Investigation of atypical seismic response of a base-isolated bridge

The seismic response of a base-isolated bridge is investigated with the help of acceleration data recorded during four moderate to small earthquakes. It is observed that the dynamic behavior of the bridge is not typical of base-isolated bridges as some of the transverse side-stoppers obstructed the movement of isolation bearings. Examination of the recorded transfer functions revealed that the dynamics of the bridge is dominated by the fundamental mode. Fundamental modal frequency and damping ratio of the bridge are identified and consequences of malfunctioning of isolation bearings are examined. It is found that malfunctioning of base-isolation bearings at one pier resulted in substantially unequal lateral load distribution to the substructure which signifies the attention to be devoted to such structural details for desired working of the whole system.