1、Section 18 BEARINGS 18.1 SCOPE This section covers the construction and installation of structural bearings that consist of one or more of the fol- lowing component types: metal rocker and roller bearings, PTFE sliding bearings (flat and curved), plain elastomeric pads, fiberglass reinforced elastom
2、eric pads, cotton duck reinforced pads, steel reinforced elastomeric bearings, pot bearings, disc bearings, and bronze and copper alloy bear- ings (flat and curved). At the discretion of the Engineer, other component types may be used, but the construction, installation and testing requirements must
3、 then be agreed by the Engineer before the start of fabrication. The section also covers ancillary items such as ma- sonry, sole and load distribution plates, bedding materials, anchor bolts, lubricants and adhesives. 18.2 APPLICABLE DOCUMENTS 18.2.1 AASHTO Standards The following AASHTO Standards a
4、re relevant to this section. AASHTO M 102 AASHTO M 107 AASHTO M 108 AASHTO M 164 AASHTO M 25 1 AASHTO M 253 AASHTO M 270 Steel Forgings, Carbon and Alloy for General Use (ASTM A 668) Bronze Castings for Bridges and Turntables (ASTM B 22) Rolled Copper-Alloy Bearing and Expansion Plates and Sheets fo
5、r Bridges and Other Industrial Uses (ASTM B 100) High-Strength Bolts for Structural Steel Joints (ASTM A 325) Specifications for Plain and Steel Laminated Bearings for Bridges (ASTM D 4014) Heat-Treated Steel Structural Bolts 150 Ksi Minimum Tensile Strength (ASTM A 490) Structural Steel for Bridges
6、 (ASTM A 709) 18.2.2 ASTM Standards The following ASTM Standards are relevant to this section. ASTM A 167 ASTM A 240 ASTM A 307 ASTM A 781 ASTM A 788 ASTM A 802 ASTM B 22 ASTM B 29 ASTM B 36 ASTM B 100 ASTMB 103 ASTM B 438 ASTM D 395 ASTM D 412 ASTM D 429 ASTM D 518 ASTM D 573 Specification for Stai
7、nless and Heat- Resisting Chromium-Nickel Steel Plate Sheet, and Strip. Specification for Heat-Resisting Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels Specification for Carbon Steel Exter- nally Threaded Standard Fasteners Standard Specification for Castin
8、gs, Steel and Alloy, Common Require- ments, for General Industrial Use Specification for Steel Forgings, General Requirements Practice for Steel Castings, Textures and Discontinuities, Evaluation and Specifying by Visual Examination Bronze Castings for Bridges and Turntables (AASHTO M 107) Specifica
9、tion for Pig Lead Specification for Brass Plate, Sheet, Strip, and Rolled Bar Specification for Rolled Copper Alloy Bearing and Expansion Plates for Bridge and Other Structural Uses (AASHTO M 108) Specification for Phosphor-Bronze Plate, Sheet, Strip and Rolled Bar Specification for Sintered Bronze
10、Bearings (Oil Impregnated) Test Methods for Rubber Property- Compression Set Test Methods for Rubber Property- Tension Test Test Methods for Rubber Property- Peel Test Test Method for Rubber Deteriora- tion-Surface Cracking Test Method for Rubber-Deteriora- tion in an Air Oven 617 618 HIGHWAY BRIDGE
11、S 18.2.2 ASTM D 746 ASTM D 792 ASTM D 903 ASTM D 1043 ASTM D 1149 ASTM D 1777 ASTM D 2000 ASTM D 2240 ASTM D 2256 ASTM D 3293 ASTM D 4014 ASTM D 4894 ASTM D 4895 Test Method for Brittleness Temper- ature of Plastics and Elastomers by Impact Test Method for Specific Gravity (Relative Density) and Den
12、sity of Plastics by Displacement Test Method for Peel or Stripping Strength of Adhesive Bonds Stiffness Properties of Plastics as a Function of Temperature by Means of a Torsion Test Test Method for Rubber Deteriora- tion-Surface Ozone Cracking in a Chamber. Method of Measuring Thickness of Textile
13、Materials Classification System for Rubber Products in Automotive Applications Test Method for Rubber Property- Durometer Hardness Test Method for Breaking Load (Strength) and Elongation of Yarn by the Single-Strand Method Specification for PTFE Resin Molded Sheet Specification for Plain and Steel-
14、Laminated Elastomeric Bearings for Bridges (AASHTO M 251) Specification for Polytetrafluoroeth- ylene (PTFE) Granular Molding and Ram Extrusion Materials Specification for Polytetrafluoroeth- ylene (PTFE) Resin Produced from Dispersion 18.2.3 Other Standards ANSI/AASHTO/ Bridge Welding Code AWS D1.5
15、 MIL-S-8660C Grease for pot bearing rotational elements MMM-A-134 Epoxy (Federal specification) QQ-B-626 Brass (Federal specification) TT-S-230 Caulk (Federal specification) 18.3 GENERAL REQUIREMENTS Bearings shall be constructed in accordance with the details shown on the plans and specifications.
