Isolated Footing Design(ACI 318-11) - English Isolated Footing 1 · 2020. 12. 8. · Print...
Transcript of Isolated Footing Design(ACI 318-11) - English Isolated Footing 1 · 2020. 12. 8. · Print...
-
Print Calculation Sheet
Isolated Footing Design(ACI 318-11) - English
Footing No. Group ID Foundation Geometry
- - Length Width Thickness
1 1 1.40m 1.40m 0.30m
Footing No. Footing Reinforcement Pedestal Reinforcement
- Bottom Reinforcement(Mz) Bottom Reinforcement(Mx) Top Reinforcement(Mz) Top Reinforcement(Mx) Main Steel Trans Steel
1 12 - #3 12 - #3 12 - #3 12 - #3 20-#6 + 4-#5 #3 @ 9 mm
Isolated Footing 1
1.5 m 1.8 m
0.3 m
1.19 m
Elevation
0.7 m
1.4 m
0.8 m
0.8 m
X
Z
Plan
Input Values
Footing Geomtery
Design Type :Calculate Dimension with user
specified minimums as startingvalue
Minimum Footing Length - X(Fl) : 1.40 m
Minimum Footing Width - Z (Fw) : 1.40 m
Footing Thickness (Ft) : 0.30 m
Eccentricity along X (Oxd) : 0.00 in
Eccentricity along Z (Ozd) : 0.00 in
Column Dimensions
Column Shape : Rectangular
Column Length - X (Dcol) : 0.80 m
Column Width - Z (Bcol) : 0.80 m
Page 1 of 15
12/8/2020file:///F:/KPTL/PROJECT/MAURITANIA/TIGUENT/EQUIPMENT/225KV/CT/FOU...
-
Pedestal
Include Pedestal : Yes
Pedestal Shape : Rectangular
Pedestal Height (Ph) : 1.50 m
Pedestal Length - X (Pl) : 0.80 m
Pedestal Width - Z (Pw) : 0.80 m
Design Parameters
Concrete and Rebar Properties
Unit Weight of Concrete : 25.00 kN/m3
Strength of Concrete : 25.00 N/mm2
Yield Strength of Steel : 460.00 N/mm2
Minimum Bar Size : #3
Maximum Bar Size : #5
Top Footing Minimum Bar Size : #3
Top Footing Maximum Bar Size : #5
Pedestal Minimum Bar Size : #3
Pedestal Maximum Bar Size : #10
Minimum Bar Spacing : 75.00 mm
Maximum Bar Spacing : 200.00 mm
Pedestal Clear Cover (P, CL) : 40.00 mm
Bottom Footing Clear Cover (F, CL) : 50.00 mm
Soil Properties
Soil Type : Cohesive Soil
Unit Weight : 18.04kN/m3
Base Value of Soil Bearing Capacity : 102.00kN/m2
Multiplying factor for soil bearing capacity for ultimateloads
: 1.25
Soil Bearing Capacity Type : Gross Bearing Capacity
Soil Surcharge : 0.00kip/in2
Height of Soil above Footing : 1.20m
Type of Depth : Fixed Bottom
Cohesion : 0.00kip/in2
Bearing Capacity Input Method : Fixed Bearing Capacity
Minimum Percentage of Slab area in Contact for ServiceLoads
: 95.00
Minimum Percentage of Slab area in Contact forUltimate Loads
: 95.00
Sliding and Overturning
Coefficient of Friction : 0.50
Factor of Safety Against Sliding : 2.00
Factor of Safety Against Overturning : 2.00
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
Page 2 of 15
12/8/2020file:///F:/KPTL/PROJECT/MAURITANIA/TIGUENT/EQUIPMENT/225KV/CT/FOU...
