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26 Νοε 2013 (πριν από 3 χρόνια και 6 μήνες)

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THEORETICAL AND EXPERIMENTAL STUDY
OF
PRESTRESSED
CONCRETEBEAM’S
OF

PRESTRESSED
CONCRETE

BEAM’S

SUPPORT ZONE STRENGTHENED
WITH
FRP
COMPOSITES
WITH

FRP
COMPOSITES

Ö
NAG
Y
-GY
Ö
RGY Tamás
Lecturer, PhD
INTRODUCTIONINTRODUCTION
Shi
ih
FRP
i
i
idl
d
hd
f

S
trengt
h
en
i
ngw
i
t
h
FRP
compos
i
tes
i
saw
id
e
l
yuse
d
met
h
o
d
f
o
r
retrofittingorincreasingloadbearingcapacityofstructuralelements.
Applicabilityforreinforcedconcretememberswasdemonstratedfor
variousdomains,inthispaperbeingpresentedstudiesperformedon
dappedbeamendsstrengthenedindifferentmodes.

Theoreticalinvestigationwascarriedout,usingfiniteelement
analysisprogramsandstrut-and-tiemodels,whichwerefollowedby
experimentalinvestigationsonfourfullscalebeamends.
Objti
t
itit
th
ld
bi
it
f
th
b’

Obj
ec
ti
ves:
t
o
i
nves
ti
ga
t
e
th
e
l
oa
d
b
ear
i
ngcapac
it
yo
f
th
e
b
eam

s
supportzoneandtheeffectivenessoftheFRPstrengtheningused.
Dd
d
b
idl
d
i
t
t
bildi
RESEARCHRESEARCHSIGNIFICANCESIGNIFICANCE
D
appe
d
-en
d
b
eamsarew
id
e
l
yuse
d
i
nprecas
t
concre
t
e
b
u
ildi
ngs
andbridges,thusonespanelementsbeingsupportedon
columns,pylonsorlongitudinalbeams.
F
hi
f
b
h
idifid
fi
il
fil
d
RESEARCHRESEARCHSIGNIFICANCESIGNIFICANCE
F
o
r
t
hi
stypeo
f
b
eams,t
h
erewere
id
ent
ifi
e
d
fi
vepotent
i
a
l
f
a
il
uremo
d
es:
(1)
flexure (cantilever bending) and axial tension in the extended end
(2)
directshearatthejunctionbetweenthedappedand
undapped
zoneofthe
member
(2)
direct

shear

at

the

junction

between

the

dapped

and

undapped
zone

of

the

member
(3)
diagonal tension on the re-entrant corner
(4)
diagonal tension in the extended end and
(5)
diagonal tension in undappedzone
RESEARCHRESEARCHSIGNIFICANCESIGNIFICANCE
Theresearchprogramhasbeenperformedinthefollowingsteps:

predimensioninganddetailingtheelement,

numericalanal
y
siswithfiniteelementandstrut-and-tiemethods
,
y
,

experimentaltestingonfourdappedbeamendsstrengthenedwith
FRPcomposite

interpretingtheresultsandpreparingtheconclusions
DIMENSIONING DIMENSIONING AND DETAILING OF THE ELEMENT AND DETAILING OF THE ELEMENT
Preliminarydimensioninganddetailingofthestudieddappedbeam
endweremadeaccordingtotheRomaniancodesandverified
withthosefromEC2,
A
CI318andPCIDesignHandbook,in
ordertoattainthebearingcapacityof80t(800kN).

Beam’sheight-150cm,

Dappedzone80
/
80cm

䕬敭敮E
睩摴w
睡w



䕬敭敮E
睩摴w
睡w


.
DIMENSIONING DIMENSIONING AND DETAILING OF THE ELEMENT AND DETAILING OF THE ELEMENT
2 Ø
2 Ø
1-1
2-2
1
2
2 Ø
2 Ø
2 Ø
12 Ø
2 Ø
12 Ø
90
4 Ø
80
12 Ø
2 Ø
2 Ø
66
8 Ø
12
70
1
4 Ø
2 Ø
1 Ø
1 Ø
66
2 Ø
8 Ø
1 Ø
1 Ø
80
2
51
50
1 Ø
NUMERICAL ANALYSISNUMERICAL ANALYSIS
Inthetheoreticalmodel,therewereusedthecharacteristic
strengthsoftheconcreteandthesteelreinforcement.
We used three main methods for the analysis:
-
Elastic analysis using the AxisVMprogram
Nonlinearanalysisusingthe
Biograf
software
-
Nonlinear

analysis

using

the

Biograf
software
-
Strut-and-Tie models

It
fd
i
fiit
lt
AiVM
Th
Elastic Elastic AnalysisAnalysis

It
wasper
f
orme
d
us
i
ng
fi
n
it
ee
l
emen
t
program
A
x
i
s
VM
.
Th
erewere
obtainedthelevelandthedistributionofstressesinconcrete.Theload
levelcorrespondingtotheyieldinglimitinthehorizontalreinforcement
was
115
t
was
115
t
.

