ISSN: X Tikrit Journal of Engineering Sciences available online at:

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1 Tikrit Joural of Egieerig Siees (6) (13) 4-36 ISSN: X Tikrit Joural of Egieerig Siees available olie at: Behavior ad Desig of artially-eased Composite Beam-Colums Jasim Ali Abdullah, ad Oday Asal Salih Civil Egieerig Departmet, Egieerig College, Mosul Uiversity, Neawa rovie, Republi of Iraq (Reeived 8 May1, Aepted 1 November 1, Available olie 18 September13) ABSTRACT artially-eased omposite beam-olums subjeted to axial ompressive ad trasverse loads were aalyzed usig a proposed aalytial method, fiite elemet modelig ad iteratioal approahes, iludig ACI-318, AISC-LRFD ad Euroode4. I additio, flexural stiffess (EI) was predited usig the reommeded formulas i ACI-318 ad EC4. The results were ompared with experimetal data to verify of the reliability of these results. The aalysis proved that the proposed method ould be used for desig the partiallyeased beam-olums. Researh results also idiate that this method gives muh lose solutio to experimetal data. The behavior ad deformatio shape of speimes were lose to those foud usig FEM. The predited EI from EC4 was reliable i alulatig the bedig momet usig the proposed method while a sigifiat differee i defletio values was prooued usig predited EI from ACI formula. From alulatios, it was foud that the ACI-318 approah is aurate ad reliable i the desig of partially-eased beam-olums. Keywords: artially-eased; Composite beam-olum; Deformatio shape; Fiite elemet modelig; Flexural stiffess. سلوكية و تصميم االعمدة-الجسور الخرسانية المركبة والمغلفة جزئيا الخالصة تم في هذا البحث تحليل نماذج )عمود-جسر( من الخرسانة المسلحة و المغلفة جزئيا بمقطع حديدي معرضة الى حمل محوري واخر جانبي باستخدام طريقة مقترحة وطريقة العناصر المحددة فضال عن ثالثة طرق تصميم عالمية هي ACI-318 و AISC- LRFD و.Euroode 4 تم حساب صالبة االنحناء (EI) باعتماد طريقتين متضمنتين في ACI و. EC4 اظهرت الطريقة المقترحة نتائج مقبولة جدا عندما تكون صالبة االنحناء (EI) محسوبة من الطريقة المقترحة في EC4 و يمكن اعتمادها في تصميم هذا النوع من االعمدة-الجسور. كما اظهرت النتائج ان موديل العناصر المحددة اعطى نتائج مطابقة الى حد كبير مع النتائج العملية. اظهرت النتائج ان طريقة تصميم المقترحة في المواصفات االمريكية ACI لألعمدة المأخوذة في هذه الدراسة متطابقة الى حد كبير مع النتائج العملية. الكلمات الدالة: مغطى جزئيا, عمود-جسر مركب, شكل التشوه, نمذجة عناصر محددة, صالبة انحناء. * Correspodig author: address: Jassim4676@yahoo.om

