Research Article Effects of Concentrical Partial (Local ...downloads.hindawi.com/journals/amse/2015/491038.pdfResearch Article Effects of Concentrical Partial (Local) Compression on

Research ArticleEffects of Concentrical Partial (Local) Compression onthe Structural Behavior of Concrete Filled Steel Tubular Column

S Jayaganesh1 J Raja Murugadoss2 G Ganesh Prabhu2 and J Jegan3

1Tamil Nadu Police Housing Corporation Ltd Madurai Division Tamil Nadu 625014 India2KPR Institute of Engineering and Technology Coimbatore Tamil Nadu 641 407 India3University College of Engineering Anna University Ramanathapuram Tamil Nadu 623513 India

Correspondence should be addressed to J Jegan drjeganjoegmailcom

Received 16 June 2015 Revised 7 October 2015 Accepted 20 October 2015

Academic Editor Stefano Sorace

Copyright copy 2015 S Jayaganesh et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The objective of this present paper is to investigate the structural behavior of square and circular Concrete Filled Steel Tubular(CFST) stub columns subjected to axial partiallocal compression The experimental parameters were local compression area andsection type Among the twelve specimens six specimens were tested under full compression and the remaining six specimens weretested under local compression The experimental observation indicated that the failure pattern of the CFST column with partialcompression is fairly different from the CFST column subjected to full compression The confinement provided by the circularsection is quite different than the confinement provided by the square section when the CFST column is subjected to axially localcompression It was found that the elastic modulus (stiffness) and the ultimate bearing capacity of the CFST column decreased withthe increase in local compression ratio The circular and square CFST columns subjected to partiallocal compression achieved anultimate strength of 445 and 1415 respectively less than that of the columns subjected to full compression From the aboveobservation it can be inferred that the structural performance of the CFST column is significantly influenced by the local areacompression ratio and this effect should be taken into account in design models

1 Introduction

Over the past several decades the utilization of ConcreteFilled Steel Tubular (CFST) members is being increased inthe construction industry [1 2] due to their excellent staticand dynamic properties over equivalent steel and reinforcedconcrete members In general CFST columns are subjectedto partiallocal compression in several applications includingbearings over piers of girder bridge and the bottom bearingmembers of rigid frame or reticulate frame as shown inFigure 1 [3 4] In the past few decades boundless researcheshave been reported on the behavior of CFST column sub-jected to full compression Schneider [5] performed anexperimental and analytical study on the short CFST columnunder axial compression and found that the circular tubeshave a higher postyield strength and stiffness than those ofthe square and rectangular section Kilpatrick and Rangan[6] studied the behavior of slender and stub column filledwith high strength concrete Mursi and Uy [7] investigated

the coupled local and global buckling of the CFST columnwith three different cross-sectional slenderness ratios In sim-ilar manner Sakino et al [8] investigated the local buckling ofthe slender CFST column and derived a capacity reductionfactor for square section Liu and Gho [9] found that the EC4is unsafe to predict the ultimate capacity of CFST columnsfabricated using mild steel and high strength concrete Thetest results of De Nardin and El Debs [10] showed that theductility of the CFST column can be increased by using highstrength concrete

In the case of CFST column subjected to full compressionthe concrete core and the outer steel tube loaded simultane-ously as a result the confining pressure provided by the steeltube becomes ineffective [11] Nevertheless for a CFST col-umn subjected to partial compression a very small amountof applied load is transferred to the steel tube as a result theconfining pressure provided by the steel tubemaximized [12]It can be inferred that the behavior of the columns subjected

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2015 Article ID 491038 9 pageshttpdxdoiorg1011552015491038

