Conceptual Design of Steel Moment Frame

[jseng9]

I’m a first year engineer trying to understand how steel moment frames are detailed. I saw this simple cabana structure which has 8 columns and steel framing running North-South and East-West(photo attached). I’m assuming it has heavy girders running the long direction(North-South) and then lighter members framing into the girders with some type of moment connection on each side?

Can you give me an example of how this would be detailed? One idea I had is that the heavy girders would be shipped to the site as continuous members that get welded to column closure plates. Then there would be a moment connection on each side of the lighter East-West members for the cantilever. Would this work? Are there other ways to do it? Any descriptions or sketches would be really helpful.

 

[mmarlow]

jseng

There are many ways that this structure could have been framed to resist lateral loads. Moment connections would be required. Your ideas could work if the connections and members were sized/detailed appropriately.

Being that the surface subject to lateral wind loading is low, and the seismic weight seems to be low, cantilevered columns could work here too. The foundation would be sized to resist the overturning of the columns.


-MMARLOW EIT

 

[jseng9]

Thanks for sharing your thoughts, MMARLOW!

 

[JoshPlumSE]

Pull open the AISC manuals. Both the regular manual and the seismic design manual for examples of some moment frame connections.

Looking at this simple cabana, I'd guess it might be easiest to design it as cantilevered columns since there doesn't appear to be much weight that it's supporting. Your idea of "column closure plates" I assume is what I would normally call a flange plate moment connection. This type of connection is discussed in the AISC 14th edition steel manual page 12-4 through 12-6.