Study and Buckling Analysis of Concrete Filled Steel Tubes Columns using ANSYS

Transcription

1 Study and Buckling Analysis f Cncrete Filled Steel Tubes Clumns using ANSYS Neetu Devi Singh 1, Shubha Vaghmarey 2 1Neetu Devi Singh, MM City, Raipur 2Shubha Vaghmarey: Assistant Prfessr, Dept. f Civil Engineering, MM City Cllege, C.G, India *** Abstract - The present study is an attempt t understand the behavir f Cncrete filled steel tubular clumn under axial lad. A cncrete-filled steel tubular (CFST) clumn is frmed by filling a steel tube with cncrete. It is well knwn that cncrete-filled steel tubular (CFST) clumns are currently being increasingly used in the cnstructin f buildings, due t their excellent static and earthquake-resistant prperties, such as high strength, high ductility, large energy absrptin capacity, bending stiffness, fire perfrmance alng with favrable cnstructin ability etc. In the present research, the nn-linear analysis f cncrete filled steel tube (CFST) is dne using ANSYS WORKBENCH 15 sftware. It has been fund that perfrmance f circular crss sectin depends n:- 1) Diameter f Clumn 2) Length f Clumn 3) Thickness f Steel Tube 4) L/D rati 5) D/t rati Steel-Cncrete cmpsite clumns are used extensively in highrise building and bridges as a type f hybrid system, utilize the advantages f bth steel and cncrete. In such case, steel tube prvides frmwrk fr the cncrete and the cncrete prevents lcal buckling f the steel tube wall. Als the lad-carrying capacity and behavir in cmpressin, bending and shear are all superir t reinfrced cncrete. Key Wrds: Cncrete filled steel tubular clumn, high strength, high ductility, large energy absrptin capacity, bending stiffness, fire perfrmance alng with favurable cnstructin ability. 1. INTRODUCTION 1.1 GENERAL Cncrete filled steel tubes (CFST) are cmpsite structures cnsisting f a steel tube infilled with cncrete. In present internatinal practice, CFST clumns are used in the primary lateral resistance systems f bth braced and unbraced building structures. CFSTs may be perated fr retrfitting purpses fr strengthening cncrete clumns in earthquake prne areas. Cncrete filled steel tubes are generally used in Beams, Clumns, Piers and caissns fr deep fundatins. In innvative CFST structures, silica fume which is supplementary cementitius material, are usually added int the cncrete mix t btain higher strength and better perfrmance f the structure. CFST clumns having additin f silica with cncrete in this way are knwn as high strength cncrete filled steel tubular clumns. Fr high strength cncrete filled steel tubular clumns, there is a cmpsite actin between these tw essential elements which cntributes the cncrete t prevent inward buckling f wall f steel tube This dcument is template. We ask that authrs fllw sme simple guidelines. In essence, we ask yu t make yur paper lk exactly like this dcument. The easiest way t d this is simply t dwnlad the template, and replace(cpy-paste) the cntent with yur wn material. Number the reference items cnsecutively in square brackets (e.g. [1]). Hwever the authrs name can be used alng with the reference number in the running text. The rder f reference in the running text shuld match with the list f references at the end f the paper. 1.2 HISTORY Pre 1960 s Revlutin and requirement have been dynamism fr the structural design thrughut the histry. As early in 1930 s, the frmer SOVIET UNION cnstructed a 101m bridge by using cncrete filled steel tubes. Nminal research and experience using cncrete filled steel tubes frmed anxiety f using CFST s s In 1961 Kat Naka wrte the first technical jurnal n CFST in Japan which described circular CFST cmpressin member used in pwer transmissin twer. This technical paper study n the subject leading t additin f the architectural institute f the Japan (AIJ) standard fr cncrete and circular steel tubes as the cmpsite structures, published in China and Japan made investments in research fr setting the fundatin f CFST. 1.3 TYPES OF CFST Cncrete filled steel tubes is designed n the basis f their applicatin. It may be square, hexagnal and circular depends upn design and use f their applicatin. Cncrete filled steel tubes are divided int tw types accrding t the frm f the cncrete cre. These tw types are slid and 2018, IRJET Impact Factr value: ISO 9001:2008 Certified Jurnal Page 1259

