NAV Elastomeric Bearing

Applicable Standard: IRC:83-2018 (Part II), IS:3400 (Methods of Test for Vulcanized Rubber), MORTH Specifications for Road and Bridge Works

Elastomeric bearings comprise alternate layers of elastomer bonded to mild steel reinforcing laminates, manufactured and tested as per IRC:83-2018 (Part II). The bearing transmits vertical and horizontal loads from superstructure to substructure while accommodating rotation and translational movement due to live load, temperature and shrinkage/creep effects, as specified in IRC:6 for loading and IRC:83 for bearing design. Supplied as plain pad, fabric-reinforced or steel-laminated type as per the classification given at the end of this data sheet (Table 3 of IRC:83-2018, Part-II).

Parameter	Specification / Typical Range
Elastomer	Natural Rubber (NR) or Chloroprene Rubber (CR) conforming to IS:3400, 50-60 IRHD Shore A hardness
Design Vertical Load	Up to 10,000 kN, as per structural design and IRC:6 loading (Class A / Class 70R)
Shear Modulus (G)	0.9 – 1.15 N/mm² as specified in IRC:83 (Part II)
Permissible Compressive Stress	As per IRC:83 (Part II), governed by bearing plan area and shape factor
Rotation Capacity	Up to 0.02 rad (typical, size dependent)
Horizontal Movement	± up to 100 mm (size dependent)
Steel Laminates	Mild steel plates 3-5 mm thick conforming to IS:2062
Service Temperature	-25°C to +70°C
Ozone / Weathering Resistance	As per IS:3400 / ASTM D1149 test method
Bond Strength	Tested as per IRC:83 (Part II) type-test schedule

Key Features

Manufactured and tested as per IRC:83-2018 (Part II)

Fully bonded steel laminates with corrosion protection

Type tested for compression, shear and bond as per IRC:83 test schedule

Low maintenance, long service life under Indian climatic conditions

Typical Applications

National Highway and State Highway bridges

Railway bridges

Flyovers and ROBs/RUBs

Metro rail viaducts

Types of Elastomeric Bearings

IRC:83-2018 (Part-II), Clause 5.1.1 classifies laminated elastomeric bearings into nine types, individually or in combination, as per Table 3 of the Code, summarized below.

1)	Type A: Plain Pad / Strip Bearings
2)	Type B: Laminated Bearings
3)	Type C: Laminated Bearings with Thicker End Laminates – Laminate may be provided on either side or on both sides – Ensures better load distribution – Ensures better rotation capability – Reduces risk of back-lifting of the bearing under shear
4)	Type D: Laminated Bearings with Thicker End Laminates Exposed – Corrosion protection is required on the exposed steel surface – May improve frictional resistance at the bearing-structure interface – Friction, where taken into account, should be based on a tested and certified value – Useful where the bearing is in contact with a steel structure
5)	Type E: Bearings with Separate Steel Plate Directly Vulcanised with the Bearing – Lifting / separation of the bearing elastomer at the edges from the exposed steel plate should be avoided under all loading conditions
6)	Type F: Bearings with Positive Anchorage – Separate plates provide ease of replacement and fool-proof positive anchorage – Plates may be connected to covered / exposed end laminates – Internal fastening and positive means of location shall be adequately designed
7)	Type G: Bearings with PTFE Bonded to the Elastomer – Bond of elastomer to PTFE is critical and vulnerable, and shall be designed accordingly
8)	Type H: Bearings with Sliding Interface – Design of the sliding interface shall be as per the relevant Part of IRC:83 covering sliding elements – The opposite face of the bearing may be detailed as any of the other types described above
9)	Type I: Bearings with Restraint Against Translation to Simulate Support Condition – (a) Typical detail of restraint in the form of a central pin – (b) Typical detail of side restraint – Restraints shall be designed based on the relevant Part or other relevant IRC code