Dynamic testing and parameter identification of a base-isolated bridge

In this paper the results of a campaign of harmonically forced vibration tests conducted on a two-span post-tensioned reinforced concrete bridge with deck supported on six elastomeric isolators are presented and discussed. The bridge is built in an area of the Friuli Venezia Giulia Region (Northern Italy) having high level of seismic activity. Dynamic measurements are used to update a preliminary finite element model of the bridge. The accurate estimate of the shearing stiffness of the isolators constitutes an important issue of the updating process, both for the evaluation of the dynamic response in service or under seismic actions, and for the evaluation of possible changes in the structural behavior as a result of degradation of the elastomeric bearings. An identification procedure based on experimental data and analytical models of increasing complexity is proposed to estimate the stiffness of the isolation devices and, ultimately, to determine an accurate numerical model of the bridge.