behaviourofeccentricconcretecolumnsreinforcedwith...

Research ArticleBehaviour of Eccentric Concrete Columns Reinforced withCarbon Fibre-Reinforced Polymer Bars

Zrar Sedeeq Othman 1 and Ahmed Heidayet Mohammad2

1Ph D Student Civil Engineering Department Salahaddin University-Erbil Erbil Iraq2Assistant Professor Civil Engineering Department Salahaddin University-Erbil Erbil Iraq

Correspondence should be addressed to Zrar Sedeeq Othman zrarothmansuedukrd

Received 30 April 2019 Accepted 7 July 2019 Published 22 July 2019

Academic Editor Giulio Dondi

Copyright copy 2019 Zrar Sedeeq Othman and Ahmed Heidayet Mohammad is is an open access article distributed under theCreative CommonsAttribution License which permits unrestricted use distribution and reproduction in anymedium providedthe original work is properly cited

e use of steel bars as reinforcement is not preferred in some concrete structures because steel causes corrosion or electricmagnetic field problems One of the best alternatives to steel bars is carbon fibre-reinforced polymer (CFRP) bars e ex-perimental program consisted of 18 reinforced rectangular concrete columns under different eccentric loadings Out of the 18columns 15 were reinforced with CFRP longitudinal rebars and ties and 3 were reinforced with conventional steel rebars and tiesas reference columns e following parameters were included in this study the replacement of steel with CFRP bars eccentricityof load longitudinal reinforcement ratios and tie spacing Test results in terms of load-strain load-mid height deflection curvesand crack patterns showed that the column reinforced with CFRP bars behaved similarly to the concrete column reinforced withconventional steel bars with a slight difference in axial and flexural capacity e increment in CFRP longitudinal reinforcementratios from 14 to 20 and 36 reasonably increased the maximum carrying capacity for different eccentricities used hereine axial ratios of experimental to theoretical results (PExpPeor) were determined for specimens in the present work and thosefrom previous studies to assess the efficiency of the theoretical models

1 Introduction

Columns are the main elements of reinforced concrete (RC)structures and carry loads from the upper to the lower floorsuntil they are released to the footing Column failure cancause disaster in a building Corrosion in reinforcing steel isa problem in conventional RC especially in harsh climaticzones coastal areas or regions that contain corrosion fac-tors In some special buildings such as magnetic resonanceimage (MRI) rooms and other radiation facilities thepresence of steel around MRI apparatus must be avoidedFibre-reinforced polymer (FRP) is a good alternative for thiscondition because of its noncorrosive nonmagnetic andnonconductive materials us problems of corrosion andelectromagnetic interference can be averted using FRP

ere are three main types of FRP namely aramid glassand carbon fibres which are embedded in polymer Ex-perimental data on the role of carbon FRP (CFRP) aslongitudinal bars in compression members are limited Due

to the lack of data the current American Concrete Institute(ACI) 4401R-15 [1] design guidelines do not recommendthe use of FRP bars for resisting compressive stress

Few experimental studies have been conducted to in-vestigate the behaviour of the concrete column reinforcedwith GFRP under concentric loading [2ndash9] It was concludedthat columns reinforced with GFRP bars behave in the samemanner as those reinforced with steel bars GFRPrsquos con-tribution to the maximum capacity of the column rangesfrom 5 to 10 so they can be used in compressionmembers GFRP ties in the square column and the GFRPspiral in the circular column affect the strength and ductilityof the column and their spacing remarkably influences themode of failure

Experimental investigations on the concrete columnreinforced with CFRP subjected to concentric loading arerare Afifi et al [10] tested 11 full-scale circular concretecolumns reinforced with CFRP bars and spirals and foundthat CFRP and steel RC columns behave similarly up to their

HindawiAdvances in Civil EngineeringVolume 2019 Article ID 1769212 13 pageshttpsdoiorg10115520191769212

peak loads CFRP bars are effective in resisting compressionand contributes 12 column capacity on average Mohamedet al [11] tested 14 full-scale circular columns reinforcedwith longitudinal FRP (GFRP or CFRP) bars and confinedwith circular FRP spirals or hoops e GFRP and CFRP RCcolumns behave similarly to columns reinforced with steelUsing GFRP and CFRP spirals or hoops yields sufficientrestraint against the buckling of the longitudinal FRP barsand provide good confinement of concrete core in postpeakstages Tobbi et al [12] investigated square concrete columnsreinforced longitudinally with FRP (eg GFRP or CFRP) orsteel bars using FRP as transverse reinforcement ey re-ported that FRP bars contribute in resisting compressivestress as longitudinal reinforcement for concrete columnssubjected to concentric compression is feature must notbe neglected CFRP transverse reinforcement with largespacing and low volumetric ratio performs better than GFRPat the same spacing and volumetric ratio

ere were a limited number of studies carried out onthe behaviour of FRP RC columns under eccentric loads andrarely they were columns reinforced with CFRP bars Chooet al [13] and Deiveegan and Kumaran [14] reported thatcolumns with low reinforcement ratio of the GFRP RCcolumn exhibit brittle tension failure and the increase in thispercentage leads to the same behaviour as the column withconventional steel Columns with GFRP reinforcement showno yielding of reinforcement as that found in steel because ofthe linear elastic behaviour of GFRP bars Choo et al [15]presented an approach to calculate the minimum longitu-dinal reinforcement ratio of FRP bars which is required toavert brittle tension failure Issa et al [16] investigated thebehaviour of the GFRP RC column under eccentrically axialloads ey stated that steel-reinforced columns deform at alesser extent than GFRP-reinforced column and tie spacingminimally affects maximum lateral deflection and ductilityis finding is in contrast with our concept of using ties inreinforced columns Zadeh and Nanni [17] developed amethodology for the design of the concrete column rein-forced with GFRP bars and ties e method is applicableonly to buildings of limited size and height e ultimatedesign strain for the GFRP bar is recommended to notexceed 1 to avoid overstated deflections e contributionof the cross-sectional area of the GFRP bar in compressioncan be replaced by the equivalent area of concrete Hadi et al[18] investigated the use of GFRP bars and GFRP helices inRC columnsey concluded that the axial load and bendingmoment capacity of the GFRP RC columns are smaller thanthose of conventional steel RC columns However theductility of GFRP RC columns is very close to the that of steelRC columns us ignoring the contribution of GFRP barsin compression results in considerable difference betweenthe analytical and experimental results Hadhood et al[19 20] experimentally investigated circular high-strengthand normal strength concrete columns reinforced withCFRP as longitudinal bars and spirals ey indicated thatwith providing minimum reinforcement ratio equal to 1the failure of eccentric columns will be concrete crushing atcompression side followed by crushing of compression barse test results showed that the columns reinforced with the

CFRP bar have less axial capacity than those reinforced withthe steel bar at low moderate and high eccentricity whereasat extreme eccentricity CFRP concrete columns showedhigher capacity Guerin et al [21] tested full-scale rectan-gular concrete columns reinforced with GFRP bars ebehaviour of the GFRP bar RC columnwas comparable to itssteel RC column counterpart at the same eccentricity especimens show compression failure for a small eccentricityof up to 02 h However compression-ductile failure is theprevailing failure mode at 04 h eccentricity and tension-controlled failure occurs in GFRP RC columns at high ec-centricity (08 h) Raza et al [22] stated that the behaviour ofconcrete columns reinforced with GFRP bars can be sim-ulated by nonlinear finite element analysis using ABAQUSStandard e numerical results exhibited good agreementwith the experimental results Elmessalami et al [23]reviewed previous literatures on the behaviour of FRP RCcompression members ey gathered data and assessedequations proposed by many researchers for predicting theload-carrying capacity of columns e analysis shows thatCFRP bars have same or more contribution in load capacityof the column than steel bars whereas GFRP bars have less

Most of the previous studies have examined circularconcrete columns reinforced with GFRP bars which exhibita lowmodulus of elasticity whereas CFRP bars have a highermodulus of elasticity close to steel erefore GFRP andCFRP show different behaviours under loads that influencethe strength and ductility of the concrete column Fur-thermore studies on concrete columns reinforced withCFRP bars are rare erefore experimental investigationswere needed to study the behaviour of concrete columnsreinforced with CFRP bars is research involves in-vestigating the behaviour of square concrete columnsreinforced with CFRP bars and subjected to eccentric load Aproposed approach with other existing analytical methodswill be assessed with test results of rectangular and circularconcrete columns reinforced with FRP rebars from presentwork and previous literatures

