桁材开孔腹板的线性屈曲强度分析

船体在总纵弯曲时甲板纵桁和船底纵桁承受较大的轴向压力,而在桁材腹板上开孔会影响其腹板的屈曲强度.针对这一问题,应用有限元屈曲特征值分析方法对受轴向压力开孔腹板的屈曲载荷进行计算.通过对计算结果的分析,对开孔尺寸和开孔位置对腹板屈曲强度影响的规律进行了归纳,并对腰圆孔和圆孔对腹板屈曲的影响程度做出了比较,对船体结构中腹板开孔尺寸及位置提出了一些建议.     

组合载荷作用下有孔板的屈曲强度

舰船结构中的桁材和肋板腹板通常开有许多管系和穿舱孔，这些开孔在多数情况下会降低板的屈曲强度，而且它们对评价开孔对板的屈曲强度的影响非常重要。为了评价孔板的弹性屈曲强度，进行了一系列特征值分析。此外，邻接的无开孔板的影响也需要研究，原因是由于开孔所引起的应力集中，使其产生高应力区域和低应力区域。当在高应力区域发生屈曲变形时，屈曲强度降低，另一方面，当在低应力区域发生屈曲变化，屈曲强度增高；当一个设有大型水平防挠材的桁材腹板有开孔时，在无开孔的邻接板内产生高应力区域，在这种情况下，邻接板的屈曲将决定一个有孔腹板的屈曲强度；在某些情况下，船级社的规范计算公式对有孔板给出了比用有限元法分析的结果相对比较低的弹性屈曲强度。     

基于复变函数解法的桁材开孔腹板弹性屈曲分析

在船体梁总纵弯矩作用下,位于甲板和船底的纵桁承受着较大的轴向压力,而桁材腹板上的开孔将影响腹板结构的屈曲强度。腰圆形是桁材腹板开孔的常见形状,带这种开孔的板格屈曲计算是难以获得弹性屈曲解析解的,目前常用的算法是基于有限元的特征值屈曲分析。本文综合运用复变函数方法和Ritz法,形成了一种新的计算方法,它可以在较粗的背景网格下得到足够准确的弹性屈曲载荷。通过系统的敏感性计算对比,此方法的可用性得到了验证。     

横梁腹板开孔剪切稳定性加强方式

船体结构中,为方便管线通过,常需在横梁腹板上开孔,这将影响横梁的强度和稳定性。本文主要针对腹板开孔对其剪切稳定性影响进行讨论,并为补偿开孔后腹板剪切稳定性的损失,采用有限元弹性屈曲分析方法,探讨了常用的加强筋、围缘扁钢和复板3种加强方式在不同加强尺寸下的加强效果。本文的计算和分析结果能为横梁腹板开孔的加强设计提供一定的参考。     

管路激励下邮轮典型板架结构的声振特性

为合理评估邮轮结构的振动和噪声,并建立其振动噪声预报方法,需掌握邮轮上层建筑中典型开孔高腹板架结构的声振特性。采用试验与数值仿真相结合的方法,分析典型开孔高腹板架结构的振动特性及其在管路激励下的声振特性,探讨板架结构边界条件、管内流速和管路材料等因素对开孔高腹板架结构声振特性的影响规律。研究得到的邮轮典型开孔高腹板架结构声振特性的影响因素和影响规律,可供邮轮结构振动噪声预报和舒适度设计参考。     

波形钢腹板预应力混凝土组合梁桥——波形钢腹板力学性能有限元分析

波形钢腹板预应力混凝土组合梁桥是近年来在国内推广应用较为广泛的一种新型桥梁结构形式。由于波形钢腹板预应力混凝土组合梁的力学特性,波形钢腹板的屈曲稳定性是波形钢腹板预应力混凝土组合梁设计的重要问题。本文基于模型研究了波形钢腹板的腹板高度、腹板厚度等因素对其弹性剪切屈曲性能的影响。通过得到的屈曲特征值和屈曲模态图,对波形钢腹板的屈曲破坏情况做出总结,并且结合当前最新研究前沿,为以后的工作提供参考和改进。     

邮轮典型开孔高腹板板架结构极限强度分析

[目的]开孔高腹板板架结构是在大型邮轮上层建筑中广泛使用的一类特殊结构,为建立此类结构的设计方法,需充分掌握大型邮轮上层建筑典型开孔高腹板板架结构的力学特性。[方法]综合运用经典加筋板理论与非线性有限元方法,分析甲板初始缺陷、纵桁规格、腹板开孔对板架纵向受压极限承载能力的影响规律。[结果]发现薄板板架对于初始缺陷更为敏感且不同于厚板板架的初始变形模式,纵桁对纵压极限能力贡献度较大,纵压极限承载能力对开孔比例、开孔形状敏感性较低,开孔位置决定崩溃破坏屈曲带的位置,进而揭示了开孔高腹板板架的破坏失效模式。[结论]所得甲板初始缺陷、纵桁几何尺寸、腹板开孔诸因素对开孔高腹板板架极限强度的影响规律,可为邮轮结构轻量化设计及安全性评估提供指导。     

