Experimental investigations of fiber and steel reinforced elastomeric bearings: Shear modulus and damping coefficient

• Suggestions for improved design guidelines for reinforced elastomeric bearings.
• Appropriate design formulas developed to describe the material behavior more realistically.
• Different bearing types (fixed FREIs, unfixed FREIs, and fixed SREIs) investigated and compared.
• Stiffness not constant; depends on deflection state, vertical compression state, type of support.
• Increasing vertical compression state will significantly increase damping capacity of bearings.

In the past few decades, steel reinforced elastomeric bearings have been extensively used for seismic isolation purposes. Innovative isolation devices of elastomeric bearings reinforced with fiber sheets have begun to replace those with steel reinforcement. In the present article, a literature review on the mechanical characteristics of fiber reinforced elastomeric bearings is presented and the shortcomings of the current European standards concerning statically and dynamically loaded elastomeric bearings are discussed. An experimental procedure conducted on elastomeric bearings with various reinforcing materials and under various loading and support conditions is described for comparison purposes. The experimental procedure includes cyclic loading tests with a concurrent application of vertical stress for three bearing types of different dimensional and material properties. The influence of crucial parameters such as vertical stress, horizontal deflection, bearing height, number of elastomer and reinforcement layers, reinforcement material, and type of bearing support on the effective shear modulus and damping coefficient are examined. Moreover, comparisons between experimental and analytical results obtained by respective analytical formulations are further discussed. Appropriate analytical formulations are proposed for better adjustment to the experimental results.