Effect of ground motion characteristics on sliding response of elastomeric pad bearings in highway bridges

Facing the frequently occurred seismic damage of shifting or even unseating of girders in highway bridges whose elastomeric pad bearings are not connected appropriately with the pier and girder, this paper discusses the main influencing factors and presents the effect of ground motion characteristics on sliding response of elastomeric pad bearings based on non-linear time-history analysis of a single pier model, in which the sliding effect of elastomeric pad bearings is characterized by a flat sliding bearing element. The ground motion characteristics studied in this paper include peak ground acceleration, dominant frequency and energy content, and details of the pulses contained in ground motions. The results show that the sliding response of elastomeric pad bearings is a function of the peak ground acceleration and the ratio of peak ground acceleration to peak ground velocity. Besides, the details of the pulses contained in ground motions may have significant influence on the sliding response. Thus, in order to conduct a correct seismic design of highway bridges on elastomeric pad bearings, the seismic ground motions should be chosen according to the characteristics of the bridge site, and particular attention should be paid to the possible unexpected effect of the details of pulse in ground motion when using empirical statistical correlations to predict the sliding response in individual cases.