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- The bearing producer shall furnish certification as specified in TC-1.03. The certification shall include actual mill test results. The chemical and physical properties of the finished bearings shall also be furnished by the processing manufacturer.
910.01 BRONZE OR COPPER ALLOY BEARING AND EXPANSION PLATES
- Either of cast bronze or rolled copper alloy.
- 910.01.01 Cast Bronze. B22, Alloy No. 91100 or No. 91300.
- Self-lubricating bronze bearing plates shall be an article of standard production by an approved manufacturer of such equipment. They shall be provided with trepanned recesses (not grooves) that shall be filled with a lubricating compound consisting of graphite and metallic substances with a lubricating binder capable of withstanding the atmospheric elements. The lubrication compound shall be compressed into the recesses by pressure to form dense, nonplastic lubricating inserts. The lubricating area shall comprise at least 25 percent of the total area. The static coefficient of friction shall not exceed 0.10.
- The certification shall be as specified above and shall include the actual test results showing that bearing plates of the same design as those supplied meet the static coefficient of friction requirements.
- Test specimens shall be at least 4 in. long by 4 in. wide. The static coefficient of friction shall be determined by testing a specimen plate subjected to a vertical pressure of 1000 psi and 1000 cycles consisting of 1/2 in. horizontal strokes at a speed not to exceed 9 cycles per minute. Conduct testing at an ambient temperature of 77 ± 9 F. The static coefficient of friction on the specimen bearing plate shall be calculated by dividing the total applied vertical load on the plate into the total horizontal load required to start motion between the bearing plate and it’s mating surface while subject to the vertical load. Upon completion of the test, the bronze plate shall show no signs of galling.
- 910.01.02 Rolled Copper. Per PB 100, Alloy No. 51000.
910.02 STRUCTURAL BEARING PADS
- The manufacturer shall furnish certification as specified in TC-1.03.
- 910.02.01 Elastomeric Pads. Elastomeric bearing pads shall meet material requirements described in the AASHTO LRFD Bridge Design Specifications. The elastomeric bearing pads shall be 60 durometer hardness, Shore Type A. Accompanying the certificate for elastomeric bearing pads shall be two standard ASTM tensile slabs molded from the same compound batch as the furnished elastomeric bearings.
- The static load deflection of any layer of elastomeric bearing pads shall not exceed 7 percent at 800 psi average unit pressure when tested under laboratory conditions.
- The design load for the elastomeric bearing pads will be as specified. The manufacturer shall proof load each steel reinforced bearing design with a compressive load of 1.5 times the maximum design load and specify that the material conforms to the material certification.
- When test specimens are cut from an actual bearing pad, a reduction of 10 percent in the minimum requirements for original tensile strength and ultimate elongation will be required.
- 910.02.02 Self-Lubricating Bearing Assembly. A fabric reinforced elastomeric pad, Tetrafluoroethylene (TFE) bonded to the pad and a stainless steel sheet. All elements shall meet AASHTO LRFD Bridge Design Specification.
- Fabric reinforced elastomeric pad shall be Type A, durometer hardness of 70 to 90. Stainless steel sheet shall be Type 304, minimum thickness of 16 gauge. The surface of the stainless steel sheet in contact with TFE shall have a 2B finish and be welded to the sole plate using an approved welding procedure.
- 910.02.03 Preformed Fabric Pads for General Application. Multiple layers of 8 oz cotton duck impregnated and bound with high quality natural rubber or of equally suitable materials, approved by the Engineer and compressed into resilient pads of uniform thickness, after compression and vulcanizing. The finished pads shall withstand compression loads perpendicular to the plane of the laminations of at least 10 000 psi without detrimental reduction in thickness or extrusion.