COMBINED FOUNDATION DESIGN (ACI 318-11)
Result Summary
Left Overhang Right Overhang Length Width Thickness
Footing No.
(m) (m) (m) (m) (m)
1 0.15 1.00 3.25 2.30 0.30
Footing No. Footing Reinforcement
- Main Steel Top Main Steel Bottom Secondary Steel Top Secondary Steel Bottom
1 9 - ϕ16 9 - ϕ16 12 - ϕ16 12 - ϕ16
Combined Footing 1
Input Data
1.95 m 2m
1.7 m
0.3 m
0.15 m 1m
1.75 m
0.4 m
0.3 m
0.2 m
0.2 m
2.3 m
3.25 m
2.1 m
Geometry of Footing
For Column 58
Column Dimensions
Column Shape : Rectangular
Column Length - X (Dcol) : 0.30 m
Column Width - Z (Bcol) : 0.20 m
Pedestal
Include Pedestal : No
Pedestal Shape : N/A
Pedestal Height (Ph) : N/A
Pedestal Length - X (Pl) : N/A
Pedestal Width - Z (Pw) : N/A
Eccentricity
Column Offset in : 0.00 m
Transverse Direction
For Column 59
Column Dimensions
Column Shape : Rectangular
Column Length - X (Dcol) : 0.40 m
Column Width - Z (Bcol) : 0.20 m
Pedestal
Include Pedestal : No
Pedestal Shape : N/A
Pedestal Height (Ph) : N/A
Pedestal Length - X (Pl) : N/A
Pedestal Width - Z (Pw) : N/A
Eccentricity
Column Offset in : 0.00 m
Transverse Direction
Length of left overhang : 0.00 m
Length of right overhang : 1.00 m
Is the length of left overhang fixed : Yes
Is the length of right overhang fixed : Yes
Minimum width of footing (Wo) : 1.00 m
Minimum Thickness of footing (Do) : 300.00 mm
Maximum Width of Footing (Wo) : 10000.00 mm
Maximum Thickness of Footing (Do) : 500.00 mm
Maximum Length of Footing (Lo) : 10000.00 mm
Length Increment : 100.00 mm
Depth Increment : 50.00 mm
Cover and Soil Properties
Pedestal Clear Cover : 50.00 mm
Footing Clear Cover : 75.00 mm
Unit Weight of soil : 18.00 kN/m3
Soil Bearing Capacity : 125.00 kN/m2
Soil Bearing Capacity Type : Gross Bearing Capacity
Soil Surcharge : 0.00 kN/m2
Depth of Soil above Footing : 1.70 m
Type of Depth : Fixed Top
Depth of Water Table : 10.00 m
Concrete and Rebar Properties
Unit Weight of Concrete : 24.00 kN/m3
Compressive Strength of Concrete : 21.00 N/mm2
Yield Strength of Steel : 415.00 N/mm2
Minimum Bar Size : #16
Maximum Bar Size : #20
Minimum Pedestal Bar Size : #16
Maximum Pedestal Bar Size : #22
Minimum Bar Spacing : 100.00 mm
Maximum Bar Spacing : 300.00 mm
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Design Calculations
Footing Size Calculations
Reduction of force due to buoyancy = 0.000 kN
Area from initial length and width, Ao = = 3.25 m^2
Min. area required from bearing pressure, Amin = = 3.12 m^2
Note: Amin is an initial estimation.
P = Critical Factored Axial Load(without self weight/buoyancy/soil).
qmax = Respective Factored Bearing Capacity.
