Isolated Footing Design
Page 1 of 40
Isolated Footing Design(ACI 318-05)
Design For Isolated Footing 1
Design For Isolated Footing 3
Design For Isolated Footing 5
Design For Isolated Footing 7
Footing No.
-
Group ID
-
1
3
5
7
1
2
3
4
Footing No.
-
1
3
5
7
Bottom Reinforcement(Mz)
#16
#16
#16
#16
@
@
@
@
300
300
300
300
mm
mm
mm
mm
c/c
c/c
c/c
c/c
Foundation Geometry
Width
Length
2.200
2.200
2.200
2.200
m
m
m
m
2.200
2.200
2.200
2.200
Footing Reinforcement
Bottom Reinforcement(Mx) Top Reinforcement(Mz)
#16
#16
#16
#16
@
@
@
@
300
300
300
300
mm
mm
mm
mm
c/c
c/c
c/c
c/c
#16
#16
#16
#16
@
@
@
@
300
300
300
300
mm
mm
mm
mm
c/c
c/c
c/c
c/c
m
m
m
m
Thickness
0.300
0.300
0.300
0.300
m
m
m
m
Pedestal Reinforcement
Top Reinforcement(Mx)
#16
#16
#16
#16
@
@
@
@
300
300
300
300
mm
mm
mm
mm
c/c
c/c
c/c
c/c
Main Steel
Trans Steel
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Isolated Footing 1
Input Values
Footing Geomtery
Design Type : Calculate Dimension
Footing Thickness (Ft) : 300.000 mm
Footing Length - X (Fl) : 2200.000 mm
Footing Width - Z (Fw) : 2200.000 mm
Eccentricity along X (Oxd) : 0.000 mm
Eccentricity along Z (Ozd) : 0.000 mm
Column Dimensions
Column Shape : Rectangular
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 2 of 40
Column Length - X (Pl) : 0.350 m
Column Width - Z (Pw) : 0.350 m
Pedestal
Include Pedestal? No
Pedestal Shape : N/A
Pedestal Height (Ph) : N/A
Pedestal Length - X (Pl) : N/A
Pedestal Width - Z (Pw) : N/A
Design Parameters
Concrete and Rebar Properties
Unit Weight of Concrete : 24.000 kN/m3
Strength of Concrete : 21.000 N/mm2
Yield Strength of Steel : 420.000 N/mm2
Minimum Bar Size : #16
Maximum Bar Size : #16
Minimum Bar Spacing : 100.000 mm
Maximum Bar Spacing : 300.000 mm
Pedestal Clear Cover (P, CL) : 50.000 mm
Footing Clear Cover (F, CL) : 50.000 mm
Soil Properties
Soil Type : Drained
Unit Weight : 18.000 kN/m3
Soil Bearing Capacity : 75.000 kN/m2
Soil Surcharge : 20.000 kN/m2
Depth of Soil above Footing : 1500.000 mm
Cohesion : 30.000 kN/m2
Sliding and Overturning
Coefficient of Friction : 0.500
Factor of Safety Against Sliding : 1.500
Factor of Safety Against Overturning : 1.500
------------------------------------------------------
Design Calculations
Footing Size
Initial Length (Lo) = 2.200 m
Initial Width (Wo) = 2.200 m
Load Combination/s- Service Stress Level
Load Combination
Number
Load Combination Title
3001
1.0DL+0.714EQX
3002
1.0DL-0.714EQX
3003
1.0DL+0.714EQZ
3004
1.0DL-0.714EQZ
Load Combination/s- Strength Level
Load Combination
Number
Load Combination Title
1000
1.2DL+1.6LL
1001
1.2DL+1.0EQX
1002
1.2DL-1.0EQX
1003
1.2DL+1.0EQZ
1004
1.2DL-1.0EQZ
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 3 of 40
2001
0.9DL+1.0EQX
2002
0.9DL-1.0EQX
2003
0.9DL+1.0EQZ
2004
0.9DL-1.0EQZ
Applied Loads - Service Stress Level
LC
Axial
(kN)
Shear X
(kN)
Shear Z
(kN)
Moment X
(kNm)
Moment Z
(kNm)
3001
3002
45.869
7.892
1.004
0.000
0.000
78.373
-5.884
1.004
0.000
0.000
3003
45.869
1.004
7.892
0.000
0.000
3004
78.373
1.004
-5.884
0.000
0.000
LC
Axial
(kN)
1000
1001
Applied Loads - Strength Level
Shear X
(kN)
Shear Z
(kN)
Moment X
(kNm)
Moment Z
(kNm)
80.945
1.743
1.743
0.000
0.000
51.783
10.852
1.205
0.000
0.000
1002
97.307
-8.442
1.205
0.000
0.000
1003
51.783
1.205
10.852
0.000
0.000
1004
97.307
1.205
-8.442
0.000
0.000
2001
33.147
10.551
0.904
0.000
0.000
2002
78.670
-8.743
0.904
0.000
0.000
2003
33.147
0.904
10.551
0.000
0.000
2004
78.670
0.904
-8.743
0.000
0.000
Reduction of force due to buoyancy = 85.397 kN
Effect due to adhesion = 0.000 kN
Area from initial length and width, Ao = L X W = 4.840 m2
o
o
2
Min. area required from bearing pressure, Amin = P / q
max = 3.327 m
Note: Amin is an initial estimation.
P = Critical Factored Axial Load(without self weight/buoyancy/soil).
qmax = Respective Factored Bearing Capacity.
Final Footing Size
Length (L2) = 2.200 m
Governing Load Case :
# 3001
Width (W2) = 2.200 m
Governing Load Case :
# 3001
Depth (D2) = 0.300 m
Governing Load Case :
# 3001
Area (A2) = 4.840 m2
Pressures at Four Corners
Pressure at
corner 1
(q1)
Pressure at
corner 2
(q2)
Pressure at
corner 3
(q3)
Pressure at
corner 4
(q4)
(kN/m2)
(kN/m2)
(kN/m2)
(kN/m2)
(m2)
3004
52.3828
52.7223
50.7330
50.3935
0.000
3004
52.3828
52.7223
50.7330
50.3935
0.000
3002
52.3828
50.3935
50.7330
52.7223
0.000
3002
52.3828
50.3935
50.7330
52.7223
0.000
Load Case
Area of footing
in uplift (Au)
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
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 4 of 40
and the pressure will be redistributed to remaining corners.
Summary of Adjusted Pressures at 4 corners Four Corners
Pressure at
corner 1 (q1)
Pressure at
corner 2 (q2)
Pressure at
corner 3 (q3)
Pressure at
corner 4 (q4)
Load Case
(kN/m2)
(kN/m2)
(kN/m2)
(kN/m2)
3004
52.3828
52.7223
50.7330
50.3935
3004
52.3828
52.7223
50.7330
50.3935
3002
52.3828
50.3935
50.7330
52.7223
3002
52.3828
50.3935
50.7330
52.7223
Check for stability against overturning and sliding
Factor of safety against
sliding
-
Factor of safety against
overturning
Load Case
No.
