Isolated footing with axial load and moment Design

Isolated footing with axial load and moment Design Input • Grade of concrete - 35 • Grade of steel - 460 • Allowable soil pressure – 200 KN/m 2 • Column load – 1260 KN(D. L+L. L) • Moment – 100 k. N. m • Condition about overburden of soil - No L&T-GES

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

Finding factored loads • Factored column load=1. 4 xdead load+1. 7 xlive 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 q 1 and q 2 • Service load equation • Vertical equilibrium L&T-GES

Check for One 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 ) 1. find pressure at critical section 2. Find the value of bo 2. find Vu 3. find Vu is smallest of these L&T-GES

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

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. 0018 bh • Max spacing=18 in Development length L&T-GES

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

Final comparison CODE manual design and spread sheet design Area of steel IS 456 mm 2 3366 ACI 318 5. 55 in 2 (3580. 64 mm 2) % difference in steel quantity 10. 6% L&T-GES STAAD DESIGN Area of steel Not available in STAAD 5. 15 in 2 (3322. 57 mm 2) 1. 3%

Thank You L&T-GES