Residual drift demands in moment‐resisting steel frames subjected to narrow‐band earthquake ground motions

This paper presents the main results of the evaluation of residual inter-story drift demands in typical momentresisting steel buildings designed accordingly to the Mexican design practice when subjected to narrow-band earthquake ground motions. Analytical 2D-framed models representative of the study-case buildings were subjected to a set of 30 narrow-band earthquake ground motions recorded on stations placed in soft-soil sites of Mexico City, where most significant structural damage was found in buildings as a consequence of the 1985 Michoacan earthquake, and scaled to reach several levels of intensity to perform incremental dynamic analyses. Thus, results were statistically processed to obtain hazard curves of peak (maximum) and residual drift demands for each frame model. It is shown that the study-case frames might exhibit maximum residual inter-story drift demands in excess of 0.5%, which is perceptible for building’s occupants and could cause human discomfort, for a mean annual rate of exceedance associated to peak inter-story drift demands of about 3%, which is the limiting drift to avoid collapse prescribed in the 2004Mexico City Seismic Design Provisions. The influence of a member’s post-yield stiffness ratio and material overstrength in the evaluation of maximum residual inter-story drift demands is also discussed. Finally, this study introduces response transformation factors, Tp, that allow establishing residual drift limits compatible with the samemean annual rate of exceedance of peak inter-story drift limits for future seismic design/evaluation criteria that take into account both drift demands for assessing a building’s seismic performance. Copyright © 2013 John Wiley & Sons, Ltd.