1、Standard Specification for Cotton Duck Fabric Bridge Bearings AASHTO Designation: MP 26-151American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-4e MP 26-1 AASHTO Standard Specification for Cotton Duck Fabric Bridge Bear
2、ings AASHTO Designation: MP 26-1511. SCOPE 1.1. This specification covers the material requirements for cotton duck fabric bridge bearings. Cotton duck fabric bearings furnished under this specification shall adequately provide for thermal expansion and contraction; rotation; camber changes; and cre
3、ep and shrinkage, where applicable, of structural members. Cotton duck fabric bearings may be either fixed bearings or sliding bearings. Cotton duck fabric bearings as herein defined shall include fabric bearings, preformed fabric bearings, cotton duck pads, and cotton duck bearings. 2. REFERENCED D
4、OCUMENTS 2.1. AASHTO Specifications: Standard Specifications for Highway Bridges AASHTO LRFD Bridge Design Specifications 2.2. ASTM Standards: A240/A240M, Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications
5、 A264, Standard Specification for Stainless Chromium-Nickel Steel-Clad Plate D2240, Standard Test Method for Rubber PropertyDurometer Hardness D4849, Standard Terminology Related to Yarns and Fibers D4894, Standard Specification for Polytetrafluoroethylene (PTFE) Granular Molding and Ram Extrusion M
6、aterials D4895, Standard Specification for Polytetrafluoroethylene (PTFE) Resin Produced from Dispersion E4, Standard Practices for Force Verification of Testing Machines E29, Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications 2.3. Military Speci
7、fications: MIL-C-882E, Cloth, Duck, Cotton or Cotton-Polyester Blend, Synthetic Rubber, Impregnated, and Laminated, Oil Resistant MIL-E-5272, General Specification for Environmental Testing, Aeronautical, and Associated Equipment 2.4. Society for Protective Coatings: SSPC-SP 10/NACE No. 2, Near-Whit
8、e Blast Cleaning SSPC-VIS 1-01, Visual Standard for Abrasive Blast Cleaned Steel 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-4e MP 26-2 AASHTO 3. GENERAL REQUIREMENTS 3.1. All bearings shall be de
9、signed in accordance with specifications contained in the latest edition of AASHTOs Standard Specifications for Highway Bridges or the AASHTO LRFD Bridge Design Specifications. 3.2. The dimensions of the furnished bearings shall be the dimensions required by the design documents within the tolerance
10、s shown in Section 6 of this specification. The bearings shall be composed of the specified materials; shall be tested at the appropriate level; and shall satisfy any special requirements of the purchaser. 3.3. The contractor shall provide the purchaser with written notifications 30 days prior to th
11、e start of bearing production. This notification shall include the contract number, quantity, and size of bearings being produced; manufacturers name, location, and the representative who will coordinate production, inspection, sampling, and testing with the purchaser. 3.4. In addition to material r
12、equirements for the bearings individual components, this specification provides acceptance criteria for finished bearings. 3.5. Perform calculations using significant digits in accordance with ASTM E29 using the rounding method for determining compliance to the specification requirements herein, unl
13、ess otherwise specified by the purchaser. 4. MATERIALS 4.1. Properties of Cotton Duck FabricFabric shall be cotton or cotton-polyester 50-50 blend, and weigh a minimum of 8 oz. per square yard. The fabric warp count shall be 50 1 threads per in. and the fill count shall be 40 2 threads per in. 4.2.
