Shallow Footings Design Considerations -...

Shallow Footings:

Design Considerations

With / Without Reinforcement

Zone of compression in

lightly loaded footings

Typical section

Rebars

Material

Concrete

Plumstone

Bricks

Design Chart:

Bearingcapacitywithrespect to acceptablesettlement

Settlement

Structuralrigidityon differentialsettlement

a) very flexibleb) more rigid

Structuraldesign ofcombinedfootings:

a) idealized beam strips,b) longitudinal beam strip,c) transverse beam strip.

Note:

k = E/Edef . (t/l)3

If k > 1.0 Rigid Footing

Total and differential settlement(Adapted from Bjerrum, 1963)

Settlement

Structure: statically determined

not statically determined - concretenot statically determined - steel

Rigid str. made of reinforced concretestack – smokestack up to 100 m

higher than 100 m

Value (mm) Type Value

Buildings + Structures not sensitive to differential settlement

Methods of leveling the base plate:a) Double Nuts

b) Blocks and Shims

Mat Foundation

Pile-/Shaft-supported Mat Foundation

Mat:Rigid / Flexible

Influence ofsubsoil/rock

stiffness

Coefficient ofSubgrade Reaction:

k = σ / δ(per Winkler analysis)