T/F: minimum wind speed for tower strength

FALSE.

Tower strength must be enough for the worst (maximum) loading the tower may face during its life. So the maximum design wind speed or pressure of the zone is used (for example the basic wind speed with a return period of 50 years or more, as in IS 802), together with the minimum temperature and ice where applicable.

• Wind on the conductors, earth wires, insulators and tower body gives the transverse load and the overturning moment. Both rise with the square of the wind speed.
• Minimum wind speed would underestimate the loads and the tower could collapse in a storm.

Minimum (low) wind speed is used for a different purpose: ampacity (thermal rating) calculations, where low wind means poor cooling and is the conservative case. It is also used in the still-air, maximum-temperature condition that gives the maximum sag for ground clearance.