FOUNDATIONFOUNDATION: IN ITS WIDEST SENSE ,THE TERM : IN ITS WIDEST SENSE ,THE TERM FOUNDATION MAY BE DEFINED AS “AN EXPANDED BASE OF A FOUNDATION MAY BE DEFINED AS “AN EXPANDED BASE OF A WALL OR PIER IN ADDITION TO THE GROUND OR SUB SOIL WALL OR PIER IN ADDITION TO THE GROUND OR SUB SOIL WHICH SUPPORTS IT”.WHICH SUPPORTS IT”.

COMPONENTS OF A FOUNDATIONCOMPONENTS OF A FOUNDATION:: A CONCRETE BED ONLY –BASE OF FOUNDATIONA CONCRETE BED ONLY –BASE OF FOUNDATION FOOTINGS :ONE OR MORE COURSES OF STONE WORK OR FOOTINGS :ONE OR MORE COURSES OF STONE WORK OR

BRICK,WIDER THAN THE WALL OR PIER THEY SUPPORT.BRICK,WIDER THAN THE WALL OR PIER THEY SUPPORT.• OBJECTIVES OF A FOUNDATIONOBJECTIVES OF A FOUNDATION:: TO DISTRIBUTE THE WEIGHT OF THE SUPERSTRUCTURE TO DISTRIBUTE THE WEIGHT OF THE SUPERSTRUCTURE

OVER A SUFFICIENT BEARING AREA .OVER A SUFFICIENT BEARING AREA . TO PREVENT THE SUBSOIL FROM SPREADING.TO PREVENT THE SUBSOIL FROM SPREADING. TO AVOID SETTLEMENT OF STRUCTURE.TO AVOID SETTLEMENT OF STRUCTURE. OR WHEREVER SUBSIDENCE IS UNAVOIDABLE,IT SHALL BE OR WHEREVER SUBSIDENCE IS UNAVOIDABLE,IT SHALL BE

UNIFORM.UNIFORM. IT MUST ALSO ANCHOR THE BUILDINGS SUPERSTRUCTURE IT MUST ALSO ANCHOR THE BUILDINGS SUPERSTRUCTURE

AGAINST UPLIFTING N RACKING DUE TO WIND OR AGAINST UPLIFTING N RACKING DUE TO WIND OR EARTHQUAKE FORCES.EARTHQUAKE FORCES.

FOUNDATIONSFOUNDATIONS

LOADS ON FOUNDATIONLOADS ON FOUNDATION:: DEAD LOAD – FORCE DUE TO STATIC WEIGHT OF DEAD LOAD – FORCE DUE TO STATIC WEIGHT OF

ALL WALLS, PARTITIONS, FLOORS, ROOFS & ALL WALLS, PARTITIONS, FLOORS, ROOFS & FINISHES & ALL OTHER PARAMENT FINISHES & ALL OTHER PARAMENT CONSTRUCTION. CONSTRUCTION.

IMPOSED LOAD – LOAD ASSUMED TO BE IMPOSED LOAD – LOAD ASSUMED TO BE PRODUCED BY THE INTEATED USE OF BUILDING, PRODUCED BY THE INTEATED USE OF BUILDING, INCLUDING DISTRIBUTED, CONCENTRATED, INCLUDING DISTRIBUTED, CONCENTRATED, IMPACT, INERTIA AND SNOW. IMPACT, INERTIA AND SNOW.

WINDLOAD – EFFECTS OF WIND PRESSURE AND WINDLOAD – EFFECTS OF WIND PRESSURE AND SUCTION.SUCTION.

SIESMIC FORCES - DURING EARTHQUAKES.SIESMIC FORCES - DURING EARTHQUAKES.

Differing ground conditions, proximity of trees, backfilled land, Differing ground conditions, proximity of trees, backfilled land, soil types, proximity of drains, wind speeds,  all dictate the form soil types, proximity of drains, wind speeds,  all dictate the form our foundation work will take.our foundation work will take.

FOUNDATION SYSTEMS CAN BE CATOGORIZED IN BASIC 3 FOUNDATION SYSTEMS CAN BE CATOGORIZED IN BASIC 3 CATEGORIES ACCORDING TO THE GEOMETRIC ANALYSIS CATEGORIES ACCORDING TO THE GEOMETRIC ANALYSIS OF POINT, LINE AND PLANE. OF POINT, LINE AND PLANE.

