EXAMPLE: An RCC column of size 300 mm x 600 m

carries a characteristic load of 800 KN a

its major axis and My = 50 KNm about i
thrust of 60KN along longer side of the
on soil is 200 KN/m2. Design an isolated
shall be M20 concrete and HYSD reinfo
from 1.6m to 5.6m depth is hard yellow
c = 70 kPa, φ = 0° , ϒ = 16 KN/m3, adhes
 mm x 600 mm reinforced with 8 no. 28mm dia. bars
d of 800 KN and service moments Mx = 80KNm about
KNm about its minor axis.It also carries a horizontal
r side of the column. The allowable bearing pressure
gn an isolated pad footing. The materials for footing
HYSD reinforcement of grade Fe 415. The soil strata
s hard yellow silty clay of high plasticity having cohesion
N/m3, adhesion β = 80 kPa.
 a. bars
m about
zontal
essure
ooting
l strata
g cohesion
 Design of Eccentric footing for a column of a multi-storeyed building
Enter the values in these cells only.
1) Column data
Size of column Shorter a1 300 mm = 0.3 m
Longer a2 600 mm = 0.6 m
Unfactored Load P 800 KN 80 KNm
horizontal thrust along longer side Hy 60 KN 50 KNm
Unfactored BM about major axis Mux 80 KNm y y
Unfactored BM about minor axis Muy 50 KNm
x
2) Soil data
ABP of soil ABP 200 KN/m2
Type of soil silty clay (cohesive)
cohesion c 70 kPa
Adhesion β 80 kPa 800
Angle of internal friction φ 0° 80 KNm
Unit weight of soil ϒsoil 16 KN/m3

3) Concrete data 60 KN
Grade of concrete fck 20 N/mm2 96 KN
Grade of steel fy 415 N/mm2 550
Xumax/d 0.48
Clear cover c 50 mm
Assume overall depth of footing D 550 mm = 0.55 m

3) Loads at the base of the footing

Unfactored Load 800 KN
Self weight of footing 96 KN
Total unfactored load (including self wt.) P 896 KN
Net B.M along longer direction Mux 113 KNm
Net B.M along shorter direction Muy 50 KNm
896 KN
4) Size of footing 60 113 KNm 𝐴=(𝑈𝑛𝑓𝑎𝑐𝑡𝑜𝑟𝑒𝑑 𝑡𝑜𝑡𝑎𝑙 𝑙𝑜𝑎𝑑 )/𝐴𝐵𝑃
Area of footing required A 4.48 m2

Trial L(m) B(m) A (m2) Zx Zy P/A Mx/Zx My/Zy pmax pmin

1 2.3 2 4.6 1.763333 1.533333 194.7826 64.0832 32.609 291.4745 98.091
2 2.7 2.4 6.48 2.916 2.592 138.2716 38.7517 19.29 196.3134 80.23

Hence adopt L 2.7 m such that pmax <ABP and pmin > 0
B 2.4 m

5) Net upward pressures

For Mx
𝑞 =𝑃_𝑢/𝐴−𝑀_𝑢𝑥/𝑍_𝑥
qmax 243.3128 KN/m2 𝑞𝑚𝑎𝑥=𝑃_𝑢/𝐴+𝑀_𝑢𝑥/𝑍_𝑥 &𝑚𝑖𝑛
qmin 127.0576 KN/m 2

For My
𝑞𝑚𝑎𝑥=𝑃_𝑢/𝐴+𝑀_𝑢𝑦/𝑍_𝑦 𝑞𝑚𝑎𝑥=𝑃_𝑢/𝐴−𝑀_𝑢𝑦/𝑍_𝑦
qmax 214.1204 KN/m2 &
qmin 156.25 KN/m2
6) Dimensions and pressure diagram

2.7 m
214.1204 KN/m2
1.05

2.4 1.05
m

156.25 KN/m2

127.06
243.3128 KN/m2

7) BM at the face of column

For Mux:
1.05 m

1
2
127.06
198.10 243.3128 KN/m2

A1 249.6091 mm2 𝑀𝑥=𝑓𝑜𝑟𝑐𝑒∗𝐶.𝐺

A2 306.5741 mm2
𝑓𝑜𝑟𝑐𝑒=𝑎𝑟𝑒𝑎 𝑜𝑓 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑑𝑖𝑎𝑔𝑟𝑎𝑚
C.G 1 0.35 m
C.G 2 0.7035 m

Mx 303.038 KNm 𝑀𝑥=(𝐴_1∗ 〖𝐶 .𝐺 〗 _1+𝐴_2∗ 〖𝐶 .𝐺 〗 _2)*B

For Muy:
214.12 KN/m2
2
1.05 1
188.80 KN/m2

156.25 KN/m2

A1 267.627
A2 303.5156
C.G 1 0.35
C.G 2 0.7035

My 307.1927 KNm 𝑀𝑦=(𝐴_1∗ 〖𝐶 .𝐺 〗 _1+𝐴_2∗ 〖𝐶 .𝐺 〗 _2)*L

8) Depth of footing
Qlim 2.75927
dx,req. 213.9173 mm
dy,req. 203.061 mm
D 550 mm
φx 12 mm
φy 12 mm
dx 494 mm
dy 482 mm

