When to NOT Use Composite Steel

[KootK]

Whenever I go through a costing exercise for a concrete deck over steel framing system (joists / beams), it seems as though composite steel beams always come out on top. The system is shallower, the tonnage is reduced, vibration characteristics are improved... Fire protection issues seem to push the pendulum even further in the direction of composite steel beams.

So my question is this: should ALL steel beams be composite beams when there's a suitable topping slab above? Is there any simple span deck slab / beam framing situation in which it would make more sense to use non-composite steel framing?

Thanks.

 

[WillisV]

SteveGregory - I still generally put about a stud/ft on a moment frame beam even though I design it as noncomposite in order to transfer the collector force into the frame.

 

[dik]

Sometimes when smaller composite purlins are fastened to girders the studs on the purlins are field installed by fusing through the deck and the studs on the girders are shop applied.

Dik