• Structural Engineering and Mechanics
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• 제42권4호
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• pp.531-549
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• 2012

Numerous oil tanker losses have been reported and one of the possible causes of such casualties is caused by the structural failure of aging ship hulls in rough weather. In aging ships, corrosion and fatigue cracks are the two most important factors affecting structural safety and integrity. This research is about effect on hull girder ultimate strength behavior of double hull oil tanker according to corrosion after Part I: stiffened panel. Based on corrosion data of Part I (time-dependent corrosion wastage model and CSR corrosion model), when progressing corrosion of fourtypes of double hull oil tankers (VLCC, Suezmax, Aframax, and Panamax), the ultimate strength behavior of hull girder is compared and analyzed. In case of the ultimate strength behavior of hull girder, when occurring corrosion, the result under vertical and horizontal bending moment is analyzed. The effect of time-dependent corrosion wastage on the ultimate hull girder strength as well as the area, section modulus, and moment of inertia are also studied. The result of this research will be useful data to evaluate ultimate hull girder strength of corroded double hull oil tanker.

• 대한조선학회논문집
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• 제52권4호
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• pp.349-355
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• 2015

Through the recent accident, the checking of ultimate hull girder capacity for container ship should be needed. Smith’s method is well known as the only simplified method to access rapidly for ultimate hull girder capacity except very expensive nonlinear F.E approach. This simplified method, however, is admitted to apply only to bulker and tanker in accordance with Classification Rules up to now. The targets of this study are to verify effectiveness of the simplified method for container ship’s ultimate hull girder strength and to propose the safety factor considering the local bending in double bottom structures due to out of plane loads through the nonlinear F.E analyses. Two different sized ships and three loading conditions which are pure bending, homo-loading and one-bay empty condition were used for this study. Based on the F.E results, the present study showed that CSR’s simplified method is available for the ultimate hull girder strength of container ship and over 1.2 of safety factor should be applied to consider the local bending effect in double bottom structures due to out of plane loads such as sea pressure an cargo.

• Journal of Ship and Ocean Technology
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• 제12권1호
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• pp.45-56
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• 2008

Recently, International Association Classification Societies (IACS) has adopted the Common Structural Rules (CSR) for Bulk Carriers and Tankers, which specifies the requirement associated with the ultimate strength of hull girder structure. The theoretical background and the results of verification study are neither well summarized nor released. Furthermore, the requirement is not a form of deterministic formula but a form of program in which source code is not disclosed. The reliability of the non-linear structural analysis program is verified through the comparison with the results of the analysis and the model test. Then, the reliability of the ultimate strength requirement in CSR is checked by comparing with the results of rigorous non-linear analysis.

• Structural Engineering and Mechanics
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• 제78권4호
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• pp.473-484
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• 2021

Similar to other structures, ultimate strength values showing the maximum load that the structure can resist without damaging has great importance on ships. Therefore, increasing the ultimate strength values will be an important benefit for the structure. Low carbon steels used in ships due to their low cost and good weldability. Improving the ultimate strength values without interfering with the chemical composition to prevent of the weldability properties of these steels would be very beneficial for ships. Grain refinement via severe plastic deformation (SPD) is an essential strengthening mechanism without changing the chemical composition of metallic materials. Among SPD methods, equal channel angular pressing (ECAP) is one of the most commonly used one due to its capacity for achieving bulk ultrafine-grained (UFG) materials. When the literature is examined, it is seen that there is no study about ultimate strength calculation in ships after ECAP. Therefore, the mean purpose of this study is to apply ECAP to a shipbuilding low carbon steel to be able to achieve mechanical properties and investigate the alteration of ship hull girder grillage system's ultimate strength via finite element analysis approach. A fine-grained (FG) microstructure with a mean grain size of 6 ㎛ (initial grain size was 25 ㎛) was after ECAP. This microstructural evolution brought about a considerable increase in strength values. Both yield and tensile strength values increased from 280 MPa and 425 MPa to about 420 MPa and 785 MPa, respectively. This improvement in the strength values reflected a finite element method to determine the ultimate strength of ship hull girder grillage system. As a result of calculations, it was reached significantly higher ultimate strength values (237,876 MPa) compared the non-processed situation (192,986 MPa) on ship hull girder grillage system.

• Structural Engineering and Mechanics
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• 제15권2호
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• pp.225-238
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• 2003

In the present study, the finite strip analysis of a box girder to simulate a ship's hull model is carried out to investigate its inelastic post-buckling behavior and to predict its ultimate flexural strength. Residual stresses and initial geometrical imperfections are both considered in the combined material and geometrical nonlinear analysis. The von-Mises yield criterion and the Prandtl-Reuss flow theory of plasticity are applied in modeling the elasto-plastic behavior of material. The Newton-Raphson iterative process is also employed in the analysis to achieve convergence. The numerical results agree well with the experimental data. The effects of some material and geometrical parameters on the ultimate strength of the structure are also investigated.

