Modeling of High Strength Concrete Columns Confined with GFRP Wraps

Transcription

1 Mdeling f High Strength Cncrete Clumns Cnfined with GFRP Wraps Ramamrthy.K* Assistant Prfessr CKCET Tamilnadu, INDIA ramu.sep5@gmail.cm Tamilamuthan.B Assistant Prfessr CKCET Tamilnadu, INDIA b.tamilamuthan@gmail.cm Abstract :Fibre reinfrced plymer cnfined clumns have been develped fr new cnstructin rehabilitatin f cncrete structures such as piers/piles in civil engineering field. The design riented cnfinement mdel predminant in designing FRP cnfined cncrete clumns. The design mdel is directly based n in interpretatin f experimental result. In this study ne mdel is presented fr reinfrced cncrete clumns externally reinfrced with fibre reinfrced plymer wraps using finite element methd adpted by ANSYS sftware. The finite element mdel was develped using fr cncrete and the three dimensinal layer elements fr the fibre reinfrced plymer cmpsites. The result btained frm thse finite element analysis results were cmpared n the experimental data fr respective cncrete clumn with different cnditins frm researcher. Frm the analysis lad-deflectin, stress strain relatinship, perfrmance characteristics f GFRP wrapped clumn were als t be studied. The predictin f ANSYS mdel agreed with the experimental results. Key wrds: ANSYS, Fibre reinfrced plymer, Finite element analysis 1.1General R 1.0 INTRODUCTION einfrced Cncrete clumns have an imprtant functin in the structural cncept f many structures. Often, these clumns are vulnerable t exceptinal lads (such as impact, explsin, r seismic lads), cnfinement f cncrete is an efficient technique t increase the lad-carrying capacity and ductility f cncrete clumns primarily subjected t cmpressin. By prviding lateral cnfining pressure, the cncrete is subjected t a triaxial state f stress, s that the cmpressive strength and defrmability increase. The lateral cnfining actin is mstly induced in a passive way by restraining the lateral expansin f the cncrete thrugh clsely spaced stirrup r hp reinfrcement. Since the intrductin f FRP as externally bnded reinfrcement, cnfinement by means f FRP wrapping has been f cnsiderable interest fr upgrading clumns, piers, and chimneys. * Crrespnding Authr 1.2 Finite Element Mdeling Reinfrced cncrete structures are cmmnly designed t satisfy bth serviceability and safety criteria. T ensure the serviceability requirement, predictin f cracking and estimatin f deflectin under service lads need t be cnsidered. T meet the safety r strength Requirement, an accurate estimatin f the ultimate lad is essential but it is als desirable t predict lad-defrmatin characteristics f the structure. Because f the cmplexities assciated with the develpment f ratinal analytical prcedures fr reinfrced cncrete, many design methds still rely n the empirical apprach, using the test results frm a large number f experiments. Nwadays, with the availability f inexpensive and high-perfrmance cmputers and well-develped FEA sftware, FEA is nw a pwerful and general analytical tl t mdel the behavir f structural cncrete. Thrugh FEA, imprtant parameters like

2 stress-strain relatinships, cracking mdel, etc., thse have significant influence n the structural cncrete behavir can be cnveniently and systematically investigated. Hwever, the need fr sme frm f experimental research still cntinues t prvide a firm basis fr design equatins. Experimental data als supply the much needed infrmatin, e.g. material prperty, t validate the mathematical mdels fr FEA. On the ther hand, reliable FE mdels can cnsiderably cut dwn the number f experiments required, hence reducing bth time and cst f slving a given prblem (.H. Maneetes A. M. Memari Electrnic Jurnal f Structural Engineering, 2009) The study als lks int the strength mdeling f FRP cnfined cncrete that is the effective circumferential FRP failure strain and the effect f increasing cnfining actin. Different mdels are reviewed and were used t predict the ultimate strength. The experimental and analytical results are cmpared with thse result btained by the previusly published mdels. 