512Bearing Device

Bearing Device

Description

512.01This work consists of furnishing and placing bearing devices per these specifications and

in conformity with the plan details.

Materials

512.02Elastomeric bearing pads shall include plain bearings and laminated bearings. Plain

bearings are unreinforced pads, consisting of elastomer only, and laminated bearings are reinforced with steel laminates. The elastomer compound shall be classified as being of low temperature grade 3, 4 or 5. The grades are defined by the testing requirements of subsection

705.06, Tables 705-1 and 705-2. A higher grade of elastomer may be substituted for a lower

grade. Elastomer grade, AASHTO Design method (A or B), elastomer shear modulus and elastomer hardness shall be shown in the contract documents. The sheer modulus shall be within 15 percent of the specified value. Materials requirements for elastomeric bearing pads, sheet lead, polytetrafluoroethylene (PTFE) sheets, stainless-steel sheets and adhesive material shall conform to the requirements of subsection 705.06.

Leveling pads are unlaminated bearings as called for on the plans. They shall be cut or molded from AASHTO elastomer grade 3, 4, or 5 as described in Tables 705-1 and 705-2 with a durometer (duro) (Shore “A”) hardness of 60.

The sealing mechanism used in pot bearing devices to prevent extrusion of the elastomer shall be of brass or bronze metal.

All steel, except stainless-steel, used in fabricating bearing devices shall conform to AASHTO M 270 (ASTM A709) Grade 36 unless otherwise required in the Contract. ASTM A709 Grade 50W or ASTM A709 Grade 50 may be substituted for ASTM A709 Grade 36. Anchor bolts shall be ASTM A449 zinc plated. All welding shall conform to the applicable requirements of ANSI/AWS D1.1 and Standard Specification 509.

Structural steel elements of Type II Bearing Devices shall be painted per Section 509.

All metal surfaces of Type III Bearing Devices shall be completely zinc metallized per AWS C2.2 to a thickness of 8 mils, except the surfaces covered with PTFE and surfaces with stainless- steel. The internal pot cavity and bottom surface of the piston for Type III bearings shall be zinc metallized to a thickness of 3 mils and polished to 125 microinches after zinc metallizing.

Fabrication

512.03Type I Bearing Device. A Type I Bearing Device consists of either a plain or laminated

elastomeric bearing pad with an optional machined sole plate as shown on the plans. Pads 3/4 inch or less in thickness may be either laminated or plain. Pads over 3/4 inch in thickness shall be laminated.

512.04 Laminated pads shall be individually molded and shall consist of alternate laminations of elastomer and metal laminates. The bearings shall be vulcanized under heat and pressure. The mold finish shall conform to standard shop practice. The internal steel laminates shall be sandblasted and cleaned of all surface coatings, rust, mill scale, and dirt before bonding, and shall be free of sharp edges and burrs. Laminations of elastomer shall be 1/2 inch, plus or minus 1/8 inch in thickness. Unless otherwise noted on the plans, the top and bottom layers of metal shall be uniformly covered with a maximum of 1/8 inch of elastomer. The edges of the metal shall be uniformly covered with a minimum of 1/8 inch of elastomer, except at laminate restraining devices and around holes that will be entirely closed on the finished structure. Variations in the location of the metal reinforcement from its theoretical location shall not exceed 1/8 inch. Plain bearings may be molded individually, cut from previously molded strips or slabs, or extruded and cut to length. Cut edges shall conform to the requirements of ANSI B46.1.

512.04Type II Bearing Device. The upper sliding element shall consist of a polished

stainless-steel sheet finished to a No. 7 high luster polish (glossy, bright, buffed finish) and attached to a sole plate. The stainless-steel sheet shall be seal welded to the sole plate. The operating coefficient of either static friction or sliding friction between the stainless-steel and the PTFE sheet, when loaded to 1,000 psi, shall not exceed 0.06. Pads less than 3/4 inch in thickness may be either laminated or plain. Pads 3/4 inch and greater in thickness shall be laminated. The lower sliding element shall consist of a filled or unfilled PTFE sheet with a minimum thickness of 3/32 inch, vulcanized to a stainless-steel substrate. The stainless-steel substrate shall be capable of resisting bending stresses that the sliding surface may be subjected. The other side of the substrate material shall be vulcanized to an elastomeric pad as described in subsection 512.03 and as shown on the plans. The stainless-steel substrate material shall have a thickness as shown on the plans or shall have sufficient tensile strength to restrain the elastomeric pads.

