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Isolated Footing Design
Isolated Footing F2Input Values
Concrete and Rebar Properties
Unit Weight of Concrete : 23.000 kN/m3
Strength of Concrete : 20.000 MPa
Yield Strength of Steel : 415.000 MPa
Minimum Bar Size : # 3
Maximum Bar Size : # 8
Minimum Bar Spacing : 2.20 in
Maximum Bar Spacing : 18.00 in
Concrete Covers
Pedestal Clear Cover (P, CL) : 1.50 in
Footing Clear Cover (F, CL) : 3.00 in
Soil Properties
Unit Weight : 22.00 kN/m3
Soil Bearing Capacity : 150.00 kN/m2
Soil Surcharge : 0.00 ksi
Depth of Soil above Footing : 4.00 ft
GeometryInitial Footing Dimensions
Thickness (Ft) : 6.00 inLength - X (Fl) : 60.00 in
Width - Z (Fw) : 60.00 in
Eccentricity along X (Oxd) : 0.00 in
Eccentricity along Z (Ozd) : 0.00 in
Pedestal
Include Pedestal? Yes
Pedestal Shape : Rectangular
Pedestal Height (Ph) : 48.00 in
Pedestal Length - X (Pl) : 30.00 in
Pedestal Width - Z (Pw) : 30.00 in
Footing Design CalculationsFooting Size
Initial Length (Lo) = 60.00 in
Initial Width (Wo) = 60.00 in
Min. area required frombearing pressure, Amin =
P / qmax = 1786.491in
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Area from initial length andwidth, Ao =
Lo * Wo = 3600.00in
Final dimensions for design.
Length (L2) = 94.00 in Governing Load Case : # 13
Width (W2) = 94.00 in Governing Load Case : # 13
Area (A2) = 8836.00 in
Calculated pressures at 4 corners.
Load CasePressure atcorner 1 (q1)
(kip/in^2)
Pressure atcorner 2 (q2)
(kip/in^2)
Pressure atcorner 3 (q3)
(kip/in^2)
Pressure atcorner 4 (q4)
(kip/in^2)
Area of footing inuplift (Au)
(in2)
11 0.01 0.01 0.01 0.01 0.00
11 0.01 0.01 0.01 0.01 0.00
20 0.01 0.01 0.01 0.01 0.00
20 0.01 0.01 0.01 0.01 0.00
If Au is zero, there is no uplift and no pressure adjustment is necessary. Otherwise, to account for uplift, areas of negative pressube set to zero and the pressure will be redistributed to remaining corners.Summary of adjusted pressures at 4 corners.
Load Case
Pressure atcorner 1 (q1)
(kip/in^2)
Pressure atcorner 2 (q2)
(kip/in^2)
Pressure atcorner 3 (q3)
(kip/in^2)
Pressure atcorner 4 (q4)
(kip/in^2)
11 0.01 0.01 0.01 0.01
11 0.01 0.01 0.01 0.01
20 0.01 0.01 0.01 0.01
20 0.01 0.01 0.01 0.01
Adjust footing size if necessary.
Check for stability against overturning and sliding:-
Factor of safety againstsliding
Factor of safety againstoverturning
LoadCase No.