2 5 Nomelatures δ The maximum defletio. : the relative slederess. A : Area of orete. A r : area of steel profile. A s : area of steel reiforemet. C m : a oeffiiet based o elasti first-order aalysis. COV: the oeffiiet of variae. E : elastiity modulus of orete. E m : seat modulus of elastiity of orete. EI: the flexural stiffess. E m : modulus of elastiity. E s : elastiity modulus of steel. f / : ompressive stregth of orete. F my : modified yield stress. F y : tesile stregth of steel reiforemet. F yr : tesile stregth of steel profile. I g : gross momet of iertia. I s : the steel momet of iertia. KL: the effetive legth of olum. L: the legth of the speime. M : Fatored momet. M : the magifiatio momet. M it : the iteral momet. M max : the maximum momet. M Sd : the desig momet. : the axial load. : ritial load of olum. e : Euler load. : omial axial apaity. o : pure axial apaity. Q: the lateral load. r m : radius of gyratio. SD: the stadard deviatio. y o : the defletio that would exist (if the axial fore were abset). α: the level of sigifiae differee Itrodutio artially eased steel profiles are oe type of omposite members used i omposite strutures. The partially eased steel omposite member osists of strutural steel setio plaed i a reifored orete betwee the flages. The strutural steel is rolled or built-up shape. Derivig beefits from ombiig the strutural steel ad reifored orete, the omposite members possess great load-arryig apaity ad stiffess owig to omposite atio. Further, the two edges orete easemet a partially serve for fire protetio, the use of ovetioal steel oetios to the flages as well as the redutio or omissio of formwork. Therefore, the use of the omposite members i multi-storey buildigs has bee proved more popular i reet years. May studies have evaluated the members resistaes aordig to the iteratioal odes ad suggested whih ode was loser to the experimetal data that have bee obtaied from previous studies. Mirza ad Laroix[1] have determied omparisos of stregths from 15 physial tests of retagular omposite steel orete olums available i the published literature with the stregths alulated from seleted omputatioal proedures are oduted. The omputatioal proedures ompared i their study iluded ACI 318, AISC-LRFD ad Euroode4. They reommeded that the ACI 318 proedure is loser to experimetal data. ACI 318 ad AISC-LRFD were used by Weg ad Ye[] to ivestigate the differee betwee these two approahes ad to evaluate the auray of their stregth preditios by omparig to 78 physial test results of orete-eased omposite olums doe by previous researhers. It idiated that the ACI-318 approah geerally gives loser preditios tha the AISC-LRFD approah. The ACI-318 permits the use of a momet magifier approah for the desig of sleder omposite olums. This approah is strogly iflueed by the effetive flexural stiffess (EI), whih varies due to the oliearity of the orete stress-strai urve ad the rakig alog the olum legth amog

3 6 other fators. Tikka ad Mirza[3] determied the ifluee of a full rage of variables o EI used for the desig of sleder, tied, omposite olums i whih steel shapes were eased i orete, ad also examied the existig ACI EI equatios. Approximately 1, isolated square omposite olums, eah with a differet ombiatio of speified properties of variables, were simulated ad used to geerate the stiffess data. The olums studied were subjeted to short-term ultimate loads ad equal opposite ed momets ausig symmetrial sigle urvature bedig about the major axis of the eased steel setio. They suggested a ew oliear equatio for EI i desig of sleder omposite olums subjeted to major axis bedig ad was proposed as a alterative to the existig ACI EI equatios. However, this study is a attempt to satisfy the followig objetives: 1. roposig aalytial method to predit the defletios ad momet apaities of partially-eased beam-olums sited i Elghazouli ad Treadway[4].. Testig the auray of flexural stiffess formulas reommeded by Euroode4 (EC4) ad ACI Developig FEM to predit the deformatio shape whih will be ompared with that foud usig the proposed method. 4. Usig three iteratioal approahes iludig ACI-318[7], AISC-LRFD[8] ad EC4[9] to predit the load resistae of the same beam-olum speimes. 5. Usig a statistial aalysis approah to examie whih approah gives lose experimetal-to-predited results. ACI 318[7], AISC-LRFD[8] ad EC4[9] are used to determie the resistaes of rosssetios for the beam-olums that have bee applied extreme lateral loadig, with or without o-existig axial loads represetig gravity oditios as show i Fig. 1, ad ompare the results with the experimetal data sited i Elghazouli ad Treadway[4]. Utilized Methods roposed Method The beam defletio ad olum stability are the mai problems oer with beamolum strutural members. These problems are aused by i-spa trasverse loadigs ad the axial fores (at ertai ritial values). The axial fore ats elarge the lateral defletio aused by the bedig effet to produe additioal lateral defletio ad momet i the member. These momet ad lateral defletio are alled seodary momet ad defletio[5]. The aalysis of a beam-olum is more ompliated tha a beam or a olum, losed-form solutio of the preset beamolums are available so log as they stay withi the elasti behavior i whih the momet a be related to the urvature by a liear relatioship. Approximate method was suggested by Che[6] for beam-olums subjeted to ed momets but i this paper is proposed to use the assumptio of this method to predit the ielasti behavior ad maximum momet of the beam-olums adopted herei that assumig the defleted shape of the member resembles a half-sie wave, so the defletio equatio will be x y si. (1) L from whih obtai x y os....() L L ad