Final footing dimensions are:
Length of footing, L : 3.25 m
Width of footing, W : 2.30 m
Depth of footing, Do : 0.30 m
Area, A : 7.48 m^2
Length of left overhang, Lleft_overhang : 0.15 m
Length of right overhang,
1.00 m
Lright_overhang :
Footing self weight : 53.82 kN
Soil weight on top of footing : 228.73 kN
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Load Combinations
Load Load Soil Self
Combination Load Combination Title Combination Bearing Weight
Number Factor Factor Factor
201 1.0DL 1.00 1.00 1.00
202 1.0DL + 1.0LL 1.00 1.00 1.00
203 1.0DL + 1.0LR 1.00 1.00 1.00
204 1.0DL + 0.75LL 1.00 1.00 1.00
205 1.0DL + 0.6WL X-DIR 1.00 1.00 1.00
206 1.0DL + 0.6WL X-DIR_R 1.00 1.00 1.00
207 1.0DL + 0.6WL Z-DIR 1.00 1.00 1.00
208 1.0DL + 0.6WL Z-DIR_R 1.00 1.00 1.00
209 1.0DL + 0.714E X-DIR 1.00 1.00 1.00
210 1.0DL + 0.714E X-DIR_R 1.00 1.00 1.00
211 1.0DL + 0.714E Z-DIR 1.00 1.00 1.00
212 1.0DL + 0.714E Z-DIR_R 1.00 1.00 1.00
Load Load Soil Self
Combination Load Combination Title Combination Bearing Weight
Number Factor Factor Factor
111 1.4DL 1.00 1.00 1.00
112 1.2DL + 1.6LL + 0.5LR 1.00 1.00 1.00
113 1.2DL + 1.6LR + 0.5LL 1.00 1.00 1.00
114 1.2DL + 1.6LR + 0.5WL X-DIR 1.00 1.00 1.00
115 1.2DL + 1.6LR + 0.5WL X-DIR_R 1.00 1.00 1.00
116 1.2DL + 1.6LR + 0.5WL Z-DIR 1.00 1.00 1.00
117 1.2DL + 1.6LR + 0.5WL Z-DIR_R 1.00 1.00 1.00
118 0.9DL + 1.0WL X-DIR 1.00 1.00 1.00
119 0.9DL + 1.0WL X-DIR_R 1.00 1.00 1.00
120 0.9DL + 1.6WL Z-DIR 1.00 1.00 1.00
121 0.9DL + 1.6WL Z-DIR_R 1.00 1.00 1.00
122 1.2DL + 1.0E X-DIR 1.00 1.00 1.00
123 1.2DL + 1.0E X-DIR_R 1.00 1.00 1.00
124 1.2DL + 1.0E Z-DIR 1.00 1.00 1.00
125 1.2DL + 1.0E Z-DIR_R 1.00 1.00 1.00
126 0.9DL + 1.0E X-DIR 1.00 1.00 1.00
Load Load Soil Self
Combination Load Combination Title Combination Bearing Weight
Number Factor Factor Factor
127 0.9DL + 1.0E X-DIR_R 1.00 1.00 1.00
128 0.9DL + 1.0E Z-DIR 1.00 1.00 1.00
129 0.9DL + 1.0E Z-DIR_R 1.00 1.00 1.00
130 1.2DL + 0.5LL + 1.0E X-DIR 1.00 1.00 1.00
131 1.2DL + 0.5LL + 1.0E X-DIR_R 1.00 1.00 1.00
132 1.2DL + 0.5LL + 1.0E Z-DIR 1.00 1.00 1.00
133 1.2DL + 0.5LL + 1.0E Z-DIR_R 1.00 1.00 1.00
Applied Loads on Top of Pedestal
Before consideration of self weight and load safety factor table
Applied Loads - Service Stress Level
Axial Shear X Shear Z Moment X Moment Z
LC
(kN) (kN) (kN) (kNm) (kNm)
-
Column Number : 58
201 31.61 -0.54 0.21 0.00 0.00
202 27.97 -0.57 0.25 0.00 0.00
203 30.44 -0.58 0.19 0.00 0.00
204 28.88 -0.57 0.24 0.00 0.00
205 31.61 -0.54 0.21 0.00 0.00
206 31.61 -0.54 0.21 0.00 0.00
207 31.61 -0.54 0.21 0.00 0.00
208 31.61 -0.54 0.21 0.00 0.00
209 -56.27 15.64 -0.06 0.00 0.00
210 119.50 -16.73 0.48 0.00 0.00
211 37.02 -0.47 6.04 0.00 0.00
212 26.20 -0.61 -5.62 0.00 0.00
