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1.
It is well known that pitting corrosion occurring on surface of hull structural plate will surely result in a significant degradation of the ultimate strength of the hull structural plate. This report aims at development of an assessing formula for ultimate strength of hull plate with pitting corrosion damage under the biaxial in-plane compression loading. The ultimate strength assessment model that is in terms of the corroded volume loss was deduced in theory, and which was then completed through numerical experiment by employing nonlinear finite element analyses for series of corroded plate models. Meanwhile, pitting corrosion in actual ship hull was analyzed and simulated, which ensured that all the assumptions for the finite element model parameters were in accord with the actual hull plate with pitting corrosion damage. Furthermore, the effects of plate slenderness, the linear factors at the plate edges and the ratio between the transverse and the longitudinal in-plane stresses on the ultimate strength reduction related to the corroded volume loss were discussed. The ultimate strength assessment formula being in terms of corroded volume loss developed in this research is expected to be applicable to assess the ultimate strength of the hull structural plate with pitting corrosion damage. 相似文献
2.
M. Mukhopadhyay 《Ocean Engineering》1981,8(5):497-505
The response of thin elastic plates having edges elastically restrained in rotation to different degrees and subjected to sinusoidal excitation has been investigated. The displacement and bending moment amplitudes have been determined for plates having different aspect ratios, rotational restraints at supports and frequency values. Comparison with available results indicated good accuracy. The formulation is based on a simple numerical procedure. 相似文献
3.
The fundamental frequency of vibration of plates elastically restrained against rotation along the edges and with centrally located circular or square holes is determined by means of the optimized Rayleigh's method. Independent solutions are also obtained using the finite element method.A comparison with experimental values is also presented in the case where the plate is rigidly clamped along the four edges. 相似文献
4.
为了研究循环载荷作用下扶强材初始损伤对其极限强度的影响,进行了14组扶强材的循环加载试验和分析。构造了考虑材料累积损伤完整、断筋和大变形的扶强材单元极限承载力计算公式,提出了相应循环载荷作用下损伤扶强材单元的端缩曲线表达式和船体梁极限强度计算的简化逐步破坏法。编制了循环载荷作用下船体梁损伤极限强度计算程序,进行了船体梁极限强度计算,并与有限元结果进行对比。研究结果表明：改进的损伤扶强材模型可较为准确地描述扶强材材料损伤的完整、断筋和大变形的极限承载力退化情况,扶强材腹板断裂的损伤相较初始大变形及材料累积损伤形式承载力下降程度更明显;所提出的循环载荷作用下损伤船体梁极限强度计算的简化逐步迭代方法,能定量地计算扶强材在不同类型损伤下的极限承载力退化程度,具有较高精度,方便易行,可应用于工程设计。 相似文献
5.
The new simple design equations for predicting the ultimate compressive strength of stiffened plates with initial imperfections in the form of welding-induced residual stresses and geometric deflections were developed in this study. A non-linear finite element method was used to investigate on 60 ANSYS elastic–plastic buckling analyses of a wide range of typical ship panel geometries. Reduction factors of the ultimate strength are produced from the results of 60 ANSYS inelastic finite element analyses. The proposed design equations have been developed based on these reduction factors. For the real ship structural stiffened plates, the most general loading case is a combination of longitudinal stress, transverse stress, shear stress and lateral pressure. The new simplified analytical method was generalized to deal with such combined load cases. The accuracy of the proposed equations was validated by the experimental results. Comparisons show that the adopted method has sufficient accuracy for practical applications in ship design. 相似文献
6.
This paper firstly figures out a similar scale model regarding ultimate strength experiment of a typical ultra large container ship (ULCS) through combined ultimate longitudinal bending and torsion analysis, in which the similarity theory is proposed to design the scale model for reflecting the progressive collapse behaviors of true ships in ultimate strength model test. The present study presents the similarity between scale model and true ship in cross-section considering the height of neutral axis, the section modulus, the inertia moment about neutral axis and the polar inertia moment should fit the geometrical similarity theory, and in strength considering buckling strength and shear ultimate strength of plates and stiffened panels should fit the strength similarity theory. Numerical investigations are conducted on the ultimate strength of a 10,000 TEU container ship and the similar scale model under pure hogging bending, pure torsion and combined bending and torsion, respectively. The nonlinear finite element method (NFEM) is adopted considering the effects of initial deformations and both material and geometric nonlinearities. Finally, the numerical results are compared with each other and discussed showing a good agreement in both elastic and inelastic range during the progressive collapse behaviors, which means the similar scale model can represent the true ship regarding ultimate strength test. And the similarity theory is verified quite stable after the uncertainty analysis. 相似文献
7.
