Bar Bending - Minimum Distances

[briancpotter]

As part of a lifting insert, we have some #4 rebar with the following dimensions (see attached). This is a bar that has been used successfully elsewhere, but our rebar supplier is balking at it with claims of "overstressing the rebar".

Is there any guideline for minimum distances when multiple rebar bend radiuses are adjacent?

 

[TehMightyEngineer]

First off, what lifting insert setup would require this? Cranking the bar like this sets off weird alarms in my head that the bar wont take tension as well as you would like.

As for overstressing the bar, I've heard guys in our shop complain when I give them multiple bends or other tight bend geometry for larger bars. They've reported that sometimes the bar will fracture if they have to have a series of bends, one bend gets bent at more than 90°, and when trying to adjust it back the bar cracks. I suspect their real complaint is that it takes them a lot of time to make sure all the bars are bent perfectly or they end up out of place if the tails after the bend are long. For shorter bars this usually isn't as much of a concern it seems.

Assuming they nail the bend angles I doubt you would see any cracking as those bend radii meet the standard rebar bend dimensions for stirrups and tie hooks.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

http://www.americanconcrete.com