Asimov wrote:
"How can one estimate stress cycles from a wind load?"

Tower failure usually results from a single event or cycle of
overstress.

Radio towers are rated according to the mph or wind load ( pounds per
square foot) they will withstand while carrying all their other loads,
dead or live.

Towers do vibrate in a breeze as any tower climber can affirm. Resonant
frequency depends on construction.

Wind vibration has brought down structures. A famous example is
"Galloping Gertie", a suspension bridge in the western U.S.A.

Deflection is limited in radio towers and elastic limits are not
exceeded. The tower section returns to its original form after each
flexing.

Stress cycles enlarge certain microscopic cracks. Examples are the Comet
airliner. Three aircraft flew apart in mid-air. It was determined that
stress cracks in the angular corners of its windows were enlarged by
pressurization / depressurization cycles. This was fixed by rounded
corners but it was too late. The first jet airliner was scrubbed.

Another example is found in high pressurre gas pipelines. Their internal
pressure cycles and this tends to enlarge microscopic cracks, if any, in
the pipe. Pipes are hydrostatically tested before placed in service (no
energy storage in water as it is incompressible) so a pipe blow out of
water won`t likely hurt a bystander. After the pipe is put in service it
is retested each year.

Radio towers are not usually flexed beyond limits by vibration but come
down due to an accident and / or extreme wind.

Best regards, Richard Harrison, KB5WZI