Along XDirection
Along ZDirection
About XDirection
About ZDirection
3001
13.750
108.084
792.617
100.837
3002
21.205
124.271
911.321
155.505
3003
108.084
13.750
100.837
792.617
3004
124.271
21.205
155.505
911.322
Critical Load Case And The Governing Factor Of Safety For Overturning And Sliding - X Direction
Critical Load Case for Sliding along X-Direction : 3001
Governing Disturbing Force : 7.892 kN
Governing Restoring Force : 108.518 kN
Minimum Sliding Ratio for the Critical Load Case : 13.750
Critical Load Case for Overturning about X-Direction : 3003
Governing Overturning Moment : 2.368 kNm
Governing Resisting Moment : 238.736 kNm
Minimum Overturning Ratio for the Critical Load Case : 100.837
Critical Load Case And The Governing Factor Of Safety For Overturning And Sliding - Z Direction
Critical Load Case for Sliding along Z-Direction : 3003
Governing Disturbing Force : 7.892 kN
Governing Restoring Force : 108.518 kN
Minimum Sliding Ratio for the Critical Load Case : 13.750
Critical Load Case for Overturning about Z-Direction : 3001
Governing Overturning Moment : -2.368 kNm
Governing Resisting Moment : 238.736 kNm
Minimum Overturning Ratio for the Critical Load Case : 100.837
Shear Calculation
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 5 of 40
Punching Shear Check
Total Footing Depth, D = 0.300m
Calculated Effective Depth, deff =
For rectangular column,
=
D - Ccover - 1.0 = 0.225 m
1 inch is deducted from total depth to cater bar dia(US Convention).
Bcol / Dcol = 1.000
Effective depth, deff, increased until 0.75XVc
Punching Shear Force
Punching Shear Force, Vu = 90.669 kN, Load Case # 1002
From ACI Cl.11.12.2.1, bo for column=
2.298 m
Equation 11-33, Vc1 =
1178.571 kN
Equation 11-34, Vc2 =
1160.658 kN
Equation 11-35, Vc3 =
785.714 kN
Punching shear strength, Vc =
0.75 X minimum of (Vc1, Vc2, Vc3) =
589.286 kN
0.75 X Vc > Vu hence, OK
Along X Direction
(Shear Plane Parallel to Global X Axis)
From ACI Cl.11.3.1.1, Vc =
376.038 kN
Distance along X to design for shear,
Dx =
0.700 m
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.
From above calculations,
0.75 X Vc =
Critical load case for Vux is # 1004
282.028 kN
32.478
kN
0.75 X Vc > Vux hence, OK
One-Way Shear Check
Along Z Direction
(Shear Plane Parallel to Global Z Axis)
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 6 of 40
From ACI Cl.11.3.1.1, Vc =
376.038 kN
Distance along X to design for shear, Dz =
0.700
m
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.
From above calculations,
0.75 X Vc =
Critical load case for Vuz is # 1002
282.028 kN
32.478
kN
0.75 X Vc > Vuz hence, OK
Design for Flexure about Z Axis
(For Reinforcement Parallel to X Axis)
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 # 1002
The strength values of steel and concrete used in the formulae are in ksi
Factor
0.850
from ACI Cl.10.2.7.3 =
From ACI Cl. 10.3.2,
=
0.02125
From ACI Cl. 10.3.3,
=
0.01594
From ACI Cl. 7.12.2,
=
0.00177
From Ref. 1, Eq. 3.8.4a, constant m =
23.529
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 =
0.925
m
Ultimate moment,
19.888
kNm
Nominal moment capacity, Mn =
22.098
kNm
Required
=
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
0.00048
24/11/2021
Isolated Footing Design
Page 7 of 40
Since
OK
Area of Steel Required, As =
876.044 mm2
Selected bar Size = #16
Minimum spacing allowed (Smin) = = 100.000 mm
Selected spacing (S) = 300.000 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 = 250.272 mm
UnSafe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 7620.000 mm o.c.
Required development length for bars =
=0.305
m
0.875
m
Available development length for bars, DL
=
Try bar size
# 16
Area of one bar = 201.064 mm2
Number of bars required, Nbar =
7
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) =
1407.449 mm2
deff = D - Ccover - 0.5 X (dia. of one bar)
=
Reinforcement ratio,
m
0.00264
=
From ACI Cl.7.6.1, minimum req'd clear
distance between bars, Cd =
0.242
max (Diameter of one bar, 1.0,
Min. User Spacing) =
300.000
mm
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 # 1004
The strength values of steel and concrete used in the formulae are in ksi
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 8 of 40
Factor
0.850
from ACI Cl.10.2.7.3 =
From ACI Cl. 10.3.2,
=
0.02125
From ACI Cl. 10.3.3,
=
0.01594
From ACI Cl.7.12.2,
=
0.00177
23.529
From Ref. 1, Eq. 3.8.4a, constant m =
Calculate reinforcement ratio
for critical load case
Design for flexure about X axis is
performed at the face of the column at
a distance, Dz =
0.925
m
Ultimate moment,
19.888
kNm
Nominal moment capacity, Mn =
22.098
kNm
Required
0.00055
=
Since
OK
Area of Steel Required, As =
813.637 mm2
Selected Bar Size = #16
Minimum spacing allowed (Smin) = 100.000 mm
Selected spacing (S) = 300.000 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 = 250.272 mm
UnSafe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 7620.000 mm o.c.
Required development length for bars =
=0.305 m
Available development length for bars, DL
0.875 m
=
Try bar size
# 16
Area of one bar = 201.064 mm2
Number of bars required, Nbar =
7
Because the number of bars is rounded up, make sure new reinforcement ratio < ρmax
Total reinforcement area, As_total =
deff =
Nbar X (Area of one bar) =
1407.449 mm2
D - Ccover - 0.5 X (dia. of one bar)
0.226
m
=
Reinforcement ratio,
0.00283
=
From ACI Cl.7.6.1, minimum req'd clear
distance between bars, Cd =
max (Diameter of one bar, 1.0,
Min. User Spacing) =
300.000
mm
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.
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 9 of 40
Design For Top Reinforcement Parallel to Z Axis
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
0.850
from ACI Cl.10.2.7.3 =
From ACI Cl. 10.3.2,
=
0.02125
From ACI Cl. 10.3.3,
=
0.01594
From ACI Cl. 7.12.2,
=
0.00177
From Ref. 1, Eq. 3.8.4a, constant m =
23.529
Calculate reinforcement ratio
for critical load case
Design for flexure about A axis is
performed at the face of the column
at a distance, Dx =
0.925 m
Ultimate moment,
51.010 kNm
Nominal moment capacity, Mn =
56.678 kNm
=
0.00143
Since
OK
Required
813.637 mm2
Area of Steel Required, As =
Selected bar Size = #16
Minimum spacing allowed (Smin) = 100.000 mm
Selected spacing (S) = 300.000 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 = 250.272 mm
UnSafe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 300 mm o.c.
