• Title, Summary, Keyword: towers

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Experimental study of dynamic interaction between group of intake towers and water

  • Wang, Haibo;Li, Deyu;Tang, Bihua
    • Earthquakes and Structures
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    • v.6 no.2
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    • pp.163-179
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    • 2014
  • Dynamic test with scaled model of a group of intake towers was performed to study the dynamic interaction between water and towers. The test model consists of intake tower or towers, massless foundation near the towers and part of water to simulate the dynamic interaction of tower-water-foundation system. Models with a single tower and 4 towers were tested to find the different influences of the water on the tower dynamic properties, seismic responses as well as dynamic water-tower interaction. It is found that the water has little influence on the resonant frequency in the direction perpendicular to flow due to the normal force transfer role of the water in the contraction joints between towers. By the same effect of the water, maximum accelerations in the same direction on 4 towers tend to close to each other as the water level increased from low to normal level. Moreover, the acceleration responses of the single tower model are larger than the group of towers model in both directions in general. Within 30m from the surface of water, hydrodynamic pressures were quite close for a single tower and group of towers model at two water levels. For points deeper than 30m, the pressures increased about 40 to 55% for the group of towers model than the single tower model at both water levels. In respect to the pressures at different towers, two mid towers experienced higher than two side towers, the deeper, the larger the difference. And the inside hydrodynamic pressures are more dependent on ground motions than the outside.

Development of Eco-friendly Electric Transmission Towers in KEPCO (환경조화형 철탑 개발)

  • Lee, Won-kyo;Mun, Sung-Duk;Shin, Kooyong
    • KEPCO Journal on Electric Power and Energy
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    • v.5 no.3
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    • pp.135-140
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    • 2019
  • Lattice towers and tubular steel poles have been commonly used for electrical power transmission in Korea. They are durable, structurally stable, simple and can easily be constructed in limited spaces. However, residents are opposed to construct transmission lattice towers in their areas because they are not visually attractive, and electrical field occur at the transmission lines. Underground transmissions have been used instead of the traditional towers to resolve these problems, however they are not cost effective to construct and run. Therefore, we have developed eco-friendly towers that are more attractive, well blending into the surrounding environment, and much more economical than underground transmissions. There are four categories of the eco-friendly electric transmission towers about design aspects. Firstly, there is decoration type such as tree tower and ensemble tower. Tree tower looks like actual trees with leaves and branches so it blends into surroundings. Ensemble towers were designed after pair of crane birds. Those towers have decoration features and art works. Structural examination and manufacturing this type would be very similar to the conventional transmission towers. Secondly, there is arm design type such as traditional tower. Design features are added to the existing towers. As partial design can be adoptable on these types, it can easily meet height regulations and attach to conventional lattice towers and tubular steel poles. Also, these towers are more economical than others. Third category is multipurpose type such as Sail Tower. These towers have simple pole or tubular structure with features which can be used as information message board, public relations and much more. This type will face greater wind pressure because of the area of the board, also visibility must take into consideration. Lastly, there is moulding type such as arc pylon. It is different shape to the conventional towers - lattice towers and tubular steel poles. Dramatic design changes have been adapted - from a hard and static tower to a soft and curved tower. These towers will well stand out in the field. However, structural examination and manufacturing this type would be difficult and costly. Also certain towers of this type would require scaffolding or false work to construct, which will result in limitations of the construction area. This paper shows KEPCO 154 kV Sail tower in detail. KEPCO 154 kV Sail tower that is included in fabrication of sample tower and tower testing has developed and the results are presented in this paper. We hope that sail tower is also considered as a solution to have public acceptance or to create a familiar atmosphere among towers and people in coastal area.

Economical design for power transmission steel towers (경제적인 송배전철탑설계)

  • 이재숙
    • 전기의세계
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    • v.16 no.5
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    • pp.37-50
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    • 1967
  • The economical design of steel towers fortrausmission line. This study has been made on the design criteria of steel towers for power trasmission line adopted in the United States of America, France, Japan and Korea in order to find out any access to design the economical steel twers in Korea following to our own climate conditions. As the result of this study, involved in this description. Writer belive that the weight of steel towers can be saved by 10% to 20% approximately on the steel towers which will be constructed in the near future in Korea, by the possibility of reducing the design wind pressures on towers and cables in those areas of inland of Korea, the increase of number of standard towers from four types to five, the adoption of comparative narrower base towers than those in past practice and improvement on the assumption of manimum delection angle of suopension type insulator strings.

