Comparison of Retrofitting Techniques for Existing Steel Moment Resisting Frames

Seismic protection of critical facilities such as hospitals, emergency response centers, and schools is crucial as these buildings must remain in full service after major earthquakes. A new modular, multiple-panel infill system made of a ductile, high performance fiber reinforced concrete (HPFRC) is currently under investigation with a focus on protecting such critical facilities wherein the primary structural system is a steel, moment-resisting frame. The primary objective of this paper is to compare the proposed HPFRC infill panel retrofit system with the alternative retrofit techniques of buckling-restrained braces (BRBs) and viscous dampers for seismic protection of existing steel moment resisting frames. The effectiveness of the three seismic retrofit techniques is evaluated based on analytical simulations after retrofitting the SAC 3-story structure. It is shown that the HPFRC infill panel system when installed in an existing steel moment resisting frame designed prior to major earthquake events (Northridge, 1994, Kobe, 1995) limits residual story drifts as well as frame damage at a design and a maximum considered event. Its seismic response is very comparable with the state-of-the art BRB and viscous damper retrofitting techniques.