Experimental Study on Train-Induced Longitudinal Movements and Control Measures for a Suspension Bridge Using a Scaled Model

This study investigates the longitudinal reciprocating movement of the stiffening girder caused by trains passing over suspension bridges, which can adversely impact expansion joints, bearings, dampers, and overall train running safety. In contrast to previous studies, this work employs a scaled model experiment to investigate the longitudinal motion and its control strategies. A 1:100 scale model of a suspension bridge and a trainset model are designed and fabricated, based on a railway suspension bridge currently under construction. The design and fabrication processes of these models are described in detail, with particular attention on how the scaling factor is utilized to approximate the dynamic behavior of the full-scale structure. The dynamic characteristics of the scaled model, including key modal frequencies and damping ratios, are rigorously tested and analyzed, particularly the influence of friction at bearings and switches on the structural dynamics. Additionally, train-running tests under various conditions (such as changes in driving direction, train weight, and speed) are conducted to measure the longitudinal and vertical displacement responses of the stiffening girder. The resulting measured data provided invaluable insights into the bridge's behavior under different operational scenarios. For the purpose of response mitigation, the study also evaluates the effectiveness of three cable-based structural control measures and an eddy current damping technique. The scaled model testing approach adopted in this study, together with the validated effectiveness of various longitudinal motion control strategies, not only provides direct insight into the characteristics and mechanisms of train-induced longitudinal movements, but also offers practical methodological guidance for the design of longitudinal restraint systems in long-span railway suspension bridges.