Gerry KA2MGE wrote:
>>I have a few questions regarding antenna wind survival
>>requirements in NY state and possibly the whole US. A
>>local building inspector is telling me that just like
>>with towers, NY requires any antenna mounted
>>on a tower to be able to withstand a 3-second wind
>>gust at 115 mph, but I know that can't be right.
In general here's how design wind speeds are
determined:
* The city, county or state adopts the Int'l Bldg Code
* IBC in Chapter 31, Section 3108, defers all design
matters relating to towers to the TIA-222-H code.
* TIA-222-H requires a site-specific design wind
speed determination
* On the web the ASCE 7 Hazard Tool provides a
map-based tool to get the basic wind speed.
The default in TIA for amateur radio towers is
a 300-year wind storm (Class I Risk). If a
falling tower might endanger people, i.e.,
your neighbor's house is in the fall zone,
then a 700-year wind storm is prudent
(Class II).
The state, county or city can pass ordinances or
regulations that override TIA-222-H if they want.
That should be formally approved in writing by
the local agency, not just an opinion by an
inspector.
Jim Varney, P.E. (Calif.), K6OK
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