• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.1
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• pp.33-41
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• 2011

This study presents modeling technologies applicable to an unbonded post-tension system using a finite element software package. In this study, both direct modeling method and multiple spring method were used. The direct modeling method adopts tube-to-tube contact elements to represent the physical feature of a post-tension system. The multiple spring method uses virtual tendons attached to the real tendons using a number of rigid axial springs that freely rotate at the ends. Both modeling technologies provide accurate predictions. However, only the multiple spring method provides numerically stable and reliable responses with a consideration of concrete tension stiffening effects. Therefore, the multiple spring method turned out to be a generally applicable modeling technology for the unbonded post-tension system. Comparisons were made for the analytical and experimental results for the verification of the selected method, and parameter studies were carried out to confirm the appropriateness of the modeling assumptions and parameters adopted in the analysis.

• The KSFM Journal of Fluid Machinery
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• v.18 no.3
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• pp.38-45
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• 2015

In this study, two computational methodologies were compared to consider an effective conjugate heat transfer analysis technique for the cooled vane with thermal barrier coating. The first one is the physical modeling method of the TBC layer on the vane surface, which means solid volume of the TBC on the vane surface. The second one is the numerical modeling method of the TBC layer by putting the heat resistance interface condition on the surface between the fluid and solid domains, which means no physical layer on the vane surface. For those two methodologies, conjugate heat transfer analyses were conducted for the cooled vane with TBC layer having various thickness from 0.1 mm to 0.3 mm. Static pressure distributions for two cases show quite similar patterns in the overall region while the physical modeling shows quite a little difference around the throat area. Thermal analyses indicated that the metal temperature distributions are quite similar for both methods. The results show that the numerical modeling method can reduce the computational resources significantly and is quite suitable method to evaluate the overall performance of TBC even though it does not reflect the exact geometry and flow field characteristics on the vane surface.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.645-654
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• 2011

Temporal supports is proposed for the large block construction of a double-deck truss girder of a bundle type cable-stayed bridge. The design force of the temporal bents cannot be evaluated by a conventional design procedure with gust factored static wind loads. The uplift forces in BS5400 also can not estimate the design forces of the temporal bents properly for the turbulent wind loads. A frequency-domain buffeting analysis is performed to evaluate the design forces of the temporal bents considering the interactions between the girder and temporal supports. Two cases of modeling are compared to estimate the stiffness contribution of temporal supports in determining design forces, i.e., an analysis model including temporal bents in the structural analysis modeling and an analysis model with fixed supports at the bent tops neglecting the stiffness of temporal bents. The consideration of bent stiffness usually generates smaller reaction forces than rigid support modeling. Consequently, the effectiveness and usefulness of the buffeting analysis procedure with full modeling of temporal supports are demonstrated for the design of a temporal bents of the construction of a bundle type cable-stayed bridge.

• ETRI Journal
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• v.29 no.3
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• pp.393-395
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• 2007

Analytic modeling and computational simulation for the protection of DTV from cognitive radio interference are performed. Protection is achieved by using the protection ratio, which is derived through system modeling and its analysis. On the frequency coordination between digital TV and cognitive radio, an analysis in a co-channel environment, in a rural area in Korea, is performed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.902-909
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• 2006

In this study, three-dimensional rotordynamic analyses have been conducted using equivalent beam, hybrid and fun three-dimensional models. The Present computational method is based on the general finite element method with rotating gyroscopic effects of a rotor system. General purpose commercial finite element code, SAMCEF which includes practical rotordynamics module with various types of rotor analysis methods and bearing elements is applied. For the purpose of numerical verification, comparison study for a benchmark rotor model with support bearings is performed first. Detailed finite element models based on three different modeling concepts are constructed and then computational analyses are conducted for the realistic and complex three-dimensional rotor system. The results for rotor stability and mass unbalance response are presented and compared with the experimental vibration test conducted in this study.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.1
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• pp.1-15
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• 1998