2 hllw cncrete cre CFSTs. In Fig.1.1 sme shapes f CFST are shwn which indicates these bth types. Slid cncrete cre is made by placing the plain cncrete in the steel tube and cmpactin is dne by vibratin. Hllw cncrete filled steel tubes is made by spinning methd. The methd f insertin f the wet cncrete in the rtatinal muld is knwn as spinning methd, where wet cncrete is cmpacted by vibratin using centrifugatin due t rtatin f the muld. 1.5 OBJECTIVES In the present study, the nn-linear respnse f cncrete filled steel tubular clumns using FE Mdeling under the axial lading has been carried ut with the purpse t examine the relative imprtance f several factrs in the nn-linear finite element analysis f cncrete filled steel tubular clumns. This includes the variatin in lad defrmatin graph and the crack patterns n the analytical results and the effect f the nn-linear behavir f cncrete and steel n the respnse f defrmed CFST clumn. The main bjectives f the present study are as fllws- 1. T mdel the cncrete filled steel tubular clumns using finite element sftware. 2. T cmpare the results f lad carrying capacities by Eulers frmulas and ANSYS sftware.. 2. LITERATURE REVIEW Fig.1.1 Crss-sectins f slid and hllw CFST cmpsite clumns. 1.4 BEHAVIOUR OF CFST Many previus studies have shwn that square cncrete filled steel tubes is nt as gd cmpare t circular cncrete filled steel tubes. This is due t the cnfining pressure acts in cncrete cre by square steel tube is less and that s why lcal buckling mre likely t ccur. The structural behavir f the cncrete filled steel tube is affected by the Pissn s rati f bth steel and cncrete. At the initial stage f lading, Pissn s rati f the cncrete is lwer than that f steel. Hence the steel tube des nt cntribute cnfining effect t the cncrete. When the lngitudinal strain increases, lateral expansin f the cncrete gradually becmes greater than the expansin f the steel tube. At this stage f lading, steel tube becmes biaxially stressed and cncrete cre becmes triaxially stressed. S due t the biaxial stress in the steel tube, the steel tube cannt sustain nrmal yield stress and hence transfer the lad frm tube t cre. The lad transfer mechanism is same fr bth circular and square cncrete filled steel tubes. 2.1 General It wuld be difficult t present the detailed review f the literature related t FE mdeling f cncrete filled steel tubular clumns s a brief review f previus studies n the applicatin f the finite element methd and experiment analysis f cncrete filled steel tubular clumns is presented in this chapter. This literature review fcuses n recent cntributins related t cncrete filled steel tubular clumns, materials used fr cncrete filled steel tubular clumns and past effrts mst clsely related t the needs f the present wrk. 2.2 Histrical Backgrund With the advent f steel and reinfrced cncrete, the cncepts in cnstructin has changed frm ne f securing stability t that f stressing the materials t the ptimum values. This has resulted in very light structures cmpared t the pre-19th century cnstructins. This has been made pssible by eliminating in the newer materials, the shrt cmings f pr tensile strength f the traditinal materials. The histry f the first applicatin f cmpsite clumns in cnstructin industry dates back t the 1940 s. The year 1970 marked the evlutin f cncrete filled steel tubes in Japan and this practice was fllwed by many cuntries arund the wrld. On the basis f the research results, many cuntries have develped their design cdes fr use by their engineers. The current design standards and specificatins have riginated either frm the steel r cncrete design apprach f that time. 2.3 Review On Cmpsite Clumns Fig 2.1 Stress cnditin in steel tube and cncrete cre at different stages f lading. Researchers like Elr y and Azizinamini1 (2002) investigated the behavir f cncrete-filled steel tube clumns under seismic lads were als by testing six clumns 2018, IRJET Impact Factr value: ISO 9001:2008 Certified Jurnal Page 1260

