Using post-installed adhesive anchors is commonplace in concrete construction and especially in renovations of concrete structures. However, field conditions can often dictate changes to the original design, and anchors are often relocated due to unforeseen circumstances. If you have been a design engineer for any length of time, you have undoubtedly encountered the situation where a hole was misdrilled, or the contractor is requesting to relocate the anchor due to existing rebar or or other conflicts. Having this happen on a project may lead to the question – What are the effects of the abandoned hole on the newly installed anchor?
In September 2017, Kevin Davenport, PE with Simpson Strong-Tie gave a presentation on Code Provisions for Post-Installed Adhesive Anchors into Concrete for SE University. Kevin reviewed recent changes in ACI addressing adhesive anchors and the new requirements for design engineers, as well as new mandates for installation and inspections. Kevin also responded to a variety of audience questions in reference to adhesive anchors, and the topic of anchor installation near mis-drilled holes was addressed.
Recently, Simpson Strong-Tie conducted several laboratory tests on adhesive anchors in tension adjacent to abandoned holes. These tests helped to provide some guidelines for design engineers when dealing with unforeseen field conditions such as misdrilled or abandoned holes near tension anchors. Kevin provided this memorandum from Simpson StrongTie which summarizes the results of the testing, and also provided this blog post which further describes each anchor and situation that was tested in their ISO 17025-accredited anchor testing laboratory in Illinois. Using these spacing and reduction factor guidelines, engineers can more accurately consider the effects of misdrilled holes and make appropriate recommendations when field conditions are not as anticipated.