船体结构总纵极限强度的简化逐步破坏分析方法

本文基于Smith方法,应用梁-柱理论、理想弹塑性假设、平截面假设和塑性铰理论建立了加筋板单元的应力-应变关系曲线,导出了船体结构总纵极限强度的简化逐步破坏分析方法并编制成FORTRAN计算程序.应用作者导出的简化逐步破坏分析方法分析计算了Reckling 23号模型总纵极限强度.计算结果表明,本文导出的简化逐步破坏分析方法和计算程序正确可靠,可供船体结构设计和使用.本文还对船体结构总纵极限强度的影响因素进行了分析,其中包括加筋板单元的载荷-缩短行为、横向压力、材料屈服强度和腐蚀等.     

冰载荷对加筋板轴向压缩极限强度的影响

船舶在冰区航行时,将遭受浮冰的挤压,船舷侧部位的加筋板会受到冰载荷的作用。以单筋单跨加筋板为研究对象,采用非线性有限元法对冰载荷下加筋板轴向压缩极限强度进行分析。研究冰载荷的大小、加载区域面积和加载区域位置的不同对极限强度的影响规律。结果表明,冰载荷大小一定,冰载荷作用区域面积逐渐增加时,加筋板的轴向压缩极限强度随着面积的增加基本呈线性增加。冰载荷作用区域位置距离加筋板中心点距离逐渐增加时,加筋板的轴向压缩极限强度逐渐增加,且随着相对距离的增加,对加筋板轴向压缩极限强度的影响越来越大。这些结果可用于指导冰区船舶结构的设计以及维护。     

Interactive flexural-torsional buckling behaviour of stiffened plating

Results from a series of studies on stiffened plates under axial compression are presented in this paper. The large-deflection elasto-plastic behaviour of each panel component is described by the von Karman equations, thus enabling the lateral-torsional buckling of the stiffener to be modelled in a rigorous manner. Material nonlinearity is represented using the von Mises yield criterion in conjunction with the Prandtl-Reuss flow rule. Results are presented in the form of average stress-strain curves which are used to generate maximum strength curves for the stiffener and plate.     

不同焊接顺序下加筋板变形及残余应力的三维有限元研究

针对焊接过程的二维有限元计算与实际情况存在一定差别的问题，使用三维热弹-塑性有限元法对不同焊接顺序下加筋板焊接过程进行了仿真，获得了加筋板焊接引起的温度场、位移场和应力场。结果表明：在4点约束条件下，加筋板横截面的变形为中垂变形，纵筋的变形为中拱变形，方案1横截面变形更小，方案2纵筋变形更小。焊接引起的加筋板残余应力主要表现为横向应力，其在近焊缝区为拉应力，达到材料屈服强度，远离焊缝区表现为压应力，达到0.2倍材料屈服强度。加强筋横向应力峰值出现在起弧端和收弧端，约为0.85倍材料屈服强度，纵向应力峰值出现在焊接起弧端，约为0.3倍材料屈服强度。在加筋板横截面位置，焊接顺序主要影响加强筋处的残余应力；在加强筋位置，焊接顺序主要影响纵向应力。每组焊缝同时同向焊接，且每根纵筋从左向右依次焊接的焊接方案产生更小的残余应力。     

浮式平台上部模块非管节点SCF控制方法

应力集中系数（Stress Concentration Factor，SCF）是评估节点疲劳损伤的重要参数。针对浮式平台上部模块非管节点的SCF控制，设计5种加强形式，采用Ansys软件对非管节点进行SCF分析。结果表明：筋板加强可有效改善面外弯矩作用下的应力集中；扣管加强对轴向力、面内弯矩和面外弯矩均具有较好的改善效果。     

Ultimate strength of container ships subjected to combined hogging moment and bottom local loads,Part 2: An extension of Smith's method