3 subjected t an axial lad. Test cnducted fr cyclic lateral lads. An analytical mdel was develped t predict the capacity f circular CFST beam-clumns accunting fr the interactin between the steel and cncrete. The develped analytical mdel was cmpared with the experimental data. Gd cncurrence was bserved between the predicted values using the anticipated mdel and the experimental utput. The CFST clumns shwed high ductility and maintained their strength till it fails. They cncluded that the clumn capacity had significantly imprved due because f the cncrete strength gained frm the cnfinement prvided by the steel tube. Mrin and Tsuda2 (2003) intrduced the structural system and discussed the advantages, research findings and recent trends f the CFT clumn system in Japan. Extensive research wrk has been dne in Japan in the last 15 years, including the New Urban Husing Prject and the US-Japan C-perative Earthquake Research Prgram, in additin t the wrk dne by individual universities and industries that were presented at the annual meeting f the Architectural Institute f Japan (AIJ). A ratinal design methd fr the CFT clumn system has been established thrugh extensive research by the AIJ. Authrs cncluded that the characteristics f CFT make the system especially applicable t high-rise and lng-span structures, because the system s cnstructin efficiency saves cnstructin cst, time, and manpwer. 2.4 Studies On Gemetrical Effects Shams and Saadeghvaziri5 (1999) presented an evaluatin f the nnlinear respnse f cncrete filled steel tubular clumns that were subjected t axial lading. They develped a three-dimensinal finite element mdel fr CFST clumns and cmpared the results against existing experimental values. They indicated that the stress-strain prperties f the cnfined cncrete were highly affected by the gemetrical cnfiguratin f the clumns as well as material prperties f cncrete. It was fund that the cnfinement effect in circular clumns was higher than that in square clumns due t mre unifrm stress distributin. Cncrete with a lwer uncnfined cmpressive strength exhibited higher cnfinement rati than higher strength cncrete. The amunt f increase in the maximum cmpressive strength f cncrete mainly depended n the D/t rati, uncnfined cncrete cmpressive strength and crss-sectinal shape. The strain at maximum stress depended n the D/t rati and crss sectinal shape. Anther interesting investigatin was carried ut by Zheng et al.6 (2000) that studied a ratinal ductility evaluatin prcedure fr thin-walled steel structures. This methd invlved an elast-plastic push-ver analysis and failure criterin based n the empirical ductility equatins prpsed fr stub-clumns. Lcal buckling was cnsidered as the failure criterin and they suggested that the lcal buckling culd be neglected in the push ver analysis, which facilitated practical applicatin. The implementatin f the prpsed prcedure was demnstrated by applicatin t the ductility evaluatin f sme cantilever clumns and nestrey frame. Extensive parametric analysis were carried ut t investigate the relatin f the stub clumn ductility t varius parameters such as the flange width-thickness rati, axial frce, stiffeners slenderness rati, crss sectinal shape, and clumn aspect rati. An elast-plastic large defrmatin FEM analysis was emplyed and bth residual stresses and initial deflectins were taken int cnsideratin. Cnsequently, empirical frmulae were prpsed. 2.5 Studies On Slenderness Effects Brain Uy9 (2000) carried ut experimental study n the effect f steel plate slenderness limits. A numerical mdel develped elsewhere was augmented and calibrated with these results. The authr develped a simple mdel fr the determinatin f the strength-interactin diagram which was verified against bth the test results and the numerical mdel develped. This mdel based n the rigid plastic methd f analysis, was existent in internatinal cdes f practice, but did nt accunt fr the effects f lcal buckling, which were fund t be significant with large plate slenderness values, particularly fr large values f axial frce. Based n