Method and apparatus for broadband earthquake resistant foundation with variable stiffness

摘要

An earthquake resistant foundation based on the method of longitudinal wave filtration by periodic or quasi-periodic septate waveguides. The generic septate waveguide comprises either a series of cylindrical or annular polymer members or a stratified medium with air- filled cylindrical channels. In all cases, the polymer members are reinforced along their torsional surfaces. As the waveguides are distributed into a specific matrix, they serve as an isolating and damping device which is placed between the source of sound, shock or vibration waves and the object of protection. The elements of the waveguide are the individual septate cylindrical cross sections, which comprise a configuration of polymer, viscous or non-viscous liquid and air constituents bonded to and separated by the rigid end plates. The method postulates that radial displacement be zero at the boundary between the polymer member and the septum. Furthermore, the polymer member should be incompressible, and the septa are rigid. The admittance matrix Y of the element is constructed within the framework of the hypothesis for planar cross sections. The elastic parameters of the polymer element and the specific geometry relating the cylinder's radius to its height are defined theoretically on the basis of the wave filtration condition for the transfer matrix of periodic waveguides. Each element is tuned on an appropriate resonance frequency within the broadband of filtration. The synergy of combining waveguide elements results in a system which is a high-efficiency broadband filter. This system of waveguides with periodic or quasi- periodic structures exhibits shock isolation and damping properties which are superior to other systems, even for the case when the latter is constructed with high-loss materials.