Isolated Footing Design(ACI 318-14) - Metric · 2020. 7. 4. · Isolated Footing Design(ACI 318-14) - Metric Footing No. Group ID Foundation Geometry - - Length Width Thickness 1

Isolated Footing Design(ACI 318-14) - Metric

Footing No. Group ID Foundation Geometry - - Length Width Thickness 1 1 2.80m 2.80m 0.50m

Footing No.

Footing Reinforcement Pedestal Reinforcement

- Bottom Reinforcement

(Mz) Bottom Reinforcement

(Mx) Top Reinforcement

(Mz) Top Reinforcement

(Mx) Main Steel Trans Steel

1 13 - 16 mm 13 - 16 mm 13 - 16 mm 13 - 16 mm 12-#22 + 16-#1910 mm @ 300

mm

Isolated Footing 1

1.55 m 2.05 m

0.5 m

1.3 m

Elevation

1.4 m

2.8 m

0.95 m

0.95 m

X

Z

Plan

Input Values

Footing Geomtery

Design Type : Set Dimension

Minimum Footing Length - X(Fl) : 2800.00 mm

Minimum Footing Width - Z (Fw) : 2800.00 mm

Footing Thickness (Ft) : 500.00 mm

Eccentricity along X (Oxd) : 0.00 mm

Eccentricity along Z (Ozd) : 0.00 mm

Column Dimensions

Column Shape : Rectangular

Column Length - X (Dcol) : 0.30 m

Column Width - Z (Bcol) : 0.30 m

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Pedestal

Include Pedestal : Yes

Pedestal Shape : Rectangular

Pedestal Height (Ph) : 1.55 m

Pedestal Length - X (Pl) : 0.95 m

Pedestal Width - Z (Pw) : 0.95 m

Design Parameters

Concrete and Rebar Properties

Unit Weight of Concrete : 25.00 kN/m3

Strength of Concrete : 25.30 N/mm2

Yield Strength of Steel : 420.00 N/mm2

Minimum Bar Size : 16 mm

Maximum Bar Size : 25 mm

Top Footing Minimum Bar Size : 16 mm

Top Footing Maximum Bar Size : 25 mm

Pedestal Minimum Bar Size : 16 mm

Pedestal Maximum Bar Size : 25 mm

Minimum Bar Spacing : 150.00 mm

Maximum Bar Spacing : 250.00 mm

Pedestal Clear Cover (P, CL) : 50.00 mm

Bottom Footing Clear Cover (F, CL) : 50.00 mm

Soil Properties

Soil Type : Cohesionless Soil

Unit Weight : 20.00kN/m3

Base Value of Soil Bearing Capacity : 120.00kPa

Multiplying factor for soil bearing capacity for ultimate loads : 1.00

Soil Bearing Capacity Type : Gross Bearing Capacity

Soil Surcharge : 0.00kN/m2

Height of Soil above Footing : 1.30m

Type of Depth : Fixed Top

Undrained Shear Strength : 0.00kN/m2

Bearing Capacity Input Method : Fixed Bearing Capacity

Minimum Percentage of Slab area in Contact for Service Loads : 80.00

Minimum Percentage of Slab area in Contact for Ultimate Loads : 80.00

Sliding and Overturning

Coefficient of Friction : 0.50

Factor of Safety Against Sliding : 1.50

Factor of Safety Against Overturning : 1.50

Global Settings

Top Reinforcement Option : Always calculate based on self weight

Concrete Design Option : Net Pressure(Gross Pressure - Self Weight Pressure)

Top Reinforcement Factor : 1.00

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

Design Calculations

Footing Size

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Initial Length (Lo) = 2.80 m

Initial Width (Wo) = 2.80 m

Load Combinations

Load Combination/s- Service Stress Level Load

Combination Number

Load Combination Title Load Case Multiplier

(a)

Soil Bearing

Factor (b)

Self Weight

Factor (c) Code

a - Value specified in the Load Multiplier table b - Value specified in the Pile/Soil Bearing Capacity Factors table c - Value specified in the Apply Self Weight and Dead Weight Factor table

