What means bend diameter for steel reinforcement?

[dirtsqueezer]

Alright, guys and gals,

I am asking this with full knowledge of the implications as to the obviousness of the answer. I also didn't find a forum for discussing the 97 UBC, and I realize this may be out of place.
What the heck is meant by bar diameter sec. 1907.2.1? The best information I could find is that it describes "the measurement along the inside of the bend". Is this simply to describe the distance from the start of the bend from the main bar to the end of the bend where the extention begins? It seems also that this would only apply to a 180 degree hook, as the 90 degree hook would be in the shape of a half square instead of a half circle. This would leave even less room for reason when inspecting a the middle ground of a 135 degree hook.
What the heck? It seems like a lot of hassle for code that's practically impossible to enforce! ("Excuse me, Sir, but the inside diameter of your 90 degree hook is 1/8 of an inch too tight. You can't re-bend it because this would structurally compromise the steel in the bend, but you can replace the whole thing! Oh and by the way, please don't slash my tires before I go...&quot
Just a little nag to get me through some downtime.

 

[Ingenuity]

It is the diameter of the steel pin used in the bending/fabrication of the bent rebar. eg if a bend must be 6 x rebar diameter then for a #5, that would be 6x0.5"=3" diameter pin be used to achieve the bend.

If the bend diameter is too small, the rebar will not be ductile and will fail at a signbificantly lesser load than its yeild.

I have seen #6 rebar bent around about 3 bar diameter pin and you can fracture the rebar at the bend by hand - the bar had a 24" extension from the 90 deg bend but easily fractured via human effort.

See CRSI "Manual of Standard Practice" for addit info.

HTH

 

[dirtsqueezer]

Outstanding. So it applies to the method of bend. Continuing the logic, this would be a good thing to look for in inspection because it may be an indicator of weak bar. Thanks very much for the reply.