Eurocodes give guidance how to design built-up columns having effective bending stiffness, smeared shear stiffness and local bow imperfection amplitude e0= L/500 under compression. The guidance is valid only for columns supported by hinges at their ends. The second order theory is presented, which allows analysis of the battened and laced built-up columns with initial imperfection under combined compression and bending with the bottom end fixed and the upper one free in the case of in-plane buckling. The application of the theory in several numerical examples is given in Part II.
EN 1993-1-1:2005 and Corrigendum AC: February 2006, Eurocode 3, Design of steel structures – Part 1-1: General rules and rules for buildings, CEN, Brussels, 2005.
Steel Structures. Handbook for study and practice, Part 1, (in German) Stahlbau-Verlags-GmbH, Köln, 1982.