footing

Isolated Footing Design(ACI 318-05)

Design For Isolated Footing 2

Isolated Footing 2

Input Values

Footing Geomtery

Column Dimensions

Footing No. Group ID Foundation Geometry - - Length Width Thickness 2 1 4500.000 mm 4500.000 mm 1000.000 mm

Footing No. Footing Reinforcement Pedestal Reinforcement

- Bottom Reinforcement(Mz) Bottom Reinforcement(Mx) Top Reinforcement(Mz) Top Reinforcement(Mx) Main Steel Trans Steel

2 #16 @ 125 mm c/c #20 @ 195 mm c/c #20 @ 195 mm c/c #16 @ 125 mm c/c 20 - #25 #8 @ 380 mm

Design Type : Calculate Dimension

Footing Thickness (Ft) : 1000.000 mm

Footing Length - X (Fl) : 4500.000 mm

Footing Width - Z (Fw) : 4500.000 mm

Eccentricity along X (Oxd) : 0.000 mm

Eccentricity along Z (Ozd) : 0.000 mm

Column Shape : Rectangular

Column Length - X (Pl) : 799.998 mm

Column Width - Z (Pw) : 799.998 mm

of 14Isolated Footing Design

11/2/2015file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml

Pedestal

Design Parameters

Concrete and Rebar Properties

Soil Properties

Sliding and Overturning

Design Calculations

Footing Size

Include Pedestal? Yes

Pedestal Shape : Rectangular

Pedestal Height (Ph) : 1100.000 mm

Pedestal Length - X (Pl) : 1400.000 mm

Pedestal Width - Z (Pw) : 1400.000 mm

Unit Weight of Concrete : 25.000 kN/m3

Strength of Concrete : 30.000 MPa

Yield Strength of Steel : 420.000 MPa

Minimum Bar Size : #8

Maximum Bar Size : #25

Minimum Bar Spacing : 100.000 mm

Maximum Bar Spacing : 500.000 mm

Pedestal Clear Cover (P, CL) : 75.000 mm

Footing Clear Cover (F, CL) : 75.000 mm

Soil Type : Drained

Unit Weight : 20.000 kN/m3

Soil Bearing Capacity : 200.000 kN/m2

Soil Surcharge : 0.000 kN/m2

Depth of Soil above Footing : 1500.000 mm

Cohesion : 0.000 kN/m2

Coefficient of Friction : 0.500

Factor of Safety Against Sliding : 1.500

Factor of Safety Against Overturning : 1.500

------------------------------------------------------

Initial Length (Lo) = 4500.000 mm

Initial Width (Wo) = 4500.000 mm

Load Combination/s- Service Stress Level Load Combination

Number Load Combination Title

25 1DL + 1LL(1)

26 1DL + 1LL(R)

27 1DL + 0.6WL(+X)

28 1DL + 0.6WL(+Z)

29 1DL + 0.6WL(-X)

30 1DL + 0.6WL(-Z)

31 1DL + 0.7WL(+X)

32 1DL + 0.7WL(+Z)



33 1DL + 0.7WL(-X)

34 1DL + 0.7WL(-Z)

35 1DL + 0.45WL(+X) + 0.75LL(1)

36 1DL + 0.45WL(+X) + 0.75LL(R)

37 1DL + 0.45WL(+Z) + 0.75LL(1)

38 1DL + 0.45WL(+Z) + 0.75LL(R)

39 1DL + 0.45WL(-X) + 0.75LL(1)

40 1DL + 0.45WL(-X) + 0.75LL(R)

41 1DL + 0.45WL(-Z) + 0.75LL(1)

42 1DL + 0.45WL(-Z) + 0.75LL(R)

43 1DL + 0.75LL(1)

44 1DL + 0.75LL(R)

Load Combination/s- Strength Level Load Combination

Number Load Combination Title

9 1.4DL

10 1.2(DL + TL) + 1.6LL + 0.5LR

11 1.2DL + 1.6LR + LL

12 1.2DL + 1.6LR + 0.8W(+X)

