A rubber bearing is defined as a device which permits constrained relative
motion between two partsrotation or linear movement. The fundamental
purpose of a bearing is to reduce friction and wear between rotating parts
which come in contact with one another in any kind of mechanism. Bearings
are classified broadly into categories according to the motions they allow
and according to their principle of operation. Each type of bearing is used
for different purposes. Bearings are made of various materials but rubber is
a widely demanded material for making bearings. Rubber has proved to be an
excellent bearing material, especially under circumstances in which
abrasives may be present in the lubricant. The rubber used to make bearings
is a tough resilient compound similar in texture to that in an automobile
Types of rubber used in making bearings
Types of Rubber Bearings
- Plain and Laminated elastomeric bearings: Bearings
for construction industry in neoprene and natural rubber compound.
Laminated rubber bearings provide the simplest method of isolation and
are most suitable for high frequency ground motions.
- High Damping Rubber Bearing (HDRB): This is ideal
for seismic isolation. They are vertically stiff, capable of supporting
vertical gravity loads, while being laterally flexible, capable of
allowing large horizontal displacements. In effect, during an
earthquake, the ground is allowed to move back and forth under a base
isolated, while leaving the building to remain "stationary."
These HDRB bearings are flexible and have energy absorption capability.
The rubber bearings isolation system partly reflects and partly absorbs
some of the earthquake input energy. Significant reductions of
structural and non-structural damage can also be attained through the
use of HDRB rubber bearings seismic isolation.
- Low Damping rubber bearing: In the isolation
system, the different types of rubber bearings are designed and used
along with dampers. The system that is popularly adopted for buildings
is the elastomeric or rubber bearings with low damping. These rubber
bearings are widely acceptable because of their longevity, economy and
better control on dynamic properties.
- Lead Rubber Bearings (LRB): A lead rubber bearing
is a much larger laminated bearing manufactured from layers of rubber
which are sandwiched together with layers of steel and in the middle of
the bearing there will be a solid lead "plug." Top and bottom
of the LRB is fitted with steel plates, which are used to attach bearing
to building through its foundation. Lead rubber bearings are designed in
a way that the bearing is stiff and strong in vertical direction and
flexible in horizontal direction. Lead, inserted as center of LRB
dissipates the energy of earthquake and the rubber, reinforced with
steel plates helps in providing stability, supports structure and