Analysis and Design of Strap Cantilever Footing According To Aci 318 PDF Free

Analysis and Design of Strap (Cantilever) Footing According to ACI [email protected]

Footing No 5

Job:

Project :

R

PA

X

Strap Beam

h

C

B1

a c.g

bA

Z

L

L1

q1 e

R1

Values Need to be Intered by the User Characteristic Results

Axial Load on Column A , PA Axial Load on Column B , PB Moment on Column A , MA Moment on Column B , MB

300 200

KN KN KN.m KN.m

Proposed External Footing Length L1 Proposed Footing Thickness h

2 0.4

m m

Concrete Compressive Str Reinforcement Yielding Str

Distance Between Columns (Z)

6.2

m

Net Allowable Soil Bearing

Service Service Service Service

C Column A Width bA Column A Length aB Column A Width bB

Design Summary Required Width of External Footing ( B1 )

1.95

m

Required Area of Internal Footing (AB)

1.73

m2

2

m

0.90

m

Maximum Soil Pressure under footings

98.84

KN/m2

Assumed Width of Strap Beam b strap=

250

mm

Minimum Required Effective Depth of Strap Beam

450

mm

Proposed Length of Internal Footing (L2) Required Width of the internal footing (B2)

10

Shear Forc

-1.00 0.00

1.00

2.00

3.00

Bending Mom -1.00 0.00

1.00

2.00

3.00

Maximum Shear Force in Strap Beam

398.0

KN

Maximum Bending Moment in Strap Beam

298.5

KN

800

mm

1034.4 T20 1.04 4*T12@

mm2 4 mm2/mm 435

Provided Strap Beam Depth Required Longitudinal Reinforcment Area Required Shear Reinforcment Area

Bending Mom -1.00 0.00

1.00

2.00

3.00

Proportion Footing Dimensions

X B The location of forces resultant that give uniform pressure under both footing relative to the center of column

According to the proposed length of footing "A" the eccentricity of footing reactions Taking moments about the center of column B,

R1 =

344.44

KN

Taking moments about the center of column A,

R2 =

155.56

KN

e (

L1 C )  2

According to the allowable pressure under the footing the minimum width of external footing

Minimum

According to the allowable pressure under the footing the minimum area of internal footing

Minimum

Sequar Foot OR

L2  Acual location of force resultant

A A ( Z  e )  (A A  A B ) * X  X 

3.695

Soil pressure under the external footing q1=

98.84

KN/m2

OK

Soil pressure under the external footing q2=

95.29

KN/m2

OK

m

Strap Beam Analysis and Design Considering Ultimate Load Magnification

q1ult   * q1 



1.5

Therefore the ultimate soil pressu

q 2ult   * q 2 

259.86 KN/m

R

PA

115.14

X

Strap Beam

h

C

a

B1

c.g

bA

Z

L

L1

qu1 x

Shear Force Diagram

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

6.00

Bending Moment Diagram

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

6.00

Design of Strap Beam Bending Moment Design



 2M u 0.85* fc `  1  1    2 fy 0.85*  * b * d * fc `   strap eff

 As   *bstrap * d eff 

0.0052

1034.44 mm2

>

 min

0.0033

4 T20

I recommond to provide of the

Shear Design

V c  0.17 *0.75* fc `*bstrap * d eff (V u  V c )   A sv  Shear Reinforcement S VS 



134.93

KN

Strength of Concrete Se

350.79 KN

1.04

mm2/mm==>

Shear Force need to be

4*T12@ 435

Required Shear Reinfo

Footing Design d e  h  75 

The effective Depth

325

mm

119.94

KN

438.53

KN

-19.19

KN

438.53

KN

1- Exterior Footing

V u1 

q1ult * L1  B 1  b A  *  d eff   B1  2 

V c  0.17 * 0.75* fc `* L1 * d eff



> Applied Shear Force =

2- Interior Footing

Vu2 

q 2ult * L 2  B 2  b B  *  d eff   B2  2 

V c  0.17 *0.75* fc `* L 2 * d eff Punching Shear



> Applied Shear Force =

Will not be considered due to the presence of strap beam

Bending Moment 1- Exterior Footing 2

M u1

q * L1  B 1  b A   1ult *   2* B 1  2 



 2M u 1 0.85* fc `  1  1     A s   * L1 * d eff  2 fy 0.85*  * L * d * fc ` 1 eff  

80.04

KN.m

Bottom Flexure Reinforcement

Shrinkage Reinforcement

2- Interior Footing 2

M u2

4

As  0.0018* L1 * d eff 

For shrinkage reinforcement in longitudinal direction

q * L2  B 2  bB   2ult *   2* B 2  2 

1170.00

8.00

KN.m

6



 2M u 2 0.85* fc `  1  1    A s   * L 2 * d eff  2 fy 0.85*  * L * d * fc ` 2 eff  

Bottom Flexure Reinforcement

1170.00 6

As  0.0018* L 2 * d eff 

For shrinkage reinforcement in longitudinal direction

Shrinkage Reinforcement

Developed by Walid Matar Sr. Structural Engineer [email protected]

6

ilever) Footing According to ACI 318 X Project

R

PB

X

rap Beam

aB c.g

B2

bB

L2

q2

R2 C Column A Width bA Column A Length aB Column A Width bB

0.2 400 200 400

m mm mm mm

Concrete Compressive Strength fc` Reinforcement Yielding Strength fy

28 420

N/mm2 N/mm2

Net Allowable Soil Bearing Capacity

100

KN/m2

Shear Force Diagram

-1.00 0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

7.00

8.00

Bending Moment Diagram -1.00 0.00

1.00

2.00

3.00

4.00

5.00

6.00

Bending Moment Diagram -1.00 0.00

1.00

2.00

3.00

4.00

5.00

6.00

PA * Z  PA  PB

X B h footing relative to the center of column

7.00

8.00

3.72

m

B1 

1.95

m

AB 

1.73

m2

1.40

m

0.80

m

Sequar Footing with B = 2.00

Variation =

B2  0.0253 m

0.90

Therefore the ultimate soil pressure under footings KN/m

R

PB

X

trap Beam

aB c.g

B2

bB

L2

q u2

e Diagram

4.00

5.00

6.00

7.00

8.00

6.00

7.00

8.00

ment Diagram

4.00

5.00

OK

I recommond to provide similar steel at top and bottom of the strap beam

Strength of Concrete Section

Shear Force need to be Resisted by Steel

> Applied Shear Force ==> OK

> Applied Shear Force ==> OK

mm2 T20

1170 T16

Along L1 mm2 Along B1

tar Sr. Structural Engineer

[email protected]

mm2 T16

1170 T16

Along L2 mm2 Along B2

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