Eccentric Footing

PROJECT

DESIGN OF ECCENTRIC FOOTING

Load from column (P)

=

200

kN

Column breath ( B)

=

230

mm

Column depth (D)

=

230

mm

Effective of cover (d')

=

60

mm

Grade of concrete (f ck  )

=

20

 N/mm

Grade of steel (f  y )

=

415

 N/mm

S.B.C of soil

=

120

kN/m

Load from column

=

200

kN

Self weight of footing (10 %)

=

20

kN

Total load

=

220

kN

Area of footing required

=

1.83

m

L

=

1.5

m

B

=

1.5

m

=

2.25

=

200/2.25

=

88.89

2 2

2

DESIGN

Footing Size Provided

Area provided  Net upward soil pressure

2

O.K 

2

kN/m

O.K  =

Overall depth of footing slab Bending moment

Mu

Factored moment Q

=

250

mm

88.89 x 0.635^2 / 2

=

17.92

kNm

=

26.88

kNm

=

 M u 2

bd  =

26.88 x 10 ^ 6 1000 x 190 ^ 2

=

0.74

PROJECT

DESIGN OF ECCENTRIC FOOTING

Pt

Percentage of steel

=

50

1- 1- (4.6 / f ck  ) x Q  f  y  / f ck 

Area of steel

Pt

=

Ast

=

Ast

=

0.22  P t  x b x d 100 2

410

mm

 P t,min  x b x d

Ast,min

=

Ast,min

=

228

mm

=

10

mm

100

Diameter of bar 

2

1000 x ast  Spacing of bars

=

 A st  =

Provide

191

mm

mm # bars @

10

150

mm c/c

DISTRIBUTORS

Ast,min

=

228

Diameter of bar 

=

Spacing of bars

=

2

mm

10

mm

1000 x ast   A st  =

Provide

10

344

mm # bars @

mm 150

mm c/c

PROJECT

DESIGN OF ECCENTRIC FOOTING

BEAM DESIGN

=

Load from footing slab

88.89 x 0.635

=

56.45

Breath of beam ( B)

=

300

mm

Depth of beam (D)

=

600

mm

Self weight of beam

=

Total load Span of beam Bending moment

Mu

300 x 600 x 25

=

4.5

kN/m

=

60.95

kN/m

=

1.5

=

m

60.95 x 1.5^2 / 2

=

68.57

102.85 kNm

Factored moment

Mu

=

Torsional moment

Tu

=

Factored moment

kN/m

kNm

88.89 x 0.635^2 / 2

=

17.92

kNm

Tu

=

26.88

kNm

Mt

=

T u ( 1+ D / b) 1.7 

=

47.44

kNm

Mu > Mt Equivalent bending moment

Me

=

Q

=

150.29 kNm  M u 2

bd  =

150.29 x 10 ^ 6 300 x 540 ^ 2

= Percentage of steel

Pt

=

Pt

=

1.72 50

1- 1- (4.6 / f ck  ) x Q  f  y  / f ck 

0.54

PROJECT

DESIGN OF ECCENTRIC FOOTING

Area of steel

Ast

=

Ast

=

 P t  x b x d 100

=

Ast,min

=

324

Diameter of bar 

=

20

 Number of Required

=

2.763

3

mm

 P t,min  x b x d

Ast,min

Provide

2

868

100

numbers

2

mm

mm

20

# bars Top and Bottom

=

60.95 x 1.5

CHECK FOR SHEAR 

Maximum shear force

Factored shear force Equivalent shear force

Ve

=

91.425 kN

=

137.138 kN

=

V u + 1.6 T u  / b 280.498 kN

 Nominal shear stress

τv

=

1.73

Percentage of reinforcement

 Pt

=

0.58

β

=

0.8 x fck  6.89 x P t 

=

3.99

PROJECT

DESIGN OF ECCENTRIC FOOTING

Design shear strength of concrete τc

=

0.85 x 0.8 fck x( 1+ 5 β - 1 ) 6xβ

=

0.51

Diameter of stirrups

=

8

Spacing

=

mm

legged

0.87 x fy x A  sv b x ( τv-τc)

Provide

2

legged

=

99

8

# stirrups

mmm 100

mm c/c

2