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RE: Joints in concrete floor slab on bar joists

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Control joints are normally not used in an elevated slabs.


Slab section may check as an unreinforced section per ACI design provisions.


If slab doesn’t check for span, consider installing additional sub-framing to reduce slab span in lieu of demolishing concrete. External reinforcement placed on slab soffit may also work.


D. Matthew Stuart, P.E., S.E.


Senior Project Manager

Schoor DePalma Engineers and Consultants

200 State Highway Nine

Manalapan, NJ 07726

732-577-9000 (Ext. 1283)

732-431-9428 (Fax)

908-309-8657 (Cell)



-----Original Message-----
From: DSmith7367(--nospam--at) [mailto:DSmith7367(--nospam--at)]
Sent: Thursday, July 08, 2004 3:35 PM
To: seaint(--nospam--at)
Subject: Joints in concrete floor slab on bar joists


I have run into an interesting problem.  Hopefully, one of our list members will have a comment.


I am investigating a cracked concrete mezzanine floor.  The floor is to be used for parts storage but is presently very lightly loaded.  The floor is 44' x 51' and has cracked badly throughout into sections approximately 16' x 18'.


It turns out that the architect specified 1.5" composite deck and a total depth of 3 inches.  No reinforcement was specified.  The contractor, without notifying anyone, substituted 0.6" x 28 ga slabform.  No reinforcement was provided.  No joints were provided in the floor.


As I started looking into the problem, I realized that I could not find a specific reference recommending  the use or nonuse of joints in such a floor system.  I would appreciate some help on this.


Since there is essentially no theoretical floor strength, it appears that the entire floor may have to be removed and replaced with reinforcing.  There are occupied offices directly under this floor.


Any comments?



Dave Smith