POINT SYSTEM:- ISOLATED FOUNDATION POINT SYSTEM:- ISOLATED FOUNDATION

LINE SYSTEM:- STRIP FOUNDATION LINE SYSTEM:- STRIP FOUNDATION

PLANE SYSTEM:- RAFT FOUNDATION PLANE SYSTEM:- RAFT FOUNDATION THIS CHOICE ALSO EFFECT THE POTENTIAL FORM OF THE THIS CHOICE ALSO EFFECT THE POTENTIAL FORM OF THE

SUPERSTRUCTURE.SUPERSTRUCTURE. THIS IS TO UNDERSTAND THE INNOVATIONS IN THIS IS TO UNDERSTAND THE INNOVATIONS IN

FOUNDATION SYSTEMS.FOUNDATION SYSTEMS.

CLASSIFICATION OF FOUNDATION SYSTEMCLASSIFICATION OF FOUNDATION SYSTEM

TYPES OF FOUNDATION:- SHALLOW FOUNDATIONS (d<w): FOOTINGS(ISOLATED) STRIP FOOTINGS RAFTS, COMBINED,CANTILEVER,ECENTRIC. DEEP FOUNDATIONS (d>w): PILE

SELECTION OF A TYPE

* STEEL REINFORCEMENT IS REQUIRED WHEN FOOTING PROJECTS MORE THAN HALF OF FOUNDATION WALL THICKNESS & BECOME SUBJECT TO BENDING.

* THICKNESS OF CONCRETE SHOULD NOT BE LESS THAN THE PROJECTION TO AVOID SHEAR FAILURE.

* REINFORCEMENT SHOULD BE PROVIDED IN THE UNDERSIDE OF THE FOOTING.FACTORS AFFECTING FOUNDATION :-* LOAD * SOIL * WATER* FROST

GENERAL CRITERIA FOR DESIGN OF A FOOTING :

(THICKNESS, WIDTH, PROJECTION)

TYPES OF FOUNDATIONSTYPES OF FOUNDATIONS

ISOLATED FOOTINGISOLATED FOOTING COMBINED FOOTINGCOMBINED FOOTING ECCENTRIC FOOTINGECCENTRIC FOOTING CANTILEVER FOOTINGCANTILEVER FOOTING

ISOLATED FOOTINGISOLATED FOOTING ALSO KNOWN AS COLUMN FOOTING.ALSO KNOWN AS COLUMN FOOTING. IN CASE OF HEAVY LOADED COLUMNS, STEEL IN CASE OF HEAVY LOADED COLUMNS, STEEL

REINFORCEMENT IS PROVIDED IN BOTH THE DIRECTIONS IN REINFORCEMENT IS PROVIDED IN BOTH THE DIRECTIONS IN CONCRETE BED.CONCRETE BED.

THE FOOTING IS REINFORCED BOTH WAYS BY MEANS OF THE FOOTING IS REINFORCED BOTH WAYS BY MEANS OF MILD STEEL RIBBED BARS PLACED AT RIGHT ANGLES TO ONE MILD STEEL RIBBED BARS PLACED AT RIGHT ANGLES TO ONE ANOTHER AT EQUAL DISTANCES APART.ANOTHER AT EQUAL DISTANCES APART.

GENERALLY, 15cm OFFSET IS PROVIDED ON ALL SIDES OF GENERALLY, 15cm OFFSET IS PROVIDED ON ALL SIDES OF CONCRETE BED.CONCRETE BED.

8 CM THICK LAYER OF PLAIN CEMENT CONCRETE IS 8 CM THICK LAYER OF PLAIN CEMENT CONCRETE IS PROVIDED BEFORE REINFORCED CONCRETE FOOTING IS PROVIDED BEFORE REINFORCED CONCRETE FOOTING IS CONSTRUCTED OVER IT.CONSTRUCTED OVER IT.

AREAS OF USAGEAREAS OF USAGE IF A MASONARY WALL IS SUBJECTED TO A VERY HEAVY IF A MASONARY WALL IS SUBJECTED TO A VERY HEAVY

LOAD & BEARING CAPACITY OF THE SOIL ON WHICH LOAD & BEARING CAPACITY OF THE SOIL ON WHICH FOOTING IS TO REST IS VERY LOW, RCC FOOTING MAY BE FOOTING IS TO REST IS VERY LOW, RCC FOOTING MAY BE PROVIDED.PROVIDED.

