When to NOT Use Composite Steel
When to NOT Use Composite Steel
(OP)
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.
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.






RE: When to NOT Use Composite Steel
RE: When to NOT Use Composite Steel
We've been contemplating joists for this application too. I'm concerned about the vibration characterisics however.
RE: When to NOT Use Composite Steel
RE: When to NOT Use Composite Steel
I am interested to hear the results of this "poll".
RE: When to NOT Use Composite Steel
RE: When to NOT Use Composite Steel
RE: When to NOT Use Composite Steel
Yes, 1,000 studs is a good round number to consider when deciding on whether or use composite steel or not.
I have had converstations with one of the owners of a local steel erection company (who also used to be a practicing structural engineer) and its his opinion, through looking at the costs of raw material, fabrication, and erection, that somewhere between 750 and 1,000 studs is where the material saving of using composite beams begins to overcome the cost of setting up the stud welding machine and calibrating it at each job site. I forget what he says he figures into a bid for setting up and calibrating the welder, but I do remember it was a surprisingly large number. More than a nominal amount.
RE: When to NOT Use Composite Steel
RE: When to NOT Use Composite Steel
RE: When to NOT Use Composite Steel
What I look for is simplicity, whatever system has the simplest erection procedure is generally the one I choose as up to two thirds of the cost is in the non material costs.
There are a few areas where I would definately NOT use composite beams - those areas where propping is difficult and you would need to use unpropped beams and those buildings where it is very likely that additional openings will be required.
RE: When to NOT Use Composite Steel
That the case appears in practice may depend upon the case, but is a feasible one.
RE: When to NOT Use Composite Steel
We have typically used composite beam construction for fire rated commercial buildings. For unrated commercial buildings, we have gone with open web joists.
RE: When to NOT Use Composite Steel
Why aren'e composite studs welded to their respective beams in the shop. Tripping hazzard for workmen during the transportation / erection process?
RE: When to NOT Use Composite Steel
For projects without metal deck, how can an ironworker walk along the top of the beam without tripping? "Cooning" would also be a problem!
RE: When to NOT Use Composite Steel
RE: When to NOT Use Composite Steel
RE: When to NOT Use Composite Steel
Hg
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RE: When to NOT Use Composite Steel
RE: When to NOT Use Composite Steel
RE: When to NOT Use Composite Steel
RE: When to NOT Use Composite Steel
Dik