# Flat Slab Excel

#### Short Description

Excel Sheet for Civil Engineers for Designing FLAT SLAB...

#### Description

Mu = Vu = Yr = C1 = C2= d= a= b= c= Ac = J/c =

87.9 50 0.4 24 24 6.75 27.375 30.75 8.764803 577.125 5634.237

Vu = Vu/Ac +Yr x Mn / ( J/c ) =

Mu = Vu = Yr = C1 = C2= d= a= b= c= c' = a - c = Ac = J/c' =(J/c)(c/c') =

161.5214

87.9 50 0.4 18 24 6.75 21.375 30.75 6.216199 15.1588 496.125 2310.443

Vu = Vu/Ac -Yr x Mn / ( J/c' ) =

-81.8333

FLAT SLAB DATA L1 = L2 = C1 = C2 = Ln = fc' = fy =

20.5 16 18 18 19 3,000 50,000

ft. ft. in. in. ft. psi psi

DESIGN Preliminary design of slab thickness "h" a) Control of deflection h = Ln / 33 = 7.6 in. This is larger than the 5 in. minimum specified for slabs without drop panels. Therefore use a slab thickness h = 9 in. Average effective depth = d = h - 0.75 - 1/2" bar = 7.75 in. b) Shear strength of slab Factored dead load = wd = Factored live load = wl = Total factored load = wu =

(h*12.5+FF+SD)*1.4 = LL*1.7 =

312.9 psf 102 psf 414.9 psf

Investigation for wide beam action on 12" wide strip at "d" distance from face of support L1/2 - C1/2 - d = 8.854167 ft. Vu = 3.67 kip Vc = 2* fc' *bw*d = 10.19 kip  Vc =0.85*Vc= 8.66 kip 3.67 is less than 8.66 OK Shear strength in two way action at d/2 distance around a support 4*(C1+d/2+d/2) = bo = 103 in. 2 Vu = wu*[L1*L2 - ((C1+d/2+d/2)/12) ] = 134.18 kip Vc = 4* fc' *bo*d = 174.89 kip  Vc =0.85*Vc= 148.65 kip 134.18 is less than 148.65 OK

60 91 20

Factored moments in slab Total factored moment per span 2 Mo = wu*L2*Ln / 8

=

299.6 k-ft.

Distribution of the total factored moment Mo per span into negative and positive moments

TOTAL MOMENT ( k-ft.)

COLUMN STRIP MOMENT ( k-ft )

MIDDLE STRIP MOMENT ( k-ft )

End span: Exterior Negative Positive Interior Negative

0.26*Mo= 0.52*Mo= 0.70*Mo=

77.9 0.26*Mo= 155.8 0.31*Mo= 209.7 0.53*Mo=

77.9 92.9 158.8

0.21*Mo= 0.17*Mo=

62.9 50.9

Interior span: Positive Negative

0.35*Mo= 0.65*Mo=

104.8 0.21*Mo= 194.7 0.49*Mo=

62.9 146.8

0.14*Mo= 0.16*Mo=

41.9 47.9

SPAN LOCATION

Mu

0

Spacing of #12 bar provided

b

d

As=Mu/3.9d

As (min.))

77.9 92.9 158.8

120 120 120

6.75 6.75 6.75

2.959 3.528 6.031

1.944 1.944 1.944

10" 8"

0 62.9 50.9

120 120 120

6.75 6.75 6.75

0.000 2.390 1.934

1.944 1.944 1.944

10" 10" 10"

146.8 62.9

120 120

6.75 6.75

5.576 2.390

1.944 1.944

10"

47.9 41.9

120 120

6.75 6.75

1.821 1.593

1.944 1.944

10" 10"

END SPAN COLUMN Exterior Negative STRIP Positive Interior Negative MIDDLE STRIP

Exterior Negative Positive Interior Negative

INTERIOR SPAN COLUMN Interior Negative STRIP Positive . MIDDLE STRIP

Interior Negative Positive

Transfer of gravity load shear and moment at exterior column.

a) Factored shear force transfer at exterior column: Vu = wu*L1*L2/2 = 68.0436 kip b) Unbalanced moment transfer at exterior column:

t f x Mu =

0.6*Mu =

46.73 k-ft.

unbalanced moment transfer section = t = C1+2(1.5*h) = 45 in. Above unbalanced moment must be transferred within the effective width of 45 in. Add 2 # 16 bars additional over column. Check moment strength for 4 # 12 + 2 # 16 bars with in 45 in. slab width. 2 For 4 # 12 + 2 # 16 bars: As = 1.324 in . w= As*fy/fc' *t*d = Mn / fc'*b*d2 = From table 9-2 0.0879 2 Mn = w*fc'*b*d = 59.39 k-ft  Mn = 0.9 x Mn = 53.45 k-ft

0.063

>

46.73 k-ft. Safe

psf psf psf

Spacing of #16 bar provided

8"

8"