Multi-level Response Modification Factor Estimation for Steel Moment-Resisting Frames Using Endurance-Time Method

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ABSTRACT The computational complexity and high computational costs are the main obstacles to estimate the seismic demand and capacity of non-linear structural systems and assess their seismic performance under strong earthquake events. On the other hand, the current response modification factors for seismic design of structures are mainly based on a single performance target, and therefore, cannot be directly used in modern performance-based design procedures. In this study, a low computational cost method is adopted for seismic performance assessment of steel moment-resisting frames and development of multi-level modification factors by using the newly-developed Endurance-Time method. The efficiency of the proposed method is demonstrated for 3, 5, and 7-storey frame examples. It is shown that compared to conventional methods using time-history and pushover analysis techniques, the proposed approach can significantly (up to 80%) reduce the computational costs. The results indicate that push-over analyses may lead to inaccurate results, while a good agreement is generally observed between the seismic demands predicted by Endurance-Time and Time-History methods (less than 10% error). The results of Endurance-Time method are then used to develop multi-level response modification factors for steel moment-resisting frames by taking into account the effects of earthquake intensity and the target performance level. It is shown that Endurance-Time method can accurately estimate the response modification factors and the corresponding earthquake intensity levels with significantly less computational cost compared to the conventional methods using incremental dynamic analysis. The proposed multi-level response modification factors should prove useful in performance-based seismic design of steel moment-resisting frames.