EC8-based seismic design and assessment of self-centering post-tensioned steel frames with viscous dampers

•SC-MRFs designed according to the EC8 strength and stiffness criteria, eliminate the probability of collapse under the MCE.•Dampers along with strict design criteria for the PT connections can achieve immediate return to occupancy under the DBE.•SC-MRFs with dampers have superior collapse resistance compared to conventional steel MRFs.

This paper focuses on seismic design and assessment of steel self-centering moment-resisting frames (SC-MRFs) with viscous dampers within the framework of Eurocode 8 (EC8). Performance levels are defined with respect to drifts, residual drifts and limit states in the post-tensioned (PT) connections. A preliminary pushover analysis is conducted at the early phase of the design process to estimate rotations and axial forces in post-tensioned (PT) connections instead of using approximate formulae. Different designs of an SC-MRF with viscous dampers are considered to investigate all possible scenarios, i.e. use of dampers to achieve drifts significantly lower than the EC8 drift limit; to significantly reduce steel weight without exceeding the EC8 drift limit; or to reduce steel weight and achieve drifts lower than the EC8 drift limit. Nonlinear dynamic analyses using models capable of simulating all structural limit states up to collapse confirm the minimal-damage performance of the SC-MRFs. It is shown that the use of the preliminary pushover analysis makes the design procedure very accurate in predicting structural and non-structural limit states. Supplemental damping along with strict design criteria for the post-tensioned connections are found to significantly improve the seismic performance of the SC-MRFs. Moreover, the paper shows that SC-MRFs with viscous dampers have superior collapse resistance compared to conventional steel MRFs even when the SC-MRF is significantly lighter than the conventional MRF.