1 WindBlnsTension90Wind 1.00 1.00 1.00 -

2 IceBlnsTension90Wind 1.00 1.00 1.00 -

3 LowTempBlnsTension 1.00 1.00 1.00 -

4 BreakWireUnBlnsTension 1.00 1.00 1.00 -

5 ABreakWireUnBlnsTension 1.00 1.00 1.00 -

6 CreakWireUnBlnsTension 1.00 1.00 1.00 -

7 UnBLnsIce 1.00 1.00 1.00 -

8 SetUp 1.00 1.00 1.00 -

9 ASetUp 1.00 1.00 1.00 -

10 LongTime 1.00 1.00 1.00 -

Load Combination/s- Strength Level Load

Combination Number

Load Combination Title Load Case Multiplier

(a)

Soil Bearing

Factor (b)

Self Weight

Factor (c) Code

a - Value specified in the Load Multiplier table b - Value specified in the Pile/Soil Bearing Capacity Factors table c - Value specified in the Apply Self Weight and Dead Weight Factor table

51 WindBlnsTension90Wind 1.00 1.00 1.00 -

52 IceBlnsTension90Wind 1.00 1.00 1.00 -

53 LowTempBlnsTension 1.00 1.00 1.00 -

54 BreakWireUnBlnsTension 1.00 1.00 1.00 -

55 ABreakWireUnBlnsTension 1.00 1.00 1.00 -

56 CreakWireUnBlnsTension 1.00 1.00 1.00 -

57 UnBLnsIce 1.00 1.00 1.00 -

58 SetUp 1.00 1.00 1.00 -

59 ASetUp 1.00 1.00 1.00 -

60 LongTime 1.00 1.00 1.00 -

Applied Loads on Top of Pedestal

Before consideration of self weight and load multiplier table

Moments are about the center of Column / Pedestal (does not include moments caused by lateral loads)For the loads shown in this table, the sign convention is the same as that for JOINT LOADS in STAAD.Pro when global Y is the vertical axis.

Applied Loads from Column - Service Stress Level

Load Case Fx(kN)

Fy(kN)

Downwards is negative Upwards

is positive

Fz(kN)

Mx(kNm)

Mz(kNm)

1 -15.10 19.55 -0.02 -0.16 157.96

2 -5.98 23.91 -0.02 -0.16 68.73

3 -1.62 19.14 -0.03 -0.20 24.20

4 -1.29 22.66 -4.79 -58.72 22.27

5 -1.29 22.66 -4.79 -48.34 22.86

6 -1.17 22.66 -6.59 -99.02 19.68

7 -8.08 23.00 -0.02 -0.16 80.42

8 -3.02 37.13 -1.75 -25.39 46.47

9 -3.02 37.13 -1.75 -23.43 47.19

10 -3.64 19.16 -0.02 -0.16 37.34

Applied Loads from Column - Strength Level

Load Case Fx(kN)

Fy(kN)


is positive

Fz(kN)

Mx(kNm)

Mz(kNm)

51 -15.10 19.55 -0.02 -0.16 157.96

52 -5.98 23.91 -0.02 -0.16 68.73

53 -1.62 19.14 -0.03 -0.20 24.20

54 -1.29 22.66 -4.79 -58.72 22.27

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Applied Loads from Column - Strength Level

Load Case Fx(kN)

Fy(kN)


is positive

Fz(kN)

Mx(kNm)

Mz(kNm)

55 -1.29 22.66 -4.79 -48.34 22.86

56 -1.17 22.66 -6.59 -99.02 19.68

57 -8.08 23.00 -0.02 -0.16 80.42

58 -3.02 37.13 -1.75 -25.39 46.47

59 -3.02 37.13 -1.75 -23.43 47.19

60 -3.64 19.16 -0.02 -0.16 37.34

Reduction of force due to buoyancy = 0.00 kN

Effect due to adhesion = 0.00 kN

Area from initial length and width, Ao = Lo X Wo = 7.84 m2

Min. area required from bearing pressure, Amin = 5.83 m2

Note: Amin is an initial estimation considering self-weight, axial load and moment against factored bearing capacity.

Final Footing Size

Length (L2) = 2.80 m Governing Load Case : # 1

Width (W2) = 2.80 m Governing Load Case : # 1

Depth (D2) = 0.50 m

Depth is governed by Ultimate Load Case

(Service check is performed with footing thickness requirements from concrete check)

Area (A2) = 7.84 m2

Final Pedestal Height = 1.55 m

Final Soil Height = 1.30 m

Weight of the footing + pedestal (if any) = 132.97 kN

Soil Weight On Top Of Footing = 180.37 kN

Gross Pressures at 4 Corners

Load Case / Combination

Pressure at top left

corner(kN/m2)

Pressure at top right

corner(kN/m2)

Pressure at bottom

right corner

(kN/m2)

