Galloping response of towers

In the present paper the extended application of the quasi-steady theory of galloping to towers of square section in simulated natural winds is examined. In the experiments, the wind was produced in a large boundary layer wind tunnel, and represented a full scale wind typical of a "suburban" exposure. The static measurements were made on towers instrumented with pressure taps so that the variation with height of the sectional pressure distribution and force could be determined. The dynamic measurements were made on rigid towers pivotted elastically at the base, and mounted with very low, but variable, viscous-type damping. In the quasi-steady theory, the variation with height of the wind speed and sectional transverse force were incorporated, an improvement over the averaged-force method used previously. The results showed that there was an important variation of sectional lateral force over the height of the towers tested, and that good agreement between predicted and observed variations of galloping amplitude with wind speed was obtained when this sectional force variation was incorporated in the theory. The paper also examines effects on galloping behaviour of the proximity of resonance of a tower with its wake vortex system, and the implications of this for the galloping of full-scale towers.