Test Methods For Elastometric Bearings On Bridges

Elastomeric bearing pads are used extensively in bridge structures. Whereas, the mechanical properties of elastomers like Young's modulus, compressive modulus, and shear modulus are usually essential for the structural engineer's work, most rubber manufacturers describe their products in terms of chemical compounds, hardness, tensile stress at some elongation, and compressive set measurements in order to meet AASHTO material specifications. This paper discusses the material properties of elastomers and the factors that influence these properties. The development of the AASHTO specifications between 1961 and 1992 on elastomeric bearings are also summarized. In addition, various sizes of bonded natural rubber blocks were tested in compression, tension, shear, and combined compression and shear. Load deformation relationships were obtained from all tests and mechanical properties of compressive modulus, tensile modulus, and shear modulus were calculated. Test results indicated that specimen size affects the material properties of an elastomer. Furthermore, the measured shear modulus values were not affected by various levels of compressive stress.