Shear reinforcement - U-stirrups
Shear reinforcement - U-stirrups
(OP)
Is there any problem with providing shear reinf by having double U stirrups lapping on the sides. I can't find anything specific in AS3600 but did find something in ACI 318M 12.13.5.





RE: Shear reinforcement - U-stirrups
This rules out double U's due to the location of the anchorage.
Presumably ACI 318M specifically rules out double U's?
RE: Shear reinforcement - U-stirrups
I don't like double U's because the top U is in practice often not well tied to the other bars, meaning that it can easily be dislodged during placement, causing a cover problem.
I never have understood subparagragh (d), as anchorage can never be in the concrete cover, as concrete cover is outside the reinforcement. But whatever it means, this is for cogs, not laps.
RE: Shear reinforcement - U-stirrups
RE: Shear reinforcement - U-stirrups
I believe it is still OK to use open topped ligs where the ends are hooked around the top corner bars. The top can then be closed with a U-bar.
RE: Shear reinforcement - U-stirrups
I wouldnt use then anyhow as it is a poor detail.
I would avoid these if at all possible with an open top lig hooks as per apsix's comment (unless there is torsion/seismic, in which case you need fully closed ties).
csd
RE: Shear reinforcement - U-stirrups
By Cl.13.1.2.5 a hook has at least a 135 deg bend. Any less and they are called cogs.
RE: Shear reinforcement - U-stirrups
ACI 318M does allow lapping in this fashion but requires lap lengths be increased by 30%.