New Steel Column Between Existing Steel Beams Detail

[bookowski]

Existing steel beams framing into cast iron columns and brick piers. We will be substantially increasing the load so we will be adding new steel columns adjacent to the existing and completely discounting the cast iron columns. This means fitting a new steel post at each floor from top of existing beam to underside of existing beam and detailed to carry all load. What's the best way to detail this such that it's reasonable to build and I can still be assured of load transfer?

I am thinking to add vertical plates to the existing members that align with the faces of the new post and transfer the load through fillet welds of plate to new post. This would allow for tolerance such that the post doesn't have to exactly fit. Loads aren't huge, around 100kip at lowest floors.

 

[mike20793]

Yes, you will definitely want stiffeners under the posts and maybe web doublers if web strength is still an issue. I prefer to use what is essentially a baseplate bolted to the top flange of the beam that the post can weld to. Same on the bottom flange cap plate connection.

 

[bookowski]

I didn't mean web stiffeners (I will be adding those). I just mean the top and bottom detail such that the contractor can get bearing/load transfer at each end while trying to fit something between two existing conditions.

 

[KootK]

I like your proposal Bookowski. Regular base plate at the bottom and the loose plates at the top. Depending on how things flush out, you may create a case where future loads impose significant accidental uplift on the existing beam-column connection due to prying. Something to ponder.

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.

 

[bookowski]

thanks, kootk. Interesting catch with the uplift/prying - hadn't thought about that.