SECTION

ISOLATED FOOTING

COMBINED FOOTINGCOMBINED FOOTINGA COMBINED FOOTING SUPPORTS TWO OR MORE COLUMNS IN A COMBINED FOOTING SUPPORTS TWO OR MORE COLUMNS IN

A ROW.A ROW. TYPES OF COMBINED FOOTINGTYPES OF COMBINED FOOTING RECTANGULARRECTANGULAR- USED WHERE BOTH COLUMNS CARRY - USED WHERE BOTH COLUMNS CARRY

EQUAL LOADS.EQUAL LOADS. TRAPEZOIDALTRAPEZOIDAL- USED- USED WHERE BOTH COLUMNS CARRY WHERE BOTH COLUMNS CARRY

UNEQUAL LOADS AS WELL AS THERE ARE SPACE UNEQUAL LOADS AS WELL AS THERE ARE SPACE LIMITATIONS.LIMITATIONS.

AREA OF USE:AREA OF USE: WHEN THE BASE OF THE COLUMN IS VERY NEAR TO THE SITE WHEN THE BASE OF THE COLUMN IS VERY NEAR TO THE SITE

BOUNDARY AND CANNOT SPREAD UNIFORMLY AROUND.BOUNDARY AND CANNOT SPREAD UNIFORMLY AROUND. WHEN FOUNDATIONS OF ADJACENT COLUMNS ARE LINKED WHEN FOUNDATIONS OF ADJACENT COLUMNS ARE LINKED TO RESIST UPLIFT,OVERTURNING OR OPPOSING FORCES.TO RESIST UPLIFT,OVERTURNING OR OPPOSING FORCES. AS A SUBSTITUTE TO ECCENTRIC FOOTING.AS A SUBSTITUTE TO ECCENTRIC FOOTING.

DESIGN OF FOOTINGDESIGN OF FOOTING

IN THE DESIGN OF FOOTINGS, THE FOOTING IS ASSUMED TO BE IN THE DESIGN OF FOOTINGS, THE FOOTING IS ASSUMED TO BE RIGID AND RESTING ON A HOMOGENEOUS SOIL.RIGID AND RESTING ON A HOMOGENEOUS SOIL.

AIMAIM THE LOCATION OF CENTRE OF GRAVITY OF COLUMN LOADS THE LOCATION OF CENTRE OF GRAVITY OF COLUMN LOADS

AND THE CENTROID OF FOOTING SHOULD COINCIDE SO THAT AND THE CENTROID OF FOOTING SHOULD COINCIDE SO THAT UNIFORM PRESSURE DISTRIBUTION TOOK PLACE.UNIFORM PRESSURE DISTRIBUTION TOOK PLACE.

• THE MAXIMUM BENDING MOMENT IS TAKEN AS THE DESIGN VALUE FOR THE RCC FOOTING & SHOULD BE CHECKED FOR MAXIMUM SHEAR AND BOND ETC.

COMBINED FOOTING

ECCENTRIC FOOTINGECCENTRIC FOOTING

(1) THE FOUNDATION MAY BE SUBJECTED TO ECCENTRIC LOAD (1) THE FOUNDATION MAY BE SUBJECTED TO ECCENTRIC LOAD UNDER THE FOLOWING CIRCUMSTANCES;UNDER THE FOLOWING CIRCUMSTANCES;

(A)(A) WHEN A WALL OR COLUMN IS SITUATED AT THE PROPERTY LINE, WHEN A WALL OR COLUMN IS SITUATED AT THE PROPERTY LINE, ITS FOUNDATION CANNOT BE EXTANDED BEYOND THE ITS FOUNDATION CANNOT BE EXTANDED BEYOND THE PROPERETY LINE THUS RESULTING ECCENTRIC LOAD ON THE PROPERETY LINE THUS RESULTING ECCENTRIC LOAD ON THE FOUNDATIONFOUNDATION

