• Title, Summary, Keyword: masts

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The dynamic stability analysis of guyed masts under random wind loads

  • He, Yan-Li;Chen, Wu-Jun;Dong, Shi-Lin;Wang, Zhao-Min
    • Wind and Structures
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    • v.6 no.2
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    • pp.151-164
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    • 2003
  • On the basis of the first Lyapunov stability theory, this paper develops a dynamic stability criterion for elastic structural systems under arbitrary dynamic loads, and shows the stability criterion using energy variation. After the dynamic stability criterion is validated through a classic example, it is used for the dynamic stability investigation of practical guyed masts under random wind loads. The criterion is reliable, simple and of advantage for structures with large number of elements and nodes. The slack guys and internal resonance between guys and mast are two main factors which induces the dynamic instability of guyed masts, at the same time, some dynamic stability characteristics of guyed masts are found.

Probability of exceeding the serviceability limit of antenna masts

  • Kammel, Christian
    • Wind and Structures
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    • v.4 no.4
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    • pp.353-366
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    • 2001
  • With respect to serviceability, antenna masts should be designed so that wind-induced motion will not cause unacceptable lack of transmission for broadcasting users and wireless communication. For such antenna masts with directional radio transmission the serviceability limit state is predominantly governed by the tolerable change of the broadcasting angle of the mounted antenna assembly and therefore by the tip distortion of the mast. In this paper it will be shown that refinements of the present state of design of antenna masts are possible by using the statistics of extremes applied to extreme wind situations and by consideration of the statistical and reliability requirements given by the operator such as frequency and return period of passing the serviceability limit.

Wind Speed Prediction in Complex Terrain Using a Commercial CFD Code (상용 CFD 프로그램을 이용한 복잡지형에서의 풍속 예측)

  • Woo, Jae-Kyoon;Kim, Hyeon-Gi;Paek, In-Su;Yoo, Neung-Soo;Nam, Yoon-Su
    • Journal of the Korean Solar Energy Society
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    • v.31 no.6
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    • pp.8-22
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    • 2011
  • Investigations on modeling methods of a CFD wind resource prediction program, WindSim for a ccurate predictions of wind speeds were performed with the field measurements. Meteorological Masts having heights of 40m and 50m were installed at two different sites in complex terrain. The wind speeds and direction were monitored from sensors installed on the masts and recorded for one year. Modeling parameters of WindSim input variables for accurate predictions of wind speeds were investigated by performing cross predictions of wind speeds at the masts using the measured data. Four parameters that most affect the wind speed prediction in WindSim including the size of a topographical map, cell sizes in x and y direction, height distribution factors, and the roughness lengths were studied to find out more suitable input parameters for better wind speed predictions. The parameters were then applied to WindSim to predict the wind speed of another location in complex terrain in Korea for validation. The predicted annual wind speeds were compared with the averaged measured data for one year from meteorological masts installed for this study, and the errors were within 6.9%. The results of the proposed practical study are believed to be very useful to give guidelines to wind engineers for more accurate prediction results and time-saving in predicting wind speed of complex terrain that will be used to predict annual energy production of a virtual wind farm in complex terrain.

Mutual Application of Met-Masts Wind Data on Simple Terrain for Wind Resource Assessment (풍력자원평가를 위한 단순지형에서의 육상 기상탑 바람 데이터의 상호 적용)

  • Son, Jin-Hyuk;Ko, Kyung-Nam;Huh, Jong-Chul;Kim, In-Haeng
    • Journal of the Korea Society For Power System Engineering
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    • v.21 no.6
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    • pp.31-39
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    • 2017
  • In order to examine if met-masts wind data can exchange each other for wind resource assessment, an investigation was carried out in Kimnyeong and Haengwon regions of Jeju Island. The two regions are both simple terrain and 4.31 km away from each other. The one-year wind speed data measured by 70 m-high anemometers of each met-mast of the two regions were analysed in detail. Measure-Correlate-Predict (MCP) method was applied to the two regions using the 10-year Automatic Weather System (AWS) wind data of Gujwa region for creating 10-year Wind Statistics by running WindPRO software. The two 10-year Wind Statistics were applied to the self-met mast point for self prediction of Annual Energy Production (AEP) and Capacity Factor (CF) and the each other's met mast point for mutual prediction of them. As a result, when self-prediction values were reference, relative errors of mutual prediction values were less than 1% for AEP and CF so that met masts wind data under the same condition of this study could exchange each other for estimating accurate wind resource.

