Abstract
Tuned mass dampers (TMDs) are applied to ensure the safety and stability of offshore platforms; however, linear dampers are effective for a single resonance frequency, providing vibration suppression only within a narrow frequency band. Therefore, this paper proposed a magnetic TMD with two pairs of permanent magnets on both sides of the structures, which can generate a nonlinearly repulsive force, making the magnetic TMD reliable and robust in damping the oscillations of structures with wide frequency range under seismic excitations. A comprehensively numerical and experimental study was processed to investigate the dynamic performances of the proposed magnetic TMD, by application of a 1 : 200‐scale prototype of the offshore platform. The results verified that the performance of the magnetic TMD can be significantly improved than that of the linear TMD, meanwhile maintaining high‐speed response characteristics. The experimental results indicated that the displacement, acceleration, and frequency responses of the offshore platform can be significantly reduced; furthermore, the evaluation indices showed that the magnetic TMD system is credible in reducing the overall vibration levels and maximum peak values.
Highlights
An offshore platform located in ocean environments is unavoidably affected by external disturbance, such as winds, water waves, and earthquakes. e large vibration amplitude can damage the structures or the secondary components and cause discomfort to its human occupants [1]
In an attempt to overcome this limitation, initially, such a drawback can be overcome through use of multiple tuned mass dampers, of which each Tuned mass dampers (TMDs) is tuned to a specific frequency of the main system [4,5,6]. e wideband multiple TMD system has been developed for reducing the multiple resonant responses of the main structure
It is important for vibration suppression under excitation by seismic waves that the magnet TMD can effectively reduce relatively high-amplitude displacements and accelerations. ese high-amplitude displacements occurred during the early period of the test, and the magnet TMD responded quickly to these early vibration excitations
Summary
An offshore platform located in ocean environments is unavoidably affected by external disturbance, such as winds, water waves, and earthquakes. e large vibration amplitude can damage the structures or the secondary components and cause discomfort to its human occupants [1]. Extensive research had been conducted to mitigate this harmful vibration, for example, structure design [2], vibration isolation systems, and auxiliary damping systems [3]. Among these methods, the tuned mass damper (TMD) has been proved to be a simple and effective vibration suppression device. In an attempt to overcome this limitation, initially, such a drawback can be overcome through use of multiple tuned mass dampers, of which each TMD is tuned to a specific frequency of the main system [4,5,6]. Some other efforts construct multi-DOF single mass TMD [7, 8]
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