512.05Type III Bearing Device. The manufacturer of Type III bearings shall be pre-inspected

and approved by the department and listed in the Contract. Type III Bearing Devices are designed as Pot type or Disc type. Bearing devices shall be fabricated as fixed, guided expansion, or non-guided expansion bearings as designated in the Contract. Bearings shall satisfactorily provide for thermal expansion and contraction, rotation, camber changes, and creep and shrinkage of the structural members they support. Bearings shall be designed and fabricated so that they can be readily inspected and easily removed and replaced during the service life of the bridge. This shall include provisions to allow removal and replacement of all components of the bearing device, excluding sole plates, by lifting the superstructure no more than 1/4 inch. The static coefficient of friction shall be determined based on the force required to cause first movement under the vertical load applied during the test. The operating coefficient of static friction or sliding friction between the stainless-steel and the PTFE sheet, when subjected to a 3,500-psi load, shall not exceed 0.03.

movement in the bearing plane.

longitudinal movement and shall restrict transverse movement in the bearing plane.

longitudinal and transverse movement in the bearing plane.

512.05

an optional guide plate, a loading piston, and a cylindrical steel retainer (pot) to confine an elastomeric pad. The piston and pot shall each be machined from a solid steel plate. The piston may be welded to a guide or top plate as approved by the Engineer. The shape characteristics, clearances, and sealing mechanism of the piston and cylinder shall be designed to prevent extrusion of the elastomer material under rotational movement, vertical load, and where applicable, horizontal load. When a bearing must accommodate movement in the plane of the bearing (guided or non-guided type), the top surface of the piston plate shall be faced with PTFE sheet and the mating surface of the steel shall be faced with polished stainless-steel finished to No. 8 mirror finish or better. When a bearing device restricts transverse movement (guided type), the device shall contain either a guide bar or a keyway system. These systems shall be designed so that the vertical interfaces are parallel throughout the range of rotation of the bearing device. The mating steel surfaces of the guide bar or keyway systems shall be faced with strips of PTFE and stainless-steel.

by upper and lower steel bearing plates. The bearing shall be equipped with a shear restricting mechanism to prevent horizontal movement of the disc. When a bearing device must accommodate movement in the plane of the bearing (guided or non-guided type), the top surface of the upper steel bearing plate shall be faced with PTFE sheet and the mating surface of the steel plate shall be faced with polished stainless-steel finished to a No. 8 mirror finish or better. Bearing devices designed to restrict transverse movement (guided type) shall contain either a guide bar or a keyway system. These systems shall be designed so that the vertical interfaces are parallel throughout the range of the rotation of the bearing device. The mating steel surfaces of the guide bar or keyway systems shall be faced with strips of PTFE and stainless-steel.

surface of a piston plate or upper steel bearing plate shall have a minimum finished thickness of 3/16 inch and shall be recessed for half its thickness into its steel substrate. The PTFE sheet shall be bonded to the steel substrate using an epoxy resin applied to the full area of the contact surfaces. The surface of the PTFE sheet to be bonded shall be treated with sodium naphthalene or sodium ammonia process before bonding. Bonding shall be performed at the manufacturer's factory under controlled conditions and per the instructions of the manufacturer of the epoxy material. At the completion of the bonding operation, the surface of PTFE shall be smooth and free of bubbles. Lubricants of any kind shall not be used in the sliding surfaces of bearing devices. The PTFE strips on the mating surfaces of guide systems shall be 3/16 inch minimum and shall be recessed and bonded or may be bonded and mechanically fastened to the mating steel surfaces of the guide bar or keyway systems. The fasteners shall provide full bearing on the PTFE strip and the steel surfaces where the PTFE is attached.