Analysis of Wind Resources of the South Seashore of JeonNam Province (전남지역 남해안 풍력자원조사 연구)

  • Kim, Young-Chan;Chung, Chin-Wha;Lee, Eung-Chae;Chun, Ch.-H.;Han, Kyung-Seop;Kim, Yong-Whan
    • 한국신재생에너지학회:학술대회논문집
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    • pp.281-285
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    • 2006
  • As the needs of wind energy increase, the more sites for the wind farm are required. As a part of searching for the prominent wind farm site, specially for offshore wind farm, we chose 4 sites along the southern part seashore of JeonNam province based on the analysis of the data gathered by meteorological observatory ud have gathered wind data for more than a year by use of 40m Met masts installed in the representative locations, ie. small islands of 4 different bay area. The siting for the Met masts were very limited by the geographical circumstances The wind data of those areas show a little lower annual average wind speeds, for the wind farm development, of 4m/s to 5.5m/s at the height of 40m above the ground level of the respective islands. The detail figures of one year wind data of those area are presented in this report.

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Accuracy Assessment of Annual Energy Production Estimated for Seongsan Wind Farm (성산 풍력발전단지의 연간발전량 예측 정확도 평가)

  • Ju, Beom-Cheol;Shin, Dong-Heon;Ko, Kyung-Nam
    • Journal of the Korean Solar Energy Society
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    • v.36 no.2
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    • pp.9-17
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    • 2016
  • In order to examine how accurately the wind farm design software, WindPRO and Meteodyn WT, predict annual energy production (AEP), an investigation was carried out for Seongsan wind farm of Jeju Island. The one-year wind data was measured from wind sensors on met masts of Susan and Sumang which are 2.3 km, and 18 km away from Seongsan wind farm, respectively. MERRA (Modern-Era Retrospective Analysis for Research and Applications) reanalysis data was also analyzed for the same period of time. The real AEP data came from SCADA system of Seongsan wind farm, which was compare with AEP data predicted by WindPRO and Meteodyn WT. As a result, AEP predicted by Meteodyn WT was lower than that by WindPRO. The analysis of using wind data from met masts led to the conclusion that AEP prediction by CFD software, Meteodyn WT, is not always more accurate than that by linear program software, WindPRO. However, when MERRA reanalysis data was used, Meteodyn WT predicted AEP more accurately than WindPRO.

Vibration mitigation of guyed masts via tuned pendulum dampers

  • Lacarbonara, Walter;Ballerini, Stefano
    • Structural Engineering and Mechanics
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    • v.32 no.4
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    • pp.517-529
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    • 2009
  • A passive vibration mitigation architecture is proposed to damp transverse vibrations of guyed masts. The scheme is based on a number of pendula attached to the mast and tuned to the vibration modes to be controlled. This scheme differs from the well-known autoparametric pendulum absorber system. The equations of motion of the guyed mast with an arbitrary number of pendula are obtained. The leading bending behaviour of a typical truss mast is described by an equivalent beam model whereas the guys are conveniently modeled as equivalent transverse springs whose stiffness comprises the elastic and geometric stiffness. By assuming a mast with an inertially and elastically isotropic cross-section, a planar model of the guyed mast is investigated. The linearization of the equations of motion of the mast subject to a harmonic distributed force leads to the transfer functions of the structure without the dampers and with the dampers. The transfer functions allow to investigate the mitigation effects of the pendula. By employing one pendulum only, tuned to the frequency of the lowest mode, the effectiveness of the passive vibration potential in reducing the motion and acceleration of the top section of the mast is demonstrated.