2 Advances in Materials Science and Engineering

Figure 1 CFST column subjected to partial compression [4]

to partial compression is different from those columns sub-jected to full compression So more research effort should beneeded on this topic In recent years some research has beenreported in the CFST column subjected to local compressionBased on the test results of 36 CFST under local compressionHan et al [11 12] recognized that the ultimate strengthcapacity of the locally loaded CFST columns decreases withthe increase in local compression area ratio Yang and Han[3] found that the ductility capacity of the CFST columnincreases while being loaded with partial cross-sectionalarea Yu et al [13] analyzed the interaction between thesteel tube and its concrete core using the FEA model Fromthe observation of studies carried out so far it can beunderstood that only few researches have been focused onthe behavior of CFST column subjected to local compressionFurthermore there is still a lack of information on the CFSTcolumn subjected to local compression Accordingly studiesare needed to address the further research in this area Withthis aim themain objective of this experimental investigationis to examine the behavior of CFST column subjected topartial compressionThe experimental parameters were localarea compression area (120573) and cross-sectional type (squareand circular) All the columns were tested to failure and theinfluence of the experimental parameters on the behavior ofCFST column was analyzed The ultimate strength capacityof the CFST column subjected to partial compression wasevaluated using a simplified equation

2 Experimental Studies

21 Materials Commercially available hollow square andcircular section conforming to IS 4923 [14] and IS 1161[14] respectively and having a size and diameter of 100 times100mm and 1016mm respectively was used in this studyThe thickness of the hollow square and circular steel tube wasabout 4mm The height of the column was 300mm whichis three times the cross-sectional dimension Three couponswere machined from the square and circular steel tube andtested for tension The measured average yield strength ofthe steel tube was 358Nmm2 and Poissonrsquos ratio (120583) wasabout 0281 The infilled concrete was designed to achieve

a compressive strength of 60Nmm2 The designed watercement ratio was 035 Ordinary Portland Cement (OPC)was used to prepare infilled concrete Natural river sandpassing through a 475mm sieve and coarse aggregate with anominal size of 10mm was used to prepare this mixture [15]To improve the workability of the concrete super plasticizerbelonging to modified melamine formaldehyde chemicalfamily was used A test was performed to determine the 28-day compressive strength using 150mm times 150mm times 150mmcubes The average strength of the concrete obtained wasabout 6155Nmm2

22 Specimen Fabrication Circular and square hollow tubes300mm in height were machined from 6m long hollowtubes To obtain a level surface both ends of the steel tubewere levelled using a lathe Before filling the tube withconcrete the inside portion was thoroughly wire brushedto remove rust and loose debris presented For concretemixtures aggregates were weighed in dry condition andthe mixtures were mixed together for 5 to 10min in acountercurrent mixer Then the steel tube was then filledwith concrete layer by layer and each layer was effectivelycompacted by the vibrator to ensure the concrete was freefrom air gaps and flaws During compaction a steel plate wasintroduced at the bottom of the steel tube to eliminate theleakage of slurry and then the concrete was allowed to curefor 28 days

23 Experimental Setup All theCFST columnswere tested ina compression testing machine having a capacity of 2000 kNand the specimens were tested under axial compression Eachmember was placed on the supports and care was takento ensure that its centerline was exactly in line with theaxis of the machine [16] On all the columns instrumentswere installed to measure the axial and lateral deformationusing linear voltage displacement transducers (LVDTs) and2000 kN load cell was used tomonitor the load Both load celland LVDTswere connected to the 16-channel data acquisitionsystem to store the dataThe load was applied to the columnsusing a jack and they were tested to failure A circular bearingplate was used to achieve the local compression All thespecimens were tested to failure and the loading rate wasmaintained as 1mmmin displacement The experimentalobservation recorded the nature of the failure axial deforma-tion and ultimate load The loading setup of CFST specimensubjected to full and partial compression is shown in Figure 2

24 Specimen Designation Theobjective of this investigationis not limited to evaluating the strength capacity of the CFSTcolumn under local compression also to understand thefailure modes and ductility response of the CFST columnunder local compression Two types of sections includingcircular and square sections were investigated Among thetwelve specimens tested under axial compression six speci-mens (three circular and three square sections) were testedunder full compression and the remaining six specimens(three circular and three square sections) were tested underlocal compression The partial compression specimens with

Advances in Materials Science and Engineering 3

P

P

End plate

CFST column

LVDTs

300

(a)

P

P

End plate

CFST column

LVDTs

Bearing plate

300

(b)

Figure 2 Full and partial compression testing setup

SCFST-F-0(1) SCFST-F-0(2) SCFST-F-0(3)

