715 - PRESTRESSED CONCRETE MEMBERS
700-83 g. Piling . Do not place piling before the specified 28 day strength has been attained. See SECTION 704
for placing piling. 715.4 MEASUREMENT AND PAYMENT The Engineer will measure the length of pr estressed concrete beams by the linear foot. The Engineer will measure the area of prestressed concrete panels by the square foot. Payment for "Prestressed Concrete Beams" and "Prestre ssed Concrete Panels" at the contract unit prices is full compensation for the specified work. 716 - POST-TENSIONING (Haunched Slab Bridges)
700-84 Section 716
POST-TENSIONING (Haunched Slab Bridges) 716.1 DESCRIPTION Provide and install all post-tensioning system components as shown in the Contract Documents to construct a post-tensioned haunched slab bridge. B I D I T E M U N I T S Post-Tensioning for Slab Bridge Pound 716.2 MATERIALS Comply with all material requirements in the Contract Documents in addition to subsection 716.2 .
a.Prestressing Steel. Provide uncoated, 7 wire, Grade 270 (1860), low-relaxation strands for prestressed concrete complying with AASHTO M 203 (ASTM A 416). Provide strands with a minimum ultimate strength of 270 ksi. Fabricate the tendons with sufficient length be yond the anchor bearing plates to allow for stressing and anchorage device installation. The Engineer will accept the strands based on subsection 716.2h . Protect all strands against physical damage and rust or other results of corrosion at all times, from manufacture to grouting or encasing in concrete. Reject strands that have sustained physical damage at any time. Use wire that is bright and uniformly colored, having no foreign matt er or surface pitting. Package the strands in containers or forms to protect against damage and corrosion during shipping and storage. Provide an inhibitor carrier type packagi ng material complying with the provisions of Federal Specifications MIL-P-3420F-87. Place a ru st preventative corrosion inhibitor or other corrosion i nhibiting material in the package, incorporate a corrosion inhibitor carrier type packaging mate rial or apply directly to the steel when approved by the Engineer. Use a corrosion inhibitor that has no deleterious effect on the strands or grout or bond strength of strands to grout. Clearly mark the shipping package or forms with a statement that the package contains high-strength prestressing steel strands, the care to be used in handling, the type, kind and amount of corrosion inhibitor used, including the date when placed, safety orders and instructions for use.
b.Post-Tensioning System. Use an approved post-tensioning system of proper size and type to construct tendons as shown on the Contract Do cuments. Do not substitute compone nts of the approved post-tensioning system. Do not use tendon couplers. Use only post-tensioning systems that utilize tendons fully encapsulated in anchorages, ducts and fully filled with approved grout. Systems which transfer prestress force by bonding the prestress steel strand directly to concrete are prohibited.
c.Post-Tensioning Anchorage. Provide anchorages meeting or exceeding: Article 5.10.9 of the AASHTO LRFD Bridge Design Specifications, latest edition and interims; and Article 10.3.2 of the AASHTO LRFD Bridge Cons truction Specifications, latest edition and interims. The Post-Tension Manufacturer shall supply the special reinfo rcement, such as spir als or grids, for the longitudinal and transverse tendons. Su ch reinforcement is required in the concrete end-zones of anchors. All anchorage devices shall develop 96% of the actual ultimate strength of the pr estressing steel, when tested in an unbonded state, without exceeding anticipated set. The design of the end anchorages and end-zone reinforcing is the sole responsibility of the Post-Tension Manufacturer. Galvanize the body of the anchor ages according to ASTM 123. Ot her components of the anchorage including wedges, wedge plate and local zone reinforcement are not required to be galvanized. Construct the bearing surface and wedge plate from ferrous metal. Equip all anchorages with a perman ent fiber reinforced plastic grout cap that encloses the whol e wedge plate. Vent grout caps and bolt to the anchorage. 716 - POST-TENSIONING (Haunched Slab Bridges)
700-85 d. Post-Tensioning Ducts. Provide semi-rigid, mortar-tight plastic ducts, including connection joints,
capable of withstanding concrete pres sures without deforming or permitting the intrusion of cement paste during the placement of concrete. Use all duct material complying w ith AASHTO and the Post Tensioning Institute (PTI) for bonded tendons. Do not use ducts manufactured from recycled materials. Provide ducts for multi-strand tendons with an inside area a minimum of 2 ½ tim es the net area of the tend ons. Provide ducts that do not cause electrolytic action or deterioration of the concrete or the duct. Provide ducts that will be nd without crimping or flattening, and with sufficient strength to maintain their correct alignment during the placement of the concrete. Provide corrugated plastic ducts for both the longitudinal and transv erse ducts. Pr ovide the proper fasteners for the ducts. Use an approved plastic on a ll parts of the clamps. Construct the ducts from either polyethylene or polypropylen e. The minimum acceptable radius of curv ature shall be established by the duct supplier according to standard testing met hods. The material thickness of ducts is 0.08 inches ± 0.01 inch. Fabricate polyethylene ducts from resins complying with ASTM D 3350 with a cell classification of 345464A. Fabricate polypropylene ducts from resins complying with ASTM D 4101 with a cell classification of PP0340B44544 or PP0340B65884.