基于空腹桁架理论的船体结构腹板开孔强度简化分析方法

大型船舶结构的设计和建造过程中考虑到电缆管路布置及结构轻量化需求,常在主要构件高腹板上开设许多开孔。为快速有效评估高腹板开孔结构的强度特性,本文利用费氏空腹桁架理论和有限元数值方法,分析腰圆形开孔的纵向位置、开孔宽度和长度对开孔周边强度的影响,并对费氏空腹桁架理论作适当修正。结果表明,本文提出的修正公式能够适用于不同尺寸结构,并有效提高理论计算精度。     

基于空腹桁架理论的船体结构腹板开孔强度简化分析方法

大型船舶结构的设计和建造过程中考虑到电缆管路布置及结构轻量化需求,常在主要构件高腹板上开设许多开孔。为快速有效评估高腹板开孔结构的强度特性,本文利用费氏空腹桁架理论和有限元数值方法,分析腰圆形开孔的纵向位置、开孔宽度和长度对开孔周边强度的影响,并对费氏空腹桁架理论作适当修正。结果表明,本文提出的修正公式能够适用于不同尺寸结构,并有效提高理论计算精度。     

基于国军标对腹板开孔强横梁加强方式的讨论

为满足船体空间的布置需要,船体横梁腹板的开孔参数往往会超出规范要求,从而对其横向极限承载能力造成不利影响。因此需要采取加强措施,以保证其原有的横向极限承载能力。针对该问题,本文选取一强横梁为研究对象,参照GJB 4000-2000对腹板开孔及加强方式的相关规定,分析强横梁在腹板开孔加强情况下的横向极限承载能力,并就超规范腹板开孔强横梁的加强方式做一些讨论。通过分析和讨论,得到一些可供超规范腹板开孔强横梁加强设计参考的结论和建议。     

Evaluation of ultimate strength of stiffened panels under longitudinal thrust

A series of collapse analyses is performed applying nonlinear FEM on stiffened panels subjected to longitudinal thrust. MSC.Marc is used. Numbers, types and sizes of stiffeners are varied and so slenderness ratio as well as aspect ratio of local panels partitioned by stiffeners keeping the spacing between adjacent longitudinal stiffeners the same. Initial deflection of a thin-horse mode is imposed on local panels and that of flexural buckling and tripping modes on stiffeners to represent actual initial deflection in stiffened panels in ship structures. On the basis of the calculated results, buckling/plastic collapse behaviour of stiffened panels under longitudinal thrust is investigated. The calculated ultimate strength are compared with those obtained by applying several existing methods such as CSR for bulk carriers and PULS. Simple formulas for stiffened panels, of which collapse is dominated fundamentally by the collapse of local panels between longitudinal stiffeners, are also examined if they accurately estimate the ultimate strength. Through comparison of the estimated results with the FEM results, it has been concluded that PULS and modified FYH formulas fundamentally give good estimation of the ultimate strength of stiffened panels under longitudinal thrust.     

加筋板格高级屈曲分析技术研究及软件开发

文章给出了基于弹性大挠度理论和刚塑性分析的加筋板格高级屈曲分析方法(EPM),该方法包括五种失效模式,即正交加筋板格整体屈曲、纵向加筋子板格整体屈曲、纵向加筋和带板的局部屈曲或屈服、纵向加筋的侧倾以及全部屈服,可以考虑初始挠度和残余应力的影响以及双向压缩和侧向载荷的联合作用。以EPM方法为核心开发了加筋板格高级屈曲分析软件系统,包括任务管理、数据输入、屈曲分析、结果查看、能力曲线和文件分析等六个模块。为验证EPM方法的精度进行了系列纵向加筋和正交加筋板格试验模型的比较计算,并计算了四种典型加筋板格的双向应力能力曲线,与板格极限状态分析（PULS）软件和协调共同结构规范（HCSR）方法进行了比较分析。结果表明EPM方法可以分析联合载荷等因素对加筋板格极限强度的影响,文中开发的软件系统可用于加筋板格高级屈曲分析。     

New simplified approach to collapse analysis of stiffened plates

A new simplified model for collapse analysis of stiffened plates is developed in the framework of the idealized structural unit method (ISUM). By idealizing material and geometrical nonlinearities, larger structural units are defined as an element in ISUM than in conventional finite element analysis (FEA). The proposed stiffened plate model consists of ISUM plate elements and beam-column elements. The formulation of the plate element is performed by introducing accurate shape functions to simulate the buckling/plastic collapse behaviour of plate panels. Combining plate and beam-column elements allows for both local buckling of the plate panel and overall buckling of the stiffener.Fundamental collapse modes of plate panels and stiffened plates are investigated by conventional FEA. According to the observed characteristics, the new simplified model is formulated. Comparisons with FEA demonstrate the accuracy of the simplified model and its high applicability to typical stiffened plates in marine structures.     

