Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
1
Du abili y o RC slabs s eng hened wi h p es essed CFRP lamina e s ips
1
unde di e en en i onmen al and loading condi ions
2
3
Luís Co eia
a
, José Sena-C uz
a*
, Julien Michels
b,c
, Paulo F ança
d
, Edua do Pe ei a
a
, Gonçalo Escusa
a
4
a
ISISE, Dep . o Ci il Enginee ing, Uni . o Minho, Azu ém, 4800-058 Guima ães, Po ugal 5
b
S uc u al Enginee ing Resea ch Labo a o y, Swiss Fede al Labo a o ies o Ma e ials Science and Technology 6
(Empa), Übe lands asse 129, 8600 Dübendo , Swi ze land 7
c
e- e AG, Oelis ase 6, 6440 B unnen, Swi ze land
d
CE is, ICIST and CCCEE, Uni e si y o Madei a, Colégio 8
dos Jesuí as, Po ugal 9
* co esponding au ho : e-mail: jsena@ci il.uminho.p ; el.: (+351) 253 510 200; ax.: (+351) 253 510 217 10
11
Abs ac : 12
O e he las decades, esea che s ha e been s udying ib e ein o ced polyme (FRP) ma e ials and hei 13
ad an ages in e o i ing o exis ing s uc u es. The ex e nally bonded ein o cemen (EBR) echnique is he mos 14
common p ac ice in imp o ing exis ing ein o ced conc e e (RC) s uc u es wi h ca bon FRP (CFRP) ma e ials. 15
In his ega d, se e al addi ional ad an ages ha e been epo ed o he use o p es essed CFRP ma e ials, mainly 16
s ips. Howe e , he expe ience wi h RC s eng hening using p es essed EBR-CFRP ma e ials is s ill limi ed. 17
Some conce ns ega ding he e iciency o he echnique s ill exis , especially he du abili y and he long- e m 18
beha iou . 19
This wo k aims a con ibu ing o he knowledge on du abili y o RC slabs s eng hened wi h p es essed 20
CFRP lamina e s ips acco ding he EBR echnique. The du abili y was s udied by exposing s eng hened RC 21
specimens o he ollowing en i onmen s o app oxima ely 8 mon hs: (i) e e ence en i onmen – specimens kep 22
in a clima ic chambe a 20 ºC; (ii) wa e imme sion in ank a 20 ºC o empe a u e; (iii) wa e imme sion in ank 23
wi h 3.5% o dissol ed chlo ides a 20 ºC o empe a u e; and (i ) we /d y cycles in a ank wi h a wa e empe a u e 24
o 20 ºC. Addi ionally, hal o he specimens we e subjec ed o sus ained loading a a load le el o 1/3 o he 25
ul ima e load, wi h he occu ence o c acking. A e he exposu e pe iod he slabs we e mono onically es ed up 26
o ailu e by using a ou -poin bending es con igu a ion. 27
The esul s showed ha he en i onmen al condi ions and he sus ained loading, sepa a ely o combined, 28
led in gene al o sligh losses o pe o mance and duc ili y. Al hough hese losses we e sub le, conside ing ha he 29
es s we e ca ied ou o 8 mon hs, clea indica ions a e gi en owa ds he impo ance o conduc ing simila es s 30
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
2
o longe pe iods. The esul s ob ained showed ha he p ocedu es implemen ed o assess he du abili y o he 1
s eng hening sys ems we e sensi i e o he mos ele an de e io a ion mechanisms and hei impac on he 2
mechanical p ope ies o he specimens. The e o e, hese p ocedu es may well con ibu e o he u u e 3
es ablishmen o s anda dized es p og ammes o he assessmen o he du abili y o p es essed CFRP 4
s eng hening sys ems. 5
6
Keywo ds: 7
EBR; du abili y; long- e m beha iou ; RC s uc u es. 8
9
1. In oduc ion 10
Fib e- ein o ced polyme s (FRP) ha e been used o s eng hen ein o ced conc e e (RC) s uc u es because o hei 11
nume ous ad an ages o e con en ional ma e ials, such as highe s eng h and a igue li e, less suscep ibili y o 12
co osion and g ea e esis ance agains agg essi e en i onmen s, as epo ed in he li e a u e [1-7]. Gene ally, he 13
Ca bon FRP (CFRP) ein o cemen ma e ials a e applied acco ding o he ex e nally bonded ein o cemen (EBR) 14
echnique. I he FRP ma e ial is p es essed, a g ea e po ion o i s ensile capaci y is u ilized, consequen ly he 15
use o i s p ope ies is mo e e ec i e. Se e al ad an ages o using p es essed FRPs o RC s uc u al 16
s eng hening ha e been epo ed in he li e a u e o e he las decades, such as he educ ion o c ack wid h and 17
de lec ion, as well as he inc ease o he ul ima e capaci y and o he esis ance o shea / a igue b i le ailu e [3, 18
6-9]. The FRP s ip can be di ec ly p es essed (i) agains he s uc u e i sel , (ii) agains an independen sys em o 19
i can be (iii) indi ec ly p es essed by cambe ing he s uc u e upwa d. P es essing agains he s uc u e i sel does 20
no equi e he use o hea y equipmen , which makes his me hod mo e e sa ile and iable o in si u applica ions. 21
Fo he case o (i) and (ii) special ancho age sys ems o ixing he ends o he p es essed FRP ein o cemen a e 22
equi ed. These end-ancho ages a e esponsible o ans e ing he shea s esses om he ein o cemen in o he 23
conc e e subs a e, allowing g ea e le els o p es essing, inc easing he elemen ’s duc ili y and a oiding he 24
p ema u e ailu e by FRP pealing-o [3, 7, 10]. Li e a u e al eady co e s se e al s udies on he sho - e m 25
beha iou o RC elemen s s eng hened wi h p es essed FRP whe e he ocus was on (i) he de elopmen o he 26
ancho age sys ems [1, 7, 11, 12] and on (ii) he se ice and ul ima e beha iou [7, 11, 13, 14]. Howe e , he 27
echnology is s ill ega ded as no el and some opics s ill dese e a en ion, such as he du abili y and long- e m 28
beha iou . 29
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
3
The unde s anding o he long- e m pe o mance and du abili y o e o i ed s uc u es is essen ial o 1
s uc u al sa e y. O he indus y sec o s (e.g. au omo i e, ma ine, indus ial and ae ospace) ha e been showing 2
success ul use o FRPs and epoxy adhesi es o mass p oduc ion o mechanical and s uc u al componen s. 3
Howe e hese esul s do no ind di ec ansla ion in o ci il in as uc u es applica ions, mainly because he e a e 4
c i ical di e ences in loading, en i onmen al exposu es and he speci ic ypes o ma e ial/p ocesses used in hese 5
applica ions [6]. Ex e nal ein o cemen may be subjec ed o a wide a ie y o en i onmen al condi ions such as 6
o ins ance mois u e cycling. The p esence o wa e in ma e ials like s eel, conc e e, epoxy esins and FRP 7
ma e ials can cause hei deg ada ion. In gene al, wi hin a CFRP/epoxy/conc e e sys em, conc e e is he weakes 8
link. Usually i s ensile s eng h go e ns he s uc u al ailu e by s ip debonding. Howe e , wi h he pene a ion 9
o a ious en i onmen al agen s (e.g. wa e ), ailu e mechanisms may change. Especially he beha iou o he 10
epoxy esin, which can conside ably in luence he o e all pe o mance o he s eng hening sys em. The abso p ion 11
o wa e by he epoxy esin may a y depending on i s deg ee o cu ing, s uc u e and empe a u e. The mois u e 12
up ake by he epoxy adhesi es can lead o physical and chemical al e a ions, leading o he educ ion o hei glass 13
ansi ion empe a u e and o hei plas iciza ion h ough hyd olysis (and consequen ly, o a educ ion o hei 14
s i ness and o hei ul ima e s eng h) [15]. Also he abso p ion o wa e by FRPs a he ib e-ma ix in e ace 15
leads o he deg ada ion o s eng h and consequen ly o he po en ial loss o s uc u al in eg i y. Fu he mo e, he 16
