Calibration of equivalent geometric imperfections for second‐order theory analysis of hot‐rolled U‐profiles

The stability behaviour of steel structures is important when performing design. Standards (such as EN 1993‐1‐1 – Eurocode 3 Part 1‐1) take the stability of steel members into account and allow for verifications using reduction factors or by second‐order theory analysis considering equivalent geometric imperfections. Eurocode 3 is well‐suited for I‐profiles as the reduction factors and equivalent geometric imperfections have been calibrated using experimental and numerical data for this profile type. However, when it comes to U‐profiles, the standard lacks clear specifications. In literature, some authors have studied the stability behaviour of U‐profiles. For example, the imperfections required for performing a detailed geometrically and materially nonlinear analysis with imperfections included (GMNIA), as well as the residual stresses for U‐profiles, have been studied. Nevertheless, there are still gaps to be addressed, such as the equivalent geometric imperfections for second‐order theory analysis (GNIA). In this paper, the lateral torsional buckling capacity of U‐profiles is determined by GMNIA, with explicit residual stresses definition, and subsequently, corresponding equivalent GNIA are calibrated and proposed.