1. Isolated footing with axial load and moment
Design Input
Grade of concrete - 35
Grade of steel - 460
Allowable soil pressure – 200 KN/m2
Column load – 1260 KN(D.L+L.L)
Moment – 100 kN.m
Condition about overburden of soil - No
L&T-GES

2. Design procedure Checking the footing area Arrive footing size
By ACI 318
Design procedure
Checking the footing area
Arrive footing size
Total load=wt of footing+column load
Average soil pressure q= total load / footing area
Allowable soil pressure > Average soil pressure
Then footing are is ok
L&T-GES

3. Finding factored loads
Factored column load=1.4xdead load+1.7xlive load
Average factored soil pressure qnet=Factored column load/footing area
Average dv=total thick – cover - bar dia
Eccentricity e = Mu/Pu
Solving two equations to get q1 and q2
Service load equation
Vertical equilibrium
L&T-GES

4. Check for One way shear Check for Two way shear
Take the critical section as ‘d’ distance from the
face of the column (as per ACI 318 )
1.find pressure at critical section
2.find Vu
3.find Vu
If Vu>Vu
Check for Two way shear
Take the critical section as ‘d/2’ distance all around
the face of the column (as per ACI 318 )
find pressure at critical section
Find the value of bo
2.find Vu
3.find Vu is smallest of these
L&T-GES

5. Safe against two way shear Otherwise increase the depth
L&T-GES

6. Check for flexural reinforcement
Max moment occurs at the face of the column
Find average pressure
Find required moment Mn=Mu/
Find required Ast
Min Ast=0.0018bh
Max spacing=18 in
Development length
L&T-GES

7. Isolated footing with axial load and moment
Word document (IS Method)
Word document (ACI method)
Spread sheet (ACI method)
STAAD output (ACI method)
L&T-GES

8. Final comparison 3366 mm2 CODE manual design and spread sheet design
STAAD DESIGN
Area of steel
IS 456
3366 mm2
Not available in STAAD
ACI 318
5.55 in2
( mm2)
5.15 in2
( mm2)
% difference in steel quantity
10.6%
1.3%
L&T-GES

9. Thank You
L&T-GES