Benchmark has a large stock of Natural Rubber Elastomeric Bearing Pad material and can offer expedited processing.
Natural Rubber Elastomeric Bearing Pads
Benchmark Stocks plain and shimmed bearings are available in standard Shore A durometers of 50, 60 or 70 based on state and/or AASHTO Code, Section 18, natural rubber or neoprene. For economy, a commercial grade is also available.
PTFE-surfaced neoprene-backed slide bearings are also available. Type CSA material is recommended bonded to a 10-gauge steel laminate which has been bonded to neoprene.
If minimum dead load pressure is less than 200 psi, it is recommended that the elastomer be epoxy-bonded to concrete. If being welded on steel, an 8 gauge tack plate is recommended for positive reinforcement and ease of application. The maximum temperature at a neoprene bearing is 200° F.
Natural Rubber Elastomeric Bearing Pad Features
- Simple but robust structure.
- Capable of carrying compressive loads.
- Vibration, sounds and shocks isolation and absorption.
- Various application in prefabricated structures.
- Top and bottom mounting plates are available.
- Holes for locating pins are supplied where specified.
- More economical than steel laminated elastomeric bearing.
elastomeric bearings are fabricated of natural rubber or neoprene. Designed and sized to meet the needs of your structure, these bearings are rigid enough to transmit the necessary loads and flexible enough to permit the rotation and movement required by the structure. They can also be used for vibration and earthquake-motion control applications.
Natural Rubber Elastomeric Bearings are made of an elastomer containing either natural rubber as the basic polymer. They are available primarily in 55 durometer hardness (Shore A) and meet the CAN/CSA-S6-06 standard, or in hardness meeting Ontario OPSS 1202. They can be molded or cut (from standard rolls) into a wide range of dimensions and thicknesses.
CAN/CSA-S6-06 Bearing Pad standard Test Results / Requirements
Property
Test Method
Results
Rubber Type = Natural
Hardness, Shore A
Tensile Strength, MPa
Ultimate Elongation, %
Specified Test Temperature
Change in Hardness, Shore A
Change in Tensile Strength, %
Change in Ultimate Elongation, %
Specified Test Temperature
Residual Compression, %
Mounting Procedure A
20% Strain, 40 +- 2 Degrees C
Bond Between Steel and Elastomer Laminate, N,mm
Brittleness at -10 degrees C
Low Temperature Crystallization Increase in Hardness, Shore A
D2240
D412
D412
D573
D573
D573
D573
D395
D395
D1149
D1149
D429
D746
D2240
55 +- 5
Minimum 17.0
Minimum 400
70h at 70 degrees C
Maximum + 10
Maximum -25
Maximum - 25
22 h at 70 Degrees C
Maximum 25
22 pphm, 48 h
No cracks
Minimum 7.0
No Failure
168 h at -25 Degrees C Maximum + 15"
Data given is from CAN/CSA-S6-06
Other hardness and other grades are available to meet AASHTO, AREMA or other standards as per engineer requirements.
DESIGN
SHAPE FACTOR(S)
The behavior of an elastomeric bearing under compression is influenced
by the shape factor (S), which is defined as the ratio between the loaded
area of the bearing and the area that is free to bulge:
MAXIMUM SHEAR DEFORMATION
Maximum shear deformation of a plain bearing pad is limited to 50% of
the total pad thickness
These maximum pressures should be limited only to meet the two following load combination requirements:
1) Compressive load without rotation
For plain bearing pads used under compressive load only, i.e. without
rotation, the maximum pad thickness can be obtained from a graph
relating the average service compressive load to the pad shape factor.
It should be noted that a positive attachment should be specified for
minimum compressive loads of less than 1.5 MPa at SLS (Serviceability Limit State).
2) Compressive load with rotation
For plain bearing pads used under compressive loads and rotation,
the maximum pad thickness should be such that under all service load
combinations, the maximum compressive deflection c does not exceed
0.07 x T and under rotation, there is no uplift at any edge.