4 7 y L x si L......(3) from the free body diagram show i Fig. (b.) a equilibrium equatio a be writte Q y x M but M it it EI y...(4)....(5) so equatio (4) a be writte as x Qx x si EI si L L L or where e x Qx si L L EI e (6)..(7) (8) e is Euler load whih ostitutes a importat referee load i the buklig ad stability aalysis of strutural members. The maximum defletio (δmax) ours at (x=l/) max QL....(9) 4 e the substitute the value of (δ) i equatio (1) ad take the first ad seod derivative to get the urvature equatio QL y 4 x si L e QL y 4 usig L L e M EIy.....(1) x si....(11)....(1) ad substitutig (x=l/) it a be yielded a maximum momet value M max QLe 4 e e... (13) omposite beam-olums. The types of elemets were arefully hose to simulate the parts of the adopted speimes with aurate model. The steel profile was simulated usig the four-ode isoparametri thi shell elemet with redued itegratio (S4R). A three-dimesioal isoparametri solid elemet (C3D8) was used to simulate the orete. Three-dimesioal truss elemet (T3D) was utilized i simulatio of the reiforig bars. The iteratio betwee reiforemet ad orete was modeled usig embedded elemet. The tie elemets were used to represet the otat betwee the thi-walled steel plates ad the orete. Differet mesh sizes were osidered to selet the reasoable mesh that provides aurate results with lesser omputatioal time. It was foud that a mesh size about 3 mm is the appropriate oe. The boudary oditios ad applyig loads of aalysis were modeled to follow the testig proedure performed by Elghazouli ad Treadway[4] as show i Fig. 1. The load was applied iremetally usig the Geeral Stati method available i ABAQUS. Mootoi uiform axial load similar to that i the tests was applied usig the displaemet otrol at odes of the ed. The time iremet of load did ot exeed 5% of the whole displaemet. I the preset model, the idealized elasti to perfetly plasti stress strai relatioship is used for utilized steel (i.e. reiforemet ad profile). The strai hardeig of steel is osidered as 1%. The orete was modeled usig damaged plastiity model available i ABAQUS software. Fiite Elemet Modelig (FEM) The software ABAQUS[11] was used to develop a oliear three-dimesioal (3D) FEM i simulatig the partially-eased

5 8 the desig of the partially-eased omposite olums follows the same proedure as that for the reifored orete olums. I otrast, the AISC-LRFD is based o aalogous to the steel olum desig. I the EC4 the resistae a be alulated from the ross setio ad olum axial fore bedig momet stregth iteratio diagrams. All ACI, AISC ad EC4 desig provisios a be applied to oreteeased strutural steel olums ad to orete-filled pipes or tubig. Setio h* b* t f* t w* r* HEA HEA HEAA * dimesio i (mm) Fig. 1.Details of partially-eased omposite profile ad applyig loads Iteratioal Approahes The most famous speifi regulatios for the desig of partially-eased omposite olums i the Uited States ad Europe are iluded i three differet sets of strutural desig speifiatios. Oe is the Buildig Code for Strutural Corete of the Ameria Corete Istitute (ACI-318), the seod is the speifiatio of Load ad Resistae Fator Desig (LRFD) published by Ameria Istitute of Steel Costrutio (AISC) ad the third is the Euroode4 (EC4). The ACI-318 for Fig.. roposed method assumptios (a.) half-sie wave alog the spa (b.) free body diagram of uttig ACI 318 Approah spa Chapter 1 of the ACI-318[7] buildig ode itrodues the oered stregth provisios for all kids of omposite olums. This approah requires that all olums be desiged as beam-olums trasferrig both shear ad bedig momet at joits. Uder uiaxial ompressio, the omial ompressive stregth, of a orete-eased omposite olum a be foud by summig up the axial-load apaities of the materials that make up the ross setio