Estimating peak wind load effects in guyed masts

  • Sparling, B.F.;Wegner, L.D.
    • Wind and Structures
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    • v.10 no.4
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    • pp.347-366
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    • 2007
  • Guyed masts subjected to turbulent winds exhibit complex vibrations featuring many vibration modes, each of which contributes to various structural responses in differing degrees. This dynamic behaviour is further complicated by nonlinear guy cable properties. While previous studies have indicated that conventional frequency domain methods can reliably reproduce load effects within the mast, the system linearization required to perform such an analysis makes it difficult to relate these results directly to corresponding guy forces. As a result, the estimation of peak load effects arising jointly from the structural action of the mast and guys, such as leg loads produced as a result of guy reactions and mast bending moments, is uncertain. A numerical study was therefore undertaken to study peak load effects in a 295 m tall guyed mast acted on by simulated turbulent wind. Responses calculated explicitly from nonlinear time domain finite element analyses were compared with approximate methods in the frequency domain for estimating peak values of selected responses, including guy tension, mast axial loads and mast leg loads. It was found that these peak dynamic load effects could be accurately estimated from frequency domain analysis results by employing simple, slightly conservative assumptions regarding the correlation of related effects.

Experimental investigation of the aeroelastic behavior of a complex prismatic element

  • Nguyen, Cung Huy;Freda, Andrea;Solari, Giovanni;Tubino, Federica
    • Wind and Structures
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    • v.20 no.5
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    • pp.683-699
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    • 2015
  • Lighting poles and antenna masts are typically high, slender and light structures. Moreover, they are often characterized by distributed eccentricities that make very complex their shape. Experience teaches that this structural type frequently suffers severe damage and even collapses due to wind actions. To understand and interpret the aerodynamic and aeroelastic behavior of lighting poles and antenna masts, this paper presents the results of static and aeroelastic wind tunnel tests carried out on a complex prismatic element representing a segment of the shaft of such structures. Static tests are aimed at determining the aerodynamic coefficients and the Strouhal number of the test element cross-section; the former are used to evaluate the critical conditions for galloping occurrence based on quasi-steady theory; the latter provides the critical conditions for vortex-induced vibrations. Aeroelastic tests are aimed at reproducing the real behavior of the test element and at verifying the validity and reliability of quasi-steady theory. The galloping hysteresis phenomenon is identified through aeroelastic experiments conducted on increasing and decreasing the mean wind velocity.

Mechanical Alignment of Hull Mounted Phased Array Radar on the Separated Mast (분리된 마스트에 설치되는 선체고정 위상 배열 레이더의 기계적 정렬)

  • Seo, Hyeong-Pil;Kim, Dae-Han;Kim, Joon-Woo;Lee, Kyung-Jin;Cho, Kyu-Lyong
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.9
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    • pp.465-473
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    • 2019
  • This paper is meaningful as the first case where a 4 - sided hull-fixed phased array radar was installed on a mast separated from Korea and the alignment was verified. The mechanical alignment method was studied for accurately mounting two separate masts for naval ships and the 3D scanner for alignment. Hull-fixed phased array radar uses very high frequency, so the short wavelength can cause a phase difference of the device due to the small positional error. Since the array antenna is fixed with the hull, it has higher accuracy control than the rotary radar for 4 array surfaces. The study describes a method of checking the flatness of two radar masts manufactured at a factory, a method of aligning masts in a shipyard, and a method of aligning four array pad mounting surfaces. As a tool for this, a 3D laser scanner and a software-based method for comparing survey results with 3D CAD are used. This paper is meaningful as the first example of installing a four-sided hull-fixed phased array radar on a separate mast from a Korean naval ship and deriving a mechanical alignment method.