Along X-Direction
Along Z-Direction
About X-Direction
About Z-Direction
11 121.193 107.604 111.150 148.385
13 46.724 1.565 1.533 55.321
16 130.762 31.290 31.232 160.723
17 116.466 50.879 49.044 142.188
20 135.012 19.604 19.462 166.334
21 108.496 21.356 20.853 132.006
Critical load case and the governing factor of safety for overturning and sliding
Critical Load Case for Sliding along X-Direction : 13
Governing Disturbing Force : 0.257 kip
Governing Restoring Force : 12.016 kip
Minimum Sliding Ratio for the Critical Load Case : 46.724
Critical Load Case for Overturning about X-Direction : 13
Governing Overturning Moment : 783.718 kip-in
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Governing Resisting Moment : 1201.604 kip-in
Minimum Overturning Ratio for the Critical Load Case : 1.533
Critical load case and the governing factor of safety for overturning and sliding
Critical Load Case for Sliding along Z-Direction : 13
Governing Disturbing Force : 7.677 kip
Governing Restoring Force : 12.016 kip
Minimum Sliding Ratio for the Critical Load Case : 1.565
Critical Load Case for Overturning about Z-Direction : 13
Governing Overturning Moment : -21.721 kip-in
Governing Resisting Moment : 1201.604 kip-in
Minimum Overturning Ratio for the Critical Load Case : 55.321
Check Trial Depth against Punching Shear strength, Vc
Calculated Effective Depth, deff= D - Ccover- 1.0 = 4.00 in
For rectangular column, = Bcol / Dcol = 1.00
Effective depth, deff, increased until 0.75*Vc Punching Shear ForcePunching Shear Force, Pu = 0.00 kip, Load Case # 13
From ACI Cl.11.12.2.1, for column = 136.00 in
Equation 11-33, Vc1 = 175.79 kip
Equation 11-34, Vc2 = 93.07 kip
Equation 11-35, Vc3 = 117.20 kip
Punching shear strength, Vc = 0.75 * minimum of (Vc1, Vc2, Vc3) = 69.80 kip
0.75 * Vc > Vu hence, OK
Check Trial Depth against One-Way Shear strength, VcShear along the Z-Z axis.
From ACI Cl.11.3.1.1, Vc = 43.09 kip
Distance along Z to design for shear, Dz = 0.00 in
Check that 0.75 * Vc > Vux where Vux is the shear force for the critical load cases at a distance deff from the face of the column caby bending about the X axis.
From above calculations, 0.75 * Vc = 0.00 kip
Critical load case for Vux is # 13 0.00 kip
0.75 * Vc > Vux hence, OK
Shear along the X-X axis.
From ACI Cl.11.3.1.1, Vc = 43.09 kip
Distance along X to design for shear, Dx = 0.00 in
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Check that 0.75 * Vc > Vuz where Vuz is the shear force for the critical load cases at a distance deff from the face of the column caby bending about the Z axis.
From above calculations, 0.75 * Vc = 0.00 kip
Critical load case for Vuz is # 13 0.00 kip
0.75 * Vc > Vuz hence, OK
Design for Flexure about Z axisCalculate the flexural reinforcement along the X direction of the footing. Find the area of steel required, A, as per Sectioof Reinforced Concrete Design (5th ed.) by Salmon and Wang (Ref. 1) Critical Load Case # 20The strength values of steel and concrete used in the formulae are in ksi
Factor from ACI Cl.10.2.7.3 for Fc' 4 ksi, 0.85
From ACI Cl. 10.3.2, = 0.02058
From ACI Cl. 10.3.3, = 0.01544
From ACI Cl. 7.12.2, = 0.00180
From Ref. 1, Eq. 3.8.4a, constant m = 24.41
Calculate reinforcement ratio for critical load case
Design for flexure about Z axis is performedat the face of the column at a distance, Dx =
35.00 in
Ultimate moment, 167.98 kip-in
Nominal moment capacity, Mn = 186.65 kip-in
Required = 0.00199
Since OK
Area of Steel Required, As =0.79 sq.in
Find suitable bar arrangement between minimum and maximum rebar sizes
Available development length for bars, DL = 32.00 in
Try bar size # 3 Area of one bar = 0.11 sq.in
Number of bars required, Nbar= 8
Because the number of bars is rounded up, make sure new reinforcement ratio