6 9. 8, o. 85 f A F A F A.. (14) o yr The olums should be desiged aordig to the fatored fores ad momets from a seod-order aalysis. As a alterative to the seod-order aalysis, desig a be based o first-order elasti aalysis ad momet magifiatio approah. The magifiatio momet is expressed as M M s Cm s u 1.75 r y...(15) 1. s.....(16) C m =1. for members with trasverse loads betwee supports, M is Fatored momet ad is ritial load of olum, take EI KL as. To aout for the variatios i stiffess due to rakig, reep ad oliearity of orete, the EI value of above equatio a be oservatively take as (.E I g +E s I s ). The defletio is summatio of the imperfetio ad (y o ) whih is the defletio that would exist (if the axial fore were abset). AISC-LRFD approah Chapter I of the AISC-LRFD[8] speifiatio itrodues the oered stregth provisios for eased omposite olums. I this approah a modified yield stress Fmy, modulus of elastiity Em ad radius of gyratio rm were iorporated ito steel olum desig equatios for the desig of omposite olums. This proedure was preseted by the Task Group of the Strutural Stability Researh Couil (SSRC) i 1979[4]. The apaity of a partially-eased olum is determied from the same equatios as that for bare steel olums exept the formulas beig etered with modified properties F my, E m ad r m. For olums desiged o the basis of elasti aalysis, the fatored momet M u should be determied by a seod-order aalysis or by the momet magifiatio method. The momet ad defletio magifier B 1 is expressed as B Cm u 1 A F 1 s my (17) Where C m is a oeffiiet based o elasti first-order aalysis assumig o lateral traslatio, for ompressio members subjeted to trasverse loadig betwee their supports, C m =.85 for members whose eds are restraied ad C m =1. for members whose eds are urestraied. For a partially-eased omposite olum symmetrial about the plae of bedig, the iteratio of ompressive ad flexural loads should be limited by the followig biliear relatioship: u Ad u 8M u 9 M b M u M b for for Where =.85 ad b =.9. Euroode4 Approah...(18) u...(19) The Euroode4 ufatored axial load stregths (or bedig momet stregths i ases of pure bedig) should be omputed from the ross setio ad olum axial fore bedig momet stregth iteratio diagrams. The stregth iteratio diagrams are geerated for partially-eased olum u

7 3 ad are based o the assumptios ad requiremets of Euroode4 (CEN 1994). Euroode4 provides a geeral method ad a simplified method for desig of omposite olums. The simplified method used ad summarized i this study. The ross-setioal resistae of fully or partially orete-eased steel setios olum to axial ompressio is the aggregate of the plasti ompressio resistaes of eah of its ostituet elemets as follows: A f A. 85 f A pl. Rd r yr s s..() The elasti ritial load r of a eased olum is alulated usig the usual Euler buklig equatio ad the relative slederess of a eased olum i the plae of bedig osidered is give by pl. Rk r...(1) the desig axial loadig Sd satisfies the iequality: Sd pl. Rd..() i whih the value of, the stregth redutio fator i the plae of buklig osidered, is a futio of the relative slederess ad the appropriate Europea buklig urve, it is possible to alulate the value of the stregth redutio fator usig: 1 [ ] i whih 1/.5[1 (.) ] 1...(3) f...(4) where is a geeralized imperfetio parameter whih allows for the ufavorable effets of iitial out-of-straightess ad residual stresses. Seod-order effets o the behavior of a isolated olum formig part of a o-sway frame a be take ito osideratio approximately by applyig a amplifiatio fator k to the maximum first-order bedig momet MSd. The fator k is give by: k 1 Sd r 1...(5) Whe axial loadig ad ed-momets are both preset, should ever be take as less tha 1. uless it is alulated by a more exat method. The desig momet MSd is the maximum momet ourrig withi the legth of the olum, iludig ay ehaemet aused by the olum imperfetios ad amplifiatio of the total first-order momets due to the M Sd.9d M pl. Rd Statistial Aalysis.....(6) Statistial aalysis iludig stadard deviatio (SD), oeffiiet of variae (COV) ad sigifiat (-tailed, p) was used to verified that a proposed method ad others approahes whih has eough auray for determiatio lateral defletio ad momet properties of beam-olums samples. Table ad 3 summarize the aalysis results of samples performed at 5% sigifiat level. The aalysis verified that the suggested method ould be used for determiatio of lateral defletio ad momet properties of beam-olums. Results ad Disussios Effet of Flexural Stiffess (EI) o roposed Method I the alulatios of the proposed aalytial method ad others approahes the most importat parameter is the flexural

