Design of Concrete Encased Composite ColumnsAccording toTheGeneral Method (prEN1994-1-1)

Eurocode 4 provides two methods for the verification of structural stability of the composite columns in steel and concrete: the simplified methods and the general method. The simplified methods have a limited scope of application related to the geometry and material parameters of steel and concrete. In engineering practice, these limitations are often exceeded and also the application of high strength materials become more important. On the other hand, the general method can be applied in any type of composite without those limitation, but as a method is more complex and more sophisticated, as the design is based on geometric and material non-linear analysis with imperfections (GMNIA), considering all the physical and material nonlinearities such as geometric imperfection, residual stresses, local instability, cracking of the concrete, yielding of the structural steel and reinforcements. The current Eurocode 4: EN 1994-1-1 includes this advanced design method but does not provide detailed information on how to apply it. However, the second draft of Eurocode 4: prEN 1994-1-1 fills this gap by explaining the application of this method in more detail. This paper is focused on the general method and demonstrates the application of the general method for composite columns in steel and concrete subjected to compressive force by case studies. In the main part of the paper, the buckling resistance of columns based on general and simplified method are compared considering different column lengths (relative slenderness λ ̅). Furthermore, different geometric imperfections are applied for this case study as they are currently under review by standard bodies. Moreover, the N-M interaction diagram evaluated with plastic and strain-limited resistance to determine the overall safety factor〖 γ〗_0 necessary for the general method is presented.