Figure 3 Failure pattern of square CFST column subjected to full compression

the local compression area ratio of 2 were continued (120573 =119860CFST119860LC 119860CFST is the cross-sectional area of the CFSTcolumn 119860LC is the area of local compression (4415mm2))and Figure 2 shows the schematic view of the CFST sectionunder full and partial compression The steel plate with thethickness of 7mm was used to apply the load to the columnThe summary of the specimen details is presented in Table 1To identify the specimen easily the columns were designatedusing names such as CCFST-F-1 CCFST-F-2 CCFST-F-3CCFST-P-1 CCFST-P-2 CCFST-P-3 SCFST-F-1 SCFST-F-2 SCFST-F-3 SCFST-P-1 SCFST-P-2 and SCFST-P-3 Forexample the name of specimens CCFST-F-2 and CCFST-P-3 specifies that the circular CFST column is subjected to fulland partial compression respectively The numeral refers tothe number of specimens

3 Results and Discussions

31 Failure Modes The CFST columns tested under fulland partial compression exhibited a ductile behavior andthe decrease in the compression loading area significantlyinfluences the behavior of CFST column In the case ofsquare CFST columns under full compression exhibited anoutward buckling of steel tube observed at the bottom andmid height of the column as shown in Figure 3There was nocracking of concrete observed on the top surface of the CFSTcolumn Due to the full compression the steel tube in theouter limits directly carried the applied load and also providesconfinement to the inner concrete core This compositeaction avoids the cracking of inner core concrete and led tothe buckling of steel tube In the case of square CFST columns

4 Advances in Materials Science and Engineering

Table1Specim

endetails

andtestdetails

Sectiontype

Specim

endesig

natio

n

Diameter

and

thickn

esso

rsiz

e(mm)

Height(ℎ)

(mm)

Com

pressiv

estr

engthof

infilledconcrete

(119891119888119896)(Nm

m2)

Yield

strengthof

steeltube

(119891119910)

(Nm

m2)

Localcom

pressio

narea

ratio

(120573=119860

CFST119860

LC)

Ultimate

axial

deform

ation

(Δ119906)

Ultimate

streng

th(kN)

Ductility

index

120583Δ=ΔΔ119910

Predicted

compressiv

estr

ength

119873119906119901(kN)

[41112]

119873119906ex

p119873119906119901

Circular

CCFST-F-1

1014times4

300

615

358

176

961

205

mdashmdash

CCFST-F-2

1014times4

300

615

358

157

958

190

mdashmdash

CCFST-F-3

1014times4

300

615

358

156

957

192

mdashmdash

CCFST-P-1

1014times4

300

615

358

268

898

206

90533

1062

CCFST-P-2

1014times4

300

615

358

291

917

249

1059

CCFST-P-3

1014times4

300

615

358

259

908

197

1057

Square

SCFST-F-1

100times100times4

300

615

358

137

933

154

mdashmdash

SCFST-F-2

100times100times4

300

615

358

132

961

139

mdashmdash

SCFST-F-3

100times100times4

300

615

358

133

931

165

mdashmdash

SCFST-P-1

100times100times4

300

615

358

237

866

176

87612

1065

SCFST-P-2

100times100times4

300

615

358

253

842

189

1097

SCFST-P-3

100times100times4

300

615

358

251

864

189

1063

Advances in Materials Science and Engineering 5

SCFST-P-0(2) SCFST-P-0(3)

Figure 4 Failure pattern of square CFST column subjected topartiallocal compression

End plate

Steel tube

Infilled concrete

Bearing plate

P

1 25

Figure 5 Load transferringmechanism of partial and full compres-sion [4]

under partial compression the concrete immediately belowthe loading area cracked noticeably due to the punching effectof load and buckling of steel tube occurred at the top of thecolumn which is shown in Figure 4 The load transferringmechanism of the CFST columns under partial compressionis shown in Figure 5 When the partial load is applied theconcrete in the top layer started to crack due to the punchingeffect of applied load and creates an increase in volume ofconcrete and this led to the faster increase on the lateralstrain in steel tube As a result the buckling of steel tubeoccurred very near to the loading area It was observed thatthe cracking of concrete was initiated beneath the loadingpoint and spread towards the four corners of the steel tubeFrom this it can be inferred that in square CFST columnsthe confinement to the concrete core mainly comes from

the corner and a small part of the concrete only effectivelyconfined by the steel tube [11 12]

