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Types of foundations and footings - Coggle Diagram
Types of foundations and footings
What is foundation?
A structure is generally considered to have two main portions
Superstructure
Substructure
The load of the superstructure is transmitted to the foundation or substructure through either columns or wall.
The substructure transmits loads of super-structure to the supporting soil and is generally, termed as the foundation
There are two types of foundation
Deep foundations (huge loads)
Shallow foundations (small loads)
What is footing?
The footing is the portion of the foundation which ultimately delivers the load to the soil, and is thus in contact with it.
Types of footings
For deep foundations
Pile foundation
For shallow foundations
Isolated footing
Strip Footing
Mat or Raft Foundation
Strapped or cantilever footing Foundation
Combined footing Foundation
Spread footing
Stepped footing
Slopped footings
The selection of footing depend on
The type and condition of soil
The depth of soil at which safe bearing strength exists
The type of the superstructure
Definition of each type of footings for shallow foundations
Strip footing
Strip footing is component of shallow foundation which distributes the weight of a load bearing wall across the area of the ground
Spread footings
A spread is given under the base of foundation so that the load of the structure is distributed on wide area of the soil in such a way that bearin capacity of the soil is not exceeded
Isolated footings
It's a square, circular or indvidually rectangular slab of uniform thickness, provided under each column
Stepped footings
The main prupose of using stepped footing is to keep the metal columns away from direct contact with soil to save them from corrosive effect. They are used to carry the load of metal columns and transmit this load to the below groiund
Definition of each type of footings for shallow foundations
Combined Footing
When individual footing has to accommodate two or in exceptional case more than Two columns is known as the combined footing. When individual footing has to accommodate two or in exceptional case more than Two columns is known as the combined footing
When the combined footing is used?
When the column is close to the property line, So that footing cannot be spread in that direction and centre of gravity of column will not coincide with the centre of gravity of footing.
When the load-bearing capacity of the soil is low, the requirement of more area under the individual footing.
When two columns are very close enough to each other such that their footing overlap.
Strapped footing
In this type of footing, the outer and inner column is connected by a strap beam, does not transfer any load to the soil
This type is used to combine the footing of the outer column to the adjacent one so that the footing of the former does not extend in the adjoining property.
Raft foundation
Raft foundation is very useful when the load coming on the soil is practically uniform while the soil is soft clay or reclaimed soil. This foundation covers the entire area under the structure.
The method consists of providing RCC slab of suitable thickness and with necessary reinforcement. The raft is designed in this way that the allowable bearing power of the soil is not exceeded. If required slab and beam construction in RCC. Can also be carried out. The raft is designed as an inverted RCC roof with a uniformly distributed load of the soil pressure and supported by wall, beam and columns.
Definition of each type of footings for shallow foundations
Sloped footings
The strapped footings having sloping top or side faces are known as sloped footings. This type of footing is useful in the construction of fromwork.
Definition of each type of footings for deep foundations
Pile foundation
A pile foundation is a long cylinder of a strong material such as concrete that is pushed into the ground to act as a steady support for structures built on top of it
Pile foundation is a deep foundation used where the topsoil is relatively weak. Piles transfer the load to a lower stratum of greater bearing capacity by way of end bearing or to the intermediate soil through skin friction. This is the most common type of deep foundation generally used for buildings where a group of piles transfer the load of the superstructure to the sub-soil.
When pile foundation is usefull
When there is a layer of weak soil at the surface. This layer cannot support the weight of the building, so the loads of the building have to bypass this layer and be transferred to the layer of stronger soil or rock that is below the weak layer
When a building has very heavy, concentrated loads, such as in a high rise structure, bridge or water tank.
I searched on internet and i found two other types of deep foundations which are
Well foundation
This type of foundation is usually adopted in the construction of the bridge and long span culverts or where the soil or quite soft and sandy generally in water. Well foundations are made to masonry or concrete.
Pier Foundation
Pier foundation is a type of deep foundation which consist of a cylindrical column of large diameter to support and transfer large superimposed loads to firm strata below. Pier is inserted down to the bedrock. Pier has a footing. Pier is typically dug out and cast in place using formwork
There are two types of pier foundation
Masonry or Concrete Pier
Drilled Cassion