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Design for Flexure about X axisCalculate the flexural reinforcement along the Z direction of the footing. Find the area of steel required, A, as per Sectioof Reinforced Concrete Design (5th ed.) by Salmon and Wang (Ref. 1) Critical Load Case # 11The strength values of steel and concrete used in the formulae are in ksi
Factor from ACI Cl.10.2.7.3 for Fc' 4 ksi, 0.85
From ACI Cl. 10.3.2, = 0.02058
From ACI Cl. 10.3.3, = 0.01544
From ACI Cl.7.12.2, = 0.00180
From Ref. 1, Eq. 3.8.4a, constant m = 24.41
Calculate reinforcement ratio for critical load case
Design for flexure about X axis is performedat the face of the column at a distance, Dz =
65.00 in
Ultimate moment, 138.47 kip-in
Nominal moment capacity, Mn = 153.85 kip-in
Required = 0.00389
Since OK
Area of Steel Required, As =1.02 sq.in
Find suitable bar arrangement between minimum and maximum rebar sizes
Available development length for bars, DL = 32.00 in
Try bar size # 3 Area of one bar = 0.11 sq.in
Number of bars required, Nbar= 10
Because the number of bars is rounded up, make sure new reinforcement ratio
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Calculate the flexural reinforcement along the X direction of the footing. Find the area of steel required The strength values of steel and concrete used in the formulae are in ksi
Factor from ACI Cl.10.2.7.3 for Fc' 4 ksi, 0.85
From ACI Cl. 10.3.2, = 0.02058
From ACI Cl. 10.3.3, = 0.01544
From ACI Cl. 7.12.2, = 0.00180
From Ref. 1, Eq. 3.8.4a, constant m = 24.41
Calculate reinforcement ratio for critical load case
Design for flexure about A axis is performedat the face of the column at a distance, Dx =
35.00 in
Ultimate moment, 279.79 kip-in
Nominal moment capacity, Mn = 310.87 kip-in
Required = 0.00446
Since OK
Area of Steel Required, As =1.56 sq.in
Find suitable bar arrangement between minimum and maximum rebar sizes
Design for top reinforcement about X axis
First load case to be in pure uplift # 13Calculate the flexural reinforcement along the Z direction of the footing. Find the area of steel required The strength values of steel and concrete used in the formulae are in ksi
Factor from ACI Cl.10.2.7.3 for Fc' 4 ksi, 0.85
From ACI Cl. 10.3.2, = 0.02058
From ACI Cl. 10.3.3, = 0.01544
From ACI Cl.7.12.2, = 0.00180
From Ref. 1, Eq. 3.8.4a, constant m = 24.41
Calculate reinforcement ratio for critical load case
Design for flexure about A axis is performedat the face of the column at a distance, Dx =
35.00 in
Ultimate moment, 279.79 kip-in
Nominal moment capacity, Mn = 310.87 kip-in
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Required = 0.00337
Since OK
Area of Steel Required, As =1.35 sq.in
Find suitable bar arrangement between minimum and maximum rebar sizes
Pedestal Design CalculationsCritical Load Case: 11
Strength and Moment Along Reinforcement in X direction
Bar size : # 8
Number of Bars : 12
Steel Area : 9.0000 sq.in
Neutral Axis Depth (Xb): 4.3826 in
Strength and Moment from Concrete
Cc = 275.55 kip
Mc = 3620.00 kip-in
Calculate strength and moment from one bar.
Distance between extreme fiber and bar, db 2.00 in
Strain in bar, = 0.0016
Maximum Strain, = 0.0021
as
47.30 kip/in^2
0.0016
as
2.47 kip/in^2
35.42 kip
460.42 kip-in
Total Bar Capacity, Cs = -238.74 kip
Capacity of Column = Cc + Cs = 36.81 kip
Total Bar Moment, Ms = 4314.31 kip-in
Total Moment = Mc + Ms = 7934.31 kip-in
Strength and Moment Along Reinforcement in Z direction
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Bar size : # 8
Number of Bars : 12
Steel Area : 9.0000 sq.in
Neutral Axis Depth (Xb): 4.3826 in
Strength and Moment from Concrete
Cc
= 275.55 kip
Mc = 3620.00 kip-in
Calculate strength and moment from one bar.
