The document discusses the components of building structures, focusing on substructures and foundations, including their types and functions. It explains shallow and deep foundations, various footing types, and the importance of load distribution. Additionally, it outlines settlement types, structural loads, and construction methods such as load-bearing, frame, and composite structures.

1. UNIT - II
Materials and Construction
• Sub Structure
• Settlement
• Types of Load
• Super Structure
- Basavaraj S Tavade

2. FOUNDATION or SUBSTRUCTURE
• Every building consists
of two basic components :
1. The Super-structure.
2. The Sub-structure.

3. FOUNDATION or SUBSTRUCTURE
The substructure or foundation is the part of structure
which is usually below the ground level and in direct
contact with the soil, through which the load of
superstructure is transmitted to the soil.
or
It is the lowest artificially prepared part of a structure
below the ground level which provides base for
superstructure and transmits all loads from
components parts of the building to the soil on which
building rests.

4. Functions of Foundation:
1. Reduction of load intensity.
Foundations distribute the load of the superstructure to a
larger area so the total intensity of load doesn't exceed the
Safe bearing capacity of soil.
2. Even distribution of load.
Foundations distribute the non uniform load of the super
structure evenly to the subsoil.
3. Provision of level surface.
Foundations provide a levelled and hard surface over which a
super-structure can be built.

5. Functions of Foundation:
4. Lateral stability.
It anchors the super-structure to the ground thus imparting
stability to the building.
5. Safety against undermining.
It provides safety against undermining or scouring due to
burrowing animals & flood water.
6. Protection against soil movements.
Special measures prevent or minimise the distress (cracks) in
superstructure, due to expansion or contraction of sub-soil.

6. Types of Foundation:
Shallow Foundation:
– when the depth of foundation is less than or equal
to its width, it is defined as Shallow foundation.
Deep Foundation:
-- when the depth of foundation is more than its
width, it is defined as Shallow foundation.

7. Types of Foundation:
Foundation
Shallow
Foundation
Wall Footing/ Strip Footing
Isolated Footing
Combined Footing
Cantilever / Strap Beam Footing
Mat / Raft Footing
Deep
Foundation
End Bearing pile
Friction pile

8. Wall Footing / Strip Footing
• It is the footing provided throughout the length of the
wall in the load bearing walls, then it is called wall
footing.
• Simple footings are used for light structure.
• the projection of Simple footings base is usually 15 to
20cm.
• Stepped footings are similar to simple footing except
that they have more than one projection or steps.
• Stepped footings are used to transfer heavy load.

10. Isolated / Spread footing
• When footing is provided to support an individual
column, it is called “isolated footing”.
• They may be square, rectangular, circular or sloped
in shape depending on the distribution of load
required.
• Isolated sloped column footing is the most
commonly used footing.

12. Combined Footing :
• A footing which Supports more than one column.
Situations where Combine Footing is provided
1. It is used when the two column are so close to each
other that their individual footings would overlap.
2. A combined footing is also provided when the
property line is so close to one column that a spread
footing would be eccentrically loaded when kept
entirely within the property line. By combining it
with that of an interior column, the load is evenly
distributed.

13. Combined Footing :
• A combine footing may be rectangular or trapezoidal
in plan.
• Rectangular Combined footing is used if sufficient
space is available beyond each column.
• If the load on the both column is same.
• And if the distance between the column is less
• Trapezoidal combined footing is provided when the
load on one of the column is different, because more
footing area is required for supporting the column
carrying heavy load and also if the distance between
the column is large.

15. Here in the above figure we can clearly see that, two columns footings are overlapping. So
instead of providing individual isolated / spread footing , they have provided the combined
footing

16. Here in the above figure we can clearly see that, two columns footings are overlapping. So
instead of providing individual isolated / spread footing , they have provided the combined
footing

17. Strap Beam / Cantilever Footing :
• A strap (or cantilever) footing consists of two
isolated footings connected with a structural strap or
a lever.
• A strap footing is more economical than a combined
footing when the allowable soil pressure is relatively
high and the distance between the columns is large.

20. Mat / Raft Footing :
• In case when the soil conditions are poor and a pile
foundation is not economical than the load of the
columns is transferred to a mesh or a mat supporting
all of the columns.
• A mat or raft is a thick reinforced concrete slab
which supports all the load bearing wall or column
loads of a structure & covers the entire area of the
building.
• Mat foundations are useful in reducing the
differential settlements on non-homogeneous soils
or where there is large variation in the loads on the
individual columns.

