BUILDING COMPONENTS AND STRUCTURES
BUILDING
COMPONENTS
1.Sub structure
2.Super structure
Weathering Course
Parapet
Roof Slab
Brick Masonry
Lintel
Door
Damp Proof Course
Floor Finish
Plinth
Floor Concrete
Step
Ground Level
Basement
Sand Filling
Foundation
Foundation concrete
COMPONENTS OF A BUILDING
FOUNDATION
Foundation is the part of the structure which is in
direct contact with the ground to which loads are
transmitted.
A weak foundation destroys the work which is built upon it.
Functions of foundation
Even distribution of load
Reduction of load intensity
Reduction of differential settlement
Safety against sliding and overturning
Safety against undermining
Provide firm and level surface
Protection against soil movement
Requirements of a good foundation
Constructed to sustain dead load and imposed load and
transmit them to underlying soil
Rigid-to avoid differential settlement
Taken to sufficient depth
Performance should not be affected due to any unexpected
future influence
Factors for the design
Ultimate bearing capacity
1. Bearing capacity of the Safe bearing capacity
soil
Allowable bearing capacity
Uniform settlement
Differential settlement
2. Settlement of foundations
BEARING CAPACITY
• Supporting power of soil without any failure
• Depends on :
1. Properties of soil
2. Position of water table
3. Physical features of foundation like type, size & shape
• Ultimate Bearing Capacity : minimum gross pressure intensity at the base of foundation that the
soil fails in shear
• Net Ultimate Bearing Capacity : minimum net pressure intensity at which the soil fails in shear
• Net safe bearing capacity : obtained by dividing the net ultimate bearing capacity of the soil with a
suitable factor of safety
• Safe bearing capacity : Maximum pressure the soil can carry safely without the risk of shear
failure
SETTLEMENT OF FOUNDATIONS
Settlement of foundations
No settlement Total settlement Differential settlement
Uniform settlement is usually of little consequence in a building,
but differential settlement can cause severe structural damage.
Settlement of foundation means the sinking of foundation as a
consequence of compression or deformation of the soil under the
foundation
Equal Settlement :
•The structures settles by uniform amount at each and every
portion of the structure
Unequal Settlement:
•The amount of settlement is different at different parts of the
building
Causes of settlement:
•Due to weight of the structure transmitted to the soil
•Due to increased load on the surrounding soil
•Due to excavation near the foundation
•Lowering of water table
•Vibrations from moving machineries
•Deterioration of concrete by the chemical action of soil, seawater etc…
•Due to mining and tunnelling operations
Causes of differential settlement:
•Non uniform load distribution on foundations
•Non uniformity of soil types
•Percolation of water
•Overlap and concentration of stresses due to presence of adjacent foundations
Causes of foundation failure
Unequal settlement of subsoil under the foundation
Unequal settlement of the masonry
Lateral movement of earth
Shrinkage of soil bed due to seasonal variation of moisture
content
The penetration of the roots of trees
Atmospheric action
Lateral escape of the soil beneath the foundation
Horizontal movement of the soil adjacent to the structure
Types of Foundations
Shallow Foundations D<=B
Deep Foundations D>B
D - Depth of foundation
B – Width of foundation
Shallow foundations
Types of shallow foundations
Isolated or column footing
Wall or strip footing
Combined footing
Continuous footing
Cantilever footing
Raft or mat foundation
Isolated or column footing
When the load on the column is less, a spread is given under
the column
Wall or strip footing
The foundation which is provided through out the length of a
continuous structure is called strip footing.
Combined footing
When a foundation or footing is
constructed for two or more
columns is called as combined
footing
Two individual footings overlap
When bearing capacity is less
when footings are constructed
near boundaries of the plot
Trapezoidal footing – when column
loads vary considerably
Continuous footing
A single continuous reinforced concrete slab is
provided as foundation for three or more columns
in a row. Continuous footing is more suitable to
prevent the differential settlement in the
structure and for the safety against earthquake.
Continuous footing
Cantilever Footing (Strap)
Consists of an eccentric footing for the exterior column
and a concentric footing for the interior column.
A strap or a cantilever beam connects them.
Strap footing
Raft or mat foundation
A raft foundation is a combined footing which
covers the entire area beneath a structure and
supports all the walls and columns
Raft or mat foundation
Mat foundation
Raft or Mat Foundation
Raft foundations are suitable when
1.The building loads are heavy
2.The allowable soil pressure is small
3.Individual footings would require more than half the building area
4.In highly compressible soil
5.Weak spots and loose pockets in soil mass are suspected
Deep Foundation
The foundations having very large depth compared
to width are called deep foundations
E.g. Pile foundations
Well foundations
Pile Foundation
Piles are long slender members driven into
ground or cast at the site.
Pile foundations are common where the soil
conditions are unfavorable for the use of
shallow foundations
Classification of Piles
1. Method of load transfer
2. Function or action
3. Composition and material
4. Installation
Classification based up on method of load transfer
1. End bearing Piles
2. Friction Piles
End bearing piles
End bearing piles-Used to transfer load
to a suitable bearing stratum
Friction piles
Friction Piles- used to transfer the loads to a
depth by friction along the surface area of the
piles.
Classification based up on material and composition
1. Timber Piles
2. Steel Piles
3. Concrete Piles
4. Composite Piles
Timber Piles perform well both in dry
condition and in submerged condition
Timber Piles
Used to resist lateral or horizontal forces. More
durable.
Steel Piles
Concrete Piles
Used when part of the pile is submerged under
water. Made up of concrete and steel
Composite Piles
Well Foundations
A well foundation is a well type structure, which built at the
ground level and sunk into the soil at the required level.
The bridge pier will be resting on the top of the well foundation.
The bottom of the well is plugged with concrete.
The top is covered with a well cap which is a thick concrete slab
The bottom edge of the well foundation consists of a cutting edge. The
different c/s adopted for well foundations are
1. Circular
2. Twin circular
3. Double D
4. Dumb bell
5. Twin hexagonal
6. Rectangular
Components of well foundation
Well curb
Cutting edge
Steining
Bottom plug
Top plug
Well cap
WELL CAP
TOP PLUG
STEINING
SAND OR SOIL
FILLING
WELL CURB
BOTTOM PLUG
CUTTING
EDGE
Well curb
Support the wt of the well
Cutting edge
Sharp angle for cutting the soil without making it too weak
Steining
Walls of the well
Bottom plug
Concrete plug provided to balance the soil pressure
Top plug
Concrete plug provided above the sand/soil filling
Well cap
Serves as platform for the supporting members of the superstructure
Machine foundation
To support the dynamic forces produced by the operation of the
machine
To avoid large settlements at resonance, natural frequency of
foundation should be different operating frequency of the
machine
Types of machines
Impact type
Presses, forge hammers
Reciprocating type
Compressors, engines
Centrifugal type
Motors, turbines
Miscellaneous types
Machine foundation
BLOCK TYPE BOX TYPE
WALL TYPE FRAMED TYPE
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