Rules on high strength steel (RUOSTE): final report

Both industry and architects are interested in increasingly wide spanned and slender structures, raising the demand in high yield stress resistance of steel structures to save weight and finally costs. Several manufactures are able to provide steel grades even higher than S1100, but the rapid development of the production outpaced the present design rules given by Eurocode 3. EN 1993-1-1 covers steel grades up to S460 and rules for higher steel grades are given in EN 1993-1-12 (although CENTC250/SC3 intends to discontinue EN 1993-1-12 by integrating higher steel grades into EN 1993-1-1). Many rules in EN 1993-1-12 were adjusted from mild steel for HSS on a very conservative basis to tackle concerns regarding unlimited transferability, as the time for further testing and dissemination of results was short. This concerns especially issues related to less ductility, based on existing definitions, of HSS and lower ductility in joints, leading to reduction factors which rely, at least partly, on engineering judgement and are in large parts not based on physical or technical background. Studies by Beg on steels of Grade S690 [2] have already established inadequacy of ductility rules in EN 1993-1- 12 in relation to high strength steels. The project Ruoste aims to contribute by means of tests and analytical approaches towards removing the most severe obstacles with regard to ductility and stability issues, as well as tubular joints. Possible benefits of such efforts were examined in the case studies, where new design recommendations were implemented in structural examples.