-
Initial Length (Lo) = 1.40 m
Initial Width (Wo) = 1.40 m
Load Combinations
Load Combination/s- Service Stress Level
LoadCombination
NumberLoad Combination Title
Load CaseMultiplier
(a)
SoilBearing
Factor (b)
SelfWeight
Factor (c)Code
a - Value specified in the Load Multiplier tableb - Value specified in the Pile/Soil Bearing Capacity Factors tablec - Value specified in the Apply Self Weight and Dead Weight Factor table
201 DL+LL 1.00 1.00 1.00 -
Load Combination/s- Strength Level
LoadCombination
NumberLoad Combination Title
Load CaseMultiplier
(a)
SoilBearing
Factor (b)
SelfWeight
Factor (c)Code
a - Value specified in the Load Multiplier tableb - Value specified in the Pile/Soil Bearing Capacity Factors tablec - Value specified in the Apply Self Weight and Dead Weight Factor table
201 DL+LL 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 CaseFx
(kN)
Fy(kN)
Downwards isnegative Upwards
is positive
Fz(kN)
Mx(kNm)
Mz(kNm)
201 0.05 -50.70 0.12 0.00 0.00
Applied Loads from Column - Strength Level
Load CaseFx
(kN)
Fy(kN)
Downwards isnegative Upwards
is positive
Fz(kN)
Mx(kNm)
Mz(kNm)
201 0.05 -50.70 0.12 0.00 0.00
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 = 1.96 m2
Min. area required from bearing pressure, Amin = 1.17 m2
Note: Amin is an initial estimation considering self-weight, axial load and moment against factored bearing capacity.
Final Footing Size
Length (L2) = 1.40 m Governing Load Case : # 201
Width (W2) = 1.40 m Governing Load Case : # 201
Depth (D2) = 0.30 m
Depth is governed by Ultimate Load Case
(Service check is performed with footing thickness requirements from concrete check)
Area (A2) = 1.96 m2
Final Pedestal Height = 1.50 m
Final Soil Height = 1.20 m
Weight of the footing + pedestal (if any) = 38.70 kN
Soil Weight On Top Of Footing = 28.57 kN
Page 3 of 15
12/8/2020file:///F:/KPTL/PROJECT/MAURITANIA/TIGUENT/EQUIPMENT/225KV/CT/FOU...
-
Gross Pressures at 4 Corners
Load Case /Combination
Pressureat top left
corner(kN/m2)
Pressureat topright
corner(kN/m2)
Pressureat bottom
rightcorner
(kN/m2)
Pressureat bottomleft corner(kN/m2)
Area offooting inuplift (Au)
(m2)
Gross
Bearing
Capacity
(kN/m2)
201 59.5537 59.9158 60.8289 60.4668 0.00 102.0000
201 59.5537 59.9158 60.8289 60.4668 0.00 102.0000
201 59.5537 59.9158 60.8289 60.4668 0.00 102.0000
201 59.5537 59.9158 60.8289 60.4668 0.00 102.0000
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
Load Case /Combination
Pressure attop leftcorner
(kN/m2)
Pressure attop rightcorner
(kN/m2)
Pressure atbottom right
corner(kN/m2)
Pressure atbottom left
corner(kN/m2)
Gross Bearing
Capacity
(kN/m2)
201 59.5537 59.9158 60.8289 60.4668 102.0000
201 59.5537 59.9158 60.8289 60.4668 102.0000
201 59.5537 59.9158 60.8289 60.4668 102.0000
201 59.5537 59.9158 60.8289 60.4668 102.0000
Stability Check
1.5 m 1.8 m
0.3 m
1.19 m
.
Frictional Force
Sliding Force
OTM
Passive Earth Pressure Resistance
Resisting Force Along X on Pedestal : 35.27 kN
Resisting Force Along Z on Pedestal : 35.27 kN
Resisting Force Along X on Footing : 34.71 kN
Resisting Force Along Z on Footing : 34.71 kN
Resisting moment about X on Pedestal : 24.54 kNm
Resisting moment about Z on pedestal : 24.54 kNm
Resisting moment about X on Footing : 5.01 kNm
Resisting moment about Z on Footing : 5.01 kNm
Page 4 of 15
12/8/2020file:///F:/KPTL/PROJECT/MAURITANIA/TIGUENT/EQUIPMENT/225KV/CT/FOU...
-
- Factor of safety against slidingFactor of safety against
overturning
LoadCaseNo.
