During the last decades modelling of inelastic structural behaviour has achieved great attention. Wherever elastic designhas reached its limita sa consequence of increased loading, the related cons titutive rela tions meanwhile have become part of the engineer's practice. However, new materials with complex behaviour, further increasing loads at higher temperatures, as well as the implementation of stronger security demands have led to theconsequence that the preferentially used phenomenological concepts need to be verified and improved continuously. Caused by the a priori non linear...