• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.4
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• pp.319-327
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• 2017

In this study, characteristics of seismic behaviors of offshore wind turbine systems using concrete-suction-type supporting structures are investigated. Applying hydrodynamic pressure from the surrounding sea water and interaction forces from the underlying soil to the structural system which is composed of RNA, the tower, and the supporting structure, a governing equation of the system is derived and its earthquake responses are obtained. It can be observed from the analysis results that the responses are significantly influenced by soil-structure interaction because dynamic responses for higher natural vibration modes are increased due to the flexibility of soil. Therefore, the soil-structure interaction must be taken into consideration for accurate assessment of dynamic behaviors of offshore wind turbine systems using concrete-suction-type supporting structures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.5B
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• pp.437-444
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• 2010

Soil moisture has been recognized as the essential parameter when understanding the complicated relationship between land surface and atmosphere in water and energy recycling system. It has been generally known that it is related with the temperature, wind, evaporation dependent on soil properties, transpiration due to vegetations and other constituents. There is, however, little research concerned about the relationship between soil moisture and these constitutes, thus it is needed to investigate it in detail. We estimated the soil moisture and then compared with field data using the hydrometerological data such as atmospheric temperature, specific humidity, and wind obtained from the Flux tower in Selmacheon, Korea. In the winter season, subterranean temperature showed highly positive correlation with soil moisture while it was negatively correlated from the spring to the fall. Estimation of seasonal soil moisture was compared with field measurements with the correlation of determination, R=0.82, 0.81, 0.82, and 0.96 for spring, summer, fall, and winter, respectively. Comprehensive relationship from this study can supply useful information about the downscaling of soil moisture with relatively large spatial resolutions, and will help to deepen the understanding of the water and energy recycling on the earth's surface.

• Journal of Korean Society of Steel Construction
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• v.18 no.1
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• pp.33-45
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• 2006

Cable-stayed bridges are more inherently vulnerable to wind during the erection stages than when they are already being used. Even if a bridge that is already being used is aerodynamically stable, it is prone to having aerodynamic instabilities within the design wind speed during construction. Therefore, when the bridge's designers deliberate on the method they will use in constructing the bridge, they must likewise come up with a suitable plan to ensure the stability of the bridge during its erection (e.g., conducting a wind-tunnel investigation). This paper describes the aeroelastic full-bridge model tests that were conducted to investigate the aerodynamic behavior of the bridge during erection, with emphasis on aerodynamic stability and the mitigation of the buffeting response through temporary stabilization. The aerodynamic performance of a cable -stayed bridge with a main span of 50 m was studied in its completed stage and in two erection stages, corresponding 50% and 90% completion, respectively. In the 50% erection stage tests, a balanced cantilever configuration, with wind cable and temporary support at the tower, was conducted. The system that was determined to be most effective in reducing wind action on the bridge during construction was proposed in the paper, based on the results of the comparative study that was conducted.

• Korean Journal of Agricultural and Forest Meteorology
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• v.16 no.3
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• pp.246-260
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• 2014

A 90-m horizontal-resolution numerical model was configured to study the micrometeorological features of local winds in the valley of Gwangneung KoFlux (Korea Flux network) Sites (GDK: Gwangneung Deciduous forest site in Korea, GCK: Gwangneung Coniferous forest site in Korea) during summer days. The U. S. Geological Survey (USGS) Shuttle Radar Topography Mission (SRTM) data were employed for high-resolution model terrain height. Model performance was evaluated by comparing observed and simulated near-surface temperature and winds. Detailed qualitative analysis of the model-simulated wind field was carried out for two selected cases which are a clear day (Case I) and a cloudy day (Case II). Observed winds exhibited that GDK and GCK, as well as Case I and Case II, had differences in timing, duration and strength of daytime and nighttime wind direction and speeds. The model simulation results strongly supported the existence of the drainage flow in the valley of the KoFlux tower sites. Overall, the simulated model fields realistically presented the diurnal cycle of local winds in and around the valley, including the morning drainage-upslope transition and the evening reversal of upslope wind. Also, they indicated the complexity of local winds interactions by presenting that daytime westerly winds in the valley were not always pure mountain winds and were often coupled with larger-scale wind systems, such as synoptic-scale winds or mesoscale sea breezes blowing from the west coast of the peninsula.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.142-154
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• 2023

As the importance of the environment has been recognized worldwide, the need to calculate and reduce carbon emissions has been drawing an increasing attention throughout various industrial sections. Thereby the discipline of LCA (Life Cycle Assessment) involving raw material preparation, production processes, transportation and installation has been established. There is a clear research gap between the need and the practice for Korean Case of renewable energy industry, particularly wind power. To bridge the gap, this study conducted LCA research on wind power generation in the Korean area of Yeongdeok, an example of a domestic onshor wind power complex using SimaPro, which is the most widely used LCA system. As a result of the study, the energy recovery period (EPT) of one wind turbine is about 10 months, and the GHG emitted to generate power of 1 kwh is 15 g CO₂/kWh, which is competitive compared to other energy sources. In the environmental impact assessment by component, the results showed that the tower of wind turbines had the greatest impact on various environmental impact sectors. The experience gained in this study can be further used in strengthening the introduction of renewable energy and reducing the carbon emission in line with reducing climate change.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.2
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• pp.93-114
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• 2011

