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
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.
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
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
Maine Professional and Structural Engineer.
RE: Reinforcement around openings in two-way RC slab
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
...and if you could spell you would not be an engineer
RE: Reinforcement around openings in two-way RC slab
Maine Professional and Structural Engineer.