Study on the fluctuating wind responses of constructing bridge towers with magnetorheological elastomer variable stiffness tuned mass damper

Abstract

Constructing bridge towers are high-rise and flexible structures subjected to significant wind induced vibrations. Tuned Mass Dampers (TMDs) have been widely used to reduce dynamic responses of high-rise structures under fluctuating wind loadings. By resonance with main structure, TMD can effectively suppress structural vibrations. However, the natural frequencies of bridge tower usually decrease continuously during its construction progress. The frequency shift characteristic will cause the detune of TMD, leading to a great control efficiency loss. As a novel stiffness tunable device made of magnetorheological elastomer (MRE), MRE-TMD can adjust its natural frequency in real-time to track the main structure, avoid detuning and achieve better control performance. To study the wind induced vibration control performance of MRE-TMD, this paper explores the fluctuating wind responses of constructing bridge towers in along wind and cross wind directions. The fluctuating wind loads are generated by harmonic superposition method with the along wind fluctuating wind speed spectrum and the empirical power spectrum of fluctuating lift force. By comparing among the uncontrolled, TMD controlled and MRE-TMD controlled constructing bridge towers, the simulation results show that the MRE-TMD system can effectively maintain the tuning state, and significantly reduce the wind induced vibrations during whole construction process.