Reinforcement around Slab Openings
Reinforcement around Slab Openings
(OP)
Article 13.4.2 of ACI 318 (and 350) require reinforcement to be added to the sides of an opening equal to the interupted reinforcing. Our standard detail has always called for this reinforcing to extend to the support. However, in the case of a tank wall, the support for the horizontal reinforcing can be 100 feet away. How far do I need to extend the additional reinforcing?






RE: Reinforcement around Slab Openings
RE: Reinforcement around Slab Openings
RE: Reinforcement around Slab Openings
RE: Reinforcement around Slab Openings
RE: Reinforcement around Slab Openings
It's a tank wall. The wall is 25 feet tall and 127 feet long. The openings for pipe penetrations can get up to 36 inches.
jt12-
Yes, the bars can be highly stressed due to out of plane bending. I've been thinking splice length plus hole radius, but 12.14.2.3 of ACI 318 doesn't recognize splices for bars further than 6 inches apart.
RE: Reinforcement around Slab Openings
Generally I would extend the bars a splice length past the opening. I can't understand why you would require the "interrupted" bars to continue to a support. In the case of a tank, the bars directly under the opening must contribute to the section capacity at some stage. Is continuing the bars to the support not doubling up the reinforcement at a lower section?
RE: Reinforcement around Slab Openings
Dik
RE: Reinforcement around Slab Openings
RE: Reinforcement around Slab Openings
pappyirl-
yes, continuing the discontinued bars and the additional bars to a support provides double the reinforcing away from the hole. That's what we've always called for in the past. I'm trying to eliminate the doubling up, by extending only the discontinued reinforcing to the support.
RE: Reinforcement around Slab Openings
As jt12 said, S&T requires more than twice the development length, i.e., Ld for each bar plus the component of the diagonal strut. For a straight #8 horizontal bar, it works out to 90 inches, or about twice the splice length.