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Re: Thickened slab detail

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        I don't think the slope of the transition is particularly relevant unless you specifically want it as a key.  The important thing is that the subgrade will provide a stable base to place concrete and not allow too much dirt into the concrete.
        I have seen owner's reps. ("inspectors", if you prefer) take a draughtsman's 45:45:90 triangle to the site and require the contractor to correct the grading until the thickened edge was exactly 1:1 slope because it was drawn that way.
H. Daryl Richardson
----- Original Message -----
Sent: Tuesday, January 04, 2005 9:11 AM
Subject: RE: Thickened slab detail

I look at the thickened slab as I would a continuous footing and select longitudinal rebar to meet the requirements for temp. / shrinkage reinforcement.  I select a width for the bottom of the thickened portion to support the load and the slope of the thickened slab is a construction issue? I show it at about 1:1.



Bruce D. Holcomb, P.E., S.E.

Structural Engineer


Butler, Rosenbury & Partners

300 S. Jefferson, Suite 505

Springfield, MO 65806

ph. 417-865-6100

fax 417-865-6102

Architecture, Engineering, Interior Design, Planning & Development

Your Vision.  Our Focus.


-----Original Message-----
From: Jim Wilson [mailto:wilsonengineers(--nospam--at)]
Tuesday, January 04, 2005 8:44 AM
To: seaint(--nospam--at)
Subject: Thickened slab detail


Is there a "correct" slope to the underside of a slab

where it changes thickness such as at a thickened edge

or under a wall?  It's commonly drawn and constructed

as steep as 1:1 or 2:1.  PCA Slab design guide has an

exerpt from the Army tech manual showing it at 5:1

under a bearing wall.  I would guess that the steeper

the angle, the more it would increase the friction

value for the subgrade drag equation.  But maybe its



On a related note, is there a specific purpose for

adding 1 or 2 longitudinal bars at a thickened slab

section?  Is it one of those details for good measure,

or has it been proven necessary?


Thanks in advance,


Jim Wilson, PE

Stroudsburg, PA





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