523Bearings

523.01 Description This work shall consist of designing, furnishing, testing and

installing bearings in accordance with this specification and in conformance with the details shown on the Plans.

523.02 Materials

E l a s t o m e r 711.11 S t a i n l e s s S t e e l 711.12 P o l y t e t r a f l u o r o e t h y l e n e ( P T F E ) 711.13 S t r u c t u r a l S t e e l 713.01 P r e f o r m e d P a d s 713.03 Bronze or Copper-Alloy Bearing and Expansion Plates 713.04 A n c h o r R o d s 720.07 Miscellaneous materials, caulking or lubricant shall be as recommended by the manufacturer of the bearings.

523.03 Submittals The Contractor shall prepare shop detail, erection and other

necessary Working Drawings in accordance with Section 105.7, Working Drawings. The drawings will be reviewed in accordance with the applicable requirements of Section 105.7. Changes and revisions to the reviewed Working Drawings shall require further review by the Fabrication Engineer.

523.04 General Requirements Requirements for the type of bearing furnished are as

follows: S t e e l B e a r i n g s S e c t i o n s 523.10 thru 523.19 E l a s t o m e r i c B e a r i n g s S e c t i o n s 523.20 thru 523.29 P o t o r D i s c B e a r i n g s S e c t i o n s 523.30 thru 523.39 S p h e r i c a l B e a r i n g s S e c t i o n s 523.40 thru 523.49 Design of bearings shall be in accordance with AASHTO LRFD Bridge Design Specifications and AASHTO/NSBA Steel Bridge Collaboration G9.1 Steel Bridge Bearing and Design Guidelines.

523.05 Fabrication Steel fabrication work, for all types of bearings, shall comply with

Section 504, Structural Steel. 5-138 523.051 Protective Coating Steel parts of bearings shall have protective coating applied to the areas described within this section in accordance with Section 506, Shop Applied Protective Coating- Steel. Masonry plates shall, at the Contractor’s option, be galvanized or metalized. The masonry plates shall be top coated to match the coating of the superstructure beams when beams are coated. Portions of bearings between the masonry plate and sole plate that will be exposed after installation shall, at the Contractor’s option, be galvanized or metalized. Steel between the masonry and sole plates shall be top coated to match the color of the superstructure beams when the adjacent superstructure beams are coated. Stainless steel and /or machined surfaces with a roughness height of 125 micro-inches or smoother shall not be coated. Machined surface finishes with a roughness height of 125 micro-inches or smoother, except stainless steel, shall be lubricated with a non-corrosive, waterproof, high pressure lubricant having a temperature range of -30 oF to 150 oF, National Lubrication and Grease Institute number not lower than 2 and an OK load of not less than 20 lbs., as measured by the requirements of ASTM D2509. Metal surfaces designed for sliding in contact with Teflon (PTFE) coated surfaces shall not be lubricated. Sole plates shall have the same finish as the adjacent structural steel. When adjacent structural steel is coated, the sole plate shall be galvanized/or metalized, at the option of the contractor. Sole plates shall be top coated to match the color of the superstructure beams. When the adjacent structural steel is bare and uncoated, the sole plate shall be bare and uncoated. When the adjacent beams are concrete, the sole plates shall be galvanized. Areas to be field welded shall not be coated prior to welding; they shall be touched up after welding. Anchor rods shall be galvanized. When anchor rods are designated to secure bare unpainted steel, a dielectric coating (epoxy or bituminous type coatings are acceptable) shall be applied to the anchor rod and/or adjacent steel to prevent contact between galvanized surfaces and bare unpainted steel. When bearings, or portions of bearings, are painted to match adjacent structural steel, the anchor rods shall also be painted.

