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The paper discusses the structural behaviour of concrete-filled steel tube columns (CFT) when applied to the top-down construction method as temporary internal supports for ceilings. Their ultimate capacity to take into account the actual boundary conditions of the column is essential for successful application in construction. The paper presents the full-scale in situ testing of four slender specimens with variable D/t ratios under concentric axial loading. The CFT columns were supported on the previously jacked concrete piles. In addition, detailed finite element numerical models in ABAQUS and PLAXIS computer programs were developed. The models include the nonlinear behaviour of materials and the nonlinear behaviour of soil. The soil–pile–column interaction and impact of the CFT column–pile connection stiffness on global column stability were considered. The numerical model was validated by comparison with the experimental results. In conclusion, the coefficient for the effective buckling length of the studied columns is proposed. Finally, the experimental results of the critical buckling forces were compared with widely used international design codes Eurocode 4-EC4, American standard-ACI and the Australian standard-AS.

Due to numerous advantages, concrete-filled steel tubular (CFST) columns have an increasingly important role in the civil engineering industry. Because of the expensive experimental testing of these members, it is beneficial to provide prognostic models. In this study, an artificial neural network (ANN) model for predicting the axial compressive strength of square CFST columns has been developed. A dataset of 1022 samples (685 stub columns and 337 slender columns) was collected from available literature in order to compare the accuracy of the fast predictive Levenberg-Marquardt algorithm (LM) and Eurocode 4 (EC4) design code. Analyses showed that the ANN model has better accuracy than EC4. Over a whole domain, the ANN model has higher coefficient of determination (R2), and lower root mean squared error (RMSE). The same conclusion is valid when two separate datasets are considered: one for stub columns and the other for slender columns. The benefit of the ANN model is its applicability in a broader range of column parameters. At the same time, EC4 puts several limitations on its use and gives satisfactory results only in limited circumstances. Empirical equations have also been proposed from the best ANN model, which is useful for engineering practice.

The composite concrete-filled steel tube columns are structural members with numerous advantages over the traditional reinforced concrete or the pure steel members. The behavior of these columns is highly nonlinear. This paper analyses the determination of the ultimate compressive capacity of circular concrete-filled tubes according to the Eurocode 4 design code and its accuracy in comparison with the experimentally available results from the literature. In order to improve the predictions of the column’s ultimate compressive capacity, two efficient machine learning algorithms are employed separately for the stub and the slender columns. The analyzed algorithms are the Decision tree and the Random forest. The research used an experimental dataset of 508 samples: 236 tests on the stub columns and 272 tests on the slender columns. It adapted the dataset to the provision of the Eurocode 4 design code. The predictions of the column’s ultimate axial capacity obtained by two ML algorithms and the Eurocode 4 are compared with the experimental test results on the validation dataset. The calculated R2 error measure has shown that the predictions obtained by the tree-based algorithms are superior compared to the design formulas offered by the Eurocode 4. The decision tree algorithm achieved the best accuracy measured with the highest value of R2 error measure between the two algorithms. The two analyzed algorithms are used to perform the sensitivity analysis on the considered problem. The sensitivity analysis used the feature importance, a technique that assigns a score to each of the input features based on their influence on the prediction of the output variable. As expected, the sensitivity analysis identified the outer diameter of the columns’ cross-section as the parameter with the most significant impact on the results.

The paper presents the numerical modelling of concrete-filled steel tube stub columns under axial compression. The nonlinear 3D finite element model for the analysis was developed using ABAQUS software. The modelling, boundary conditions, the constitutive models for steel and concrete and contact interaction between the steel tube and concrete surface are discussed in detail. Three numerical models are proposed and validated using collected experimental data results. Finally, the composite column axial capacity is compared with the Eurocode 4 calculations for composite columns.

The paper proposes an adaptive fiber section discretization scheme for inelastic frame elements. The scheme uses cubature rules for the efficient and accurate evaluation of the section response over the elastic portion of the section. As inelastic strains arise and penetrate into the section from the edges, the scheme converts the area under inelastic strains to a regular fiber discretization. This approach offers considerable advantages for the computational efficiency of large structural models with inelastic frame elements by minimizing the number of integration points in sections with limited inelastic response. The proposed scheme is presented for circular and rectangular cross sections, but the approach is applicable to other section shapes. Inelastic frame response examples demonstrate the benefits of the proposed discretization scheme for the nonlinear response history analysis of large structural models.

