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FOUNDATION FOOTING. Foundation. The foundation system of building, its substructure, is a critical link in transmission of building loads to the ground. Foundation is a structure built to transfer the dead loads and live loads or weight of building to the material below . .

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foundation
Foundation
  • The foundation system of building, its substructure, is a critical link in transmission of building loads to the ground. Foundation is a structure built to transfer the dead loads and live loads or weight of

building to the

material below.

classification
CLASSIFICATION
  • Foundation are generally classified as either deep or shallow. The depth bearing area of shallow foundation generally is no deeper than about the width of the bearing surface. Deep foundation provide support for a structure by transferring the loads to competent soil and rock at stone depth below the structure.
foundation4
Shallow

Spread

Combine

Strip

Deep

Basement

Caissons

Piles

Foundation
shallow foundation
Shallow foundation
  • Shallow foundation can be either footing or pad. They consist reinforced concrete slabs formed directly on a prepared soil base. Footing may be spread, combined, or continuous. Terzaghi and peck define that shallow foundation as the footing width equal to or greater than its depth.
spread footing
Spread footing
  • Spread footing They typically 0.9 to 2.4 to 3m square. Their bearing surface is typically less than 2.5 times their width (<2.5B).
combine footing
Combine footing
  • Combine footing are similar to spread footing but support two or more columns
continuous or strip
Continuous or Strip
  • Continuous or Strip footing is an elongated shallow foundation that typically support as single row of column or a wall or other type of strip loading.
shallow footings

D

B

Shallow Footings

By definition

D/B < 4

applications

Very Large Concentrated

Weight

Large Distributed

Weight

Low

Weight

Strong Rock

Applications

Weak

Soil

Weak Rock or

distributed over

competent Soil

load limitations
Load limitations

Shallow foundations can

cope with compression

and inclined loads

Shallow foundations are

limited in tension capacity

by the footing weight

D

C

limit states
Limit States

Serviceability

Ultimate

deep foundation
Deep Foundation
  • It is opposite to shallow foundation. It has been developed to increase bearing capacity/stability and reduce settlement by build them deeper than shallow one due to building going larger and heavier.It can be divided into 3 types as details later on.
basement

Very Large Concentrated

Weight

Large Distributed

Weight

Low

Weight

Strong Rock

Basement

Basement

Weak

Soil

Weak Rock or

distributed over

competent Soil

caissons
Caissons

Open CaissonsPneumatic Caissons Box Caisson (floating)

methods
Methods
  • Pile driving formulae
  • Static load test
  • Dynamic or Statnamic load test
  • Static formulae
pile driving formulae

F

s

tc

D

Pile driving formulae
  • e.g. Hiley formula

Ru = e.W.h .

(set + tc / 2)

  • Newton’s law - two rigid bodies
  • Efficiency?
  • Static resistance only
  • Correlate
  • MORE details later
axial capacity

Qs

Pu

Axial Capacity

W

Pu = Qb + Qs - W

Qb

axial capacity21

Pshaft

Axial Capacity

Fu

Fu + W = Pbase + Pshaft

W

Shear failure at pile shaft

Pbase

Bearing failure at the pile base

tension capacity

Pshaft,t

Tension Capacity

Tu - W = Pshaft,t < Pshaft,c

Shear failure at pile shaft

applications24

Very Large Concentrated

Weight

Large Distributed

Weight

Low

Weight

Applications

Soft to

Firm Clay

Dense Sand

Strong Rock

slide25

Pug

Group Capacity

Pile Cap

  • Overlapping stress fields
  • Progressive densification
  • Progressive loosening
  • Case-by-case basis

Pug¹n.Pup

Pug = e.n.Pup