An Evaluation of ASTM Shear Modulus Test for Elastomeric Bridge Bearings


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Title: An Evaluation of ASTM Shear Modulus Test for Elastomeric Bridge Bearings

Author(s): Y. Arditzoglou, J. A. Yura and A. H. Haines

Publication: Special Publication

Volume: 164


Appears on pages(s): 903-936

Keywords: Bearings; bridge bearings; shear properties; tests.

Date: 11/1/1996

The 1992 AASHTO Design Specification for Bridges recommends the use of shear modulus rather than durometer in specifying the elastomer in bearings for bridges. The value of the specified shear modulus can then be used directly in the design formulas to predict bearing displacements and stresses in the full size bearing. A study was undertaken to evaluate the difference, if any, between the shear modulus from the ASTM D-4014 quadruple shear test on a small sample of the elastomer and the shear modulus from the full size bearing. Reinforced bearings were ordered from three different manufacturers with a specified shear stiffness of 100 psi (0.69 MPa) and 200 psi (1.38 MPa). The effect of the ASTM specimen size and the method of computing the shear modulus were evaluated. It was found that the ASTM test gave much higher values of shear modulus than measured in the full size tests (sometimes over 30%). Some of the reasons for the difference are given along with some recommendations for changes in the ASTM method and the AASHTO Specification for elastomeric bearings.