(B)(B) CANTILIVER BALCONIES, BRACKETS, ETC ATTACHED TO THE CANTILIVER BALCONIES, BRACKETS, ETC ATTACHED TO THE WALLS OR COLUMNS BENDING MOMENT IN THEM AND THUS WALLS OR COLUMNS BENDING MOMENT IN THEM AND THUS CAUSE ECCENTRIC LOADING ON THE FOUNDATIONCAUSE ECCENTRIC LOADING ON THE FOUNDATION

ECCENTRIC LOADS CAUSE UNEVENECCENTRIC LOADS CAUSE UNEVENDISTRIBUTION OF PRESSURE ON DISTRIBUTION OF PRESSURE ON THE SOIL BELOW THE FOUNDATION. THE SOIL BELOW THE FOUNDATION. IF ECCENTRICITY IS SMALL,IF ECCENTRICITY IS SMALL,ALTHOUGH DITRIBUTION OF THE ALTHOUGH DITRIBUTION OF THE SOIL WILL BE VARYIN, BUT IT WILL SOIL WILL BE VARYIN, BUT IT WILL REMAIN COMPRESSIVE. IN THIS CASE, REMAIN COMPRESSIVE. IN THIS CASE, IT SHOULD BE ENSURED THAT THE IT SHOULD BE ENSURED THAT THE

MAXIMUM INTENSITY OF PRESSURE SHOULD NOT BE MAXIMUM INTENSITY OF PRESSURE SHOULD NOT BE MORE THEN THE SAFE BEARING CAPACITY OF SOIL. IF MORE THEN THE SAFE BEARING CAPACITY OF SOIL. IF ECCENTRICITY OF THE LOAD IS QUITE LARGE, IT IS JUST ECCENTRICITY OF THE LOAD IS QUITE LARGE, IT IS JUST POSSIBLE THAT WALL OR COLUMN MAY EVEN OVERTURN. POSSIBLE THAT WALL OR COLUMN MAY EVEN OVERTURN. FOLLOWING ARE SOME OF THE METHODS WHICH CAN BE FOLLOWING ARE SOME OF THE METHODS WHICH CAN BE USED TO ENSURE THE STABLITY OF THE WALL OR USED TO ENSURE THE STABLITY OF THE WALL OR

COLUMN WITHOUT ENCROACHING THE AREA BEYOND THE COLUMN WITHOUT ENCROACHING THE AREA BEYOND THE LIMIT OF PROPERTY LINE.LIMIT OF PROPERTY LINE.

(2)(2) OFFSETTING THE FOOTING-OFFSETTING THE FOOTING- IN THE CASE OF THE IN THE CASE OF THE BOUNDARY WALL, FOOTING IS PROVIDED WITH OFFSET BOUNDARY WALL, FOOTING IS PROVIDED WITH OFFSET ON THE INSIDE OF THE WALL ONLY, WHEREAS THE OUTER ON THE INSIDE OF THE WALL ONLY, WHEREAS THE OUTER FACE IS MAINTAINED FLUSH WITH THE BOUNDARY LINE, FACE IS MAINTAINED FLUSH WITH THE BOUNDARY LINE, RIGHT UPTO THE BOTTOM OF THE FOUNDATION. THE LINE RIGHT UPTO THE BOTTOM OF THE FOUNDATION. THE LINE OF ACTION OF LOAD WILL BE AWAY FROM THE CENTRE OF OF ACTION OF LOAD WILL BE AWAY FROM THE CENTRE OF THE FOOTING.THE FOOTING.

(3)(3) THE PRESSURE DISTRIBUTION IN THIS CASE WILL BE THE PRESSURE DISTRIBUTION IN THIS CASE WILL BE SUCH THAT MAXIMUM PRESSURE INTENSITY WILL BE AT SUCH THAT MAXIMUM PRESSURE INTENSITY WILL BE AT THE OUTER FACE THE OUTER FACE AA OF THE FOOTING AND MINIMUM AT OF THE FOOTING AND MINIMUM AT THE INNER FACE THE INNER FACE BB OF THE FOOTING. OF THE FOOTING.

(4) MASONRY STRUCTURE ARE NEVER ALLOWED TO DEVELOP TENTION AND AS SUCH, THE WIDTH OF FOOTING IS SO

PROPORTIONED THAT THE C.G. OF THE LOAD REMAINS WITHIN MIDDLE OF THE BASE OF THE WALL FOOTING SO THAT NO TENTION IS DEVELOPED ANYWHERE IN THE FOUNDATION. IT IS ALSO SEEN BY SIDE THAT INTENSITY OF PRESSURE AT POINT A DOES NOT EXCEED THE SAFE PERMISSIBLE VALUE OF THE SOIL.

