Seismic Response Of A Structure With Periodic Isolated Foundations

Since the periodic structure exhibits a unique dynamic character, the so-called frequency band gap in which the wave can not propagate, the present thesis proposes a brand new method of seismic isolation. The concept is to employ periodic foundation to block seismic wave whose frequency falls into the frequency gap. Band gaps of elastic waves propagating along arbitrary direction in one-dimensional periodic structure are mainly studied in this paper. In order to test the validity of this new kind of periodic isolated foundations, the dynamic responses of a seven-storey frame structure with three different foundations are conducted and compared, respectively. The contents include:1. The band gaps of the layered periodic structure are studied when the harmonic waves are propagating along an arbitrary direction.2. In order to realize low frequency gap, different physical and geometrical parameters such as elastic modulus, filling fraction and thickness ratio have been investigated.3. The frequency responses of a seven-storey frame structure with three different foundations are conducted and compared, respectively. Compared with the traditional isolation base, it is found that when the frequency falls into the gap, there is strong attenuation in periodic foundation.4. The thesis presents a transient response and a time history process is applied to the foundation of the structure. When the frequency of the displacement falls into the band gap, the structure with periodic isolation base enjoys displacement and acceleration attenuation effect. Its application in seismic isolation is pretty promising.5. Then seismic response of the structure in Big Bear earthquake are studied, the results show that the periodic foundation can attenuate the seismic behavior in both vertical and horizontal direction.