Non metallic rebar
Non metallic rebar
(OP)
Just curious. Do any of you use non-metallic rebar for reinforced concrete? Seems like a good idea to avoid corrosion and failure. What kind and does it work? Thanks.
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RE: Non metallic rebar
I'm not sure if there are other types of accepted non-metallic reinforcing available.
RE: Non metallic rebar
It's not too hard to design with but definitely takes a little more work than rebar and there is still some research needed to fill the gaps. Finding contractors with experience with it will also be tricky, though mostly it's not going to be too much different for them to work with. Biggest lesson learned for us is GFRP must be pre-bent when formed at the manufacturer. Thus, if the contractor mis-orders some bars the wrong shape or size then it's a multi-week lead time to get new bars made.
Fire and high temperature will cause serviceability failures (sagging and cracking) but structural performance can be maintained similar to regular rebar in terms of life-safety fire ratings. Essentially, fire = damaged structure even for small fires.
Working with the bar is annoying for the contractor. Stuff itches like crazy and they'll probably add a lot of cost due to the complexity, risk, non-standard construction, and generally larger amount of work required for GFRP.
Don't expect to save much on rebar area, even with the higher strengths. Various penalties always seem to kick out these gains when you run the numbers. Add in the dowel shear and compression issues and you might even need more rebar than with just the plain black bar.
All that said and all things equal I still prefer GFRP to other options like MMFX, epoxy coated, and stainless steel when you consider all the pros and cons. I'd use it more but it's hard to find customers who want the added durability or need something more than a 75 year structure.
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: Non metallic rebar
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: Non metallic rebar
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Non metallic rebar
Can you elaborate? I'd never considered this. What are the no go applications? Dowel action in shear friction scenarios?
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Non metallic rebar
I believe this is the majority of the concern. Essentially my understanding is shearing and compression of the bars is not fully understood. It has some strength in both but the limit states are not fully understood last I checked.
Not just deflection but also crack control and anything else involving the modulus of elasticity. We had a project recently involving prestressed bridge panels where the bursting stress resistant reinforcement was replaced with GFRP. The design engineer (not me) just did a 1:1 replacement using the AASHTO provisions and we had some panels develop large cracks along the strands due to the bursting stress opening up the concrete before the GFRP got effectively engaged.
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: Non metallic rebar
This is also why the FRP used in reinforcing scenarios has multiple layers with the strands in different orientations depending on the application.
I don't actually have further information directly available to me. I'd have to dig up some info that was provided to me by a prof that was one of the leading researchers with the stuff.
RE: Non metallic rebar
RE: Non metallic rebar
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: Non metallic rebar
RE: Non metallic rebar
If I remember correctly (again, 2 years since I last looked) this is what ACI 440 concluded and probably where the recommendation came from.
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: Non metallic rebar
RE: Non metallic rebar
I trained under an even holier FRP deity: Bank.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Non metallic rebar
Your doing this implicitly in some measure, I believe, in both of these scenarios.
1) Vc diagonal tension shear calculation and;
2) Shear friction with smooth surfaces.
#2 is the one that would make me nervous.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Non metallic rebar
RE: Non metallic rebar
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: Non metallic rebar
Sincerely,
Bruce Wayne
RE: Non metallic rebar
http://rrc.academia.edu/RobinHutchinson
RE: Non metallic rebar
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: Non metallic rebar
RE: Non metallic rebar
Probably for the best in the long run. The transition nonsense was goofy, painful, and ineffective as education. I should have done UBC.
I feel that Batman would be designing cable stayed bridges and glass vehicular bridges without a seal. He's extra-legal / maverick. That's how Batman rolls. With a seal, he's just a sad keener like superman.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Non metallic rebar
Dik
RE: Non metallic rebar
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: Non metallic rebar
Dik