(5) BY PROVIDING STRAP FOOTINGS. THE OFFSETTING METHOD DESCRIBED ABOVE IS APPLICABLE ONLY IN THE CASE OF HARD SOILS. THIS METHOD IS NOT SUTIABLE WHEN FOUNDATION SOIL IS SOFT AND LOAD TO BE TRANSMITTED IS HEAVY AS INTENSITY OF MAXIMUM PRESSURE DEVELOPED BELOW THE FOUNDATION WILL BE EXCEEDED, THE SAFE BEARING CAPACITY OF THE SOFT UNDERLYING SOIL. UNDER SUCH CIRCUMSTANCES STRAP BEAM FOOTING MAY BE ADOPTED.

IN THIS CASE,LOAD ON THE OUTERCOLUMN SITUATED AT IN THIS CASE,LOAD ON THE OUTERCOLUMN SITUATED AT BOUNDARY LINE IS BALANCED BY THE LOAD ON THEINNER BOUNDARY LINE IS BALANCED BY THE LOAD ON THEINNER COLUMN THROUGH A CANTILEVER BEAM ACTING ABOUT A COLUMN THROUGH A CANTILEVER BEAM ACTING ABOUT A FULCRUM. FULCRUM.

THIS TYPE OF FOOTING CAN BE CONTRUCTION IN THIS TYPE OF FOOTING CAN BE CONTRUCTION IN R.C.C.R.C.C. OR OR STEEL GRILLAGE. IF INTERIOR COLUMN CANNOT BE STEEL GRILLAGE. IF INTERIOR COLUMN CANNOT BE PROVIDED, A HEAVY CONCRERE BLOCK MAY BE PROVIDED, A HEAVY CONCRERE BLOCK MAY BE CONSTRUCTED TO NECESSARY LEVERAGE TO SUPPORT THE CONSTRUCTED TO NECESSARY LEVERAGE TO SUPPORT THE LOAD ON THE OUTER WALL.LOAD ON THE OUTER WALL.

CANTILEVER FOOTINGCANTILEVER FOOTING

USED WHERE THE DISTANCE BETWEEN THE COLUMNS IS SO GREAT THAT A COMBINED TRAPEZOIDAL FOOTING BECOMES QUITE NORROW WITH HIGH BENDING MOMENT

THE STRAP BEAM DOES NOT REMAIN IN CONTACT WITH THE SOIL;SO A STRAP DOES NOT TRANSFER ANY PRESSURE TO SOIL HOWEVER,BECAUSE THE STRAP IS INFINITELY STIFF,HENCE IT SERVES TO TRANSFER COLUMN LOADS ON TO THE SOIL WITH EQUAL AND UNIFORM SOIL PRESSURE UNDER BOTH FOOTING

CANTILEVER\STRAP FOOTINGCANTILEVER\STRAP FOOTING

TYPES OF FOUNDATION FAILURESTYPES OF FOUNDATION FAILURES : : OVERSTRESSING OF SOIL: OVERSTRESSING OF SOIL: IF THE SOIL IS OVERSTRESSED, IF THE SOIL IS OVERSTRESSED,

IT MAY LEAD TO A SHEAR FAILURE RESULTING IN THE SLIDING IT MAY LEAD TO A SHEAR FAILURE RESULTING IN THE SLIDING OF THE SOIL ALONG A PLANE OF RUPTURE AND THUS RESULT OF THE SOIL ALONG A PLANE OF RUPTURE AND THUS RESULT IN THE COLLAPSE OF THE STRUCTURE. IN THE COLLAPSE OF THE STRUCTURE.