14、Properties of RubberRubber shall be high quality natural rubber or equivalent material. 4.3. Properties of Polytetrafluoroethylene (PTFE)PTFE shall be made from resin satisfying the requirements of ASTM D4894 or D4895. 4.4. Properties of Preformed PadPreformed pads shall be manufactured of new mater
15、ials and composed of multiple layers of cotton duck fabric impregnated and bound with a rubber compound containing rot and mildew inhibitors and antioxidants. The number of plies shall be such as to produce the specified thickness, after compression and vulcanizing. 4.4.1. The pads shall withstand c
16、ompressive loads perpendicular to the plane of the laminations of not less than 10,000 lb per square in. without detrimental extrusion or reduction in thickness. Load deflection properties shall be in accordance with procedures of Military Specifications MIL-C-882E. 4.4.2. The rubber shall have a Ty
17、pe A Durometer hardness of 87 to 95 according to ASTM D2240. 4.4.3. The material shall not lose effectiveness throughout a temperature range of 65F to 150F. 4.4.4. There shall be no visible evidence of damage or deterioration resulting from environmental effects of sunshine, humidity, salt spray, fu
18、ngus, or dust in accordance with MIL-E-5272. 4.5. Properties of Mating SurfaceMating surfaces shall be stainless steel, Type 304, conforming to ASTM A240/A240M or A264. The mating surface shall have a surface finish of 8.0 -in. RMS or better. 2015 by the American Association of State Highway and Tra
19、nsportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-4e MP 26-3 AASHTO 5. FABRICATION 5.1. Standard Cotton Duck Fabric Bearings: 5.1.1. Any adhesive used to attach the cotton duck fabric pad shall be recommended for that purpose by the manufacturer and approved
20、by the purchaser. 5.2. Sliding Expansion Cotton Duck Fabric Bearings: 5.2.1. Any adhesive used to attach the PTFE to the cotton duck fabric pad shall be recommended for that purpose by the manufacturer of the PTFE sliding material and approved by the purchaser. 5.2.2. The stainless steel mating surf
21、ace shall be attached to the sole plate by either bonding or welding. 5.2.2.1. For bonded applications, stainless steel sheets may be affixed to sole plates with a combination of high-temperature resistant epoxy or other approved procedure. The fabricator must demonstrate that any proposed alternate
22、 procedure for attachment will maintain adhesion between the sole plate and stainless steel under loading, movement, and weather conditions anticipated to be encountered during the life of the bearing. 5.2.2.2. For welded applications, stainless steel sheets may be affixed to sole plates using eithe
23、r flux-cored arc welding (FCAW), gas metal arc welding (GMAW), or gas tungsten arc welding (GTAW). Care should be taken when selecting the filler metal. Filler metals with high levels of chromium and nickel will result in martensite. The resulting martensite will be very hard and brittle. Even a sma
24、ll amount of plastic deformation will produce cracking in the weld. The cracking could occur even without external loading or deformation, due to the action of diffusible hydrogen after welding. 5.2.3. Prior to adhesion or attachment of the stainless steel to a sole plate, the contact surface of the
25、 sole plate shall be blast cleaned to an appearance equivalent to SSPC SP 10/NACE No. 2. The contact surface of stainless steel sheets to be bonded with epoxy shall be mechanically abraded or etched prior to application of adhesive. 6. TOLERANCES 6.1. Cotton duck fabric bearing pads shall be built t
26、o the design dimensions with the following tolerances: 6.1.1. Overall Vertical Dimensions: 6.1.1.1. Design thickness 11/4in. and less 0, +1/8tolerance, in. 6.1.1.2. Design thickness over 11/4in. 0, +1/4 tolerance, in. 6.1.2. Overall Horizontal Dimensions: 6.1.2.1. 36 in. and less 0, +1/4 tolerance,
27、in. 6.1.2.2. Over 36 in. 0, +1/2 tolerance, in. 6.1.3. External Load Plate: 6.1.3.1. Thickness 1/16 tolerance, in. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-4e MP 26-4 AASHTO 6.1.3.2. Length and
28、 Width 1/4 tolerance, in. 6.1.3.3. Holes, Slots, or Inserts: 6.1.3.3.1. Size 1/8 tolerance, in. 6.1.3.3.2. Position 1/8 tolerance, in. 7. MARKING 7.1. Each cotton duck fabric bearing shall be marked with a bearing identification or lot number. 8. KEYWORDS 8.1. Bearings; bridge; camber; contraction;
29、cotton duck; creep; dimensions; expansion; fabric; fabrication; fixed; marking; mating surface; preformed; PTFE; rotation; rubber; shrinkage; sliding; structural; thermal; tolerance. 1This provisional standard was first published in 2015. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
