Buckling restrained braces as structural fuses for the seismic retrofit of reinforced concrete bridge bents

A structural fuse concept is proposed in which easily replaceable ductile structural steel elements are added to an RC bridge bent to increase its strength and stiffness, and also designed to sustain the seismic demand and dissipate all the seismic energy through hysteretic behavior of the fuses, while keeping the RC bridge piers elastic. While this concept could be implemented in both new and existing bridges, the focus here is on the retrofit of non-ductile reinforced concrete bridge bents. Several types of structural fuses can be used and implemented in bridges; the focus in this paper is on using Buckling Restrained Braces (BRB) for the retrofit of RC bridge bents. The results of a parametric formulation conducted introducing key parameters for the design procedure of the fuse system, validated by nonlinear time history analyses are presented. A proposed design procedure, using BRBs as metallic structural fuses, is found to be sufficiently reliable to design structural fuse systems with satisfactory seismic performance. A graphical representation to help find admissible solutions is used, and shows that the region of admissible solution decreases when the frame strength ratio increases as a larger fuse element is required to achieve an effective structural fuse concept.