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Moment Frame

Moment Frame

RE: Moment Frame

Theoretically yes, but why would you want to? You would need stiffeners in the beam web and those bolts are going to have relatively large loads on them to say nothing of the top plate of the column. Probably much, much easier to fix the bases of the column and design the foundation footings to create a cantilevered column (assuming this is for lateral loads).

Maine EIT, Civil/Structural.

RE: Moment Frame

(OP)
The foundation is an existing slab on grade that I don't want to rely on for moment capacity.

The lateral loads are relatively light (interior equipment stand).

RE: Moment Frame

yes, it's called a "portal frame", pinned at the base, fixed at horizontal beam

Quando Omni Flunkus Moritati

RE: Moment Frame

(OP)
Yes the design is a portal frame, the question is more about the fixity of the connection.
Stiffeners are required?
Any other design guides for this type of connection?

RE: Moment Frame

I think you would need stiffeners to get it to act as a moment frame - I think of it as extending the column flanges up, thus making the joint much like your typical moment connection as far as tension and compression plates are concerned. The column cap could be designed/analyzed as an endplate moment connection, which I believe there is an AISC design guide for.

RE: Moment Frame

It would require more substantial connections than what you've shown and the anchorage is not a trivial issue either. As noted, refer to AISC for guidance.

Simpson and a few other folks make some premanufactured versions of these if you'd like to go that route. See link.

http://www.strongtie.com/products/strongframe/inde...#

RE: Moment Frame

What struct said. I don't believe you'll find any guides covering your specific situation but if you treat it like a backwards moment connection (imagine the column is a beam and the beam is a column) it makes a lot more sense.

Stiffeners will be required in the beam web if web buckling requirements control. You would likely find it cheaper to just size the beam web such that it didn't require stiffeners. The bolts and top plate will be similar to the end plate moment connections struct mentions which AISC design guide 16 covers.

This should be sufficient to transfer moments. Make sure you check your deflections, these things will still sway a lot. Also, you'll probably want to make sure the bolts are pretensioned as with load reversals the bolts will tend to loosen if they're only snug tight.

Maine EIT, Civil/Structural.

RE: Moment Frame

If the loads are not that high, just use a beam with thick flange and a thick column cap. I have used this same detail. It will be difficult to calculate sway, but may not be an issue for an interior equipment stand.

RE: Moment Frame

analytically you can assume a pinned joint at the base, and design the frame to take the load (as above, web buckling, moment connection, ...). but if your base permits moment to be transferred to the foundation, then maybe the frame can sned enough moment that way to damage the foundation.

so if really want a pinned connection, have a base plate, 4 bolts, with a single pin to the frame so the the frame is truly pinned.

Quando Omni Flunkus Moritati

RE: Moment Frame

I'm sure I don't fully understand your constraints but could you have knee braces outside the portal?

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

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