13 1.2DL + 1.6LR + 0.8W(-X)

14 1.2DL + 1.6LR + 0.8W(+Z)

15 1.2DL + 1.6LR + 0.8W(-Z)

16 1.2DL + 1.6WL(+X) + LL + 0.5LR

17 1.2DL + 1.6WL(-X) + LL + 0.5LR

18 1.2DL + 1.6WL(+Z) + LL + 0.5LR

19 1.2DL + 1.6WL(-Z) + LL + 0.5LR

20 1.2DL + LL

21 0.9DL + 1.6 WL(+X)

22 0.9DL + 1.6 WL(-X)

23 0.9DL + 1.6 WL(+Z)

24 0.9DL + 1.6 WL(-Z)

Applied Loads - Service Stress Level

LC Axial(kN)

Shear X (kN)

Shear Z (kN)

Moment X (kNm)

Moment Z(kNm)

25 711.578 -11.069 -1.067 -2.662 7.073

26 560.683 -7.864 -1.995 -4.545 5.848

27 551.447 73.070 -1.523 -2.720 -286.399

28 565.716 -8.970 30.198 129.808 11.855

29 577.931 -55.694 -2.585 -6.657 179.128

30 570.373 -6.653 -34.619 -140.351 -0.768

31 548.681 86.552 -1.408 -2.295 -335.059

32 565.328 -9.163 35.599 152.321 12.906

33 579.579 -63.674 -2.648 -6.888 208.058

34 570.761 -6.460 -40.021 -162.864 -1.820

35 663.166 50.409 -0.836 -1.394 -212.826

36 549.985 52.854 -1.563 -2.935 -213.794

37 673.934 -11.128 22.992 98.256 11.464

38 560.754 -8.752 22.145 96.124 10.583

39 683.158 -46.170 -1.635 -4.358 137.223

40 569.990 -43.806 -2.351 -5.853 136.379

41 677.455 -9.379 -25.699 -104.885 1.916

42 564.290 -6.969 -26.294 -105.789 1.022

43 675.695 -10.254 -1.353 -3.314 6.690

44 562.522 -7.860 -2.073 -4.825 5.803

Applied Loads - Strength Level

LC Axial(kN)

Shear X (kN)

Shear Z (kN)

Moment X (kNm)

Moment Z(kNm)

9 795.263 -10.945 -3.096 -7.383 7.753

10 910.251 -85.808 -1.516 381.161 568.433

11 813.519 -12.472 -0.469 0.298 7.897

12 643.558 100.845 -1.237 -1.148 -412.548



Final Footing Size

Pressures at Four Corners

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 4 corners Four Corners

13 685.671 -74.533 -2.188 -4.464 256.076

14 665.778 -12.004 36.885 158.579 17.132

15 674.050 -6.615 -40.735 -165.772 -3.968

16 776.593 203.142 0.425 3.410 -774.972

17 848.273 -140.402 -2.424 -7.154 474.118

18 815.182 -15.821 85.186 358.297 25.511

19 827.828 -9.525 -88.039 -365.240 -8.802

20 825.188 -12.638 -1.510 -3.719 8.178

21 467.072 208.703 -0.155 2.056 -772.934

22 537.554 -134.700 -2.986 -8.434 467.462

23 505.043 -10.112 84.399 355.171 21.776

24 517.435 -3.945 -88.376 -364.674 -11.799

Reduction of force due to buoyancy = 0.000 kN

Effect due to adhesion = 0.000 kN

Area from initial length and width, Ao =Lo X Wo = 20250000.000 mm2

Min. area required from bearing pressure, Amin = P / qmax = 9101946.001 mm2

Note: Amin is an initial estimation. P = Critical Factored Axial Load(without self weight/buoyancy/soil). qmax = Respective Factored Bearing Capacity.

