512.01 512-1 SECTION 512 BEARING DEVICE DESCRIPTION
512.01 This work consists of furnishing and placing bearing devices per these specifications and
in conformity with the plan details. MATERIALS
512.02 Elastomeric 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 bein g 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), elast omer 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
512.03 Type 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. 512.04 512-2 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 sha ll 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.
512.04 Type 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 shal l have sufficient tensile strength to restrain the elastomeric pads.
512.05 Type III Bearing Device . The manufacturer of Type III bearings shall be preapproved
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 desig nated 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 read ily 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.
a.Fixed Bearing. A fixed bearing shall allow rotation but no longitudinal or transverse movement in the bearing plane.
b.Guided Expansion Bearing. A guided expansion bearing shall allow rotation and longitudinal movement and shall restrict transverse movement in the bearing plane.
c.Nonguided Expansion Bearing. A non -guided expansion bearing shall allow rotation and longitudinal and transverse movement in the bearing plane. 512.05 512-3 (d) Pot Bearings. The bearing device shall consist of a masonry plate, a sole plate, a top plate, 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.
e.Disc Bearings. The bearing shall consist of an elastomeric rotational element (disc) confined 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 throughou t 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.
f.Sliding Surfaces of Plates for Pot and Disc Bearings. The PTFE sheet affixed to the top 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 sod ium 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. 512.06 512-4 512.06 Reserved.
512.07 Reserved.
512.08 The 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.
512.09 Testing 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 presen ce 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 t o the plant and test facility would be permitted.
a.Test Specimens. One bearing per lot shall be tested. The Engineer will randomly select samples from the production bearings for testing. A lot shall be defined as the smallest number of bearings as determined by the following criteria:
1.One lot shall not exceed a single contract or project quantity.
2.One lot shall not exceed 25 bearings.
3.A lot shall consist of those bearings of the same type within a load category. The types of bearing devices are defined as fixed, guided expansion, and nonguided expansion , which includes Type I, Type II, and Type III, bearings.
4.Load categories are 0 to 999 kips, 1 ,000 to 2 ,999 kips, and 3, 000 kips or more.
b.Test Method. The test for the sliding coefficient of friction for Types II and III bearing 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.
1.Clean all bearing and sliding surfaces, assemble the bearing device and place it into the test apparatus.
2.Type III bearings shall be subjected to a rotation of 0.02 radian, or the rotation specified in the Contract, if larger.
3.The test shall be conducted at maximum working stress for the PTFE surface with the test load applied continuously for 12 to 24 hours before measuring friction.
4.At first movement, the static and dynamic coefficients of friction shall be determined 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 512.09 512-5 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.
5.Rotational Test (Type III). This test consists of applying a vertical load to the bearing 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 t he 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 compo nents 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.
6.Type I and II bearings incorporating laminated elastomeric pads shall be loaded and tested as follows:
A.Short -Duration Compression Test. The bearing shall be loaded in compression to 1.5 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 ind icating 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 gr eater 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.
B.Long-Duration Compression Test. The bearing shall be loaded in compression to 1.5 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.
c.Certification.
1.Certification for Type I, II, and III Bearings: The manufacturer shall certify that each bearing satisfies the requirements of the plans and these specifications. The manufacturer shall submit: 512.10 512-6 (1) Manufacturer’s certification of the steel, elastomer , PTFE, and other materials used in the construction of the bearings.
2.Details and calibration of the test equipment before testing.
3.Certified test results on the samples of the completed bearing devices, which show they conform to the requirements of this specification.
4.Notification when fabrication is completed and when testing is to be performed.
2.Certification for leveling pads: The supplier shall submit a Certificate of Compliance to the Engineer for acceptance.
512.10 Packaging. 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
512.11 The 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.
512.12 Masonry 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.
512.13 Placement of elastomeric bearing pads or bearing devices on grout pads will not be
permitted unless called for on the plans.
512.14 Non-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 exceed ed. 512.15 512-7 512.15 Type 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.
512.16 The Contractor shall furnish a manufacturer's certification that all components meet the
Contract requirements.
512.17 The 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, place ment, alignment, offsets, protection during welding to steel girders, protection during painting of structure, and removal of banding or retaining clamps. METHOD OF MEASUREMENT
512.18 Bearing devices will be measured by the unit.
BASIS OF PAYMENT
512.19 The 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. 512.19 512-8 THIS PAGE INTENTIONALLY LEFT BLANK 514.01 514-1 SECTION 514 PEDESTRIAN AND BIKEWAY RAILING DESCRIPTION
514.01 This work consists of the construction of the designated type of railing per these
specifications and in conformity with the details, lines and grades shown on the plans or established. MATERIALS
514.02 Pipe Railing . Pipe for railing shall be standard steel, black or galvanized as specified.
The pipe, and galvanizing when specified, shall conform to the requirements of ASTM A53, Types E or S, Grade A, schedule 40 or better, for steel pipe. Threaded fittings shall be made from malleable iron, plain or galvanized, as specified, and slip -on fittings shall be of the type shown on the plans. Steel shapes shall conform to the requirements of Section 509.
514.03 Steel Tube Railing . Steel for this type of railing shall conform to the requirements of
Section 509 and the following:
1.Steel tubes shall conform to the requirements of ASTM A500 Grade B.
2.Steel plates and bars shall conform to the requirement of ASTM A709 Grade 36.
3.Bolts shall conform to the requirements of ASTM A307.
4.Zinc coating shall conform to the requirements of ASTM A123, A153, A385 and A386.
5.Welding shall conform to the American Welding Society Structural Welding Code - Steel, D1.1. Steel for uncoated railing shall conform to the requirements of ASTM A847 for structural steel tubing and ASTM A709 Grade 50W for plates and shapes.
514.04 Timber Railing . Timber for posts and rails shall be pressure treated and shall be per
Section 508. Timber for posts shall be Douglas Fir - Larch, #2 or equivalent. Timber for rails shall be Douglas Fir - Larch #1. Pressure treated timber shall conform to the requirements of the American Wood Preservers Association (AWPA) Standards, Sectio n C1 and C2 (Soil Contact) Either Ammoniacal Copper Arsenate (ACA) or Chromated Copper Arsenate (CCA) preservative conforming to the requirements of Section P5 (Standards for Waterbor ne Preservatives of the AWPA Standards shall be utilized and total absorption shall be 0.4 pounds per cubic foot of timber. Redwood or cedar will not require a preservative treatment. All steel hardware and bolts for timber railing shall be galvanized or zinc coated.
514.05 Combination Railing . Pedestrian or bikeway railing combined with traffic railing shall
conform to the requirements of this section. Traffic Railing and Traffic portion of Combination Railing shall conform to the plans and shall be per Section 606.
Source: Colorado Standard Specifications for Road and Bridge Construction, 2023 Edition. Pages 515–522 of 943.