Longitudinal motion control of an extra-long-span double-layer steel truss suspension bridge under random traffic flow: Modeling, response characteristics, and damping solutions

Extra-long-span suspension bridges are essential for modern transportation infrastructure, but their vulnerability to excessive longitudinal displacement under random traffic loads poses significant challenges to their structural integrity and longevity. This paper addresses the challenge of dynamic analysis and longitudinal cumulative displacement mitigation for extra-long-span double-layer steel truss suspension bridges, focusing on a bridge with a main span of 2180 m. First, a novel modeling framework is proposed, balancing high accuracy with improved computational efficiency. Then, the study investigates the dynamic response characteristics of the bridge under random traffic flow loads, identifying critical vehicle speed ranges for controlling longitudinal displacement. Finally, friction and viscous dampers are evaluated for their effectiveness in mitigating cumulative displacement at the girder ends. Results show that friction dampers, with increased sliding forces, significantly reduce displacement, while viscous dampers with low damping exponents (<0.2) also provide effective control. These findings offer practical solutions for enhancing the dynamic stability and extending the service life of extra-long-span suspension bridges.