Flexural Strengthening of One-Way Continuous Reinforced

United Arab Emirates University
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Theses
Electronic Theses and Dissertations
12-2014
Flexural Strengthening of One-Way Continuous
Reinforced Concrete Slabs with Cutoffs in Sagging
and Hogging Regions
Jafar Husni Alshawa.
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Part of the Civil and Environmental Engineering Commons
Recommended Citation
Alshawa., Jafar Husni, "Flexural Strengthening of One-Way Continuous Reinforced Concrete Slabs with Cutoffs in Sagging and
Hogging Regions" (2014). Theses. Paper 135.
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�U
IU"'
#-\I;;.
olli.a.J I
College of
� J.SU I G IJ La!J I
fut.o b
United Arab Emirates U�iversity
Engineering
United Arab Elnirates University
College of Engineering
Department of Civil and Environmental Engineering
FLEXURAL STRENGTHENING OF ONE- WAY CONTINUOUS
REINFORCED CONCRETE SLABS WITH CUTOFFS IN SAGGING
AND HOGGING REGIONS
lafer Husni A l shawa
Thi s thes i s is subm itted in partial fu l fil lment of the requ i rements for the degree of
M aster of Sc ience in C i v i l Engi neering
U nder the superv i sion of Dr. Tamer E I Maaddawy
December 20 1 4
1\
Declaration of Original Work
L Jafer I l u n i A I ha\ \a. the undersigned. a graduate student at the United
rab I:mi rate' L n i " er it
trcngthen i ng
f
ne \v a
E
). and the author of the the i entitled "Flex ural
onti n Llous Rei n forced
aggl llg and I logging" hercb).
olemnl
rc carch \\ ork. done and prepared b
1aadd<1\\ ). in the
oncrete
declare that this the i s i s a n origi nal
me under the supervi ion of Dr. Tamer El
011 ge of Engi neering at U EU. This work has not been
pre" i lI'l ) formed a the bas i s for t he award of an
s i m i lar t i t l e at thi
l abs with Cutoffs i n
academic degree, d i ploma or
or an) other L1ni ersity. The materials borrowed from othe r
ollrce and i nc l uded i n m) the i s have been properly c i ted and acknowledged .
tudent's i gnature . . . . . . . . . . . . .
Date .
15.I.I!. /J.o.�� ...........
III
Copyright © 20 1 4 by J ater H usn i A lshawa
A l l R i ghts Reserved
1\
Approval of the Master Thesi
Th i M a ter The i
approved b the fol lowing Exam i n i ng Com m i ttee Member :
I ) Advi or (Com m i ttee
hair): Dr. Tamer E I Maadda\ y
ociate Profe sor
Title:
Department of C i v i l and En i ronmental Engi neering
Col lege of Engineering
Date
2)
ember ( I nternal Exam i ner) : Dr. Said E I Khou ly
Title: As i tant Professor
Department of C i v i l and E n v i ronmental Engi neering
Col l ege of Engineering
ignature
3)
� £lJU.
�
...
Member (External Examiner): DL Mark Green
Title: Professor
Department of Cl\'ll Engineering
InstItution: Queen's UD1\'ersity, Ontario, Canada
Slgnatur
e}111 ,bRA{
Date
27
De..c-- ZO ( 4--
\
I his
l aster The i s i' accepted by :
Dean of t he 'ol lege r Engi neering: Prof.
Date
10h en
J�
CLan.
0. 5j{.212 (5
I
Dean o f the Col lege or Graduate Stud ies: Prof.
ignalUre!
l1JblffP-
Cop
Dale
heri r
agi Wak i m
':2. 7
) I I 20' 5'
�of �
\I
b tract
I n tal lation
f cut ut
accol11m date ut i l i t)
i n existing rei n forced concrete (R ) floor
ervlces reduce
research exami nes the effectivene
the slab load capaci t
lab
to
and duct i l ity. Th is
of u ing near- urface-mounted (
M ) carbon
fiber-re i n forced p I ) mer ( FRP ) rei n forcement to i m prove the flex ural response of
cont i nuou
RC slab \\ ith cutouts. The tud; comprised experi menta l testi ng and
ana l )tical model i ng.
total of ele\ en two- pan RC lab stri ps, 400 x 1 25 x 3800 mm
each, \\ ere te ted . Test parameters incl uded the locat ion of the cutout, and amount
and d i stri but ion of the
M - FRP rei n forcement between the sagging and hogging
region .
I nstal lation of a cutout i n the sagging region reduced t he load capac ity and
du ti l i t) i ndex by 2 7% and 1 2%, respecti el . When the cutout was i nstal led in the
hoggi ng region, a 23<),0 reduct ion in both load capac ity and d uct i l i ty i ndex was
record d. The
al l deficien t
M-C F R P strengthen i ng fu l l y restored the ori gi nal load capaci ty of
peci mens, except one speci men \ ith a cutout in t he hoggi ng region
\\ here o n l y 900/ 0 of the original l oad capac i ty was restored. The enhancement in load
capac i ty d ue to strengtheni ng was i n the range of 53% to 8 1 % for the speci mens with
a cutout in the agg i n g region and 1 8% to 54% for the speci mens with a cutout in the
hoggi ng region. The ducti l i ty i ndex of the spec i mens trengthened in the sagg i ng
region o n l y w as. on average, 1 6% 100ver t han that of the control specimen, whereas
for the spec i mens strengthened i n the hoggi ng region only. the duct i l i ty i ndex was
al most the same as that of the control slab. For the spec i mens heav i l y strengthened i n
both saggi ng and hogging regions, the d ucti l i ty i ndex was o n average 40% lower
\11
than t hat of the control slab. A ma; imum moment red i tribut ion rat io of 2600 \\ a
recorded for the cont i nuou R
labs trengthened \\ ith
M-CFRP.
n anal) t ical model that can pred ict the load capac i t
stri p conta i n i ng
lItOlIt
and
trengthened \\ ith
rhe rati o of the pred icted to mea ured load capac it)
of t\\ O- pan R
lab
M-C F R P has been i ntroduced .
was
i n the range of 0 . 74 to 1 .02
\\ ith an a erage of 0.85. standard deviation of 0.09, and coeffici ent of variation of
1000.
Keyword
trengtheni ng. ,lab . conti n uous. cutouts. flexura l ,
S M-CFRP.
\ III
Title and Ab tract in Arabic
�\
u.<:.b.j\
� uk Y
lY'
j9:l1\ � � u� �\.b.\ � L:.llc. .�\y1\ � /123 /27
-
-
IX
ckno� ledgement
I \\ ould l i ke to thank God fI r gi v i ng me the faith and t rength to succes ful l y
complete thi \ '.ork . 1 \\ uld al
0
l i ke to expres my i ncere thanks to my fami l y w ho
1 1m e pro\. ided me \\ i th a l l the upport and trength to complete this \-\ - o rk.
I would l i ke to expres m) deepest thank to al l i nd ividuals \\ ho hel ped me
during t h i s ign i ficant p ri d of my l i fe. I n the fir t place, I \ . ould l i ke to expres my
deep t re p ct and apprcci at i n to my thesi mai n advi or Dr. Tamer EI Maaddawy
for h i s cont i n uous
upp
rt,
i ne t i mable gui dance, and the val uable k now ledge he
pro \ ided me throughout the project . My grat itude is also extended to my co-advisor
Dr. B i l al E I-Aris for hi con t i n u us support and encouragement.
I wi h also to e pre s my gratitude to my col leagues i n Combi ned G roup
Contracti ng Company for the i r support and help during fabrication of test spec i mens.
I \\ ould l i ke also to e 'press my apprec iation to Eng. Tarek Salah, Eng. ]v an A l
Khal i l , and M r. Faisal A bd u l - Wahab for the i r h e l p throughout testi ng. Special
recogn ition goes also to all facu l t
members i n the C i v i l and Envi ronmental
Engi neeri n g Oepa11ment at the U A E
for the i r h e l p and support. I wou l d l i ke also to
ackno\'vledge the fi nanc i a l support pro i ded by t he U A E U to complete t h i s research
\\ ork.
,\1
Dedication
To Ill) parent Eng. I-I usni A l sha\ a, and Fati na Kaciuora, brother Eng. Abdul Raouf
I sh3\\ 3, 3nd i ter Dr. H aya and Dr. Farah A ishm a.
XII
Table of Content
I it le
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W
Dec larat ion of O ri ginal
Copy right
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rk
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111
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pp ro\ al of t he Ma ter T he i s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . IV
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VI
T it le and
b st ract in
rab ic . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VIII
ch.n \\ ledgelllent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X
Ded icat i n . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XI
Tab le of
ontent . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XII
L i�t of TabJe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XVI
L ist of F igure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XVII
L i t of
otat ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XX
C H AP T E R 1 : INT RODUCTIO
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1 . 1 Introduct ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I
1.2 Scope and Object i es .
1 .3 Thesis Out l ine
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C HAPT E R 2: LIT E RATU R E REVI EW
2.1 Introduct i on
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2
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2.3 Studies on Strengt hen ing of Cont inuous Structures with Composites
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C H APT E R 3: EXP ERI M E T AL P ROG RAM
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2.2 Studies on St rengthen ing of RC S labs with Cutout s U s ing Composites
2.4 Research S i gn ificance
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'\i ii
3. J Int roduction
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3 .� cI e t Progralll
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3 .�. 1 Contro l
pec i mcn
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3 . 2 . 3 G rou p [8]
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3.5
laterial Propertie
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3 . 6 trengthen i n g Methodology .
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4 . 2 Test Resu lts
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4 . 2. 1 . 1 Load Capac ity
4 . 2 . 1 . 2 Fai lure Mode
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4 . 2. 1 . 5 Tens i le Steel Stra i n Response
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4 . 2 . 1 .3 Load Deflect ion Response
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4 . 2 . 1 .4 Duct i l ity I ndex
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3 .7 . 2 D i p l acement and Load M easurement
4 . 1 I nt roduction
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C H A PT ER 4 : EX PER I M E T A L R ESU LTS
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3 .7 Test Set-up and I nstrumentat ion
tra i n Measurements
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teel Re i nforcement
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4 .2 . 1 Group [ AJ
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24
peCI J1len Fabrication .
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pec imcns 0 ta i l
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3.3
3 . 5 . 1 Concrete
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XIV
4 . 2. 1 .6
FRP t ra i n Re pon e
4 . 2. 1 .7
oncrcte
train Re p nse
.2. 1 .8 'upport Rcactions
4 . 2 . 1 .9
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4.2.2
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1oll1cnt - Deflection Re p n e
10ment Red i tribut ion
roup [8]
4.2 .2 . 1 Loau
4 . 2 . 2 . 2 Fai lure Mode
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80
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. . . . . . . . . . . . . . . . .. ...... . . . . . . . . . . . . . . . . ..............
82
.........
84
. . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . .................... . . . . . . . . . . .. . . . . . ......
84
. .
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.
.
.......
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apacit)
. ................
. . ............ . . . . . . . . . . . . . . . . . . . . . . .
.2 . 1 . 1 0 Loau - Moment Relat ion h ip
4 . 2. 1 . 1 1
.
. . . . . . . . .. . . . .................
.
.
87
. . . . . . .. . .............. . . . . . . .. . .. . ......
90
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.
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4 . 2 .2 . 3 L ad-Deflect ion Respon se
. . . . ...... . . . . . . . . . . . . . . . .
4 . 2 . 2,4 Ductilil) Inde:-. .. .. . . .. . . ......... . . ....... .. . . .. . . . ........ ......... .... .. . .. . . ..... .......... . . . . . . . ... 96
4.2.2.5 Ten i le tee l Strain Respon e
4 . 2.2.6 CFRP trai n Re p n e
4.2.2.7 Concrete
. . . . . . . . . . . ..........
train Re ponse
4 .2 . 2 .8 upport React ions
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4 . 2.2.9 Moment - Deflect ion Re ponse
1 00
101
1 04
........................ . . . . . . . . . . . . . . . . . . . . . .. . . . ............
1 06
.......... .... ...... . . . . . . . . . . . . . ........................... ....
1 08
. .. . . . ............ . . ...... . . .............................................
1 09
4 . 2 . 2 . 1 0 Load - Moment Re lationship
4.2 .2. 1 1 Moment Redi tribut ion
97
4.3 E ffic iency of the Strengt he n i n g Schemes . . . . . . . . . . .. . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . .. . . . . . .. . . I I I
C HAPT E R 5: A ALYTICAL MODLEI G
5.J Introduction
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1 14
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1 14
5.2 Material Constitut ive Laws
5.2.1 Concrete
........... ...... . . . . . . . . ........ . . . . . . . . . . . . . ........
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1 14
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5.2.2 Stee l Re i n forcement
. . . . . . . . . . . . . . . ....................
5.2.3 Carbon F i be r Re i n forced Polymer
5.2.4 Compat i bi l ity Requi rements
.
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.
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. 1 16
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1 17
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1 18
5 2 5 Equ i l ib rium Requ ircments ................... . . . . . . .. . .... . .. ...... . . . .... .... . . . . . ................. . . . 1 1 9
5 . 2 .6 "v1odcl Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . 1 20
5 .2 .7
na lyt ica l Re u lts
I [ PTl.R 6:
0
L
6 . 1 Int roduct ion .
6.2
onclusion
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6.3 Rec Il1l11endation for Future
BIBL I O Rf\P I l'r'
.
o R EC MME 0 T ION
S IO
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tudies
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1 25
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1 26
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1 29
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1 22
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131
Li t of Table
a ble 3 . 1 : Test
latri;... ............................................................................................................ 23
' 1 a ble". 2:
oncrete m i. proport ion ......................... . ..................................... . ....................... 36
Table 3 .3:
ggregate d i tribut i
Table"...l:
oncrete com pres i n trength re ults....... .. . .. . ......................................... .......... 37
Table 3.5:
ollcretc spl itting �trength re ult
11
................. ................................ . .. ...... . ....... . ......... . ........ . . .
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Ta ble 3 . 6: Ten i le test re u lt of steel cou pon
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37
......................... . ............ . ..................... . . ........
39
.
.
Ta ble 4 . 1 : Re ult of load measurement fi r pecimen of group [A] ............................
Ta ble 4 . 2: Ducti lity i nd ice for pe imens of grou p [A] . . .......... . . .
.
Ta ble 4.5:
54
... . ..... . . ............................
67
I'
pecimens of grou p [ A] . ..... . .........
.
....
..........
73
. . ..... . . . .
79
...................
83
oment capacity a nd en hancement ratio for specimen of group [A] .....
10ment redistribut ion rat io fi
.
....
Ta b l e 4 .3: Rat io ofCFRP tra i n at peak load to ruptureC FRP stra i n ( group [A)) .....
Ta ble 4 .4:
36
Ta ble 4.6: Result of load mea urement for specimens of group [ 8] ................. ...
.
.
.
.
..............
84
.............
96
Tab l e 4.7: Ducti lity i ndice for pec i mens of grou p [ B] . .. . . ....................................
.
.
Tab l e 4 .8: Rati o ofCFR P tra i n at peak load to rupture CFRP trai n ( group [B)) . . ............ 1 0 1
Table 4.9: Moment capa c i ty and en hacemenet ratio for spec i mens of group [ 8]
...
. . .......... 1 07
Table 4. 1 0: Moment red i stribution rat ios for peicmens of group [ B]
................... ............
1 10
Tab l e 4 . 1 1 : Efficiency of the strengthening schemes ........
..... .. ....... . ........................ . ......
.
1 12
......... ............................... ..............
1 23
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1 24
Tabl e 5. 1 : Predicted moment capacity ........................
.
.
. .
.
.
Tab l e 5.2: Compari on between a na lyt ica l and experimenta l load capacitie
.
X\ II
Li t of Figure
Figure 1 . 1 :
M) Tec h n ique Cor a T- Beam ( I 1
ear SurCace \tlounled (
Canada.. 2004) . 2
Figure 2. 1 : Load posil ion Cor t sled s lab (Va quez a nd Karbhari 2003) ........... ... . . . ............... 6
Figure 2. 2: (a)
chcmal ic plan layout (b) sect ion
Figure 2 .3: Deb )nd i ng of FRP (Kim a nd
-A (Tan and Zhao 2004) .... . . . ......... . . ..... . . 7
m i th 2009) . . ............ . ............. ... . . ................. ... .... 9
Figure 2 .4: Te·t labs ( m ith a nd K i m 2009) . ... ... .... ..................... . . ....... . .. . . . ................ . ........ 1 0
Figure 2.5: Test selup ( e l iem et a l 20 1 1 ) . . ....... ........................... ...... ............... .................... 1 1
T'igu re 2 .6: Fa i lure Mode ( shom et a l. 2003) ..................... . . .................. .... ............. ... . . . ...... 1 3
Figure 2 . 7: Deta i l oC triaA i a l duct i le fabr ic geometry ( Grace et a l. 2004) ............................ 1 5
Figure 2 .8: Test :etu p (Farah b d a nd Mo tofi nejad 20 1 1 ) ........................................ ...... . ..... 1 8
Figure 2 . 9: Test i n progres ( A ie l l and Ombre 20 1 1 ) ... . . . ...... . ..... .... .... ... . . ................ .......... 1 9
F i gure 2. 1 0:
M- FR P lam i nate layout ( Da lCre a nd Barro 20 1 1 ) ............. . . ....... ........ . .... 20
F i gur 3. 1 : Geometf) a nd deta i I of re i n forcement of the control spec i men .
.
.... . . . . . .. ....
...
.....
Figur 3.2: Geometry a nd deta i l s of re i n forcement of spec i mens o f group [A]
. .. . . . . . . . . . .
.
F i gure 3.3: Geometl_ a nd deta i Is of re i n forcement of specimen of grou p [B)
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..
F i gure 3.4: For1l1work and stee l cage
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..
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.
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.
Figure 3.5: I n ta l lation o f tra i n gauges to stee l bar
Figure 3.6: Stee l cages i n sta l led inside the form
F igure 3.7: Concrete cast i ng .
. .
Figure 3.8: Concrete v i bration
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...
Figure 3 . 9: Preparation of concrete cy l i nder amp les .
.
F i gure 3. 1 0: Concrete fin i sh i ng
F igure 3. 1 1 : Concrete cur i ng
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.
.......
F i gure 3. 1 2: Concrete de l i very . . ..
lump test
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32
. 33
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F igure 3. 1 4: Cube a nd cy l inder compre ss ion a nd spl itt i n g tests
F igure 3. 1 5: Materi a l Llsed i n the
SM strengthen ing system ..
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29
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Figure 3. 1 3:
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27
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38
. 40
.
F igu re 3. 1 6:
tr ngthe n i n g regime fI r peCl lllen
- 2 - 1 10
. . .. . . . . . . . . . . . . . . . . . .
..
F i gure"'. 17:
trengthcn ing regime for pec irnen A- 4 - 1 1 0
. . . . . . . . . . . . .. . . . . . . . .
. .
I· igure"'. 18:
trengt he n i n g regime for pec illlen A- 2- 1 1 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
F i gure 3. 1 9:
tre ngtile n i n g regime for sp c imen
Figure 3.20:
trengtilcn i ng regime for pec imen 8- 0-112 ................................................... 45
Figure 3.2 1 :
tre ngtile n i ng regime for 'pec i lllen 8- 0-H4 ................................................... 46
F i gu re 3.2:2:
trengthe n i n g regime for spec imen 8- 2- 112
. . . .......
F i gu re 3.23:
lrengl he n i ng regime for pec imen 8- 2-1-14
. . . . . ..
F i gu re 3.24:
l rengl he i ng procedure . . . . . . . . . . . . . . . . . . . . . . . .... . . . ..... . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . ..... . . . 49
F i gure 3.25:
c helllat ic v ie\\ of the lest etu p
Figu re 3 2 6: A Ie t i n progress
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47
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48
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F igure 4 . 1 : Photo of the control pecimen at fa i lure .
..
at fa i lure
42
- 4-1-12 ................................................... 44
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......
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. 51
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F i gu re 4 . 2 : Photos of pecime n A-
41
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51
. 57
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57
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59
F i gu re 4 . 3: Photo of spec ime n A- 2-1-10
Figure 4.4: Photos of pec i lllen A-S4-HO at fai lure
. . . . . . .. . . .
F i gu re 4.5: Photos of specimen A-S2-H2 at fa i lure
. . . . . . . . . . .. . . . . . . . . . . ..
F i gu re 4.6: Photo of spec imen A-S4-H2 at fai lure
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F igure 4.7: Load-deflection response of t he control pec imen .
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. .
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..
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59
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60
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....
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61
F i gu re 4 . 8: Load-deflection re ponse of specimen A-N ...................................................... 62
Figure 4 .9: Load-deflection response of specimen A-S2-HO .
.
.. . . . . . . . . . . .
.
. . . . . . . . . . . . . . . . . .. . .. . . . . . . . . . . .
63
F i gu re 4.10: Load-deflect ion re ponse of spec ime n A-S4-1-I0 ............................................... 64
F i gu re 4.11: Load-deflect ion response of specimen A-S2-H2............................................... 65
F i gure 4. J 2: Load-deflection response of spec ime n A-S4-H2............................................... 65
F i gu re 4 . 1 3: Load-deflection response for s pec imens of grou p [A] ...................................... 66
F igure 4.14: Tensile stee l stra i n response for specime n s of group [A] .................................. 7 1
F igu re 4.15: C F R P stra i n res ponse for pec imen s of group [A] ............................................ 72
F i gure 4.16: Concrete stra i n response for spec imens of group [A] ....................................... 75
F igure 4.17: Load versus support react ions for specime ns of group [A] ............................... 77
"I"
F i gure 4 . I 8: :vloment-deflect ion re pon e for peclmen of group [ ]
. . . . ......
.
.
. . . . . .... . . . . . . . .
.
.
..
78
!' i gure 4 . 1 9: Load-moment re lation hi p curves for specimens of grou p [ ] ......................... 8 1
F i gure 4.20: E l a t ic moments
. .. . .. . ............. . . . . . . ..... . . . . . . . . . . ......... ......... . . . .. . ... . . . . . . . . . ..... . . . ..... . . . . ...
F i gure 4.2 I: Photo of pcc ill1en 8-
at fa i lure
....
.
F i gu re 4.22: Photos of pec i men 8 - O-H2 at fa i lu re
.
....... . . . . .....
.... ..........
.
82
. . . . . . .. . . . . . . ........... ... ..... . ........
. .
. . . . . . . . . .. . . . . ....... . . . ......
.
88
. . . . . .. . . . . . . .
88
Figure 4 .23: Photo of pec i men B- 0-H4 at fai lure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
hgure 4.24: Photo f peci men B- 2 - H2 at fai lure . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
Figu re 4 .25: Photo of specimen B- 2 - H4 at fai lure
.....
.
.. . . . . . . . . . . . . . . . .
90
. ........... . . . . ...... . . .
92
... . . . . . . . . . . . . ....... ......... . .
Figu re 4.26: Load-deflect ion re p n e of speci men B-N
.
. . ......
..
.
.
.... . . . . . . . . . .
.
.. . .
.
Figure 4 .27: Load-deflect ion respon e of specimen 8- 0- H2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
Figure 4 .28: Load-deflection re pon e of pecimen 8- 0- H4 . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
F i gure 4.29: Load-deflection re pon se of specimen 8-S2 - H2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . 94
F i gure 4 .30: Load-deflect ion respon e of pec imen 8- 2-1- 14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
F igure 4 .3 1 : Load-deflect ion response for pecimen of group [B] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . 9 6
F i gure 4 .32: Ten i l e tee l t rai n re ponse for specimens of group [BJ .
F i gu re 4 .33: C F RP train response for spec i mens of grou p [8]
. . . 99
. . ... . . . .. . . ...... . . . . . ..... .
.. . . . . . ... . . . . . . . . ....... . . . . . ......
Figure 4 .34: Concrete train response for spec imens of grou p [B) .
. . .....
..
.
1 0)
1 04
......... . . .. . .. . . . . . . . . . .
1 05
.......... . . . . . .... . . . . ........
1 06
..
F i gure 4 .37: Load moment relationsh i p curves for group [B]
. . . ..
......... . . . . .. . . . . . ... . . . .
F i gure 4 .35: Load ver us support reactions for specimens of group [B] .
F i gu re 4 .36: Moment-deflect ion response for specimens of group [B]
.
.
. . . . . . . . . . .........
.
. . . ....... ......... . . . . . .
1 09
F i gu re 5 . 1 : Assumed stre s-strain re lat i on ship of concrete ( Hognestad et a! . 1 95 5 ) . . . . . . . . . .. 1 1 5
Figure 5 .2: Idea l ized stress-st ra i n relationship of steel
. . .....
F i gu re 5 .3: Ideal ized stres -stra i n re lationsh i p ofCFRP .
F i gu re 5 .4: Stra i n and tre
.
..... ......... . . . . .
.
.
. . . . ....... . .. . ..... . . . . . . .
. . . .. . . . . . . . .. . . . . . . . . . ...
d i stribution s along ect ion depth .
. . . . ..
.
.
.
. . . .. . . . . . . . . . . . ........
. . . .. . . . . . . .....
.
. ..... . . .... . . . . . .
1 17
1 18
. 1 19
Li t of Notation
ro. s sect ional area of a
.1(t'{f
Effecti v e cro s ecti on area of al l
'ros. section area of al l
:Jr."
M-C F R P tri p
F R P trip u ed i n strengthen i ng
RP tri ps used i n the saggi ng regions
cct ion area of a l l C F R P trips u ed i n the hogging region
A,
rea o r concrete l ayer i
A"
ross .ct i nal area of teel bar i
h
\\'idth o r the lab section
c
Depth r the neutral ax i s mea u red from the compres ion face of the slab
FRP
arbon fi ber rei n forced polymers
C
Load capac ity of the control pec i men w ithout cutout
Cs
Load capaci ty of the trengthened pec i men with cutouts
d
Depth of the tensi l e steel measured from t he compressi on face of the s l ab
d'
Depth of the compressi on steel measured from the compressi on face of t he
slab
dCI
Distance between plastic centroid of concrete secti on and centroid of
concrete l ayer i
dr
Distance between plastic centroid of concrete sect ion and center of the C F R P
stri p
dSI
Distance between plasti c centroid of the concrete section and center of stee l
bar i
Young's mod u l us of the concrete
Young's mod u l us of the C F R P
\.:\
Ef'
EfTic ienc) fact r
£�\
lod u l u of steel rci n forcem nt before yielding ( pre-yield stage)
E�p
10d u l u o f tecl rei n forcement after ) i e l d i ng (post-) ield stage)
f:.
oncrete tre
./,:
oncrete compre 'i\ e strength
.
