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Re: Foundation Connection

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Piles resist lateral loads basically by passive pressures along their shaft whereas a spread footing could be considers slightly more redundant since you would have passive resistance on the column portion and positive resistance from the width of the spread footing portion.  The changes of a group of single piles moving around and potentially creating an unstable structure are probably higher than a group of spread footings.

Also note the exception immediately after section 1807.2.  For lightly loaded piles resistance can often be achieved by passive pressure on the pile cap.

Thomas Hunt, S.E.
ABS Consulting

"Michael L. Hemstad" <>

04/20/2004 07:05 AM

Please respond to

Foundation Connection

UBC/CaBC 1807.2 mandates connection of individual pile caps and caissons
by grade beams capable of resisting 10 percent of the column force.  It
does not say anything about spread footings.

IBC 1805.4.2.2 has similar requirements for spread footings in
high-seismic zones at sites with poor soils (Site class E or F).

What is common practice in CaBC land for spread footings carrying
non-lateral-load-resisting columns?  I can see a strong case for tieing
the footings together, but cannot find a code reference to make my case
with my client.  Can anyone shed some light on why the CaBC doesn't
require spread footings to be connected?


Mike Hemstad, P.E.
St. Paul, Minnesota

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