Mixed finite-element analysis of laminated rubber bearing using lower-order element

The laminated rubber bearing consisting of rubber and steel plates has been widely used in base structures to absorb earthquake vibration. The function of this bearing is to support all the weight of the structure and protect the structures from shear vibration by earthquake. Due to the nearly incompressible property of hyperelasticity, the displacement-based finite-element solutions cause large errors in pressure solutions. In order to overcome this shortcoming, a mixed method has been proposed, where pressure and displacement fields are developed as independent unknown variables. Finite-element solutions depend upon shape function and the numerical integration technique; however, the suitable numerical condition for a laminated rubber bearing has not been fully discussed. The present paper will show the mixed finite-element formulation in rate type for hyperelasticity, and show numerical examples of the laminated rubber bearing system in shear deformation to clarify the advantage of the analysis method and the fundamental feature of mechanical response. (author)