02571.20 1129 Section 02571 - Elastomeric Bearing Pads
Description
02571.00Scope - This Section includes the requirements for plain and laminated elastomeric
bearing pads.
Materials
02571.10Elastomeric Compound - The elastomer portion of the elastomeric compound shall be
100 percent virgin poly chloroprene ( Neoprene) or natural rubber (polyisoprene) meeting the requirements of section 18 of the AASHTO LRFD Bridge Construction Specifications including the properties from the following table:
Table 02571-1 ASTM Properties Test Method Requirements
Hardness, Durometer D D 2240 60 ± 5 Tensile strength, min., psi D 412 2,250 Ultimate elongation, min., % D 412 350 Heat Resistance: Change in durometer hardness D 2240 + 15 max. points after 70 hr. at 212 °F Change in tensile strength, D 573 - 15 max. % after 70 hr. at 212 °F Change in ultimate elongation, D 573 - 40 max. % after 70 hr. at 212 °F
Compressive set, max. % after 22 hr. D 395 35 at 212 °F Method B
Adhesion: Bond made during D 429 40 vulcanization, lb/in Method B
Tear Resistance, (psi) D 624 180 Die C
02571.15Metal Reinforcement - Metal reinforcement shall be rolled, mild steel sheets 14 gauge
thick and conforming to ASTM A1011, Grade 36 Type 1, or ASTM A1008, Grade 40.
02571.20Manufacturing Requirements :
alternate laminations of elastomer and metal. In metal reinforced pads, the top and bottom layers shall be elastomer 1/4 inch thick, and interior elastomer layers shall be 1/2 inch thick . The nominal thickness of the bearing shown reflects the thickness of the elastomer only. It does not include the steel laminates.
thickness of an individual lamination exceed 5/8 inch. Variations in thickness of an individual elastomer lamination shall not exceed 1/8 inch and the variation in thickness of all elastomer 02571.30 1130 laminations within a pad shall be such that each metal lamination shall not vary by more than 1/8 inch from a plane parallel to the top or bottom surface of the pad.
shearing to size or drilling of holes will be allowed. Cover all edges of metal laminations with a minimum of 1/8 inch, and a maximum of 1/4 inch, of elastomer except at laminate restraining devices and around holes that will be entirely closed when the pad is in place on the Structure .
Clean the exposed edge voids in the pads caused by the steel laminate restraining devices with a solvent. Shop seal with an appropriate caulking material before shipment.
Sandblast and clean the s teel laminates of all surface coatings such as grease, oil, rust and mill scale before bonding. Free the laminates of sharp edges and burrs.
Pads 1/2 inch in thickness may be sheared. The shearing shall not heat the material and shall produce a smooth f inish to 250 microinches with no tears or jagged areas.
Construction Specifications for fabrication tolerances.
Fabricate pads to meet flash tolerance, finish and appearance requirements given in the current edition of the Rubber Handbook , published by the Rubber Manufacturers Association, Inc., RMA F3 and T.063 for molded bearings and RMA F2 for extruded bearings.
02571.30Laminated Bearing Pad Tests and Acceptance Crit eria:
pads do not require these tests.
Independently test all completed bearings by compressive visual inspection according to 02571.30(b). Failure of in dividual bearings to pass the compressive visual inspection will be cause for rejection of those individual bearings.
Independently test five standard test specimens of laminated pads according to 02571.30(c). Failure of any individual specimen to meet t he peel strength test requirements will be cause for rejection of the entire bearing production lot. A lot is defined as 50 or less bearings which are manufactured in a reasonably continuous manner from the same batch of elastomer, cured under the same co nditions, and are all the same size and type.
Replace rejected bearings with new acceptable bearings at no additional cost to the Agency. Provide the sample pad and perform all testing at no additional cost to the Agency.
Mark all bearings in indelible ink or flexible paint with the Contract number, lot number, date of manufacturer, and bearing identification number. Place the marking on a side face visible after erection of the Bridge .
Clean and free the bearings of any foreign substances such as dust, grit and moisture before testing.
proof load for a compressive loaded to 1.5 times the maximum design load. The load shall be held for 5 minutes, removed, then reapplied for a second period of 5 minutes. Maintain the load constant while the bearing is inspected for visual faults. The following will be cause for rejection:
• A bulging pattern or patterns implying lack of bond between the elastomer and the laminate or bulging patterns that imply improper laminate placement. 02571.31 1131 • Three separate surface cracks which are greater than 5/64 inch wide and 5/64 inch deep, or a single crack 3/16 inch deep or wider than 1/4 inch.
the exception that the specimens shall be taken randomly and cut from a production bearing submitted for the Project. The bond between the elastomer and steel laminate in each specimen shall be not less than 40 pounds per inch.
to the requirements of AASHTO LRFD Construction Specifications when steel reinforced elastomeric bearings are designed using Method B, or when using Grade 4 elastomer.
02571.31Acceptance - Provide a quality compliance certification according to 00165.35 that the
bearing pads conform to the requirements for Materials, fabrication and testing. Provide a test result certificate according to 00165.35 that includes the manufacturer's and independent test results according to 02571.30(a).