Design of Combined Footing

For Column III & V

Input data
Column Size C1 V = 610 x 230 mm
Column Size C2 III = 610 x 230 mm
Load on Column C1, P1 = 1260 kN
Load on Column C2, P2 = 1705 kN
Concrete Grade Fck = 30 N/mm2
Grade of Steel Fy = 500 N/mm2
Distance from C1 & C2 (s) = 1 m c/c
Soil bearing Capacity SBC = 300 kN/mm2 645 NOT SAFE
Length at edge of footing at C1 = 550 mm from center
Length at edge of footing at C2 = 650 mm from center
foundation depth at site should be = 2.4 m
Calculating Size of Footing
Self Weight of Footing (15%) = 3409.7 kN
Required Area of Footing Areq = 11.366 m2
Center of gravity C.S. = 575.0 mm
Length of Footing L = 2450 mm
Provided Length of Footing L = 2743.2 mm 9 feet
Required Breadth of Footing B = 4143 mm
Provided Breadth of Footing B = 1676.4 mm 5.5 feet
Provided Area of Footing A prov = 4.599 m 2
NOT SAFE
Bending Moment & Shear Force
Factored Load Pu1 = 1890 kN
Factored Load Pu2 = 2557.5 kN
Soil pressure acting Upward = 1621 kN/m
along Length (L)
Shear Force at column C1 = 998 kN
Shear force at column C2 = 1504 kN
Shear force zero at length a = 1.58 m
Moment at Longitudianl direction
Maximum bending moment M = -77 kN-m
at shear Force is zero
Bending moment at Face of = 232 kN-m
Column C2
Moment at Transverse direction
Upward pressure at column C1 = 1127.4 kN/m
Upward pressure at column C2 = 1525.6 kN/m
Projection at Column C1 = 995 mm
Projection at Column C2 = 906 mm
Moment at column C1 = 558.08 kN-m
Moment at column C2 = 626.13 kN-m
Depth of footing Required d = 367.16 mm
Provided depth of Footing D = 535 mm
Effective depth of Footing d = 475 mm
Area of Steel at Longitudinal side
Mu = 0.87 fy Ast d ( 1 - (fy Ast)/(fck b d))
Area of Steel ,Ast = -367.9 mm2
Percentage of steel Pt% = -0.08 %
Column at C2
Area of Steel, Ast at C2 = 1171 mm2 Hence Providing minimum percentage
Percentage of steel at C2 Pt% = 0.25 % 0.1 %
Area of Steel at Transverse side
At Column C1, Area of Steel , Ast = 3021.2 mm2
Perceantage of Steel Pt% = 0.636 %
At Column C2, Area of Steel , Ast = 3447.2 mm2
Perceantage of Steel Pt% = 0.726 %
At Short direction of footing ( transverse) Spacing Provided
Providing steel of dia , in mm 12 = 37.42 mm c/c 100 mm c/c 1130.4 mm2
Providing steel of dia , in mm 12 = 32.79 mm c/c 100 mm c/c 1130.4 mm2
At Long direction of footing ( longitudinal )
Providing steel of dia , in mm 10 = -213.39 mm c/c 200 mm c/c 392.5 mm2
Providing steel of dia , in mm 10 = 67.03 mm c/c 200 mm c/c 392.5 mm2

Check for Oneway Shear

Net Shear force at column C2 , V = 547.10 kN
at distance d from column face
Permissible shear as by Pt% = 0.33 N/mm2
Permissible shear Force V = 262.78 < 547 kN
Hence provided depth is safe against Shear
Check for Two way Shear
Shear perimeter at Column C1 = 3580 mm
Shear perimeter at Column C2 = 3580 mm
Allowable Punching Shear stress = 1.37 N/mm2
Hence shear at column C1 = 1570 kN < 2329 SAFE
Hence shear at column C2 = 2237 kN < 2329 SAFE
Check for base pressure
Base pressure ( qs ) for depth, in m 2.4 = 691.69 kN/m2
< 300 kN/m2 SAFE
Check For Bearing Stress
At column Face C1 = 13.5 N/mm2
At footing Face in C1 = 27 N/mm2 > 11.25
At column Face C2 = 13.5 N/mm2
At footing Face in C2 = 27 N/mm2 > 13.5
 unit wt of concrete 25
Soil wt 18

