Determination of overall factor for the application of the General Method based on plastic and strain‐limited N‐M interaction for composite compression members

The design of composite compression members can be realized based on the General Method in accordance with Eurocode 4. This method represents a more sophisticated design based on advanced numerical analysis. It may be applied for any type of composite column. The General Method contains two steps; the first step is defined as the global nonlinear finite element analysis (GMNIA) accounting for all geometrical and physical nonlinear effect and considering geometrical and structural imperfection; while the second step represents the analysis on the cross‐section level, by N‐M interaction diagram to determine the overall safety factor γ₀. EN1994‐1‐1 requires the N‐M‐Interaction based on the plastic resistance. However, often the General Method is provided for those section, where the plastic resistance is not representing the real behavior. Therefore, the question is discussed why the N‐M‐Interaction should not be developed based on the strain‐limited resistance considering the approaches for concrete stress‐strain curve in accordance with EN 1992‐1‐1 and for structural steel in accordance with prEN1993‐1‐14.

In this paper, the application of general method is investigated for different type of composite columns with N‐M interaction diagram evaluated with plastic and strain‐limited resistance. Results are compared and discussed in terms of overall safety factor γ₀. Conclusions are provided for the further development of the General Method in Eurocode 4.