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Common rebar laps are 20 bar diameters. (10 inches for 1/2"). I usually go more.
"DaveVikingPE (Structural) 13 Feb 02 11:42Thanks, Ishvaag!I've got a CMU building that's going to be partly demolished. The building is a one-storey, multi-bay garage, with three sides closed, oneside permanently open, very simple. Basically, we're cutting the building in half and putting in a new wall. My wall design calls for connecting a new wall to the rear wall and a column at the "front" of the garage. The new wall, which is a load-bearing shear wall - of course - will be attached to the front column (a 24 x 24 CMU solid column) utilizing wall ties dowelled into the front column, connected with a high-strength epoxy chemical adhesive anchor. The manufacturer's specs, which are quite detailed, give "good numbers" were I to use a 1/2" diameter threaded rod (SAE - whatever). I, however, would prefer to use #4 rebar, Grade 60, because I can bend it and hence get the appropriate lap with the new wall's bond beams, etc. Since grade 60 rebar has "better" properties than threaded rod, I *know* I will get more positive numbers than threaded rod (i.e., tensile and shear strengths). However, I was at a loss to find shear strengths and, in desperation, threw the question to the Eng-Tips crowd. I've decided, after some more research, that I can assume a shear strength for #4 Grade 60 of around 8,000 psi.
"RiBeneke (Structural) 2 Mar 02 5:18I think that the shear strength of a steel bar in a concrete-masonary interface will seldom be the controlling factor.Under load the steel will tend to deform to an S-shape as the concrete crushes slightly at the interface. Then you will not have pure shear at the interface, and the controlling factors are concrete (or masonary) strength, and steel bending and tensile strength and also pullout strength of the steel into the concrete.Be careful that if you have changed from threaded bar to smooth bar, the pullout strength may be reduced because of less effective bond."
John: Where I am from the old guys used a lot of molten sulfur in those situations so I have been told. I have seen some cable leads anchored as such and have been there for 80+ years. Most likely a poor mans way, money was hard to come by, sulfur most likely was easy to come by and was very easy to melt and pour. I also have heard about molten lead being used. Would that be the phos/lead? But with advances in epoxies I think you could bound just about anything to anything. That is if you can get a hole bored for the anchors. A person might have to give a mining engineer a call or poke around on the internet a little.rlr
Whitlock do you recall what they used to use to embed pipe and steel into concrete and rock before the advent of epoxy. My Dad had once told me how they did it with something like phospourus/lead (?) around the post.You can usually tell if the rock is suitable when you first start drilling or go out to a surround area and take a sledge to it. Easily fractures or flakes and it will not usually work. Believe it or not a lot of rock are more pourus than you think. If you don't think so put a river rock near a flame/fire and chances are that it will break apart.
But best leave that to those like Whit and Glenn who seem to crave underground houses and mines - dirt and rust.
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