1.3 High Strength Cncrete High strength slely n the basis f cmpressive strength at a given age. Befre the advent f superplastizers, cncrete mixtures that shwed 40 Mpa r mre cmpressive strength at 28 days. Later when 60 t 120 Mpa cncrete mixtures becames cmmercially available. Cnventinal practice is t specify cncrete strength based n 28 day test result there is a grwing mvement t specify the 56- r 90 day strength because many structural elements are nt fully laded fr perid as lng as tw r three mnths r even lnger. When high strength is nt needed at an early age, it is best nt t specify it s achieve a number f benefits such as cement saving, ability t use relatively large prprtins r mineral admixtures, and a mre durable prduct Applicatins f High strength cncrete Exceptinal benefits, bth technical and ecnmical, have been derived using highstrength cncrete. Because f these benefits, High-strength cncrete is nw being regularly used in many applicatins, including buildings, ffshre structures, bridge elements, verlays, and pavements. High-strength cncrete is ften used in structures nt because f its strength, but because f ther engineering prperties that cme with higher strength, such as increased static mdulus f elasticity (stiffness), decreased permeability t injurius materials, r high abrasin resistance. 1.4 Fibre Reinfrced Plymer Fibre reinfrced plymer cmpsite are fabricated frm fibres such as glass carbn, aramid and brn, unlike materials such as steel and allys. In additin t using cmpsite fr stand alne lad carrying cmpnents such as prefabricated bridges, mdules beams and girders. They can be able t use in cnjuctin with cncrete and steel as lad shares elements. Fr example glass fibre reinfrced plymer (GFRP) can be used as reinfrcement fr cncrete members in lieu f cnventinal steel reinfrcing bars. Carbn fibre reinfrced plymer (CFRP) strips can used as a external reinfrcement fr increasing the lad carrying capacity f cnventinal steel and reinfrced cncrete Classificatin f FRP Three main fibre types are: Glass Carbn Aramid Glass fibres are silica-based glass cmpunds cntaining metal xides. E-Glass fibres are electrical insulatrs and are the mst widely used. S-type fibres exhibit higher strength than E- glass and crrsin prperties. Carbn fibres are mre brittle and shw galvanic crrsin next t metals. Aramid fibres have a high tensile strength and are very flexible Different frms f GFRP Fibres Wven Rving Rving in a grup f strand which is mre f unifrm prduct. This is the basic frm f cmmercial fibres. Rving is a grup f number f stand is als called as direct pull rving the entire rving is frmed at ne time.

3 Uni Directinal Clth These are similar t rving but differ in the weave type and ther rientatin based n the manufacturing prcess. The same rving prduct mentined is als used as input t wven rving reinfrcement. Prduct is defined by eave type, which can be at 0&90,0,+45,-45& ther rientatins depending upn the manufacturing prcess. Stranded Mats These are tw dimensinal arrays f chpped strands. The fibre strands are depsited int a cntinues cnveyr and pass thrugh a regin where thermsetting resin is dusted n them. This resin is heat set and hlds t the mat tgether. The binder resin disslves in the plyester r vinyl ester matrix there by allwing the mat t cnfirm t the muld. 1.5 Fibre Reinfrced Plymer Cnfinement f Cncrete In fibre reinfrced plymer cnfined cncrete the cncrete cre expand laterally when it is subjected t axial cmpressin lad. This expansin f cncrete cre is cnfined by the Fibre reinfrced plymer jackets, thus transfrms the cncrete cre t a three dimensinal cmpressive stress cnditin. The three dimensinal stress cnditins serve t significantly increase the strength and ductility f brittle cncrete. Cmpared with ther cylindrical clumns, FRP cnfined cncrete clumns behave uniquely when subjected t an axial cmpressin lad. The FRP begins t cnfine the cncrete shrtly after when uncnfined strength is reached. It then reverses the directin f the vlumetric respnse, and the cncrete respnds thrugh large and stable vlume cntractin. As a result, the stress-strain curve is characterized by a distinct bilinear respnse with a transitin zne at a stress level near the strength f uncnfined cncrete. 