ANALYTICAL STUDY ON AXIAL COMPRESSIVE PERFORMANCE OF CFST COLUMNS UNDER NON-PRISMATIC CONDITIONS

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 12 Issue: 05 | May 2025 www.irjet.net p-ISSN: 2395-0072

ANALYTICAL STUDY ON AXIAL COMPRESSIVE PERFORMANCE OF CFST COLUMNS UNDER NON-PRISMATIC CONDITIONS

Hafeeda Razan M M1 , Lakshmy E G2 , Fathima S Thaikudiyil3

1M.Tech Student, Structural Engineering, KMEA Engineering College, Kerala, India

2Assistant Professor, Department of Civil Engineering, KMEA Engineering College, Kerala, India

3Assistant Professor, Department of Civil Engineering, KMEA Engineering College, Kerala, India

Abstract – Concrete Filled Steel Tube (CFST) columns are composite elements that combine steel and concrete to achieve high strength and load-bearing efficiency. This study was mainly investigated to evaluate the axial loading performance of rectangular tapered CFST columns under Single-Side (SS) and Double- Side (DS) taper conditions with varying taper ratios Results obtained that higher taper ratios result in higher load capacity but also increases deflections DoubleSide Tapered columns consistently outperform than SingleSide Tapered columns in both load resistance and controlled deflections due to their symmetric design.

Key Words: Rectangular CFST column, Single-side taper, Double-sidetaper,Taperratio,Axialloading,Load-bearing capacity,AnsysWorkbench,FiniteElementAnalysis.

1. INTRODUCTION

AConcreteFilledSteelTube(CFST)columnsarestructural elements where a steel tube is filled with concrete, combiningthehighstrengthandductilityofsteelwiththe compressive power of concrete In CFST members, steel confinesconcreteforstrengthandductility,whileconcrete prevents steel tube buckling, boosting load capacity. This designimprovesloadbearing,stabilityandfireresistance, makingCFSTcolumnsidealforhigh-risebuildings,bridges andotherstructures.Non-prismaticCFSTcolumnsareCFST columns with varying cross-sectional sizes along their length. While tapered CFST columns are a type of nonprismatic CFST columns with a gradually changing cross section, typically wider at the base. In this study, tapered CFSTcolumnsweredevelopedwithvariousconfigurations, including Single-Side (SS) and Double-Side (DS) taper conditions,incorporatingdifferenttaperratiossubjectedto axial loading. This investigation is important as it aims to enhancethestructuralefficiencyandoverallperformanceof CFSTcolumns,offeringpotentialimprovementsinmaterial optimization, load-carrying capacity and durability for advancedconstructionapplications.

1.1 Non-prismatic CFST Column

Non-prismatic CFST columns feature a varying crosssectional area along their length. The design of nonprismaticcolumnsallowsformaterialoptimization,placing

more material where stresses are higher and reducing it wherestressesarelower.Thisapproachcanleadtomaterial savings,improvedaestheticsandbetteraccommodationof architectural requirements. Tapered CFST columns are a specific type of non-prismatic column where the crosssectional dimensions change gradually along the length, typically narrowing towards the top. This tapering can be symmetricalorasymmetricalintheirgeometry.Thedesign oftaperedcolumnsaimstoalignthestructuralcapacitywith thedistributionofinternalforces,providingmorematerial where needed and reducing it where possible. The key influencingparameter,taperratiosrangingfrom1to3for bothsingle-sideanddouble-sidetaperplayasignificantrole inthestructuralresponse.

2. OBJECTIVES

The main objectives of this study are to evaluatetheaxial loadingperformanceoftaperedConcreteFilledSteelTube (CFST)columnsundervariousconfigurationsandtostudy the structural behaviour of tapered rectangular CFST columnsundersingle-sideanddouble-sidetaperconditions withvaryingtaperratios

3. FINITE ELEMENT MODELLING

3.1

General

To investigate structural behavior of tapered rectangular ConcreteFilledSteelTube(CFST)columnswithsingle-side and double-side tapering conditions with varying taper ratios, finite element models were developed using Ansys Workbench2024R2