Design For Top Reinforcement Parallel to X Axis
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 10 of 40
First load case to be in pure uplift #
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
0.850
from ACI Cl.10.2.7.3 =
From ACI Cl. 10.3.2,
=
0.02125
From ACI Cl. 10.3.3,
=
0.01594
From ACI Cl.7.12.2,
=
0.00177
From Ref. 1, Eq. 3.8.4a, constant m =
23.529
Calculate reinforcement ratio
for critical load case
Design for flexure about A axis is
performed at the face of the column
at a distance, Dx =
0.925 m
Ultimate moment,
51.010 kNm
Nominal moment capacity, Mn =
56.678 kNm
=
0.00123
Since
OK
Required
Area of Steel Required, As =
876.044 mm2
Selected bar Size = #16
Minimum spacing allowed (Smin) = 100.000 mm
Selected spacing (S) = 300.000 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 = 250.272 mm
UnSafe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 300 mm o.c.
Isolated Footing 3
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 11 of 40
Input Values
Footing Geomtery
Design Type : Calculate Dimension
Footing Thickness (Ft) : 300.000 mm
Footing Length - X (Fl) : 2200.000 mm
Footing Width - Z (Fw) : 2200.000 mm
Eccentricity along X (Oxd) : 0.000 mm
Eccentricity along Z (Ozd) : 0.000 mm
Column Dimensions
Column Shape : Rectangular
Column Length - X (Pl) : 0.350 m
Column Width - Z (Pw) : 0.350 m
Pedestal
Include Pedestal? No
Pedestal Shape : N/A
Pedestal Height (Ph) : N/A
Pedestal Length - X (Pl) : N/A
Pedestal Width - Z (Pw) : N/A
Design Parameters
Concrete and Rebar Properties
Unit Weight of Concrete : 24.000 kN/m3
Strength of Concrete : 21.000 N/mm2
Yield Strength of Steel : 420.000 N/mm2
Minimum Bar Size : #16
Maximum Bar Size : #16
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 12 of 40
Minimum Bar Spacing : 100.000 mm
Maximum Bar Spacing : 300.000 mm
Pedestal Clear Cover (P, CL) : 50.000 mm
Footing Clear Cover (F, CL) : 50.000 mm
Soil Properties
Soil Type : Drained
Unit Weight : 18.000 kN/m3
Soil Bearing Capacity : 75.000 kN/m2
Soil Surcharge : 20.000 kN/m2
Depth of Soil above Footing : 1500.000 mm
Cohesion : 30.000 kN/m2
Sliding and Overturning
Coefficient of Friction : 0.500
Factor of Safety Against Sliding : 1.500
Factor of Safety Against Overturning : 1.500
------------------------------------------------------
Design Calculations
Footing Size
Initial Length (Lo) = 2.200 m
Initial Width (Wo) = 2.200 m
Load Combination/s- Service Stress Level
Load Combination
Number
Load Combination Title
3001
1.0DL+0.714EQX
3002
1.0DL-0.714EQX
3003
1.0DL+0.714EQZ
3004
1.0DL-0.714EQZ
Load Combination/s- Strength Level
Load Combination
Number
Load Combination Title
1000
1.2DL+1.6LL
1001
1.2DL+1.0EQX
1002
1.2DL-1.0EQX
1003
1.2DL+1.0EQZ
1004
1.2DL-1.0EQZ
2001
0.9DL+1.0EQX
2002
0.9DL-1.0EQX
2003
0.9DL+1.0EQZ
2004
0.9DL-1.0EQZ
Applied Loads - Service Stress Level
LC
Axial
(kN)
Shear X
(kN)
Shear Z
(kN)
Moment X
(kNm)
Moment Z
(kNm)
3001
3002
78.373
5.884
1.004
0.000
0.000
45.869
-7.892
1.004
0.000
0.000
3003
45.869
-1.004
7.892
0.000
0.000
3004
78.373
-1.004
-5.884
0.000
0.000
LC
Axial
(kN)
Shear X
(kN)
Shear Z
(kN)
Moment X
(kNm)
Moment Z
(kNm)
1000
80.945
-1.743
1.743
0.000
0.000
1001
97.307
8.442
1.205
0.000
0.000
1002
51.783
-10.852
1.205
0.000
0.000
1003
51.783
-1.205
10.852
0.000
0.000
1004
97.307
-1.205
-8.442
0.000
0.000
Applied Loads - Strength Level
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 13 of 40
2001
78.670
8.743
0.904
0.000
0.000
2002
33.147
-10.551
0.904
0.000
0.000
2003
33.147
-0.904
10.551
0.000
0.000
2004
78.670
-0.904
-8.743
0.000
0.000
Reduction of force due to buoyancy = 85.397 kN
Effect due to adhesion = 0.000 kN
Area from initial length and width, Ao = L X W = 4.840 m2
o
o
Min. area required from bearing pressure, Amin = P / q
= 3.327 m2
max
Note: Amin is an initial estimation.
P = Critical Factored Axial Load(without self weight/buoyancy/soil).
qmax = Respective Factored Bearing Capacity.
Final Footing Size
Length (L2) = 2.200 m
Governing Load Case :
# 3001
Width (W2) = 2.200 m
Governing Load Case :
# 3001
Depth (D2) = 0.300 m
Governing Load Case :
# 3001
Area (A2) = 4.840 m2
Pressures at Four Corners
Pressure at
corner 1
(q1)
Pressure at
corner 2
(q2)
Pressure at
corner 3
(q3)
Pressure at
corner 4
(q4)
(kN/m2)
(kN/m2)
(kN/m2)
(kN/m2)
(m2)
3004
52.7223
52.3828
50.3935
50.7330
0.000
3001
50.3935
52.3828
52.7223
50.7330
0.000
3001
50.3935
52.3828
52.7223
50.7330
0.000
3001
50.3935
52.3828
52.7223
50.7330
0.000
Load Case
Area of footing
in uplift (Au)
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
Pressure at
corner 1 (q1)
Pressure at
corner 2 (q2)
Pressure at
corner 3 (q3)
Pressure at
corner 4 (q4)
Load Case
(kN/m2)
(kN/m2)
(kN/m2)
(kN/m2)
3004
52.7223
52.3828
50.3935
50.7330
3001
50.3935
52.3828
52.7223
50.7330
3001
50.3935
52.3828
52.7223
50.7330
3001
50.3935
52.3828
52.7223
50.7330
Check for stability against overturning and sliding
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 14 of 40
Factor of safety against
sliding
-
Factor of safety against
overturning
Load Case
No.
