One way reinforced concrete slab on secondary steel W beams

[smcp4blo]

Hello everyone,

I would appreciate some comments about the next criteria: I have a one way reinforced concrete slab supported over secondary W steel beams. The primary beams are also W steel beams and my columns are HSS. In other words I have a steel building with a concrete slab in one direction. We place the shear connectors only to resist the seismic force per floor and obviously to attach the slab with the beams, since if we eliminate the shear connectors my systems would be separated. However, this isn't designed as composite system or composite beams.

My question follow as this: Can I consider this is a rigid diaphragm floor or not?

Thank you

 

[jdgengineer]

You are talking about different things. Whether or not you can consider the diaphragm as a rigid diaphragm or not is related to the anticipated diaphragm deflection versus your vertical-lateral-force resisting system deflections.

See ASCE 7-05 12.3

Typically, you would fall under the 12.3.1.2. which would allow you to analyze as rigid, but it depends on your layout.

 

[dik]

You should be able to treat the floor as a diaphragm. If you have shear connectors anyway, why not consider composite design for the steel beams; there could be a significant saving.

Dik

 

[structSU10]

One word of caution, specifically from AISC, is if you designed just for the beams to be collectors and not composite, it will not only utilize the shear studs for the lateral load - it will act as a composite shape first. They recommend a composite design with the addition of the drag strut load to determine the shear studs required. There is a book called 'Guide to the design of Diaphragms, Chords, and Collectors' That may give you more general information that could be helpful.