Mechanically Spliced Full Length Anchor Bolts—Bringing It All Together

In the age of rebuilding transmission, outages are shorter and more difficult to obtain, causing the construction of new transmission lines to become more difficult. Therefore, de-energizing transmission facilities to accommodate construction tasks requires careful planning, often affecting the line design. American Electric Power (AEP) and DiGioia Gray, Inc. co-developed a methodology to increase construction productivity of drilled shaft concrete foundations and reduce the overall duration of transmission outages. This methodology incorporates mechanical (bolted) splices into full length #18J anchor bolt cages so that multiple but shorter sections may be safely set underneath energized lines. Tensile testing of these splices was performed to insure conformity to current codes and establish cage assembly tolerances. The electrical clearances available at each foundation location were evaluated considering the drilling equipment and rigging, which helped determine anchor bolt cage lengths and special detailing and fabrication considerations to accommodate splicing. Collaboration between the engineers, anchor bolt supplier, and contractor was critical to ensuring a successful foundation installation. This paper provides an in-depth discussion of the development of spliced anchor bolt cages, including the testing performed and solutions to unique design challenges. Furthermore, lessons learned from actual installations and the project benefits realized from this approach will be presented.