2.0 REVIEW OF LITERATURE The Fiber reinfrced plymer (FRP) cnfined cncrete clumn shws a unique bilinear behavir when subjected t an axial cmpressive lad. Stress-strain plt reveals that FRP cnfines the cncrete shrtly after the cncrete has reached its ultimate cmpressive strength. Therefre FRP cnfinement f the cncrete a prper stress-strain mdel has t be develped. Sme f the reprts have been presented in this chapter. Salvadr Martinez, A.H.Nilsn and Flyd O.Slate (1984) investigated the respnse f high strength cncrete clumn, cnfined by steel spirals, using 94 shrt clumns f 4, 5, and 6 in. (102, 127, and 152 mm) diameter. Main variables were cmpressive strength f the cncrete, amunt f cnfinement, and specimen size. Mst were cast withut prtective cncrete cver ver the spirals, but 16 specimens with cver were used. The specimens were tested under shrt term cmpressive lading. Authrs reprted strength and defrmatin characteristics that the cnfinement frm spirals reinfrcement. Salim R. Razvi and Murat Saatciglu (1999) prpsed the stress-strain relatinship fr high strength cncrete cnfined by transverse reinfrcement. The strength f cncrete range frm 30 t 130 Mpa. The relevant parameters f cnfinement that have been bserved t play imprtant rles in clumn tests. These parameters include the type, vlumetric rati, spacing, yield strength, and arrangement f transverse reinfrcement as well as cncrete strength and sectin gemetry. Cncrete cnfined by spirals, rectilinear hps, crss ties, welded wire fabric, and cmbinatins f these reinfrcements. The specimen test under cncentric and eccentric lads, as well as slw and fast strain rates. The mdel has been verified extensively against experimental data. Girand and Bastien (2002) studied the behaviur f reinfrced cncrete clumns cnfined by lateral ties using a finite element bnd slip mdel. The mdel was capable f accunting fr the cnfinement prvided by hp reinfrcement, sftening f cncrete and fr the gradual lss f bnd between cncrete and steel. The results f finite element simulatin agreed well with the experimental results reprted by ther researchers. Legern and Paultre (2003) prpsed a mdel fr predicting the behaviur f steel tie cnfined circular clumns with nrmal strength and high strength cncrete cre. The mdel was applicable fr clumns having internal steel reinfrcement. The effectiveness f hp steel cnfinement was measured using a dimensinless parameter which was related t the amunt f transverse reinfrcement, cmpressive strength f cncrete and yield strength f transverse reinfrcement. The results predicted by the mdel agreed well with large number f published results fr bth cncentrically laded clumns and

4 clumns subjected t cnstant axial lad and reversed cyclic flexure. Umesh K.Sharma, Pradeep bhargava and S.K.Kaushik (2004) were studied the behaviur f high strength cncrete shrt clumn cnfined by spiral and square ties. The test variables Included vlumetric rati, spacing f Yield strength f transverse reinfrcement, lngitudinal reinfrcement rati, lateral steel cnfiguratin. Authrs presented effect f variables n uniaxial behaviur f high strength clumn. Authrs discussed the results indicate that mre cnfinement is required in clumns high strength cncrete than in clumns f lw strength cncrete t achieve the desired pst-peak defrmability and behaviur f high strength clumns is characterized by the sudden spalling f cncrete cver leading t a lss f axial capacity. Hadi and Li (2004) cnducted an investigatin n behaviur f high strength cncrete clumns with FRP cnfinement. The specimens were cnfined using carbn, glass and Kevlar fibre reinfrced plymer f varying thicknesses and subjected t cncentric as well as eccentric lading. The authrs cncluded that all clumns failed in a brittle manner. The failure f uncnfined clumns was highly explsive. Under cncentric lading cnditins, cnfinement using Kevlar FRP resulted in sme increase f deflectin and ductility ver the uncnfined specimens. Carbn fibre wrapped specimens with single layer failed explsively, while thse with three layers seemed t appear integral withut any damage t the wrap even after failure f the clumn. Under eccentric lading, carbn FRP cnfined clumns failed explsively, while kevlar and glass FRP cnfined specimens shwed adequate warning in the frm f white patches n FRP surface at the time f initiatin f failure. Hsia-Lin Cheng (2004) presented n a sensitivity study and design prcedure fr FRP wrapped RC circular clumns, subjected t an axial lad and equal end mments. The parameters used in the study include the uncnfined cncrete strength, steel rati, thickness f FRP wraps and the sectin diameter. Interactin equatins were als develped in this wrk t prvide a simplified and practical tl fr engineers t evaluate the ultimate strength f the FRP wrapped clumns. The authr cncluded that FRP wraps significantly increase the ultimate strength f RC clumns. The rate f increase in strength increases prprtinally t the increase in FRP layer thickness. Hwever, in terms f the