This paper proposes the use of artificial neural network (ANN) algorithms to estimate the ultimate compressive strength of slender circular concrete-filled steel tubular (CCFST) columns. A dataset of 1051 samples was applied to generate an appropriate ANN prognostic model. Empirical equations were also developed from the best neural network, and their results were compared with those obtained by Eurocode 4 (EC4) design code. Analyses show that the proposed ANN model has a better agreement with experimental results than those created with provisions of the EC4 design code.

The paper presents four different methods for viscoelastic analysis of steel-concrete composite structures: “exact” analysis method, simplified method, effective modulus method and method proposed by the European design code, Eurocode 4. The exact analysis method uses the mathematical theory of linear integral operators for presenting viscoelastic relations of the steel-concrete composite structures. The simplified analysis method is derived from the exact method. It adopts the assumption that generalized displacements change linearly with the concrete creep function. Due to this assumption, the problem equations transforms from nonhomogeneous integral equations to nonhomogeneous algebraic equations. The effective modulus method and the method proposed by the Eurocode 4 are algebraic methods where stress-strain relations for concrete are expressed through the effective modulus, which depend on time. On the numerical example of continuous steel-concrete beam, the results obtained using the mentioned approximate and the exact method are compared

Predmet disertacije je određivanje aksijalne nosivosti i stabilnosti kružnih šupljih čeličnihprofila ispunjenih betonom, u daljem CFT stubovi (eng. Concrete Filled Tubes).Problem istraživanja je određivanje stabilnosti CFT stubova, uzimajući u obzir krutostveze. Ovaj problem se javlja u ''top down'' metodi gradnje, kada se nakon izvođenja šipovau koje su ubetonirani CFT stubovi i tavanice na koti 0.00, vrši iskop ispod izvedenetavanice i izvođenje nadzemnog dela konstrukcije. U takvoj situaciji postavlja se pitanjenosivosti i stabilnosti CFT stubova koji se vezuju sa izvedenim šipovima na osnovu koga sedefiniše moguć iskop i izgradnja nadzemnog dela konstukcije...

In this paper, the methods for determination of the bending resistance of composite beams with partial shear connection and nonductile shear connectors, according to Eurocode 4, are studied. The Eurocode 4 predicts the use of two calculation methods: the method based on the nonlinear theory and the simplified method that assume linear relation between elastic and plastic bending moment resistance. The algorithm for the nonlinear section analysis is explained in detail. Using the own computer program for nonlinear section analysis, for one composite beam cross section, the differences in results obtained by these two proposed methods are discussed.

The paper presents the nonlinear section analysis for composite steel-concrete beams with different degrees of shear connection. The analysis is fiber based, i.c., integration over the cross section is performed numerically, and any uniaxial nonlinear material model can be assigned to the steel and concrete parts of the cross section or to the reinforcement bars. The analysis assumed full interaction between steel and concrete and therefore, is suitable for analysis of composite steel-concrete beam cross sections with nonductile shear connectors. Its accuracy is verified on few experimental results. The presented section analysis is used in the parameter study in order to evaluate different methods proposed by design codes for determining the bending moment resistance of composite cross sections with nonductile shear connectors and different degrees of shear connection. The following effects are considered: variation of concrete and steel material models, presence of slab reinforcement, and creep of concrete. Special attention is paid on two different constructional methods: propped and unpropped. The weaknesses of the simplified design method in determining bending moment resistance are identified and recommendations for practical design analysis are formulated.

The paper presents the simplified matrix stiffness method for analysis of composite and prestressed beams. The method is based on the previously developed "exact" analysis method that uses the mathematical theory of linear integral operators to derive all relations without any mathematical simplifications besides inevitable idealizations related to the material rheological properties. However, the method is limited since the closed-form solution can be found only for specific forms of the concrete creep function. In this paper, the authors proposed the simplified analysis method by introducing the assumption that the unknown deformations change linearly with the concrete creep function. Adopting this assumption, the nonhomogeneous integral system of equations of the "exact" method simplifies to the system of algebraic equations that can be easily solved. Therefore, the proposed method is more suitable for practical applications. Its high level of accuracy in comparison to the "exact" method is preserved, which is illustrated on the numerical example. Also, it is more accurate than the well-known EM method.

