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Re: basement wall analysis

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I suggest that a length to height ratio greater than 2 is better modeled as a one-way slab, with stem bottom, and top, pinned in cases where there is not much embedment into the ground.  More than 2 or 3 ft will result in restraint by the ground and some amount of fixity.  If the top is free then the wall starts to require a cantilever base to it, or you have to consider torsion in the stem section.  That's where the length to hgt ratio comes in.  Between 2 and 4 you would have to judge the degree of "fixity" at the stem base.
 
Sides "fixed" is not strictly true since the supporting ends are also "flexible" and moment distribution of some sort, is probably in order.
 
The results are only as good as the model.

Thor A Tandy  P.Eng
Victoria BC
Canada
e-mail: vicpeng(--nospam--at)telus.net
 
----- Original Message -----
From: Helen Zhou
Sent: Thursday, March 21, 2002 2:16 PM
Subject: basement wall analysis

** Proprietary **

One of our local engineers (MO) uses rectangular concrete tank model to design residential basement walls. (Based on PCA publish, Rectangular Concrete Tanks). He assumes that the one side of basement wall is a big concrete plate with top free, bottom hinge, and two sides fixed (limitation: length/height =<4). The book provides all the design tables for the plate models. All his designs will conclude  2 bars at top, middle and bottom of the foundation walls.

Any comments ? Please help !


Helen Zhou, PE