effect f the steel rati, it has been fund that the rate f increase in strength is lwer fr higher levels f steel rati. The prpsed interactin equatin has been verified fr a simply supprted FRP wrapped clumn subjected t equal end mments and fund that these equatins are reliable fr predicting the ultimate strength. Malvar (2004) prpsed a numerical mdel fr FRP cnfined cncrete element fr use with Finite Element Analysis (FEA) sftware. The simulatins carried ut using the mdel agreed well with experimental results published by several researchers fr cncrete withut any cnfinement and cncrete cnfined by Aramid, carbn and glass FRP. The mdel was als used t estimate the maximum pssible enhancement in strength that can be achieved by increasing the number f layers f FRP, since the additin f FRP layers did nt always lead t crrespnding increase in strength f cnfined cncrete. Tavi.T and Tata.A (2009) develped a finite element mdel fr the analysis f rectangular cncrete clumn under axial lading and mdeling f reinfrced cncrete structures failing in cmpressin. Cncrete were mdeled with 8nde slid elements and lngitudinal and transverse steels were mdeled as three dimensinal link elements available in the ANSYS element library. The authrs cncluded that the finite element mdel shwed that the peak stress, strain at the peak stress respectively. And als predicted the actual nnlinear f cnfined cncrete clumns. Under axial lading, the result f finite element simulatin such as stress strain relatinship, strength and ductility imprvement are agreed with the experimental results. 2.2 Objective and Scpe T expand the test database which cvers a larger range f design parameters which affect the cnfined cncrete strength. T develp, a three dimensinal finite element mdel fr FRP wrapped cncrete clumn, by cnsidering all the material prperties f the FRP and the cncrete. ANSYS FEM sftware was used t develp the mdel fr predicting the strength, defrmatin; perfrmance characteristics f FRP cnfined reinfrced cncrete clumns. The mdeling results were cmpared and validated using the experimental results available in the literature.

5 An attempt was made t explre a pssible apprach fr develping a cnfinement mdel based n the analyses f the test database. Analytical slutins fr limiting cases f FRP cnfined cncrete were als develped. 2.3 Methdlgy These mdels are usually divided int tw categries Design Oriented Mdels and Analysis Oriented Mdels. Design riented mdels are clsed-frm equatins and are directly based n the interpretatin f experimental results. Analysis riented mdels, n the ther hand, are generated using an incremental numerical prcedure by cnsidering radial strain cmpatibility. In this wrk, a 3-D finite element mdel was created using ANSYS. Data frm different published experimental results were cllected and the develped 3-D mdel was validated by using thse results. An analytical slutin was develped and the reliability f the develped mdel was checked. Different ranges f design parameters affecting the cnfined cncrete strength were cnsidered mdel was checked. Different ranges f design parameters affecting the cnfined cncrete strength were cnsidered. A test database was created with cmbinatins f these parameters. The test database was analysed and parameters affecting the cnfinement effectiveness were identified. Based n the analyses f the test data, perfrmance parameters such as strength, defrmatin were als predicted. 3.0 EXPERIMENTAL INVESTIGATION 3.1 General Experimental investigatin was carried ut n seven clumns having similar slenderness rati, different wrap thickness and wrap materials. The specimen cnsisted f clumn having 150mm diameter and 900mm height. All the specimens were tested in a lading frame f 2000KN capacity till failure. 3.2 Materials High strength cncrete, ribbed tr steel bars fr lngitudinal reinfrcement, mild steel fr lateral ties and Glass fibre reinfrced Plymer (GFRP) were used Cncrete The mix rati fr design strength f 60 MPa was 1:1.35:2.14:0.29:0.8(1 part f cement,1.35 parts f fine aggregate,2.14 parts f carse aggregate 0.29 parts f water and 0.8% parts super plasticizer. The characteristic cmpressive strength f cncrete btained frm labratry test was Steel High yield strength Defrmed (HYSD) having yield strength f 415 MPa were used fr lngitudinal reinfrcement.fe250 grade mild steel bars were used fr lateral ties Glass fibres A Glass fibre having the fllwing cnfiguratin was used fr the