New resin anchors are proposed to be installed in close proximity, almost attached to existing encast steel grillage that was used to accommodate a lattice tower. The tower will be removed but the steel grillage will remain embedded into the concrete base. Is there a minimum safe distance that we should adhere to so that new resin anchors' capacity will not be compromised? Or we could drill as close as possible making sure, not to hit the embedded steel.
thanks,
Thank you for your question, in this instance we would point you towards BS8539:2012 and their guidance regarding aborted drill holes with the grillage conservatively treated as such as a filled hole. Extract as follows:
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 less than 0.4 x effective embedment depth
3 x hole diameter for aborted hole depth greater than or equal to 0.4 x effective embedment depth
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 effective embedment depth, or 5 x hole diameter, whichever is the greater.