-
Column Number : 59
201 163.13 2.85 0.41 0.00 0.00
202 176.06 3.32 0.54 0.00 0.00
203 185.10 3.13 0.44 0.00 0.00
204 172.83 3.20 0.51 0.00 0.00
205 163.13 2.85 0.41 0.00 0.00
206 163.13 2.85 0.41 0.00 0.00
207 163.13 2.85 0.41 0.00 0.00
208 163.13 2.85 0.41 0.00 0.00
209 242.20 19.24 0.21 0.00 0.00
210 84.05 -13.55 0.62 0.00 0.00
211 229.84 2.92 12.92 0.00 0.00
212 96.41 2.77 -12.09 0.00 0.00
Applied Loads - Strength Level
Axial Shear X Shear Z Moment X Moment Z
LC
(kN) (kN) (kN) (kNm) (kNm)
-
Column Number : 58
111 44.26 -0.76 0.29 0.00 0.00
112 31.52 -0.72 0.30 0.00 0.00
113 34.24 -0.73 0.24 0.00 0.00
114 36.07 -0.71 0.22 0.00 0.00
115 36.07 -0.71 0.22 0.00 0.00
116 36.07 -0.71 0.22 0.00 0.00
117 36.07 -0.71 0.22 0.00 0.00
118 28.45 -0.49 0.19 0.00 0.00
119 28.45 -0.49 0.19 0.00 0.00
120 28.45 -0.49 0.19 0.00 0.00
121 28.45 -0.49 0.19 0.00 0.00
122 -85.16 22.02 -0.13 0.00 0.00
123 161.02 -23.32 0.63 0.00 0.00
124 45.51 -0.56 8.42 0.00 0.00
125 30.36 -0.75 -7.91 0.00 0.00
126 -94.64 22.18 -0.19 0.00 0.00
127 151.54 -23.16 0.57 0.00 0.00
128 36.02 -0.39 8.35 0.00 0.00
129 20.88 -0.58 -7.97 0.00 0.00
130 -86.98 22.00 -0.11 0.00 0.00
131 159.20 -23.34 0.65 0.00 0.00
Applied Loads - Strength Level
Axial Shear X Shear Z Moment X Moment Z
LC
(kN) (kN) (kN) (kNm) (kNm)
132 43.68 -0.57 8.43 0.00 0.00
133 28.54 -0.76 -7.89 0.00 0.00
-
Column Number : 59
111 228.38 3.98 0.58 0.00 0.00
112 227.43 4.31 0.71 0.00 0.00
113 237.38 4.11 0.60 0.00 0.00
114 230.91 3.87 0.53 0.00 0.00
115 230.91 3.87 0.53 0.00 0.00
116 230.91 3.87 0.53 0.00 0.00
117 230.91 3.87 0.53 0.00 0.00
118 146.81 2.56 0.37 0.00 0.00
119 146.81 2.56 0.37 0.00 0.00
120 146.81 2.56 0.37 0.00 0.00
121 146.81 2.56 0.37 0.00 0.00
122 306.50 26.37 0.21 0.00 0.00
123 85.00 -19.54 0.78 0.00 0.00
124 289.19 3.52 18.01 0.00 0.00
125 102.31 3.31 -17.02 0.00 0.00
126 257.57 25.52 0.09 0.00 0.00
127 36.06 -20.40 0.66 0.00 0.00
128 240.25 2.66 17.88 0.00 0.00
129 53.38 2.46 -17.14 0.00 0.00
130 312.97 26.61 0.27 0.00 0.00
131 91.46 -19.31 0.85 0.00 0.00
132 295.66 3.75 18.07 0.00 0.00
133 108.78 3.55 -16.95 0.00 0.00
Pressures at 4 Corners
Pressure at Pressure at
Pressure at top Pressure at top Area of footing in
bottom right bottom left
Load Case left corner right corner uplift (Au)
corner corner
(kN/m^2) (kN/m^2) (sq. m)
(kN/m^2) (kN/m^2)
210 97.7155 32.1126 32.3422 97.9451 0.00
209 2.1854 123.1279 123.1591 2.2166 0.00
209 2.1854 123.1279 123.1591 2.2166 0.00
210 97.7155 32.1126 32.3422 97.9451 0.00
If Au is zero, there is no uplift and no pressure adjustment is necessary. Otherwise, to account for uplift, areas of negative pressure
will be set to zero and the pressure will be redistributed to remaining corners.
Summary of Adjusted Pressures at Four Corners
Pressure at top left Pressure at top right Pressure at bottom Pressure at bottom
Load Case corner corner right corner left corner
(kN/m^2) (kN/m^2) (kN/m^2) (kN/m^2)
210 97.7155 32.1126 32.3422 97.9451
209 2.1854 123.1279 123.1591 2.2166
209 2.1854 123.1279 123.1591 2.2166
210 97.7155 32.1126 32.3422 97.9451
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Stability Check
Resisting
Resultant
Shear X Shear Z Sliding Resultant Required
Load Case Shear Ratio X Ratio Z
(kN) (kN) Force Ratio FOS
(kN)
(kN)
201 2.303 0.623 2.385 190.913 82.915 306.575 80.039 1.500
202 2.743 0.787 2.853 194.628 70.964 247.338 68.212 1.500
203 2.552 0.627 2.627 199.237 78.084 317.858 75.829 1.500
204 2.633 0.746 2.736 193.699 73.577 259.703 70.791 1.500
205 2.303 0.623 2.385 190.913 82.915 306.575 80.039 1.500
206 2.303 0.623 2.385 190.913 82.915 306.575 80.039 1.500
207 2.303 0.623 2.385 190.913 82.915 306.575 80.039 1.500
208 2.303 0.623 2.385 190.913 82.915 306.575 80.039 1.500
209 34.880 0.149 34.880 187.390 5.372 1258.453 5.372 1.500
210 -30.275 1.097 30.295 194.436 6.422 177.316 6.418 1.500
211 2.444 18.955 19.112 219.762 89.919 11.594 11.498 1.500
212 2.161 -17.710 17.841 162.065 74.994 9.151 9.084 1.500
Check for stability against overturning (Moments printed against Local axis)
Resisting Resisting
Moment X Moment Z Required
Load Case Moment X Moment Z Ratio X Ratio Z
(kNm) (kNm) FOS
(kNm) (kNm)
201 0.187 -56.016 548.865 775.570 2938.014 13.846 1.500
202 0.236 -69.608 559.546 790.662 2370.320 11.359 1.500
203 0.188 -71.549 572.795 809.384 3046.134 11.312 1.500
204 0.224 -66.210 556.875 786.889 2488.819 11.885 1.500
205 0.187 -56.016 548.865 775.570 2938.014 13.846 1.500
206 0.187 -56.016 548.865 775.570 2938.014 13.846 1.500
207 0.187 -56.016 548.865 775.570 2938.014 13.846 1.500
208 0.187 -56.016 548.865 775.570 2938.014 13.846 1.500
209 0.045 -244.841 538.736 761.258 12060.176 3.109 1.500
210 0.329 132.809 558.994 789.883 1699.280 5.947 1.500
211 5.687 -89.779 631.803 892.765 111.105 9.944 1.500
212 -5.313 -22.253 465.927 658.375 87.697 29.586 1.500
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Calculations of Footing Thickness
Footing thickness is calculated based on the ultimate load cases
Punching Shear Check
For Column 1
Critical Load case for Punching Shear Check : 123
Total Footing Depth, Do = 0.30 m
Calculated Effective Depth,d = 0.21 m
For rectangular column, = : 1.50
Considering the particular column as edge column, Slab
: 30.0
Edge Factor
Effective depth, d, increased until 0.75*Vc Punching Shear Force
Punchng Shear Force, Vu = 144.97kN
From ACI Cl.11.11.2, for column = 1.32 m
Equation 11-31, Vc1 = = 489.15 kN
Equation 11-32, Vc2 = = 708.27 kN
Equation 11-33, Vc3 = = 419.27 kN
Punching shear strength,Vc= 0.75 x minimum of (Vc1,Vc2,Vc3) = 314.45 kN
0.75 * Vc > Vu hence, OK
For Column 2
Critical Load case for Punching Shear Check : 130
Total Footing Depth, Do = 0.30 m
Calculated Effective Depth,d = 0.21 m
For rectangular column, = : 2.00
Considering the particular column as edge column, Slab
: 30.0
Edge Factor
Effective depth, d, increased until 0.75*Vc Punching Shear Force
Punchng Shear Force, Vu = 297.71kN
From ACI Cl.11.11.2, for column = 3.22 m
Equation 11-31, Vc1 = = 1023.67 kN
Equation 11-32, Vc2 = = 1010.47 kN
Equation 11-33, Vc3 = = 1023.67 kN
