Seismic design and performance study of self-centering moment-resisting frames with sliding rocking beams and preloaded disc springs

This paper focuses on the seismic analysis and performance assessment of the self-centering moment-resisting frames with sliding rocking beams (SCMRF-SRB) through a nonlinear numerical simulation study. In the SCMRF-SRB systems, the beam is comprised of three segments with the rocking beam placed in the middle segment. The beam growth (expansion) problem due to the gap-opening in the rocking joint is counteracted by the sliding movement of the rocking beam inside the beam brackets. The restoring force of such SCMRF-SRBs is generated by two sets of preloaded disc springs mounted on each side of the web of the beam and the energy dissipation is provided by replaceable hysteretic dampers (RHD). The relative movement of the rocking beam inside the brackets generates a friction force that contributes to the energy dissipation capacity and strength of the system based on prior experimental observations. Load vs. displacement relationships of an SCMRF-SRB modular structure were formulated and verified with nonlinear finite element analysis results. A three-story building located in downtown Seattle was designed and its seismic performance was studied through nonlinear static and dynamic analyses. According to the results of the nonlinear dynamic analyses, the prototype structure met the expected performance criteria in terms of inter-story drift ratio (IDR), re-centering behavior, and responses of the frame member at design basis earthquake (DBE). In different parametric studies, the effect of the length and location of the rocking beam on the seismic performance of the prototype structure was investigated. Moreover, the effects of the energy dissipation capacity and post-yielding stiffness on the structural responses of the prototype buildings were studied. It was also shown that an SCMRF-SRB structure with a large energy dissipation ratio of up to 90% can be utilized without adversely affecting the self-centering performance of the system.