2 Experimental Program

e test program consisted of 18 concrete columnsmeasuring150mmtimes 150mm in cross section 1500mm in overallheight and 900mm in midheight test e column could bespecified as a short column because the slenderness ratio (klur) of the specimens was equal to 20 that is less than 22 basedon ACI 318-14 [24] All of the columns have enlarged heads atboth ends to apply eccentric loading e enlargements weredesigned as a bracket to allow column failures to occur withinthe test height instead of column ends

e tested specimens were divided into six groups asshown in Table 1 Each group consisted of three concretecolumns with the same reinforcement details but testedunder different eccentricity conditions of 0 75 and 150mm(eh equal to 00 05 and 10 respectively) e specimenswere identified on the basis of the longitudinal and tie re-inforcement material (steel or CFRP) diameter of thelongitudinal bar tie spacing and eccentricity amount of theapplied load For example specimen C12-T90-E00 is

2 Advances in Civil Engineering

reinforced with CFRP bars and ties four 12mm diameterbars were used as longitudinal reinforcement tie spacingwas 90mm and it was tested under concentric loade firstgroup (S12-T90 reference specimens) consisted of threeconcrete columns reinforced with four Oslash12 longitudinalsteel bars and Oslash6 steel ties placed at a spacing of 90mmecolumns in the five other groups were reinforced with CFRPbars and tiese second group (C10-T90) consisted of threeconcrete columns reinforced with four Oslash10 longitudinalCFRP bars and Oslash6 CFRP ties placed at a spacing of 90mme longitudinal reinforcement for the columns in groupsthree and four comprised four Oslash12 and four Oslash16 barsrespectively e tie spacing was the same as that of thesecond group In the fifth and sixth groups the tie re-inforcement consisted of Oslash6 CFRP ties placed at spacing of140 and 40mm respectively and the longitudinal re-inforcement is as same as those of the columns in groupthree Figure 1 shows the dimensions and details of thereinforcement of the tested specimens All of the experi-mental works were carried out in the concrete and structurallaboratory of the Civil Engineering Department SalahaddinUniversity-Erbil

All of the specimens were casted simultaneously fromthe same ready-mix-concrete batch by using ordinaryPortland cemente average concrete compressive strengthfor the concrete based on the 100mmtimes 200mm cylindersamples was 447MPa [25] e longitudinal and tie re-inforcements for group S12-T90 specimens were Oslash12 and6mm deformed steel bars with yield strengths of 537 and533MPa and ultimate strengths of 624 and 592MPa re-spectively CFRP bars with diameters of 10 12 and 16mmwere used as longitudinal reinforcements and those of 6mmdiameter were used as tie reinforcements According to themanufacturerrsquos test sheet the average ultimate tensilestrength for all diameters was 2000MPa as shown in Table 2e CFRP bars were provided by Chongqing Yangkai Im-port amp Export Trade Co Ltd Chongqing China

Plywood sheets were used to construct the formwork usedfor all concrete columns e steel and CFRP reinforcementswere assembled and fixed in the form e manufacturerprepared CFRP ties with a 120mmtimes 120mmouter dimensione steel ties were prepared with the same dimensione clearcovers used to the face of the ties for all specimens was 15mmFigure 2 shows a typical steel and CFRP reinforcement cageassembled for the specimens e formwork moulds wereplaced horizontally on level ground Concrete was placed intothe formwork in two layers Each layer of concrete was vibratedusing an electric vibrator e columns and control specimenswere cast from the same batch and cured by covering with adamp burlap and plastic sheeting to maintain moisture con-ditions e curing process was continued for 28days

e test specimens were loaded under a computerisedcompression testing machine with a maximum capacity of2500 kN Loading was carried out by load control at a rate of11 kNsec until failure occurred Figure 3 shows a typical testsetup and loading conditions Enlargement ends of eachcolumn were confined by CFRP sheets (with 100mm height)to avoid bearing premature failure at the ends An 8mmthick rubber was used as capping on the top and bottom endsof each column specimen to ensure uniform loading dis-tribution from the machine to the column surface ecolumn specimens were approached to a pin connected atboth ends Special care was taken to ensure that the columnwas vertically aligned Eccentricity was provided by threegrooves fared beside one another that is 75mm from centreto centre e electrical resistance strain gauge was mountedon the middle of two opposite longitudinal bars that is onein the compression and the other in the tension side for themeasurement of longitudinal bar strain Another straingauge was attached to the compression face of the column atmidheight for the measurement of concrete compressionstrain In addition dial gauge was positioned at midheight tomeasure the lateral deflection of the column during theloading stage

Table 1 Details of tested specimens

G No Specimen eh ρ () Type of reinforcement Longitudinal reinforcement Transversal reinforcement

11 S12-T90-E00 00

20 Steel 4Oslash12mm Oslash690mm2 S12-T90-E05 053 S12-T90-E10 10

24 C10-T90-E00 00

14 CFRP 4Oslash10mm Oslash690mm5 C10-T90-E05 056 C10-T90-E10 10

37 C12-T90-E00 00


410 C16-T90-E00 00


513 C12-T140-E00 00


616 C12-T40-E00 00


Advances in Civil Engineering 3

3 Experimental Results and Discussion

is section presents the test results of steel RC columns andCFRP RC columns All specimens were tested until theyfailed and reached their maximum carrying capacity and themachine recorded the data Table 3 shows the maximumload lateral displacement at maximum load and maximum

moment of all of the specimens Maximum moment wascalculated as the maximum load multiplied by the sum-mation of initial eccentricity and lateral displacement atmaximum load In the following sections the behaviour andfailure modes strain in longitudinal reinforcement lateraldeflection and effect of the parameters on the maximumcarrying capacity of the columns are discussed

150

Longitudinal section of concretecolumns reinforced with CFRP bar

150

150

Section 3-3for groups 5 and 6

150Oslash6mm 40mm (C12-T40)or Oslash6mm 140mm (C12-T140)

4Oslash 12

Longitudinal section of concretecolumns reinforced with steel bar

300

1500

Test

heig

ht

150

150

900

150

150

Section 3-3for groups 2 3 and 4

2

33

2

150

Oslash6mm 90mm

4Oslash 10mm (C10-T90)4Oslash 12mm (C12-T90)or 4Oslash 16mm (C16-T90)

300

Section 1-1for group 1 (S12-T90)

Section 2-2

2

11

2

150

150

Oslash6mm 90mm4 Oslash 12mm

300

Oslash6mm 50mm(steel)

3Oslash 12mm(steel)

Figure 1 Details of reinforcement of the tested specimens (dimensions are in mm)

Table 2 Mechanical properties of CFRP bars

Diameter (mm) Area (mm2) Density (gcm3) Weigh (gm) Tensile strength (MPa) Ultimate tensilestrain () Modulus of elasticity (GPa)

6 28 17 476 2000 135 14810 785 17 1335 2000 133 15012 113 17 1921 2000 138 14516 200 17 340 2000 132 151

Figure 2 Typical reinforcement cage


e

150

300

Loading condition at both ends

Steel roller 50mm dia

Rubber

Dial gauge

Steel base plate 50mmthickness

P

Three grooves (spacing 75mm each)

Strengthening ofenlargement endby CFRP sheets

Steel anchor bolts6 Oslash 12mm

900

150

150

150

150

Pe

Pe

Figure 3 Loading condition at both ends of column specimens

Table 3 Experimental test results and effect of test parameters on the column axial capacity

No G Specimen eh ρ () Pmax (kN) Δmax (mm) Mmax (kNmiddotm)

Change (increase or decrease) in column axial capacity

Due to eccentricityRelative toconventionalsteel bars

Due toincrease in ρ

Due todecrease

tiespacing

11

S12-T90-E00 0020

916 155 142 00 00 mdash mdash2 S12-T90-E05 05 297 1381 2638 minus676 00 mdash mdash3 S12-T90-E10 10 130 1900 2197 minus858 00 mdash mdash4

2C10-T90-E00 00

14855 347 297 00 mdash 00 mdash

5 C10-T90-E05 05 258 1796 2398 minus698 mdash 00 mdash6 C10-T90-E10 10 119 2368 2067 minus861 mdash 00 mdash7

3C12-T90-E00 00

20909 354 322 00 minus08 63 11

8 C12-T90-E05 05 262 1800 2437 minus712 minus118 16 minus089 C12-T90-E10 10 126 1809 2118 minus861 minus31 59 minus2310

4C16-T90-E00 00

36960 080 077 00 mdash 123 mdash

11 C16-T90-E05 05 290 1834 2711 minus698 mdash 126 mdash12 C16-T90-E10 10 137 2062 2337 minus857 mdash 151 mdash

13

5

C12-T140-E00 00

20

899 130 117 00 mdash mdash 00

14 C12-T140-E05 05 264 1398 2349 minus706 mdash mdash 00


166

C12-T40-E00 0020

925 119 110 00 mdash mdash 2917 C12-T40-E05 05 2377 1723 2192 minus743 mdash mdash minus10018 C12-T40-E10 10 113 1901 1910 minus878 mdash mdash minus124e negative sign in front of the numbers represent the reduction in strength of the specimen relative to the column that is considered reference for therespective specimens