.1:1
for given concrete train
Concrete stre s at the center of the layer i
./:,
oncrete pl i tt i ng st rcngth
Ii
trc
c
S
in
M-
F R P rei n fl rcement
./;,
Tensi Ie strength of the
./;
'teel tre s correspondi ng to t:s
II
tre
ISII
teel u l t i mate trength
FRP
i n thc stee l bar i
.h
Steel yield stre
h
Thickne s of l ab
L
Length o f one span of the slab stri p
Ie
Length of the cutout
LER
Load enhancement rati o
Lfs
Length of a l l C F R P stri ps used i n the sagging regi on s
Lf;'
Length o f a l l C F R P stri ps used i n the hogg i n g region
LI
Length of span i of t he conti n uous slab
LVDT L inear ariable deferential t ransfollT1er
.vo. 10
J 0 mm d i ameter steel rei n forci ng bar
No. 8 8 m m d i ameter steel rei n forc i n g bar
MER
Moment enhancement ratio
XII
\ I/? II'
loment from clastic anal}
\ /"" /1
10ment rr m experi ment
\ fJ"
I logg i n g m ment from elastic analysis
J /h/?Ip
I logg i n g moment from experi m nt
\ 1"
om i na l moment trength
M""
omi nal moment trength oC the hogging sect i on
J Im
o m i nal m ment trength of the saggi ng ect ion
l\ /u
aggi ng moment rrom e l ast ic anal ysi
J /, t't1'
agg i ng moment from experi ment
,\', .\ 1
'\lear nurrace m unted
Po
rac k i ng load
PII
omi nal l oad capacity pred i cted by the model
PII
U l t i mate load
P,
Y i el d i ng load
Sg
Strength gai n
Tje
E ffect i ve ten i l e strength of al l C F R P strips
)I'e
Width of the c utout
£c
Concrete strai n for a g i en loadi ng condi tion
£eo
Concrete strai n correspond i ng to the concrete compressi ve strength
cJ
Stra i n i n longi t ud i nal NSM-C F R P rei n forcement
c/mo"
C F R P stra i n at peak load
cft
R upture C F R P strai n
Cs
Stra i n i n tensi Ie steel rei n forcement
Gs
tra i n i n the compression steel rei n forcement
GSII
teel stra i n correspondi ng to the steel u l t i mate strength /su
:\e l l I
Steel t ra i n correspond i ng t the ) ield sIre sf;
J.l
Duct i l i t) i ndex
1 id- pan deflect ion at peak load
"
1 id- pan detlection at f i r t y ie l d i ng (second change
rcspon e)
[3%
loment red i tri bution rat i
Pr
F R P rei nforcement rati o
In
l oad-deflecti on
C HA PT E R 1 :
I N T RO D U CT I O N
1 . 1 I n t ro d u c t i o n
I n tal lati n of cutout i n exi t i ng rei n forced concrete ( R ) conti n uou slab
r r the pa
age
r er i ce d uct \\ i l l reduce the flexural capac ity. When such cutouts
are unavoidable, adequate measure shal l be undertak n to trengthen the oncerned
l ab and re t re th
fle,' ural
pre encc or opening of an
trength. The A I 3 J 8-08 B u i l d i ng C de perm its
i ze in flat plate fl oor systems provided that an analysis
i per rormed to en LIre that t rength and er i ceabi l i ty requ i rements are sati fled .
E:\.terna l l } -bonded composite plates or sheets are vul nerable to premature
delami nation \\ h i c h \\ ould l i m i t the gai n in flexural capac i ty and reduce the slab
duct i l it) .
udden fai l ure of the e terna l ly-bonded compo ite system woul d not al lo\
moment redi tribution betvv een agg i ng and hogg i ng region . Con equently, most of
t he urrent de ign guidel i nes on the u e of com posi tes i n strengtheni ng do not al low
moment redi stribution i n conti n uous RC
t ructures strengthened with external ly­
bonded composites. The external ! -bonded composite system is a l so su cept i b l e to
acts oh andal i sm, fi re, mechanical damage, and other weather cond i t ions.
To protect the composite rei n forcement from mechan ical and environmental
damage, it has been proposed to use a near-surface-mounted (NS M ) composite
sy stem, where composi te stri ps or rei n forc i ng bars are i nsetied i nto grooves precut
on the concrete surface and held in p l ace usi ng an epoxy adhesive as shown in Figure
1.1
(l I S Canada. 2004). The N S M composite plates are Ie s suscepti b l e to
premature delami nation t han composite sheets or plates bonded on the urface of the
concrete. The use of post-i nstal led N S M composi te rei n forcement as an alternati ve
sol ution to upgrade conti nuous RC sl abs with cutouts wou l d reduce the risk of
2
premature delami nation and could a l l \V for moment red i tribution i n conti n uou
structure .
Longitudinal grooves
F R P strips placed
G rooves fi l led with
cut Into soffit
in grooves
epoxy grout
Figure 1 . 1
ear urface Mounted
M ) Technique for a T- Beam ( J
Canada, 2004 )
1 . 2 S c o p e a n d O bj ec t ives
Th i
re earch ::lI m
to examl l1e the viab i l i ty of using post-i nstal led N S M
compo i te rei n for ement t o upgrade t h e flexural response of one-way conti n uous R C
l ab \ \ ith cutout in eit her t he sagg i ng and hogging regions. The mai n objectives of
t he pre ent study are:
1.
to i n vesti gate the effect of creati ng c utouts i n eit her t he sagging or hogg i n g
regIons on t h e fl ex ural response of one-way conti n uous rei n forced concrete
s l ab .
')
to
exami ne
the
e ffect i veness
of uSlll g
post-i nstal led
SM
composi te
rei n forcement to u pgrade the fl ex ural response of one-\ ay cont i n uous rei n forced
concrete slabs with cutouts.
3.
to i nvestigate the effect of vary i n g the amount of NSM composite rei nforcement
i n the saggi ng and hoggi ng regi ons on the flex ural response.
3
4.
to i ntroduce a n anal ytical approa h for pred i ction o f the flexural capac i t) o f one­
\\ <1) un trcngthcn d and strengthened cont i nuous rei n G rced concrete slabs \\ i th
and \\ i thout c utout .
1 . 3 T h es i s O u t l i n e
r h i ' re carch thesi con i t of six chapters a fol l ow .
Chapter I : I ntroduct ion
Thi chapter h i gh l i ghts the i mp0l1ance of the research topic. I t d i scusses the
problem briefl)
and i denti fie
th
major objecti ves. The thesis out l i ne and
organizat ion of thi re earch work is a l so pro ided i n the same chapter.
Chapter 2: Lit rature Re ie\
Thi s chapter presents a l i terature revie\ of the avai lable previous stu d i es on
flexural strengthening of RC el ements conta i n i ng open i ngs using composites.
Avai lable tudies on strengthening of cont i n uous RC structures with composi tes are
al 0 re\ i ewed and d i sc ussed .
Chapter 3 : Experi mental Program
Th i s chapter presents deta i l s of the experi mental program, descript ion of test
speci mens, fabricati on process, material propert ies, and strengthe n i ng methodology.
Detai l s of test set-up and i n strumentation are a l so presented i n t h i s chapter.
Chapter 4: Experi mental Results
Results of the experi mental test i ng are presented
tn
t h i s chapter. The
effecti veness of using N S M composite rei n forcement to upgrad
the flexural
capaci ty of cont i n u us RC l ab tri ps i d i cu ed. The experi mental re ult i nc l ude
l oad capac i ty , fai l ure l1loJ�, denection re pon e, duct i l it
i nd x , train response o f
i nternal 'teel and N M c mpo ite rei n forcement, concrete train respon e, support
reaction . moment-dencct ion respon e, and l oad ver u moment relation h i ps, The
moment redi tri bution rat io
of the sagging and hogging region
have been
a l c u l ated and d i cu sed . The effici ency of strengthen ing schemes are discus ed at
the end of the chapter.
Chapter 5 : Anal ) t ical
del i ng
This chapter i ntroduces an anal y t ical approach that can pred ict the l oad
carr) ino capac ity of one-way continuous rei n forced concrete l ab with cutouts and
strengthened
\\
ith
M composite rei n forcement . The accuracy of t h e proposed
anal yt i cal approach has been demon t rated b
compari ng its pred ictions
v
ith the
experi mental resu l t .
Chapter 6: Concl u ions and Recommendations
General conc l u ions of the work along with recommendation for fut ure
studi es are presented i n t h i s chapter.
5
C HA PT E R
2:
L I T E RA T U RE RE V I E W
2 . 1 I n t ro d u c t i o n
A l though, igni (jcant research v" ork ha been carried out during the la t three
decaues t
i m e t i gate the tructural performance of RC tructure strengthened \\ ith
compo, i tcs. fe\\
tudie
focLl ed on cont i n uou
RC
tructure
with cutouts. Thi
chapter presents a brief re\- ie\\ of the avai l able experi mental research \\- ork on
trengthcning 0 1' R
lab' \\- ith cutouts u i ng composite rei n forcement. A ai l able
t uu i c' n trengthen i ng f cont i n uous RC flexural el ements have al
0
been re iewed
and rre,enled i n thi chapter.
2.2
t u d i es o n S t re n g t h e n i n g o f RC S J a bs w i t h C u t o u ts U s i n g
Co m po s i tes
Vasq u ez and Karbh a ri ( 2003 ) exam i ned the v i ab i l ity of usi ng external ly­
bonded p u ltruded carbon fi ber rei n forced polymer ( C F R P ) strips to u pgrade the
capaci t ) of RC slabs \ i t h cutout . A total of four slabs with a rectangular cross
ect ion were constructed and tested . A typical test speci men had a length of 6000
mm and a c ross section d i mensions of 3200 x 1 80 m m . Each s l ab contai ned a central
cutout with a s ize of 1 x 1 .6
m.
The test spec i mens were d i v i ded i nto two groups
based on the app l i ed load position as shown in F igure 2 . 1 . Each group contai ned a
slab w i t hout strengthen i ng to act as the base l i ne. Test parameters incl uded the
l ocation of the app l i ed load and the external l y bonded C F R P con figurat ion. The
concrete compressi ve strength was 2 7 . 6 M Pa and t he steel rei n forcement nom i nal
yield strength was 420 M Pa. The strengtheni ng regime consisted of bond i ng of
6
F R P str i p \\ ith a \\ idth of either 50 mm or l Oa mm
pultrudcd
n the concrete
urface around the cutout. The pul truded C F R P stri ps had a ten i l e mod u l us of 1 5 5
Pa, ten ' i l e trength o f 2400
fai led b) debond ing of the
bonded
f 1 .2 mm. The trengthened slab
I Pa, and thickne
F R P strip and pee l i ng of concrete co er. The e terna l l y
F R P tri ps incrca ed the ne ' ural capac ity of the s labs
\
ith cutouts. The
trength of the 'trengthened slabs \\ as al most the ame as the origi nal strength before
th cutout.
T
..
Roller
Supporu
t
�m
1 .6
�
14
..
0 38
1 .85
3.2 m
�
1 .0 m
6.0 m
(a)
�I
1
m
T
m
�
3.2 m
Opening
Roller
Supports
6.0 m
14
·1
(b)
1
Figure 2 . 1 : Load position for tested l abs ( Vasquez and Karbhari 2003 )
T a n a n d Zhao (200"') i n vestigated the structural behav ior of one way
rei nforced concrete sl abs \ i t h open i ngs strengt hened
of eight
l ab
v
i t h C F R P composi tes. A total
"" i t h a rectangul ar c ross section were constructed and tested. Test
speci men had a length of 2700 mm and c ross sect ion d i mensions of 2400 x I S O
Each s l ab had t\-'vo edge beams with cross section d i mensions of 200
x
300
mrn .
mm
as
sho\\TI i n Figure 2.2. Test parameters i nc l uded the l ocation of the c utout, the size of
t he c utout, the load app l i cat ion, and t he strengthen i ng system . The concrete
compressi ve strength was 30 M Pa. The steel yield strength was 600 M Pa for t he
longitud i na l bars and 640 M Pa for the t ransversal bars. The strengtheni ng reg i me
consi sted of two systems app l ied using an externa l l y bonded technique. The fi rst
system consisted of fi ber sheets. The second system consisted of precured strips. The
7
strengthened pec l lnen experienced a h i gher load capac it)- than the un trengthened
speci mens \\ ith or \\ ith llt a ut ut. The fai l ure mode depended on the opening size.
The 'pe i men experienced flexural mode of fai l ure i n i t i ated by C F R P debond i ng.
The ' F R P heet
prccurcd
1
1
\\ ere more effective in i mpro i ng the flexural capac i ty than the
F R P tri p becau e or th ir better b nd ing cond i t ion.
,
m
RA J
1""
F'1
'
�b � l
,
- SID_ a..-
i
L
A
fT§I
r-�
�oo
!J!>.i.lOO
J
��-L---1�� _�
RAl. AS I . ASS
A
I�
-'" I�
m
I
100
yc.;.
AS2
"
,
:::;
:::
=
::
::
�
::::
§
�
::;
,
�
II
I""
11M
I Z!OO
I"", :"l
(a)
a i09 I
iM
l
AS6
I
600 a
} =L='�f:�f-t--'..i:=:=�=�=�=-i�t::- --[===,:
.
1 2001
(b)
2)00
1 2001
F igure 2 . 2 : ( a) c hemat i c plan l ayout ( b ) section A-A ( Tan and Zhao 2004)
Boon
et a1. ( 2009) stud i ed the flexural behav ior of rei n forced concrete slabs
\", i t h an openi ng. A total of fi ve s labs with a rectangular cross section were
constructed and tested. Test speci men had a length of 1 1 00 mm and a cross sect ion
d i mension of 300
x
75 mm. Test parameters i nc l uded the d i rect ion of the add itional
rei nforcement surround i n g the open i ng. The ope n i ng size was 1 50
x
300
01 01 .
The
opening reduced the slab area by 1 5%. The concrete compressi ve strength was 25
2
Imm . The strengt heni ng regime consi sted of addi ng add it ional steel surrounding
8
the ope n i ng. fhe test pec i mens were d i \ i ded accord i ng to t he strengthen i ng regi me,
hence the fir t speci men d id not conta i n an add i t i onal steel or open i ng. The second
spe i men d i d not contai n add i t ional steel but it contai ned an open ing. The t h i rd
spec i men contai ned an open i ng \\ ith longitud i nal and transverse steel surroundi ng it.
The fourth speci men contai ned an opening \-\ ith d i agonal steel placed at the comers
or the ope n i ng. The la t spec i men contai ned an opening with longi tudi nal, tran
and d i agonal
teel
erse
urround i ng i t . The rectangu l ar open i n g reduced t he flex ural
,trength of the ' J ab b) 3 7 0 '0 . A lthough, the add i tional steel i ncreased the flexural
strength of th
pec i men w i th t he openi ng, it could not re tore t he flexural capaci t)
of the contr I slab without the ope n i ng. The use of longitud i nal, transverse and
d iagonal add i t i onal rei n forcement was the most effect i ve method to i ncrease the slab
capa it) .
K i m a n d S m i t h ( 2009 ) conducted a study on strengthen i ng of rei n forced
concrete l ab \\ i t h l a rge penetrati ons usi ng an hored C F R P composi tes. A total of
three one-way rei n forced concrete s labs \- ith a rectangu l ar c ross section were
constructed and tested. Te t speci mens had a l ength of 3400 mm and cross section
d i mension
of 3200 x 1 60 mm. Test parameters i ncl uded the avai l abi l ity of an
anchorage system to support the CFRP sheet. The concrete compressive strength \-
as
i n the range of 3 5 to 42 M Pa. The steel yield strength was 546 M Pa. The
strengthen i ng reg i me consisted of usi ng external l y-bonded C F R P sheets attached to
the s l ab surface with and w i t hout C F R P spi ke anchors. TIle control spec i men
experienced crushi ng of the compressive concrete in the constant moment region.
The strengthened unanchored speci men fai led by debond i ng of t he CFRP as shown
i n F igure 2 . 3 . The strengthened anchored spec i men fai led by i ni t i a l debond i ng of the
C F R P fol lowed by concrete compressi ve fai l ure and rupture of the i nternal steel
9
rei n forcement. Te t re u lt
ind icated that flexural strengthen i n g with C F R P sheets
around the openi ng increa ed the load capacit of the slab compared
speci men . The u e of
FRP
p i ke anchor
\
ith the control
delayed the debond i ng of the C F R P
heets. and hence l ightly increa ed the load capacity. The sp ike anchors offered also
a po t-peak re er e of strength and im pro ed the s lab duct i l i ty.
F i gu re 2 . 3 : Debon d i ng of CFRP ( K i m and Sm ith 2009)
S m i t h a n d K i m ( 2009) carried out a study on strengthen ing of one-v ay
pan n i n g rei n forced concrete slabs
six
\
ith cutouts using C F R P com posites. A total of
l abs w ith a rectangu lar cross sect ion were constructed and tested. Tested
peci men had a lengt h of 3400 mm and cross section d i mensions of 2500
x
1 60 mm
for type ] and 800 x 1 60 mm for type 2 as shown i n F igure 2.4. Test parameters
i ncluded the position of the app l ied load and the presence of the cutouts. The average
concrete compressi ve strength was 44 M Pa. The steel y i e l d strength was 557 M Pa.
The strengtheni n g regi me consisted of add i n g two l ayers of C F R P sheets using
external l y bonded techn ique. Two control speci mens without a cutout acted as a
base l i ne. Test resu lts i n d i cated that the unstrengthened specimens encountered a peak
l oad of 48.5 kN ; however, the strengthened specimen experienced an enhanced
average peak l oad of 75.9 k N . A l l strengthened slabs fai led due to debon d i ng of
C F R P sheets. The range of debon d i n g was dependent on the locat ion of the app l i ed
10
load . The spec imen \\- jth a l i ne load adj acent to the cutout experienced a trans erse
bend ing act ion. \\- h i ch delayed debonding of the CFRP heet and thu i ncreased the
load capacit .
Figure 2 .4 : Test slabs ( S m ith and K im 2009)
Seliem et a l. ( 2 0 1 1 ) reported a case study on restoration of flexural capacity of
continuou one-wa, rei n forced conc rete s labs \ ith cutouts. A total of five field tests
\\ ere conducted on RC b u i l d i ng slab requ i red demo l i tion as shown in Figure 2 . 5 . The
concrete compressive strength
\
as 1 7. 5 M Pa and the steel y i e l d strength was 586
M Pa. Two strengthening techn i ques were i nvesti gated, nam e l y extemal l y bonded
C F R P sheets with and w ithout spike anchors, and
S M -C F R P rei n forcement. The
test was conducted under four point bend ing con figuration to develop a constant
moment zone. The effic i ency of each method was eval uated based on the fai l ure
mode. F lexure started at the m i d span, and then developed from the four comers of
the cutouts in longitudinal d i rect ion . The slab without a cut - out fai led i n flexure due
to a m ajor crack developed on the top surface. The spec i mens strengthened with
S M -C F R P rei n forcement had h i gher e ffect i ve CFRP strain than the speci men with
extemal l y bonded CFRP sheets. The
SM-C F R P strengthen ing system i ncreased the
load capac i ty of the s l ab with a cut-out by 1 0%, but i t d id not enhance the st i ffness of
the spec i men . The use of extema l l y bonded C F R P w ithout anchors i nsign i ficantly
1 1
increa ed the lab trength. The strength of the slabs strengthened with
or extern a l ! ) bonded
FRP
v.
ithout anchor was lower than that of the contro l . On
the contrary, externa l l y bonded
D e u ral capac i t
•
-CF R P
FRP
stem w i t h p i ke anchors restored t h e fu l l
.
IiSS 1.S2.. 1x 1.S2..1x 12.7-1067 ,.."
HiSS 101.61101.6119.5- I98J mm
ll53 ,.."
._-- I+fdnIuIJc ]ar:: 1:s
-
p-.
HSS lOI.60101.6119.5- I067 mm
F igure 2 . 5 : Test setup ( Sel iem et al 20 1 1 )
2.3 S t u d i es o n Strengt h e n i n g of Con t i n u o u s Struct u res with
C o m posites
EI-Refa ie et al.
(2003 ) carried out a study i n saggIng and hogging
strengthen i n g of conti n uous rei n forced concrete beam s using CFRP sheets. A total
of eleven rei n forced concrete two-span beams with a rectangu lar cross section were
const ructed and tested. Test spec i men had a lengt h of 4250 mm and cross section
d i mensions of 1 50
x
250 m m . Test parameters i n c l uded the position, l ength, and
2
n u m ber of C F R P l ayers. The concrete compress i ve strength was 30 N/mm . The
12
n m i naJ tecl ) ield trength was 520 N/mm 2 . The pecl men were d i v i ded i nto two
gr up . Each group contai ned one un t rengthened contr I spec i men. An ext rnal ly
b nded tec h n i q ue \ a
used to strengthen the spec imens with CFRP sheet . Te t
re u l t i ndicated that the external
F R P sheet i ncreased the beam load capac i t
by
more than 1 8% for the fi r t group and more than " 4% for the second group relat i ve
to til
load capac i ty of the c rre pon d i ng control beam. The moment red i stri bution
\v as reduced for both groups compared with the correspond i ng contro l peci men i n
both agging and hogging regi n s . The duct i l i ty i ndex was reduced a the number of
C F R P heet i ncreased, si nce as the trengthe n i ng increased the struct ure el ement
t nded to be more britt le. It was also on l uded that the add i ng add i t i onal number of
F R P layer more than an opt i mal l i m i t did not have an. effect on the flexural
re pon e.
I 0, i ncreas i ng the lengt h of the C F R P sheet d i d not prevent a pee l i ng
mode of fai l ure i n the strengthened beams. I t was noted that the moment capacity
enhancement d ue to strengtheni ng was h i gher than the load capac ity enhancement.
Ash o u r et a l .
(2004) performed a study on flexura l strengtheni ng of rei n forced
conti n uous beams using C F R P l a m i nates. A total of sixteen rei n forced concrete
conti n uous beams with a rectangular cross section were constructed and tested . Test
speci men had a length of 8500 mm and c ross section d i mensions of 1 50 mm x 250
mm. Test parameters i nc l uded l e n gth, thickness, posi tion and form of t he C F R P
2
lami nates. The average concrete compress I ve strength was 3 7 N/mm . The
2
l ongitud i nal steel had nomi nal y i e l d strength of 520 N/mm . The speci mens were
d i i ded i n to three groups and each group had
a d i fferent arrangement of i nternal
steel bars and external C F R P rei n forcement. A l l strengthened spec i mens had h i gher
l oad capac ity and l ower d uct i l ity than those of the control speci men. The
strengthened speci mens fai led by either pee l i ng fai l ure of the concrete cover adj acent
)3
to the
F R P heet or tensi le rupture of C F R P a
length of the
hown in F i gu re 2 . 6 . I ncreasi ng the
F R P heet to co er the ent i re negat i ve or pos i t i ve moment zones d i d
not a lter t h e mode of fai l ure and \\ as not effect ive i n fu rther i mpro i ng the capaci t
of cont i n uous beam with a tensi le rupture mode of fai l ure. I t was also conc l uded
that the enhancement of the bending moment capac ity of a conti n uous beam due to
external strengthen ing w a h igher than the enhancement of the load capacity. Th is
happened becau e i ncrea i ng the moment capac ity loca l l y may not always lead to a
corre pond ing i ncrease i n the load capac ity app l i ed to the continuous beam . The load
capac i ty in cont i nuou RC structure depends on the global beha ior rather than local
beha" ior.
Tensi le rupture of C F R P
Pee l i ng fai l ure o f concrete cover
F igure 2 . 6 : Fai l ure Mode (Ashour et a J . 2003)
A rd u i n i et at
(2004) studied the performance of one-way rei n forced concrete
slabs strengthened w i t h an external l y bonded fi ber rei n forced polymer system . A
total of tv,,' enty s i x slabs with and w i thout an overhang were constructed and tested .
The geometry and l oad ing configuration a l l owed for the study of positi ve and
negati ve moment regions. Test spec imen had a length of either 5000 mm or 6500
mm and cross section d i mensions of 1 5 00
x
240
m m . The strengthen ing regime
consi sted of manual l y l ay-up CFRP l a m i nates. Test parameters i n c l uded the amount
of i nternal steel rei n forcement, n u m ber and width of the C F R ? pl ies. The concrete
14
c mprcssl \'e trength \\ a 3 8 .
I Pa. The teel ) i e l d trength \\ a 5 5 7 M Pa. The test
results i nd i cated that th un trengthened peci men fai l ed due to teel y i el d i ng, w h i le
the domi nate fai l ure mode for the strengthen d p c i men was fi ber rupture fol lowed
b) pee l i ng i n the con rete cover. The
F R P strengthening enhanced the peak load b
up tc 1 22°'0 relat i \'e to that of the benchmark spec i men. It was also concl uded that
tlc:\ ural cracks de\ eloped at th tangential tre s d i stribution at the surface between
the C F R P l a m i nate and concrete.
G ra ce ct a l . (200-t) cond ucted a study on strengt hen i ng of cant i lever and
c ntinu us beams usi ng a tria i a l l } braided d uct i le fabric sho\ n in Figure 2 . 7 . A
total or i x beams
\\
ith a rectangul ar c ro s section were constructed and tested . Test
speci men had a length o f 4267 mm and eros
Te t paral11eter
ection d i mensions of 1 5 2 x 254 111111 .
i nc l uded the location of the support and the n umber of triaxial
d uct i Ie fabric or CFRP l ayers. The concrete compressi ve strength was 4 1 .5 M Pa. The
teel ) i el d strength was 490 M Pa. The spec i mens were d i v i ded i nto two groups.
pec i l11ens of the fi rst group were tested with one overhangin g cant i l ever, whi le
pec i men of the second group were tested with two conti n uous spans. Each group
i nc l uded an u nstrengt hened peci men to act as a control spec i men. The rema i n i ng
t wo beams i n the fi rst group were strengthened with two l ayers of triaxial d uct i l e
fabric for t h e fi rst beam. a n d four C F R P l ayers for t h e second beam. The rem a i n i n g
t w o beams i n t h e second group were strengthened w i t h one l ayer of triax i al d uct i le
fabric for t he fi rst beam, and two C F R P l ayers for t he second beam. Test resu l ts
i nd i cated t hat flexura l strengtheni ng \ ith triax i a l duct i l e fabric and C F R P sheets
i ncreased the fai l ure load by 3 6% and 42%, respectively. I t was a l so noted that the
strength of the spec i mens strengthened with C F R P sheets was hi gher than that of the
spec i mens strengthened with the triaxial d uct i l e fabric system. A lt hough the
·trengthened spec i men
exh ibited Jo\\ er d ucti l i ty than the c ntrol
peci men , the
triax i al d uct i le fabric \\ a capabl o f pro i d i ng rea onabl duct i l i ty.
H E ll..'\ial yarn
(E-gJass fibers)
LE 3lCia.1 yarns
(Ulrra hi h modulus
carbon
fibers)
'IE a..'( ial yarns
(High modulus carbon fibers)
HE dia unal yarns
(E-gJass fibers)
ME d i.l onal . ams
(High modulu� carbon fibers)
Figure 2 . 7 : Detai l s of triaxial d uct i l e fabric geometry ( G race et al . 2004)
Liu
et a l . (2006) i n esti gated the moment red istribution of F R P and steel
urface p lated RC beams and slabs. There were several types of debondi ng
mechani m
such a
plate end debon d i ng, crit ical diagonal crack debondi ng, and
i ntermediate crack debondi ng. The rate of moment red istri bution for the p lated
strengthened speci men
was l ower than the unplated speci mens. I t
v
as noted that
strengt hening the hogging and saggi ng regions of the spec i men with a steel plate
tended to have an i ntermedi ate debond i ng in the hogging region before y i e l d i ng of
the steel plate. I t was found that t he moment red i stribution occurred on l y i f
debondi ng took place after yield i ng of i nternal steel rei n forcement. I t was concl uded
t hat in poorly desi gned conti n uous beams, premature debond ing of external
rei n forcement can happen in a certai n region before the other region has achieved its
moment capacity. H ence, i t was suggested to consider moment red istri bution i n the
16
anal ) si s of trengthened RC
tru ture
because simpl) al lo\'\ ing for no moment
red istri bution m ight not ah\ a) be a are a umpt i on .
Coccia et a l . (2008) carried
ut a tudy to in e t i gate the red i stri bution of
bend i ng moment in c nti nuous r i n forced concrete beams trengthened wi th FRP.
n anal)1ieal model \\ a de eloped to defi ne the relat ionsh i p of bend ing moment
\ er u '
un ature. The moment-curvature relation h i p \Va d i v i ded i nto three phases.