The paper presents nonlinear analysis of square CFT columns using distributed plasticity fiber elements. Behaviour of CFT columns is nonlinear and it is necessary to include different nonlinear effects into the numerical model in order to simulate their behaviour properly. Model proposed in this work considers: nonlinear behaviour of concrete and steel using nonlinear stress-strain models, confinement effect and geometrical nonlinearities. Tests exposed to static loading with different slenderness, different D/t ratio (where D is the total dimension of a cross section and t is the thickness of steel tube) and different loading conditions are analyzed. Stress-strain models that best approximate the behaviour of CFT columns are determined from a detailed parametric study. The proposed numerical model is validated by comparing numerical with experimental results available in the literature., U radu je prikazana nelinearna analiza kvadratnih CFT stubova, pomoću fiber konačnog elemenata raspodeljene plastičnosti. CFT stubove karakteriše nelinearno ponašanje, što je potrebno imati u vidu u numeričkom modelu. Model predložen u ovom radu uzima u obzir sledeće nelinearne uticaje: nelinearno ponašanje betona i čelika primenom odgovarajućih konstitutivnih relacija, efekat utezanja betona i geometrijske nelinearnosti. Analizirani su uzorci izloženi delovanju statičkog opterećenja koji imaju različitu vitkost, odnos D/t (odnos ukupne dimenzije čeličnog profila [D] i debljine čeličnog profila [t]), kao i uzorci izloženi različitim tipovima naprezanja. Na osnovu parametarske analize, određeni su modeli materijala za čelik i beton, kao i njihovi parametri koji najbolje aproksimiraju ponašanje CFT stubova. Tačnost modela proverena je zatim i upoređivanjem sa eksperimentalnim podacima dostupnim u literaturi.

The paper discusses two formulations for the fiber based distributed plasticity beam/column element. For force based and displacement based formulations, basic details and main differences are emphasized. The differences in results of analysis when elements with these two formulations are used are demonstrated on two numerical examples. The first example involves the nonlinear static pushover analysis of low-rise frame with distributed element loading. The second example is nonlinear time history analysis of two-story frame subjected to earthquake loading. The differences in global and local response depending on the used finite element discretization are shown. In conclusion, the advantages of force based formulation and directions for the use of the two elements are summarized., U radu su prikazane dve formulacije fiber konačnog elementa raspodeljene plastičnosti. Za metodu sila i metodu deformacija, ukazano je na osnovne razlike dve metode. Razlike u rezultatima analize koje se dobijaju primenom fiber elementa prema ove dve formulacije prikazane su putem dva numerička primera. Prvi primer obuhvata statičku pushover analizu rama s raspodeljenim opterećenjem duž greda. Drugi primer je nelinearna dinamička analiza dvospratnog rama izloženog zemljotresnom opterećenju. Prikazane su razlike kod dobijenog globalnog i lokalnog odgovora u zavisnosti od formulacije i diskretizacije rama. U zaključku, rezimirane su primene dve formulacije fiber elementa i date napomene u vezi s njihovim korišćenjem.

This paper presents a nonlinear 3d concentrated plasticity beam column element for the analysis of RCFT columns. The element consists of a linear elastic component with a plastic hinge at each end whose inelastic response is described by extending the concept of generalized plasticity to stress resultants. With independent yield and limit surfaces it is possible to describe the gradual yielding of composite sections and their post-yield hardening behavior. The geometric nonlinearity under large displacements is accounted for with the corotational formulation. The paper discusses the calibration of the model parameters and assesses the accuracy of the model through correlation studies.

Bending resistance of a composite steel and concrete section apart from shape and dimensions of a cross section and mechanical characteristics of materials, depends also on type of shear connection, i.e. connectors and shear steel-concrete interface. In the paper, ductile and nonductile headed studs are considered. Bending resistance of composite sections with partial shear connection, which is a connection where a number of shear studs is smaller than necessary for fully plastic bending resistance of a section to be achieved, is analysed. The reduced bending resistance is found. The calculaton in accordance with Eurocode 4 is presented., Nosivost na savijanje spregnutog preseka od čelika i betona pored oblika i dimenzija poprečnog preseka i mehaničkih karakteristika materijala, zavisi i od načina sprezanja, tj. tipova sredstava za sprezanja i oblikovanja kontaktnog (smičućeg) spoja između betona i čelika. U radu se koriste duktilni i neduktilni moždanici sa glavom. Određuje se nosivost na savijanje spregnutih preseka sa parcijalnim smičućim spojem u kome, za razliku od punog smičućeg spoja, broj moždanika nije dovoljan da se ostvari moment pune nosivosti, tako da se određuje redukovani moment nosivosti. Proračun se sprovodi prema Evrokodu 4.

