3741Elastomeric Bearing Pads

3741.1SCOPE

Provide elastomeric bearing pads for use in Bridges and other Structures.

3741.2REQUIREMENTS

A General The basis of design for bearing pads is in conformance with Method A of the AASHTO LRFD Bridge Design Specifications. Before the start of Work, the supplier will be qualified on Approved Suppliers for Fabricated Structural Metals Products list as maintained by the Structural Metals Engineer on the Bridge Office website, or become qualified. To become qualified, the supplier is to submit a MnDOT Quality Manual

QM is to meet the requirements of the MnDOT Supplier Qualification Standard which will be the basis for acceptance by the Engineer. Upon acceptance of the QM, a supplier is qualified and will be listed on the Approved Suppliers for Fabricated Structural Metals Products. In addition to routine inspections, the

Engineer will audit suppliers with approved QMs on a biannual or annual basis or as otherwise directed by the Engineer to ensure the implementation of the QM. The Department will invoke its Corrective Action Process if the routine inspections or audits indicate non-conformance. Corrective actions deemed appropriate by the Engineer, are effective immediately and apply to any Work remaining on a current Project and future Projects. If the Engineer determines that Work does not comply with the QM or that fabrication does not follow approved fabrication procedures, the Engineer will deem the Materials as non-conforming in accordance with 1503, ”Conformity with Contract Documents,” and 1512, “Unacceptable and Unauthorized Work.” If the Engineer finds non-conforming Work, direct the supplier to immediately correct the procedure and submit a written non-conformance report, containing data required by the Engineer to ensure compliance with the QM, Specifications, and drawings. Perform additional testing as required by the Engineer at no additional cost to the Department. For repeat offences or negligence, the Department will require corrective action of hiring a third-party Quality Control Inspector at no additional cost to the Department. The Contractor may obtain a copy of the Department’s Corrective Action Process from the Engineer. Provide bearing pads no greater than 1/2 inch thick, fabricated of all elastomer. Plain elastomer pads may be cut from larger sheets cast to the thickness shown on the P lans. Avoid heating or damaging the Material when cutting. Ensure the cutting produces smooth edges at least meeting the requirements of ANSI 250 finish. Provide bearings of laminated construction when pads are greater than 1/2 inch thick. Refer to AASHTO M 251 Standard Specification for Plain and Laminated Elastomeric Bridge Bearings , for tolerances, dimensions, and configurations, except provide elastomer to a thickness of 1/4 inch within a range from +1/8 inch to –1/16 inch to cover the top and bottom steel plates. Provide laminated pads meeting the following requirements or characteristics:

together

bottom surfaces of the pad

flexible paint of contrasting color Do not expose the finished laminated pad to temperatures greater than 400 °F. Cover the edges of metal reinforcement with 1/4 inch of elastomer. B Physical Properties Substitute the requirements of sections 4.1 and 4.2 of AASHTO M 251; comply with B.1 & B.2 in this Specification. B.1 Elastomer Use elastomer compound containing only virgin crystallization resistant polychloroprene

Material with no reclaimed Material incorporated in the finished bearing. Provide elastomer for bearing pads meeting the requirements of AASHTO M 251 with durometer hardness of 60 on the Shore “A” scale. Provide elastomer compounds classified as Low-Temperature Zone D, Grade 4 or 5 meeting the requirements of AASHTO LRFD Bridge Design Specifications, Table 14.7.5.2-1, “Low-Temperature Zones and Minimum Grades of Elastomer.”

Utilize cotton duck bearing pads (CDP) where Bridge Details Part 1 B310 and B354 are included in the Plans or when Bridge Details Part 1 B311 or B355 utilize plain (non-steel reinforced) elastomeric bearing pads. Test and manufacture CDP in accordance with Military Specification MIL-C-882E. For CDP, waive additional sampling and testing requirements listed in this Specification. B.2 Properties Test and accept sampled bearings in accordance with the following: Table 3741.2-1 Elastomeric Bearing Requirements

Natural Polyisoprene (Natural Rubber) Polychloroprene (Neoprene) Durometer 60±5 60±5 Physical properties Hardness (ASTM D2240#) 60±5 60±5 Tensile strength (ASTM D412§) 2250 psi 2250 psi Ultimate elongation (ASTM D412§), minimum 400 percent 400 percent Heat resistance (ASTM D573*) Temperature / Aging Time 158°F/168 hours 212°F/70 hours Hardness, maximum Shore “A” points change +10 +15 Tensile strength, maximum percent change –25 –15 Ultimate elongation, maximum percent change –25 –40 Compression set (ASTM D395ǁ, Method B) 22 hours at 158°F, maximum percent 25 NA 22 hours at 212°F, maximum percent NA 35 Low Temperature Test (ASTM D746†, Procedure B) Brittleness at –54.4°F No Failure No Failure Laminated Pad Adhesion Test (ASTM D429‡, Method B) Bond Strength (Peel Test) 40 psi 40 psi * ASTM D573, Standard Test Method for Rubber-Deterioration in an Air Oven ǁ ASTM D395, Standard Test Methods for Rubber Property-Compression Set † ASTM D746, Standard Test Method for Brittleness Temperature of Plastics and Elastomers by Impact ‡ ASTM D429, Standard Test Methods for Rubber Property-Adhesion to Ridged Substrates # ASTM 2240, Standard Test Method for Rubber Property-Durometer Hardness § ASTM D412, Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomers-Tension

Compressive Strain of Laminated Bearings Test each sampled laminated pad for compressive strain. The compressive strain in any Layer of a laminated pad shall not exceed 9 percent at 1250 pounds per square inch average unit pressure for the full size laminated pad. Proof Load Testing Proof load each bearing pad per AASHTO M 251 Standard Specification for Plain and Laminated Elastomeric Bridge Bearings, Section 8.8.2. Use a compressive load of 1800 pounds per square inch for laminated pads and 1,200 pounds per square inch for plain elastomeric pads. Reject bearing pads if bulging patterns imply laminate placement does not satisfy design criteria

and manufacturing tolerances, or if bulging suggests inadequate laminate bond. Also reject bearing pads if there are 3 separate surface cracks greater than 1/16 inches wide by 1/16 inches deep. B.3 Metal Reinforcement Provide mild steel plates at least 1/8 inch thick for use as metal reinforcement. C Certification Submit to the Engineer a manufacturer's Certificate of Compliance.

3741.3SAMPLING AND TESTING

A Manufacturer Sampling and Testing Sample and test in accordance with AASHTO M 251, Section 8 except as modified in this Specification. Destructive test finished laminated and plain bearing pads at a rate of 2 full size bearing pads per lot (produced from the same raw Material utilizing the same processes and procedures). A lot shall not exceed 100 pads and is not limited to finished sizes or thickness . Destructive testing is defined as any test that renders the product not usable for its intended purpose. Provide bearing pad test data and certification prior to shipping . Test results of samples must verify compliance to product Specifications. Any bearing tested that does not meet the Specifications will result in the rejection of the entire lot. When applicable, the supplier shall retain a copy of the passing test results for one year and supply the document with subsequent jobs. Concrete Curing Materials