Seismic risk evaluation of steel structures based on low-cycle fatigue

A methodology to incorporate low-cycle fatigue as part of the ductility requirement in seismic risk assessment of steel structures is presented. As expected, the correction factor γ for the conventional ductility (i.e., ratio of maximum deformation to yield deformation) is proportional to strong motion duration and structural system characteristics (i.e., the expected number and distribution parameters of plastic excursions). For the example presented in this paper, γ was calculated to be between 1,35 to 2.6 for a strong motion duration of 7.5 seconds to 20 seconds. (orig./HP)