Hennepin County

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PROJECT QUESTION: What are the finish and flatness tolerances required for the cap beam and deck slab plates? This will also impact what lengths can be supplied, if machined or polished surfaces are required on the deck slab plate surfaces in contact with the PTFE.

Question: What are the finish and flatness tolerances required for the cap beam and deck slab plates? This will also impact what lengths can be supplied, if machined or polished surfaces are required on the deck slab plate surfaces in contact with the PTFE.

Response: SB-14.1.B.5 states to provide stainless steel plates per MnDOT 3312. MnDOT 3312 calls for stainless steel plates to meet requirements of ASTM A240 for Type 302 or 304. ASTM S 240 references ASTM A 480 which contains plate tolerance requirements. The plans contain tolerances on precast elements the plates are embedded into and the plates are flush with precast element surfaces. Plan sheet B5, Construction Note 6.A.IX notes to ensure beam seat areas are flat and true. The minimum of the tolerance requirements provided should be met. See answers to other questions for the finish requirements. The plates embedded in the deck panels are to have a No. 8 polished surface. SB-14.1.B.5 states - Sliding surfaces in contact with PTFE shall be polished to a No. 8, bright mirror finish. Surfaces bonded to PTFE shall be etched. - The deck panel plates are to be polished to a No. 8 finish and the plates in the cap beams where PTFE is adhered is etched.