Biaxial compression in class 4 orthotropic steel panels using Eurocode methods: Fid-Bau Portal

Biaxial compression in class 4 orthotropic steel panels using Eurocode methods

Gren, Simon Mathias / Hansen, John Elnegaard / Kærn, Jens Christian

When designing class 4 steel sections in accordance with EN1993‐1‐5, two different methods are proposed; The Effective Section Method (ESM) and the Reduced Stress Method (RSM). The ESM is generally known for leading to results closest to the post‐buckling capacity, with the RSM considered more conservative. The RSM is much more general though, and a combination formula is present for combining longitudinal stresses, transverse stresses and shear stresses, whereas a suitable combination formula is not available for the ESM.

In connection with the steel design of the orthotropic composite deck on the Queensferry Crossing, an investigation into the suitability of the ESM was made. This, as it was believed that the use of this method would lead to the most cost‐efficient design. The Queensferry Crossing (1) has stay cable planes positioned near the middle of the deck, leading to a transverse continuous compressive stress in the bottom steel plate. As EN1993‐1‐5 (2) does not provide a method for combining longitudinal stresses with continuous transverse stresses when using the ESM, a need for a suitable combination formula was evident.

In this paper a combination formula for combining longitudinal stresses, uniform transverse stresses and shear stresses in an orthotropic steel panel using the ESM is proposed. A typical panel from the Queensferry Crossing is used, when results from the ESM and RSM are compared for various stress distributions, with results from a fully non‐linear FE shell model. A good relation between the ESM and the fully non‐linear FE shell model is found, when the combination formula is used, and it is shown that significant savings to the steel quantities can be made by utilizing this combination formula.