p esence o sal wa e can accele a e he de e io a ion p ocess due o he osmo ic p essu e e ec [6] . 17
An expe imen al s udy [16] on he e ec o mois u e and sal wa e (NaCl) on he du abili y o FRP-based 18
s eng hening sys ems has shown ha he maximum mois u e up ake by ca bon pul uded s ips is signi ican ly 19
lowe han in he we layup sys ems. The au ho s also s udied he bond pe o mance o FRP sys ems a e 2 yea s 20
o exposu e o i e en i onmen s including he imme sion in sal wa e and he imme sion in deionized wa e . 21
Resul s showed ha he imme sion in sal -wa e can p oduce highe educ ion on bond s eng h (65% o ca bon 22
pul uded s ips) han o he en i onmen al condi ions like imme sion in deionized wa e (38% o ca bon pul ude 23
s ips). 24
Om an and El-Hacha [17] conduc ed an in es iga ion on he assessmen o he e ec s o sus ained load 25
and eeze- haw cyclic exposu e (500 cycles) on he lexu al beha iou o eigh RC beams s eng hened wi h 26
p es essed CFRP s ips acco ding o he NSM echnique. The esul s showed ha he specimens exposed o he 27
combined e ec o eeze- haw cycles and sus ained loading (47% o he heo e ical ul ima e capaci y o a non-28
p es essed NSM beam) had an a e age dec ease in he yielding load, ul ima e load and duc ili y o 18%, 24% and 29
19%, espec i ely. The au ho s also obse ed ha , a e being subjec ed o he combined e ec o eeze- haw 30
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
4
cycling and sus ained loading, p es essed specimens ailed by s ip end debonding a he conc e e-epoxy in e ace. 1
S ip end debonding did no occu on non-p es essed beams. 2
The e ec o oom (22 °C) and low empe a u es (-28 °C) combined wi h sus ained load (50% o he 3
s eng hened beam capaci y) on p es essed EBR-CFRP RC beams was also s udied by El-Hacha e al. [18]. A 4
o al o eigh beams we e used in his expe imen al p og am ( ou pe s udied empe a u e: (i) one uns eng hened 5
con ol beam, (ii) one s eng hened beam, (iii) one s eng hened beam subjec ed o i s own weigh o one yea and 6
(i ) one s eng hened beam subjec ed o sus ained load o one yea ). The ollowing main conclusions we e 7
ob ained: (i) he s eng hening p oduced a conside able enhancemen in s i ness and s eng h; (ii) he isola ed 8
e ec o sus ained load had no impac on he beams ul ima e s eng h; (iii) he combined e ec o sus ained load 9
and low empe a u es educed he ul ima e s eng h o he beams by 8%. 10
Despi e he ecen esea ch de elopmen s on he du abili y and long- e m beha iou o p es essed RC 11
elemen s wi h FRPs, he e ec s o en i onmen al exposu e (imme sion in wa e , imme sion in wa e wi h chlo ides 12
o we /d y cycles wi h wa e ) on RC elemen s s eng hened wi h p es essed EBR CFRP lamina es was no ye 13
add essed by he scien i ic communi y. 14
The main objec i e o his esea ch is o s udy he e ec o di e en en i onmen al condi ions on he 15
du abili y o RC slabs s eng hened wi h p es essed CFRP lamina es acco ding o EBR echnique. Two di e en 16
ypes o ancho age sys ems we e s udied: (i) mechanical ancho age (MA), a sys em ha ixes he lamina e ends 17
wi h me allic pla es; and, (ii) g adien ancho age (GA), which uses he abili y o he epoxy o cu e as e a highe 18
empe a u es, allowing o g adually educe he p es essing o ce o e se e al consecu i e sec o s a he s ip end. 19
The expe imen al p og am is composed o wen y slabs, six een o which we e exposed o ou di e en 20
en i onmen al condi ions, along wi h g a i y loading o a pe iod o eigh mon hs. Then, specimens we e 21
mono onically es ed unde displacemen con ol up o ailu e by using a ou -poin bending es con igu a ion. 22
The obse ed pe o mance o he es ed RC slabs allowed se e al conclusions ega ding he du abili y and o e all 23
pe o mance o bo h ancho age sys ems. 24
25
2. Expe imen al In es iga ion 26
2.1. Expe imen al p og am, specimens and es con igu a ion 27
The expe imen al p og am included wen y ein o ced conc e e (RC) slabs as p esen ed in Table 1: (i) ou con ol 28
specimens (se ies T0); (ii) eigh slabs subjec ed o dis inc en i onmen al condi ions (labelled wi h he su ix _U); 29
and, (iii) eigh slabs subjec ed o he combined e ec o en i onmen al and loading condi ions (labelled wi h he 30
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
5
su ix _C). Loading and he exposu e o di e en en i onmen al condi ions las ed o app oxima ely eigh mon hs. 1
Fou dis inc en i onmen al condi ions we e conside ed: (i) specimens subjec ed o labo a o y p emises wi h a 2
con olled empe a u e o 20°C and ela i e humidi y o 55% (se ies REF and T0); (ii) specimens imme sed in ap 3
wa e a 20ºC (se ies TW); (iii) specimens imme sed in wa e a 20ºC wi h 3.5%
i
o chlo ides (se ies CW); and, 4
(i ) specimens subjec ed o we /d y cycles in ap wa e a 20ºC and wi hou chlo ides (se ies WD). As i is shown 5
in Table 1, all specimens a e labelled wi h a gene ic denomina ion: X_Y_Z, whe e X indica es he ype o 6
ancho age (MA o GA), Y s ands o he en i onmen al ac ion (REF, TW, CW and WD) and Z indica es he 7
c acking s a e when he specimen is i s exposed o he en i onmen al condi ion (U o unc acked and C o 8
c acked) o T0. 9
The geome y o he specimens and es con igu a ion a e p esen ed in Fig. 1. The RC slabs we e 2600 mm 10
long, wi h a c oss-sec ion o 600 mm (wid h) by 120 mm (heigh ). All slabs we e ein o ced wi h 5 s eel ba s o 11
8 mm o diame e (5Ø8) in he ension zone and 3Ø6 in he comp ession zone. The ans e se ein o cemen was 12
composed o closed s eel s i ups o Ø6 wi h 300 mm o longi udinal spacing. S eng hening was pe o med by 13
using 2200 mm long CFRP lamina e s ips wi h a ec angula c oss-sec ion o 1.2 mm by 50 mm. 14
In o de o assess he beha iou o all specimens in se ice and ul ima e design condi ions, mono onic 15
es s up o ailu e we e pe o med using a ou -poin bending scheme wi h he wo o ces imposed cen ally a a 16
dis ance o 300 mm om he mid-span sec ion (see Fig. 1). This con igu a ion esul ed in a shea span o 900 mm, 17
since he o al span is equal o 2400 mm. All es s we e ca ied ou wi h a se o-con olled equipmen unde 18
displacemen con ol a he a e o 1.2 mm/min o he ac ua o c oss-head displacemen . The ins umen a ion 19
included: (i) 5 linea a iable di e en ial ansduce s (LVDTs) o eco d he de lec ion along he longi udinal axis 20
o he slab; (ii) a minimum o 6 s ain gauges pe slab o measu e he s ain a ia ion in he CFRP lamina e, conc e e 21
and s eel ein o cemen ; (iii) one load cell o measu e he applied load (F). As shown in Fig. 1, LVDT2, LVDT3 22
and LVDT4 ( ange o ±75 mm and a linea i y e o o ±0.10%) we e placed in he pu e bending zone, whe eas 23
LVDT1 and LVDT2 ( ange o ±25 mm and a linea i y e o o ±0.10%) we e ins alled be ween he suppo s and 24
he applied load poin s. The load cell (maximum measu ing capaci y o 200 kN and a linea i y e o o ±0.05%) 25
i
In he p esen con ex , he pe cen age o chlo ides was de ined as he a io mass o he added NaCl in a cubic
me e o wa e .

Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
6
was placed be ween he ac ua o and he s eel de ice ha dis ibu ed he load in o wo equal pa s. TML BFLA-5-3 1
s ain gauges we e placed along he CFRP lamina e s ip and on he ensile s eel ein o cemen , whe eas 2
TML PFL-30-11-3L s ain gauges we e used o moni o s ains on he conc e e. SG1 and SG4 we e glued on he 3
lamina e nea he end ancho age (30 mm away om he pla e ancho – MA; 630 mm away om he ex emi ies 4
o CFRP lamina e – GA), SG2 was placed on he lamina e a mid-span and SG3 unde he applied load poin . 5
Specimens s eng hened wi h he GA sys em we e also moni o ed wi h wo ex a s ain gauges a he middle o 6
he ancho age zones (SG1’ and SG4’ nea SG1 and SG4, espec i ely). The conc e e s ain was assessed wi h a 7
s ain gauge (SG5) placed a mid-span on he op su ace, and he s eel ein o cemen s ain by means o ano he 8
s ain gauge (SG6) ixed in he ensile eba posi ioned in he middle o he c oss-sec ion, a mid-span. In addi ion, 9
c ack wid h e olu ion du ing es ing was measu ed h ough a handheld USB mic oscope (VEHO VMS-004D). 10
To documen he e olu ion o he p ocesses ha lead o he deg ada ion o he s eng hening e ec 11
p o ided by he CFRP lamina e, he bo om su ace o he specimens a which he lamina es we e inse ed was 12
analysed using a Digi al Image Co ela ion p ocedu e [19]. The lens used had an ape u e o 11 and he ocal 13
leng h was 36 mm. Led ligh s we e used o illumina e he su ace o he specimen. The came a senso was a ull 14
ame size, wi h 36 Mpix. Conside ing ha he p io i y was o ace he ini ia ion and p opaga ion o he c acks a 15
he ensioned ace o he specimens du ing es ing, he p incipal ensile s ain ields we e mapped using a ine ace 16
mesh. 17
18
2.2. Ma e ial cha ac e iza ion 19
Ma e ial cha ac e iza ion included he e alua ion o he mechanical p ope ies o he ma e ials in ol ed in his 20
expe imen al p og am, namely: conc e e, s eel, CFRP lamina e s ip and epoxy adhesi e. The eady-mixed 21
conc e e (g ade o C30/37) was p oduced based on he p opo ions o mixing componen s by weigh o 1: 2.95: 22
2.93: 0.02: 0.56 (cemen : ine agg ega e: coa se agg ega e: supe plas icize : wa e ). Agg ega es we e composed o 23
c ushed g ani e wi h a maximum size o 12.5 mm and Po land cemen ype CEM II/A-L 42,5R was used. A single 24
ba ch was mixed o cas all slabs and es ing samples. Fo cha ac e izing he mechanical p ope ies o he conc e e, 25
six cylind ical specimens wi h 300 mm o heigh and 150 mm o diame e we e used o each se ies. The modulus 26
o elas ici y and he comp essi e s eng h we e e alua ed 28 days a e cas ing ollowing he 27
LNEC E397-1993:1993 [20] and NP EN 12390-3:2011 [21] ecommenda ions, espec i ely. Addi ionally, he 28
modulus o elas ici y and he comp essi e s eng h we e also cha ac e ized a he ime when he s a ic es s o he 29
slabs up o ailu e occu ed (see Table 2). Resul s show he e olu ion o he modulus o elas ici y (E
c
) and he 30
comp essi e s eng h (
c
) o specimens in con ac wi h wa e (se ies TW, CW and WD), which is ela ed o he 31
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
7
p ocess o hyd a ion o he cemen [22]. When compa ing he specimens ully imme sed in wa e (se ies TW) wi h 1
he e e ence se ies (T0), an addi ional inc ease o 20% and 35% o he E
c
and
c
, espec i ely, we e obse ed. 2
S eel eba s o ype A400 NR SD wi h a diame e o 8 mm (∅8) and 6 mm (∅6) we e used as in e nal 3
ein o cemen . In o de o de e mine he ensile p ope ies o s eel ein o cemen , ou samples o each ba ype 4
we e used. Tensile es s we e ca ied ou acco ding o NP EN ISO 6892-1:2012 [23] ecommenda ions and he 5
esul s in e ms o mean alues o he modulus o elas ici y (E
s
), as well as yield (
y
) and ul ima e (
u
) ensile 6
s eng hs a e p esen ed in Table 2. 7
The pul uded CFRP lamina e s ips (Type: S&P Lamina es CFK) we e used in he expe imen al wo k. 8
These composi e lamina e s ips possess a smoo h ex e nal su ace and consis o unidi ec ional ca bon ib es ( ib e 9
olume con en is highe han 68%) held oge he by an epoxy inyl es e esin ma ix [24]. Tensile p ope ies 10
we e assessed using six samples and he expe imen al p ocedu e ollowed was he one desc ibed by ISO 527-11
5:1997 [25]. A Young’s modulus (E
) o 168 GPa and an ul ima e s eng h (
) o 2944 MPa we e ob ained (see 12
Table 2). 13
The wo-componen epoxy adhesi e (Type: S&P Resin 220) used o bond he CFRP lamina e o he 14
conc e e su ace is sol en ee, hixo opic and g ey. P e ious s udies ha e shown ha , a e 7 days o cu ing a 15
21 ºC, a modulus elas ici y o 8.7 GPa (CoV=6.0%) and a ensile s eng h o 20.7 MPa (CoV=11.0%) a e ob ained 16
[26]. 17
18
2.3. S eng hening p ocedu es 19
The expe imen al p og am included eigh een slabs s eng hened wi h a p es essed CFRP lamina e s ip. P es ess 20
was achie ed h ough he di ec p es essing me hod, in which he lamina e s ip may be jacked agains an ancho 21
sys em ha is moun ed on he slab i sel . Two ancho age sys ems we e s udied in his wo k: (i) he mechanical 22
ancho age (MA), which uses he me allic pla es a he end o he CFRP s ip; and, (ii) he g adien ancho age (GA), 23
in which a non-me allic ancho age is c ea ed due o he adhesi e’s abili y o cu e as e a highe empe a u es. 24
Bo h sys ems a e comme cially a ailable and ha e been applied on si e o s eng hen se e al RC s uc u es, being 25
a ailable by he same manu ac u e company o he CFRP ein o cemen and epoxy adhesi e. As shown in Fig. 2 26
and Fig. 3, he MA and GA me hods in ol e he use o common componen s (clamp uni s, guides, aluminium 27
ame, hyd aulic jack and hoses, and a manual hyd aulic pump) and speci ic componen s. Fo ins ance, he me allic 28
ancho pla e is a ha d-aluminium ec angula pla e (200 mm × 270 mm × 10 mm) wi h six holes o 18 mm 29
diame e and is used only on he MA sys em. The hea ing de ice is an elec onic equipmen wi h se e al hea ing 30
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
8
elemen s (100 mm × 100 mm, ype ‘Te mo oil’) and is used exclusi ely on he GA me hod [27, 28]. The 1
s eng hening p ocedu es using he MA and GA sys ems, sha e some common applica ion s eps, mainly: 2
(i) P epa ing he su ace o he conc e e subs a e is he i s s ep o bo h me hodologies. The zone whe e 3
he lamina e s ip is applied was sand-blas ed and hen cleaned wi h a comp essed ai blowe . The 4
expec ed a e age oughness (R
a
) o he sand-blas ed su ace was 0.01 mm [9] (see Fig. 2a and Fig. 3a); 5
(ii) Se e al holes we e d illed o accommoda e empo a y and pe manen bol ancho s. The a e age d ill hole 6
had a dep h o 85 mm and was cleaned wi h an ai b ush a e d illing. GA sys em in ol es empo a y 7
bol s only, while o he case o he MA sys em, six M16 8.8 pe manen bol ancho s (s ainless s eel) we e 8
used o ix each me allic ancho age pla e. A chemical bond agen (HIT-HY 200-A
®
) was used o ix hese 9