Nonlinear Nonlinear AnalysisAnalysis

It
fd
i
BIOGRAF
ft
lti
th
k
tt

It
wasper
f
orme
d
us
i
ng
BIOGRAF
so
ft
ware,resu
lti
ng
th
ecrac
k
pa
tt
ern
atdifferentloadlevels,thefailureloadandthecollapsemechanismofthe
element.Yieldinginthehorizontalreinforcementstartedattheloadlevel
of
90
t
of
90
t
.
StrutStrut--andand--Tie Tie ModelsModels
Duetothefactthatinourcasethesteelreinforcementwasknown,
theanalysiswasperformedtodeterminethemaximumforcein
theelementwhenthehorizontalbarsfromthedapped-endare
startingtoyield.Inthisassumption,therewereusedseveral
modelswhichcanapproximateaccuratelythestudiedzone.The
maximumforceatwhichthemosttensionedreinforcementstarted
toyieldwas94t.
NUMERICAL ANALYSISNUMERICAL ANALYSIS
ELASTIC (AXIS VM)
NON-LINEAR (BIOGRAF)
STRUT-AND-TIE

EXPERIMENTAL EXPERIMENTAL PROGRAMPROGRAM
Twodappedbeamswiththesamedimensionsandinternalreinforcement
weremanufactured;themid-spanwasover-reinforced.Beforecasting,
twostraingageswereaddednearlythere-entrantcorner,onetothe
hitl
ift
(S
1
)
d
th
th
t
th
til
ti
(S
2
)
h
or
i
zon
t
a
l
re
i
n
f
orcemen
t
(S
1
)
an
d
th
eo
th
e
r
t
o
th
ever
ti
ca
l
s
ti
rrup
(S
2
)
.
W
80
E
VIEW
O
NT VIE
W
70
7
0
175
100
SID
E
RC
FR
O
7
FLOOR
STRENGTHENING STRENGTHENING OF THE ELEMENTS OF THE ELEMENTS
S
CALE
D
-ENDS
C1 PRIOR TO FAILURE (REFERENCE)
C2
4 FULL
S
DAPPE
D
C3UP TO 800 KN(SERVICEABILITY)
C4
STRENGTHENING 3 SYSTEMS OF CFRP COMPOSITES

4R䕔剏䙉呔䥎ES佌啔䥏乓

4

剅呒但䥔呉乇

协䱕呉低S
䅉ATO INCREASE THE SERVICE LOAD BY 20%.
R
C1
/
R
C3

3LA奅剓
㌰䍍
坉䑅啎䥄䥒䕃呉低䅌䍁剂低
F
䥂剅
R

/

R


3

䱁奅剓




坉䑅

啎䥄䥒䕃呉低䅌

䍁剂低

F
䥂剅

F䅂剉A䅐偌䥅䐠低⁂佔䠠卉䑅匠䥎㐵뀯グ⼹グ䑉剅䍔䥏乓
R䌲 R䌴
10 CMWIDE CFRPPLATES
,
APPLIED IN45°
/
90°
,
,
,
RESPECTIVELY IN 0°/ 90°DIRECTION, ON BOTH SIDES
FRPFRPCOMPOSITE SYSTEMSCOMPOSITE SYSTEMS
SystemComponents
Tensile
Strength
[N/mm2]
Tensile
Modulus
[N/mm2]
Strain at
Failure
[‰]
SikW
230CFbi
4100
231000
17
System 1
(RC1)
Sik
a
W
rap
230C

F
a
b
r
i
c
4100
231000
17
SikaDur330 Resin303800-
St2
SikaCarboDurS1012Plate
2800
165000
17
S
ys
t
em
2
(RC2/
RC4)
Sika

