• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.4
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• pp.389-403
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• 2004

This study presents the structural model modification based on the modal data such as natural frequencies and mode shapes. Preliminary structural model can be obtained using design drawings and field measurement, and therefore the deteriorated stiffness of a structure and the effect of the boundary conditions are difficult to be evaluated in preliminary analysis model, and the preliminary model can be modified using structural response data including static and/or dynamic characteristics. In this study, the structural model is modified based on the structural modal data using genetic algorithm. Modal testing were carried out for Imjin River Bridge and Hangjoo Bridge, the modal properties were estimated using modal identification techniques, and finally the structural models were updated using genetic algorithm. The modified structural model could give us more reliable structural analysis results and therefore those can be used for structural performance evaluation such as load carrying capacity and seismic capacity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.1
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• pp.85-94
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• 2016

In this study, a non-linear FEM model is presented to predict the static flexural performance of precast bridge decks with ribbed joint and is verified with previous experiment results through comparison. The several theory of material properties were applied to each mechanical properties in FEM model and FEM model's input variables were determined through experiment result and parametric study. The FEM results showed good accuracy in predicting the structural performance of the specimens and FEM model's average error rate was 5%. Also, each specimen's cracking aspect and failure mode can be predicted through FEM's plastic strain distribution. Thus, this FEM model can be used effectively for predicting the ultimate behavior and parametric study to development of design formula for joint.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.9 s.90
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• pp.903-909
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• 2004

A CFA(cooling fan assembly) is composed of a fan, motor and shroud, which is at the back of the automotive radiator. By forcing the wind to pass, the CFA controls the cooling performance of the radiator. The noise and vibration of the CFA may be primarily due to the resonance between the CFA and engine. The Interference among the fan, shroud and radiator by deformation is considered when the CFA is designed. In this paper, in order to analyze the structural vibration of the CFA for automobiles, a finite element model of the CFA is established by using a commercial FEM code. After the finite element modeling, the natural frequencies and the mode shapes are obtained from the FE analysis. The natural frequencies are obtained from the vibration test as well. Then, the results of the vibration test are compared with those of the FE analysis. The natural frequencies obtained by experiment have a great similarity to the results from FE model. We have confirmed the validity of the FE model and verify the structural safety for the resonance. The stress and displacements are obtained from FE analysis. We have confirmed the safety for the interference and failure.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.5
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• pp.23-32
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• 2012

Research on steel plate concrete (SC) structures for the modularization of nuclear power plants have been performed recently in Korea. In this study, the seismic capacity and stiffness characteristics of unstiffened SC shear walls under the effects of earthquakes were investigated through static pushover tests. Failure modes, sectional strength, and stiffness characteristics of SC structures under lateral loads were inspected by analyzing the experimental results. The strengths obtained by the experiments were also compared with those derived by the design code of the SC structures. One of the main failures of unstiffened SC shear walls was found to be the type of bending shear failure due to the debonding of the steel plate at the concrete interface. The ductility capacity of SC structures was also confirmed to be improved, which is considered to be a confining effect on steel plates in the longitudinal behavior of SC structures.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.2
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• pp.69-75
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• 2017

The gas turbine static starter rotates the stationary synchronous machine by the interaction of the rotor and the stator. The detection from the initial position of the rotor has been an important issue to drive with optimum torque. Previously, the gas turbine starter was used by attaching the encoder to the synchronous machine, but the position and velocity of the rotor have been estimated by sensor-less method until recently due to the difficulty in attaching and detaching and damage caused by the shaft voltage noise. In this paper, Rotor initial(stationary state) position estimation, forced commutation control(speed less than 10%), and natural commutation control(speed more than 10%) method using magnetic flux with integrated terminal voltage were presented and the sensor-less speed control performance was verified. As a result of making and evaluating the 29 kVA synchronous machine and the starting device, the performance of each control mode was satisfactory. Furthermore, the applied technology is expected to be used for the development of the gas turbine starter of tens of MW class and the field application.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.5
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• pp.429-437
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• 2008