This paper is the second of two companion papers concerning the ultimate hull girder strength of container ships subjected to combined hogging moment and bottom local loads. The nonlinear finite element analysis in Part 1 has shown that local bending deformation of a double bottom due to bottom lateral loads significantly decreases the ultimate hogging strength of container ships. In this Part 2, extending Smith's method for pure bending collapse analysis of a ship's hull girder, a simplified method of progressive collapse analysis of ultimate hogging strength of container ships considering bottom local loads is developed. The double bottom is idealized as a plane grillage and the rest part of the cross section as a prismatic beam. An average stress-average strain relationship of plate/stiffened plate elements employed in Smith's method is transformed into an average stress-average plastic strain relationship, and implemented in the conventional beam finite element as a pseudo strain hardening/softening behaviors. The extended Smith's method is validated through a comparison with nonlinear finite element analysis.     

基于J积分的含裂纹加筋板在单轴拉伸载荷下的极限强度计算

为研究含裂纹加筋板的极限拉伸强度,本文建立一系列不同长细比、不同裂纹长度、不同裂纹位置的含裂纹加筋板有限元模型,并基于J积分理论对其在单轴拉伸载荷下的极限强度进行了计算。结果发现含裂纹加筋板极限拉伸强度随加筋板长细比的增大略有减小,但减小的程度并不明显;含裂纹加筋板极限拉伸强度随裂纹长度的增大而减小,且减小的幅度逐渐增大;加强筋上的裂纹对含裂纹加筋板极限强度的影响小于底板上的裂纹,而裂纹同时出现在底板和加强筋上时对含裂纹加筋板极限拉伸强度的影响最大。表明含贯穿型裂纹的加筋板在单轴拉伸载荷下的剩余强度对加筋板长细比不敏感,而对裂纹长度较为敏感。     

组合应力作用下含腐蚀缺陷海管安全工作压力评价方法

在较高温度和压力作用下,由于土壤的摩擦阻力,海管会产生很大的轴向压力,以及由侧向屈曲引发的弯矩。因此对含腐蚀缺陷管道安全工作压力的评价,须考虑轴向压应力的影响。对目前工程界的评价方法进行对比分析,在内压和轴向压应力组合作用下,含腐蚀缺陷海管的安全压力评价方法还很不完善,尤其是复杂缺陷,目前的规范还不完全适用。通过对许用应力法安全系数的讨论和分析,基于Von Mises准则和有限元分析,提出了组合应力作用下含腐蚀缺陷海管的安全工作压力评价方法。通过该方法对某运行了近三十年的管道进行了安全工作压力的评估,同时考察了轴向压应力对安全工作压力的影响。此方法对应的轴向压应力限值和安全等级以及安全系数相关,当安全等级低时,其值和DNV-RP-F101规范值基本一致,当安全等级高时,其值比DNV-RP-F101规范值大。     

Effect of pitting corrosion on the ultimate strength of steel plates subjected to in-plane compression and bending

Corrosion pits with a circular cone shape are typically observed on coated hold frames of aged bulk carriers which carry exclusively coal and iron ore. In order to ensure the safety of these types of bulk carrier, it is necessary to understand the effect of pitting corrosion on the local strength of hold frames. In order to investigate this effect, a series of nonlinear finite-element (FE) analyses has been performed with pitted plates subjected to in-plane compressive loads and bending moments. It has been shown that the ultimate compression load or bending moment of pitted plates is smaller than that of uniformly corroded plates in terms of average thickness loss, and that predictions of the ultimate strength using the average thickness loss at the minimum cross section would be conservative. In order to establish a method of evaluating strength reduction due to pitting corrosion, it is important to identify the failure mode that would be most detrimentally affected by pitting corrosion. It was found that the reduction of the ultimate compressive load or bending moment due to pitting corrosion is smaller than that of the tensile strength in terms of equivalent thickness.     

