## 2 Pulse-Type near Fault Ground Motion  
In recent decades, many destructive strong earthquakes occurred throughout the world. Some researchers have obtained a large amount of data records for near-fault strong earthquakes. These earthquakes produced very serious damage to engineering structures, which aroused the attention to the seismological community and the engineering field [22]. A large number of previous studies indicated that some near-fault earthquakes have unique characteristics compared with far-field earthquakes, such as permanent ground displacement, significant rupture forward directivity and fling-step effect. Among these characteristics, pulse effects, such as rupture forward directivity and fling-step effect, can cause remarkable velocity pulses. Thus, compared with non-pulse-type near-fault earthquakes and far-field earthquakes, there exist significant differences in the amplitude, frequency and duration in pulse-type near-fault earthquakes, which aggravates the damage to the engineering structure. In general, for pulse-type near-fault earthquakes, the amplitudes of displacement, velocity and acceleration are all large. The low frequency component is abundant and the characteristic period is prolonged. Therefore, the near-fault earthquakes have high energy in the initial stage, which will result in large structural damage [23]. Previous research results indicate that, for pulse-type near-fault earthquakes, the ratio of peak ground velocity (PGV) to peak ground acceleration (PGA) is large. Some scholars have pointed out that PGV/PGA is mainly utilized to identify the pulse-effect of near-fault earthquakes. When PGV/PGA is more than 0.2, the pulse-effect is very obvious. Therefore, PGV/PGA of pulse-type near-fault earthquakes is more than 0.2 in this paper, and the fault distances are less than 20 km. In addition, for the selection of pulse-type near-fault earthquakes, the following criteria are used to distinguish the velocity pulse: the velocity time history curve of pulse-type near-fault earthquake contains a sharp bulge, and the duration for velocity pulse is above 0.5 s. In order to compare the control effectiveness and adaptability of the proposed control strategy under different types of earthquakes, non-pulse-type near-fault earthquakes and far-field earthquakes are selected. Table 1 shows the selected seismic records and the characteristics of the data. The data source is from the Pacific Earthquake Engineering Research (PEER) Center strong earthquake database: [[http://peer.berkeley.edu](http://peer.berkeley.edu)]([http://peer.berkeley.edu](http://peer.berkeley.edu)). In this table, code A represents near-fault earthquakes with fling-step effect, code B represents near-fault earthquakes with rupture forward directivity, code C represents non-pulse-type near-fault earthquakes, and code D represents far-field earthquakes. The acceleration and velocity time history curves of the selected four types of earthquakes are shown in Figure 1. It can be seen that the energy of pulse-type near-fault earthquakes accumulates rapidly. This will result in an impact-type ground motion with immense amplitude, obvious pulse waveform and short seismic duration. In addition, from the time history curves, it can be shown that velocity pulse induced by fling-step effect has the characteristic of a single pulse, and the velocity pulse induced by rupture forward directivity has the characteristic of bidirectional velocity pulses. In addition, the velocity time history curve with rupture forward directivity possesses multiple-pulse characteristics. The average elastic acceleration and velocity response spectra for the selected earthquakes with 5% damped ratio are shown in Figure 2. It can be seen from the figure that, with respect to non-pulse-type near-fault earthquake and far-field earthquake, the spectra of acceleration and velocity for pulse-type near-fault earthquake in long period section significantly increase. For a base-isolated structure, the basic period is generally large.