Optimization of plate girders

The costs of the self-weight of a structure have never been a real issue in the design of steel girders, since the material costs of a structural element are mainly determined by labour costs. The booming economies of China and India cause a continuously increasing demand for steel. This and the now stringent regulations regarding sustainability make material economy in design much more interesting.
In a material economy-driven plate girder design, the lever arm between the flanges will increase. This leads to a higher stiffness and bending moment resistance, but also to an increase in the web slenderness of the girder. This means that high-strength steels can be used, leading to a large reduction in steel consumption.
Eurocode 3, EN-1993-1-5, [1] restricts the web slenderness based on the formula to avoid flange-induced buckling, originally derived by Basler [2]. However, experimental and theoretical research conducted on 10 unstiffened plate girders with high web slenderness ratios at the Stevin II Laboratory of Delft University of Technology shows that this formula is too conservative.
This paper presents the results of this research and suggestions for a new plate girder design strategy.