Distance between extreme fiber and bar, db 2.00 in
Strain in bar, = 0.0016
Maximum Strain, = 0.0021
as
47.30 kip/in^2
0.0016
as
2.47 kip/in^2
35.42 kip
460.42 kip-in
Total Bar Capacity, Cs = -238.74 kip
Capacity of Column = Cc + Cs = 36.81 kip
Total Bar Moment, Ms = 4314.31 kip-in
Total Moment = Mc + Ms = 7934.31 kip-in
Check for bi-axial bending, 0.003
Design Moment Mnx= 33.652 kip-in
Design Moment Mnz= 39.656 kip-in
Total Moment Mox= 7934.310 kip-in
Total Moment Moz= 7934.310 kip-in
if Mnx or Mnz = 0, then = 1.0
otherwise, = 1.24
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Isolated Footing F5Input Values
Concrete and Rebar Properties
Unit Weight of Concrete : 23.000 kN/m3
Strength of Concrete : 20.000 MPa
Yield Strength of Steel : 415.000 MPa
Minimum Bar Size : # 3
Maximum Bar Size : # 8
Minimum Bar Spacing : 2.20 in
Maximum Bar Spacing : 18.00 in
Concrete Covers
Pedestal Clear Cover (P, CL) : 1.50 in
Footing Clear Cover (F, CL) : 3.00 in
Soil Properties
Unit Weight : 22.00 kN/m3
Soil Bearing Capacity : 150.00 kN/m2
Soil Surcharge : 0.00 ksi
Depth of Soil above Footing : 4.00 ft
GeometryInitial Footing Dimensions
Thickness (Ft) : 6.00 in
Length - X (Fl) : 60.00 in
Width - Z (Fw) : 60.00 in
Eccentricity along X (Oxd) : 0.00 in
Eccentricity along Z (Ozd) : 0.00 in
Pedestal
Include Pedestal? Yes
Pedestal Shape : Rectangular
Pedestal Height (Ph) : 48.00 in
Pedestal Length - X (Pl) : 30.00 in
Pedestal Width - Z (Pw) : 30.00 in
Footing Design CalculationsFooting Size
Initial Length (Lo) = 60.00 in
Initial Width (Wo) = 60.00 in
Min. area required frombearing pressure, Amin =
P / qmax = 6751.470in
Area from initial length andwidth, Ao =
Lo * Wo = 3600.00in
Final dimensions for design.
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Minimum Overturning Ratio for the Critical Load Case : 5.149
Critical load case and the governing factor of safety for overturning and sliding
Critical Load Case for Sliding along Z-Direction : 13
Governing Disturbing Force : 21.908 kip
Governing Restoring Force : 103.743 kip
Minimum Sliding Ratio for the Critical Load Case : 4.735
Critical Load Case for Overturning about Z-Direction : 13
Governing Overturning Moment : 96.169 kip-in
Governing Resisting Moment : 11930.502 kip-in
Minimum Overturning Ratio for the Critical Load Case : 124.058
Check Trial Depth against Punching Shear strength, Vc
Calculated Effective Depth, deff= D - Ccover- 1.0 = 7.00 in
For rectangular column, = Bcol / Dcol = 1.00Effective depth, deff, increased until 0.75*Vc Punching Shear ForcePunching Shear Force, Pu = 106.82 kip, Load Case # 13
From ACI Cl.11.12.2.1, for column = 148.00 in
Equation 11-33, Vc1 = 334.79 kip
Equation 11-34, Vc2 = 217.16 kip
Equation 11-35, Vc3 = 223.19 kip
Punching shear strength, Vc = 0.75 * minimum of (Vc1, Vc2, Vc3) = 162.87 kip
0.75 * Vc > Vu hence, OK
Check Trial Depth against One-Way Shear strength, VcShear along the Z-Z axis.
From ACI Cl.11.3.1.1, Vc = 86.71 kip
Distance along Z to design for shear, Dz = 79.50 in
Check that 0.75 * Vc > Vux where Vux is the shear force for the critical load cases at a distance deff from the face of the column caby bending about the X axis.
From above calculations, 0.75 * Vc = 65.03 kip
Critical load case for Vux is # 13 58.19 kip
0.75 * Vc > Vux hence, OK
Shear along the X-X axis.
From ACI Cl.11.3.1.1, Vc = 86.71 kip
Distance along X to design for shear, Dx = 35.50 in
Check that 0.75 * Vc > Vuz where Vuz is the shear force for the critical load cases at a distance deff from the face of the column caby bending about the Z axis.
