CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)

DESIGN OF FOOTING
Isolated Footing 54

Input Values

Footing Geomtery

Design Type : Calculate Dimension

Footing Thickness (Ft) : 300.000 mm
Footing Length - X (Fl) : 1400.000 mm

PREPARED BY : ENGR CAREN HAZEL ORTIZ

CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)
DESIGN OF FOOTING
Footing Width - Z (Fw) : 1400.000 mm
Eccentricity along X (Oxd) : 50.000 mm
Eccentricity along Z (Ozd) : 0.000 mm

Column Dimensions

Column Shape : Rectangular

Column Length - X (Pl) : 0.350 m
Column Width - Z (Pw) : 0.300 m

Design Parameters

Concrete and Rebar Properties

Unit Weight of Concrete : 23.000 kN/m3

Strength of Concrete : 20.700 N/mm2
Yield Strength of Steel : 248.000 N/mm2
Minimum Bar Size : #16
Maximum Bar Size : #32
Minimum Bar Spacing : 200.000 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 : 22.000 kN/m3
Soil Bearing Capacity : 100.000 kN/m2
Soil Surcharge : 0.000 kN/m2
Depth of Soil above Footing : 0.000 mm
Cohesion : 0.000 kN/m2

Sliding and Overturning

Coefficient of Friction : 0.500

Factor of Safety Against Sliding : 1.500
Factor of Safety Against Overturning : 1.500
------------------------------------------------------

PREPARED BY : ENGR CAREN HAZEL ORTIZ

CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)
DESIGN OF FOOTING
Design Calculations

Footing Size

Initial Length (Lo) = 1.400 m

Initial Width (Wo) = 1.400 m

Load Combination/s- Service Stress Level

Load Combination
Load Combination Title
Number
3 DL + LL
Load Combination/s- Strength Level
Load Combination
Load Combination Title
Number
3 DL + LL
Applied Loads - Service Stress Level
Axial Shear X Shear Z Moment X Moment Z
LC
(kN) (kN) (kN) (kNm) (kNm)
3 80.175 0.112 -2.103 -1.158 -4.091

Applied Loads - Strength Level

Axial Shear X Shear Z Moment X Moment Z
LC
(kN) (kN) (kN) (kNm) (kNm)
3 80.175 0.112 -2.103 -1.158 -4.091

Reduction of force due to buoyancy = 0.000 kN

Effect due to adhesion = 0.000 kN
Area from initial length and width, Ao =Lo X Wo = 1.960 m2
Min. area required from bearing pressure, Amin =P / qmax = 0.937 m2

Note: Amin is an initial estimation.

P = Critical Factored Axial Load(without self weight/buoyancy/so
qmax = Respective Factored Bearing Capacity.

PREPARED BY : ENGR CAREN HAZEL ORTIZ

CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)
DESIGN OF FOOTING

Final Footing Size

Length (L2) = 1.400 m Governing Load Case : #3

Width (W2) = 1.400 m Governing Load Case : #3
Depth (D2) = 0.300 m Governing Load Case : #3
Area (A2) = 1.960 m 2

Pressures at Four Corners

Pressure at Pressure at Pressure at Pressure at Area of footing

Load Case corner 1 (q1) corner 2 (q2) corner 3 (q3) corner 4 (q4) in uplift (Au)
(kN/m2) (kN/m2) (kN/m2) (kN/m2) (m2)
3 42.6976 60.7373 52.9136 34.8739 0.000
3 42.6976 60.7373 52.9136 34.8739 0.000
3 42.6976 60.7373 52.9136 34.8739 0.000
3 42.6976 60.7373 52.9136 34.8739 0.000

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 Pressure at Pressure at Pressure at

corner 1 (q1) corner 2 (q2) corner 3 (q3) corner 4 (q4)

Load Case (kN/m2) (kN/m2) (kN/m2) (kN/m2)

3 42.6976 60.7373 52.9136 34.8739
3 42.6976 60.7373 52.9136 34.8739
3 42.6976 60.7373 52.9136 34.8739

