Local and global buckling of box columns made of high strength steel

The international increased competition of the steel industry requires modern construction solutions to save material and thus labour costs. Combined with architectural trends to lightweight structures, the development of high strength steels, with steel grades exceeding a yield strength of 460 MPa, is a logical solution. These materials are not fully covered yet in the European Design Standards, especially in regard to stability issues. In Eurocode 3-1-5, the resistance curve for plated elements due to local failure is based on the Winter-curve from 1947. The within this study conducted tests on stub columns made of S500 up to S960 as well as tests from other researchers, showed its un-conservativeness, independently of steel grade. A new reduction curve was derived, representing the mean function for all test data available. The mandatory safety concept of EN 1990 was applied on the existing and the newly proposed resistance definition to derive the corresponding safety γM*. Different approaches and variations are presented and discussed in this work, leading to scientifically justified γM*-values. The continuative interaction design check for local and global buckling in Eurocode 3-1-1 is based on the Ayrton-Perry format, which allows for separate assessment of several effects, but additional correction factors are to calculate. The study at hand provides an analytic approach to determine a slenderness depending reduction factor such that additional factors can be neglected. This „generalised slenderness approach“ includes local effects by adding an additional equivalent global imperfection. The magnitude of this imperfection is based on the earlier derived new reduction curve. Design charts for box sections were developed to ease the application.