Is there any special wind load provisions necessary at airport facility structures due to jetwash or rotor wash from helicopters? I haven't seen or found anything. Any military specs maybe??
I've never heard of such a thing in any code body anywhere. The only special item may be that the airport is considered an essential facility and would require an importance factor higher than 1.0.
Check "Planning and Design of Airports" by R. Horonjeff, McGraw Hill, Chapter 9.
Some of the elements in the proximity of the runways and taxiways (signage, blast fences) may have design wind (jet wash) speed in excess of the regular local code, until it requires 200mph.
See also
Check out the FAA Advisory Circulars. They have an entire group of circulars pertaining to design of airports. Maybe the info you seek would be there. They have different topics, like planning, and design, etc. Here is their main advisory circular page: