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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
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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.
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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.
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Following points may be consider in design of beam footing…………
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.
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Following points may be consider in design of beam footing…………
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.
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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
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Length and loading for footing in problem
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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
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Solution……
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7/27/2019 Foundation Beam Footing
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