9) Reinforcement Calculations
R/F along longer side 𝑝𝑡𝑟𝑒𝑞=50∗𝑓𝑐𝑘/𝑓𝑦∗{1−√(1−(4.6∗𝑀𝑢)/(𝑓𝑐𝑘∗𝑏∗𝑑^2 ))}
pt,req 0.148 %
Astreq 1753.713 mm2
Ast,min 1584 mm2 〖𝐴𝑠𝑡〗 _𝑟𝑒𝑞=(𝑝_𝑡𝑟𝑒𝑞∗𝐵∗𝑑)/100
Nreq 15.51409
Nprov. 16
Ast,prov. 1808.64 mm2 OK
c/c spacing 152.5333 mm
clear spacing 140.5333 mm OK

Hence provide16-12mm # along longer direction

R/F along shorter side

pt,req 0.140 %
Astreq 1818.84 mm2
Ast,min 1782 mm2
β 1.125
2/(β+1) 0.941176
Ast,central 1711.849 mm2
𝐴𝑠𝑡,𝑐𝑒𝑛𝑡𝑟𝑎𝑙=2/(𝛽+1)*Ast
Nreq,central 15.14375
Nprov. 16
Ast,provided,central 1808.64 mm2
Ast,corner 106.9906 mm2
Nreq,corner 0.946484
Nprov. 2
Width of central band 2400 mm
width of each corner band 150 mm

Hence provide 16 bars of 12mm dia. In central band and 2 bars of 12mm dia. In corner portion
10) Check for one-way shear
Along longer direction
2.7

494
2.4

0.556

127.06
219.37 243.31 KN/m2

V 308.7038 KN
τv 0.26 N/mm2
pt,prov 0.15
β 16.17394
τc 0.281975 N/mm2 1
NOTE: The check for one-way shear along shorter direction is not required as the cantilever length is smaller.

11) Check for two way shear

2.7

2.4

1.894 0.806

127.06
208.61 243.31 KN/m2

Avg. depth d 488 mm

Width at crictical section b 788 mm
Upward pressure at d/2 w 225.9606 KN/m2
Area of crictical section (trapezoid) 1.163864 m2
Shear at crictical section V 262.9874 KN
τv 0.683894 N/mm2
τc 1.118034 N/mm2 1

12) Factor of safety against sliding

𝑅=2∗𝑐∗𝐵∗ℎ+0.5∗𝛾∗ℎ^2∗𝐵+𝛽∗𝐿∗𝐵
R 709.008 KN
H 60 KN
FOS 11.8168 OK 𝐹𝑂𝑆=𝑅/𝐻
<1.6

13) Detailing drawings

16-12mm # along longer direction

16 - 12mm #

550

0.15 2.4 0.15 2.7 m

2.7
 Design of Eccentric footing for uniaxial moment
Enter the values in these cells only.
1) Basic data
Size of column Shorter a1 500 mm = 0.5 m
Longer a2 300 mm = 0.3 m
factored Load Pu 1000 KN
factored BM about major axis Mux 120 KNm 120 KNm
ABP of soil ABP 200 KN/m2
Unit weight of soil ϒsoil 16 KN/m3 y y
Grade of concrete fck 25 N/mm2
Grade of steel fy 415 N/mm2 x
Xumax/d 0.48
Clear cover c 75 mm

2) Size of footing
Unfactored Load 666.6667 KN
Self weight of footing 100 KN
Total unfactored load (including self wt.) P 766.6667 KN/m 𝐴=(𝑈𝑛𝑓𝑎𝑐𝑡𝑜𝑟𝑒𝑑 𝑡𝑜𝑡𝑎𝑙 𝑙𝑜𝑎𝑑 )/𝐴𝐵𝑃
Area of footing required A 3.833333 m2

Trial L(m) B(m) A (m2) Zx P/A Mx/Zx pmax pmin

1 2.3 2 4.6 1.763333 166.6667 45.36862 212.035 121.3
2 2.45 2 4.9 2.000833 156.4626 39.98334 196.446 116.48 p𝑚𝑎𝑥=𝑃/𝐴+𝑀_𝑥/𝑍_𝑥

Hence adopt L 2.45 m such that pmax <ABP and pmin > 0 p𝑚𝑖𝑛=𝑃/𝐴−𝑀_𝑥/𝑍_𝑥
B 2m

3) Net upward pressures

𝑞𝑚𝑎𝑥=𝑃_𝑢/𝐴+𝑀_𝑢𝑥/𝑍_𝑥
qmax 264.0566 KN/m2
qmin 144.1066 KN/m2 𝑞𝑚𝑖𝑛=𝑃_𝑢/𝐴−𝑀_𝑢𝑥/𝑍_𝑥
4) Dimensions and pressure diagram