Pressure at bottom left corner(kN/m2)

Area of footing in uplift (Au)

(m2)

Gross Bearing Capacity (kN/m2)

1 89.1633 -14.1081 -14.2180 89.0535 1.48 120.0000

6 73.8681 61.7988 0.2839 12.3532 0.00 120.0000

3 45.1187 30.0742 29.9312 44.9758 0.00 120.0000

1 89.1633 -14.1081 -14.2180 89.0535 1.48 120.0000

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 Gross Pressures at four Corners

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Load Case / Combination

Pressure at top left corner

(kN/m2)

Pressure at top right corner

(kN/m2)

Pressure at bottom right

corner(kN/m2)

Pressure at bottom left

corner(kN/m2)

Gross Bearing Capacity (kN/m2)

1 92.4763 0.0000 0.0000 92.3408 120.0000

6 73.8681 61.7988 0.2839 12.3532 120.0000

3 45.1187 30.0742 29.9312 44.9758 120.0000

1 92.4763 0.0000 0.0000 92.3408 120.0000

Stability Check

1.55 m 2.05 m

0.5 m

1.3 m

.

Frictional Force

Sliding Force

OTM

- Factor of safety against sliding Factor of safety against overturning

Load Case No.

Along X-Direction

Along Z-Direction Resultant

Required FOS

About X-Direction

About Z-Direction

Required FOS

1 9.73 7344.65 9.73 1.50 2046.24 2.18 1.50

2 24.20 7235.65 24.20 1.50 2015.87 5.00 1.50

3 90.80 4903.26 90.79 1.50 1575.02 14.97 1.50

4 112.67 30.34 29.30 1.50 5.94 16.33 1.50

5 112.67 30.34 29.30 1.50 7.00 15.96 1.50

6 124.22 22.05 21.71 1.50 3.62 18.43 1.50

7 17.97 7258.40 17.97 1.50 2022.21 4.19 1.50

8 45.73 78.92 39.57 1.50 13.34 7.34 1.50

9 45.73 78.92 39.57 1.50 14.31 7.24 1.50

10 40.41 7354.40 40.41 1.50 2048.96 9.19 1.50

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

Critical Load Case for Sliding along X-Direction : 1

Governing Disturbing Force : -15.10 kN

Governing Restoring Force : 146.89 kN

Minimum Sliding Ratio for the Critical Load Case : 9.73

Critical Load Case for Overturning about X-Direction : 6

Governing Overturning Moment : -112.53 kNm

Governing Resisting Moment : 406.94 kNm

Minimum Overturning Ratio for the Critical Load Case : 3.62

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

Critical Load Case for Sliding along Z-Direction : 6

Governing Disturbing Force : -6.59 kN



Critical Load Case for Overturning about Z-Direction : 1

Governing Overturning Moment : 188.91 kNm

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Governing Resisting Moment : 411.29 kNm

Minimum Overturning Ratio for the Critical Load Case : 2.18

Critical Load Case And The Governing Factor Of Safety For Sliding Along Resultant Direction

Critical Load Case for Sliding along Resultant Direction : 1

Governing Disturbing Force : 15.10 kN



Compression Development Length Check

Development length calculation skipped as column reinforcement is not specified in input (Column Dimension Task Pane)

Ultimate Gross Pressures

The base pressures reported in this table and the area of footing in contact include the effect of buoyancy (if any).

Load Case / Load

Combination ID

Pressure at top left corner

(kN/m2)

Pressure at top right corner

(kN/m2)

Pressure at bottom right

corner(kN/m2)

Pressure at bottom left

corner(kN/m2)

Area of footing in

Contact with soil (Au)

(m2)

51 92.4763 0.0000 0.0000 92.3408 6.36

52 59.1080 14.8349 14.7251 58.9982 7.84

53 45.1187 30.0742 29.9312 44.9758 7.84

54 62.6196 48.9999 11.5324 25.1521 7.84

55 59.9437 46.0015 14.2083 28.1505 7.84

56 73.8681 61.7988 0.2839 12.3532 7.84

57 63.5960 10.5792 10.4693 63.4861 7.84

58 57.5444 28.7570 12.9162 41.7037 7.84

59 57.2055 28.0244 13.2552 42.4362 7.84

60 49.8230 25.3317 25.2219 49.7131 7.84

Minimum Required Contact Area for Ultimate Loads : 6.27 m2

Actual Area in Contact for all ultimate load cases exceeds the minimum required. Hence Safe