650

a 7.25 7.25 7.25

b 206625 206625 206625
 c -76994178 2.32E+08 5.58E+08
-367.879 1171.06 3021.23

m percentage

NOT SAFE
NOT SAFE

SAFE
NOT SAFE

705
705

2 4.48
2 4.48
 7.25
206625
6.26E+08
3447.23
 Design of Combined Footing
For Column VI & V
Input data
Column Size C1 V = 230 x 460 mm
Column Size C2 VI = 300 x 460 mm
Load on Column C1, P1 = 270 kN
Load on Column C2, P2 = 170 kN
Concrete Grade Fck = 25 N/mm2
Grade of Steel Fy = 500 N/mm2
Distance from C1 & C2 (s) = 0.74 m c/c
Soil bearing Capacity SBC = 170 kN/mm2 132 SAFE
Length at edge of footing at C1 = 620 mm from center
Length at edge of footing at C2 = 620 mm from center
foundation depth at site should be = 2.6 m
Calculating Size of Footing
Self Weight of Footing (15%) = 506 kN
Required Area of Footing Areq = 2.98 m2
Center of gravity C.S. = 285.9 mm
Required Length of Footing L = 1812 mm
Provided Length of Footing L = 2438 mm 8 feet
Required Breadth of Footing B = 1221 mm
Provided Breadth of Footing B = 1372 mm 4.5 feet
Provided Area of Footing A prov = 3.34 m2 SAFE
Bending Moment & Shear Force
Factored Load Pu1 = 405 kN
Factored Load Pu2 = 255 kN
Soil pressure acting Upward = 271 kN/m
along Length (L)
Shear Force at column C1 = 237 kN
Shear force at column C2 = 87 kN
Shear force zero at length a = 0.95 m
Moment at Longitudianl direction
Maximum bending moment M = 17 kN-m
at shear Force is zero
Bending moment at Face of = 31 kN-m
Column C2
Moment at Transverse direction
Upward pressure at column C1 = 295.28 kN/m
Upward pressure at column C2 = 185.91 kN/m
Projection at Column C1 = 535 mm
Projection at Column C2 = 535 mm
Moment at column C1 = 63.386 kN-m
Moment at column C2 = 39.91 kN-m
Depth of footing Required d = 135.55 mm
Provided depth of Footing D = 380 mm
Effective depth of Footing d = 320 mm
Area of Steel at Longitudinal side
Mu = 0.87 fy Ast d ( 1 - (fy Ast)/(fck b d))
Area of Steel ,Ast = 125.0 mm2
Percentage of steel Pt% = 0.04 %
Column at C2
Area of Steel, Ast at C2 = 225 mm2 Hence Providing minimum percentage
Percentage of steel at C2 Pt% = 0.07 % 0.12 %
Area of Steel at Transverse side
At Column C1, Area of Steel , Ast = 469.12 mm2
Perceantage of Steel Pt% = 0.147 %
At Column C2, Area of Steel , Ast = 292.04 mm2
Perceantage of Steel Pt% = 0.091 %
At Short direction of footing ( transverse) Spacing Provided
Providing steel of dia , in mm 10 = 167.34 mm c/c 150 mm c/c 523 mm2 SAFE
Providing steel of dia , in mm 10 = 268.80 mm c/c 150 mm c/c 523 mm2 SAFE
At Long direction of footing ( longitudinal )
Providing steel of dia , in mm 10 = 628 mm c/c 200 mm c/c 393 mm2 SAFE
Providing steel of dia , in mm 10 = 348.92 mm c/c 200 mm c/c 393 mm2 SAFE

Check for Oneway Shear

Net Shear force at column C2 , V = -62 kN
at distance d from column face
Permissible shear as by Pt% = 0.28 N/mm2
Permissible shear Force V = 122.9 < -61.7 kN
Hence provided depth is safe against Shear
Check for Two way Shear
Shear perimeter at Column C1 = 2660 mm
Shear perimeter at Column C2 = 2800 mm
Allowable Punching Shear stress = 1.25 N/mm2
Hence shear at column C1 = 325.0 kN < 1064.0 SAFE
Hence shear at column C2 = 175.0 kN < 1120.0 SAFE
Check for base pressure
Base pressure ( qs ) for depth, in m 2.6 = 180.64 kN/m2
< 170 kN/m2 SAFE

Check For Bearing Stress

At column Face C1 = 11.25 N/mm2
At footing Face in C1 = 22.5 N/mm2 > 9
At column Face C2 = 11.25 N/mm2
At footing Face in C2 = 22.5 N/mm2 > 11.25
 unit wt of concrete 24
Soil wt 18

620

a 8.7 8.7 8.7

b 139200 139200 139200
 c 17265244 30876680 63386442
125.0086 224.98 469.12

780
780

2 4.216816
2 3.692223
 8.7
139200
39909982
292.04