Foundation Beam Footing

7/27/2019 Foundation Beam Footing

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M U H A M M A D Z A H I D

1 2 - F T - M S C - S T R - 0 7

FOUNDATION BEAM FOOTING

Dr. Liaqat Ali Qureshi



FOUNDATION BEAM FOOTING

To resist the contact pressure, in this type of footing, a slab strip is provided at the bottom for

more than one columns, which in turn is supported by a beam running along the column centre line.



Following points may be consider in design of beam footing…………

1. The point of application of the resultant loadmust coincide with the centroid of the contactarea.

2. The soil pressure may approximately be assumedto be uniform.

3. Only one way shears in the beam and in theoverhanging slab are to be satisfied and there areno chances of two way shear failure.




4. The longitudinal section of beam is then considered with uniformly distributed load equal to qn,u X Bacting over the full length.

5. If the BMD do not change in sagging-hogging sensealong the length of the beam at mid-span & columnsection, this type of footing must be seriously analyzed.

6. The minimum width of foundation beam is to betaken equal to column width + 75mm on both side.




7. The depth of beam usually lies b/w ℓ/10 & ℓ/8, ascompared to with ℓ/12 for superstructure due toheavy loads.

7. The beam may either be designed as rectangularsections as a conservative approach or the mid-spanmay be considered as T-beams.



D E S I G N A C O M B I N E D F O O T I N G U S I N G F O U N D A T I O N B E A M F O R T H E A R R A N G E M E N T O F C O L U M N S S H O W N I N F I G U R E . F C ’ = 2 0

M P A , F Y = 3 0 0 M P A A N D N E T A L L O W A B L E B E A R I N GC A P A C I T Y I S E Q U A L T O 8 0 K P A . T H E S I Z E O F A L L C O L U M N S I S 3 0 0

X 3 0 0 M M .

Problem



Length and loading for footing in problem



Solution……

L = 19.3 m

qn,u = 80 kPa

P1, P5 = 300 kN

P2, P3, P4 = 650 kN Pu1, Pu5 = 400 kN

Pu2, Pu3, Pu4 = 875 kN

∑P = 2250 kN

∑Pu = 3425 kN f c’ = 20 Mpa

fy = 300MPa



Solution……

2,

,

2

,

,

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875.3180

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force,shear design

10390.81 beamsreinforcedsinglyfor d

mm52575-h d

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2s

2

min

MPa

f y


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yvv

max

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mm175d

mm)250(saymm21875143hminmm,143d

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dx1000x200.17x0.75x8.0

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b-B length,Cantilever

Design

ucv

Slab



(om0.625m0.4231000

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cc mm250@13#Use

mmm 500 250x1000x0.0026,A

mmm 455 175x1000x0.0026A

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m-kN20.392

0.625x104.39

2

m ins

2

s

2

6

2

2

d

u

u

bd M

M





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Foundation Beam Footing