• Journal of Korean Society of Steel Construction
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• v.16 no.2 s.69
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• pp.181-190
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• 2004

A new inelastic design method performing iterative calculations using secant stiffness was developed. Since the proposed design method uses linear analysis, it is convenient and stable in numerical analysis. At the same time, the proposed design method can accurately estimate the inelastic strength and ductility demands of the members by performing iterative calculation. In the present study, the procedure of the proposed design method was established. Design examples using the proposed method were presented, and its advantages were highlighted by comparisons with existing design methods using elastic or plastic analysis. Unlike the existing inelastic design methods performing the preliminary design on the structure and checking its validity using nonlinear analysis, the proposed integrated analysis-design method can directly calculate the strength and ductility demands of each member. In addition, the proposed design method can address the inelastic design strategy intended by the engineer, such as strength and ductility limits of members and the design concept of strong-column and weak-beam. As a result, economical and safe design can be achieved.

• Computational Structural Engineering
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• v.10 no.4
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• pp.217-228
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• 1997

The high precision analysis by the p-version of the finite element method are fairly well established as highly efficient method for linear elastic problems, especially in the presence of stress singularity. It has been noted that the merits of the p-version are accuracy, modeling simplicity, robustness, and savings in user's and CPU time. However, little has been done to exploit their benefits in elasto-plastic analysis. In this paper, the p-version finite element model is proposed for the materially nonlinear analysis that is based on the incremental theory of plasticity using the constitutive equation for work-hardening materials, and the associated flow rule. To obtain the solution of nonlinear equation, the Newton-Raphson method and initial stiffness method, etc are used. Several numerical examples are tested with the help of the square plates with cutout, the thick-walled cylinder under internal pressure, and the circular plate with uniformly distributed load. Those results are compared with the theoretical solutions and the numerical solutions of ADINA

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.22-25
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• 2009

대부분의 공학 재료는 다결정으로 이루어져 있으며 정확한 다결정 재료의 거동을 파악하고 예측하는 기술은 구조물의 성능을 검증하고 보장하는데 매우 중요하다. 본 연구에서는 강한 연결 멀티스케일 해석을 수행하는 중 마이크로 스케일의 거동, 특히 다결정 응력의 평균법에 대하여 연구하였다. 널리 사용되고 있는 체적평균법의 가정에 대하여 정리하고 표면평균법의 근사해로서의 정확도를 평가하였다. 랜덤(random)한 상(phase) 분포 및 적층 상 분포 구조의 2상 다결정 미세구조를 이용하여 평균법의 성능을 비교한 결과 사용된 미세구조의 크기와 구조에 대해서 유사한 결과를 얻을 수 있었다. 그러나 소성 흐름이 큰 이방성 재료의 경우 두 평균법으로 구한 거동의 차이가 증가하여, 미세구조에 따라서는 체적평균법을 적용할 때 주의를 요구할 수 있는 가능성이 있다는 결론을 얻었다.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.985-988
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• 2008

A linear analysis method using reduced secant stiffness was developed for inelastic earthquake design of reinforced concrete structures. In the proposed method, the beam-column element and plane element, which are the same as used in conventional elastic analysis, are used for structural modeling. Based on the structural plastic mechanism intended by engineer, the distribution of inelastic members is determined. The secant stiffness of the inelastic members is determined based on the target ductility of the structure. Inelastic strengths of the members are calculated by using linear analysis on the structure modeled with secant stiffness. Plastic rotations in the inelastic members are calculated with the nodal rotations resulting from the secant stiffness analysis. For verification, the proposed method was applied to the inelastic earthquake designs of a moment-resisting frame and a dual system of two dimensions, and also a dual system of three dimensions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.277-280
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• 2008

Multi layer bellows are being manufactured for commercial vehicle because of the characteristic of high durability compared with single iaγor bellows used to passenger vehicle. Finite Element Method (FEM) study and optimization about single layer bellows are actively progressed, but FEM study about multi layer bellows which have gap between layer is rarely processed. Therefore, this article presents finite element modeling of multi layer bellows for the improvement of simulation reliability. For the shape optimization of multi layer bellows, design of experiment and Taguchi method are used.

• Transactions of Materials Processing
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• v.7 no.5
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• pp.474-480
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• 1998

In the present study a domain decomposition scheme using the substructuring method is developed for the computational efficiency of the finite element analysis of metal forming processes. in order to avoid calculation of an inverse matrix during the substructuring procedure, the modified Cholesky decomposition method is implemented. As obtaining the data independence by the substructuring method the program is easily paralleized using the Parallel Virtual machine(PVM) library on a work-station cluster connected on networks. A numerical example for a simple upsetting is calculated and the speed-up ratio with respect to various number of subdomains and number of processors. The efficiency of the parallel computation is discussed by comparing the results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.246-249
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• 1998

In the present study, domain decomposition using the substructuring method is developed for the computational efficiency of the finite element analysis of metal forming processes. In order to avoid calculation of an inverse matrix during the substructuring procedure, the modified Cholesky decomposition method is implemented. As obtaining the data independence by the substructuring method, the program is easily parallelized using the Parallel Virtual Machine(PVM) library on a workstation cluster connected on networks. A numerical example for a simple upsetting is calculated and the speed-up ratio with respect to various domain decompositions and number of processors. Comparing the results, it is concluded that the improvement of performance is obtained through the proposed method.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.7
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• pp.1314-1321
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• 1992

In analyzing the plastic flow of axisymmetric tube extrusion a new method of formulation using the stream function approach and upper-bound theorem is proposed which permits the prediction of plastically deformed zone in analytic expression as well as metal flow. It is shown that the formulation proposed in this work covers the solid extrusion and tube extrusion in axisymmetric case. The effect of some process parameters such as area reduction, the ratio of radii(inner radius to outer radius) and friction factor on extrusion pressure, deformation zone and plastic flow through stream-lined dies has been studied. The presented theoretical analysis can be effectively used for the prediction of deformation zone and plastic flow.

• Journal of Korean Association for Spatial Structures
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• v.6 no.3 s.21
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• pp.131-137
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• 2006

This study presents a new stress analysis method to be substituted for the elastic analysis in such a plastic design procedure. This method is accompanied by an efficient mathematical tool which can be easily handled by personal computer. The method also easily accepts arbitrary strategies by the designer for selection member size.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.6
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• pp.792-802
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• 2010

A plastic analysis method is commonly used in ship and offshore structural system to utilize the ultimate strength. In this paper, the basic principle of plastic analysis method is applied to ship grillages such as transverse oil-tight bulkheads. The main emphasis is placed on the optimum arrangement of grillage system to give minimum weight. Additional parametric study is carried out to find the effect of various arrangement of grillage system. The above methods are applied to oil-tight bulkhead design, and results are compared with the existing one.