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RE: Pile/Pier tie beam interpretation

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The rest of the BOCA section to which you referred (1815.2) gives you
three firm outs (in addition to the "other approved means" item).  One
of these could make sense in the situation you described.  The section
says, "Individual tie beams are not required when it is demonstrated
that equivalent restraint will be provided by structural members
within slabs on grade or reinforced concrete slabs on grade or
confinement by competent rock, hard cohesive soils, very dense
granular soils or other approved means."

I read "structural members within slabs on grade" to include a
thickened slab.  "Reinforced concrete slabs on grade" (even
unthickened) can be used to satisfy the requirement.  Also, very
competent soil may confine the movement adequately.

When I have designed buildings with heavy floor loads and long spans
between foundations (probably similar to your aircraft maintenance
facility) I have reinforced and detailed my thick slab (not thickened)
to serve as the ties.

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Michael Valley, P.E., S.E.                   E-mail: mtv(--nospam--at)skilling.com
Skilling Ward Magnusson Barkshire Inc.              Tel:(206)292-1200
1301 Fifth Ave, #3200,  Seattle  WA 98101-2699      Fax:        -1201

-----Original Message-----
From: Bowling, Kevin [mailto:kbowling(--nospam--at)lgt.lg.com]
Sent: Wednesday, December 06, 2000 10:13 AM
To: 'seaint(--nospam--at)seaint.org'
Subject: Pile/Pier tie beam interpretation


I need some assistance interpreting a requirement in BOCA (this
requirement
is also in most other codes) regarding interconnected ties for pier
foundations.  Section 1815.2 states "Pier foundations shall be
interconnected by ties for buildings assigned to Seismic Performance
Category C, D, or E.  It is the term "interconnected" that I am having
a
problem with.  Does this mean that all pier need to be connected with
a tie
beam system?  My situation stems from the design of an aircraft
maintenance
building which has a clear span of 163'.  I will have tie beams
connecting
the piers longitudinally but I would like to avoid constructing a tie
beam
across the entire span. Can the intent of the code be met by adding
additional piers to the inside of the building (say 15'), and
constructing a
tie beam from this pier to the main pier and longitudinal tie beam?

Any help with this would be greatly appreciated,

Thanks,

Kevin Bowling, P.E.
Lockwood Greene Technologies
865.220.4411