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Fwd: Re: Isolated pad footings - To tie or Not to tie?

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Dennis:

I feel that while it is true that "tying the footings will not prevent a =
differential settlement", I do believe that a moment carrying =
connection, between the tie-beam and the post, would greatly alleviate =
the effect of vertical displacement caused by differential settlements, =
on to your truss superstructure. This, on this account alone, should be =
a requirement only if you are expecting substantial differential =
settlements. In general, large total settlements are likely to be =
accompanied by large differential settlements.

As a separate consideration, if you do consider a lateral restraint =
necessary, and wish to depend upon the patio slab for this, you might =
wish to compute the order of available reastraint that the patio slab is =
likely to offer. The weight of the patio slab, multiplied by the =
applicable coefficient of friction, should serve as a good estimate of =
the available restraint. If the available restraint is adequate, with a =
factor of safety, you might like to connect the post, through =
reinforcement flaring out, in a semicircular fashion, into the slab for =
some distance, even if the slab itself is unreinforced. Check the =
tensile stresses, in the slab, at the termination of the reinforcement.

I have successfuly used something very similar, by depending upon the =
reinforced floor slab for connecting the two opposite columns of a gable =
frame, 120'-0" apart, and subjected to a horizontal column reaction. I =
used this technique as an alternate to connecting the two opposite =
columns through a 120'-0" tie-beam, and in preference to the even more =
difficult alternate of having to design the isolated footings, for the =
hrizontal reaction.


Rizwan Mirza, P.E.
amirr(--nospam--at)paknet1.ptc.com



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Subject: Re: Isolated pad footings - To tie or Not to tie?
Date: Fri, 14 Feb 1997 14:46:05 +-500
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Richard Lewis, P.E.
Missionary TECH Team
rlewis(--nospam--at)techteam.org

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