523.06 Fabrication Tolerances Fabrication tolerances for all bearings shall comply with

Section 18.1 of AASHTO, LRFD Bridge Construction Specifications (Table 18.1.4.2-1) unless otherwise noted on the Plans or in this Section 523, Bearings. 523.061 Material Friction Test The coefficient of friction (‘cof’) between the two mating surfaces shall be measured. Tests shall be made either on samples taken from the same batch of materials as those used in the prototype bearings or the tests may, at the manufacturer’s option, be conducted on finished bearings. Only new materials shall be used; material that has been previously tested shall not be used. The surfaces shall be thoroughly cleaned with a degreasing solvent. No lubrication, other than that specified for the prototype bearings, shall be used. The mating surfaces for 5-139 the test pieces shall have a common area no less than the smaller of the bearing area or 7.0 square inches. The test piece shall be loaded in compression to a stress corresponding to their maximum service dead load plus live load, which shall be held for one hour prior to, and throughout the duration of, the sliding test. At least 100 cycles of sliding, each consisting of at least 1.0 inch of movement, shall then be applied at a temperature of 68 oF ± 2 oF. The uniform sliding speed shall be 2.5 inches per minute. The breakaway ‘cof’ shall be computed for each direction of each cycle and its mean and standard deviation shall be computed for the sixth through twelfth cycles. The initial static breakaway ‘cof’ for the first cycle shall not exceed twice the design ‘cof’. The maximum ‘cof’ for all subsequent cycles shall not exceed the design ‘cof’. Failure of a single sample shall result in rejection of the entire lot. Following the 100 cycles of testing, the breakaway ‘cof’ shall be determined again and shall not exceed the initial value. The bearing or specimen shall show no appreciable sign of wear, bond failure, or other defects.

523.07 Inspection The Contractor shall notify the Fabrication Engineer at least 10 days

in advance of the start of fabrication so that inspection of the work can be provided by the Department. All work will be subject to inspection by the Fabrication Engineer. Quality Control (QC) is the responsibility of the Contractor. The Quality Control Inspector (QCI) shall inspect all aspects of the work and shall supervise all testing. The QCI shall record measurements and test results in a Job Control Record (JCR). The QCI shall reject materials and workmanship that do not meet contract requirements. The Contractor may perform testing in addition to the minimum required. The results of all measurements and testing shall be made available to the Quality Assurance Inspector (QAI). Quality Assurance (QA) is the prerogative of the Fabrication Engineer. The QAI will ensure that the Contractor’s QC is performing properly, verify documentation, periodically inspect workmanship and witness testing. QA testing deemed necessary by the Fabrication Engineer in addition to the minimum testing requirements shall be scheduled to minimize interference with the production schedule.

523.08 Certification The Contractor shall furnish a materials certification letter in

accordance with Division 700.

523.09 Installation of Bearings Bearings shall be placed upon bridge seats that are

properly finished. Bridge seat elevations shall be within + ¼ inch of the elevation shown on the Plans and the differential elevation between any two adjacent bearing areas shall not exceed + ⅜ inch. When the bearings are to be set directly on the concrete bridge seats, as indicated on the Plans, the bridge seats shall be dressed 1 inch larger all around than the bottom member of 5-140 the bearing and to the exact elevations shown on the Plans or as determined by the Resident. If dressed areas are lower than the surface of the surrounding bridge seat, a channel 2 inches wide and with a minimum slope of 4 percent, shall be cut to the edge of the bridge seat for drainage. Masonry plates shall be set level in their exact position and shall have a full and even bearing upon the masonry. They shall be placed on a preformed pad, the same size and shape as the masonry plate with holes to match the masonry plate. 523.091 Anchor Rods The contractor shall drill the holes and set the anchor rods with a chemical or cementitious Anchoring Material from the Department Qualified Products List. The Anchoring Material shall completely fill the holes. In place anchor rods shall be capable of developing unconfined pullout strength of 30 kips and 70 kips for M24 and M36, 1 inch and 1-½ inch anchor bolts, respectively. 523.092 Grout Pads When the bearings are to be set on a grout pad, the grout shall be a non-shrink cementitious grout from the Grout Materials list of the Department Qualified Products List. The grout shall have a minimum design compressive strength of 6,000 psi at 28 days, unless otherwise specified in the Contract.” The grout shall be well bonded to the adjacent concrete and shall be placed under pressure to ensure that all anchor holes and the entire area under the masonry plate is free of voids. 523.093 Sliding Surfaces The sliding surfaces of bearings shall be installed level. Special care shall be exercised at all times to ensure protection of the stainless steel and the PTFE surfaces from coming in contact with any foreign matter. At no time shall any forms, debris, or other material interfere with the free action of the bearing assemblies. When bronze or copper-alloy bearing and expansion plates are used, the sliding surfaces or the steel in contact with the bearing and expansion plates shall be recoated immediately prior to installation with a lubricant recommended by the manufacturer of the bronze or copper-alloy plates. 523.094 Final Adjustment Bearings shall not be connected in place until the deck is in place. Final adjustment of the bearings for temperature shall be made after the deck is in place. Connecting of the bearing sole plate to the girder flange shall be done only after all adjustments have been made. Sliding expansion bearings shall be set so that slotted holes in the sole plate will be centered on the anchor bolts, and rocker bearing assemblies shall be set so as to be plumb at 45 ºF. When determining temperature adjustments for bearings, the difference between the steel temperature (not the ambient temperature) and 45 ºF shall be used. 5-141 Nuts on anchor rods shall be brought in contact with the masonry plate or sole plate as shown on the Plans. Threads on anchor rods shall be upset with a punch to prevent easy removal of the nuts. When anchor rods extend through slotted holes in a sole plate, the lower of double nuts shall be left loose, bring to contact and loosen approximately ¼ turn, to allow movement of the sole plate. STEEL BEARINGS