31 Behaviour and Failure Modes In general the columnspecimens under concentric loading displayed good ap-pearance without evident cracks or deflection but suddenlyfailed with little or no advance warning However thecolumns subjected to eccentric loading (05h and 10h) failedwhen the concrete was crushed in the compression face ofthe column after a clear lateral displacement and appearanceof cracks that propagated at tension face ese signs wereremarkably more pronounced at a high eh of 10 than at 05

311 Concentric Loading Columns (e 0) No cracks wereobserved in column S12-T90-E00 when load was increasedup to the measured failure load At the failure load theconcrete suddenly crushed explosively near the bottom endof the test height region e failure unexpectedly occurrede crushing of concrete was followed by the buckling of thelongitudinal reinforcement bars as shown in Figure 4

Column specimens reinforced with CFRP bars and tiesbehaved similarly to the specimens reinforced with steelFailure occurred in the test height by sudden and unexpectedcrushing of the concrete While the longitudinal CFRP barsruptured after crushing the concrete and the ties wereopened or ruptured except for column specimen C12-T40-E00 which has less tie spacing (40mm) the longitudinalbars were partially ruptured is finding indicates that thisspacing was more effective than the others and can be greatlybeneficial for longitudinal CFRP under pure compression

312 Columns with Medium Eccentric Loading (e 05h)e columns subjected to eccentricity loading starting frome 05h showed significantly different behaviours andstrengths relative to concentric loading After the columnswith e 05h were loaded the first crack occurred hori-zontally in the middle region of the column in the tensionside when the load reached 155ndash189 of the maximumload for columns reinforced with CFRP bars and 158 ofthe maximum load for the column reinforced with con-ventional steel With increasing the load cracks appearedparallel to this first crack along the tension side of thecolumn As the load on the column increased these crackswere extended and the neutral axis moved opposite to theface of the first crack (ie the depth of the compressionstress area was decreased)emidheight cracks were longerand wider than the rest as shown in Figure 5 Towards theenlarged ends area the parallel cracks became shorter andtheir width became smaller compared with the midheightcracks Vertical cracks immediately occurred at the com-pression side with close to the maximum load resulting inthe concrete crushing and column collapse

313 Columns with High Eccentric Loading (e 10h)After the specimens were loaded the first cracking in themiddle area of the column occurred at a lower load com-pared with the columns with e 05h due to high eccentricityapplied is high eccentricity led to the occurrence ofmoments that caused high tensile stress at the opposite sideto the applied load position e first cracks occurred at

loads of 8 to 9 of the column strength e distributionand propagation of the cracks that occurred after the firstcrack were similar to those of specimens with e 05h withdifference in length and width due to the increase of ec-centricity An appreciable increase in lateral displacementwas also observed Column curvature during loading wasclear even before failure occurred with high percentage Inthe final stages before failure 45deg cracks occurred in thecolumn head at 70ndash75 of the maximum load

Figure 6 shows the failure mode and crack pattern of thespecimens with e 10h For the columns reinforced withCFRP bars except C16-T90-E10 and C12-T40-E10 failureoccurred almost near to the ends of test height of the columnwhen the concrete was crushed in a limited concrete partcompared with specimens with e 05h However failure ofthe models C16-T90-E10 and C12-T40-E10 was observedwhere the crushing of the concrete occurred which wassomewhere near the midheight of the column For thecolumn reinforced with steel S12-T90-E10 the concrete wascrushed exactly at the middle of test height of the column ina limited concrete part e deformation of the longitudinalsteel bar slightly exceeded the yield point us failure inthis column could be described as tension failure which ledto the final crushing of compression concrete In all of thespecimens with high eccentric loading cracking near theconcrete crushing region was longer and wider than that ofthe rest

For the CFRP-reinforced column specimens after thefailure occurred and the load was released the cracks wereclosed and the column returned to its straight structure afterit was curved under the load is phenomenon is an in-dication of the elastic behaviour of the CFRP bars until thefailure point e CFRP bars returned to their originallength and the column straightened again because thelongitudinal bars did not reach failure point

32 Strain in Longitudinal Bars Strain in the longitudinalCFRP bar in the corresponding specimens reinforced withCFRP bars was higher than that in steel bars at the sameload level is finding was due to the lower modulus ofelasticity of the CFRP bar compared with that of steel estrain of the compression bars reached minus3590 με at amaximum load in the C12-T90-E00 model which wasequal to 26 of the ultimate tensile strain of the CFRP baris amount of strain was higher than that recorded forspecimens C12-T90-E05 and C12-T90-E10 at theirmaximum load For bars subjected to tension the strain forspecimen C12-T90-E10 was higher than that of C12-T90-E05 and reached 3960 με which was equal to 287 of theultimate tensile strain of the CFRP bars us the stress inthe tension bar was approximately 574MPa and was veryclose to the yield stress of steel in the correspondingspecimens reinforced with steel

33 Lateral Deflection e lateral deflection of the testedcolumns at midheight is an indication of column stiffness Ingeneral for all of the tested columns the slope of load-deflection curves was decreased and deflection at maximum


load was increased as eccentricity was raised from 00 to10h Figure 7 shows that the slope of the load-deflectioncurves of CFRP-reinforced columns was lesser than that ofthe corresponding column specimens reinforced with steel

Column reinforced with CFRP bars exhibited greater de-flection at the maximum column capacity except in cases ofspecimens subjected to high eccentricity (e 10h) in whichdeflections at the maximum load were close to each other

S12-T90-E05 C10-T90-E05 C12-T90-E05 C16-T90-E05 C12-T40-E05C12-T140-E05

Figure 5 Crack pattern and mode of failure of column specimens with e 05h

S12-T90-E10 C10-T90-E10 C12-T90-E10 C16-T90-E10 C12-T140-E10 C12-T40-E10



Figure 4 Crack pattern and mode of failure of concentric column specimens


CFRP-reinforced columns showed lesser slope than steel-reinforced columns because the modulus of elasticity ofCFRP bars was smaller than that of steel which affected thecolumn stiffness

When the longitudinal reinforcement ratio of CFRP-reinforced columns was increased from 14 to 36 theslope of the load-deflection curves was increased (Figure 7)for the three cases of eccentricity e concentric loadingcolumn with different tie spacings (eg 140 90 and40mm) demonstrated different slopes of load-deflectioncurves Since concentric columns are deflected in a weakerdirection which is not expected the relation between theirdeflection curves is not more reliable to be compared whilethe direction of lateral deflection for the eccentric columnwas known For the columns with e 05h specimen C12-T40-E05 exhibited lesser slope and the slopes of C12-T140-E05 and C12-T90-E05 were approximately equale same phenomenon was observed for columns withe 10h

34 Effect of the Parameters is section discusses the effectof test parameters including type of reinforcement ec-centricity longitudinal reinforcement ratio and tiespacing on the maximum carrying capacity of the columns(Table 3)

341 Type of Reinforcement e CFRP-reinforced columnsexhibited lower strength than the steel-reinforced columnswith a small difference for concentric-loaded columns andcolumns with e 10h However the difference was high forcolumns with e 05h e ratio of maximum load of CFRP-reinforced columns to that of those reinforced with steel barswas 992 882 and 969 for eccentricity levels equal to00 05 h and 10 h respectively

342 Eccentricity to Depth Ratio (eh) e test resultsshown in Table 3 and load deflection curves in Figure 7 showthat eccentricity plays a remarkable role on the axial capacity

0

200

400

600

800

1000

ndash2 2 6 10 14 18 22

Load

(kN

)

Mid-height lateral displacement (mm)

S12-T90-E00S12-T90-E05S12-T90-E10

(a)

ndash2 2 6 10 14 18 22Mid-height lateral displacement (mm)

0

200

400

600

800

1000

Load

(kN

)C10-T90-E00C10-T90-E05C10-T90-E10

(b)


0

200

400

600

800

1000

Load

(kN

)

C12-T90-E00C12-T90-E05C12-T90-E10

(c)


0

200

400

600

800

1000

ndash2 2 6 10 14 18 22

Load

(kN

)

C16-T90-E00C16-T90-E05C16-T90-E10

(d)


0

200

400

600

800

1000

Load

(kN

)

ndash2 2 6 10 14 18 22

C12-T140-E00C12-T140-E05C12-T140-E10

(e)


0

200

400

600

800

1000

Load

(kN

)

ndash2 2 6 10 14 18 22

C12-T40-E00C12-T40-E05C12-T40-E10

(f )

