Footing Design.pdf

7/28/2019 Footing Design.pdf

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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)


(kip/in^2)


(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


(kip/in^2)


(kip/in^2)


(kip/in^2)


(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 for Sliding along Z-Direction : 13




Critical Load Case for Overturning about Z-Direction : 13

Governing Overturning Moment : -21.721 kip-in



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



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.


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


5/15

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


From ACI Cl. 10.3.2, = 0.02058

From ACI Cl. 10.3.3, = 0.01544

From ACI Cl.7.12.2, = 0.00180



Design for flexure about X axis is performedat the face of the column at a distance, Dz =

65.00 in



Required = 0.00389

Since OK








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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


From ACI Cl. 10.3.2, = 0.02058

From ACI Cl. 10.3.3, = 0.01544

From ACI Cl. 7.12.2, = 0.00180



Design for flexure about A axis is performedat the face of the column at a distance, Dx =

35.00 in



Required = 0.00446

Since OK



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


From ACI Cl. 10.3.2, = 0.02058

From ACI Cl. 10.3.3, = 0.01544

From ACI Cl.7.12.2, = 0.00180



Design for flexure about A axis is performedat the face of the column at a distance, Dx =

35.00 in




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Required = 0.00337

Since OK



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




Cc

= 275.55 kip

Mc = 3620.00 kip-in





as

47.30 kip/in^2

0.0016

as

2.47 kip/in^2

35.42 kip

460.42 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


9/15

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.


10/15


11/15



Critical Load Case for Sliding along Z-Direction : 13




Critical Load Case for Overturning about Z-Direction : 13

Governing Overturning Moment : 96.169 kip-in



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




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.


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.


12/15


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


From ACI Cl. 10.3.2, = 0.02058

From ACI Cl. 10.3.3, = 0.01544

From ACI Cl. 7.12.2, = 0.00180



Design for flexure about Z axis is performedat the face of the column at a distance, Dx =

42.50 in



Required = 0.00503

Since OK








13/15

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


From ACI Cl. 10.3.2, = 0.02058

From ACI Cl. 10.3.3, = 0.01544

From ACI Cl.7.12.2, = 0.00180



Design for flexure about X axis is performedat the face of the column at a distance, Dz =

72.50 in



Required = 0.00790

Since OK








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Cc = 417.71 kip

Mc = 5086.25 kip-in





as

60.19 kip/in^2

0.0016

as

2.47 kip/in^2

45.60 kip

592.84 kip-in





Strength and Moment Along Reinforcement in Z direction

Bar size : # 8

Number of Bars : 12


Neutral Axis Depth (Xb): 6.6437 inStrength and Moment from Concrete

Cc = 417.71 kip

Mc = 5086.25 kip-in




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as

60.19 kip/in^2

0.0016

as

2.47 kip/in^2

45.60 kip

592.84 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

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Footing Design.pdf