16、When com- plete details are not provided, bearings shall be furnished that conform to the limited details shown on the plans and shall provide the performance characteristics specified. 18.4 MATERIALS 18.4.1 General 18.4.1.1 Steel 18.4.1.1.1 Rolled steel shall be of the type required on the plans an
17、d shall satisfy the testing requirements of the standard to which it conforms. Unless otherwise spec- ified, it shall conform to AASHTO M 270 (ASTM A 709) Grade 36 and shall cause no adverse electrolytic or chem- ical reaction with other components of the bearing. It shall be free of all rust and mi
18、ll scale. 18.4.1.1.2 Unless Otherwise specified by the Engineer, steel laminates in steel reinforced elastomeric bearings shall be made from rolled mild steel conforming to M 270 Grade 36, Grade 50 (ASTM A 36, A 572), or equivalent, and shall have a nominal thickness not less than 16 gage. Holes in
19、laminates, not specified on the plans but used for manufacturing purposes, shall be permitted only with the written approval of the Engineer. 18.4.1.1.3 Cast steel shall satisfy the requirements of ASTM A 802 and be free of all blow-holes and impurities larger than l/8 inch. The inside wall of the p
20、ot in pot bear- ings and the contact surface of metal rocker or roller bear- ings shall be free of blow-holes or impurities of any size. 18.4.1.1.4 Forged steel shall satisfy the requirements of ASTM A 788. 18.4.1.1.5 Unless otherwise specified by the Engi- neer, stainless steel shall conform to AST
21、M A 167 or A 240 type 304, and have a minimum thickness of 20 gage. Stainless steel in contact with PTFE sheet shall be pol- ished to a #8 mirror finish. 18.4.1.1.6 Steel weld metal shall be chosen to be compatible with the parent materials and the welding process used and shall be approved by the E
22、ngineer. Stainless steel weld used for overlays shall be type 309L. 18.4.1.1.7 Bolts shall conform to AASHTO M 164 (ASTM A 325), AASHTO M 253 (ASTM A 490) or ASTM A 307 unless specified otherwise. 18.4.2 Special Material Requirements for Metal Rocker and Roller Bearings The steel at the contact surf
23、ace of a metal bearing may be hardened provided that, after hardening, it satisfies the strength and ductility requirements of the contract plans and material specifications. 18.4.3 DIVISION II-CONSTRUCTION 619 18.4.3 Special Material Requirements for PTFE Sliding Surfaces 18.4.3.1 PTFE 18.4.3.1.1 F
24、TFEresin shall be 100% pure new mate- rial and shall comply with ASTM D 4894 or D 4895. It shall satisfy the requirements of Table 18.4.3.1-1. No re- claimed material shall be used. Finished PTFE sheet, strip and fabric shall be resistant to acids, alkalis, and petroleum products, stable at tem- per
25、atures from - 360F to + 500“F, nonflammable, and nonabsorbing of water. 18.4.3.1.2 Filler material, when used in PTFE, shall be milled glass fiber, carbon fiber or other approved fiber. The filler shall not react chemically with the PTFE but shall adhere to it so that the two act compositely. 18.4.3
26、.1.3 Finished PTFE sheet shall be made from virgin PTFE resin or virgin PTFE resin uniformly blended with approved filler. The maximum filler content shall be 15% for fiberglass and 25% for carbon fibers. The maxi- mum filler content for other materials shall be determined by the Engineer. The PTFE
27、sheet shall satisfy the require- ments of Table 18.4.3.1-1. Values for intermediate filler contents may be obtained by interpolation. 18.4.3.1.4 Woven fabric PTFE shall be made from oriented multi-filament PTFE fibers or from a mixture of PTFE fibers made from twisted, slit PTFE tape and other fiber
