Inerter-added transmissibility to control base displacement in isolated structures

Validation of One Predominant Frequency Presence in Seismic Ground Displacement by Means of Deformation Response Spectra

“…This is what is carried out in this study; the research gap encountered is that there was no reliable or direct confirmation of the fact that seismic ground displacement has a clear and neat predominant frequency close to 0.1 Hz, which was demonstrated first by power spectral density (PSD) analyses [10,11]. More lately, the result has been corroborated indirectly by solving an actual earthquake engineering problem, the LBD, by controlling the isolator displacement by the inerter [5]. This solution or good time-domain results on the control of the base relative displacement would not have been possible if the ground displacement did not have a prominent peak close to 0.10 Hz, as that is the main hypothesis in the frequencydomain design or optimization procedure.…”

“…It has been previously demonstrated that Fourier or power spectra of horizontal ground displacement have the general form shown in Figure 1 [10,11,13]; although most of this graphic is pictorial, the frequency axis is exact to a certain degree, as there is clear similarity to what is observed in the actual power spectrum results in the literature. These highly narrow-band results have been validated by a solution to an actual earthquake engineering problem [5] where the standard ground acceleration is used as input in the simulations, which is independent of the displacement signal that one is analyzing. Another type of corroboration of the existence of clear and neat predominant frequencies in ground displacement, which is also independent of that record, is presented herein.…”

“…However, there are also many reasons to give more attention to ground displacement. The displacement record is important in the analysis of long-span structures, long pipes and tunnels [2], and in the control of base-isolated structures [3,4], which have a large base displacement (LBD) problem under earthquakes [5]. More generally, in earthquake engineering there has lately been some displacement in interest, from force-based design to displacement-based design (DBD) [6].…”

“…More generally, in earthquake engineering there has lately been some displacement in interest, from force-based design to displacement-based design (DBD) [6]. It has recently been asserted, e.g., for the LBD problem in isolated buildings, that if structural displacement is the problem, the focus regarding excitation should be on ground displacement rather than ground acceleration [5]. Finally, it is pointed out that it is not an absolute fact that the forcing function (equation's right-hand side) must be ground acceleration; in fact, that input term can also be written in terms of ground velocity and displacement or a combination thereof [4,7].…”

Predominant Frequency in Near-Field Strong Ground Motion by Analysis of Displacement Response Spectra

“…The present results suggest an adjustment and improvement towards 0.15 Hz, or 0.18 if liquefaction is considered; we talk about improvement because the results are based on a more robust and reliable method, as explained. Moreover, a similar isolation design methodology has been presented lately but with a more advanced device, the inerter, and also great results are attained in controlling the base displacement [20]. These 2 successful solutions in time domain on controlling isolator deformation would have been impossible if seismic excitation did not have one predominant period near 7 s as this is the main hypothesis in those 2 frequency-domain optimization procedures.…”