Expansion bolt near cut off anchor rod

[tvar]

I have a problem where some anchor rods are located in the wrong spot. Instead of cutting off the base plate and re-welding would it be possible to use an expansion anchor (25mm diameter) 70mm away from the existing anchor rod and cut off the existing rods? The existing the bolts have loads that are 2.25 k tension and .16 k shear. Looking at the Hilti information it gives spacing for both bolts being loaded not just one. Because of the heat epoxy anchors can not be used. Thanks

 

[Ron]

Yes, this can be done. Keep in mind that the existing anchor rods that will be cut off will interrup the pullout cone and thus disrupt the stress distribution of the pullout at failure. I would suggest that you embed the anchors more than your pullout loading requires. Your loads are relatively low for the size of anchor you are going to use, so that should not be an issue.

 

[wannabeSE]

There is a 1982 Journal of Structural Engineering article, "Effect of Abandoned Roles on Capacity of Wedge Bolts"

http://cedb.asce.org/cgi/

http://WWWdisplay.cgi?34048

. I don't think the abandoned anchors will significantly affect the expansion anchor capacity. However, I would contact expansion anchor manufacture for their opinion. The change in bolt group geometry (eccentricity, prying and force distribution) may have a more significant impact than the abandoned bolts.

 

[southard2]

Both are good advice. If within an inch of another cut off anchor I have never been real comfortable using post installed anchors. In general the data is based on testing so any change could affect the strength numbers. If the steel column has not been fabricated yet I'll have them fabricate an oversized base plate and reposition the anchors on the base plate. If the column and base plate are already fabricated then you could have no holes punched in the base plate between the original ones and then go from there. Your uplift loads aren't very high so that should be OK. If trying to reuse the existing holes then I kind of like the suggestion of going deeper into the footing if you have room to do that.

John Southard, M.S., P.E.

http://www.pdhlibrary.com/