the study, the authr suggested sme mdificatins fr the inclusin f slender plated clumns in design. Brain Uy10 (2001) als carried ut an extensive set f experiments n the strength f shrt cncrete filled high strength steel bx clumns. In his study a numerical mdel was presented with these tests. Furthermre, cmparisns with the Eurcde4 fr cmpsite clumns were als undertaken and this was fund t be un-cnservative in its predictin f axial and cmbined strengths. Therefre a mixed analysis technique was presented, which treated cncrete as rigid plastic and steel as linear elastic. This mdel was cmpared well with the numerical mdel presented and bth these mdels were fund t be cnservative in predicting the test results. 2.6 Reviews On Finite Element Analysis Chu et al.15 (2000) adpted finite element analysis n the pst-buckling behavir f stub clumns under axial cmpressin. They have btained numerical predictins n the lad versus end-shrtening characteristics and ultimate lad capacity f the structures using a nn linear finite element analysis. Standard design prcedures were develped fr pst-buckling analysis fr stub clumns using finite element methd. In this study they cncluded that the ultimate lad btained using the design prcedure cnsistently under estimated the experimental results and analytical predictins using BS Sme studies have als been cnducted by Liang et al.16 (2000), as they studied the pst-lcal buckling behavir f steel plates in thin walled CFST welded bx clumns using the finite element methd. The effects f varius gemetric imperfectins, residual stresses and B/t ratis n the pstlcal buckling characteristic were investigated. A new methd was develped fr evaluating the initial lcal buckling lads and pst-lcal buckling reserve strength f 2018, IRJET Impact Factr value: ISO 9001:2008 Certified Jurnal Page 1261

4 steel plates with imperfectins based n the lad-transverse deflectin relatins assciated with the theretical analysis. The accuracy f the design mdels were verified by a classical slutin and experimental results. The results indicated that the theretical predictins fr the ultimate strength f steel plates and CFST bx clumns using the prpsed design mdels agree very well with the experimental data. Therefre, the authrs prpsed that effective width frmula be used in the ultimate strength calculatin f shrt thin walled CFST bx clumns that were subjected t an axial lad. 2.7 Summary Of Review Of Literature The behavir f CFST clumns and its advantages ver the existing cnventinal cnstructin systems has nw gained mre imprtance and has attracted the attentins f researchers all ver the wrld. Frm the literatures reviewed, it is evident that cnsiderable prgress ver the last 40 years has been made in the investigatin f CFST clumns. Fr studies in the past waste materials were utilized as a replacement fr aggregate in cncrete. It nt nly reduced the cst f cnstructin but als saved large quantity f natural sand used in cnstructin industry Behavir f circular thin walled steel tube with medium strength cncrete r thick walled steel tubes with high strength cncrete has been studied. In the past, the researchers have studied the behavir f CFST clumns, which had the value f L/D = 2 t 5 with strength f cncrete frm 60 t 120 MPa. Sme studies have been cnducted fr CFST clumns with L/D rati varying frm 12 t 25. And s, in this study, the L/D rati f the CFST clumns has been varied frm 2.5 t 12.5 and its behavir was studied with M 20 grade f cncrete. Fiber Reinfrced Cncrete (FRC) has been used by sme f the researchers instead f plain cncrete fr the purpse f high stiffness and high ductility than plain cncrete filled clumns. The lateral displacements f CFST clumns were fund t be less than the lateral displacements f plain cncrete in-filled clumns. 