Th po�t c rac k i ng phase ( fi r t pha e) \\ a i m portant to reveal the transition between
the uncracked and cracked stages. I n the second phase, a l l the clements i n the
p c i men \\ ere ubj ected to tre s and t rai n. Therefi re; after cracking the concrete
and F R P i nterference occurred with a red i stri but ion of stress and stra i n . I n the fai l ure
tage. the steel
\\, h i l e the
tress tended to have a l i near behav ior along the rei n forc i ng bar,
t ra i n patterns were bi l i near. 1l1e add ition of F R P at the hogg i n g and
agg l l1 g regions of the beam
enhanced the u l t i mate load by 20 %; however. it
produced the \\'01' t ca e senior in terms of global duct i l i ty. It was a l so concl uded that
i ncreas i n g the amount of F R P at the saggi ng or hogg i n g region reduced the moment
red i tri bution ratio b
20% and 50% for speci mens with one and four F R P sheets,
re pecti e l y .
S i lva a n d I be l l (2008) conducted a n analyt i cal study t o eval uate the moment
red istri bution in conti n uous FR P-strengthened rei n forced concrete beams. The
i nvest i gati o n of moment redistri bution in F R P-strengthened concrete tructures was
cond ucted by connec t i ng such behavior to the level of duct i l i ty at the critical sect ion .
Generated results from a theoret ical model were based on d uct i l i ty demand . Resu l ts
of an analytical model were compared to l i m i ted experi mental data publ i shed by
others. Eval uation of the moment red i stri bution i n FR P-strengthened RC sections
17
\\ a founu to be more com pie, than that of con venti nai l ) rei n forced concrete
sections.
loment
reu i tri buti n
i m mcdi atel ) aftcr y ie ld i ng
developed
in
F R P-strengthened
f the I ngitudi nal steel rei n forc i ng.
ho\\ cd that if a section can d
RC
beams
nalyt i cal result
elop a cur ature duct i l ity capaci ty gr ater than 2.0,
m ment rcd i tribution i n the order of at lea t 7 .5% can be achieved.
J u m a a t et al ( 20 1 0) re ie\\ ed publ i shed art i c les on flexural strengtheni ng of
rei n forced c ncretc beam
focuscd on cont i n uou
and
lab . The re em-chers conc l uded that few studies
beam . Particularly, experi ments on strengthen ing the
negat i \t! moment region' of cont i n uous T beams \ver
beam LI I ng
FRP lami nate. The researcher
rare to fi nd continuous T­
poi nted out that studyi ng the
trengt hen i ng of the negati ve moment region was important because this region
i nc l uded ma" i m ul1l moment and hear s i m u l taneo us l . Externa l ly bonded technique
enhanced the load capac i ty of the beams but reduced the duct i l ity . A simple method
of appl) i ng C F R P sheets in the negative moment regions \ as proposed.
Farahbod a n d Mostofi n ejad ( 20 1 1 ) exam i ned the moment red i stri bution i n
rei n for e d concrete frames strengthened with C F R P sheets. A total of s i x t\vo-span
rei n forced frames \\ i th a rectangular c ross section were constructed and tested . The
length
of the bemTI and col um n of the frames were 4300 mm and 2200 mm,
respecti \ e l ) \\ i t h cross secti on d i mensi ons of 200 x 200 mm as shown in Figure 2 . 8 .
The stud) i n esti gated the response of unstrengthened frames, and strengthened
frames with di fferent l ayers of C F R P with and without mechan ical anchors. The
concrete compressi ve strength was 33 M Pa. The C F R P had u l t i mate strength of 3900
M Pa, tensi l e mod u l us of 230 G Pa, and u l t i mate stra i n of 1 .69%. Test results
i nd icated that the load carry ing capac i t i es of the frames i ncreased by 20% to 38%
after trengthen i ng, w h i l e the flexural capac i t i es had an i ncrease of 9% to 20% and
18
3 5% to 55% at the negati e and po i t i e moment regions, re pecti ely. I t \ a al 0
concluded that the load capac ity o f the str ngthened frames V\ ith mechanical anchors
\\ a enhanced by 3% to 5% 0 er that of the strengthen d frames without anchors. On
the other hand. the fle ural moment capac it
of the strengthened frames \ ith
mechan ical anchor exh ibited an enhancement of 6% to 8% compared to the frames
\\ ithout anchors. I t \Va
conti nuou
frame
concl uded that moment red i stribution can occur i n
trengthened with C F R P sheets as a resu lt of concrete cracki ng,
ield i ng o f ten i l e tee l . and grad ual s l i p of the strengthen ing sheet at the contact
point w ith concrete. The moment red i stributi on value depended on quantity and
con figu ration of C F R P retrofitti ng, and presence of mechan ical anchorage. A
max i m um m oment red i stribution val ue of around 56% was recorded .
red i tribution in frame
Moment
strengthened with C F R P and mechan ical anchorage was
reduced b) 1 0% to 1 5% com pared to thei r correspond i ng strengthened frames
without mechan ical anchorage.
F i gu re 2 . 8 : Test setup ( Farah bod and Mostofinej ad 20 1 1 )
Aiello a n d O m b res ( 20 1 1 ) studied the moment red i stribution i n continuous
concrete beam s strengthened with F R P . A total o f six beams with a rectangu lar cross
19
section were con tructed and tested. Test pec i m en had a length of 3500 mm and
cro
ection d i men ion of 1 50
200 m m . The concrete com pres i e strength \\ as
2 1 . 1 M Pa. The teel yield strength wa 5 5 7 M Pa. The strengthen i ng regime consi ted
of add i ng C F R P trip
at the
agging and hogging regions. A te t in progress i s
ho\\ n i n Figure 2 . 9 . Test resu lts ind i cated that strengthen ing t h e spec imen
In
agging region on I ) re u l ted in approxi matel y 3 5% increase i n load capacity. The
load capac ity of the pec i men trengthened in both sagging and hoggi ng regions was
approx i mately 6° 0 h i gher than that of the spec i men strengthened on ly in the saggi ng
regIOn.
1 2% enhancement i n l oad capaci t y wa recorded when the spec i men \ as
strengthened I n the hogging region onl . I t was also concl uded that proper
strengthen ing con figuration a l l owed for up to 20% moment red i stribution in F R P­
trengthened conti nuous RC beams.
F igure 2 . 9 : Test in progress ( A i e l l o and Ombres 20 1 1 )
D a l fre a n d Ba rros
( 20 1 1 ) studied the effecti veness of using N S M - C F R P
flexura l strengthening techn ique t o i mprove t h e flexura l response of continuous R C
slabs. A total of two slabs w ith a rectangu lar c ross section were constructed and
20
tested . I e l pe i men had a length of - 850 mm and c ro s section d i men ion of 375
mm x 1 20 mm. fhe le't parameters i nc l uded the location of the app l i ed C F R P
lami nate . The con rete compres i ve strength w a 30 M Pa. The teel ) i e l d strength
\\ as 446 M Pa. The strengthen i ng reg i me con i st d of usi ng
M - C F R P technique as
shO\\ 11 in Figure 2. 1 0. The test results indi cated t hat N M-C F R P strengtheni ng
en hanced th
load capac it
b) 29%. Apprec iable moment redi stribution val ues of
2 1 0 0 and 27°'� \\ ere recorded � r the trengthened l ab stri ps.
!� '
;/1
.
(hI
,
. .
;
-�
' f�
F igure 2 . 1 0: N M-C F R P lami nates la out ( Da l fre and Barros 20 1 1 )
K a i e t a 1 (20 1 1 ) conducted experi ments on fou r t wo-span cont i n uous RC T-
beams. The test spec i men had a length of 5400 mm, web width of 200, flange width
of 900 mm, flange thickness of 80 mm, and total depth of 300 m m . Three spec i mens
were pre-heated for 75 m i n utes and one speci men was not. Two of the pre-heated
spec i mens \vere stren gthened
com pressi e strength wa
30
\
ith external l y bonded C F R P sheet . The concrete
2
Imm , The steel nominal y i e l d strength was 350
2
Imm . The strengthen i ng regi me consi sted of apply i n g C F R P sheet using external l y
bonded tec h n ique at either the hoggi n g o r sagging regions. The test re u lts indicated
that pre-heat i ng s l i ghtl y reduced the l oad capaci ty by 3 , 5%. F l ex ural strengtheni ng i n
the hoggi n g region o n l y had i ns i gn i ficant effect o n the l oad capacity.
A 1 6%
i ncrease i n the load capac ity was recorded after strengthe n i ng i n the sagging region
21
only .
The load capaci t) of the pre-heated trengthened pecl men \\ ere the same a
or h igher than that
r the contr I peci men. The trengthened pec i mens exhibited a
tensi le rupture or the
F R P heet ' a a fai l ure mode. The pec i men strengthened i n
the hogging region and that strengthened i n the agging region experienced C F R P
errect i ve tra i n v al ue of 63% and 68% r the u l t i mate CFR P strength, respectivel .
The
trengthcned
pec i men
experienced signi ficant reduction i n d uct i l ity i ndex
compared \\ ith that of the control spec i men.
2.4
Rese a rc h S i g n i fi c a n c e
I n tal lation of cutouts i n ex i st i ng RC conti nuous slabs for the passage of
sen ice d uct \\ould result i n a sign i ficant reduct i on i n the flex ural capac i ty . When
uch op n i ngs are una o idable, adequate measures shal l be undertaken to strengthen
the concerned
l ab and restore the flexural strengt h . Few stud ies on flexural
trengtheni ng of simpl -suppOlted slab with cutouts were found i n the l i terature.
The response of conti n uous RC beams or slab stri ps strengthened w i th composites
ha a l so been i nvestigated by fey re earchers. To the best knowled ge of the author,
no stud i e were carri ed out on flexural strengthen i ng of conti n uous RC slab stri ps
\vith cutouts. T h i s research exami nes the v i abi l i ty of using N S M composi te
rei n forcement as a potential sol ut i on to afeguard an acceptable marg i n of safety and
serviceabi l i ty of conti n uous RC s l abs \ i th cutouts. The results are expected to assi st
practi t ioners and researchers i n obtai n i ng a sat i s factory design sol ut ion for
retrofitt i ng one-way RC conti nuous s l abs with cutouts. F i nd i ngs of t h i s research are
antic ipated to develop existi ng desi gn gui del i nes and standard s for flexure-defi c i ent
RC con t i n uous structures strengthened with composite rei n forcement.
C H A PT E R 3 :
E X P E R I M E N T A L P ROG R A M
3 . 1 ) n t ro d u c t i o n
The experi mental program of th
current
tud
consi ted of te t i n g ele\ en
one-\\ a) !\\ o pan ont i n uou rei n forced concrete ( RC ) slab . Fi e l abs had a cutout
in the 'agg i n6 region , fi \ e s lab had a cutout i n the h gging region, and
had no c utout t
act as a b"nchmark. The cutout
thickne
slab. The , lab
of th
\\ itb cutout
\
ne slab
en! complete ly through the fu l l
were e i t her un trengt hened or
trengthened in Ilex ure \\ ith near- urface-mounted (
M ) carbon fi ber-re i n forced
pol ) mer ( F R P ) compo i te tri ps.
Th i s chapter presents deta i l s of the experimental program, de cript ion of test
peci men '. fabrication proce s, material properties, and strengthen i ng methodology.
Detai l o f the test et-up and i n t rumentation are a l so presented i n t h i s chapter.
3 . 2 Test P ro g ra m
The mai n objecti ves of t h i s experimental work are to:
•
I n e t i gate the e ffect o f creati ng a c utout i n the agg i n g or hogg i n g region on the
flex ural response of one-way conti nuous RC slabs.
•
examme
the effect i veness of uSll1 g post-i nstal l ed
S M -C F R P composite
rei n forcement to upgrade t he flexural response of one-way conti n uous RC slabs
\v i t h c utouts.
•
tud)
the e fTect
r v a!") I ng amount
and d i tribution of the
rei n forcement between the agging and h ggi ng regions o n the fl
of conti n u u R
M- FRP
x ural
respon e
lab \\ i t h c utout .
The te t matri x i given i n TabJe 3 . 1 .
two pan continuou R
he test program consi sted of eleven one-\ ay
s labs with a cutout i n either the hogg i n g or saggi ng region,
exc pt t he control slab that had no cutouts. The control slab
w as
not strengthened .
The rema i n i ng ten speci mens were d i v i ded i nto two groups, [ AJ and [ BJ , ba ed on
the I cat ion f the c utout.
Table 3 . 1 : Te t Matri
Ten ion Steel
Rei n forcement
Grou p
o Cutouts
4
Designation
Hoggi n g
agg l llg
Control
Strengthening Regime
o. 1 0
4
. 10
Grou p [ A]
C u tout i n
Sagging
Region
Group [ B]
C utout in
Hogging
Region
4 No. 1 0
2 No. 1 0
2
4 No. 1 0
Diameter of No. 1 0 st eel bar
=
0. 1 0
1 0 mm
Sagg i n g
Hoggi n g
-
-
Control
-
-
A -N S
N S \ -CF R P
( 2 strips)
-
A-S2-HO
N M-CF R P
( 4 strips)
-
A-S4-HO
S M-CF R P
( 2 strips)
NSM-CF RP
(2 stri ps)
A-S2-H2
N S M-CF R P
(4 strips)
N SM-CF R P
(2 stri ps)
A-S4- H 2
-
-
B-NS
-
N SM -CF R P
( 2 strips)
B-SO-H2
-
N SM-CF RP
(4 strips)
B-SO-H4
NSM-CF RP
( 2 stri ps)
NS M-CF RP
( 2 strips )
B-S2- H2
N S M -CF R P
(2 strips)
N S M-CF R P
(4 strips)
B-S2- H4
24
I n Table 3 . 1 ,
mm.
o. l O r fer to a rei n forc i ng teel bar \\ ith a nomi nal d i ameter of 1 0
1 he s) mb I A and 8 refer to pec i men o f groups [ A ] and [ 8 1 , respect i \'el y .
The s ) mb I
refer
to no
trengtheni ng. The
strengtheni ng \\ ith zero. two, and four
ymbol
M- FRP strip
0,
2,
4 refer to
i n the sagging region,
r pect i \ c l . The ) mbo l s HO. 1--1 2, H 4 refer to trengthen i ng \\ ith zero, two, and four
1- FRP trip i n the hogging region, respective l .
3.2 . 1
o n t ro l
pec i m e n
The control peci men d i d not have a cutout in neither the saggi ng nor hogging
region to act as benchmark for the other test peci mens. The slab i rei n forced \\ ith 4
o. 1 0
teel bars i n the hogg i n g region and 4
o. 1 0 steel bars i n t he sagg i n g
region . Geometry a n d deta i l s o f rei n fo rcement o f t he control spec i men i s shown i n
Figure 3 . 1 a n d descri bed i n section 3 . 3 .
3.2.2 G ro u p [ A ]
Th i
cutout
1 11
group comprised fi ve spec I mens. A l l spec I mens of t h i s group had a
each sagg i n g region. The c utout had a widt h of 1 50 mm i n transverse
d i rect ion and a lengt h o f 450 mm i n longitudi nal d i rection. The centre o f the c utout
coi nci ded w i th the m id-po i n t of the sagg i n g region. I nstal l ation of the cutout reduced
the ten ion steel rei n fo rcement i n the saggi ng region to be 2
o . 1 0 instead o f 4
o.
1 0 rei n forc i ng bars. S i nce the cutout was only in the saggi ng region, the steel
rei nforcement in the hogging reg i on remai ned unchanged as 4 No. 1 0 bars.
Four
slabs were strengthened i n flexure using NSM-C F R P rei n forcement, and one slab
was not strengt hened. S peci mens A-S2-HO and A-S4-HO were strengthened i n each
sagg i n g region with two and four N S M -C F R P stri ps, respectively. S peci men A-S2H2 was strengthened with two
S M- C F R P str i ps i n bot h sagging and hogg i n g
'25
regIon
' reci men
- '+ - 1 1 2 \Va strengtJlened \\ ith four
'aggl llg regl n and t\v
specI men
- FRP
trip
M-C F R P tri p i n each
in the hogging region, Re ults of
ha e been u ed to t udy the effect of c reati on of a cutout in the
agging region on the flexural resp ns of one-way cont i n uous RC slabs. Re ult or
the
trength ned speci m n
strength n i ng
ont i nuou R
have been used to exam I ne the effect i vene
of the
ystem to restore the flexura l capac it) of one-way
lab with a cutout i n t he saggi ng regions.
3.2.3 G ro u p r B I
Thi group inv o l ed five peci men . A l l spec i mens had a cutout o f 1 50x450
111m in the hogging region
0
er the central support . I nstal l ation of the cutout reduced
the tension st el rei n forcement i n the hogg i n g region to be 2
o. l O bar . TIle ten ion steel i n the agg i ng region, 4
o. 1 0 bars i nstead of 4
o. 1 0 bars,
v
as not changed .
Four lab were strengthened with N M - C F R P rei n forcement \ h i l e one l ab was not
strengthened.
four
pec i mens B- O- H 2 and B-SO- H4 were strengthened \ ith two and
M-CFR P stri ps in the hogging region respecti vely . S peci mens 8-S2-H2 and
8- 2-H4 were strengthened with t'.\'o and four N S M - C F R P strips i n the hogg i n g
region, respec t i vely a n d two N S M - C F R P stri ps i n each saggi ng region. Resu l ts of
pec i men 8-
have been used to stud
the effect of creat ion of a cutout i n t he
hoggi ng region on the slab's flexural response, Results of other spec i mens of t h i s
group ha e been used to eval uate t h e v i ab i l ity of t he N S M -C F R P strengtheni ng
system to restore the flexural capaci t y of conti n uous RC slabs wi th a cutout i n the
hogg i n g region.
26
3.3
pcc i m e n
Figure 3 . 1
control test
gr lipS r
De t a i l
h ws geometry . rei nforcement. and load con figurat ion of the
peci men. The geometry and deta i l
of rei n forc ment of spec i mens of
] and [ 8 J arc hown i n Fi gure 3 . 2 and 3 .3 , respect i vely. The control te t
pec i men \\ as 3800 mm l ng, 400 mm \ ide, and 1 25 mm deep. The spec imen
pan of J 800 mm each. The speci men was tested to fai l ure
compriseu t\\ O eq ual
under t\\ O poi nt load , one i n the mid of ach
rei nforced b) 4
pan. The control spec i men was
o. 1 0 longitud i nal steel rei n forcement i n tension zone of both
agg i n g and hogging regions as hown in Fi gure 3 . 1 . The c l ear concrete cover was
25 mm \\- h i l e the c
er to centre of steel wa
38 mm. The compression steel
rei n forcement i n both the agg i n g and h ggi ng regions consi sted of 2 No. 1 0 steel
bars.
hear rei n forcement i n the form of 4-leg
paced at
=
50 mm
mode of fai l ure.
\
o. 8 ( 8 mm d iameter) c losed sti rrups
as pro i ded along the length of the speci men to avoid shear
hear rei n forcement i s often u ed at t he supports (co l u mns) in fl at
p l ate fl oor systems to i mprove the punc h i ng shear resistance. For RC members
subjected to bend ing moments w ithout axi a l compression forces, the confinement
pro\ i ded b
the shear rei nforcement wou l d have a negl igible effect on the flex ural
capac ity.
S pec i mens of group [ A ] had the same d i mensions as that of t he contro l
peci men but a cutout was i nsta l l ed i n t h e sagg i n g regi on of each pan. The c utout
had a width of We = 1 50 mm and l ength of Ie
=
450 mm. The centre of the cutout
coi nc i ded with the m i d-span poi nt . The cutout width-to-sl ab width ratio, w/b, was
0.375 and the c utout l ength-to-span l ength rati o, IlL, was 0.25. S i m i larly, speci mens
of group [ B] had the same d i mension as t hat of t he contro l speci men but a cutout
27
h:1\ i ng a \\ idth of
1\',
= 1 50 mill and length or Ie = 4 5 0 mm was i n tai led i n the
hogg i n g region over the m iddle upport . The steel rei n forcement i nter ected by the
cutout \\ a remov d t resemble the case of i nc l u i n of a utout i n an e. i t i ng fl or
lab \\ h i ch wou l d typical l y result in cutt i ng of exi t i ng teel rei n forcement.
result. spec i mens of grour> [
J had 2
a
o. 1 0 ten ion steel rei n forcement i n the mid-
pan ect i n ( sagging region) and pec i men of group [ 8 ] had 2 No. 1 0 ten ion steel
rci n for ement over the midd l e upport ( h gging region).
I I
r .l
r
• r
I
F i gu re 3 . 1 : Geometry and detai l s of rei n forcement of the control speci men
28
+
�
T=:rt----rrr
ro ..!.i
...L.
--;:...;.
-
+�
t
r
If�" �LI=ii '
"""--
f
�
1 ,
C'
II
'1
'
I,
_-
---c��-.-:
r
-'--�
� ,
F_" E
" n ' FE! r EI E' T
Figure 3 . 2 : Geometry and detai l s of rei n forcement of peci mens of group [ A]
29
t
rl
r
r<
1.. [
't-
r
�
�
rr
£
E �
- I
r
T '
I
TIT;
4 '
F - ' .[
[ IT f m F F H £1 T
I
�I
t
01
- I
E T
f E
E TI
Figure 3 .3 : Geometry and deta i l s of rei n forcement of speci mens of group [ 8]
30
3.4
pec l m e n
W
Fa b r i ca t i o n
den form
were fabricated usi ng 1 8 mm pi) wood sheet
mm \\ h ite t i m ber as shO\ n i n Fi gure 3 .4(a).
1 50 -4 - 0 111m wa
\ ooden b
and 2-l0x240
with d i mension of
fabricated and then in tai led i n the form at the l ocat ion of the
cutout to prO\i de the req u i r d opening i n t
bent to de i red d i men ions. The steel bars
\\ l re to forl11 the steel cage .
t pec i men . The steel bar \\ ere cut and
\
ere t ied together using bend i ng steel
photo of teel c ages i s hO\ n i n F i gure 3 .4(b).
tra i n gauge ( .G.) were bonded to the tensi l e teel rei n forcement at the mid
span and
0 \ er
the central
upport. The surface of steel \\as first prepared using a
gri nder at the locat ion of the
t hen c leaned by alcoho l . The
.
G to acq u i re a smooth surface. The steel surface was
.
. G . was t hen bonded to the steel surface using an
adhe i ve. The \\ i re of t he S . G . were isolated from bei ng i n contact w i t h the steel
bar .
coati n g material was then appl i ed to protect the S . G . and w i res duri ng
concrete cast i ng. Photos taken d ur i ng i nstal l ation of a typical S.G. are shown i n
F igure 3 . 5 .
mal l concrete cubes h av i ng t he same d i men ions a s those of the clear
concrete cover were prepared. The concrete c ubes were attached to the main steel
bars prior to casti ng at d i screte locations to mai ntai n the concrete c l ear co er. The
steel cages were then i nsta l led i nside the forms prior to cast i ng as shown i n Fi gure
3.6.
31
(a) Fabricated w ooden form
(b)
teel cages
Figure 3 .4 : Fonm\ ork and steel cages
(a)
urface preparation using grinder
(c) Bondi n g of S .G . to steel surface
( b ) Cl ean i n g of steel surface by alcohol
( d ) App l i cation of coating tape
F igure 3 . 5 : I n stal l at ion of strain gauges to steel bars
Figure 3 . 6 : teel cages i n stal led i nside the forms
The concrete v" as prepared and del ivered b
a local ready-m i x concrete
producer. A l l pecimens were cast in a horizonta l po ition as sho\ n in Figure 3 . 7 .
T h e concrete \ a com pacted u s i n g hand-held v i bratos t o prohibit a n y segregation as
sho\\ n in F i gu re 3 . 8 . Concrete cubes and c y l i n ders were sam pled during cast i n g as
how n i n F i gu re 3 .9. The concrete surface was fin i shed and Ie eled using a trowel as
sho\\"n in F i gu re 3 . 1 0. After casti ng. polythene sheets, 500 gauges each, were
wrapped around test spec i mens for one day. The sides of the forms were then
rem oved . Fol l ow i n g rem oval of forms, concrete spec i mens were covered with burlap
sheets as shown i n F igure 3 . 1 I . The burlap sheets were sprayed with water fi e ti mes
per da
for seven days. The spec imens were then left a i r-cured unt i l the t i me of
strengthen i n g and/or testi ng.
33
Figure 3.7: Concrete cast ing
Figure 3 . 8 : Concrete v ibration
34
F igure 3 .9 : Preparation of concrete cyli nder samples
F igure 3 . 1 0 : Concrete fi n i sh i ng
35
Figu re 3 . 1 1 : Concrete curing
3.5 M a te ria l P roperties
3.5. 1 Co n c rete
The concrete m i x proportion i s given in Table 3 . 2 . The concrete m i xtures
i n c l uded ord i nary Type [ Portland Cement. The course aggregate i n c l uded crushed
l im estone \ ith nom i n a l sizes in of 5 m m , 1 0 mm, and 20 m m . The fine aggregate
\\ as dune sand . The aggregate d i stribution is demonstrated in Tabl e 3 . 3 . The water
cement ratio was 0.42. Before cast i n g of concrete, a s l u m p test was conducted to
ensu re workab i l ity of concrete as shown in F igures 3 . 1 2 and 3 . 1 3 . The concrete
slump was 1 20 mm which was w i t h i n the acceptable l i m its ( 1 60±40 m m ) .
Six
concrete cyl i nders 1 50x300 mm each, and s i x concrete cubes, 1 50x 1 5 0 mm each ,
were sampled during casti ng. T h e concrete cubes a n d c y l i nders were subjected t o the
same curing regime as that of test spec imens.
36
Table '" . 2 :
oncret m i x proport ion
M ix Prop rtion
Batch
kglm3
laterial
Cement
eight
360
20 mm cr. LIS
gg.
600
1 0 mm cr. LIS Agg.
400
5 mm cr. US Agg.
600
Dune Sand
325
Free Water
1 50
Total Weight
244 1
Table 3 . 3 : Aggregate d i stribution
ggregate Percentage
l ze
Type
%
20 mm
Crushed L i mestone
3 1 .2
1 0 mm
Crushed L i mestone
20.8
0-5 mm
Crushed Li mestone
3 1 .2
Dune Sand
Alain
1 6. 9
The cubes a n d c y l i nders were tested a t t h e t i me of structural testing a s shown
i n F i gure 3 . 1 4. The cubes were tested under compression to determi ne the concrete
c u be compression strength. Three cyl i nders were tested under compression to
determi ne the concrete cyl i nder compression strength and three c y l i nders were used
to determ i ne the concrete spl itting strengt h . The compression and spl itt i ng strength
resul ts are given in Tables 3.4 and 3 . 5 , respectively. The concrete cyl i nder and cube
strengths were on average 24.8±3 M Pa and 4 1 . 2±2 M Pa with coeffi cient of
variations of 1 2% and 5%, respec t i ve l y. For general construction testi ng, t he
37
coeffic ient of 'v ariation for strength re u l t of t h e concrete cy l i nder i con i dered fai r
\\ hercas for the strength re u l t of the c ncrete cubes, i t i s c n idered e cel lent ( A I
2 1 � R-02). The concrete p l i tt i ng strength \\ as on average 2.6 M Pa \ i th a tandard
dc\ iation o r OA
l Pa.
Table 3 .4 :
oncrete compression strength results
Propert)
ample
o. I
ample
0. 2
ample
o. 3
C) l i nder
Ie ( l Pa )
23 . 65
28.29
22.47
C ubes
fcu C 1 Pa)
� 1 .56
40
42.22
ample
No. 4
ample
No. 5
ample
No. 6
-
-
-
3 8. 89
40
44.44
AVG.
( M Pa )
D
( M Pa )
24 . 8
3
41 2
2
.
