Sloped Intermediate Moment Frame 1

[kmead]

I am working on the design of a one story building with a Seismic Category D and a 4:12 roof pitch. I am using Intermediate Steel Moment Frames, however, since there are no prequalified sloped Intermediate Moment Frames, my thought is to use a typical Intermediate Moment Frame (i.e. not sloped) and have a truss (maybe with HSS or wide flange) to transfer the shear force from the roof diaphragm to the moment frame. I realize that I still need to brace the top and bottom flanges per AISC 358-05 but, I would like to know if there's there in inherent problem with my proposed solution.

Any thoughts would be appreciated.

 

[msquared48]

No insurmountable problems, but instead of a truss endwall, I would use a gable endwall and sheath the verticals with CDX ply to transfer the lateral forces. This means that the frame will also have to carry some vertical load, but so what.

Mike McCann
MMC Engineering

 

[kmead]

Mike,
I will definitely do so on the end bays, but I neglected to mention that these frames also occur inside the building where I have to use a truss to allow the passage of ducts, sprinkler pipes and such.
Thanks for the reply.

 

[msquared48]

Inside the building is a different matter as trusses are usually not designed to transfer lateral shear, especially to a steel frame. You will have to tell the truss manufacturer what you intend to do here so he can properly design the interior trusses.

Mike McCann
MMC Engineering

 

[Gumpmaster]

Make your life way easier and use a SidePlate Frame connection. They have a tested sloped connection. It's a really slick system.

 

[kmead]

Can the SidePlate frame connection be used for an Intermediate Moment Frame? I always thought they were considered as OMF connections but I may be wrong?

 

[InDepth]

Sideplate used for anything!

 

[msquared48]

Never heard of that for shear. Can you describe it?

Mike McCann
MMC Engineering

 

[kmead]

Mike,
SidePlate is a moment connection that the manufacturer claims it saves time and money over other prequalified moment connections. What Gumpmaster was suggesting is that instead of having a typical IMF and adding a truss on top of it to transfer the shear from the diaphragm is having a sloped frame with the SidePlate connection since it is prequalified for use with an IMF and can be sloped. This would actually work out great since it would allow for the Cathedral ceiling that was originally intended. However, I have I contacted Sideplate to verify that it can actually be used in a sloped IMF and have not yet heard back from them.

If you would like to check it out, here's their website address:

http://www.sideplate.com/

 

[Gumpmaster]

I just had a web conference with them a couple of weeks ago. It actually qualifies for an SMF, but would work fine for an IMF too.

I asked about large sloped roofs, and they said not a problem. The only tricky part (for them) is how thick the side plates need to be to prevent buckling at the connection. They run LS-Dyna in house, so they can figure it out no sweat.

 

[kmead]

Thank you all for your input, it's very much appreciated.