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Developments of Structural Systems Toward Mile-High Towers

  • Moon, Kyoung Sun
    • International Journal of High-Rise Buildings
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    • v.7 no.3
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    • pp.197-214
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    • 2018
  • Tall buildings which began from about 40 m tall office towers in the late $19^{th}$ century have evolved into mixed-use megatall towers over 800 m. It is expected that even mile-high towers will soon no longer be a dream. Structural systems have always been one of the most fundamental technologies for the dramatic developments of tall buildings. This paper presents structural systems employed for the world's tallest buildings of different periods since the emergence of supertall buildings in the early 1930s. Further, structural systems used for today's extremely tall buildings over 500 m, such as core-outrigger, braced mega-tube, mixed, and buttressed core systems, are reviewed and their performances are studied. Finally, this paper investigates the potential of superframed conjoined towers as a viable structural and architectural solution for mile-high and even taller towers in the future.

Development of Compact Towers with Insulation Arm in Korea (절연암 적용 컴팩트 철탑 개발)

  • Lee, Won-kyo;Yun, Cheol-Hee
    • KEPCO Journal on Electric Power and Energy
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    • v.4 no.2
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    • pp.63-66
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    • 2018
  • Lattice towers and tubular steel poles have been commonly used for electrical power transmission in Korea as well as the other countries. They are durable, structurally stable, simple and can easily be constructed in limited spaces. However, residents are opposed to construct transmission lattice towers in their areas because they are not visually attractive, and electrical field occur at the transmission lines. Underground transmissions have been used instead of the traditional towers to resolve these problems, however they are not cost effective to construct and run. Therefore, we have developed compact towers that are more attractive, well blend into the surrounding environment and much more economical than underground transmissions. This paper shows the design of a compact towers with insulation arm, in order to reduce the height of tower and the separation between phases. The compact tower can be installed in a narrow right-of-way. Insulation arms are easily applied to lattice and steel tubular towers instead of steel arms. Compact towers with insulation arm are also considered as a solution to have public acceptance or to create a familiar atmosphere among towers and people. Compact tower compared with a conventional tower, insulation arms reduces the width and height of the tower by 20% and 15% respectively.

A comparison of structural performance enhancement of horizontally and vertically stiffened tubular steel wind turbine towers

  • Hu, Yu;Yang, Jian;Baniotopoulos, Charalambos C.;Wang, Feiliang
    • Structural Engineering and Mechanics
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    • v.73 no.5
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    • pp.487-500
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    • 2020
  • Stiffeners can be utilised to enhance the strength of thin-walled wind turbine towers in engineering practise, thus, structural performance of wind turbine towers by means of different stiffening schemes should be compared to explore the optimal structural enhancement method. In this paper two alternative stiffening methods, employing horizontal or vertical stiffeners, for steel tubular wind turbine towers have been studied. In particular, two groups of three wind turbine towers of 50m, 150m and 250m in height, stiffened by horizontal rings and vertical strips respectively, were analysed by using FEM software of ABAQUS. For each height level tower, the mass of the stiffening rings is equal to that of vertical stiffeners each other. The maximum von Mises stresses and horizontal sways of these towers with vertical stiffeners is compared with the corresponding ring-stiffened towers. A linear buckling analysis is conducted to study the buckling modes and critical buckling loads of the three height levels of tower. The buckling modes and eigenvalues of the 50m, 150m and 250m vertically stiffened towers were also compared with those of the horizontally stiffened towers. The numbers and central angles of the vertical stiffeners are considered as design variables to study the effect of vertical stiffeners on the structural performance of wind turbine towers. Following an extensive parametric study, these strengthening techniques were compared with each other and it is obtained that the use of vertical stiffeners is a more efficient approach to enhance the stability and strength of intermediate and high towers than the use of horizontal rings.