Along XDirection
Along ZDirection
About XDirection
About ZDirection
3001
21.205
124.271
911.321
155.505
3002
13.750
108.084
792.617
100.837
3003
108.084
13.750
100.837
792.618
3004
124.271
21.205
155.505
911.321
Critical Load Case And The Governing Factor Of Safety For Overturning And Sliding - X Direction
Critical Load Case for Sliding along X-Direction : 3002
Governing Disturbing Force : -7.892 kN
Governing Restoring Force : 108.518 kN
Minimum Sliding Ratio for the Critical Load Case : 13.750
Critical Load Case for Overturning about X-Direction : 3003
Governing Overturning Moment : 2.368 kNm
Governing Resisting Moment : 238.736 kNm
Minimum Overturning Ratio for the Critical Load Case : 100.837
Critical Load Case And The Governing Factor Of Safety For Overturning And Sliding - Z Direction
Critical Load Case for Sliding along Z-Direction : 3003
Governing Disturbing Force : 7.892 kN
Governing Restoring Force : 108.518 kN
Minimum Sliding Ratio for the Critical Load Case : 13.750
Critical Load Case for Overturning about Z-Direction : 3002
Governing Overturning Moment : 2.368 kNm
Governing Resisting Moment : 238.736 kNm
Minimum Overturning Ratio for the Critical Load Case : 100.837
Shear Calculation
Punching Shear Check
Total Footing Depth, D = 0.300m
0.225 m
1 inch is deducted from total depth to cater bar dia(US Convention).
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 15 of 40
Calculated Effective Depth, deff =
For rectangular column,
=
D - Ccover - 1.0 =
Bcol / Dcol = 1.000
Effective depth, deff, increased until 0.75XVc
Punching Shear Force
Punching Shear Force, Vu = 90.669 kN, Load Case # 1001
From ACI Cl.11.12.2.1, bo for column=
2.298 m
Equation 11-33, Vc1 =
1178.571 kN
Equation 11-34, Vc2 =
1160.658 kN
Equation 11-35, Vc3 =
785.714 kN
Punching shear strength, Vc =
0.75 X minimum of (Vc1, Vc2, Vc3) =
589.286 kN
0.75 X Vc > Vu hence, OK
Along X Direction
(Shear Plane Parallel to Global X Axis)
From ACI Cl.11.3.1.1, Vc =
376.038 kN
Distance along X to design for shear,
Dx =
0.700 m
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.
From above calculations,
0.75 X Vc =
Critical load case for Vux is # 1004
282.028 kN
32.478
kN
0.75 X Vc > Vux hence, OK
One-Way Shear Check
Along Z Direction
(Shear Plane Parallel to Global Z Axis)
From ACI Cl.11.3.1.1, Vc =
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
376.038 kN
24/11/2021
Isolated Footing Design
Page 16 of 40
Distance along X to design for shear, Dz =
1.500
m
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.
From above calculations,
0.75 X Vc =
Critical load case for Vuz is # 1001
282.028 kN
32.478
kN
0.75 X Vc > Vuz hence, OK
Design for Flexure about Z Axis
(For Reinforcement Parallel to X Axis)
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 # 1001
The strength values of steel and concrete used in the formulae are in ksi
Factor
0.850
from ACI Cl.10.2.7.3 =
From ACI Cl. 10.3.2,
=
0.02125
From ACI Cl. 10.3.3,
=
0.01594
From ACI Cl. 7.12.2,
=
0.00177
From Ref. 1, Eq. 3.8.4a, constant m =
23.529
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 =
0.925
m
Ultimate moment,
19.889
kNm
Nominal moment capacity, Mn =
22.099
kNm
Required
0.00048
=
Since
OK
876.044 mm2
Area of Steel Required, As =
Selected bar Size = #16
Minimum spacing allowed (Smin) = = 100.000 mm
Selected spacing (S) = 300.000 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
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 17 of 40
Max spacing for Cracking Consideration = 250.272 mm
UnSafe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 7620.000 mm o.c.
Required development length for bars =
=0.305
m
0.875
m
Available development length for bars, DL
=
Try bar size
# 16
Area of one bar = 201.064 mm2
Number of bars required, Nbar =
7
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) =
1407.449 mm2
deff = D - Ccover - 0.5 X (dia. of one bar)
=
Reinforcement ratio,
m
0.00264
=
From ACI Cl.7.6.1, minimum req'd clear
distance between bars, Cd =
0.242
max (Diameter of one bar, 1.0,
Min. User Spacing) =
300.000
mm
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 # 1004
The strength values of steel and concrete used in the formulae are in ksi
Factor
0.850
from ACI Cl.10.2.7.3 =
From ACI Cl. 10.3.2,
=
0.02125
From ACI Cl. 10.3.3,
=
0.01594
From ACI Cl.7.12.2,
=
0.00177
23.529
From Ref. 1, Eq. 3.8.4a, constant m =
Calculate reinforcement ratio
for critical load case
Design for flexure about X axis is
performed at the face of the column at
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
0.925
m
24/11/2021
Isolated Footing Design
Page 18 of 40
a distance, Dz =
Ultimate moment,
19.888
kNm
Nominal moment capacity, Mn =
22.098
kNm
Required
0.00055
=
Since
OK
Area of Steel Required, As =
813.637 mm2
Selected Bar Size = #16
Minimum spacing allowed (Smin) = 100.000 mm
Selected spacing (S) = 300.000 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 = 250.272 mm
UnSafe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 7620.000 mm o.c.
Required development length for bars =
=0.305 m
Available development length for bars, DL
=
0.875 m
Try bar size
# 16
Area of one bar = 201.064 mm2
Number of bars required, Nbar =
7
Because the number of bars is rounded up, make sure new reinforcement ratio < ρmax
Total reinforcement area, As_total =
deff =
Reinforcement ratio,
Nbar X (Area of one bar) =
0.226
m
0.00283
=
From ACI Cl.7.6.1, minimum req'd clear
distance between bars, Cd =
1407.449 mm2
D - Ccover - 0.5 X (dia. of one bar)
=
max (Diameter of one bar, 1.0,
Min. User Spacing) =
300.000
mm
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
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 19 of 40
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
0.850
from ACI Cl.10.2.7.3 =
From ACI Cl. 10.3.2,
=
0.02125
From ACI Cl. 10.3.3,
=
0.01594
From ACI Cl. 7.12.2,
=
0.00177
From Ref. 1, Eq. 3.8.4a, constant m =
23.529
Calculate reinforcement ratio
for critical load case
Design for flexure about A axis is
performed at the face of the column
at a distance, Dx =
0.925 m
Ultimate moment,
51.010 kNm
Nominal moment capacity, Mn =
56.678 kNm
=
0.00143
Since
OK
Required
Area of Steel Required, As =
813.637 mm2
Selected bar Size = #16
Minimum spacing allowed (Smin) = 100.000 mm
Selected spacing (S) = 300.000 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 = 250.272 mm
UnSafe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 300 mm o.c.
