What the thickest concrete floors/ceiling truss florring system?

[GWHH]

What the thickest concrete floors/ceiling you have seen when using the standard floor truss system, with concrete over metal decking and I beam construction?

Never seen over 6 inch myself. Just curious if anyone else have seen thicker.

[dchan]

Theoretically speaking, the concrete doesn't need to be that thick if we're only talking about required yield strength. That's because the floor truss system is already carrying the loads that the floor will be carrying (dead loads and live loads).

Of course, the 'bounciness' of the floor is another concern, one that has to do with the stiffness of the overall floor structure (the floor truss system, metal deck, and concrete floor combined together). The truss system alone would likely be a bit too lightweight to provide the proper stiffness that a floor needs. That's probably the reason why concrete is used - it provides enough material to increase the overall modulus (stiffness) of the whole floor system without being too expensive (as adding steel would be).

[mthd]

you wouldn't normally see an extremely heavy slab used in conjunction with a metal deck and trusses or w section beams.

more commonly, very heavy concrete slabs (up to around 16") are used in one or two-way all-concrete systems where loads are very very heavy... e.g. plazas with paving, soil, fire truck loads, standing water, pools, heavy equipment areas in factories, etc etc. these are usually formed with plywood or steel forming, with or without beams depending on the spans, and the finished product is just concrete.

for the original question, i have never seen more than about 6" of concrete including the max depth of the deck itself when using that type of system.

[GWHH]

i know 6 inches is the max. but i always get some old timer or someone who worked out the USA saying they have done or seen it poured with more than six!

[JohnMarko]

Originally Posted by GWHH

What the thickest concrete floors/ceiling you have seen when using the standard floor truss system, with concrete over metal decking and I beam construction?

Never seen over 6 inch myself. Just curious if anyone else have seen thicker.

Always use 9 inches for floor slabs with 30 foot column spacing. Usually 13 inches for the suspended ground floor in commercial construction where heavy point loads are concerned. We do tons of resort hotels/casinos and high-rise residences and commercial structures. Never ever used 6 inch thick.

Minimum of 3 1/2 inch decking withi 4 inch concrete topping. Now we're using 4 1/2 inch decking with 5 inch concrete topping. Of course, we're in the most severe hurricane and earthquake zones. And that's with 30 foot column spacing. Smalles I've ever used is 8 inch concrete slab. Only place we've used 5 or 6 inches is for the "throat" on concrete stairs.