bol s o conc e e (see Fig. 2b and Fig. 3b); 10
(iii) Two me allic guides we e placed in hei p ede ined loca ion o guide and ix he clamp uni s. Then, he 11
clamp uni was placed in-be ween he guides a each ex emi y o he slab; 12
(i ) The CFRP lamina e s ip was cu wi h he p ecise leng h (2200 mm) and cleaned wi h a sol en . The 13
epoxy adhesi e was p epa ed acco ding o he equi emen s included in he p oduce speci ica ions. 14
Subsequen ly, he adhesi e was applied on he su ace o he lamina e and on he conc e e su ace egion 15
in con ac wi h he lamina e. The special gluing se used o apply he epoxy on he lamina e gua an ees a 16
minimum hickness o 2 mm o such bonding agen (see Fig. 2c and Fig. 3c). Subsequen ly he CFRP 17
lamina e was placed in i s inal posi ion and sligh ly p essed agains he conc e e subs a e (see Fig. 2c 18
and Fig. 3c); 19
( ) The clamping uni s we e closed o ix he CFRP lamina e s ip. A o que o 170 N·m was applied o each 20
sc ew using a dynamome ic w ench (see Fig. 2d and Fig. 3d); 21
( i) The me allic ancho pla es and he hea ing de ice we e placed in hei p ede ined loca ions o he case 22
o he MA (see Fig. 2e) and GA (see Fig. 3e) sys ems, espec i ely. I should be poin ed ou ha he 23
me allic ancho pla es we e always sligh ly g inded wi h sandpape and cleaned wi h a sol en ; 24
( ii) Aluminium ames we e placed a hei p ede ined posi ions and ixed agains he conc e e subs a e wi h 25
ancho s o accommoda e he hyd aulic jack (see Fig. 2 and Fig. 3 ); 26
( iii) E en ually, he hyd aulic jack was ins alled on he aluminium ame and, using a manual hyd aulic pump, 27
he p es ess was applied o he CFRP lamina e s ip (see Fig. 2g and Fig. 3g). 28
29
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
9
A e he p es ess applica ion on he CFRP s ips (see Fig. 2h and Fig. 3h), di e en p ocedu es we e 1
ollowed o MA and GA sys ems. In he MA sys em, each bol ancho o he me allic ancho pla es was igh ened 2
wi h a o que o 150 N∙m in o de o inc ease he con inemen p o ided by he me allic pla es a he ancho ’s egion 3
and educe he p obabili y o he CFRP lamina e o slide a he ends. Addi ional ixing sc ews we e moun ed 4
be ween he ame and he clamp uni s in o de o block he p es essing sys em and, consequen ly, a oid p es ess 5
losses du ing he cu ing o he adhesi e. The s eng hening applica ion was concluded a e app oxima ely 24 6
hou s. Finally, he equipmen was emo ed ( ixing sc ews, clamp uni s, guides and aluminium ames) and 7
empo a y ancho s and he CFRP lamina e ou side o he ancho pla es we e cu o . 8
Wi hin he scope o he p esen wo k, g adien ancho ages o 600 mm in leng h, composed o h ee sec o s 9
(50 mm wide and 200 mm long each) we e used. Du ing he applica ion o he g adien , he specimens we e always 10
moni o ed in e ms o applied o ce by he hyd aulic jacks and empe a u e a he dis inc sec o s composing he 11
hea ing de ices. The e olu ion o he empe a u e, jack o ce and s ain o e ime a e ep esen ed in Fig. 4: he 12
i s sec o was hea ed o 160ºC o a pe iod 15 minu es, ollowed by an exponen ial empe a u e dec ease du ing 13
20 minu es (down o 120ºC), and inally by a cooling phase. In he ollowing sec o s he same hea ing p ocess was 14
ca ied ou 10 minu es a e he beginning o he cooling phase o he p e ious one. App oxima ely 15 min a e 15
he ini ia ion o he cooling phase o each sec o , 1/3 o he o al applied o ce was eleased. This wai ing ime was 16
chosen in o de o ensu e ha he epoxy adhesi e has cooled down o empe a u es below 50ºC.
17
The p es ess le el was con olled by s ain gauges p e iously placed a he mid-span o he CFRP 18
lamina e s ip. The a e age p es ain imposed was app oxima ely 0.4%. Table 1 shows he alues o he egis e ed 19
p es ain and p es ess o ce a he middle o he CFRP lamina e o all specimens a he end o he s eng hening 20
p ocedu e. 21
A schema ic schedule ep esen ing he main asks pe o med du ing his wo k is shown in Fig. 5. 22
App oxima ely six mon hs a e he s eng hening, he slabs we e exposed o he di e en s udied en i onmen al 23
condi ions. Ini ially, he p o o ypes we e placed in he emp y wa e anks, o inside a clima ic chambe in he case 24
o he slabs REF. In each ank, o clima ic chambe , ou slabs we e placed: wo slabs (one MA and one GA) o 25
be subjec ed o he co esponding en i onmen al condi ion and wo o he s (one MA and one GA) o be subjec ed 26
o he combined e ec o he en i onmen al condi ion and he sus ained loading. Se e al g ani e blocks (weigh 27
om 0.8 kN o 4.6 kN) we e used o achie e he p ede ined load (20 kN). While he weigh s we e being laid, a 28
con inuous obse a ion o he slab’s bo om su ace was ca ied ou . C ack ini ia ion was obse ed in all “_C” 29
specimens o an a e age mid-span de o ma ion o 1.7 mm and a load o app oxima ely 17 kN. As shown in Fig. 30
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
16
de lec ion (δ
max
/δ
y
) and cu a u e (φ
max
/φ
y
) a ios be ween he yielding and he ailu e s ages was highe o MA 1
specimens. The MA_REF_T0 p esen ed he highes duc ili y pa ame e s (F
max
/F
y
=1.33, δ
max
/δ
y
=3.15 and 2
φ
max
/φ
y
=2.13) and simila esul s we e obse ed o MA slabs exposed o REF, CW and WD en i onmen s. Again, 3
he imme sion in wa e (se ies TW) esul ed in he highes duc ili y educ ion o MA specimens, being he a io 4
δ
max
/δ
y
o specimen MA_TW_U 49% lowe han he one ob ained o MA_REF_T0. This obse a ion may be 5
jus i ied by he deg ada ion expe ienced by he epoxy adhesi e when exposed o ce ain en i onmen s [15]. 6
Specimens p es essed wi h he GA sys em p esen ed he highes duc ili y pa ame e on se ies TW and CW. 7
8
3.6 In luence o sus ained loading 9
In eal-li e si ua ions, a RC s uc u e can be subjec ed o combined e ec s o physical and en i onmen al ac o s, 10
which in some cases may be syne ge ic. In o de o e alua e hei in luence, as p e iously e e ed, a sus ained 11
load o 20 kN was applied simul aneously o he ou s udied en i onmen s. The sus ained load led o he p e-12
c acking o all specimens allowing a g ea e exposu e o he ein o cemen and s eng hening elemen s o he 13
en i onmen al condi ions and, as a consequence, he g ea e deg ada ion o he composi e sys em. Du ing he 14
sus ained loading, he maximum de o ma ion o he slab almos eached 10 mm and c acks we e isible by naked 15
eye. When loading was emo ed, mo e han 50% o he p e iously eached de o ma ion was eco e ed. 16
Du ing he s a ic es s, a sudden s i ness loss was obse ed when he applied load was close o 25 kN 17
indica ing ha he c acking p ocess was no s abilized du ing he applica ion o he sus ained load. Up o his poin , 18
he s i ness o he slab assumed an in e media e alue be ween he s i ness K
I
and K
II
o he “_U” specimens. As 19
shown in Table 3, he sus ained load and consequen c acking did no ha e a signi ican in luence on he ul ima e 20
