SELF-CENTERING DAMAGE-FREE STEEL PORTAL FRAME-TYPE BRIDGE PIERS WITH POST-TENSIONED ENERGY-DISSIPATING CONNECTIONS

Abstract

A new self-centering damage-free seismic resisting system is proposed for steel portal-frame type bridge piers by applying post-tensioned energy dissipating connections (PTED connections) to the beam-to-column connections together with the columnbase-to-footing connections. In this system, the two columns of the portal frames are connected to the footing and the beam by the post-tensioned high strength strands running parallel to the column axes. At the same time, both the beam-to-column and columnbase-to-footing connections include energy dissipation rods installed at the column flanges in the vertical direction. The post-tensioned high strength strands remove the residual deformation of the energy dissipation rods after earthquake, while the semi-rigid action of the PTED connections controls the magnitude of the connection moment and dissipates the kinetic energy of the frames. The advantages of the proposed seismic resisting system over the conventional regid-frame system are examined in terms of the volume of steel obtained as a result of optimum design. In addition, the characteristic seismic behavior of the self-centering damage-free seismic resisting frames is discussed.