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| Public domain image courtesy Manfredrichter on Pixabay |
Back
of envelope calculations suggests a 760 N (approximately 76 kg) load on
poles for force 10 winds, which doesn't seem like much. But that's for
average wind speed. I've asked Kildare Weather have they any recorded
gust speeds. Forces increase exponentially with wind velocity. So
doubling the wind speed quadruples the load. Presumably poles break when
they're rotten at the base and I would think "healthy" poles are
unlikely to fail under normal circumstances unless there's a split in
the timber.
Edit:
Kildare Weather have come back to me with a figure of 85 km/h for Naas
and 95 km/h for Maynooth. (Both gust speeds). The latter figure gives a
load of 710 N or 72 kg. (For a flat surface. There's probably a factor
in the force calculation for round profile objects). Poles are fixed at
one end. I.e They're cantilevered. The wind load spread over a pole
creates a torque at the base of the pole equal to half the force on the
pole multiplied by its length (are poles longer than around 7 m above
ground?)