Neoprene Bearing Pads,neoprene bridge bearings, laminated elastomeric bearings,seismic isolators etc are generally known as bridge bearing pads in Construction industry. We manufacture them in our purpose built plant using high-grade virgin Neoprene - Polychloroprene Grade- 2 elastomer- mixed with carbon black and rubber chemicals to form into a rubber compound to match AASHTO M 251 Specification under controlled heat and pressure.
In house Quick Production Test of all bearings shall be done at Clients/Representative presence. Tests confirming to AASHTO specification in accordance with Acceptance Testing on either Level I or Level II or Short/Long-Duration Compression Test up to 4200 kN with horizontal shear up to 400kN can be carried out in our facility.
Why Laminated Neoprene Elastomeric Bridge bearings?
Neoprene bridge bearings - plain or laminated - elastomeric bearings are much easier to install in a bridge than compared to other types of bearing used and require nil maintenance. Unlike most other elastomers, Neoprene rubber undergoes no marked stiffening at low temperatures when the thermal contraction of the bridge deck is at maximum. Such stiffening could be deleterious to bearing and/or structure. Correctly-designed and suitably-compounded laminated Neoprene Rubber bridge bearings can be confidently expected to function efficiently for at least a decade.
Advantages of Neoprene Elastomeric bearings
As efficient bearing plates for pre-cast, pre-stressed concrete or steel beams in bridges and buildings, Neoprene Pads - plain and laminated - manufactured by us permits a smooth and uniform transfer of load from the beam to the substructure and allow beam rotation at the bearing due to deflect ion of the beam under load. They further allow lateral and longitudinal movement of the beam caused by thermal forces. Neoprene Pads have no movable parts and thermal expansion and contraction are absorbed by the pad's ability to give and take in shear. There is no sliding motion between pad and beam or between pad and abutment.
Neoprene bridge bearing specifications
The material specifications for the elastomeric bearing shall meet all the current requirements of AASHTOM M 251.Bearing pads and elastomeric bearings will comply with Articles 18.2.3 through 18.2.6 of Section 18, Bearing Devices, Division II, Construction, of the AASHTO Standard Specifications for Highway Bridges.
Bearing pads and laminated bearings shall be of the compound known as neoprene and shall be cast in molds under pressure and heat. A plain elastomeric bearing pad and steel load distribution plate combination shall be classified as a laminated elastomeric bearing. Test specimens shall be in accordance with ASTM D 3182 or D 3183. Where test specimens are cut from the finished product, a 20 percent variation from the original physical properties is allowed.
Difference between a plain rubber block and laminated elastomeric bearings
The capability of plain rubber block to carry vertical load increases as the number of laminations/mild steel shims increases.
How a plain rubber block and laminated bearing reacts against vertical load
Plain rubber block under vertical load compressed down where as a laminated bearing bulge out with each laminations absorbing most of the vertical load.
How a plain rubber block and laminated bearing reacts against horizontal load
Manufacturing procedure - Compression moulding
Elastomeric bearings shall be composed of multiple laminate of elastomeric material separated by steel reinforcing. The overall size of the bearing, the number of laminate and thickness of laminate are designed in accordance to the requirement of Load to be Transferred. Bearings having steel plates as reinforcement shall be cast/compression moulded/vulcanized as a single unit in a mould under pressure and heat.
Internal plates shall be ASTM A 36/A 36M or A 570/A 570M, Grade 36 or Grade 40. All plates shall be deburred. The internal plates shall not be less than 1.88 mm (0.074 inch) thick.The steel plates separating the elastomeric layers will be completely bonded by vulcanization to the elastomeric material on all surfaces using special metal to rubber bonding adhesive. All external load bearing steel plate(s) if present, shall be factory vulcanized to the elastomeric bearings during the primary molding process.
Bearing Acceptance Tests
Acceptance Tests of the pads and bearings shall be according to Level I acceptance criteria of Article 18.2.5. This testing shall be included in the price bid for the bearings.
Mechanical Bridge Bearings
Mechanical bearings are also manufactured and supplied by us and further investments for plant up-gradation is under way.Please send us your requirement for Pot Bearings
Testing of Neoprene Bridge Bearings
In house Quick Production Test of all bearings shall be done at Clients/Representative presence. Tests confirming to AASHTO specification in accordance with Acceptance Testing on either Level I or Level II or Short/Long-Duration Compression Test up to 4200 kN with horizontal shear up to 400kN can be carried out in our facility. For more details and pictures click here.
BS 5400 - with Natural Rubber
Natural Rubber Compounds are used where Laminated Elastomeric bearings are designed, manufactured and tested in accordance to requirements with BS 5400 Part 9.
High Damping Rubber Bearing (HDRB)
High Damping Rubber Bearing (HDRB) - as an alternative to the lead rubber bearing. We offer high damping rubber bearing which is ideal for seismic isolation with one device - supporting the structure, providing the elastic restoring force and also the required amount of damping up to a maximum of 10-15% of critical. High Damping rubber bearing are most advantageous when the movements encountered are not large and there is room for the increased height of the bearing. Moderate damping is achieved with this type of the bearing.
Lead Rubber Bearings
A lead rubber bearing a bigger laminated bearing manufactured from layers of rubber, sandwiched together with layers of steel, except for that in middle of bearing there will be a solid lead "plug." Top and bottom of the bearing is fitted with steel plates, which are used to attach bearing to building through its foundation.
These lead rubber bearings are designed in such a way that bearing is very stiff and strong in vertical direction, but flexible in horizontal direction. Lead, inserted as center core of bearing dissipates the energy of earthquake while the rubber, reinforced with steel plates, provides stability, supports structure and isolates vibrations.
Bearing calculations and design
We can verify load calculations for your bearings. Send us sizes, construction and load details of your bearings and we will send results on design parameters compared to AASHTO LRFD.
To View a sample page of bearing design calculations click here (PDF).
Allow us to help you design bearings according to your requirements. Please visit our form page and fill up with required details.