The isolation system is installed at the base of a structure for reduction of the earthquake damage to the structure. In the 1970', when the laminated rubber bearing (LR type) is developed, the isolation system is put in practice. And recently a new isolation system (SR type), including the laminated rubber bearing with the friction plate beneath, is developed.
In this thesis, a study on the base isolation effect, for various of the isolation system and structure properties, is performed. For this purpose, a computer program for analysis of isolated building structures is developed. Matrix condensation technique is used to compose the stiffness matrix. Lumped mass and Rayleigh damping is used to compose the mass and damping matrices. The dynamic equilibrium equations are established considering the equilibrium of the upper structure and the isolator in horizontal direction.
The isolation effects with various periods of the isolation system and number of story is compared to non-isolated case. The results of this parameter study show that the isolation systems can reduce the earthquake damage of the building structures significantly. As the period of isolation system increases, the isolation effect increases and converges to zero damage. As the number of story increases, the isolation effect reduces. It is found that SR type isolation system is more effective than LR type because SR type base isolation system reduces acceleration, drift and total displacement. When the isolated building is designed, the results of this study can help to decide the isolator stiffness properly.
