NRB Natural Rubber Bearing

Natural rubber bearing that uses natural rubber. It has low damping performance (about 2~3% at equivalent damping factor), excellent linearity, and stable restoring force characteristic.
Separate damper is required, but with combination of damper types, attenuation, etc., it is possible to design with greater flexibility.
Rubber material has four different kinds of elastic modulus(referred as G0.30,G0.35,G0.40, G0.45), able to support wide range of column loads.

Natural rubber bearings containing steel laminates are located between components of a concrete structure to prevent damage to the structure when relative movements occur between the structural components. The stiffnesses of rubber bearings are markedly shape dependent, and stiffness relations enable bearings suitable for particular applications to be designed.

Applications include bridge bearings, antivibration mountings for buildings and for the rail tracks of underground railways and, but still under development, foundation bearings for earthquake protection. As these bearings are made by rubber manufacturers a brief discussion of the manufacturing processes and of the engineering properties of natural rubber should be an aid to meaningful dialogue between engineers and rubber technologists.

These types of dampers are integrated of several steel rings which are considered with two configurations namely, continual steel ring damper and separate steel ring damper and are inserted between top and bottom plates. The performance characteristics of the system such as effective horizontal stiffness, energy dissipation, equivalent viscous damping and residual deformation are calculated and then compared with the results of high damping rubber bearings and also shape memory alloy (SMA)-lead core rubber bearing (SMA-LRB). The results show that the energy dissipation in steel rings are mainly based on plastic deformation due to flexural behavior of the rings. NRB-SRD shows better performance in energy dissipation comparing to SMA-LRB and HDRB.

These additional dampers show higher stability and energy dissipation in low shear strains due to developing of link between structure and substructure having desirable initial stiffness under weak earthquakes and wind loads and also in higher shear strains due to creation of higher energy dissipation, stability and secondary stiffening.