Excessively Oversized Basplate Holes
Excessively Oversized Basplate Holes
(OP)
I have am currently working on a design for columns that have moment resisting baseplates. The original installation was to use post-installed, epoxy anchors. Due to geometric and design constraints, the anchor rods were sized so that they just met the requirements for the loading. However, the foundations have changed, and the concrete contractor now wants to use cast-in-place head studs. The original anchors were 1" diameter. As the anchor capacity is no longer dependent on bond failure, and in turn rod diameter, we have changed the anchors to 3/4" to ensure ductile failure of the rods before brittle failure of the concrete. The new problem I have is that the baseplates have already been cut and drilled with 1 13/16" holes, sized for 1" anchors per AISC Design Guide 1. This seems to be an excessively large hole for the 3/4" anchor. Is this allowable, and if so are there any special modifications that I need to incorporate? I've already sized up to PL 1/2" x 3 1/2" x 3 1/2" washers.






RE: Excessively Oversized Basplate Holes
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Excessively Oversized Basplate Holes
I would expect the plate deformations to play a significant role in the fixity of that base.
RE: Excessively Oversized Basplate Holes
Do you have to transmit shear? That can change thing.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: Excessively Oversized Basplate Holes
RE: Excessively Oversized Basplate Holes
@paddington, minor shear in this case, the friction of the baseplate on the grout is sufficient without lugs or the anchor rods bearing. The floor and foundation are the responsibility of another company, who we have been working with, but have not been directing them how to design. Since I have no control over the rebar sizing/placement, I sized the rods with the assumption that the rebar won't contribute to the capacity of the anchor rod. This is conservative, but I don't want to incorporate rebar into my portion of the design if I have no influence over the foundation design other than providing baseplate layout and loading information.
RE: Excessively Oversized Basplate Holes
RE: Excessively Oversized Basplate Holes
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Excessively Oversized Basplate Holes