Design For Top Reinforcement Parallel to X Axis
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 20 of 40
First load case to be in pure uplift #
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
0.850
from ACI Cl.10.2.7.3 =
From ACI Cl. 10.3.2,
=
0.02125
From ACI Cl. 10.3.3,
=
0.01594
From ACI Cl.7.12.2,
=
0.00177
From Ref. 1, Eq. 3.8.4a, constant m =
23.529
Calculate reinforcement ratio
for critical load case
Design for flexure about A axis is
performed at the face of the column
at a distance, Dx =
0.925 m
Ultimate moment,
51.010 kNm
Nominal moment capacity, Mn =
56.678 kNm
=
0.00123
Since
OK
Required
Area of Steel Required, As =
876.044 mm2
Selected bar Size = #16
Minimum spacing allowed (Smin) = 100.000 mm
Selected spacing (S) = 300.000 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 = 250.272 mm
UnSafe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 300 mm o.c.
Isolated Footing 5
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 21 of 40
Input Values
Footing Geomtery
Design Type : Calculate Dimension
Footing Thickness (Ft) : 300.000 mm
Footing Length - X (Fl) : 2200.000 mm
Footing Width - Z (Fw) : 2200.000 mm
Eccentricity along X (Oxd) : 0.000 mm
Eccentricity along Z (Ozd) : 0.000 mm
Column Dimensions
Column Shape : Rectangular
Column Length - X (Pl) : 0.350 m
Column Width - Z (Pw) : 0.350 m
Pedestal
Include Pedestal? No
Pedestal Shape : N/A
Pedestal Height (Ph) : N/A
Pedestal Length - X (Pl) : N/A
Pedestal Width - Z (Pw) : N/A
Design Parameters
Concrete and Rebar Properties
Unit Weight of Concrete : 24.000 kN/m3
Strength of Concrete : 21.000 N/mm2
Yield Strength of Steel : 420.000 N/mm2
Minimum Bar Size : #16
Maximum Bar Size : #16
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 22 of 40
Minimum Bar Spacing : 100.000 mm
Maximum Bar Spacing : 300.000 mm
Pedestal Clear Cover (P, CL) : 50.000 mm
Footing Clear Cover (F, CL) : 50.000 mm
Soil Properties
Soil Type : Drained
Unit Weight : 18.000 kN/m3
Soil Bearing Capacity : 75.000 kN/m2
Soil Surcharge : 20.000 kN/m2
Depth of Soil above Footing : 1500.000 mm
Cohesion : 30.000 kN/m2
Sliding and Overturning
Coefficient of Friction : 0.500
Factor of Safety Against Sliding : 1.500
Factor of Safety Against Overturning : 1.500
------------------------------------------------------
Design Calculations
Footing Size
Initial Length (Lo) = 2.200 m
Initial Width (Wo) = 2.200 m
Load Combination/s- Service Stress Level
Load Combination
Number
Load Combination Title
3001
1.0DL+0.714EQX
3002
1.0DL-0.714EQX
3003
1.0DL+0.714EQZ
3004
1.0DL-0.714EQZ
Load Combination/s- Strength Level
Load Combination
Number
Load Combination Title
1000
1.2DL+1.6LL
1001
1.2DL+1.0EQX
1002
1.2DL-1.0EQX
1003
1.2DL+1.0EQZ
1004
1.2DL-1.0EQZ
2001
0.9DL+1.0EQX
2002
0.9DL-1.0EQX
2003
0.9DL+1.0EQZ
2004
0.9DL-1.0EQZ
Applied Loads - Service Stress Level
LC
Axial
(kN)
Shear X
(kN)
Shear Z
(kN)
Moment X
(kNm)
Moment Z
(kNm)
3001
3002
45.869
7.892
-1.004
0.000
0.000
78.373
-5.884
-1.004
0.000
0.000
3003
78.373
1.004
5.884
0.000
0.000
3004
45.869
1.004
-7.892
0.000
0.000
LC
Axial
(kN)
1000
1001
Applied Loads - Strength Level
Shear X
(kN)
Shear Z
(kN)
Moment X
(kNm)
Moment Z
(kNm)
80.945
1.743
-1.743
0.000
0.000
51.783
10.852
-1.205
0.000
0.000
1002
97.307
-8.442
-1.205
0.000
0.000
1003
97.307
1.205
8.442
0.000
0.000
1004
51.783
1.205
-10.852
0.000
0.000
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 23 of 40
2001
33.147
10.551
-0.904
0.000
0.000
2002
78.670
-8.743
-0.904
0.000
0.000
2003
78.670
0.904
8.743
0.000
0.000
2004
33.147
0.904
-10.551
0.000
0.000
Reduction of force due to buoyancy = 85.397 kN
Effect due to adhesion = 0.000 kN
Area from initial length and width, Ao = L X W = 4.840 m2
o
o
Min. area required from bearing pressure, Amin = P / q
= 3.327 m2
max
Note: Amin is an initial estimation.
P = Critical Factored Axial Load(without self weight/buoyancy/soil).
qmax = Respective Factored Bearing Capacity.
Final Footing Size
Length (L2) = 2.200 m
Governing Load Case :
# 3001
Width (W2) = 2.200 m
Governing Load Case :
# 3001
Depth (D2) = 0.300 m
Governing Load Case :
# 3001
Area (A2) = 4.840 m2
Pressures at Four Corners
Pressure at
corner 1
(q1)
Pressure at
corner 2
(q2)
Pressure at
corner 3
(q3)
Pressure at
corner 4
(q4)
(kN/m2)
(kN/m2)
(kN/m2)
(kN/m2)
(m2)
3002
52.7223
50.7330
50.3935
52.3828
0.000
3002
52.7223
50.7330
50.3935
52.3828
0.000
3003
50.3935
50.7330
52.7223
52.3828
0.000
3003
50.3935
50.7330
52.7223
52.3828
0.000
Load Case
Area of footing
in uplift (Au)
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
Pressure at
corner 1 (q1)
Pressure at
corner 2 (q2)
Pressure at
corner 3 (q3)
Pressure at
corner 4 (q4)
Load Case
(kN/m2)
(kN/m2)
(kN/m2)
(kN/m2)
3002
52.7223
50.7330
50.3935
52.3828
3002
52.7223
50.7330
50.3935
52.3828
3003
50.3935
50.7330
52.7223
52.3828
3003
50.3935
50.7330
52.7223
52.3828
Check for stability against overturning and sliding
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 24 of 40
Factor of safety against
sliding
-
Factor of safety against
overturning
Load Case
No.
Along XDirection
Along ZDirection
About XDirection
About ZDirection
3001
13.750
108.084
792.617
100.837
3002
21.205
124.271
911.321
155.505
3003
124.271
21.205
155.505
911.322
3004
108.084
13.750
100.837
792.617
Critical Load Case And The Governing Factor Of Safety For Overturning And Sliding - X Direction
Critical Load Case for Sliding along X-Direction : 3001
Governing Disturbing Force : 7.892 kN
Governing Restoring Force : 108.518 kN
Minimum Sliding Ratio for the Critical Load Case : 13.750
Critical Load Case for Overturning about X-Direction : 3004
Governing Overturning Moment : -2.368 kNm
Governing Resisting Moment : 238.736 kNm
Minimum Overturning Ratio for the Critical Load Case : 100.837
Critical Load Case And The Governing Factor Of Safety For Overturning And Sliding - Z Direction
Critical Load Case for Sliding along Z-Direction : 3004
Governing Disturbing Force : -7.892 kN
Governing Restoring Force : 108.518 kN
Minimum Sliding Ratio for the Critical Load Case : 13.750
Critical Load Case for Overturning about Z-Direction : 3001
Governing Overturning Moment : -2.368 kNm
Governing Resisting Moment : 238.736 kNm
Minimum Overturning Ratio for the Critical Load Case : 100.837
Shear Calculation
Punching Shear Check
Total Footing Depth, D = 0.300m
0.225 m
1 inch is deducted from total depth to cater bar dia(US Convention).