beha iou . In he s a ic es s, he ailu e occu ed o he same load le el as o he “_U” slabs bu , as expec ed, o 21
lowe de lec ion alues (23.6% and 6.4% lowe o he MA and GA sys ems, espec i ely). Fo he specimens subjec ed 22
o he sus ained loading he sepa a ion be ween he debonding ini ia ion s age and he ancho age slippage s age has 23
dec eased, educing he duc ili y. Duc ili y pa ame e s p esen ed in Table 3 can quan i y he educ ion o he slabs 24
duc ili y due o he e ec o he syne gies be ween sus ained loading en i onmen al condi ions exposu e. The GA 25
specimens (GA_TW_C; GA_CW_C and GA_WD_C) p esen ed simila duc ili y pa ame e s o hose ob ained o he 26
GA_REF_T0. Howe e , all “_C” specimens s eng hened wi h he mechanical ancho age showed signi ican duc ili y 27
educ ions. The lowes F
max
/F
y
, δ
max
/δ
y
and φ
max
/φ
y
a ios o he MA slabs we e obse ed o se ies TW (F
max
/F
y
= 28
1.14), WD (δ
max
/δ
y
= 1.64) and TW (φ
max
/φ
y
= 1.67), espec i ely. In his ma e , he less damaging syne gy 29

Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
17
comp ehended he sus ained loading and he REF en i onmen . Ye , he MA_REF_C showed a dec ease highe 1
han 20% in each o i s duc ili y pa ame e s when compa ed o he MA_REF_T0. 2
In summa y, he duc ili y o each slab was e alua ed h ough h ee pa ame e s (F
max
/F
y
, δ
max
/δ
y
and φ
max
/φ
y
) 3
and h ee majo ac o s ha e been obse ed: (i) specimens s eng hened wi h he GA sys em showed mino a ia ions 4
in hei duc ili y pa ame e s a e being exposed o he di e en en i onmen al condi ions solely (se ies “_U”) o 5
combined wi h he sus ained loading (se ies “_C”); (ii) he duc ili y o MA specimens on se ies “_U” and “_C” was 6
conside ably lowe han he duc ili y obse ed on slab MA_REF_T0; and (iii) he combined e ec s (sus ained loading 7
+ en i onmen al ac ion) p oduced a mo e se e e e ec on he duc ili y educ ion o MA specimens han he exposu e 8
o each en i onmen sepa a ely. 9
10
4. Conclusions 11
This wo k p esen ed an expe imen al p og am in which he main objec i e was o assess he du abili y o RC slabs 12
s eng hened wi h p es essed CFRP lamina e s ips using wo di e en ancho age sys ems: he mechanical 13
ancho age (MA) and g adien ancho age (GA). Du ing eigh mon hs, six een slabs we e subjec ed o he e ec o 14
ou en i onmen al condi ions ( e e ence en i onmen - REF; imme sion in ap wa e a 20 ºC - TW; imme sion 15
in wa e wi h 3.5% o chlo ides - CW; and we /d y cycles in ap wa e a 20 ºC - WD). Addi ionally, hal o hese 16
specimens we e subjec ed o a sus ained load o 20 kN. Ou o he p esen ed esul s, se e al conclusions can be 17
d awn: 18
• In gene al, p es ess allowed highe CFRP s ains a ailu e, hus a be e use o he in ol ed 19
ma e ials; 20
• A simila esponse was obse ed o bo h ancho age echniques, bu he mechanical ancho s o he 21
MA sys em p e en ed a p ema u e ailu e and allowed he slabs o suppo g ea e ul ima e loads and 22
de lec ions; 23
• Fo he GA specimens, he ini ial debonding p ocess was apidly ans o med in o he comple e s ip 24
de achmen , esul ing in a b i le ailu e, simila o con en ional ex e nally bonded ein o cemen 25
wi hou any end-ancho ages; 26
• The MA_REF_T0 slab was he only ha ailed by CFRP up u e a i s maximum ensile capaci y, 27
whe eas he emaining s eng hened slabs seemed o ha e ailed by s ip in e media e debonding 28
om he conc e e; 29
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
18
• The exposu e o wa e (se ies TW, CW and WD) imp o ed he conc e e s eng h and he 1
co esponding modulus o elas ici y, which inc eased he ini ial slabs’ s i ness and delayed he c ack 2
ini ia ion; 3
• All es ed en i onmen al condi ions led o a educ ion o he yielding and he ailu e loads o bo h 4
ancho age sys ems, bu he in luence o each en i onmen was di e en on each ancho age sys em: 5
TW and REF en i onmen condi ions seemed o ha e he highes deg ada ion in luence o e he MA 6
and GA slabs, espec i ely; 7
• Debonding ini ia ion on bo h sys ems was obse ed a ea lie es s ages o specimens exposed o all 8
en i onmen s. The main eason esides in he ac ha he epoxy adhesi e’s p ope ies a e suscep ible 9
o deg ada ion when exposed o humidi y o wa e ; 10
• The duc ili y o all s eng hened specimens was e alua ed h ough h ee duc ili y pa ame e s. In 11
gene al, all es ed exposu e en i onmen s led o a educ ion o he MA slabs duc ili y, especially in 12
he case o c acked specimens. The MA specimens p esen ed he lowes duc ili y a e he imme sion 13
in wa e (se ies TW); 14
• The sus ained loading ampli ied he e ec o each en i onmen al ac ion. This e ec was mo e 15
p onounced on MA specimens, which p esen ed lowe s uc u al duc ili y when compa ing he 16
de lec ion be ween ailu e and yielding; 17
• The pe o mance and duc ili y losses o he s eng hening sys ems when subjec ed o en i onmen al 18
condi ions and sus ained loading, sepa a ely o combined, we e sub le. Howe e , conside ing ha 19
he es s we e ca ied ou in only 8 mon hs, he esul s gi e clea indica ions owa ds he impo ance 20
o conduc ing simila es s o e longe pe iods; 21
• Du ing he s a ic es s, he con ol specimens (se ies T0) exhibi a a supe io pe o mance and 22
duc ili y compa ed o he emaining specimens. I is clea ha he s udy o he e ec s o 23
en i onmen al ac ions and sus ained loading is an essen ial opic o uly unde s and he long- e m 24
p ope ies o p es essed CFRP s eng hening sys ems; 25
• Based on he ob ained esul s i is impo an o, in u u e wo ks, e alua e he in luence o he same 26
en i onmen al ac ions o a longe pe iod, unde he in luence o empe a u e cycles and highe 27
concen a ion o sal s. Howe e , he p ocesses used in his wo k has e ealed g ea po en ial o he 28
es ablishmen o s anda dized p ocedu es o du abili y assessmen o p es essed CFRP 29
s eng hening sys ems. 30
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
19
1
Acknowledgemen s 2
This wo k was suppo ed by he ollowing p og ams: FEDER (Eu opean Funds o Regional De elopmen ) unds 3
h ough he Ope a ional P og am o Compe i i eness Fac o s – COMPETE, Ope a ional P og am o 4
Compe i i eness and In e na ionaliza ion (POCI) and Na ional Funds h ough FCT - Po uguese Founda ion o 5
Science and Technology unde he p ojec s FRP eDu FCOMP-01-0124-FEDER-028865 (FCT e e ence 6
PTDC/ECM-EST/2424/2012), FRPLongDu POCI-01-0145-FEDER-016900 (FCT e e ence PTDC/ECM-7
EST/1282/2014) and POCI-01-0145-FEDER-007633. The au ho s also like o hank all he companies ha ha e 8
been in ol ed suppo ing and con ibu ing o he de elopmen o his s udy, mainly: S&P Cle e Rein o cemen 9
Ibé ica Lda, S&P Cle e Rein o cemen Company (Swi ze land), Tecnipo - Gomes & Ta ei a Lda., Vialam – 10
Indús ias Me alú gicas e Me alomecânicas, Lda, Hil i Po ugal-P odu os e Se iços, Lda. The i s au ho wish 11
also o acknowledge he g an SFRH/BD/98309/2013 p o ided by FCT.