TILTING OF STRUCTURE:TILTING OF STRUCTURE: IF THE FOUNDATION AREA OF A IF THE FOUNDATION AREA OF A STRUCTURE IS SUCH THAT THE CENTRE OF GRAVITY OF THE STRUCTURE IS SUCH THAT THE CENTRE OF GRAVITY OF THE LOADS DOES NOT COINCIDE (IN PLAN) WITH THE CENTRE OF LOADS DOES NOT COINCIDE (IN PLAN) WITH THE CENTRE OF GRAVITY OF THE FOUNDATION AREA THE CONSEQUENT GRAVITY OF THE FOUNDATION AREA THE CONSEQUENT BEARING ACTION WILL BE NON UNIFORM. AT THE EDGE BEARING ACTION WILL BE NON UNIFORM. AT THE EDGE CLOSER TO THE CENTRE OF THE GRAVITY OF THE LOADS THE CLOSER TO THE CENTRE OF THE GRAVITY OF THE LOADS THE PRESSURE INTENSITY WILL BE HIGHER RESULTING IN A PRESSURE INTENSITY WILL BE HIGHER RESULTING IN A GREATER SETTLEMENT OF THE SOIL AT THIS EDGE.GREATER SETTLEMENT OF THE SOIL AT THIS EDGE.

SETTLEMENT: SETTLEMENT: TO ENSURE UNIFORM SETTLEMENT,IT IS TO ENSURE UNIFORM SETTLEMENT,IT IS NECESSARY THAT THE FOUNDATION AREA IS SO PROVIDED, NECESSARY THAT THE FOUNDATION AREA IS SO PROVIDED, THE INTENSITY OF SOIL REACTION IS THE SAME UNDER ALL THE INTENSITY OF SOIL REACTION IS THE SAME UNDER ALL THE FOOTINGS OF A STRUCTURE. THE FOOTINGS OF A STRUCTURE.

DIFFERENTIAL SETTLEMENTDIFFERENTIAL SETTLEMENT:: IN PRACTICE, THERE ARE IN PRACTICE, THERE ARE VARIOUS POSSIBLE GROUND MOVEMENTS VARIOUS POSSIBLE GROUND MOVEMENTS UNDER THE FOUNDATION OF A BUILDING THAT MAY CAUSE UNDER THE FOUNDATION OF A BUILDING THAT MAY CAUSE ONE PART OF THE FOUNDATION TO SETTLE AT A DIFFERENT ONE PART OF THE FOUNDATION TO SETTLE AT A DIFFERENT RATE AND TO DIFFERENT EXTENT THAN ANOTHER PART OF RATE AND TO DIFFERENT EXTENT THAN ANOTHER PART OF FOUNDATION. THIS MUST BE LIMITED TO AVOID DAMAGE TO FOUNDATION. THIS MUST BE LIMITED TO AVOID DAMAGE TO SUPER STRUCTURE.SOME STRUCTURAL FORMS SUPER STRUCTURE.SOME STRUCTURAL FORMS ACCOMMODATE DIFFERENTIAL FOUNDATION MOVEMENT ACCOMMODATE DIFFERENTIAL FOUNDATION MOVEMENT WITHOUT DAMAGE MORE THAN OTHERS.WITHOUT DAMAGE MORE THAN OTHERS.E.G. A BRICK WALL CAN ACCOMMODATE LIMITED E.G. A BRICK WALL CAN ACCOMMODATE LIMITED DIFFERENTIAL MOVEMENT OF THE FOUNDATION OR THE DIFFERENTIAL MOVEMENT OF THE FOUNDATION OR THE STRUCTURE BY SLIGHT MOVEMENT OF THE SMALL BRICK STRUCTURE BY SLIGHT MOVEMENT OF THE SMALL BRICK UNITS & MORTAR JOINTS, WHERE AS A RIGID FRAMED UNITS & MORTAR JOINTS, WHERE AS A RIGID FRAMED STRUCTURE CAN’T TO THE SAME EXTENT.STRUCTURE CAN’T TO THE SAME EXTENT. SO, FOUNDATIONS ARE DESIGNED TO LIMIT DIFFERENTIAL SO, FOUNDATIONS ARE DESIGNED TO LIMIT DIFFERENTIAL SETTLEMENT.SETTLEMENT.

OVERTURNING OF SUPERSTRUCTURE

SLIDING OF SUPERSTRUCTURE :

THANK YOUTHANK YOU

PRESENTED BY:PRESENTED BY: CHAITANYACHAITANYA K.V ABHISHEKK.V ABHISHEK SHIVIKA SINGHSHIVIKA SINGH SHIREEN JAMALSHIREEN JAMAL