Along X-Direction
Along Z-Direction
ResultantRequired
FOS
About X-Direction
About Z-Direction
Required
FOS
201 2803.66 1111.80 1033.50 2.00 537.08 1354.37 2.00
Critical Load Case And The Governing Factor Of Safety For Overturning And Sliding - X Direction
Critical Load Case for Sliding along X-Direction : 201
Governing Disturbing Force : 0.05 kN
Governing Restoring Force : 128.97 kN
Minimum Sliding Ratio for the Critical Load Case : 2803.66
Critical Load Case for Overturning about X-Direction : 201
Governing Overturning Moment : 0.21 kNm
Governing Resisting Moment : 112.14 kNm
Minimum Overturning Ratio for the Critical Load Case : 537.08
Critical Load Case And The Governing Factor Of Safety For Overturning And Sliding - Z Direction
Critical Load Case for Sliding along Z-Direction : 201
Governing Disturbing Force : 0.12 kN
Governing Restoring Force : 128.97 kN
Minimum Sliding Ratio for the Critical Load Case : 1111.80
Critical Load Case for Overturning about Z-Direction : 201
Governing Overturning Moment : -0.08 kNm
Governing Resisting Moment : 112.14 kNm
Minimum Overturning Ratio for the Critical Load Case : 1354.37
Critical Load Case And The Governing Factor Of Safety For Sliding Along Resultant Direction
Critical Load Case for Sliding along Resultant Direction : 201
Governing Disturbing Force : 0.12 kN
Governing Restoring Force : 128.97 kN
Minimum Sliding Ratio for the Critical Load Case : 1033.50
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)
201 59.5537 59.9158 60.8289 60.4668 1.96
Minimum Required Contact Area for Ultimate Loads : 1.86 m2
Actual Area in Contact for all ultimate load cases exceeds the minimum required. Hence Safe
Gross Bearing Capacity for Ultimate Loads : 127.50 kN/m2
Maximum Corner Pressure from all ultimate load cases is less than the allowable. Hence Safe
Shear Calculation
Punching Shear Check
Page 5 of 15
12/8/2020file:///F:/KPTL/PROJECT/MAURITANIA/TIGUENT/EQUIPMENT/225KV/CT/FOU...
-
0.7 m
0.12 m
Plan
X
Z
Total Footing Depth, D = 0.30m
Calculated Effective Depth, d = D - Ccover - 1 * db = 0.24 m
For rectangular column, = Bcol / Dcol = 1.00
Effective depth, d, increased until 0.75XVc Punching Shear Force
Punching Shear Force, Vu = 34.65kN, Load Case # 201
From ACI Cl.11.11.2.1, bo for column= = 4.16 m
Equation 11-31, Vc1 = = 2493.12 kN
Equation 11-32, Vc2 = = 1791.39 kN
Equation 11-33, Vc3 = = 1662.08 kN
Punching shear strength, Vc = 0.75 X minimum of (Vc1, Vc2, Vc3) = 1246.56 kN
0.75 X Vc > Vu hence, OK
One-Way Shear in XY Plane
(Shear Plane Parallel to Global X Axis)
0.7 m
0.06 m
0.06 m
Plan
X
Z
Page 6 of 15
12/8/2020file:///F:/KPTL/PROJECT/MAURITANIA/TIGUENT/EQUIPMENT/225KV/CT/FOU...
-
From ACI Cl.11.2.1.1, Vc = = 274.01 kN
Distance of critical section from top left corneralong Z, DZ = = 0.06 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 = 205.51 kN
Critical load case for Vux is # 201 = 3.95 kN
0.75 X Vc > Vux hence, OK
One-Way Shear in YZ Plane
(Shear Plane Parallel to Global Z Axis)
0.7 m
0.06 m 0.06 m
Plan
X
Z
From ACI Cl.11.2.1.1, Vc = = 274.01 kN
Distance of critical section from top left corner alongX, DX = = 0.06 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 = 205.51 kN
Critical load case for Vuz is # 201 = 3.93 kN
0.75 X Vc > Vuz hence, OK
Flexure About Z-Axis
Design For Bottom Reinforcement Parallel to X Axis
12 - #3
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.) bySalmon and Wang (Ref. 1)
Page 7 of 15
12/8/2020file:///F:/KPTL/PROJECT/MAURITANIA/TIGUENT/EQUIPMENT/225KV/CT/FOU...
