development of threaded rod 1

[bootsy]

Does anybody know of a good reference for determining the development length of threaded rod in concrete? Is it simply a factor of the development of rebar in concrete?

 

[JAE]

I would say that would be a starting point - with all the threads, I can't imagine it would be more than a rebar - the bond between the cement matrix and the rod would be great or greater than that of the rebar.

 

[Bbird]

I have come across threaded bars in the design. The threaded bars were there for other reasons as I cannot imagine an engineer in his/her right mind would want to thread a bar to save in the development length. I would just specify the development length of unthreaded bar even if it is threaded. In practice the threaded bar will have a superior grip and should never develop a bond failure. Being marginally smaller than the un-threaded equivalent (due to the thread) it actually needs a shorter development length too.

 

[azcats]

My gut feel tells me that threaded rod would need more embeddment than rebar. Say that each "V" in the thread is a little bit of concrete to be sheared off. The depressions between the deformations in a rebar are much further apart and then give much more surface to be sheared. Also, I beleive the deformations are much higher/deeper than those from a threaded rod.

If it were me, I'd put some nuts and a washer or a steel plate at the end of the bar and design it as a regular anchor.

For some reason I don't think embedding a straight bar is the way to go.