Modern rubber bearings have been used for passive protection of civil and industrial structures since the mid of the ‘70s. Among such devices there are Low Damping (LDRB) and High Damping (HDRB) Rubber Bearings, consisting of alternating layers of rubber and steel shims, and Lead Rubber Bearings (LRB) provided with a high damping lead plug. The dynamic properties of the bearings, that are the damping capacity and the stiffness, depend on the characteristics of the compound, and today a large variety of elastomers is available on the market with different damping ratio (generally ranging between 4 and 15%), shear modulus, and vulcanization profile, according to proprietary techniques developed by bearing manufacturers. However the mechanical properties of elastomeric compounds are largely affected by ageing, loading and environmental factors, therefore precise information on the upper and lower bound values is necessary for the proper design of rubber bearings.

The study investigates the mechanical behavior of several commercial rubber compounds, including either low damping and high damping formulations, with design shear moduli covering the range between 0.35 and 1.50 MPa. Tests are carried out on rubber blocks loaded in shear and the influence of several factors is investigated, including: (a) strain amplitude, (b) frequency of loading, (c) extreme ambient temperatures, especially the low temperatures, (d) cyclic loading, (e) ageing, and (f) application of concurrent shear and normal (compressive) load.

Results are analyzed and used to calculate property modification factors of design values for each compound. The variability of the mechanical properties depending on the individual factors is studied and compared to the requirements on production rubber bearings set in the current European and American standards on antiseismic devices.