• 한국지진공학회논문집
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• 제21권6호
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• pp.295-301
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• 2017

This paper relates to the study of load characteristics applicable to wind turbine generators induced by earthquakes. An artificial design earthquake wave generated through the target spectrum and the envelope function of Richter Magnitude Scale (ML) 7.0 as in ASCE4-98 was created. A simulation of earthquake loads were performed according to the design load cases (DLC) 9.5~9.7 of GL guidelines. Additionally, simulation of seismic loads experienced by Wind Turbines installed in the Gyeongju region were carried out utilizing artificial earthquakes of ML 5.8 simulating the real earthquakes during the Gyeongju Earthquakes of Sept. 2016.

• 한국지리정보학회지
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• 제16권3호
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• pp.126-135
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• 2013

국토의 70%이상이 산지로 구성되어 있는 한국은 도시내부에 크고 작은 산, 언덕이 위치하고 있다. 따라서 건축구조기준에서는 건물의 풍하중 설계 시 지형의 영향에 따른 풍속의 증가를 고려하도록 하고 있지만 지형에 의한 풍속할증계수 산정 시 건물 주변에 두 개 이상의 산지가 위치하거나 지표면의 정의와 높이가 명확하지 않을 경우 설계자의 주관에 의해 지형에 의한 풍속할증계수를 산정함으로써 비합리적인 내풍설계가 이루어지고 있다. 따라서 본 논문에서는 이러한 문제점을 해결하고 보다 합리적인 지형에 의한 풍속할증계수를 산정하기 위하여 ArcGIS를 이용하여 지형에 의한 풍속할증계수를 산정하는 방법을 제시하고자 한다. 이를 위해 본 논문에서는 비교적 높은 위치정확도를 가진 1:5,000 수치지형도를 이용하여 지형에 의한 풍속할증계수 산정 시 적용범위를 명확하게 정의함으로서 지표면과 정점을 명료하게 산정하여 보다 합리적으로 지형에 의한 풍속할 증계수를 산정하였다.

• 한국기계가공학회지
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• 제11권6호
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• pp.115-122
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• 2012

The purpose of this study is to optimize the design of the jack-up platform for 5MW offshore wind turbine system. Considering all the environmental loads such as currents, waves, winds and so on, the members of structures have been designed and optimized based on the AISC and API-RP-2A to be within the allowable stress even in the most critical and severe condition. In addition to the above strength check of structural members, the joint punching shear check and the hydrostatic collapse check are also performed where they are required for the design. The design life of the jack-up platform is 50 years for the static strength check and the fatigue design life is 100 years including to the DFF(Design Fatigue Factor) of 2.0 to have enough stability and workability for the design optimization.

• Wind and Structures
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• 제11권6호
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• pp.427-440
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• 2008

Estimates of wind-induced wind effects on tall buildings are based largely on 1980s technology. Such estimates can vary significantly depending upon the wind engineering laboratory producing them. We describe an efficient database-assisted design (DAD) procedure allowing the realistic estimation of wind-induced internal forces with any mean recurrence interval in any individual member. The procedure makes use of (a) time series of directional aerodynamic pressures recorded simultaneously at typically hundreds of ports on the building surface, (b) directional wind climatological data, (c) micrometeorological modeling of ratios between wind speeds in open exposure and mean wind speeds at the top of the building, (d) a physically and probabilistically realistic aerodynamic/climatological interfacing model, and (e) modern computational resources for calculating internal forces and demand-to-capacity ratios for each member being designed. The procedure is applicable to tall buildings not susceptible to aeroelastic effects, and with sufficiently large dimensions to allow placement of the requisite pressure measurement tubes. The paper then addresses the issue of accounting explicitly for uncertainties in the factors that determine wind effects. Unlike for routine structures, for which simplifications inherent in standard provisions are acceptable, for tall buildings these uncertainties need to be considered with care, since over-simplified reliability estimates could defeat the purpose of ad-hoc wind tunnel tests.

• Wind and Structures
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• 제31권6호
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• pp.483-493
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• 2020

Large cylindrical floating-roof tanks, constructed as oil containers, are usually distributed regularly in open area and easily exposed to severe wind loads. However, wind pressures around these grouped squat tanks appear to have not been clearly given in design codes or thoroughly studied in existing researches. This paper conducts a detailed investigation on wind loads on the external wall of a four-tank group in square arrangement. To achieve that, wind tunnel tests are carried out on both empty and full tank groups, considering various wind angles and spacing. Results show that 3 regions in elevation can be identified on the tank shell according to the circumferential wind pressure distribution. The upper 2 regions cover a relatively small portion of the shell where excessive negative pressures are spotted, setting an alarm to the design of the top angle and stiffening rings. By comparing results on grouped tanks to those on an isolated tank, grouping effects concerning wind angle, tank position in group and spacing are discussed. Deviations on pressure distributions that will compromise structural safety are outlined, including the increase of negative pressures, the shift of maximum pressure locations as well as the change of positive pressure range. And, several potentially unfavourable wind pressure distributions are selected for further analyses.

