Column Base Moment Connection

[Serhiy2]

Good day,

I'm working on addition of crane in the existing shop that has 6" slab on grade floor. I will be using cast-in-place piles for crane support columns. One constraint I have is that I don't really have anything to tie into to resist lateral forces caused by crane operation (forces perpendicular to crane runway beams). The only element where I could put some forces is roof diaphragm but I don't want to put much into it.

Making column base connection as moment connection does help but involves many-many anchors. My column base plate will sit below the slab so I was thinking of relying on lateral force resistance by slab working in pair with regular column base connection to produce some moment resistance.

One concern I have is about the rigidity of this slab resistance deteriorating with time after many cycles of loading. I'm basically looking for some feedback on this idea as I'm sure many of you have considered/used this approach before.

Thanks

 

[r13]

If any suggestion to tie the interior columns, you should have a good understanding on the operation of both cranes, the interaction of two moving loads can be quite difficult to manage. If unavoidable, or somehow desirable, make the connection as flexible as possible, not rigid, otherwise it will tear apart very soon.

 

[Serhiy2]

My moments at column base are too high to be taken by moment connection because of column bracket is about 16" long so together with wheel load and p-delta analysis it adds up.

The way I got 4kip lateral load is from CISC Crane Supporting Steel Structures design guide by taking 40% of the load lifted by trolley.

I can't tie into the existing crane supporting structure because my columns won't line up and because existing structure uses roof diaphragm to bring loads to end walls.

I've decided to bring columns up to roof level and tie them to open web steel joist top chords with iron angles. Also, I will fasten columns located next to the firewall to the top of the firewall. This way wall will not experience any bending because it will be laterally supported on the other face by the building frame. Client will have to live with vibration if it happens.

Regarding the moment frame it would be nice but the beam on top of the columns would span 50ft so I would need some heavy section for that matter not to mention lateral bracing for it.

 

[r13]

Can you grout the CMU wall solid, and stiffen it with reinforcing and a few bond beams along wall height.

 

[Serhiy2]

I will have it partially grouted and reinforced like every third core and bond beams one at the top and one mid-height I believe. Also, I won't be relying on wall bending in order to take crane lateral force so it should be fine regardless.

 

[r13]

Sounds like you got good handle of situations. Good luck.

 

[Serhiy2]

Thank you for all the feedback. Have a nice weekend!