investigatin. i. Chpped Strand Mat(CSM) ii. iii. Uni-Directinal Clth(UDC) Wven Rven(WR) The glass fibre fabrics were applied n the surface f the clumn using is-phthalic resin t frm the wrap material. The aspect rati f fibres used in chpped strand mat was The CSM fabric was prepared using interwven, randmly riented E- glass fibres, WR had fibres running at 45º t the lngitudinal axis f the fabric, UDC had fibres riented at 0º t the lngitudinal axis f the fabric. All the fibres had a fibre distributin f 450 GSM. Table 1: Prperties f Resin Sl.N Prperty Value 1. Density(Kg/m3) Elasticity mdulus(gpa) Shear Mdulus (GPa) 8 4. Pissn s Rati Tensile strength (Mpa) Cmpressive strength (MPa) Shear strength (MPa) Tensile strain at Break (%) Apprximate Fracture Energy s (j/m2) Water Absrptin: 7-days -25 C (%) C-efficient f thermal expansin (10-6/ C) Glass transitin temperature ( C)

6 3.2.4 Resin fr FRP Is-pthalic plyster resin was used fr the preparatin f the fibre Reinfrced Plymer. The prperties f the epxy resin used fr the study are presented in table. Table 2: Prperties f FRP Typical Prperties E-glass S-glass Carbnhigh strength Carbnhigh mdulus Carbn- Ultra- high mdulus Kel var 29 Kel var 49 Density (g/cm 3 ) Tensile Elngatin (%) Tensile strength (%) Yung s mdulus (Gpa) THREE DIMENSIONAL MODELING OF FRP WRAPPED REINFORCED CONCRETE COLUMN 4.1 Intrductin Typically, the behaviur f reinfrced cncrete clumns is studied by full scale experimental investigatins the result are cmpared t theretical calculatins that estimates internal stress/strain distributins within the clumns. Finite element analysis can als be used t mdel the behaviur numerically t cnfirm these calculatins, as well as t prvide a valuable supplement t the labratry investigatins. Particularly in parametric studies finite element analysis as used in structural Engineering. The verall behaviur f a structure by dividing it int a number f simple elements, each f which has well defined mechanical and physical prperties. Mdeling the cmplex behaviur f reinfrced cncrete which is bth Nn- hmgeneus and anistrpic, mst early finite element mdels f reinfrced cncrete included the effects f cracking based n a predefined crack pattern (Ng and Scrdelis 1967, Nilsn 1968) with this apprach changes in the tplgy f the mdels were required at the lad increased. Therefre the ease and speed f the analysis were limited. A smeared cracking apprach was intrduced using isparametric frmulatin t represent the cracked cncrete. As a rthtrpic material (Rashid 1980).In the smeared Apprach, cracking f cncrete ccurs when the principle tensile stress exceeds the ultimate tensile strength f the elastic mdulus f the material is then assumed t be zer in the directin (suidan and schnbrich1978). Recently sme researchers attempted t stimulate the behaviur f reinfrced cncrete cnfined fiber reinfrced plymer cmpsite using the finite element methd. M. Rashidi and M.N.S Hadi (2007) develped a nn-linear finite element mdel t stimulate the behaviur f high strength cncrete clumns cnfined by carbn -fibre-reinfrced plymer (CFRP) jackets and reinfrced with axial and helical steel bars. The authr prpsed in the finite element analysis, the material and gementric nnlinearities are taken int accunt and the results f material testing f the cnstituent materials are explred t set up the mdel, creating the whle clumn has had the mst accurate utcmes amng all the alternatives which were examined t achieve an apprpriate mdel as a representative f the true specimen. The authr cncluded there was a gd crrelatin between the axial lad deflectin results f experimental test and the finite element mdel f the cncentrically laded clumns shwing that the develped mdel t be viable. Mran and Pantelides (2002) develped a stress-strain mdel using bilinear mdel. Their mdel was based n tw cncepts which were, increase in plastic cmpressive strength f FRPcnfined cncrete and the kinematic restraint prvided by the FRP jacket and a variable strain ductility rati in which the increase in plastic cmpressive strain as a functin f the stiffness f

