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Re: pointed stem wall under a PEMB?

[Subject Prev][Subject Next][Thread Prev][Thread Next] My thoughts are (1) knife points don't exist in concrete (2) a vertical force on the sloped interior surface still has a vertical component and (3) It's probably rare in modern times that significant frost penetration would occur and cause damage. IOW, I don't think its a good detail, but it probably wont fail that often.

A better solution would be to excavate to frost depth and fill with a porous material which is socked with geotextile, and make sure there is a drain to daylight. from the bottom of the trench. Then thin your grade beam to the structurally allowable minimum.

Jordan

Foy, Warren wrote:

While I have not used such a detail, I have seen it in as-built drawings
for some buildings in New Jersey.  It was used for the bottom of a grade
beam spanning between pile caps so that the bottom of the grade beam was
not required to be below frost depth.

-----Original Message-----
From: Jim Wilson [mailto:wilsonengineers(--nospam--at)yahoo.com]
Sent: Tuesday, April 26, 2005 10:16 PM
To: seaint(--nospam--at)seaint.org
Subject: pointed stem wall under a PEMB?


A contractor explained a detail to me today where the
perimeter stemwall of a PEMB building was shaped with
a pointed bottom at about 18" below grade in an area
with 36" frost depth.  There is no footing under the
stem.  The concept is that the frost heave will not
push on the pointed bottom.

The steel frame still sits on concrete piers with
footings, hairpins, etc.  The stem won't be figured in
the structural load resisting system.

This sounds a little bit clever, but I'm not
convinced.  He claims that he has used it before and
it has been accepted (by the building inspector, the
structural engineer, etc.)

Is there such a detail and does it actually work?  I'm
suspicious, but who knows, maybe I learned something
today...

Jim Wilson, PE
Stroudsburg, PA


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