• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.9-13
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• 2008

The moving load such as a shock wave in a pipe propagates with a specific velocity. This internal load speed determines the level of flexural wave excitation and the possibility of resonant response leading to a large deformation. In this paper, we present particular solutions of displacements and the resonance conditions when the moving load is propagating in a pipe. These analytical results are compared to numerical simulations obtained using a hydrocode. We expect to identify potential explosion hazards in the general power industries.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.739-744
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• 2000

Concrete structures generally have cracks, so for the safety and durability of structures, studies to detect cracks using nondestructive tests have been treated in great deal. In order to assure the reliability of concrete structure, microscopic fracture behavior and internal damage progress of concrete under the loading should be fully understood. The purpose of this study predicts location of initial crack and measures direction of crack propagation for on-line monitoring before the crack really grows in structures by using two-dimensional Acoustic Emission(AE) source location based on rectangular method with three-point bending test. This will allow efficient maintenance of concrete structure through monitoring of internal cracking based on AE method.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.5
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• pp.1229-1242
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• 1995

The thermal shock stress intensity factors of semi-elliptical surface crack in finite plate and the stress intensity fractors of embedded elliptical crack in turbine rotor is determined by means of Vainshtok weight function method. In case of semi-elliptical surface crack, the solution is compared with previous solution. The stress intensity factor for embedded elliptical crack in turbine rotor loaded by centrifugal and thermal loading is also determined. In this case, the value of stress intensity factor is larger at crack contour near internal radius surface and is almost constant at the crack contour farther from internal radius surface.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.347-354
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• 2006

In this paper, we work with steel circular tubes and propose analysis model which can consider local buckling that it has an effect on failure of steel structures and induce the relation between loading and deformation. First of all, in respect to axial symmetry local buckling, which is simplest case, elasto-plastic behavior acting only axial loads is object Therefore, it suggests analysis model for axial symmetry local buckling. And that is explainable the process from increasing internal force to decreasing passing maximum internal force. Besides, we induce the relation between the axial force and axial deformation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1573-1580
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• 2006

In this study, fatigue tests were carried out under push-pull loading condition using spheroidal graphite cast iron in order to clarify the internal fatigue fracture mechanism in an extremely low cycle fatigue regime. It is found that a successive observation of internal fatigue damage it is found that the fracture processes go through three stages, that is, the generation, growth and coalescence of microvoids originated from debonding of graphite-matrix interface. It is also found that the crack which is initiated from the void propagates by coalescence of neighboring cracks and the fatigue crack growth rate can be expressed in form of the Manson-Coffin rule type. In this paper, quantitative analyses of fatigue properties for realization of simulation about fatigue life evaluation are also presented.

• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.1180-1183
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• 1997

This paper addresses the issues of the external system modeling and power system state estimation with the external model. A set of significant measurements is identified in the external system based on their sensitivities on the tie-lines. These measurement data are transferred to internal system and updated in real-time. The state estimator is run for different loading conditions by using the actual values for the internal system and selected significant external system measurements while keeping the rest of the external system measurements at their base case values. Simulation results are presented using the IEEE 118 bus system as an example.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.04a
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• pp.183-190
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• 1993

The seismic response of the reactor structures depends on the dynamic charact-eristics of the structures and the input earthquake loadings. The stuctural integ-rity of the reactor internal components can be verified by the dynamic response analyses to implement the effects of the design loadings like earthquakes. The sensitivity analyses of the dynamic characteristics for the analytical model of reactor structures considering the possible variations of the stiffnesses of the CSB upper flange and the snubber were performed to improve the dynamic characteri-stics of the structures against seismic loading. And to enhance the structural design margin of the reactor internal components the nonlinear time history analyses were attempted for the modified analytical model, and the results were compared between the reference model and the modified ones.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.325-332
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• 1998

The use of air-supported membrane has considerable attention in recent years. There are, however, a number of problems in the behavior of these structures that have not been fully investigated. For example, the problem of local loafing on such membranes has not been analyzed yet. The paper presents an analysis of internal and external potential energy of a spherical air-supported membrane with vertical longitudinal axis, subjected to local loadings. An internal pressure value of the applied load is established at which tile potential of these structures change positive. During such change the loading portion of the membrane comes into work beyond stable state. The mathematical method is used throughout the paper in obtaining solution. For the mathematical modeling, two assumption are used. One is the theta's elimination and the other is the infinite condition. The paper is illustrating the examples of spherical air membrane dome subjected to local load.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.533-540
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• 2002

Tubular joints having a large diameter are reinforced using internal ring stiffener in order to increase the load carrying capacity. In this study, the static strengths of Internally ring-stiffened tubular T-joints subjected to compressive brace loading are assessed. Nonlinear finite element analyses are used to compute the behavior of unstiffened and ring-stiffened T-joints. From the numerical results, Internal ring stiffener is found to efficient in improving the ultimate capacity, and reinforcement effect are calculated. The influence of geometric parameters for members and ring is evaluated. Based on the FE results, regression analysis is performed considering practical sizes of ring stiffener, finally strength estimation formulae for ring-stiffened T-joints are proposed.

• Structural Engineering and Mechanics
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• v.14 no.2
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• pp.237-243
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• 2002

It is well known that torsionally unbalanced buildings are more vulnerable to earthquake hazards than are the regular structural systems. In this paper, a parametric investigation is presented, in order to observe the amplification in the internal forces, when increased eccentricities are used instead of the ones corresponding to the 5% accidental eccentricity. A series of five, ten-story framed and walled structures, with rather high torsional irregularity coefficients, are selected and a numerical test procedure is applied. Numerical results show that the maximum amplification in the internal forces at the most critical beams and columns at the flexible sides of the structures is about 10%. It is concluded that, more serious measures in the codes are needed in the case of this rather dangerous type of irregularity.