2.45 m

0.85

2 0.975
m
264.06

###
144.11
264.06 KN/m2
5) BM at the face of column
For Mux:
0.975 m

1
2
144.11
211.43 264.0566 KN/m2

A1 103.0699 mm2 𝑀𝑥=𝑓𝑜𝑟𝑐𝑒∗𝐶.𝐺

A2 128.7276 mm2 𝑓𝑜𝑟𝑐𝑒=𝑎𝑟𝑒𝑎 𝑜𝑓 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑑𝑖𝑎𝑔𝑟𝑎𝑚
C.G 1 0.325 m
C.G 2 0.65325 m

Mx 235.1781 KNm 𝑀𝑥=(𝐴_1∗ 〖𝐶 .𝐺 〗 _1+𝐴_2∗ 〖𝐶 .𝐺 〗 _2)*B

For Muy:
1

1
2
144.11
204.08 264.0566 KN/m2

𝑀𝑦=𝑤∗ 〖𝑙 _𝑦 〗 ^2/2*L𝑤=(𝑞_𝑐𝑒𝑛𝑡𝑒𝑟+𝑞_𝑚𝑎𝑥)
My 207.1658 KNm & /2

6) Depth of footing 𝑄𝑙𝑖𝑚=0.36∗𝑥𝑢𝑚𝑎𝑥/𝑑∗(1−0.42∗𝑥𝑢𝑚𝑎𝑥/𝑑)∗𝑓𝑐𝑘

Qlim 3.449088
dx,req. 184.6423 mm 𝑑𝑥= √(𝑀𝑢𝑥/(𝑄𝑙𝑖𝑚∗𝐵)) 𝑑𝑦= √(𝑀𝑢𝑦/(𝑄𝑙𝑖𝑚∗𝐿))
dy,req. 156.5755 mm &
Assume D 500 mm
φx 16 mm
φy 12 mm 𝑑𝑥=𝐷−𝑐𝑙𝑒𝑎𝑟 𝑐𝑜𝑣𝑒𝑟−∅_𝑥/2
dx 417 mm
dy 403 mm 𝑑𝑦=𝑑𝑥−∅_𝑥/2−∅_𝑦/2
7) Reinforcement Calculations
R/F along longer side 𝑝𝑡𝑟𝑒𝑞=50∗𝑓𝑐𝑘/𝑓𝑦∗{1−√(1−(4.6∗𝑀𝑢)/(𝑓𝑐𝑘∗𝑏∗𝑑^2 ))}
pt,req 0.194 %
Astreq 1614.722 mm2
Ast,min 1200 mm2 〖𝐴𝑠𝑡〗 _𝑟𝑒𝑞=(𝑝_𝑡𝑟𝑒𝑞∗𝐵∗𝑑)/100
Nreq 8.035042
Nprov. 9
Ast,prov. 1808.64 mm2 OK
c/c spacing 229.25 mm
c/c spacing provided 220 mm OK
Hence provide 9-16mm # @220mm c/c along longer direction

R/F along shorter side

pt,req 0.148 %
Astreq 1460.357 mm2
Ast,min 1470 mm2
β 1.225
2/(β+1) 0.898876
Ast,central 1321.348 mm2
𝐴𝑠𝑡,𝑐𝑒𝑛𝑡𝑟𝑎𝑙=2/(𝛽+1)*Ast
Nreq,central 11.68921
Nprov. 12
Ast,provided,central 1356.48 mm2
( 〖𝐴𝑠𝑡〗 _(𝑝𝑟𝑜𝑣𝑖𝑑𝑒𝑑,𝑐𝑒𝑛
c/c spacing 166.6667 mm c/c spacing in central band =
𝑡𝑟𝑎𝑙)∗𝐵)/(𝐴𝑟𝑒𝑎 𝑜𝑓
c/c spacing provided 160 mm OK 𝑜𝑛𝑒 𝑏𝑎𝑟)
Ast,corner 148.6517 mm2
Nreq,corner 1.315036
Nprov. 2
Width of central band 2000 mm
width of each corner band 225 mm

Hence provide 12 bars of 12mm dia. In central band and 2 bars of 12mm dia. In corner portion

8) Check for one-way shear

Along longer direction
2.45

417
2

0.658

144.11
231.84 264.06 KN/m2

V 326.301 KN
τv 𝛽=
0.39 N/mm2 (0.8∗𝑓𝑐𝑘)/(6.89∗
pt,prov 0.22 𝑝𝑡)
β 14.22177 𝜏𝑐=0.85∗√(0.8∗𝑓𝑐𝑘)∗(√(1+5∗𝛽)−1)/(6∗𝛽)
τc 0.333741 N/mm2 1
NOTE: The check for one-way shear along shorter direction is not required as the cantilever length is smaller.
 9) Check for two way shear
2.45

1.58 0.87

144.11
221.46 264.06 KN/m2

Avg. depth d 410 mm

Width at crictical section b 910 mm
Upward pressure at d/2 w 242.7594 KN/m2
Area of crictical section (trapezoid) 1.30935 m2
Shear at crictical section V 317.857 KN
τv 0.851935 N/mm2
τc 2.708333 N/mm2 1

10) Detailing drawings

9-16mm # @ 160 mm c/c

12 - 12mm # @160 mm c/c

500 mm

0.225 2 0.225 2.45 m

2.45