28、s. It shall conform to the requirements of Table 18.4.3.1-1. 18.4.3.2 Adhesives Adhesive used for bonding sheet PTFE shall be an epoxy material satisfying the requirements of federal specification MMM-A-134, FEP film or equal, as ap- proved by the Engineer. 18.4.3.3 Lubricants Lubricant, if used, sh
29、all consist of a combination of solids which does not react chemically or electrolytically with the PTFE and its mating surface and shall remain sta- ble in the environmental conditions expected at the bridge site. 18.4.3.4 Interlocked Bronze and Filled PTFE Structures The phosphor bronze back plate
30、 shall conform to AASHTO M 108 (ASTM B 100) and the porous bronze layer shall conform to ASTM B 103. 18.4.4 Special Material Requirements for Pot Bearings 18.4.4.1 The rotational element of the pot bearing shall be made from an elastomeric compound, with a hard- ness of 50 ? 10 on the Shore A scale.
31、 It shall be made from all new material. The raw polymer on which it is based shall be either polychloroprene (neoprene) or polyisoprene (natural rubber). The compound shall satisfy the physical property requirements for a 50 hardness material as speci- fied in Tables 18.4.5.1-1Aor -lB. 18.4.4.2 The
32、 elastomer may be lubricated with a sili- cone grease which does not react chemically with the elas- tomer and which does not alter its properties within the range of environmental conditions expected at the bridge site. 18.4.4.3 The sealing rings shall be made of brass con- forming to ASTM B 36 (ha
33、lf hard) for rings of rectangular cross-section, and to federal specification QQ-B-626, com- position 2, for rings of circular cross-section. The Engineer TABLE 18.4.3.1-1 Physical Properties of PTFE ASTM Sheet Sheet with 15% Sheet with 25% Woven Physical Property Test Method (Unfilled) glass fibers
34、 carbon fibers fabric Specific Gravity D 4894, D 4895, 2.16 2 0.03 2.20 ? 0.03 2.10 2 0.03 - Melting point (OF) D 4894, D 4895, 623 t 2 621 ? 18 621 ? 18 - or D 5977 or D 5977 or D 5977 or D 5977 Tensile Strength (psi) D 4894, D 489.5, 2800 20002 1 3002 24,000 Elongation at Break (%) D 4894, D 4895,
35、 2001 1502 752 351 I Using Test Method ASTM D 2256 2 Using Test Method ASTM D 638 620 HIGHWAY BRIDGES 18.4.3.1.1 may, at own discretion, approve other sealing ring materi- als on the basis of test evidence which demonstrates ade- quate sealing properties and durability of the material. 18.4.5 Specia
36、l Material Requirements for Steel Reinforced Elastomeric Bearings and Elastomeric Pads 18.4.5.1 Elastomer The raw elastomer shall be either virgin neoprene (polychloroprene) or virgin natural rubber (polyisoprene). The elastomer compound shall be classified as being of low temperature grade O, 2, 3,
37、4 or 5. The grades are de- fined by the testing requirements in Tables 18.4.5.1-1A and -1B. A higher grade of elastomer may be substituted for a lower one. In the absence of more specific informa- tion, bearings shall be Grade 3,60 durometer elastomer. The elastomer compound shall meet the minimum r
38、e- quirements of Tables 18.4.5.1-lA and -lB except as oth- erwise specified by the Engineer. The nominal hardness of the compound shall lie between 50 and 60 for reinforced bearings and between 50 and 70 for plain pads. Test re- quirements may be interpolated for intermediate hardness. If the materi
