Determination of restoring moments of elastomeric bearings for buildings

As the former national rules for the use of elastomeric bearings in buildings could not be transferred completely to the current European Standard for elastomeric bearings or the current national approvals and due to the lack of a new document covering the use of bearings in buildings such a document is desirable. The existing national design rules for the determination of restoring moments (also named as restraint moment) are based on investigations using elastomeric bearings with a specified load bearing capacity much lower than commonly used today. Considering that the increase of the load leads to an increase of the resistance due to rotations an experimental verification of the restoring moments is necessary. Based on this background tentative tests for the restoring moments for two product types of solid plain pad elastomeric bearings were carried out at MPA Karlsruhe. The vertical load level, the velocity of rotation, the geometry of the bearings and the rotation axis of the bearings were investigated as relevant parameters. The restoring moments measured during the tests were much higher than the restoring moments calculated according to the known design rules and current national approvals. Based on these results the design rules for the determination of the resistance due to rotation of plain pad elastomeric bearings for buildings must be improved.