3.2 Geometry

Thegeometryof0°SSandDStaperrectangularCFSTcolumn wascreatedusingANSYSDesignModeler.AtotalofsixCFST column models were developed using nonlinear static analysis includes 0° single-side and double-side prismatic CFSTwithtaperratio1:1(160mmX160mm),0°single-side anddouble-sidetaperrectangularCFSTcolumnwithtaper ratio1:2(160mmX320mm)and0°single-sideanddoublesidetaperrectangularCFSTcolumnwithtaperratio1:3(160 mmX480mm).Eachmodelhadaheightof1386mmand

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 12 Issue: 05 | May 2025 www.irjet.net p-ISSN: 2395-0072

the steel tube thickness of 2.92 mm were considered. Detailed geometric details of 0° SS and DS taper CFST columnsarepresentedinTable1andmaterialpropertiesof steelandconcretepresentedinTable2 3Dmodelsandtop view of the CFST column models of 0° single-side and double-sidetaperCFSTcolumnswithtaperratio1,2and3 were created in ANSYS workbench and are illustrated in Figures1,2,3,4,5and6respectively

Table -1: Dimensionaldetailsof0°SSandDStaperCFST columns

Table -2: Materialpropertiesofsteelandconcrete

Yieldstrength 389MPa

63MPa

Poisson’sRatio 0.3 0.12 Young’smodulus 206GPa 35GPa

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 12 Issue: 05 | May 2025 www.irjet.net p-ISSN: 2395-0072

3.3 Meshing

Meshing is the process of dividing a complex object into smaller,simplerpartscalledelements,enablingengineersto analyzehowtheobjectbehavesundervariousconditions.A mesh size of 50 mm with a shape of hexahedron and adaptivesizingofmeshingtypeforbothsteelandconcrete has been utilized in the finite element simulation. The elementtypeusedforbothsteelandconcreteisSOLID186. Figure7showsthemeshingofCFSTcolumn.

3.4 Loading and Boundary Condition

The boundary conditions are crucial in Finite Element Analysis(FEA)becausetheydirectlyinfluencetheaccuracy and realism of the simulation results. They represent the physical constraints and interactions that a structure or system experiences in the real world, ensuring that the model behaves as expected under various loading and

environmental conditions. Without proper boundary conditions,themodelwouldlackthenecessaryrestraintsor forces,leadingtounrealisticormeaninglessresults.Inthis study, the boundary condition is both ends are hinged support,inwhicheachendofthemember,movementinall directions(X,YandZ)isprevented,sotheendscannotslide orlift,butthememberisfreetorotateatthosepointsand axiallyloadingwasconsidered.

Applicationofboundaryconditions

4. RESULTS AND DISCUSSIONS

4.1 Comparative Study of RectangularCFST Column with 0° Single-Side (SS) and Double-Side (DS) Taper with Taper Ratio 1, 2 and 3

Acomparativestudyof0°single-sideanddouble-sidetaper CFSTcolumnwithvaryingtaperratiosunderaxialloading was done. In this study, models of 0° with taper ratios rangingfrom1to3withwidthoftopsectionofcolumnwas

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 12 Issue: 05 | May 2025 www.irjet.net p-ISSN: 2395-0072

160mmforallmodelsandwidthofbottomsectionof160 mm,320mmand480mmwasconsideredforbothsinglesideanddouble-sidetaper.Thethicknessofsteeltubewall of2.92mmandtheheightofCFSTcolumnof1386mmfor allmodelswasalsoconsidered.

Total Deformation represents the overall displacement experienced by a structure due to applied loads. Total deformationof0°SSandDStaperCFSTcolumnsareshown inFigures9and10respectively

Equivalent Plastic Strain quantifies the accumulated irreversibledeformationinamaterialduetoplasticloading and Equivalent von Mises Stress is a scalar value derived from the stress tensor at a point. The von Mises yield criterionisacommonlyappliedapproachtodeterminethe onsetofyieldinginductilematerialssubjectedtocomplex loading. In this study, the effective CFST column was obtained as 0° Double-side taper CFST column with taper ratio 3 The equivalent plastic strain and equivalent vonmisses stress was presented in Figures 11 and 12 respectively.

