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.
|Award date||26 Oct 1984|
|Place of Publication||Espoo|
|Publication status||Published - 1984|
|MoE publication type||G4 Doctoral dissertation (monograph)|
- mathematical models
- wind pressure