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CONTENTS
Volume 8, Number 2, March 2005
 

Abstract
This paper deals with a unified way for calculating vortex-induced vibrations (Aeolian vibrations in transmission line parlance) of undamped single overhead conductors. The main objective of the paper is to identify reduced parameters which would unify the predicted vibration response to the largest possible extent. This is actually done by means of a simple mathematical transformation resulting, for a given terrain (associated to a given wind turbulence intensity), into a single, unified response curve that is applicable to any single multi-layered aluminium conductor. In order to further validate the above process, the predicted, unified response curve is compared with measured response curves drawn from tests run on a full-scale test line using several aluminium-conductor-steel-reinforced (ACSR), all-alloyaluminium-conductor (AAAC) and aluminium-conductor-alloy-reinforced (ACAR) conductors strung at different tensions. On account of the expected scatter in the results from such field tests, the agreement is shown to be good. The final results are expressed by means of only four different curves pertaining to four different terrain characteristics. These curves may then be used to assess the vibration response of any undamped single, multi-layer aluminium conductor of any diameter, strung at any practical tension.

Key Words
Aeolian vibrations; vortex-induced vibrations; conductors; wind power input; self-damping; energy balance principle.

Address
Andre Leblond; Hydro-Qu?bec Trans?nergie, 800, boul. de Maisonneuve Est, 21st Floor, Montreal, Qu?bec H2L 4M8, CanadarnClaude Hardy; Claude Hardy International Inc., 95 rue Lamarche, St-Bruno, Quebec, J3V 5A6, Canada

Abstract
For estimating the vortex excited vibrations of overhead transmission lines, the Energy Balance Principle (EBP) is well established for spans damped near the ends. Although it involves radical simplifications, the method is known to give useful estimates of the maximum vibration levels. For very long spans, there often is the need for a large number of in-span fittings, such as in-span Stockbridge dampers, aircraft warning spheres etc. This adds complexity to the problem and makes the energy balance principle in its original form unsuitable. In this paper, a modified version of EBP is described taking into account in-span damping and in particular also aircraft warning spheres. In the first step the complex transcendental eigenvalue problem is solved for the conductor with in-span fittings. With the thus determined complex eigenvalues and eigenfunctions a modified energy balance principle is then used for scaling the amplitudes of vibrations at each resonance frequency. Bending strains are then estimated at the critical points of the conductor. The approach has been used by the authors for studying the influence of in-span Stockbridge dampers and aircraft warning spheres; and for optimizing their positions in the span. The modeling of the aircraft warning sphere is also described in some detail.

Key Words
energy balance principle; overhead transmission lines; Stockbridge damper; warning sphere; transcendental eigenvalue problem.

Address
Himanshu Verma and Peter Hagedorn; Institut f?r Mechanik, Technische Universit?t Darmstadt, Hochschulstra

Abstract
The quasi-steady approaches to simulate the wind induced vibrations of inclined cables, especially on the rain-wind induced vibration, have been tried by many researchers. However, the steady wind force coefficients used in those methods include only the effects of water rivulet, but not the axial flow effects. The problem is the direct application of the conventional techniques to the inclined cable aerodynamics. Therefore, in this study, the method to implement the axial flow effects in the quasisteady theory is considered and its applicability to the inclined cable aerodynamics is investigated. Then, it becomes clear that the perforated splitter plate in the wake of non-yawed circular cylinder can include the effects of axial flow in the steady wind force coefficients for inclined cables to a certainrnextent. Using the lateral force coefficients measured in this study, the quasi-steady theory may explain the wind induced instabilities of the inclined cables only in the relatively high reduced wind velocity region. When the Scruton number is less than around 40, the high speed vortex-induced vibration occurs around the onset wind velocity region of the galloping, and then, the quasi-steady approach cannot be applied for estimating the response of wind-induced vibration of inclined cable.

Key Words
inclined stay cable; rain-wind induced vibration; galloping; high-speed vortex-induced vibration; steady wind force coefficients; quasi-steady theory.

Address
Masaru Matsumoto

Abstract
Wind-induced vibrations measured in the Tsuruga Test Line are characterized in this paper by single-channel data analysis based on piecewise application of Prony

Key Words
galloping; buffeting; transmission line; bundled conductors; Prony

Address
Hiroki Yamaguchi, Chandra B. GurungrnDepartment of Civil and Environmental Engineering, Saitama University, Shimo-Ohkubo 255, Sakura-Ku, Saitama 338-8570, JapanrnTeruhiro YukinornTechnical Research Center, Kansai Electric Power Co., Nakoji 3-11-20, Amagasaki 661-0974, Japan

Abstract
Divergent galloping-like motion of a dry inclined cable has been observed in a limited number of experimental studies, which, due to the uncertainties in its onset conditions, has induced serious concerns in the bridge stay cable design. A series of dynamic and static model wind tunnel tests have been carried out to confirm the existence of the phenomenon and clarify its excitation mechanism. The present paper focuses on exploring the spatial flow structure around an inclined cable. The pattern of resultant aerodynamic forces acting at different longitudinal locations of the model and the spatial correlation of the forces are examined. The results lead one step closer in revealing the physical nature of the phenomenon.

Key Words
cable aerodynamics; inclined circular cylinder; dry inclined cable galloping; correlation; Reynolds number.

Address
Shaohong Cheng and Hiroshi TanakarnDepartment of Civil Engineering, University of Ottawa, 161 Louis Pasteur, Ottawa, ON K1N 6N5 Canada


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