Experimental and numerical study on adaptive-passive variable mass tuned mass damper

Tuned Mass Dampers (TMDs) are widely used in human-induced vibration control of footbridges. When they are tuned to the footbridges' fundamental frequency, they have good effects in vibration control. However, TMDs are highly sensitive to deviations in the natural frequency of footbridges, which leads to mistuned TMDs and their control effects will decrease sharply. Traditional in-service TMDs used in the footbridges cannot retune themselves. In this paper, a new TMD named Adaptive-Passive Variable Mass TMD (APVM-TMD) is proposed, which is an upgrade device of the formally invented Self-Adjustable Variable Mass TMD (SAVM-TMD). It can retune itself through varying its mass by an acceleration sensor, a microcontroller and actuating devices, without any manual operations. The structural acceleration under ambient excitation is recorded and processed by an acceleration sensor and a microcontroller, then the footbridge's fundamental frequency can be identified by Short-Time Fourier Transformation (STFT) - based algorithm. Subsequently, the microcontroller will retune the APVM-TMD by controlling actuating devices to vary its mass. The performance of APVM-TMD is studied via both experimental studies and numerical simulations under different human-induced excitations. The damper's working performance with an identified frequency, optimal frequency and structural actual frequency is investigated, and the influencing parameters (e.g., mass ratio, optimal frequency ratio and damping ratio) are studied. The detailed comparative study and the advantages of APVM-TMD over SAVM-TMD are highlighted. The results show that the proposed APVM-TMD can easily retune its frequency with little power consumption. Although the footbridge frequency may change for certain reasons, this damper can still effectively reduce structural acceleration response and increase equivalent damping ratio. APVM-TMD is better than SAVM-TMD in the robustness, economy and operational convenience. (C) 2019 Elsevier Ltd. All rights reserved.