Civil Engineering Association

Elastomeric Bridge Bearings: Recommended Test Methods

Fifteen tests currently required by the American Association of State Highway and Transportation Officials (AASHTO) for determining the properties of elastomeric bridge bearings were evaluated with respect to their effect on the performance of the bearing. Experimental research was conducted in principally four areas: shear modulus, aging, creep, and low temperature. Theoretical studies were undertaken on the effect of misaligned steel laminates on the stresses and deformation within the elastomeric bearing. It was found that significant misalignments do not have a significant effect on the internal stresses and strains. Crack growth studies established that ozone induced surface cracks or cracks from manufacturing defects on the surface will not propagate significantly into the bearing within its lifetime. Delaminations at the interface of the elastomer and steel laminate were found to be very significant, so bearings with such defects should be rejected. Three new test methods were developed: an inclined compression test, a creep test and a compressive stiffness test. The inclined compression test was developed primarily to determine the shear modulus of the elastomer, but it can also be used to determine the shear bond strength and the compressive stiffness of the bearing. The elimination of eight current test procedures in AASHTO is recommended. New low temperature bearing performance criteria were developed because the current criteria unnecessarily restrict the use of certain elastomeric material.