Longitudinal displacement control of a long-span suspension bridge under random traffic loads using a polyimide friction damper

This paper proposes a novel method to control the cumulative displacement of the girder end of a long-span suspension bridge caused by traffic loads using friction dampers. Friction dampers have Coulomb damping characteristics and high initial stiffness, providing a significant damping force at low speed to suppress the longitudinal deformation of the girder end. The working mechanism of the friction damper is explained, and the performance of the proposed polyimide (PI) friction damper is tested. A random traffic load model of a long-span suspension bridge is established, and the longitudinal displacement, reaction force time history, longitudinal peak displacement, and cumulative longitudinal displacement (CLD) under different yield forces of the PI friction damper are analyzed. We propose the excess ratio & delta; of the yield displacement to determine the optimum yield force. The influences of different vehicle speeds and traffic flows on the performance of the PI friction damper are discussed. The results show that the PI friction damper substantially reduces the longitudinal displacement, longitudinal peak displacement, and CLD of the girder end; the reduction rate of the CLD exceeds 57% when the yield force of the PI friction damper is 1000 kN. The vehicle speed and traffic flow have negligible influences on the CLD of the long-span suspension bridges equipped with PI friction dampers in the normal working range.