• Journal of the Korean Society for Railway
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• v.14 no.1
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• pp.39-48
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• 2011

The paper describes four practical cases of railway structure concerning a three-dimensional numerical approach to analyse dynamic soil-structure interaction(SSI)of railway tracks on layered soil under transient load in the time domain. The SSI-Model has been implemented in TDAPIII accounting for nonlinear properties of the track and soil. The approach can be also be used to calculate vibration propagation in the soil and its effect on nearby buildings and structure. The Method is applied to analyse the dynamic response of railway tracks due to a moving wheel set. Finally some sample are given in order to reduce the vibration at the point of emission, at the transmission path and the structure itself.

• Journal of the Korean Geotechnical Society
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• v.24 no.2
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• pp.15-25
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• 2008

A soft ground improvement method is used for structures which are constructed on soft ground to decrease settlement and Increase bearing capacity. The Floating Base Plate has been developed for such purposes. In this study, the load-settlement characteristics were investigated by numerical analysis on various Floating Base Plate shapes to select an optimum shape, different from the conventional shape. The selected optimum shape was used to perform plate bearing test and numerical simulations. It was found that the Floating Base Plate is very effective In reducing the settlement and increasing the bearing capacity.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.5
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• pp.543-550
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• 2010

Earthquake resistant design should provide a description of the structural failure mechanism under earthquakes as well as satisfy the requirement of other designs, e.g. design strengths of each structural member should be equal or greater than the required strengths. The reason of such a requirement is the randomness of seimic loads different from other loads. In this study, a typical bridge is selected as an analysis bridge and the procedure is given to get the ductile failure mechanism through connection design. It is shown with the procedure that the earthquake resistant capacity can be ensured within structural member's strengths required by other designs, without cost raise by strength increase of structural members or by use of shock absorbing device e.g. shock transfer unit.

• Journal of the Korean Solar Energy Society
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• v.32 no.5
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• pp.31-40
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• 2012

This paper introduces a methodology for NREL 5MW wind turbine, which is the variable speed and variable pitch(VSVP) control system. This control strategy maximizes the power extraction capability from the wind in the low wind speed region and regulates the wind turbine power as the rated one for the high wind speed region. Also, pitch control efficiency is raised by using pitch scheduling.Torque schedule is made of torque table depending on the rotor speed. Torque control is used for vertical region in a torque-rotor speed chart. In addition to these, mechanical loads reduction using a drive train damper and exclusion zone on a torque schedule is tried. The NREL 5MW wind turbine control strategy is comprised by the generator torque and blade pitch control. Finally, proposed control system is verified through GH Bladed simulation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.11
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• pp.855-864
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• 2013

Active tab is one of the promising technology for the BVI (blade-vortex interaction) noise reduction, and analysis of noise reduction performance is very important phase of the technology development. For the purpose of analysing the performance of noise reduction using active tab, CAMRAD II model for a model-scale rotor system was constructed utilizing structural design result and airfoil aerodynamic data generated by CFD (computational fluid dynamics) calculation. HHC strategy was applied to descent flight condition and air-load was calculated by CAMRAD II then variations of BVI noise was calculated by in-house program. Calculation result with respect to tab length and control phase changes showed BVI noise could be reduced by -3.3dB.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3D
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• pp.271-278
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• 2010

Semi rigid pavement is a pavement type using advantages of both flexibility of asphalt pavement and rigidity of concrete pavement by infiltrating cement paste into voids of open graded asphalt mixtures. The semi rigid pavement has better smoothness and smaller driving vibration or noise comparing to the concrete pavement, and has smaller permanent deformation and has temperature falling effect comparing to the asphalt pavement. The temperature falling effect were investigated at a semi rigid overlay pavement test section, and the temperature falling and water retaining effects were verified by measuring the temperature and weight of specimens at a housetop. Horizontal and vertical stresses and strains were compared by structural analysis of the semi rigid pavement and asphalt pavement using the Abaquser o, a commercial 3D finite element analysis program. The results were verified by Bisar 3.0, a multi-layered elastic analysis program. Performance of the semi rigid pavement and asphalt pavement were compared by predicting fatigue cracking based on the structural analysis results.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.4
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• pp.407-416
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• 2023

Demand for leisure facilities such as mooring facilities for berthing leisure vessels and floating pensions based on floating bodies is increasing owing to the rapid growth of the population and related industries for marine leisure activities. Owing to its relatively light weight as a fluid, inclination is easily generated by waves and surcharges flowing to the coast, resulting in frequent safety accidents because of the low stability. As a solution to this problem, a motion reduction device for floating bodies is proposed in this study. The device (motion reduction device based on the air pressure dif erence) was attached to a floating body and the effect was analyzed by comparing the results with those of a floating body without motion reduction. The effect analysis was further analyzed using a computer analysis test, and the method for increasing the stability of the floating body was studied, and its the effect was verified. Based on the analysis of the test results, the stability of the floating body increased with a motion damping device is higher than that of the floating body without a motion reducing device as the wave momentum reduces, owing to the air pressure difference. Therefore it was concluded that the use of such a device for reducing motion a floating body is useful not only for non-powered ships but also for powered and semi-submersible ships, and further research should be conducted by applying it to various fields.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.492-497
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• 2011

Helicopter uses a rotor system to generate lift, thrust and forces, and its aerodynamic environment is generally complex. Unsteady aerodynamic environment arises such as blade vortex interaction. This unsteady aerodynamic environment induces vibratory aerodynamic loads and high aeroacoustic noise. Those are at N times the rotor blade revolutions (N/rev). But conventional rotor control system composed of pitch links and swash plate is not capable of adjusting such vibratory loads because its control is restricted to 1/rev. Many active control methodologies have been examined to alleviate the problem. The blade using active control device manipulates the blade pitch angle at arbitrary frequencies. In this paper, Active Trailing-edge Flap blade, which is one of the active control methods, is designed to modify the unsteady aerodynamic loads. Active Trailing-edge Flap blade uses a trailing edge flap manipulated by an actuator to change camber of the airfoil. Piezoelectric actuators are installed inside the blade to manipulate the trailing edge flap.

• Geotechnical Engineering
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• v.13 no.4
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• pp.163-176
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• 1997

It has long been recognized that the H-beam steel rib has many shortcomings when used as a steel support in tunneling. One of the major shortcomings is the shotcrete shadow created behind H-beam flange which eventually reduces the load bearing capacity of shotcrete shell. In many European countries, plate girder as the H-beam steel rib has been replaced by lattice girder which has many advantages over the H-beam steel rib. Successful application of the lattice girder as a steel support requires a thorough investigation on the load bearing capacity of the lattice girder. Therefore, laboratory bending and compression tests were conducted on lattice girders with the aim of investigating the load bearing capacity of the lattice girders. The results of tests show that the load bearing capacity of laIn twice girders is higher than that of H-beams, which indicates that the lattice girder can be effectively used as a support in tunneling.

• Journal of Korean Association for Spatial Structures
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• v.8 no.5
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• pp.75-82
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• 2008

In this study, the possibility of vibration control of high-rise building structures by applying top-story isolation has been investigated. To this end, El Centro NS (1940) earthquake load is applied to 20- and 50-story building structures for numerical analysis. Artificial wind loads are used to evaluate the serviceability of example structures against wind vibration. As the number of isolated stories of example buildings is changed, structural responses has been evaluated to investigate optimal isolated building mass. And the natural period of isolation systems for top-story isolation is varied to investigate the improvement of control performance compared with the fixed base structure. Based on the analytical results, the top-story isolation system can be used as a hued mass damper and effectively reduce the structural responses of high-rise buildings against wind and seismic loads.