The current status of Canadian research on rotor-based actively controlled technologies for helicopters is reviewed in this paper. First, worldwide research in this field is overviewed to put Canadian research into context. Then, the unique hybrid control concept of Carleton University is described, along with its key element, the "stiffness control" concept. Next, the smart hybrid active rotor control system (SHARCS) projected's history and organization is presented, which aims to demonstrate the hybrid control concept in a wind tunnel test campaign. To support the activities of SHARCS, unique computational tools, novel experimental facilities and new know-how had to be developed in Canada, among them the state-of-the-art Carleton Whirl Tower facility or the ability to design and manufacture aeroelastically scaled helicopter rotors for wind tunnel testing. In the second half of the paper, details are provided on the current status of development on the three subsystems of SHARCS, i.e. that of the actively controlled tip, the actively controlled flap and the unique stiffness-control device, the active pitch link.

• Journal of the Korean Society of Hazard Mitigation
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• v.3 no.4 s.11
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• pp.103-109
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• 2003

A numerical analysis of cable-stayed bridge is conducted to determine optimum longitudinal modulus of elasticity which represents the boundary condition between the tower and main girder. The effect of longitudinal modulus of elasticity is investigated for different loading condition (live load, wind load, seismic load), respectively. There are significant changes in the member forces as variations of longitudinal modulus of elasticity, such as, $k_h$=e=100tonf/m/bearing (live load), $k_h$=e=1000tonf/m/bearing (seismic load), However, the wind loads do not affect member forces. The optimum longitudinal modulus of elasticity is determined from considering minimum member forces in the numerical analysis results.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.331-336
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• 2012

Nowaday the conventional solar collector material prices are rising up because of pricy metal material over the world. The solar collector is too expensive to recycle to save the earth. Advanced polymer research is founded a high thermal resistant polymer and also it has high sun energy transmission. It also has cheaper material and easy manufacturing process, compare with conventional solar collector material. This paper is focussing on glazing simulation of polymer solar collector against wind pressure. The modeling geometry of polymer solar glazing are purposed by single layer, double layer hollow, zig-zag and tower. A simulation by using the Finite Volume was conducted to get Factor of Safety (FoS). The purpose of this paper is to find the best polymer glazing design, which can be as reference for the solar collector company to build Polymer. Hope fully new model of polymer solar collector has cheap, light, high sun energy transmitter, easy to be made and strong against wind force characteristics.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.04a
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• pp.291-300
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• 1998

This paper demonstrates how ambient vibration measurements at a limited number of locations can be effectively utilized to estimate parameters of a finite element model of a large-scale structural system involving a large number of elements. System identification using ambient vibration measurements presents a challenge requiring the use of special identification techniques, which ran deal with very small magnitudes of ambient vibration contaminated by noise without the knowledge of input farces. In the present study, the modal parameters such as natural frequencies, damping ratios, and mode shapes of the structural system were estimated by means of appropriate system identification techniques including the random decrement method. Moreover, estimation of parameters such as the stiffness matrix of the finite element model from the system response measured by a limited number of sensors is another challenge. In this study, the system stiffness matrix was estimated by using the quadratic optimization involving the computed and measured modal strain energy of the system, with the aid of a sensitivity relationship between each element stiffness and the modal parameters established by the second order inverse modal perturbation theory. The finite element models thus identified represent the actual structural system very well, as their calculated dynamic characteristics satisfactorily matched the observed ones from the ambient vibration test performed on a large-scale structural system subjected primarily to ambient wind excitations. The dynamic models identified by this study will be used for design of an active mass damper system to be installed on this structure fer suppressing its wind vibration.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.200-206
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• 2010

본 논문은 풍력발전 시스템의 하부 지지 구조물인 타워의 플랜지 연결부 설계 평가를 위한 플랜지 모델건전성 평가 기법에 대해 다룬다. 일반적으로 풍력발전 시스템 타워의 연결부는 Ring-형 플랜지의 형태를 가지고 있다. 이러한 ring-형 플랜지에 대한 설계 기준 및 방법은 풍력 발전 시스템 기술기준 등 에 명시되어있다. 이러한 설계 기준을 따르는 플랜지 연결부에 대해 구조 및 체결 볼트의 건전성 평가를 위해 하중평가 전용 프로그램인 GH-Bladed 3.8를 통해 생성된 하중 데이터를 유한요소 범용 프로그램인 Ansys 12.0에 접목하여 구조해석을 수행 하였다. 해석 방법은 풍력발전시스템의 타워를 셸 요소로 모델링하여 계산한 해석 결과를 플랜지 모델의 경계면에 적용 시켜 해석하는 submodeling 기법과 타워를 빔의 형태로 단순화 화여 계산한 거동 결과를 플랜지 모델에 적용하는 기법을 사용 하였다. 이 두 가지의 해석 기법으로 도출된 결과의 비교를 통하여 해석 결과 신뢰성을 평가하고 효율적이고 합리적인 방법을 제시하고자 하였다.