Determination of the behaviour factor of steel moment-resisting (MR) frames by a damage accumulation approach

In most countries, seismic codes are changing, reflecting a new design philosophy based on multiple performance levels. A procedure that defines behaviour factors to reduce the elastic spectrum for different types of structures, considering all possible types of failure, is needed. The paper presents a method for the definition of the behaviour factor (q-factor) for multi-storey steel frames, accounting for cumulative damage in structural components, by means of linear elastic time history analysis, of the Palmgren-Miner rule and of S-N (constant stress or strain range versus number of cycles to failure) curves extrapolated in the low-cycle fatigue range. This technique has been verified by a non-linear procedure that is different from the previous one, as a non-linear time history analysis with damage control has been performed instead of a linear one. The proposed approach can be useful in performance based design, since the linear procedure allows the definition of the q-factor corresponding to different level of damage or collapse prevention. (C) 2009 Elsevier Ltd. All rights reserved.