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From above calculations, 0.75 * Vc = 65.03 kip
Critical load case for Vuz is # 13 37.67 kip
0.75 * Vc > Vuz hence, OK
Design for Flexure about Z axisCalculate the flexural reinforcement along the X direction of the footing. Find the area of steel required, A, as per Sectioof Reinforced Concrete Design (5th ed.) by Salmon and Wang (Ref. 1)
Critical Load Case # 11The strength values of steel and concrete used in the formulae are in ksi
Factor from ACI Cl.10.2.7.3 for Fc' 4 ksi, 0.85
From ACI Cl. 10.3.2, = 0.02058
From ACI Cl. 10.3.3, = 0.01544
From ACI Cl. 7.12.2, = 0.00180
From Ref. 1, Eq. 3.8.4a, constant m = 24.41
Calculate reinforcement ratio for critical load case
Design for flexure about Z axis is performedat the face of the column at a distance, Dx =
42.50 in
Ultimate moment, 1059.07 kip-in
Nominal moment capacity, Mn = 1176.75 kip-in
Required = 0.00503
Since OK
Area of Steel Required, As =3.47 sq.in
Find suitable bar arrangement between minimum and maximum rebar sizes
Available development length for bars, DL = 39.50 in
Try bar size # 6 Area of one bar = 0.44 sq.in
Number of bars required, Nbar= 8
Because the number of bars is rounded up, make sure new reinforcement ratio
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Calculate the flexural reinforcement along the Z direction of the footing. Find the area of steel required, A, as per Sectioof Reinforced Concrete Design (5th ed.) by Salmon and Wang (Ref. 1) Critical Load Case # 11The strength values of steel and concrete used in the formulae are in ksi
Factor from ACI Cl.10.2.7.3 for Fc' 4 ksi, 0.85
From ACI Cl. 10.3.2, = 0.02058
From ACI Cl. 10.3.3, = 0.01544
From ACI Cl.7.12.2, = 0.00180
From Ref. 1, Eq. 3.8.4a, constant m = 24.41
Calculate reinforcement ratio for critical load case
Design for flexure about X axis is performedat the face of the column at a distance, Dz =
72.50 in
Ultimate moment, 1225.44 kip-in
Nominal moment capacity, Mn = 1361.60 kip-in
Required = 0.00790
Since OK
Area of Steel Required, As =4.77 sq.in
Find suitable bar arrangement between minimum and maximum rebar sizes
Available development length for bars, DL = 39.50 in
Try bar size # 7 Area of one bar = 0.60 sq.in
Number of bars required, Nbar= 8
Because the number of bars is rounded up, make sure new reinforcement ratio
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Steel Area : 9.0000 sq.in
Neutral Axis Depth (Xb): 6.6437 in
Strength and Moment from Concrete
Cc = 417.71 kip
Mc = 5086.25 kip-in
Calculate strength and moment from one bar.
Distance between extreme fiber and bar, db 2.00 in
Strain in bar, = 0.0021
Maximum Strain, = 0.0021
as
60.19 kip/in^2
0.0016
as
2.47 kip/in^2
45.60 kip
592.84 kip-in
Total Bar Capacity, Cs = -186.13 kip
Capacity of Column = Cc + Cs = 231.58 kip
Total Bar Moment, Ms = 4895.38 kip-in
Total Moment = Mc + Ms = 9981.64 kip-in
Strength and Moment Along Reinforcement in Z direction
Bar size : # 8
Number of Bars : 12
Steel Area : 9.0000 sq.in
Neutral Axis Depth (Xb): 6.6437 inStrength and Moment from Concrete
Cc = 417.71 kip
Mc = 5086.25 kip-in
Calculate strength and moment from one bar.
Distance between extreme fiber and bar, db 2.00 in
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Strain in bar, = 0.0021
Maximum Strain, = 0.0021
as
60.19 kip/in^2
0.0016
as
2.47 kip/in^2
45.60 kip
592.84 kip-in
Total Bar Capacity, Cs = -186.13 kip
Capacity of Column = Cc + Cs = 231.58 kip
Total Bar Moment, Ms = 4895.38 kip-in
Total Moment = Mc + Ms = 9981.64 kip-in
Check for bi-axial bending, 0.040
Design Moment Mnx= 571.916 kip-in
Design Moment Mnz= 261.643 kip-in
Total Moment Mox= 9981.636 kip-in
Total Moment Moz= 9981.636 kip-in
if Mnx or Mnz = 0, then = 1.0
otherwise, = 1.24