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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. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 4.51 Loading on combined footing 
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. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 4.51 Loading on combined footing 
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. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 4.51 Loading on combined footing 
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. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 4.51 Loading on combined footing 
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 
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