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 25 of 40
Calculated Effective Depth, deff =
For rectangular column,
=
D - Ccover - 1.0 =
Bcol / Dcol = 1.000
Effective depth, deff, increased until 0.75XVc
Punching Shear Force
Punching Shear Force, Vu = 90.669 kN, Load Case # 1002
From ACI Cl.11.12.2.1, bo for column=
2.298 m
Equation 11-33, Vc1 =
1178.571 kN
Equation 11-34, Vc2 =
1160.658 kN
Equation 11-35, Vc3 =
785.714 kN
Punching shear strength, Vc =
0.75 X minimum of (Vc1, Vc2, Vc3) =
589.286 kN
0.75 X Vc > Vu hence, OK
Along X Direction
(Shear Plane Parallel to Global X Axis)
From ACI Cl.11.3.1.1, Vc =
376.038 kN
Distance along X to design for shear,
Dx =
1.500 m
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.
From above calculations,
0.75 X Vc =
Critical load case for Vux is # 1003
282.028 kN
32.478
kN
0.75 X Vc > Vux hence, OK
One-Way Shear Check
Along Z Direction
(Shear Plane Parallel to Global Z Axis)
From ACI Cl.11.3.1.1, Vc =
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
376.038 kN
24/11/2021
Isolated Footing Design
Page 26 of 40
Distance along X to design for shear, Dz =
0.700
m
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.
From above calculations,
0.75 X Vc =
Critical load case for Vuz is # 1002
282.028 kN
32.478
kN
0.75 X Vc > Vuz hence, OK
Design for Flexure about Z Axis
(For Reinforcement Parallel to X Axis)
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 # 1002
The strength values of steel and concrete used in the formulae are in ksi
Factor
0.850
from ACI Cl.10.2.7.3 =
From ACI Cl. 10.3.2,
=
0.02125
From ACI Cl. 10.3.3,
=
0.01594
From ACI Cl. 7.12.2,
=
0.00177
From Ref. 1, Eq. 3.8.4a, constant m =
23.529
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 =
0.925
m
Ultimate moment,
19.888
kNm
Nominal moment capacity, Mn =
22.098
kNm
Required
0.00048
=
Since
OK
876.044 mm2
Area of Steel Required, As =
Selected bar Size = #16
Minimum spacing allowed (Smin) = = 100.000 mm
Selected spacing (S) = 300.000 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
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 27 of 40
Max spacing for Cracking Consideration = 250.272 mm
UnSafe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 7620.000 mm o.c.
Required development length for bars =
=0.305
m
0.875
m
Available development length for bars, DL
=
Try bar size
# 16
Area of one bar = 201.064 mm2
Number of bars required, Nbar =
7
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) =
1407.449 mm2
deff = D - Ccover - 0.5 X (dia. of one bar)
=
Reinforcement ratio,
m
0.00264
=
From ACI Cl.7.6.1, minimum req'd clear
distance between bars, Cd =
0.242
max (Diameter of one bar, 1.0,
Min. User Spacing) =
300.000
mm
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 # 1003
The strength values of steel and concrete used in the formulae are in ksi
Factor
0.850
from ACI Cl.10.2.7.3 =
From ACI Cl. 10.3.2,
=
0.02125
From ACI Cl. 10.3.3,
=
0.01594
From ACI Cl.7.12.2,
=
0.00177
23.529
From Ref. 1, Eq. 3.8.4a, constant m =
Calculate reinforcement ratio
for critical load case
Design for flexure about X axis is
performed at the face of the column at
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
0.925
m
24/11/2021
Isolated Footing Design
Page 28 of 40
a distance, Dz =
Ultimate moment,
19.889
kNm
Nominal moment capacity, Mn =
22.099
kNm
Required
0.00055
=
Since
OK
Area of Steel Required, As =
813.637 mm2
Selected Bar Size = #16
Minimum spacing allowed (Smin) = 100.000 mm
Selected spacing (S) = 300.000 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 = 250.272 mm
UnSafe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 7620.000 mm o.c.
Required development length for bars =
=0.305 m
Available development length for bars, DL
=
0.875 m
Try bar size
# 16
Area of one bar = 201.064 mm2
Number of bars required, Nbar =
7
Because the number of bars is rounded up, make sure new reinforcement ratio < ρmax
Total reinforcement area, As_total =
deff =
Reinforcement ratio,
Nbar X (Area of one bar) =
0.226
m
0.00283
=
From ACI Cl.7.6.1, minimum req'd clear
distance between bars, Cd =
1407.449 mm2
D - Ccover - 0.5 X (dia. of one bar)
=
max (Diameter of one bar, 1.0,
Min. User Spacing) =
300.000
mm
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
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 29 of 40
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
0.850
from ACI Cl.10.2.7.3 =
From ACI Cl. 10.3.2,
=
0.02125
From ACI Cl. 10.3.3,
=
0.01594
From ACI Cl. 7.12.2,
=
0.00177
From Ref. 1, Eq. 3.8.4a, constant m =
23.529
Calculate reinforcement ratio
for critical load case
Design for flexure about A axis is
performed at the face of the column
at a distance, Dx =
0.925 m
Ultimate moment,
51.010 kNm
Nominal moment capacity, Mn =
56.678 kNm
=
0.00143
Since
OK
Required
Area of Steel Required, As =
813.637 mm2
Selected bar Size = #16
Minimum spacing allowed (Smin) = 100.000 mm
Selected spacing (S) = 300.000 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 = 250.272 mm
UnSafe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 300 mm o.c.
Design For Top Reinforcement Parallel to X Axis
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 30 of 40
First load case to be in pure uplift #
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
0.850
from ACI Cl.10.2.7.3 =
From ACI Cl. 10.3.2,
=
0.02125
From ACI Cl. 10.3.3,
=
0.01594
From ACI Cl.7.12.2,
=
0.00177
From Ref. 1, Eq. 3.8.4a, constant m =
23.529
Calculate reinforcement ratio
for critical load case
Design for flexure about A axis is
performed at the face of the column
at a distance, Dx =
0.925 m
Ultimate moment,
51.010 kNm
Nominal moment capacity, Mn =
56.678 kNm
=
0.00123
Since
OK
Required
Area of Steel Required, As =
876.044 mm2
Selected bar Size = #16
Minimum spacing allowed (Smin) = 100.000 mm
Selected spacing (S) = 300.000 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 = 250.272 mm
UnSafe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 300 mm o.c.
