Trough bolt on concrete wall 2

[Jandra11]

In this kind of connection where the bolt goes trough the wall and bolted at the other side of the wall.Should I only check concrete edge failure and ignore the pry out failure.because when i try to model it to hilti. it is failing in pry out categor. Thank you in advance

 

[KootK]

Is your 16"x16" column okay for the bending and shear that will result from the accompanying, 135 kip lateral load that will be imposed upon it? How high up on the column span is this?

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.

 

[XR250]

That seems like alot of load to dump into the side of a concrete column.

 

[MrHershey]

I'm kind of with XR250. Pryout failure mechanism is generally your anchor being stiff enough to remain in single curvature and popping out the concrete behind it. Really have a hard time seeing throughbolts with a shared backing plate kick back and pop that wedge out. Sharing the anchor plate on the back would tend to restrain the heads and enforce double curvature on the anchors which should preclude the failure mechanism. In theory I think I agree pryout may technically still be a failure method, but would seem like it would be more of a group pryout rather than individual bolts (which is different than the group effect Appendix D considers).

Great old PCI article for anyone interested. Believe this is where XR250's image came from: Link (PDF). Authors seem to imply that headed studs over 4.5d in length aren't really subject to pryout, though then go on to note that test results for studs over 4.5d actually came out lower than pryout equations would predict. Not sure if that's because pryout stopped governing (they mention earlier in paper that anchor shear starts to govern at about 4.5d) or if the actual equations are low.

Also old threads on eng-tips regarding this and discussions of pryout not governing or not being applicable when anchors are over a certain depth.

Concrete Pryout Strength of anchors in Shear (thread507-356645)
Anchor Pryout Check Limitation (ACI 318 Appendix D) (thread507-330541)

 

[KootK]

The version of "pryout" that I was envisioning for a thru bolted connection is shown below. Hence my prior recommendation on treating it like punching shear. I was originally envisioning a situation with proportions that were more wall like and a load dominated by shear. With a massive lateral load in play and a 16x16 in column, it probably looks more like a traditional shear wedge popping out the back side.

@kootk any advise to improve this connection?

Given that you've got vertical load and horizontal thrust in equal measure, you probably don't need a ton of anchors to get this done. You can mostly get by on shear friction. I've shown a concept below. Not for the faint of heart of course. At the other end of the cowboy/conservative spectrum, you could cast a 6", full height bearing ledge on to the side of the column.

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.

 

[KootK]

Yeah, that's just a lot of load. You might weld side plates on to the front and back plates and claim to be using each through bolt sort of in double shear.

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.

 

[Jandra11]

@kootk you're correct we need to check the adequacy of column given high lateral load. I made some assumptions that the column has the maximum rho (3%) and it shows that the maximum length in order the withstand the 850kn lateral load is up to 3 meters.

@mrhershey thank you for the reference. when I model it to HILTI they consider it a individual due to the eccentricity of the profile. and I also found out that the higher the embedment I use the higher the ratio became maybe its because of Ac/Ac0. it contradicts the statement that the higher the embedment the lower the risk of the connection to fail on pry-out.

@Kootk there's a little bit misunderstanding about the loading. what I mean on 850kn compression is horizontal load towards the column and 600 kn downward. well the output will still be the same because the 850kn doesnt have big impact on the bolt. and the profile has eccentrity of 90mm to the side of the column. and the detail that you provided do you have any reference that i can use to make it on paper. well its kinda complex but if thats the only way i think we should go with that.

 

[Jandra11]

@kootk regarding welding the bolts on the plate to consider it double shear meaning the front and back will share the load equally?

 

[XR250]

If the column is existing, how are you getting all those bolts in without compromising the rebar?

 

[Jandra11]

@xr250 yeah youre right that one should be taken into accounts. thanks for the reminder.by the way were still @ the stage of designing a proper detail that can withstand all possible failure.

 

[KootK]

and the detail that you provided do you have any reference that i can use to make it on paper. well its kinda complex but if thats the only way i think we should go with that.

I don't have a reference. At it's heart though, it's really just shear friction.

@kootk regarding welding the bolts on the plate to consider it double shear meaning the front and back will share the load equally?

Not welding the bolts onto the plates but rather, welding on side plates to form a complete steel box around the column. Then you'd have a double shear-ish scenario I'd think.

Before you invest too much time in the bolted connection, I'd recommend ensuring that the column itself works in shear for the applied load. My preliminary calculations indicate that you'll need a LOT of ties in your column. Unless the existing column was designed anticipating the future installation of this brace, I doubt that those ties exist.

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.

 

[Jandra11]

@kootk yeah I already try that detail but they rejected it. Thank you guys for sharing your knowledge

 

[Yves De Lathouwer]

Wise guys shouldn't forget that most columns are working under pression and have usually much more rebars than standard walls.
The probability of a pry-out failure, for what I learned when I was sent in Hilti university had been reached in tests only in very small anchors in very low depths.
One of the reason of the introduction of this failure mode was for the calculation of the interaction between shear and tension loads but in the reality of the tests, it's pretty hard to get a pry-out failure.

Now, if you add to your equation the constant pression of your columns, and the rebars within, I think that rationally, without entering to all the calculations, this failure is impossible because a column in pression is neutralizing any most of the traction applied by your anchors.

In resume, what you should check is the capacity of the column to resist to the loads applied.

Regards
Yves De Lathouwer
Head of Engineering Department Adit Ltd

http://www.adit.org.il