Foundation Week3

7/30/2019 Foundation Week3

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2. FOUNDATIONS

By- Kokebe Yifru -Adama University Department of Civil Engineering & Arc- 20010/2011


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2. FOUNDATIONS2.1 Introduction2.1 Introduction| All engineered construction resting on the earth

must be carried by some kind of interfacingelement called a foundation.

| The foundation is the part of an engineeredsystem that transmits to, and into, theunderlying soil or rock the loads supported bythe foundation and its self-weight.


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2. FOUNDATIONS2.1 Introduction2.1 Introduction

| The term superstructure is commonlyused to describe the engineered part of the

system bringing load to the foundation, orsubstructure.


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2. FOUNDATIONS

A building has two basic parts A building has two basic parts|| SubSub --structurestructure|| SuperSuper --structurestructure

| A FOUNDATIONFOUNDATION is a part of a building whichis in direct contact with the ground to support

the weight of the building and other loads andtransmits the loads to underlying soil or rock.

What are the Loads on a building?What are the Loads on a building?


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2. FOUNDATIONS


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2.2 FUNCTION OF

FOUNDATION


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2.2 FUNCTION OF

FOUNDATIONFoundations have the following purposes:

1.

Even distribution of load of the structure over alarge bearing area so as to bring the intensity

of loading within the safe bearing capacity of the foundation soil .

2. To Load the bearing surface at a uniform rate soas to prevent unequal settlement


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2.2 FUNCTION OF

FOUNDATIONpurposes:-

3 . For Lateral stability of the structure

4. For Provision of level and firm bed

5. To Increases the stability of the structure asa whole.


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2.3 ESSENTIALREQUIREMENTS OF GOOD

FOUNDATION


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2.3 ESSENTIAL REQUIREMENTS OFGOOD FOUNDATION

Good Foundations:Good Foundations: --

1.1.

Shall be constructed toShall be constructed to Sustain the loadsSustain the loads

( dead & imposed ) and to( dead & imposed ) and to transmittransmit

to the subto the sub

soil safely.soil safely.

2.2.

The base shouldThe base should be rigidbe rigid to prevent differentialto prevent differentialsettlements.settlements.


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2.3 ESSENTIAL REQUIREMENTS OFGOOD FOUNDATION

Good Foundations:Good Foundations: --

3. Should be taken sufficiently deep to3. Should be taken sufficiently deep to guard theguard thebuildingbuilding

against damage or disaster caused byagainst damage or disaster caused by

swelling or shrinkage of the subswelling or shrinkage of the sub --soil.soil.

4. Should be erected in an exact position & well4. Should be erected in an exact position & well

built tobuilt to withstand unexpected naturalwithstand unexpected natural

calamitiescalamities ..


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2.3 ESSENTIAL REQUIREMENTS OFGOOD FOUNDATION CONT

The selection of foundation type depend onThe selection of foundation type depend on

a number of factors which include:a number of factors which include:

|| Nature of the soilNature of the soil|| Size and weight of the structureSize and weight of the structure|| Variation of ground water level Variation of ground water level

(due to season); and(due to season); and|| Building lawsBuilding laws


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2.4 TYPES OF FOUNDATION


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2.4 TYPES OF FOUNDATION

Foundations may be broadly classifiedFoundations may be broadly classified

|| Shallow foundations, andShallow foundations, and|| Deep foundations.Deep foundations.

|| A foundation A foundation isis ShallowShallow if its depth is equal to orif its depth is equal to orless than its width.less than its width.

|| Deep foundationsDeep foundations , the depth is greater than its, the depth is greater than itswidth. (width. ( TerzaghiTerzaghi ))


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SHALLOW FOUNDATIONSSHALLOW FOUNDATIONS CONT..Type of SF from the design point of viewType of SF from the design point of view

1)1) CombinedCombined

footingfooting2)2) SpreadSpread

footingfooting

|| Strip Footing for wallStrip Footing for wall|| Pad FootingPad Footing --isolatedisolated

for columnfor column

3)3) StrapStrap footingfooting4)4) MatMat

foundationfoundation


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SHALLOW FOUNDATIONSSHALLOW FOUNDATIONS

CONT..1)1)

CombinedCombined

FootingFooting

Reinforced concrete combinedfootings carry more thanone column load .

Are often Rectangular or trapezoidal(for unequal load) in plan view.

1)1)

Combined footingCombined footing


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SHALLOW FOUNDATIONSSHALLOW FOUNDATIONS CONT..

2)2) SpreadSpread

footingfooting

(open trench foundation)(open trench foundation)

a)a)

Strip Footing for wallStrip Footing for wall| Used for load-bearing walls.| Are usually long reinforcedconcrete members of uniformwidth and shallow depth.


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2)2) SpreadSpread

footingfooting

b) Pad Footingb) Pad Footing --isolated for columnisolated for column| ~ Spread footings are often square in plan view,

are of uniform reinforced concrete thickness, and

are used to support a single column load locateddirectly in the center of the footing.


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3) Strap3) Strap

footing (cantilever footing)footing (cantilever footing)

If two independent footings of twocolumns are connected by a beam| May be used where the distanceb/n

the columns is so great that

a combined footing is not used.| And, Near property lineN.B-

strap beam does not remain in

Contact with soil. But, serve to transferthe column loads with equal and uniformsoil pressure under both footings.


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SHALLOW FOUNDATIONSSHALLOW FOUNDATIONS

CONT..

4)4) MatMat

foundationfoundation| A large and thick reinforced

concrete foundation, often of uniform thickness, that isContinuous and supports

the entire structure.

| Suitable where the ground

conditions are very poor andbearing capacity of the soil is

so low that individual spread

footings can not be provided.


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FOUNDATIONSFOUNDATIONS

Assignment

1. Name the different types of foundations you

recommend under different situations and thesoil. Explain them briefly. (max 10 pages)

Summary

By Group 2


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Thank You!!

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Foundation Week3