• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.465-469
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• 2006

In recent years there has been considerable interest in the construction of super high-rise buildings. From the prior art, various procedures and devices for surveys during and after the phase of erection of a high-rise building are known. High-rise buildings are subject to strong external tilt effects caused, for instance, by wind pressures, unilateral thermal effects by exposure to sunlight, and unilateral loads. Such effects are a particular challenge in the phase of construction of a high-rise building, in as much as the high-rise building under construction is also subject to tilt effects, and will at least temporarily lose its - as a rule exactly vertical - alignment. Yet construction should progress in such a way that the building is aligned as planned, and particularly so in the vertical, when returning into an un-tilted basic state.It is essential that a straight element be constructed that theoretically, even when moving around its design centre point due to varying loads, would have an exactly vertical alignment when all biasing conditions are neutralised. Because of differential raft settlement, differential concrete shortening, and construction tolerances, this ideal situation will rarely be achieved. This paper describes a procedure developed by the authors using GPS observations combined with a network of precision inclination sensor to provide reliable coordinated points at the top of the worldwide highest-rise building under construction in Dubai.

• Journal of Biosystems Engineering
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• v.41 no.4
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• pp.337-341
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• 2016

Purpose: Evaluation of atmospheric conditions for proper timing of spray application is important to prevent off-target movement of crop protection materials. Susceptible crops can be damaged downwind if proper application procedure is not followed. In our previous study, hourly data indicated unfavorable conditions, primarily between evening 18:00 hrs in the evening and 6:00 hrs next morning, during clear conditions in the hot summer months in the Mississippi delta. With the requirement of timely farm operations, sub-hourly data are required to provide better guidelines for pilots, as conditions of atmospheric stability can change rapidly. Although hourly data can be interpolated to some degree, finer resolution for data acquisition of the order of 15 min would provide pilots with more accurate recommendations to match the data recording frequency of local weather stations. Methods: In the present study, temperature and wind speed data obtained at a meteorological tower were re-sampled to calculate the atmospheric stability ratio for sub-hour and hourly recommendations. High-precision evaluation of temperature inversion periods influencing atmospheric stability was made considering strength, time of occurrence, and duration of temperature inversion. Results and Discussion: The results indicated that atmospheric stability could be determined at different time intervals providing consistent recommendations to aerial applicators, thereby avoiding temperature inversion with minimal off-target drift of the sprayed liquid.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.652-654
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• 2007

본 논문에서는 국가의 기간 에너지원인 전력망을 구성하는 구조물인 송전철탑의 설계하중에 가장 큰 요인으로 작용하는 기준풍속 산정을 위한 연구내용을 고찰하고자 한다. 현행의 송전용 지지물 설계 기준은 전기설비기술기준에 고시된 가공전선로 지지물에 관한 기준을 토대로 전력사의 실무적인 설계를 위하여 보다 구체화하여 작성된 한국전력공사 송전설계기준에 근거하고 있다. 이러한 기존 설계기준은 1985년 이전의 기상자료를 토대로 제정되어 본 논문에서는 1980년대 후반부터 약 20년간의 기상청의 풍향, 풍속자료를 추가로 확보하고 이를 분석하여 재현기간을 반영한 지역별 설계기준 풍속 Map을 제시하였다. 이러한 흐름으로 최근의 기상자료를 포함하여 보다 정확한 분석을 도모하고, 사회 환경의 급변함에 따라 우려되는 기상이변 등을 고려한 안전성과 경제성이 향상된 기준풍속 산정과정을 고찰하고, IEC 등 해외 주요국의 풍하중 설계기준에서 반영하고 있는 국부지형을 고려한 설계방법에 대한 국내 기준 적용성 평가를 위한 비교분석 결과를 소개하였다.

• Journal of the Korean Geotechnical Society
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• v.29 no.4
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• pp.23-32
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• 2013

In order to evaluate the bearing capacity behaviour of a monopod suction bucket foundation for an offshore wind tower at the western sea of Korea, a centrifuge load test and numerical analyses were performed. The monopod bucket foundation was designed to be installed in a silty sand layer. The model soil was prepared to simulate a target site by using soil samples having similar properties and controlling relative density. In-flight miniature cone penetration test and bender element array were used to confirm that the model soil had represented the target site conditions. The load - rotation curve of the centrifuge load test was analysed. A series of numerical analyses were performed to validate the experimental conditions. Self-weight of the model, distance to the boundary and elastic modulus of the soil layer were varied to study their effects on the load - rotation curves.

• Journal of Korea Water Resources Association
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• v.57 no.2
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• pp.139-150
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• 2024

This study introduced a method of estimating water surface evaporation using the physical-based Penman combination equation (PCE) and the Penman wind function (PWF). A set of regression parameters in the PCE and PWF models were optimized by using the observed evaporation data for the period 2016-2017 in the Yongdam Dam watershed, and their effectiveness was explored. The estimated evaporation over the Deokyu Mountain flux tower demonstrated that the PWF method appears to have more improved results in terms of correlation, but both methods showed overestimation. Further, the PWF method was applied to the observed hydro-meteorological data on the surface of Yongdam Lake. The PWF method outperformed the PCE in the estimation of water surface evaporation in terms of goodness-of-fit measure and visual evaluation. Future studies will focus on a regionalization process which can be effective in estimating water surface evaporation for the ungauged area by linking hydrometeorological characteristics and regression parameters.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1885-1889
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• 2006

제주지역은 대륙과 해양을 연결하는 요충지로서 한라산을 중심으로 동서사면은 $3{\sim}5^{\circ}$의 완만한 경사를 이루고 있다. 연평균 강우량은 1,975mm로서 국내 최다우 지역이나 제주도의 지질 특성상 도내 대부분의 지역이 투수성이 높은 다공질 현무암으로 구성되어 있는 관계로 지표수의 발달이 미약한 반면 지하수가 풍부하게 부존되어 있으며 기저지하수, 준 기저지하수, 상위지하수, 기반암지하수로 이루어져 있다. 최근 우리나라의 교토의정서 비준으로 인한 온실가스 감축이 불가피함에 따라 대체 재생가능한 에너지를 이용한 풍력발전시대가 도래하고 있으며, 제주 행원풍력발전단지에 설치된 총 15기 발전장치의 현실성과 경제성 입증을 통해 제주지역의 풍력에너지를 이용한 지하수 취수시스템을 제안하였다. 본 연구는 제주, 고산, 서귀포, 성산포지역에 대한 제주지방기상청 연평균 풍속자료$(2004{\sim}2005)$를 통하여 대상지역내 적용 가능한 로터(Roter), 나셀(Nacelle), 타워(Tower), 발전기를 포함한 발전장치를 선정하였으며, 공기역학적(Aerodynamic)특성에서 전기에너지로 변환한 풍력에너지를 지하수 취수시스템으로 적용하기까지의 전력공급절차를 도출하였다. 또한 생산되어진 풍력에너지 용량에 적용 가능한 수중.육상모터펌프를 산정하여 '제주도 지하수개발.이용시설 설치 및 관리기준(2004)'에서 제시한 구조도를 바탕으로 대상지역내 지하수위를 고려한 지하수 취수시스템을 도시하였다. 제주도는 지형 및 지질적인 특성상 수자원을 지하수에 의존할 수밖에 없는 특수한 지역이므로 2002년말 통계를 살펴보면 생활용, 공업용, 농업용으로 각각 57만$m^2$, 11만$m^2$, 56만$m^2$를 포함한 1일 최대 124만$m^2$의 지하수를 사용하고 있다. 따라서 풍력에너지를 이용한 지하수 취수시스템을 도입하여 재생가능한 에너지이용 효과와 세계인이 공감하는 청정한 관광자원으로 활용 가능할 것이라 판단된다.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.163-163
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• 2011

