Design of Footing for Corner Column

DESIGN

OF FOOTING FOR CORNER COLUMN

Data :Load from side or edge column = 220 KN Column size = 230 x 230 mm SBC of soil =120 KN /m2 Concrete Mix =M20 Steel Grade = Fe 415 Clear cover of bottom slab =50 mm Design :-

1. SIZE OF FOOTING : Load on column

P

=220 KN

Self weight of footing 10%

=

22 KN

SBC of soil

------242 KN --------=120 KN/m2

Area of footing required

=

Total load on soil

P1

242 / 120 =2.02 m2

Provide 1.50 x 1.50 m square footing. Area provided

=2.25 m2 > 1.83 m2

2. NET UPWARD SOIL PRESSURE : Load from column

=220 KN

Area of footing

=2.25 m2

Net upward soil pressure

=220 / 2.25 =97.80 KN/m2 < 120 KN/m2(SBC)

O.K.

3. FOOTING SLAB : Provide overall depth of slab Bending moment

=

=250 mm 97.8 x 0.8852/2 =38.30 KN.m

Factored moment

Mu

=1.5 x 38.30 =57.45 KN.m

K=Mu /b d2

= 57.45 x 106 / 1000 x 2852 = 0.71

100 Pt from Table 2 of Design Aid Ast =

0.206/100x1000x 285 = 587 mm2

Provide 12 Φ RTS @ 150 mm C / c 

=0.206 (Ast=754 mm2

587 mm2 ).

Distributors:

Minimum Ast =0.20/100x1000x 300 =600 mm2 Provide 12 Φ RTS @ 150 mm C / c 

(Ast=754 mm2

600 mm2 )

4. BEAM DESIGN : Load /m run on beam Load from footing slab (1/2x2.12x0.885)x97.8 2.12

} x2

}

=86.55 KN/m

Self weight of beam assuming size as 300 x 600 mm 0.35 x (0.60 – 0.35) x 25 Total udl Span

= 2.63 KN/m --------= 89.18 KN/m ----------

w

l

=2.12 m

Maximum bending moment

=wl2/2 = 89.18x 2.122 /2 = 200.41 KN.m

Factored B.M.

Mu

=1.50 x 200.41 =300.62 KN.m

K = 300.62 x 106

= 3.18

350 x 5202 Increase depth of beam to 750 mm. K = 300.62 x 106

= 1.91

350 x 6702 100 Pt from Table 2 of Design Aid = 0.605 Ast

= 0.605 100

x 350 x670

= 1419 mm2 Provide 6 Nos. 20 Φ RTS 2 bottom. Provide 3 Nos. 16 Φ RTS @ top. (Ast = 1884 mm2 > 1419 mm2 ).

Check for shear: Maximum Shear Force = 89.20 x 2.12 = 189.10 KN. Factored SF Vu = 1.5 x 189.10 = 283.66 KN. Shear stress = 283.66 x 103 350 x 670 =0.12 N/ mm2 < 2.80 N/mm2 Provide 8 Φ RTS

O.K.

4 legged stirrups @ 200 mm c/c.