Ultimate strength of container ships subjected to combined hogging moment and bottom local loads part 1: Nonlinear finite element analysis

This paper is the first of two companion papers concerning the ultimate hull girder strength of container ships subjected to combined hogging moment and bottom local loads. In the midship part of container ships, upward bottom local loads are usually larger than the downward ones. This leads to the increase of biaxial compression in the outer bottom plating and the reduction of the ultimate hull girder strength in the hogging condition. In this Part 1, the collapse behavior and ultimate strength of container ships under combined hogging moment and bottom local loads are analyzed using nonlinear finite element method. Buckling collapse behavior of bottom stiffened panels during the progressive collapse of a hull girder is closely investigated. It has been found that major factors of the reduction of ultimate hogging strength due to bottom local loads are (1) the increase of the longitudinal compression in the outer bottom and (2) the reduction of the effectiveness of the inner bottom, which is on the tension side of local bending of the double bottom. The obtained results will be utilized in the Part 2 paper to develop a simplified method of progressive collapse analysis of container ships under combined hogging moment and bottom local loads.     

A Simplified Model for the Effect of Weld-Induced Residual Stresses on the Axial Ultimate Strength of Stiffened Plates

The present work investigates the compressive axial ultimate strength of fillet-welded steel-plated ship structures subjected to uniaxial compression, in which the residual stresses in the welded plates are calculated by a thermo-elasto-plastic finite element analysis that is used to fit an idealized model of residual stress distribution. The numerical results of ultimate strength based on the simplified model of residual stress show good agreement with those of various methods including the International Association of Classification Societies (IACS) Common Structural Rules (CSR), leading to the conclusion that the simplified model can be effectively used to represent the distribution of residual stresses in steel-plated structures in a wide range of engineering applications. It is concluded that the widths of the tension zones in the welded plates have a quasi-linear behavior with respect to the plate slenderness. The effect of residual stress on the axial strength of the stiffened plate is analyzed and discussed.     

爆炸载荷作用下单向加筋板的塑性动力响应分析

从加筋板面板以及加强筋的运动方程出发,分析了爆炸载荷作用下单根加筋固支方板的大挠度塑性动力响应。分析表明:加筋板的运动,取决于加强筋的相对刚度以及载荷峰值的大小,将呈现出3种不同的模式。研究仅限于讨论加筋板的总体变形模式,具体讨论了单向加筋固支方板在忽略弯矩影响下的薄膜解法。得到的理论结果与已有的试验结果在多数情况下符合良好,表明简化理论分析方法能对爆炸载荷下单向加筋固支方板的永久变形做出较为合理的预报。     

Ultimate strength design of stiffened plates under axial compression and bending

The basis for design of stiffened plates under longitudinal compression is outlined and predictions using several codes are compared against numerical results from an inelastic beam-column formulation and test results. In order to explore the inherent differences in column behaviour separately from discrepancies arising due to plate panel behaviour, the code predictions are re-evaluated adopting a common plate panel effective width formulation. On this basis, a critical review of code methods is made and some modifications are proposed.

The effect of the magnitude and direction of applied uniform bending on the axial capacity of stiffened plates is investigated by comparing two alternative design approaches, namely an interaction equation and a method based on the Perry equation, against results from numerical analyses and from rigid plastic theory. The interaction equation is invariably more conservative than the Perry approach but its simplicity tends to be convenient for routine design applications. Finally, results of numerical analyses, together with experimental results from previous studies, on continuous stiffened plates under combined axial compression and lateral pressure are presented and available design guidance is discussed.     

焊接诱导的残余应力对加劲板轴向极限强度影响的简化模型研究（英文）

The present work investigates the compressive axial ultimate strength of fillet-welded steel-plated ship structures subjected to uniaxial compression, in which the residual stresses in the welded plates are calculated by a thermo-elasto-plastic finite element analysis that is used to fit an idealized model of residual stress distribution. The numerical results of ultimate strength based on the simplified model of residual stress show good agreement with those of various methods including the International Association of Classification Societies(IACS) Common Structural Rules(CSR), leading to the conclusion that the simplified model can be effectively used to represent the distribution of residual stresses in steel-plated structures in a wide range of engineering applications. It is concluded that the widths of the tension zones in the welded plates have a quasi-linear behavior with respect to the plate slenderness. The effect of residual stress on the axial strength of the stiffened plate is analyzed and discussed.     

