Numericals of flat slab
Design an interior panel of a flat slab with panel size 6 x 6 m supported by columns of size 500 x 500 mm. Provide suitable drop. Take live load as 4 kN/m2. Use M20 concrete and Fe 415 steel.
Thickness : Since Fe 415 steel is used and drop is provided, maximum span to thickness ratio permitted is 32
Thickness of flat slab
Provide 190 mm thickness. Let the cover be 30 mm and Overall thickness D = 220 mm
Let the drop be 50 mm. Hence at column head, d = 240 mm and D = 270 mm
Size of Drop
It should not be less than
Let us provide 3 m x 3 m drop so that the width of drop is equal to that of column head.
hence Width of column strip = width of middle strip = 3000 mm.
For the purpose of design let us take self-weight as that due to thickness at column strip
= 17.625 x 6 x 5.5
= 581.625 kN
Design Total Moment
Total negative moment = 0.65 x 400 = 260 kNm
Total positive moment = 0.35 x 400 = 140 kNm
The above moments are to be distributed into column strip and middle strip
Width of column strip = width of middle strip = 3000 mm
= 476.928 kNm
Thus Mu lim > Mu. Hence thickness selected is sufficient