Column Splice for OMF

[MattJM]

I am working on a building whose SLRS is Ordinary Moment Frames. I have additional requirements per the UFC, one in particular has me designing columns considering the loss of lateral support at any floor (i.e. they must be designed for "double height" with a reduced load). I have designed this thus far in LRFD, and cannot change from this.

My splices, therefore, are designed to be full moment splices.

Q1: Is this true: For this, CJP flange weld cannot be used in combo with a bolted web when the column is designed just about to capacity - as many are. This is because I cannot get my splice to develop the full Mn of the column without counting on the web splice a bit in flexure (and its contribution to Zx or Sx). Using the web splice plates/channels would need load sharing for bolts and welds that is not allowed.

Q2: I'd like to detail considering compression transferred by bearing only (no axial load in web splice, which is back-back channels). However, what ry do I use in my KL/r calcuation for Pn - ry of flanges only? ry of the splice configuration?

I'm thinking I may need full pen all around.

I have a bundle more, but these are the most important.

Thanks

 

[WillisV]

If you need full moment, you need to CJP flanges and web. Typically we see this done with a channel on one side of the web used as a pick point to erect the lower column. The upper column is then put into place, the flanges are CJPd, and the web is then CJPd using the channel as essentially the backing bar.

 

[MattJM]

Thanks. I thought so. CJP all around solves both Q's.

Additionally, with web ratholes for my flange CJP, my MP gets somewhat reduced. Do you typically recommend or allow ratholes for flange welding?

Thanks again.

 

[WillisV]

You have to have ratholes in the web to properly CJP the flange, the effect on the moment strength is typically minimal and ignored.