• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.1
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• pp.47-61
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• 2013

This study compares the Residual ultimate longitudinal strength - grounding Damage index (R-D) diagrams produced by two analysis methods: the ALPS/HULL Intelligent Supersize Finite Element Method (ISFEM) and the design formula (modified Paik and Mansour) method - used to assess the safety of damaged ships. The comparison includes four types of double-hull oil tankers: Panamax, Aframax, Suezmax and VLCC. The R-D diagrams were calculated for a series of 50 grounding scenarios. The diagrams were efficiently sampled using the Latin Hypercube Sampling (LHS) technique and comprehensively analysed based on ship size. Finally, the two methods were compared by statistically analysing the differences between their grounding damage indices and ultimate longitudinal strength predictions. The findings provide a useful example of how to apply the ultimate longitudinal strength analysis method to grounded ships.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.3
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• pp.509-525
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• 2015

Predicting residual strength of corroded plates is of crucial importance for service life estimation of aged structures. A series of nonlinear finite element method is employed for ultimate strength analysis of stiffened plates with pitting corrosion. Influential parameters, including plate thickness, type and size of stiffeners, pit depth and degree of pitting are varied and more than 208 finite element models are analyzed. It is found that ultimate strength is reduced by increasing pit depth to thickness ratio. Thin and intermediate plates have minimum and maximum reduction of ultimate strength with stronger stiffeners, respectively. In weak stiffener, reduction of ultimate strength in thin and intermediate plates depends on DOP. Reduction of ultimate strength in thick plates depends on thickness of plate and DOP. For intermediate plates, reduction for all stiffeners regardless of shape and size are the same.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.257-264
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• 2005

This paper presents the estimation of buckling coefficients and an ultimate strength for a longitudinally profiled plate (LP plate). From the buckling analysis of the LP plate compressed in one direction, the buckling coefficients for the thickness ratio are obtained by Rayleigh-Ritz method and Galarkin method. This paper also provides the technique of a finite element analysis considering the residual distributions of residual stresses and forces equilibrium in the LP plate. The strength behavior of the LP plate obtained from the analysis shows that the ultimate strength differs from the strength which is calculated from the current design code. Based on the results, this paper presents some new proposals about the strength evaluations of the LP plate.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.4
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• pp.439-444
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• 2007

A damage analysis simulator, which is applicable for evaluating the residual strength of damaged ship, was developed in this paper. For this process, CDM (Continuum Damage Mechanics) approach has been implemented to the simulator by virtue of the numerical technique for evaluation of crack initiation and/or enlargement. A damage calculation program has been linked with a commercial finite element analysis code (NASTRAN) and a ultimate strength evaluation program (LSAP) in order to assess residual strength of damaged ship. As a results of series calculation for the frigate model, giving the quantitative structural damage to the ultimate strength evaluation, a residual strength with damage is predicted to be at least 70 percentage lower than the case of intact condition. It was found that the proposed technique can be used as a design support tool in the field of simulation based ship design.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.3
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• pp.246-253
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• 2011

This paper presents estimation of deterministic damage extents and locations due to collision and grounding which are defined by ABS guideline and DNV ship rules. It is noted that the overall extents of damages from DNV are larger than those from ABS. Nonlinear FEAs are carried out to predict residual longitudinal strength of hull girder with asymmetric severe damages. The accuracy of the applied FEA procedure is proved by comparing FEA result with test result of a 1/3-scaled frigate. The investigated vessels are a VLCC and a large-sized bulker for which evenly distributed heeling angles from $0^{\circ}$(sagging) to $180^{\circ}$(hogging) by $30^{\circ}$ due to damage-induced flooding are taken into account. The reduction ratios of the ultimate residual strength for the damaged cases to those for the intact sagging case are shown. It is proved that the grounding damage case under DNV assumption reveals most critical the residual strength. The design formulas are presented to assure minimum residual ultimate moment after damage.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.9
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• pp.1452-1460
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• 2001

A new method of parameter determination in the fatigue residual strength degradation model is proposed. The new method and minimization technique is compared experimentally to account for the effect of tension-compression fatigue loading of spheroidal graphite cast iron and graphite/epoxy laminate. It is shown that the correlation between the experimental results and the theoretical prediction on the fatigue life and residual strength distribution using the proposed method is very reasonable. Therefore, the proposed method is more adjustable in the determination of the parameter than minimization technique for the prediction of the fatigue characteristics.

