[TowerTalk] windload rating of triex LM470e tower to be independently ver...

[K7LXC@aol.com]

In a message dated 9/26/00 11:24:52 AM Pacific Daylight Time, 
alwilliams@olywa.net writes:

> Yesterday, after an hours long session with the county engineer and his
>  supervisor reviewing the analysis  I was informed that I would have to have
>  the tower and foundation analysis reviewed and certified by a Washington
>  State Professional Engineer.  I believe they were uncomfortable with the
>  analysis (copy including  stamped by a California State registered
>  professional engineer) because of the following:

    They are uncomfortable because you *have* to have a local state PE stamp. 
Every state and/or tower construction permit I've ever run into is the same 
way. 

    It's easy enough for a PE to get reciprocity with other states since it's 
just a paperwork deal but most are only licensed in their own state. Rohn is 
a tower company that can provide PE stamps for all states because there 
business is national and this way they're in control of the situation (and 
can get you to pay for it!).
>  
>    1.  The county engineers were informed several times that the California
>  engineer would call to discuss the      analysis but not call was received.
>  
    What's to discuss? The local building department has their book of 
building codes and YOU have the responsibility of complying with them. Even 
if they actually did talk to someone, they still require locally stamped 
plans. 

    The big problem is that virtually no one that you talk to in the building 
department has ever seen or reviewed the plans for a radio tower. They look 
at it likes it's a habitable structure (which it isn't obviously) and try to 
apply other rules that you can argue don't apply (like a soil test). My most 
*memorable* experience with a local building department inspector was having 
to take the time to show him that the four things he dinged us with either 
were totally wrong to begin with or didn't apply. Many times YOU have to help 
THEM to understand what's going on. 

>    2.  The Foundation Installation stated that "The tower footing design
>  shown is based on normal soil criteria...."  and "Normal soil is defined as
>  cohesive soil with an allowable vertical bearing load capacity of 4000
>  pounds per square foot".  The analysis contains a table listing various
>  soils.  The listing for 4000 pounds is defined as massive crystalline
>  bedrock !!!!!!!!

    This sounds really fishy but I'm not a soils engineer so can't give a 
definitive answer. Maybe Hank, KR7X, can weigh in on this one.  The TIA-222 
Tower Standard calls 4kpsf "normal soil" - and says that "rock" is not to be 
considered normal soil". 
>  
>    3.  The county engineer asked several times who crossed out 70 and hand
>  wrote 80 for the wind speed and who crossed out 24 and hand wrote 15 for 
the
>  maximum antenna wind area.
>  
    Huh? Another excellent reason for locally stamped drawings. When a PE 
stamps plans, they are accepting responsibility for the design and it's 
compliance to all germane regs (as well as paying big bucks for 'Errors and 
Omissions' insurance). THAT'S what the building department wants to see - 
they want SOMEONE ELSE to take responsibility for the design. They just 
'check' the plans.

>    4.  The county engineer was also uncomfortable with the diagrams and
>  anaylsis of the rebar in the footing but I am not knowledgable to describe
>  this concern.

    You're talking to the wrong people - these guys don't have a clue. Get a 
local PE to stamp your drawings and THEN take them to the building 
department. 

    DO NOT take your plans to an engineering firm (read $1k or more to do 
it). I can give you the name of a PE who can do it for you at a significantly 
lower price. He's done more than six sets of plans for me including a US 
Tower crank-up with a high windspeed and seismic calcs. Volunteer Engineers 
are easily locatable from the ARRL website for just about anywhere in the 
country. 

Cheers,   Steve    K7LXC
Tower Tech

--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com