Combined & Raft Footing

# Combined & Raft Footing | Foundation Engineering - Civil Engineering (CE) PDF Download

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``` Page 1

FOOTINGS AND RAFTS

Page 2

FOOTINGS AND RAFTS

Footing

=800kN
=1000kN
=20 t/m
2
,M15,  =415kN/m
2

Column size: 400x400mm.

Design of Combined

See Fig 4.54 for details of footing.   Column design

Let pt=0.8%

=.008A; =0.992A
Clause.39.3 of IS 456-2000
A=146763.8mm
2

=1174.11 mm
2
,  =145589.746mm
2

Provide footing of 400x400size for both columns.

Using 8-16  as main reinforcement and 8  @250c/c as lateral tie

Design of Footing
Page 3

FOOTINGS AND RAFTS

Footing

=800kN
=1000kN
=20 t/m
2
,M15,  =415kN/m
2

Column size: 400x400mm.

Design of Combined

See Fig 4.54 for details of footing.   Column design

Let pt=0.8%

=.008A; =0.992A
Clause.39.3 of IS 456-2000
A=146763.8mm
2

=1174.11 mm
2
,  =145589.746mm
2

Provide footing of 400x400size for both columns.

Using 8-16  as main reinforcement and 8  @250c/c as lateral tie

Design of Footing

Resultant of Column Load
Fig. 4.52 Forces acting on the footing

R =1800 kN acting 3.08m from the boundary.
Area of the footing :
Taking length L=6m, Depth of footing =0.9m, ,

Width of footing,  =1.549m.
Therefore, provide footing of dimension 6m x 1.6m

Soil Pressure q =  =18.75 t/m
2
< 20 t/m
2
OK.

=28.125 t/m
2

Soil pressure intensity acting along the length =B x  =1.6x28.125 =45t/m.

R
B
=119.88kN, R
C
=150.12kN.

Thickness of Footing   i. Wide beam shear:
Maximum shear force is on footing C,SF=115.02KN

for percentage reinforcement  =0.2%

0.32 x d x 1.6=45 [2.556-0.2-d]

d=1.1m
Page 4

FOOTINGS AND RAFTS

Footing

=800kN
=1000kN
=20 t/m
2
,M15,  =415kN/m
2

Column size: 400x400mm.

Design of Combined

See Fig 4.54 for details of footing.   Column design

Let pt=0.8%

=.008A; =0.992A
Clause.39.3 of IS 456-2000
A=146763.8mm
2

=1174.11 mm
2
,  =145589.746mm
2

Provide footing of 400x400size for both columns.

Using 8-16  as main reinforcement and 8  @250c/c as lateral tie

Design of Footing

Resultant of Column Load
Fig. 4.52 Forces acting on the footing

R =1800 kN acting 3.08m from the boundary.
Area of the footing :
Taking length L=6m, Depth of footing =0.9m, ,

Width of footing,  =1.549m.
Therefore, provide footing of dimension 6m x 1.6m

Soil Pressure q =  =18.75 t/m
2
< 20 t/m
2
OK.

=28.125 t/m
2

Soil pressure intensity acting along the length =B x  =1.6x28.125 =45t/m.

R
B
=119.88kN, R
C
=150.12kN.

Thickness of Footing   i. Wide beam shear:
Maximum shear force is on footing C,SF=115.02KN

for percentage reinforcement  =0.2%

0.32 x d x 1.6=45 [2.556-0.2-d]

d=1.1m

for percentage reinforcement     =0.6%

0.6 x d x 1.6=45 [2.556-0.2-d]

d=0.847m.D=900mm.OK.

ii.Two way Shear Thickness of Footing   i. Wide
beam shear:

Maximum shear force is on footing C,SF=115.02KN

for percentage reinforcement  =0.2%

0.32 x d x 1.6=45 [2.556-0.2-d]

d=1.1m

for percentage reinforcement  =0.6%
Page 5

FOOTINGS AND RAFTS

Footing

=800kN
=1000kN
=20 t/m
2
,M15,  =415kN/m
2

Column size: 400x400mm.

Design of Combined

See Fig 4.54 for details of footing.   Column design

Let pt=0.8%

=.008A; =0.992A
Clause.39.3 of IS 456-2000
A=146763.8mm
2

=1174.11 mm
2
,  =145589.746mm
2

Provide footing of 400x400size for both columns.

Using 8-16  as main reinforcement and 8  @250c/c as lateral tie

Design of Footing

Resultant of Column Load
Fig. 4.52 Forces acting on the footing

R =1800 kN acting 3.08m from the boundary.
Area of the footing :
Taking length L=6m, Depth of footing =0.9m, ,

Width of footing,  =1.549m.
Therefore, provide footing of dimension 6m x 1.6m

Soil Pressure q =  =18.75 t/m
2
< 20 t/m
2
OK.

=28.125 t/m
2

Soil pressure intensity acting along the length =B x  =1.6x28.125 =45t/m.

R
B
=119.88kN, R
C
=150.12kN.

Thickness of Footing   i. Wide beam shear:
Maximum shear force is on footing C,SF=115.02KN

for percentage reinforcement  =0.2%

0.32 x d x 1.6=45 [2.556-0.2-d]

d=1.1m

for percentage reinforcement     =0.6%

0.6 x d x 1.6=45 [2.556-0.2-d]

d=0.847m.D=900mm.OK.

ii.Two way Shear Thickness of Footing   i. Wide
beam shear:

Maximum shear force is on footing C,SF=115.02KN

for percentage reinforcement  =0.2%

0.32 x d x 1.6=45 [2.556-0.2-d]

d=1.1m

for percentage reinforcement  =0.6%

0.6 x d x 1.6=45 [2.556-0.2-d]

d=0.847m.D=900mm.OK.

ii.Two way Shear

Column B

d=0.415m.
Column A
2d[(0.4+d)+(0.42+d/2)] x 96.8=120-28.125[(0.4+d)(0.42+d/2)]
d=0.3906m

=0.85mm
=900mm,  =850mm.OK.

Flexural reinforcement

Along Length Direction

Table 1of SP16

=0.354%

provided=0.6%
=1.15N/mm
2

required=5100 mm
2
/mm
Provide 28  @120mmc/c at top and bottom of the footing
Along width direction
```

## Foundation Engineering

18 videos|46 docs|27 tests

## Foundation Engineering

18 videos|46 docs|27 tests

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