×
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

Reinforcement around openings in two-way RC slab

Reinforcement around openings in two-way RC slab

Reinforcement around openings in two-way RC slab

(OP)
I've been having problems finding the arrangement of how reinforcement should be placed in an opening. I have been looking at the ACI 318-08, section 13.4 and I am aware that the same amount of reinforcement within the opening is suppose to be split and placed on the both sides of that opening. My real question is how close to the opening do you install the replaced/redistributed reinforcement? I have also found information on adding additional bars diagonally across the corners to prevent cracking, but I'm not sure how far from the corner these bars should be placed or how long these bars should be.

RE: Reinforcement around openings in two-way RC slab

Quote (NKOTB)

My real question is how close to the opening do you install the replaced/redistributed reinforcement?

As close as practical, without violating code spacing limits and causing congestion problems. I'll typically put the first bar 50 mm in from the edge and specify them at 3" o/c inwards after that. The replacement bars essentially need to form a non-contact lap with the cut bars. The farther away from the edge you place your replacement bars, the further into the slab they'll need to project. For large openings, this can be cumbesome.

Quote (NKOTB)

I have also found information on adding additional bars diagonally across the corners to prevent cracking, but I'm not sure how far from the corner these bars should be placed or how long these bars should be.

Same answer as above for locating the bars. The length should be at least a tension development length on either side of the anticpated 45 deg crack emanating from the corner. Typically I see these called out as two #5 x 4'-0" top and bottom.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Reinforcement around openings in two-way RC slab

Funny, I also typically space them at 3" o.c., for exactly the same reasons (forming a non-contact lap splice).

I have the exact same advice about corner bars. Great minds think alike? ;)

Maine Professional and Structural Engineer.

RE: Reinforcement around openings in two-way RC slab

As an additional thought; if you want to actually run the numbers on the reinforcement required around an opening you'll likely find that much less rebar is required. This can be tedious and you'll end up costing someone more in billable hours than in rebar but for repetitive openings it can save some steel.

Maine Professional and Structural Engineer.

RE: Reinforcement around openings in two-way RC slab

Quote (TME)

Great minds think alike?

If I didn't steel stuff from others, I wouldn't have much at all.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Reinforcement around openings in two-way RC slab

Quote (KootK)

If I didn't steel stuff from others, I wouldn't have much at all.

...and if you could spell you would not be an engineer smile

RE: Reinforcement around openings in two-way RC slab

Maine Professional and Structural Engineer.

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