풍력타워 기둥구조물에는 유지관리 등의 이유로 출입구 역할을 하는 개구부가 존재하게 된다. 다각형 타워구조물에 개구부형상이 존재하게 되면 압축좌굴 강도에 영향이 있을 것으로 예상되지만, 이를 정량적으로 평가하거나 예측하기는 용이하지 않고 간접적으로 판단할 만한 관련 기준이나 지침도 부족한 상태이다. 이에 최병호 등(2011)에서 다룬 다각형 단면 기둥구조물의 하단에 개구부를 형상화한 수치해석 모델을 수립하고 축방향 압축하중을 재하하는 탄성좌굴 해석 및 비선형비탄성해석을 수행하였다. 본 논문에서는 기존 다각형 단면 기둥모델 중에서 6각형 단면모델에 관해 중점적으로 다루고 있다. 다각형 단면 기둥 해석모델은 단순한 다각형 단면 타워구조에 대해서 뿐 만 아니라, 각 subpanel에 종방향 보강재를 둔 모델에 대해서도 추가적으로 검토하였다. 개구부의 형상은 높이 2000mm, 폭 800mm이며 상하부에 만곡부를 둔 형태이다. 수치해석은 3차원 유한요소해석프로그램인 ABAQUS를 이용하여 수행하였으며, 보강방안으로는 일정범위까지의 모듈 subpanel의 판두께를 보강하는 방안과 edge stiffener를 적용하는 방안에 대해서 검토하였다. 각각의 보강방식에 따른 효과를 비교해 보기 위해 개구부가 없는 모델, 단순히 개구부만 설정한 모델, 판두께를 보강한 모델, edge stiffener로 보강한 모델에 대해 비교해석을 수행하였다. 보강재 없는 단순 다각형 타워구조 모델에 대한 해석결과로부터 개구부로 인한 강도저하는 미미한 수준인 것으로 나타났다. 반면, 종방향 보강재가 적용된 6각형 단면 타워구조 모델에서는 개구부로 인한 강도저감이 22.9%로 높게 나타났으며 상당한 영향이 있는 것으로 분석되었다. 또한 개구부 주변의 판두께 보강이나 edge stiffener보강 등으로 상당한 강도향상 효과가 확인되었으나, 개구부로 인해 손실된 강도 수준을 완전히 회복하는 수준에 미치지 못하는 것으로 나타났다. 따라서, 향후 다양한 보강방식에 대한 보다 포괄적인 변수연구를 통해 개구부의 영향 없이 온전한 다각형 단면 타워 구조의 극한강도에 도달되기 위한 보강 조건에 대해 검토될 필요가 있을 것으로 사료된다.

• Structural Engineering and Mechanics
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• v.40 no.4
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• pp.471-488
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• 2011

The Ting Kau Bridge in Hong Kong is a cable-stayed bridge comprising two main spans and two side spans. The bridge deck is supported by three towers, an end pier and an abutment. Each of the three towers consists of a single reinforced concrete mast strengthened by transverse cables and struts. The bridge deck is supported by four inclined planes of cables emanating from anchorages at the tower tops. In view of the heavy traffic on the bridge, and threats from typhoons and earthquakes originated in areas nearby, the dynamic behaviour of long-span cable-supported bridges in the region is always an important consideration in their design. Baseline finite element models of various levels of sophistication have been built not only to match the bridge geometry and cable forces specified on the as-constructed drawings but also to be calibrated using the vibration measurement data captured by the Wind and Structural Health Monitoring System. This paper further describes the analysis of axle loading data, as well as the generation of random axle loads and simulation of vibrations of the bridge using the finite element models. Various factors affecting the vehicular loading on the bridge will also be examined.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.7
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• pp.731-738
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• 2012

In this study, the evaluation of the aerodynamic characteristics of the NREL Phase VI Rotor System has been performed, for the 7 m/s upwind case using commercial FEA and CFD tools which are ANSYS Mechanical 12.1 and CFX 12.1. The initial operating conditions of the rotor blade include a $3^{\circ}$ tip pitch angle. A numerical simulation was carried out on only the rotor parts, excluding the tower structure based on the equivalent stiffness model, to consider the aeroelastic effect for the numerical simulation using the loosely coupled 2-way fluid-structure interaction method. The blade root bending moment was monitored in real time to obtain reasonable results. To verify the analysis results, the numerical simulation results were compared with the measurements in the form of the root bending moment and the pressure distributions of the NREL/NASA Ames wind tunnel test.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3C
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• pp.105-111
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• 2012

Bucket foundations, which are used in the foundations of offshore wind turbines, should be able to withstand large amounts of horizontal and moment loads. Tripod bucket foundation, which combines three single buckets, has been used to increase horizontal and moment capacities. This study performed numerical analysis using ABAQUS (2010), to analyze the group effect and the bearing capacity of a tripod bucket in clay. Parametric studies were performed varying the bucket spacing ratio S/D (S=spacing between the centers of the bucket and the tower; D=diameter of the bucket) and depth ratio L/D (L=embedded length of skirt). The applied constitutive models were a linear elastic perfectly plastic model with Tresca yield criteria for normally consolidated clay and an elastic model for buckets. Loading in the vertical, horizontal, and moment directions was simulated with an increase in each movement at a reference point. The bearing behavior and the capacities of a single and a tripod bucket were compared. Capacity evaluation method of the tripod bucket was suggested using the capacity of a single bucket.