Base Plate On Existing Concrete - Anchorage
Base Plate On Existing Concrete - Anchorage
(OP)
I have an existing 12" thick equipment slab for mechanical equipment. Slab has single layer of minimum reinf.
We are installing a large structural steel canopy (sunshade) over equipment. Very high seismic zone (SDS=1.2g).
The canopy columns are square tube steel HSS5x5x1/4. I believe it is good practice and probably a code requirement to develop the moment strength of the column thru the anchor bolts.
Based on Hilti and Simpson ESR reports and ACI 318 Appendix D, the max embedment permitted for a 3/4" dia rod is about 8" (min slab thickness = hmin = heff+5*do).
I know that 8" of the best post-installed epoxy anchor in the world will not "calculate out" to develop the yield strength of a 3/4" dia F1554-36 ksi. However, I believe that this is because of the very high factors of safety on epoxy bond stress values.
As an alternate, what about tension pull load testing each and every installed epoxy anchor to, say 80% of anchor bolt yield? This will demonstrate adequate "in-situ" bond. Is this reasonable and within the realm of Code acceptance?
I believe the only other choice is taking the equipment out of service, breaking up the existing concrete, and using cast-in-place anchors in a new thickened concrete equipment slab.
Any comments or other ideas are appreciated.
We are installing a large structural steel canopy (sunshade) over equipment. Very high seismic zone (SDS=1.2g).
The canopy columns are square tube steel HSS5x5x1/4. I believe it is good practice and probably a code requirement to develop the moment strength of the column thru the anchor bolts.
Based on Hilti and Simpson ESR reports and ACI 318 Appendix D, the max embedment permitted for a 3/4" dia rod is about 8" (min slab thickness = hmin = heff+5*do).
I know that 8" of the best post-installed epoxy anchor in the world will not "calculate out" to develop the yield strength of a 3/4" dia F1554-36 ksi. However, I believe that this is because of the very high factors of safety on epoxy bond stress values.
As an alternate, what about tension pull load testing each and every installed epoxy anchor to, say 80% of anchor bolt yield? This will demonstrate adequate "in-situ" bond. Is this reasonable and within the realm of Code acceptance?
I believe the only other choice is taking the equipment out of service, breaking up the existing concrete, and using cast-in-place anchors in a new thickened concrete equipment slab.
Any comments or other ideas are appreciated.






RE: Base Plate On Existing Concrete - Anchorage
RE: Base Plate On Existing Concrete - Anchorage
RE: Base Plate On Existing Concrete - Anchorage
There is no reason to develop the moment capacity of the post into the slab. Design and detail it as pinned.
RE: Base Plate On Existing Concrete - Anchorage
You're right, it won't. Fix the base, but only design for the moment needed, not to develop the moment capacity of the HSS post.
RE: Base Plate On Existing Concrete - Anchorage
RE: Base Plate On Existing Concrete - Anchorage
RE: Base Plate On Existing Concrete - Anchorage
If you analyze this thing as a true pinned base, it will flop right over, no?
RE: Base Plate On Existing Concrete - Anchorage
RE: Base Plate On Existing Concrete - Anchorage
RE: Base Plate On Existing Concrete - Anchorage
I do know that the subject of moment bases has been argue on this site many times.
RE: Base Plate On Existing Concrete - Anchorage
All, please see the OP attached sketch
RE: Base Plate On Existing Concrete - Anchorage
It is a flagpole, there is only one column with a cant'd arm in both directions. Pinned base won't work.
RE: Base Plate On Existing Concrete - Anchorage
RE: Base Plate On Existing Concrete - Anchorage
RE: Base Plate On Existing Concrete - Anchorage
Then you can rely on a little frame action.
This, of course, assumes there is nothing in the way ...which I'm sure there is.
RE: Base Plate On Existing Concrete - Anchorage
It will not work as a pinned connection.
RE: Base Plate On Existing Concrete - Anchorage
I agree with the others, design for the design forces, not the column capacity.
Michael.
Timing has a lot to do with the outcome of a rain dance.