• Journal of Korean Association for Spatial Structures
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• v.5 no.1 s.15
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• pp.91-98
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• 2005

Membrane structures, a kind of lightweight soft structural system, are used for spatial structures. The material property of the membrane has strong axial stiffness, but little bending stiffness. Therefore membrane structures are unstable structures initially. These soft structures need to be introduced initial stresses first because of its initial unstable state, and it happens large deformation phenomenon. To find the structural shape after large deformation caused by initial stiffness introduced, we need the shape analysis considering geometric nonlinearity in structural design procedure In this study, we analyze the soft spatial structures by the NASS which is the program for nonlinear analysis. The analytic model is a roof membrane structures of Barrel Vault-Type. We have done the shape analysis and the stress-deformation analysis considering the orthotropic material, and then study the safety.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.2
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• pp.129-138
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• 2010

Technical ceramics, due to their unique physical properties, are excellent candidate materials for engineering applications involving extreme thermal and chemical environments. When ceramics are rapidly cooled, they receive thermal shock. The thermal shock parameter is defined as the critical temperature difference. The critical temperature difference for ceramic parts is influenced by its size, the convective heat transfer coefficient, etc. The thermal shock for a component is analyzed by using the transient thermal stress. If the transient thermal stress exceeds the modulus of rupture (MOR), cracking by thermal shock is initiated. The critical temperature difference for water is less than the critical temperature difference for air. The three-way catalyst substrate used in this study has an adequate performance against thermal shock because its radial and axial temperature differences existed below the critical temperature differences.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.69-84
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• 2002

In this papers, an analytical model which can simulate the post-cracking behavior and tension stiffening effect in a reinforced concrete(RC) tension member is proposed. Unlike the classical approaches using the bond stress-slip relationship or the assumed bond stress distribution, the tension stiffening effect at post-cracking stage is quantified on the basis of polynomial strain distribution functions of steel and concrete, and its contribution is implemented into the reinforcing steel. The introduced model can be effectively used in constructing the stress-strain curve of concrete at post-cracking stage, and the loads carried by concrete and reinforcing steel along the member axis can be directly evaluated on the basis of the introduced model. In advance, the prediction of cracking loads and elongations of reinforced steel using the introduced model shows good agreement with results from the previous analytical studies and experimental data.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.6
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• pp.947-954
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• 2016

A simplified analysis method is first proposed in order to determine an optimized initial shape of cable-stayed bridges including all unstrained element lengths without using complicated nonlinear FE analysis. The unstrained-length based FE method is then presented using the unstrained lengths by the simplified analysis. To demonstrate validity and accuracy of the proposed method, Incheon bridge model having the fabrication camber is constructed and initial shaping analysis is performed using the presented method and commercial finite element analysis program, MIDAS. Resultantly it is shown that the initial solutions by the proposed algorithm are well optimized and in good agreement with those by MIDAS except for axial displacements of the main member.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.8
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• pp.751-757
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• 2016

The aim of this study is to estimate the reliability of fatigue limit of the material used for crank throw components according to the staircase method. The material used for crank throw components is forged S34MnV grade steel, which is heat treated by normalizing and tempering. In this work, to predict the reliability of the design fatigue strength, axially loaded constant amplitude fatigue testing was conducted. The test specimens were loaded with an axial push/pull load with a mean stress of 0 MPa, which corresponds to a stress ratio of R=-1. The fatigue test results were evaluated by Dixon-Mood formulas. The values of mean fatigue strength and standard deviation predicted by the staircase method were 296.3 MPa and 10.6 MPa, respectively. Finally, the reliability of the fatigue limit in some selected probability of failure is predicted. The proposed method can be applied for the determination of fatigue strength for design optimization of the forged steel.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.3
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• pp.75-83
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• 2018

