Buckling Restrained Braces Applications for Superstructure and Substructure Protection in Bridges

Keywords: Earthquake engineering; buckling restrained braces; bridge; seismic protection; structural fuse; bi-directional end diaphragm.

Abstract: This report considers two applications of implementing Bucking Restrained Braces (BRBs) as structural fuses into new and existing bridge structures: (i) added between columns of a bridge bent, and (ii) inserted in the end-diaphragms of slab-on-girder steel superstructures. Design procedures are proposed for designing BRBs in both applications based on analytical and experimental results. Dynamic nonlinear time history analyses were performed on the bridge models to investigate their global behavior after adding the BRBs, and to understand the magnitude of local demands on the BRBs and other bridge members. Analytical and experimental studies are conducted for BRB’s gusset plates welded to CFT columns to investigate the connection strength for seismic applications. Quasi-static experiments are performed to subject two types of BRBs to a regime of relative end displacements representative of the displacement demands when BRBs are implemented in ductile diaphragms. The use of BRBs in these applications was found to enhance the seismic performance of bridges.