Choice of steel material to avoid brittle fracture for hollow section structures

European cold-formed hollow sections in general exhibit better toughness properties than required by EN 10219. However, limits in applying the toughness related rules for the choice of steel material in EN 1993 1 10 to cold-formed hollow sections still constitute barriers to free marketing. By requests from European producers a conservative assessment procedure has been developed which is based on toughness measurements and a concept using effective strains. Due to the cold-forming process such plastic strains may occur in the bent areas of the profiles associated with a noticeable reduction in material toughness. For the degradation of these toughness properties an appropriate temperature shift ΔTcf has been derived for both circular and rectangular hollow sections. In order to guarantee the proper application of this temperature shift Table 2.1 in EN 1993 1 10 had to be extended to lower temperatures down to -120 °C.