This pape is dedica ed o Tiago Teixei a 12
(1988–2015), o me doc o al s uden a he ISISE R&D Resea ch Cen e a he Uni e si y o Minho. 13
14
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p es essed ca bon ib e ein o ced polyme shee s subjec ed o sus ained loading and low empe a u e.
20
Canadian Jou nal o Ci il Enginee ing. 2004;31(2):239-52.
21
[19] Blabe J, Adai B, An oniou A. Nco : Open-Sou ce 2D Digi al Image Co ela ion Ma lab
22
So wa e. Expe imen al Mechanics. 2015;55(6):1105-22.
23
[20] E397-1993 L. Conc e e - De e mina ion o he elas ici y Young modulus unde comp ession.
24
Po uguese speci ica ion om LNEC: LNEC; 1993.
25
[21] 12390-3 NE. Tes ing ha dened conc e e. Pa 3: Comp essi e s eng h o es specimens.
26
Capa ica: IPQ - Ins i u o Po uguês da Qualidade; 2011.
27
[22] Te mkhajo nki P, Nawa T, Ku umisawa K. E ec o wa e cu ing condi ions on he hyd a ion
28
deg ee and comp essi e s eng hs o ly ash–cemen pas e. Cemen and Conc e e Composi es.
29
2006;28(9):781-9.
30
[23] 6892-1 NEI. Me allic Ma e ials. Tensile Tes ing. Pa 1: Me hod o es a oom empe a u e.
31
Capa ica: IPQ - Ins i u o Po uguês da Qualidade; 2012.
32
[24] S&P. CFRP Lamina es, Technical da ashee . Seewen, Swi ze land2014. p. 6.
33
[25] 527-5 I. Plas ics — De e mina ion o ensile p ope ies — Pa 5: Tes condi ions o
34
unidi ec ional ib e- ein o ced plas ic composi es. Genè e: ISO - In e na ional O ganiza ion o
35
S anda diza ion; 1997. p. 11.
36
[26] Michels J, Sena C uz J, Ch is en R, Czade ski C, Mo a alli M. Mechanical pe o mance o cold-
37
cu ing epoxy adhesi es a e di e en mixing and cu ing p ocedu es. Composi es Pa B: Enginee ing.
38
2016;98:434-43.
39
[27] Michels J, Zile E, Czade ski C, Mo a alli M. Debonding ailu e mechanisms in p es essed
40
CFRP/epoxy/conc e e connec ions. Enginee ing F ac u e Mechanics. 2014;132:16-37.
41
[28] S&P. P e-s essed S&P Lamina es CFK. Manual o applica o s. 2010. p. 20.
42
[29] FIB. The ib Model Code o Conc e e S uc u es. Model Code 2010. Lausane, Swi ze land: The
43
n e na ion ede a ion o s ucu al conc e e (FIB); 2010. p. 653.
44
[30] Ko ynia R, Walendziak R, S oecklin I, Meie U. RC Slabs S eng hened wi h P es essed and
45
G adually Ancho ed CFRP S ips unde Mono onic and Cyclic Loading. Jou nal o Composi es o
46
Cons uc ion. 2011;15(2):168-80.
47
[31] Fe nandes PMG, Sil a PM, Co eia LLG, Sena-C uz J. Du abili y o an epoxy adhesi e and a
48
CFRP lamina e unde di e en exposu e condi ions. In: P oceedings o SMAR2015 – Thi d
49
Con e ence on Sma Moni o ing, Assessmen and Rehabili a ion o Ci il S uc u es. An alya, Tu key,
50
Con e ence 07 - 09 Sep . 2015, Con e ence 2015. p. 8.
51
52
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
21
Nomencla u e 1
E
a
A e age ensile modulus o epoxy adhesi e
E
c
A e age modulus o elas ici y o conc e e a slab es ing day
E
A e age elas ic modulus o CFRP lamina e
E
s
A e age Modulus o Elas ici y o s eel ba s
c
A e age comp essi e s eng h on cylinde 150mm/300mm o conc e e a slab es ing day
F
c
Fo ce a c ack ini ia ion
a
A e age ensile s eng h o epoxy adhesi e
A e age ensile s eng h o CFRP lamina e
F
max
Maximum o ce
A e age ul ima e s eng h o s eel ba s
y
A e age yield s eng h o s eel ba s
F
y
Fo ce a yielding ini ia ion
K
I
S i ness o he slab a unc acked s a e
K
II
S i ness o he slab a ully c acked s a e
δ
c
Mid-span displacemen a c acking load F
c
δ
max
Mid-span displacemen a ul ima e load F
max
δ
y
Mid-span displacemen a yielding load F
y
ε
max
CFRP s ain a F
max
ε
p
CFRP ini ial s ain
φ
y
Mid-span cu a u e a yielding load Fy
φ
max
Mid-span cu a u e a ul ima e load F
max
2
3

Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
22
Lis o Tables 1
Table 1: Expe imen al p og am 2
Table 2: Ma e ials cha ac e iza ion (a e age alues) 3
Table 3: Main esul s 4
5
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
23
Table 1: Expe imen al p og am
Se ies Specimen En i onmen al
condi ion/Obse a ions Ancho age
sys em
Ini ial
s ain,
ε
p
P es ess
o ce Sus ained
load
[%] [kN]
T0 REF_T0 Specimens es ed a he
beginning o he
expe imen al p og am
- - - -
EBR_REF_T0 - 0.00 0.00 -
MA_REF_T0 MA 0.42 41.6 -
GA_REF_T0 GA 0.40 39.6 -
REF MA_REF_U Specimens subjec ed o
labo a o y p emises:
20 ºC and 55% o RH
MA 0.41 40.6 No
GA_REF_U GA 0.41 40.6 No
MA_REF_C MA 0.37 36.6 Yes
GA_REF_C GA 0.41 40.6 Yes
TW MA_TW_U Specimens imme sed in
ap wa e a 20 ºC MA 0.40 39.6 No
GA_TW_U GA 0.41 40.6 No
MA_TW_C MA 0.41 40.6 Yes
GA_TW_C GA 0.41 40.6 Yes
CW MA_CW_U Specimens imme sed in
ap wa e a 20 ºC wi h
3.5% o chlo ides
MA 0.40 39.6 No
GA_CW_U GA 0.41 40.6 No
MA_CW_C MA 0.41 40.6 Yes
GA_CW_C GA 0.40 39.6 Yes
WD MA_WD_U Specimens subjec ed o
we /d y cycles in ap
wa e a 20 ºC
MA 0.40 39.6 No
GA_WD_U GA 0.40 39.6 No
MA_WD_C MA 0.42 41.6 Yes
GA_WD_C GA 0.42 41.6 Yes
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
24
Table 2: Ma e ials cha ac e iza ion (a e age alues)
Conc e e
Se ies E
c
[GPa] ∆E
c
[%]
c
[MPa] ∆
c
[%]
T0 (28 days)
(a)
27.78 (2.9%) - 37.32 (1.9%) -
(209 days)
(b)
30.03 (-) 8.09 40.24 (0.7%) 7.82
REF (570 days)
(b)
26.98 (2.4%) -2.88 39.49 (5.3%) 5.81
TW (570 days)
(b)
33.44 (1.3%) 20.37 50.22 (1.3%) 34.57
CW (570 days)
(b)
33.87 (1.1%) 21.92 45.85 (8.0%) 22.86
WD (570 days)
(b)
32.20 (5.1%) 15.91 48.58 (2.1%) 30.17
S eel
Ba Type E
s
[GPa]
y
[MPa]
u
[MPa]
Ø6 206.9 (0.4%) 519.4 (6.1%) 670.2 (5.1%)
Ø8 235.1 (4.6%) 595.9 (4.1%) 699.0 (2.1%)
CFRP
Geome y [mm
2
] E
[GPa]
[MPa]
50×1.2 167.7 (2.9%) 2943.5 (1.6%)
No es:
(a)
Tes s a 28 days;
(b)
Tes s a he age o he mono onic es s o he slabs; The alues be ween
pa en heses a e he co esponding coe icien s o a ia ion (CoV).