7 the FRP cmpsite jacket, the type f bnd between the FRP cmpsite and the cncrete cre and the extent f internal damage in cncrete cre. Seven full size reinfrced clumns each clumns had a different cnfining schemes as described belw. A clumn with n fiber reinfrced plymer wrapping A clumn with unidirectinal GFRP wraps wrapped arund the sides.the directin f fiber was perpendicular t the length f the clumn. A clumn with Wven Rven GFRP wraps wrapped arund the sides.the directin f fiber was perpendicular t the length f the clumn. Similarly a clumn with chpped strand mat GFRP wraps. The current study presents results frm the finite element analysis f seven full scale clumns. The finete element mdel used a smeared cracking apprach and three dimensinal layered elements t mdel FRP cmpsite cmparisn between finete element results and thse frm the experimental clumns are shwn. Fig.1: Slid65 Element Gemetry A Link8 element was used t mdel the steel reinfrcement. Tw ndes are required fr this element. Each nde has three degrees f freedm, translatins in the ndal x, y, and z directins. The element is als capable f plastic defrmatin. The gemetry and nde lcatins fr this element type are shwn in Figure 4.2 The ANSYS finete element prgram (ANSYS 10.0) perating n a UNIX system was used in this study t stimulate the behaviur f seven experimental clumns.in general cnclusins and methds wuld be very similar using ther nnlinear FEA prgrams each prgram, hwever has its wn nmenclature and specialized elements and analysis prcedure that need prperly. 4.2 Element Types 4.2.1Reinfrced Cncrete An eight-nde slid element, Slid65, was used t mdel the cncrete. The slid element has eight ndes with three degrees f freedm at each nde translatins in the ndal x, y, and z directins. The element is capable f plastic defrmatin, cracking in three rthgnal directins, and crushing. The gemetry and nde lcatins fr this element type are shwn in Figure 2 Fig.2: Link8 Element Gemetry FRP Cmpsites A layered slid element, Slid46, was used t mdel the FRP cmpsites. The element allws fr up t 100 different material layers with different rientatins and rthtrpic material prperties in each layer. The element has three degrees f freedm at each nde and translatins in the ndal x, y, and z directins. The gemetry, nde lcatins, and the crdinate system are shwn in Figure 3

8 The shear transfer cefficient, β t, represents cnditins f the crack face. The value f β t ranges frm 0.0 t 1.0, with 0.0 representing a smth crack (cmplete lss f shear transfer) and 1.0 representing a rugh crack (n lss f shear transfer) A number f preliminary analyses were attempted in this study with varius values fr the shear transfer cefficient within this range, but cnvergence prblems were encuntered at lw lads with β t less than 0.2. Therefre, the shear transfer cefficient used in this study was equal t 0.2 Table 3: Summary f material prperties fr cncrete Fg 3: crdinate system 4.3 Material Prperties Cncrete: Cncrete is a quasi-brittle material and has different behavir in cmpressin and tensin. The tensile strength f cncrete is typically 8-15% f the cmpressive strength (Shah, et al. 1995). Ec 5000 Fr cncrete, ANSYS requires input data fr material prperties as fllws: Elastic mdulus (E c ).Ultimate uniaxial cmpressive strength (f c ).Ultimate uniaxial tensile strength (mdulus f rupture, fr).pissn s rati (ν).shear transfer cefficient (β t ).Cmpressive uniaxial stress-strain relatinship fr cncrete. The ultimate cncrete cmpressive and tensile strengths fr each clumn mdel were calculated by Equatins 4.1, and 4.2, respectively (IS ). Mdulus f Elasticity [ Ec ] f r 0.7 fck fck N / mm N / mm Where fck = Cmpressive strength (N/mm 2 ) Pisns rati [υ] υ =0.2 Mdulus f Rupture [ fr ], (Ultimate tensile strength) 2 2 (4.1) (4.2) MATERIAL PROPERTIES ELEMENT TYPE MATERIAL Cncrete Slid65 Elastic Mdulus Ex: Cncrete Pissn s Rati PRXY: 0.20 Multilinear Elastic STRAIN STRESS (N/mm 2) Shear crack at clsed face shfcl: 0.2 Shear crack at pen face shfp: 0.9 Ultimate tensile stress Utens: 5.09 N/mm 2 Ultimate cmpressive stress: N/mm Steel Reinfrcement The steel fr the finite element mdels was assumed t be an elastic-perfectly plastic material and identical in tensin and cmpressin. Pissn s rati f 0.3 was used fr the steel reinfrcement in this study (Gere and Timshenk 1997) Fibre Reinfrced Plymer Cmpsites The FRP cmpsites are anistrpic materials; that is, their prperties are nt the same in all directins. The xyz crdinate axes are

