rcfootingdesignweb.xls

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Disclaimer: The person using this spread sheet is responsible for its use.

Computation Sheet No

Client Job No

Project/Job By

Subject Date:

Reinforced Concrete Rectangular Pad Footing Design

Calculates the reinforcement required for a reinforced rectangular or square concrete footing with a

rectangular or square columns at the centre of the footing, for flexure and checks 1 way and 2 way shear

at the concrete column, using ductility class N reinforcement

For rectangular or square pads only, with no applied moment or horizontal forces

Does not design for shear reinforcement.

Not suitable for mesh reinforcement which is usually insufficient as minimum reo anyway

AS3600 - 2009 (Incorporating Amendment 1, 2010 )

Warner, Rangan, Hall & Faulkes, Concrete Structures , Longman, Melbourne, 1999

Foster, Kilpatrick and Warner, Reinforced Concrete Basics 2E, Pearson, 2010

Symbols and notation as generally used in AS3600.

Yellow cells require data input by the designer

Geometry for the pad footing , etc

Concrete strength etc

Geometry of column etc

Applied actions and allowable bearing capacity

Area of tension reinforcement in both directions based on initial calculations and minimum reinforcement

Iterate if does not meet minimum design values

Where pink fill is used it alerts designer to options or information

Boxed cells with green background calculated automatically using formulae.

Footing weight, working load, total ultimate load, load factor and actual bearing pressure under the footingUltimate moment in each direction and initial area of reinforcing along with minimum reinforcement

Number, size and spacing of reinforcing bars

Maximum bending capacity in both directions Muo

Moment capacity fMu in both directions for the chosen reinforcement

Checks for minimum reinforcement

Checks one way and two way shear

Provides summary of the results

For comments, corrections, suggestions or other feedback regarding this spread sheet,

please contact the CCAA

Version 1.2

Revisions Minor revisions

Date 30/09/2012

Title :

General Description :

Limitations :

Codes / Theoretical Basis

:

Nomenclature :

Input :

Output :

Feedback :


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Disclaimer: The person using this spread sheet is responsible for its use.

Computation Sheet NoClient Job No

Project/Job By

Subject Date:

Reinforced Rectangular Concentric Concrete Footing Design - Bending and Shear

Design for footings that are under reinforced, with N Class bar reinforcement

Preliminary overall depth of footing assuming starter bars need full development

Bar size N12 N16 N20 N24 N28 N32 N36

Overall depth 400 500 600 700 800 900 1000

Data Input Capacity Reduction FactorsGeometry of Pad Footing & Material Properties

Length L1 3,350 mm f 0.8 Bending

Width L2 3,350 mm f'c 32 MPa

Pad area 11.22 m2 fsy 500 MPa

Overall Nominal Depth, D 1,000 mm kuo 0.36

Bottom cover to bottom bars (allowing for Clause 4.10.3.5) 75 mm f 0.7 Shear

Effective depth for flexure d and one way shear d o 900 mm

(Usually = Depth D - cover to bottom bars - bar size bottom - distanceto the centroid of upper layer of the tensile reo, rounded to nearest 5mm )

dom mean value of do for punching shear 910 mm

(can be taken as do conservative) Concrete column

Geometry of Column Plan

Column Length C1 parallel to L1 450 mm

Column Width C2 parallel to L2 450 mm

Column Area 0.203 m2

Applied actions and Bearing Capacity

Allowable Bearing Capacity (Working Loads) qa 300 kPa

Dead or Permanent Load G (Excl ftg weight but including any surchar 2,169 kN

Live or Imposed Load Q (Including any surcharge) 898 kN

Density of concrete in footing (Insert 0 if footing not to be included ) 25 kN/m3

Footing Weight (Calculated by the program) 281 kN

Total Working Load (Calculated by the program) 3,348 kN

Total Ultimate Load N* (Calculated by the program) 4,286 kN Section

Load Factor(Calculated by the program) 1.280 kN Percentage

Actual Bearing Capacity at Underside of Footing qactual 298.3 kPa qactual < qa OK 101%

