Case Study on Applications of Structural Fuses in Bridge Bents

In seismic design, bridges are typically designed to undergo inelastic deformations during a severe earthquake. In those instances, most of the seismic energy is dissipated through hysteretic behavior of the critical load-resisting components, which results in permanent system deformations and damage and could make repairs expensive or, in some cases, impossible. Thus, concentrating earthquake damage in structural fuses inserted in bridge bents is desirable; the performance objective is for the main gravity load-bearing members (the columns, in this case) to be intact after an earthquake, limiting repairs to fuses that can be removed and replaced easily. This paper presents results from case studies that considered the use of buckling-restrained braces (BRBs) as hysteretic energy-dissipation devices inserted in bridge bents to dissipate earthquake energy and improve structural performance by minimizing inelastic demands on the columns. A typical California bridge was used for this purpose. For structural fuse application only in the transverse direction (along the bent), results indicate that BRBs are implementable. Alternative bent configurations were also considered to provide the benefit of structural fuses for seismic excitations in the bridge's longitudinal and transverse directions. Findings are presented along with observations from a comparison of seismic responses between bridges with and those without structural fuses in their bents.