7. RAFFLES October 2012
Raffles International Institute LOADS
STATIC LOADS: DYNAMIC LOADS:
CONSOLIDATION OF LOADS AND STRESSES
8. Raffles International Institute FOUNDATION MATERIAL
STRENGTH OF MATERIAL
is measured by its power to resist tensile & compressive force.
• Foundation is subject to compressive forces.
• Materials used must be strong enough to resist the
forces.
9. Raffles International Institute TYPOLOGY AND ELEMENTS
FOUNDATION
is the lowest supporting layer of a supporting system
of the building (structure) that is transferring the loads to the ground and uniformly
distributing to the area under structure.
Foundations are generally divided into two categories:
1.shallow foundations and
2.deep foundations
Types of materials used :
Concrete :
Strong in compression but weak in tension. Can be reinforced with steel bars
Steel :
Used with concrete for heavy foundation
10. Raffles International Institute TYPOLOGY AND ELEMENTS
DECISION ABOUT FOUNDATION TYPES FOR THE BUILDING
Depends on :
1. Total building loads (building size & form, ways of transmitting loads to
ground)
2. Soil conditions - nature & bearing capacity of soil, The ground consists of
compressible soil of varying degrees.
(Bearing capacity refers to the site load per unit area which the ground can take.
Note that these will be advised by the engineer)
11. Raffles International Institute TYPOLOGY AND ELEMENTS
TYPES OF FOUNDATIONS:
1.Pad Foundation
2. Pole Foundation
3. Strip Foundation
4. Raft / Mat Foundation
5. Combined Foundation
6. Pile Foundation
7. Caisson Foundation
SHALLOW FOUNDATION
DEEP FOUNDATION
12. Raffles International Institute STRUCTURAL SYSTEMS
SHALLOW FOUNDATION TYPOLOGY
1.shear walls
2.continuous under a series of columns
3. pedestal types under walls; isolated types under columns
4.combination with beams, under walls; combination types in the form of
uniform or ribbed slabs (under an entire structure or part of a structure); and
mat, or rafT.
Figure 1. Cast shallow foundations: (a) continuous under a wall, (b) continuous under columns, (c)
isolated under a column, (d) combination under columns; (1) lower continuous footing of reinforced
concrete, (2) foundation wall (3) column
19. Raffles International Institute
SHALLOW FOUNDATION
Shallow foundations, often called footings, are usually embedded around
0.8 m - 1.2m into soil.
1. One common type is the spread footing which consists of STRIPS OR
PADS of concrete (or other materials such as steel, wood) which extend below
the frost line and transfer the weight from walls and columns to the soil or
bedrock.
2. Another common type of shallow foundation is the SLAB-ON-GRADE
foundation where the weight of the building is transferred to the soil
through a concrete slab placed at the surface.
DIMENSIONS
Dimensioning of shallow foundation elements is based according to the
permitted load capacity of the soil on which the building rests. Load
bearing Capacity of the soil can be to pressure and friction. Footing area is
placed to reach bellow the level of soil freezing.
TYPOLOGY AND ELEMENTS
20. Raffles International Institute
SHALLOW FOUNDATION
Used when stable soil of adequate bearing capacity occurs near to
the ground surface.
• Placed directly below the lowest part of a substructure and transfer
building loads directly to the supporting soil by vertical pressure.
• Consists of bearing pads of reinforced concrete of sufficient plan size to
resolve vertical forces into a low value of bearing pressure* on the soil.
(*Bearing Pressure : Pressure produced on ground by building loads)
TYPOLOGY AND ELEMENTS
25. Raffles International Institute
DEEP FOUNDATION
A deep foundation is used to transfer the load of a structure down through the
upper weak layer of topsoil to the stronger layer of subsoil below.
Used when the soil underlying a foundation is unstable or of inadequate
bearing capacity. Extend down through unsuitable soil to transfer building
loads to a more appropriate bearing stratum of rock or dense sands and
gravels below the superstructure.
TYPES OF DEEP FOUNDATION are:
1.pile foundations and
2.caisson foundations (special types of buildings, bridges, industry etc)
Types of deep footings including:
impact driven piles, drilled shafts, caissons, helical piles and earth stabilized
columns.
PILES MATERIALS:
wood, later steel, reinforced concrete, and pre-tensioned concrete.
TYPOLOGY AND ELEMENTS