker–Planck equation. Spatially varying translation speed and turn frequency have different effects on population distributions. Validation requires extra information either in the form of the well-mixed condition for physical diffusion, or in detailed information on the sensing ability, internal state modulation and swimming response for plankton motility.     

Stress Field Analysis of Carburized Specimen and Its Numerical Simulation

IntroductionCarburiZingiswidelyaPPiedheattre8boellttechnologyinindustry.Duringcarburizing,acasewithcarboncontellthigherthanthatofthecoreisformd;andaftethecarburzedmachinepwtbeingquenched,sdsehardenedlayeconsistedmainlyofmartensite,aswellasresidualstfOssfieldappearinit.Theresidua1stressfieldofcarburizedsteelanditsinfluenceonfatiguestrengthhavebeenstudiedexPerimenally["'],whilefewrePortscanbefoundaboatnumericalsimulationofresidualstressfieldincarburizedsPecmenaswellasitsinstataneousstressdist…     

碎石化后沥青加铺层应力对比分析

碎石化是一种旧水泥混凝土路面处治重要技术,它能降低建设成本,加快建设周期。文章基于有限元分析方法,首先对比分析了碎石化后加铺沥青面层和同厚度级配碎石层上加铺沥青面层的应力,结论认为碎石化后沥青加铺层底的拉应力要小于级配碎石的情况,证明碎石化后水泥混凝土板块优于级配碎石的力学性能;然后,通过改变碎石化层中两个主要分层的厚度和模量,分析不同的破碎程度对加铺层应力的影响,结论认为,碎石化下层厚度在10cm左右时,既能保证碎石化层仍然具有一定强度使沥青层底拉应力不至于过大,又能起到防止反射裂缝的作用。碎石化下层厚度不变时,加铺沥青层的受力状况随着碎石化下层模量的增大会稍有改善,拉应力、拉应变和弯沉都会有所减小,总体幅度在3%~9%之间。     

采用简化方法的船体结构疲劳强度校核

本文介绍用简化方法进行船体结构疲劳强度校核的基本原理。这一方法已为中国船级社近期编制的《船体结构疲劳强度指南》所采纳。文中介绍了疲劳载荷的计算,疲劳应力的计算及疲劳累积损伤的计算,并给出例题说明这一方法的具体应用。