The circular CFST column tested under full compressionfailed through outward buckling of steel tube observed atthe center of the column as shown in Figure 6 Furthermoreno obvious cracking was observed in top concrete In thecase of a circular column tested under partial compressiononce cracking of concrete initiated beneath the loading areathe steel tube in the outer limits provided more confinementto the concrete core loading further the concrete crackswere spread uniformly around the steel tube providing moreconfinement to the concrete core Finally the columns failedthrough outward buckling of steel tube observed at midheight of the column as shown in Figure 6 The load trans-ferring mechanism to the mid height of the circular columnis shown in Figure 5 With reference to the crack pattern ofthe concrete core it can be inferred that the confinementprovided by the circular steel tube is uniform and the wholepart of the concrete effectively is confined by the steel tube[11] Furthermore it can be inferred that the confinementprovided by the circular section is quite different than theconfinement provided by the square section In the case ofcolumn tested under partial compression in both square andcircular sections a sudden drop-off in loading was observedat the failure load particularly this observation was veryobvious in square section under partial compression Thissudden drop-off in the loading is attributed to the crushingfailure of concrete

32 Axial Stress-Strain Behavior and Ductility The experi-mental results with regard to ultimate axial deformation ofthe columns are listed in Table 1 The ultimate axial deforma-tion (Δ

119906) of the column obtained is the axial deformation of

the column when the load falls to 80 of its ultimate loadThe axial applied stress-strain behavior of all the columnsis shown in Figures 7 and 8 From Figures 7 and 8 itcan be understood that the elastic modulus of the columnwith partial compression is lower than the column with fullcompression in both square and circular columns Moreoverthe immediate fall in the curve was observed at the ultimatestage in columnwith partial compression due to the crushingfailure of concrete In the case of circular columns the axialstress-strain behavior of the columnwith partial compressionwas relatively similar to the column with full compressionHowever the column with full compression achieved higherultimate strength when compared to the column with partialcompression At the respective failure load of a circular col-umnwith partial compression (CCFST-P-3) the deformationof the circular column with full compression (CCFST-F-3)was about 39mm which is 6388 lesser than the columnwith partial compression As said earlier the decrease in thestiffness of the column with partial compression may be dueto the punching effect of the partial compression Due to thispunching effect the concrete core beneath the compressionarea started to crack and creates an increase in volume ofconcrete and this led to the faster increase on the lateral strainin steel tube As a result the buckling of steel tube occurredvery near to the loading area The above similar trendwas observed in the case of square columns under partial

6 Advances in Materials Science and Engineering

CCFST-F-0(3) CCFST-P-0(1) CCFST-P-0(2)

Figure 6 Failure pattern of circular CFST column subjected to full and partial compression

0

10

20

30

40

50

60

70

80

90

100

CCFST-P-1 CCFST-P-2CCFST-P-3 CCFST-F-1CCFST-F-2 CCFST-F-3

0 002Axial strain

004 006 008

Axi

al st

ress

(Nm

m2 )

Figure 7 Axial stress-strain behavior of circular CFST columnsubjected to full and partial compressionmdashcomparison

compression furthermore the immediate fall in the curveat the ultimate state was very abrupt when compared to thecircular column The column with full compression (SCFST-F-2) achieved a deformation of 28mm at the respectivefailure load of column with partial compression in additionthis deformation was 8928 lesser than the column withpartial compression (53mm) Han et al [11 12] documentedthat for square section the formation of lateral strain at thetop corresponding to the ultimate strength is larger than thatof the lateral strain in the middle The obtained experimentalresults fairly agreed with the finding of Han et al [11 12]

0

10

20

30

40

50

60

70

80

90

100

0 002 004 006 008Axial strain

SCFST-F-1 SCFST-F-2SCFST-F-3 SCFST-P-1SCFST-P-2 SCFST-P-3

Axi

al st

ress

(Nm

m2 )

Figure 8 Axial stress-strain behavior of square CFST columnsubjected to full and partial compressionmdashcomparison

and this can be evident from Figure 4 The crack in theconcrete beneath the partial compression led to the fasterincrease in the lateral strain at the top and this led to thebuckling of steel tube very near to the loading area FromFigure 7 it can be understood that the fall in the curve ofthe circular specimen at the ultimate load was very smoothdue to the even confining pressure provided by the circularsteel tube For square specimen it was abrupt due to theconfining pressure provided only from the corners From theobservation it can be inferred that the confinement actionbetween the concrete and the steel tube for square section

