This paper presents two inerter-based isolation systems, namely, an inerterdamper (ID)-based isolation with an inerter in parallel with a viscous damper and a tuned ID (TID)-based isolation composed of an inerter in series with a spring-damper pair. A base-isolated building with two degrees of freedom (DOF) is considered, where the superstructure above the base is simplified as a single DOF. The H 2 norm performances of the ID-and TID-based isolation systems are introduced in comparison with the traditional isolation system, with the aim to minimize structure damage under random excitation from ground acceleration. The closed-form solutions are obtained, including the damping ratio of the traditional isolation, the damping ratio and the inertance-to-mass ratio of the ID-based isolation, and the damping ratio and inerter frequency tuning ratio of the TID-based isolation. It is shown that the TID-based isolation is superior to both the traditional and ID-based isolation systems for vibration control. Specifically, the optimal H 2 norm of the transmission from the ground acceleration to the building relative displacement in the TID-based isolation can be reduced by 7.5%. The influence of the primary damping of the building structures is also studied numerically, in both the frequency and time domains, and compared with the exact optimal solution of the undamped structure. The simulations using recorded earthquake spectra show that the ID-and TID-based isolations can further reduce the story drift, the base displacement as much as 48.5% and 66.3% (root mean square) and 37.8% and 71.9% (peak) for the El Centro record compared with the traditional isolation system.

In this paper, 30 magnetorheological (MR) dampers used for vibration control of stay cables after one decade of service were selected to study their long-term mechanical behavior. The damping capacity of the used MR dampers, including the damping force amplitude and the equivalent damping coefficient, was compared with those of new MR dampers. One used damper still with considerable damping capacity was utilized for the comparative study with a new MR damper under various input voltages, excitation frequencies, and excitation amplitudes. A modified phenomenological mechanical model for used MR dampers was developed based on the experimental observation. Moreover, some used dampers were cut in half, and the remaining volumes of the MR fluid were measured. The iron particles of the MR fluid in the used damper with the worst damping capacity were analyzed using a scanning electron microscopy (SEM). The results show that 24 dampers among the used dampers can still generate considerable damping force. However, the equivalent damping coefficient and the damping force amplitude of these 24 used MR dampers decreased by 32.4% and 29.8%, respectively, on the average. Furthermore, six dampers among the used dampers failed to provide enough damping.The proposed modified mechanical model is more accurate to reflect the mechanical behavior of used MR dampers. It was found that the performance degradation of the used dampers is related to the leakage of the MR fluid and the factor that the surface of MR iron particles became rough and uneven, as observed by the SEM. KEYWORDS damper durability, damping capacity, magnetorheological (MR) damper, magnetorheological (MR) fluid, modified mechanical model

This paper proposes a novel inerter-based dynamic vibration absorber, namely, electromagnetic resonant shunt tuned massdamper-inerter (ERS-TMDI). To obtain the performances of the ERS-TMDI, the combined ERS-TMDI and a single degree of freedom system are introduced. 2 criteria performances of the ERS-TMDI are introduced in comparison with the classical tuned mass-damper (TMD), the electromagnetic resonant shunt series TMDs (ERS-TMDs), and series-type double-mass TMDs with the aim to minimize structure damage and simultaneously harvest energy under random wind excitation. The closed form solutions, including the mechanical tuning ratio, the electrical damping ratio, the electrical tuning ratio, and the electromagnetic mechanical coupling coefficient, are obtained. It is shown that the ERS-TMDI is superior to the classical TMD, ERS-TMDs, and series-type double-mass TMDs systems for protection from structure damage. Meanwhile, in the time domain, a case study of Taipei 101 tower is presented to demonstrate the dual functions of vibration suppression and energy harvesting based on the simulation fluctuating wind series, which is generated by the inverse fast Fourier transform method. The effectiveness and robustness of ERS-TMDI in the frequency and time domain are illustrated.