Elastomeric supports for bridges and structures are designed to absorb the forces generated by expansion/contraction movements, braking effects, and wind loads, preventing these forces from being transmitted to the structure.
The Rubber Group, S.A., has developed elastomeric compounds and processing conditions specified by AASHTO (American Association of State Highway and Transportation Officials) and NCHRP (National Cooperative Highway Research Program) for the manufacturing of elastomeric bearings.
The elastomeric compounds used by The Rubber Group for the production of bearing pads comply with the specifications of AASHTO 251-90 in its two variants: Polychloroprene (Neoprene) and polyisoprene (natural rubber).
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The Rubber Group manufactures elastomeric support elements according to the design and needs of the clients, which can be either pure elastomer or elastomer with inserts of A-36 steel sheets and in various geometric shapes.
The selection of hardness; whether 50±5, 60±5, or 70±5, should be based on the structure design, climatic conditions, and foreseeable movements, as well as the choice of shape and dimensions.
The choice of elastomer type; (polychloroprene or polyisoprene) is not of major importance, as the compounds of both elastomers have similar functional characteristics, provided they comply with the relevant official standards.
Regardless of the mandatory requirement that the elastomeric compounds used in the manufacturing of support elements comply with the specifications of AASHTO 251-90 or its equivalent ISO 6446, certain fundamental functional requirements must also be met for the calculation and design of these devices:
Vertical Stiffness: This property is related to the compound’s resistance to deformation, the maximum anticipated vertical load, and the shape factor, determined by the ratio between the area receiving the load and the free area susceptible to vertical deformation. This deformation should not exceed 15% of the thickness or sum of thicknesses of the elastomeric compound.
Horizontal Stiffness: This property allows the calculation of the horizontal deformation of a support device under a specific horizontal load and should not exceed 50% of the thickness or sum of thicknesses of the elastomeric compound. This is based on the value of the shear modulus (G) of the compound (Table IV). Excessive stiffness can lead to undesired effects such as rotation or sliding of the support device.
Creep in Compression: Creep in compression refers to the additional vertical deformation experienced by an elastomeric compound over a specific period due to a creep effect. It is expressed as a percentage of the initial deformation. For support elements, this creep should stabilize around 100 days after the initial load is applied and remain consistent throughout the device´s lifespan.
The elastomeric support bearings for bridges and structures, manufactured by The Rubber Group, S.A., meet all the requirements outlined by various international official standards, as well as accepted dimensional tolerances and other manufacturing requirements.