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Re: Crack control for swimming pool.

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There are a couple of tricks you can do with this.  The first is to check your cross section as if it was plain concrete.  If your stresses are low then there is a chance that fb < M/S < 5 sqrt fc' and therefore your concrete should not crack.  The next thing is to calculate the "actual" unfactored steel stress and not just use the default 0.6fy.  Another trick is to reference ACI 350, "Environmental Engineering for Concrete Structures", which has a provision that states you only need to consider the first two inches of cover for the purpose of calculating "z".  Hope this gives you some ideas.

Thomas Hunt, S.E.
ABS Consulting

"Bill Marczewski" <bmarczewski(--nospam--at)>

02/18/2003 11:45 AM
Please respond to seaint

        To:        "SEOC Engineering Forum (E-mail)" <seaint(--nospam--at)>
        Subject:        Crack control for swimming pool.

We are designing a swimming pool that has grade beams and one-way slabs spanning between the grade beams.  Strength analysis does not require a lot of reinforcing, however meeting the crack control requirements is becoming a tedious iterative process, only to find out we can't achieve the appropriate z-value.  We need a z-value of 43 corresponding to crack width,w = 0.004 inch (water retaining structures).  We need 3" of clear cover as we are pouring the slab on grade, then expect soil settlement on the order of 12 inches per the geotechnical investigation.  I have tried a lot of different bar sizes, and spacings.  Has anybody else been in a similar situation?  Thanks.

Bill S. Marczewski, P.E.
Peratrovich, Nottingham & Drage, Inc.
503-325-1250 Main; 503-325-9789 Fax