Table2illustratesthedisplacementvaluesatpeakloadfor eachmodel,asobtainedfromFiniteElementAnalysis(FEA).

Chart1depictstheLoad-deflectionbehaviorof0°SS&DS tapered rectangular CFST column, providing insights into theirdeformationpatternsunderappliedloads.

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 12 Issue: 05 | May 2025 www.irjet.net p-ISSN: 2395-0072

Table -2: FEAnalysisResultsof0°SS&DStaperCFST columns

Typeof column

Singleside(SS) taper

0°SS-1

0°SS–2 20 23973 13422

0°SS–3 30 25081 15245 Doubleside(DS) taper

0°DS–2 20 25254

Chart -1: Loadv/sdeflectioncurveof0°SS&DStaper CFSTcolumn

In Single-Side Tapered (SS) CFST columns, increasing the taperratiofrom1to3resultsindeflectionrisingfrom8.03 mmto15.24mm,whileaxialloadcapacityimprovesfrom 2272.4 kN to 2508.3 kN. This increase in taper enhances axial strength by promoting more favorable stress distributionalongthecolumnbutreducesstiffness,leading to greater lateral displacement. Conversely, Double-Side Tapered (DS) columns exhibit a moderate increase in deflection from 8.03 mm to 13.08 mm and a higher load capacitygain,reaching2615.4kN.Thesymmetrictaperingin DScolumnsensuresbetterloadpathcontinuityandreduces stress concentrations, thereby improving stiffness and overallstructuralstabilitycomparedtoSScolumns.

5. CONCLUSION

The load-carrying capacity of rectangular tapered CFST columns was enhanced by increasing the taper ratio in double-side taper conditions. These rectangular CFST columns were tested under axial loading conditions by varyingparameteroftaperratio.

Thekeyconclusionsdrawnfromtheanalysisare:

 DoubleSideTapered(DS)columnsexhibitshigherload bearingcapacitycomparedtoSingle-SideTapered(SS)

columns,becausetheirsymmetricaltaperingfromboth sidesmaintainsabalancedcross-sectionalprofilealong theirlength,leadingtouniformstiffnessandimproved structuralstability

 Increasing the taper ratio in double-side tapered rectangularconcrete-filledsteeltubular(CFST)columns leadstoasignificantenhancementintheirload-carrying capacity.

 The improved performance is attributed to better confinementoftheconcretecoreandoptimizedstress distributionalongthecolumnlength,whichdelayslocal bucklingandincreasesaxialstrength

REFERENCES

[1]Qing-Xin Ren, Lin-Hai Han, Chao Hou, You-Xing Hua., ExperimentalbehavioroftaperedCFSTcolumnsunder combined compression and bending, Journal of constructionalsteelresearch,128(2017)39–52.

[2]D.Lam,X.H.Dai,L.H.Han,Q.X.Ren,W.Li,Behaviorof inclined, tapered and STS square CFST stub columns subjectedtoaxialload,Thin-walledstructures,54(2012) 94–105

[3]K.H. Aleena Binth, E. K.Amritha,Analysisofaxial load behaviorofnon-prismaticcircularandrectangularCFST columns,InternationalResearchJournalofEngineering Technology,09(2022).

[4]AnsymolAnaz,RanjanAbraham.,StudyonPrismaticand Non-Prismatic Concrete Filled Steel Tube Columns encased with Engineered Cementitious Composite, International Research Journal of Engineering Technology,07(2020).

[5]FaridAbed,MohammadAlHamaydeh,SulimanAbdalla., Experimental and numerical investigations of the compressive behavior of concrete filled steel tubes (CFSTs), Journal of constructional steel research, 80 (2013)429–439.

[6]ShaikMadeenaImamShah,G.MohanGanesh.,Impactof diametertothickness(D/t)onaxialcapacityofcircular CFSTcolumns:Experimental,parametricandnumerical analysis, International Journal of Applied Science and Engineering,19(2)(2022)2021486

[7]JelenaNikoNc,SvetlanaM.Kostic,SasaStosic.,Numerical modellingofconcrete-filledsteeltubularshortcolumns under axial compression, Building Materials and Structures66(2023)2300004N.

