02570.10 1125 Section 02570 - Composite Bearings Description
02570.00 Scope - This Section includes the requirements for composite bearings.
Materials
02570.10 Materials - Provide Material s meeting the following requirements:
Structural Steel ..................................................................................... 02530.20 Stainless Steel Sliding Surfaces ................. ASTM A240, Type 304 or Type 316 Flat Brass Rings for Pot Bearings ......................................ASTM B36, half hard Cap Screws ............................................................. ASTM A574 or ASTM F835 Bolts and Nuts .............................................................................. Section 02560 Galvanized Bolts, Nuts, Washers, Cap screws, Sole Plates and Base Plat es ......................................... 02530.70 and 02560.40 Woven Polytetrafluoroethylene (PTFE) ......... section 18 of the current AASHTO ............................................................ LRFD Bridge Construction Specifications Welded Stainless Steel Overlay - Produce welded stainless steel overlay for the convex rotational surface of spherica l bearings using Type 309L electrodes. Elastomer - Elastomer for elastomeric discs of pot bearings shall be 100 percent virgin natural polyisoprene (natural rubber) or 100 percent virgin chloroprene (neoprene) meeting the following requirements: NATURAL POLYISOPRENE (Natural Rubber): Physical Properties ASTM Test Method Value Hardness, Durometer D D 2240 50 ± 5 Tensile strength, minimum, psi D 412 2,250 Ultimate elongation, minimum, % D 412 450 Heat Resistance Change in durometer hardness, D 573 maximum points 70 hour + 10 Change in tensile strength, at 158 °F maximum, % - 25 Change in ultimate elongation, maximum, % - 25 Compression Set 22 hours at 158 °F, maximum, % D 395, 25 Method B Ozone 25 pphm ozone in air by D 1149 No volume, 20% strain, Cracks 100 °F ± 2 °F 48 hours mounting Procedure D518, Procedure A 02570.10 1126 Adhesion Bond made during vulcanization, D 429 40 lb/in Method B Low Temperature Test Brittleness at -40 °F D 746 No Procedure B Failure VIRGIN CHLOROPRENE (Neoprene): Physical Properties ASTM Test Method Value Hardness, Durometer D D 2240 50 ± 5 Tensile strength, minimum, psi D 412 2,250 Ultimate elongation, minimum, % D 412 400 Heat Resistance Change in durometer hardness, D 573 maximum points 70 hour + 15 Change in tensile strength, at 212 °F maximum, % - 15 Change in ultimate elongation, maximum, % - 40 Compression Set 22 hours at 212 °F, maximum, % D 395, 35 Method B Ozone 100 pphm ozone in air by D 1149 No volume, 20% strain, Cracks 100 °F ± 2 °F 100 hours mounting Procedure D518, Procedure A Adhesion Bond made during vulcanization, D 429 40 lb/in Method B Low Temperature Test Brittleness at -40 °F D 746, No Procedure B Failure When test specimens are cut from the finished product a 10 percent variation in physical properties will be allowed. Polyether Urethane - The properties of polyether urethane for polyether urethane discs of disc bearings shall meet the values of the following tests : 02570.20 1127 Property Test Method Range of Values Hardness, Durometer D ASTM D2240 65 ± 5 Tensile stress, psi at 100% elongation ASTM D412 2,300 min. at 200% elongation 4,000 min. Tensile strength ASTM D412 6,000 min. Ultimate elongation % ASTM D412 220 min. Compression set, 22 hrs. at 158 °F ASTM D395 40 max. Fabric Pads - Make preformed fabric pads for fabric pad bearings of multiple layers of duck, impregnated and bound with high quality oil resistant synthetic rubber compressed into resilient pads of uniform thickness according to the following: • Cotton duck reinforcement shall be either a two-ply cotton yarn or a single- ply 50- 50 blend cotton polyester with a minimum of 8 ounces per square yard. • The fabric shall have a minimum tensile strength of 1 50 pounds per inch width when tested by the grab method. • The filling count of the duck shall be 40 ± 2 threads per inch. • The warp count of the duck shall be 50 ± 1 threads per inch. • The number of plies shall produce the specified thickness after compression and vulcanizing. • The finished pads shall withstand compression loads perpendicular to the plane of the laminations of not less than 10,000 psi without any sign of distress after the load is removed. The tested pad shall have a shape factor greater than 2.5. The preformed fabric pad shall have a Shore A hardness of 90 ± 5.
