Data :Load from side or edge column = 200 KN Column size = 230 x 230 mm 2 SBC of soil =120 KN /m Concrete Mix =M20 Steel Grade = Fe 415 Clear cover of bottom slab =50 mm Design :1. SIZE OF FOOTING : Load on column
P
Self weight of footing 10%
=200 KN =
20 KN
SBC of soil
------220 KN --------2 =120 KN/m
Area of footing required
=
Total load on soil
P1
2
220 / 120 =1.83 m
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
=200 KN
Area of footing
=2.25 m2
Net upward soil pressure p
=200 / 2.25 =88.90 KN/m2 < 120 KN/m2(SBC)
3. FOOTING SLAB : Provide overall depth of slab Bending moment
=250 mm = 88.9 x 0.6352/2
O.K.
=17.90 KN.m Factored moment
K=Mu /b d2
Mu
=1.5 x 17.90 =26.90 KN.m
= 26.90 x 106 / 1000 x 1822 = 0.81
100 Pt from Table 2 of Design Aid Ast =
0.236/100x1000x 182 =430 mm2
Provide 10 Φ RTS @ 150 mm C / c
=0.236 (Ast=524 mm2
430 mm2 ).
Distributors:
Minimum Ast =0.20/100x1000x 250 =500 mm2 Provide 10 Φ RTS @ 150 mm C / c
500 mm2 )
(Ast=524 mm2
4. BEAM DESIGN : Load /m run on beam Load from footing slab
}
= 56.50 KN/m
88.90 x 0.635 Self weight of beam assuming size as 300 x 600 mm 0.30 x (0.60 – 0.25) x 25 Total udl Span
300 x 5262 100 Pt from Table 2 of Design Aid = 0.553 Ast = 0.553 100
x 300 x 526
=872.63 mm2 Provide 3 Nos. 20 Φ RTS 2 bottom. Provide 3 Nos. 16 Φ RTS @ top. (Ast = 942 mm2 > 872.63 mm2 ). Check for shear: Maximum Shear Force = 59.10 x 1.50 = 88.65 KN. Factored SF Vu = 1.5 x 88.65 = 132.98 KN. Equivalent Shear Ve = Vu + 1.6 Tu /b = 132.98 + {1.6 x 26.88 x10 3/300 } = 132.98 + 143.36 =276.34 KN Shear stress = 276.34 x 103 300 x 526 =1.75 N/ mm2 < 2.80 N/mm2 Pt = 942 x100 300 x 526 =0.60
O.K.
ζc from Table 61 Design Aid =0.51 N/mm2 Asv = Tu Sv b1d1(0.87 Fy)
+
Vu Sv 2.5 d1 (0.87 Fy)
b1= 300-25-25-20-8 =222 mm d1= 600- 50-8-10-50-8-8=466 mm Asv= (0.87 x fy) Sv
=
26.88 x 106 222 x 466
+
132.98 x 103 2.5 x 466
= 260 + 114.24 = 374.24 mm Asv x( 0.87 fy) Sv
= (1.75 -0.51) x 300
=372 mm Using 8 Φ RTS stirrups spacing Sv = 2x 50x0.87x415 372 = 97 mm Using 4 legged stirrups spacing Sv = 2x 97=194 mm say 180 mm c/c X1 =shorter dimension of hoop stirrups =300-40-8=282mm. y1=longer dimension of hoop stirrups =600-32-16=552mm.
Spacing of stirrups provided should not exceed the least of (i) x1 =282 mm (ii) (x1 + y1 ) 4 (iii) 300 mm. Provide 8 Φ RTS
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