Figure 7 Load-lateral deflection curves at midheight of the columns


and stiffness of the column specimens For the steel-rein-forced column themaximum load of S12-T90-E05 and S12-T90-E10 was 324 and 142 of that of the column S12-T90-E00 respectively us compared with the concen-trically loaded specimen the specimens with eccentricityequal to 05h and 10h showed decreased column axial ca-pacity by 676 and 858 respectively e maximum loadof columns with 140 and 90mm tie spacing and differentlongitudinal reinforcement ratios decreased by an average of703 and 859 for specimens with e 05 and 10hcompared with the concentric-loaded specimens re-spectively But specimens with tie spacing equal to 40mmshowed a slightly larger effect of eccentricity e maximumload was decreased to 743 and 878 for e 05 and 10hrespectively

343 Longitudinal Reinforcement Ratio For concentricallyloaded columns raising the longitudinal reinforcementratio from 14 to 20 and 36 increased carrying ca-pacity by 6 and 12 respectively For columns withe 05h axial capacity was unremarkably increased by 2when longitudinal reinforcement ratio was changed from14 to 20 Axial capacity increased by 13 at a lon-gitudinal reinforcement ratio of 36 For column speci-mens with e 10h a 6 increase and a 15 increase inaxial capacity of the column were marked for longitudinalreinforcement ratios equal to 20 and 36 respectivelyis result showed that with increasing eccentricity theinfluence of increasing longitudinal reinforcement to 36was evident

344 Tie Spacing is section considers the effect of CFRPtie spacing (transverse reinforcement) on the maximumcarrying capacity of the columns e test results forconcentric columns in Table 3 showed that the axial ca-pacity of the column slightly increased by 111 and 289when the tie spacing decreased from 140mm to 90 and40mm respectively For the column with e 05h de-creasing tie spacing from 140mm to 90 and 40mm reducedaxial capacity by 076 and 996 respectively e axialcapacity for the column with e 10h was reduced by 233and 1240 when tie spacing decreased from 140mm to 90and 40mm respectively For columns with e 05 and 10hunremarkable change in axial capacity was observed whentie spacing decreased from 140mm to 90mm Axial ca-pacity evidently changed when tie spacing decreased from140mm to 40mm Decreasing tie spacing to 40mm (closedistance) created a separated plane between the shellconcrete cover and the concrete core which caused theconcrete cover to spall off or break and leads to failure[18 26]

4 Theoretical Analysis

41 8eoretical Capacity Calculation In this section the-oretical axial capacity and bending moment were calcu-lated for columns reinforced with FRP (CFRP and GFRP)bars at different eccentricity levels e calculations were

based on strain compatibility and equilibrium of internalforces for the column e calculation was applied on 61FRP bar-reinforced column specimens from the presentstudy and previous works [18ndash21 27ndash29] ree differentcalculation methods were used to determine the axial loadcapacity and bending moment In the first calculationmethod the contribution of the FRP bar in resistingcompression stress was ignored as recommended by ACI4401R-15 and CSACAN S806-12 [18] In the secondmethod [18] the contribution of the FRP bars in com-pression was included e FRP bar strain for concentric-loaded columns was approximately equal to the ultimateconcrete strain (0003) FRP bars are assumed to exhibitthe same modulus of elasticity in compression and tension[30]

In the third calculation method many trials were ap-plied to determine the contribution of FRP in resistingcompression stress Different ratios of compressive mod-ulus of elasticity ranging between 70 and 90 of theirtensile modulus of elasticity were used e results of theproposed theoretical model were compared with the ex-perimental results e best ratios were 80 and 75 forCFRP and GFRP bars respectively

e analytical nominal axial and bending momentcapacity (Pn and Mn respectively) were calculated on thebasis of strain compatibility and internal force equilibriumon the cross-sectional area of the column as shown inFigure 8

Equivalent rectangular stress block as defined by ACI318-14 [24] was used to compute the contribution ofconcrete in the compression zone A linear stress-strainrelationship for FRP bars was used to calculate the forceresisted by compression and tension in the FRP bars Eachcompression stress strain and force in this analysis wasconsidered positive and the tensile stress strain and forcewere considered negative

For the first calculation method the nominal axial ca-pacity of the concentric-loaded column can be calculatedusing the following equation

Pn 085fcprime Ag minusAf1113872 1113873 (1)

where Pn is the nominal axial capacity of the column fcprime isthe concrete cylinder compressive strength at 28 days Ag isthe gross area of the column cross section and Af is the totalcross-sectional area of FRP bars

For the second and third calculation method wherecontribution of FRP bars in compression was considered thenominal axial capacity of the concentric column wascomputed by the following equation

Pn cfcprime Ag minusAf1113872 1113873 + 0003 kEfAf( 1113857 (2)

where Ef is the tensile modulus of elasticity of the FRP bark 1 is used for the second calculation method [18] andk 080 and 075 is used for CFRP and GFRP bars in theproposed third calculation method respectively

e following equations were adopted to determine Pnand Mn for the rectangular column under eccentric loading(Figure 8(a))


ϵfi 0003cminus dic

( )

ffi ϵfi middot Ef

Ffi Afi middot ffi

(3)

where c is the neutral axis depth di is the the distancebetween the extreme compression bre and ith bar centre ϵand f are the strain and stress in ith FRP bars and F is thethe force in ith FRP bars

a β1c

Cc cfcprime middot ab(4)

where a is the height of the equivalent rectangular blockstress of concrete β1 is the factor dened by ACI 318-14used for calculating a with respect to c c 085 for ACI-4401R-15 and Hadi et al [18] and c 08 for the proposedmethod and Cc is the internal compression force developedin concrete

Pn Cc +sumFfi

Mn Cch

2minusa

2( ) +sum Ffi

h

2minusdi( )( )

(5)

where Pn and Mn are the nominal axial load and bendingmoment resisted by the column cross section respectively

e same strain compatibility and force equilibriumequations mentioned above are used for circular columns(Figure 8(b)) considering the shape change of cross sectionfrom rectangular to circular e following equations wereused to calculate the compressive force resisted by theconcrete and its moment about centroid

θ cosminus1(h2)minus ah2

( )

Cc 085fcprime middot h2 θminus sin θ cos θ

4( )

y h

3( )

sin3θθminus sin θ middot cos θ( )

(6)

where y is the distance from the centroid of the section to thecentroid of the concrete compressive stress block

42 Dierence amongeoreticalModels To verify the threemethods ACI 4401R-15 [1] Hadi et al [18] and Proposalthe ratio of experimental to theoretical axial load capacity(PExpPeor) was calculated for the 61 rectangular andcircular concrete columns reinforced with GFRP or CFRP asrebars from present works and available in the literatureemean standard deviation (SD) and coecient of variation(COV) were computed and are listed in Table 4

e better mean value (105) for the three methods wasobtained from the method proposed e proposed methodalso showed the least COV value (988) Conservativevalues for mean (108) and COV (1162) were observed inthe ACI 4401R-15 method e conservative values of ACI4401R-15 were reected in the minimum and maximumvalues of PExpPeor which are equal to 087 and 149respectively and the minimum value of the number ofspecimens that got PExpPeor less than 10 is equal to 16

Figure 9 shows the experimental versus theoreticalvalues of axial capacity for the three calculation methodsese three graphs show that most of the data were dis-tributed diagonally (the diagonal represent the best agree-ment between experimental and theoretical equationsresults) e ACI-4401R-15 data were scattered most ofwhich occurred above the diagonal area Hadi et alrsquos graphshows that most of the data were below the diagonalwhereas the proposed graph showed improved data distri-bution and less data scattered around the diagonal area

43 Eect of theParameters e ratios of PExpPeor for thethree methods were plotted versus the eccentricity to depthratio (eh) concrete compressive strength (fcprime) and longi-tudinal reinforcement ratio (ρf ) for the 61 FRP concretecolumns to assess the inuence of the main parameters onthe theoretical models used (Figure 10) A decreasing trendin PExpPeor occurred in the ACI 4401R-15 method wheneh was increased up to 10 However no remarkablechanges were observed for the two other methods As fcprimewasincreased to approximately 45MPa an evident decrease inthe factor of safety (ratio of PExpPeor) was observed isobservation was true for the three methods It is seen thatthere is lack of experimental data in high-strength concreteexcept a few data at 702MPa erefore further researchstudies forfcprime greater than 45MPa are needed An increase infactor of safety was observed in the three methods for ρf upto 22is increase was remarkable in ACI-4401R-15 For

h d1

d2

P

ec

єcu = 0003єf2

Ff1

Ff2a

єf1

085f primec

Cc

(a)

h d1d2

d3d4 e

c aθ

P

єcu = 0003

єf4єf3

єf2єf1

Ff2Ff1

Ff4

Ff3

085f primecCc

(b)

