METALLIC DAMPERS FOR SEISMIC DESIGN AND RETROFIT OF BRIDGES

A practical bearing scheme is proposed in this study, consisting of expansion rocker bearings and steel rods (metallic dampers). It can accommodate seismic effects while it allows for free thermal expansion. Tests of metallic dampers have shown that dampers of straight rods can contribute over 10% damping at the small-to-medium displacement range. Extensive tests on a 1/10-scale bridge model indicated that metallic dampers can also significantly reduce the dynamic responses of the bridge by isolating vibration propagating from the substructure to the superstructure. High rocker bearings provided considerable damping to the bridge-damper system by dissipating energy along the friction surface between pin and web of the bearings. They remain stable even at the peak ground acceleration of 0.54g at resonance. To account for pounding effect at the expansion joints of bridges, design equations for determining the equivalent viscous damping corresponding to various sizes of bridge joints were developed. Integrating the equivalent damping into the response spectrum analysis procedure allows engineers to analyze the bridges with pounding effect in a linear fashion.