Train-Induced Vibration Control of Simple Beams Using String-Type Tuned Mass Dampers

Since a long-term oscillation of a tuned mass damper (or TMD) in vibration control may impair the spring stiffness of the TMD, this phenomenon will directly down-tune the target frequency of the TMD. For this reason, this study intends to present a string-type tuned mass damper (or STMD) with an adjustable tuning frequency to mitigate the resonant response of a simple beam due to moving loads. The STMD device is installed inside the inner room of a bridge box girder and is composed of a distributed spring-dashpot-mass with a stretched string. Considering a linear beam-STMD model, a generalized two-degrees-of-freedom system is employed to determine the optimum tuning frequency condition and parameters of the STMD in vibration control. Compared with a traditional TMD device, the proposed STMD has the advantage of being adjustable in tuning frequency. From the numerical examples, the results indicate that the proposed STMD is a potential vibration control device in suppressing the train-induced vibration of railway bridges. Even though the tuning frequency of the STMD down-deviate from the target one by 10%, the control effectiveness of such a detuning STMD can still achieve about 90% as that of an optimal STMD by tuning its frequency to fit the optimum tuning frequency condition presented in this study.