Currently, computational analysis is a popular technology in automobile engineering. Finite element analysis is an excellent method for body analysis. For finite element analysis, accurate modeling is very important to obtain precise information. Stick modeling is a convenient way in that it is easy and simple. When a stick model is utilized, the joints are modified in the tuning process. A tuning method for the joint has been developed. The joints are modeled by designated beam elements. An optimization method called "Goal Programming" is employed to impose the target values. With the tuned joints, the entire optimization has been carried out. Using the "Recursive Quadratic Programming" algorithm, the optimization process determines the configuration of the entire structure and sizes of all the sections. For example, the structure of an electrical vehicle is modeled and analyzed by the method. The stick model works well since the structure is made of aluminium frames. Although the example handles an electrical vehicle, this method can be applied to general vehicle structures.

• Structural Engineering and Mechanics
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• v.46 no.2
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• pp.213-229
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• 2013

Although performance based assessment procedures are mainly developed for reinforced concrete and steel buildings, URM (Unreinforced Masonry) buildings occupy significant portion of buildings in earthquake prone areas of the world as well as in IRAN. Variability of material properties, non-engineered nature of the construction and difficulties in structural analysis of masonry walls make analysis of URM buildings challenging. Despite sophisticated finite element models satisfy the modeling requirements, extensive experimental data for definition of material behavior and high computational resources are needed. Recently, nonlinear equivalent frame models which are developed assigning lumped plastic hinges to isotropic and homogenous equivalent frame elements are used for nonlinear modeling of URM buildings. The equivalent frame models are not novel for the analysis of masonry structures, but the actual potentialities have not yet been completely studied, particularly for non-linear applications. In the present paper an effective tool for the non-linear static analysis of 2D masonry walls is presented. The work presented in this study is about performance assessment of unreinforced brick masonry buildings through nonlinear equivalent frame modeling technique. Reliability of the proposed models is tested with a reversed cyclic experiment conducted on a full scale, two-story URM building at the University of Pavia. The pushover curves were found to provide good agreement with the experimental backbone curves. Furthermore, the results of analysis show that EFM (Equivalent Frame Model) with Dolce RO (rigid offset zone) and shell element have good agreement with finite element software and experimental results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.6
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• pp.933-941
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• 1997

In the analysis of thin elastic structures such as plate and shell-like structures, classical lower-order theories like Kirchhoff and Reissner-Mindin theories are insufficient to describe the behavior of such structures in the region where the state of stresses is complex. On the other hand, the fully three dimensional theory of linear elasticity can provide desired analysis accuracy, but requires expensive computational implementation compared to the classical theories. This paper is concerned with the development of hierarchical models for elastic structures which can be used for hierarchical modeling for the analysis of such structures. Derivation and limit model analysis (when the thickness of structures tends to zero) of hierarchical models are presented together with a introduction of modeling error estimation. Also, numerical results supporting theoretical results are given.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.1
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• pp.7-15
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• 2017

This paper presents the results of the parametric study to investigate the effects of several analysis modeling parameters such as support conditions, member connectivities and cable member stiffness on the main mode shapes and natural frequencies of a representative disaster resilient greenhouse structure. In addition, an ambient vibration test was performed on the representative greenhouse structure and its main mode shapes and natural frequencies were obtained. By comparing the experimental and analysis results, a proper analysis modeling method of the representative greenhouse structure was proposed.

• International Journal of CAD/CAM
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• v.2 no.1
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• pp.1-12
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• 2002

Computer-Aided Reliable and Optimal Design (CAROD) system is an efficient tool defining the best compromise between cost and safety. Using the concurrent engineering concept, it can supply the designer with all numerical information in the design process. This system integrates several fields such as multidisciplinary optimization, reliability analysis, finite element analysis, geometrical modeling, sensitivity analysis and concurrent engineering. When integrating these disciplines, many difficulties are found such as model coupling and computational time. In this paper, we propose a new concurrent methodology satisfying the reliability requirement, allowing the coupling of different models and reducing the computational time. Two applications (rotating disk and hook structures) demonstrate that CAROD system can be a practical concurrent engineering application for designers.