Checks on concrete failure for through bolt

[Mohamed Maher]

HI ALL!

if I use anchors through bolt should i make checks on concrete cone failures and why? for example using base plate at top of concrete slab and bottom base connected by through anchors ....kindly let me know your opinions and thanks.

regards
Maher

 

[KootK]

kindly let me know your opinions and thanks.

While through bolting has an undeniable structural logic to it, I know of know accepted design procedure for evaluating these joints. So I don't use them except as "belt and suspenders" where I've already designed the connection to ACI appendix D procedures. I've yet to actually see a published design example for a through bolt connection. And I've heard engineers express wildly different opinions about how these joints ought to work. One of my old mentors swore that all through bolt joints had to be prestressed and worked via friction. I disagree with that and don't actually feel that would even get you out of having to consider concrete breakout modes of failure.


Yes, because there's no way to transfer connection forces to the concrete without... transferring connection forces to the concrete. I'd need a sketch of exactly what you're proposing but I'd be willing to be that things like shear breakout and prying breakout are still at play. As far as I'm concerned, a thru bolt connection is really just an appendix D connection with the anchor depth equal to the concrete depth.

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.

 

[BridgeSmith]

You would use the same procedure as you would to evaluate punching shear capacity. Calculate the surface area of the failure planes and multiply by the shear strength. Start at the edges of the anchor plate and go through the slab out at a 45 degree angle on each side.

 

[hokie66]

What are the through bolts doing? If just in shear, just check as any other kind of bolt. If in tension, then the slab must be designed to resist that force, and punching shear is one mode of failure. Now, punching shear checks need a "d" to the reinforcement, so you need some on the side opposite where the bolts bear.