02570.20 Testing - Test all bearings except where lot testing is permitted. A lot is defined
as 25 bearings per type and size. Where lot testing is required, previous test results on a typical bearing of equal or greater capacity is acceptable provided the data is no more than 2 years old. Test typical bearings either by an independent testing laboratory, or have the testing witnessed and attested to by an independent testing laboratory, for compliance with specified performance requirements as listed below. Provide a test results certificate according to 00165.35 with the submittal of shop drawings. Perform the following tests:
a.Clearance Test - Move the components of the bearing through their design displacements or rotations to verify that the required clearances exist. If the test is conducted on a rotational component which is not under simultaneous full vertical load, make allowance for the displacem ents which would be caused by that load.
b.Long -Term Deterioration Test - Conduct test on one full scale bearing per lot. Load the bearing in compression to a stress corresponding to 100 percent of the maximum dead plus live service load while subjected to plus and minus the design rotational displacement amplitude for 5,000 cycles. Flat sliding systems shall be displaced th rough at least 1,000 cycles with an amplitude of at least ± 1.0 inch (2.0 inch peak to peak). The sliding may take place at up to 10.0 inch per minute, except when readings of the coefficient of friction are taken, at which time the sliding speed shall be 2.5 inches per minute. Bearings will be rejected when: • There are visible cracks, splits, or excessive wear on disassembly of the bearing. • The coefficient of friction exceeds two-thirds the value used in design. 02570.30 1128 (c) Friction Test - Conduct test on one full scale bearing per lot. The coefficient of friction between the sliding surfaces shall not be greater than 0.06 when the maximum working stress for the polytetrafluoroethylene (PTFE) surface is 2,000 psi. It shall not be greater than 0.045 when the maximum working stress for the PTFE surface is above 3,000 psi. Determine the coefficient of friction at 68 °F according to the requirements of section 18.3.4.3.2 of the AASHTO LRFD Bridge Construction Specifications .
d.Proof Load Test:
1.Vertical Proof Load Test - Apply a vertical load equal to 150 percent of the vertical design capacity of the tested bearing for 5 minutes, unload, then reapply for an additional 5 minutes. Place the bearing in a rotated position during the test. Rotation shall be 0.015 radians or the design rotation, whichever is greater. The test bearing shall show no indication of failure or other defects such as weld cracking, plate distortion, extrusion of the elastomer or bearing material, or displacement of the elastomer s eal while under load or subsequently upon disassembly and inspection. The successful test of a bearing with a vertical design capacity of 50 Tons or less will be accepted as qualification for all bearings of a similar design with a lesser design capacity.
2.Horizontal Proof Load Test - A horizontal proof load test is required when the design horizontal capacity exceeds 10 percent of the design vertical capacity and no engineer's calculations are submitted. Apply a horizontal load equal to 100 percent of the horizontal design capacity while also applying a vertical load equal to 100 percent of the dead load for a period of 2 minutes. The bearing does not need to be in the rotated position. The bearing shall show no indication of failure or other defec ts such as weld cracking, plate distortion, extrusion of the elastomer or bearing material, or displacement of the elastomer seal while under load or subsequently upon disassembly and inspection. The bearing tested for horizontal proof load may be either a bearing specified for use on the Project or a similar type bearing with both a vertical design capacity and a horizontal design capacity within 10 percent of the design capacities of bearings specified for use on the Project.
02570.30 Acceptance - For each composite bearing used in the Structure , provide the
manufacturer's quality compliance certificate according to 00165.35 that verifies the bearing has been manufactured according to the design of the tested bearing.
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Source: Oregon Standard Specifications for Construction, 2024 Edition. Pages 1191–1194 of 1,268. View official source ↗