PREPARED BY : ENGR CAREN HAZEL ORTIZ

 CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)
DESIGN OF FOOTING
3 42.6976 60.7373 52.9136 34.8739

Check for stability against overturning and sliding

Factor of safety against Factor of safety against

-
sliding overturning
Load
Along X- Along Z- About X- About Z-
Case
Direction Direction Direction Direction
No.
3 416.986 22.282 36.662 14.928

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

Critical Load Case for Sliding along X-Direction : 3

Governing Disturbing Force : 0.112 kN
Governing Restoring Force : 46.849 kN
Minimum Sliding Ratio for the Critical Load Case : 416.986
Critical Load Case for Overturning about X-Direction : 3
Governing Overturning Moment : -1.789 kNm
Governing Resisting Moment : 65.588 kNm
Minimum Overturning Ratio for the Critical Load Case : 36.662

Critical Load Case And The Governing Factor Of Safety For Overturning And Sliding - Z
Direction
PREPARED BY : ENGR CAREN HAZEL ORTIZ
 CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)
DESIGN OF FOOTING
Critical Load Case for Sliding along Z-Direction : 3
Governing Disturbing Force : -2.103 kN
Governing Restoring Force : 46.849 kN
Minimum Sliding Ratio for the Critical Load Case : 22.282
Critical Load Case for Overturning about Z-Direction : 3
Governing Overturning Moment : -4.125 kNm
Governing Resisting Moment : 61.579 kNm
Minimum Overturning Ratio for the Critical Load Case : 14.928

Shear Calculation

Punching Shear Check

Total Footing Depth, D = 0.300m

Calculated Effective Depth, deff = D - Ccover - 1.0 = 0.225 m

For rectangular column, = Bcol / Dcol = 1.167

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

Punching Shear Force, Vu = 67.845 kN, Load Case # 3

From ACI Cl.11.12.2.1, bo for column= 2.198 m

Equation 11-33, Vc1 = 1012.619 kN

Equation 11-34, Vc2 = 1135.367 kN

Equation 11-35, Vc3 = 746.141 kN

PREPARED BY : ENGR CAREN HAZEL ORTIZ

CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)
DESIGN OF FOOTING
Punching shear strength, Vc = 0.75 X minimum of (Vc1, Vc2, Vc3) = 559.605 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 = 237.581 kN

Distance along X to design for shear,

0.325 m
Dx =

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 = 178.186 kN

Critical load case for Vux is # 3 20.003 kN
0.75 X Vc > Vux hence, OK

One-Way Shear Check

Along Z Direction

(Shear Plane Parallel to Global Z Axis)

PREPARED BY : ENGR CAREN HAZEL ORTIZ

CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)
DESIGN OF FOOTING

From ACI Cl.11.3.1.1, Vc = 237.581 kN

Distance along X to design for shear, Dz = 1.150 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 = 178.186 kN

Critical load case for Vuz is # 3 16.936 kN
0.75 X Vc > Vuz hence, OK

Design for Flexure about Z Axis

(For Reinforcement Parallel to X Axis)

PREPARED BY : ENGR CAREN HAZEL ORTIZ

CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)
DESIGN OF FOOTING
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 # 3

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

Factor from ACI Cl.10.2.7.3 = 0.850

From ACI Cl. 10.3.2, = 0.04267

From ACI Cl. 10.3.3, = 0.03200

From ACI Cl. 7.12.2, = 0.00140

From Ref. 1, Eq. 3.8.4a, constant m = 14.095

Calculate reinforcement ratio for critical load case

Design for flexure about Z axis is

performed at the face of the column at a 0.575 m
distance, Dx =
Ultimate moment, 7.952 kNm

Nominal moment capacity, Mn = 8.835 kNm

Required = 0.00051

Since OK

Area of Steel Required, As = 440.216 mm2

Selected bar Size = #16

Minimum spacing allowed (Smin) = = 200.000 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 = 508.433 mm

Safe for Cracking Aspect.