Figure 8 Strain compatibility and force equilibrium of cross section of FRP-reinforced concrete column (a) Rectangular column(b) Circular column


Table 4 Comparison of PExpPeo by the three calculation methods for 61 concrete columns reinforced with FRP bars

Calculation method Method 1 ACI 4401R-15 [1] Method 2 Hadi et al [18] Method 3 proposalEquation used (1) and (3) to (6) (2) and (3) to (6) (2) and (3) to (6)Mean 108 097 105SD 013 010 010COV () 1162 995 988RangeMin 087 079 085Max 149 118 126

Number lt10lowast 16 35 24lowastNumber of specimens (out of 61) having PExpPeo less than one

0

1000

2000

3000

4000

5000

0 1000 2000 3000 4000 5000PTheor (kN)

P Exp

(kN

)

(a)

0 1000 2000 3000 4000 50000

1000

2000

3000

4000

5000P E

xp (

kN)

PTheor (kN)

(b)

0 1000 2000 3000 4000 50000

1000

2000

3000

4000

5000

P Exp

(kN

)

PTheor (kN)

(c)

Figure 9 Experimental versus theoretical axial load capacity (a) ACI 4401R-15 (b) Hadi et al [18] (c) Proposal

07

08

09

10

11

12

13

14

15

00 04 08 12eh

30 50 70f primec (MPa)

1 2 3 4ρf ()

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(a)

eh f primec (MPa) ρf ()1 2 3 430 40 50 60 70 80

0708

09

10

11

12

13

14

15

00 04 08 12

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(b)

Figure 10 Continued


ρf from 22 to 36 the factor of safety for the threemethods was decreased is decrease was less evident in theproposed method

5 Conclusions

e following conclusions and recommendations could bedrawn on the basis of the experimental and the theoreticalanalysis results

(1) e CFRP concrete columns behaved similarly totheir conventional steel-reinforced concrete columncounterparts with insignicant reduction in axialand exural capacity

(2) e percentage of eccentricity considerably aectedthe behaviour and mode of failure of the CFRP RCcolumns

(3) Decreasing tie spacing from 140mm to 40mmunremarkably aected the axial capacity for theconcentric-loaded columns as shown by the 29increase while decreasing tie spacing for columnssubjected to eccentric load reduced axial capacityreaching 124 for a column with eh 10

(4) All eccentric concrete columns reinforced withCFRP bars failed by concrete crushing in com-pression side and the maximum tensile strain in thelongitudinal bars which was recorded in columnswith 14 reinforcement ratio did not exceed 34 ofthe ultimate tensile strain of the bar

(5) A theoretical approach was proposed to predict theaxial and moment carrying capacity of the concretecolumns reinforced with FRP barse axial ratios ofPExpPeor computed by this approach and by twoother methods for 61 specimens showed that theproposed model exhibited the better mean value of105 and the least COV of 988

(6) A theoretical analysis based on ACI 4401R-15 leadsto conservative prediction of axial carrying capacityratios (PExpPeor) for concrete columns reinforcedwith FRP bars

(7) Experimental data in high-strength concrete exceptfor few ndings at 702MPa are lacking ereforefurther research for fcprime greater than 45MPa isrequired

Data Availability

e data used to support the ndings of this study are in-cluded within the article

Conflicts of Interest

e authors declare that there are no conicts of interestregarding the publication of this paper

References

[1] American Concrete Institute Guide for the Design andConstruction of Structural Concrete Reinforced with FiberReinforced Polymer (FRP) Bars (ACI 4401 R-15) AmericanConcrete Institute Farmington Hills MI USA 2015

[2] S H Alsayed Y A Al-Salloum T H Almusallam andM A Amjad Concrete Columns Reinforced by Glass FiberReinforced Polymer Rods Vol 188 American Concrete In-stitute Farmington Hills MI USA 1999

[3] A D Luca F Matta and A Nanni ldquoBehavior of full-scaleglass ber-reinforced polymer reinforced concrete columnsunder axial loadrdquo ACI Structural Journal vol 107 no 5p 589 2010

[4] E M Lotfy ldquoBehavior of reinforced concrete short columnswith Fiber Reinforced polymers barsrdquo International Journal ofCivil and Structural Engineering vol 1 no 3 p 545 2010

[5] H Tobbi A S Farghaly and B Benmokrane ldquoConcretecolumns reinforced longitudinally and transversally with glassber-reinforced polymer barsrdquo ACI Structural Journalvol 109 no 4 2012

[6] M Z A H M Mohamed and B Benmokrane ldquoAxialcapacity of circular concrete columns reinforced with GFRPbars and spiralsrdquo Journal of Composites for Constructionvol 18 no 1 article 04013017 2014

[7] W Prachasaree A Sangkaew S Limkatanyu andH V S GangaRao ldquoParametric study on dynamic response ofber reinforced polymer composite bridgesrdquo International

eh f primec (MPa) ρf ()

07

08

09

10

11

12

13

14

15

00 04 08 12 30 50 70 1 2 3 4

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(c)

Figure 10 Eect of eh fcprime and ρf on the test results (a) ACI 4401R-15 (b) Hadi et al [18] (c) Proposal


Journal of Polymer Science vol 2015 Article ID 56530113 pages 2015

[8] H Karim B Noel-Gough M N Sheikh and M N HadiStrength and Ductility Behavior of Circular Concrete ColumnsReinforced with GFRP Bars and Helices Southeast UniversityNanjing China 2015

[9] H Karim M N Sheikh and M N S Hadi ldquoAxial load-axialdeformation behaviour of circular concrete columns rein-forced with GFRP bars and helicesrdquo Construction andBuilding Materials vol 112 pp 1147ndash1157 2016

[10] M Z Afifi H M Mohamed and B Benmokrane ldquoStrengthand axial behavior of circular concrete columns reinforcedwith CFRP bars and spiralsrdquo Journal of Composites forConstruction vol 18 no 2 article 04013035 2013

[11] H M Mohamed M Z Afifi and B Benmokrane ldquoPerfor-mance evaluation of concrete columns reinforced longitu-dinally with FRP bars and confined with FRP hoops andspirals under axial loadrdquo Journal of Bridge Engineering vol 19no 7 article 04014020 2014

[12] H Tobbi A S Farghaly and B Benmokrane ldquoBehavior ofconcentrically loaded fiber-reinforced polymer reinforcedconcrete columns with varying reinforcement types and ra-tiosrdquo ACI Structural Journal vol 111 no 2 2014

[13] C C Choo I E Harik and H Gesund ldquoStrength of rect-angular concrete columns reinforced with fiber-reinforcedpolymer barsrdquo ACI Structural Journal vol 103 no 3 p 4522006

[14] A Deiveegan and G Kumaran ldquoExperimental and reliabilitystudies on the behaviour of concrete columns reinforcedinternally with glass fibre reinforced polymer re-inforcementsrdquo Journal of Structural Engineering vol 38 no 5pp 457ndash475 2011

[15] C C Choo I E Harik and H Gesund ldquoMinimum re-inforcement ratio for fiber-reinforced polymer reinforcedconcrete rectangular columnsrdquo ACI Structural Journalvol 103 no 3 p 460 2006

[16] M Issa I Metwally and S Elzeiny ldquoStructural performanceof eccentrically loaded GFRP reinforced concrete columnsrdquoInternational Journal of Civil and Structural Engineeringvol 2 no 1 p 395 2011

[17] H J Zadeh and A Nanni ldquoDesign of RC columns using glassFRP reinforcementrdquo Journal of Composites for Constructionvol 17 no 3 pp 294ndash304 2013

[18] M N Hadi H Karim and M N Sheikh ldquoExperimentalinvestigations on circular concrete columns reinforced withGFRP bars and helices under different loading conditionsrdquoJournal of Composites for Construction vol 20 no 4 article04016009 2016

[19] A Hadhood H M Mohamed and B Benmokrane ldquoAxialloadndashmoment interaction diagram of circular concrete col-umns reinforced with CFRP bars and spirals experimentaland theoretical investigationsrdquo Journal of Composites forConstruction vol 21 no 2 article 04016092 2017

[20] A Hadhood H M Mohamed and B Benmokrane ldquoStrengthof circular HSC columns reinforced internally with carbon-fiber-reinforced polymer bars under axial and eccentricloadsrdquo Construction and Building Materials vol 141pp 366ndash378 2017

[21] M Guerin H M Mohamed B Benmokrane A Nanni andC K Shield ldquoEccentric behavior of full-scale reinforcedconcrete columns with glass fiber-reinforced polymer barsand tiesrdquo ACI Structural Journal vol 115 no 2 2018

