Quote:
Originally Posted by natelox
Another advantange is the thickness of floors. Steel is hierarchical: Decking rests on joists, joists on beams, beams on girders. This can make for a very thick floor. Concrete only requires 8" in which all electrical and mechanical can be run. Over a whole building, a developer may be able to fit another floor in given the height limit.
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Yes and no. All floor systems are hierarchical as you noted, but they do not normally rest upon one another. Instead we frame them into one another so that T/Steel is a common elevation at each floor. The hierarchy applies more to the load transfer sequence, as in: slab/sheathing - purlin/girt - joist - beam - girder - column - footing.
In both systems (str'l steel and RC) we usually find the best economy when the Span (btw. columns or walls) to Depth (of floor) ratio is ~25, although anything between 20 and 30 is reasonable.
One serious drawback to long span steel floors in particular is their tendency to "bounce" or develop unwanted dynamic characteristics. RC slabs, waffle slabs, and P/T slabs can span as long (or longer) than steel and don't bounce as much (again they have better damping), but it does cost to use these construction techniques.