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Re: Basement wall restrained by wood floor

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James:

I agree with you, here in Western New York almost all residential basements
are unreinforced  concrete or CMU and restrained at the top by the floor
system.  This works well where granular backfill and drainage is provided,
however I have investigate dozens of failures clays were used as backfill
and or no drainage was provided.  Additionally, structures with a walkout
type of basement require  cantilever type foundation walls.  In my opinion
these need to be designed as  restrained cantilevers since the floor system
provides some restraint.  Also it has been my practice to use the at rest
pressure against basement walls, since they may not rotate enough to develop
active pressures.

John Schenne, PE
East Aurora, NY
-----Original Message-----
From: James F Fulton <James_F_Fulton(--nospam--at)RohmHaas.Com>
To: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org>
Date: Thursday, August 26, 1999 6:36 AM
Subject: Basement wall restrained by wood floor


>In 99.9% of the residential construction I've seen, the basement wall is
>supported by a strip footing, usually 20" wide or so. This type of wall
>relies on the support at the top provided by the first floor. In one
>direction, the direction of the floor joists, not only the floor deck but
>also the joists act to provide the restraint. Pretty stiff and pretty
strong
>in this direction. In the other direction, parallel to the joists, a
blocking
>or bridging system has to be used to transfer the transverse shear at the
>bottom of the rim joists, that bears on the sill plate that's anchored
bolted
>into the top of the wall, to the level of the floor deck.  In this case,
the
>floor deck is indeed providing most of the strength and stiffness it would
>seem. But I don't see why it cannot be relied upon do its job. To design
the
>wall as a cantilever against backfill loads has expensive implications for
>residential construction now that a structural footing is needed.
>
>