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Trough bolt on concrete wall
2

Trough bolt on concrete wall

Trough bolt on concrete wall

(OP)
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

RE: Trough bolt on concrete wall

you cannot really check it adequately in Hilti (Profis software I assume) since it does not do thru-bolted anchors. You are also out of the scope of ACI appendix D provisions. You basically have a 2-sided bearing plate condition at edge. The pryout will not govern, most likely the side face blowout or breakout (depending on loads you have on this connection) will be your failure mode.
IF I was to check it, I would do a base plate design/check and then try to apply appendix D ignoring the back plate.

RE: Trough bolt on concrete wall

(OP)
@mjkkb2 thank you for feedback. I agree that HILTI cant compute it exactly but i just assume same embedment of anchor to the thickness of the concrete.The governing load here is vertical force that leads to concrete edge failure. and due to some reason its failing in pry out but with the presence of the plate at the other side of the concrete is enough to bypass the pry out checking. And i dont have any problem on the thickness of the plate because its only compression and downward force. is there any other way to increase the concrete edge capacity other than increasing the number of bolts from top and bottom?.

RE: Trough bolt on concrete wall

I'd still check it as per Appendix D because (in my opinion) a lot of the failure modes are still applicable. (Probably even (for example) side face blow out. That is if the bearing stress on the bolt head is high enough and the edge distance is close enough. And that is ignoring the stiffness of the back plate, which I think is appropriately conservative.)

I'd definitely limit how much of the anchor embedment I'd consider using for shear. Probably about 8*diameter (of the bolt) or the minimum edge distance. (Whichever is less.)

RE: Trough bolt on concrete wall

(OP)
@warose thank you for the feedback. Is side face blow out different on concrete edge failure? I actually using ETAG annex C and I havent seen any section telling we should limit the anchor embedment considering shear failure. But I notice in HILTI they are limiting le to maximum 12d not 8d? is hef or 12d.

RE: Trough bolt on concrete wall

Quote:

Is side face blow out different on concrete edge failure?

It is caused (in part) by being close to an edge.

RE: Trough bolt on concrete wall

Quote (OP)

and due to some reason its failing in pry out but with the presence of the plate at the other side of the concrete is enough to bypass the pry out checking.

I disagree with this and believe that you still need to contend with pryout. Pryout arises from the eccentricity between where the shear is delivered and where it is resisted. And you still have that here. If HILTI says you've got a pryout problem with the anchors modelled at full thickness, then I'd still be worried about it.

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: Trough bolt on concrete wall

The limit on load bearing length of an anchor in shear is codified at 8*d in ACI and CSA codes, it will likely be limited in your code as well somewhere. Unintuitively, the limit is the definitions portion in the CSA annex for example. If you're code allows 12d I'd take it.
For pryout, I think you can make the case the back side plate adds some resistance but I have no idea how to quantify it.

RE: Trough bolt on concrete wall

Quote:

The limit on load bearing length of an anchor in shear is codified at 8*d in ACI and CSA codes, it will likely be limited in your code as well somewhere. Unintuitively, the limit is the definitions portion in the CSA annex for example. If you're code allows 12d I'd take it.

Good point. But I am now wondering if the "le" to use in the shear breakout equations in Appendix D shouldn't be something more conservative than 8d or 12d. Maybe closer to the value called out in Sect. D.6.2.2 (for "torque-controlled expansion anchors"): le= 2da?

My reasoning would be: if it is a post-installed anchor (with a oversized hole).....you'd think that would cut down on how much would be in bearing.

(Kootk, if you are reading this....what do you think?)

RE: Trough bolt on concrete wall

Quote (canwest)

For pryout, I think you can make the case the back side plate adds some resistance but I have no idea how to quantify it.

Some ideas:

1) Look at the usual app D frustum but consider the depth of it to be the full concrete depth. And remove the back side resistance as there's no concrete to concrete boundary there upon which to exert tension.

2) Seriously eccentric punching shear.

I like the punching shear as I can tie that back to codified stuff more cleanly.

Quote (WARose)

Kootk, if you are reading this....what do you think?

I think the same and probably for the same reasons. In an oversized, ungrouted hole, you're not going to get that spiffy laterally loaded pile stress distribution that we simplify with 6d/8d. Instead, you're just going to lean up against the edge of the hole in a way that concentrates all of the force there. This is part of why I rarely do through bolt connections unless:

1) It's straight axial load and I deal with it as punching shear or;
2) I treat is as a pretensioned friction connection which has it's own issues.

For something like this, if it can't be done with anchor theory, I consider that to mean that it can't be done. Sure, the back side plate feels good mechanically. But we aren't able to quantify that rigorously and, conspicuously, there doesn't seem to be much testing on these kinds of connections. And if I learned one thing from appD, it's this: our instincts suck when it comes to concrete anchorage. Can't. Trust. Self.

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: Trough bolt on concrete wall

(OP)
@warose yeah I thinks its almost the same as the concrete edge failure.

RE: Trough bolt on concrete wall

(OP)
@kootk this connection is failing due to pry out but it is the same with this one its a through bolt and has base plate at the end
its failing because the hilti is considering the pry out due to individual bolt which i think it should by group because of the presence of the base plate at the back? does it make sense?

RE: Trough bolt on concrete wall

It may well be that pryout would occur in groups >1 but I'm not sure that all of the fasteners would be forced to pry out in unison. You've got a pretty good lateral spread on your anchors and the plates have little torsional stiffness.

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: Trough bolt on concrete wall

Do you have just axial force in the connected member - no tension?

RE: Trough bolt on concrete wall

(OP)
@kootk any advise to improve this connection? Btw im really grateful for all the feedback guys all your comments are very much appreciated.

@jlnj yup compression and vertical force to be exact

RE: Trough bolt on concrete wall

Quote (OP)

@kootk any advise to improve this connection?

I'll try.

1) What are your loads?

2) What direction do your loads act? Are they reversible?

3) Where abouts are any concrete edges located that might affect the design?

4) What size is the steel member?

5) How thick is the concrete wall?

6) In general, what is this thing?

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: Trough bolt on concrete wall

7) Is the concrete new or existing?

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: Trough bolt on concrete wall

(OP)
@KOOTK
1) What are your loads?850KN COMPRESSION 600KN VERTICAL LOAD

2) What direction do your loads act? Are they reversible?NO

3) Where abouts are any concrete edges located that might affect the design? ITS CONNECTED TO 400X400MM COLUMN (FC=50MPA)

4) What size is the steel member?UB203X203X60

5) How thick is the concrete wall? 400MM

6) In general, what is this thing? ITS A BRACING END PLATE SUPPORT

7) Is the concrete new or existing? YES EXISTING

thank you

RE: Trough bolt on concrete wall

(OP)
@xr250 thank you for the reference. yup im thinking the same way but i dont have any solid reference to back that up.

RE: Trough bolt on concrete wall

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.

RE: Trough bolt on concrete wall

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

RE: Trough bolt on concrete wall

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

RE: Trough bolt on concrete wall

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.

Quote (OP)

@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.

RE: Trough bolt on concrete wall

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.

RE: Trough bolt on concrete wall

(OP)
@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.

RE: Trough bolt on concrete wall

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

RE: Trough bolt on concrete wall

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

RE: Trough bolt on concrete wall

(OP)
@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.

RE: Trough bolt on concrete wall

Quote (OP)

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.

Quote (OP)

@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.

RE: Trough bolt on concrete wall

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

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