Improving inter-story drift distribution of steel moment resisting frames through stiff rocking cores

Abstract

This investigation assesses adequacy of the Stiff Rocking Core (SRC) technology for rehabilitating steel Moment Resisting Frames (MRFs) vulnerable to drift concentrations and soft-story failures. The technology installs a single or multiple SRCs pinned to the foundation and connected to a deficient multi-story steel MRF to re-distribute seismic forces along its height and create more uniform inter-story drift and ductility demand distributions. This research team implemented the SRC technology in two archetype steel MRFs including one three-story and one nine-story. Results from nonlinear static analyses show that the SRC technology can reduce inter-story drift concentration in both steel MRFs regardless of the seismic force distributions and drift limits considered in design. Additionally, the SRC extending along the entire height of a steel MRF is more preferable than the one extending over the bottom portion of the system, although these two SRC options can be both valid in many cases.