304 STRUCTURAL PLATE PIPE AND STRUCTURAL PLATE PIPE ARCH CULVERTS

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304.01 DESCRIPTION
Furnish and install structural plate pipe and structural plate pipe arch culverts.
304.02 MATERIALS
No. 57 Aggregate       901.01
Crusher Run Aggregate CR-6       901.01
Portland Cement Concrete       902.10, Mix No. 2
Curing Compound       902.07.03
Structural Plate for Pipe and Pipe Arches       Section 905
Detectable Utility Marking Tape       921.11
304.03 CONSTRUCTION
304.03.01 Fabrication. Submit working drawings, including erection diagrams and strutting tables, for approval. Include proposed lengths and lifting locations of preassembled sections in the erection diagrams. Upon approval, shop fabricate the plates, including all required holes, to the required dimensions. Ship the plates complete, with proper markings and all necessary connection devices.
Ensure the plate configurations have radii and curvature according to AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications. When bottom plates of circular pipes are specified to the thicker than top and side plates, cover at least 25 percent of the periphery of the circle with the thicker plate. For pipe arches, the thicker plates include corner plates as well as bottom plates. Lay these culverts on a firm bed, true to the specified line and grade.
Along those edges of the plates that will form longitudinal seams in the finished structure, stagger bolt holes in rows 2 in. apart, with one row in the valley and one in the crest of the corrugations unless otherwise specified. Along those edges of the plates that will form circumferential seams in the finished structure, provide a bolt spacing of not more than 12 in. Ensure the diameter of the bolt holes in the longitudinal seams do not exceed the diameter of the bolt by more than 1/8 in.
Shop cut all edges to line and grade, and keep them free from oxide and burrs. Stagger connections so that no more than three plates come together at any one point. Form plates to provide lap joints.
304.03.02 Excavation. When a structural plate pipe or structural plate pipe arch is to be laid on existing ground, on or under fill, construct embankment to a height of at least 18 in., but not more than 3 ft above the proposed top of the pipe. Then excavate the trench to a width of twice the outside diameter of the pipe or the outside diameter plus 18 in. on each side, whichever is less. Handle excavated material as specified in 402.03.01.
304.03.03 Foundation Preparation. Provide bedding as specified in 303.03.01(b). Set rails and then screed the foundation to the exact shape of the bottom plates immediately prior to erection.
304.03.04 Erection. When strutting is required, ensure it is uniform from end to end. Keep struts in place until backfilling is complete. Tighten nuts and bolts to between 100 and 200 ft·lb of torque.
When washers are specified, place them under the turned element. Distribute bolts over the section being assembled. Align holes by shifting the plates. For bottom plates, place the nuts inside the structure. Do not draw the nuts tight until the section is assembled. Before placing backfill, tighten all nuts and test to ensure it meets specified torque requirements.
304.03.05 Backfill
The presence of large lumps, clods, frozen material, or rocks in the backfill are unacceptable.
Place backfill material along the side of the pipe for the full width of the trench in layers not exceeding an uncompacted depth of 6 in. Compact each layer simultaneously on both sides of the pipe using an approved mechanical tamper and as specified in Section 210. Compact the backfill thoroughly under the haunches of the pipe.
Continue this method of filling and compacting until the compacted backfill material is at least 18 in. above the top of the structure. For structures without headwalls, begin placing backfill at the center of the structure. If the structure includes headwalls or spandrel walls, begin placing backfill at one wall and work toward the opposite side. When batteries or multi-barrel installations are specified, elevate backfill between cells equally on each side of each pipe or pipe arch.
Protect pipes from damage due to construction activities. Do not drive equipment within 4 ft when measured horizontally from the pipe nor drive equipment over the pipe until at least 24 in. of compacted fill is over the pipe.
Place detectable utility marking tape in the trench immediately above the structural backfill. Demark the tape as to its purpose, i.e., "STORM DRAIN".
Inspection and Acceptance. Within 30 days following installation, and in the presence of the Engineer, visually inspect all pipe culverts. Any cracks, differential movement, efflorescence, rust stains, spalls, exposed reinforcement, slabbing, dents, buckling, holes, damaged coating, obstructions, improperly engaged joints, improper gasket placement, excessive joint gaps, misaligned joints, excessive deflection, or undue horizontal or vertical misalignment will be cause for repair or replacement. Video inspect pipe which cannot be physically accessed for inspection. Ensure that thermoplastic pipe deflection does not exceed 5 percent
304.03.06 Concrete Invert. When specified, pave the pipe or arch pipe invert using Concrete Mix No. 2. Place and cure the concrete as specified in Section 420.
304.03.07 End Treatment. Shop fabricate the ends of structural plate pipes and structural plate pipe arches on a bevel to fit and be flush with the slope and alignment of the surface through which they protrude, except that where an end wall or masonry slope protection is specified, shop fabricate the ends to fit that construction. Ensure the ends of all structural plate pipes and structural plate pipe arches that require an end treatment (end wall or slope protection) contain hook bolts for anchorage into the concrete.
Furnish and install headwalls for structural plate pipes and pipe arches as specified in Section 305. Unless otherwise specified, construct these structures parallel to the proposed outer edge of the roadway shoulder.
304.04 MEASUREMENT AND PAYMENT
The payment will be full compensation for all applicable fabrication, assembly, excavation, sheeting, shoring, strutting, dewatering, hauling, invert paving, storing, rehandling of material, removal and disposal of excess and unsuitable material, tamped fill, foundation preparation, backfill, bedding, compaction and for all material, labor, equipment, tools, and incidentals necessary to complete the work.
304.04.01 Structural Plate Pipe and Structural Plate Pipe Arch Culverts will be measured and paid for at the Contract unit price per linear foot. The basis of measurement and payment will be as follows: measure the top length and the bottom length and average. The average length will be the pay length for each pipe in the structure. For multiple pipes, the length will be totaled to obtain the total pay length.
304.04.02 Excavation required below the planned elevation will be measured and paid for as specified in 301.04.
304.04.03 Selected backfill will be measured and paid for as specified in 302.04.
304.04.04 Headwalls will be measured and paid for as specified in 305.04.