Parameter studies on imperfections for the LTB‐design of members based on EN 1993‐1‐1

Abstract

AbstractSelected, extended paper from the SDSS 2019 special session ECCS/TC8 – Structural StabilityThe stability design of members and structures based on a geometrically nonlinear analysis with equivalent initial geometric imperfections (GNIA) is a commonly used method. In the case of lateral torsional buckling (LTB) of members, the regulations in EN 1993‐1‐1 are unsatisfactory. With the current code, but also with the new draft prEN 1993‐1‐1 results are achieved, some of which are significantly too conservative as well as lacking in terms of safety. The reasons for this are the specified shape of imperfection as bow imperfections e0 out of plane, an inappropriate differentiation related to the cross‐section shape and yield strength, as well as neglecting the influence of the moment distribution over the member lengths. Parameter studies have shown that a distinction is required due to the different structural behaviours of members loaded with pure bending, pure compression, or a combination of bending and compression. This article presents current research results that consider the case of pure bending of I‐ and H‐profiles. The dependencies of the profile shape, the cross‐sectional resistance model and the influence of steel grades are analysed with respect to the height of the equivalent geometric imperfection to be applied.