Proposal to evaluate the ultimate limit state of slender structures. Part 1: Technical aspects

This paper presents a design method to evaluate the ultimate limit state in slender structures. The method addresses the main two features in this type of analysis: how to deal with the nonlinear geometric behaviour and the possible imperfections, incorporating all frame and member imperfections into a process that only requires cross-sectional checking. The method is based on a simplified second-order elastic analysis of the structure including lateral buckling with an equivalent geometric imperfection. The second order effects are calculated using the orthogonal properties of the buckling modes. The geometric imperfection is obtained from the buckling mode by a suitable scaling procedure using a generalization of Dutheil’s method.