Rebar Field Fix : 2-#5 instead of 1-#6 2

[palves]

A contractor on a project of mine accidentally installed a grid of #5 bars in a foundation when he should have used #6's. So, as a field fix, he just added an extra #5 bar at each bar he had already laid down. He's getting me pictures tomorrow, but I'm assuming 2-#5 bars sitting right next to each other acting as a single bar. Does anybody see a problem with this? I've thought about it and feel like it is acceptable. Sure, if the bars are right next to each other, they both won't be 100% encased in concrete but will be pretty close. I also don't think they need to have any space in between to allow for aggregate to flow through since they're intended to act as one bar. Also, I feel good that the ductility of steel will allow the bars to yield and share the load with each, therefore acting more like a single bar with an area greater than the #6 that was originally specified. Thoughts?

 

[Ron]

Two bars side-by-side for the full length of the reinforcement will not yield the equivalent of the two bars separated such that full paste embedment is achieved. In short, what you have might not be equivalent to the required #6.

 

[ToadJones]

maybe you could have just checked the foundation for the as-built condition and see if it was adequate and charge the contractor some engineering time.
Or, just add more #5's in between what is there....if there is enough space and check that design

 

[bridgebuster]

It might work, but, you need to make sure the contractor complies with ACI 318 requirements for bundled bars.

 

[Teguci]

second what Bridgebuster said. Your development length is increased due to bundling. There is a small concern with voids under the doubled bars as well. This can be corrected with a higher slump requirement and additional vibration (probably won't happen unless you are standing there).

 

[palves]

Unfortunately I didn't find out about this until after the footing had been poured so I'm dealing with an in-place condition. But, reading through the Bundled Bars section in ACI 318-08 I feel like it might work except for provision 7.6.6.2. Because this is a footing the rebar is laid down in both directions so that stirrups aren't exactly feasible like in a concrete beam. I believe the bars run the full width of the footing so I don't need to worry about increased development lengths, and 7.6.6.5 say that I can treat both bars as a single bar. So, I feel like I'm close to getting this to work as long as I can resolve the stirrup/tie issue. Any ideas?

 

[MiketheEngineer]

Right - he SAID he put the extra bar in. Anyway to check??

Probably OK but check it. And remember, the loads we use are usually fairly conservative -- if you are within 10% - probably OK

And CHARGE the contractor. Maybe he will pay closer attention next time.

Like the old saying "It is easier to ask forgiveness then seek permission"

 

[palves]

True, he did only say he put them in there but he supposedly is sending pictures to confirm this.

As for checking it I don't feel like I need to look at my model as long as I can use the full area of 2-#5 bars to replace the #6 bar. If people think I can't use the full 100% area of the 2-#5 bars then I would need to be able to use at least 70% of the .62 in2. area to keep it within the area of a #6.

And when you say to charge him are you referring the investigative time I have spent on this so far because I will do that. I don't deal with billing, but I'll write it on my time card and my boss will decide what to do with it.

Unfortunate about the forgiveness/permission saying. While it may be easier for him I'd rather these things get addressed before the concrete sets.

 

[MiketheEngineer]

BEFORE is always BETTER - seldom happens!!

 

[ATSE]

At the risk of appearing pro-contractor, I say there is no problem with (2) #5 replacement (1) #6. Might even be better.
Bundled or spaced 2" apart. ACI 318 7.6.6 is intended for more serious conditions.
This is concrete foundation work.

 

[racookpe1978]

Yeah - But did he actually "bundle" the two #5 rods, or just "place" them next to each other - with voids almost guaranteed below and around the two rods so there is less bonding?

Even if "bundled" how did he actually tie them together: with wraps every 12 inches - or 24 inches, or 36 inches, or just at the ends? At every intersection with the other lattice bars?

Get your money back. And get a way so HIS insurance pays the structural warrantee when it breaks under load.