The "Newman Lug"

[bones206]

Has anyone ever used this approach for column baseplates (particularly for PEMB's)?

If you've read the book you know what I'm talking about. Basically a leveling plate with a shear lug. I can see the pros but wondering what cons may be lurking...

 

[JoeCK.]

From my limited experience, I would think it requires more coordination with the foundation engineer unless you are taking both on yourself. Keep in mind the compressive strength of concrete so the lug has to be deep/wide enough for concrete withstand pressure.

Makes the anchor rod design much easier.

 

[dik]

Unless your load is substantial, it's more work...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[bones206]

One of the issues raised by Newman in the book is that the baseplate may slip an unacceptable amount before engaging the anchors, depending on how oversize the holes are. This leveling plate with the shear lug would have just 1/16" oversized holes.

 

[dik]

If critical... use a plate washer and weld...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[WARose]

Used it a bunch of times. One drawback is (and I don't have Newman's book so I don't know what formula he uses but....).....a lot of people use the 45 degree method given in AISC DG 1 for the shear lug capacity in concrete.....and testing has shown that it is is light in certain circumstances. Ergo I've typically used this:

https://www.aisc.org/globalassets/a...ar-transfer-in-exposed-column-base-plates.pdf

You are right about the slip....and dik has a good suggestion.

 

[hokie66]

Is that really a leveling plate, or rather the column base plate? If the column base plate is separate, its oversized holes may still present a slip issue.

See WARose's link. No leveling plate shown.

 

[bones206]

Sorry, I realized it doesn’t make much sense without showing you guys the other figure. It shows how the column baseplate is field-welded to the leveling plate with the lug after the column is set.

 

[bones206]

I'm mostly curious about the constructability aspects and history of success (or headaches) on real projects. I think I would like it if I was a contractor, but I might start to hate it if I found an elevation bust in the midst of steel erection and had to try to demo and re-grout the leveling plate.

 

[NorthCivil]

without diving into the numbers on it, surely you can arrive at the same capacities if you add a couple extra bolts?

seems like a lot of work

 

[bones206]

I think the premise for using something like this would be that you are intentionally not using the anchors to resist shear. I’ve always done the welded plate washers, but AISC seems to not want us to use anchors for shear if we can avoid it. I’m not planning to stop using anchors for shear any time soon, but I’m open minded if someone’s built a better mousetrap. As long as I don’t have to send Newman a royalty check every time I use it

 

[phamENG]

I don't get a lot of really big PEMBs, so this hasn't really been an issue for me. Also, all the PEMBs I do tend to have AISC standard bolt holes in the base plates, which of course is hell for the concrete guys placing the anchors. As a result, the slip that occurs is not substantial enough to matter.

Not that I get any say in it, of course. I don't usually get them until somebody comes to me complaining that the City wants a foundation drawing after they submitted the building drawing for permit...

 

[jaskamakkara]

I would say that welding washers down over the anchors after installation is best, also means that you can leave nice big holes in the plates for installation tolerances. Just have to be careful with any shear loads that might be incident during construction (i.e. before they've managed to weld the washers down).

 

[dik]

Unless the shear is substantial... I'll use anchor rods... easier and less costly.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[bones206]

@WARose - how did these fare when you've used them? any constructability feedback from the contractors?

 

[dik]

Wouldn't a levelling plate and a base plate have the same 'oversized holes'? The baseplate being on top would have the welded plate washers if the oversized hole is an issue.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[bones206]

As a side note FYI, ACI 318-19 now has provisions for shear lug design at the end of Chapter 17.

 

[dik]

Thanks...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[WARose]

@WARose - how did these fare when you've used them? any constructability feedback from the contractors?

No issues as far as I know. Of course, I was talking about something a little different. I was talking about the column directly welded to the "Newman plate/lug". (I thought the pic in the OP was omitting the column for clarity.) Not sure if I have ever done it like the second pic in your 25 Feb 21 02:04 post.

 

[bones206]

Thanks. Fair to say based on the responses so far that this isn't a detail being used in practice. If I try it someday I'll let everyone know how it went.