Tabl e 3 . 5 : Concrete spl i tt i ng strength results
Property
ample
o. I
let (
Pa)
2 . 89
Sample
No. 2
ampl e
No. 3
( M Pa )
Standard
deviation
( M Pa )
2. 1 8
2.57
2.6
0.4
Average
38
F i gure 3 . 1 2 : Concrete del ivery
F igure 3 . 1 3 : S l ump test
( a) Cube compression test
(b) Cyl i nder compression test
(c) Cy l i nder spl itting test
F igure 3 . 1 4 : Cube and cyl inder com pression and spl itting tests
39
3.5.2
teel Rei n force m e n t
T h e longitud inal teel rei n forcement wa
hear rei n forcement w as
d i ameter
o. 1 0 ( 1 0 mm diameter), wh i le the
o. 8 ( 8 mm diameter). Three steel coupons from both
\\ ere te ted under uniaxial tension force to detenn i ne the yield and
u l t i mate trength . The ten i le te t re u lts of the steel coupons are prov ided in Tab le
3 .6. The
o. 1 0 teel r i n for ing bar had average y i e ld and u l t imate strength of 5 1 5
M Pa and 599 M Pa, respecti e l y with corre pond i ng tandard deviations of 30 M Pa
and 22 M Pa, re pect i e l y . Th
u lt i mate
0, 8 steel re inforc i ng bars had average y i e ld and
trength of 530 M Pa and 609 M Pa, respecti e l y \ i th correspond ing
tandard deviat ion of 3 7 M Pa and 22 M Pa, respect ively.
Table 3.6: Ten i le test resu l ts of steel coupons
Nom i nal
Propert
Sampl e
Sample
Sampl e
bar size
( M Pa )
o. 1
0. 2
o. 3
o. 1 0
o. 8
"
No. 1 0
o. 8
·
"
=
=
Average
( M Pa )
Y ield Strength
520
542
483
5 ] 5 ± 30
U lt imate Strength
598
622
578
599
Y ield Strength
514
503
5 72
530 ± 3 7
U lt i mate Strength
605
589
633
609 ± 22
±
22
1 0 mm diameter steel rei nforc i n g bar
8 mm d i ameter steel rei nforc i ng bar
3.5.3 Com posite Rei n force m e n t
T h e C F R P composi te strips used in the N S M strengthen i n g had cross section
d i mensions of 2.5 x 1 5 mm average ten s i l e mod u l u s and strength of 1 65 GPa and
3 1 00 M Pa, respecti ely, and a strain at break of approximate l y 1 .9 % ( S i ka®
CarboDur
P l ates) . The NSM composi te strips were bonded to s ides of the concrete
40
groo\ e
u mg an epoxy adhesi e ha ing a ten i le mod u l u
strength of 24.8
Pa, and elongation at break of 1% ( ikadu
of 4.5 GPa, tensi le
30). Propert ies of the
F R P trip and epox) adhe i e " ere obtai ned from the manufacturer. F igure 3 . 1 5
ho\\ the materia l u ed i n strengtheni ng.
(a) C F R P strips ( ika
Carbo Dur)
F i gu re 3 . 1 5 : Materi a l used i n the
(b) Epoxy adhesive ( S i kadur 30)
S M strengthen ing system
3 . 6 Stre n gt h e n i n g Method ology
The trengthening reg imes adopted for speci mens of group [ A ] are shown i n
F igure 3 . 1 6 through F igu re 3 . 1 9 wh i l e those of spec imens of group [ 8 ] are shown in
Figure 3 .20 through F i g u re 3 .2 3 . The C F R P strips used in the sagging region were
cut to length of ] 530 mm which corresponded to 85% of the span lengt h . The C F R P
strips i n t h e hogging region were c u t t o a l ength o f 1 200 mm and extended i nside
each span for a 600 mm. The extended l ength of the hogging C F R P rei n forcement
corresponded to one-t h i rd of the span length ( i .e. L /3) which wou l d resemble
practical appl ications. A sl itting mach ine was used to cut grooves on concrete surface
at desi red locations. Each groove had a width of 1 0 mm and depth of 23 mm. The
grooves were c l eaned of d ust and loose partic les using an air blower. The grooves
were part i a l l y fi l led with the epoxy adhes i ve. The C F R P strips were then inserted
41
i nto th groo \ e and l ight l
concrete surface wa
procedure ar
pre ed unt i l the ad he i \ e overflowed around them. The
then c leaned and Ie eled u i ng a tr \ el . The
trengthening
ummarized in Figure 3 .24. The l ab were l eft ai r-cured unt i l time f
t ruct ural te t i ng.
1
r
.lo r
F igure 3 . 1 6: Strengthen i ng regi me for speci men A-S2- HO
42
� t t
-
r
T�I
f
I t f'- FRF TR
I
;:r
CJa
�
P
E! II ' " E E �TI I
4 I
' -
(PF TR P
�
E0Tni
.
\ -
Fr·
TFIF
E
;1 P = TE REII.F R EI [I T IN
� NSIJ<FRF JF P
' _r
II
RE 1 )1,
Figure 3 . 1 7 : Strengthen i ng regi me for spec i men A-S4-H O
43
I I
• I
-I
..
!�
III
-
1
•
IT
-I
EI
D
,p 1[ ,
E'J�I T
'
H
- rq 'PIF
�E I '
�
D
D' �
I
-t
.p
-
1:
EL
-
It �t. ' F
I
I
I
IE ,
t I 'EI .I III
F�F - �' F
hE I t
;7/
I
'-
( I
�
... ...,
,
\
-
E T
�
Fi gure 3 . 1 8 :
ET �I_ 8
- HL
E TI t
-f
trengtheni ng regime for speci me n A-S2-H2
.
r�
T':
I
1 '""'";r
--
f
I
�
--
- -I
�
r
1R
I
!
-
p
t • TI
r
Cl
I
T f
IIF
.
E
II
'E
I
I
I
I
'
.. ') , - FF � TF.
Df
I
1 ;1
- ,
-
0
IF
E,-n I , E '
E [ I
r·
- /
lET
_
'/
1V
1
� �
-
DET -I B
E -I J . - .
�-�
E TI ' [ E-R
Figure 3 . 1 9: Strengthen i ng regime for speci men A-S4- H 2
I
45
1-
f T IF
�
T ;:
E
= [ 1
I - FF
I
[I
Te
ET-I [
E
-
�-E
-H
Figure 3 .20: Strengthen i ng regime for speci men B-SO-H 2
I
46
,
,
-
-
I
•
r
r
IE
tI
I
E
�
r
F i g u re 3 .2 1 :
I
T
trengthen i ng reg i m e for speci men B-SO-H4
-+7
Ff
- F
I
r l_
�
�
!
�
OJ
E TI � ·l E E. �TI I
, f
J
T�II
I�-
�----
r
0
�
I
I
,I
IJ
' IP
TE
Ii
F[
II
lE]_1
�J
--'-I---l -1
! ------------------�
------------------�
!
I
O
'--'_
--'_
_
_
'
---_
---'_
_
8
I ' IE
T �E IIF fl"EI'E ,T
,-f
-
FFF
II, �4 � '
T IF
FE I I
r-
t -
E TI I r-
Figure 3 .22: Strengthe n i ng regime for spec i men B-S2-H2
,
48
L
r F
T
F
F
r
T Ir
I
�.
OJ,! .
'If
It
l:. 1 F F
4 � t
T
IE ,
F
EI E
-
T
[IiF
ItI
-
TFIF
1
lE I
II
'
- 1
� 1-
��
I
I
I
I \,
J.
r
-
bN
IF
-,
�
E TT I� IE /.
r TE RE I F 'F :[1 E' T IN � II , R[,I
I 1 ' - F�P TPIF-
-
4
t,
-
(
I
-
.
�E
-
I
-
H- _-H l
E -I
'
.
LET�I [
-
N
-
E-E
F igure 3 .23 : Strengt hen i ng reg i me for spec i men B-S2-H4
.
I U
49
(a) Cutting of C F R P trips
(b) Cutt ing of grooves
-
( c ) C lean ing of grooves
(e) I n stal lation of C F R P stri ps
C d ) I n stal lation of epoxy adhesive
(f) F i n ishing of concrete surface
F igure 3 .24: Strengtheing proced ure
3 . 7 Test Set- u p a nd I n s t ru m e n tation
T h e test spec I mens consisted of two equal spans, 1 800 mm each. The
spec i mens were tested in flexure u nder two point loads, one at the m i d of each span.
The spec i mens rested on three supports 1 .8 m apart during test i n g .
50
3.7. 1
t ra i n Mea u re m e n t
E lectrical r e i tance train gauges ( .G . ) ,\ ith a gauge length of 5 mm and
coefficient of the rmal expan ion of I I
bonded to the internal ten i le
o
1 0.6 IC and a gauge re i tant of 1 20 n
teel rei n forcement and external
,
ere
M -C F R P
rei n forcement at the m id- pan and 0 er the middle upport .
train gauge
e pan ion of 1 1
\\ i t h a gauge length o f 6 0 mm and coeffic ient o f thermal
1 0.6 IC
o
and a gauge re i tant of 1 20 n , ere bonded to the
concrete urface at the extreme com pre sion fi ber in the m i d span section s and over
the central su pport.
3.7.2 D i place m e n t a n d Load M easu rem e n t
A chematic d i agram show ing the test set-up i s gi e n i n F i gure 3 . 2 5 . The load
\\ as appl ied i ncrementa l ly b means of a hydrau l ic jack located at the m id-point of
the pecimen. A preader steel beam , as used to spread the load equal ly into two
point loads. Each poi n t load is located at the m i dd l e of each span . I n order to
measure the m id-span deflections of the sl ab, one L i near Variable Di fferential
Transformer ( L V DT) was placed below the slab at the m id-point of each span. The
total app l ied load was measured using a 500 k
load cel l placed between the
hydrau l ic jack and the steel spreader beam. The reaction of the m iddle support was
measured using a 200 kN load c e l l placed between the slab soffit and the top surface
of the m iddle support. A data acq u i s ition system was used to record the data during
testing. A photo of a test in progress i s shown i n F i gure 3 .26.
51
/
\
•
•
1
•
I
I
,
F i gure 3 .2 5 : Schematic v ie\ of the test setup
F igure 3 .26: A test in progress
•
I
52
C HA PT E R 4 :
E X P E R I M E NTA L R E S U LT
... . 1 I n t rod u c t i o n
The feas i bi l ity of flex ural
(R )
lab
t ri ps using
trengthening
f cont i n uoll
rei n forced concrete
M -C F R P rei n forcement has been i ll e t igated i n th i s
re ear h \\ ork. Results of t h e e , peri mental \\ ork are presented i n t h i s chapter. The
re u l t are pre ented i n teml of l oad mea urement, deflection resp nse, tensi Ie strai n
re pan e. can rete trai n response, C F R P tra i n response, support reactions, and load
\.
r us moment rel at ionsh i p.
4.2 T e s t Res u l t
The results were col l ected d uri ng te t i ng usi n g a data acqu i s i tion sy tem. The
r sults \\·ere mai ntai ned i n Excel sheet format where a l l the nece sary graphs and
fi gu re
were produced. Resul ts of test spec i mens with cutouts, before and after
trengthening were com pared with those of the contro l spec i men to eval uate the
effect ivenes of the
M - C F R P strengtheni ng system.
·t2. 1 G ro u p [ A ]
I n t h i s secti on, resu l t s o f the fi e speci mens o f group [ A ] \ i t h a cutout i n
each sagging region are presented. Four spec i mens were strengthened with
C F R P rei n forcement
in
the sagg i n g region,
w h i l e one
speci men
was
SM­
not
strengthened. Res u l ts of spec i mens of t h i s group are a l so compared to those of the
control speci men that d i d not i nc l ude a cutout and was not strengthened .
53
�.2. 1 . 1 Load
a pacity
Re u l t of the load measurement
tho
e
for pec l men
of group [
of the ontrol are ummarized in Table 4. 1 . The ymbols
Per, PI'
] along v. ith
and
Pu refer to
the crac k i ng, ) ield, and u l ti mate I ad , resp cti ely. The u l t i mate load enhancement
rat io
( LER) for the strengthened sp c i mens with
unstrengthcned
pe Imen
are gi ven
In
the
re pect to that
ame table.
f t he
The cracking and
) i t: l d i ng load of the agg i n g and hogging regions were taken from the teel stra i n
graph . T h e crac k i ng load was taken a s t h e load \\ here t h e fi r t change i n t h e slope o f
the ten i l
teel
\\ here the
econd chan ge i n the slope of the tens i l e steel
train resp n e took place. The yield load was taken as the load
tra i n response was
acq u i red. The crac k i ng and yield loads of some speci mens were not reported due to
mal function of the corre pond ing steel strai n gauges.
The control peci men exh ibi ted flexural crac k i ng in t he west and east saggi ng
regions at load
a lues of appro i matel y 1 4.6 kN and 2 7 . 1 kN, respect i vely. For t he
hoggi ng region, fl ex ural c racks i n i t i ated at a load val ue of approx i matel y 29.8 kN .
The tensi le teel i n the west and east saggi ng regions y i e l ded al most at the same t i me
at load al ues of approxi matel y 83.4 k
and 94. 3 k , respectively. The tensi Ie steel
i n the hogg i n g region y i el ded at a load val ue of approxi mately 8 7 . 8 k N . The u l t i mate
load of the control speci men was 1 1 6. 9 kN.
pec i men A-
with a cutout i n the saggin g regions \ i t hout strengthen i ng
experienced flex u ral c rac k i ng i n the west and east sagging regions at load val ues of
approxi matel y 5 .9 kN and 1 1 .4 kN, respectively. For the hogging region, flexural
cracks i n i t i ated at a l oad val ue of approxi mately 7 . 5 kN. The tensi l e steel i n the west
and east saggi ng regions y i elded al most at load val ues of approx i mately 54.5 k
and
54
64 .4 k , re pect i \- e l ) . The ten i l e te I i n the hoggi n g regi n yielded at a load \ al ue
of appro x i mate l ) 70.'2 k . The ten i le teel i n the agging region yiel ded prior to the
ten i le
teel i n the hoggi ng rcgi n, becau
or t he pre ence of the cutout i n the
,agging regions, \\ hich reduced the amount of steel and r d uced the concrete section
i Zl;. The \\- c t and ea t agg i n g
lo\\- er than tho e of the contr I
p c i men A -
ield load
r peci men A- S were 3 5% and 32%
p c i m n, respecti ely. The hogging y i e l d load of
wa '20% lo\\ er than that of the control peci men.
pec i men A-NS
ach ie\ ed an u l t i mate load of 5 . 80 k . The u l t i mate load of speci men
- S
'V
as
27% l o\\ er than that or the control pec i men.
Table 4 . 1 : Re ults o f load mea urement for speci mens of group [ A ]
Per ( kN)
p) ( kN )
aggl llg
pec l lnen
PII
aggmg
Hogging
We t
We t
Ea t
Hogging
( kN )
LER+
Ea t
-
control
1 4 .6
27. 1
29 . 8
83 .4
94.3
87.8
1 1 6 .90
A-NS
5.9
1 1 .4
7.S
S4.S
64.4
70.2
8 S .80
l .00
A-S2-HO
1 0.9
-
36.7
97.S
-
98.3
1 3 1 .02
l . S3
A-S4-HO
8.4
8.5
3 2 .2
1 33
1 20 . 3
1 0S . 3
ISI.12
l .7 6
A-S2-H2
1 8 .2
1 8.2
30.S
94
1 04 . 2
1 2 1 .6
1 40 .00
1 .63
A-S4-H2
1 7 .6
32.S
30.8
1 43
1 1 S .4
1 36.6
I S S . OO
1 .8 1
.
Load en hancement rat io with respect to t hat of spec imen A-NS
Flex u ral cracks i n i t i ated in the west sagging region of speci men A-S2-HO at a
load val ue of approxi mate l y 1 0. 9 k
whereas they were i n i t i ated i n the hogg i n g
region a t a load val ue o f 3 6 . 7 k . The cracking and yield loads of t he east sagging
regi on were not reported d ue to mal function of the correspond i n g steel stra i n gauges.
55
fhe stee l i n the agging and hogg i n g regi n yielded almo t at the am time
at a load \ alue o f appro. i matel) 98 k . The yield I ad of spec i men A- 2 - H O of the
'agging region, \'v as approxi mately 64% higher than that of s peci men
a 40% i ncrea
\ hereas
in the ) i Id load \\ a rec rded i n the hogging regi n. Speci men A­
� - I I O :\ pcrienced a load enhancement ratio of 5 3 % relati e t o the ulti mate load o f
pCCI men
. The load capa it)' o f pe i men
of the ontrol pec i men by appr
peCI men
-
- 2-HO was even h i gher than that
i lllate ly 1 _%.
4- 1 10 w i th four N M-C F R P stri p
1 11
each
aggmg regIon
c:--. perienced flexural c rack in the sagg i n g and hogging regions at load val ues of
approxi matel ) 8 .45 k
and 3 _ . 2 k , respectively. Y ie l d i n g o f steel i n the hogg i n g
region occurred fi r t a t a load val ue o f approxi mately 1 05 . 3 k N fol lowed b y y i e l d i ng
o f teel i n the \\ e t and east sagg i ng region at load val ues of approxi mately 1 33 kN
and LO.3 k , respecti vely. Ths occ u rred because o f the h ig h amount of
SM­
C F R P rei n forcement ( fo u r N M - C F R P strips) i nstal led i n the saggi n g region. The
yield loads o f speci men A- 4-HO recorded in the west and east sagg i n g regions were
1 44 % and 8 7 %, h i gher than those of speci men A -
, respectively. F o r t h e hogg i n g
region, a 50% enhancement i n ield l oad was recorded compared to that o f spec i men
A-
. The load capaci ty o f s pec i men A - 4-HO was 76% h igher than t hat of
peci men A -
a n d 3 0 % h i gher than that o f t h e control spec i men .
Flexural c racks i ni t i ated i n the saggi ng regions of speci men A-S2- H2 at a
load
a l ue of approxi mate l y 1 8.2 kN. For the hogg i n g region, the flexural cracks
i ni t i ated at a load val ue of approxi mately 3 0 . 5 kN .
peci men A-S2-H2 exh i bi ted
west and east sagg i n g yield loads of 94 kN and 1 04.2 kN, respectively. The average
sagg i n g yield load of speci men A-S2-H2 was al most the same as that of spec i men A 2-HO. T h e hogg i n g yield load of s pec i mens A-S2-H 2 was, however, h igher than
56
that o f ' pec i men
,
- 2-1 10 by appro.' i mately 24%. Thi indicate that the addi t ion of
1 - ' F R P rei n fl rcement i n the h gging r gion had no effe t on the agging
ield
load, but , l i ghtl y increased the h ggi ng y i l ei I ad. The u l t i mate load of pec i m n A S2-1 12 \\ as 63% h i gher than that
f pec i men
and on l ) 7% h i gher than that of
pcc i men A- 2-1 10.
pcc l men
- 4- 1- 12 xperienced De ural cracks in the \\ est and east sagging
regl n at l oad \ al uc of approxi matel
1 7.6 kN and 3 2 . 5 k , re pectively. For the
hoggi ng region, n exliral crack i n i t iated at a load val ue of approx i mately 30.8 kN .
The ten i le
teel i n the west and e a t saggi ng regions yielded at load val ues o f
appro i mate l ) 1 4 " k
SpCCl lll n
and 1 1 5 .4 k , respecti e l y . The average sagg i n g yield load of
- 4-1 -1 2 was a l mo t the same as that of peci men A- 4-1-10. Thi s confi rms
that i nstal lation
M-C F RP rei n forcement i n the hogging region had no effect on
f
t he aggi ng ) ield load. For the hogg i n g region, the tens i l e steel yielded at a load
yai lle of 1 36.6 kN . The hogging y i e l d l oad of spec i men A- 4- 1 -1 2 was approx i matel y
300 0 h i gher than that of spec i men A-S4-HO. The u l t i mate l oad of spec i men A-S4-H2
\\ as in i gn i ficantl
h i gher than that o f spec i men A-S4-HO, 8 1 % h i gher t han that of
pec i men A-N , and 33% h i gher than t hat of the control spec i men .
.t.2 . 1 .2 Fai l u re M od e
The control speci men fai led i n a flexural mode of fai l ure. The tensi le steel i n
the saggi ng and hogging regions y i e l ded al most at the ame t i me. Fol l owi ng the
y i e l d i ng of tens i l e stee l , crush i ng of concrete occ urred at the top face of t he speci men
in t he m id-span sect i on and at the bottom face over the middle support. Photos of t he
contro l speci men at fai l ure are shown i n F igure 4. 1 .
57
pec l men
fai led in a fie u ral mode of fai l u re. The ten i l e teel ) ielded
fi rst in the agging region then in the hogging region . Follov,ling yielding of tensile
tee!' cru h i ng of concrete occurred at the top face of the pe i men i n the m i d- pan
ect ion then at the bottom face over the m iddle support. Photo of spec i men Afai l ure are ho\\ n in F igure 4.2.
Fai l u re of mi d-span sect ion
( sagging region)
Fai lure of section
0
er central suppoti
( hoggi ng regi on )
F igure 4. 1 : P hotos of the control spec i men at fai l u re
F a i l u re of mi d-span sect ion
( sagging regio n )
Fail ure of section over central support
( hogging region )
F i gu re 4 . 2 : Photos of spec i men A -N S at fai l u re
at
58
Fail u re of peC l men
- 2-HO i n i t i ated by format ion of fle ural cracks in both
aggmg and hogging region . A
the load progre ed, yield i ng of ten s i l e steel
occu rred i n both agg i n g and hogging region almost at the same t i me. Fol lowing
y ield i ng of ten i le teeL cru h i ng of concrete occuned at the top face of the spec imen
i n the m id-span sect ion. A shear crack de eloped in the m id-span section at the onset
of concrete ru h i ng. Th i
hear crack occu rred d ue to the weaknes of the concrete
e tion in the agg i n g region caused b the cutout. A photo of pec imen A-S2-HO at
fai l ure i
ho\\ n i n Figure 4 . 3 .
pec l men
- 4-HO fai led i n a flexural mode of fai l ure. The tensi le steel
j ielded fi r t i n the hoggi n g region then i n the sagging region. Fol lowing y i e l d i ng of
ten i le steel , crush ing of concrete occ u rred at the top face of the pec i men i n the m id ­
pan section a n d a t t h e bottom face 0 e r t h e m i dd l e support .
0 shear cracks were
de\ eloped at the on et of concrete crush i ng. This can be attributed to the h igh
amount of longitud i nal
M - C F R P rei n forcement u ed around the cutout i n each
agging region , which rna have i m proved the shear resistance by the dowel action,
and hence, kept the concrete section i ntact at fai l u re. More research i s needed to
in estigate the effect of longitud inal
S M -C F R P rei n forcement on the shear
re i stance of concrete. Photos of spec imen A -S4-HO at fai l ure are shown in F i gure
4.4.
Spec imen A-S2-H2 fai led i n a flexural mode of fai l u re. The tensile steel
y i el ded fi rst i n the sagging region then i n the hogging region . Fol lowing yielding of
ten s i l e steel . crush ing of concrete OCCUlTed at the top face of the spec i men in the m id ­
span section then a t t h e bottom face over t h e m iddle support . Photos of spec i men A ­
S 2 - H 2 a t fai l u re are shown i n F i gu re 4 . 5 .
59
Figure 4.3 : Photo of pec imen A- 2-HO at fai l ure
Fai l ure of mi d-span section
( saggi ng region)
Fai l ure of section
0
er central support
( hogging region )
Figure 4.4: P hotos of spec i men A-S4-HO at fai l ure
Fai l ure of mi d-span section
(saggi ng regio n )
Fail ure of sect ion over central suppOIi
( hoggi ng regio n )
Figure 4 . 5 : P hotos of speci men A-S2-H2 at fai l ure
60
Fail u re of pec l men
-
4-H2 i n i t i ated b format ion of fle 'ural cracks in both
agging and hogging region then y ield ing of ten i l e teel . The tensi le steel
i n the hogging region at a load
\\ e t agging region at a load
ie lded
alue of 1 36.6 k . The last yielding occurred in the
alue of J 43 kN . Fol lowing yielding of tensile teeL
cru h i ng of concrete occurred at the top face of the specimen i n the m id- pan
ect ion .
hear c rack de eloped i n the \ e t m i d -span
concrete cru h i ng due to the weakne
ection at the on et of
caused by the cutout. A photo of spec imen A-
4-H2 at fai l u re i s shown i n F igure 4.6.
F igure 4.6: Photo of spec imen A- 4-H2 at fai l u re
".2. 1 .3 Load Deflection Response
The l oad-deflection response of the control spec i men i s shown i n F i gu re 4 . 7 .
The load-deflection response o f spec i mens of group [ A J are depicted in Figures 4 . 8
to 4. 1 2. F rom F i gu re 4 . 7 , i t can be seen that t h e east a n d west spans of t h e control
spec i men featured a very si m i lar deflection response. Both spans exh i b i ted a l i near
deflection response unt i l i n i ti ation of fl exural cracks. I n the post-cracking stage, the
deflection increased at a h igher rate after i n it i ation of cracks unti l yield ing of tensile
steel took p l ace i n the sagging and hogging region concurrently. Fol l owing y i e l d i ng
of stee l , the deflection conti n ued to i ncrease at a h i gher rate unt i l the spec i men
reached its peak load at an average m id-span deflection value of approximately 26.4
61
m m . Then, the pec imen featured a pia tic deflection respon e until fai l ure a
hO\\ TI
i n Figu re 4 . 7 .
For
pec lmen
, both spans e perienced a
ery s i m i lar deflection
re pon e . A l i near re pon e \\ as mai ntained up to an average m i d -span deflection of
appro i mately 1 .2 m m . Then, the spec imen exhib ited a q uasi -l inear deflection
re pon e until fi r t yielding took place i n the sagging region at an average deflection
of 7.5 m m . The econd ( I a t )
ielding occurred i n t h e hogging region at a n average
1 0 m m . Fol lowing last yield ing, the deflection
m id- pan defl ection of appro i mate l
conti nued to increase but at a h igher rate unt i l the specimen reached its peak load of
85 .80 k
at corresponding east and west span deflections of 1 9.9 m m and 24.4 m m ,
respecti\ ely as shown i n F igu re 4 . 8
200
- control
1 75
(east span)
- control (west span)
1 50
z
.::.:.
"
III
.2
5
�
1 25
1 00
I
/
- yielding in
s a g g i ng &
hogg i n g
75
50
25
0
0
5
10
15
20
Deflection
25
30
35
(mm)
Figure 4 . 7 : Load-deflection response of the control specimen
40
62
200
1 75
-
A-NS (east span)
-
A-NS (west span)
1 50
z
.x
"C
nI
.2
1 25
1 00
yield i n g i n
hog g i n g
.!3
�
75
50
25
0
0
5
10
15
20
Deflection
25
30
35
40
(mm)
F i gure 4 . 8 : Load-deflection re ponse of speci men A-NS
Speci men A - 2-HO featured a l i near deflection response in both spans until
i n itiat i on of crack at a deflection value of approx i mately 2 m m where the fi rst
de iation from l inearit took place. Fol low i ng cracki ng, the spec i men experienced a
quas i - l inear deflection response unti I yielding of ten s i l e steel took place i n the
sagging and hoggi n g regions concurrent ly at an average deflection of approx i mately
1 1 m m . Fol lowing y i e l d i ng, the deflection conti n ued to increase but at a h i gher rate
u n t i l the specimen reached its peak load of 1 3 1 .02 k
at correspond i n g east and west
span deflections of 22.2 1 m m and 24.40 m m , respectively as shown in F i gure 4.9.
