Study On Seismic Performance Of One-dimensional Periodic Composite Foundations

Periodic composite structures with a band gap characteristic,that is,the elastic wave is low transmittance and high reflectivity if its frequency is in the frequency band gap in the periodic composite structure.Seismic wave is also one kind of elastic wave.This paper aims to design a functional seismic-isolated foundation using the frequency band gap principal of one-dimensional periodic composite structure, by inhibiting the transmission of seismic waves to reduce earthquake damage to the superstructure.The lump-mass method is used to calculate the first band gap of one-dimensional two-component and three-component periodic structure.The effect of the material parameters(elastic modulus,density,Poisson's ratio,etc.) and structural parameters (lattice constant or the thickness of each component,material component ratio) of each periodic composite structure element on the first band gap were also discussed.Finally three types of periodic foundations were designed.The concrete-nitrile rubber-steel periodic structure model was selected for its best seismic-isolation performance and for practical purpose.Transient response analysis and harmony response analysis of the periodic foundations were conducted using Patran/Nastran and ANSYS in Chapter five.Numerical results show that the three-component periodic foundation has a good character of seismic-isolation subjected to a S-wave ranged from 7.6Hz-10.0Hz;while as to P-wave,the character of seismic-isolation is depended on the rubber's energy-consumption ability.