-
Critical Load Case # 201
The strength values of steel and concrete used in the formulae are in ksi
Bars parallel to X Direction are placed at bottom
Effective Depth d = 0.24 m
Factor from ACI Cl.10.2.7.3 =
= 0.85
From Appendix B 8.4.2, = = 0.02222
From Appendix B 10.3.3, = = 0.01667
From ACI Cl. 7.12.2, = = 0.00162
From Ref.1, Eq. 3.8.4a, constant m=
= 21.65
Calculate reinforcement ratio for critical load case
Design for flexure about Z axis is performed at the faceof the column at a distance, Dx =
= 0.30 m
Ultimate moment = = 2.41 kNm
Nominal moment capacity required, Mn = = 2.68 kNm
(Based on effective depth) Required = = 0.00007
(Based on gross depth) x d / Depth = 0.00006
Since ρ < ρmin, select ρ= ρmin ρmin Governs
Area of Steel Required, As = = 1.05 in2
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 = #3
Minimum spacing allowed (Smin) = 75.00mm
Selected spacing (S) = 117.32mm
Smin
-
12 - #3
X
Z
First load case to be in pure uplift # 201
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
Bars parallel to X Direction are placed at bottom
Effective Depth d = 0.24 m
Factor from ACI Cl.10.2.7.3 ==
0.85
From Appendix B 8.4.2, = = 0.02222
From Appendix B 10.3.3, = = 0.01667
From ACI Cl. 7.12.2, = = 0.00162
From Ref. 1, Eq. 3.8.4a, constant m=
= 21.65
Calculate reinforcement ratio for critical load case
Design for flexure about Z axis is performed at theface of the column at a distance, Dx =
= 0.30 m
Ultimate moment = = 1.84 kNm
Nominal moment capacity required, Mn = = 2.04 kNm
(Based on effective depth)Required = = 0.000057
(Based on gross depth) x d / Depth = 0.000045
Since ρ < ρmin, select ρ= ρmin ρmin Governs
Area of Steel Required, As = = 1.05 in2
Note - "Area of Steel required" reported here is thelarger 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) = 1.33 in2
Provided Steel Area / Required Steel Area = 1.26
Selected bar Size = #3
Minimum spacing allowed (Smin) = 75.00mm
Selected spacing (S) = 143.39mm
Smin
-
#3 @ 127mm o.c.
Flexure About X-Axis
Design For Bottom Reinforcement Parallel to Z Axis
12 - #3
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.) bySalmon and Wang (Ref. 1)
Critical Load Case # 201
The strength values of steel and concrete used in the formulae are in ksi
Bars parallel to X Direction are placed at bottom
Effective Depth d = 0.24 m
Factor from ACI Cl.10.2.7.3 =
= 0.85
From Appendix B 8.4.2, = = 0.02222
From Appendix B 10.3.3, = = 0.01667
From ACI Cl. 7.12.2, = = 0.00162
From Ref.1, Eq. 3.8.4a, constant m=
= 21.65
Calculate reinforcement ratio for critical load case
Design for flexure about X axis is performedat the face of the column at a distance, Dz =
= 0.30 m
Ultimate moment = = 2.42 kNm
Nominal moment capacity required, Mn = = 2.69 kNm
(Based on effective depth) Required = = 0.00008
(Based on gross depth) x d / Depth = 0.00006
Since ρ < ρmin, select ρ= ρmin ρmin Governs
Area of Steel Required, As = = 1.05 in2
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 = #3
Minimum spacing allowed (Smin) = 75.00mm
Selected spacing (S) = 117.32mm
Smin
-
Max spacing for Cracking Consideration = 217.64mm
Safe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#3 @ 102mm o.c.
Required development length for bars = = 0.42 m
Available development length for bars,DL =
= 1.05 m
Try bar size #3 Area of one bar = 0.11 in2
Number of bars required, Nbar= = 12
Because the number of bars is rounded up, make sure new reinforcement ratio < ρmax
Total reinforcement area, As_total = Nbar X (Area of one bar) = 1.32 in2
d = D - Ccover - 1.5 X (dia. of one
bar)=
0.24 m
Reinforcement ratio, = = 0.00258
From ACI Cl.7.6.1, minimum req'd clear distance between bars
Cd = max (Diameter of one bar, 1.0" (25.4mm), Min. User Spacing) = 75.00mm
Provided Steel Area / Required Steel Area = 1.25
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 surchargeonly, top reinforcement value for all pure uplift load cases will be the same.
Design For Top Reinforcement Parallel to Z Axis
12 - #3
X
Z
First load case to be in pure uplift # 201
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
Bars parallel to X Direction are placed at bottom
Effective Depth d = 0.24 m
Factor from ACI Cl.10.2.7.3 = = 0.85
From Appendix B 8.4.2, = = 0.02222
From Appendix B 10.3.3, = = 0.01667
From ACI Cl. 7.12.2, = = 0.00162
Page 11 of 15
12/8/2020file:///F:/KPTL/PROJECT/MAURITANIA/TIGUENT/EQUIPMENT/225KV/CT/FOU...
