SECTION 811 - BRONZE OR COPPER-ALLOY BEARING AND EXPANSION PLATES
811.01 Description. This work consists of furnishing and installing metal plates of the
kind and type specified and in the manner shown on the plans.
811.01.1 Disc Bearing. The disc bearing devices shall be adequate for the design loads,
movements and other criteria shown on the plans or specified herein, and shall be tested at the appropriate level. This work shall consist of furnishing Multi-Rotational, Hi gh Load Disc Bearings and installing Disc Bearing Devices at the loca tions shown on the plans in accordance with these specifications and the current AASHTO LRFD Bridge Design Specifications, and the current AASHTO LRFD Bridge Construction Specifications. Disc bearing devices shall include bearings, distribution plates, distribution pads, and connection hardware. The disc bearings shall consist of polyether urethane structural element (disc) confined by upper and lower steel bearing plates. The bearing shall be equipped with a shear restriction mechanism to prevent movement of the disc. The bearings shall adequately provide for the thermal expansion and contraction, rotation, camber changes, and creep and shrinkage of structural members, where applicable. For expansion bearings, the upper steel beari ng plate shall have a Polytetrafluorethylene (PTFE) sheet recessed and bonded into the top half of the plate to accommodate the horizontal movement of the s uperstructure. The PTFE surface of the upper steel bearing plate shall support an upper steel plate fitted with a continuously welded, highly polished stainless steel face. For unidi rectional expansion bearings, the upper steel plate shall be fitted with guide bars or a keyway system to restrict the lateral movement of the structure. The guide bars and their opposing guided surfaces shall be faced with opposing strips of PTFE/stainless steel. Guiding off of the fixe d base or any extension of it will not be permitted. Disc bearings shall be designed and constructed in accordance with Section 14 of the current AASHTO LRFD Bridge Design Specifications and Section 18 of the current AASHTO LRFD Bridge Construction Specifications. The supplier of the disc bearing devices sha ll show previous history in the design and fabrication of disc bearings. Documentation showing a minimum of five bridge installations and five years of experience in plan production within the last five years shall be provided to the Director of Structures, State Bridge Engineer. Sliding bearings shall be stiff in shear, i.e. negligible shear displacements shall occur within the load-bearing element.
811.01.2 Shop Drawings. The following shall be shown on the working drawings:
• The total quantity of each kind of bearing required (fixed, guided expansion, or nonguided expansion), grouped first according to type (load range) and then by actual design capacity. • The plan view and section elevation view showing all relative dimensions of each type of bearing, along with a placement plan to show location of each bearing. • The maximum design coefficient of friction as noted on the Contract Drawings. • The type of materials to be used for all bearing elements. • If applicable, any welding pr ocess used in the bearing manufacturer that does not conform to the approved processes of th e American Welding Society (AWS) shall be clearly described and detailed. • Vertical and horizontal load, rotation, and movement capacity. • Coating requirements. • Complete design calculations verifying conformance with these specifications. • Anchorage details. • If applicable, bearing preset details. • The location of the fabrication plant. • The Manufacturer’s name and representative who will be responsible for coordinating production, inspection, sampling, and testing. • Bearing-to-girder bolt template details.
811.02 Materials. Bearing and expansion plates, of the type and kind specified shall meet
the requirements of Subsections 716.06 or 716.07 or 716.08, as applicable.
811.02.1 Bronze Plates. Plates shall be cast according to details shown on the plans.
Sliding surfaces shall be planed parallel to the movement of the spans and polished unless detailed otherwise.
811.02.2 Copper-Alloy Plates. Plates shall be furnishe d according to details shown on
the plans. Finishing of the rolled plates will not be required provided they have a plane, true, and smooth surface.
811.02.3 Disc Bearing. All materials for disc bearing devices shall be new and unused
with no reclaiming material incorporated in the finished bearing. The finished properties of the polyether urethane shall conform to the requirements of the current AASHTO LRFD Bridge Construction Specifications, Section 18. All steel, except stainless steel component s of the bearing, shall conform to the requirements of the type of steel designated on the contract drawings. Coating of non- stainless steel components shall be in accordance with the structural steel construction notes per the contract drawings. Stainless steel shall conform to the requirements of ASTM A167 Type 304, ASTM A240 Type 304. Higher grades of stainless are permissible. Stainless steel in contact with PTFE Sheet shall be polished to a No. 8 bright mirror finish, less than 5 micro-inches root mean square. The minimum thickness of the stainless steel shall be 16 gauge. PTFE shall be manufactured from pure virgin (not reprocessed) unfilled PTFE resin. The PTFE sheet shall be bonded and recessed into the upper steel bearin g plate. The PTFE sheet shall have a minimum thickness of 1/8 of an inch and be recessed one-half of its thickness into its steel substrate. The PTFE sheet shall be acid-etched on the bonded side and polished on the side facing the stainless steel to insure a low coefficient of friction. The PTFE properties shall conform to the re quirements of the current AASHTO LRFD Bridge Construction Specifications, Section 18.
