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RE: RFP Reinforcing

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I just used GFRP on a mat foundation under some equipment that was particularly sensitive to magnetic fields.  The problem we ran into was that since since the mod of E is lower you wind up using a lot more bar that what you may be used to seeing.  Thomas alluded to some design differences - one is that it is suggested that over-reinforcing the member actually leads to a more "ductile" member than conventionally using a minimum amount of reinf (idea is that you would see concrete crushing before failure.  I had a 14" thick mat with the equivalent of #8 bars at about 6" on center each way, top and bottom.  The contractor had a fit about it until he realized they were so quick and easy to install.  They were able to vibrate without too much problem.  Another reason for so much reinforcing is to control crack widths - especially in overhead conditions.
If I had to do it over again - I'd look into the different types of fibers listed in ACI 440.  You should talk to Hughes Brothers - they manufacture GFRP rods and are extremely helpful.  They have a consultant that may be able to look at a lot of things for you.  Look at  for some good information - it looks like they updated it within the last couple of months.
-----Original Message-----
From: THunt(--nospam--at) [mailto:THunt(--nospam--at)]
Sent: Tuesday, June 17, 2003 1:41 PM
To: seaint(--nospam--at)
Subject: Re: RFP Reinforcing


I am guessing you mean "FRP" reinforcing (i.e. plastic rebar).  If this is the case then you can find detailed information in ACI 440R-96 (Reapproved 2002) and ACI 440.1R-01.

On the design side, the issues are that the strengths are very high but with little ductility.  The stress-strain curves are very straight then, boom, it breaks.  This requires a different design proceed than we are normally use to with steel reinforcements.  The other design issue is that these products normally have a very low modulus of elasticity compared to steel so deflection can be a real problem for elevated structures.  The coefficient of thermal expansion between FRP and concrete can be another issue.

On the installation side, the big problem is that this stuff can not be field bent.  Typically you have straight bars and put them together with pre-manufactured "L" or corner bars.  This can make certain applications very congested.

Thomas Hunt, S.E.
ABS Consulting


06/17/2003 09:46 AM
Please respond to seaint

        To:        seaint(--nospam--at)
        Subject:        RFP Reinforcing

Has anyone used RFP bars for reinforced concrete members? If so, any lessons learned that can be passed along(i.e., cost, is bonding a problem, etc.)?

Charlei Canitz