THE CONCRETE BRIDGE MAGAZINE

Summer 2019

ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.

Issue link: http://www.aspiremagazinebyengineers.com/i/1134112

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C O N C R E T E B R I D G E T E C H N O L O G Y 32 | ASPIRE Summer 2019 by Gregory Hunsicker, OnPoint Engineering and Technology LLC, and Miroslav Vejvoda, Post-Tensioning Institute The Right Materials and the Right Quality: Important Updates to Post-Tensioning #SJEHF4QFDJƋDBUJPOT.BOE. For decades, long-span concrete bridges have relied on post-tensioning (PT) as the primar y reinforcement because it enables the designer to achieve long spans and attractive, slender shapes. Two specifications represent the industry standards for PT and should be used in design and construction. The Post- Tensioning Institute (PTI) is proud to announce that the latest updates of these two specifications will be published in summer 2019: • PTI/ASBI M50.3-19, Specification for Multistrand and Grouted Post- Tensioning • PTI M55.1-19, Specification for Grouting of Post-Tensioned Structures These two specifications include the newest state-of-the-art provisions and uphold the fundamental principle of construction that must be satisfied to achieve the desired performance and longevity: We must have the right materials and the right quality of work. The specifications include mandatory minim u m r e q u i r e m e n t s r e ga r din g materials, testing, installation, tensioning, grou ting, finishing, and inspec tion. Commentaries provide guidance, explaining the background and showing options on how to meet the mandatory requirements. It is important to emphasize that these specifications are prepared following American National Standards Institute requirements for a full consensus process, including public review at the end of the development process. The PTI committees producing these documents represent a wide range of interested parties, including owners (Federal Highway Administration and state departments of transportation), designers, researchers, contractors, and PT system suppliers. All provisions or provision changes are balloted, and all negative votes are resolved by the committee consensus, as required by the PTI Technical Committee Manual. A major advantage of a s tandard specification is that it establishes best- practice procedures and reduces or eliminates unnecessary differences in requirements of specifications developed b y va rio u s d e s ig n er s a n d ow n er s . Consistency and standardization to the new specifications help ensure that the focus in projects remains on properly execu ting the work using indus tr y- established best practices. It has been noted that some specifications are silent on important aspects of the PT system. Use of the M50 and M55 specifications helps project stakeholders address this lack of information. In 2014 the Texas Depar tment of Transportation (TxDOT) incorporated both standards, with a few minor modifications, into the TxDOT Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges. TxDOT's efforts serve as a good example of how the specifications can be adapted if the owner and designer think that some modifications are necessary for a locality or project. PTI/ASBI M50.3-19 PTI first published the M50 specification in 2012, and PTI/ASBI M50.3-19 is the second edition. This specification was developed in cooperation with the American Segmental Bridge Institute (ASBI), which provided expertise from their membership to the the committee. The title of the specification was modified for the second edition to better reflect the scope. It is applicable to all multistrand and grouted PT for any application and in any environment. It addresses all multistrand and grouted PT issues except for the grout materials, testing, and grouting operation. Those latter items are covered in the companion specification, PTI M55, which specifically addresses grouting. The M50 specification includes tendon protection levels (PLs), which simplify and standardize the selection of the PT systems and procedures by allowing the owner and designer to determine the appropriate degree of corrosion protection necessary for the PT system based on the environment of the structure, the design life, and the importance factor. The PLs provide a specific set of requirements to address the durability expectations for each level. PTI/ASBI M50.3-19 allows for innovation by stating the testing requirements for prequalification of existing and new systems. These standard requirements will simplify the PT system prequalification. All the testing must be witnessed by a certified agency, the requirements of which are identified in the specification. The PTI PT System Prequalification Testing and Certification Program (PTI CRT-70) will be based on the M50 requirements and is expected to be launched in early 2020. The updated specification also spells out requirements for installation items, such Wd/^/DϱϬϯϭ 6SHFLILFDWLRQIRU0XOWLVWUDQG DQG*URXWHG3RVW7HQVLRQLQJ All Figures: Post-Tensioning Institute.

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