• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.04a
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• pp.327-334
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• 1999

Steel box girders are popular to the Practicing engineers for the its large Pure torsional constant. But closed box girders at-e susceptible to the eccentric loading due to the distortion of the cross section. Distorton of the box girder develops the warping normal stress and transverse flexural stress in the cross section and their magnitudes can be large unless internal diaphragms are installed sufficiently. In this study, stiffness matrix and equivalent nodal force vector are formulated on the basis of displacement method. Shape functions are directly derived from the homogeneous solution of the governing differential equation of the distortion. New finite element formulations were coded into a computer program. Several numerical examples were presented to show the validity of developed program.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.04a
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• pp.335-342
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• 1999

It is well known that l-girders are weak in torsion and it might be more economical to use a box girder, which has great torsional rigidity. The use of box beams does, however, present a potential problem in that cross-sectional distortions can induce large warping normal stresses and transverse bending stress. Accordingly a sufficient number of diaphragms are provided to make the distortional effects minimal. In engineering practice, diaphragms are spaced in 5m intervals without reasonable basis. It is considered to be noneconomical design to the almost design engineers, and it may produce the unsafe structural systems in special cases such as curved bridges with large initial curvature. These problems have not been solved for the lack of adequate tools of structural analysis. In this study, on the basis of the parametric studies, the design formulas for the distortional warping stress and the reasonable diaphragm spacing of box girder were presented.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.816-819
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• 1997

The operation of femoral non-union after IM(Intramedullary) nailing in distally femoral fractures is considered. Augmentive plate fixation is the management of femoral non-union after IM nailing. The purpose of this study is to compare the bending, torsional stiffness and stress distribution of the two operations by the FEM(Finite Element Method). Augmentive plate fixation is better than IM nail fixation. These results conclude that plate augmentation is a useful method for the unstable femoral non-union after interlocking IM nailing.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.489-493
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• 2000

Turbine blade has trouble of cracking at root region. Fracture surface of blade root is surveyed by SEM and AFM to clear relation between fracture mechanical parameter and surface parameter (striation width and surface roughness). Service stress is predicted by maximum height roughness $R_{max}$, on fractured surface and stress analysis on turbine blade. It is to thought that turbine blade is fractured by abnormal condition such as incorrect fittings between pin and pin hole but isn't fractured by normal service conditions such as steam pressure, centrifugal force and torsional force.

• Composites Research
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• v.13 no.5
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• pp.37-43
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• 2000

In this paper an analytical investigation pertaining to the elastic shear buckling behavior of transversely stiffened orthotropic plate under in-plane shear forces is presented. All edges of plate are assumed to be simply supported and the evenly placed stiffener is considered as a beam element neglecting its torsional rigidity. For the solution of the problem Rayleigh-Ritz method is employed. Using the derived equation, the limit of buckling stress of transversely stiffened plate is suggested as a graphical form. Based on the limit of buckling stress of stiffened plate, graphical form of results for finding the required stiffener rigidity is presented when one and two stiffeners are located, respectively.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.585-590
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• 2001

Turbine blade is subject to torsional load by torsion-mount, centrifugal load by rotation of rotor and repeated bending load by steam pressure. Turbine with partially cracked blade has normal working condition at initial repair time but vibratory working condition at middle repair time due to crack growth. Finite element analysis on turbine blade indicates that repeated bending load out of all loads is the most important factor on fatigue strength of turbine blade. Therefore, this study shows root mean square roughness has linear relation with stress intensity factor range in 12% Cr steel and can predict loading condition of fractured turbine blade.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.170-177
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• 2001

Turbine blade is subject to torsional load by torsion-mount, centrifugal load by rotation of rotor and repeated bending load by steam pressure. Turbine with partially cracked blade has normal working condition at initial repair time but vibratory working condition at middle repair time due to crack growth. Finite element analysis on turbine blade indicates that repeated bending load out of all loads is the most important factor on fatigue strength of turbine blade. Therefore, this study shows root mean square roughness has linear relation with stress intensity factor range in 12% Cr steel and can predict loading condition of fractured turbine blade.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.515-520
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• 2005

The behavior of jointed rock mass is much different from that of intact rock due to the presence of joints. Similarly, the characteristics of elastic wave propagation in jointed rock are considerably different from those of intact rock. The propagation of elastic waves in jointed rock is greatly dependent on the state of stress. The roughness, filling materials, and spacing of joints also affect wave propagation in jointed rock. If the wavelength of elastic waves is much larger than the spacing between joints, wave propagation in jointed rock mass can be considered as wave propagation in equivalent continuum. A rock resonant column testing apparatus is made to measure elastic waves propagating through jointed rock in the state of equivalent continuum. Three types of wave, i.e, torsional, longitudinal and flexural waves are monitored during rock resonant column tests. Various roughness and filling materials are applied to joints, and rock columns with various spacings are used to understand how these factors affect wave propagation under a small strain condition. The experimental results suggest that the characteristics of wave propagation in jointed rock mass are governed by the state of stress and influenced by roughness, filling materials and joint spacings.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.6 s.237
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• pp.815-821
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• 2005

Biaxial low cycle fatigue test was carried out to predict fatigue life under combined axial-torsional-loading condition which is that of in-phase and out-of-phase for CF8M cast stainless steels. Fatemi-Socie(FS) parameter which is based on critical plane approach is not only one of methods but also the best method that can predict fatigue life under biaxial loading condition. But the result showed that, biaxial fatigue life prediction by using FS parameter with several different parameters for the CF8M cast stainless steels is not conservative but best results. So in this present research, we proposed new fatigue life prediction parameter considering effective shear stress instead of FS parameter which considers the maximum normal stress acting on maximum shear strain and its effectiveness was verified.

• Bulletin of the Society of Naval Architects of Korea
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• v.13 no.3
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• pp.11-19
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• 1976

Grillages are abundant in ship structures and in many other types of structures such as bridges and building floors. Clarkson has shown that plated grillages can be satisfactorily analyzed as gridworks if an appropriate effective breadth is taken into account. Also, it has previously been pointed out, by Nielsen, that grillage calculations could be simplified by use of the Laplace transformation. In this paper, it is assumed that the torsional rigidity of the members and axial load are negligible, also that girders have the same scantling and spacing each other and so stiffeners do. Then the grillages composed of both-end-fixed girders and both-end-hinged stiffeners, which are subjected only to uniform normal loads are investigated. The calculus of variation is used to set up the differential equations and the Laplace transformation is applied to solve the differential equations. The program has been tested by FACOM 28 and the results show good agreements with those by the STRESS, which was developed in M.I.T.. The amount of the data input and computing time are much less than those of the STRESS. But this program has so much restrictions that it is urgent to extend the program to the grillage problems of arbitrary loading and boundary conditions.