• Structural Engineering and Mechanics
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• v.3 no.2
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• pp.163-172
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• 1995

A simple numerical method is applied to calculate the large deflection of a cantilever beam under an elastic-plastic deformation by dividing the deformed axis into a number of small segments. Assuming that each segment can be approximated as a circular arc, the method allows large deflections and plastic deformation to be analyzed. The main interests are the load-deflection relationship, curvature distribution along the beam and the length of the plastic region. The method is proved to be easy and particularly versatile. Comparisons with other studies are given.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.812-815
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• 2002

The shape of K-R curve for an ideally brittle material is flat because the surface energy is an unvaried material property. However, the K-R curve can take on a variety of shapes when nonlinear material behavior accompanies fracture. By the way, a general metallic material is nonlinear, structural steel is such. Therefore, the J-R curve form J-integral value instead of K parameters can be used to evaluate elastic-plastic materials with flaws in terms of ductile fracture that can be significant to design. In this paper, R-curve behaviors form K and J parameter is considered for the precise assessment of fracture analysis, in case of JS-SS400 steels.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.04a
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• pp.33-40
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• 1998

Although a structural analysis based on e linear elastic theory yields good results for deformations and stresses produced by working loads, it fails to assess the teal load-carrying of the plates on the verge of yielding. In case of a limit analysis of plates, the yield line theory is widely used on the basis of the upper bound theorem and theoretically it overestimates the strength of the plate. There is, therefore, a general need for analytical methods of predicting the inelastic behavior and load-carrying capacities of plate subjected to arbitrary loadings and boundary conditions. The $\rho$-version of finite element method has been presented for determining the accurate limit load of plates. The numerical results by $\rho$-version model compares with the results obtained by the h-version software ADINA as well as with the available analytical solutions in literatures.

• Structural Engineering and Mechanics
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• v.27 no.4
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• pp.477-499
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• 2007

The main purpose of this paper is to investigate the ultimate behavior of steel cable-stayed bridges with design variables and compare the validity and applicability of computational methods for evaluating ultimate load capacity of cable-stayed bridges. The methods considered in this paper are elastic buckling analysis, inelastic buckling analysis and nonlinear elasto-plastic analysis. Elastic buckling analysis uses a numerical eigenvalue calculation without considering geometric nonlinearities of cable-stayed bridges and the inelastic material behavior of main components. Inelastic buckling analysis uses an iterative eigenvalue calculation to consider inelastic material behavior, but cannot consider geometric nonlinearities of cable-stayed bridges. The tangent modulus concept with the column strength curve prescribed in AASHTO LRFD is used to consider inelastic buckling behavior. Detailed procedures of inelastic buckling analysis are presented and corresponding computer codes were developed. In contrast, nonlinear elasto-plastic analysis uses an incremental-iterative method and can consider both geometric nonlinearities and inelastic material behavior of a cable-stayed bridge. Proprietary software ABAQUS are used and user-subroutines are newly written to update equivalent modulus of cables to consider geometric nonlinearity due to cable sags at each increment step. Ultimate load capacities with the three analyses are evaluated for numerical models of cable-stayed bridges that have center spans of 600 m, 900 m and 1200 m with different girder depths and live load cases. The results show that inelastic buckling analysis is an effective approximation method, as a simple and fast alternative, to obtain ultimate load capacity of long span cable-stayed bridges, whereas elastic buckling analysis greatly overestimates the overall stability of cable-stayed bridges.

• Nuclear Engineering and Technology
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• v.56 no.4
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• pp.1347-1356
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• 2024

Measuring the residual stress in the components in nuclear power plants is crucial to their safety evaluation. The instrumented indentation technique is a minimally invasive approach that can be conveniently used to determine the residual stress in structural materials in service. Because the indentation behavior of a structure with residual stresses is closely related to the elastic-plastic behavior of the indented material, an accurate understanding of the elastic-plastic behavior of the material is essential for evaluation of the residual stresses in the structures. However, due to the analytical problems associated with solving the elastic-plastic behavior, empirical equations with limited applicability have been used. In the present study, the impact of the non-equibiaxial residual stress state on indentation behavior was investigated using finite element analysis. In addition, a new nonequibiaxial residual-stress prediction methodology is proposed using a convolutional neural network, and the performance was validated. A more accurate residual-stress measurement will be possible by applying the proposed residual-stress prediction methodology in the future.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.257-262
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• 2009

Elastic-Plastic structural analysis was performed to evaluate structural characteristic and integrity for rocket motor case of solid propulsion system. The structural analyses were compared and evaluated using the simplified 2-D axisymmetric model and 3-D full model for rocket motor case with torispherical dome type. And pre-tension load for bolt model was considered in structural analysis. The results of displacement and stress for the simplified 2-D axisymmetric model and 3-D full model were in an good agreement with each other. Therefore, the simplified 2-D axisymmetric model for rocket motor case was recommended to verify quickly the structural integrity and save the modeling and calculating time in initial design stage. Also, the structural characteristic and integrity for rocket motor case according to 5 dome types was evaluated to select the optimal dome shape.

