Stairs Design concrete ACI 318-11 12-02-14

Design of Stairs: Level 2 and above f'c Fy Phi

4000 psi 60000 psi 0.9

Enter total rise Enter guess for riser height Guess for number of stairs

4 ksi

14 ft 6.9 in 24.34783 in

168 in (Total rise/guess riser height) 11

Choose number of stairs to get riser height closer to the guess No. of Stairs 24 Riser height 7 in ok Estimate tread depth using emperical equations d1 11 in d2 10.5 in d3 10.714 in Tread depth selected 11 in Calculate horizontal run Treads= Stairs -1 Run = Treads*Depth

10'

[25-(2*Riser height)] [17.5-Riser height] [75/Riser height] 24 R @ 7''

23 253 in

For Waist Slab b height of slab d LL DL Total Wu

12 in 6 in 5 in 96 psf 144 psf 240 psf

Mu Mu/(phi*f'c*b*d2) w Rho As Use #4 at 12 o.c. For landing slab b height of slab d LL DL Total 11 treads at 11'' Stair total load Wu total Mu Mu/(phi*f'c*b*d2) w Rho As Use (4) #5

[60*1.6] [120*1.2]

0.240 ksf 4.502 k/ft 0.050 0.050 0.003335 ok 0.20 in2/LF 0.2 in2/LF

4 ft 6 in 5 in 384 plf 576 plf 960 plf

[w*f'c/Fy]

48 in

[60*b*1.6] [120*b*1.2]

slab

10.08 ft 1210 plf 2170 plf 24 ft-k 0.068 0.068 0.004533 1.09 in2 1.24 in2

[Wu*l2/8]

4

[Total Wu*10.08/2] 2.17 klf 4

ok 4

5

12''

Reinforcing Bar Area for Various Bar Spacings (in.^2/ft.)

Spacing (in.) 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 9 10 12

Bar size #3 #4 #5 #6 #7 #8 #9 #10 #11 #14

#3 0.44 0.38 0.33 0.29 0.26 0.24 0.22 0.20 0.19 0.18 0.17 0.25 0.13 0.11

#4 0.78 0.67 0.59 0.52 0.47 0.43 0.39 0.36 0.34 0.31 0.29 0.26 0.24 0.20

Area (in^2Weight (lb/ft) 0.11 0.376 0.2 0.668 0.31 1.043 0.44 1.502 0.6 2.044 0.79 2.670 1 3.400 1.27 4.303 1.56 5.313 2.25 7.650

#5 1.23 1.05 0.92 0.82 0.74 0.67 0.61 0.57 0.53 0.49 0.46 0.41 0.37 0.31

#6 1.77 1.51 1.32 1.18 1.06 0.96 0.88 0.82 0.76 0.71 0.66 0.59 0.53 0.44

Bar Size #7 2.40 2.06 1.80 1.60 1.44 1.31 1.20 1.11 1.03 0.96 0.90 0.80 0.72 0.60

#8 3.14 2.69 2.36 2.09 1.88 1.71 1.57 1.45 1.35 1.26 1.18 1.05 0.94 0.78

#9 4.00 3.43 3.00 2.67 2.40 2.18 2.00 1.85 1.71 1.60 1.50 1.33 1.20 1.00

#10 5.06 4.34 3.80 3.37 3.04 2.76 2.53 2.34 2.17 2.02 1.89 1.69 1.52 1.27

#11 6.25 5.36 4.68 4.17 3.75 3.41 3.12 2.89 2.68 2.50 2.34 2.08 1.87 1.56

Design of Stairs: Level 1 to 2 f'c Fy Phi

4000 psi 60000 psi 0.9

4 ksi

Enter total rise Enter guess for riser height Guess for number of stairs

10 ft 6.9 in 17.39 in

120

(Total rise/guess riser heigh

Choose number of stairs to get riser height closer to the guess No. of Stairs 18 Riser height 6.67 in ok Estimate tread depth using emperical equations d1 11.67 in d2 10.83 in d3 11.250 in Tread depth selected 12.00 in Calculate horizontal run Treads= Stairs -1 Run = Treads*Depth

[25-(2*Riser height)] [17.5-Riser height] [75/Riser height]

