•DEFINITION OF FOUNDATION
The lowest part of a structure is generally referred to as foundation.
•FUNCTION OF A FOUNDATION
To transfer load of the superstructure to the soil on which it is resting.
A properly designed foundation is one that transfers the structural load
throughout the soil without overstressing of soil which can result in either
excessive settlement or shear failure, both of which can damage the structure.
LOADS ON FOUNDATION
Dead Load : Refers to the overall weight of the structure. Includes weight
of the materials permanently attached to the structure (such as flooring)
and fixed service equipment (such as air conditioning)
Live load : Refers to the weight of the applied bodied that are not permanent
parts of the structure. Applied to the structure during part of its useful life
(e.g. people, warehouse goods). Specified by code.
Wind loads : Acts on all exposed parts of the structure. Calculated using
Earthquake Forces : Building code is consulted.
CLASSIFICATION NOF FOUNDATIONS
This type of foundation usually refers to those being rested on stratum with
adequate bearing capacity and laid less than 3m below ground level.
Common examples include pad, strip or raft foundations.
The selection of the right type of shallow foundation normally depend on
the magnitude and disposition of the structural loads and the bearing capacity
of subsoil. A combination of two or three type of shallow foundation in one single
structure is not uncommon.
PAD FOUNDATION / SQUARE SPREAD FOOTING FOUNDATION
PAD FOUNDATION / SQUARE SPREAD FOOTING FOUNDATION……..
•Support a single centrally located column
•Use concrete mix 1:2:4 and reinforcement
•The reinforcement in both axes are to resist/carry tension loads.
Circular Spread Footings
• Are round in plan view
• Most frequently used as foundation for
• Light standards, flagpoles and power
• Transmission lines.
CONTINUOUS SPREAD FOOTINGS / STRIP FOUNDATION
•Used to support bearing walls
• support more than one column
• useful when columns are located too close together for each to
have its own footing
Raft foundation is a large combined thick slab designed to seat and
support the whole or a large part of a structure.
A raft is usually used when subsoil is weak, or columns are closely located and with
deviated loadings. It also serves as a transfer slab to combine and tie up all the
vertical loading elements to the plate-form foundation. By doing so, differential
settlement can be avoided.
ADVANTAGES AND DISADVANTAGES OF SHALLOW FOUNDATION
•Construction Procedure (simple)
•Materials (mostly concrete)
•Labor (does not need expertise)
•Limit Capacity Soil Structure
•Irregular ground surface (slope, retaining wall)
•Foundation subjected to pullout, torsion, moment.