3.0 PROBLEM IDENTIFICATION 3.1 GENERAL The mathematical mdel takes int accunt the cmbined influence f the physical and gemetric characteristics f the clumns such as their- clumn in terms f strength, resistance t axial lad, shear r buckling. Sme f the cmmn prblems arises are- In simple reinfrced cncrete, the high amunt f cnfining lateral steel required by seismic design prvisins fr clumn can cause steel cngestin. The high amunt cnfining steel may hinder the placement f cnventinal cncrete (CC). Dead weight f Reinfrced Cncrete Clumn is mre, hence mre lad will be there n the fundatin. Cncrete can take up a gd amunt f cmpressin but is nt gd enugh fr tensin whereas steel can take up bth cmpressin and tensin. At the end f life, cncrete can be crushed and recycled but the material cannt be used fr new building cncrete. Therefre the scrap value f cncrete is almst nil. In seismic znes, it is less preferred due t its brittleness and n flexibility leading t direct damage f the structure withut warning. Figure 3.1 Failure f RC clumn 3.3 STEEL AS A PROBLEM RECTIFIER In rder t have a slutin f all the prblems discussed abve and als t have a better usage f steel is as in tubular frm instead f using them as reinfrced steel bars. Steel can bend withut cracking which acts as a warning in seismic znes. New steel made frm scrapped steel uses abut ne third f the energy necessary fr steel frm virgin materials. Althugh initial cst may be high in this tubular cncept but maintenance cst can be quite cnvenient as cmpared t RC clumns and very imprtant fact that these tubular steel can be recycled. Length Crss-Sectinal area Casing Thickness Prism Strength f Cncrete Yield Strength f Cncrete Mdulus f Elasticity f Steel Mdulus f Elasticity f Cncrete 3.2 BASIC PROBLEMS There are many prblems in relatin with using the simple hllw steel clumns r simple reinfrced cncrete Figure 3.1 Hllw Steel Tube 2018, IRJET Impact Factr value: ISO 9001:2008 Certified Jurnal Page 1262

5 4.0 METHODOLOGY 4.1 GENERAL This chapter deals with the behavir f cmpsite clumns and its shrt term and lng term behavir are discussed elabrately. The mdes f failure and the bnd between steel and cncrete clumns are discussed in the subsequent headings cmprehensively. Cdal prvisins and methd f design are als discussed in the last headings. 4.2 BEHAVIOUR OF COLUMNS Shrt cmpsite clumns exhibit a failure mechanism characterized by yielding f steel and crushing f cncrete. Medium length clumns behave in-elastically and fail because f partial yielding f steel, crushing f cncrete in cmpressin and cracking f cncrete in tensin. Stcky cncrete filled tubes are als susceptible t lcal buckling f the uter skin, and this is f imprtance in very thin walled tubes which are nwadays ften used in building cnstructin. A shrt r stcky clumn is s shrt that flexural buckling will nt ccur, althugh lcal buckling may ccur. Stcky clumns are designed primarily n the material strengths f the cncrete and steel elements. The clumn is usually defined as a structural member wh carries nly cncentric axial cmpressin. The member is a steel element and is subjected t bending as well as axial cmpressin, as ccurs when the lad is applied eccentrically; it is referred t as a beam-clumn. The varius natinal standards present lad - mment interactin equatins which are slenderness-dependent, and which must be satisfied fr the strength limit state. Cmpsite members subject t bth cmpressin and bending are referred t as clumns. Because f the presence f bth steel and cncrete in a cmpsite clumn, the behavir f such a member is a kin bth t a steel beam clumn and a reinfrced cncrete clumn. Generally speaking, shrt r stcky cmpsite clumns are treated by the reinfrced cncrete apprach based n sectin material strengths. Slender cmpsite clumns, which d nt cntain appreciable bending actins are treated by the steel apprach which is based n a design strength that is affected by the slenderness f the clumn. There are a few structural cnsideratins that must be brne in mind when cmparing and cntrasting the fundamental behavir f encased clumns and cncrete filled steel tubes. Firstly, cncrete filled steel tubes are susceptible t lcal buckling f the steel skin, the prspect f which in many cases is very thin. The secnd pint pertains t the lateral cnfinement prvided by the tube t the expansin f the cncrete cre in cmpressin, which enhances the strength f shrt clumns, but it is insignificant in slender clumns. Thirdly, the steel skin inhibits the egress