how to design composite slab also minizing the cost along the way?

Answer 1

This is really a loaded question. I assume that by composite slab you mean concrete on metal deck supported by steel beams with steel studs on the top flange. (Composite can mean other systems in other countries.)

Typically, you want to use the lightest concrete slab that you can. However, lightweight concrete typically costs more than regular weight and is difficult to get in some locations. You also need to consider the fire rating you need to achieve for the floor - that will typically require a minimum concrete thickness.

Your best bet is to take the time at the beginning of design to design a typical bay for your building using several different floor slabs - 3" deck vs 1.5" deck, etc. Then figure the total steel weight and total concrete weight for each design option. Assign a money value for steel and concrete each (you can get a typical number for this from a Sweet's catalog) and price that typical bay. It's worth the extra effort up front.

Answer 2

If you mean by composite slab a reinforced concrete slab, you need to know the dimensions first, then to select the type (flat, ribbed, continous or others). then you can go to apply some structural formulas to find the economical thickness of concrete and reinforcement needed.

Answer 3

Samantha is right. Lots of options to consider. One option is to "rib" the concrete. If you look at the underside of some concrete floors, they will look like they were poured over spaced blocks. This provides "beams" of concrete running in 2 directions to strengthen the floor without the cost and weight of a thicker flat pour.