DYNAMIC RESPONSE OF STRUCTURES SUPPORTED ON ELLIPTICAL ROLLING RODS

In this paper, effectiveness of a new base isolation system i. e. elliptical rolling rods between the base and the foundation of structure is investigated. Equations governing the motion of a multi-storey shear type building supported on the elliptical rolling rods are derived. The dynamic response of the system to both harmonic and real earthquake ground motions is obtained by integrating the incremental equations along with an iterative technique. The iterations are required due to non-linear force-deformation behaviour of the elliptical rolling rods. Effectiveness of the elliptical rolling rods is studied by comparing the response between isolated and corresponding fixed base system. In addition, a parameteic study is conducted to investigate the effects of important parameters on the effectiveness of elliptical rolling rods. The parameters considered are: the fundamental time period of the superstructure, the coefficient of rolling friction and the eccentricity of the elliptical rolling rods and the frequency content of ground motion. It is shown that the elliptical rolling rods are quite effective in reducing the dynamic response of the system without undergoing the large displacements or living the large residual base displacement.