Metal deck connection Welded VS pined

[RHT2020]

Hi, I am designing a building for heavy overhead cranes(2 x 175 T). It is a conventional steel building with double column for crane runway beams. Each bent is designed as moment frame and I have vertical bracing in runway direction at every 4-5 bays. Also I have roof horizontal bracing to tie each bent together.


This building is pretty high (65’), the allowable drift due to crane is over 2” at roof level.

I have some questions:

1)My building looks like a “pre-eng” building, it seems I only have to select roof deck for gravity loads. Less stiff metal deck is better?

2)I feel I should use mechanical fastener for metal deck instead of puddle welds because pin connection are more ductile. And connection spacing should be as large as possible?

Please let me know if I am right or wrong.

Thanks.

 

[phamENG]

Why do you only need it for gravity loads? What kind of framing do you have between bents? Where are you getting diaphragm action?

Metal Building Systems get away with flimsy standing seam "roof deck" because they have cross bracing in the plane of the roof. If you don't have that, and you don't have a steel deck diaphragm, it sounds to me like you may not have a stable structure.

Remember, allowable drift based on generic code requirements may not be suitable for a bridge crane runway. You may want to look into getting this book.

 

[phamENG]

Oh, and you mention bracing every 4-5 bays. Do you have it one or both of the double column (often referred to as "laced" columns)? Hopefully it's both - you need one set to handle in plane loading from the crane and the other for stability of the structure as a whole. You could probably get away with only one, but I think you'd get some impressive torsion in the laced column assembly.

 

[Ron]

RXX...I agree with your approach. Puddle welds are a bit difficult to do correctly and are very brittle.

 

[WiSEiwish]

I have not given it much thought, but I suppose that the welds are less ductile. I tend to design my fastening pattern for diaphragm action using the #12 tek screws as the main fastener and #10 tek for sidelaps. Since that is the lowest capacity I'll give the GC the option to use the pins or puddle welds. I'm finding that the pins are a preference for many contractors.