[8]Lin-Hai Han, Wei Li, Reidar Bjorhovde., Developments andadvancedapplicationsofconcrete-filledsteeltubular (CFST) structures: Members, Journal of Constructional SteelResearch100(2014)211–228

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 12 Issue: 05 | May 2025 www.irjet.net p-ISSN: 2395-0072

[9]K.K.Choi,Y.Xiao.,AnalyticalStudiesofConcrete-Filled CircularSteelTubesunderAxialCompression,J.Struct. Eng.,136(5)(2010)565-573.

[10]Zhong Tao, Zhi-Bin Wang, Qing Yu., Finite element modelling of concrete-filled steel stub columns under axial compression, Journal of Constructional Steel Research89(2013)121–131

[11]Lin-HaiHana,Qing-XinRena,WeiLi.,Testsoninclined, tapered and STS concrete-filled steel tubular (CFST) stubcolumns,JournalofConstructionalSteelResearch 66(2010)1186-1195.

[12]Qing Yua, Zhong Tao, Ying-Xing Wu., Experimental behavior of high-performance concrete-filled steel tubular columns, Thin-Walled Structures 46 (2008) 362–370

[13]E.Ellobody,B.Young,NonlinearanalysisofconcretefilledsteelSHSandRHScolumns,Thin-WalledStruct. 44(8)(2006)919–930.

[14]L.H.Han,Y.Ye,F.Y.Liao.,Effectsofcoreconcreteinitial imperfection on performance of eccentrically loaded CFST columns, ASCE J. Struct. Eng. 142 (2016) 04016132.

[15]K.V.Akshay,P.Aswathy,AParametricstudyonCore shapes of a Concrete-Encased CFST Column, International Journal of Scientific & Engineering Research,Volume10,(2019)ISSN2229-5518

[16]C.Zhang,Z.Y.Shen,Z.Y.Lin.,Experimentalresearchon seismic behavior of concrete-filled L-shaped steel tubularframes,J.Build.Struct.31(8)(2010)1–7(in Chinese).

[17]B.Uy,Z.Tao,L.H.Han,Behaviorofshortandslender concrete-filled stainless-steel tubular columns, J. Constr.SteelRes.67(3)(2011)360–378.

[18]W.Li,Q.X.Ren,L.H.Han,X.L.Zhao,Behavioroftapered concrete-filleddoubleskinsteeltubular(CFDST)stub columns,Thin-WalledStruct.57(2012)37–48.

[19]Z.Tao,B.Uy,L.H.Han,Z.B.Wang,Analysisanddesign of concrete-filled stiffened thin-walled steel tubular columns under axial compression, Thin-Walled Structures47(12)(2019)1544-56.

[20]Cai, Z.Q. He, Axial load behavior of square CFT stub column with binding bars, Journal of Constructional SteelResearch,62,(2005)472–483.

[21]Pengfei Li, Tao Zhang, Chengzhi Wang, Behavior of Concrete-FilledSteelTubeColumnsSubjectedtoAxial Compression, Advances in Materials Science and Engineering,Volume12(2018).

[22]Jingming Cai, Jinlong Pan, Cong Lu, Mechanical behaviorofECC–encasedCFSTcolumnssubjectedto eccentric loading, Journal of Engineering Structures 162,(2018)22-28.

[23]Huang Yuan, Huan-Peng Hong, Huang Deng, Yu Bai, Displacement ductility of staged construction-steel tube-reinforced concrete columns, Construction and BuildingMaterials188,(2018)1137–1148.

[24]TrayanaTankova,JoaoPedroMartins,LuisSimoesda Silva, Rui Simoes, Helder D. Craveiro, Experimental buckling behaviour of web tapered I-section steel columns,JournalofConstructionalSteelResearch147, (2018)293–312.

[25]C.W.Roeder,D.E.,E.Bishop,Strengthandstiffnessof circular concrete-filled tubes, Journal of Structural Engineering,vol.136,no.12,pp.,(2010)1545–1553.

[26]42.SchneiderS.P.,Axiallyloadedconcrete-filledsteel tubes,JournalofStructuralEngineering,ASCE124(10) (1998)1125–38.