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RE: Pile Ties

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1921.4.1 

You would have to meet both criteria, (1) resisting eq induced forces AND
(2) having a factored axial force exceeding Agf'c/10.

AND is the key word, keep your axial load below Agf'c/10 and you won't have
to design as frame with associated detailing requirements.

Mark

 
-----Original Message-----
From: lrhauer(--nospam--at)earthlink.net [mailto:lrhauer(--nospam--at)earthlink.net] 
Sent: Tuesday, April 26, 2005 11:00 AM
To: SEAOC
Subject: Pile Ties

I am designing a pile foundation which is required due to the site having
potentially consolidating soils at about a 5 to 10 foot depth in the event
of a major earthquake, (South. Calif.). The soils engineer has given me the
lateral resistance of the soils for individual piles based on the program
"LPILEPLUS." The pile head is assumed fixed against rotation, (i.e. a grade
beam at the top), for the program output. Given this information, I can
determine the allowable lateral force at the top of the piles, (to resist
earthquake forces).

The BIG question is: Does this pile and grade beam foundation system have to
be designed as a ductile moment resisting frame- i.e. per section 1921.4 of
the '97 UBC?? If so, the cost will be prohibitive- so I am hoping someone
can give me an explanation as to why it does not.

My second question is: How is formula 21-2 of the '97 UBC interpreted? It is
a simple formula, but when you get a p-s of 0.008 for the materials used,
and a core area of 227 in. sq. for a 24" diam. pile, how is this converted
into a tie spacing?

Thanks in advance,

Larry Hauer SE



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