In this study the progressive collapse potential of braced frames were investigated using the nonlinear static and dynamic analyses. All of nine different brace types were considered along with a special moment-resisting frame for comparison. According to the pushdown analysis results, most braced frames designed per current design codes satisfied the design guidelines for progressive collapse initiated by loss of a first story mid-column; however most model structures showed brittle failure mode. This was caused by buckling of columns after compressive braces buckled. Among the braced frames considered, the inverted- V type braced frames showed superior ductile behavior during progressive collapse. The nonlinear dynamic analysis results showed that all the braced frame model structures remained in stable condition after sudden removal of a column, and their deflections were less than that of the moment-resisting frame.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.6
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• pp.539-545
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• 2016

UPS system in the liquefied natural gas(LNG) receiving terminal is one of the fundamental equipment that need to sustain operation during earthquake. In this study, modal identification test of UPS system was performed based on IEEE Std. 693-2005 and natural frequencies and modal damping, mode shapes had been identified. In addition, tri-axial time history test was performed to check the behavior and stress of the equipment during earthquake. Eigenvalue analysis was performed and analysis model was modified by reflecting the results of the test. Static analysis by dead weight and response spectrum analysis were performed to compare the combined stresses with the stress results of test. Dynamic characteristics and combined stresses under seismic load condition of the improved analysis model were similar to the test results and in this regard the compatibility was proved.

• Steel and Composite Structures
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• v.37 no.2
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• pp.175-191
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• 2020

In this article, for the first time, the seismic behavior of elliptic-braced moment resisting frame (ELBRF) is assessed through a laboratory program and numerical analyses of FEM specifically focused on the development of global- and local-type failure mechanisms. The ELBRF as a new lateral braced system, when installed in the middle bay of the frames in the facade of a building, not only causes no problem to the opening space of the facade, but also improves the structural behavior. Quantitative and qualitative investigations were pursued to find out how elliptic braces would affect the failure mechanism of ELBRF structures exposed to seismic action as a nonlinear process. To this aim, an experimental test of a ½ scale single-story single-bay ELBRF specimen under cyclic quasi-static loading was run and the results were compared with those for X-bracing, knee-bracing, K-bracing, and diamond-bracing systems in a story base model. Nonlinear FEM analyses were carried out to evaluate failure mechanism, yield order of components, distribution of plasticity, degradation of structural nonlinear stiffness, distribution of internal forces, and energy dissipation capacity. The test results indicated that the yield of elliptic braces would delay the failure mode of adjacent elliptic columns and thus, help tolerate a significant nonlinear deformation to the point of ultimate failure. Symmetrical behavior, high energy absorption, appropriate stiffness, and high ductility in comparison with the conventional systems are some of the advantages of the proposed system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.8A
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• pp.613-619
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• 2003

Bluetooth is a communication technology enabling short-range devices to be wirelessly connected. A master and one or more slave devices are connected to form a piconet, and piconets are joined to form a scatternet. The units participating in two or more piconets in a scatternet, is called bridge or gateway nodes. In order to operate the scatternet efficiently, both piconet scheduling for the master and slaves of a piconet, and scatternet scheduling for the bridge nodes are playing important roles. In this paper, we propose a traffic-adaptive dynamic scatternet scheduling algorithm based on rendezvous points and rendezvous windows. The performance of the proposed algorithm is compared and analyzed with that of a static scheduling algorithm via simulations. Simulation results show that our algorithm can distribute wireless resources efficiently to bridge nodes depending on the traffic characteristics.

• Journal of Biomedical Engineering Research
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• v.22 no.6
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• pp.551-557
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• 2001

Occlusion of the dural-sac in the lumbar spine was quantitatively analysed using a one motion segment finite element mode developed in this study. Occlusion was quantified by calculating the cross sectional area chance of the dural-sac. In static analysis. less than 2 kN of compressive load could Produced no dural-sac occlusion. whereas 6kN load reduced cross sectional area by 4%, and produced 7.4%, 10.5% occlusion for additional 8 Nm. 10 Nm extension moments. respectively. In creep analysis, 10 Nm extension reduced cross sectional area and volume of the dural-sac by 6.9% and 2.4%, respectively. However. flexion moment could not produce any occlusion. The results suggested that occlusions may result mainly from slackening of ligamentum flavum and disc budging.