APPLICATION OF CONTROLLED ROCKING MECHANISM TO THE SEISMIC UPGRADING OF UPPER-DECK TYPE STEEL ARCH BRIDGES

Abstract

A new seismic upgrading method that employs a controlled rocking mechanism is proposed to improve the performance of upper-deck type steel arch bridges under transversely input earthquake waves. In this method, a rocking behavior that accompanies uplifts is allowed both for end piers and arch ribs. Furthermore, the rocking behavior is controlled by the energy dissipation rods installed at the bases of piers and arch ribs. The validity of the newly proposed seismic upgrading system is numerically examined under severe earthquake waves. As a result, the damages and the reaction forces observed in the original arch bridges are considerably reduced by the use of the new upgrading mechanism. Specifically, reduction of the damages and reaction forces in arch bridges is remarkable in case when the end piers and the arches have high shear rigidity and large aspect ratio. Since the proposed seismic upgrading system is installed at the bases of piers and arch ribs, this system will be easily implemented in the existing bridges. In addition, the installation or change of the energy dissipation rods is possible under dead load because the arch bridges can carry the dead load without these rods.