Dynamic and aeroelastic action of guy cables

Dissertation

Tuomo Kärnä

Research output: ThesisDissertationMonograph

10 Citations (Scopus)

Abstract

The models have been derived for the computation of the dynamic stiffness of guy cables.Both the complete mathematical model and the simplified spring-mass model can be used in a linear three-dimensional dynamic analysis of guyed masts in connection with the frequency response method and a substructure technique where frequency dependent springs and dashpots are substituted for the guys.The mathematical model can also be used in the design of linear guy dampers which are included in the model.The analytical formulas for the static configuration of the guy evolve in both models from the assumption of uniformity of the guy.The three-dimensional motion of the guy attachment point to the mast and the two-dimensional sectional guy motions under the influence of mechanical and aerodynamic damping are considered.The computational procedure incorporates a variety of mechanisms of aerodynamic instability, which may result in galloping oscillations.These mechanisms include the lift and drag instabilities as well as the wake galloping phenomenon.Examples of the dynamic and aeroelastic behaviour of guys are computed in terms of the complex dynamic stiffness.The cross-over behaviour of the natural frequencies is shown to exert significant effects on the guy action.The dynamic sensitivity of a guy can be assessed using a single stiffness parameter which depends both on gravity and wind load.The results disclose that the direction and intensity of the mean wind force have a marked influence on the dynamoc behaviour of Light guys.Further examples show various effects of the aerodynamic instabilities on iced and non-iced guy cables.The mechanism of a galloping phenomenon of guys, which carry an ice banner below the cable, is explained referring to reported wind tunnel results.It is shown that mitigation of the galloping problem entails additional damping in a broad frequency range.The result indicate also that measures taken to arrest galloping of guy cables should not rely on any single mechanism of aerodynamic instability.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • Helsinki University of Technology
Award date26 Oct 1984
Place of PublicationEspoo
Publisher
Print ISBNs951-38-2005-X
Publication statusPublished - 1984
MoE publication typeG4 Doctoral dissertation (monograph)

Fingerprint

Aerodynamics
Cables
Stiffness
Damping
Mathematical models
Dynamic analysis
Frequency response
Wind tunnels
Ice
Drag
Natural frequencies
Gravitation

Keywords

  • guys
  • vibration
  • aeroelasticity
  • mathematical models
  • ice
  • wind pressure

Cite this

Kärnä, T. (1984). Dynamic and aeroelastic action of guy cables: Dissertation. Espoo: VTT Technical Research Centre of Finland.
Kärnä, Tuomo. / Dynamic and aeroelastic action of guy cables : Dissertation. Espoo : VTT Technical Research Centre of Finland, 1984. 98 p.
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Kärnä, T 1984, 'Dynamic and aeroelastic action of guy cables: Dissertation', Doctor Degree, Helsinki University of Technology, Espoo.

Dynamic and aeroelastic action of guy cables : Dissertation. / Kärnä, Tuomo.

Espoo : VTT Technical Research Centre of Finland, 1984. 98 p.

Research output: ThesisDissertationMonograph

TY - THES

T1 - Dynamic and aeroelastic action of guy cables

T2 - Dissertation

AU - Kärnä, Tuomo

PY - 1984

Y1 - 1984

N2 - The models have been derived for the computation of the dynamic stiffness of guy cables.Both the complete mathematical model and the simplified spring-mass model can be used in a linear three-dimensional dynamic analysis of guyed masts in connection with the frequency response method and a substructure technique where frequency dependent springs and dashpots are substituted for the guys.The mathematical model can also be used in the design of linear guy dampers which are included in the model.The analytical formulas for the static configuration of the guy evolve in both models from the assumption of uniformity of the guy.The three-dimensional motion of the guy attachment point to the mast and the two-dimensional sectional guy motions under the influence of mechanical and aerodynamic damping are considered.The computational procedure incorporates a variety of mechanisms of aerodynamic instability, which may result in galloping oscillations.These mechanisms include the lift and drag instabilities as well as the wake galloping phenomenon.Examples of the dynamic and aeroelastic behaviour of guys are computed in terms of the complex dynamic stiffness.The cross-over behaviour of the natural frequencies is shown to exert significant effects on the guy action.The dynamic sensitivity of a guy can be assessed using a single stiffness parameter which depends both on gravity and wind load.The results disclose that the direction and intensity of the mean wind force have a marked influence on the dynamoc behaviour of Light guys.Further examples show various effects of the aerodynamic instabilities on iced and non-iced guy cables.The mechanism of a galloping phenomenon of guys, which carry an ice banner below the cable, is explained referring to reported wind tunnel results.It is shown that mitigation of the galloping problem entails additional damping in a broad frequency range.The result indicate also that measures taken to arrest galloping of guy cables should not rely on any single mechanism of aerodynamic instability.

AB - The models have been derived for the computation of the dynamic stiffness of guy cables.Both the complete mathematical model and the simplified spring-mass model can be used in a linear three-dimensional dynamic analysis of guyed masts in connection with the frequency response method and a substructure technique where frequency dependent springs and dashpots are substituted for the guys.The mathematical model can also be used in the design of linear guy dampers which are included in the model.The analytical formulas for the static configuration of the guy evolve in both models from the assumption of uniformity of the guy.The three-dimensional motion of the guy attachment point to the mast and the two-dimensional sectional guy motions under the influence of mechanical and aerodynamic damping are considered.The computational procedure incorporates a variety of mechanisms of aerodynamic instability, which may result in galloping oscillations.These mechanisms include the lift and drag instabilities as well as the wake galloping phenomenon.Examples of the dynamic and aeroelastic behaviour of guys are computed in terms of the complex dynamic stiffness.The cross-over behaviour of the natural frequencies is shown to exert significant effects on the guy action.The dynamic sensitivity of a guy can be assessed using a single stiffness parameter which depends both on gravity and wind load.The results disclose that the direction and intensity of the mean wind force have a marked influence on the dynamoc behaviour of Light guys.Further examples show various effects of the aerodynamic instabilities on iced and non-iced guy cables.The mechanism of a galloping phenomenon of guys, which carry an ice banner below the cable, is explained referring to reported wind tunnel results.It is shown that mitigation of the galloping problem entails additional damping in a broad frequency range.The result indicate also that measures taken to arrest galloping of guy cables should not rely on any single mechanism of aerodynamic instability.

KW - guys

KW - vibration

KW - aeroelasticity

KW - mathematical models

KW - ice

KW - wind pressure

M3 - Dissertation

SN - 951-38-2005-X

T3 - Publications / Technical Research Centre of Finland

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Kärnä T. Dynamic and aeroelastic action of guy cables: Dissertation. Espoo: VTT Technical Research Centre of Finland, 1984. 98 p.