×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Shear reinforcement - U-stirrups

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

Cl 8.2.12.4(d); "fitment cogs shall not be used when the anchorage of the fitment is solely in the concrete cover of the beam."

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 read Cl 8.2.12.4 as prohibiting double U's.  They are not commonly used because the required lap length can govern the beam depth.

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

After posting, I looked at the Commentary, which says that lapping shear fitments "should be avoided".  Don't know why they didn't just say they the practice is prohibited.

RE: Shear reinforcement - U-stirrups

I agree it doesn't seem to be directly applicable to double U's. I had the advantage of learning it at a seminar introducing AS3600:2001.

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

Check that 90 degree hooks are okay, I think this is the reason why they dont work.

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 hook I meant a 180 deg hook.
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

(OP)
Thanks all, but especially hokie66. I checked the commentary and it says "Lapping fitments in the manner illustrated in Figure C8.2.12.4 should be avoided."

ACI 318M does allow lapping in this fashion but requires lap lengths be increased by 30%.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources