Transient Response of Guyed Telecommunication Towers Subjected to Cable Ice-Shedding

by Ghyslaine McClure, (M.ASCE), McGill Univ, Montreal, Canada,
Na Lin, McGill Univ, Montreal, Canada,



Document Type: Proceeding Paper

Part of: Spatial, Lattice and Tension Structures

Abstract:

This paper presents the results of a numerical study of the transient response of guyed telecommunication towers subjected to sudden ice shedding from the guy wires. Detailed nonlinear dynamic analyses were conducted for three guyed towers with heights of 24.4, 60.7 and 213.4 m, and with two, four and seven stay levels, respectively. Six ice-shedding scenarios were simulated for each structure, with a radial thickness of 40 mm on the cables and on the mast members, in still air conditions. The transient response of the supports is examined for the first 4-5 s following ice shedding. Results indicate that the tilt rotation of the tallest support exceeds the assumed serviceability limit of 0.5°, whereas in all other cases the displacements and rotations are within the limits. In the most critical shedding scenarios, it was found that some of the internal forces in the mast were in the order of 50% of the estimated capacities in shear, bending and axial compression. In general, the largest dynamic amplifications are observed for shedding scenarios that affect the top part of the mast where the antennae are attached. Further studies should focus on very tall towers (more than 100 m), and should address the combined effects of ice shedding and cable galloping. This is an even more complex problem that will require proper numerical modelling of damping.



Subject Headings: Cables | Guyed towers | Transient response | Communication systems | Ice | Numerical analysis | Rotation | Compression members

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