The application of reliability methods in the design of tophat stiffened composite panels under in-plane loading

Composite materials have been widely used in modern engineering fields such as aircraft, space and marine structures due to their high strength-to-weight and stiffness-to-weight ratios. However, structural efficiency gained through the adoption of composite materials can only be guaranteed by understanding the influence of production upon as-designed performance. In particular, topologies that are challenging to production including panels stiffened with pi or tophat stiffeners dominate many engineering applications and often observe complex loading. The design of stiffened composite panels against buckling is a key point of composite structures. While a growing number of studies are related to the reliability analysis of composites few of these relate to the local analysis of more complicated structures. Furthermore for the assessment of these structures in a design environment it is important to have models that allow the rapid assessment of the reliability of these local structures. This paper explores the use of a stochastic approach to the design of stiffened composite panels for which typical applications can be found in composite ship structures. A parametric study is conducted using Navier grillage theory and First-order Reliability Methods to investigate any detectable trend in the safety index with various design parameters. Finally, recommendations are made to provide guidance on applications.     

基于CSR-H要求的加筋板屈曲评估方法研究

对CSR-H屈曲规范与现有规范在方法论上的差异进行分析,针对系列典型加筋板结构,对CSR-H规范、CSR-OT规范、CCS钢制海船入级规范中不同屈曲评估方法及EPM高级屈曲评估方法等进行数值比较研究。通过典型实船结构的屈曲强度评估和规范影响分析,分析CSR-H屈曲规范对于未来船体结构设计的影响。     

船体结构屈曲强度评估方法的规范研究及应用

论述了船舶结构规范中应用的结构屈曲强度评估方法的规范,如二维屈曲规范指定性要求,三维有限元模型中高级屈曲方法及其技术发展等。对其中的高级屈曲方法中的两种不同方法论的技术背景,包括理论基础和实际应用情况做了阐述,并对其中的非线性有限元加筋板格极限强度分析工作做了阐述,及时掌握目前国际领域新技术新标准发展信息。     

加筋板整体屈曲临界应力计算与分析

利用解析法对加筋板稳定性进行了研究,忽略材料非线性的影响,利用理论方法求解四边简支加筋板的整体屈曲临界应力。对有一根加强筋的加筋板,定义板的挠曲函数,将其代入边界方程和协调方程,求解线性方程组的特征方程得到加筋板的临界应力。对有2根或多根加强筋的规则加筋板,利用能量法导出统一计算的公式得到临界应力。最后,利用有限元软件Abaqus和Nastran进行数值仿真,与理论解比较后得出本文计算方法是正确的,可以准确求解加筋板的稳定性问题。     

Assessment of IACS-CSR implicit safety levels for buckling strength of stiffened panels for double hull tankers

The present study aims at applying structural reliability methods to assess the implicit safety levels of the buckling strength requirements for longitudinal stiffened panels implemented in the IACS Common Structural Rules (CSR) for double hull oil tankers. The buckling strength requirements considered are used in the initial stage of the hull girder scantlings’ design to control the buckling capacity of longitudinal stiffened panels subjected to the compressive loads induced by the hull girder vertical bending. The following buckling collapse failure modes are explicitly considered in the design formulation: uniaxial buckling of the plating between stiffeners, column buckling of stiffeners with attached plating and lateral-torsional buckling or tripping of stiffeners.The paper presents the procedure used to assess the implicit safety levels of the strength requirements for the three buckling collapse failure modes above mentioned, which includes the optimization of the scantlings of the plate panels and longitudinal stiffeners in order to reflect the minimum strength required by the formulation. A first order reliability formulation is adopted, and stochastic models proposed in the literature are used to quantify the uncertainty in the relevant design variables. A sample of five oil tankers representative of the range of application of the IACS-CSR design rules is considered. The effect of corrosion in the implicit safety levels is quantified based on the three corrosion levels of the Net Thickness Approach (NTA) adopted in the design rules. Sensitivity analyses are also performed to quantify the relative contribution or importance of each design random variable to the implicit safety levels.     

循环荷载作用下加筋板格单元的损伤累积及力学模型研究

为了计算加筋板和船体梁在循环荷载作用下的极限强度,将一种能够考虑损伤累积和构件局部屈曲的一维钢材等效本构模型引入到加筋板格单元中,提出加筋板格单元在轴向循环荷载作用下的损伤累积力学模型,采用Visual Basic程序编制了计算程序,对若干加筋板格单元在双向轴向循环荷载作用下的承载性能进行计算研究,并使用非线性有限元软件Abaqus进行对比验证,结果表明所提理论方法具有较好的精度。