Improved design concepts for steel structures subjected to large strain amplitudes Ultra low cycle fatigue (ULCF) describes the material fatigue behavior when steels structures are subjected to cyclic loads with large strain amplitudes as they appear during earth quakes. ULCF poses great challenge for the development of design rules and safety assessments for steel constructions placed in seismic active zones. In the frame of this work, a coupled damage mechanics model especially for ULCF loading is developed motivated by the horrible accident in Fukushima. The model is based on the two yield surface plasticity model developed by Yoshida and Uemori in 2003 and a damage mechanics approach following the MBW model as presented from Lian in 2015. In order to depict material behavior under ULCF loading, small scale samples are tested. Hereinafter, the material behavior is reproduced by the simulation with the finite element software ABAQUS.