Flat plate and Seismic Design Cat D 3

[Galambos]

Is it permissible to use a flate plate moment frame (no beams, no shear walls) in a IBC 2003 seismic design category d? i see that ACI318 permits it for intermediate moment frames, but makes no mention of it for special. i understand that int. requirements are still required for D, but I thought i heard at one point that this type of structure was not permitted. the building is in the southeast.

 

[prsconsultant]

Galambos:
It is not permitted to use flat slabs as the primary lateral system in SDC "D". I had asked the same question to ACI a while back and below is the official response I had received from ACI subcommitte on moment frames:

As stated in Paulay and Priestly, Seismic Design of Reinforced Concrete and Masonry Buildings, "flat slab systems supported by columns is considered to be unsuitable on its own to provide satisfactory performance under seismic actions because of excessive lateral displacements and the difficulty to providing the adequate and dependable shear transfer between columns and slabs, necessary to sustain lateral forces, in addition to gravity loads."