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

[Lonberg, Hank]

Steve:

I've already responded to Al directly on this matter but in the case of the
"normal soil"  thingie, I'll respond to the reflector in general.

When you do not have a soils report done by a soils engineer that discusses
the allowable vertical bearing pressure and other parameters for your
project's specific site then, in the case of UBC jurisdictions, the local
building people default to Table 18-I-A  - Allowable Foundation and Lateral
Pressure in the UBC itself. In this table the soils are classified 1 to 5
with 1 being Massive Crystalline Bedrock with an allowable bearing pressure
of 4000 pounds per square foot. Class 5 or worst case soil is clay, or sandy
silty clay etc. and has an allowable bearing pressure of 1000 pounds per
square foot.

I normally use the class 5, worst case, as most hams do not want to pay the
$5000 to $10000 for a proper, by engineering standards, soils investigation
and report. This approach placates the building officials usually.

Again if you don't have to get a permit then what you do is what you are
liable for.

Ciao

Hank Lonberg P.E. / KR7X


	-----Original Message-----
	From:	K7LXC@aol.com [SMTP:K7LXC@aol.com]
	Sent:	Tuesday, September 26, 2000 12:31 PM
	To:	alwilliams@olywa.net; towertalk@contesting.com
	Subject:	Re: [TowerTalk] windload rating of triex LM470e
tower to be independently ver...


	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

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