Advances in Materials Science and Engineering 7

Full compression Partial compressionLoading type

0

05

1

15

2

25

Duc

tility

inde

x (D

I)

Figure 9 Ductility behavior of circular CFST column subjected tofull and partial compressionmdashcomparison

Full compression Partial compressionLoading type

000

050

100

150

200

250

Duc

tility

inde

x (D

I)

Figure 10 Ductility behavior of square CFST column subjected tofull and partial compressionmdashcomparison

is not significant when compared to the composite actionbetween the concrete and the steel tube for circular section

The displacement ductility index of all the CFST columnswas calculated using (1) obtained from the idealized bilinearcurve [17] that was ascertained from the load-deformationbehavior of the column where 120583

Δis the displacement

ductility index of the columnΔ is the axial deformation of thecolumn when the load falls to 85 of the ultimate load Δ

119910

is the deformation at the respective yield load of the column

120583Δ=Δ

Δ119910

(1)

From Figures 9 and 10 it can be understood thatthe column subjected to local compression showed higherductility when compared to the column subjected to fullcompression however the difference in the ductility indexwas not significant The experimental finding of Yang andHan [3] also revealed the same The increase in the ductilityindex may be due to the fact that for columns subjected topartial compression the steel tube in the outer limit did notbear the load directly and provides effective confinement tothe concrete As a result the ductility of the column increasedsomewhat more For instance the square column subjectedto full compression (SCFST-F-1) exhibited a ductility indexof 154 whereas the square column subjected to partialcompression achieved a ductility index of 174 which is1081 higher than that of the column subjected to full com-pressionThe above similar trendwas observed in the circular

Full compression Partial compressionLoading type

600650700750800850900950

1000

Ulti

mat

e stre

ngth

(kN

)

Figure 11 Ultimate strength of circular CFST column subjected tofull and partial compressionmdashcomparison

Full compression Partial compressionLoading type

600650700750800850900950

1000

Ulti

mat

e stre

ngth

(kN

)

Figure 12 Ultimate strength of square CFST column subjected tofull and partial compressionmdashcomparison

columns subjected to partial and full compression howeverthe ductility behavior of the circular columns was moreobvious when compared to the square column

33 Ultimate Strength The measured ultimate strength ofall the CFST columns under partial and full compression islisted in Table 1 and presented in Figures 11 and 12 FromFigures 11 and 12 it can be understood that both square andcircular CFST columns under partial compression achievedlower strength whereas the columns under full compressionshowed higher strength The column CCFST-P-2 achieveda strength of 917 kN which is 445 lesser than that ofthe CCFST-F-2 In a similar manner the square sectionunder full compression (SCFST-F-2) exhibited an ultimatestrength of 961 kN whereas the column SCFST-P-2 achieveda strength of 842 kN which is 1415 less The decrease inultimate strength of the column under partial compressionis attributed to the cracking of the core concrete due to thepunching load Moreover the decrease in ultimate strengthof the square section was significant when compared to thecircular section The difference in ultimate strength betweenthe circular sections under full and partial compression wasabout 51 kN whereas the square section showed a differenceof 69 kN From this observation it can be inferred that theconfinement effect provided by the circular steel tube is moreeffective than that of the square section and the decreasein the compression area significantly affects the strengthcapacity of the CFST column

8 Advances in Materials Science and Engineering

4 Theoretical Evaluation of Bearing Capacity

In the design model of the CIDECT report [18] and EN 1994-1-1 [19] the influence of local compression on the ultimatestrength capacity of CFST columns was considered and theeffects of the confinement of the steel tube were addressedEquation (2) was proposed to evaluate the bearing capacityof the CFST column subjected to partial compression (119873

119906119901)

119873119906119901= 11986011198911015840119888119889(1 + 120578

119888119897

119905

119886

119891119910

1198911015840119888119896

)radic119860119888

1198601

le (1198911015840119888119889119860119888+ 1198911199101198891198601)

(2)

where 1198601is the local compression area 1198911015840

119888119889and 1198911015840

119888119896are the

design and characteristic compressive strength of concreterespectively 120578

119888119897is the factor depending upon the confinement

of the steel tube (generally 49 and 35 for circular and squaresteel tubes resp) 119886 and 119905 are the size and thickness of thesteel tube 119891

