Return to index: [Subject] [Thread] [Date] [Author]

Re: pointed stem wall under a PEMB?

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Jim,
 
Pennsylvania is no Canada, and the frost penetration and heave are incomparably less dramatic.  However, in my experience with design in the areas of frost penetration of 5 feet or more, frost heave can do pretty weird and destructive things to a structure.
 
For the subject case, the wall panels will be pushed up no matter how sharp the edge is.  Even in PA, that thrust can be quite substantial.  Will the wall panel and its connection to the frame take it?  Will the frame anchor bolts take the uplift? 
 
Now, all that is based upon the assumption of uniform upheaval.  What if it won't be? 
 
To a point of a serious accident, the owners will not care about anchor bolts and other structural components. However, damage to the walls can be easily observed by anybody.  Of course, the contractor will be the first in line, but the engineer will be definitely the next one.
 
Be careful.
 
Sorry, for the diatribe, I just came from the site (a mansion, 5 years old, ocean view, etc.).  The house is leaking through the balconies, inadequate drainage, fungal attack, and, unfortunately, some design flops.  I was hired by a new architect for the repair design; everybody on the original design/construction team is being sued.  Quite sad and discouraging.
 
V. Steve Gordin, PhD
Registered Structural Engineer
Irvine CA  
 
 
 
 
 
   
 
 
 
 
 
----- Original Message -----
Sent: Wednesday, April 27, 2005 11:58 AM
Subject: Re: pointed stem wall under a PEMB?

Jim,

        My personal thoughts are that the pointed grade beam would not work
as expected.  The generally accepted method in Western Canada is to use
Voidform of an appropriate thickness.  One possible shortcoming is that
after the Voidform has deteriorated the void may fill in over a long period
of time.

        In the past some engineers used low strength insulation but even a
material that resists 10 p.s.i. resists 1440 p.s.f.  Mind you, the
insulation would be the method of choice if the grade beam can resist much
more than 1440 p.s.f.  The material would crush as required and it may also
expand back to keep the void from filling in.

Regards,

H. Daryl Richardson

----- Original Message -----
From: "Jim Wilson" <wilsonengineers(--nospam--at)yahoo.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, April 26, 2005 8:15 PM
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
>
> ******* ****** ******* ******** ******* ******* ******* ***
> *   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> *
> *   This email was sent to you via Structural Engineers
> *   Association of Southern California (SEAOSC) server. To
> *   subscribe (no fee) or UnSubscribe, please go to:
> *
> *   http://www.seaint.org/sealist1.asp
> *
> *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> *   send to the list is public domain and may be re-posted
> *   without your permission. Make sure you visit our web
> *   site at: http://www.seaint.org
> ******* ****** ****** ****** ******* ****** ****** ********
>



******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********