Gross Bearing Capacity for Ultimate Loads : 120.00 kN/m2

Maximum Corner Pressure from all ultimate load cases is less than the allowable. Hence Safe

Shear Calculation

Punching Shear Check

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1.4 m

0.215 m

Plan

X

Z

Total Footing Depth, D = 0.50m

Calculated Effective Depth, d = D - Ccover - 1 * db = 0.43 m

For rectangular column, = Bcol / Dcol = 1.00

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

Punching Shear Force, Vu = 15.83kN, Load Case # 53

From ACI Cl. 22.6.5.2, bo for column= = 5.54 m

Table 22.6.5.2, (b), Vc1 = = 6165.21 kN

Table 22.6.5.2, (c), Vc2 = = 5153.58 kN

Table 22.6.5.2, (a), Vc3 = = 3989.25 kN

Punching shear strength, Vc = 0.75 X minimum of (Vc1, Vc2, Vc3) = 2991.94 kN

0.75 X Vc > Vu hence, OK

One-Way Shear in XY Plane

(Shear Plane Parallel to Global X Axis)

1.4 m

0.495 m

0.495 m

Plan

X

Z

From ACI Cl. 22.5.5.1, Vc = = 1020.30 kN

Distance of critical section from top left corner along Z, DZ = = 0.50 m

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

From above calculations, 0.75 X Vc = 765.23 kN

Critical load case for Vux is # 56 = 38.12 kN

0.75 X Vc > Vux hence, OK

One-Way Shear in YZ Plane

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(Shear Plane Parallel to Global Z Axis)

1.4 m

0.495 m 0.495 m

Plan

X

Z

From ACI Cl. 22.5.5.1, Vc = = 1020.30 kN

Distance of critical section from top left corner along X, DX = = 0.50 m

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

From above calculations, 0.75 X Vc = 765.23 kN

Critical load case for Vuz is # 51 = 65.84 kN

0.75 X Vc > Vuz hence, OK

Flexure About Z-Axis

Design For Bottom Reinforcement Parallel to X Axis

13 - 16 mm

X

Z

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 # 51

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

Bars parallel to X Direction are placed at bottom

Effective Depth d = 0.43 m

Factor from ACI Cl. 22.2.2.4.3 = = 0.85

From ACI318-2011 Appendix B 8.4.2, = = 0.02560


From ACI Cl. 7.6.1.1, = = 0.00180

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From Ref.1, Eq. 3.8.4a, constant m = = 19.53

Calculate reinforcement ratio for critical load case

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

= 0.93 m

Ultimate moment = = 53.13 kNm

Nominal moment capacity required, Mn = = 59.03 kNm

(Based on effective depth) Required = = 0.00028

(Based on gross depth) x d / Depth = 0.00024

Since ρ < ρmin, select ρ= ρmin ρmin Governs

Area of Steel Required, As = = 2519.97 mm2

Note - "Area of Steel required" reported here is the larger value between the calculated area of steel and minimum steel required as per code stipulations

Selected bar Size = 16 mm

Minimum spacing allowed (Smin) = 150.00mm

Selected spacing (S) = 223.67mm

Smin

13 - 16 mm

X

Z

First load case to be in pure uplift # 51

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

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



Factor from ACI Cl. 22.2.2.4.3 = =

0.85



From ACI Cl. 7.6.1.1, = = 0.00180

From Ref. 1, Eq. 3.8.4a, constant m = = 19.53


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

= 0.93 m



(Based on effective depth)Required = = 0.000240




Note - "Area of Steel required" reported here is the larger value between the calculated area of steel

and minimum steel required as per code stipulations

Total reinforcement area, As_total = Nbar X (Area of one bar) = 2581.24 mm2

Provided Steel Area / Required Steel Area = 1.02




Smin

Flexure About X-Axis

Design For Bottom Reinforcement Parallel to Z Axis

13 - 16 mm

X

Z

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 # 56

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



Factor from ACI Cl. 22.2.2.4.3 =

= 0.85



From ACI Cl. 7.6.1.1, = = 0.00180

From Ref.1, Eq. 3.8.4a, constant m = = 19.53


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

= = 0.93 m







Note - "Area of Steel required" reported here is the larger value between the calculated area of steel and minimum steel required as per code stipulations

Selected Bar Size = 16 mm



Smin

Based on spacing reinforcement increment; provided reinforcement is

16 mm @ 220mm o.c.

