# The Role of a Simple Inerter in Seismic Base Isolation
## 5 Flexible Isolated Structure under Real Earthquakes
However, the peak top floor acceleration increases with \(\beta\) for the isolated structure with supplemental FID. This can be explained with the help of Figure 6, which shows that the grounded inerter connected to the base mass will directly transmit the vibration (i.e., accelerations) associated with high-frequency amplitudes in the earthquake ground motion. This affirms that the inclusion of an inerter in the Fluid Inerter Damper (FID) as a supplementary device to the isolation system has adverse consequences, leading to raised structural accelerations. As \(\beta\) increases, the maximum displacement at the base of the base-isolated structure diminishes when supplemented with devices. A contrast of the peak base displacement of the base-isolated structures with TMDI and the corresponding ADAS indicates a greater reduction in the base displacement by ADAS compared to TMDI. Further, there is a greater reduction in base displacement for the isolated structures with FID than with FD. The variation of peak force in the isolation system has a similar trend to base displacement. The peak force in the supplemental devices increases with the increase in \(\beta\). However, the force in the FID is substantially higher in comparison to the force of other supplemental devices. The peak total base shear of isolated structures with TMDI, ADAS, and FD is not very sensitive to \(\beta\), but it increases for the FID. Thus, it can be concluded that the inerter in the FID increases the structural acceleration as well as the total base shear. The effects of \(\beta\) on the peak top floor absolute acceleration, relative base displacement, the force in the isolation system, the force in the supplemental device, and the total base shear of the base-isolated structures with \(T_{b}\) = 4 s for different earthquakes are shown in Figure 11. The trends of the results in Figure 11 are similar to those observed in Figure 10 for considering \(T_{b}\) = 3 s.  
Figure 10: The effects of the \(\beta\) on the peak response of a flexible base-isolated building subjected to various earthquakes (\(T_{b}\) = 3 s). Based on the discussion of the presented results, it can be concluded that there is a greater or comparable reduction in the base displacement by the corresponding ADAS in comparison to the optimal TMDI. Further, an inerter of the FID attached to the ground and an isolated structure have detrimental effects on seismic isolation by transmitting the vibrations associated with high-frequency accelerations and increasing the base shear. The study's overall conclusion is that inerter-based supplemental devices such as TMDI and FID may not be very effective for the base-isolated structures to warrant their practical application. On the other hand, a pair of inerters with a clutching effect might be able to significantly reduce the displacement in the base-isolated structure's isolation system [50; 51; 52; 53]. Also, the performance of the inerter-based dampers in conjunction with negative stiffness devices was somewhat encouraging for the base-isolated structures [54; 55]. The current study is primarily concerned with the inerter's function in the recently investigated supplemental dampers for base-isolated structures. However, it is strongly recommended to compare their performance with the widely researched dampers, such as magnetorheological dampers, negative stiffness dampers, semi-active variable friction and stiffness devices, etc. It is also recommended that the findings of the present study be experimentally validated.