63
200
- A-S2-HO (east span)
- A-S2-HO (west span)
1 75
1 50
Z
�
�
-0
(II
.2
(II
1 25
1 00
-
r=
75
) yielding i n
sagging &
hoggintj
50
25
0
0
5
10
15
20
25
30
35
40
Deflection (mm)
F igure 4.9: Load-deflect ion response of speci men A-S2-HO
pec imen A- -+-HO e h i bi ted a l i n ear deflection response up to an average
deflection of approximately 1 .5 mm where fi rst change in slope took place due to
c racking. I n the second stage, the deflection cont i n ued to i ncrease but at a h i gher rate
u nt i l fi rst
i e l d i ng took place in the hogging region at an average deflection of
approximatel 9.3 mm. Fol lo\ i ng fi rst yield i ng, the deflection i nc reased rapidly unti l
the specimen reached its l ast y i e l d i n g i n the sagging region at east and west
deflections of 1 4. 8 mm and 1 8 .5 m m , respectively. In the last stage, the m i d -span
deflection of the west span experienced a p l astic response unt i l a peak load of 1 5 1 . 1 3
k
was ach ie ed, shortly after the l ast yieldi ng, at a deflection of 2 1 .4 1 mm as
shown in F i gu re 4 . 1 0.
For spec imen A-S2-H2_ the l i near deflection response was maintai ned up to
an a erage m id-span deflection of approximately 1 . 5 m m . Then, the deflection
i ncreased at a h igher rate unt i l first yielding of steel took place i n the saggi ng region
64
at ea t and \\ est m id- pan deflections of 7.4 mm and 1 0 mm, respecti ely. Fol lo\'; ing
fi r t ) ielding, the deflection further i ncrea ed at a h igher rate until second yielding
occ u rred i n the hogging region at ea t and we t de flection of 1 2.4 mm and \ 8. 1 mm,
re pectively. I n the la t tage. the defl ection in th
we t span exhibited an almost
pIa tic re pon e unt i l the spec i men reached its peak load of 1 53 . 3 7 kN at a m id- pan
deflection of ... 3 . 5 3 mm in the we t pan as hown in Figu re 4. 1 1 .
- 4-H2, the de iation from l i nearit
For pecimen
started at east and west
deflection of 1 .3 mm and I 111m , re pecti ely d ue to fle u ral cracking. T n the postc rac k i ng
tage, the deflect ion increa ed al most l i nearly up to ea t and \ est
deflect ion of I 1 . 5 mm and 1 3 . 8 m m . respective I , where fi rst yield i ng of steel took
place in hogging region . Then, the deflection conti n ued to increase unt i l last yielding
of teel took place i n the
Fol lo\\ i ng
aggi ng region at west span deflection of 1 7 . 5 mm.
i e l d i n g of tee l i n the sagging region, the specimen fa i led shortly at a
peak load of 1 5 5 k
and a con'espond i ng west span deflection of 1 8 .8 mm as shown
in F i gu re 4 . 1 2 .
200
1 75
yield i n g in
sagging
-
A-S4-HO (east span)
-
A-S4-HO (west span)
1 50
z
�
-0
<II
E
S
�
1 25
J
/
- yield i n g in
hogging
1 00
75
50
25
0
0
5
10
15
20
25
30
35
Deflection ( m m )
F igure 4 . 1 0 : Load-deflect i on response of specimen A-S4-HO
40
65
200
- A-S2-H2 (east span)
1 75
- A-S2-H 2 (west span)
yielding i n
hogging
1 50
z
�
"C
IV
E
(
1 25
..... - -.. "------.......
1 00
,!9
{:.
75
50
25
0
0
5
10
15
20
Deflection
25
30
35
40
(mm)
F igure 4. 1 1 : Load-deflection respon se of spec imen A-S2-H2
200
- A-S4-H 2 (east span)
1 75
- A-S4-H 2 (west span)
1 50
z
:.
"C
IV
E
1 25
yielding i n
hog g i n g
1 00
,!9
{:.
75
50
25
0
0
5
10
15
25
20
Deflection
30
35
(mm)
F i gu re 4. 1 2 : Load-deflection response of speci men A -S4-H2
40
66
F igur 4 . 1 3 com pare the deflection re pon e of a l l speci mens of group [ A ]
\ \ ith a cutout i n t h e
agging region . T h e deflection o f t h e control
pec imen i
inc luded in the arne figure for the pu rpose of compari on. The response of only one
of the tv. o
pan
that had the greatest deflections \ a
c 1arit) . F rom t h i s fi gure. it i
plotted in F i gure 4. 1 3 for
e i dent that i n tal lation of a cutout i n the sagging
regi n compro m i sed the st i ffnes and l oad capac ity of spec imen A -N
relative to
that of the contro l . For i n tance at 50 kN, the deflection of the control specimen \ as
3 .6 mm \\ hereas for pec i men A pec imen A-N
i t was 5 . 8 m m . The deflection at peak load for
\Va insigni ficant l y lower than that of the control spec i men . Flexural
M-C F R P system signi ficantly i m proved the st i ffness and load
strengthen ing \\ ith
capac it) of the speci men \ ith cutout. The t i ffness of spec i mens A-S2-HO and AS2-H2 was almost the same as that of the control whereas spec imens A -S4-HO and
A- 4-H2 had h igher ti ffness than that of the contro l . The deflection capacity of the
trengthened speci mens
\
as l ov. er than that of the contro l .
200
1 75
A·S4·H2
""- -
1 50
z
.:t:.
-0
C1I
.2
n;
-
0
�
A.S4.HO
1 25
control
1 00
A·NS
75
--
control
-- A·NS
50
-- A·S2·HO
- - A·S2·H2
25
-- A·S4·HO
- - A·S4·H2
0
0
5
10
15
20
25
30
35
Deflection (mm)
F i gu re 4. 1 3 : Load-deflection response for speci mens of group [ A ]
40
67
4.2. 1 .4 D u c t i l itv I n dex
Duct i l i ty i
an im portant aspect i n RC structures. W hen RC structures are
trengthened \\ ith compo ite . the duct i l ity could be comprom i sed . A l so, the moment
red i tribution in continuou R
tructures i m ajorly control led by the duct i l ity ratio
of the tructure ( L i u et al. 2006). The duct i l i t i ndex given i n Equation 4. 1 i s defi ned
a the rat io of the m id- pan deflection at peak load to the m i d -span deflect ion at first
) ield i ng ( econd chan ge in slope of the load-deflection response). The deflection
\ alue used to calcu late the ducti l it
i nde ' w ere taken from Figure 4. 1 3 . Table 4.2
give the d uct i l i t) indice for pec i m en of group [ A ] along with that of the control
pec l men .
J1 =
.1p
( 4. 1 )
­
..111
W here:
J1 = duct i l it
i ndex
.1p = m id -span deflection at peak load
.1.1 1
=
m i d -span deflection at second change of load-deflection response ( fi rst
yielding)
Table 4 . 2 : Duct i l ity i n d ices for speci mens of group [ A ]
.1.1' 1
(mm)
(mm)
Ji
control
1 0.5
23 . 8
2.27
A-NS
1 0.0
20.0
2.00
A-S2-HO
1 0.5
20.3
1 . 93
A-S4-HO
1 l .0
20.6
1 .87
A-S2-H2
1 2.0
23.0
1 .9 1
A-S4-H2
1 4. 0
1 8. 8
1 .2 8
pec lmen
.1p
68
The d u t i l it; i nde
pe I men
of the contro l
pecl lnen \ a 2.27. The un strengthened
with a cutout i n the agging region had a d uct i l ity i n de of 2 . This
ind icate that i n tal lat ion of a utout i n the agging region re u l ted in s l i ght reduction
of 1 2% in duct i l ity i nde . . The duct i l it
- 4--H2, \va approx i m ately 1 .9. Th i
i nde
a1ue was 5% lower than that of spec imen A ­
a n d 1 6°/0 10\\ er than that o f t h e contro l .
trengthened \\ i t h fou r
of a l l strengthened spec imens, e cept
pec i men A - 4 - H 2 that w a heav i l y
M-C F R P trips i n t h e aggi n g region a n d
tv
0 N SM -CF R P
stri p i n the hogging region \V as appro i m ately 36% lower than that of specimen A ­
a n d 4-4-% lov. er than that of the contro l specimen. The d uct i l i ty i ndex of
trengthened
pec l mens tended
to decrease as the amount of N S M -C F R P
rei n forcement increa e d .
.t.2. 1 .S Ten i l e Steel S t ra i n Respon e
The ten s i l e steel train responses of speci mens of group [ A ] along \ ith those
of the control pecimen are depicted in F i gure 4 . 1 4 . The steel stra i n response in the
\\ e t and east sagging regions was s i m i lar, and hence only one of them i s shown in
F i gu re 4 . 1 4- for clarity. The ten s i l e steel strain response featured three phases.
I n itial ly, the steel was not strai ned u nt i l i n i tiation of flexural c racks. Then, the steel
stra i n i ncreased grad ual l y u n t i l yield i n g of ten s i l e stee l . I n the last stage, the ten si le
steel i ncreased rap i d l y or exh i bi ted a stra i n plateau t i l l fai l ure. General ly, the N S M ­
C F RP rein forcement decreased t h e rate of i nc rease o f the ten s i l e steel stra i n re lative
to that of spec i men A -N S . The steel strain i n a spec ific region typically decreased by
i nc reasing the amount of the N SM - C F R P rei n forcement i n the corresponding region.
The control spec imen featured a sudden increase i n steel strain i n the sagg i ng
region at the onset of cracking. F l exural c rack ing occurred first i n the sagging region
69
then i n the hogging regIon . I n itiation of c racks i n the hogging region was
accompan ied by a change i n lope o f the teel train re pon e. Fol lo\\ i n g cracki ng.
the steel train in the agging and hogging regions contin ued to i ncrease as the load
progre ed. The steel i n the hogging region
ielded h0l11y after yielding of steel in
the agg i n g region. Fol lowing ) ielding of teel, the spec i men featured a pia tic steel
train re pon e in both agging and hogging regions.
The u n trengthened pec imen
exh i b ited flexural cracks i n the sagging
region fi r t then i n the hoggi n g region. I n itiation of flex ural cracks was accom pan ied
b) a udden i ncrea e in steel tra i n in the sagging region and a change in slope of the
c u rve in the hogging region. Fol lowing c racki ng, the steel strain in the sagging and
hoggi n g region cont i nued to increase as the load progressed at a rate h i gher than
that of the control spec i men. The steel in the sagg i n g region yielded earl ier than the
steel in the hogg i n g regi o n . T h i s occ u rred because spec i men A- S had a cutout i n
the aggi ng region without strengthen i n g which signi ficantly reduced the concrete
section size and amount of i nternal steel rei n forcement i n the saggi n g region .
Fol lowing yielding of steel , the spec i men featu red a strain pl ateau i n both sagging
and hogg i n g regions.
Spec imen A-S2-HO experienced flexural cracks in the sagging and hogging
regions at load val ues h i gher than those of specimen A- S . I n the post cracking
stage. the ten s i l e steel i n both saggi n g and hogging regions exh i b i ted s i m i lar strains,
and hence they yielded s i m ultaneously at a load val ue of approxi m ately 98 kN .
Fol lowing yield i ng, the ten s i l e steel i n both regions exh i b i ted a p l astic response.
Spec imen A -S2-H2 exh ib ited a sagging steel strain response si m i lar to that of
spec i mens A- 2-HO because both spec i mens were strengthened with two N S M ­
C F R P strips i n t h e sagging region . On the contrary, speci men A-S2-H2 exh i b ited
70
lov.. er train
I n the hogging regIon relat i e to those of pec l lnen
occurred because
region but
pec l men A- 2 - H 2 had t\'. o
pec lmen
- 2-HO had no
regi n . Con equent l . , the hoggi ng
h igh r than that of pec l lnen
- 2-HO. T h i s
M -C F R P strips
In
the hogging
-C F R P rei n forcement
In
the hogging
i Id load for spec imen A- 2-H2 was sl i ghtly
- 2-HO. I t hould be noted that the ten ile steel in the
agging region of peC l men A - 2-H2 yield earl ier than the ten s i l e steel i n the
h ggi ng region.
pec imen A- 4-HO experienced flexural cracks i n the sagging and hogging
regIOn at load val ues h igher than those of speci men A - R. Fol lo\ ing crack i ng, the
ten i l e teel i n the hogg i ng region experienced h igher strai n s than the ten s i l e steel in
the sagging region. A a result. the stee l i n the hogging region yielded earl ier than the
steel i n the aggi n g region . Fol I o\: ing y i e l d i ng, the ten s i l e steel exh ibited a plast ic
response in the hogging region whereas in the saggi n g region the ten s i l e steel stra i n
cont i n ued t o i ncrease b u t a t a h igher rate t i l l fai l ure. T h e sagging y i e l d load o f
pec i men A - 4 - H O "" ith four
SM-C F R P strips i n the sagging region was h igher
than that of its counterpart A -S2-HO
\
ith two
SM-C F R P strips in the sagging
region. O n the contrar , the hogging y i e l d load of both spec imens was insignificantly
d i fferent because both spec i mens, A-S2-HO and A-S4-HO, were not strengthened in
the hoggi n g region.
Specimen A- 4-H2 experienced a tensi le steel response i n the sagging region
s i m i lar to that of specimen A -S4-H O because both specimens had the same concrete
geometr , same amount of i nternal steel and
S M -C F R P rei n forcement in the
sagging region . The ten s i l e steel of spec imen A -S4-H2 i n the sagging region yielded,
howe er, at a l oad val ue s l ightly h igher than that of spec imen A-S4-H O possi bly due
to moment red i stribution. I n the hogging region, spec imen A -S4-H2 experienced a
71
lovv er rate of increa e of ten i le steel
result. the yield load of speci men
h i gher than that of pec imen
'v\ a
trengt hened by t\\ O
A- 4-HO had no
train than that of peC l l11en
- 4-HO. A a
- 4-H2 in the hogging region was i gn i ficantly
- 4-HO. Thi
occurred becau e speci men A - 4-H2
M - C F R P trips i n the hogging region whereas spec imen
M - C F R P reinforcement i n the hogging reg ion. The tensile teel
of peci men A - 4-H2 i n the agging region
ie lded short l y after yielding of stee l in
the hogging region. Fol lowing yield i ng, the steel train cont i n ued to increase but at a
h i gher rate i n both agging and hogg ing region unt i l fai l ure.
Total load (kN)
-
control
A-NS
A-S2-HO
- - A-S2-H2
A-S4-HO
- - A-S4-H2
-
1 75
-
-
control
20000
1 5000
control
1 0000
5000
o
5000
1 0000
1 5000
20000
Bottom at mid-span
Top over central support
(Sagging)
(Hoggi ng)
Steel strai n (microstrain)
F i gure 4. 1 4 : Tensi le steel stra i n response for spec i mens of group [ A J
4.2. 1 .6 C F R P Stra i n Respon se
The C F R P stra i n responses of speci mens of group [ A J along with that of the
control are shown i n F igure 4 . 1 5 . The C F R P stra i n s were not recorded i n some
speci mens due to m a l fu nction of the strain gauge. The spec imens exh ibited no or
m in i mal C F R P stra i n s prior to flexural cracking. The C F R P strain increased
n
gradu a l l ) i n the po t-cracki n g stage a
the load progressed . The C F R P
increased at a h i gher rate after ielding of the ten i l e teel re inforcement .
- 2-HO and
M-CFRP rei n forcement in the agging
i m i larly.
peci men
- 4-HO and A- 4-H2 featured simi lar FRP strain
re pon e i n the agging region . lncrea ing the amount of
in the
pec imens
- 2-H2 featured sim i lar FRP train re pon e i n the sagg ing reg ion
becau e both of them had the amount of
region.
train
S M -C F R P reinforcement
agging region decrea ed the rate of increase of the C F R P strains in the
corre pond ing region and hence pec i mens A - 4-HO and A -S4-H2 e h i b ited lower
F R P strain
train i n
than
pecimen s A- 2-HO and
pecimen
sagg i n g region delayed
-S2-H2. The reduced rate of C F R P
4-HO and A- 4-H2
ith four N S M -C F R P strips in the
ielding of ten s i l e steel and hence i ncreased their load
capac ity to a Ie el h igher than that of pec i mens A -S2-HO and A-S2-H2 with two
M - C F R P trip in the sagging region. It should be noted that the C F R P strain at
peak load decreased as the amount of the N S M -C F R P rei n forcement i ncreased .
Total load ( k N )
-
A-S2-HO
- - - A-S2-H2
1 75
-
A-S4-HO
- - - A-S4-H2
1 50
1 25
\
1 5000
1 0000
\
5000
Top over central s upport
( Hogging)
1 00
\
\
�
\
\
75
o
5000
1 0000
Bottom at mid-span
(Sagging)
CFRP stra i n (microstrain)
F igure 4 . 1 5 : C F R P strain response for spec i mens of group [ A ]
1 5000
73
pecimen
- 2-HO.
load at agging C F R P strain
m lcr
- 4-HO.
alu
- 2-H2, and
- 4-H2 reached thei r peak
of appro i mate l) 7 1 67. 7098. 9596. and 5 7 1 6
trai n , re pecti eJ . The ratio of the
FRP train at peak load to the rupture
F R P tra i n for pe imen of group [ ] are gi en i n Table 4 . 3 . I n thi table tfm(LY
refer to the
F R P train at peak load \\ hereas tfr refer to the rupture C F R P stra i n .
T h e rat io of
FRP tra i n at peak load to the rupture CFRP tra i n were 3 8%, 3 7%,
- I �o. and 3 0% for spec i men
- 2-HO, A- 4-HO, A- 2-H2. and A - 4-H2.
re pectively. The CFRP train at peak load i n the hoggi n g region for spec i men A- 2H 2 \\ a 7689 m icrostra i n . \ h ich corresponded to approxi mately 4 ] % of the C F R P
rupt ur e train prov ided b y t h e man u factu rer.
Table 4 . 3 : Ratio of C F RP train at peak load to rupture C F R P strain ( group [ A J )
(tfmQ.Y)
pec l men
C F R P stra i n at peak load
( m icrostra i n )
(tfmax / tfr)
(%)
Sagging
Hogg i n g
Sagging
Hogging
A- 2-HO
7 1 67
-
38
-
A- 4-HO
7098
-
37
-
A-S2-H2
9596
7689
51
4]
A-S4-H2
57 1 6
30
-
-
4.2. 1 . 7 Co n c rete Stra i n Respo n se
The concrete strain responses of spec i mens of group [ A ] along with that of
the control are shown in F igure 4 . 1 6. The concrete stra i n s were not recorded i n some
spec imens due to m a l fu nction of the stra i n gauge. The concrete stra i n in both sagging
and hoggi n g regions featu red a tri-l i near response as shown i n Figure 4 . 1 6. Prior to
c racking, the concrete experienced m i n i mal concrete stra i n . Fol lowing c racki ng, the
concrete stra i n i ncreased gradu a l l y u nt i l yielding of tensi le steel . I n the final stage,
74
the concrete train conti nued to increa e at a higher rate. Genera l l y, the trengthened
pe imens exh i bited 10Vv er rate o f concrete strain than that of the un trengthened
pec l men
The concrete train in the sagging region of pec lmen
increased at a
h i gher rate than that of the hogging region. The concrete strain i n the sagging and
hogging region
r pecti el) .
at yielding
peclmen
\
a
appro i mate ly 1 400 and
1 1 00 m i c rostrains,
reached its peak l oad at concrete strain val ues of
approximately 3000 and 2300 m icrostrain
1 11
the
agging and hogging regIOns,
re pecti e l ) .
Flexural strengthen i n g sign i ficant ly red uced the rate of i ncrease o f concrete
strain rel at i ve to that of spec imen A -N .
pec imen A -S2-H2 with two
SM-CFRP
trip i n the sagging region exh ibited h i gher concrete strains i n the sagg i ng region
than those of their counterpart specimen A - 4-H2
\
ith four
SM-C F R P strips in the
aggi n g region . The concrete strain response i n the hogging region of spec i mens A2-H2 and A -S4-H 2 were i ns i g n ificantl
d i fferent because both spec i mens had two
M -CF R P strips in the hogging region .
I t sho u l d be noted that due to the presence o f the load and support plates, the
concrete strain gauges were not placed on the top surface of the spec imen at the m id­
spans or at the bottom surface over the m i dd l e support. The concrete strain gauges
were p l aced on the concrete lateral faces s l ightly away from the extreme
compression fi bers. T h i s expl ains why some concrete strain values at peak load were
l ower than the concrete crus h i ng strain value of 3000 m ic rostrai n speci fied by the
A C I 3 \ 8 -0 8 .
75
Total load ( k N )
1 75
1 50
-
A·NS
- - A·S2·H2
-
A·S4·HO
- - A·S4·H2
4000
3000
2000
1 000
o
1 000
2000
3000
4000
Bottom over central support
Top at mid·span
(Hogging)
(Sagging)
Concrete strain (microstrain)
Figure 4 . 1 6: Concrete stra i n respon e for spec imens of group [ A J
For peci men A-S2-H2.
regIOn
i e l d i ng of tensi le steel in the sagging and hogging
occurred at an average concrete strain
alue of approx imate ly 1 500
m ic rostra i n . The spec imen reached its peak load at concrete stra i n values of 2000 and
2 1 50 m icrostrains in the sagging and hoggi n g regions, respecti vely.
S pec imens A-S4-HO and A -S4-H2 featured s i m i lar concrete stra i n response
in the sagging region because both of them were strengthened with fou r N S M -C F R P
strip i n t h e sagging regio n .
pec i mens A -S4-HO experienced y i e l d i ng o f steel i n the
sagg i n g region at a conc rete strain of approximately 1 275 m icrostra i n . A maximum
concrete strain of 2600 m icrostra i n was recorded in the sagging region of spec imen
A-S4-HO j u st prior to fai l u re.
Spec imen A -S4-H 2 experienced s i m i lar rate of increase i n the conc rete strain
111
both sagg i n g and hogg i n g regions, and hence y i e l d i ng of ten s i l e steel i n both
sagging and hogging regions occu rred al most at the same t i m e at a concrete strain
76
\ alue of appro imatel) J 500 m icro tra i n .
oncrete strain value of appro imately
22 0 and 2000 were recorded in the agging and hogging regions, respecti el at the
on et of fai l ure of pec i men A - 4-H2.
4.2. 1 .8
u pport Reaction
The m iddle upport reaction \Va mea u red during te ting b means of a load
cel l . The end upport rea tion from the experi ment \ as calcu lated from equ i l i brium
of force . The upport reactions from the experi ment are com pared to the elastic
reactions i n Fi gure 4 . 1 7 . The elast ic react ions were calculated using structural
anal ) si a u m ing that the lab spec i mens had u n i form stiffness along the two spans.
F rom th i s figure. i t can be seen that the m i ddle and end suppOli react ions of the
control
peC l men \'v as s i m i l ar to the elastic reactions. Th i s occurred because the
aggl l1g and hogging regIOns had same concrete geometry and amount of steel
rei n forcement, which res u lted i n an almost u n i form flexural rigidity i n both sagging
and hogg i n g region . The reactions of pec imen A- S with a cutout i n the sagging
region deviated from the elastic reactions. The m iddle support reactions were h i gher
than the elastic reactions whereas the end support reactions were lower. T h i s
occurred because of the presence of a cutout i n t h e sagging region that red uced
flexural rig i d i ty of the spec imen in the sagging region, reduced the end support
reaction. and hence i ncreased the load transferred to the m iddle support.
Flex ural strengthe n i n g of a deficient spec i men using two
111
S M - C F R P strips
the sagging region o n l y control led propagat ion and growth of cracks in the
sagging region. and hence the m i dd l e and end support reactions of speci men A -S2H O almost coi nci ded with the elastic reactions. The end support reactions of
speci men A -S4-HO with fou r N S M -C F R P str i ps i n the sagg i n g region were sl ight l y
77
h igher than the ela tic reaction and the midd l e support reactions \'" ere sl ightl lo\\ er.
Th i s ccurr d becau e pec i men
- 4-HO w a heav i l
rei n forced \ ith
M-CF R P
t r i p i n t h e agging region, \\ h ich sign i ficantly reduced c rack propagation i n the
agging region and hence red uced the load tran ferred to the m iddle support .
F lex-ural strengthen i n g of spec i mens A - 2 - H 2 and A- 4 - H 2 i n the hogging
reg ion \\ ith t\\ O
reduced th
end
M -C F R P
trips increased the m iddle support reactions and
upport react ions relative to elastic reactions.
pec imen A -S4-H2
featured h igher end upport reaction than those of spec i men A -S2-H2 because it had
doubled the amount of the
end
upport reaction
M -C F R P strips in the sagging region . The i ncreased
of spec i men
- 4-H2 reduced the load transferred to the
m iddle support, and hence the spec i men exh i bited 10\ er middle suppOli reactions
than those of spec imen A- 2-H2.
200
1 75
1 50
Z
:.
"C
nl
1 25
.2
1 00
�
75
�
50
25
-
control
-
A-N S
-
A-S2-HO
-
A-S2-H2
-
A-S4- H O
-
A-S4-H2
0
0
25
50
75
1 00
Support reaction ( k N )
F igure 4. 1 7 : Load versus support reactions for spec imens of group [ A ]
1 25
78
4.2. 1 .9 M o m e n t - Deflect ion Re pon e
The moment-deflect ion re pon e of pec i mens of group [A] along with that
of the control pec i men are depicted in Figur 4. 1 8 . In t h i s figu re, the deflection was
v. e
taken a the a erage of the
t and east m id-span deflections. and the moments
\\ ere calc u lated ba ed on the mea ured suppo rts reactions. The maximum moments
from e).. p eriments in the agging and hogging regions are given in Tab le 4.4 along
\\ ith the moment enhancement ratio cause by trengthen ing. In Figure 4. 1 8, the fi rst
change in slope of the moment-deflection response corresponds to the cracki n g
moment \ \ herea t h e econd change corresponds t o t h e yield moment. General ly,
pec imen having same amount of rei n forcement i n the sagging region experienced
i m i lar saggi n g moment-deflection response " hereas spec i mens with same amount
of rein forcement i n the hogging region exh i bited s i m i lar hogging moment-deflection
respon e.
-
\.
E
;i
:.
....
c:
G)
control
control
- A-NS
30
- A-S2-HO
- - A-S2-H2
- A-S4-HO
- -A-S4-H2
25
E
z
"'"
C
20
Q)
E
0
E
0
control
E
E
Cl
c:
Cl
Cl
<IS
(/)
Cl
.:
Cl
Cl
0
J:
so
40
30
20
10
o
10
20
30
40
Ave rgae midspan deflection (mm)
F igure 4. 1 8 : Moment-deflection response for spec i mens of group [A]
so
79
Table 4.4:
oment capac ity and enhancement ratio for spec imens of group [A]
Moment capac ity from
pec lln en
e peri ment
Ms' exp
Mh,exp
J.. 1ER *
(kN . m )
( kN . m )
1 6.3
20. 1
8.5
2 1 .7
1 .0
-S2-HO
1 7.8
23.4
2. 1
A-S4-HO
22.3
23.5
2.6
A-S2-H2
1 5 .9
31.1
1 .9
A-S4-H2
1 9. 8
30.2
2.3
contro l
A=NS
-
M oment enhancement ratio with respect t o sagging moment o f spec i men A-N S
The un trengthened spec i men A - S featured a signi ficant reduction i n the
J ield and u l t i m ate sagging moments re lative to those of the control because of the
cutout that reduced the concrete section and amount of steel rei n forcement. The yield
and u l t i m ate moments of spec imen A -N S were approxi mately 50% lower than those
of the contro l pecimen. The hoggi n g moment o f spec imen A -N S was i nsign i ficantly
d i fferent from that of the contro l .