针对受均匀轴向压力的矩形开孔板剩余极限强度的问题,考虑矩形板中间开圆孔和腰圆孔两种典型形状,四种边界条件下,以板的柔度系数、开孔率为主要影响参数通过大量非线性有限元数值计算分析,采用一种新的拟合方式提出了矩形开孔板轴向受压剩余极限强度的简化计算公式,新经验公式能够很好地反映开孔所导致板极限强度的衰减趋势。将所提出的经验公式计算结果分别与相应的试验结果、非线性有限元计算结果及其他经验公式计算结果进行对比分析。结果表明所提出的经验公式相比已有的经验公式计算更为准确,适用范围更广,可以用来预报不同边界条件下轴向均匀受压开孔矩形板的极限强度。 相似文献
8.
Artificial neural networks and their application to assessment of ultimate strength of plates with pitting corrosion 总被引：1，自引：0，他引：1
The potential for the structural capability degrading effects of both corrosion and fatigue induced cracks are of profound importance and must be both fully understood and reflected in vessel's inspection and maintenance programme. Corrosion has been studied and quantified by many researchers, however its effect on structural integrity is still subject to uncertainty, particularly with regards to localized corrosion. The present study is focused on assessing the effects of localized pitting corrosion on the ultimate strength of unstiffened plates. Over 265 non-linear finite-element analyses of panels with various locations and sizes of pitting corrosion have been carried out. The results indicate that the length, breadth and depth of pit corrosion have weakening effects on the ultimate strength of the plates while plate slenderness has only marginal effect on strength reduction. Transverse location of pit corrosion is also an important factor determining the amount of strength reduction. When corrosion spreads transversely on both edges, it has the most deteriorating effect on strength. In addition, artificial neural network (ANN) method is applied to derive a formula to predict ultimate strength reduction of locally corroded plates. It is found out that the proposed formulae can accurately predict the ultimate strength of locally corroded plates under uniaxial in-plane compression. 相似文献
9.
Jeom Kee Paik Anil K. Thayamballi P. Terndrup Pedersen Young Il Park 《Ocean Engineering》2001,28(8):51
For a ship hull with large deck openings such as container vessels and some large bulk carriers, the analysis of warping stresses and hatch opening deformations is an essential part of ship structural analyses. It is thus of importance to better understand the ultimate torsional strength characteristics of ships with large hatch openings. The primary aim of the present study is to investigate the ultimate strength characteristics of ship hulls with large hatch openings under torsion. Axial (warping) as well as shear stresses are normally developed for thin-walled beams with open cross sections subjected to torsion. A procedure for calculating these stresses is briefly described. As an illustrative example, the distribution and magnitude of warping and shear stresses for a typical container vessel hull cross section under unit torsion is calculated by the procedure. By theoretical and numerical analyses, it is shown that the influence of torsion induced warping stresses on the ultimate hull girder bending strength is small for ductile hull materials while torsion induced shear stresses will of course reduce the ship hull ultimate bending moment. 相似文献
10.
The present paper, of a tutorial nature, solves two different thermoelastic problems using a unified approach: (a) thermoelastic stresses and deflections in thin, rectangular plates with edges elastically restrained against rotation when small-deflection theory is used and stress resultants in the middle plane of the plates are neglected; and (b) thermoelastic plane stress situations in rectangular plates with stress-free edges subjected to a two-dimensional temperature distribution.The first problem is attacked using polynomial coordinate functions which identically satisfy the governing boundary conditions, and the Ritz method is used to determine the plate response. When the flexibility coefficients approach zero (clamped edge conditions) the calculated results practically coincide with the exact solution for the test case treated in this paper. On the other hand this degenerate solution turns out to be a very convenient approximation for obtaining a solution to Airy's problem described in the second place and which is also solved in a straightforward manner using a variational approach. 相似文献
11.