Analysis of Wind and Wave Force acting on the Foundation of the Offshore Wind Tower (해상 타워의 기초에 작용하는 풍력과 파력 해석)

  • Kim, Nam-Hyeong;Go, Myeong-Jin
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • pp.273-274
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    • 2013
  • Recently, as offshore wind towers are developed, the size of wind towers have become larger and larger, and offshore wind towers are exposed to various external forces such as wave and current compared with onshore wind towers. Thus, the stability of offshore wind towers is more required than onshore wind towers. In this study, when the wind celerity of 60m/s blows to the cylinder, cone, and stair typed towers, the wind and wave forces on foundation are calculated by p-y relation.

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Double controller of wind induced bending oscillations in telecom towers

  • Battista, Ronaldo C.;Pfeil, Michele S.;Carvalho, Eliane M.L.;Varela, Wendell D.
    • Smart Structures and Systems
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    • v.21 no.1
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    • pp.99-111
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    • 2018
  • Wind induced large bending oscillation amplitudes in tall and slender telecommunication steel towers may lead to precocious fatigue cracks and consequent risk of collapse of these structures, many of them installed in rural areas alongside highways and in highly populated urban areas. Varying stress amplitudes at hot spots may be attenuated by means of passive control mechanical devices installed in the tower. This paper gives an account of both mathematical-numerical model and the technique applied to design and evaluate the performance of a double controller installed in existing towers which is composed by a nonlinear pendulum and a novel type of passive controller described herein as a planar motion disk mounted on shear springs. Results of experimental measurements carried out on two slender tubular steel towers under wind action demonstrate the efficiency of the double controllers in attenuating the towers bending oscillation amplitudes and consequent stress amplitudes extending the towers fatigue life.

Fundamental aspects on the seismic vulnerability of ancient masonry towers and retrofitting techniques

  • Preciado, Adolfo;Bartoli, Gianni;Budelmann, Harald
    • Earthquakes and Structures
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    • v.9 no.2
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    • pp.339-352
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    • 2015
  • Ancient masonry towers constitute a relevant part of the cultural heritage of humanity. Their earthquake protection is a topic of great concern among researchers due to the strong damage suffered by these brittle and massive structures through the history. The identification of the seismic behavior and failure of towers under seismic loading is complex. This strongly depends on many factors such as soil characteristics, geometry, mechanical properties of masonry and heavy mass, as well as the earthquake frequency content. A deep understanding of these aspects is the key for the correct seismic vulnerability evaluation of towers and to design the most suitable retrofitting measure. Recent tendencies on the seismic retrofitting of historical structures by means of prestressing are related to the use of smart materials. The most famous cases of application of prestressing in towers were discussed. Compared to horizontal prestressing, vertical post-tensioning is aimed at improving the seismic behavior of towers by reducing damage with the application of an overall distribution of compressive stresses at key locations.

Aerodynamic response of articulated towers: state-of-the-art

  • Zaheer, M. Moonis;Islam, Nazrul
    • Wind and Structures
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    • v.11 no.2
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    • pp.97-120
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    • 2008
  • Wind and wave loadings have a predominant role in the design of offshore structures in general, and articulated tower in particular for a successful service and survival during normal and extreme environmental conditions. Such towers are very sensitive to the dynamic effects of wind and wind generated waves. The exposed superstructure is subjected to aerodynamic loads while the submerged substructure is subjected to hydrodynamic loads. Articulated towers are designed such that their fundamental frequency is well below the wave frequency to avoid dynamic amplification. Dynamic interaction of these towers with environmental loads (wind, waves and currents) acts to impart a lesser overall shear and overturning moment due to compliance to such forces. This compliancy introduces geometric nonlinearity due to large displacements, which becomes an important consideration in the analysis of articulated towers. Prediction of the nonlinear behaviour of these towers in the harsh ocean environment is difficult. However, simplified realistic mathematical models are employed to gain an important insight into the problem and to explore the dynamic behaviour. In this paper, various modeling approaches and solution methods for articulated towers adopted by past researchers are reviewed. Besides, reliability of articulation system, the paper also discussed the design, installation and performance of articulated towers around the world oceans.