Punching shear strength,Vc= 0.75 x minimum of (Vc1,Vc2,Vc3) = 757.85 kN
0.75 * Vc > Vu hence, OK
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One-Way Shear
Shear Diagram
110
100
90
80
Shear [kN]
70
60
50
40
30
20
10
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
0 0.5 1 1.5 2 2.5 3 3.25
Position [m]
1.84 m
2.74 m 0.59 m
Shear Plane Parallel to Foundation Width
Critical load case for maximum shear force along the length of footing : 130
Critical Shear force,Vu: = 130.20 kN
Point of occurance of Vu: = 2.65 m
From ACI Cl.11.2.1.1, Vc : = 351.82 kN
0.75 x Vc = 263.87 kN
Since 0.75 * Vc > Vu hence, OK
0.84 m 0.84 m
Shear Plane Parallel to Foundation Length
0.84 m 0.84 m
Critical load case for maximum shear force along the width of footing : 132
Critical Shear force,Vu: = 130.09 kN
Point of occurance of Vu: = 1.45 m
From ACI Cl.11.2.1.1, Vc : = 497.14 kN
0.75 x Vc = 372.85 kN
Since 0.75 * Vc > Vu hence, OK
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Design for Flexure
Design of flexure
Moment Diagram
200
Moment [kNm]
-200
0 0.5 1 1.5 2 2.5 3 3.25
Position [m]
Bottom Reinforcement
Critical load case : 130
Required Effective Depth : 0.20 m
, from ACI Cl.10.2.7.3 = max[0.85-0.05x(Fc-4),0.65] = 0.8500
From ACI Cl. 10.3.2, = = 0.02161
From ACI Cl. 10.3.3, = = 0.01621
From ACI Cl. 7.12.2, = = 0.00200
Modular Ratio,m = = 23.2493
Ultimate Moment (Mz) : 83.98 kNm
Point of occurrence of the ultimate moment along the length of footing : 2.05 m
Nominal Moment Capacity : 93.32 kNm
Required (based on effective depth) : 0.0030 kNm
x d / Depth (based on gross depth) : 0.0020 kNm
Area of main steel required, As = : 1380.00 mm2
Top Reinforcement
Critical load case : 123
Required Effective Depth : 0.20 m
, from ACI Cl.10.2.7.3 = max[0.85-0.05x(Fc-4),0.65] = 0.8500
From ACI Cl. 10.3.2, = = 0.02161
From ACI Cl. 10.3.3, = = 0.01621
From ACI Cl. 7.12.2, = = 0.00200
Modular Ratio,m = = 23.2493
Ultimate Moment (Mz) : 61.75 kNm
Point of occurrence of the ultimate moment along the length of footing : 1.06 m
Nominal Moment Capacity : 68.61 kNm
Required (based on effective depth): 0.0030
x d / Depth (based on gross depth) : 0.0020
Area of main steel required, As = : 1380.00 mm2
Distribution Reinforcement
Critical load case : 132
Critical Moment for distribution steel (Mx) : 84.7898 kNm
Nominal moment Capacity : 94.2109 kNm
Point of occurance of the critical moment along length: 1.2500 m
Required (based on effective depth): 0.0030
x d / Depth (based on gross depth) : 0.0020
Area of distribution steel required, As = : 1950.00 mm2
Top surface disribution reinforcement
Moment at column face : 67.7174 kNm
Provided Area for distribution steel along Z(Top 1950.00 mm2
reinforcement):
Provided Reinforcement
Main bar no. for top Reinforcement: #16
Spacing of top reinforcement bar : 268.75 mm
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 265mm o.c.
Main bar no. for bottom Reinforcement: #16
Spacing of bottom reinforcement bar : 268.75 mm
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 265mm o.c.
Distribution bar no. (Bottom): #16
Spacing of distribution bars (Bottom): 281.82 mm
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 280mm o.c.
Distribution bar no.(Top): #16
Spacing of distribution bars(Top) : 280.36 mm
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 280mm o.c.
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