Required development length for bars = = 0.63 m

Available development length for bars, DL =

= 1.82 m

Try bar size 16 mm Area of one bar = 199.00 mm2

Number of bars required, Nbar= = 13

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


d = D - Ccover - 1.5 X (dia. of one bar) =

0.43 m

Reinforcement ratio, = = 0.00217

From ACI Cl. 25.2.1, minimum req'd clear distance between bars

Cd = max (Diameter of one bar, 1.0" (25.4mm), Min. User Spacing) = 150.00mm


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

13 - 16 mm

X

Z

First load case to be in pure uplift # 51

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

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



Factor from ACI Cl. 22.2.2.4.3 = = 0.85



From ACI Cl. 7.6.1.1, = = 0.00180

From Ref. 1, Eq. 3.8.4a, constant m = = 19.53


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Design for flexure about X axis is performed at the face of the column at a distance, Dx

= = 0.93 m

Ultimate moment, = = 46.12 kNm






Note - "Area of Steel required" reported here is the larger value between the calculated area of steel and

minimum steel required as per code stipulations






Smin

Serial No. P

(kN) M

(kNm) Strength Reduction Factor

(Φ) 18 6379.03 2183.45 0.6519 6772.73 2148.84 0.6520 7153.81 2111.68 0.6521 7523.25 2070.85 0.6522 7876.29 2027.23 0.6523 8230.52 1979.83 0.6524 8578.64 1928.94 0.6525 8921.26 1874.37 0.6526 9258.90 1815.97 0.6527 9592.04 1753.58 0.6528 10238.40 1617.83 0.6529 10912.57 1455.07 0.6530 11547.27 1279.92 0.6531 12161.35 1089.18 0.6532 12777.52 875.97 0.6533 13372.92 647.22 0.6534 13946.25 405.36 0.6535 14275.15 261.22 0.6536 14378.05 228.59 0.6537 14466.26 200.61 0.6538 14540.89 176.26 0.6539 14603.70 154.81 0.6540 14659.12 135.88 0.6541 14708.39 119.06 0.6542 14751.54 104.06 0.6543 14787.91 90.70 0.6544 14850.72 67.64 0.6545 14899.95 48.97 0.6546 14939.32 33.58 0.6547 14969.94 21.31 0.6548 14993.35 11.60 0.6549 15005.95 0.00 0.65

Moment [kNm]

0 500 1000 1500 2000 2500 2750.271331-6000

-3000

0

3000

ϕM (0.06 deg) (kNm)

ϕPn,max = 12004.7639056

Shear - Governing Load Case Details

Critical Load Case for Shear Along X = 51

Critical Load Case for Shear Along Z = 56

Shear force along X = -15.10 kN

Shear force along Z = -6.59 kN

Transverse Stirrups Details

Rebar Links = 10 @ 300 mm

No. of Legs in X direction = 8

No. of Legs in Z direction = 8

Material Take Off

Footing Reinforcement

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Direction Size Number Total Length (m) Weight (kg)

Along Z on Bottom Face

16 mm 13 35.10 54.48

Along X on Bottom Face

16 mm 13 35.10 54.48

Along Z on Top Face

16 mm 13 35.10 54.48

Along X on Top Face

16 mm 13 35.10 54.48

Pedestal Reinforcement

Type Size Number Total Bar Length

(m)Weight (kg)

Main Steel 1 (Vertical)

22 mm 12 31.19 94.87

Main Steel 2 (Vertical)

19 mm 16 37.82 84.55

Transverse Steel (Ties)

10 mm 3 10.66 5.96

Internal Steel (Ties)

10 mm 36 36.09 20.19

Total Reinforcement Weight : 423.49 kg

Concrete

- Length (m) Width (m) Thickness (m) Volume (m3)

Footing 2.80 2.80 0.50 3.92

Pedestal 0.95 0.95 1.55 1.40

Total Concrete Volume : 5.32 m3

Formwork

Footing : 5.60 m2

Pedestal : 5.89 m2

Total : 11.49 m2

Soil Excavation

Pit Depth : 1.80 m

Pit Slope (a : b) : 1 : 1 (Assumed)

Side Distance, s : 0 (Assumed)

Excavation Volume : 40.03 m3

Backfill Volume : 34.94 m3

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1.4 m1.4 m

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Documents

Isolated Footing Design(ACI 318-14) - Metric · 2020. 7. 4. · Isolated Footing Design(ACI 318-14) - Metric Footing No. Group ID Foundation Geometry - - Length Width Thickness 1