The mating surfaces of structural steel elements shall be ground to a flatness of 0.01 inch per linear foot. Maximum surface roughness shall be ANSI 500 per American National Standards Institute B 46.1.

Bearing devices shall be designed so that stainless-steel will cover the PTFE throughout the range of movement for the bearing device. The surface of stainless-steel that slides on the PTFE shall have a flatness of 0.01 inch per linear foot.

512.06

512.06Reserved

512.07Reserved

512.08The bearings shall be completely factory-produced assemblies and shall include all

directly connected or welded anchorage hardware. The bearings shall adequately provide for the amount of movement due to temperature changes, post tensioning offsets, or girder rotation as shown on the plans.

512.09Testing and Acceptance. The materials for elastomeric bearings and finished

bearings shall be subjected to the tests described in this subsection. Material tests shall be per Table 705-1 or 705-2 and as described. The manufacturer shall furnish facilities for the testing and inspection of the completed bearings in the plant or at an independent test facility. At the Engineer’s discretion, testing may be performed in the presence of the Engineer or a designated representative. The Engineer or the Engineer’s representative shall be allowed free access to the necessary parts of the manufacturer’s plant and test facility, as arranged by the Contractor. The Contractor shall inform the Engineer a minimum of two weeks in advance of a date and time when a visit to the plant and test facility would be permitted.

samples from the production bearings for testing. A lot shall be defined as the smallest number of bearings as determined by the following criteria:

types of bearing devices are defined as fixed, guided expansion, and nonguided expansion, which includes Type I, Type II, and Type III, bearings.

devices consists of determining the sliding coefficient of friction between the PTFE and stainless-steel elements of an expansion type bearing device by using equipment and a test procedure approved by the Engineer. Specially made bearings shall not be used; only actual bearings to be used in the project shall be tested.

the test apparatus.

specified in the Contract, if larger.

test load applied continuously for 12 to 24 hours before measuring friction.

by applying an approximate horizontal force to the bearing device in a cyclic manner to cause slipping along the PTFE stainless-steel surface at a speed of less than 1 inch per minute and shall not exceed the coefficient of friction specified. The bearing shall then be subjected to a minimum of 100 movements of at least 1 inch in each direction from the centerline of the device at a speed of less than 12 inches per minute. After cycling, the static and dynamic coefficients of friction

512.09

shall be determined again at a speed of less than 1 inch per minute and shall not exceed the coefficient of friction specified. After the load is removed the bearings shall be disassembled and the components carefully examined. Any visible damage to a component shall be cause for rejection.

device equal to 150 percent of its rated capacity and subjecting the bearing to the greater value of either rotation of 0.02 radians or the designed rotation for a period of one hour. During the testing of pot bearings, if the confined elastomer extrudes beyond the sealing mechanism, the bearing shall be rejected. During the testing of disc bearings, any observed lift off between the rotational element and other components of the bearing shall be cause for rejection. After the load is removed the bearing device shall be disassembled and the components carefully examined. Any visible damage to the disk bearing components shall be cause for rejection.

tested as follows:

times the maximum design load. The load shall be held constant for 5 minutes, removed and reapplied for another 5 minutes. The bearing shall be examined visually while under the second loading. Bulges indicating laminate nonparallelism or a layer thickness that is outside the specified tolerances, or poor laminate bond, shall result in the bearing being rejected. If there are three or more separate surface cracks that are greater than 0.08-inch-wide and 0.08-inch-deep, the bearing shall be rejected. The short duration test shall be performed for bearings designed under AASHTO method A or B.

times its maximum design load for a minimum period of 15 hours. If during the test, the load falls below 1.3 times the maximum design load, the test duration shall be increased by the period of time that the load is below this limit. The bearing shall be examined visually at the end of the test while it is still under load. If the bulging pattern suggests laminate non-parallelism or a layer thickness that is outside the specified tolerances, or poor laminate bond, the bearing shall be rejected. If there are three or more separate surface cracks that are greater than 0.08-inch-wide and 0.08-inch-deep, the bearing shall be rejected. The long duration test shall be performed for bearings designed under AASHTO Method B.

