Seismic performance of railway rocking hollow tall piers under near-fault ground motions

Railway round-ended hollow tall piers are widely used in the high-intensity mountainous areas of Southwest China. However, this gravity/tall pier based on the ductility design approach has a large mass and significant inertia force. To control the plastic damage of the pier under strong ground motion and reduce the seismic force transmitted to the foundation, this paper proposes the method of damage control through the design of a rocking pier with energy dissipation devices and applies it to the typical hollow tall piers of a railway. Static and nonlinear time-history analyses were performed using 3D finite element models to compare the near-fault seismic responses of a conventional fixed base pier (FB-P), a free rocking pier (F-RP), and a rocking pier with additional energy dissipation devices (D-RP). The results show that under the action of near-fault ground motions, the D-RP system based on the pier damage control design accurately controls the pier column to avoid exceeding the expected damage level; the F-RP and D-RP systems basically achieve "zero" residual displacement after ground motion. The additional energy dissipation devices at the bottom of the rocking pier effectively suppress the collisional action at the rocking interface and significantly reduce the responses of both the internal force at the pier bottom and the displacement at the pier top. The velocity pulse effect of the near-fault ground motion has a significant amplification effect. The addition of energy dissipation devices at the pier bottom can effectively reduce the amplification effect and the discreteness of the seismic response and improve the postearthquake predictability of this type of bridge pier.