CarboDur

S1012

Plate
2800
165000
17
SikaDur 30 Resin3012800-
System 3
(RC3)
SikaWrap 400C HiMod NW Fabric26006400004
SikaDur 300 Resin45350015
TEST RESULTS TEST RESULTS 
1
1ST
ST
PHASE
PHASE
Theelementsshowedasimilarbehaviourwithrespecttothe
maximumforceanddeflection.Thedesignvalueofthe
serviceabilit
y
limitstatewasof80t.
y
Forthisvalueoftheexperimentalload:
(a)thestresslevelrecordedinthereinforcementwas
comparableforalltheelements;
(b)
the
unloading
behaviour
was
similar
for
all
the
specimens
(b)
the
unloading
behaviour
was
similar
for
all
the
specimens
,
veryclosetotheinitialstartingpoint;
(c)itwasnotedagoodsimilaritybetweenthecrackpatternfor
ll
th
i
th
l
t
bi
idtil
a
ll
th
espec
i
mens,
th
egenera
l
aspec
t
b
e
i
ng
id
en
ti
ca
l
;
TEST RESULTS TEST RESULTS 
2
2ND
ND
PHASE
PHASE
C1/RC1C1/RC1
SpecimenC1wastestedclosetofailureandservedascontrolelement.
-Thefirstcrackstartedatanangleof60°,fromthere-entrantcornerandupto74t
didnotappearother.Thefinalcrackpatternwasuniformlydistributedaroundthere-
entrantcorner,asexpected.Thefirstcrackhadthemajo
r
width(approx.3.5mm).
-Themaximumdisplacementwas30mm,theremanentwas14mm.Straingages
attachedtoreinforcementdidnotfunction.Thepeakloadwas160t.
-
A
fte
r
that,thespecimenwasretrofittedandretested.
ThespecimenRC1hadalinearbehaviourupto160t,whentherewereobservedthefirst
fibreruptures.
-Themaximumreachedloadwas178tandafterthatitfollowedalongyieldinglevel
(approx.14mm)untilcollapse.Thefailurewasductile,producedbysuccessive
bki
f
th
b
fib
l
iil
k
d
t
d
t
fib
dbdi
b
rea
ki
ngo
f
th
ecar
b
on
fib
resa
l
ongapr
i
nc
i
pa
l
crac
k
an
d
no
t
d
ue
t
o
fib
re
d
e
b
on
di
ngo
r
delamination.
-Inthesametimeconcretecrushedinthecompressedzoneatthemaximumload.
The
maximum
displacement
was
35
mm
and
the
remanent
one
19
mm
The
strain
in
The
maximum
displacement
was
35
mm
and
the
remanent
one
19
mm
.
The
strain
in
fibresreachedthemaximumvalues.
180
TEST RESULTS TEST RESULTS 
2
2ND
ND
PHASE
PHASE
C1/RC1C1/RC1
100
120
140
160
180
D
[t]
V
20
40
60
80
LOA
D
C1
R
C
1
V
0
024681012141618202224262830323436
DISPLACEMENT [mm]
C
180
2
1
3
100
120
140
160
A
D [t]
G3 - RC1
G4 - RC1
G5 - RC1
G6 - RC1
V
0
20
40
60
80
LO
A
G4/G6
G3/G5
0
0246810121416182022
STRAIN [‰]
TEST RESULTS TEST RESULTS 
2
2ND
ND
PHASE
PHASE
C1/RC1C1/RC1
180
100
120
140
160
180
D
[t]
20
40
60
80
LOA
D
C1
R
C
1
0
024681012141618202224262830323436
DISPLACEMENT [mm]
C
Specimen
C
2
was
tested
up
to
80
t
TEST RESULTS TEST RESULTS 
2
2ND
ND
PHASE
PHASE
C2/RC2C2/RC2
Specimen
C
2
was
tested
up
to
80
t
.
-Thefirstcrackstartedata42°anglefromthere-entrantcornerandupto65titdid
notappearothers.Atthisloadleveltheredevelopedfourmajorcracks,buttheir
