Composite slab thickness
Composite slab thickness
(OP)
Fellers,
When we design elevated slabs for an office bldg we always use a nominal thickness for the concrete slab such as 4", 4.5" or 5". I've seen other dwgs for floors like this where they use 5-1/4" total slab thickness. this requires the use of a bent plate on the perimeter which is much more expensive. Is there a reason to use a dimension such as this? Is it possibly because of the studs used in composite construction?
thanks
When we design elevated slabs for an office bldg we always use a nominal thickness for the concrete slab such as 4", 4.5" or 5". I've seen other dwgs for floors like this where they use 5-1/4" total slab thickness. this requires the use of a bent plate on the perimeter which is much more expensive. Is there a reason to use a dimension such as this? Is it possibly because of the studs used in composite construction?
thanks






RE: Composite slab thickness
RE: Composite slab thickness
Beam spacing is dictated by the spanning capacity of the decking under the given thickness of wet concrete. Slab thickness is then dictated by the required permanent load capacity.
I would say the 5.25" comes from someone being overzealous with refining the slab thickness.
RE: Composite slab thickness
RE: Composite slab thickness
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RE: Composite slab thickness
Regarding your bent plate comment, you need something as a pour stop around the perimenter anyway, regardless of thickness. And depending on the edge condition, something stronger than a light gage pour stop might be required. We use bent plates around the perimeter on most of our projects. Again, it's not uncommon.
RE: Composite slab thickness
RE: Composite slab thickness
Just a slight correction: unprotected deck 3 1/4" LW over deck or 4 1/2" NW over deck. The 2 1/2" NW is for protected deck (spray-on, etc.).
As JKStruct said these slab thicknesses and bent plate pour stops are not uncommon in rated construction. It is done all the time.
Tdog67: LW is more expensive than NW but it is less concrete. The selection is often a matter of what costs less. In floor construction, pour stops are not usually used to transfer diaphragm forces. Diaphragm forces usually get transfered thru headed studs into framing.
RE: Composite slab thickness