Single Span Flat Slab Design with Projection

[Faizan23]

Hello!
I have to design a flat slab with a dimensions 12m x 8m with four Columns on all sides.
1m Projection is to be provided on all sides.
My question is can i use the direct design method for the Structure Design?
Direct Design requires at least 3 spans and there are some other restrictions as well.
Can i consider my projection as a span?
or should i use an equivalent frame method?

Or is there any other method for the design?

 

[r13]

Do you have walls on any two opposite sides? You can design one way slab, use FEM, or use equivalent frame method for two way design.

 

[KootK]

1) I feel that the direct design method is still applicable for this condition and I've certainly seen other engineers take that approach in the past. In some ways, a modest perimeter overhang is actually a benefit to your structural system:

a) It reduces unbalanced punching shear moment demand at the column which is often critical.

b) It often allows your to have a four sided punching shear condition at your perimeter columns rather than a three sided one.

c) It reduces first span deflections and positive moments.

2) I would not consider the overhangs as spans in the context of the direct design method. Rather, I'd just consider their effect as boundary condition on the slab edge.