With the adoption of its eighth edition, the AASHTO LRFD Bridge Design Specifications, Section 5.13, Anchors, is noted as being applicable to headed studs, headed bolts, certain hooked bolts, adhesive anchors, post installed expansion anchors, and post installed undercut anchors. The design specification references American Concrete Institute (ACI) 318-14, ACI 355.2, and ACI 355.4. These documents cover structural design of anchors and qualification testing for mechanical and adhesive anchors. Many design, materials, and construction engineers in state departments of transportation (DOTs) and the transportation industry may not be familiar with these ACI documents or the proper application of these documents and other related documents for design, specification, procurement, or inspection of the various anchor types.
NCHRP Project 20-07/Task 255, “Development of a Test Method to Determine the Ability of Adhesive Anchors to Resist Sustained Tensile Load,” and NCHRP Project 04-37, “Long-Term Performance of Epoxy Adhesive Anchor Systems,” conducted extensive research on adhesive anchor systems.
NCHRP Project 20-07/Task 255 (published as NCHRP Report 639: Adhesive Anchors in Concrete Under Sustained Loading Conditions) provided an initial basis for developing AASHTO standards for sustained loads on adhesive anchors in response to recommendations from the National Transportation Safety Board to the FHWA, AASHTO, and the state DOTs.
NCHRP Project 04-37 (published as NCHRP Report 757: Long-Term Performance of Epoxy Adhesive Anchor Systems) resulted in a draft specification for design and construction of adhesive anchor systems. NCHRP Report 757 includes a draft workflow process chart to aid agencies in the appropriate selection and specification of adhesive anchors. The report also contains appendices with draft AASHTO standards pertaining to the use of adhesive anchors in concrete including:
· Test methods and specifications and material specifications and commentary for inclusion in the AASHTO Standard Specifications for Transportation Materials and Methods of Sampling and Testing,
· Design guidelines,
· Design specifications and commentary for inclusion in the AASHTO LRFD Bridge Design Specifications,
· Quality assurance guidelines, and
· Construction specifications and commentary for inclusion in the AASHTO LRFD Bridge Construction Specifications.
These testing and material specifications made reference to the extensive and well-vetted testing program found within ACI 355.4 with a proposed exception for sustained-load testing. Design provisions for adhesive anchors in tensile loading were developed for AASHTO under given limitations. For cases that fall outside those restrictions, the designer was referred to ACI 318-11. Construction specifications were drafted for incorporation into the existing Section 29 “Embedment Anchors” of the AASHTO LRFD Bridge Construction Specifications, which previously addressed adhesive anchors. Quality assurance guidelines were drafted to orient construction and inspection personnel to adhesive anchor installation.
The objective of this research was to develop and execute a plan for dissemination and successful application of research products presented in NCHRP Reports 639 and 757 through a series of pilot workshops and national webinars.
The project is complete. Webinar resources are available upon request to NCHRP.