Hybrid Testing of Seismically Isolated Bridges

TitleHybrid Testing of Seismically Isolated Bridges
Publication TypeReport
Year of Publication2012
Tsitos A, Bousias S
Series TitleSEE Reports series
Date PublishedJanuary 2012
InstitutionUniversity of Patras
CityPatras, Greece
ISBN Number978-960-89691-8-6
Report NumberReport no. SEE 2012-03

Elastomeric bearings have long been employed in bridge structures and their response under horizontal loading action has been experimentally studied by applying – slow or real-time – displacement cycles to failure. The experimental study of the actual response of bridges on elastomeric bearings under earthquake action presents difficulties due to the required size of the test specimens and thus one resorts to substructuring methods.
In this report a pre-test characterization procedure for determining the rate-dependent response of bearings - to be accounted for in non-real-time, sub-structured hybrid testing - is presented. The results of this phase are then employed to calculate an additional force term that is taken to depend on certain parameters of the response (level of bearing deformation, velocity, force and force rate). The latter force term is added to the restoring force measured at each step during hybrid testing, so that the displacement to be applied at the next step (at a slow rate) encompasses an approximate estimation of the effect of rate on material response.
The procedure was applied to commonly used isolation bearings and results from a testing campaign on a series of isolators are presented. It is shown that the rate-dependent response of bearings can be approximately accounted for in non-real-time testing and that in isolated bridges the deformation demand placed on plain low damping elastomeric bearings may exceed their capacity under actual earthquakes.

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