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Behavior of

Concrete ColumnsConned by FRPFATIMA KHAI!C"#$%$&'($)#'($*

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Overview

• Introduction to FRP

•+tructural A,,lications

•

Parameters•Column Connement

•Models

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Why Columns needConfnement?•confne the concrete core toprovide increased strength

and sucient deormability(ductility)

• The confnement

reinorcement was developedso that the compressivestrength o the confned core

o a column ater spalling

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Ways o columnconfnement•"einorced Concrete Cage

•#teel $ac%ets

•&"' Wraps

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Fibres

Provide strength

and stiffness

Carbon, glass, aramid

Matrix

Protects and transfers load

between fibres

Epoxy, polyester, vinyl ester

Fibre MatrixComposite

Creates a material with attributes superior to either component alone!

What is &"'?

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What is &"'?

•Fibre#reinforced,lastic (FRP) is a compositematerial made o flaments ohigh perormance fbers suchas glass carbon and *evlarthat are woven into a abricthen saturated in an epo+ymatri+ and bonded to the

concrete substrate!

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,dvantages•

 Typical fber tensile strength rangesrom -.. to /.. %si!

• The specifc gravity o the fbers isabout one fth that o steel!

• 0igh1strength and lightweight abrics

• 2ot prone to electrochemical corrosion

• 3asily installable

• 4ess labor intensive• 0ighly durable

• 5t is available in various si6es

geometry and dimensions

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+tructural a,,lications

• &"' can be applied to strengthenthe beams- columns- and slabs obuildings and bridges!

• 5t is possible to increase the strength ostructural members even ater they havebeen severely dama/ed dueto loading conditions!

• Two techniues are typically adopted or the

strengthening o beams relating to thestrength enhancement desired7 0e1uralstren/thenin/ or shear stren/thenin/2

• Columns are typically wrapped with &"'

around their perimeter as with closed or

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Type Application Schematicibre ir"

Confinement Aroundcolumn

Circumferential

Section

Shear Side face ofbeam #u$wrap%

Perpendicularto long" axis

of beam   Section

lexural side face ofTension and&or

beamaxis of beamAlong long"

Section

+tren/thenin/ a,,lications

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&"' column wrapping• 5mprovements in ductility actors o up to $(

fold have been achieved through the use o &"'column wrapping!

• The ma8ority o structural defciencies in e+isting

concrete columns can be attributed to lac% otransverse reinorcement!

• Columns with insucient transversereinorcement su9er:

•

 i) premature shear ailure•  ii) brittle crushing o unconfned concrete and

• iii) reinorcement splice ailure i thelongitudinal reinorcement is spliced at or near

a potential plastic hinge region!• &"' sheets rovide an e+cellent o ortunit to

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CO2T;<• The wrap is made o layers o fbres! 3ach layer

may have the fbres oriented in multipledirections to protect the column rom reversecyclic loading or other loadings due to seismic

activity!• The &"' wrap method also protects the "C

column rom the =e+ural plastic hinge ailuremode!

• Continuous fbres wrap helps prevent concretespalling and provides lateral support to the steellongitudinal reinorcements!

• The wrap acts as a 8ac%et around the columnproviding support in all the principal load

directions! The wrap also does not have 8oints or

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'arameters

• #ti9ness o the confnement

• #hape o the section

• Concrete strength

• Type o fbre and resin

• The number o layers

• &iber volume and fber orientation in

the 8ac%et• $ac%et thic%ness

• The interace bond between the coreand the 8ac%et

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;i9erent

#tudies

• >a+imum gain in

strength whencolumns are ullywrapped along thelength or @Ard o the

length

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• 'P properties

#versus steel%(

•

)inear elastic behaviorto failure

• *o yielding

• +igher ultimate strength

• )ower strain at failureStrain [%]

1 2 3

500

1000

1500

2000

2500

    S   t   r   e   s   s    [    M    P   a

    ]

Steel

CFRP

GFRP

&"' >aterials

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Circular Column #uare Column

   $    l  a  y  e  r

   '    l  a  y  e  r

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Confinement all around Confinement only in some areas

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•

'P sheets can be wrapped around concrete columns toincrease strengt! load capacity, deformation capability

• +ow it wors(

Concrete

shortens-

-and dilates-

-'P confines

the concrete-

fl frp

-and places it in

triaxial stress-

.nternal reinforcing steelConcrete

'P wrap

Column #trengthening

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• /ased on e0uilibrium, the lateral confinementpressure exerted by the 'P, flfrp(

flfrp   " 1 *bφfrp ffrpu tfrp

g

*b 2 number of 'P layers

φfrp 2 material resistance factor for 'P

ffrpu 2 ultimate 'P strength

tfrp 2 'P thicness

Column #trengthening

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• The benefit of a confining pressure is to increase

the confined  compressive concrete strengt, f3cc

f3cc 2 f3c 4 5 fl frp

f3c 2 ultimate strength of unconfined concrete

5 2 empirical coefficient from tests

Column #trengthening

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f3cc 2 f3c 4 5 fl frp

#O>3 >O;34#

M4!" 5  $

"ichart et al (BAD) E!B

2ewman and 2ewman(B/B)

#aatcioglu and"6vi(B)

*arbhari and FaoGs(B/)

#amaan et al! (BD)

>iyauchi et al! (B) !D

#aaf et al! (B)

 Toutan8i (B)

M4!" 5  $

"ichart et al (BAD) E!B

2ewman and 2ewman(B/B)

#aatcioglu and"6vi(B)

*arbhari and FaoGs(B/)

#amaan et al! (BD)

>iyauchi et al! (B) !D

#aaf et al! (B)

 Toutan8i (B)

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Conclusion• The observed increase in concretecompressive strength o &"' wrapped columnas compared with the un8ac%eted columnranged rom BBA to B-H!

•

 The eciency o the small1scale suarespecimens is appro+imately /.H o that othe circular specimens

• Inia+ial compression tests on concrete1flled&"' tubes indicates that fbre composites arean e9ective means o confnement as theysignifcantly increase both strength andductility o concrete!

• #ignifcant increase in strength and ductility

o concrete can be achieved by carbon fbre