On the plastic design of high-strength steel beams

Particularly efficient steel components can be designed by performing a plastic global analysis of a structure made of high-strength steel (HSS) as well. However, plastic design of HSS structures is not embodied in current standards, which is why a broad research study was carried out to address different aspects of the use of HSS for plastic design. This paper deals with verified numerical investigations of the rotation capacity of HSS I-girders considering realistic true stress-strain curves, local plastic instability and damage mechanics approaches to predict ductile crack initiation. Various influences on the rotation capacity of HSS beams were assessed by varying flange and web slenderness ratios, material characteristics, system dimensions, stiffness of lateral supports and loading conditions so that recommendations for the plastic design of HSS girders can be given. It is apparent that, apart from the slenderness of the flange and the material properties, the slenderness of the web is one of the main influencing characteristics. The results show that the plastic design of HSS structures is possible when limits for cross-section class 1 are more severe for HSS grades over S460 up to S690 compared with the current limits in EN 1993-1-1.