Net Design Bearing at Underside of Footing for Design of Concrete 273.3 kPa

Ultimate Bearing Capacity for Concrete Design qu 349.9 kPa

Design Results

Bending

Ultimate Moment in the L1 direction (M*= qu x L2 x ((L1-C1)/2)

2

/2) 1,232.4kN.m for total width of footing at the face of column

Ultimate Moment in the L2 direction (M*= qu x L1 x ((L2-C2)/2)2/2 ) 1,232.4 kN.m for total width of footing at the face of column

Initial Ast in L1 direction required for M* < fMu Ast.required 4,027 mm2

This figure is an approximation of the required reo. Check minimum reo

Initial Ast in L2 direction required for M* < fMu Ast.required 4,027 mm2

This figure is an approximation of the required reo. Check minimum reo

Proposed reinforcement arrangement

Suggested bar numbers & sizes for limit state requirement M* < fM or Minimum ReoBar size 12 16 20 24 28 32 36 40

Area of bar mm2 113 201 314 452 616 804 1020 1260

L1 Direction Flexure

Theoretical No. of bars 35.6 20.0 12.8 8.9 6.5 5.0 3.9 3.2

Actual bars required 36 21 13 9 7 6 4 4 Minimum no of bars 36 21 13 9 7 6 4 4

Area of bars mm2 Total 4,028 4,221 4,082 4,068 4,312 4,824 4,080 5,040Nominal Spacing of bars mm 94 163 271 406 542 650 1083 1083

L1 Direction Min Reo 12 16 20 24 28 32 36 40


Actual bars required 43 24 16 11 8 6 5 4

Minimum no of bars 43 24 16 11 8 6 5 4

Area of bars mm2 Total 4,859 4,824 5,024 4,972 4,928 4,824 5,100 5,040

Nominal Spacing of bars mm 77 141 217 325 464 650 813 1083

L2 Direction Flexure 12 16 20 24 28 32 36 40




Area of bars mm2 Total 4,068 4,221 4,082 4,068 4,312 4,824 4,080 5,040Nominal Spacing of bars mm 93 163 271 406 542 650 1083 1083

L2 Direction Min Reo 12 16 20 24 28 32 36 40




Area of bars mm2 Total 4,859 4,824 5,024 4,972 4,928 4,824 5,100 5,040

Nominal Spacing of bars mm 77 141 217 325 464 650 813 1083

L1

L2

C1

C2

d &

D

Coverq

N*

dom

C/

C/L

Critical section for bending

Critical section for shear


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Ast.provided in L1 direction 5,024 mm2 Choose no of bars, spacing and area using the above table for L1 and input area into the yellow box left.

Ast.provided in L2 direction 5,024 mm2 Choose no of bars, spacing and area using the above table for L2 and input area into the yellow box left.

d 900 mm

Minimum reo in L1 direction 4,801 mm2

Minimum reo in L2 direction 4,801 mm2

Design Calculations

Maximum Moment Muo at kuo=0.36 PercentageCheck fMuo L1 direction = 2 f'c kuo (1-0.5 kuo) b d

2 fMuo 14,947.3 kNm M* < fMuo OK 1213%Check fMuo L2 direction = 2 f'c kuo (1-0.5 kuo) b d

2 fMuo 14,947.3 kNm M* < fMuo OK 1213%Check Moment Capacity Using Stress Blocks

L1 Direction

Check fMu = Ast fsy d(1- 0.5/2 (Ast fsy / (b d f'c)) = M* with As =Ast.provided fMu 1,780.9 kNm M* < fMu OK 145%Check fMu = f'c ku (1-0.5 ku) b d

2for concrete stress block fMu 1,780.9 kNm M* < fMu OK 145%

Check ku calculated using Ast.required ku 0.04 ku < kuo OK 971%

L2 Direction

Check fMu = Ast fsy d(1- 0.5/2 (Ast fsy / (b d f'c)) = M* with As =Ast.provided fMu 1,780.9 kNm M* < fMu OK 145%Check fMu = f'c ku (1-0.5 ku) b d

2

for concrete stress block fMu 1,780.9 kNm M* < fMu OK 145%Check ku calculated using Ast.required ku 0.04 ku < kuo OK 971%

