Natural Rubber Elastomeric Bearing Pads

Benchmark has a large stock of Natural Rubber Elastomeric Bearing Pad material and can offer expedited processing.

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.

Natural rubber (polyisoprene) pads carry vertical load while flexing enough to take up the rotation and small horizontal movements of the member they support. They also damp vibration and shock, which makes them a common choice under precast, steel and concrete members.

Our standard bridge-grade natural rubber is 55 durometer (Shore A), supplied to meet CAN/CSA-S6-06, with a harder grade available where Ontario OPSS 1202 is specified. Pads are cut from stock sheets and rolls to the size, thickness and shape on your drawings.

CAN/CSA-S6-06 Bearing Pad standard Test Results / Requirements

Property	Test Method	Results
Rubber Type = Natural
Hardness, Shore A	D2240	55 +- 5
Tensile Strength, MPa	D412	Minimum 17.0
Ultimate Elongation, %	D412	Minimum 400
Specified Test Temperature	D573	70h at 70 degrees C
Change in Hardness, Shore A	D573	Maximum + 10
Change in Tensile Strength, %	D573	Maximum -25
Change in Ultimate Elongation, %	D573	Maximum - 25
Specified Test Temperature	D395	22 h at 70 Degrees C
Residual Compression, %	D395	Maximum 25
Mounting Procedure A	D1149	22 pphm, 48 h
20% Strain, 40 +- 2 Degrees C	D1149	No cracks
Bond Between Steel and Elastomer Laminate, N,mm	D429	Minimum 7.0
Brittleness at -10 degrees C	D746	No Failure
Low Temperature Crystallization Increase in Hardness, Shore A	D2240	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)

Shape factor (S) is the loaded plan area of a pad divided by the area around its edges that is free to bulge. The higher the shape factor, the stiffer the pad is in compression, so it sets how thick a plain pad can be for a given load.

MAXIMUM SHEAR DEFORMATION

Keep shear deformation of a plain pad to no more than half of its total thickness.

Sizing a plain pad: two load cases to check

Compressive load without rotation

Compression only: pick the pad thickness from the relationship between average service pressure and shape factor. Specify a positive attachment (epoxy, dowels or keeper bars) when the minimum compressive stress at SLS drops below 1.5 MPa.

Compressive load with rotation

Compression with rotation: keep total compressive deflection at or below 7% of the pad thickness under every service load combination, and check that no edge of the pad lifts off under the design rotation.