PREPARED BY : ENGR CAREN HAZEL ORTIZ

CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)
DESIGN OF FOOTING
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 = 0.475 m

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

Number of bars required, Nbar = 5

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) = 1005.321 mm2
deff = D - Ccover - 0.5 X (dia. of one bar) = 0.242 m

Reinforcement ratio, = 0.00297

From ACI Cl.7.6.1, minimum req'd clear max (Diameter of one bar, 1.0, Min. 300.000 mm
distance between bars, Cd = User Spacing) =

Check to see if width is sufficient to accomodate bars

Design for Flexure about X axis

(For Reinforcement Parallel to Z Axis)

PREPARED BY : ENGR CAREN HAZEL ORTIZ

CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)
DESIGN OF FOOTING
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 # 3

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

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PREPARED BY : ENGR CAREN HAZEL ORTIZ

CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)
DESIGN OF FOOTING

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Calculate reinforcement ratio for critical load case

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PREPARED BY : ENGR CAREN HAZEL ORTIZ

CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)
DESIGN OF FOOTING
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PREPARED BY : ENGR CAREN HAZEL ORTIZ

CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)
DESIGN OF FOOTING
Selected Bar Size = #16
Minimum spacing allowed (Smin) = 200.000 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 = 508.433 mm

Safe 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 = 0.500 m

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

Number of bars required, Nbar = 5

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) = 1005.321 mm2
deff = D - Ccover - 0.5 X (dia. of one bar) = 0.218 m

Reinforcement ratio, = 0.00329

From ACI Cl.7.6.1, minimum req'd clear max (Diameter of one bar, 1.0, Min. 300.000 mm
distance between bars, Cd = User Spacing) =

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.

PREPARED BY : ENGR CAREN HAZEL ORTIZ

CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)
DESIGN OF FOOTING

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 from ACI Cl.10.2.7.3 = 0.850

From ACI Cl. 10.3.2, = 0.04267

From ACI Cl. 10.3.3, = 0.03200

From ACI Cl. 7.12.2, = 0.00140

From Ref. 1, Eq. 3.8.4a, constant m = 14.095

Calculate reinforcement ratio for critical load case

Design for flexure about A axis is

performed at the face of the column at 0.550 m
a distance, Dx =
Ultimate moment, 1.461 kNm

Nominal moment capacity, Mn = 1.623 kNm

Required = 0.00011

PREPARED BY : ENGR CAREN HAZEL ORTIZ

CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)
DESIGN OF FOOTING
Since OK

Area of Steel Required, As = 408.856 mm2

Selected bar Size = #16

Minimum spacing allowed (Smin) = 200.000 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 = 508.433 mm

Safe for Cracking Aspect.

Based on spacing reinforcement increment; provided reinforcement is

#16 @ 300 mm o.c.

Design For Top Reinforcement Parallel to X Axis

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 from ACI Cl.10.2.7.3 = 0.850

PREPARED BY : ENGR CAREN HAZEL ORTIZ
CONSTRUCTION OF TWO STOREY RESIDENTIAL BUILDING (SOFT STOREY AT GROUND FLOOR)
DESIGN OF FOOTING
From ACI Cl. 10.3.2, = 0.04267

From ACI Cl. 10.3.3, = 0.03200

From ACI Cl.7.12.2, = 0.00140

From Ref. 1, Eq. 3.8.4a, constant m = 14.095

Calculate reinforcement ratio for critical load case

Design for flexure about A axis is

performed at the face of the column at 0.575 m
a distance, Dx =
Ultimate moment, 1.597 kNm

Nominal moment capacity, Mn = 1.774 kNm

Required = 0.00010

Since OK

Area of Steel Required, As = 440.216 mm2

Selected bar Size = #16

Minimum spacing allowed (Smin) = 200.000 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 = 508.433 mm

Safe for Cracking Aspect.

Based on spacing reinforcement increment; provided reinforcement is

#16 @ 300 mm o.c.

PREPARED BY : ENGR CAREN HAZEL ORTIZ