Predmet disertacije je efikasna nelinearna analiza okvirnih konstrukcija grednim konačnim elementima sa težištem na modeliranju materijalnih nelinearnosti. Geometrijska nelinearnost se uzima u obzir poznatim metodama. U tezi su analizirana i unapređena dva gredna konačna elementa: fiber element i element koncentrisane plastičnosti i napisan je sopstveni kompjuterski program kojim su elementi implementirani u postojeći open-source program za analizu konstrukcija – FEDEASLab. Tokom rada na tezi, ostvareni su sledeći ciljevi. Izvršena je optimizacija integracije poprečnog preseka čeličnih i armirano-betonskih elemenata u cilju poboljšanja efikasnosti fiber elemenata kako pri cikličnom pseudo-statičkom opterećenju, tako i pri nelinearnoj dinamičkoj analizi pojedinih delova i čitave konstrukcije. Formulisana su praktična pravila i definisane jasne smernice za diskretizaciju poprečnog preseka čeličnog I profila i pravougaonog armiranobetonskog preseka, u zavisnosti od vrste analize koja se sprovodi i željene tačnosti. Razvijen je novi konačni elementa iz grupe elemenata koncentrisane plastičnosti koji prevazilazi ograničenja postojećeg elasto-plastičnog elementa kao što su nemogućnost opisivanja postepene plastifikacije poprečnog preseka i opisivanja ponašanja materijala sa ojačanjem. Pri tome, element je zadržao svoju veliku kompjutersku efikasnost koja je osnovna prednost elemenata koncentrisane plastičnosti. Za određivanje stanja elementa razvijena su dva algoritma prema “general closest point projection” i “convex cutting plane” return mapping algoritmima i analizirana je zavisnost konvergencije od implementiranog algoritma. Mogućnosti novog elementa za modeliranje okvirnih konstrukcija pri delovanju statičkog i dinamičkog opterećenja su potvrđene kroz niz numeričkih primera. Specijalna pažnja je posvećena primeni novog GP elementa za modeliranje CFT stubova spregnutih konstrukcija..., The objective of this study is the efficient nonlinear analysis of space frames with beam/column finite elements considering material nonlinearity. Geometric nonlinearity is taken into account using known methods. Two different nonlinear beam/column elements are analyzed and improved: a fiber element and a concentrated plasticity element. Own computer code is written and implemented into the existing matlab toolbox for nonlinear structural analysis – FEDEASLab. During this study, the following objectives are achieved. By the optimization of the number and position of material integration points at monitored steel and reinforced concrete cross-sections, the significant improvement in efficiency of the fiber beam-column element under cyclic static and dynamic loading conditions is gained. The practical rules for an efficient discretization of steel wide-flange sections and rectangular reinforced-concrete sections are defined, depending on the desired level of accuracy and the type of analysis. In addition, the new three-dimensional nonlinear beam-column element is formulated. The element is of concentrated plasticity type and overcomes the common limitations of the existing elasto-plastic elements, such as the inability to describe gradual plastification of a cross-section and the hardening behavior. Also, the element keeps its high computational efficiency which is one benefit of concentrated plasticity elements. Two algorithms for element state determination are developed in accordance with the general closest point and convex cutting plane return mapping algorithms. Their influence on element convergation is studied. The ability of the element to simulate frame behavior is confirmed on a number of numerical examples. The special attention is devoted to model CFT composite column behavior...

In the paper, an efficient three-dimensional concentrated plasticity nonlinear beam-column element is used for the simulation of the response of square CFT columns. The element adopts the concept of the generalized plasticity material model for the section resultant - element deformation relation and has plastic hinges located at the ends of the element and described with yield and limit surfaces. Determination of the adequate element parameters which are essential for a successful description of the CFT member behavior is discussed. Among these parameters, most important are the stiffness and yield surface parameters.