Ultimate strength assessment of a tanker hull based on experimentally developed master curves

A geometrically similar scaling was made from small-scale specimen to full-scale stiffened panels and then their collapse behaviour is investigated. It is considered that the stiffened panel compressive ultimate strength test was designed according to geometrical scaling laws so that the output of the test could be used as representative of the stiffened panels of the compressive zone of a tanker hull subjected to vertical bending moment. The ultimate strength of a tanker hull is analysed by a FE analysis using the experimentally developed master stress-strain curves which are obtained by the beam tension test and the compressive test of the stiffened panel, and are then compared with the result achieved by the progressive collapse method.     

基于试验获取主应力应变曲线的油船极限强度评估研究(英文)

A geometrically similar scaling was made from small-scale specimen to full-scale stiffened panels and then their collapse behaviour is investigated. It is considered that the stiffened panel compressive ultimate strength test was designed according to geometrical scaling laws so that the output of the test could be used as representative of the stiffened panels of the compressive zone of a tanker hull subjected to vertical bending moment. The ultimate strength of a tanker hull is analysed by a FE analysis using the experimentally developed master stress-strain curves which are obtained by the beam tension test and the compressive test of the stiffened panel, and are then compared with the result achieved by the progressive collapse method.     

复合材料船体纵向极限强度可靠性分析

把船体甲板或船底板结构视为是一系列加筋板单元的组合，然后利用复合材料梁柱理论计算船体加筋板单元构件的极限承载能力，最后用Smith法计算复合材料船体的极限承载能力。由于复合材料船体纵向极限强度的极限状态方程不能简单地用船体各参数显式表达，故将近年发展起来的响应面法与JC法相结合，对复合材料船体纵向极限强度进行了可靠性分析。并讨论了影响船体纵向极限强度可靠性各变量的敏感性。     

玄武岩纤维复合材料层合加筋板轴向动力压缩破坏分析

基于通用有限元软件,结合复合材料失效准则对玄武岩纤维复合材料层合加筋板在轴向动力压缩载荷作用下的破坏问题进行了研究,并比较了玄武岩纤维复合材料层与S-2玻璃纤维增强复合材料帽形层合加筋板轴向动力压缩破坏的差异.研究结果表明,玄武岩纤维复合材料层合加筋板具备与S-2玻璃纤维复合材料层合加筋板相当的轴向压缩性能.本研究可以为选用玄武岩纤维作为高速舰船船体材料提供参考依据.     

具有裂纹缺陷的加筋板的剩余拉伸强度分析

对具有裂纹缺陷的加筋板的剩余强度进行了数值分析.考虑了加筋板上的三种缺陷形式,即板和筋上的垂直裂纹,板和筋上的倾斜裂纹以及板上的裂纹和筋上的圆孔.对板和筋上的相对裂纹长度、材料属性、板和筋的厚度、裂纹开裂角度以及圆孔的直径等影响参数进行了分析.同时,将无加筋板剩余强度的经验公式推广到加筋板,并验证了公式的有效性.     

Parametric dependencies of the post-ultimate strength behavior of a ship’s hull girder in waves

To rationally assess the consequence of a ship’s hull girder collapse, it is necessary to know the post-ultimate strength behavior of the hull girder including the global deformation and motions under extreme wave-induced loads. In the foregoing research, the authors proposed a numerical analysis system to predict the collapse behavior in waves including the post-ultimate strength behavior. The primary objective of the present paper is to clarify the parametric dependencies of the severity of the collapse in a rational manner. The parameters may include those related to load-carrying capacity and the extreme loads. To this end, an analytical solution to describe the post-ultimate strength behavior is derived. Assuming that a plastic hinge is formed at the midship during the collapse procedure, the whole ship is modeled as a two-rigid-bodies system connected to each other amidship via a nonlinear rotational spring, which represents the nonlinear relationship between the bending moment and the rotational angle. The relationship may be modeled as piece-wise linear curves. It is further assumed that large motions and elastic/plastic deformations of the hull girder may not affect the load evaluations, and that the hull girder is subjected to a large single wave. Some important parameters to predict the severity of the collapse are specified based on the analytical solution.