We are looking to install a machine in an existing industrial unit that previously had anchors in the concrete floor.
Some of the locations of the anchors we would like to install are close to the remains of these previous anchors and holes. Is there guidance to determine if this is acceptable?
Thanks for your question, I’d suggest looking at the information provided within BS8539:2012 regarding this topic, extract follows:
The new hole should be located away from the aborted hole by at least the depth of the aborted hole. A smaller distance is allowed if the aborted hole is filled with high strength non-shrinkable mortar.
If no shear or oblique tension is acting in the direction of the aborted hole, then the minimum distance between aborted and new drill hole should be:
1 x hole diameter for aborted hole depth ≤0.4 x hef*
3 x hole diameter for aborted hole depth ≥ 0.4 x hef
If shear or oblique tension is acting in the direction of the filled aborted hole, then the minimum distance should be at least 1 x hef, or 5 x hole diameter, whichever is the greater. (Different recommendations might be made by the manufacturer in the case of particularly deep embedment depths.) This might mean designing and fabricating new brackets or base plates, in which case the anchor spacing criteria of the manufacturer should be taken into account along with the effect on loadings.
*hef effective embedment depth from the surface of the load-bearing structure.
If threaded anchors were mis-located when set into the concrete and the Contractor would like to install epoxy anchors adjacent to the abandoned holes, do they need to drill through the existing threaded anchors to make an annulus for the addition of grout?
Does the existence of set-in threaded rods result in similar behavior to that of post-installed anchorage adjacent to abandoned holes filled with grout - meaning can the specifications provided in the original response be applied to such a condition?
Does HILTI specify a minimum distance that anchors installed with a drill/epoxy system (such as HY200) must be from an abandoned hole and/or anchor left in place?