Using Buckling-Restrained Braces on Long-Span Bridges. II: Feasibility and Development of a Near-Fault Loading Protocol

Abstract

Buckling-restrained braces (BRBs) are reliable energy-dissipating axial members that recently became popular in the seismic design of buildings. Using the Vincent Thomas Bridge (VTB) as a case study, this research investigates the feasibility of using BRBs for seismic response mitigation of long-span bridges, especially those located adjacent to seismic faults. A satisfactory set of BRBs was identified through a parametric study using a finite-element model of the bridge. Simulated deformational demands on the BRB elements included loading features that are not reflected in current BRB design and testing provisions. Therefore, two new BRB loading protocols were developed for physical testing and prequalification. The simulated seismic response of the bridge was improved by using BRB parameters consistent with those that are commercially available. Therefore, the use of existing BRB technology was deemed feasible as a relatively maintenance-free seismic response mitigation system for long-span bridges near seismic faults. A companion paper discusses a testing program of full-scale BRBs subjected to these new protocols along with the implications for seismic-capacity-based design and testing procedures.