• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.971-972
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• 2010

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1419-1420
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• 2011

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.353-361
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• 2001

Recently the boundary element method has been developed swiftly. The boundary element method is an efficient and accurate means for analysis of two dimensional elastic crack problems. This paper is concerned with the evaluation and the prediction of the stress intensity factor(SIF) for the crack emanating from the circular hole using boundary element method-neural network. The SIF of the crack emanating from the hole was calculated by using boundary element method. Neural network is used to evaluate and to predict SIF from the results of boundary element method. The organized neural network system (structure of four processing element) was learned with the accuracy 99%. The learned neural network system could be evaluated and predicted with the accuracy of 83.3% and 71.4% (in cases of SIF and virtual SIF). Thus the proposed boundary element method-neural network is very useful to estimate the SIF.

• Steel and Composite Structures
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• v.27 no.3
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• pp.327-335
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• 2018

This paper presents structural assessment of a steel railway bridge for current condition using modal parameter to upgrade finite element modeling in order to gather accurate result. An adequate monitoring, such as acceleration, displacement, strain monitoring, is important tool to understand behavior and to assess structural performance of the structure under surround vibration by means of the dynamic analysis. Evaluation of conditions of an existing steel railway bridge consist of 4 decks, three of them are 14 m, one of them is 9.7 m, was performed with a numerical analysis and a series of dynamic tests. Numerical analysis was performed implementing finite element model of the bridge using SAP2000 software. Dynamic tests were performed by collecting acceleration data caused by surrounding vibrations and dynamic analysis is performed by Operational Modal Analysis (OMA) using collected acceleration data. The acceleration response of the steel bridge is assumed to be governing response quantity for structural assessment and provide valuable information about the current statute of the structure. Modal identification determined based on response of the structure play significant role for upgrading finite element model of the structure and helping structural evaluation. Numerical and experimental dynamic properties are compared and finite element model of the bridge is updated by changing of material properties to reduce the differences between the results. In this paper, an existing steel railway bridge with four spans is evaluated by finite element model improved using operational modal analysis. Structural analysis performed for the bridge both for original and calibrated models, and results are compared. It is demonstrated that differences in natural frequencies are reduced between 0.2% to 5% by calibrating finite element modeling and stiffness properties.

• Journal of Forest and Environmental Science
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• v.27 no.3
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• pp.205-210
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• 2011

This study aims to assess MEE(management effectiveness evaluations) on PAs(protected areas) for forest genetic resources which play an important role in biodiversity conservation, and then to suggest better ways to manage PAs for forest genetic resources. This study applies same indicators of the MEE on PAs as the ones described in the prior study(Ryu et al. 2011). The indicators applied are composed of five elements, thirty-two indicators which all would be grouped into one element by each traits. Overall indicators belonging to the element of output and outcome are comparatively low. Especially the ones related to the change of biodiversity, degree of ecosystem health, variation of civil complaint and visitor satisfaction are ranked mostly low. The element of input shows the low rank on the number of staff and budget. The score of indicators related to the identification of the threats of PAs and local communities' supports turn out to be low in the element of Context. The element of process, however, has scored low on Staff management, Education/Awareness programs and Governance, while the law enforcement, management regulation and capacity to prevent forest disasters have made relatively high score. Meanwhile, all indicators in the element of planning have scored relatively high as compared to the indicators belonged to other elements. This study suggests to strengthen a few constructive proposals, such as facilitating efficient management framework for PAs, developing local community cooperation program, establishing survey, research and monitoring system, and registering PAs to the WDPA(World Database on Protected Areas) according to the IUCN categories.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.237-246
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• 2006

In order to evaluate the seismic performance of damaged reinforced concrete members, particularly bridge piers, an inelastic time-dependent element is proposed. The proposed element enables increased characteristics due to structural intervention(i.e., repair or retrofitting) to be accurately reflected to the degraded strength and stiffness of the members. The inelastic time-dependent element having both birth and death time can freely be activated within the user-defined time intervals during static and dynamic time-history analysis. Comparative studies are carried out for reinforced concrete bridge piers that are repaired and retrofitted. Analytical predictions using the developed element show reasonable correlation with experimental results. Also conducted is a nonlinear time-history analysis of a reinforced concrete bridge under multiple earthquakes. The comparative analytical results prove the validation of current development. In all, it is concluded that the present element is capable of providing salient features for the healthy evaluation of seismic performance and hence seismic stability assessment of RC bridge piers being repaired and retrofitted.

• Corrosion Science and Technology
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• v.4 no.4
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• pp.164-170
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• 2005

Pipelines have the highest capacity and are the safest and the least environmentally disruptive means for transmitting gas or oil. Recently, failures due to corrosion defects have become a major concern in maintaining pipeline integrity. A number of solutions have been developed for the assessment of remaining strength of corroded pipelines. In this paper, a Fitness-For-Purpose(FFP) type limit load solution for corroded city gas pipelines is proposed. For this purpose, a series of burst tests with various types of machined defects were performed. Finite element simulations were carried out to derive an appropriate failure criterion. Based on such solution along with existing solutions, an integrity evaluation program for corroded city gas pipeline, COPAP-CITY, has been developed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2277-2286
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• 2002

The application of bonded dissimilar materials to industries as automobiles, aircraft, rolling stocks, electronic devices and engineering structures is increasing gradually because these materials, compared to the homogeneous materials, have many advantages for material properties. In spite of such wide applications of bonded dissimilar materials, the evaluation method of quantitative strength considering the stress singularities for its bonded interface has not been established clearly. In this paper, the stress singularity for Bctors and the stress intensity factors were analyzed by boundary element method(BEM) for the scarf joints of Al/Epoxy with and without a crack, respectively. From static fracture experiments of the bonded scarf joints, a fracture criterion and a evaluation method of interface strength in bonded dissimilar materials were proposed and discussed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.06a
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• pp.75-86
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• 1996

Three-Dimensional finite element analysis is performed using PAM-STAMP for design evaluation of automotive back door inner panel die. Gravity process by blanks own weight, binder-wrap process, and drawing process in the forming operations are sequentially simulated with Virtual Manufacturing Method. The most valuable result in this research is that 3-D FEM analysis can be applied to the design evaluation of draw die in the die try-out, though effects of mesh size and drawbead resistance force on the numerical accuracy are much sensitive. For the intensive application to draw-die design and try-out, the experimental know-hows about the forming variables such as friction coefficient, punch velocity, drawbead force, etc are necessary.

• Journal of the Korean Society for Railway
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• v.8 no.4
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• pp.321-329
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• 2005

This paper has established the strength evaluation procedure of the bogie frame for the Korean tilting train that is being developed in KRRI, In order to establish the strength evaluation procedure, firstly, the loading conditions imposed on the tilting train were investigated. In addition, the static and fatigue strength of the bogie frame has been evaluated. In order to derive the dynamic loads according to the carbody tilting, the load redistribution effect by carbody tilting, the unbalanced lateral acceleration effect by high-speed curving and the tilting actuator force effect have been considered. Multi-body dynamic analyses have been carried out to evaluate the tilting load cases and the strength analysis has been performed by finite element analyses. From this study, the structural safety of the bogie frame could be ensured.