This paper presents a simplified method for calculation of bearing capacity of composite columns according to the European standard for the calculation of composite steel and concrete structures - Eurocode 4. Resistance analysis, and also the stability analysis of the isolated column under axial compression is based on the application of the European buckling curves. Verification of the column capacity subjected to axial compression and bending is based on the N-M interaction curve. For the presented numerical example, construction of the interaction curve is explained for the composite column with the circular concrete filled steel tube cross section. The influence of the concrete core confinement on the increase of concrete strength and the column bearing capacity of a CFT column is discussed. The [N, M] coordinates of the continuous interaction curve are calculated from the derived expressions for determination of the area and the static moment of the cut-off portion of the circular CFT section. For the presented example, the effects of the strength of concrete, strength of steel and the diameter and wall thickness of the steel tube on the composite CFT cross section capacity is discussed., U radu je prikazana uprošćena metoda proračuna nosivosti spregnutih stubova prema važećem evropskom standardu za proračun spregnutih konstrukcija od čelika i betona - Evrokodu 4. Analiza nosivosti, a time i stabilnosti pri aksijalnom pritisku izolovanog stuba bazira se na primeni evropskih krivih izvijanja. Provera nosivosti pri kombinaciji aksijalnog pritiska i momenta savijanja zasniva se na N-M interakcionoj krivoj. Na konkretnom brojnom primeru prikazano je konstruisanje krive interakcije za spregnuti stub poprečnog preseka u obliku kružnog šupljeg profila ispunjenog betonom. Razmatran je uticaj utezanja betona na povećanje čvrstoće betona i nosivosti preseka CFT stuba. Izvođenjem izraza za određivanje odsečenih površina i statičkih momenata odsečenih površina kod kružnog CFT stuba, a zatim i određivanjem koordinata tačaka koje pripadaju krivoj interakcije, konstruisana je kontinualana kriva interakcije. Za navedeni poprečni presek kod proračuna nosivosti pri kombinaciji aksijalnog pritiska i savijanja, analizirani su sledeći uticaji na graničnu nosivost spregnutog preseka: uticaj promene marke betona, uticaj promene klase čelika i uticaj promene odnosa prečnika i debljine čeličnog profila.

Beam-column elements with section resultant plasticity for the hysteretic behavior of the end plastic hinges are widely used for numerical simulations in earthquake engineering practice because of the good compromise between accuracy and computational cost. This chapter presents a three-dimensional inelastic beamcolumn element of this type with significant capabilities for the description of the global and local response of frames under monotonic and cyclic loads. In the proposed element the concept of generalized plasticity is extended to section resultants and element deformations and is used to describe the hysteretic behavior of the plastic hinges forming at the element ends. The element accounts for the interaction of the axial force with the bending moments about the principal section axes with suitably defined yield and limit surfaces that permit the description of the gradual yielding and the post-yield hardening behavior of the end sections. Comparisons of the hysteretic response of structural elements and small structural models between the proposed element and the more accurate, but computationally more expensive fiber section description of the cross section demonstrate the capabilities of the proposed model.

This paper presents a simplified method for calculation of bearing capacity of composite columns according to the European standard for the calculation of composite steel and concrete structures - Eurocode 4. Resistance analysis, and also the stability analysis of the isolated column under axial compression is based on the application of the European buckling curves. Verification of the column capacity subjected to axial compression and bending is based on the N-M interaction curve. For the presented numerical example, construction of the interaction curve is explained for the composite column with the circular concrete filled steel tube cross section. The influence of the concrete core confinement on the increase of concrete strength and the column bearing capacity of a CFT column is discussed. The [N, M] coordinates of the continuous interaction curve are calculated from the derived expressions for determination of the area and the static moment of the cut-off portion of the circular CFT section. For the presented example, the effects of the strength of concrete, strength of steel and the diameter and wall thickness of the steel tube on the composite CFT cross section capacity is discussed., U radu je prikazana uprošćena metoda proračuna nosivosti spregnutih stubova prema važećem evropskom standardu za proračun spregnutih konstrukcija od čelika i betona - Evrokodu 4. Analiza nosivosti, a time i stabilnosti pri aksijalnom pritisku izolovanog stuba bazira se na primeni evropskih krivih izvijanja. Provera nosivosti pri kombinaciji aksijalnog pritiska i momenta savijanja zasniva se na N-M interakcionoj krivoj. Na konkretnom brojnom primeru prikazano je konstruisanje krive interakcije za spregnuti stub poprečnog preseka u obliku kružnog šupljeg profila ispunjenog betonom. Razmatran je uticaj utezanja betona na povećanje čvrstoće betona i nosivosti preseka CFT stuba. Izvođenjem izraza za određivanje odsečenih površina i statičkih momenata odsečenih površina kod kružnog CFT stuba, a zatim i određivanjem koordinata tačaka koje pripadaju krivoj interakcije, konstruisana je kontinualana kriva interakcije. Za navedeni poprečni presek kod proračuna nosivosti pri kombinaciji aksijalnog pritiska i savijanja, analizirani su sledeći uticaji na graničnu nosivost spregnutog preseka: uticaj promene marke betona, uticaj promene klase čelika i uticaj promene odnosa prečnika i debljine čeličnog profila.