F lexural strengtheni n g i n t h e sagging region on l y significantly i ncreased the
saggmg
ield and u lt i mate moments but had almost no effect on the hogging
moments. The add i tion of N S M -C F R P rei n forcement i n the hogging region increased
the hoggi n g yield and u lt i mate moments but had almost no effect on the sagging
moment.
The yield and u l t i mate sagging moments of spec i mens A -S2-HO and A-S2H 2 with two N SM - C F R P strips in each sagging region were approximately 1 00%
h i gh er than those of spec i men A -N S and almost the same as those of the control
spec imen. T h i s i n d i cates that flexural strengthen i n g with two N SM -C F R P strips fu l l y
80
re tored the agging moment capac it of the spec i men w ith a cutout in the agging
regIon
I ncrea ing the amount of
M - C F R P rei n forcement in the sagging region
further increased the u l t i mate agging moment to a I e el e en h i gher than that of the
control pec imen. For pec i men
- 4-HO and A- 4-H2 with four N M -C F R P stri ps
in the agging region. the u l t imate agging moment was on average 1 48% h igher
than that of peci men A The
a n d 30% h igher than that o f t h e contro l .
ield and u lt i mate hoggi n g moments of spec i men A -S2-HO and A-S4-
HO \\ ere almost the same a
pecl mens
tho e of speci men A-
. Th i s occurred because
- 2-HO and A-S4-HO \ ere not strengthened in the hoggi n g region. On
the contrary. the hogg i ng yield and u lt i mate moments of spec i mens A - 2-H2 and A4-H2 \ ith t\'vO
M-CFRP
trips in the hogg i n g region were on average 40%
h igher than those of spec imen A- S.
4.2. 1 . 1 0 Load - Moment Rela t i on s h i p
F i gu re 4 . 1 9 depict the load-moment re lationsh i p of spec i mens of group [ A J
a n d that of the contro l spec i men i n the sagging a n d hogging regions. T h e moment­
deflection response in the saggi n g and hogg i n g regions fol lowed the same trend as
that of the load versus end and m iddle support reactions respecti vely. The sagg i n g
a n d hogging moments i n t h e control speci men in add ition t o spec i mens A -S2-HO and
A-S4-HO were nearly elastic with i n s ign i ficant moment red i stribution because of the
s i m i lar d i stribution, propagation, and growth of flexura l cracks in both sagging and
hoggi n g regions. Conversel y, the experimental sagging and hogging moments in
specimens A- S, A-S2-H2 and A -S4-H2 devi ated from the elastic moments because
of the non - u n i form fl exural rigi d i ty of the sagging and hogging regions. The
81
unstrengthened
pec lmen
\v ith a cutout in the sagging region featured the
greate t dev iation from the ela tic behavior because of the sign i ficant variation i n
flexural rigidit) bet\\ een the agging and hogging regions. T h e sagging moments in
pec i m n A -
were lov" er than t h e ela tic moments w herea the hogg i ng moments
\\ ere h igher than the elast ic one .
moment
pec l men
and low er hogging moment
than tho e of
occu rred becau e spec i men A- 4-H2 had fou r
region \\ herea spec i men A- 2-H2 had onl
region. Both spec i mens had
- 4-H2 exh i bited h i gher sagging
pec imen A - 2-H2. Thi
M-CFRP strips in t h e sagging
two N S M - C F R P strips i n the sagging
ame amount of N M-CFRP rei n forcement i n the
M - C F R P rei n forcement in the agging
hogging region. The i ncrea ed amount of
region l i m ited propagation of flexural cracks i n the sagging region, i ncreased the end
upport reactions, and hence increased the sagging moment in spec imen A -S4-H2
relat i v e to that of spec imen A- 2-H2.
Total load ( k N )
I
- control
-A-NS
-
-
-
A S2 HO
-A-S2-H2
-A-S4-HO
-A-S4-H2
-40
-30
-20
-1 0
o
Hogging moment
10
20
Sagging moment
30
Moment ( k N . m )
F igu re 4 . l 9 : Load-moment relationsh i p curves for spec i mens of group [A J
40
82
4.2 . 1 . 1 1 M o m e n t Red i t ri b u t ion
on the d i fference i n Dexural rigid ity
The moment red istribution depend
bel\\ CCn the . agg i ng and hoggi ng region . The moment redistri bution rat io, /3. can be
alculated using Equati on 4 . 2 . A P ' i t i e val ue of moment redi stribution rati o
i nd i cate
that the con erned region h a
gai ned moment
greater t han the e l astic
moment \\ herea a negati ve val ue i nd icate that the concerned region has gai ned
moment I
than the ela tic m ments. The e l ast ic moments were calculated u i ng
'trll tural anal)- i a umi ng that the slab pec i men had u n i form sti fmess along the
t\\ O
pan . The e l asti c moment
are
ho\\'n i n Figure 4.20. Tabl e 4.5 gi ves the
moment red i tri bution rati o II r spec i men
of gr u p [ AJ along with that of the
ontr I .
/3 %
=
M
e:.p
- M
Me
e
X
I 00%
(4.2)
here :
/3 = moment redi stribution ratio
Afexp = moment from experi ment
AIe = moment from e l ast i c ana l ysis
M h•• =
p
z
3
32
PL
p
1
Ms . •
=
5
64
PL
Figure 4.20: E l ast ic moments
Ms ...
=
5
64
PL
83
Table 4 . 5 : Moment red i tribut ion ratios for spec i mens of group [ ]
Moment form
lab
ame
e peri ment
.\ [s, , '"
(k .m)
control
1 6. '"
-NS
8.5
-S2- I JO
1 7.8
A-S2- 1 1 2
1 5 .9
-S4- H O
22. '"
- S4- H 2
1 9. 8
/0;1, exp
( k .m)
20. 1
2 1 .7
_3.4
31.1
23.5
" 0. 2
l astic Moment
A is.e
(k .m)
1 6. 5
1 2. 1
1 8.4
2 1 .5
2 1 .3
2 1 .8
fJ (%)
A fh.e
(kN.m)
Saggi ng
Hogg i ng
1 9. 7
- 1 .2
+2.0
1 4. 5
-29.8
+49 . 7
22. 1
-3.3
+5.9
25.9
-26
+20. 1
25.5
+4.7
-7.8
26.2
-9.2
+ 1 5 . '"
From Tab l 4.5. i t i s e i dent t hat t h e unst rengthened spec i men A - N S with a
cutout i n t he aggi ng region exhi b i ted the h i ghest moment redi stribution ratios of
approx i matel y -30% and +50% i n the sagging and hoggi ng regions, respecti vely.
Thi
occurred becau e of the presence of a cutout i n the agging region, which
i gn i fi cantl y reduced the concrete section and amount of i n ternal steel rei n forcement.
Thi
in tum re u lted in a signifi cant d i fference in flexural rigidity between the
agging and hogging region. The contro l speci men exh i b i ted al most no moment
redi stribution becau e both sagging and hogg i ng regions had the same concrete
geometr
and amount of steel reinforcement. S pec i men A-S2-HO and A-S4-HO
exh i bi ted i nsignificant moment red istri buti on in the ran ge of 3 . 3% to 7 . 8%.
pec i men A-S2-H2 featured appreci ab l e moment red i stri bution val ues of -26% and
+20% i n the saggi ng and hoggi ng regions, respectively whereas for spec i men A -S4H2. moment red istri bution values of-9.2% and + 1 5 .3% were recorded in t he sagging
and hogg i n g regions, respectively.
8--1
..t 2.2 G ro u p I B ]
Re�ults of fi e pec i men. or gr up [ 8 ] hav i ng a cut ut in the hoggi ng region
are presented i n th i " .e tion. Four pe i men
were trengthened with
M-C F R P
r i nrorcement i n the hoggi ng regi n. wh i le one spe i men w a not strengthened .
R
o r the contr I
ult
peCl ll1en that d i d not i nc l ude a cutout and \Va
not
tr ngthened are i nc l uded f r the pu rpo e of com paris n .
... . 2.2 . 1 Load Capacity
Re lilt
tho e of th
rat io
of the load mea urements for
contro l are ummarized i n Table 4.6. The u l t i mate load en hancement
( LER) for the strengthened
un trengthened spec i men 8l oad
pec i mens of group [ 8 ] along with
pecl m n
\ ith
respect to that
of the
are given in t he ame table. The crac k i ng and yield
\\ ere taken from the tensile steel stra i n response. The sagging crac k i ng and
yield load of the west
pan in some
peci men
were not recorded because of
malfunction of the stra i n gauge.
Table 4 . 6 : Resu lts of l oad mea urement for peci mens of group [ 8 ]
p) ( kN )
Per ( kN )
Sagging
pec l men
Hogging
Pu
( kN )
94.3
87.8
1 1 6 .90
7 1 .2
62.9
89.80
1 .00
Sagging
Hogging
West
LER'
Ea t
West
Ea t
control
1 4. 6
27. 1
29.8
B-NS
-
1 1 .4
25
B .. SO-H2
-
1 5 .2
24.7
-
75 . 1
81.1
1 05 . 50
1 .18
B-SO-H4
-
1 5 .4
22.6
-
96. 7
1 1 2.5
1 22 . 5 0
1 .3 6
B-S2-H2
23.2
2 1 .7
23.9
1 08 . 5
1 24 . 7
1 1 2.0
1 3 6.9
1 .5 2
B - S2-H4
3 0. 9
27.8
29.6
1 26 . 8
1 2 1 .5
1 25 .9
1 3 8.00
1 . 54
83 .4
-
Load en hancement rati o W i th respect to that of spec I men B-NS
-
85
The un'trengthened spec i men Bi n tht: east agging regi n and 25 k
1 1 .4 k
c racked at I ad v al ue of approximatel_
i n the hogg i ng region. The ten i le steel
in the h ggi ng region ) ielded prior to the ten i le teel in the ea t aggi ng region,
because
f the presence of the cut ut in the hogging regi n. \\ hich reduced the
amount o f steel and al
reduced the concrete cct ion i ze. The ten ile teel in the
hogging regi n y ielded at a I ad a l ue of approx i mateJ
63 k
\<
hereas i n the east
'agging region. it y i elded at a load aJue of approx i mately 7 1 .2 k .
ach ie\(�d it
peak load at a load val ue of 89.80 kN. Thi
pec i me n B­
val ue \Va approx i mately
23°'0 km er than that of the control s pec i men.
Flexural
c rack
approx i matel) 1 5 . 2 k
The
i n i t iated
I II
specI men
B-SO- H 2 at a load
val ue of
in the east agging region and 24. 7 kN i n t he hogging region.
teel i n the saggi n g and hogg i n g regions yielded al most concurrently at load
\ al ue. of approxi matel
7 5 . 1 kN and 8 1 . 1 k , respecti vely. The sagg i ng yield load
of pec i men B- 0-H2 \Va al most the same as that of spec i men B-NS, \< hereas the
hogg i n g yield load \Vas approxi mately 29% h igher than that o f speci men B -NS.
peci men B- 0-H2 strengthened with two CFRP stri ps in the hoggi ng regIOn
experienced a load enhancement ration of 1 8% relative to the ulti mate load of
speci men B-
. The load capaci ty of peci men B-SO- H 2 was, however, 1 0% lower
than that of the control speci men. Th i s i nd i cates that two
S M - C F R P strips \< ere not
suffic ient to restore the l oad capac ity of the control s pec i men.
pec i men B- 0-H4 with four NSM-C F R P strips i n the hogging region
experienced flexural c racks i n the saggi n g and hogging region at load val ues of
approxi mately 1 5.4 kN and 22.6 kN, respectively. Y i e l d i ng of tens i l e occurred fi rst
in the agging region at a load val ue of approx i mately 96. 7 kN fol l m ed by yielding
of steel i n the hogg i n g region at a load val ue of approx i mately 1 1 2 . 5 kN. Thi s
86
ccurrcd bccau e of the i ncrea cd amount of
region, \\ hich delay ed } i c l d i ng of steel
0
M- FRP
tri p
In
the hogging
er the middle suppo rt . The sagging and
hoggi ng ield load of pe i m n B- 0- 1 1 4 \\ ere appro. i mately 36% and 80% h i gher
than tho e of pec i men B-
, re rect i e l y . The I ad capac ity of peci men B- 0-1 14
\\ as 3 0'0 h i gher than that of pe i men B­
and a l
0
5% h i gher t han that of the
control pcci men.
F r pec i men B- 2- 1 12 , ne ura l crack occurred i n t he
\.
est and ea t sagging
region a l mo t at the same t i me at I ad val ue of appro. i mate l y 23.2 kN and 2 1 . 7
k . re pect i \ el) . For the h ggi ng region, flexural crack i n i t i ated at a load
a l ue of
appro:-. i matel) 23 .9 k . The tens i l e steel of t he \\ est and east sagging regions yielded
at load
al ue
f approxi n1ate l ) 1 08 . 5 k
and 1 24.7 kN, respect i vel y. For t he
hogging region. the tensi l e teel ) i l ded at a load val u
of approx i mate ly 1 1 2 k .
The u l t i mate load of speci men B- 2-H2 was 52% h i gher t han that of speci men B- S
and 1 7% h igher than that of the contro l spec i men. I t shou ld be noted that the u l t i mate
l oad of speci men B-S2- H 2 was approxi mate l y 30% h igher than that of spec i men B O - H 2 . Thi s i nd icates that the addi t ion o f N S M -C F R P rei nforcement i n t h e saggi ng
regIon signj fi cant l y i mpro ed the load c arry i ng capacity.
pec i men B-S2-H4 experi enced flexural cracks in t he west and east saggi ng
regions at l oad val ues of approx i matel y 30.9 kN and 2 7 . 8 k , respective l y . Flexural
cracks i n itiated i n the hogging region at a load val ue of 29.6 kN. The tensi l e stee l
yielded i n t he west and east agg i n g regions a l most concurrentl y at load val ues of
] 26.8 k
and 1 2 1 . 5 k . respecti ve l y . For the hogg i n g region, the tens i l e steel
yielded at a load val ue o f 1 25 . 9 kN. The u l t i mate load of spec i men B- 2-H4 was
54% h i gher than t hat of spec i men B-NS and 1 8% h i gher than that of t he contro l
speci men. The u l t i mate load of spec i men B-S2-H4 was approxi matel y 1 3% h i gher
87
than that of p c i men 8- 0-1 14 becau e of the addition of
M - FRP rei n forcement
in the aggi ng region , w h ich i m pro ed the load carl) i n g capac it . The i ncrea e i n
load capac it) due t
i ncrea i ng the
M - C F R P rei n forcement i n the sagging region
was Ie' pronounced i n pec i men B- _-H4 ( 1 3% ) than i n s peci men 8- 2-H2 ( 3 0%).
rhis i ndicate
that the gam i n load capac ity d ue to
region d e rea e as the a m u n t
trengthen i n g i n t he aggi n g
f rei n forcement i ncrease
i n the hogging region.
Fi nal ly, it hou ld be n ted that the load capacit of peci men 8-S2- H4 was the same
as
that
f pecimen B-S_-1-I 2 . Th i s demon trate that for R
hea i l ) rei n forced i n the
conti nuolls slab stri p
agg i n g region, i ncreasi ng the amount of
M-C F R P
rei n forcem n t i n the h gging region h a i ns i gn i ficant effect o n t he load capac ity .
... . 2 . 2 .2 Fai l u re M od e
peci men B -
fai led i n a flexural mode of fai l ure. The ten i l e steel yielded
fir t in the hogg i n g region then in the saggi n g region. Fol IO\ i ng yielding o f tensi le
steel, crushi ng of concrete occurred at the bott m face of the spec i men over t he
middle u pport then at the top face i n the mi d-span sect ion. Photos of specimen B a t fai lu re are shown i n Figure 4.2 1 .
pec i men B-SO-H2 fai led i n a fl ex ural mode o f fai l ure. The tensi l e steel
y i el ded fi rst i n the saggi ng region then i n t he hogging region. Fol lowing yielding of
tensile stee l , c rush i ng of concrete occurred at the top face of the speci men in the mid­
span section and at the bottom face over the middle support. D ue to the
\
eakness o f
the section over t h e middle suppo rt caused by t h e cutout, a shear crack developed i n
the hogg i n g region a t t h e o nset of fai l u re after concrete crushing.
speci men B-SO-H2 at fai l ure are shown in F igure 4.22.
P hotos of
88
pec imen B- O-H4 fai l ed i n a flexural mode of fai l u re. The tens i l e
teel
) ielded fi r t i n the saggi ng region tben in the hogging region . Fol lowing yielding of
ten i le teeL cru h ing of concrete occu rred at the top face of tbe spec imen i n the m idpan ection and at tbe bottom face 0 er the m i dd le upport. A photo of spec i men BO-H4 at fai l u re i s sho\\ n i n F igu re 4.23.
Failu re of mi d-span section
F a i l u re of section over central support
(sagging regio n )
( hogging region )
F igure 4 .2 1 : P hoto of spec i men B - S a t fai l ure
(. �:'!IIIIt. ,
�
,
I
<P
Fail ure of mi d-span section
(sagging region )
•
Fai l ure of section over central support
( hoggi ng region )
F igure 4 . 2 2 : Photos of spec i m en B-SO-H2 at fai l u re
89
F igure 4 . 2 3 : P hoto of spec imen B - O-H4 at fai l u re
pec lmen B- 2-H2 fai l ed in a flexural mode of fai l u re . The ten i l e steel
)- ielded in the hogging region at a load alue of 1 1 2 kN . The l ast yielding occurred in
the ea t sagging region at a load value of 1 24 . 7 kN . Fol lowing yielding of tensile
teel. cru hing of concrete occurred at the bottom face of the spec i men over the
m iddle upport and at the top face in the m id-spans . A m i nor shear crack developed
in the hogging region at the onset of concrete crush ing d ue the weakness caused by
the cutout. A photo of spec i men B-S2-H2 at fai l ure is shown in F igure 4.24.
The pec imen B-S2-H4 fai led in a fl exural mode of fai l ure. The tens i le stee l
I n the sagging and hogging regions yielded a l most at the same time. Fol lowing
yielding of tens i le stee l , crush ing of concrete occ u rred at the top face of the spec imen
in the m id-spans and at the bottom face over the m iddle support. At the onset of
fai l u re, crushing of concrete took place in the concrete section over the m i ddle
support accompanied by formation of a shear crack in the hogging region. The shear
crack developed because of the red uced concrete section caused by the cutout. A
photo of speci men B -S2-H4 at fai l ure is shown in F igure 4.25.
90
F i gu re 4.24: Photo of specimen 8-S2-H2 at fai l ur e
F igure 4.25 : P hoto of spec imen 8-S2-H4 a t fai l ure
.t.2.2.3 Load-Deflection Response
The l oad-deflection responses for spec I mens of group [ B ] are gIven
m
Figures 4.26 to 4.30. For speci men B -N S , both spans experienced a very sim i l ar
deflection response. A l i near response was mai ntai ned up to an average m i d -span
deflection of approxi mately 1 m m . Then, the spec i men exh i b ited a quas i - l i n ear
deflection response unt i l fi rst y i e l d i ng took p Jace in the hogging region at an average
91
deflection of approximatel
8 . 5 m m . The
econd ( l a t ) yielding occurred i n the
hogging region at an average m id- pan deflection of approx i matel
1 1 .2 m m .
Follo\\ i ng la t ) ield ing, t h e defle t ion cont i nued t o increa e b u t a t a h i gher rate unt i l
a peak load o f 89.80 k
20.6 mm a
wa ach i e ed at corre pond i n g east m id- pan deflection of
ho\\< n i n Figure 4.26.
pec imen B- O-H2 featured a l inear deflect ion response in both spans unt i l
i n itiat ion o f c rack a t a deflect ion
a l u e o f approx imatel
1 mm where the fi rst
dev iation from l i nearity took place. Fol lo\ ing cracki ng, the spec imen experienced a
qua i - l i near deflection re ponse u nt i l y i e l d i ng of ten s i l e steel took place i n the
sagging region at approxi m ately 1 0 m111 . then, the deflection increased at a h i gher
rate u n t i l y i e l d i ng of ten s i le teel i n the hogg ing region ( last yielding) took place at a
deflection of approx i m ately 1 7 m m . Fol l owing last yield i ng, the spec i men exh i b i ted
a plast ic deflection respon se unt i l a peak load of 1 05 . 5 kN at correspond i n g east and
west span deflections of 24.4 m111 and 24.2 m 111, respectively as shown i n F igure
4.27.
pec i men B - 0-H4 exh i bi ted a l i near deflection response up to an average
deflection of approxi mately 1 .2 mm where fi rst change in slope took place due to
c racking. I n the second stage, the deflection conti nued to increase but at a h igher rate
u nt i l fi rst yield i ng took place in the sagging region at an average deflection of 9.5
mm. Fol lowing fi rst yield i ng, the deflection increased rapidly unt i l the speci men
reached its l ast y i e l d i ng in the hogging region at east and west deflections of 1 0 m m
a n d 1 6 m m , respectively. I n t h e last stage, t h e m i d-span deflection o f t h e west span
experienced a plastic respon se unt i l a peak load of 1 22 . 5 kN was ach ieved at a west
m id-span deflection of 3 3 .2 mm as shown i n Figure 4.28.
200
- 8-NS (east span)
- 8-NS (west span)
1 75
1 50
Z
�
"'0
to
1 25
E
1 00
0
�
75
�
yielding i n
s a g g i ng
(
...... -
(yielding i n
hogging
50
25
0
0
5
10
20
15
25
30
35
40
Deflection (mm)
F i gu re 4.26: Load -deflection respon se of spec imen B - S
200
- 8-S0-H2 (east spa n )
- 8-S0-H2 (west span)
1 75
1 50
z
:.
"'0
!II
E
.!9
(:.
1 25
yielding in
h o ggi n g
..... - -..
1 00
75
50
25
0
0
5
10
15
20
25
30
35
Deflection (mm)
F i gu re 4.27: Load -deflection response of spec i men B-SO-H2
40
93
200
1 75
-
8-S0-H4 (east span)
-
8-S0-H4 (west span)
1 50
z
�
yiel d i n g in
h oggin g
1 25
"C
"'
.2
:§
�
1 00
-
75
-
yielding in
sagging
50
25
0
0
5
10
15
20
Deflection
25
30
35
40
(mm)
F igu re 4.28: Load -deflection re ponse of spec imen B-SO-H4
For pec imen B-S2-H2, the l i near deflection response
as m aintai ned up to
an average m id-span deflection of approx imately 3 . 5 m m . Then, the deflection
i n c reased at a h i gher rate unt i l fi rst yiel d i ng of steel took place in the hogging region
at east and west mid- pan deflect ions of 1 0 m m and 1 2 mm, respectively. Fol lowi ng
fi rst yielding, the deflection fu rther increased at a h i gher rate unti I second ( last)
yielding occurred i n the sagging region at east and west deflections of 1 3 mm and
1 5 .2 m m , respecti ely. I n the l ast stage, the deflection conti nued to increase at a
h igher rate u nt i l the spec imen reached its peak load of 1 36.9 kN at east and west
m id-span deflections of 22.30 mm and 24.4 m m , respectively as shown in F igure
4 .29.
94
pec imen B- 2-H4 featured a l i near deflection respon e in both spans u nti l
i n itiation of crack at a deflection
alue of appro. i matel
1 .25 mm \vhere the fir t
dev iation from l i nearity took place. Fol lo\\ i n g cracki ng, the deflection increased
l inearly until y ielding of ten s i l e teel took place in the sagging and hogging region at
an a\ rage defl ection of 1 0.3 m m . Fol lo\ ing yielding of steel, the deflection
ont in ued to i ncrea e but at a h igher rate unt i l the pec i men reached a peak load of
1 38 k
at an a erage m i d- pan deflection of approx imately 1 4. 5 mm as shown in
F i gu re 4.30.
200
-
1 75
- 8-S2-H2 (west span)
1 50
z
�
8-S2-H2 (east span)
yielding in
sagging
1 25
"0
1'0
.2
]
�
1 00
75
50
25
0
0
5
10
15
20
Deflection
25
30
35
(mm)
Figure 4.29: Load -deflection response of spec imen B-S2-H2
40
95
200
- S-S2-H4 (east span)
1 75
-
S-S2-H4 (west span)
1 50
z
,:,t;
1 25
"C
t1l
�
(Q
....
�
yielding in
sagging &
hogging
1 00
75
50
25
0
0
5
10
15
20
Deflecti o n
25
30
35
40
(mm)
Figure 4.30: Load-defl ection response of peci men B-S2-H4
The load-deflection respon ses of all spec imens of group [B] with a cutout i n
t h e hogging region a l o n g with that of the control spec imen are plotted i n Fi gure 4.3 1 .
The deflection response of the span that featured the greater m i d-span deflections
was considered in F i gu re 4 . 3 1 .
It i s clear that the flexural stiffness and load capac ity
of speci men B-NS v,,'ere sign i ficantly lower than those of the control spec i men . For
instance at 50 kN. the deflection of the control spec imen was 3 . 6 mm whereas for
spec i men B - S i t was 6 . 5 m m . The deflection at peak load for spec imen B - S was
sl ightly lower than that of the control specimen. A lthough the sti ffuess of specimens
B- O-H2 and B-S2-H2 ha ing 1\\10 N S M -C F R P strips i n the hogging region was
h i gher than that of the un strengthened speci men B -NS, it was s l ightly lower than that
of the control specimen. Speci men B-SO-H4 with fou r N S M -C F R P strips i n the
hogging region fu l ly restored the sti ffness of the control spec imen . The sti ffness of
96
pec i men B- 2-H4 \\ ith fou r I M - F R P strip i n the hoggi n g region and tw o
M-
F R P t r i p i n t h e agging region \\ a even better than that of t h e contro l .
F i gu re 4.3 1 : Load-deflect ion response for speci m en s of group [ B )
4.2.2.4 D u ct i l i ty I n dex
The ducti l ity indices for speci mens of group [ B) are com pared to that of the
contro l speci men in Table 4 . 7 . The deflection values at fi rst yield i ng and at peak load
are taken from Figure 4 . 3 ] .
Tab l e 4 . 7 : Duct i l ity indices for specimens of group [ B )
(mm)
Lip
(mm)
f-L
control
1 0. 5
23.8
2.27
B-NS
1 1 .8
20.6
1 . 75
B-SO-H2
9.2
24.4
2 .65
B-SO-H4
1 1 .4
33.2
2 .90
B-S2-H2
1 1 .2
22.3
2.0
B-S2-H4
1 0.4
1 4. 5
1 .4
peclmen
LIy J
97
The d uct i l it� inde
1 . 75, v. a
of pec lmen 8-
\\ ith a cutout in the hogging region.
23% lo\\ er than that of the control
in tal lation of a cutout in the hogging region
pec i men.
ign i ficantl
Th i s i nd icates that
compri ed the
lab
d uct i l it) and re u lted in in igni ficant reduction in ducti l it i nde . The ducti l i t i nde
f peci men
8- O-H2 and 8- 0-H4 trengthened on l
h i gher than that of pec imen 8oc u rred becau e i n the e t\ 0
in the hogging region \ a
and even better than that of the contro l . Thi
pec imens
ield ing of steel occu rred fi rst i n the
agging region that \v a un trengthened, and then the specimens had to u ndergo a
i g n i fi cant deformation unt i l yielding of steel fol lo\\ ed b crush ing of concrete took
place in the hogging region. I n stal lat ion of
M-CFRP rei n forcement in both
agging and hogging regions reduced the slab duct i l ity index. The ducti l i ty index of
pec imen 8- 2-H4 was 50% lower than that of spec imen 8 -N S . The duct i l ity of
pec imen
8- 1-H4
trengthened \ \ ith 1\\ 0
\\- as
comprom i sed
sign i ficantly
because
it
was
M - C F R P strips i n the sagging region and fou r
heav i l y
M -C F R P
stri ps i n t h e hogging region .