[22] A Raza Q U Z Khan and A Ahmad ldquoNumerical in-vestigation of load-carrying capacity of GFRP-reinforced

rectangular concrete members using CDP model in ABA-QUSrdquo Advances in Civil Engineering vol 2019 Article ID1745341 21 pages 2019

[23] N Elmessalami A El Refai and F Abed ldquoFiber-reinforcedpolymers bars for compression reinforcement a promisingalternative to steel barsrdquo Construction and Building Materialsvol 209 pp 725ndash737 2019

[24] American Concrete Institute Building Code Requirements forStructural Concrete (ACI 318-14) Commentary on BuildingCode Requirements for Structural Concrete (ACI 318R-14) AnACI Report American Concrete Institute (ACI) FarmingtonHills MI USA 2014

[25] ASTM Standard Test Method for Compressive Strength ofCylindrical Concrete Specimens ASTM International WestConshohocken PA USA 2001

[26] S R Razvi and M Saatcioglu ldquoStrength and deformability ofconfined high-strength concrete columnsrdquo Structural Journalvol 91 no 6 pp 678ndash687 1994

[27] A Hadhood H M Mohamed F Ghrib and B BenmokraneldquoEfficiency of glass-fiber reinforced-polymer (GFRP) discretehoops and bars in concrete columns under combined axialand flexural loadsrdquo Composites Part B Engineering vol 114pp 223ndash236 2017

[28] A Hadhood H M Mohamed and B Benmokrane ldquoEx-perimental study of circular high-strength concrete columnsreinforced with GFRP bars and spirals under concentric andeccentric loadingrdquo Journal of Composites for Constructionvol 21 no 2 article 04016078 2017

[29] W Xue F Peng and Z Fang ldquoBehavior and design of slenderrectangular concrete columns longitudinally reinforced withfiber-reinforced polymer barsrdquo ACI Structural Journalvol 115 no 2 pp 311ndash322 2018

[30] D H Deitz I E Harik and H Gesund ldquoPhysical propertiesof glass fiber reinforced polymer rebars in compressionrdquoJournal of Composites for Construction vol 7 no 4pp 363ndash366 2003


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Submit your manuscripts atwwwhindawicom

peak loads CFRP bars are effective in resisting compressionand contributes 12 column capacity on average Mohamedet al [11] tested 14 full-scale circular columns reinforcedwith longitudinal FRP (GFRP or CFRP) bars and confinedwith circular FRP spirals or hoops e GFRP and CFRP RCcolumns behave similarly to columns reinforced with steelUsing GFRP and CFRP spirals or hoops yields sufficientrestraint against the buckling of the longitudinal FRP barsand provide good confinement of concrete core in postpeakstages Tobbi et al [12] investigated square concrete columnsreinforced longitudinally with FRP (eg GFRP or CFRP) orsteel bars using FRP as transverse reinforcement ey re-ported that FRP bars contribute in resisting compressivestress as longitudinal reinforcement for concrete columnssubjected to concentric compression is feature must notbe neglected CFRP transverse reinforcement with largespacing and low volumetric ratio performs better than GFRPat the same spacing and volumetric ratio

ere were a limited number of studies carried out onthe behaviour of FRP RC columns under eccentric loads andrarely they were columns reinforced with CFRP bars Chooet al [13] and Deiveegan and Kumaran [14] reported thatcolumns with low reinforcement ratio of the GFRP RCcolumn exhibit brittle tension failure and the increase in thispercentage leads to the same behaviour as the column withconventional steel Columns with GFRP reinforcement showno yielding of reinforcement as that found in steel because ofthe linear elastic behaviour of GFRP bars Choo et al [15]presented an approach to calculate the minimum longitu-dinal reinforcement ratio of FRP bars which is required toavert brittle tension failure Issa et al [16] investigated thebehaviour of the GFRP RC column under eccentrically axialloads ey stated that steel-reinforced columns deform at alesser extent than GFRP-reinforced column and tie spacingminimally affects maximum lateral deflection and ductilityis finding is in contrast with our concept of using ties inreinforced columns Zadeh and Nanni [17] developed amethodology for the design of the concrete column rein-forced with GFRP bars and ties e method is applicableonly to buildings of limited size and height e ultimatedesign strain for the GFRP bar is recommended to notexceed 1 to avoid overstated deflections e contributionof the cross-sectional area of the GFRP bar in compressioncan be replaced by the equivalent area of concrete Hadi et al[18] investigated the use of GFRP bars and GFRP helices inRC columnsey concluded that the axial load and bendingmoment capacity of the GFRP RC columns are smaller thanthose of conventional steel RC columns However theductility of GFRP RC columns is very close to the that of steelRC columns us ignoring the contribution of GFRP barsin compression results in considerable difference betweenthe analytical and experimental results Hadhood et al[19 20] experimentally investigated circular high-strengthand normal strength concrete columns reinforced withCFRP as longitudinal bars and spirals ey indicated thatwith providing minimum reinforcement ratio equal to 1the failure of eccentric columns will be concrete crushing atcompression side followed by crushing of compression barse test results showed that the columns reinforced with the

CFRP bar have less axial capacity than those reinforced withthe steel bar at low moderate and high eccentricity whereasat extreme eccentricity CFRP concrete columns showedhigher capacity Guerin et al [21] tested full-scale rectan-gular concrete columns reinforced with GFRP bars ebehaviour of the GFRP bar RC columnwas comparable to itssteel RC column counterpart at the same eccentricity especimens show compression failure for a small eccentricityof up to 02 h However compression-ductile failure is theprevailing failure mode at 04 h eccentricity and tension-controlled failure occurs in GFRP RC columns at high ec-centricity (08 h) Raza et al [22] stated that the behaviour ofconcrete columns reinforced with GFRP bars can be sim-ulated by nonlinear finite element analysis using ABAQUSStandard e numerical results exhibited good agreementwith the experimental results Elmessalami et al [23]reviewed previous literatures on the behaviour of FRP RCcompression members ey gathered data and assessedequations proposed by many researchers for predicting theload-carrying capacity of columns e analysis shows thatCFRP bars have same or more contribution in load capacityof the column than steel bars whereas GFRP bars have less

Most of the previous studies have examined circularconcrete columns reinforced with GFRP bars which exhibita lowmodulus of elasticity whereas CFRP bars have a highermodulus of elasticity close to steel erefore GFRP andCFRP show different behaviours under loads that influencethe strength and ductility of the concrete column Fur-thermore studies on concrete columns reinforced withCFRP bars are rare erefore experimental investigationswere needed to study the behaviour of concrete columnsreinforced with CFRP bars is research involves in-vestigating the behaviour of square concrete columnsreinforced with CFRP bars and subjected to eccentric load Aproposed approach with other existing analytical methodswill be assessed with test results of rectangular and circularconcrete columns reinforced with FRP rebars from presentwork and previous literatures

2 Experimental Program

e test program consisted of 18 concrete columnsmeasuring150mmtimes 150mm in cross section 1500mm in overallheight and 900mm in midheight test e column could bespecified as a short column because the slenderness ratio (klur) of the specimens was equal to 20 that is less than 22 basedon ACI 318-14 [24] All of the columns have enlarged heads atboth ends to apply eccentric loading e enlargements weredesigned as a bracket to allow column failures to occur withinthe test height instead of column ends

e tested specimens were divided into six groups asshown in Table 1 Each group consisted of three concretecolumns with the same reinforcement details but testedunder different eccentricity conditions of 0 75 and 150mm(eh equal to 00 05 and 10 respectively) e specimenswere identified on the basis of the longitudinal and tie re-inforcement material (steel or CFRP) diameter of thelongitudinal bar tie spacing and eccentricity amount of theapplied load For example specimen C12-T90-E00 is








11 S12-T90-E00 00


24 C10-T90-E00 00


37 C12-T90-E00 00


410 C16-T90-E00 00


513 C12-T140-E00 00


616 C12-T40-E00 00






150


150

150



4Oslash 12


300

1500

Test

heig

ht

150

150

900

150

150


2

33

2

150

Oslash6mm 90mm


300


Section 2-2

2

11

2

150

150


300


3Oslash 12mm(steel)




6 28 17 476 2000 135 14810 785 17 1335 2000 133 15012 113 17 1921 2000 138 14516 200 17 340 2000 132 151



e

150

300



Rubber

Dial gauge


P




900

150

150

150

150

Pe

Pe







Due todecrease

tiespacing

11

S12-T90-E00 0020


2C10-T90-E00 00

14855 347 297 00 mdash 00 mdash


3C12-T90-E00 00

20909 354 322 00 minus08 63 11


4C16-T90-E00 00

36960 080 077 00 mdash 123 mdash


13

5

C12-T140-E00 00

20

899 130 117 00 mdash mdash 00



166

C12-T40-E00 0020




























0

200

400

600

800

1000

ndash2 2 6 10 14 18 22

Load

(kN

)


