Straight bars in tension, development length reduction
Straight bars in tension, development length reduction
(OP)
By ACI 12.2.5, you can reduce the development length of rebar when there is excess reinforcing provided for flexural members. You can also do this for hooked bars in tension by 12.5.3d. But what about straight bars in direct tension, for example when transferring uplift from anchor rods to a concrete pedestal? By ACI, if the development length is less than required for fy, does that mean the straight bars are completely ineffective?






RE: Straight bars in tension, development length reduction
I would still hate to have to try to pull a #3 bar out of concrete when it was embedded only four inches.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Straight bars in tension, development length reduction
RE: Straight bars in tension, development length reduction
I'm not sure I understand your question there. Can you elaborate?
If you are developing straight bars from a pedestal into a footing, the length of development could be reduced if you provide more rebar than is necessary for the strength calculation (As(req'd) / As(provided)). But I think you still have to provide a minimum development of 12" right?
So if you provided twice the rebar you needed, you would only need half the development length of that particular bar size.
RE: Straight bars in tension, development length reduction
RE: Straight bars in tension, development length reduction
RE: Straight bars in tension, development length reduction
RE: Straight bars in tension, development length reduction
It appears you are trying to get away from Appendix D and using reinforcing bars to transfer uplift forces into the pedestal. If you look in Appendix D, their suggestion is that you use a U bar (see page ACI 318-08 page 426).
I am attaching a couple of documents for similar calculations.
RE: Straight bars in tension, development length reduction
RE: Straight bars in tension, development length reduction
RE: Straight bars in tension, development length reduction
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Straight bars in tension, development length reduction
RE: Straight bars in tension, development length reduction
It seems to me that the principle of As(req'd) / As(prov) would be the same other than perhaps there is concern that with a flexural member there might be built-in redundancies while in a pure tension member you might be non-redundant and thus taking liberties with a full development would be undesirable.
RE: Straight bars in tension, development length reduction
As a side note, for shear friction it is also required to have full development on either side of the crack.