Buckling load of seismic isolators affected by flexibility of reinforcement

Using the thinner steel reinforcing plates in the elastomeric multilayer isolators could reduce the weight of the isolators but would have a large effect on the buckling load of an isolator, which cannot be analyzed by the Haringx theory, a traditional approach on the stability analysis of rubber bearings. The buckling load of the isolators, which includes the effect of the flexibility of the steel reinforcing plates, is analyzed by a beam theory in which shear deformation and warping of the cross-section are considered. Pressure distributions in the elastomeric layer bonded to flexible reinforcements under compression force, bending moment and warping moment are derived from an assumed displacement field, from which the warping-related parameters used in the beam theory are established. The thickness of the steel reinforcement in the isolators is determined from the buckling load of the isolators, which is solved from a cubic equation established by the beam theory.