8 31 stiffess (EI), partiularly i preditig of Euler fore (e) that reasoably approximates the variatios i stiffess due to rakig, reep, ad oliearity of the Table 1: Desriptios of materials, profiles ad loads Steel lae of Exp. Q Exp. Speime fy(ma) rofile Bedig (kn) (kn) C14Z HEA14 Z-Z C14YB HEA14 Y-Y C14YA HEA14 Y-Y C14Y HEA14 Y-Y CZ HEA Z-Z CY HEA Y-Y CY HEA Y-Y C4Y1 HEAA4 Y-Y C4Y HEAA4 Y-Y C4Y HEAA4 Y-Y f u=44 Ma, f =35. Ma L=.44 m omelature of speimes: for C14YB,C meas olum,14 meas the height of the steel profiley is the plae of the bedig, meas the axial load is about % of the ritial fore. HEA is the ame of steel-setio; f y is yield stregth of the steel profile (Ma);f u is the ubi ompressive stregth of orete (Ma); f is the ylidrial ompressive stregth of orete (Ma); L is the legth of the beamolum; Exp is the axial ompressive load (kn) ad Q Exp is the trasverse load (kn). ACI ode reommeded two equatios to predit EI i short-term oditios (i.e. egletig reep effet), they are EI. E I E I....(7) g s s EI. 4E I g....(8) orete stress-strai urve, so some of speifi regulatios reommeded to use equatios to predit it. From these regulatios are ACI ode ad EC4. Where I g ad I s are the seod momet of are of gross-setio ad steel profile, respetively, E s ad E are the modulus of elastiity of steel ad orete, respetively. E a be alulated usig Es 4733 f (Ma). Equatio (7) was derived for small eetriity ratios ad high levels of axial load where slederess effets are most prooued. Equatio (8) is a simplified approximatio to equatio (7) ad is less aurate. Euroode4 reommeded a equatio to predit the effetive flexural stiffess (EI) eff whe was eeded to determie the iteral fores, this equatio is ( EI ) eff Ko( EaIa EsIs KeEmI)...(9) Where K e is a orretio fator whih should be take as.5; K o is a alibratio fator whih should be take as.9; I a, I s ad I is the seod momet of areas of steel profile, logitudial reiforemet ad orete, respetively; E a ad E s is the elastiity modulus of steel profile ad logitudial reiforemet, respetively ad E m seat modulus of elastiity of orete whih a be alulated from (EC-199). E m f Ma.....(3) It was proposed to use the equatios (7 ad 9) to predit the EI for beam-olums adopted i this study. After preditig momet ad defletio values for speimes ad aalyzed the results statistially by alulatig the mea value of the rate of alulated to experimetal momet ad defletio, stadard deviatio, oeffiiet of

9 Calulated momet(kn.m) Calulated defletio(mm Calulated momet(kn.m Calulated defletio(mm 3 variatio ad t-test. It was foud that the proposed aalytial method gives losed results to predit the momets ad defletio whe equatio (9) was used, sie the mea value of the alulated-to-experimetal momet was 1. with (SD=.36), (COV=3.5%) ad from t-test aalysis foud that there is o sigifiatly differet at level α=.5 ad test mea µo=1, but whe equatio (7) used to predit (EI) the alulatios of momets were losed ad the alulatios of defletios were ot losed, sie the mea value of alulated-toexperimetal momet was 1.3 with (SD=.4598), (COV=4.46%) ad t-test proved that o sigifiatly differet, ad the mea value of alulated-to-experimetal defletio was 1.14 with (SD=.1391), (COV=1.%) ad t-test proved that a sigifiae differee at level α=.5 ad test mea µo=1. From the above it a be idiated that the equatio (9) is more aurate to preset the proportios of the ross-setio elemets speially the orete beause it's otributio i the equatio is a half of seod momet area of the et orete area ad the short-term load seat modulus of elastiity for orete have take a osideratio the harateristis of raked omposite setios. While the equatio (7) reommeded by ACI to predit the flexural stiffess showed a little aurate with proposed method, this iauray is the osequees of ACI equatio (7) usig a ostat value of the oeffiiet. assiged to E I g as well as igorig the otributio of logitudial steel bars to the effetive flexural stiffess, it is evidet from differee show i Table, Fig. 3 ad Fig. 4 that there appears to reommed usig equatio (9) reommeded by Euroode4 with proposed method proposed method(ei-ec4) Experimetal momet(kn.m) (a) proposed method(ei-aci) Experimetal momet(knm) proposed method(ei-ec 4) Experimetal defletio(mm) (b) proposed method(ei-aci) Experimetal defletio(mm) () (d) Fig. 3.Comparisos betwee experimetal ad predited momets ad defletio for proposed method The experimetal data have bee give at yield stage; evaluatig the yield stage of the member was required for assessig the effetive stiffess, apaity ad dutility of a member. I reifored orete members, it is ustomary to osider this poit as that orrespodig to first yieldig of the reiforemet bars. O the other had, i steel setios, first yield is ot ormally aompaied by sigifiat irease i urvature. A alterative approah is to osider the effetive yield stage, relatig to the iitiatio of a plasti hige i the member, as that orrespodig to reahig yield withi the two extreme steel fibers of the setio. Fiite Elemet Modelig Results A ompariso betwee the experimetal ad aalysis results was adopted to verify the developed fiite elemet model. The ompariso of failure mode is show i Fig. 4 ad seemed to be losed. The ultimate lateral