Length (L2) = 4500.000 mm Governing Load Case : # 25

Width (W2) = 4500.000 mm Governing Load Case : # 25

Depth (D2) = 1000.000 mm Governing Load Case : # 25

Area (A2) = 20250000.000 mm2

Load Case

Pressure at corner 1

(q1)(kN/mm2)


(q2)(kN/mm2)


(q3)(kN/mm2)


(q4)(kN/mm2)

Area of footing in uplift (Au)

(mm2)

33 0.0001 0.0001 0.0001 0.0001 0.000

31 0.0000 0.0001 0.0001 0.0000 0.000

31 0.0000 0.0001 0.0001 0.0000 0.000

33 0.0001 0.0001 0.0001 0.0001 0.000

Pressure at Pressure at Pressure at Pressure at



Check for stability against overturning and sliding

Critical Load Case And The Governing Factor Of Safety For Overturning And Sliding - X Direction

Load Case

corner 1 (q1)

(kN/mm2)

corner 2 (q2)

(kN/mm2)

corner 3 (q3)

(kN/mm2)

corner 4 (q4)

(kN/mm2)

33 0.0001 0.0001 0.0001 0.0001

31 0.0000 0.0001 0.0001 0.0000

31 0.0000 0.0001 0.0001 0.0000

33 0.0001 0.0001 0.0001 0.0001

- Factor of safety against sliding

Factor of safety against overturning

Load Case No.

Along X-Direction

Along Z-Direction

About X-Direction

About Z-Direction

25 82.231 852.701 835.321 135.099

26 106.142 418.339 430.004 167.967

27 11.361 545.033 631.182 8.493

28 93.344 27.726 19.499 122.761

29 15.143 326.204 313.993 12.818

30 126.202 24.252 17.733 286.154

31 9.575 588.466 710.077 7.216

32 91.356 23.514 16.588 117.170

33 13.258 318.834 305.159 11.115

34 130.004 20.984 15.305 321.736

35 17.576 1060.372 1266.233 12.510

36 15.692 530.795 600.411 11.491

37 80.099 38.768 27.372 115.153

38 95.386 37.696 26.338 129.707

39 19.406 548.002 517.468 17.217

40 19.162 356.999 350.036 16.540

41 95.226 34.754 25.301 185.961

42 120.041 31.815 23.381 240.445

43 87.017 659.310 652.262 142.263

44 106.319 403.042 409.666 168.567

Critical Load Case for Sliding along X-Direction : 31

Governing Disturbing Force : 86.552 kN



Critical Load Case And The Governing Factor Of Safety For Overturning And Sliding - Z Direction

Shear Calculation

Punching Shear Check

Effective depth, deff, increased until 0.75XVc Punching Shear Force

Punching Shear Force, Vu = 672.545 kN, Load Case # 10

Along X Direction

(Shear Plane Parallel to Global X Axis)

Governing Restoring Force : 828.746 kN

Minimum Sliding Ratio for the Critical Load Case : 9.575

Critical Load Case for Overturning about X-Direction : 34

Governing Overturning Moment : -246.906 kNm

Governing Resisting Moment : 3778.968 kNm

Minimum Overturning Ratio for the Critical Load Case : 15.305

Critical Load Case for Sliding along Z-Direction : 34

Governing Disturbing Force : -40.021 kN

Governing Restoring Force : 839.786 kN

Minimum Sliding Ratio for the Critical Load Case : 20.984

Critical Load Case for Overturning about Z-Direction : 31

Governing Overturning Moment : -516.815 kNm

Governing Resisting Moment : 3729.289 kNm

Minimum Overturning Ratio for the Critical Load Case : 7.216

Total Footing Depth, D = 1000.000mm

Calculated Effective Depth, deff = D - Ccover - 1.0 = 899.600 mm

1 inch is deducted from total depth to cater bar dia(US Convention).

For rectangular column, = Bcol / Dcol = 1.000

From ACI Cl.11.12.2.1, bo for column= 9198.400 mm

Equation 11-33, Vc1 = 22580.480 kN

Equation 11-34, Vc2 = 22249.242 kN

Equation 11-35, Vc3 = 15053.653 kN

Punching shear strength, Vc = 0.75 X minimum of (Vc1, Vc2, Vc3) = 11290.240 kN

0.75 X Vc > Vu hence, OK



Check that 0.75 X Vc > Vux where Vux is the shear force for the critical load cases at a distance deff from the face of the column caused by bending

about the X axis.