f misture that cntributes t creep and shrinkage effects. Research int mnitring the time dependent defrmatins f cncrete filled tubes has indicated a reduced creep and shrinkage induced respnse. In all clumn analysis appraches used at bth ultimate and serviceability limits, it is assumed that there is full interactin between the cncrete element and the steel element. This implies that the strain prfile acrss the sectin remains linear, s that there is n step change r slip-strain acrss the steel / cncrete interface, as is ften assumed in cmpsite beam design. This assumptin is reasnable, since the area f the interface is generally and fairly large and hence a gd bnd is prvided at relatively lw bnd stresses. It is wrth nting that the bnd stresses in cmpsite clumns are generally lwer than thse in beams, because the clumns are mainly subjected t cmpressin. 4.3 SHORT TERM BEHAVIOUR In a shrt cncentrically laded cncrete filled steel tube, the cncrete cre f the clumn is subjected t a cnfining stress, and as a result the clumn can carry cnsiderably larger axial frces than if the cncrete was uncnfined. The results f triaxial tests n cncrete have illustrated this, where cncrete subjected t a lateral cnfining pressure can carry a greater axial lad than uncnfined cncrete. Of curse, this is utilized in reinfrced cncrete cnstructin where spirally reinfrced clumns prvide a lateral stress that increases the axial lad carried by the cncrete cre. Hwever, the behavir f an axially laded steel tube filled with cncrete will vary accrding t the methd in which the ands f the member are laded as shwn in Figure 3.1. Essentially, there are three fundamentally different methds f applying the lading, and these are discussed belw. Lad the Steel and nt the Cncrete - This cnditin f lading may nt increase the axial capacity f the clumn abve that f the steel tube alne, because the Pissn s effect causes the steel tube t separate frm the cncrete, nce the adhesive chemical bnd between the cncrete and steel has exceeded. The clumn will generally fail at the maximum lad which the hllw steel tube alne can carry, but the cncrete cre may tend t delay the clumn lcal buckling. Fr slender clumns, the failure lad will increase significantly due t the increase in flexural stiffness. Lad the Cncrete and nt the Steel - In this principle, which is the mst favrable lading methd, the cncrete takes the maximum lad as the steel des nt resist axial lad, but nly prvides a cnfining stress t the cncrete in an analgus manner t a spirally reinfrced cncrete clumn. Hwever, since there is sme adhesin between the steel and cncrete, the cnditin is hard t attain as sme axial lad is prduced in the steel. Lad the Steel and Cncrete - This is the methd mst ften encuntered in practice, and it may be enfrced by welding stud shear cnnectrs t the inside f the steel tube where practicable. If the steel is axially stressed in cmpressin as well as circumferentially because f the expansin f the cncrete, it will be subjected t a state f biaxial stress which, in accrdance with the vn-mises yield criterin, will reduce the yield stress in the circumferential directin. This has the effect f lwering the cnfining effect, and hence reduces the maximum lad n the cncrete. Thugh the reductin in the 2018, IRJET Impact Factr value: ISO 9001:2008 Certified Jurnal Page 1263

6 cnfining effect is ffset, since the steel nw carries sme f the cmpressive frce the lad-carrying capacity f the clumn is increased by this steel and cncrete. 5.0 MODELLING 5.1 ABOUT THE SOFTWARE Fr many engineering prblems analytical slutins are nt suitable because f the cmplexity f the bundary cnditins, the material prperties and the structure. The finite element methd is the representatin f a bdy r a structure by an assemblage f subdivisins. ANSYS is finite element based sftware which gives gd results n analysis f any structural elements. The finite element mdel f the Cncrete filled Steel Tube (CFST) was mdeled using the sftware ANSYS 15. ANSYS is a cmmercial FEM package having the capabilities ranging frm a simple, linear, static analysis t a cmplex, nnlinear, transient dynamic analysis. The finite element mdel was mdeled using direct mdeling by bth Bttm Up apprach and Tp Dwn apprach. Fig 5.3:- Mdel f CFST clumn Fig 5.4:- Meshing f CFST clumn 5.2 MODELLING IN ANSYS Fig 5.5:- Frce and Supprts acting n CFST clumn 1) Fig 5.1:- Input data required fr CFST COLUMN Fig 5.6:- Equivalent Stress acting n CFST clumn Fig 5.2:- Prperties f CFST materials Fig 5.7:- Ttal Defrmatin n CFST clumns 2018, IRJET Impact Factr value: ISO 9001:2008 Certified Jurnal Page 1264