• Wind and Structures
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• 제36권4호
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• pp.263-275
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• 2023

As a new kind of construction facility for high rise buildings, the integral steel platform scaffold system (ISPS) consisting of the steel skeleton and suspended scaffold faces high wind during the construction procedure. The lattice structure type and existence of core tubes both make it difficult to estimate the wind load and calculate the wind-induced responses. In this study, an aeroelastic model with a geometry scale ratio of 1:25 based on the ISPS for Shanghai Tower, with the representative square profile, is manufactured and then tested in a wind tunnel. The first mode of the prototype ISPS is a torsional one with a frequency of only 0.68 Hz, and the model survives under extreme wind speed up to 50 m/s. The static wind load and wind vibration factors are derived based on the test result and supplementary finite element analysis, offering a reference for the following ISPS design. The spacer at the bottom of the suspended scaffold is suggested to be long enough to touch the core tube in the initial status to prevent the collision. Besides, aerodynamic wind loads and cross-wind loads are suggested to be included in the structural design of the ISPS.

• 전기학회논문지
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• 제61권12호
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• pp.1820-1827
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• 2012

This paper is to present a new method of cogging torque reduction for axial flux PM machines of multiple rotor surface mounted magnets. In order to start softly and to run a power generator even the case of weak wind power, reduction of cogging torque is one of the most important issues for a small wind turbine, Cogging torque is an inherent characteristic of PM machines and is caused by the geometry shape of the machine. Several methods have been already applied for reducing the cogging torque of conventional radial flux PM machines. Even though some of these techniques can be also applied to axial flux machines, manufacturing cost is especially higher due to the unique construction of the axial flux machine stator. Consequently, a simpler and low cost method is proposed to apply on axial flux PM machines. This new method is actually applied to a generator of 1.0kW, 16-poles axial flux surface magnet disc type machine with double-rotor-single-stator for small wind turbine. Design optimization of the adjacent magnet pole-arc which results in minimum cogging torque as well as assessment of the effect on the maximum available torque using 3D Finite Element Analysis (FEA) is investigated in this design. Although the design improvement is intended for small wind turbines, it is also applicable to larger wind turbines.

• 한국해양공학회지
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• 제28권3호
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• pp.218-226
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• 2014

Since the support structure of an offshore wind turbine has to withstand severe environmental loads such as wind, wave, and seismic loads during its entire service life, the need for a robust and reliable design increases, along with the need for a cost effective design. In addition, a robust and reliable support structure contributes to the high availability of a wind turbine and low maintenance costs. From this point of view, this paper presents a design process that includes design optimization and reliability analysis. First, the jacket structure of the NREL 5-MW offshore wind turbine is optimized to minimize the weight and stresses, while satisfying the design requirements. Second, the reliability of the optimum design is evaluated and compared with that of the initial design. Although the present study results in a new optimum shape for a jacket support structure with reduced weight and increased reliability, the authors suggest that the optimum design has to be accompanied by a reliability analysis during the design process, as well as reliability based design optimization if needed.

• Wind and Structures
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• 제23권6호
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• pp.559-575
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• 2016

In order to investigate the influence of different blade positions on aerodynamic load and wind loads and load-effects of large scale wind turbine tower under the halt state, we take a certain 3 MW large scale horizontal axis three-blade wind turbine as the example for analysis. First of all, numerical simulation was conducted for wind turbine flow field and aerodynamic characteristics under different halt states (8 calculating conditions in total) based on LES (large eddy simulation) method. The influence of different halt states on the average and fluctuating wind pressure coefficients of turbine tower surface, total lift force and resistance coefficient, circular flow and wake flow characteristics was compared and analysed. Then on this basis, the time-domain analysis of wind loads and load-effects was performed for the wind turbine tower structure under different halt states by making use of the finite element method. The main conclusions of this paper are as follows: The halt positions of wind blade could have a big impact on tower circular flow and aerodynamic distribution, in which Condition 5 is the most unfavourable while Condition 1 is the most beneficial condition. The wind loads and load-effects of disturbed region of tower is obviously affected by different halt positions of wind blades, especially the large fluctuating displacement mean square deviation at both windward and leeward sides, among which the maximum response occurs in $350^{\circ}$ to the tower top under Condition 8; the maximum bending moment of tower bottom occurs in $330^{\circ}$ under Condition 2. The extreme displacement of blade top all exceeds 2.5 m under Condition 5, and the maximum value of windward displacement response for the tip of Blade 3 under Condition 8 could reach 3.35 m. All these results indicate that the influence of halt positions of different blades should be taken into consideration carefully when making wind-resistance design for large scale wind turbine tower.

• 설비공학논문집
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• 제28권1호
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• pp.1-6
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• 2016

This paper studies the wind pressure distribution over the Commonwealth Advisory Aeronautical Council building model (CAARC model) using CFD. We also considered the interaction between the CAARC model and other buildings. The Reynolds number based on the building height was 380,000. The number of sells for the simulation was about 500,000. The wind pressure was lowest when the wind direction was blowing at an angle 45 degrees of the CAARC model. When the gap between the two buildings in front of the CAARC was over 1/2 the horizontal length of the CAARC model, the wind pressure was higher than the pressure without the two buildings. When the distance between the two front buildings and the CAARC was less than 1.5 times the vertical length of the CAARC model, the wind pressure increased. Accordingly, the relative distance between two buildings or the distance from the CAARC model should be considered when extra wind exists due to other buildings.