One-Way Shear Check

Along Z Direction

(Shear Plane Parallel to Global Z Axis)

Check that 0.75 X Vc > Vuz where Vuz is the shear force for the critical load cases at a distance deff from the face of the column caused by bending

about the Z axis.

Design for Flexure about Z Axis

(For Reinforcement Parallel to X Axis)

From ACI Cl.11.3.1.1, Vc = 3682.240 kN

Distance along X to design for shear, Dx = 650.400 mm

From above calculations, 0.75 X Vc = 2761.680 kN

Critical load case for Vux is # 19 210.342 kN

0.75 X Vc > Vux hence, OK

From ACI Cl.11.3.1.1, Vc = 3682.240 kN

Distance along X to design for shear, Dz = 650.400 mm

From above calculations, 0.75 X Vc = 2761.680 kN

Critical load case for Vuz is # 10 254.981 kN

0.75 X Vc > Vuz hence, OK



Calculate the flexural reinforcement along the X direction of the footing. Find the area of steel required, A, as per Section 3.8 of Reinforced Concrete Design (5th ed.) by Salmon and Wang (Ref. 1)

Critical Load Case # 21

The strength values of steel and concrete used in the formulae are in ksi

Calculate reinforcement ratio for critical load case

Based on spacing reinforcement increment; provided reinforcement is

Factor from ACI Cl.10.2.7.3 = 0.832

From ACI Cl. 10.3.2, = 0.02973

From ACI Cl. 10.3.3, = 0.02230

From ACI Cl. 7.12.2, = 0.00177

From Ref. 1, Eq. 3.8.4a, constant m = 16.471

Design for flexure about Z axis is performed at the face of the column

at a distance, Dx = 1550.000 mm

Ultimate moment, 949.717 kNm

Nominal moment capacity, Mn = 1055.241 kNm

Required = 0.00069

Since OK

Area of Steel Required, As = 7177.208 mm2

Selected bar Size = #20

Minimum spacing allowed (Smin) = = 100.000 mm

Selected spacing (S) = 196.818 mm

Smin <= S <= Smax and selected bar size < selected maximum bar size...

The reinforcement is accepted.

According to ACI 318-05 Clause No- 10.6.4

Max spacing for Cracking Consideration = 187.772 mm

UnSafe for Cracking Aspect.

#20 @ 4953.000 mm o.c.



Because the number of bars is rounded up, make sure new reinforcement ratio < ρmax

Check to see if width is sufficient to accomodate bars

Design for Flexure about X axis

(For Reinforcement Parallel to Z Axis)

Calculate the flexural reinforcement along the Z direction of the footing. Find the area of steel required, A, as per Section 3.8 of Reinforced Concrete Design (5th ed.) by Salmon and Wang (Ref. 1)

Critical Load Case # 10



Required development length for bars = =304.800 mm

Available development length for bars, DL=

1475.000 mm

Try bar size # 20 Area of one bar = 314.161 mm2

Number of bars required, Nbar = 23

Total reinforcement area, As_total = Nbar X (Area of one bar) = 7225.695 mm2

deff = D - Ccover - 0.5 X (dia. of one bar)

=

915.000 mm

Reinforcement ratio, = 0.00175

From ACI Cl.7.6.1, minimum req'd clear distance between bars, Cd =

max (Diameter of one bar, 1.0, Min. User Spacing) =

196.818 mm


From ACI Cl. 10.3.2, = 0.02973

From ACI Cl. 10.3.3, = 0.02230

From ACI Cl.7.12.2, = 0.00177


Design for flexure about X axis is performed at the face of the column

at a distance, Dz = 1550.000 mm





Because the number of bars is rounded up, make sure new reinforcement ratio < ρmax

Check to see if width is sufficient to accomodate bars

Bending moment for uplift cases will be calculated based solely on selfweight, soil depth and surcharge loading.

