Dynamics of a rocking bridge with two-sided poundings: A shake table investigation

During strong earthquakes, the footing of a rockable bridge can temporarily and partially separate from the support. This rocking motion can activate rigid-like motions, reducing the deformation along the height of bridge piers and leading to smaller bending moments. As a result, rockable footing has been considered as a possibility for low-damage seismic design of structures. For bridges, the seismic-induced interaction between girders and adjacent abutments can change the structural dynamics due to the impeded girder movements. Although bridges with rockable footing, for example, the South Rangitikei viaduct, have been constructed, research on rockable bridges mainly focused on a single-segment case. Physical experiments on rockable bridges considering pounding are very limited. In this work, large-scale shake table experiments were performed on a two-segment bridge model with abutments. The cases without pounding and with girder-girder pounding alone were considered as references to help interpret the results. To investigate the consequence of footing rocking, the results of the rockable bridge on a rigid base were compared to that of the fixed-base bridge. The study reveals that compared to a fixed-base segment, the girder of a rockable segment is easier to move laterally. This change in dynamics due to rocking leads to less maximum pounding forces and thus reduces the damage potential to girders and abutments.