DESIGN OF FOOTING
DESIGN OF FOOTING
DATA:
Load from column = 500
kN
Concrete grade = 20 N/mm2
Steel grade = 415
N/mm2
SIZE OF FOOTING:
Load from column = 500 KN
Assume self weight of footing as
10% of column load
self weight of
footing = 0.1 
500
= 50 KN
Total load on soil = 500 + 50
= 550 KN
Safe bearing of the soil = 200
KN / m2
AREA OF FOOTING:
Area of footing = 
B2 = 2.75 m2
B = 1.65 m
Say square footing of 1.7 m 1.7m
1.7m
NET UPWARD PRESSSURE:
Net upward design pressure at the
base
W = 
= 
W = 259.71 KN/m2
BENDING MOMENT:
Projection of footing on
the column = 
= 0.70 m
Maximum Bending moment @ section
Mn = 259.51 1.7 0.7 
1.7 0.7
Mn = 108.
08 KNM
Mn = 108.
08 106
Nmm
106
Nmm
DEPTH OF FOOTING:
For M20 grade of
concrete Y Fe415 steel
M.R = 2.07
bd2
D = 
D = 175.25 mm = 200 mm
Considering the
effect of shear, provide an effective depth of 400 mm for top layers of bars
Assume 25 mm 
bars
bars
Nominal cover = 50 mm
Total thickness = 400
+ 12.5 + 25 + 50
= 487.5 mm
= 490 mm
D = 490
mm
TENSION REINFORCEMENT:
Maximum BM = 108. 08 106
N mm
106
N mm MU =
0.87 fy Ast 
108.08 106
= 0.87 415 Ast 
106
= 0.87 415 Ast
Ast = 732. 03 mm2
Minimum Area of Steel = 
= 816
mm2
Provide 4 nos of 25mm diabars
(ast) = 1963.49 mm2 in each direction
Percentage of steel = 0.3%
DEVELOPMENT LENGTH:
= 
Ld = 1880.46 mm
The projection of footing from the
face of column = 700 mm
Providing on end cover of 50 mm
Length of bar of column face 650
mm < 1880 mm
Hence OK
CHECK FOR TRANSVERSE SHEAR:
Effective depth (d) = 400 mm
Length of footing = 700 – 400
= 300 mm
Tranverse shear (VY) = 259.
51 1.7 0.45
1.7 0.45
VY = 198.
52 KN
Nominal Shear Stress 
= 
= 
= 0.291 N/mm2
From Table 19 of
IS 456 – 2000 Permissible shear stress in concrete (M20 grade)
= 0.379 N/mm2
Hence
OK
CHECK FOR PUNCHING SHEAR:
In the distance of (½ eff. Depth)
Distance = 
= 200 mm
= 200 mm side of section
= 300 + 2(200) = 700 mm
VZ = 259.
51 ( 1.7 .7 – 0.7 0.7)
.7 – 0.7 0.7)
= 622.
82 KN
VZ = 622.
82 103
N
103
N
Nominal Shear Stress (
As per clause 31.6.3.1 of Is 456 – 2000 permissible shear stress in
concrete = 
for square column
= KS = 1
for square column
= KS = 1
= 0.25 
= 1.118 N/mm2
= 1.118 N/mm2
Hence OK
CHECK FOR SAFE BEARING CAPACITY OF SOIL:
Column load = 500 KN
Self weight of footing
= 1.7 1.7 0.40 25
1.7 0.40 25
= 28.9 KN
Total Load on Soil = 500
+ 28.9 =
528. 9 KN
Pressure on the soil
= 
= 183.01 KN/mm2
183.01 KN /m2 < 200 KN/m2
Hence it
is Safe
About Author:
I am Thomas Britto here to share my experiences in the civil engineering field to all my readers.Today many students are struggling to buy books at high prices. So I decided to start a blog and share my experience and knowledge with all my readers.
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