The failure of a ship hull girder is governed by buckling and plastic collapse of the deck, bottom and side shell steel stiffened plates. The stiffened steel plating in ships is generally subjected to both in-plane and out-of-plane loading and is more important to understand the characteristics of these panels under buckling. Tests are reported on the collapse load of stiffened plates with and without cutout and with reinforced cutout under uniaxial compression. A generalized computer program for the semi-analytical solutions proposed by various investigators based on strut approach and orthotropic plate approach, and a finite element analysis program based on orthotropic plate approach are developed. The panels are also analysed using the finite element analysis software ANSYS. An approximate method based on strut approach is proposed to calculate the collapse load of stiffened plates with cutouts and initial imperfections. The reduction in strength of the panels due to the presence of square cutout, rectangular cutout and increase in strength due to reinforcement around rectangular cutout are calculated based on the test results. Comparisons are made between the test results and predictions based on semi-analytical solutions and finite element analyses, and the uncertainty parameters calculated are discussed. Based on this study it is concluded that the cutout can be reinforced with a maximum increase in strength up to 19% for plate initiated failures. 相似文献
12.
3-D geometric modeler for rapid ship safety assessment 总被引：1，自引：0，他引：1
CAD systems are used broadly in the shipbuilding industry. CAD systems for naval architecture are a useful tool for hull form, internal arrangement and the structural design of ships. These systems require high precision and expertise for efficient use. Therefore, these systems are not appropriate in supporting emergency responses, which require rapid modeling even if it generates some errors.This paper describes a geometric modeler for rapid ship safety assessment. The modeler is developed based on the 3-D geometric modeling kernel ACIS. The definition of hull form, internal arrangement and major longitudinal structural members is a fundamental function of the modeler. The developed modeler is interfaced with other applications used for ship safety assessment such as hydrostatic calculation, ship motion analysis in wave condition, longitudinal strength analysis and so on. In addition, it can generate a new ship model by making variations in a previously defined ship model. 相似文献
13.
This paper deals with the determination of an approximate fundamental frequency equation for a rectangular plate with two edges (y = 0, b) elastically restrained against rotation while the edges x=0, a are free but internal supports parallel to the free edges are present in the structural system. The algorithmic procedure can be easily implemented on a micro computer or even a hand, programmable calculator.Good engineering agreement with experimental results is shown to exist in the case of a plate with edges y=0,b rigidly clamped. 相似文献
14.
Diana V. Bambill Raúl E. Rossi Verónica Jederlinic Carlos A. Rossit 《Ocean Engineering》1997,24(1):45-49
Transverse vibrations of a rectangular plate with three edges elastically restrained against rotation while the fourth is free are studied using (a) an analytical approach based on the optimized Rayleigh-Ritz method and (b) the finite element method. The study was motivated by the necessity of finding out how the lower frequencies of vibration were affected by introducing a step discontinuity in the plate thickness. This variation in the plate thickness was practiced in order to obtain a reduction in the total plate weight. 相似文献
15.
GPU-Based DEM Simulations of Global Ice Resistance on Ship Hull During Navigation in Level Ice 总被引：1，自引：0，他引：1
The ice resistance on a ship hull affects the safety of the hull structure and the ship maneuvering performance in icecovered regions.In this paper,the discrete element method(DEM)is adopted to simulate the interaction between level ice and ship hull.The level ice is modeled with 3D bonded spherical elements considering the buoyancy and drag force of the water.The parallel bonding approach and the de-bonding criterion are adopted to model the freezing and breakage of level ice.The ship hull is constructed with rigid triangle elements.To improve computational efficiency,the GPU-based parallel computational algorithm was developed for the DEM simulations.During the interaction between the ship hull and level ice,the ice cover is broken into small blocks when the interparticle stress approaches the bonding strength.The global ice resistance on the hull is calculated through the contacts between ice elements and hull elements during the navigation process.The influences of the ice thickness and navigation speed on the dynamic ice force are analyzed considering the breakage mechanism of ice cover.The Lindqvist and Riska formulas for the determination of ice resistance on ship hull are employed to validate the DEM simulation.The comparison of results of DEM,Lindqvist,and Riska formula show that the DEM result is between those the Lindqvist formula and Riska formula.Therefore the proposed DEM is an effective approach to determine the ice resistance on the ship hull.This work can be aided in the hull structure design and the navigation operation in ice-covered fields. 相似文献
16.