• Advances in concrete construction
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• v.10 no.2
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• pp.113-125
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• 2020

This paper presents experimental results on bond-slip behavior of steel reinforced high-strength concrete (SRHC) after exposure to elevated temperatures. Three parameters were considered in this test: (a) high temperatures (i.e., 20℃, 200℃, 400℃, 600℃, 800℃); (b) concrete strength (i.e., C60, C70, C80); (c) anchorage length (i.e., 250 mm, 400 mm). A total of 17 SRHC specimens subjected to high temperatures were designed for push out test. The load-slip curves at the loading end and free end were obtained, the influence of various variation parameters on the ultimate bond strength and residual bond strength was analyzed, in addition, the influence of elevated temperatures on the invalidation mechanism was researched in details. Test results show that the shapes of load-slip curves at loading ends and free ends are similar. The ultimate bond strength and residual bond strength of SRHC decrease first and then recover partly with the temperature increasing. The bond strength is proportional to the concrete strength, and the bond strength is proportional to the anchoring length when the temperature is low, while the opposite situation occurs when the temperature is high. What's more, the bond damage of specimens with lower temperature develops earlier and faster than the specimens with higher temperature. From these experimental findings, the bond-slip constitutive formula of SRHC subjected to elevated temperatures is proposed, which fills well with test data.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.4
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• pp.182-190
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• 2020

This study reports a series of drop impact tests performed to generate denting damages on stiffened plates and their residual ultimate strength tests under axial compression. The models were fabricated of general structural steel, and each model has six longitudinal stiffeners and two transverse frames. Among six fabricated models, four were damaged, and two were left intact for reference. To investigate the effects of collision velocity and impact location on the extent of damage, the drop height and the impact location were changed in each impact test. After performing the collision tests, the ultimate axial compression tests were conducted to investigate the residual strengths of the damaged stiffened plates. Finite element analyses were also carried out using a commercial package Abaqus/Explicit. The material properties obtained from a quasi-static tensile tests were used, and the strain-rate sensitivity was considered. After importing the collision simulation results, the ultimate strength calculations were carried out and their results were compared with the test data for the validation of the finite element analysis method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6521-6526
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• 2013

Elastic and nonlinear ultimate strength analyses were conducted to examine the effects of the stiffness and slenderness of flat-type stiffeners on ultimate in-plane strengths of a stiffened plate system. Although it is not feasible to consider local buckling in the stiffeners in elastic analysis, it was confirmed that the in-plane strengths of the stiffened plate system can be achieved by antisymmetric buckling mode when a certain level of stiffness in the stiffeners is provided. Nonlinear ultimate strength analysis, in which initial imperfection and residual stress are incorporated, showed that the ultimate strengths are sensitively affected by the mode shapes for initial imperfections. The slenderness limit for flat-type stiffeners in KHBDC (Korean Highway Bridge Design Code) was evaluated as conservative compared to the analysis results.

• Structural Engineering and Mechanics
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• v.2 no.4
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• pp.383-393
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• 1994

The residual stress distribution in a unidirectional graphite/epoxy laminate induced during the fabrication process is investigated at the microstress level within the scope of linear viscoelasticity. To estimate the residual stresses, the fabrication process is divided into polymerization phase and cool-down phase, and strength of materials approach is employed. Large residual stresses are not generated during polymerization phase because the relaxation modulus is relatively small due to the relaxation ability at this temperature level. The residual stresses increase remarkably during cool-down process. The magnitude of final residual stress is about 80% of the ultimate strength of the matrix material at room temperature. This suggests that the residual stress can have a significant effect on the performance of composite structure.