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DESIGN OF DOG-LEGGED STAIR
Name of work :- pkn
1 Stair hall measure 2.50 x 5.00 m
2 Available verical space between floor 3.00 m 3000 mm
3 Horizontal Span of stair case 1.20 mtr 1200 mm
4 Risers 0.15 mtr 150 mm
5 Treads 0.25 mtr 250 mm
6 Conrete M - 20 wt. of concrete 25000
7 m 13.
7 Steel fy 415 230
8 Nominal cover 25 Effective cover 30 mm
Reinforcement
Main Bottom slab 10 100 mm c/c
Anchor bars (Bottom ) 8 2 Nos.
Strirrups 8 270 mm c/c
10 200 mm c/c
2050
1750 1200
150 1.
250
1200
10 100 mm c/c
3.00 150
8 270 mm c/c 250
10 200 mm c/c
180 mm
1050
1050 2.75 1200
N/m
3
s
cbc
N/mm
2
s
st
N/mm
2
mm F bars
mm F bars
mm F bars
mm f
mm f
mm f
mm f
pk_nandwana@yahoo.co.in
DESIGN OF DOG-LEGGED STAIR
Name of work :- pkn
Stair hall measure 2.50 x 5.
Available verical space between floor 3.00 m
Horizontal Span of stair case 1.20 m 1200 mm
Risers 0.15 m 150 mm
Treads 0.25 m 250 mm
Concrete M- 20 wt. of concrete 25000
7 m 13.
Steel fy- 415 230
Nominal cover 25 mm Effective cover 30 mm
1 Genral arrngment:-
Fig. shows plan of stair hall.
= 3.00 / 2 = 1.50 m minimum 1.8 m which is heigher
No. of risers required = 1.80 / 0.15 = 12
No. of treads required = 12 - 1 = 11 No. in 1st flight.
Spce occupied by treads = 11 x 0.25 = 2.75 m
Keep width of landing equal to = 1.20 m
= 1.05 m
= 1.20 m
No. of risers required = 1.20 / 0.15 = 8
No. of treads required = 8 - 1 = 7 No. in 2nd flight.
Spce occupied by treads = 7 x 0.25 = 1.75 m
Keep width of top landing = m
2 Design Constants:- For HYSD Bars Cocrete M = 20
230 wt. of concrete = 25000
= 7 m = 13.
m*c
x 7
13.33 x 7 + 230
= 0.5 x 7 x 0.904 x 0.289 = 0.
3 Loading Each Flight :-
The landing slab is assume to span in the same direction as stair, and is considered
as acting together to form a single slab. Let the bearing of landing slab in wall be = 160 mm
The effective span = 2.75 + 1.20 +( 0.16 / 2 )'= 4.03 m say = 4.00 m
Let the thickness of waist slab '= 5.00 x 40 = 200 mm
= 0.2 x 1 x 1 x 25000 = 5000
x = 5000 x
T 250
x
x ### = 1875 N/m
= 7706 N
Weight of fiishing etc. = 100 N
Live load = 2500 N
Total weight = 10306 N
Note. The load w on the landing portion will be 10306 - N, since weight of step will not come on it. However, 1875 = 8431
a uniform value of w has been adopted here.
N/mm
2
s
cbc
N/mm
2 s
st
N/mm
2
Height of 1
st
flight.
No. in 1
st
flight.
\ Space left for passage
Height of 1
st
flight.
No. in 2
nd
flight.
sst N/mm
2
N/mm
2
scbc N/mm
3
k =
m*c+sst
j =1-k/
R =1/2xc x j x k
\Weight of slab w' on slope N/m
2
Dead weight of horizontal area w
1
= w'
R
2
+T
2 2
2
N/m
2
Dead weight of step is w
2
\ Total Dead weight per meter run
pk_nandwana@yaho.co.in
ich is heigher
s considered
e on it. However,
DESIGN OF DOG-LEGGED STAIR
UP
11
10
9 8 270
8
7
### 6
250
5
150
4
3
2
1
Foor level
1.20 2.75 1.
mm F c/c
mm F c/c
2050
1750 1200
150 1.
250
1200
10 100 mm c/c
3.00 0
8 270 mm c/c 0
180 mm
1050
1050 2.75 1200
mm f
mm f
pk_nandwana@yahoo.co.in
M-10 M-15 M-20 M-25 M-30 M-35 M-40 M-45 M-
Development Length in tension
Plain M.S. Bars H.Y.S.D. Bars
(N/mm2) (N/mm2) (N/mm2)
Permissible Bond stress Table t
bd
in concrete (IS : 456-2000)
t
bd
(N / mm2) k
d
= L
d
F t
bd
(N / mm2) k
d
= L
d
F
Permissible stress in concrete (IS : 456-2000)
Permission stress in compression (N/mm
2
Permissible stress in bond (Average) for
plain bars in tention (N/mm
2
Bending a )
cbc
Direct (a
cc
Kg/m
2
Kg/m
2
in kg/m
2