523.10 Steel Bearings Structural steel bearings- rocker type and sliding plate type-

shall be fabricated in accordance with the dimensions and finishes shown on the Plans, Standard Details and the requirements of Section 504, Structural Steel. Bearings, base plates and other contact surfaces shall be finished to the following tolerances: Surface Roughness Requirements Steel slabs ANSI 2000 micro-inches Bearing sole plates ANSI 1000 micro-inches Milled ends to compression members, milled or ground ends of stiffeners or rockers ANSI 500 micro inches Bridge rockers and rollers ANSI 250 micro-inches Sliding bearings ANSI 125 micro-inches Pins and pin holes ANSI 125 micro-inches Bearing mating surfaces (including steel to steel, or steel to bronze and steel to elastomeric material) shall have a minimum of 90% contact area. Flatness (the permissible variation from a true plane) shall be a maximum of 1/32 inch.

523.11 Materials Materials shall conform to Section 523.02, Materials.

ELASTOMERIC BEARINGS

523.20 Description Two types of bearings are applicable for the following Sections:

Laminated Elastomeric Bearings, which shall consist of layers of elastomer laminated to steel plates; and Plain Elastomeric Bearings, which shall consist of a single layer of elastomer.

523.21 Materials Materials shall conform to Section 523.02, Materials.

If the elastomer material is specified by its shear modulus on the Plans, the measured shear modulus value shall lie within the specified range. When the elastomer material is specified by shear modulus, the Contractor shall supply a consistent value of hardness for the purposes of defining limits for the tests of Table A and B in Section 711.11. Laminated Elastomeric bearings shall have a Shore A Durometer hardness of 50 or 60. Plain Elastomeric bearings shall have a Shore A Durometer hardness of between 50 and 70. 5-142 Shear modulus tests shall be carried out using the apparatus and procedure described in Annex A of the ASTM D4014 specifications.

523.22 Fabrication All components of Laminated Elastomeric Bearings shall be molded

as an integral unit. Plain Elastomeric Bearings may be molded individually, cut from previously molded slabs, or extruded and cut to length. Cut edges shall have an ANSI 250 mils finish. Steel laminates shall be abrasive blast cleaned to an SSPC SP-6 and protected from contamination. The Fabricator must be on the Departments Qualified Supplier List.

523.23 Testing The following testing shall be performed prior to delivery of the

bearings:

523.30 Design Pot or Disc bearings shall be designed for the loads and movements

given on the Plans. Configurations and dimensions shall conform to AASHTO/NSBA G 9.1, Steel Bridge Bearing Design and Detailing Guidelines. Configurations and dimensions other than those given on the Plans or AASHTO/NSBA G 9.1 may be accepted subject to the approval of the Fabrication Engineer. Design calculations to substantiate all the requirements stated in this specification shall be submitted as part of the Working Drawings and shall be stamped and signed by a Professional Engineer licensed in the State of Maine. Except where indicated on the Plans, the design shall also include the connections between the bearings and the superstructure, and the bearings and the substructure, along with adequate provisions for hold-downs equal to the tensile strength of the anchor rods. The bearings shall be designed to accommodate a rotation of not less than 0.015 radians. The static coefficient of friction between the PTFE and the stainless steel surface, for each size and type of bearing, shall not exceed 0.20 at the average unit bearing pressure for the minimum vertical load indicated on the Plans. 5-144 The bearings shall be designed for a horizontal force at least equal to 10% of the vertical capacity of the bearing. No more than two bearings, with guide bars, per bearing line, shall be considered to be carrying the total maximum lateral horizontal load as indicated on the Plans. Bearing friction shall not be considered when the horizontal load capacity of guided or fixed bearings is calculated. The PTFE sliding surface for pot or disc bearings shall be designed to meet the following:

