Epoxying #4 rebar dowels


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Old 12-30-05, 02:56 PM
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Epoxying #4 rebar dowels

I'm in a hurricane zone and need to design for uplift and shear; the tensile uplift loads will end up being about 60lbs per dowel, and shear about 500lb maximum. I've got some Simpson epoxy that, according to their website, will hold 16,000lbs if I epoxy #4 rebar into my footer 4". It's expensive stuff though- do I have to epoxy it in 4" or can I just epoxy in the bottom 1" for 4,000lbs of tensile strength?
 
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Old 12-30-05, 06:22 PM
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Epoxying #4 rebar dowels

Probably good for the uplift. Elmer's might even work for an uplift as small as that.

Shear is a different problem. You will be expecting a very small area of expoxy to take the extra load from the 3" un-epoxyed length (500 pounds at 3" away - not good). Theoretically, you would probably get some crushing at the top of the 1" grout.

Just fill the hole. It probably isn't oversized that much.

Dick
 
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Old 12-30-05, 06:50 PM
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Thanks, Dick. Why would the epoxy come into play at all for shear though; wouldn't the dowel loose in the hole handle shear just as well as one epoxied in place?
 
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Old 12-30-05, 07:33 PM
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Epoxying #4 rebar dowels

A loose dowel will permit horizontal movement before it picks up any load.

If you have 1" in epoxy and 3" up to the level of the concrete, the shear resistance of the cantilevered bolt depends on the deflection or bending of the bolt.

Also because of the triangular stress distribution (over only 1"), the load on the epoxy due to the moment (3" x 500#) is magnified and is many times that if the bolt was properly surrounded to the top of the concrete.

You will not find any tables on something like this, because material suppliers do not want to be responsible for every possible application.

Dick
 
 

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