ACI 318 / PCI Base plate with through bolts

[boobathims]

Hi
Please find the attachment. I would like to have reference to design plates and concrete checks.

Regards
M.S.Boobathi

 

[KootK]

Reference... I wish. Nobody ever seems to want to commit to a through bolt connection procedure nowadays. I`ll share what I know/think:

1) I'd treat it as an an eccentric punching shear problem with the lower plate defining the origin of the critical shear perimeter. Moment = Shear x 0.5 x slab depth.

2) I'll prestress the bolts so that I can transfer shear to the concrete via shear friction at the base plate interface. Trouble is, prestressing short bolts reliably is tough. And they tend to relax over time as a result of concrete creep etc.

3) In addition to shear friction, I'll check the bolts for bearing against the concrete assuming that the bolts bear uniformly over a distance of six times the bolt diameter. This is just something that somebody told me to do once and I don't have a whole lot of faith in it.

4) If you're near a free edge in the direction of shear, you'll need to approximate a breakout failure check similar to what we do with ACI appD checks.

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.

 

[SAIL3]

not sure how I would handle the shear transfer...it obviously transmits a moment into the concrete....would be hesitant in using it for any sizable shear transfer....as Koot pointed out, what would be the assumed effective length of uniform bolt bearing on the concrete...

 

[BUGGAR]

Without being covered by Appendix D, I don't know where to begin.

 

[hokie66]

As to vertical load, it is just like any point load on a concrete slab, except you have to check it both up and down. For shear, the bolts could take load in shear in much the same fashion as any post-installed bolt, say adhesive ones. If that is not enough, you have a problem. References (including Appendix D), you don't need, just analytical thinking.

 

[KootK]

@Hokie: I'm curious about your "like any other PI bolt" comment. I've been asssuming holes slightly larger than bolts. Would that change anything for you?

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.

 

[hokie66]

Yes, I would want a tight fit. Either drilled the same size and driven in or set in epoxy.