SL.
No DESCRIPTION REFERENCE
1 FOOTING DESIGN- F1
1.1 INPUT
Grade of concrete fck 25 N/mm2
Grade of steel fy 500 N/mm2
Density of soil s 1.8 T/m3
Density of concrete c 2.5 T/m3
Depth- bottom of base plate to bottom of raf D 2.5 m
Ht of pedestal above FGL h 0.3 m
SBC of soil 15 T/m2
Clear Cover to reinforcement(Earth face) 0.075 m
Clear Cover to reinforcement 0.05 m
L B d
Size of Raf 6 2.5 0.5 m
Size of pedestal 6 0.5 2.0 m
1.2 DEAD WEIGHT OF SOIL AND CONCRETE
Area of Footing
= (LxB) 15 m2
Weight of Concrete
= Vol of(Raf + Pedestal) x density of Concrete 33.75 T
Weight of Soil
= (Area of footing - Area of pedestal) x (depth of
foundation - depth of raf) x density of Concrete 36.72 T
1.3 SECTION MODULUS
Zxx = L x B2/6 6.25 m3
Zzz = B x L2/6 15.00 m3
1.4 LOAD INPUT FROM STAAD
All loads are in "Tons"
Critical Load P
Sl no. Combinations
Fx Fy Fz Mx My Mz M'x M'z M'x = (Fz X D) + Mx
1 13 21.00 8.00 0.00 0.00 0.00 0.00 0 52.5 M'z = (Fx X D) + Mz
1.5 BASE PRESSURE CHECK Base Pressure
P1 P2 P3 P4 P=(Fy/A) (M'x/Zxx)
(M'z/Zzz)
8.7 1.7 8.7 1.7
Pmax 8.73 T/m2
Pmin 1.73 T/m2
1.6 CONVERTING NEGETIVE PRESSURE TO POSITIVE PRESSURE
To calculate Qmax 1.73 Interpolation method
To find out X X
i.e (+VE Pr) + (-VE Pr)/span= +VE Pr/x
X = 5.007
P = 1/2 x (+ve pr) x span
P = 26.19 T 8.73
P = 1/2 x Qmax x X 6.00
Qmax = 10.5 T/m2
SBC shall be increased by 33% for wind load As per IS 875 Part-3
Allowable SBC = 15 T/m2
IF Qmax < Allowable SBC SAFE
Hence Base pressure W 8.731 T/m2
1.7 DESIGN OF RAFT
Bottom Reinforcement - Xdirection
Cantilever bending moment
Cantilever distance lx 0 m
At support Mx= W X lx2/2 Mx 0.0 T-m
Partial factor of safety 1.5
Ultimate moment in x dir Mux 0.0 T-m
Mux / bd2 0.00 N/mm2
Required Min
ANNEX G-1.1 IS456:2000
Percentage of steel Ptx = 0.000 0.12 %
Hence Ptx 0.12 % Cl.26.5.2.1 IS456:2000
Required Area of steel Astx 510 mm2 Astx = (Ptxbxd)/100
Providing 12 dia 200 Spacing
Provided Area of steel Astx 565 mm2 Astx= xdia2/4xspacing
Provided percentage of steel Ptx 0.13 %
Bottom Reinforcement - Y direction
Cantilever bending moment
Cantilever distance ly 1 m
At support My= W X ly2/2 My 4.37 T-m
Partial factor of safety 1.5
Ultimate moment in y dir Muy 6.5 T-m
Muy / bd2 0.36 N/mm2
Required Min
ANNEX G-1.1 IS456:2000
Percentage of steel Pty 0.08 0.12 %
Hence Pty 0.12 % Cl.26.5.2.1 IS456:2000
Required Area of steel Asty 510 mm2 Asty = (Ptxbxd)/100
Providing 12 dia 200 Spacing
Provided Area of steel Asty 565 mm2 Asty= xdia2/4xspacing
Provided percentage of steel Pty 0.13 %
Top Reinforcement - X&Ydirection Min
Providing 0.06% of Raf area(Both X and Y dir) Pt 0.06 %
Required Area of steel Ast 270 mm2
Providing 10 dia 200 Spacing
Provided Area of steel Ast 393 mm2
Provided percentage of steel Pt 0.09 %
1.8 CHECK FOR SINGLE SHEAR
SHEAR CHECK IN X DIR
Shear distance in cantilever portion dx -0.43 m
Shear force in X- dir Vx -22.3 T Vx = W X L X dx
Shear stress along X-dir vx=Vx/Bd -0.13 N/mm2 Cl 40.1 (IS 456 :2000)
Maximum Shear Stress of Concrete c (max) 3.10 N/mm2 Table-20 (IS 456 :2000)
Pt provided Ptprovd 0.13 %
Beeta = 0.8Xfck/6.89XPt 21.8 1.00 Cl 4.1 (SP-16:1980)
Design shear strength of concrete c 0.28 N/mm2 Cl 4.1 (SP-16:1980)
c = (0.85 X sqrt(0.8fck)X sqrt(1+(5-1)))/6
Hence v < c SAFE
SHEAR CHECK IN Y DIR
Shear distance in cantilever portion dy 0.575 m
Shear force in Y- dir (Vy) Vy 12.6 T Vy = W X B X dy
Shear stress along Y-dir(Tvy) vy=Vy/Bd 0.18 N/mm2 Cl 40.1 (IS 456 :2000)
Maximum Shear Stress of Concrete c (max) 3.10 N/mm2 Table-20 (IS 456 :2000)
Pt provided Ptprovd 0.09 %
Beeta = 0.8Xfck/6.89XPt 31.4 1.00 Cl 4.1 (SP-16:1980)
Design shear strength of concrete c 0.23 N/mm2 Cl 4.1 (SP-16:1980)
c = (0.85 X sqrt(0.8fck)X sqrt(1+(5-1)))/6
Hence v < c SAFE
1.9 CHECK FOR PUNCHING SHEAR
Perimeter of critical section bo 14.7 m
Area of critical section A 5.943 m2
Shear Vu 119 T/m2
= W X (LXB) of Raf-area
v = Vu/bod 0.19 N/mm2 IS456:2000 cl.31.6.2.1
c = 0.25 xsqrt fck 1.25 N/mm2 IS456:2000 cl.31.6.3.1
IF c>v c > v SAFE
