• International Journal of High-Rise Buildings
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• v.7 no.3
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• pp.255-264
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• 2018

This paper introduces three distinctive means for the use of a 189-meter high damped structure ensuring safety against earthquake: 1. Realization of L-shaped elevational structural planning: The bottom and top of the tower have belt trusses and hat trusses respectively to restrain the bending deformation. Furthermore, large-capacity oil dampers (damping force 6,000 kN) are installed in the middle part of the tower to restrain the higher-mode deformation. 2. Realization of L-shaped planar structural planning: We devised a means of matching the centers of gravity and rigidity by adjusting planar rigidity. Moreover, viscous damping devices are located at the edges of the L-shaped plan, where torsional deformation tends to be amplified. We call this the "Damping Tail" system. 3. Composite foundation to equalize deformations under different loading conditions: We studied the vertical and horizontal deformations using sway-rocking and 3D FEM models including the ground, and applied multi-stage diameter-enlarged piles to the tower and a mat foundation to the podium to keep the foundations from torsional deformations and ensure structural safety.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.3
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• pp.173-179
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• 2017

This paper analyzes actuator characteristics for main wing and tail surfaces of an ornithopter by using a motion capture test. Experiments with the ornithopter are conducted indoor, and its fuselage is held on a jig to reduce interaction with vibration generated by flapping motion. The motion capture system detects the movement of markers attached on the main wing and tail wing tip. Experimental results show that the main wings tend to change its amplitude according to the flapping frequency, and the lift and thrust generation simulation is implemented by applying the experimental results and the ornithopter specification to Modified Strip Theory. Step input excitation is applied for experimental analysis of the tail wing in horizontal and vertical directions. As a result, horizontal and vertical tail wings have different characteristics in terms of overshoot, final value, damping ratio and natural frequency because they have different wing structures and linkages.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.9
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• pp.765-771
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• 2014

During the acceptance test of KTX, unexpectedly great lateral vibration in 14th~16th train at 150km/h~200km/h was appeared on a straight line in the winter season. Generally, stiffness of secondary suspension in KTX vehicle is one of the most sensitive components on air temperature. So, we examined that the secondary suspension to be mounted heating system was able to reduce the lateral vibration in the tail car of KTX. Also, we verified that lateral vibration from test results on KTX train with wheel conicity 1/20 disappeared. In this paper, we analysis effective reduction methods and the cause of the lateral vibration using model of KTX train and compare with the test results. The analysis results agree well with test ones. From mode analysis result, lateral vibration is occurred at natural frequency range 0.5~0.6Hz with a negative damping value and its natural frequency disappear gradually according to increasing of wheel concinicy.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.3
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• pp.29-35
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• 1997

The megastructure combined with the modular concept is an effcient structural system adequate for ultra-tail buildings for the future. An ingeneous structural control system can be developed by separating the internal subframe in one or many modules from the external megaframe, thus taking advantage of the effect of tuned mass dampers without adding any aditional mass. This so called mega-subcontrol system is generally modeled by a 20DF system for parametric study and for finding optimal values of the parameters. In this study the equation of motion for the system is obtained frist and the preconditions for the simplified modeling are investigated. Finally the optimal value for the subsreucture strffness is fomputed with given mass and damping ratios and transfer functions for responses are abtained for white noise ground exitation to verify the effectiveness of the mega-subcontrol system.