7 6.0 RESULTS AND DISCUSSIONS Table 6.1 Variatin f crippling lad fr different L/D ratis L/D CRIPPLING LOAD(KN) Table 6.3 Cmparisn f crippling lad and ANSYS fr different L/D ratis L/D CRIPPLING LOAD (KN) ANSYS(KN) Fig 6.1 Graph shwing variatin f crippling lad fr different L/D ratis Frm the abve graph, as value f L/D rati increases value f crippling lad decreases gradually Table 6.2 Variatin f crippling lad in ANSYS fr different L/D ratis L/D ANSYS(KN) Fig 6.3 Graph shwing variatin f crippling lad and ANSYS fr different L/D ratis Graph shws the variatin f crippling lads by EULERS frmula and ANSYS fr different values f L/D rati Table 6.4 Variatin f crippling lad fr different D/t ratis D/t CRIPPLING LOAD(KN) Fig 6.2 Graph shwing variatin f crippling lad in ANSYS fr different L/D ratis Fig 6.4 Graph shwing variatin f crippling lad fr different D/t ratis Frm the abve graph, as value f L/D rati increases value f crippling lad in ANSYS decreases gradually Frm the abve graph, as value f D/t rati increases value f crippling lad increases gradually 2018, IRJET Impact Factr value: ISO 9001:2008 Certified Jurnal Page 1265

8 Table 6.5 Variatin f crippling lad in ANSYS fr different D/t ratis D/t ANSYS(KN) Graph shws the variatin f crippling lads by EULERS frmula and ANSYS fr different values f D/t Frm the abve graph, as value f D/t rati increases value f crippling lads in Euler s frmula and ANSYS increases gradually. Table 6.7 Defrmatin and Stress crrespnding t varius thickness f CFST cncrete Thickness(mm) Stress(MPa) Defrmatin(mm) SUMMARY AND CONCLUSIONS 7.1 SUMMARY Fig 6.5 Graph shwing variatin f crippling lad in ANSYS fr different D/t ratis Frm the abve graph, as value f D/t rati increases value f crippling lad in ANSYS increases gradually Rle f cncrete and steel in cnstructin is s prlific that research and develpmental effrts t augment, mdify and supplement these tw materials are a cntinuus prcess. Twards this, intrductin f new materials r new technlgy either in cnstructin r in design t cmpensate fr weaknesses in bth materials is n the rise. Cncrete cmpsites, cnfined cncrete, cncrete filled steel tubular sectins. Table 6.6 Cmparisn f crippling lad and ANSYS fr different D/t ratis D/t Crippling ANSYS(KN) lad(kn) Fig 6.6 Graph shwing variatin f crippling lad and ANSYS fr different D/t ratis 7.2 CONCLUSIONS Based n these extensive experimental and analytical investigatins, imprtant cnclusins have been arrived at and they are as fllws: 2018, IRJET Impact Factr value: ISO 9001:2008 Certified Jurnal Page 1266 Fr cmpsite clumn with cncrete filled circular sectins, the cnfinement effect f cncrete increases the resistance t axial lad. As the value f L/T rati increases, the lad carrying capacity f the CFST clumns decreases As the value f D/t rati increases, the lad carrying capacity f the CFST clumn increases. The lcal buckling f steel tube gets delayed due t the in-filled cncrete. Results f the numerical simulatins were cmpared with the theretical frmulae. Apparently, gd agreement has been btained frm the cmparisn. The buckling failure can be avided and the lad carrying capacity can be increased by lwering the slenderness rati fr CFST clumns. It was bserved frm the analysis f different data, the failure mde f the CFST cmpsite clumn depends n slenderness rati. When the slenderness rati is very less, the clumn fails due t lcal buckling f steel nearer t the supprt and crushing f cncrete under direct cmpressin. When the

