Transcript
SHALLOW FOUNDATION-: CREATED BY :-
ALAY MEHTASHIVANI PATELKAVIN RAVALKUNTAL SONI
AMIRAJ COLLEGEOF
ENGINEERING AND TECHNOLOGY
FOUNDATION Foundation is the
lowest part of a structure which provides a base for the super‐structure and transmit the loads (live load, wing load) on the structure including the dead weight of the structure itself to the soil below.
TYPES OF FOUNDATION Types of Foundation:
Foundation can be broadly classified into two types :
1. Deep Foundations 2. Shallow Foundations
SHALLOW FOUNDATION
Foundation is placed immediately lowest part of the super structure, is termed as Shallow foundation:
Why we use shallow foundation?
To distribute the structural loads over a wide horizontal area at a shallow depth below the ground level.
TYPES OF SHALLOW FOUNDATIONS
The various types of shallow foundations are :
Spread footing Combined footing Mat or Raft foundation. Grillage footing Eccentrically loaded footing
SPREAD FOOTINGS
Spread footings are structural members used to support columns and walls and to transmit and distribute their loads to the soil.
SPREAD FOOTING
Types of spread footing
Wall footings Reinforced concrete footings Inverted arch footing Column footings
WALL FOOTING
Why Wall Footing?
Support walls that may be either bearing or nonbearing walls.
Commonly required to support direct concentric loads.
WALL FOOTING
Why Wall Footing?
Footings carry relatively light loads on well drained cohesive soil.
A wall footing under concentric load behaves similarly to a cantilever beam.
Used in low rise buildings.
REINFORCED CONCRETE FOOTING
REINFORCED CONCRETE FOOTING
Why Reinforced concrete footing?
Relatively heavy loading than wall footing.
Bearing capacity of the soil is low.
REINFORCED CONCRETE FOOTING
In a reinforced concrete wall footing, the behavior is identical to that of wall footing.
Reinforcing steel is placed in the bottom of the footing in a direction perpendicular to the wall like a reinforced concrete beam or slab.
INVERTED ARCH FOOTING
INVERTED ARCH FOOTING When a wall is
composed of isolated piers, it is well to combine all their footings into one, and to step the piers down .
COLUMN FOOTINGS
COLUMN FOOTINGS
WHY COLUMN FOOTINGS?
This is one of the most economical types of footings.
Used when columns are spaced at relatively long distances.
COLUMN FOOTINGS
WHY COLUMN FOOTINGS?
Low bending strength.
When bearing capacity of soil is good.
Carry heavy loads.
Used to support single columns.
To distribute the load uniformly.
COLUMN FOOTINGS
CHARACTERISTICS OF COLUMN FOOTINGS
Constructed with brick, stone or plane concrete.
Circular, rectangular or square in plan.
COMBINED FOOTINGS Usually support two
columns, or three columns not in a row.
Combined footings are used when tow columns are so close that single footings cannot be used or when one column is located at or near a property line.
COMBINED FOOTINGS WHY COMBINED
FOOTINGS?
When two columns are close together, causing overlap of adjacent isolated footings.
When soil bearing capacity is low, causing overlap of adjacent isolated footings.
GRILLAGE FOUNDATIONS Grillage foundations
consist of a number of layers of beams usually laid at right angles to each other and used to disperse heavy point loads from the superstructure to an acceptable ground bearing pressure.
RAFT FOUNDATION Foundation which consists of thick reinforced
concrete slab covering the entire area of the bottom of the structure like a floor. This foundation was invented by John Root at Chicago in 19th century.
RAFT FOUNDATION Why Raft Foundation?
Base soil has low bearing capacity or the column loads are so large that more than 50% of the area is covered by conventional spread footings.
Resist unequal settlement due to earthquake.
Quickness of the construction work
LIMITATIONS OF SHALLOW FOUNDATION
A huge amount of earthwork is to be done in Mat foundation.
If the shoring system can not resist the pressure of outside land, then the structure surrounding the area may be damaged by deflection of soil.
Ground water may come out when the earthwork is done.
Limited to dealing with point loads. foundation
ADVANTAGES OF SHALLOW FOUNDATION
It is a quick process compared to others in the construction work.
This type of foundation is also economically cheaper than any other foundations.
Though there are some limitations in mat foundation still it is economical in some cases.
ADVANTAGES OF SHALLOW FOUNDATION
It can resist ground water absorption.
The damage due to earthquake is lesser than any other type of foundation.
It consists of a reinforced concrete slab which is more thicker than footing foundation.
It prevents unequal settlements.
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