• Structural Engineering and Mechanics
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• v.61 no.2
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• pp.267-274
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• 2017

In this study was investigated of possibility using the recorded micro tremor data on ground level as ambient vibration input excitation data for investigation and application Operational Modal Analysis (OMA) on the bench-scale earthquake simulator (The Quanser Shake Table) for model steel structures. As known OMA methods (such as EFDD, SSI and so on) are supposed to deal with the ambient responses. For this purpose, analytical and experimental modal analysis of a model steel structure for dynamic characteristics was evaluated. 3D Finite element model of the building was evaluated for the model steel structure based on the design drawing. Ambient excitation was provided by shake table from the recorded micro tremor ambient vibration data on ground level. Enhanced Frequency Domain Decomposition is used for the output only modal identification. From this study, best correlation is found between mode shapes. Natural frequencies and analytical frequencies in average (only) 2.8% are differences.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.476-478
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• 2006

A prescaler is an essential building block for PLL-based frequency synthesizers and must satisfy high-speed and low-power characteristics. The design of D-flip flips used in the prescaler implementation is thus critical. In this paper a 64/65, 128/129 dual-modulus prescaler is designed using a $0.25{\mu}m$ CMOS process. In the design a new dynamic D-flip flop is employed, where glitches are minimized using discharge suppression scheme, speed is improved by making balanced propagation delay, and low power consumption is achieved by removing unnecessary discharge. The designed prescaler operates up to 2.5GHz and consumes 3.1mA at 2.5GHz operation.

• The Journal of Engineering Research
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• v.8 no.1
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• pp.5-11
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• 2006

In order to evaluate the seismic performance of a reinforced concrete building structure, four different analyses are carried out. Firstly, conventional pushover analysis with code-specified inverted triangular load pattern is conducted. Secondly, the pushover analysis with uniform load pattern is performed. Thirdly, adaptive pushover analyses with spectral amplification for both EC 8 artificial and Northridge earthquake are carried out. Lastly, Incremental dynamic analyses under a number of scaled PGA for both EC 8 artificial and Northridge earthquake record are performed. Comparative studies demonstrate that the adaptive pushover analysis may be able to explain the response characteristics that conventional pushover analysis with fixed load distribution fails to capture.

• International Journal of High-Rise Buildings
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• v.5 no.3
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• pp.155-165
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• 2016

A much higher level of seismic performance is needed for supertall buildings due to increased demands for their functional continuities and the recognized needs for their continuing emergence in metropolitan areas. This paper analyzes, compares, and contrasts responses recorded during the 2011 Tohoku-oki Earthquake of different supertall buildings featuring conventional and vibration-controlled engineering systems. The superior performance and advantage of the latter are pointed out, and the typical dynamic properties, response characteristics, and effects on the secondary system are discussed. Ongoing efforts to enhance vibration control performance are described, covering the development of specifications, use of performance curves and targeted displacement design, and methods to find appropriate locations of damper installation resulting in a minimized amount of dampers.

• Wind and Structures
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• v.8 no.3
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• pp.163-178
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• 2005

Wind-induced mean and dynamic interference effects of tall buildings are studied in detail by a series of wind tunnel tests in this paper. Interference excitations of several types of upwind structures of different sizes in different upwind terrains are considered. Comprehensive interference characteristics are investigated by artificial neural networks and correlation analysis. Mechanism of the wakes vortex-induced resonance is discussed, too. Measured results show significant correlations exist in the distributions of the interference factors of different configurations and upwind terrains and, therefore, a series of relevant regression equations are proposed to simplify the complexity of the multi-parameter wind induced interference effects between two tall buildings.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.109-112
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• 2006

Recently, when we conducted meteorological observations, complicated land or building around weather station has influenced on the wind distribution. So, we should understand the effect of geometry to get more accurate data. In this study, we analyze the ideal geometry whose shape is hemisphere using CFD method. And then we apply this method to real geometry. And we investigate the velocity at the location of weather station. As the results, we could find out an important relationship between geometry and flow field.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.371-378
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• 2002

The design concepts using vibration reduction techniques, or structural control, have been proposed recently to protect infrastructure against earthquakes. The magnetorheological(MR) fluid damper is one of the most promising new devices for structural vibration reduction because of its mechanical simplicity, high dynamic range, low power requirement, large force capacity and robustness. In this study, the seismic performance of MR devices are compared with that of NZ systems as an attempt to provide some data for improving seismic design techniques applied to structures. For nonlinear time domain analysis of a base isolation system, a six-story building model is considered as a numerical example. The ground acceleration data of El Centre 1940, Mexico City 1985 and Kobe 1995 earthquakes are used as seismic excitations. The results show that MR damper systems for outperform NZ systems in wide-ranging seismic excitations with respect to intensity and period characteristics.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.228-232
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• 2003

It has recently been shown that the instability of thin film of a nanoscale can be used in the processes of building nano-size structures, which have potential practical importance in nanotechnology. Molecular dynamics simulation is conducted to probe the thin fluid film of a nano-size and its dynamic behavior during destabilization and structure formation. Non-continuum characteristics are shown in the properties like pressure tensor, viscosity, and thermal conductivity. The thermocapillary force induces a slow growth of long waves in the scale considered. A long-range interaction with the solid wall induces vertical structures, whose formation time and space between neighbors are proportional to the strength of the interaction.

• International Journal of Highway Engineering
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• v.19 no.6
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• pp.31-36
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• 2017

PURPOSES : The computational fluid dynamics of flow and fine particles in a road were set to determine the insert flow and occurrence characteristics. METHODS : The road extension was 100 m with two lanes. A one-ton truck traveled a 50-m distance. After a noise barrier was installed on one side of the road, the flow and a collision analysis were tested. RESULTS : The flow that occurred was 5 m/s beside the vehicle, and fine particulate was $5.0{\times}10^2{\mu}g/m^3$ after 20 m from the exhaust vent. CONCLUSIONS : After a collision analysis of the fine particulate on the noise barrier to find the most suitable position of the filter panel in height, the bottom 1 m was the most optimum position because 88.1% of the distribution was concentrated there.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.5
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• pp.140-146
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• 2008

A friction damper is installed in the passenger car driveline in order to dissipate the torsional vibration energy. The frictional damping hysteresis has considerable influences on the driveline vibration characteristics and, therefore, it is one of the most important parameters in the damper design. To investigate the hysteresis effects on the driveline vibration, a dynamic model of the passenger car driveline with manual transmission has developed, and simulations were executed on the several different driving conditions for various hysteresis values. To verify the model, vehicle tests are preformed and the test data were compared with the simulations results. The simulation and test results show good agreements and the model could be used to determine the optimal hyteresis values in early design stage of the damper.