In study, Structural stability was considered when applying the high strength strut method with improved general strut method. considered whether there is sufficient stiffness to so as not buckling to the maximum hypothetical earth pressure. also structure stability of the strut component was reviewed. The high strength strut method is a technique used in place of the general strut method. high strength prefabricated Strut method is a technique that has bolt holes drilled in the upper flange at regular intervals. As a result of the buckling analysis, it was considered that the safety factor increased by about 5 %. also Since the stress generated is below the allowable stress, it is judged that structural stability of the strut is ensured. In particular, the safety factor of axial compressive stress increases about 16 % with use of high strength steel when applying the high strength prefabricated strut method. the high strength strut method is construction method may shorten the construction period and there is no expense to purchase additional materials.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.11
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• pp.1125-1130
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• 2017

The tooth shapes of serration-type and spline-type reactors are optimized using finite element methods to improve the working life of the part and to lower the stress concentration during rotation resulting from contact with the outer race for a reactor operating with $170^{\circ}C$ transmission oil. The results of thermal expansion analyses between an Al reactor and the steel outer race indicate that, before optimization, the gap between the two parts increases further as the serration-type reactor expands by 0.1 mm and the spline-type one strains by 0.08 mm. Because of shape optimization, a trapezoidal shape is obtained from the initial triangular serration and the rectangular spline of the two reactors. The maximum von Mises stress of the serration-type convertor decreased by 24.5 ％, and by 9.3 ％ for the spline-type convertor. In addition, there is a 13 ％ reduction in the axial thickness, as compared to the initially designed model.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.3
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• pp.56-65
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• 1996

Recently, with development of mechanics of materials, as pursuing the high speed of the ships, there has been an increasing demand on the composite construction which satisfies high strength and low weight at the same time. A sandwich element is a type of composite construction, which is composed of thin, strong, stiff and relatively high density faces and a thick, light, and weaker core material. As the second moment is increased by faces separated from the neutral axis farther, a sandwich element is most effective light structural form. In this study, Rayleigh-Ritz Energy Method is adopted, which can analyze sandwich plate relatively simply and exactly. Stresses and buckling loads are analyzed exactly, when uniform lateral pressure load, inplane compression and inplane shear are acting at the sandwich plate. Including a wrinkling stress, this study can be applied to the initial design and minimum weight design of sandwich plates.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.933-936
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• 2008

An engineered cementitious composite (Engineered Cementitious Composite) had been developed in previous study. Theoretical prediction of the tensile stress-strain relation of ECC is important in providing the material constitutive relation necessary for designing structural members. But, few studies have been reported with regard to predicting the tensile stress-strain relation of ECC. Prediction of the tensile stress-strain relation of ECC accounting for actual bridging curve, such as fiber dispersion is needed. The present study extends the work as developed by Kanda et al., by modeling the bridging curve, accounting for fiber dispersion, the degree of matrix spalling, and fiber rupture to predict the tensile stress-strain relation of ECC. The role of material variation in the bridging curve, such as number of effective fiber actually involved in the bridging capacity and how it affects the multiple cracking process is discussed. The approach for formulating the tensile stress-strain relation is discussed next, where the procedure for obtaining the necessary parameters, such as the crack spacing, is presented. Finally, the predicted stress-strain relation will be validated with experimental tests results.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.4
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• pp.353-367
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• 2003

This paper describes the extension of the numerical model, which was developed to simulate the nonlinear behavior of reinforced concrete (RC) structures subjected to monotonic in plane shear and introduced in the companion paper, to simulate effectively the behavior of RE structures under cyclic loadings. While maintaining all the basic assumptions adopted in defining the constitutive relations of concrete under monotonic loadings, a hysteretic stress strain relation of concrete, which across the tension compression region, is defined. In addition, unlike previous simplified stress strain relations, curved unloading and reloading branches inferred from the stress strain relation of steel considering the Bauschinger effect we used. The modifications of the stress strain relation of steel are also introduced to reflect pinching effect depending on the shear span ratio and an average stress distribution in a cracked RC element. Finally, correlation studies between analytical results and experimental studies are conducted to establish the validity of the proposed model.