Experimental seismic performance of a hybrid sliding-rocking bridge for various specimen configurations and seismic loading conditions

This paper presents the major findings of a shake table testing program on a large-scale (1:2.39) novel segmental concrete single-span bridge specimen. Emphasis is given on various specimen configurations and seismic loading conditions. The bridge specimen, termed hybrid sliding-rocking bridge, incorporated a box-girder superstructure with rocking joints and internal unbonded posttensioning (PT), and two single-column piers with internal unbonded PT. The pier columns included end rocking joints and intermediate sliding joints along the column height. Various configurations of the bridge specimen were considered with respect to the seismic mass and the superstructure-to-substructure connectivity. These configurations were subjected to far-field (F-F) and near-fault (N-F) ground motion ensembles scaled to various seismic hazard intensities. Asynchronous support excitation was also considered. The testing program included approximately 145 seismic tests. The dynamic response of the specimen was found to increase with the seismic hazard intensity and the seismic mass. Near-fault motions resulted in larger deformations in comparison to far-field (F-F) motions, particularly in the vertical direction. Asynchronous support excitation resulted in smaller system deformations compared with in-sync shaking. The system residual deformations, including sliding at the column joints, were small.