17 204.00 in

For Waist Slab b height of slab d LL DL Total Wu

12 in 6 in 5 in 96 psf 144 psf 240.00 psf

Mu Mu/(phi*f'c*b*d2) w Rho As Use #4 at 12 o.c. For landing slab b

[60*1.6] [120*1.2]

0.240 ksf 4.502 k/ft 0.050 0.050 0.003335 ok 0.20 in2/LF 0.2 in2/LF

4 ft

[Wu*l2/8]

[w*f'c/Fy]

48 in

height of slab d LL DL Total 8 treads at 12'' Stair total load Wu total Mu Mu/(phi*f'c*b*d2) w Rho As Use (4) #5

6 in 5 in 384 plf 576 plf 960 plf

slab

8.00 ft 960 plf 1920 plf 22 ft-k 0.060 0.060 0.004011 0.96 in2 1.24 in2

[60*b*1.6] [120*b*1.2]

[Total Wu*8/2] 1.92 klf

ok

Reinforcing Bar Area for Various Bar Spacings (in.^2/ft.)

Spacing (in.) 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 9 10 12

Bar size #3 #4 #5 #6 #7 #8 #9 #10 #11 #14

#3 0.44 0.38 0.33 0.29 0.26 0.24 0.22 0.20 0.19 0.18 0.17 0.25 0.13 0.11

Area (in^2) 0.11 0.2 0.31 0.44 0.6 0.79 1 1.27 1.56 2.25

#4 0.78 0.67 0.59 0.52 0.47 0.43 0.39 0.36 0.34 0.31 0.29 0.26 0.24 0.20

Weight (lb/ft) 0.376 0.668 1.043 1.502 2.044 2.670 3.400 4.303 5.313 7.650

#5 1.23 1.05 0.92 0.82 0.74 0.67 0.61 0.57 0.53 0.49 0.46 0.41 0.37 0.31

Bar Size #6 #7 1.77 2.40 1.51 2.06 1.32 1.80 1.18 1.60 1.06 1.44 0.96 1.31 0.88 1.20 0.82 1.11 0.76 1.03 0.71 0.96 0.66 0.90 0.59 0.80 0.53 0.72 0.44 0.60

1 0.11 0.2 0.31 0.44 0.6 0.79 1 1.27 1.56 2.25

2 0.22 0.4 0.62 0.88 1.2 1.58 2 2.54 3.12 4.5

in

Total rise/guess riser height)

8

12'' 8'

25-(2*Riser height)] 17.5-Riser height] 75/Riser height] 18 R @ 6.67''

60*b*1.6] 120*b*1.2]

4

Total Wu*8/2] 4

4

5

12''

acings (in.^2/ft.)

4

ize #8 3.14 2.69 2.36 2.09 1.88 1.71 1.57 1.45 1.35 1.26 1.18 1.05 0.94 0.78

3 0.33 0.6 0.93 1.32 1.8 2.37 3 3.81 4.68 6.75

#9 4.00 3.43 3.00 2.67 2.40 2.18 2.00 1.85 1.71 1.60 1.50 1.33 1.20 1.00

4 0.44 0.8 1.24 1.76 2.4 3.16 4 5.08 6.24 9

#10 5.06 4.34 3.80 3.37 3.04 2.76 2.53 2.34 2.17 2.02 1.89 1.69 1.52 1.27

5 0.55 1 1.55 2.2 3 3.95 5 6.35 7.8 11.25

#11 6.25 5.36 4.68 4.17 3.75 3.41 3.12 2.89 2.68 2.50 2.34 2.08 1.87 1.56

6 0.66 1.2 1.86 2.64 3.6 4.74 6 7.62 9.36 13.5

7 0.77 1.4 2.17 3.08 4.2 5.53 7 8.89 10.92 15.75

8 0.88 1.6 2.48 3.52 4.8 6.32 8 10.16 12.48 18

9 0.99 1.8 2.79 3.96 5.4 7.11 9 11.43 14.04 20.25

10 1.1 2 3.1 4.4 6 7.9 10 12.7 15.6 22.5

11 1.21 2.2 3.41 4.84 6.6 8.69 11 13.97 17.16 24.75

12 1.32 2.4 3.72 5.28 7.2 9.48 12 15.24 18.72 27