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.”
Composi es Pa B, 125: 71–88. DOI: 10.1016/j.composi esb.2017.05.047
25
Table 3: Main esul s
Specimen
S i ness C ack
ini ia ion Yielding Ul ima e E iciency and duc ili y
pa ame e s FM
K
I
K
II
δ
c
F
c
δ
y
F
y
φ
y
δ
max
F
max
φ
max
ε
max(c)
[kN/mm]
[kN/mm]
[mm] [kN] [mm] [kN]
[10
-3
m
-1
]
[mm] [kN]
[10
-3
m
-1
]
[%] F
max
/F
y
δ
max
/δ
y
φ
max
/φ
y
REF_T0 8.8 0.9 0.71 7.9 18.90 24.5 - 100.00
(a)
28.1
(b)
- - - - - -
EBR_REF_T0 8.1 1.2 0.68 8.5 25.87 37.1 49.24 40.69 44.0 72.04 0.76 1.2 1.57 1.46 D
MA_REF_T0 10.2 1.3 1.82 17.9 26.88 50.6 48.21 84.78 67.5 102.67 1.48 1.3 3.15 2.13 F
GA_REF_T0 9.7 1.2 1.55 16.2 29.04 50.2 52.65 43.31 57.4 76.49 1.16 1.1 1.49 1.45 D
MA_REF_U 8.3 1.3 2.04 16.1 26.26 46.1 50.36 67.34 59.9 97.87 1.40 1.3 2.56 1.94 D
GA_REF_U 8.0 1.2 1.85 15.9 28.45 48.6 51.14 38.21 53.5 68.33 1.10 1.1 1.34 1.34 D
MA_REF_C -- 1.3 -- -- 26.22 48.1 71.75 65.85 61.6 108.63 1.26 1.3 2.51 1.51 D
MA_TW_U 8.6 1.3 1.68 15.6 24.54 47.1 46.06 39.56 54.4 68.17 1.13 1.2 1.61 1.48 D
GA_TW_U 10.9 1.3 1.05 12.8 25.60 47.1 47.98 41.65 55.8 78.32 1.19 1.2 1.63 1.63 D
MA_TW_C -- 1.5 -- -- 22.02 50.5 55.74 41.33 57.7 83.76 1.15 1.1 1.88 1.50 D
GA_TW_C -- 1.2 -- -- 23.58 49.30
42.2 37.05 56.2 63.23 1.06 1.1 1.57 1.50 D
MA_CW_U 11.5 1.3 1.92 18.5 24.57 47.35
43.7 65.45 60.9 81.68 1.23 1.3 2.66 1.87 D
GA_CW_U 8.4 1.3 2.11 17.0 24.71 46.94
45.8 41.70 56.4 77.44 1.19 1.2 1.69 1.69 D
MA_CW_C -- 1.4 -- -- 19.65 47.42
47.0 38.38 58.7 79.43 1.12 1.2 1.95 1.69 D
GA_CW_C -- 1.3 -- -- 21.92 47.04
49.4 39.01 57.0 80.83 1.05 1.2 1.78 1.64 D
MA_WD_U 10.7 1.3 1.30 14.2 25.53 47.64
46.3 61.33 58.8 86.20 1.27 1.2 2.40 1.86 D
GA_WD_U 10.3 1.2 1.49 16.5 26.98 48.62
47.7 40.21 55.3 69.09 1.08 1.1 1.49 1.45 D
MA_WD_C -- 1.3 -- -- 20.10 48.61
38.0 32.89 55.6 63.57 1.04 1.1 1.64 1.67 D
GA_WD_C -- 1.2 -- -- 23.67 49.15
49.0 37.55 56.3 73.24 1.17 1.2 1.59 1.50 D
No es:
(a)
These slabs eached he maximum p e-de ined de lec ion wi hou ailing;
(b)
Values o he mid-span de lec ion o 100 mm;
(c)
The maximum CFRP s ain
did no necessa ily occu a he mid-span; Failu e modes: D = Debonding (cohesi e ailu e a he conc e e); F = CFRP ensile ailu e.
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
32
(a)
(b) (c)
(d) (e)
Fig. 6: To al o ce e sus mid-span de lec ion: (a) Con ol specimens; (b) unc acked MA specimens;
(c) unc acked GA specimens; (d) c acked MA specimens; and (e) c acked GA specimens.
0 20 40 60 80 100
0
20
40
60
80
To al load, F [kN]
Mid-span displacemen ,
δ
[mm]
REF_T0
EBR_REF_T0
MA_REF_T0
GA_REF_T0
0 20 40 60 80 100
0
20
40
60
80
To al load, F
[kN]
Mid-span displacemen ,
δ
[mm]
MA_REF_T0
MA_REF_U
MA_TW_U
MA_CW_U
MA_WD_U
0 20 40 60 80 100
0
20
40
60
80
To al load, F [kN]
Mid-span displacemen ,
δ
[mm]
GA_REF_T0
GA_REF_U
GA_TW_U
GA_CW_U
GA_WD_U
0 20 40 60 80 100
0
20
40
60
80
To al load, F
[kN]
Mid-span displacemen ,
δ
[mm]
MA_REF_T0
MA_REF_C
MA_TW_C
MA_CW_C
MA_WD_C
0 20 40 60 80 100
0
20
40
60
80
To al load, F
[kN]
Mid-span displacemen ,
δ
[mm]
GA_REF_T0
GA_TW_C
GA_CW_C
GA_WD_C

Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
33
(a) (b)
(c) (d)
( ) (g)
Fig. 7: C ack wid h e olu ion o : (a) Typical pho o o a c ack (MA_REF_U); (b) Con ol specimens;
(c) unc acked MA specimens; (d) unc acked GA specimens; (e) c acked MA specimens; and ( ) c acked GA
specimens.