The paper presents studies of the effect of the number of material integration points at the monitored sections of fiber beam-column elements on the local response of typical structural cross sections under an extensive set of cyclic biaxial load conditions with constant and variable axial load. The study covers wide-flange steel sections and rectangular reinforced concrete sections. The integration over the section uses the midpoint rule and shows that a standard section discretization with relatively few fibers is a good compromise between accuracy and economy of means. The proposed coarse section discretization schemes are computationally efficient while ensuring the accurate representation of important aspects of the three-dimensional response of structural members, such as interaction of axial force with biaxial bending moment, effect of residual stress in steel members, and effect of cracking in reinforced concrete members. The local strain response is also represented with good accuracy by the coarse discretization schemes. DOI: 10.1061/(ASCE)ST.1943-541X.0000501.

Different analytical methods, with different levels of approximations and accuracy, are available for analysis of continuous composite steel-concrete beams. The Eurocode 4 recommends few simple methods for calculation of creep, shrinkage, cracking of concrete and shear lag effects that are explained in the paper. Through the numerical examples of four continuous composite steel-concrete beams, the proposed methods of analyses are evaluated and compared. Practical recommendations for analysis of this type of girders are formulated., Za analizu spregnutih kontinualnih nosača od čelika i betona postoje različite analitičke metode, različitog stepena tačnosti. Evrokod 4 dozvoljava i preporučuje nekoliko jednostavnih metoda kojima se u proračun uvode nelinearni efekti kao što su skupljanje i tečenje betona, ispicalost betonske ploče i shear-lag efekat, i one su objašnjene u radu. Kroz numeričku analizu četiri spregnuta kontinualna nosača ove metode su upoređene i date su praktične preporuke za analizu ove grupe nosača.

The paper deals with the design of composite steelconcrete columns according to Eurocode 4. The simplified design method and limitations for its use are explained in details. A column is analysed as an individual member, subjected to lateral loadings over the column height and axial forces and bending moments at the element ends, determined from global analysis, i.e. from the analysis of the whole structure. The resistance of a composite column subjected to axial compression and biaxial bending is analysed. The verification of bending resistance of a composite steelconcrete column cross section is based on theory of plasticity, while resistance of individual column is based on the theory of elasticity, but include the second-order effects and imperfections. Capacity and stability analysis under axial compression is based on the use of European buckling curves. The verification of column bearing capacity is based on the use of interaction diagram determined from capacity analysis of composite cross-section. Since the Eurocodes are being accepted as our national standards, the main aim of this paper is to simplify the use of this standard in our ordinary engineering practice through the detailed explanations of the design procedure of composite steel-concrete columns., U radu se prikazuje proračun nosivosti spregnutih stubova prema važećem evropskom standardu za proračun spregnutih konstrukcija od čelika i betona - Evrokodu 4 (EC4). Daje se detaljni prikaz približne metode proračuna i uslovi za njenu primenu. Stub se posmatra kao izolovani element opterećen mogućim poprečnim opterećenjem i opterećen na krajevima aksijalnom silom pritiska i momentima određenim globalnom analizom tj. analizom konstrukcije kojoj pripada posmatrani stub. Analizira se nosivost spregnutog stuba izloženog samo aksijalnom pritisku i izloženog istovremenom uticaju aksijalnog pritiska i savijanja momentima. Provera nosivosti poprečnog preseka spregnutog stuba vrši se u okviru teorije plastičnosti, a analiza nosivosti izolovanog stuba u okviru teorije elastičnosti, vodeći računa o uticajima drugog reda i imperfekcijama stuba. Analiza nosivosti, a time i stabilnosti, pri aksijalnom pritisku izolovanog stuba bazira se na primeni Evropskih krivih izvijanja. Provera nosivosti pri kombinaciji aksijalnog pritiska i savijanja momentima zasniva se na interakcionom dijagramu koji se određuje pri analizi nosivosti poprečnog preseka posmatranog stuba. Kako je u toku usvajanje Evrokodova za konstrukcije kao naših zvaničnih standarda, cilj ovog rada je da detaljnim prikazom proračuna spregnutih stubova prema Evrokodu 4 olakša primenu ovog standarda u našoj inženjerskoj praksi.