e.Inlets and Outlets. Use inlets for injecting grout into the duct. Use outlets to allow the escape of air, water, bleed water and grout. Provide inlets and outlets at locations shown in the Cont ract Documents. Provide ¾ inches minimum internal diameter plastic pipe for inlets and outlets made of ASTM A 240 Type 316 stainless steel, nylon or polyolefin materials. If nylon inlets/outlets are used, a cell class of S- PA0141 (weather resistant) is required. Only use polyolefin products which contain antioxidant(s) with a minimum Oxidation Induction Time (OIT) according to ASTM D 3895 a minimum of 20 minutes. Test the remolded finished polyolefin material for stress crack resistance using ASTM F 2136 at an applied stress of 350 psi, resulting in a minimum failure time of 3 hours. Provide pipes that are mortar-tight. Provide plas tic components that do not react with concrete or enhance corrosion of the strands, and are free of water soluble chlorides. Provide the proper plastic connectors and fasteners to attach the pipes to the ducts. Provide positive mechanical shut-off valves for all inlets for a minimum pr essure rating of 100 psi. Provide cap, valves or other devices capable of withstanding the pumping pressures for all outlets. No tape is allowed at any connection.
f.End Anchorages Permanent Grout Cap. Use permanent grout caps made from fiber reinforced polymer or ASTM A 240 Type 316L stainless steel. Use nylon, Acrylonitrite Butadiene Styrene (ABS) or polyester resins in the fiber reinforced polymer. For products made from nylon, a cell class of S-PA0141 (weather resistance) is required. Seal the cap with “O” ring seals or precision fitted flat gaskets placed against the bearing plate. Equip the grout cap with a top grout vent. Use grout caps rated for a minimum pressure of 100 psi. Use ASTM A 240 type 316L stainless steel bolts to secure the cap to the anchorage. When stainless steel grout caps are supplied, provide certified test reports documentin g the chemical analysis of the steel.
g.Grout. Provide grout that complies with DIVISION 1700 . Use only one supplier for any single structure.
h.Testing Requirements. Provide all materials for testing. Co nduct all tests according to the applicable AASHTO and ASTM specifications. (1) Testing by the Engineer. Provide 3 samples of prestressing strand of sufficient length to provide 5 feet measured between fittings for each size st rand from each heat, reel or coil. Provide the Engineer with a certification stating the manufacturer’s minimum guaranteed ultimate strength of the strand for each size supplied from each lot.
2.Testing by the Contractor. Provide the Engin eer with a certificate of te st performance from the manufacturer of the strand for each size from each heat, reel or coil to determine the modul us of elasticity prior to stressing the initial tendon in the bridge. Re-evaluate the theoretical elongations shown on the post-tensioning working drawings using the results of the tests and correct as required. Submit revisions of the theoretical elongations to the Engineer for approval. 716.3 CONSTRUCTION REQUIREMENTS
a.Post-Tensioning Designs. Use 0.6 inch diameter strands longitudinal and transverse post-tensioning systems as shown in the Contract Documents.
Source: Kansas Standard Specifications for State Road and Bridge Construction, 2015 Edition. Pages 414–416 of 978.