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NCHRP Project 12-102 13 C H A P T E R 2 Project Approach The approach to this project was to synthesize previous work into a document that can facilitate the proliferation of ABC technologies, while improving quality and consistency in both design and construction with ABC. A significant amount of excellent applicable research has already been completed by a number of research agencies including NCHRP. This work includes, but is not limited to: ⢠Deck Elements o Deck to deck connections o Deck to girder connections o Grout used in decks o UHPC o Link slabs for jointless deck end connections ⢠Precast columns o Seismic details for column-to-footing connections o Seismic details for column to cap connections (including integral caps) o Alternate column materials and types ⢠Decked Beam Elements o Flange to flange connections ⢠Abutments o Precast integral abutments using corrugated metal pipe voids o GRS/IBS ⢠Bridge Systems o SPMTs o Lateral Sliding The approach to synthesizing these studies and other work is to investigate recommended design and construction specification language for consideration by the AASHTO SCOBS. In some cases, there was conflicting recommendations from different research projects. The project team, working with the project panel objectively reviewed the past research and recommended a course of action. Once this was agreed by the project panel, the appropriate guide specification language was developed. The number of potential ABC technologies available to designers is large. However, for the sake of limiting the number and complexity of design specifications, the technologies can be grouped into similar categories based on element and connection construction. The teamâs vision for controlling the range of design specification modifications required is to use categories of technologies, to the extent possible, to simplify the recommended specifications. The categories that are advanced to the point to be included in the AASHTO specifications are those technologies that most nearly emulate reinforced concrete or structural steel, for example bar coupler, grouted duct, pocket and socket connections. Other categories, for instance the seismic hybrid connections where unbonded post-tensioning is used in conjunction with deformed bars to improve seismic performance, require development of provisions covering a seismic analysis method that is not
NCHRP Project 12-102 14 currently covered by the AASHTO documents. Therefore this category of technologies were not feasible to include in the recommended specifications. The status of any new guide specification in the AASHTO family of specifications is always a concern. In some cases, guide specifications are written, adopted and never fully integrated into the main LRFD bridge design and construction specifications. The approach for this project was to develop a guide specification that can be more easily integrated into the current LRFD specifications at some time in the future when the community is fully comfortable with the ABC technologies. In order to facilitate this, the guide specifications were written to supplement the current specifications, not replace them. The guide specifications could be written as proposed ânew ABC Sectionsâ that could eventually be added to the current AASHTO design and construction specifications. This approach has benefits, but also drawbacks. Having one location for ABC technologies in the AASHTO specifications may facilitate its use, but could result in potential conflicts with the current specifications as they are modified in the future. Another approach could be to supplement the current specifications with ABC articles that are consistent with the current AASHTO specifications. The ABC Guide Specification could be used âhand- in-handâ and supplement the current AASHTO specifications. An advantage of this approach is it facilitates clearly delineating additions, changes or exceptions to the current AASHTO provisions. This approach increases the potential for future incorporation into the current AASHTO specifications since incorporation is essentially an editorial process. The problem with this approach is that the ABC Guide Specification would be disjointed and more difficult to use. Each of these approaches has merits and drawbacks. The first approach was recommended by the research team and accepted by the project panel. The project team worked in conjunction with the project panel to develop a document that has the highest likelihood of use by engineers and adoption by the AASHTO SCOBS.
