Seismic response comparison of steel MRFs with yielding and low-damage connections

The development of low-damage steel moment resisting connections for seismic applications provides designers with techniques to dissipate energy without relying on plastic deformations of beam sections, thus avoiding connection strength and stiffness deterioration and providing the opportunity of adding a self-centering mechanism to avoid residual displacements. In this paper, the system-level performance of two low-damage connections, the sliding hinge joint (SHJ) connection and the self-centering sliding hinge joint (SCSHJ) connection, is evaluated using analytical models. New component models are developed for each of the connections and validated using available experimental results. The global performance of three steel frames of different heights, using either the SHJ connection or SCSHJ connection, are then compared to otherwise identical frames with either pre-Northridge (PRENORTH) connections or reduced beam section (RBS) connections. The benefits of these new connections for the global performance of the frames are presented through fragility curves for 27 response indices, comprising three engineering demand parameters (maximum inter-story drift, residual drifts, and accelerations) under three earthquake hazard types (shallow crustal, subduction, and main-shock-after-shock combinations) for three performance objectives. The global performance of the frames with the SHJ connection is similar to that of frames with the RBS connection, while avoiding yielding and damage in the connections. The SCSHJ connections further enhance the good performance of the SHJ connection by also reducing residual drifts and peak floor accelerations. This improvement in performance translates directly to reductions in the expected annual loss, particularly for structures exposed to longer duration ground motions or main-shock-after-shock sequences.