1. SUB-STRUCTURE
foundations

3. Definition of Sub-Structure
The supporting part of a structure; the foundation.
(i.e.: footing / piling, pile cap, column stump )
Sub-structure will include ground beams,
ground floor column and ground floor slab.

4. Foundation An essential part of any building
Spread out concentrated structural loads from walls and columns onto the generally softer material that form the surface of the earth’s crust.
Structure who support the weight of the upper structure and applied loads.
Designed to transmit building load to the supportive soils or rock.
Foundation failure :
- collapse or excessive settlement of a building supporting structure resulting from soil movement.
Types of foundation include footings, piles and piers.

5. Foundation Anatomy

6. Foundation Causes of settlement are;
Design and selection of foundation depends on:
Total load of building
Nature and bearing capacity of soil
Causes of settlement are;
Deformation of soils causing by an imposed load
Volume changes of soil cause by seasonal conditions.
Mass movements of ground in an unstable areas.

7. Foundation Shallow Foundations 1. Spread Foundations / Footings
Foundations can be considered under two groups:
Shallow Foundations
Deep Foundations
Shallow Foundations
1. Spread Foundations / Footings
- Isolated Foundations, Strip Foundations and Combine Both
2. Raft Foundation
Deep Foundations
- Pile, Pier and Caissons

8. Foundation Shallow Foundations
Shallow foundations are those founded near
to the finished ground surface; generally
where the founding depth (Df) is less than
the width of the footing and less than 3m

9. Foundation Deep Foundations Deep foundations are those founding too
deeply below the finished ground surface
for their base bearing capacity to be
affected by surface conditions, this is
usually at depths >3 m below finished ground
level

10. Foundation

11. Foundations The principal types of RC Foundation for buildings are :
Strip Foundation
Isolated Foundation
Raft Foundation
Combination of 1, 2 and 3
Piled Foundation

12. Foundations – Strip Foundation
BACK

13. Foundations – Strip Foundation
Strip foundations are used to support a line of loads, either due to a load-bearing wall, or if a line of columns need supporting where column positions are so close that individual pad foundations would be inappropriate.

14. Foundations – Pad @ Isolated Foundation

15. Foundations – Pad @ Isolated Foundation
Pad foundations are used to support an individual point load such as that due to a structural column. They may be circular, square or rectangular. They usually consist of a block or slab of uniform thickness, but they may be stepped or hunched if they are required to spread the load from a heavy column. Pad foundations are usually shallow, but deep pad foundations can also be used.

16. Foundations – Raft Foundation
BACK

17. Foundations – Raft Foundation
Raft foundations are used to spread the load from a structure over a large area, normally the entire area of the structure. They are used when column loads or other structural loads are close together and individual pad foundations would interact.

18. Foundations – Pile Foundation

19. Foundations – Pile Foundation
Structures place on top of the piles.
Piles + Pile Cap = Pile foundation
Function : Distributes load to the individual piles.
Pile Cap will connect the pile together and distributes the superstructure loads to the layer beneath.

20. Foundations – Pile Foundation (Pile Cap)

21. Pile Foundation Pile foundations are the part of a
structure used to carry and transfer
the load of the structure to the bearing
ground located at some depth below
ground surface
The main components of the foundation are the pile cap and the piles

22. Pile Foundation
Piles are long and slender members which transfer the load to deeper
soil or rock of high bearing capacity avoiding shallow soil of low bearing capacity
The main types of materials used for piles are Wood, steel and concrete

23. Pile Foundation Functions of Piles
- to transmit a foundation load to a solid ground
- to resist vertical, lateral and uplift load
Piles
Pile Cap
Column Stump

24. Pile Foundation
Classifications of piles with respect to type of material
1. Timber 2. Concrete 3. Steel 4. Composite piles

25. Pile Foundation
Classifications of Piles – Timber Piles

26. Pile Foundation
Classifications of Piles – Concrete Piles

27. Pile Foundation
Classifications of Piles – Steel Piles

28. Design of reinforced concrete pad foundations
The size of pad is determined from unfactored column load and the permissible bearing pressure
Table : Permissible soil bearing pressure (kN/m2)
Permissible pressure, not ultimate pressure…..
used in conjuction with unfactored loads
Soil types
kN/m2
Medium dense sand and gravel mix
300
Loose sand and gravel mix
150
Loose sand 75
Stiff clay
200
Firm clay
100
Soft clay
<75

29. Design of reinforced concrete pad foundations
Size column : 300 x 300 mm Axial load, N ; dead load = 900 kN live load = 400 kN soil bearing pressure = 200 kN/m2 Determine the dimension for a suitable square pad foundation. Assume self weight of pad footing is 120 kN Solution ; Total unfactored load = =1420 kN Required pad area = 1420 / 200 = 7.1 m2 Square pad footing, B = H = √7.1 = 2.66 m Depth of pad ≈ 2.66 / 6 = 0.44 say 0.45 m :- Use pad footing 2.66 m square and 0.45 m deep. Sketch isometric drawing of pad footing including the column and typical steel reinforcement arrangement in a footing and column

30. Design of reinforced concrete pad foundations
Exercise A 325 mm square concrete column support the following characteristic loads : Dead load = 758 kN Imposed load = 630 kN Determine the dimension for a suitable square pad foundation if it bears on stiff to firm clay with a permissible bearing pressure of 150 kN/m2