Study on self-adjustable tuned mass damper with variable mass

Tuned mass dampers (TMDs) represent a quite mature technology for controlling human-induced vibrations of footbridges, when they are tuned to the primary structure's fundamental frequency. However, the TMD is very sensitive to even a small change in the tuning ratio. This paper proposes a novel TMD named self-adjustable variable mass TMD (SAVM-TMD), which is capable of varying its mass and retuning its frequency on the basis of the acceleration ratio between the primary system and the TMD. The accelerations are obtained from two acceleration sensors, and the frequency adjustment is achieved by using a microcontroller and actuating devices. The acceleration ratio limit value should be set in the microcontroller firstly, and when the adjustment begins, the microcontroller will retune the TMD to a reasonable frequency region, under a specific harmonic excitation. The SAVM-TMD can be regarded as a passive control device capable of adjusting its frequency. The performance of SAVM-TMD is studied via both experimental studies and numerical simulations under different pedestrian excitations. It is found that the SAVM-TMD is effective in reducing the response and improving the equivalent damping ratio of the primary system when the structural frequency changes, with little power consumption. The results obtained from the experimental studies and the numerical simulations agree with each other very well. More pedestrian vibration situations are studied in the numerical simulations, and the results also show that the SAVM-TMD has excellent performance in controlling human-induced vibrations.