• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.7
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• pp.645-652
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• 2015

In this study, a method for determining Ramberg-Osgood constants for leak-before-break evaluation was investigated. The Ramberg-Osgood constants were calculated for SA312, TP316, and SA-508 Gr.1a in an operating temperature of $316^{\circ}C$. Incremental plasticity, using stress-strain data obtained from experiment, and deformation plasticity, using the Ramberg-Osgood constants, were considered in a finite element analysis. Using incremental plasticity and deformation plasticity, J-integrals and crack opening displacement values were calculated and compared. By comparing the results of incremental plasticity and deformation plasticity, a suitable method for determining Ramberg-Osgood constants for leak-before-break evaluation was confirmed.

• Journal of Korean Society of Steel Construction
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• v.24 no.5
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• pp.559-569
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• 2012

Cross-beam in the existing temporary bridge system is usually installed to prevent the lateral-torsional buckling of girders and to promote the construction efficiency. However, most of this cross-beams are connected to the girder web by bolts, and therefore, gravitational load resisting capacity of the cross-beams are negligibly small. In recent years, new temporary bridge system, in which the cross-beams and girders are connected to resist the external loads as a unit, was developed. In this paper, we present the experimental and analytical study results pertaining to the structural behavior and load carrying capacity of new temporary bridge system. From the results of study, it was found that the continuous cross-beam increased the flexural rigidity and reduced the maximum flexural stress in the girder. In addition, it was also found that the new temporary bridge system developed is more appropriate for the application in the long-span temporary bridge.

• Computational Structural Engineering
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• v.5 no.1
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• pp.119-132
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• 1992

The objective of this study is to perform extensive parametric studies of the lateral-torsional buckling of short 1-beams under repeated loadings, and to gain a further insight into the lateral-torsional beam buckling problem. A one-dimensional geometrically (fully) nonlinear beam model is used, which includes superposed infinitesimal transverse warping deformation in addition to finite torsional warping deformation. A multiaxial cyclic plasticity model is also implemented to better represent cyclic metal plasticity in conjunction with a consistent return mapping algorithm. The general response for the lateral-torsional buckling of short I-beams under repeated loadings is examined through several parametric studies around the standard case : the material yield strength, the yield plateau, the strain hardening, the kinematic hardening, the residual stresses, the load eccentricity with respect to the shear center, the height of the load with respect to the cross-section of the beam, the location of the load along the length of the beam, the dimensions of the cross-section of the beam and the fixity of the supported end remote from the load.

• Computational Structural Engineering
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• v.5 no.1
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• pp.133-142
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• 1992

This paper presents a method to apply the linear goal programming, which has rarely been used to the structural opimization problem due to its unique formulation, to large scale nonlinear structural optimization. The method can be used as a multicriteria optimization tool since goal programming removes the difficulty in defining an objective function and constraints. The method uses the finite element analysis, linear goal programming techniques and successive linearization to obtain the solution for the nonlinear goal optimization problems. The general formulation of the structural optimization problem into a nonlinear goal programming form is presented. The successive linearization method for the nonlinear goal optimization problem is discussed. To demonstrate the validity of the method, as a design tool, the minimum weight structural optimization problems with stress constraints are solved for the cases of 10, 25 and 200 trusses and compared with the results of the other works.

• Journal of Aerospace System Engineering
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• v.12 no.3
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• pp.38-44
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• 2018

Military aircraft may have fatigue cracks in structurally weak areas due to multiple factors such as the accumulation of flight time while perform various missions and unpredictable air conditions. As a fatigue crack progresses, there is a risk that the structure will be destroyed in extreme cases, which can have a significant impact on flight safety. In this study, a cracking phenomenon was observed during the periodic inspection the inner support of the fairing, which is installed to protect the connection between the wing and the body of the aircraft. Therefore, a study on a series of quality improvement processes for reformation was described. In order to identify the causes of cracks, pre-load generation occurrence during the wing assembly process was investigated and a fracture analysis was performed. Also, the design of the support structure was suggested in terms of preventing recurrence of cracks. The structural integrity was verified using a stress and fatigue life analysis.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.91-97
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• 2016

Evaluation on the test of actual concrete member to confirm the fire resistance of the concrete member using ultra-high strength concrete is required. However, test equipment which has large loading capacity is needed to the actual member experiment. So, many researchers evaluated the fire performance through analytical studies using the material models. This study experimentally evaluated strain properties on ultra-high-strength concrete of 80, 130 and 180 MPa with heating and examined to apply the existing strain model about ultra-high-strength concrete. As a results, constants are drawn by method of least squares applying experimental values and calculated values by the existing strain model, it proposed strain model that can be applied to ultra-high-strength concrete.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.711-717
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• 1999

A multilayer-structure material containing ductile and brittle layer simultaneously was examined and compared with a single layer material using fracture mechanical properties. We found that impact strength of multilayer structure material was considerably higher than single layer's and toughness was enhanced by about two times or higher in similar glass transition temperature($T_g$) region and the same dimension. The superposition principle of impact pulse was used for interpretation of kinetic stress wave as a high-velocity crack proceeds in the plastic. It was understood that the optimum condition of ductile/brittle thickness ratio could be designed in the final toughness enhancement of multilayer.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.629-640
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• 2007

In this paper an analytical study is carried out to improve the capacity of absorbing boundary using dashpot, one of the most widely used absorbing boundaries in FEM. Using 2-D harmonic plane wave equation, absorbing boundary condition is modified to maximize its capacity according to the incident angle. Validity of the absorbing boundary conditions which is modified is investigated by adopting the solution of Miller and Pursey. The Miller and Pursey's problem is then numerically simulated using the finite element method. The absorption ratios are calculated by comparing the displacements at the absorbing boundary to those at the free field without the absorbing boundary. The numerical study is carried out through comparison of displacement at the interior region and the boundary of the numerical model.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.641-652
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• 2007

In this paper, a half-scaled substructure test was performed to evaluate the buckling and structural safety of an existing transmission tower subjected to wind load. A loading scheme was devised to reproduce the dead and wind loads of a prototype transmission tower, which uses a triangular jig that is mounted on the reduced model to which the similarity law of a half length was applied. As a result of the preliminary numerical analysis carried out to evaluate the stability of a specimen for the design load, is was confirmed that the calculated axial forces of tower leg members were distributed to $80{\sim}90%$ of an admissible buckling load. When the substructured transmission tower was loaded by 270% of its maximum admissible buckling load, it was failed due to the local buckling that is occurred in joints with weak constraints for out-of-plane behavior of leg members. By inspection of load-displacement curves, displacements and strains of members, it is considered that this local buckling was due to additional eccentric force by unbalanced deformation because the time that is reached to yielding stress due to the bending moment is different at each point of a same section.

• Journal of the Korean GEO-environmental Society
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• v.7 no.4
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• pp.43-52
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• 2006

There were huge damages of human beings and their properties in many areas of the basin of the Nak-Dong river by the unusual weather and the localized downpour recently. In this research against disasters, we want to know strength of the cemented sand that is mixed with cement and poor-graded sand, to estimate CSG(Cemented Sand and Gravel) method used coffer dam in Japan, which is the materials of riverbed in the basin of the Nak-Dong river for levee's construction. For that, we want to provide the fundamental data which need in the examination of adaptation of levee's material, design and analysis by investigating compressive strength by curing period and cement content, elastic modulus and stress by transformation from compaction test, CBR test, unconfined compression test and triaxial compression test as changing cement content from 2% to 8% at two sites in the basin of the Nak-Dong river.