9 referred t as the principal material crdinates where the x directin is the same as the fiber directin, and the y and z directins are perpendicular t the x directin. Ey EE f m EmEf EV f m (4.7) In this study, the specially rthtrpic material is als transversely istrpic, where the prperties f the FRP cmpsites are nearly the same in any directin perpendicular t the fibers. Thus, the prperties in the y directin are the same as thse in the z directin. Fig.4: schematic f FRP cmpsite The prperties f istrpic materials, such as elastic mdulus and Pissn s rati, are identical in all directins; therefre n subscripts are required. This is nt the case with specially rthtrpic materials. Subscripts are needed t define prperties in the varius directins. Fr example, E x E y and ν xy ν yx. E x is the elastic mdulus in the fiber directin, and E y is the elastic mdulus in the y directin perpendicular t the fiber directin. Therefre, the rthtrpic material data are supplied in the ν xy r majr Pissn s rati frmat fr the ANSYS prgram. Table 4: Summary f material prperties fr FRP cmpsite Materials Elastic Mdulus Pissn s Rati Tensile Strength(MPa) Thickness Laminate(mm) f Chpped strand mat Chpped strand mat Wven Rven Wven Rven Uni directinal clth Uni directinal clth The material prperties f the FRP cmpsites are calculated using micr mechanics apprach. The equatins used fr the analysis are given belw E X = E f V f + E m V m (4. 6) Where E f = Mdulus f elasticity f the Fiber, Em = Mdulus f elasticity f the Matrix υ xy =V fυ f '+V m υ m Where υf = Pissn s rati f fiber, υm = Pissn s rati f matrix Frmatin f target parameters Output values were cnsidered as the target parameters. These values were taken frm the experimental result. Ultimate lad Axial deflectin Lateral deflectin Axial strain Lateral strain

10 Axial stress(n/mm2) Table 6 Training Mdel-1- Experimental Results Specimen Designatin Ultimate Lad (KN) Ultimate Axial Deflectin (mm) Ultimate lateral Deflectin (mm) Ultimate Axial strain με Ultimate Lateral strain με R UDC UDC CSM CSM WR WR RESULTS AND DISCUSSIONS The ANSYS finite element mdel has been created, trained and validated with the result cllected frm the literature. ANSYS results and actual values were cmpared and the percentages f errr were als predicted. Failure lad was taken when the maximum failure strain is t be arrived.the maximum failure strain was taken in the previus literature fr applied grade f cncrete. The axial stress distributins f clumn specimens R0, UDC, WR, and CSM, btained frm the ANSYS slutin are shwn in table.5.1. The axial stress cncentratins arund the lngitudinal reinfrcement als indicate similar axial stress distributins with the axial stress distributin in the actual clumn specimens. The axial stress-strain curves btained frm the ANSYS slutin are cnfirmed by the training mdel results. Frm the cmparisns shwn in Fig. 5.2, it shws that the predictins are in clse agreement with the experimental curves The linear stress-strain curves btained frm the ANSYS slutin are cnfirmed by the training mdel results fr FRP strengthening clumns. Frm the cmparisns shwn in Fig. 5.4, it shws that the predictins are in clse agreement with the experimental curves. Figure 5.5 illustrates the differences in laddeflectin behavir fr the fur clumns, and Figure 5.6 cmpares the seven finite element mdels figures shw that the stiffness f the clumn befre and after applying FRP strengthening is apprximately the same in the linear range. The accuracy f the prpsed prcedure is als cnfirmed by the clse values f maximum stress, strain at the maximum stress as well as strain when the stress drps t percent f the maximum stress btained frm the FEM analysis and the experimental test. Output frm the ANSYS finite element Analysis is given in tables EXPERI Lad(KN) ANSYS Fig 5: lad-stress plt fr cntrl clumn R0

11 Stress(N/mm2) Axialstress(N/mm2) Axial Stress(N/mm2) EXPERI ANSYS 10 ANSYS EXPERI Lateral Strain(mm/mm) Axial Strain(mm/mm) Fig 6: stress-strain plt fr cntrl clumn R ANSYS EXPERI Lateral Strain(mm/mm) Fig 7: stress-strain plt fr clumn CSM3 Fig 8: stress-strain plt fr wrapped clumn UDC3 The strain data frm the finite element analysis and the experimental data fr the FRP wrapped clumn have similar trends. Similar plt f strains in the FRP cnfined cncrete clumn has lwer strains than the experiment results, because f cracking lad frm the finite analysis als smaller in rder cmparing actual results. The finite element mdel fr the cmpressin member then has lwer strains than the experimental results at whatever ultimate lad cmes frm the ANSYS mdel. In case f S24CSM3 clumn the strain als reduced in rder cmparing training mdel results. This shws 24% reductin in strain cmparing actual result. In the case lad deflectin plt, the cntrl clumn, ther wrapped clumn frm bth the experimental and the finite element analysis are reasnable gd agreements. Finite element mdel is stiffer than actual clumns in the linear range by apprximately 6.8% and 10% respectively. In this case, in cntrl clumn the laddeflectin plt frm the finite element analysis mdel is stiffer than that frm the experimental

