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Re: FRP - Temp Reinf.

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Your calculation looks about right and you discovered one of the main problems with using GFRP rebar; it's modulus of elasticity is 5 times less than steel.  If you absolutely have to use FRP rebar you may want to consider Carbon FRP (CFRP)  which has a MOE much closer to steel.  It will cost more than GFRP but you will probably end up using less.

Thomas Hunt, S.E.
ABS Consulting

"Seth W. Cutler" <seth(--nospam--at)>

07/17/2003 12:28 PM

Please respond to

FRP - Temp Reinf.

I'm designing a lid for a water catchment tank and I'm planning on using
GFRP for my reinforcement.  It's also being planned to be used as an
exterior basketball court.  Per ACI 440.1R-01 I need to calculate the
temp/shrinkage reinf. using eqn.  (10-1).  Ok, so I check it and it's
requiring a reinforcement ratio of 0.0066.  This requires #7 @ 12" o/c.

1.  Does this sound right for a 10" slab?  Seems excessive.

2.  Is there a maximum ratio?  I saw in someone's calcs on the web showed a
max of 0.0036 but that was for a slab on grade design.  Not sure where that
0.0036 comes from.  Didn't see a reference in ACI 318, either.

Thank's in advance!