Isolated Footing Design by Sefian

ISOLATED FOOTING DESIGN

FORCES DETAILS :

Axial Load = P1 = Moment along Major axis = Mx = Moment along Minor axis = Mz =

65.2 T 0.32 T-m -6.0341 T-m G.L

COLUMN DETAILS :

Length = ( Larger Dimension of Column ) Width = ( Smaller Dimension of Column )

0.45 m 0.23 m

FOOTING DETAILS :

Length = L = Width = B = Depth = D =

1.5 m 1.5 m 0.35 m

Cover to Main R/f = Diameter of R/f in Footing =

0.05 m 12 mm

1.2

0.4 SOIL DETAILS :

Density of Soil = g = Depth of foundation below G.L = H =

3 1.7 T/m 1.5 m

1.50 X

MATERIAL CONSTANT :

M - 25 N/mm2 Fe - 415 N/mm2 1.5

Concrete Grade = R/f Grade = Load Factor = gf =

1.50 Z

Z

DESIGN FORCES :

Axial load = P = Self Weight of Footing =

65.20 T 1.97 T

X

1.50

Total Vertical Load =

67.17 T

Moment along Major axis Moment along Minor axis

0.3182 T-m -6.0341 T-m

PRESSURE CALCULATION :

SBC = 20 T/m2 1.25 x FOR EARTHQUAKE CONDITION ALLOWABLE S.B.C =

P=

P A

+ -

Mx Zx

+ -

\ Pmax =

29.85 +

0.57 +

-10.727 =

19.69

T/m2

\ Pmin =

29.85 -

0.57 -

-10.727 =

40.01

T/m2

20 =

25 T/m2

Mz Zz

< S.B.C

SAFE

TENSION NOT CREATED

R/F CALCULATION FROM BENDING CONSIDERATION :

1500

635

1500

230 450 525

40.0 T/M2

19.7 T/M2

MOMENT AT CRITICAL SECTION ALONG WIDTH :

M = Pmax x 0.635 x 0.635 / 2 M= 3.97 T-m Mu = 59.55 KN-m 2 Ast = 567.90 mm ( To be distributed in 1.5 m Length ) 2 Min Req = 420 mm ( Ast = 0.12 x b x D ) Required Spacing of Bar = 12 # @ 195 C/C ALONG WIDTH PROVIDE 12 # @ 150 C/C ALONG WIDTH \ Ast =

753.98

mm2

MOMENT AT CRITICAL SECTION ALONG LENGTH :

M = Pmax x 0.525 x 0.525 / 2 M= 2.71 T-m Mu = 40.71 KN-m 2 Ast = 384.16 mm ( To be distributed in 1.5 m Length ) 2 Min Req = 420 mm ( Ast = 0.12 x b x D )

PROVIDE 12 # @ 265 C/C ALONG LENGTH \ Ast =

426.78

mm2

CHECK FOR ONE WAY SHEAR ALONG LENGTH : Critical Section is at diatance of ' d ' from face of column

0.635 1.50

0.525

0.225

1.50 \ Shear force at critical section = V = \ Actual Shear stress tv =

= = Pt =

\

tc

100 x As b x d

=

0.28 <

=

N / mm2

tv HENCE SAFE

19.69 x 4.43

0.225 T

Vu bxd 1.5 x 1000 x 0.222 100 x 1000 x

4.43 300

x 10000

N / mm2 426.78 300

=

0.14

Pt 0.15 0.2

tc 0.28 0.33

CHECK FOR ONE WAY SHEAR ALONG WIDTH : Critical Section is at diatance of ' d ' from face of column

0.635 1.50

0.525

0.335 1.50 \ Shear force at critical section = V = \ Actual Shear stress tv = = = Pt = \

tc

100 x As b x d

=

0.36 <

= N / mm2

tv HENCE SAFE

19.69 x 6.60

0.335 T

Vu bxd 1.5 x 1000 x 0.330 100 x 1000 x

6.60 300

x 10000

N / mm2 753.98 300

=

0.25

CHECK FOR TWO WAY SHEAR : Critical Section is at distance of 'd/2' from face of column 1.50

0.75 1.50

0.53

d/2 d/2

\ Shear force at Critical Section = = = Critical Perimeter = =

2 x

19.69 x

Area of Shadeded Portion

19.69 x

1.8525

36.48 T 0.75

+

2 x

2.56 m

\ Actual Shear stress tv =

Vu bxd

=

1.5 x 36.48 2560.00 x 300

=

0.712

( CLAUSE 31.3.3 IS 456 : 2000 )

where, ks = ( 0.5+b ) Short Side of Column = 0.23 Long Side of Column = 0.45

ks = 1.01

but not greater than 1.0

x 10000

N / mm2

Allowable Shear stress = ks.tc

b=

0.53

=

0.51

Where,

tc = 0.25  fck tc = 0.25  M - 25

=

Allowable Shear stress = ks.tc =

1.25

1.25

N/mm2

N/mm2

SAFE

CHECK FOR OVERTURNING : ALONG LENGTH : Rm

Restoring Moment = Rm = Applied Moment =

F.O.S. = P

=

65.20

x 0.75

48.90

T.m

0.3

T.m

Restoring Moment Applied Moment 48.90 0.3182

= >

153.68 2.2 SAFE

0.75