10 33 loads obtaied from the tests ad the FEM, as well as the load-defletio urves were reported i Fig.4 ad Fig.5, respetively. As idiated i Table (), a good orrelatio is ahieved betwee both results for adopted olums. Fig. 6 shows the failure mode of steel profile ad seems to be aeptable. From these Figures, it a be idiated the rapprohemet betwee the experimetal ad FEM results. Table : Calulated to Experimetal Ratios Aalysis for roposed method roposed Aalytial Method Speime EI:Euroode4 EI:ACI 318 EI:Euroode4 EI:ACI 318 M al al M al al M al /M exp al / exp M al /M exp al / exp C14Z C14YB C14YA C14Y CZ CY CY C4Y C4Y C4Y Mea SD COV% T-test(alulated) p-robability (that R-square is zero) α(sigifiae level) Not Not Not sigifiatly sigifiatly sigifiatly sigifiatly differet differet differet differet Fig. 4. Verifiatio of deformatio shape (speime C14Y)

11 Calulated momet(knm) Calulated defletio(mm Calulated momet(knm) Calulated defletio(mm Calulated momet(knm) Calulated defletio(mm lateral load (kn) defletio (mm) FEM EX Fig. 5. Compariso of Experimetal ad FEM load-defletio of speime C14Z Fig. 6. Deformed profile of speime CY Iteratioal Approahes Differees Table 3 ad Fig. 7 show the omparisos amog three iteratioal approahes used to predit the momet apaity ad defletio of adopted speimes. The table reveals the predited to experimetal momets ad defletios ratios ad there statistial aalysis. The table ad figure are evidet that the ACI 318 approah is loser tha AISC-LRFD ad Eurood4 approahes i preditig of momet ad defletio simultaeously but the Euroode4 is loser tha the others i preditig of momet, sie for ACI the mea value of alulated-toexperimetal momet was 1. with (SD=.3714), (COV=3.63%) ad from t- test aalysis foud that there is o sigifiatly differet at level α=.5 ad test mea µo=1,ad for defletio was.981 with (SD=.1339), (COV=13.6%) ad from t-test aalysis foud that there is o sigifiatly differet at level α=.5 ad test mea µo=1. While Euroode4 has the mea value of the momet apaity-toexperimetal momet was 1.1 with (SD=.3843), (COV=3.6%) ad from t- test aalysis foud that there is o sigifiatly differet at level α=.5 ad test mea µo= ACI Experimetal momet(kn.m) (a) AISC-LRFD ACI Experimetal defletio(mm) (b) AISC-LRFD Experimetal momet(kn.m) Experimetal defletio(mm) () Euroode (d) Euroode Experimetal momet(kn.m) Experimetal defletio(mm) (e) Fig. 7.Comparisos betwee experimetal ad predited momets ad defletio for ACI 318, AISC-LRFD ad Euroode4 Regardig the differee of desig philosophy adopted i the ACI-318, AISC ad EC4 speifiatio, it is oted that the ACI-318 treats the desig of orete partially-eased omposite olums through the extesio of the desig provisios for ordiary reifored orete olums. The ACI-318 approah osiders the steel shape as a equivalet amout of reiforemet ad alulates the apaity of a partially-eased omposite (f)