-
From Ref. 1, Eq. 3.8.4a, constant m=
= 21.65
Calculate reinforcement ratio for critical load case
Design for flexure about X axis is performed at theface of the column at a distance, Dx
= = 0.30 m
Ultimate moment, = = 1.84 kNm
Nominal moment capacity required, Mn = = 2.04 kNm
(Based on effective depth) Required = = 0.00006
(Based on gross depth) x d / Depth = 0.00004
Since ρ < ρmin, select ρ= ρmin ρmin Governs
Area of Steel Required, As = = 1.05 in2
Note - "Area of Steel required" reported here is thelarger 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) = 1.33 in2
Provided Steel Area / Required Steel Area = 1.26
Selected bar Size = #3
Minimum spacing allowed (Smin) = 75.00mm
Selected spacing (S) = 143.39mm
Smin
-
Serial No.P
(kN)
M
(kNm)
Strength Reduction Factor
(Φ)
14 3454.17 1348.21 0.73
15 3713.48 1313.10 0.70
16 3998.52 1275.73 0.68
17 4246.92 1231.55 0.66
18 4547.92 1202.49 0.65
19 4901.12 1187.13 0.65
20 5222.27 1167.88 0.65
21 5581.42 1142.26 0.65
22 5903.87 1113.30 0.65
23 6238.15 1078.21 0.65
24 6560.87 1038.46 0.65
25 6851.92 997.31 0.65
26 7191.47 943.69 0.65
27 7488.26 891.05 0.65
28 8107.03 763.61 0.65
29 8655.52 629.83 0.65
30 9116.93 500.30 0.65
31 9489.42 382.47 0.65
32 9770.95 284.62 0.65
33 9983.22 205.49 0.65
34 10109.43 158.62 0.65
35 10161.25 144.03 0.65
36 10232.98 127.81 0.65
37 10293.18 113.65 0.65
38 10344.81 101.27 0.65
39 10389.98 90.45 0.65
40 10428.86 80.76 0.65
41 10463.05 72.12 0.65
42 10492.54 64.29 0.65
43 10519.09 57.25 0.65
44 10563.26 45.04 0.65
45 10597.57 34.89 0.65
46 10625.38 26.40 0.65
47 10647.44 19.31 0.65
48 10665.69 13.30 0.65
49 10700.75 0.00 0.65
Moment [kNm]
0 200 400 600 800 1000 1200 1397.099586-4000
-2000
0
2000
ϕM (68.37 deg) (kNm)
ϕPn,max = 8560.596616
Shear - Governing Load Case Details
Critical Load Case for Shear Along X = 201
Critical Load Case for Shear Along Z = 201
Shear force along X = 0.05 kN
Shear force along Z = 0.12 kN
Transverse Stirrups Details
Rebar Links = #3 @ 9.84 inches
No. of Legs in X direction = 7
No. of Legs in Z direction = 7
Material Take Off
Footing Reinforcement
Page 13 of 15
12/8/2020file:///F:/KPTL/PROJECT/MAURITANIA/TIGUENT/EQUIPMENT/225KV/CT/FOU...
-
Direction Size Number Total Length (m) Weight (kg)
Along Z on Bottom
Face#3 12 15.60 8.73
Along X on Bottom
Face#3 12 15.60 8.73
Along Z on Top
Face#3 12 15.60 8.73
Along X on Top
Face#3 12 15.60 8.73
Pedestal Reinforcement
Type Size NumberTotal Bar Length
(m)Weight (kg)
Main Steel 1
(Vertical)#6 20 45.24 101.12
Main Steel 2
(Vertical)#5 4 8.54 13.26
Transverse Steel
(Ties)#3 8 24.26 13.57
Internal Steel
(Ties)#3 80 69.79 39.05
Total Reinforcement Weight : 201.92 kg
Concrete
- Length (m) Width (m) Thickness (m) Volume (m3)
Footing 1.40 1.40 0.30 0.59
Pedestal 0.80 0.80 1.50 0.96
Total Concrete Volume : 1.55 m3
Formwork
Footing : 1.68 m2
Pedestal : 4.80 m2
Total : 6.48 m2
Soil Excavation
Pit Depth : 1.50 m
Pit Slope (a : b) : 1 : 1 (Assumed)
Side Distance, s : 0 (Assumed)
Excavation Volume : 13.74 m3
Backfill Volume : 12.38 m3
Page 14 of 15
12/8/2020file:///F:/KPTL/PROJECT/MAURITANIA/TIGUENT/EQUIPMENT/225KV/CT/FOU...
-
0.7 m0.7 m
Page 15 of 15
12/8/2020file:///F:/KPTL/PROJECT/MAURITANIA/TIGUENT/EQUIPMENT/225KV/CT/FOU...