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. 716 - POST-TENSIONING (Haunched Slab Bridges)
700-86 b. Qualification of the Post-Tensioning System Manufacturer (S ystem Manufacturer). Select a
system manufacturer with experience (in the United States) in post-tensioning concrete haunched slab or concrete box girder bridges that were designed and constructed according to AASHTO LRFD Construction specifications. Before materials are provided and any post-tensioning operations begin, the system manufacturer must be approved by the State Bridge Office (SBO). If the system manufacturer has not been previously approved, provide the SBO with the necessary information to consid er their qualifications. Provide the SBO with: Certificate of compliance with OSHA and other applicable industry standards for safety; In-house capability to design end anchorage assemblies, local zone and general zone design according to AASHTO specifications, sealed by a Professi onal Engineer licensed in the state of Kansas; Certificate of complian ce with AASHTO LRFD Construction specifications for testing of the end anchorage assemblies, performed by an independent testing laboratory, and sealed by a Professional Engineer licensed in the state of Kansas; In-house QC/QA implementation for manufacturing, assembling, storage, delivery, installation, stressing and grouting supervision; Names, qualification and experience of the field personnel to be assigned to assist the Contractor to supervise installation, stressing and grouting; The technician that supervises all grouting operations must be a valid American Segmental Bridge Institute (ASBI) Certified Grouting T echnician. Provide the SBO with verification of the technician’s ASBI Certification; Proof of continuous post-tensioning operations. Firms with less than 10 years of experience may be approved if sufficient related proj ect experience is demonstrated, bu t in any event a minimum of 7 years of experience is required; List of post-tensioned haunched slab bridges completed within the past 5 years including owner and identifying bridge information; and List any unfavorable claims within the last 10 years. The SBO will approve (or disappro ve) the system manufacturer within 5 working days of receiving the required information. A system manufacturer may submit the necessary inform ation to be considered for qualification at any time. The SBO will maintain a list of approved system manufacturers. Any change in a system manufacturer’s system or evidence of poor performa nce will require re-approval.
c.Shop Drawings. Submit shop drawings from the system manuf acturer to the State Bridge Office (SBO) for all work related to post-tensioning according to SECTION 105 . The shop drawings must be sealed by a Professional Engineer licensed in the state of Kansas. The shop drawings must be approved by the SBO before beginning fabrication. As a minimum, include in the shop drawings: A Post-Tensioning System that meets the re quirements in the Contract Documents; Tendon geometry and layouts; Distance from the bottom of slab to bottom of duct; Duct support detail and spacing accord ing to the Contract Documents; The locations of grout ports and grout vents; Connection details such as duct coupler, anchorage to duct and grout ports/ vents to duct; Anchorage local-zone reinforcement; Permanent grout cap details, concrete reces s, pour backs and temporary protection; Jacking forces and initial forces; Anchor set; Stressing operation and equipment data; All material specifications (e.g. strands, ducts and grout); Grouting operation and equipment data; Safety procedures; Elongation calculations and tolerances; All required computations;
Source: Kansas Standard Specifications for State Road and Bridge Construction, 2015 Edition. Pages 416–417 of 978.