4.2.2.5 Tensile Steel Stra i n Respo n se
The ten s i l e steel strain response of spec i mens of group [ B ] along that of the
control speci mens are shown i n F i gure 4 . 3 2 . The spec imens exh i bi ted a tri - l i near
tens i l e steel stra i n response.
0 steel stra i n s were recorded prior to i n i tiation of
flexural c racks. Fol lo\ ing cracking. the steel stra i n i ncreased at an almost constant
rate u nt i l yielding. I n m ost of spec i mens. a plast ic steel strain response was then
recorded after yield i ng . In some other spec i mens heav i l y rei n forced with
SM­
C F R P strips. the steel strain increased a t a h igher rate after yielding u nt i l t h e peak
load " as reached.
98
The tee) train in the hogging region for the un trengthened specimen B \\ i t h a cutout in t h e hogg ing region, increased at a rate h i gher than that of t h e control
pec l me n .
a re ult. t h e ten i l e
agging region ) ielded at load
teel of spec imen 8 -
in both hogging and
alue lower than those of the contro l .
exhibited yiel d i ng o f ten i le
pec imen B -
tee l i n t h e hogging region at a load
appro i mate l. 63 k . The post-yield teel train re ponse of spec i men B -N
alue of
i n the
hoggi n g region w a not recorded due to fai l ure of the strain gauge. The tensile steel
in the agging ) elded at a load value of approxi mate ly 7 1 k , after yielding of steel
i n the hogging region.
The hogging yield load of spec i men B- O-H2, w ith two
SM-CFRP strips in
the hoggi n g region. was h i gher than that of spec i men B -N S and s l i ghtly lower than
that of the contro l . The teel in the sagging region yielded fi rst at approximately 75
k
fol lo\ ed by . ield i ng of steel i n the hogging region at approxi mately 8 1 k . The
post-yield ten i l e steel strain response of spec i m en B -SO-H2 in the saggi ng region
was not recorded due to fai l ure of the stra i n gauge.
pec imen B -SO-H4, with four N S M - C F R P strips
111
the hogging regIon,
experienced yielding of ten s i l e steel i n the sagg i ng region fi rst then i n the hogging
region.
Th i s
occurred
because
of the
sign i ficant
amount
of
S M -C F R P
rei n forcement provi ded i n t h e hogging region that delayed yielding o f tensi le steel i n
that region . The yield load o f spec imen B-SO- H 4 i n both sagging and hogging
regions \-vas h i gher than that of the control spec imen .
The ten s i l e steel of spec imen B-S2-H2, with two N S M - C F R P strips i n both
sagging and hoggi n g regions, yielded earl ier in the hogging region than the steel i n
t h e sagging region . Thi s occu rred because t h e spec imen was strengt hened with the
same amount of N S M -C F R P reinforcement in both sagging and hogging regions but
99
it had a cutout i n the hogging region. The rate of increa e of tensi l e steel train In
pec imen B- 2-H2 v" as ign i ficant l) 10\\ er than that of pec imen B-
This i n tum
.
increa ed the y ield load of peci men B- 2-H2 i n both agging and hogging regions
to a le\ el e en h i gher than that of the control pec imen.
The ten i l e teel of spec imen B- 2-H4 i n both agging and hogging regions
) ielded concurrent l) .
hogging region
becau e
pe i m en
hogging
regIon
pec i men 8- 2-H4 experienced tensile steel strains i n the
l ight ly lo\\ er than tho e of spec imen B- 2-H2. Th i s occulTed
- 2-H4 \ a
w hereas
trengthened with fou r
A- 2-H2
pec l Inen
had
M-CFRP strips in the
only
two
N S M -C F R P
rei n forcements i n t h e hogging region . As a result, t h e yie ld load o f spec i men A-S2H4 i n the hogging reg ion wa sl i ghtl
h i gher than that of spec i men A -S2-H2. The
tensi le teel respon e of spec imen 8 -S2-H4 in the sagg i n g region coinc ided with that
of spec i men 8-S2-H2 because both spec i mens had the same concrete geometry,
arne amount of i nternal steel and
S M -C F R P rei n forcement i n the sagging region.
Total load ( k N )
-
control
8-NS
8-S0-H2
- - 8-S2-H2
8-S0-H4
- - 8-S2-H4
-
175
-
1 50
-
control
20000
control
1 5000
1 0000
5000
o
5000
1 0000
1 5000
8ottom at m id-span
Top over central support
(Sagging)
(Hogging)
Steel strain (microstrain)
F i gu re 4 . 3 2 : Ten s i l e steel strain response for spec i mens of group [ 8 ]
20000
1 00
4 . 2. 2.6 C F R P
tra i n Re pon e
of peci mens of group [ B] are plotted in Fi gure
4 . 3 3 . The C F R P train re pon e featured three pha es during loading. I n itial l , no or
m i n i mal F R P t rain
w ere recorded . Fol lo\V ing flexural cracki ng. the C F R P strain
increa d at an almo t con tant rate a the load progressed unt i l yielding of steel took
place. Fol lo\\ ing :> ielding, the C F R P train continued t o increase but a t a h igher rate
unt i l fai l ure. [t i e ident that pec i mens B- O-H4 with fou r N M-CFRP strips in the
hogging region e;.. h i bi ted lower C F R P strain than those exh ibited by spec i men B O - H 2 \\ ith t\\ O
M -C F R P trips.
i m i larly, spec imen 8-S2-H4 exh ibited lower
C F R P train i n the hogging region than those exh i b ited by spec i men 8 -S2-H2. This
i n d icate that the C F R P strain i n a certain regions decreases \ ith an increase i n the
amount of
M -C F R P rei n forcement in the correspond ing region. The C F R P strain
re ponse of spec imens B - 2-H4 and 8-S2-H2 i n the sagging region was almost
identical a
t\\ 0
hown i n F igure 4 . 3 3 because both spec imens were strengthened with
M-CFRP strips i n the sagging region.
Spec i mens B-SO-H2. 8-S0-H4, B-S2-H2, and B-S2-H4 reached their peak
loads at hogg i n g C F R P strain val ues of 8647, 6843, 4939. and 5232 m icrostrain,
respecti e l ) . The ratios of the e F R P strain at peak load to the rupture e F R P strain
for spec i mens of group [B] are given i n Table 4.8. In th i s table Cfl1lC1X refers to the
eFRP strain at peak load whereas Cjr refers to the rupture eFRP stra i n . The ratios of
e F RP stra i n at peak load to the rupture e F R P stra i n for spec imens B-SO-H2, B-SO­
H4. B - 2-H2. and B -S2-H4 \ ere 46%, 36%, 26%, and 2 8%, respectively. The e F R P
strain a t peak load i n t h e sagging region for spec imens B-S2-H2 and B-S2-H4 were
6252 and 64 1 1 m icrostra i n , which corresponded to e F R P strain ratios of 3 3% and
34%.
101
Tota l load ( k N )
"I , "
\
\
,
- 8-S0-H2
1 75
- - 8-S2-H2
1 50
- - 8-S2-H4
- 8-S0-H4
1 25
\
\
\
1 00
\
' 5
y
\
5�
1 5000
1 0000
5000
\
o
5000
1 0000
1 5000
B o ttom a t m i d -s p a n
Top over centra l s u p po rt
( Ho g g i n g )
(Sagging)
C F R P stra i n ( mi c rostra i n )
F i gu re 4 . 3 3 : C F R P train response for spec i mens o f group [ B ]
Table 4 . 8 : Rat io of C F R P stra i n at peak .l oad to rupture C F R P strain ( group [ B ] )
(ej.mmJ
pec imen
(ej.max l eji)
C F R P stra i n at peak load
( m icrostrai n )
(%)
Saggi n g
Hoggi n g
Sagg ing
Hogging
B- O-H1
-
8647 .0
-
46
8-S0-H4
-
6843 .0
-
36
B- 2 - H 2
6252.0
4939.0
33
26
B-S2-H4
64 1 1 .0
5232.0
34
27
4.2.2.7 C o nc rete Stra i n Respon e
The concrete stra i n responses for speci mens of group [ B ] along with that of
the control speci men are depicted in F i gure 4.34. The concrete stra i n response was
not recorded or incomplete i n some spec i mens due to m a l function of the strain
1 02
gauge. General ly, the rate of increa e of concrete train increased after crack ing then
increa ed further after } ielding of tensile tee l .
From Figure 4.34. it can b e een that t h e unstrengthened spec I men 8 exh i bited h i gher concrete strains than tho e exh i bited b y the control spec imen. The
ten i le
teel in the hogging and sagging region s of spec imen 8 -
corre pond i n g concrete
re pect i vel) .
train
pec l men 8-
of approx i matel
900 and
yielded at
1 250 m i cro train .
reached its peak load at concrete strain values of
approxi matel) 1 800 and _200 m i c ro trains
m
the hoggi n g and sagging regions.
re pecti vely.
The trengthened spec i mens exh i bited a lower rate of i ncrease of concrete
tra i n than that of the un trengthened
pec i men 8- S. I n c reasing the amount of
M -C F R P rei n forcement in a certai n region decreased the rate of increase of the
C F R P train i n that region.
The concrete strai n of spec imen B - O-H2 at the onset of yielding was on
av erage 1 000 m icrostra i n . peci men B-SO-H2 reached i t s peak load a t concrete strain
values of approximately 3 J 00 and 2700 m icrostrains i n the hogging and sagging
regions. respectively.
pec imen B-SO-H4 exh i bi ted lower concrete stra i n than that of spec i men B­
SO-H2. particularly i n the sagging region, because of the i ncreased amount of
SM­
CFRP strips. Maximum concrete strain values of 2500 and 3 750 m i crostrains were
recorded in the hoggi n g and sagging regions of spec i men B-SO-H4, respectively
prior to fai l u re.
Spec imen 8-S2-H2 experienced lower rate of increase of concrete strain than
that of spec i men B-SO-H2, part i c u l arly in the sagg i n g region . Th i s occurred because
1 03
pec l m n 8- 2-H2 had t\\ O
M-CFRP trip in the sagging region but pec imen B-
O-H2 did not i n c l ude any
M- F R P trip in the agging region . The strain gauge
in the hogging reg ion \ a
debonded at appro imately 2000 m icro t rain prior
reach ing the peak load becau e of local conc rete crushi ng.
peC l lllen B- 2-H2
reached it peak load at a concrete strain a l ue of appro imatel y 2000 m icrostrain i n
t h e agging region .
pec i men B- 2-H4 experienced a concrete strain response 1 11 the saggl l1g
regIOn i m i lar to that of pec imen 8- 2-H4 because both had two
in the
M - C F R P strips
agg l l1g regIOn. The concrete strains of pec imen 8-S2-H4 in the sagging
regIOn i ncrea ed at a 10\\ er rate than that of speci men 8-S0-H2. This occurred
becau e pec lmen 8- 2-H2 had two N SM - C F R P strips in the sagging region but
spec imen B- 0-H2 did not i n c l ude N S M -C F R P rei n forcement in the sagging region .
The concrete stra i n response of pec imen B-S2-H4 in the hogging region was not
re orded due to malfu nction of the stra i n gauge. A max i m um concrete strain of 1 7 1 5
m i cro t rain was recorded i n the sagging region of spec imen B-S2-H4 j ust prior to
fai l ure.
I t should be noted that d ue to the presence of the load and support plates, the
concrete strain gauges were not placed on the top surface of the spec imen at the m i d ­
spans or a t t h e bottom surface over t h e m iddle support. The concrete strain gauges
were placed on the concrete l ateral faces sl ightly away from the extreme
compression fi bers. T h i s explains why some concrete stra i n val ues at peak load were
l ower than the concrete crush ing stra i n value of 3000 m icrostrain spec i fied by the
ACI 3 1 8 -08.
1 04
Total load ( k N )
1 75
1 50
1 25
-
control
8-NS
8-S0-H2
- - 8-S2-H2
8-S0-H4
- - 8-S2-H4
-
-
4000
3000
2000
1 000
o
1 000
2000
3000
4000
Top at m id-span
Bottom over central support
(Sagging)
(Hogging)
Concrete strain (microstram)
F i gure 4.34: Concrete train response for speci mens of group [ B ]
4.2.2.8 S u pport Reacti o n s
T h e load
ersus support reactions from the experiments are plotted in Figure
4 . 3 5 . The support reactions of spec i men B- 2-H4 were not recorded d ue to
mal funct ion of the load cel l placed between the spec i men and m iddle support during
testi ng. The m iddle and end support reactions of the control specimen were nearly
elasti c . On the contrary, the m iddle support react ions of specimen B - S \ ere lower
than the elasti c react ions whereas the end support reactions were h i gher than the
elastic ones. The presence of a cutout i n the hogging region reduced the flexural
rigidity of the specimen in the hogging region, reduced the m i ddle support reaction,
and hence increased the l oad transferred to the end supports.
The m iddle and end support reactions of spec i men B -SO-H2 almost coincided
w ith the e l astic reactions. This occurred because of fl exural strengthen ing in the
hoggi n g region with two
S M -C F R P strips, which counteracted the weakness in
1 05
fie u ral rigid i t)
au ed b) the cutout and control led pr pagat ion and grO\v1h of
cra k. in the hogging reg i n. I ncr a ing the amount of
- F R P reinforcement i n
t h e h gging r gion further i n rea ed t h e m iddle upport reaction and decrea d th
end
upp rt r act i n . Thi
supp
e:-.. p lain
\v h
pe i men 8- O-H4 exh i bi ted m iddle
l ightl) high r than the ela tic reaction and end upport reaction
l ightl) lo\\ er than the ela t i react ion
pec i men 8- 2-H2
ela ti
:-.. p rienced midd l e
upport reactions lo\\ er than the
upport reaction h i gher than the ela tic one .
pe I men had t\\ 0
M- FRP
trip
m both
Ithough thi
aggmg and hogging regions, it
ontai ned a cutout in the hoggi n g region. The cutout reduced the concrete ection
and amount of i nternal teel in the hogging region . T h i s in turn reduced the flexural
rigid it) of the hogging region relati e to that of the
agging region, and hence
redu ed the load tran ferred to the m iddle upport and increased the load tran ferred
to the end upport.
200
1 75
1 50
1
Z 1 25
�
"0
IV
1
#1
iff 1
1
/
1
1
E. 1 00
5
�
75
- control
50
25
-
B-NS
-
B-SO-H2
-
B-S2-H2
-
B-SO-H4
0
0
25
50
75
1 00
1 25
S u p port reaction ( k N )
F igure 4 . 3 5 : Load ersus support reactions for spec imen of group [ 8 ]
1 06
4.2.2.9 M o m e n t - Deflection Re pon e
The moment-deflect ion re pan es of spec imen of group [ B ] along \ ith that
of the control pec imen are sho\\ n i n F igure 4.36. The moment-deflection re ponse
of B- 2-H4 \', a not p lotted becau e the support rea l ions w ere not recorded during
te t i ng of thi speci m en . In thi fi gure. the de flection wa taken as the average of the
\\ e t and ea t m id -span deflect ions, and the moment \ ere calcu lated based on the
mea ured
lIpports react ions. The max i m u m moments from experiments in the
aggi n e and hogging regions are given i n Tab le 4.9 along \ ith t h e moment
enhancement ratio call e b) trengthen ing.
30
-
control
-
8-NS
-
8-S0-H2
- - 8-S2-H2
�
z
--
:.
c
E
:i
:.
c
8-S0-H4
control
Q)
E
0
Q)
E
0
control
E
E
OJ
C
OJ
C
'0,
'0,
OJ
tV
(/)
OJ
0
J:
50
40
30
20
10
o
10
20
30
40
Average midspan deflection (mm)
Figure 4 . 3 6 : Moment-deflection response for spec i mens of group [ B]
50
1 07
Table 4.9:
oment capac ity and enhacemenet rat io for spec imens of group [ B]
Moment capac ity from
experi ment
pec i men
Ms
x!'
••
MER ·
J.. fh.exp
(k . m )
( kN . m )
control
1 6. 3
20. 1
-
B-NS
1 5. 1
1 0. 3
1 .0
B-SO-H2
1 3 .5
20.5
2.0
B-SO-H4
1 4 .5
26. 1
2.5
B-S2-H2
22.0
1 7.6
1 .7
M oment enhancement rat io w Ith respect to hogging moment of spec imen B -N S
From F i gu re 4.36. it i clear that i nstal lation of a cutout i n the hoggi ng region
sign i fi cantl
reduced the hogging
i eld and u l t im ate moments of speci men B -N S
relative t o t h o e of t h e control specimen. T h e hogging y i e l d a n d u lt i m ate moments o f
pec i men B- S were approximately 50% 10\ er than t hose of the control specimen.
The sagging moment response of spec imen B-NS was i n s i gn i ficantly d i fferent from
that of the contro l .
Spec imen B-SO-H2 w i t h two N S M-CFRP strips
111
the hogging region
featured a hoggi n g moment response s i m i l ar to that of the contro l . This demonstrates
the effecti veness of the
S M -C F R P system i n restoring the moment capacity of the
deficient section . The hoggi n g moment capacity further increased as the amount of
S M -CF R P rei n forcement increased in the hogg ing region . The hogging moment
capac ity of speci men B-SO-H4 with fou r N SM - C F R P strips in the hogging region
was approx i m ately 2.5 t imes that of spec i men B -N S and 1 .3 t i mes that of the control
( i .e. flexural strengthen i n g with fou r N SM -C F R P strips not only restored but
exceeded the hoggi n g moment capac ity of the control spec imen).
The sagging moment response of spec i mens B -SO-H2 and B-SO-H4 were
i n s i g n i ficantly d i fferen t from that of the control spec i m en . Th i s occurred because
) 08
both pec lmen had neither a cutout nor
M - F R P reinforcemen t i n the
agging
region. On the contrar) , the agging moment capac it) of pec imen B - 2-H2 \\ as
igni ficant l ) h i gher than that of the control because it had two
the
agging region. The hogoing moment capac ity of
appro. imatel} 70% higher than that of sp c i men B-
-C F R P trip in
pec imen B - 2-H2 \Va
and 1 2% 10\ er than that of
the contro l . The agging moment capac ity of pec imen B - 2-H2 was 46% and 35%
h igher than those of spec imen 8-
and the control spec imen, re pect iveJ
.t.2.2. 1 0 Load - M o m e n t Relation s h i p
The load-moment relation h i p for spec imens of group [ 8] along with that of
the control are shO\\ n in F igure 4 . 3 7 . The load-moment respon e of spec i men 8-S2H 4 \\ as not plotted becau e the support reaction of t h i s spec imen were not recorded
during te ting. The sagg ing and hogging moments are proportional to the end and
m iddle upport reactions. re pect ively. The moments in spec imens 8 -N S and 8- 2H2 de i ated from the elastic respon se because of a variation in flexural rigid ity of the
agging and hogging regions caused by the presence of the cutout in the hogging
region. The presence of the cutout i n the hogging region reduced the load transferred
to the m iddle support. and hence red uced the hogging moment and increased the
sagging moment relative to the elastic ones.
F lexural strengthen i n g of specimen 8 -S0-H2 with two
SM-CFRP strips i n
t h e hogging region counteracted t h e defic iency caused b y t h e cutout, a n d hence the
sagging and hogging moments of speci men B -SO-H2 coincided with the elast ic
moments up to a load value of approximately 7 5 k
where yielding of tensi le stee l i n
the sagging region took place. Fol lowing y i e l d i n g of stee l i n t h e saggi n g region, the
sagging moment tended to be lower than the elastic whereas the hogging moment
tended to be h i gher.
1 09
F ie. u ral
trengthening \\ ith four
M-CFRP
111
trips
the hogging region,
\\ here the cutout \ a i n tai led, further i mproved the flexural rigid it of the specimen
i n the hogging region to a Ie el e en better than that of the i ntact sagging region that
contai ned no cutout . T h i s in turn increased the hogging moment and reduced the
agging moment of pec i men B - 0-1-14 relat i e to the elastic moments. The dev iation
from the ela tic beha ior further increased after yielding of tensi le steel in the
agging region at approximately 97 kN . Fol lowi n g
ield i n g of teel i n t h e sagging
reoion. the pec imen exhib ited aggi n g moments lower than the elast ic moments and
hogging moment h igher than the elast ic moments.
Total load (kN)
\
\
�
\
1 75
ij'Iq,
\
\
\
tl
0'1)I I
1 50
\
\
\
1 25
I
I
I
I
I
I
-
control
- 8-NS
- 8-S0-H2
-
8-S2-H2
- 8-S0-H4
-40
-30
-20
-10
o
Hogging moment
10
20
Sagging moment
30
40
Moment (kN.m)
F igure 4.3 7 : Load moment rel at ionsh ip curves for group [ B ]
4.2.2. 1 1 M o m e n t Red is t r i b u t ion
The moment red i stribution ratios for spec i mens of group [ B] along that of the
control spec i m en are given i n Table 4. 1 0. The moment redistri bution ratio, /3, was
1 10
calculateJ u i ng
quat i on 4 . 2 . A po i t i ve val ue or moment red istri bution rat io
i nJ i cates that t he concern d region ha
gai ned moment
greater t han the elast ic
moment \\ hereas a negat i e val ue i nd icate that the concerned region ha gained
m ment le's than the ela tic m ment .
Tabl e 4. 1 0:
ment redi stri bution rati o fI r peicmens of group [ 8 ]
M ment rorm
lab
ame
experi ment
Afs•np
(k .m)
control
1 6.3
8-NS
1 5. 1
8-S0- I 12
1 3 .5
8-S0- H4
1 4.5
8-S2 - H 2
22.0
A II/,exp
(k .m)
20. 1
1 0. 3
_0.5
26. 1
1 7. 6
Ela tic Moment
M\,e
(k .m)
1 6. 5
1 2. 6
1 4. 8
1 7. 2
1 9. 3
fJ (%)
Af,,,e
(k .m)
Sagging
Hoggi ng
1 9. 7
- 1 .2
1 5 .2
+ 1 9.8
+2 . 0
-32.2
1 7. 8
-8.8
+ 1 5 .2
20. 7
- 1 5.7
+26. 1
23. 1
+ 1 4.0
-23 8
From Table 4. 1 0, i t can be een t hat the unstrengthened speci men 8 -
.
with
a cutout in the hogging region exh i bi ted signi ficant moment red i stribution ratios of
+ 1 9. 8�o and -32.2% in the sagging and hogging regions, respecti vely. Th i occurred
becau e of the presence of a cutout i n the hogg i n g region which reduced the flexural
rigi d i ty of the hogging regi on rel at i ve to that of the sagging region. The control
peci men exh i bi ted almost no moment redi stri bution because both sagging and
hoggi ng regions had same concrete geometry and amount of steel rei n forcement .
pec i men 8-S0- H 2 exh i bited moment red i stri bution ratios of - 8 . 8% and + 1 5 .2% i n
t he agg i n g and hoggi ng regions, respective l . S pec i men A-SO-H4 exh i bi ted higher
moment redi stri bution ratios than those of speci men 8-S0-H4 because i ncreasi ng the
amount of
M - C F R P rei n forcement i n the hogging region i ncreased the variation
in flex ural rigidity between the sagg i n g and hogging regions. The moment
red i stri but i on ratios for speci men 8-S0-H4 were - 1 5 . 7% and + 26. 1 % in the saggi ng
and
hogging
regions
respecti vely.
S peci men
8-S2- H2
featured
moment
I I I
reJ i stri buti n rati o
and -23 . 8% I n the saggl l1g and hogging regions,
of + J 4%
respccti eJ � .
4 . 3 E ffi c i e n cy o f t h e S t r'e n g t h e n i n g S c h e m e
rable 4. 1 1 compares the e rtl c i ncy of t h e strengthen ing scheme adopted i n
tud . Equat i n 4.3 to 4 . 5 ha e been used to calculate the effic iency
th ' pre ent
f3ctor of each trengthen ing cheme. The e ffi c i enc
l11 u l t i p l y i ng the rati
been cal c u l ated b
cherne ha
factor ( EF) for a strengthen i ng
of the
trength gai n to the
e1Tecti , e ten i le trength of a l l C F R P tri ps used in strengtheni ng
(SglTje)
t i mes the
rat io o f the load capa i t)' of the control speci men wi thout cutouts to the load capac i ty
of the
peci m 11 after
trengtheni ng (CcICs ) . The strength gai n i s the d i fference
between the load capac i ty before and after strengt heni ng. To fu l ly re tore the load
capac i t) , the rati o
cl
s
mu t be l ess than or equal to unity, otherwise t he
considered i neffi ci en t \ ith an effic i ency factor of EF =
strengtheni ng scheme
::ero.
Sg
-
EF =
Ttl
Cc
-
::ero
C\
for
for
Co
C,
CL
-
S1
(4.3)
>
1
(4.4)
(4.5)
where:
Aje = effect i ve c ross section area o f al l C F R P stri ps used i n strengthen ing
1 12
.
.
aggmg regIon
II; \
c ros� sect ion area I' a l l
F R P tri p u e d i n th
A/ h
cros 'ecti n area 0 r aI l
F R P trip used i n t he h ggi n g regi n
C
load apaci t ) of the
\ - I ad eapa it)
ntrol peci men \\ ith ut cutouts
r t he trengthened peci men with cutout
L(s - l ength of a l l C F R P trips u ed in the saggi ng regions
If h = length r ai l C F R P tri p
Ll
cd in the hoggi ng region
I, - length f pan i of the continuou
l ab
Table 4. 1 1 : E rfic iency of the trengtheni ng chemes
pec i men
Group
[ ]
[ 8]
Aje
1
Tje
Sg
SglTje
(%)
CclCs
EF
(%)
(mm-)
( kN )
( kN )
- 2-HO
24 1 .6
748 .9
45.2
6.0
0.89
5.4
- 4-HO
966.3
2995.6
65.3
2.2
0.77
1 .7
- 2-H2
289
895 . 7
54.2
6. 1
0.84
5.0
A- 4-H2
1 0 1 3.7
3 ] 42.4
69.2
2.2
0.75
1 .7
B - 0-H2
4 7.4
1 46.8
1 5.7
1 0. 7
1.1
0
B- 0-H4
1 89.5
5 87 .4
32.7
5.6
0.95
5.3
8- 2-H2
289
895 . 7
47. 1
5.3
0.85
4.5
B-S2-H4
43 1 . 1
1 33 6 . 3
48.2
3.6
0.85
3. 1
For peC l lnen of group [ A J \ ith a c utout i n each sagging region, i t can be
seen t hat scheme S2-HO with two
S M -C F R P strips in each saggi ng regi on and no
strengtheni ng in the hoggi ng region was the most effic ient strengtheni ng scheme
fol l mved by scheme S2-H2 with two
regions.
chemes S4- H O with four
S4- H 2 with four
S M-CF R P str i ps i n both saggi ng and hogg i ng
SM-CFRP stri ps i n each sagging region, and
SM-C F R P stri ps i n each saggi ng region and two N S M -C F R P
stri ps i n t h e hogging region, were the least effici ent strengt he n i ng schemes. A l though
1 13
cherne ' 2 - 1 1 0 had hal f
c
fai l ure f trengthened p
t han rupture of
imen \V a control led by c ncrete crushing rather
F R P, and hence the added amount
aggi ng region ha i ng
each
t rengt hen ing sol ution
a
3 - fold h i gher. Th is occurred
f
M-C F R P rei n forcement
not dTi ientl} uti l ized. It can t lpn be concl uded that for a slab strip with a cutout
\\
1 11
F R P rei n forcement u ed i n
4- HO, i t effic iency factor \\ a approxi mat I
heme
becau
f the amount of t he
We
We' b
U i ng t\\ O
of 0.375 and IC"L of 0.25, the opt i ma l
M- FRP strips i n each sagging region \\ ith
F R P rei n forcement rat io of PI = 0.3 5%.
