Conduit in Composite Slab

[ship4885]

On a job I am working on, the electrical eng wants to run conduit through our composite slab. It is 3" deck with 4 1/4" concrete over the deck with 3/4" DIA. 6" long studs. In areas where conduit runs, he shows each flute with 2 1" DIA conduits running parallel and on top of each rib anothe 2 1" DIA conduit. This seems unacceptable to me, but what is general consensus? Are there any papers written on this or code recommendations on spacing, placement and maximum daiameter conduits??? I looked through ACI but didn't see anything regarding conduits. Thanks

 

[JAE]

This is a type of note we use on our designs:

MECHANICAL AND ELECTRICAL CONDUIT IN SUSPENDED SLABS SHALL RUN UNDER TOP LAYER OF SLAB REINFORCING. PROVIDE A MINIMUM OF 1 1/2" CLEAR BETWEEN CONDUITS AND BETWEEN REINFORCING AND ADJACENT CONDUITS PARALLEL TO REINFORCING. IF MAXIMUM SIZE OF CONDUIT EXCEEDS ONE THIRD OF THE SLAB DEPTH, CONTACT ENGINEER FOR ADDITIONAL FRAMING OR REINFORCING.

 

[strguy11]

Check the standard specs and commentary from the deck manufacturer. I know the Vulcraft and New Millenium information has it, but i belive it is part of the standard SDI spec, so it should cover most all manufacturers. It specifies the maximum condiut size and spacing.

Where i think this is a problem, is that the condiuts will need to converge at an electrical room, so you may get many condiuts spaced very close together.

 

[structuresguy]

we never allow them to run continuously in the flutes. our reasoning being that the concrete needs to interlock with the deck in the flutes for composite action, and we don't want to interupt that. We allow them to go down into a flute only to cross conduits. We then require 6" minimum being conduits. We also require that the maximum size conduit OD be not more then 1/3 the slab thickness above the deck, so in your case that would be 1.4" max OD. We also require all conduit in slabs to be steel, and tied securely to the deck.

Our requirements are pretty stringent. A lot of times, the installer will have PVC priced, and won't want to bother, so they install under the deck (which is our preference). Using these requirements, we have not had any issues with our slabs related to embedded conduits.