119910119889is the design yield strength value of the steel

tube In the above model [18 19] the load distribution overthe thickness of the steel plate was assumed with the ratio of1 25 as shown in Figure 6 if the CFST column is subjectedto local compression

Based on the experimental results obtained Han et al[2 3 12] proposed (3) to predict the bearing capacity of theCFST column subjected to partial compression In thismodelthe bearing capacity of the local compression CFST columnwas determined from the CFST column subjected to fullcompression by applying strength index factor

119873119906119901= 119896119901sdot 119873119906 (3)

where 119873119906is the bearing capacity of the CFST column

subjected to full compression and 119896119901is the strength index

factor and can be evaluated through the following equationstaking into account the section type

For circular section [2 3 12]

119896119901= (1198600sdot 120573 + 119861

0sdot 12057305 + 119862

0)

sdot (1198630sdot 119899119903

2 + 1198640sdot 119899119903+ 1)

(4)

where1198600= (minus0171205853 + 191205852 minus 684120585 + 7)100 119861

0= (1351205853 +

141205852 + 46120585 minus 608)100 1198620= (minus1081205853 + 10951205852 minus 351120585 +

1509)100 1198630= (minus053120573 minus 5412057305 + 46)100 119864

0= (6120573 +

6212057305 minus 67)100 120585 and 119899119903are the confinement factor and

relative rigidity radius of the end plate respectively which aredetermined using (5) and (6) [2 4 12]

120585 =119860119904

119860119888

sdot119891119910

1198911015840119888119896

(5)

119899119903= (

16

12 (1 minus 120583119904

2))

025

sdot (119864119904119905119886

3119886

1198641198864)

025

(6)

where 119860119904and 119860

119888are the cross-sectional area of the steel and

concrete respectively and 119864 ([119864119904sdot 119860119904+ 119864119888sdot 119860119888]119860119904119888) is the

elastic modulus of the composite CFST column

Circular section-local compSquare section-local comp

Circular section-full compSquare section-full comp

Pred

icte

d ul

timat

e bea

ring

capa

city

(Nup

) (kN

)

800

830

860

890

920

950

830 860 890 920 950800Experimental ultimate bearing capacity (Nuexp) (kN)

Figure 13 Correlation between predicted and experimental ulti-mate strength of square and circular CFST column subjected topartial compression

For square section [2 12]

119896119901= (1198600sdot 120573minus1 + 119861

0sdot 120573minus05 + 119862

0) sdot (119863

0sdot 119899119903+ 1) (7)

where 1198600= (3545120585 + 269)100 119861

0= (minus4062120585 + 74508)

100 1198620= (52120585 minus 093)100 119863

0= (103212057305 minus 5311)100

The ultimate bearing capacity of the CFST column subjectedto local compression of the present study was evaluated usingthe above proposedmodels [4 11 12] and the predicted valuesare summarized in Table 1 Figure 13 shows the correlationmade between the tested and predicted bearing capacityof the CFST column subjected to local compression FromFigure 13 it can be understood that the models proposed byHan et al [4 11 12] are conservative to predict the bearingcapacity of the CFST column subjected to local compressionfurthermore the model provided the closest prediction

5 Conclusion

An experimental investigation was performed to understandthe structural behavior of CFST stub columns subjected topartiallocal compression Based on the test results of twelvespecimens the following conclusions were made

(i) The failure pattern of the CFST column subjected topartial compression was obviously different than thatof the CFST column subjected to full compression

(ii) While being the CFST column subjected to partialcompression the confinement provided by the cir-cular section is quite different than the confinementprovided by the square section furthermore the con-finement action between the concrete and the steel

Advances in Materials Science and Engineering 9

tube for circular section was significant compared tothat of the square section

(iii) The columns subjected to local compression achievedthe low stiffness and bearing capacity when com-pared to the column subjected to full compres-sion The circular column with partial compressiondecreased its stiffness andultimate strength by 6388and 445 respectively when compared to the col-umn with full compression

(iv) The higher confinement provided by the steel tubein partial compression increased the ductility perfor-mance of the CFST column furthermore it was veryobvious in circular section