As the footing size has already been determined based on all servicebility load cases, and design moment calculation is based on selfweight, soil depth and surcharge only, top reinforcement value for all pure uplift load cases will be the same.

Design For Top Reinforcement Parallel to Z Axis


Required = 0.00029

Since OK


Selected Bar Size = #16

Minimum spacing allowed (Smin) = 100.000 mm






Safe for Cracking Aspect.

#16 @ 3175.000 mm o.c.

Required development length for bars = =304.800 mm

Available development length for bars, DL=

1475.000 mm

Try bar size # 16 Area of one bar = 201.064 mm2

Number of bars required, Nbar = 35

Total reinforcement area, As_total = Nbar X (Area of one bar) = 7037.244 mm2

deff = D - Ccover - 0.5 X (dia. of one bar)

=

892.500 mm

Reinforcement ratio, = 0.00175

From ACI Cl.7.6.1, minimum req'd clear distance between bars, Cd =

max (Diameter of one bar, 1.0, Min. User Spacing) =

127.471 mm



Calculate the flexural reinforcement for Mx. Find the area of steel required




Design For Top Reinforcement Parallel to X Axis


From ACI Cl. 10.3.2, = 0.02973

From ACI Cl. 10.3.3, = 0.02230

From ACI Cl. 7.12.2, = 0.00177


Design for flexure about A axis is performed at the face of the column




Required = 0.00023

Since OK









UnSafe for Cracking Aspect.

#16 @ 127 mm o.c.



First load case to be in pure uplift #

Calculate the flexural reinforcement for Mz. Find the area of steel required




Pedestal Design Calculations


From ACI Cl. 10.3.2, = 0.02973

From ACI Cl. 10.3.3, = 0.02230

From ACI Cl.7.12.2, = 0.00177


Design for flexure about A axis is performed at the face of the column




Required = 0.00022

Since OK









Safe for Cracking Aspect.

#20 @ 196 mm o.c.



Strength and Moment Along Reinforcement in X direction

Strength and Moment from Concrete

Calculate strength and moment from one bar.

Strength and Moment Along Reinforcement in Z direction

Strength and Moment from Concrete

Calculate strength and moment from one bar.

Critical Load Case: 10

Bar size : 25 mm

Number of Bars : 20

Steel Area : 9799.9995 sq.mm

Neutral Axis Depth (Xb): 81.8671 mm

Cc = 2432.944 kN

Mc = 1620.129 kNm

Distance between extreme fiber and bar,

db 87.500 mm

Strain in bar, = -0.0002

Maximum Strain, = 0.0021

as

-0.041 kN/mm2

0.0020

as

0.000 kN/mm2

-20.260 kN

-12.409 kNm

Total Bar Capacity, Cs = -3007.872

kN

Capacity of Column = Cc + Cs = -

574.928kN

Total Bar Moment, Ms = 683.192 kNm

Total Moment = Mc + Ms = 2303.320 kNm

Bar size : 25 mm

Number of Bars : 20

Steel Area : 9799.9995 sq.mm

Neutral Axis Depth (Xb): 81.8671 mm

Cc = 2432.944 kN

Mc = 1620.129 kNm

Distance between extreme fiber and bar,

db 87.500 mm



Strain in bar, = -0.0002

Maximum Strain, = 0.0021

as

-0.041 kN/mm2

0.0020

as

kN/mm2

-20.260 kN

-12.409 kNm

Total Bar Capacity, Cs = -3007.872

kN

Capacity of Column = Cc + Cs = -

574.928kN

Total Bar Moment, Ms = 683.192 kNm

Total Moment = Mc + Ms = 2303.320 kNm

Check for bi-axial bending, 0.158

Design Moment Mnx= 17.931 kNm

Design Moment Mnz= 513216.688 kNm

Total Moment Mox= 2303362.617 kNm

Total Moment Moz= 2303362.617 kNm

if Mnx or Mnz = 0, then = 1.0

otherwise, = 1.24

Print Calculation Sheet



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