Isolated Footing 7
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 31 of 40
Input Values
Footing Geomtery
Design Type : Calculate Dimension
Footing Thickness (Ft) : 300.000 mm
Footing Length - X (Fl) : 2200.000 mm
Footing Width - Z (Fw) : 2200.000 mm
Eccentricity along X (Oxd) : 0.000 mm
Eccentricity along Z (Ozd) : 0.000 mm
Column Dimensions
Column Shape : Rectangular
Column Length - X (Pl) : 0.350 m
Column Width - Z (Pw) : 0.350 m
Pedestal
Include Pedestal? No
Pedestal Shape : N/A
Pedestal Height (Ph) : N/A
Pedestal Length - X (Pl) : N/A
Pedestal Width - Z (Pw) : N/A
Design Parameters
Concrete and Rebar Properties
Unit Weight of Concrete : 24.000 kN/m3
Strength of Concrete : 21.000 N/mm2
Yield Strength of Steel : 420.000 N/mm2
Minimum Bar Size : #16
Maximum Bar Size : #16
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 32 of 40
Minimum Bar Spacing : 100.000 mm
Maximum Bar Spacing : 300.000 mm
Pedestal Clear Cover (P, CL) : 50.000 mm
Footing Clear Cover (F, CL) : 50.000 mm
Soil Properties
Soil Type : Drained
Unit Weight : 18.000 kN/m3
Soil Bearing Capacity : 75.000 kN/m2
Soil Surcharge : 20.000 kN/m2
Depth of Soil above Footing : 1500.000 mm
Cohesion : 30.000 kN/m2
Sliding and Overturning
Coefficient of Friction : 0.500
Factor of Safety Against Sliding : 1.500
Factor of Safety Against Overturning : 1.500
------------------------------------------------------
Design Calculations
Footing Size
Initial Length (Lo) = 2.200 m
Initial Width (Wo) = 2.200 m
Load Combination/s- Service Stress Level
Load Combination
Number
Load Combination Title
3001
1.0DL+0.714EQX
3002
1.0DL-0.714EQX
3003
1.0DL+0.714EQZ
3004
1.0DL-0.714EQZ
Load Combination/s- Strength Level
Load Combination
Number
Load Combination Title
1000
1.2DL+1.6LL
1001
1.2DL+1.0EQX
1002
1.2DL-1.0EQX
1003
1.2DL+1.0EQZ
1004
1.2DL-1.0EQZ
2001
0.9DL+1.0EQX
2002
0.9DL-1.0EQX
2003
0.9DL+1.0EQZ
2004
0.9DL-1.0EQZ
Applied Loads - Service Stress Level
LC
Axial
(kN)
Shear X
(kN)
Shear Z
(kN)
Moment X
(kNm)
Moment Z
(kNm)
3001
3002
78.373
5.884
-1.004
0.000
0.000
45.869
-7.892
-1.004
0.000
0.000
3003
78.373
-1.004
5.884
0.000
0.000
3004
45.869
-1.004
-7.892
0.000
0.000
LC
Axial
(kN)
Shear X
(kN)
Shear Z
(kN)
Moment X
(kNm)
Moment Z
(kNm)
1000
80.945
-1.743
-1.743
0.000
0.000
1001
97.307
8.442
-1.205
0.000
0.000
1002
51.783
-10.852
-1.205
0.000
0.000
1003
97.307
-1.205
8.442
0.000
0.000
1004
51.783
-1.205
-10.852
0.000
0.000
Applied Loads - Strength Level
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 33 of 40
2001
78.670
8.743
-0.904
0.000
0.000
2002
33.147
-10.551
-0.904
0.000
0.000
2003
78.670
-0.904
8.743
0.000
0.000
2004
33.147
-0.904
-10.551
0.000
0.000
Reduction of force due to buoyancy = 85.397 kN
Effect due to adhesion = 0.000 kN
Area from initial length and width, Ao = L X W = 4.840 m2
o
o
Min. area required from bearing pressure, Amin = P / q
= 3.327 m2
max
Note: Amin is an initial estimation.
P = Critical Factored Axial Load(without self weight/buoyancy/soil).
qmax = Respective Factored Bearing Capacity.
Final Footing Size
Length (L2) = 2.200 m
Governing Load Case :
# 3001
Width (W2) = 2.200 m
Governing Load Case :
# 3001
Depth (D2) = 0.300 m
Governing Load Case :
# 3001
Area (A2) = 4.840 m2
Pressures at Four Corners
Pressure at
corner 1
(q1)
Pressure at
corner 2
(q2)
Pressure at
corner 3
(q3)
Pressure at
corner 4
(q4)
(kN/m2)
(kN/m2)
(kN/m2)
(kN/m2)
(m2)
3001
50.7330
52.7223
52.3828
50.3935
0.000
3001
50.7330
52.7223
52.3828
50.3935
0.000
3001
50.7330
52.7223
52.3828
50.3935
0.000
3003
50.7330
50.3935
52.3828
52.7223
0.000
Load Case
Area of footing
in uplift (Au)
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
Pressure at
corner 1 (q1)
Pressure at
corner 2 (q2)
Pressure at
corner 3 (q3)
Pressure at
corner 4 (q4)
Load Case
(kN/m2)
(kN/m2)
(kN/m2)
(kN/m2)
3001
50.7330
52.7223
52.3828
50.3935
3001
50.7330
52.7223
52.3828
50.3935
3001
50.7330
52.7223
52.3828
50.3935
3003
50.7330
50.3935
52.3828
52.7223
Check for stability against overturning and sliding
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 34 of 40
Factor of safety against
sliding
-
Factor of safety against
overturning
Load Case
No.
Along XDirection
Along ZDirection
About XDirection
About ZDirection
3001
21.205
124.271
911.321
155.505
3002
13.750
108.084
792.617
100.837
3003
124.271
21.205
155.505
911.321
3004
108.084
13.750
100.837
792.618
Critical Load Case And The Governing Factor Of Safety For Overturning And Sliding - X Direction
Critical Load Case for Sliding along X-Direction : 3002
Governing Disturbing Force : -7.892 kN
Governing Restoring Force : 108.518 kN
Minimum Sliding Ratio for the Critical Load Case : 13.750
Critical Load Case for Overturning about X-Direction : 3004
Governing Overturning Moment : -2.368 kNm
Governing Resisting Moment : 238.736 kNm
Minimum Overturning Ratio for the Critical Load Case : 100.837
Critical Load Case And The Governing Factor Of Safety For Overturning And Sliding - Z Direction
Critical Load Case for Sliding along Z-Direction : 3004
Governing Disturbing Force : -7.892 kN
Governing Restoring Force : 108.518 kN
Minimum Sliding Ratio for the Critical Load Case : 13.750
Critical Load Case for Overturning about Z-Direction : 3002
Governing Overturning Moment : 2.368 kNm
Governing Resisting Moment : 238.736 kNm
Minimum Overturning Ratio for the Critical Load Case : 100.837
Shear Calculation
Punching Shear Check
Total Footing Depth, D = 0.300m
0.225 m
1 inch is deducted from total depth to cater bar dia(US Convention).
