Frequently Asked Questions ptfe Teflon, bridge bearing, rubber bearing, bearings, neoprene bridge, bridge bearings elastomeric bearings, teflon sliding, laminated elastomeric, pot bearing, molded rubber, rubber products sliding bearings pipe supports, elastomer expansion joint bridge bearing rubber bearing  ptfe teflon elastomeric bearing expansion joint pot bearing sliding bearing neoprene bridge bearings bridge bearing

Many of general Frequently Asked Questions (FAQ) on laminated bearings, slide bearings and pot bearings are answered in this page. Your suggestions and comments about this page will be highly appreciated so we could serve you better. Please email us comments and suggestions. (use the right side task bar to go to next Question)

1. What are Laminated Neoprene Elastomeric Bridge bearings?

2. Explain further on advantages of Neoprene Elastomeric bearings to block of rubber.

3. Explain on neoprene bridge bearing specifications to AASHTO, BS and EN 1337 and other specifications.

4. Explain on Manufacturing procedure - Compression molding:

5. Explain on Internal Laminates or MS Mild Steel Shim?

6. What is Bearing Acceptance Tests?

7. Do you manufacture Mechanical Bridge Bearings or Pot Bearings?

8. Do you carry out Testing of Neoprene Bridge Bearings?

9. Which is the Polymer( rubber) specified in AASHTO Specification?

10. Which is the Polymer( rubber) specified in BS 5400 and EN 1337 ?

11. Advantages in sourcing Laminated  Bearings and other rubber products from pretread.com?

12. Can we get help from www.pretread for Bearing Load Calculations

13. Does www.pretread.com manufacture and supply ptfe -Teflon sliding bearings ?

14. What are the advantages on ptfe sliding bearing .?

15. Can we get help from www.pretread for PTFE-TEFLON sliding bearing designing?

16. Does www.pretread.com manufacture pot bearings, does you have in house facility for pot bearing designing?

17. Does www.pretread.com provide additional accessories and fixtures for installation of pot bearings like temporary bearings, ptfe sliding bearings, studs, base plates, masonry plates etc ?.

18. Does www.pretread.com design and manufacture ptfe-TEFLON sliding bearings ?.

19. What are the advantages of ptfe-sliding bearings ?

20. Does www.pretread.com carry out testing on Laminated Bearings?

21. Does www.pretread.com carry out testing on Teflon Sliding Bearings?

22.Explain on Shear Modules of Rubber Compound - value used for bearing design and relation with result obtained from Stress Strain Tests?

23.Can these tests be witnessed by Client.

24.What is initial type test as per EN 1337.

25.Is pretread.com approved for initial type test as per EN 1337.

26.Will pretread.com provide copy of initial type test appovel certificate as per EN 1337 on request.

We request you to feel free to send any other questions on laminated elastomeric bearings, pot bearings as well as ptfe teflon sliding bearings to us and will be glad to answer you or assist you in your requirements

1. What are 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 elastomeric bearings require nil maintenance. Unlike most other elastomer, Neoprene rubber under-goes no marked stiffening at low temperature 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 even at different high variances of temperature.

2. Explain further on advantages of Neoprene Elastomeric bearings against block of rubber.

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 deflection of 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.

3. Explain on neoprene bridge bearing specifications to AASHTO, BS, EN 1337 and other specifications.

The material specifications for the elastomeric bearing shall meet all current requirements of AASHTO 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 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 original physical properties is allowed.

4. Explain on Manufacturing procedure - Compression molding:

Elastomeric bearings shall be composed of multiple laminates of elastomeric material separated by steel reinforcing. The overall size of the bearing, number of laminate and thickness of laminates are designed in accordance to requirement of Load to be Transferred. Bearings having steel plates as reinforcement shall be cast/compression molded/vulcanized as a single unit in a mold under pressure and heat.

5. Explain on Internal Laminates or MS Shim?

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 elastomeric layers will be completely bonded by vulcanization to  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 through hot vulcanization.

6. What is 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.

7. Do you manufacture Mechanical Bridge Bearings or Pot Bearings?

Yes, 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

8. Do you carry out 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 3400 kN with horizontal shear up to 300 kN can be carried out in our facility.

9. Which is the Polymer( rubber) specified in AASHTO Specification?

Neoprene or Polychloroprene Rubber Compounds are used where Laminated Elastomeric bearings are designed, manufactured and tested in accordance to requirements with AASHTO M 251 .

10. Which is the Polymer( rubber) specified in BS 5400 Part 9 and EN 1337 - 3 ?

Natural Rubber Compounds are usually  used where Laminated Elastomeric bearings are designed, manufactured and tested in accordance to requirements with BS 5400 Part 9 as well as EN 1337 unless otherwise specified by Client / Consultant.

11. What are the advantages in sourcing Neoprene Laminated Bearings and other rubber products from www.pretread.com?

www.pretread.com you have your single reliable source for all your requirements of sliding bearing, expansion joints neoprene pads, manufactured from Polychloroprene. Even for building bearings, expansion joints, elastomeric bearings, shock absorber mountings, and custom bridge bearings, manufactured to your specification, with approval from American Association of State Highway and Transportation Officials. Our PTFE laminated elastomeric bearings, bridge bearings, isolation pads, seismic isolators, and pot bearings are manufactured complying to US road transportation authority specifications.

