Tensile Stiffness of Elastomeric Isolation Bearings Under Shear Deformation

Abstract

The compression–shear behavior of rubber bearings is investigated by theoretical analysis and confirmed by extensive experimental work. Nevertheless, whether theoretical analysis predicts the tension–shear behavior of isolators is unclear. To clarify the variation rule of the tensile stiffness of the bearing under shear deformation, Haringx’s theory is extended and the tensile stiffness is presented considering shear deformation. The variation of the stiffness of the bearing in the shear deformation is analyzed based on the derived expressions. Results show that the magnitude of the shear strain does not affect the vertical tensile stiffness and the vertical tensile stiffness is equal to the pure tensile stiffness when the tension is equal to the critical value, which is the product of the shear modulus and the shear area of the bearing. When the tension is not equal to the critical value, the vertical tensile stiffness is less than the pure tensile stiffness, decreasing with increasing shear strain. The change rule of vertical tensile stiffness is different in the different tensile forces. When tensile force is less than the critical value, tensile stiffness increases with the increasing tensile force. When tensile force is more than critical value, tensile stiffness decreases with the increase of tensile force, and the mechanics of isolators in tension are not exactly the mirror image of those for the isolators in compression. In the tension–shear state, the tensile component perpendicular to the rubber layer is smaller than that in the pure tension state. Therefore, compared with pure tension, tensile failure does not easily occur in bearings experiencing a large horizontal displacement. This phenomenon is consistent with the shaking table test.