21. COLUMN

25. Deep Foundation / Pile Foundation:
• A pile is basically 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 foundations are used in the following situations:
1. When a building has very heavy concentrated loads,
such as in a high rise structure, bridge, or water tank.
2. When there is a layer of weak soil at the surface.
There are two types of pile foundations.

26. 1. End bearing pile :
• In end bearing piles, the bottom end of the pile rests
on a layer of especially strong soil or rock.
• The load of the building is transferred through the
pile onto the strong layer.
• End bearing piles are useful when hard strata is
available within reasonable depth in loose soil
having low bearing capacity.

27. 2. Friction Piles :
• The principle of this type of piles is, “The pile
transfers the load of the building to the soil across
the full height of the pile by friction”
• These piles are used where hard strata is available at
a very great depth.
• Friction files are useful in cohesive soil with low
bearing capacity

29. Settlement:
• The downward movement of the base of footing is
known as settlement
The rate of settlement depends on
1. Magnitude of bearing capacity and load acting.
2. Time elapsed since loading
The settlement is classified into two categories

30. 1. Uniform Settlement:
If the vertical movement of all the parts structure
is equal in magnitude, it is known as uniform
settlement
Structures on rigid foundation undergo uniform
settlement.
Reasons for uniform settlement
1. Lowering of the ground water table.
2. Swelling and shrinkage of expansive soil caused by
seasoned variations.

31. 2. Differential Settlement:
If one part the structure settles more than the
other part, then the difference between two
settlements is known as differential settlement.
It induces heavy stresses in the structure leading
to cracks in superstructure.
The ratio of the differential settlement between
two footings to the distance between them is known
as angular distortion.

32. 2. Differential Settlement:
Causes of differential settlement:
1. Unequal intensity of loading on the foundation by
superstructure.
2. Unequal swelling and shrinkage of soil.
3. Overstressing of soil by changes in adjoining
structure.
4. Erosion of soil.
5. Presence of deep roots of trees below one
foundation.

35. SUPER STRUCTURE :
Dead Load:
“It is defined as the force whose magnitude, position, and
direction remains constant”.
The weight of all the permanent parts of a building such
as walls, columns, beams, floors, roofs, stairs, doors etc is
considered as dead load.
The unit weight of common materials used in building
construction is given by IS 875-1 1987

36. Building Material Unit Weight (KN/m3)
Stones 20 to 28
Steel 78
Plain cement concrete 22 to 24
Reinforced cement concrete 25
Structural Timber 7
Sand and Loose gravel 16 to 20
Commonly Used Building Materials and their Unit
weight

37. SUPER STRUCTURE :
Live Load:
The load which consist of moving or variable loads due to
occupants, weight of furniture, home appliances, equipments
etc.
Live load should be considered as per the
recommendation of IS 875-2 1987.

38. Type of Floor
Minimum Live Load
(KN/m2)
Residential building, hospital
work
2.0
Office rooms, small work
places
2.5
Bank and reading rooms 3.0
Shops, class rooms, assembly
halls
4.0
Warehouses, workshops,
factories, dance halls
5.0
The minimum live load to be considered as per IS 875-
2 1987 is as below

39. Number of Floors Reduction in Live Load
One floor No reduction
Two floor 10%
Three floor 20%
Four floor 30%
Five floor 40%
Six floor and all other
subsequent floor
50%
The live load for upper floor is reduced by applying
reduction factor as below

40. SUPER STRUCTURE :
Wind load:
When wind is obstructed by the structure, it exerts a
pressure on the structure known as wind pressure.
as per IS 875-3 1987 basic wind pressure may be obtained
by
P = KV2
where P = wind pressure in kg/m2
V = Wind velocity in kmph
K = Coefficient which depends on wind velocity,
air temperature, size of the building.

41. SUPER STRUCTURE :
Types of construction:
1. Load bearing structures :
• In this type of construction, load of the structure is
transferred to the walls as, roof and floors are directly
supported on walls.
• walls in turn transfer the load to the underlying soil
through wall footing.
• this type of construction is suitable and economical up to
two storey's.
• The load transfer mechanism is shown in figure.

43. SUPER STRUCTURE :
Types of construction:
2. Frame structures :
• In this type of construction, load is transferred through a
frame of slab, beam, column and footing to the underlying
soil.
• Slab and beams are the flexural members of the structure.
• Columns and footings are the compression members of
the frame.
• Walls do not carry any load.
• The load transfer mechanism is shown in figure.

45. SUPER STRUCTURE :
Types of construction:
3. Composite structures :
• This is a combination of load bearing and frame structure
• The composite structure is shown in figure.
• Here the outer walls can be of load bearing type where as
column and beam structure can be provided internally.