• Journal of Korean Society of Steel Construction
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• v.11 no.2 s.39
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• pp.213-222
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• 1999

Elastic-plastic methods have been used for the better prediction of the actual behavior of continuous-composite plate girder bridges in the overload and maximum load analysis. The structural evaluation using ALFD(Alternate Load Factor Design) uses the elastic-plastic analysis. The plastic rotations that remain after the load is removed can be occurred by the yielding locations of the maximum moment section. This situation can occur due to the residual stresses even if the moment is below the theoretical yield moment. The local yielding causes positive automoments that assure elastic behavior under subsequent overloads. In this study, the automoments at the piers occurred due to the unit plastic rotations and other locations were calculated by the conjugate-beam method and three-moment equation, using the nine design span with progressively smaller pier sections. The automoments were determined by the developed computer programs in this study in which the moments and plastic rotations from the continuity and moment-inelastic rotation relationships must be equal. And also the ratings of 3-span continuous composite plate girder bridges with non-compact section were carried out according to the Korean Highway Bridge Specification.

• Nuclear Engineering and Technology
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• v.49 no.4
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• pp.838-849
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• 2017

This paper proposes penalty factor equations that take into consideration the weld strength over-match given in the classified form similar to the revised equations presented in the Code Case N-779 via cyclic elastic-plastic finite element analysis. It was found that the $K_e$ analysis data reflecting elastic follow-up can be consolidated by normalizing the primary-plus-secondary stress intensity ranges excluding the nonlinear thermal stress intensity component, $S_n$ to over-match degree of yield strength, $M_F$. For the effect of over-match on $K_n{\times}K_{\nu}$, dispersion of the $K_n{\times}K_{\nu}$ analysis data can be sharply reduced by dividing total stress intensity range, excluding local thermal stresses, $S_{p-lt}$ by $M_F$. Finally, the proposed equations were applied to the weld between the safe end and the piping of a pressurizer surge nozzle in pressurized water reactors in order to calculate a cumulative usage factor. The cumulative usage factor was then compared with those derived by the previous $K_e$ factor equations. The result shows that application of the proposed equations can significantly reduce conservatism of fatigue assessment using the previous $K_e$ factor equations.

• Structural Engineering and Mechanics
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• v.35 no.1
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• pp.67-82
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• 2010

The beam string structure (BSS) has been widely applied in large span roof structures, while no analytical solutions of BSS were derived for it in the existing literature. In the first part of this paper, calculation formulas of displacement and internal forces were obtained by the Ritz-method for the most commonly used arc-shaped BSS under the vertical uniformly distributed load and the prestressing force. Then, the failure mode of BSS was proposed based on the static equilibrium. On condition the structural stability was reliable, BSS under the uniformly distributed load would fail by tensile strength failure of the string, and the beam remained in the elastic or semi-plastic range. On this basis, the limit load of BSS was given in virtue of the elastic solutions. In order to verify the linear elastic and limit state solutions proposed in this paper, three BSS modal were tested and the corresponding elastoplastic large deformation analysis was performed by the ANSYS program. The proposed failure mode of BSS was proved to be correct, and the analytical results for the linear elastic and limit state were in good agreement with the experimental and FEM results.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.649-659
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• 2002

For a variety of elastic-plastic stress fields of plane strain specimens, many research works verified the validity of J-T approach. To generalize the validity of J-T method, however, further investigations are needed for more practical 3D structures than the idealized geometries as plane strain specimens. In this work, selecting two main types of structures such as plate and straight pipe, we perform 3D finite element(FE) modeling, and accompanying elastic, elastic-plastic FE analyses. We then study the validity of J-T application to 3D structures, and present some useful informations for the design or assessment of pipe welds by comparing the stress fields from the detailed 3D FE analyses to those predicted with J-T two parameters.