523.31 Materials Materials shall conform to Section 523.02, Materials, and the

following: Sealing rings shall be brass. Flat rings shall conform to the requirements of ASTM B36, half hard. Round sealing rings shall conform to the requirements of Federal Specification QQB626, Composition 22, half hard. Elastomeric Disc hardness shall be: 5-147 Shore A Durometer scale, between 50 and 60, for Pot Bearings Shore D Durometer scale, between 45 and 65, for Disc Bearings

523.32 Fabrication Bonding of PTFE sheets to the piston shall be under factory-

controlled conditions and in accordance with written instructions of the manufacturer of the adhesive. After completion of the bonding operation, the PTFE surface shall be smooth and free from bubbles. PTFE surfaces shall not be polished, but shall be wiped clean using a solvent appropriate for the material. The stainless steel sliding surfaces shall be seal welded around the entire perimeter. The surfaces shall be smooth and flat and the back of the stainless steel shall remain in intimate contact with the sole plate. Pots shall be machined from a solid plate or fabricated by welding a cut shape to a plate. Fabricated pots shall be 100% ultrasonically tested at the inside weld and magnetic particle tested at the exterior weld. The elastomeric discs in pot bearings shall be manufactured from no more than three pieces. Each bearing shall be assembled at the plant and, following assembly, shall be sealed at the joint between the piston and the pot with a continuous ¼ inch, minimum, bead of a flexible silicone rubber sealing compound approved by the Fabrication Engineer. Each bearing shall have permanent match marks to indicate the neutral 45 °F position of the bearing. Each bearing shall also be marked for identification by die stamping on all steel parts (edge of sole plate, piston, masonry plate, and top edge of pot). Each bearing shall be shipped and stored in moisture-proof and dust-proof covers until they are to be erected.

523.33 Fabrication Tolerances Tolerances shall comply with Section 523.06,

Fabrication Tolerances, and as noted below. Brass sealing rings shall have finished surfaces of less than 63 mils (ANSI B 46.1).

523.34 Testing and Certification The manufacturer of the pot or disc bearings shall

furnish test facilities for testing and inspection of the completed bearings. The Fabrication Engineer, or an authorized representative, shall be allowed free access to the manufacturer's plant and test facility. The Fabrication Engineer will select two completed bearings for testing. The test shall be arranged so that the static coefficient of friction on the first movement can be determined. The test shall first be conducted at an average bearing pressure of 3,500 psi on the PTFE surface with the test load applied continuously for not less than 12 hours nor more than 14 hours prior to measuring the friction. The first movement static coefficient of friction shall then be determined. The above test shall then 5-148 be repeated for the minimum vertical load indicated on the Plans for the bearings selected. The results shall not exceed that specified for the design. A proof load test shall also be performed on each test bearing by applying a load equal to 150% of the maximum vertical load indicated on the Plans for the bearings selected for a period of one hour. The test bearings shall show no sign of failure or other defects while under load or subsequently upon disassembly and inspection. Before testing, the testing equipment and procedure shall be submitted to the Fabrication Engineer for review.

523.40 thru 523.49 Reserved - Spherical Bearings

523.50 Method of Measurement Bearings will be measured for payment by each unit,

tested and accepted. Bearing installation will be measured for payment by each unit in place and accepted.

523.51 Basis of Payment Bearings will be paid for at the contract unit price each, which

price shall be full compensation for the design, fabrication, testing, and delivery. Bearing installation will be paid for at the contract unit price each which price shall be full compensation for installation, including all materials, equipment, labor and incidentals necessary for installing the bearings in accordance with the Plans and this specification. Removal of the existing bearings, if present, including all materials, equipment, labor and incidentals necessary for jacking the superstructure, removal of the existing bearings and preparation of the bridge seat in accordance with the Plans and this Specification, shall be considered incidental to bearing installation. Payment will be made under: Pay Item Pay Unit

523.52 Bearing Installation E a c h

523.5301 Steel Bearings, Fixed, Sliding Plate E a c h 523.5302 Steel Bearings, Expansion, Sliding Plate Each 523.5303 Steel Bearings, Fixed, Rocker E a c h 523.5304 Steel Bearings, Expansion, Rocker E a c h 523.5401 Laminated Elastomeric Bearings, Fixed Each 523.5402 Laminated Elastomeric Bearings, Expansion Each 523.5403 Plain Elastomeric Bearings E a c h 523.5551 Pot or Disc Bearings, Fixed E a c h 523.5552 Pot or Disc Bearings, Expansion E a c h 523.5601 Spherical Bearings E a c h

Bearings in other states

• Alaska 720 · BEARINGS
• Illinois 521 · BEARINGS
• Louisiana 814 · Bearings
• Maryland 432 · Bearings