Non-linear design for composite structures in steel and concrete in reference to Eurocode 4, Part 1-1

The design of composite structures in steel and concrete for buildings follows the rules according to Eurocode 4: EN 1994-1-1. In the last years more and more individual composite members and cross-section types have been developed. Those sections are not always fulfilling the requirements for the application of simplified design methods given by EN 1994-1-1 and therefore plastic resistance cannot always be applied. Furthermore there is an increasing demand for optimization in the design by using more advanced design methods. This optimization is concentrating on the use of individual shaped cross-sections and their efficiency, the composite shear connectors and consideration of their ductility and flexibility, investigation in the sequence of loading, time effects as well as concrete cracking and yielding of steel within the analysis. In addition it is to be mentioned that the draft for the second generation of Eurocode 4 provides more opportunities for advanced numerical methods. At least, the demand for more advanced numerical design methods is permanently increasing also due to the availability of powerful hardware and software applications.
The target of this chapter is to introduce the advanced numerical design for composite structural members in steel and concrete and to explain the boundary conditions given by Eurocode 4 and related Eurocodes. Thereby the focus is more on the member and not on the global analysis. The computer-aided global analyses for the determination of action effects are well-known for years while the possibilities for nonlinear analysis based on shell and volume elements considering physical and geometrical nonlinearity becoming more important and will be further developed in future. However, there is not so much information available explaining the application of e.g. the general method in detail and guidance is missing by the code. Therefore the general method acc. to EN 1994-1-1/prEN1994-1-1 is the main focus of this contribution.
In the following, some principles for the design according to EN 1994-1-1 are explained. Thereby the basics for the classification of cross-sections as well as the determination of inner forces for continuous beams will be pointed out. However, the focus is on the general method for the design of composite compression members. While in the case studies additional information for the structural analysis and the numerical investigation in composite beams is provided.
This chapter will not repeat well-known explanations from the literature, which have been published many times but limits itself to the most important normative fundamentals, rather concentrate on the application of numerical methods for the design of composite structures. More details for global structural analysis and the design according to EN 1994-1-1 [1] are provided by the literature, e.g. [8], [40] and will not be further commented here.
It should be noted that the here referred methods according to prEN 1994-1-1, prEN 1993-1-14 and prEN 1992-1-1 do not represent officially introduced design standards, until the introduction of the second generation of Eurocodes modification is not finalized. Therefore this references are to be understood as informative. Until the introduction of the second generation of Eurocodes further changes and adjustments may also to be expected.