Bearings represented by test specimens passing the above requirements will be approved for use in the structure subject to on-site inspection for visible defects.

The manufacturer shall certify that each bearing satisfies the requirements of the plans and these specifications.

The manufacturer shall submit:

512.10

used in the construction of the bearings.

they conform to the requirements of this specification.

The supplier shall submit a Certificate of Compliance to the Engineer for acceptance.

512.10Packaging. The bearings shall be packaged and protected in such a manner that

they will not be damaged, and the contact surfaces of the sliding elements will not be contaminated while being handled, transported, or stored. Each completed bearing shall have its components clearly identified and marked with an upstation arrow and the location on the structure. Except for Type I bearings, the markings shall be on a face that is visible after erection of the bridge. The bearing assemblies shall be furnished as a complete unit from one manufacturing source, unless otherwise approved.

Construction Requirements

512.11The concrete where the bearings are to be placed shall be free of honeycomb. The

concrete bearing contact surface shall be finished to a level plane with a flatness tolerance of 1/16 inch for bearing seats up to 30 inches, 3/32 inch for bearing seats over 30 inches and under 45 inches, and 1/8 inch for bearing seats over 45 inches as measured using a straight edge placed in any direction across the area. The finished plane shall not vary more than 1/8 inch from the elevation shown on the plans. The initial installations of Type III bearings shall be performed by the Contractor in the presence of a representative of the manufacturer. This representative shall be experienced in such installations and provide information to the Contractor on handling and installation procedures. The representative shall provide information to the Engineer on inspection of the bearing installation and shall provide assistance until the Contractor and the Engineer agree that they understand the installation and inspection procedures.

Upon completion of the superstructure placement, the Contractor, Engineer and bearing manufacturer's representative, together, shall inspect each bearing's placement and alignment for Type III bearings. Subsequent to the inspection, and after correction of all deficiencies, the Contractor shall certify in writing that the bearing installation is correct.

512.12Masonry plates of Type III bearing assemblies shall be set on a single thickness of

sheet lead or preformed fabric pad when a monolithic cap seat is used.

512.13Placement of elastomeric bearing pads or bearing devices on grout pads will not be

permitted unless called for on the plans.

512.14Non-metallic bearing pads shall be protected from damage due to welding heat. The

Contractor shall submit a welding procedure for approval before beginning welding. Field welding to steel plates that have a bonded PTFE surface will be permitted provided that the welding procedure used does not increase the temperature of the area of the steel where PTFE is bonded above 300 °F. Temperature indicating wax pencils or other approved means shall be used to determine whether this temperature limit is being exceeded.

512.15

512.15Type II and Type III Bearing Devices shall not be disassembled during installation unless

otherwise permitted. The Contractor shall protect all bearings from contamination and damage due to paint overspray or when placing concrete or other materials.

512.16The Contractor shall furnish a manufacturer's certification that all components meet the

Contract requirements.

512.17The Contractor shall submit shop drawings, design calculations and load data for review

of Type III Bearing Devices as specified in subsection 105.02. The shop drawings shall include installation procedures and address storage, handling, disassembly, placement, alignment, offsets, protection during welding to steel girders, protection during painting of structure, and removal of banding or retaining clamps.

Method of Measurement

512.18Bearing devices will be measured by the unit

Basis of Payment

512.19The accepted quantities of bearing devices will be paid for at the contract unit price

each. Payment will be made under:

Pay Item Pay Unit Bearing Device (Type______) Each

Elastomeric bearing pads, preformed fabric pads, and sheet lead when not included in Bearing Device (Type) will not be measured and paid for separately but shall be included in the work. Leveling pads will not be paid for separately but shall be included in the work. The presence of a manufacturer’s representative will not be measured and paid for separately but shall be included in the work.

512.19

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514.01