12. Can we get help from www.pretread for Bearing Load Calculations

Yes, we could assist you in 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. Click to see sample report

13. Does www.pretread.com manufacture and supply ptfe -Teflon sliding bearings ?

Yes, we are the first manufacture to produce ptfe -TEFLON sliding bearings successfully in the middle east. Various projects have been supplied with our ptfe -Teflon sliding bearings and will be glad to provide references on these Projects.

14. What are the advantages on ptfe sliding bearing ?

When horizontal movements are expected at high values over 50 mm and the vertical shear is low instead of using a thicker laminated bearing, it would be ideal to use a ptfe sliding bearing with SS 316 mirror finish for a smoother long term application.

15. Can we get help from www.pretread for PTFE-TEFLON sliding bearing designing?

Yes, we will be happy to do designing of ptfe sliding bearings for you, and please send us available details.

16. Does www.pretread.com manufacture pot bearings, does you have in house facility for pot bearing designing?

Yes we have in house facility to design and manufacture pot bearings, Fixed pot bearings, Guided Sliding pot bearings and Free Sliding pot bearings. These are designed and manufactured to AASHTO standards.

17. Does www.pretread.com provide additional accessories and fixtures for installation  like temporary bearings, ptfe sliding bearings, studs, base plates, masonry plates etc and fixing methods ?.

Yes we can supply you with additional accessories and fixtures for installation of pot bearings like temporary bearings, ptfe sliding bearings, studs, base plates, masonry plates etc to AASHTO specifications as well as bearing installation methodology meeting AASHTO / BS  / EN  1337 norms.

18. Does www.pretread.com manufacture ptfe-TEFLON sliding bearings ?.

Yes we do design, manufacture ptfe - Teflon sliding bearings and provide  support on installations of ptfe -TEFLON sliding bearings.

19. What are the advantages of ptfe-sliding bearings ?

Due to seismic design requirements, when  lateral movements required for structure are of greater values than the height of bearing it would be ideal to use a ptfe-TEFLON sliding bearing which provide a very low   friction coefficient between ptfe and Stainless Steel surface  which will be less than 0.05 .Also ptfe - teflon bearing provide a  service life over 50 years.

20. Does www.pretread.com carry out testing on Laminated Bearings?

Yes, we are the only manufacturer in Middle East who has in-house facility to test Laminated Bearings / Pot Bearings  by applying Vertical Load and Lateral Shear to confirm that Shear Modules confirms to specified for bearing designing. In our test facility bearings can be tested to any higher values and this facility provides structure designs more confidence on their own bearing designs.

21. Does www.pretread.com carry out testing on Teflon Sliding Bearings?

Yes on our in-house Bearing Testing Machine can be used to test Teflon Sliding Bearing to note lateral sliding on required vertical loads.

22.Explain on Shear Modules of Rubber Compound - value used for bearing design and relation with result obtained from Stress Strain Tests?

Internal Lamination construction of Elastomeric Bearings are designed based on required Vertical Load /Lateral Shear, keeping Shear Modules value of rubber compound as required by Client / Bearing designer. Only through results obtained from Stress Strain Tests and graph plotted will prove that bearing manufactured meets the required values for Lateral Shear under vertical load. We are the only manufacturer in Middle East who has in-house facility to carry out these tests and confirm that Laminated Bearings manufactured by us meets the design parameters.

23.Can these tests be witnessed by Client.

Clients / Consultants are welcomed to witness these tests and see our facility to test Laminated Bearings up to 3400 kN Vertical Load and Lateral Shear Load of 180 kN ( which can be increased to 300 kN) and a lateral movement of 100 mm.

24.What is initial type test as per EN 1337.

To be qualified as an approved and caipable manufacturer of laminated elastomeric bearings meeting EN 1337 norms effective from 2004, every laminated elastomeric  bearing manufacturer have to manufacture and test certain sizes of bearings witnessed by an accredited 3rd party independent agency . The largest size as per EN 1337 requirement is 700x600x160 mm.

25.Is pretread.com approved for initial type test as per EN 1337.

Yes, pretread.com have manufactured and tested laminated elastomeric bearings meeting EN 1337 norms and these bearings manufactured by us have been tested and certified by tests witnessed by an accredited 3rd party independent agency in UAE and Spain in 2007.

26.Will pretread.com provide copy of initial type test approval certificate as per EN 1337 on reques.

Yes, pretread.com will be glad to provide copy of approval of laminated elastomeric bearings tested to meet EN 1337 norms certified by tests witnessed by an accredited 3rd party independent agency from UAE and Spain.

To view: List of Plain Neoprene Bridge Bearing manufactured by us, Plain Elastomeric Bearings: Sizes and physical properties

To view: List of Laminated Elastomeric Bearings manufactured by us Laminated Elastomeric Bearings: Sizes and physical properties in .pdf printable format

To view: List of Laminated Neoprene Bridge Bearing manufactured by us to DIN 4141 Part 14 Laminated Elastomeric Bearings to DIN 4141 Part 14: Sizes and physical properties

Let us help you to design your requirements of elastomeric bearings. Please click on the links to visit our form fill up page and we can design bearings to your requirement