811.02.3 1--Fabrication. The Contractor shall provide the Director of Structures, State
Bridge Engine er with written notificatio n sixty (60) days prior to the start of bearing fabrication. This no tification shall include all of th e information shown on the shop drawings. Fabrication and testing shall not commence until a MDOT representative is on site. Final shipment shall not be made until an approved final inspection is made and the material is appropriately stamped by a MDOT representative. All non-weathering steel surfaces exposed to the atmosphere, except stainless steel surfaces and metal surfaces to be welded, shall be shop painted in accordance with the contract plans. Prior to painting, the exposed steel surfaces shall be cleaned in accordance with the recommendations of the coating's manufacturer. No painting will be done to these surfaces prior to the completion of welding. All weathering steel surfaces exposed to the atmosphere shall be cleaned in accordance with the contract plans. The fabricator shall provide a bearing-to-girder bolt template with hardened bushings to the steel girder fabricator and contractor to ensure proper fit-up. Details of these templates shall be included in the shop drawing submittal. Stainless steel sheet shall be attached to its steel substrate with a continuous seal weld. All welding shall conform to, and all welders shall be qualified in accordance with the requirements of the American Welding Society (AWS). The finish of the mold used to produce the rotational el ement shall conform to good machine shop practice. Each bearing shall have a project identification number and lot number marked on a side that will be visible after erection. Gross bearing dimensions shall have a tolerance of ±1/8 of an inch. Overall thickness tolerance shall be ±1/8 of an inch. All bearing surfaces of steel plates shall be finished flat within 0.01 inch. Every bearing shall have the Project Identification Number, Lot Number, and individual bearing number indelibly marked with ink on a side that will be visible after erection. After assembly, including sole plates and masonry plates, bearing components shall be held together with steel strapping or other mean s, to prevent disassembly until the time of installation. Packaging shall be adequate to prevent damage from impact as well as from dust and moisture contamination during shipping and storage.
811.02.3 2--Sampling. Requirements for lo t size shall be in accordance with the
requirements of the current AASHTO LRFD Bridge Construction Specifications, Section 18.3.4.
811.02.3 3--Testing. The bearing devices to be tested shall be selected by the Director of
Structures, State Bridge Engineer at random. The bearing device will be visually examined both during and after the test. Any visual defects shall be cause of rejection.
811.02.3 4--Coefficient of Friction. Sliding coefficient of friction tests will be performed
by the manufacturer of one e xpansion bearing device from each lot. A lot will be the quantity as defined by the Director of Structures, State Bridge Engineer with a maximum of 25 bearings per lot. The coefficient of fri ction will be measured at the bearing design capacity on the 5th, 50th, and 100th cycle at a speed of one inch/minute. The sliding coefficient of friction shall be cal culated as the horizont al load required to maintain continuous sliding at a given speed divided by the bearing's design capacity vertical load. The ve rtical load shall have been app lied continuously for a minimum of one-hour prior to testing. The measured sliding coefficient of friction shall not exceed 0.03.
811.02.3 5--Rotation. Rotation tests will be performed by the manufacturer on one
bearing device from each lot. The polyether urethane element shall be capable of maintaining its initial uniform contact with th e steel bearing plates through a rotation of 1.15 degrees under a comprehensive load equal to 150% of the design capacity of the bearing device. Any observed separation between the edge of the rotational elements and the bearing plates shall be cause for rejection.
811.03 Construction Requirements. Bearing plates shall be accurately set in correct
position as shown on the plans a nd shall have a uniform bearing over the whole area. Provision shall be made to keep the plates in correct position as the concrete is being placed.
811.03.1 Disc Bearing. Disc bearing devices delivered to the bridge site shall be stored
under cover on a platform above the ground surf ace. Disc bearings shall be protected at all times from injury. When placed, bearings shall be dry, cl ean, and free from dirt, oil, grease, or other foreign substances. Disc bearing devices shall not be disassembled unless otherwise permitted by the Director of Structures, State Bridge Engineer or manufacturer. Disc bearing devices shall be installed in accordance with the alignment plan and installation scheme as shown in the contract plans. Upon final installation of the bearings, the Director of Structures, St ate Bridge Engineer, in the presence of the manufacturer's representative, shall inspect the bearing com ponents to assure that they are level and parallel to within 0.0311 inch per one foot. Any deviations in excess of the allowed tolerances shall be corrected.
811.03.1 1--Certificate of Compliance. In addition to records of test results, the
Contractor's disc bearing supplier shall subm it Certificates of Compliance for the disc bearings indicating the material s, fabrication, testing, and installation are as specified herein.
811.04 Method of Measurement. Accepted bearing and expansion plates of the type
specified will be measured by the pound. Unless otherwise provided, the measurements will be the Inspector's certified shop scale weight of plates placed in the structure. If specified in the contract, measurement will be computed weights, obtained by methods shown on the plans. Disc bearing device will be measured per each. Lubricants will not be measured for separate payment.
811.05 Basis of Payment. Bearing and expansion plates, measured as prescribed above,
will be paid for at the contract unit price per pound which price shall be full compensation for completing the work. Disc bearing device, measured as prescribed above, will be paid for at the contract unit price per each; which price shall be full compensation for completing the work. Payment will be made under: 811-A: Bronze Plates - per pound 811-B: Copper-Alloy Plates - per pound 811-C: Self-Lubricating Type Plates - per pound 811-D: Disc Bearing Device - per each
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