• Structural Engineering and Mechanics
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• 제50권6호
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• pp.709-722
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• 2014

Ultra-High Performance Concrete (UHPC) is an innovative new material that, in comparison to conventional concretes, has high compressive strength and excellent ductility properties achieved through the addition of randomly dispersed short fibers to the concrete mix. This study presents the results of an experimental investigation on the behavior of axially loaded UHPC short circular columns wrapped with Carbon-FRP (CFRP), Glass-FRP (GFRP), and Aramid-FRP (AFRP) sheets. Six plain and 36 different types of FRP-wrapped UHPC columns with a diameter of 100 mm and a length of 200 mm were tested under monotonic axial compression. To predict the ultimate strength of the FRP-wrapped UHPC columns, a simple confinement model is presented and compared with four selected confinement models from the literature that have been developed for low and normal strength concrete columns. The results show that the FRP sheets can significantly enhance the ultimate strength and strain capacity of the UHPC columns. The average greatest increase in the ultimate strength and strain for the CFRP- and GFRP-wrapped UHPC columns was 48% and 128%, respectively, compared to that of their unconfined counterparts. All the selected confinement models overestimated the ultimate strength of the FRP-wrapped UHPC columns.

• 한국해양공학회지
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• 제22권2호
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• pp.85-90
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• 2008

Ships in bad weather conditions are likely to be subjected to accidental loads, such as high bending moment, collision, and grounding. Once she has damage to her hull, her ultimate strength will be reduced. This paper discusses an investigation of the effect of collision damage on the ultimate strength of a ship structure by performing a series of collapse tests. For the experiment, five box-girder models with stiffeners were prepared with a cross section of $720mm\;{\times}\;720mm$ and a length of 900mm. Of the five, one had no damage and four had an ellipse shaped damage area that represented the shape of the bulbous bow of a colliding ship. The amount of damage size was different between models. Among the damaged models, the damage in three of them was made by cutting the plate and stiffener, and in one by pressing to represent collision damage. Experiments were carried out under a pure bending load and the applied load and displacements were recorded. The ultimate strength was reduced as the damage size increased, as expected. The one with the largest amount of damage had damage to 30% of the depth, and its ultimate strength was reduced by 19% compared to the undamaged one. The pressed one has higher ultimate strength than those that were cut. This might be due to the fact that the plate around the pressed damage area contributes to the ultimate strength, whereas the cut one has no plate to contribute.

• 한국해양공학회지
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• 제6권2호
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• pp.103-112
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• 1992

The calculation method which takes into account the shear lag effects on the ultimate transverse bending moment of a SWATH(Small Waterplane Area Twin Hull) ship has been developed. In case of the ultimate bending strength analysis of conventional monohull ships and general box girder structures, the hypothesis that plane section remains plane after bending can be employed but not in the case of the structures having wide flange. For the ultimate bending strength analysis of such structures, a new method which can take into account the effect of shear lag on the ultimate bending strength has been developed by adopting more reasonable assumption that warping distortion of the section takes place inthe same way as the actual stress distribution. Finally, the proposed method has been applied to a a SWATH cross deck structure.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 가을 학술발표회 논문집
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• pp.101-109
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• 2004

Ship structures is thin-walled structures and she has lots of curved platings. In these days, lots different kinds of closed-formulas are development for ultimate strength of flat plate but for curved panels, there are not enough study or papers for this field. In this study, the ultimate strength characteristics for ship curved plates are studied. The ship plating is generally subjected to combined in-plane and lateral pressure loads. In-plane loads included biaxial compression/tension and edge shear. This is first report about the developing of ultimate compressive strength for ship curved plating. A closed-form formula for predicting the ultimate compressive strength of curved plates are empirically derived by curve fitting based on the computed results. The results and insights developed in the present study will be useful for damage tolerant design of curved plated structures.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 추계학술대회 논문집
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• pp.271-274
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• 2000

Despite the increasing necessity of accurate estimation of ring-stiffened cylinders' ultimate strength, the complex structural behavior of cylinders has made their design mainly depend on empirical formulas mostly based on insufficient test data rather than theoretical background. This paper has developed the imperfection method which enables the ultimate strength analysis of buckling sensitive structures by combining two general functions of common commercial finite element softwares, linear elastic buckling analysis and nonlinear stress analysis. Developed method was applied to two of the world most renowned commercial softwares, MSC/NASTRAN and ABAQUS, for the analysis of ring-stiffened cylinders and unexpectedly big difference in their analysis results was found. This tells that many widely used commercial softwares has their different strong points and week points and the choice of commercial software should be cautiously made after thorough inspection. This paper ends with some useful information about which of the aforementioned two softwares is more appropriate respectively for linear elastic buckling analysis and ultimate strength analysis of ring-stiffened cylinders.

• 한국해양공학회지
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• 제16권1호
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• pp.36-40
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• 2002

Despite the frequent use of ring-stiffened cylinders as a submarine pressure hull or members of various types of offshore structure, their ultimate strength analysis methods have not been well established because of their complex structural characteristics. This paper has established the method how to use commercial softwares based on the finite element method to implement the ultimate strength analysis of ring-stiffened cylinders covering both types of initial imperfection, i.e. initial deformation and initial stress by combining two separately offered functions of common commercial finite element softwares, linear elastic buckling analysis and nonlinear stress analysis. Developed method was applied to one of the world-widely used commercial softwares. ABAQUS for the analysis of ring stiffened cylinders. This paper ends with some useful information about the imperfection sensitivity of ultimate strength ring stiffened cylinders.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.114-118
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• 2001

Despite the frequent use of ring-stiffened cylinders as a submarine pressure hull or members of various types of offshore sutructures, their ultimate strength analysis methods have not been well established because of their complex structural characteristics. This paper has established the method how to use commercial softwares based on the finite element method to implement the ultimate strength analysis of ring-stiffened cylinders covering both types of initial imperfections, I. e. initial deformation and initial stress by combining two separately offered functions of common commercial finite element softwares, linear elastic buckling analysis and nonlinear stress analysis. Developed method was applied to one of the world-widely used commercial softwares, ABAQUS for the analysis of ring-stiffened cylinders. This paper ends with some useful information about the imperfection sensitivity of ultimate strength of ring-stiffened cylinders.

• 한국해양공학회지
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• 제15권2호
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• pp.120-123
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• 2001

Despite the increasing necessity of accurate estimation of ring-stiffened cylinders'ultimate strength, the complex structural behavior of cylinders has made their design mainly depend on empirical formulas mostly based on limited test data rather than theoretical background. This paper has developed the imperfection method which enables the ultimate strength analysis of buckling-sensitive structures by combining two separate functions covered by common commercial finite element softwares, which are linear elastic buckling analysis and nonlinear stress analysis. Developed method was applied to two of the world most renowned softwares, MSC/NASTRAN and ABAQUS, for the analysis of ring-stiffened cylinders and unexpectedly big difference in their analysis results was found. This tells that many widely used commercial softwares have their different strong points and weak points and the choice of commercial software should be cautiously made after thorough inspection. This paper ends with some useful information about which of the two aforementioned softwares is more respectively for the linear elastic buckling analysis and the ultimate strength analysis of ring-stiffened cylinders.

• 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.

• 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.