9 slenderness rati is large, the clumn fails by elastic buckling. 2) SCOPE FOR FURTHER RESEARCH WORK 1. A detailed study needs t be made n beam clumn and clumn-clumn cnnectins t the CFST clumns. 2. Further research is required t cnsider general bundary cnditins and the effect f this n the laddeflectin behavir f the cncrete filled steel tubular clumns. This culd prvide mre helpful recmmendatins fr varius design aspects. 3. The study f cnfinement effect can be extended t ther L/D ratis and D/t ratis and the behavir can als be studied fr different supprt cnditins. 4. Experimental investigatins can als be carried ut n eccentrically laded cmpsite clumns. 5. The study can als be extended t cyclic lading and transverse lading. 6. In the present investigatin t study the influence f cnfinement f cncrete M 30 grade f cncrete alne has been used. The study can als be extended t cver ther higher grades f cncrete. 7. Experimental investigatins can als be carried ut n design and detailing f shear cnnectrs between steel and cncrete interface, when the mment is the predminant frce. REFERENCES [1] Ahmed Elr y and Azizinamini (2002) Behavir and Strength f Circular Cncrete-Filled Tube Clumns, Jurnal f Cnstructinal Steel Research, Vl. 58, pp shsuke [2] Mrin and KeigTsuda (2003) Design and Cnstructin f Cncrete Filled Steel Tube Clumn System in Japan, Earthquake Engineering and Engineering Seismlgy, Vl. 4, N. 1, pp [3] Hatzigergiu G.D. and Besks D.E. (2005) Minimum Cst Design f Fiber Reinfrced Cncrete Filled Steel Tubular Clumns, Jurnal f Cnstructinal Steel Research, 61, pp [4] Jane Helena H., Neelamegam M. and Samuel Knight G.M. (2007) Investigatin n the Behavir f Cncrete Filled Clumns, Jurnal f Structural Engineering, Vl. 34, N. 4, pp [5] Shams M. and Saadeghvaziri M.A. (1999) Nn-linear Respnse f Cncrete-Filled Steel Tubular Clumns under Axial Lading, ACI Structural Jurnal, Vl. 96, N. 6, pp [6] Yi Zheng, Tsutmu Usami and HanbinGe (2000) Ductility f Thin-Walled Steel Bx Stub Clumns, Jurnal f Structural Engineering, ASCE, Vl. 126, N. 11, pp [7] Dalin Liu (2005) Tests n High - Strength Rectangular Cncrete Filled Steel Hllw Sectin Stub Clumns, Jurnal f Cnstructinal Steel Research, Vl. 61, pp [8] Lin-Hai Han, Wei Liu and Yu-Fu Yang (2008) Behavir f Cncrete Filled Steel Tubular Stub Clumns Subjected t Axially Lcal Cmpressin, Jurnal f Cnstructinal Steel Research, Vl. 64, pp [9] [9] Brain Uy (2000) Strength f Shrt Cncrete Filled Steel Bx Clumns Incrprating Lcal Buckling, Jurnal f Structural Engineering, ASCE, Vl. 126, N. 3, pp [10] Brain Uy (2001) Lcal and Pst-lcal Buckling f Fabricated Steel and Cmpsite Crss Sectins, Jurnal f Structural Engineering, ASCE, Vl. 127, N. 6, pp [11] Brain Uy (2001) Strength f Shrt Cncrete Filled High Strength Steel Bx Clumns, Jurnal f Cnstructinal Steel Research, Vl. 57, pp [12] Brain Uy (2003) High Strength Steel-Cncrete Cmpsite Clumns fr Buildings, Structures and Buildings Prceedings f the Institutin f Civil Engineers, Vl. 156, N. 1, pp [13] Zeghichea J. and Chaui K. (2005) An Experimental Behavir f Cncrete Filled Steel Tubular Clumns, Jurnal f Cnstructinal Steel Research, Vl. 61, pp [14] Gpal S.R. and Manharan P.D. (2006) Experimental Behavir f Eccentrically Laded Slender Circular Hllw Steel Clumns In-filled with Fiber Reinfrced Cncrete, Jurnal f Cnstructinal Steel Research, Vl. 62, pp [15] Chu S.M., Chai G.B. and Ling L. (2000) Finite Element Technique fr Design f Stub Clumns, Thin Walled Structures, Vl. 37, pp [16] Liang Q.Q., Uy B. and Liew J.Y.R. (2000) Nnlinear Analysis f Cncrete Filled Thin-Walled Steel Bx Clumns with Lcal Buckling Effects, Jurnal f Cnstructinal Steel Research, Vl. 62, pp [17] Huang C.S., Yeh Y.K., Liu G.Y., Hu H.T., Tsai K.C., WengY.T.,Wang S.H. and Wu M.H. (2002) Axial Lad Behavir f Stiffened Cncrete-Filled Steel Clumns, Jurnal f Structural Engineering, ASCE, Vl. 128, N. 9, pp [18] Hsuan-Teh Hu, Huang C.S., Wu M.H. and Wu Y.M. (2003) Nnlinear Analysis f Axially Laded Cncrete Filled Tube Clumns with Cnfinement Effect, Jurnal f Structural Engineering, ASCE, Vl. 129, N. 10, pp [19] Shilpa Sara Kurian, Dinu Paulse, Sreepriya Mhan, Study n Cncrete Filled Steel Tubes, IOSR Jurnal f Mechanical and Civil Engineering (IOSR-JMCE) e- ISSN: , p-issn: x pp , IRJET Impact Factr value: ISO 9001:2008 Certified Jurnal Page 1267