Calculations (Table 2.2.2) with kuo=0.36

= (1.19 13kuo/12) = 0.80 limits 0.6 0.8

Calculations (Cl 8.1.3) g = 1.05 - 0.007 f'c = 0.826 limits 0.67 g 0.85

2 = 1.0 0.003 fc = 0.85 limits 0.67 2 0.85

Initial Strength Requirements

Requirements based on ultimate strength moment M* and d

Initial calculation of reo L1 direction Ast = M* / ( *fsy * 0.85 *d) = 4,027 mm2

Initial calculation of reo L2 direction Ast = M* / ( *fsy * 0.85 *d) = 4,027 mm2

Minimum Strength Requirements (Cl 16.3.1)

f'ctf = 0.6 ( f'c )0.5 = 3.39 MPa Percentage

In the L1 direction deemed to comply A st.min L1 = 0.19 ( D/d )2

f'ctf / fsy bw d = 4,801 mm2 Astmin< Ast prov OK 105%

In the L2 direction deemed to comply A st.min L2 = 0.19 ( D/d )2

f'ctf / fsy bw d = 4,801 mm2 Astmin< Ast prov OK 105%

One Way Shear Requirements (Cl 8.2)

Calculate shear strength of a footing without shear reinforcement Cl 8.2.7.1 Vuc= 1 2 3 bv do fcv { Ast }1/3

bv do

Assumes no shear reinforcement 1 = 1.1(1.6 do/1000) 0.8 1 = 0.8 1 0.8

2 = 1

3 = 1

fcv = fc1/3

4MPa fcv = 3.17 MPaShear strength of a footing without shear reinforcement in the L 1 direction Cl 8.2.7.1 Vuc L1 = 907.9 kN

vuc L1 = 635.5 kN

Shear strength of a footing without shear reinforcement in the L 2 direction Cl 8.2.7.1 Vuc L2 = 907.9 kN

vuc L2 = 635.5 kN

Requirement for shear reinforcement Cl 8.2.5 V* vu Percentage

V* in L1 direction V* = qu*L2*((L1-C1)/2-do) = 644.8 kN Vuc L1 = 635.5 kN Vuc> V* FAIL 99%

V* in L2 direction V* = qu*L1*((L2-C2)/2-do)) = 644.8 kN Vuc L2 = 635.5 kN Vu> V* FAIL 99%

Two Way Shear Requirements (Cl 9.2.3 (a))

Requirements based on ultimate strength moment M*=0

V* Punching V* = qu*(L1* L2* - (C1+dom)*(C2 +dom)) = 3,280 kN u Shear Perimeter = 2*(C1+C2+2do = 5,440 mm

a1 Shear Perimeter a1 = 2*(Cl+dom) = 2,720 mm a2 Shear Perimeter = 2*(C2+dom) = 2,720 mm

a Shear Perimeter a > of a1 or a2 = 2,720 mm

h Ratio dimension h > of Bh1 or Bh2 = 1.00

fcv 2 way shear 0.34f'c = 1.92 MPa

or fcv 2 way shear 0.17(1+2/h)f' = 2.88 MPa

fcv 2 way shear = 1.92 MPa

Vuo u dom fcv = 9,521 kN Percentage

Vuo = = 6,665 kN Vuo> V* OK 203%

Results based on size, concrete strength and area of tensile reinforcement chosenL1 Direction Design Moment in the L1 directio M* 1,232.4 kNm

Depth to neutral axis dn 33.4 mm Actual bending capacity f Mu 1,780.9 kNmNeutral axis parameter ku 0.037 Reinforcement ratio p 0.002

Depth of compression block g ku do 27.6 mm Area of steel chosen Ast 5,024 mm2L2 Direction Design Moment in the L2 directio M* 1,232.4 kNm

Depth to neutral axis dn 33.4 mm Actual bending capacity f Mu 1,780.9 kNmNeutral axis parameter ku 0.037 Reinforcement ratio p 0.002

Depth of compression block g ku do 27.6 mm Area of steel chosen Ast 5,024 mm2

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