12 results by apprximately 6.8% the first failure lad fr the finite element analysis is 1020kN which is higher than the lad f 1000kN frm the experimental results by 2%. In the case f cntrl clumn large strains ccur fr the finite element mdel, whereas at a lad f 825KN t 900KN similar behaviur takes place fr the actual clumn. These lads are clse t the yielding lads f the steel. Fr applied lads frm 600 KN t maximum lad, the lad-strain plts frm the finite element mdel and the experimental results d nt crrelate well. That may cncluded experimental clumn exhibits nnlinear behaviur. The increases in failure strain values f cnventinal and GFRP wrapped clumns by 5.43% and 20 t 24% respectively when cmparing finite element mdel values t experimental values. 6.0 CONCLUSIONS Based n Experimental results and thse btained thrugh finite element analysis ANSYS based mdeling. Values f strain at the maximum stress as well as strain drps 20% t 25%.The maximum stress btained 75t 80 percent frm the FEM analysis cmpared t experimental test values. Clumns wrapped with unidirectinal clth glass reinfrced plymer shwed higher stress and higher ultimate strains result when cmpared t thse wrapped with ther type f FRP. Based n analytical mdeling fr FRP wrapped clumn, Energy ductility increased in the range f 13% t38% fr 5 mm thick wrapped clumn cmpared t 3mm thick wrapped clumns. Based n analytical mdeling fr FRP wrapped clumn, Deflectin ductility increased in the range f 3.7 % t 35% fr 5 mm thick wrapped clumn cmpared t 3mm thick wrapped clumns. The finite element mdel (FEM) has had the capability f ultimate stress and axial displacement predictin with an acceptable margin f errrs. It ffers very gd crrelatin between the nnlinear results f the axially laded clumns and the experimental utcmes. References [1] Matthews FL, GAO Davies, D Hitching and C Swuti finite element mdeling f cmpsite materials and structures. [2] Mta V.S Taly P.V.Vijay Gunga Ra Nasendra Reinfrced cncrete Design with FRP cmpsite. [3] Agarwal, B.D and Brutman, L.J. Analysis and perfrmance f fibre cmpsites, secnd editin, Wiley Intercurse, New Yrk. [4] Adams, V. and Askenazi, A. (1998), Building Better Prducts with Finite Element Analysis, On Wrd Press, Santa Fe, New Mexic. [5] Amir Mirmiran, Kenneth Zagers and Wenqing Yuan (2000), Nnlinear finite element mdelling f cncrete cnfined by fiber cmpsites, Published by Elsevier Science Ltd. [6] Amir Mirmiran, Mhsen Shahawy and Thmas Beitleman, (2001), Slenderness Limit fr Hybrid FRP-Cncrete Clumns Jurnal f cmpsites fr cnstructin Vl. 5, N. 1, [7] Ching Au and Oral Buyukzturk, Effect f Fiber Orientatin and Ply Mix n FRP-cnfined Cncrete. [8] Desayi.P and Krishnan, S. (1964), Equatin fr the Stress-Strain Curve f Cncrete, Jurnal f the American Cncrete Institute, 61, pp [9] Frederic Legern and Patrick Paultre, M.ASCE, (2003), Uniaxial Cnfinement Mdel fr Nrmal and High-Strength cncrete Clumns, Jurnal f Structural Engineering, Vl. 129, N. 2. [10] Frederic Legern and Patrick Paultre, (2003), Uniaxial Cnfinement Mdel fr Nrmal and High-Strength Cncrete Clumns, Jurnal f Structural Engineering, Vl. 129, N.2. [11] Gebran Karam and Mazen Tabbara, (2005), Cnfinement Effectiveness in Rectangular Cncrete Clumns with Fiber Reinfrced Plymer Wraps, Jurnal f cmpsites fr cnstructin Vl. 9, N. 5.

13 [12] Guqiang Li, Denesh Maricherla, Kumar Singh, Su-Seng Pang and Manu Jhn (2006) Effect f fiber rientatin n the structural behavir f FRP wrapped cncrete cylinders, Published by Elsevier Science Ltd. Authr s Bigraphy K.Ramamrthy btained his PG degree frm Annamalai University. His area f specializatin is Cnstructin Engineering and Management. He has Published 02 research papers in Internatinal Jurnals & 01 papers in internatinal cnferences. He has guided mre than 8 UG Prjects. B.Tamilamuthan btained his PG degree frm Annamalai University. His area f specializatin is Cnstructin Engineering and Management. He has Published 02 research papers in Internatinal Jurnals & 01 papers in internatinal cnferences. He has guided mre than 8 UG Prjects