0.00 0.15 0.30 0.45 0.60
0
15
30
45
F=34.92·w + 4.21
R
2
= 0.93
F=60.68·w + 4.67
R
2
= 0.98
F=56.79·w + 14.37
R
2
= 0.99
REF_T0
EBR_REF_T0
MA_REF_T0
GA_REF_T0
To al load, F
[kN]
C ack wid h, w [mm]
F=80.56·w + 13.23
R
2
= 0.98
0.00 0.15 0.30 0.45 0.60
0
15
30
45
F=80.56·w + 13.23
R
2
= 0.98
F=61.14·w + 18.04
R
2
= 0.97
F=126.08·w + 12.19
R
2
= 0.97
F=61.94·w + 15.52
R
2
= 0.99
F=47.11·w + 13.48
R
2
= 0.98
MA_REF_T0
MA_REF_U
MA_TW_U
MA_CW_U
MA_WD_U
To al load, F
[kN]
C ack wid h, w [mm]
0.00 0.15 0.30 0.45 0.60
0
15
30
45
F=56.79·w + 14.37
R
2
= 0.99
F=58.18·w + 15.92
R
2
= 0.98
F=65.11·w + 15.87
R
2
= 0.99
F=73.17·w + 9.33
R
2
= 0.97
F=49.34·w + 18.79
R
2
= 0.95
GA_REF_T0
GA_REF_U
GA_TW_U
GA_CW_U
GA_WD_U
To al load, F
[kN]
C ack wid h, w [mm]
0.00 0.15 0.30 0.45 0.60
0
15
30
45
F=80.56·w + 13.23
R
2
= 0.98
F=104.90·w + 2.33
R
2
= 0.85
F=83.96·w + 1.39
R
2
= 0.97
F=209.90·w + 2.06
R
2
= 0.97
F=129.62·w + 9.03
R
2
= 0.97
MA_REF_T0
MA_REF_C
MA_TW_C
MA_CW_C
MA_WD_C
To al load, F
[kN]
C ack wid h
, w
[
mm
]
0.00 0.15 0.30 0.45 0.60
0
15
30
45
F=185.60·w + 14.50
R
2
= 0.81
F=121.94·w + 15.91
R
2
= 0.83
F=130.68·w + 4.50
R
2
= 0.89
F=56.79·w + 14.37
R
2
= 0.99
GA_REF_T0
GA_TW_C
GA_CW_C
GA_WD_C
To al load, F [kN]
C ack wid h, w [mm]
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
34
Fig. 8: C ack pa e n a he end o he es o each slab and a e age c ack spacing.
G.Z.
G.Z.
MA_REF_U
GA_REF_U MA_REF_C
MA_TW_C
GA_TW_C
MA_TW_U
GA_TW_U
MA_CW_U
GA_CW_U
MA_CW_C
GA_CW_C
MA_WD_U
GA_WD_U
MA_WD_C
GA_WD_C
EBR_REF_T0 MA_REF_T0
GA_REF_T0
G.Z.
G.Z.
G.Z.
G.Z.
G.Z.
G.Z.
G.Z.
G.Z.
G.Z.
G.Z.
G.Z.
G.Z.
G.Z.
G.Z.
11.47
10.66
11.03
10.33
10.91
10.27
9.99
10.23
10.22
10.26
9.08
8.42
9.77
9.44
10.42
9.15
10.79
8.91
9.75
9.43
9.85
9.26
10.98
11.37
9.94
8.83
9.89
8.44
9.41
10.09
9.08
8.90
10.79
10.49
9.62
8.32
A e age C ack Spacing in
pu e bending zone (mm)
A e age C ack Spacing
(mm)
G.Z.- G adien Zone
0 mm 15 mm
REF_T0 15.24
15.50
0 mm 15 mm
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
35
Fig. 9: C ack pa e n obse ed on he bo om su ace and ailu e modes.
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
36
(a) (b)
(c) (d)
(e)
Fig. 10: Ma e ials s ain a ia ion: (a) CFRP s ain a ia ion in MA_REF_U; (b) CFRP s ain a ia ion in
GA_REF_U; (c) conc e e and s eel s ain a ia ion in MA_REF_U and MA_REF_C; (d) conc e e and s eel
s ain a ia ion in GA_REF_U; and (e) CFRP sliding a ancho ages o MA_REF_C.
0 650 1300 1950 2600
0
3
6
9
12
15
F = F
max
F
slip2
< F<F
max
F
c
< F < F
y
F < F
c
F
y
< F< F
slip1
F
slip1
< F < F
slip2
CFRP s ain a ia ion, ∆ε
[%]
Dis ance om he le end o he slab (mm)
MA_REF_U:
10 kN
30 kN
48 kN
51 kN
54 kN
60 kN
SG4 SG3 SG2 SG1
0.0
0.3
0.6
0.9
1.2
1.5
0 650 1300 1950 2600
0
3
6
9
12
15
F
c
< F < F
y
F < F
c
F
y
< F< F
max
F = F
max
CFRP s ain a ia ion
,
∆ε
[
%
]
Dis ance om he le end o he slab [mm]
GA_REF_U:
10 kN
30 kN
50 kN
54 kN
SG3 SG2SG4'
SG4
SG1'SG1
0.0
0.3
0.6
0.9
1.2
1.5
-0.5 -0.4 -0.3 -0.2 -0.1 0.0
0
20
40
60
80
0.0 0.5 1.0 1.5 2.0
2.5
To al load, F [kN]
MA_REF_U:
SG05
MA_REF_C:
SG05
SG06
SG06
Conc e e s ain
a ia ion, ∆ε
c
[%] a ia ion, ∆ε
s
[%]
S eel s ain
-0.5 -0.4 -0.3 -0.2 -0.1 0.0
0
20
40
60
80
0.0 0.5 1.0 1.5 2.0 2.5
Conc e e s ain
To al load, F [kN]
a ia ion,
∆ε
c
[%]
GA_REF_U:
SG05
a ia ion,
∆ε
s
[%]
S eel s ain
SG06
32 34 36 38 40 42 44 46 48 50 52
50
52
54
56
CFRP sliding a acho age 1
MA_REF_C:
Fo ce
CFRP s ain a ia ion,
∆ε
[%]
To al load, F [kN]
Midspan displacemen ,
δ
[mm]
CFRP sliding a acho age 2
0.0
0.3
0.6
0.9
SG01
SG04
SG02
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
37
Fig. 11: Failu e modes: (a) CFRP up u e in unidi ec ional ension (MA_REF_T0); (b) obse ed longi udinal
c acks a he epoxy egion (GA_TW_C); (c) CFRP s ip pull-ou om he mechanical end/ancho age
(MA_WD_C); and (d) de ail o a cohesi e a he conc e e debonding (GA_WD_U).

Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
38
Fig. 12: Digi al image co ela ion on MA_W_C slab (maximum p incipal s ain ield).
Co eia, L.; Sena-C uz, J.; Michels, J.; F ança, P.; Pe ei a, E.; Escusa, G. (2017) “Du abili y o RC slabs s eng hened wi h p es essed
CFRP lamina e s ips unde di e en en i onmen al and loading condi ions.” Composi es Pa B, 125: 71–88. DOI:
10.1016/j.composi esb.2017.05.047
39
Fig. 13: Digi al image co ela ion on GA_W_C slab (maximum p incipal s ains).