S12-T90-E00S12-T90-E05S12-T90-E10

(a)


0

200

400

600

800

1000

Load

(kN

)C10-T90-E00C10-T90-E05C10-T90-E10

(b)


0

200

400

600

800

1000

Load

(kN

)

C12-T90-E00C12-T90-E05C12-T90-E10

(c)


0

200

400

600

800

1000

ndash2 2 6 10 14 18 22

Load

(kN

)

C16-T90-E00C16-T90-E05C16-T90-E10

(d)


0

200

400

600

800

1000

Load

(kN

)

ndash2 2 6 10 14 18 22

C12-T140-E00C12-T140-E05C12-T140-E10

(e)


0

200

400

600

800

1000

Load

(kN

)

ndash2 2 6 10 14 18 22

C12-T40-E00C12-T40-E05C12-T40-E10

(f )




















ϵfi 0003cminus dic

( )

ffi ϵfi middot Ef

Ffi Afi middot ffi

(3)


a β1c



Pn Cc +sumFfi

Mn Cch

2minusa

2( ) +sum Ffi

h

2minusdi( )( )

(5)




( )


4( )

y h

3( )


(6)






h d1

d2

P

ec

єcu = 0003єf2

Ff1

Ff2a

єf1

085f primec

Cc

(a)

h d1d2

d3d4 e

c aθ

P

єcu = 0003

єf4єf3

єf2єf1

Ff2Ff1

Ff4

Ff3

085f primecCc

(b)






0

1000

2000

3000

4000

5000

0 1000 2000 3000 4000 5000PTheor (kN)

P Exp

(kN

)

(a)

0 1000 2000 3000 4000 50000

1000

2000

3000

4000

5000P E

xp (

kN)

PTheor (kN)

(b)

0 1000 2000 3000 4000 50000

1000

2000

3000

4000

5000

P Exp

(kN

)

PTheor (kN)

(c)


07

08

09

10

11

12

13

14

15

00 04 08 12eh


1 2 3 4ρf ()

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(a)

eh f primec (MPa) ρf ()1 2 3 430 40 50 60 70 80

0708

09

10

11

12

13

14

15

00 04 08 12

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(b)

Figure 10 Continued



5 Conclusions









Data Availability




References









07

08

09

10

11

12

13

14

15

00 04 08 12 30 50 70 1 2 3 4

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(c)































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia








11 S12-T90-E00 00


24 C10-T90-E00 00


37 C12-T90-E00 00


410 C16-T90-E00 00


513 C12-T140-E00 00


616 C12-T40-E00 00






150


150

150



4Oslash 12


300

1500

Test

heig

ht

150

150

900

150

150


2

33

2

150

Oslash6mm 90mm


300


Section 2-2

2

11

2

150

150


300


3Oslash 12mm(steel)




6 28 17 476 2000 135 14810 785 17 1335 2000 133 15012 113 17 1921 2000 138 14516 200 17 340 2000 132 151



e

150

300



Rubber

Dial gauge


P




900

150

150

150

150

Pe

Pe







Due todecrease

tiespacing

11

S12-T90-E00 0020


2C10-T90-E00 00

14855 347 297 00 mdash 00 mdash


3C12-T90-E00 00

20909 354 322 00 minus08 63 11


4C16-T90-E00 00

36960 080 077 00 mdash 123 mdash


13

5

C12-T140-E00 00

20

899 130 117 00 mdash mdash 00



166

C12-T40-E00 0020




























0

200

400

600

800

1000

ndash2 2 6 10 14 18 22

Load

(kN

)


S12-T90-E00S12-T90-E05S12-T90-E10

(a)


0

200

400

600

800

1000

Load

(kN

)C10-T90-E00C10-T90-E05C10-T90-E10

(b)


0

200

400

600

800

1000

Load

(kN

)

C12-T90-E00C12-T90-E05C12-T90-E10

(c)


0

200

400

600

800

1000

ndash2 2 6 10 14 18 22

Load

(kN

)

C16-T90-E00C16-T90-E05C16-T90-E10

(d)


0

200

400

600

800

1000

Load

(kN

)

ndash2 2 6 10 14 18 22

C12-T140-E00C12-T140-E05C12-T140-E10

(e)


0

200

400

600

800

1000

Load

(kN

)

ndash2 2 6 10 14 18 22

C12-T40-E00C12-T40-E05C12-T40-E10

(f )




















ϵfi 0003cminus dic

( )

ffi ϵfi middot Ef

Ffi Afi middot ffi

(3)


a β1c



Pn Cc +sumFfi

Mn Cch

2minusa

2( ) +sum Ffi

h

2minusdi( )( )

(5)




( )


4( )

y h

3( )


(6)






h d1

d2

P

ec

єcu = 0003єf2

Ff1

Ff2a

єf1

085f primec

Cc

(a)

h d1d2

d3d4 e

c aθ

P

єcu = 0003

єf4єf3

єf2єf1

Ff2Ff1

Ff4

Ff3

085f primecCc

(b)






0

1000

2000

3000

4000

5000

0 1000 2000 3000 4000 5000PTheor (kN)

P Exp

(kN

)

(a)

0 1000 2000 3000 4000 50000

1000

2000

3000

4000

5000P E

xp (

kN)

PTheor (kN)

(b)

0 1000 2000 3000 4000 50000

1000

2000

3000

4000

5000

P Exp

(kN

)

PTheor (kN)

(c)


07

08

09

10

11

12

13

14

15

00 04 08 12eh


1 2 3 4ρf ()

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(a)

eh f primec (MPa) ρf ()1 2 3 430 40 50 60 70 80

0708

09

10

11

12

13

14

15

00 04 08 12

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(b)

Figure 10 Continued



5 Conclusions









Data Availability




References









07

08

09

10

11

12

13

14

15

00 04 08 12 30 50 70 1 2 3 4

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(c)































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia





150


150

150



4Oslash 12


300

1500

Test

heig

ht

150

150

900

150

150


2

33

2

150

Oslash6mm 90mm


300


Section 2-2

2

11

2

150

150


300


3Oslash 12mm(steel)




6 28 17 476 2000 135 14810 785 17 1335 2000 133 15012 113 17 1921 2000 138 14516 200 17 340 2000 132 151



e

150

300



Rubber

Dial gauge


P




900

150

150

150

150

Pe

Pe







Due todecrease

tiespacing

11

S12-T90-E00 0020


2C10-T90-E00 00

14855 347 297 00 mdash 00 mdash


3C12-T90-E00 00

20909 354 322 00 minus08 63 11


4C16-T90-E00 00

36960 080 077 00 mdash 123 mdash


13

5

C12-T140-E00 00

20

899 130 117 00 mdash mdash 00



166

C12-T40-E00 0020




























0

200

400

600

800

1000

ndash2 2 6 10 14 18 22

Load

(kN

)


S12-T90-E00S12-T90-E05S12-T90-E10

(a)


0

200

400

600

800

1000

Load

(kN

)C10-T90-E00C10-T90-E05C10-T90-E10

(b)


0

200

400

600

800

1000

Load

(kN

)

C12-T90-E00C12-T90-E05C12-T90-E10

(c)


0

200

400

600

800

1000

ndash2 2 6 10 14 18 22

Load

(kN

)

C16-T90-E00C16-T90-E05C16-T90-E10

(d)


0

200

400

600

800

1000

Load

(kN

)

ndash2 2 6 10 14 18 22

C12-T140-E00C12-T140-E05C12-T140-E10

(e)


0

200

400

600

800

1000

Load

(kN

)

ndash2 2 6 10 14 18 22

C12-T40-E00C12-T40-E05C12-T40-E10

(f )




















ϵfi 0003cminus dic

( )

ffi ϵfi middot Ef

Ffi Afi middot ffi

(3)


a β1c



Pn Cc +sumFfi

Mn Cch

2minusa

2( ) +sum Ffi

h

2minusdi( )( )

(5)




( )


4( )

y h

3( )


(6)






h d1

d2

P

ec

єcu = 0003єf2

Ff1

Ff2a

єf1

085f primec

Cc

(a)

h d1d2

d3d4 e

c aθ

P

єcu = 0003

єf4єf3

єf2єf1

Ff2Ff1

Ff4

Ff3

085f primecCc

(b)






0

1000

2000

3000

4000

5000

0 1000 2000 3000 4000 5000PTheor (kN)

P Exp

(kN

)

(a)

0 1000 2000 3000 4000 50000

1000

2000

3000

4000

5000P E

xp (

kN)