For spec i men' of gr up [ B ) \ itb a cutout in t he hoggi ng region, the u e of
t\\ O
1 - F R P trip i n the hogging region onl
was not efficient b cause the load
capac ity after strengthen i ng was Ie s than the load capac i t of the control spec i men
\\ ith ut cutouts ( i .e.
capa i ty).
0-H4) to ful l
M-C F R P
n t able to restore t he origi nal load
tri p had to be used in the hogging
re tore tbe origi nal load capacity. Scheme
0-H4
M - C F R P strips in the hogg i n g region was the most efficient scheme
fol lowed by scheme
two
0-1 1 2 \Va
m i n i mum of four
regi on ( cherne
with four
cheme
2 - H 2 with two
S M -C F R P strips in each sagging region and
SM-C F R P trips in the hogging region . A lt hough scheme S2-H4 had double
the amount of the hoggi ng
S M -C F R P rei n forcement used i n scheme S2-H2, i ts
efficiency factor was approxi matel y 3 0% l ower. This occurred because strengt hened
speci mens fai led by concrete crush i ng without rupture of C F R P . This mode o f fai l ure
conceal ed the effect of i nc reasing the amount of the
S M - C F R P rei n forcement. It
can then be conc l uded that for a slab stri p with a cutout i n t he hoggi ng region havi ng
H'/b o f 0 . 3 75 and
l/L of 0.25, t he opt i mal strengthe n i ng sol ution wa usi ng four
S M - C F R P strips in the hogging region with a C F R ? rei n forcement rat io of PI
0. 7%.
1 1 -1
H
PT E R 5 :
A
A LYTI
L MODLE I
G
5 . l l n t ro d u c t i n
' T h i ' chapter present a n anal ) tical
t \\ o<pan conti n uoul., R '
, 1- TRP
concrde. stL:cl and
" i\. t -
del that can prcd i t the load capac i ty of
lab . tri ps \\ i th cutout
n.: i n forccment. 1 h e analyti al
the en'l:ct of
111
III
trengthened \\ i th
1-C F R P
d c l adopt rca l i -tic material l a\-, , and ace unt for
trengthcn ing on the I ad capacit). Propcrtie
F R P rei n forcement d e cri bed i n
of the
hapter 3 were used a
i nput data i n the anal) 'is. The ac urac) of the anal)1ical approach \\ a exam i ned b
comparing it, pred iction \\ ith te't re u l t .
5 . 2 M a t e ri a l Co n s t i t u t i ve L a w
5.2. 1
oncrete
The
1 11
as
u med tre - tra i n relat i n hip of concr te in compre i on i i l l ustrated
F i gure 5 . 1 ( Hogne tad et a l . 1 95 5 ) . The a cendi ng branch of the
relat i on h i p o f t he concrete i n compre
ion i de cribed by a econd-degree parabola.
The ofte n i n g concrete l aw in compres i n i
concrete cru h i ng at a t ra i n
t re
al ue of
tress-strai n
Cell
assumed l i nearly de cend i ng unti l
= 0.003 8 and a corre p n d i ng post-peak
\ al ue o f lc = 0.85lc ( Hogne tad et a l . 1 95 5 ) . The as umed
tre
-stra i n
rel at ion h i p i g i en b y Equation 5 . 1 to 5 . 3 .
Ie =
(5. 1 )
1 15
(5.2)
(5.3)
Where :
=
e strength.
concrete 'tra i n corr spond i ng to the concrete compre i ve strength.
Eco
Cc
conCr t e comrre
-
concrete tra i n for a gi en load i ng cond ition.
f
= concrete tres for a gi ven concrete stra i n .
E
= Young's mod u J u of concrete.
L
c
,
O. 15[
I
Figure 5 . 1 : Assumed stress-strai n rel ationsh i p o f concrete ( Hogne tad e t a l . 1 95 5 )
1 16
5.2.2 � t d R i n for
mcnt
I h � sire ' - trai n relat ion ' h i p o f the <;tcel rei n forcement i
l i near e1clst ic-pl a tic \\ ith a post-) i e l d
i dcal i led t o be
t ra i n harden ing of 1 % ( lac reg r and
Bart lett 1 997; Park and Pau l a) 1 (75 ) a
:ho\\ n in Figur e 5 . 2 . The
tres - t ra i n
rel ationsh i p or teel i ' gi \ cn b) E:q uat i n - A .
Pre - yield slage
Post - yield lage
( 5 A)
\\ here:
_
f:,
teel trai n for a given load c n d i tion .
c rre pon d i ng to
.I,
teel tre
.I;
tecl ) ie l d i ng tre
f, .
.
.k
cn
=
Es
= mod u l u of the teel rei n forcement before
E,I'
= mod u l u o f t he steel rei n forcement after ) i e l d i ng ( po t- i e l d stage) .
fsu
f'll
=
teel t ra i n corre pondi ng to the y ield t re
_
ield i ng ( pre-) ield tage) .
teel u l t i mate t rength.
tee I t ra i n corre pond i ng to the teel u l t i mate trength ./;u.
1 17
Figure 5 . 2 : I dea l i zed tres -stra i n relationsh i p of steel
5.2.3 Carbon Fiber Rei n forced Polymer
The stre -stra i n re lati onsh i p o f the CFRP compo ite strips i s ideal ized to be
l i near-el ast i c up to fai l ure a shown i n Figure 5 . 3 . The tress-strai n rel at ionshi p of
steel i gi ven by Equation 5 . 5 .
(5.5)
\\ here:
.Ii
f:j
Ej
fr,
tres
111
SM- F R P rei n forcement.
=
C F R P stra i n for a g i ven load con d i tion.
=
Young " s modu l us of the C F R P .
=
tensi l e strength of the C F R P.
1 18
E,
Figure 5 . ..., : I deal i zed tres -st ra i n relationsh i p of C F R P
S.2A
o m pa t i b i l i ty Req u i rem e n t
t ra i n and stres d i stribut i ons a l ong section depth are shown i n Figure 5 .4 . The
t rai n
i n th
com pres ion
teel . tensi l e
teel , and N S M -C F R P rei nforcement are
eiven by Equations 5 .6, 5 . 7, and 5 . 8, respecti vel
G (e - i---'-)
_
G,
c
�
= -,
G,
= -"---
Gf
C
G (d - c )
c
£s
£1
(5.7)
(h - c )
G
" = --=-
c
\\ here :
£s
(5.6)
=
stra i n i n compression steel rei n forcement.
=
stra i n i n ten s i l e steel rei n forcement.
=
stra i n i n l ongitud i nal N S M-C F R P rei n forcement.
(5.8)
1 19
c
depth of neutral
'
c/
depth of ompres. ion steel mea ·ured fr
<1.
i s measured from the cOll1pre · ion face of the lab.
In
the c mpre i n face of the lab.
depth of tt:nsi le steel ll1ca5u red from the cOll1pre
II
n face of the l ab.
= thickne<;s l) f slab.
b
-.-=: .(
���
!=:::=:
( �
�
ql
d
I
. ,'" d "
I
I
�
rp
.
.
cg
.
' ·�
I ��
' __�IL-�______�_LLL__
.
�'
L
::
E:
0
strain
Idealized concrete
distribution stress dlstnbutlon
Cross section
Figure 5 A :
.1
i:\]c r,
NA
train and tre s d i tri buti n a long ection depth
5.2.5 E q u i l i b ri u m R eq u i remen t
Equ i l i bri um condi t ion are i mpo ed i n t rm of axial force and bend ing moment
( Eq uation 5 . 9 and 5 . 1 0) . I n order to cal cul ate the compre ion force i n concrete, the
ere - ection i
di c retized i nto fi n i te l ayer . The compression force in concrete i
a l c u l ated by n umerical i ntegration o f force i n each l ayer. The steel rei n forc i ng bar
and F R P tri p are r pre ented b} di crete elements.
( 5 .9)
Lf,A,d, + L A,,/,,d,, + L Ajfjdf
"
\\ here:
AI
=
area of concrete l ayer i.
=
M"
( 5 . 1 0)
1 20
.1)/
cros
ect ional area of steel bar i.
eros se tional area f a
M- F R P trip.
d i tanee bet\\ een pia tic centro i d o f conc r te secti n and center of the
cll
FRP
trip.
d"
d i tance bet\v een pia tic centroid of concrete section and centroid of concrete
lay er i.
dH
d i tance bet\\ een plastic centroid of concrete sect ion and center o f steel bar i.
jj
tre
.r
jCl
= concrete tre
tre
j;,
J \ fn
In
=
l-C F R P rei n forcement.
at the center 0 f the l ayer i.
i n the steel bar i.
nomi nal moment strength .
I n Equat ion 5 . 9 and 5 . 1 0, compressi ve stresse are taken as po i t i e and tens i l e
tresses are taken a s negati e. The d i stance dCI i s taken a s positive i f the
corre pon d i ng conc rete l ayer is located above the p l asti c centroid of the concrete
ection, otherwise the d i stance \ i l l be taken as negati e as shown i n Figure 5.4.
i m i l arl ) , the d i stance cis ' i
taken as pos i t i ve \ hereas the d istances ds and dj are
taken a negati ve.
5.2.6 Model P roced u re
For a gi ven stra i n d i stribution along the section depth at peak load, the sectional
forces are i ntegrated n umerical l y and the nomi nal moment capacity of both sagging
and hogg i n g regions was calculated usi ng an i terati ve process. I t should be noted t hat
al l speci mens fai l ed by concrete c rush i ng wi thout rupture of the
S M -C F R P
I �O
AI/
cro s ecti onal area of teel bar i.
cro s ect ional area of a
£If
M-CF R P strip.
d i tanc beh\ ecn pia tic cent roid o f concrete ection and center of the
FRP
:trip.
du
d i tance bet\\ een pia t i c n l r i d o f concrete sect ion and centroid of concrete
=
la) er i.
dH
= d i tance bet\\ een plastic centroid of concrete sect ion and center of steel bar
.Ii
tre
.fe,
=
•
\ I1l
=
l - C F R P rei n forcement.
concrete t re s at the center of the l ayer i.
tre
'/;,
In
i.
i n t he steel bar i.
nom i na l moment t rength.
In Equations 5 .9 and 5 . 1 0 compressi ve stresses are taken as pos i t i ve and tens i l e
tres e s are taken a s negati e. The d i stance
dc,
i s taken a s positive i f the
corre pon d i ng concrete l ayer is l ocated above the p l asti c cent roid of the concrete
ection, otherwi e the d i tance wi l l be taken as negati ve as shown i n Figure 5.4.
i m i larl ) , the d i stance
ds '
i s taken as posi t i ve whereas the d i stances
ds
and elf are
taken as negati ve.
5.2.6 M o d e l P roced u re
For a gi en strai n d i stribution along the section depth at peak load the sectional
forces are i ntegrated n umerical l y and the nomi nal moment capacity of both sagging
and hogg i n g regions was cal c u l ated usi ng an iterati ve process. I t hould be noted that
al l spec i mens fai l ed by concrete crush i ng without rupture of t he
S M -C F R P
121
rci n rorcement, and hence the c n rete
0.00'"
=
ummari 7cd a rol low :
llme depth or the neutral a.x i s
•
E:w
( ee ect ion 5.2. 1 ). The model procedure used to pred ict the nomi nal moment
trengt h can b
•
t rai n at peak load \vas as llmed a
c.
alcu late the 'tra i n i n each l ayer of concrete, steel bars, and
M -C F R P
rei n I' rcement usi ng com pat i bi I i ty r q u i rements.
•
al u l ate the
tr '
i n each layer o r concrete steel bars, and
M -C F R P
stri p u i ng the material s ' con t i t u t i e I a\vs.
•
a l c u J ate th force
In c
ncrete, steel and
S M -C F R P rei n forcement.
•
I terate the assumed neutral axi depth unt i l eq ui l i brium of forces i s sati s fied.
•
Cal c u l ate t he moment capac i ty that sati sfle equi l i brium req u i rements.
Once the
agg1 l1g and hoggi ng moment capac i ties are calculated the load
carryi ng capac ity for a t \\.' o equal -span cont i n uOLlS slab, with a concentrated load of
P
_
at each m id-span. can be pred icted using Equati on 5 . 1 1 ( Park and Paul ay ] 975).
(5. 1 1 )
where:
Pn
=
nomi na l l oad capaci ty pred icted by the model .
L
=
len gt h of one of the two equal spans.
Ains
=
nomi na l moment strength of the sagging secti o n .
Mnh = nom i nal moment strength of t h e hogg i n g sect ion.
1 22
5.2 . 7 A n a ly t i c a l Rc u l t
Thc pred icted n mi nal moment strength o f the agging and h ggi ng section
arc presented in Table 5 . 1 . The concrete d i men ion . amount of i nternal steel
rei n forcement. and
pre ented i n t h
M- F R P rei n fl rcement u ed a i nput data i n the anal} is are
ame table.
Propert ie
rei n forcement u ed in the analri
of c ncrete.
teel and
are de cri bed i n Chapter 3 .
M- F R P
A companson
bet\\ cen the experi mental and pr d i c ted load carry i ng capac it ies is given i n Table
5 . _ . The model tended t
te t
provide a can elvati e pred iction for the load capac i ty of
peci men . The pred icted
load capac i ty of the control
appro:\ i matel ) 2200 lower than t he e. peri mental load capac i t
For
pec l men was
pec i mens o f
group [ ] , \\ ith a cutout i n the saggi ng region. the rat io o f the pred icted to measured
load capac ity was i n the range of 0 . 74 to 0 . 8 7 . The model provided m re accurate
predi ction
for the load capaci ti es of speci mens of group [ 8] \vith a cutout i n the
hoggi ng region \\ here the rati o of the predicted to measure I ad capac i ty was in the
range of 0.85 to 1 .02 . The contribut ion of the saggi ng moment to the load capac i ty i s
two t i mes that of t h e hogg i n g moment (see Eq uation 5 . 1 1 ) . A a result, the predicted
l oad capac ity i s les
en i t i ve to the pred icted hoggi ng moment capac ity than the
agging moment capac i ty. Th i s expl ai ns why the model had better pred iction
for
speci mens of group [ 8] with a cutout i n the hogg i ng region.
The ratio of the pred icted to measured l oad capac i ty wa on average 0.85 with
a standard devi at i on of 0.09, and a coeffic ient of variation of 1 0%. The d i fference
between the predicted load capacity and t hat measured experi mental ly is w i t h i n the
acceptable margin of error for such a comp l ex problem. It can then be stated that the
anal}1 i cal approach adopted in t h i s study can give reasonable pred ictions for the load
1 23
capac it) of t\\ o- pan cont i n u u R
1-
lab tri p \\ ith a cut ut and strengthened w ith
FRP rei n forcement.
Table 5 . 1 : Pred icted moment capac ity
Sagging
Sp cil11cn
Af",
ction
/l. 1,,/,
Hogging ect ion
b
A,
A,
Ar
(kN.m)
b
A,
A,
AI
( k .m)
control
400
3 1 4. 2
1 57. 1
0
1 3.7
400
3 1 4.2
1 57. 1
0
1 3. 7
-NS
250
1 5 7. 1
1 57. 1
0
7.5
400
3 1 4.2
1 57. 1
0
1 3.7
A-S2-HO
250
1 57. 1
1 57. 1
75
1 5 .24
400
3 1 4.2
1 5 7. 1
0
1 3.7
-S4 - 1 1 0
250
1 5 7. 1
1 57. 1
1 50
1 9. 2 5
400
3 1 4. 2
1 57. 1
0
1 3. 7
A-S2 - 1 1 2
250
1 57. 1
1 57. 1
75
1 5 . 24
400
3 1 4.2
1 57. 1
75
22. 1
-S4-H2
250
1 5 7. 1
1 57. 1
1 50
1 9. 2 5
400
3 1 4.2
1 57. 1
75
22. 1
8-NS
400
3 1 4. 2
1 57. 1
0
1 3.7
250
1 57. 1
1 5 7. 1
0
7.5
8-S0-H2
400
3 1 4.2
1 57. 1
0
1 3.7
250
1 57. 1
1 57. 1
75
1 5 .24
8-S0-H+
400
3 1 4.2
1 57. 1
0
1 3 .7
250
1 57. 1
1 57. 1
1 50
1 9.25
8-S2-H2
400
3 1 4. 2
1 57. 1
75
22. 1
250
1 57. 1
1 57. 1
75
1 5 . 24
8-S2-H4
400
3 1 4. 2
1 57. 1
75
22. 1
250
1 5 7. 1
1 57. 1
1 50
1 9.25
1 24
I 'ahle :- . 2 . 'om pari
J f() U P
Control
-
I
n bct\\ een anal) ti al and e\.perimental load apac i ties
Pred icted load
[:\.peri mental
capac it)
load capac ity
Di fference
Ratio
Pn
Pu
(% )
( PI1IPII)
(k )
(k )
9 1 . '"
1 1 6.9
-2 1 .9
0.78
6 "' . 8
85.8
-25 .6
0.74
,\-S2- I IO
98.2
1 3 1 .0
-25 .0
0.75
,\-, 4-1 10
1 1 6. 0
151.I
-23 . 2
0.77
t\-S2- 1 1 2
1 1 6. 8
1 40.0
- 1 6.6
0.83
'\-S4- 1 12
1 34 . 7
1 55.0
- 1 3. 1
0.87
B-NS
7 7. 6
89.8
- 1 3.6
0.86
B-'-'0- H 2
94. 8
1 05 . 5
- 1 0. 1
0.90
8-S0- 1 14
1 03 . 7
1 22 . 5
- 1 5.3
0.85
B-S2- H2
1 32 . 1
1 36.9
-3.5
0.96
8-S2-H4
1 4 1 .0
1 3 8.0
+2.2
1 .02
.' pcci men
-
cont rol
-
-
r---
\- I S
[ \]
[8J
0.85
\ erage
Standard dc\ i ation
0.09
Coeffi c i ent of ariat i n C Olo)
1 0%
D i fference (%)
=
1 00
\.
( Pn - Pu)/(Pu)
1 �5
C H A PT E R
6:
CO N C L U S I O N S A N D
R E CO M M E N D A T I O N S
6 . 1 I n t ro d u c t i o n
The n exural respon
strengthened \ ith
The
1-
c
of t\\ O- pan continuou
slab strip
wi th cutouts
F R P rei n forcement has been i nvesti gated i n this thesis.
re earch comprised experi mental
experi menta l
R
te t i ng and analytical
mode l i ng.
The
tudy compri ed te t i ng of ele en s labs. One unst rengthened slab
\\ i thout a cutout acted a' a benchmark. Fi ve slabs had a cutout in each saggi ng
region and fi e l ab had a cutout i n the hoggi ng region. The speci mens w i th cutouts
\\ re
trengthened in the
rei n forcement.
An
aggi ng, hoggi ng, or both regions USIng NSM-C F R P
anal) t ical
model
that can
pred ict the
load capacity of
un trengthened and strengthened two-span RC slab tri ps \: ith a cutout either i n t he
m id-span ecti ons or over the middle supp011 has been i ntroduced . The val i d i ty of the
model has been demonstrated by compari ng its pred ictions with the experi mental
r suIts of the pre ent stud .
M a i n concJ u ion of the work along with recommendations for future studies
on the ubj ect are presented i n t h i s chapter. The outcomes of t he present study are
l i m i ted to two-span RC slab strips with a \ idth o f b = 400
mm,
depth of h = 1 25
mm, and span l ength of L = 1 800 mm subjected to monotonic load i ng. The cutout
went completel y t h rough t he fu l l thickn ess of the slab, and was i nstal led ei ther in tbe
m id-span sections or over t he middle support. The c utout bad a width of W e = 0.375b
and a lengt h o f le = 0.25L. A vari ation in the location and/or size of t he cutouts \ ould
change t he structural response of the slabs before and after strengthen i ng.
1 26
6 . 2 C o n c l u IO n
8 a ed on re u l t o r th i research \\- ork, the fol low i ng conc l u ion can be d ra\\n :
•
I n tal lation
r a cutout i n the aggi ng region reduced the load capaci ty by
appr xi matel) _ 7% and du t i l it_ i ndex b
approxi matel
1 2%. Wh n the
cutout \\ us in tai led in the hoggi ng region, a 23% reduction in both load
capac it) and duct i l i ty i nde was recorded .
•
The
1-
F R P trength n i ng s) stem \\ as very effecti ve in i mprov i ng the
load capacit) but tended to r d uce the slab duct i l i ty . For the speci mens with a
cutout i n the sagg i n g region, the strengthen i ng system ful ly restored the load
capac ity of the control slab regard l ess of the amount and distribution of the
M - C F R P rei n forcement. For the speci mens with a cutout i n the hogging
region, two
M-C F R P strip restored only 90% of the l oad capacity of the
contro l spec i men. The load capac i t of a l l other strengthened spec i men with
a c utout i n the hogging region was h i gher than that of the control spec i men.
The i ncrease i n l oad capaci ty due to trengthen i ng was more pronounced
when the
•
M-C F R P rei n forcement was i nstal led in the sagging region.
trengtheni ng of conti n uous RC s l ab strips having a cutout i n the sagging
region usi ng two and four N S M -C F R P strips i ncreased the load capacity by
53% and 76%. respective l y rel ative to that of the unstrengthened spec i men
with a cutout. I nsta l l ation of
S M - C F R P rei n forcement in the hogging
region, i n add ition to the N S M -C F R P rei n forcement in the agging region ,
resu l ted i n an i nsign i ficant add it ional i nc rease i n the load capacity. The
addi tional i ncrease in load capac i ty due to i nsta l l ation of N S M -C F R P
rei n forcement i n the hogging region was 3% for the spec i men with two
1 27
, M- F R P stri ps i n the sagging region and 7% for the peci men \\ i t h four
FRP
trips in the agging region. Thi
i ncrease in l oad capac it) d ue t
in tal l ation
f
i nd icated that th
add itional
M-C F R P rei n f rcement i n
the hogging region decreased \ \ i t h a n i ncrea e i n the amount of
M- F R P
rei n forcement i n the aggi ng region.
•
trengthen i ng of conti n uol!
region u i ng t\V
and four
R
slab str i p ha i ng a cutout i n the hoggi ng
M - FRP trip i ncreased the load capac ity by
1 8°'0 and 36° 0, re pecti \ ely rel ati e to that of the unstrengthened speci men
\\ ith a cutout. In tal l ati n of
region, i n add i t ion to the
M - C F R P rei n forcement in the
aggi ng
M - C F R P rei n forcement in the hogging region,
re u l ted in 3 0% add itional i ncrease i n the load capacity for the spec i men with
t\\O
i-C F R P trips i n the hogging region and 1 3% i ncrease i n the load
capaci t for the pec i men with four
S M -C F R P stri ps i n the hogg i n g region.
This i nd icated that the addi t i onal i ncrease in load capac ity d ue to i nsta l lation
of
M-CFRP rei n forcement i n the sagg i n g region decreased with an
i ncrease in the amount of
•
M-CFRP rei n forcement i n the hogging region.
The duct i l it) i nde of the strengthened speci mens \ ith a cutout, except those
heav i l y strengthened i n both sagging and hogging regions, was the same as or
h igher than that of the correspondi ng unstrengthened spec i men with a cutout.
The spec i men heav i l y strengthened in both saggi n g and hogging regions was
an average 2 8% lower than that of the correspondi ng speci men with a cutout.
•
U n l i ke simpl y-supported structures, the enhancement i n moment capacity of
the critical secti ons i n conti n uous RC slab strips d ue to strengtheni ng was not
the same as the enhancement in the l oad capacity. Two and four N S M -C F R P
strips enhanced the moment capac i ty b y approxi matel y 2 and 2 . 5 folds
1 28
rcspect i \ el . l he enhancem nt i n the I ad capaci t d ue t o trengthen i ng was
i n the range of 53°'0 to 8 1 % Cor the pec i men \\ ith a cutout i n the agging
regi n and 1 8°'0 t
•
54.0/0 for the
pec i men
with a
The m ment red i tri but ion \Va dependent on
between the
ariati on 1 11 flex ural rigidi ty
aggl l1g and hogging regions. The control unstrengt hened
sp ci men exhi bi ted al most n
ame amount
utout i n the hogging
f i nternal
teel rei n forcement i n both saggi ng and hogging
region . The un trengthened
red i tribution rat io
moment red i tri bution because i t contai ned the
pec l men
with a cutout exh i b i ted moment
1 11 the range of 20% to 50% due to the signi ficant
variation in cro s section and amount of steel rei nforcement between the
agging and
hogging
regions.
The
moment
redi stri bution
al ues
in
trengthened
pec l m n s depended o n the amount and d i stribution o f t he
M-C F R P rei nforcement between the saggi ng and hoggi ng regions. Proper
di tribution of
M - C F R P rei n forcement bet\ een the saggi ng and hoggi ng
regions resu l ted i n up to 26% moment redi stri bution i n con t i n uous RC slab
trip with cutouts.
•
The C F R P rei nforcement used i n strengthen i ng was not ful ly uti l i zed . The
rati o of the C F R P strain at peak l oad to the ruptured C F R P strain was i n the
range of 37% to 5 1 % for the speci mens with a cutout i n each saggi ng region,
and 33% to 46% for the spec i mens with a cutout in t he hogging region.
•
The opti mal strengthe n i ng sol ut ion for the s l abs with a c utout i n each sagg i ng
region was using t wo
S M -C F R P strips i n each sagg i n g region with a C F R P
rei nforcement ratio o f Pj = 0.3 5%. For t h e slabs w i t h a c utout i n t h e hogging
1 29
region. th opti mal trengthening s l ution wa u i ng four
i n the hogging region \\ ith a
•
F R P rei n � rcement rati
The analyti a l model propo ed in l h i
pred icti n for the load apaCi l} o f t
- FRP trip
f Pj = 0.7%.
tud) tended t o provide a conservati ve
t peci mens. The pred icted load capaci ty
or the contr I pec i men \\ a approxi matel y 22% I wer than the experi mental
load capaci ty . For the peci men \\ ith a cutout in the sagging region, the rat io
of the pred icted to mea ured load capac ity was i n the range of 0.74 to 0 . 8 7 .
The m d e l pro ided mor accurate pred iction for t h e load capaci t ies of the
pe i men \\ ith a cutout in the hogging region where t he rati o of the pred i cted
to measure l oad capac ity
was
i n the range of 0.85 to J .02. The rat io of the
predicted to mea ured I ad capac i ty \, as on average 0 . 85 with a standard
de\ i ation of 0.09, and a coefficient of ariation of 1 0%.
6.3 Reco m m e n d a t i o n s fo r F u t u re S t u d i es
The fol lo\ i ng are recommendations for future studi es
l J1
the field of
t rengthening of conti n uous structures " ith composi tes.
•
tudy the e ffect of vary i ng the location and size of the cutouts on the flexural
response of strengthened and unstrengthened conti n uous RC slab stri ps.
•
tudy the v i ab i l i ty of usi ng externa l l y- bonded composites with and without
anchors rather than
S M -C F R P rei n forcement to upgrade the flexural
response of conti n uous RC beams and slab stri ps.
•
I nvesti gate the d urabi l i ty performance of conti n uous RC beams and s l ab
stri ps strengthened with composi tes under elevated temperatures and h igh
h u m i d i ty.
1 30
•
I Jl \ e. t i gate the resp n e of conti nuou R
beam and lab trip
trengthened
\\ ith c m po ite under fat igue load i ng.
•
De\. elop fi nite element ( F ) model
for the pec l m n tested i n the present
'tud) . The F E m del can be u ed as a numerical platform for performance
pred icti n of cont i nuou
\\ ith compo i te .
R
l ab tri ps c ntai n i ng cutouts and trengthened
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