Seismic resonance in base-isolated structures under long-period excitation: application of novel earthquake predominant periods

The engineering concept of resonance demands one excitation frequency that dominates over a spectrum. As one definitive predominant frequency of seismic action has been quite elusive in seismology and earthquake engineering, resonance is presently much more studied and dealt with in mechanical engineering than in civil engineering. However, when isolated buildings – which have a clearly dominant and “insulated” (distinct) first natural frequency – are subjected to near-field ground motions, resonance can be a serious problem because these long-period structures can see their response amplified greatly by the long-period signals usually present in that type of seismic motion. Now, for this case of near-fault seismic records, clear predominant frequencies of earthquakes have been recently obtained, where the spectral analysis has been based – disruptively – on displacement rather than the common acceleration. Therefore, the vibrations concept of resonance can now be formally studied in isolated structures under near-field excitation. The objective here is to verify if clear structural resonance can be observed in this earthquake engineering situation. Furthermore, another hypothesis or objective is to verify if that clear amplification occurs near the recent earthquake or input predominant periods.