Assessing the Rigidity of Frame Column to Footing Connection & Discussion on HSS Moment Connecti 2

[jakedoug]

Hello!

Welcome to my initiation (first post on this site.)

I've spent quite a lot of time on this design going back on forth on a few critical assumptions and would love to hear what others think/would do to get out of this rut.

Project parameters: Design a 20' tall by 20' wide by 60' long freestanding shed using HSS sections. Structure needs to take moment at the top of columns and footings for wind resistance.

1. In terms of the moment connection at beam-column connection, I was thinking of a welded "flange" plate connection. Does anyone with HSS experience object to such a connection? Will this provide the proper amount of rigidity?

2. I'd like to anchor the column + baseplate to the isolated footing. Is it possible/good to design a "moment" connection like this for this type of small structure? I'm used to always assuming anchored baseplates as pinned so this doesn't feel right. The only alternative I've found is embedding the hot rolled profile into the concrete footing... Is this really what is necessary to assume a rigid column support?

I've scoured the internet to find examples for my specific (or partially representative) cases but I've had very little luck.

As you can see, I'm mostly worried about critical support/node conditions being invalid due to poor detailing. Also, if anyone has any useful guides or, by some miracle, example calculations that they'd be willing to share, I'd be forever in your debt.

I've attached snips of sketches I made to illustrate what I had in mind.

All the best to all/any of the good people who will take the time to help me out.
Thanks!

 

[DaveAtkins]

A four bolt base plate detail is very common to create a fixed base. The base plate, anchor rods, and footing must designed for the moment.

For a beam to column moment connection, you must weld the flanges of the beam to plates which pass through the tube column. There are details of this in the AISC Manual, I believe.

DaveAtkins

 

[dik]

Can you use three 20' bays and frame them using conventional W shapes connected to eight HSS columns? The Moment connection can be a plate welded to the face and bolts to connect the plate to the W section or something of that ilk.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[jakedoug]

Gentlemen,

Thank you for your insight. I was already using 20' bays and connecting HSS rafters to HSS columns to create the frame. All of the components were designed for the effects of all loads (axial, shearing, and moments) along the entire load path all the way to the ground. In terms of the connection at the eaves, why is passing the plate through the square HSS column necessary? Could the attached detail work instead? (The plates would also be welded to both "flanges" of the square HSS but this isn't yet shown on the snip.) Would this detail not be rigid enough to create an FR connection?

Thanks again for all the help!

 

[jakedoug]

Here's an additional snip of a half-section of my concept for reference.

 

[Celt83]

This document should be relevant to the discussion (should be a free download from AISC): Determination of Column Fixity at Column Bases

I'm making a thing:

http://www.thestructuraltoolbox.com

(It's no Kootware and it will probably break but it's alive!)

 

[jakedoug]

That document is fantastic. Thank you for sharing! I can finally justify my assumption