• 대한조선학회논문집
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• 제43권3호
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• pp.340-350
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• 2006

This paper is concerned with a practical guide for the ultimate longitudinal strength assessments of ships' hull structure. Rigorous non-linear structural analysis for three tanker models has been carried out to examine the ultimate strength behavior. Formula of estimating the ultimate longitudinal strength has been proposed which is modified with the results of non-linear finite element analysis of hull girders. Computational reliability and accuracy of the large-scale non-linear finite element analysis and the proposed simplified formula are verified through comparing their results with that of 1/3 scale frigate model test and DNVs program. Additionally, the ultimate longitudinal strength for ten tanker models is compared with those by the method specified in the 2nd Draft of common structural rule for tankers, which is being developed by IACS.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 춘계학술대회 논문집
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• pp.77-82
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• 2004

노후선박의 구조적 안전성을 확보하기 위해서는 부식이나 피로균열 및 기계적인 손상에 의하여 선체 구조 강도가 어떠한 영향을 받는지 충분히 검토하여 적절한 수리 보수 등 이에 대한 대책을 강구할 필요가 있다. 본 연구에서는 이러한 관점에서 부식, 피로균열, 기계적인 손상과 같은 노후 선박에 발생할 수 있는 여러 가지 손상이 선체강도에 미치는 영향을 이론적, 수치적, 실험적인 방법을 통하여 조사하고, 이를 통하여 선각거더의 소성붕괴강도 저하를 고려한 신뢰성 평가법 및 보수, 수리를 통한 인정수준 이상의 선각강도를 유지하게 하는 지침도 연구하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권6호
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• pp.705-719
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• 2017

Progressive Collapse Method (PCM) has been broadly applied to predict moment-carrying capacity of a hull girder, however accuracy of PCM has not been much studied. Accuracy of PCM is known to be dependent on how Load-Shortening and -Elongation (LSE) curve of a structural units are well predicted. This paper presents a new procedure to determine LSE datum based on box girder Finite Element Analyses (FEAs) instead of using finite element model of stiffened panels. To verify reliability of FEA results, the simple box girder collapse test results are compared with FEA results of same box girders. It reveals one frame-based box girder model is sufficiently accurate in terms of ultimate strengths of the box girders. After extracting LSE data from the box girders, PCM-based moment-carrying capacities are compared with those from FEAs of the box girders. PCM results are found to be equivalent to FEAs in terms of moment-carrying capacity if accurate LSE data are secured. The new procedure is applied to well-known 1/3 scaled frigate full section. Very excellent moment-carrying capacity of frigate hull section is obtained from PCM with LSE data from box girder FEAs.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.325-342
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• 2020

The current study is focused on the evaluation of the ultimate strength of stiffened panels found in ship hull structures that are subjected to combined uniaxial thrust, in-plane and out-of-plane bending moments. This loading condition, which is in general ignored when performing buckling checks, applies to representative control geometries (stiffener with attached plating) as a consequence of the linearly varying normal stresses along the ship's depth induced by the hull-girder vertical bending moment. The problem is generalized by introducing a non-uniform thrust described by a displacement ratio and rotation angle and by introducing the slenderness ratios, within the practical range of interest. The formed design space is explored through methods sourcing from Design of Experiments and by applying non-linear finite element procedures. Surrogate empirical models have been constructed through regression analysis and Response Surface Methods. An additional empirical model is provided to the literature for predicting the ultimate strength under uniaxial thrust. The numerical experimentation has shown that is a significant influence on the ultimate strength of stiffened panels as the thrust non-uniformity increases.

• 대한조선학회논문집
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• 제50권4호
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• pp.255-261
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• 2013

This paper presents prediction of ultimate longitudinal strength of a VLCC, "Energy Concentration" for which many benchmark studies have been carried out, based on kinematic displacement method proposed by Tayyar and Bayraktarkatal (2012). Kinematic displacement theory provides semi-analytical solution of average compressive strengths for various kinds of stiffened panels. The accuracy of average compressive strengths obtained from formulas of CSR(common structural rules) for tankers and kinematic displacement method are discussed in the fore part of this paper. Hull girder ultimate strengths using Smith method are also compared for different average compressive strengths. By comparing them with other benchmark results, it is concluded that the new method provides lower bounds, because hull girder strengths under the sagging and hogging moment conditions approach nearly lower bounds.