openingswerenotsignificant.
-Themaximumdisplacementwas6mm,theremanentwas2mm.Straingages
attachedtothesteelreinforcement(S1)indicated1.87‰,whichmeantthatitwasat
theyieldinglevel.Afterthatthespecimenwasretrofittedandretested.
ThespecimenRC2hadalinearbehaviourupto130t,when,besidesomecracks,it
developedacrackaroundtheinclinedplates,which,forasmallincreaseinload(143
t),determinedthepeeling-off.
Th
l
id
16
h
l
h
il
l
fild
hh
-
Th
ee
l
ementres
i
ste
d
upto
1
7
6
t,w
h
ena
l
sot
h
evert
i
ca
l
p
l
ates
f
a
il
e
d
t
h
roug
h
peeling-off.Thefailurewasbrittleatthemaximumdisplacementof20mm,the
remamentbeing5mm.
-Themaximummeasuredstraininsteelreinforcementwas2.59‰at148tand1.87
‰at116t,whichindicatedanincreaseofserviceloadby45%,comparedwiththe
samestrainlevelofthereferencespecimen(C2).
-Themaximumstrainincompositereached7‰,whichcorrespondto41%ofthe
com
p
osite’sultimatevalue.
p
200
TEST RESULTS TEST RESULTS 
2
2ND
ND
PHASE
PHASE
C2/RC2C2/RC2
100
120
140
160
180
A
D [t]
V
0
20
40
60
80
LO
A
RC2
C2
2
3
4
0
024681012141618202224262830323436
DISPLACEMENT [mm]
160
180
1
80
100
120
140
160
L
OAD [t]
S1 - C2
S1 - RC2
G3 - RC2
G4 - RC2
G5 - RC2
V
0
20
40
60
012345678
L
G
4
/G5
G3
S1
STRAIN [‰]
TEST RESULTS TEST RESULTS 
2
2ND
ND
PHASE
PHASE
C2/RC2C2/RC2
200
100
120
140
160
180
A
D [t]
0
20
40
60
80
LO
A
RC2
C2
0
024681012141618202224262830323436
DISPLACEMENT [mm]
TEST RESULTS TEST RESULTS 
2
2ND
ND
PHASE
PHASE
C3/RC3C3/RC3
SpecimenC3wastestedupto80t.
-Thefirstcrackstartedata45°anglefromre-entrantcornerandupto65titdidnot
appearothers.Afterthatfournewmajorcracksdeveloped,butwithoutsignificant
openings
openings
.
-Themaximumdisplacementwas5mm,theremanentwas0.5mm.Straingages
attachedtothesteelreinforcement(S1)indicate1.95‰,whichmeantthatitwasat
theyieldinglevel.Afterthat,thespecimenwasretrofittedandretested.
ThespecimenRC3hadalinearbehaviourupto90t,butstartingfrom64titwas
observedthecompositestepbystepfailurethroughaninclinedcrack,whichcouldbe
observedalsointheload-displacementcurve.Thecurveaspectisveryclosetothe
oneofC1specimen,withoutsignificantdifferencesover100t.
-Thestraingagesattachedtocompositewereoutofworkafter50t.However,
comparingthemaximumstraininsteelreinforcementsinC3at80twiththesame
levelinRC3
,
itcouldbeobservedanincreaseinserviceloadof25÷50
%
.
,
%
-ThemaximumloadandremanentdisplacementwereidenticalwiththeonefromC1.
Thefailurewasbrittle,producedbysuccessivebreakingofthecarbonfibresalongthe
principalcrack.
180
TEST RESULTS TEST RESULTS 
2
2ND
ND
PHASE
PHASE
C3/RC3C3/RC3
100
120
140
160
180
D
[t]
V
20
40
60
80
LOA
D
C3
RC3
V
0
024681012141618202224262830323436
DISPLACEMENT [mm]
180
S1-C4
2
1
3
80
100
120
140
160
O
AD [t]
S1

