Development Length

[NeoMoose]

CSA A23.3 only considers deformed bars when calculating development length. What factor or equation do you use if the bars are threaded? or is it normal practise to assume that threaded bar are the equivalent to deformed bars?

 

[sdz]

There is no gaurentee that the development length will be the same; it probably won't be.
One option is to thread the end of a reinforcing bar and either use it directly or connect to threaded rod with a hexagonal joiner.
You will usually need to thread the bar a size smaller than the nominal bar diameter and you will need to check with the bar manufacturer what affect it will have on strength and ductility.

 

[Ron]

Put a nut and washer on the embedded end. Development is then a function of concrete strength at the failure cone.

 

[sdz]

Ron's suggestion is also a good one. Why didn't I think to say that?

 

[TXStructural]

Threaded rod DOES NOT develop in concrete like deformed bar does. The depth and spacing of deformations is critical to bond and development. Refer to ASTM A615 or A706 (or CSA G30.18, I think) for the requirements.

Use of a headed anchor or nut and washer on the rod (as suggested above) should comply with ACI 318 App D, or equivalent. Where the anchorage has significant embedment and/or confinement by reinforcement, look at ACI 318 requirements for headed bars, since App D doesn't really do justice to supplemental reinforcement and confinement.

 

[slickdeals]

@TX:
I am having a similar situation with a threaded rod in tension, 28" deep with a nut/washer. The edge distance is 14". What requirements for headed bars are you referring to?

 

[Duwe6]

Skip the headed bar, and the standard washer.

If using a washer, it needs to be a plate washer stiff enough to transfer the anchor tension into the concrete, something like 2.5" x 2.5" x 5/16". Standard washers are too 'limp'. Now, the bottom nut will also need to be 'locked' in place. Staking HARD in 2-3 places works, and tack-welding it twice is best. Too much work/$$ for me.

Just put an "L" or "J" bend in your anchors. Done.