P.M. CiancioJ.A. Reyes 《Ocean Engineering》2003,30(11):1323-1333
This paper deals with the determination of the critical load in the buckling of isotropic, circular annular thin plates whose thickness varies slightly according to an exponential law.The outer edge of the plate is elastically restrained against rotation while the inner boundary is free. Classical small-deflection theory is used. An hidrostatic pressure acting in the middle plane is considered.The eigenvalues of the problem are obtained by means of an analytical approach based on the optimized Rayleigh-Ritz method. It is shοwnι that the results are in good agreement from an engineering viewpoint, with those available in the literature. 相似文献
17.
大型集装箱船（LCS）具有较大的甲板开口，抗扭刚度非常低。在恶劣海况下航行时，大型集装箱船可能会遭遇斜浪的作用，此时船体将受到三向载荷的联合作用，水平波浪弯矩和扭转波浪弯矩可能会接近甚至超过垂向波浪弯矩，船体可能因发生组合变形而破坏。因此有必要研究大型集装箱船在三向载荷联合作用下的结构可靠性。在研究三向载荷联合作用下各维度极限强度的相互关系的基础上，提出了大型集装箱船的极限承载能力的可靠性评估方法，并对目标船在各浪向角下的结构可靠性进行评估。结果表明：目标船在0°浪向角下的失效概率最高；考虑水平波浪弯矩影响后目标船的结构可靠性有所降低；扭转波浪弯矩对目标船船中剖面的结构可靠性影响较小。 相似文献
18.
未埋设的海底管道在高温高压运行条件下可能发生侧向屈曲,情况严重时影响海底管道的结构安全。侧向屈曲临界力作为判定海底管道发生侧向屈曲的重要依据,主要影响因素有初始缺陷、管土相互作用等。现有关于侧向屈曲临界力的公式并未考虑管土相互作用、缺陷不平直度和管道自身材料特性对侧向屈曲临界力的综合影响。建立含有通用几何初始缺陷海底管道的数值模型,使用Riks算法进行参数分析以研究极限侧向土壤阻力、管道缺陷不平直度和截面几何尺寸对海底管道侧向屈曲的具体影响。基于量纲分析法和多元线性回归,推导出海底管道侧向屈曲临界力关于上述3个影响参数的一般公式,并对该公式进行了检验,结果表明文中推导的公式在参数涵盖的研究范围内有效。 相似文献
19.
The present paper is Part II of a series of three papers on methods useful for the ultimate limit state assessment of ships and ship-shaped offshore structures. In contrast to Part I [Paik et al., 2007a. Methods for ultimate limit state assessment of ships and ship-shaped offshore structures: Part I unstiffened plates, Ocean Engineering, doi:10.1016/j.oceaneng.2007.08.004] that deals with unstiffened plates, the present paper (Part II) is focused on methods for the ultimate limit state assessment of stiffened plate structures under combined biaxial compression and lateral pressure actions. The object structure is the bottom part of an AFRAMAX-class hypothetical double-hull oil tanker structure designed by IACS common structural rules (CSR) method, that is the same ship studied in Part I. Three candidate methods, namely ANSYS nonlinear finite element method, DNV PULS method, and ALPS/ULSAP method, are employed for the present study. The results and insights developed from the present study are summarized in terms of ultimate strength characteristics of bottom-stiffened plate structures. 相似文献
20.
An optimization approach for fairing of ship hull forms 总被引：2，自引：0，他引：2
Ebru Sariz 《Ocean Engineering》2006,33(16):2105-2118
This paper presents a numerical fairing procedure to be used at the preliminary design stage to create high-quality ship hull form geometry. The procedure is based on a variational optimization approach in which a fairness measure related to the surface curvature is the objective function to be minimized subject to a set of geometric constraints to ensure that the final form has the required geometric characteristics. The optimization variables are selected as the control points of a B-spline surface representing the initial hull form. A nonlinear direct search technique is employed to solve the problem. The methodology is applied for typical ship forms to indicate that, provided that the designer can specify appropriate design objectives and geometric constraints, the methodology can produce alternative hull forms with significantly improved fairing characteristics. The choice of the fairness objective function is shown to have a crucial effect on the quality of the hull surface. Highly nonlinear exact fairness functionals yield surfaces of high quality at the expense of high-computerized effort. 相似文献