Test Method for Determining the Shear Modulus of Elastomeric Bearings

Abstract

The shear modulus of the elastomer is the most important material property related to the behavior of elastomeric bearings used principally at supports in bridges. Current methods for determining the shear modulus usually require small test samples cut from manufactured bearings. Such tests are costly, do not necessarily represent the performance of the full-size bearing, and are destructive. A new shear test method, called the inclined compression test, is reported that is nondestructive and only requires a compression test machine to apply shear to the full-size bearing. The results from the inclined compression test show good correlation with results from an independent full-scale test setup. To develop reliable test procedures various test parameters were evaluated such as testing speed, platen surface conditions, and specimen dimensions. The test results show that the inclined compression method is a practical alternative to more traditional test methods. The new method works very well on bearings reinforced with steel laminates, but plain bearings require cold bonding to attachment plates in order to obtain reliable shear moduli.