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wind force design criteria

To: <towertalk@contesting.com>
Subject: wind force design criteria
From: Henry Knoll <Henry.Knoll-1@tc.umn.edu> (Henry Knoll)
Date: Mon, 5 Aug 1996 18:51:50
On Mon, 5 Aug 1996 14:36:36 -0700 (PDT),
w7ni@teleport.com wrote...
>Steve:  a number of times I've seen references ON A COUNTY basis to
>>>wind force design criteria.  do you know where I can obtain this info,
>>>hopefully on line?  my old, old, old Rohn book only has a map of the
>>>US.  I'm curious as to the design criteria for Cheshire country in the
>>>stick of NH.
>>>
>>Hi, Charlie --
>>
>>      It's listed in the EIA/TIA-222-E and F, the newest revision 
>effective
>>June 1, 1996.  I have copies and am happy to look them up for interested
>>folks.  My plan is to get my Tower Tech web page up and running and
>>eventually have the info on-line as I don't think it exists anywhere 
else.
>> The pubs run $80.00 each so not everyone is inclined to have them in 
>their
>>library.
>>
>>      Cheshire County is a 75 MPH zone but is within 100 miles of 
>hurricane
>>coastline and the values have been adjusted in accordance with ASCE 7-88 
>to
>>obtain 50-year recurrence intervals.  In other words, check with you 
local
>>building department to see if you are subject to higher winds at your 
>site.
>> BTW, 70 is the lowest value that the charts contain so your zone isn't 
>too
>>bad except for the proximity to hurricane coastline. 
>>
>>73 and good luck,  Steve  K7LXC
>>
>>    TOWER TECH -- professional tower supplies and services for amateurs 
>>
>
>Since 70 mph is the minimum listed wind velocity for ANYWHERE in the US, 
>how
>come crankup towers are always rated for 50 mph?  I think I know why.  You
>can't put any load on them at 70 mph, at least with any kind of safety
>factor.  I think we, as a group, should demand 70 mph ratings from crankup
>manufacturers.  I know this will negatively impact their business . . . as
>it should!!
>
>Stan w7ni@teleport.com
>
>





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