39、al is specified by its shear modulus, its mea- sured shear modulus shall lie within 15% of the specified value. A consistent value of hardness shall also be sup- plied for the purpose of defining limits for the tests in Ta- bles 18.4.5.1-1A and -lB. If the hardness is specified, the measured shear m
40、odulus must fall within the range of Table 14.6.5.2.1 in Article 14.6.5.2 of Division I. When test specimens are cut from the finished product, the phys- ical properties shall be permitted to vary from those spec- ified in Tables 18.4.5.1-1A and -lB by 10%. All material tests shall be carried out at
41、 73” ? 4F unless otherwise noted. Shear modulus tests shall be carried out using the apparatus and procedure described in annex A of ASTM D 4014, amended where necessary by the requirements of Tables 18.4.5.1-1Aor -lB. 18.4.5.2 Fabric Reinforcement Fabric reinforcement shall be woven from 100% glass
42、 fibers of “E type yarn with continuous fibers. The mini- mum thread count in either direction shall be 25 threads per inch. The fabric shall have either a crowfoot or an 8 Harness Satin weave. Each ply of fabric shall have a min- imum breaking strength of 800 lb/in. of width in each thread directio
43、n. 18.4.5.3 Bond The vulcanized bond between fabric and reinforce- ment shall have a minimum peel strength of 30 lb/in. Steel laminated bearings shall develop a minimum peel strength of 40 lbhn. Peel strength tests shall be performed by ASTM D 429 Method B. 18.4.6 Special Material Requirements for B
44、ronze or Copper Alloy Sliding Surfaces 18.4.6.1 Bronze and Copper Alloys 18.4.6.1.1 Bronze Bronze components shall conform to the requirements of AASHTO M 107 (ASTM B 22) alloy C90.500, C91100 or C86300. Alloy C91100 shall be furnished unless otherwise specified. Components may be cast, rolled or fo
45、rged. Cast- ings shall be free of blow-holes larger than Ys inch and con- tact surfaces shall be free of all blow-holes of any size. 18.4.6.1.2 Rolled Copper-Alloy Rolled copper-alloy bearing and expansion plates shall conform to the Specification for Rolled Copper-Alloy Bear- ing and Expansion Plat
46、es and Sheets for Bridge and Other Structural Uses, AASHTO M 108 (ASTM B 100). Alloy No. C51000 or No. C51100 shall be furnished unless otherwise specified. 18.4.6.2 Oil Impregnated Metal Powder Sintered Material Metal powdered sintered material shall conform to ASTM B 438, Grade 1, Type II or Grade
47、 2, Type I. 18.4.7 Special Material Requirements for Disc Bearings 18.4.7.1 Elastomeric Rotational Element The rotational element of the disc bearing shall be made from an elastomeric compound with a hardness which lies between 45 and 65 on the Shore D scale. The raw polymer on which it is based sha
48、ll be polyether ure- thane. The compound shall satisfy the physical property requirements appropriate to the materials hardness in Table 18.4.7.1-1. 18.4.8 Special Material Requirements for Guides 18.4.8.1 Low-Friction Material The sliding interface shall be made from a material which is approved by
49、 the Engineer and which will provide a friction coefficient no greater than the one used in the design. 18.4.3.1 DIVISION II-CONSTRUCTION 621 TABLE 18.4.5.1-1A Material Tests-polychloroprene PHYSICAL PROPERTIES D 2240 Hardness (Shore A Durometer) D 412 Tensile Strength, Minimum psi Ultimate Elongation, Minimum % HEAT RESISTANCE D 573 Change in Durometer Hardness, 70 Hours Maximum Points at 212F Change in Tensile Strength, Maximum % Change in Ultimate Elongation, Maximum % COMPRESSION SET D 395 22 Hours 212F Maximum % Method B OZONE D 1149 100 pphm ozone in air by volume, 20% strain 1
