Seismic Design Parameters Assessment of Special Steel Moment Resisting Frames Using the Collapse Margin Ratio (CMR) Method

This research intends to quantitatively evaluate the seismic parameters of special steel resisting moment frames designed via the prescribed values in the Iran standard No. 2800. Sixteen designed frames having 4, 6, 8, and 12 stories and grouped into four types are dynamically non-linearly analyzed by means of OPENSEES software incorporating the element stiffness degradation. The general far-fault 22 record pairs presented by FEMA_P695 is used in the process of preparing the frame’s fragility curves where are localized with multiplying their medians by corresponding predicted spectral shape factors (SSF). The frame’s seismic parameters (R factor and over-strength factor) are calculated using two methods; FEMA_P695 criteria, developed on the basis of epsilon as the spectral shape parameter, and the proposed approach, developed on the actual definition of spectral shape parameter. The results of this study showed that use of FEMA_P695’s rules end up with acceptable groups’ seismic parameters, opposed to those groups where have been associated with rock and soft soil conditions and judged by the other approach. It is expected that the whole seismic parameters presented in the standard No. 2800 will be evaluated based on the currently used analytical methods in the near future.