Stair Design

Stair TypesStraight stairs

Stair Type based on the structural loading type

Simply supported stair (transversely supported)

Longitudinally supported stair

Cantilever stair

Simply supported stair Design a straight flight stair in a residential building supported on reinforced concrete wall 1.5 m )(center to center)L.L = 3kN/m2Covering Material = 0.5kN/mThe riser are 16cm and goings are 30 cm

Loads and Analysis

cmh

cml

h

ave 5.165.7

8cos

5.78

5.720

150

20

22 1630

16

min

D.L(D.L(O.WO.W) =0.34*0.075*25 + 0.5*0.16*0.3*25=1.24 kN/m) =0.34*0.075*25 + 0.5*0.16*0.3*25=1.24 kN/mD.L (covering material) = 0.5 kN/mD.L (covering material) = 0.5 kN/m

D.L (total) = 1.74 kN/m D.L (total) = 1.74 kN/m L.L =3*(0.3) =0.9 kN/mL.L =3*(0.3) =0.9 kN/m

0.30.16

0.34

Design for moment

stepeach for 121

9.01.89165*300*0018.0

0005.0139003 25 9.0 85.0

110211

420

2585.0

9.0

30030

1399.136.025.16

.1

22min

min2

6

lim

use

cmmmAs

assume

mmcmb

mmcmd

mkNM

w

u

uC VkNV 261000/3001396

2575.0

Design for shear

Longitudinal – Supported stairs

Design a U- stair in a residential building L.L = 3 kN/m2Covering Material = 2 kN/m2

The riser are 16 cm and goings are 30 cm

Longitudinal – Supported stairs (Example)

1 3 1

0,255,25

1,05

Loads and Analysis

cml

h 2220

525

2085.0min

D.L (D.L (slabslab) ) = 0.22*25 =5kN/m2 = 0.22*25 =5kN/m2 D.L (step) = 0.5*0.16*25=2 kN/m2D.L (step) = 0.5*0.16*25=2 kN/m2D.L (covering material) = 2 kN/m2D.L (covering material) = 2 kN/m2

D.L (flight) = 9 kN/m2 D.L (flight) = 9 kN/m2 D.L (landing) = 7 kN/m2D.L (landing) = 7 kN/m2L.L =3 kN/m2L.L =3 kN/m2

WWu u (flight) = 1.2(9)+1.6(3)=15.6kN/m(flight) = 1.2(9)+1.6(3)=15.6kN/mWWuu (landing) = (landing) = 1.2(7)+1.6(3)=13.2kN/m1.2(7)+1.6(3)=13.2kN/m

Design for moment

128

33.732.733194*1050*0036.0

0036.01940501 25 9.0 85.0

2.5210211

420

2585.0

9.0

1050105

1944.196.0222

.2.52

22min

2

6

lim

use

cmmmAs

assume

mmcmb

mmcmd

mkNM

w

u

uC VkNV 3.1271000/10501946

2575.0

Design for shear

Reinforcement Notes

Cantilever Stair

Cantilever stairs (Example)

Design a cantilever straight flight stair in a residential buildingL.L = 3kN/m2Covering Material = 0.5kN/mThe riser are 16cm and goings are 30 cm

cml

h 1510

150

10min

D.L(D.L(O.WO.W) =0.15*0.075*25 + 0.15*0.075*25=0.6 kN/m) =0.15*0.075*25 + 0.15*0.075*25=0.6 kN/mD.L (covering material) = 0.5 kN/mD.L (covering material) = 0.5 kN/m

D.L (total) = 1.1 kN/m D.L (total) = 1.1 kN/m L.L =3*(0.3) =0.9 kN/mL.L =3*(0.3) =0.9 kN/m

Wu = 1.2(1.1)+1.6(0.9) = 2.76 kN/mWu = 1.2(1.1)+1.6(0.9) = 2.76 kN/mVu = 2.76(1.5) = 4.14 kNVu = 2.76(1.5) = 4.14 kNMu = WMu = WuuLL22/2 = 3.1 kN.m/2 = 3.1 kN.m 15

15

7.5

Design for moment

102

72.061.71124*75*0077.0

0077.012457 25 9.0 85.0

1.310211

420

2585.0

9.0

755.7

1944.126.0215

.1.3

22min

2

6

lim

use

cmmmAs

assume

mmcmb

mmcmd

mkNM

w

u

uC VkNV 8.51000/751246

2575.0

Design for shear

Longitudinal – Supported stairs

Open-well stairs

General Example