-

C4
S2 - C4
S1 - RC4
S2 - RC4
G3 - RC4
G4 - RC4
G5 - RC4
V
0
20
40
60
80
L
O
G4
G3
G
5
S1
012345
STRAIN [‰]
TEST RESULTS TEST RESULTS 
2
2ND
ND
PHASE
PHASE
C3/RC3C3/RC3
180
100
120
140
160
180
D
[t]
20
40
60
80
LOA
D
C3
RC3
0
024681012141618202224262830323436
DISPLACEMENT [mm]
TEST RESULTS TEST RESULTS 
2
2ND
ND
PHASE
PHASE
C4/RC4C4/RC4
SpecimenC4wastestedupto80tthefirstcrackstartedata46°anglefromre-entrant
cornerandupto60titdidnotappearothers.
-Afterthatfournewmajorcracksdeveloped,butwithoutsignificantopenings.The
maximumdis
p
lacementwas5mm
,
theremanentwassmalle
r
than0.5mm.
p
,
-Straingagesattachedtosteelreinforcement(S1)indicated1.44‰,consequently
wasatyieldinglevel.Afterthatthespecimenwasretrofittedandretested.
Th
i
RC
4
hd
li
bhi
t
98
t
h
it
d
th
fit
Th
espec
i
men
RC
4
h
a
d
a
li
nea
r
b
e
h
av
i
ou
r
up
t
o
98
t
,w
h
en
it
appeare
d
th
e
fi
rs
t
new
crack.At119tacrackdevelopedaroundthehorizontalplates.
-Theelementfailedat169tthroughdebondingofverticalplateswithanimmediate
peeling-offofthehorizontalplates.Thefailurewasbrittleatthemaximum
displacementof19mm,theremamentbeingove
r
6mm.
-Themaximummeasuredstraininsteelreinforcementwas3.78‰at153tand1.44
‰at100t,whichindicateanincreaseofserviceloadby25%,comparedwiththe
samestrainlevelofthereferences
p
ecimen
(
C2
)
.
p
(
)
-Themaximumstrainincompositereached6.72‰,whichcorrespondedto40%of
thecomposite’sultimatevalue.
180
TEST RESULTS TEST RESULTS 
2
2ND
ND
PHASE
PHASE
C4/RC4C4/RC4
100
120
140
160
180
D [t]
0
20
40
60
80
LOA
C4
RC4
4
3
0
024681012141618202224262830323436
DISPLACEMENT [mm]
180
1
2
4
3
80
100
120
140
160
O
AD [t]
S1 - C3
S1 - RC3
G3 - RC3
G4 - RC3
G5 - RC3
1
0
20
40
60
80
L
O
G4/G5
G3
S2
S1
012345678
STRAIN [‰]
TEST RESULTS TEST RESULTS 
2
2ND
ND
PHASE
PHASE
C4/RC4C4/RC4
180
100
120
140
160
180
D [t]
0
20
40
60
80
LOA
C4
RC4
0
024681012141618202224262830323436
DISPLACEMENT [mm]
TEST RESULTS TEST RESULTS 
FAILURE MODES
FAILURE MODES
V
V
V
2
1
3
1
2
3
4
2
1
3
1
2
4
3
V
V
V
CONCLUSIONSCONCLUSIONS
THEUSEDFRPSYSTEMSPROVEDTOBE
V
IABLEFORTHESE
KINDSOFAPPLICATIONS,INCREASINGTHESERVICELOADBY25%
FORRC3,40%FORRC4AND45%FORRC2
(COMPAREDWITHTHE
REFERENCE
STRAIN
IN
THE
STEEL
REINFORCEMENT
AT
800
KN
)
REFERENCE
STRAIN
IN
THE
STEEL
REINFORCEMENT
AT
800
KN
)

THEMAXIMUMLOADBEARINGCAPACITYOFTHEELEMENTS
INCREASED
BY
11
%
FOR
RC
1
10
%
FOR
RC
2
6
%
FOR
RC
4
AND
0
%
FOR
RC
3
INCREASED
BY
11
%
FOR
RC
1
,
10
%
FOR
RC
2
,
6
%
FOR
RC
4
AND
0
%
FOR
RC
3
.
Furtherincreaseoftheultimateloadsupplementingthefabriccross-
sectionalarea(RC1/RC3)andbyusinganchoragesforplates(RC2/RC4)
ELEMENTSSTRENGTHENEDWITHFABRICSFAILEDMORE
DUCTILECOMPAREDWITHTHEPLATESRETROFITTEDELEMENTS
THESTRENGTHENEDELEMENTSSHOW
A
DELAYINCRACKING,
THEFAILUREOCCURRINGBY
PEELING-OFFTHEHORIZONTALORINCLINEDPLATES
FIBRERUPTURE
A
LONGTHEMAINDIAGONALCRACKIN
THECASEOFFABRICSTRENGTHENING
CONTINUED
CONCLUSIONSCONCLUSIONS
WITHRESPECTTOTHEBASELINESPECIMEN(C1),THE
MAXIMUMDISPLACEMENTHADAVERYCLOSEVALUEFORFABRIC
RETROFITTEDELEMENTS,BUTADECREASEDVALUE,BYMORE
THAN30%,INTHECASEOFPLATERETROFITTEDELEMENTS
1800
V
2
1
3
1200
1500
]
RC1
V
V
1
2
3
4
600
900
LOAD [kN
]
RC1
RC2
RC3
RC4
C1
V
2
1
3
4
3
300
600
1
2
0
05101520253035
DISPLACEMENT [mm]
THANK YOUTHANK YOU
FOR YOUR KIND
FOR YOUR KIND
ATTENTION!
ATTENTION!
ATTENTION

!ATTENTION

!