Conduit in Beams
Conduit in Beams
(OP)
My contractor has placed 4" electrical conduit running in my grade beams in the same directions as span for a decent length at 2 locations.
At 1 location it is about 2" above the bottom steel. At the other it actually rests on the bottom steel. I am having them move the pipe higher up in the beams.
My question is is there a ACI reference on how much concrete i need above the bottom bars to transfer the load into the bars?
I am thinking 2"-3" but not sure how i would calculate or if there is a code reference.
Thanks
At 1 location it is about 2" above the bottom steel. At the other it actually rests on the bottom steel. I am having them move the pipe higher up in the beams.
My question is is there a ACI reference on how much concrete i need above the bottom bars to transfer the load into the bars?
I am thinking 2"-3" but not sure how i would calculate or if there is a code reference.
Thanks






RE: Conduit in Beams
BA
RE: Conduit in Beams
RE: Conduit in Beams
BA
RE: Conduit in Beams
I am familiar with the ACI 318 Section 6 requirements.
But i feel that applies conduit to conduit, not conduit to rebar.
The reason i am making the distinction is, what if we were talking about a 12" x 24" deep concrete beam, and we blocked out a large section in center of the beam for a penetration. If we provided say 1 1/2" cover each side of the stirrups, made sure the penetration wasnt in the compression block, and there was adequate concrete for horizontal shear transfer, i dont think we could come up with a reason why not.
I guess the question i am asking is how much concrete is required to fully bond and transfer the load into the rebar?
How would i calculate that?
Thanks you again, i value your opinions and help.
RE: Conduit in Beams
RE: Conduit in Beams
BA
RE: Conduit in Beams
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Conduit in Beams
Yes it is PVC.
I think the key to calculating it is the development length. The requirement for development length is to assure bond.
I am looking through ACI 408, i think i may find something in there.
http://www.google.com/url?sa=t&rct=j&q=min...
RE: Conduit in Beams
Thanks
Again
RE: Conduit in Beams
BA
RE: Conduit in Beams
If I got paid for every hour I worked, I'd be a wealthy man.
RE: Conduit in Beams
I used the formula for maximum bond stress in Aci 408, which came from Aci 318-63.
Then set that equal to the average bond stress at failure equation by Orangun, Jirsa, and Breen in ACI 408.
Rearanged the queation to solve for Cmin, which is "smaller of minimum concrete cover or 1/2 of
the clear spacing between bars". When rearanged there is a ld in the equation that only reduces Cmin as it goes up, so i took it as 0.
I know this isnt exact or meant to be used in this manner. But it was the best i could come up with on short notice.
If we had 6" slab with #5s in each direction in the center, i dont think we would even question if we had enough concrete for bond.