RAFT FOUNDATION DESIGN

Project :

Raft Foundation Design

Ref: Date : Design By : Checked By :

Raft design assume raft thk fy fcu Assume reinforcement dia. Cover Edge beam length cantilever Edge beam length Maximum line load Load factor Ultimate line load Ultimate moment (dn) Ultimate moment (up) M Edge beam size d k= M/bd^2*fcu zd z As = M/0.87fyz There fore use As provided As min

= = = = = = = = = = = = = = = = = = = = = =

300 410 30 20 40 2 6.096 60 1.5 90 334.450944 180 475.2 600 550 0.087272727 0.891190878 490.1549829 2717.940222 6 2946 468

mm

= = = = = = = = =

180 0.545454545 0.892727273 1.427783264 250 168.2085786 R 0.75d 412.5

kN N/mm2

= = = =

3700 kN 6.096 x 107.435904 m2 34.43913871 kN/m

mm mm m m kN/m kN/m kNm kNm KnM x mm

600

mm mm2 Y mm2 mm2

mm

25

Shear V v 100As/bd vc minimum links required (s) Asv there fore use links maximum spacing of links

N/mm2 mm mm2 8

ok

at

125

mm

Raft slab design Total load on raft Load spread on

average bearing preasure below slab Assume slab span simply supported and max. span = 4 Ultimate design load = 51.65870806 kN/m2 less weight of slab = 10.08 kN/m2 = 41.57870806 kN/m2

17.624

m

m

(uplift pressure)

Project :

Raft Foundation Design

Ref: Date : Design By : Checked By :

Try 2 way spanning slab simply supported at edges. Provide spine beam across centre of raft lx = 6.35 ly = 6.096 msx = asx n lx2 msy = asy n lx2 From table 3.14 lx/ly = 1.041666667 asx = 0.074 asy = 0.061 msx = 124.0652517 msy = 102.2700048 max M = 120 d k= M/bd^2*fcu zd z As = M/0.87fyz There fore use As provided As min

= = = = = = = =

250 0.064 0.922952585 230.7381462 1458.004075 Y 1609 299.95959

m m

kNm kNm kNm mm

mm mm2 16 mm2 mm2

at

125