Retrofitting Suspension Bridges Using Distributed Dampers

Abstract

Suspension bridges in the Central and Eastern United States (CEUS) were built before recent advances in earthquake engineering, and may be susceptible to seismic ground motions. A retrofit strategy is proposed in which damping devices are distributed throughout the suspended truss structure in order to reduce the bridge response. Six ground motions suites are assembled; three synthetic motion suites representing expected CEUS motions, with special attention paid to the long-period range. The three remaining motions are recordings of actual events. A finite element model of a suspension bridge typical of those found in the CEUS was subjected to the assembled ground motions both in a baseline and retrofitted condition. The proposed retrofit strategy successfully reduced the demands on both the superstructure and substructure of the subject bridge. Specific locations for the damping devices were identified as being especially effective. The inclusion of spatial variations in the input ground motions can have a large effect on the response. The method may be useful for mitigating dynamic responses caused by wind.