Report No.: CCEER-13-18
Title: Seismic Response of a Highway Bridge with Structural Fuses for Seismic Protection of Piers
Authors: Mohebbi, A., Ryan, K. and Sanders, D
Department of Civil Engineering/258
University of Nevada, Reno
Reno, NV 89557
Previous research and experience demonstrates that post-earthquake downtime can cripple the transportation network, damage the economic viability of the region, and possibly have more far-reaching consequences due to the trickle down effects. Thus, the current bridge research addresses not only life safety, but also continued operation after earthquakes.
A new strategy for seismic protection of bridge piers is proposed that uses sliding bearings as structural fuses that can capacity protect the pier columns and limit their response to the linear elastic range. The strategy was applicable to bridges with dropped bent cap, and integral and semi-integral abutments. In this study, the influence of the structural fuses on the seismic response of a representative 3-span highway bridge with 3 column piers and integral abutments was investigated. Utilizing OpenSees software, the bridge was modeled with and without structural fuses, and the model included the effect of soil interaction at the abutments.
Two different types of analysis were applied to the model: (1) static pushover analysis to determine the elastic capacity and the nonlinear behavior of bridge components such as columns, piles, and abutments in both the longitudinal and transverse directions, and (2) nonlinear response history analysis to compare the seismic responses of the bridge components with and without structural fuses. Nonlinear response history analysis was performed on the model for a suite of 20 ground motions scaled to 100%, 150%, and 200% of the design spectrum. Six different friction coefficients (2%, 6%, 9%, 14%, 18%, and 22%) of the structural fuses were considered to evaluate the influence of friction coefficient on the bridge and abutment responses.
Results showed that the structural fuses constrained the columns to linear elastic response in both the longitudinal and transverse direction. Furthermore, the abutment ductility demand in the fused bridge was nearly identical to that of the conventional bridge and insensitive to the friction coefficient in both the longitudinal and transverse directions.
This case study demonstrated that structural fuses have the potential to improve the seismic performance of bridges by eliminating plastic hinging and associated damage in pier columns without significant changes to the abutment displacement demands.