PTheor (kN)

(b)

0 1000 2000 3000 4000 50000

1000

2000

3000

4000

5000

P Exp

(kN

)

PTheor (kN)

(c)


07

08

09

10

11

12

13

14

15

00 04 08 12eh


1 2 3 4ρf ()

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(a)

eh f primec (MPa) ρf ()1 2 3 430 40 50 60 70 80

0708

09

10

11

12

13

14

15

00 04 08 12

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(b)

Figure 10 Continued



5 Conclusions









Data Availability




References









07

08

09

10

11

12

13

14

15

00 04 08 12 30 50 70 1 2 3 4

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(c)































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia


e

150

300



Rubber

Dial gauge


P




900

150

150

150

150

Pe

Pe







Due todecrease

tiespacing

11

S12-T90-E00 0020


2C10-T90-E00 00

14855 347 297 00 mdash 00 mdash


3C12-T90-E00 00

20909 354 322 00 minus08 63 11


4C16-T90-E00 00

36960 080 077 00 mdash 123 mdash


13

5

C12-T140-E00 00

20

899 130 117 00 mdash mdash 00



166

C12-T40-E00 0020




























0

200

400

600

800

1000

ndash2 2 6 10 14 18 22

Load

(kN

)


S12-T90-E00S12-T90-E05S12-T90-E10

(a)


0

200

400

600

800

1000

Load

(kN

)C10-T90-E00C10-T90-E05C10-T90-E10

(b)


0

200

400

600

800

1000

Load

(kN

)

C12-T90-E00C12-T90-E05C12-T90-E10

(c)


0

200

400

600

800

1000

ndash2 2 6 10 14 18 22

Load

(kN

)

C16-T90-E00C16-T90-E05C16-T90-E10

(d)


0

200

400

600

800

1000

Load

(kN

)

ndash2 2 6 10 14 18 22

C12-T140-E00C12-T140-E05C12-T140-E10

(e)


0

200

400

600

800

1000

Load

(kN

)

ndash2 2 6 10 14 18 22

C12-T40-E00C12-T40-E05C12-T40-E10

(f )




















ϵfi 0003cminus dic

( )

ffi ϵfi middot Ef

Ffi Afi middot ffi

(3)


a β1c



Pn Cc +sumFfi

Mn Cch

2minusa

2( ) +sum Ffi

h

2minusdi( )( )

(5)




( )


4( )

y h

3( )


(6)






h d1

d2

P

ec

єcu = 0003єf2

Ff1

Ff2a

єf1

085f primec

Cc

(a)

h d1d2

d3d4 e

c aθ

P

єcu = 0003

єf4єf3

єf2єf1

Ff2Ff1

Ff4

Ff3

085f primecCc

(b)






0

1000

2000

3000

4000

5000

0 1000 2000 3000 4000 5000PTheor (kN)

P Exp

(kN

)

(a)

0 1000 2000 3000 4000 50000

1000

2000

3000

4000

5000P E

xp (

kN)

PTheor (kN)

(b)

0 1000 2000 3000 4000 50000

1000

2000

3000

4000

5000

P Exp

(kN

)

PTheor (kN)

(c)


07

08

09

10

11

12

13

14

15

00 04 08 12eh


1 2 3 4ρf ()

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(a)

eh f primec (MPa) ρf ()1 2 3 430 40 50 60 70 80

0708

09

10

11

12

13

14

15

00 04 08 12

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(b)

Figure 10 Continued



5 Conclusions









Data Availability




References









07

08

09

10

11

12

13

14

15

00 04 08 12 30 50 70 1 2 3 4

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(c)































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



























0

200

400

600

800

1000

ndash2 2 6 10 14 18 22

Load

(kN

)


S12-T90-E00S12-T90-E05S12-T90-E10

(a)


0

200

400

600

800

1000

Load

(kN

)C10-T90-E00C10-T90-E05C10-T90-E10

(b)


0

200

400

600

800

1000

Load

(kN

)

C12-T90-E00C12-T90-E05C12-T90-E10

(c)


0

200

400

600

800

1000

ndash2 2 6 10 14 18 22

Load

(kN

)

C16-T90-E00C16-T90-E05C16-T90-E10

(d)


0

200

400

600

800

1000

Load

(kN

)

ndash2 2 6 10 14 18 22

C12-T140-E00C12-T140-E05C12-T140-E10

(e)


0

200

400

600

800

1000

Load

(kN

)

ndash2 2 6 10 14 18 22

C12-T40-E00C12-T40-E05C12-T40-E10

(f )




















ϵfi 0003cminus dic

( )

ffi ϵfi middot Ef

Ffi Afi middot ffi

(3)


a β1c



Pn Cc +sumFfi

Mn Cch

2minusa

2( ) +sum Ffi

h

2minusdi( )( )

(5)




( )


4( )

y h

3( )


(6)






h d1

d2

P

ec

єcu = 0003єf2

Ff1

Ff2a

єf1

085f primec

Cc

(a)

h d1d2

d3d4 e

c aθ

P

єcu = 0003

єf4єf3

єf2єf1

Ff2Ff1

Ff4

Ff3

085f primecCc

(b)






0

1000

2000

3000

4000

5000

0 1000 2000 3000 4000 5000PTheor (kN)

P Exp

(kN

)

(a)

0 1000 2000 3000 4000 50000

1000

2000

3000

4000

5000P E

xp (

kN)

PTheor (kN)

(b)

0 1000 2000 3000 4000 50000

1000

2000

3000

4000

5000

P Exp

(kN

)

PTheor (kN)

(c)


07

08

09

10

11

12

13

14

15

00 04 08 12eh


1 2 3 4ρf ()

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(a)

eh f primec (MPa) ρf ()1 2 3 430 40 50 60 70 80

0708

09

10

11

12

13

14

15

00 04 08 12

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(b)

Figure 10 Continued



5 Conclusions









Data Availability




References









07

08

09

10

11

12

13

14

15

00 04 08 12 30 50 70 1 2 3 4

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(c)































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



















ϵfi 0003cminus dic

( )

ffi ϵfi middot Ef

Ffi Afi middot ffi

(3)


a β1c



Pn Cc +sumFfi

Mn Cch

2minusa

2( ) +sum Ffi

h

2minusdi( )( )

(5)




( )


4( )

y h

3( )


(6)






h d1

d2

P

ec

єcu = 0003єf2

Ff1

Ff2a

єf1

085f primec

Cc

(a)

h d1d2

d3d4 e

c aθ

P

єcu = 0003

єf4єf3

єf2єf1

Ff2Ff1

Ff4

Ff3

085f primecCc

(b)






0

1000

2000

3000

4000

5000

0 1000 2000 3000 4000 5000PTheor (kN)

P Exp

(kN

)

(a)

0 1000 2000 3000 4000 50000

1000

2000

3000

4000

5000P E

xp (

kN)

PTheor (kN)

(b)

0 1000 2000 3000 4000 50000

1000

2000

3000

4000

5000

P Exp

(kN

)

PTheor (kN)

(c)


07

08

09

10

11

12

13

14

15

00 04 08 12eh


1 2 3 4ρf ()

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(a)

eh f primec (MPa) ρf ()1 2 3 430 40 50 60 70 80

0708

09

10

11

12

13

14

15

00 04 08 12

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(b)

Figure 10 Continued



5 Conclusions









Data Availability




References









07

08

09

10

11

12

13

14

15

00 04 08 12 30 50 70 1 2 3 4

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(c)































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia





0

1000

2000

3000

4000

5000

0 1000 2000 3000 4000 5000PTheor (kN)

P Exp

(kN

)

(a)

0 1000 2000 3000 4000 50000

1000

2000

3000

4000

5000P E

xp (

kN)

PTheor (kN)

(b)

0 1000 2000 3000 4000 50000

1000

2000

3000

4000

5000

P Exp

(kN

)

PTheor (kN)

(c)


07

08

09

10

11

12

13

14

15

00 04 08 12eh


1 2 3 4ρf ()

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(a)

eh f primec (MPa) ρf ()1 2 3 430 40 50 60 70 80

0708

09

10

11

12

13

14

15

00 04 08 12

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(b)

Figure 10 Continued



5 Conclusions









Data Availability




References









07

08

09

10

11

12

13

14

15

00 04 08 12 30 50 70 1 2 3 4

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(c)































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



5 Conclusions









Data Availability




References









07

08

09

10

11

12

13

14

15

00 04 08 12 30 50 70 1 2 3 4

P Exp

PTh

eo

P Exp

PTh

eo

P Exp

PTh

eo

07

08

09

10

11

12

13

14

15

07

08

09

10

11

12

13

14

15

(c)































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia






























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia


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