Development of a semi-active MR inerter for seismic protection of civil structures

Civil engineering structures are susceptible to collapsing when exposed to severe vibrations. Therefore, it is essential to protect them from undesirable vibrations triggered by natural calamities like earthquakes or strong winds. This paper proposes an innovative semi-active Magnetorheological (MR) inerter system with a compact structure for seismic protection. The inerter system consists of four rubber bearings and the semi-active MR inerter. The inertance of the semi-active MR inerter can be switched according to different working scenarios. This unique operating principle enhances the adaptability of the system. To assess the performance of the proposed inerter system, a scaled three-storey building was constructed following scaling laws. Four scaled earthquake signals with different dominant frequencies were used as ground motion excitations. An inertance switch controller based on short-time Fourier transformation (STFT) methodology was built to determine the desired inertance of the inerter. Both the simulation and experimental results indicated that the proposed semi-active MR inerter system provides superior vibration mitigation capacity over the passive inerter systems. Specifically, the employment of the semi-active MR inerter effectively reduces the acceleration responses of the structures under different seismic excitations.