SHALLOW FOUNDATION PRESENTED BY:- SHARIQ AHMED

B.ARCH. 3RD YEAR THEORY OF STRUCTURES

FOUNDATION

THE FOUNDATION CAN BE DEFINED AS THE SUBSTRUCTURE WHICH INTERFACES THE SUPERSTRUCTURE AND THE SUPPORTING GROUND.

ITS PURPOSE IS TO TRANCEFER ALL LOADS FROM THE SUPERSTRUCTURE TO THE GROUND SAIFLY AND PROVIDE STABLE BASE TO THE SUPERSTRUCTURE.

SHALLOW FOUNDATION• IT HAS SMALLER DEPTH LIMITED TO THE WIDTH OF FOOTING.• IT SPREADS THE LOAD FROM SUPERSTRUCTURE ON A LARGER AREA OF SOIL SO THAT STRESS INTENSITY IS REDUCED TO A VALUE WHICH CAN BE CARRIED SAIFLY BY SOIL.

CLASSIFICATIONSHALLOW FOOTING IS CLASSIFIED INTO TWO TYPES :-

ISOLATED FOOTING COMBINED FOOTING

IT SUPORTS ONE WALL OR ONE COLUMN.

A WALL FOOTING IS A CONTINUOUS STRIP, EITHER FLAT OR STEPPED WHICH DISTRIBUTES THE LOAD OF WALL TO THE SOIL.

A COMBINED FOOTING SUPPORTS TWO OR MORE COLUMNS.

THEY ARE FURTHER CLASSIFIED AS THOSE WHICH SUPPORT TWO COLUMNS AND THOSE WHICH SUPPORT MORE THEN TWO COLUMNS.

AN ISOLATED FOOTING SUPPORTING A SINGLE COLUMN IS COMUNLY USED WHERE THE LOADS ON COLUMNS ARE SMALL AND COLUMNS ARE NOT CLOSELY SPACED.

THEY ARE SQUARE, RECTANGULAR, CIRCULER, OR OF OTHER SHAPES.

COMBINED FOOTING SUPPORTING TWO COLUMNS MAY BE USED FOR COLUMNS ON PROPERTY LINES.

FOOTING FOR WALL.

FOOTING FOR COLUMN

EXAMPLES FOR ISOLATED FOOTING

COMBINED RECTANGULAR FOOTING

COMBINED TRAPEZOIDAL FOOTING

COMBINED FOOTING FOR TWO COLUMN

T-SHAPED FOOTING

STRAP FOOTING

COMBINED FOOTING FOR TWO COLUMN

Secondary Factors Affecting Foundation Choice

Construction access, methods & site

conditions

Environmental factors

Building Codes & Regulations

Impact on surrounding structures

Construction schedule

Construction risks

SUITABLE FOOTING

AN ISOLATED FOOTING FOR COLUMN ON PROPERTY LINE WOULD EXTEND BEYOND IT WHICH CAN BE AVOIDED BY COMBINING SUCH FOOTING WITH THAT OF INTERIOR COLUMN.

SUCH FOOTING CAN BE OF SHAPES LIKE RECTANGULAR, TRAPEZOIDAL OR T-SHAPED IN PLAN OR MAY CONSIST OF ISOLATED FOOTINGS CONNECTED WITH A NARROW BEAM.

WHEN THE BEARING CAPACITY OF SOIL IS LOW, RESULTING IN LARGE AREA OF FOOTING AND THE COLUMNS ARE CLOSELY SPACED SO THAT NORMALLY DESIGNED ISOLATED FOOTING SHALL APPROACH EACH OTHER, CONTINUOUS STRIP FOOTING SUPPORTING MORE THEN TWO COLUMNS IN A ROW ARE PROVIDED.

GRID FOUNDATION

SUCH STRIP FOOTINGS PROVIDED IN BOTH DIRECTIONS ARE KNOWN AS GRID FOUNDATION.

MAT FOUNDATION

• FOR VERY LOW BEARING CAPACITY OF SOIL, THE STRIP OR ISOLATED FOOTING MERGE RESULTING IN THE MAT FOUNDATION .• IT IS A SINGLE LARGE CONTINUOUS FOOTING SUPPORTIN THE ENTIRE STRUCTURE.• IT ALSO REDUCES THE DIFFERENTIAL SETTLEMENT BETWEEN THE COLUMS.

BEAM AND SLAB SYSTEM AMD PLATE WITHPEDESTAL

PLATE THICKENED UNDER COLUMN AND FLAT PLATE

EXAMPLES OF MAT FOUNDATION