Column Splice

[SteelPE]

This is related to another thread I have which can be found here:

https://www.eng-tips.com/viewthread.cfm?qid=477959

This is a column in the same mezzanine but not the specific column in the above-referenced thread (It's a completely different column approximately 100' away).

I am now being told, that the owner needs to move some equipment into the building during the construction process. The equipment can not be in place during steel erection. The splice will occur @ approximately 15'-0" above the floor.... and the column is approx 21' tall).... Yuck. Code is AISC/IBC-15.

We have gone around with the owner about this requirement. We tried moving the columns such that they don't interfere with his equipment moving plan and we have been denied in all instances, so we have been asked to coming up with a splice detail (which is attached).

This splice, by my calculations, should be sufficient to completely replace the bending strength of the column.... and replace the loss in moment of inertia (Ix and Iy). I am just looking to see if it passes the "smell" test.

 

[sbisteel]

Why the end plates? Seems like a pair of channels bolted to the web would get the same job done with less risk of gaps between the 2 shafts.

 

[KootK]

I am just looking to see if it passes the "smell" test.

- In general, it passes for me. There's no canned, AISC splice for W18 columns but I'd say that you've achieved a similar intent and then some.

- Even if it's not specifically required, I'd be tempted to design for:

a) 50% of the compression load as a tension load in the connection and;

b) 2% of the compression load as a lateral load applied at the splice.

c) OSHA erection loads.

I don't see any of these being a challenge for your setup though.

 

[azcats]

For my understanding, are the bolts designed as SC? Or is the potential slop in the holes for a bearing connection not a concern here?

 

[r13]

If the end plate connection is required for shear, I suggest to use the typical bolted splice plates instead.

 

[rowingengineer]

Smells ok to me.

 

[KootK]

I kind of figured that this might be erection without a crane and the end plates might ease setting.

 

[SteelPE]

I pulled the end plates out of my a**. It's literally the first detail I came up with... but it seems to solve a few issues.... and I think erection is going to be with a lull as this is a new mezzanine inside an existing building.

There is absolutely no tension in the connection, not even a little. There is bending as the column is part of the lateral force resisting system, but the connection can handle those loads (maybe I will make the plates 50ksi as we are just shy of the full bending capacity.... which I didn't think we were).

 

[JoshPlumSE]

Your splice smells fine to me. I don't usually like end plates for column splices, but I don't see a real problem with them. I think the steel fabricator has to be a lot more precise with their member lengths and such. But, I think the contractors would think it would be easy enough to deal with.

 

[Agent666]

So about the erection, what is the splice achieving here? I'm a little confused, are you just putting the bottom part of the column in after the rest of the steel is in position (top of column and any connecting beams hang in space), surely that steel needs to be propped then close to the ends of the beams which defeats the point of removing the column potentially in terms of the access gained?

Or is the top part and beams coming after the equipment is in position? You did note it couldn't go in at the time of erection or before though, so that's the reason for clarifying how this will be erected.

I guess in terms of the connection, provided you can get it over the bolts at the base and swing it under the top part of the column and get it aligned will be the challenge. May need some extra grout allowance to achieve this to give room to tilt it upright, and also propping the top part of the column slightly higher to lower it down under control on the bottom part may be considered.

Just ignore if not relevant....

 

[Enable]

There is nothing inherently wrong with your splice, provided you’ve designed the bolt groups to resist the desired loads. In fact, you will see this exact detail proposed as an alternative column splice on page 219 of Design and Analysis of Connections in Steel Structures by Alfredo Boracchini (see attached picture).

As a matter of preference, I would specify the bolts to be pre-tensioned in such a connection. And as others have pointed out, this type of splice allows for some slop or gap at the faying surface between end plates that may not be noticed until the column is experiencing loads in service. Since this is a one off, I would be more conservative and spec an end plate on the lower section and weld the upper section to that end plate in the field. No slop and no worries (though you may need to redesign flange plates depending on your view of bolt/weld combo loads in such a circumstance).