(v) A theoretical bearing capacity of the CFST columnssubjected to partial compression was predicted usingsimple equations and the predicted values were ingood agreement with the experimental results

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] G Muciaccia F Giussani G Rosati and F Mola ldquoResponse ofself-compacting concrete filled tubes under eccentric compres-sionrdquo Journal of Constructional Steel Research vol 67 no 5 pp904ndash916 2011

[2] G G Prabhu and M C Sundarraja ldquoBehaviour of concretefilled steel tubular (CFST) short columns externally reinforcedusing CFRP strips compositerdquo Construction and Building Mate-rials vol 47 pp 1362ndash1371 2013

[3] Y-F Yang and L-H Han ldquoExperiments on rectangularconcrete-filled steel tubes loaded axially on a partially stressedcross-sectional areardquo Journal of Constructional Steel Researchvol 65 no 8-9 pp 1617ndash1630 2009

[4] Y F Yang and L H Han ldquoConcrete filled steel tube (CFST)columns subjected to concentrically partial compressionrdquoThin-Walled Structures vol 50 no 1 pp 147ndash156 2012

[5] S P Schneider ldquoAxially loaded concrete-filled steel tubesrdquoJournal of Structural Engineering vol 124 no 10 pp 1125ndash11381998

[6] A E Kilpatrick and B V Rangan ldquoTests on high-strengthconcrete-filled steel tubular columnsrdquo ACI Structural Journalvol 96 no 2 pp 268ndash274 1999

[7] M Mursi and B Uy ldquoStrength of concrete filled steel boxcolumns incorporating interaction bucklingrdquo Journal of Struc-tural Engineering vol 129 no 5 pp 626ndash639 2003

[8] K Sakino H Nakahara SMorino and I Nishiyama ldquoBehaviorof centrally loaded concrete-filled steel-tube short columnsrdquoJournal of Structural Engineering vol 130 no 2 pp 180ndash1882004

[9] D Liu and W-M Gho ldquoAxial load behaviour of high-strengthrectangular concrete-filled steel tubular stub columnsrdquo Thin-Walled Structures vol 43 no 8 pp 1131ndash1142 2005

[10] S De Nardin and A L H C El Debs ldquoAxial load behaviourof concrete-filled steel tubular columnsrdquo Proceedings of the

Institution of Civil Engineers Structures and Buildings vol 160no 1 pp 13ndash22 2007

[11] L-H HanW Liu and Y-F Yang ldquoBehavior of thin walled steeltube confined concrete stub columns subjected to axial localcompressionrdquoThin-Walled Structures vol 46 no 2 pp 155ndash1642008

[12] L-H Han W Liu and Y-F Yang ldquoBehaviour of concrete-filled steel tubular stub columns subjected to axially localcompressionrdquo Journal of Constructional Steel Research vol 64no 4 pp 377ndash387 2008

[13] Q Yu Z TaoW Liu and Z-B Chen ldquoAnalysis and calculationsof steel tube confined concrete (STCC) stub columnsrdquo Journalof Constructional Steel Research vol 66 no 1 pp 53ndash64 2010

[14] IS 49231997 Indian standard Hollow steel sections for struc-tural usemdashSpecification Second revision

[15] Bureau of Indian Standards IS 2720(Part 3) Methods of Test forAggregates formdashSpecification Bureau of Indian Standards NewDelhi India 1980

[16] M C Sundarraja P Sriram and G Ganesh Prabhu ldquoStrength-ening of hollow square sections under compression using FRPcompositesrdquoAdvances inMaterials Science and Engineering vol2014 Article ID 396597 19 pages 2014

[17] M C Sundarraja and G G Prabhu ldquoExperimental studyon CFST members strengthened by CFRP composites undercompressionrdquo Journal of Constructional Steel Research vol 72pp 75ndash83 2012

[18] R Bergman C Matsui C Meinsma and D Dutta CIDECTDesign Guide for Concrete-Filled Hollow Section Columns underStatic and Seismic Loading TUV Rheinland 1995

[19] EN ldquoEurocode 4 design of composite steel and concretestructures part 1-1 general rules and rules for buildingsrdquo EN1994-1-1 British Standards Institution EuropeanCommittee forStandardisation London UK 2004

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