Applicability of flatslab system in Seismic Category D, E and F

[ArcTangent]

Dear All,

Is flat slab system allowed in high seismic area particularly Seismic Design Category D, E or F. The lateral frame system is RC shear wall and gravity frame system consist of flat slab and gravity columns. Is there are reference or design guides that allows flat slab system in high seismic zone?

Thank you

 

[KootK]

It is allowed per ACI code. However, nowadays we take special precautions to preclude the particular failure mode which has historically plagued these systems under conditions of high seismic drift: moment exacerbated punching shear failure at the slab to column joints. This is most commonly precluded by:

1) Estimating the seismic story drift of the building assuming that the columns do not participate in resisting that drift and;

2) Designing the column to slab connections for the angular deformation in the joint implied by #1.

ACI does describe this method in its seismic chapter but I don't recall exactly where off of the top of my head (and I'm too lazy to dig for it).

 

[lexpatrie]

Not in high seismic, I don't think so. It might be allowed with a shear wall system (combined or dual system, is that term still used?) I'd be concerned with the seismic drift wrecking the flat plate - columns due to drift, even if it's allowed. Not that I design this kind of structure routinely.

 

[KootK]

At worst, you can do flat slab + shear wall in high seismic areas by way of performance based design. Most of the skylines of the west coast of North America are flat slab buildings and, from what I can tell, this is primarily what PBD is used for these days. There's just no way in hell that the big money developers that drive these things would let high-rise floor plates switch beam and slab at the cost of lost floor space or a bunch of extraneous cladding.