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 35 of 40
Calculated Effective Depth, deff =
For rectangular column,
=
D - Ccover - 1.0 =
Bcol / Dcol = 1.000
Effective depth, deff, increased until 0.75XVc
Punching Shear Force
Punching Shear Force, Vu = 90.669 kN, Load Case # 1001
From ACI Cl.11.12.2.1, bo for column=
2.298 m
Equation 11-33, Vc1 =
1178.571 kN
Equation 11-34, Vc2 =
1160.658 kN
Equation 11-35, Vc3 =
785.714 kN
Punching shear strength, Vc =
0.75 X minimum of (Vc1, Vc2, Vc3) =
589.286 kN
0.75 X Vc > Vu hence, OK
Along X Direction
(Shear Plane Parallel to Global X Axis)
From ACI Cl.11.3.1.1, Vc =
376.038 kN
Distance along X to design for shear,
Dx =
1.500 m
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.
From above calculations,
0.75 X Vc =
Critical load case for Vux is # 1003
282.028 kN
32.478
kN
0.75 X Vc > Vux hence, OK
One-Way Shear Check
Along Z Direction
(Shear Plane Parallel to Global Z Axis)
From ACI Cl.11.3.1.1, Vc =
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
376.038 kN
24/11/2021
Isolated Footing Design
Page 36 of 40
Distance along X to design for shear, Dz =
1.500
m
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.
From above calculations,
0.75 X Vc =
Critical load case for Vuz is # 1001
282.028 kN
32.478
kN
0.75 X Vc > Vuz hence, OK
Design for Flexure about Z Axis
(For Reinforcement Parallel to X Axis)
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 # 1001
The strength values of steel and concrete used in the formulae are in ksi
Factor
0.850
from ACI Cl.10.2.7.3 =
From ACI Cl. 10.3.2,
=
0.02125
From ACI Cl. 10.3.3,
=
0.01594
From ACI Cl. 7.12.2,
=
0.00177
From Ref. 1, Eq. 3.8.4a, constant m =
23.529
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 =
0.925
m
Ultimate moment,
19.889
kNm
Nominal moment capacity, Mn =
22.099
kNm
Required
0.00048
=
Since
OK
876.044 mm2
Area of Steel Required, As =
Selected bar Size = #16
Minimum spacing allowed (Smin) = = 100.000 mm
Selected spacing (S) = 300.000 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
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 37 of 40
Max spacing for Cracking Consideration = 250.272 mm
UnSafe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 7620.000 mm o.c.
Required development length for bars =
=0.305
m
0.875
m
Available development length for bars, DL
=
Try bar size
# 16
Area of one bar = 201.064 mm2
Number of bars required, Nbar =
7
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) =
1407.449 mm2
deff = D - Ccover - 0.5 X (dia. of one bar)
=
Reinforcement ratio,
m
0.00264
=
From ACI Cl.7.6.1, minimum req'd clear
distance between bars, Cd =
0.242
max (Diameter of one bar, 1.0,
Min. User Spacing) =
300.000
mm
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 # 1003
The strength values of steel and concrete used in the formulae are in ksi
Factor
0.850
from ACI Cl.10.2.7.3 =
From ACI Cl. 10.3.2,
=
0.02125
From ACI Cl. 10.3.3,
=
0.01594
From ACI Cl.7.12.2,
=
0.00177
23.529
From Ref. 1, Eq. 3.8.4a, constant m =
Calculate reinforcement ratio
for critical load case
Design for flexure about X axis is
performed at the face of the column at
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
0.925
m
24/11/2021
Isolated Footing Design
Page 38 of 40
a distance, Dz =
Ultimate moment,
19.889
kNm
Nominal moment capacity, Mn =
22.099
kNm
Required
0.00055
=
Since
OK
Area of Steel Required, As =
813.637 mm2
Selected Bar Size = #16
Minimum spacing allowed (Smin) = 100.000 mm
Selected spacing (S) = 300.000 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 = 250.272 mm
UnSafe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 7620.000 mm o.c.
Required development length for bars =
=0.305 m
Available development length for bars, DL
=
0.875 m
Try bar size
# 16
Area of one bar = 201.064 mm2
Number of bars required, Nbar =
7
Because the number of bars is rounded up, make sure new reinforcement ratio < ρmax
Total reinforcement area, As_total =
deff =
Reinforcement ratio,
Nbar X (Area of one bar) =
0.226
m
0.00283
=
From ACI Cl.7.6.1, minimum req'd clear
distance between bars, Cd =
1407.449 mm2
D - Ccover - 0.5 X (dia. of one bar)
=
max (Diameter of one bar, 1.0,
Min. User Spacing) =
300.000
mm
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
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 39 of 40
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
0.850
from ACI Cl.10.2.7.3 =
From ACI Cl. 10.3.2,
=
0.02125
From ACI Cl. 10.3.3,
=
0.01594
From ACI Cl. 7.12.2,
=
0.00177
From Ref. 1, Eq. 3.8.4a, constant m =
23.529
Calculate reinforcement ratio
for critical load case
Design for flexure about A axis is
performed at the face of the column
at a distance, Dx =
0.925 m
Ultimate moment,
51.010 kNm
Nominal moment capacity, Mn =
56.678 kNm
=
0.00143
Since
OK
Required
Area of Steel Required, As =
813.637 mm2
Selected bar Size = #16
Minimum spacing allowed (Smin) = 100.000 mm
Selected spacing (S) = 300.000 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 = 250.272 mm
UnSafe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 300 mm o.c.
Design For Top Reinforcement Parallel to X Axis
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021
Isolated Footing Design
Page 40 of 40
First load case to be in pure uplift #
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
0.850
from ACI Cl.10.2.7.3 =
From ACI Cl. 10.3.2,
=
0.02125
From ACI Cl. 10.3.3,
=
0.01594
From ACI Cl.7.12.2,
=
0.00177
From Ref. 1, Eq. 3.8.4a, constant m =
23.529
Calculate reinforcement ratio
for critical load case
Design for flexure about A axis is
performed at the face of the column
at a distance, Dx =
0.925 m
Ultimate moment,
51.010 kNm
Nominal moment capacity, Mn =
56.678 kNm
=
0.00123
Since
OK
Required
Area of Steel Required, As =
876.044 mm2
Selected bar Size = #16
Minimum spacing allowed (Smin) = 100.000 mm
Selected spacing (S) = 300.000 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 = 250.272 mm
UnSafe for Cracking Aspect.
Based on spacing reinforcement increment; provided reinforcement is
#16 @ 300 mm o.c.
Print Calculation Sheet
file:///C:/Staad.foundation%205.3/CalcXsl/footing.xml
24/11/2021