Experimental Study of Bridge Seismic Isolation Systems with or without Supplemental Energy

Abstract eng:
The seismic response of isolated bridges is studied experimentally for three different isolation systems which provide, separately or in combination, lengthening of the period and additional energy dissipation. A multi-span highway bridge is subjected to hybrid (sub-structured pseudodynamic) testing, with on-line correction of the measured restoring forces for the velocity-dependent properties of the isolation devices. Common (low damping) elastomeric bearings, lead-rubber bearings (LRBs) and elastomeric bearings coupled with magneto-inductive dissipation devices were tested at several levels of excitation. A broad parametric experimental study was conducted regarding the influence of certain parameters such as the mass of the deck and the level of ground motion. The elastomeric bearings did not satisfy the design requirement of 200% strain at ultimate, but displayed a somewhat higher damping ratio than anticipated. The LRBs provided effective bridge protection reaching almost a strain level of 175% at ultimate and an effective damping ratio of 16%. The combination of elastomeric bearings with a magneto-inductive damper proved to be extremely efficient in containing the response and protecting both the bridge and the bearings.

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