12 35 olum based o a strai ompatibility aalysis proedure. O the other had, the AISC-LRFD approah treats the desig of oreteeased omposite olums through the extesio of the provisios reommeded for bare steel olums. That is, the desig of a partially-eased omposite olum is proeeded by trasformig the reifored orete portio ito a equivalet otributio of steel shape. The, the omposite olum is desiged usig the formulas developed for steel olums. This philosophy may provide a part of the reasos why the AISC-LRFD approah gives less aurate ad wider spread preditios as ompared with the te beam-olum test results. Euroode4 whih makes use of the Europea buklig urves for steel olums, whih impliitly take aout of imperfetios. The simplified method is limited i appliatio to omposite olums of bisymmetri ross-setio whih does ot vary with height ad based o assumptios that there is full iteratio betwee the steel ad orete setios util failure ours; geometri imperfetios ad residual stresses are take ito aout i the alulatio, although this is usually doe by usig a equivalet iitial out-of-straightess, or member imperfetio ad plae setios remai plae whilst the olum deforms. Colusios The aalytial preditio of momet ad defletio of te partially-eased omposite beam-olums was preseted i this paper. A proposed aalytial method, fiite elemet modelig ad three iteratioal desig approahes were used to predit the momet apaity ad lateral defletio; these approahes are ACI 318, AISC-LRFD ad Euroode4. From the yielded results ad the statistial aalysis, the followig fidigs were made: 1. The proposed method gives satisfatory results of momet ad defletio estimatio based o the predited EI from EC4.. The fiite elemet results whih predited usig the developed model are losed to that experimetally aptured. 3. Geerally, it was foud that the ACI 318 desig approah is losed i preditig the momet ad the defletio simultaeously. 4. The statistial aalysis proved that the Euroode4 is losed i preditig the momet apaity of members. Referees 1. S. A. Mirza ad E. A. Laroix, Comparative Stregth Aalyses of Corete-Eased Steel Composite Colums, Joural of Strutural Egieerig, Vol. 13, No. 1, Deember 4, pp C. C. Weg, S. I. Ye, Comparisos of Corete-Eased Composite Colum Stregth rovisios of ACI Code Ad AISC Speifiatio, Egieerig Strutures, Volume 4, Issue 1, Jauary, pp Timo K. Tikka ad S. Ali Mirza, Noliear Equatio for Flexural Stiffess of Sleder Composite Colums i Major Axis Bedig, Joural of Strutural Egieerig, Vol. 13, No. 3, Marh 6, pp A.Y. Elghazouli ad J. Treadway, Ielasti Behaviour of Composite Members Uder Combied Bedig ad Axial Loadig, Joural of Costrutioal Steel Researh, Volume 64, Issue 9, September 8, pp Che, W.F. ad Lui, E.M., Strutural Stability: Theory ad Implemetatio, Book published by Elsevier, 1987, New York, 486 pp. 6. Che, W. F., Approximate Solutio of Beam-Colums, Joural of the strutural Divisio, ASCE, 97(ST), 1971, pp Ameria Corete Istitute (ACI),

13 36 Buildig Code Requiremets for Strutural Corete (ACI 318-8) Ad Commetary (318R-8), Ameria Istitute of Steel Costrutio (AISC-LRFD) (), Load ad Resistae Fator Desig Speifiatios for Strutural Steel Buildigs, 1999, Chiago. 9. EN 1994 Desig of omposite steel ad orete strutures art 1.1 Geeral Rules ad Rules for Buildigs, Europea Committee For Stadardizatio, EN 199-1:x, CEN (Europea Normalisatio Cetre), Brussels Euroode: Desig of Corete Strutures,. 11. ABAQUS Stadard User s Maual, Hibbitt, Karlsso ad Sorese, I. vol. 1, ad 3, Versio 6.6, USA, 6.