Beam framing into continuous beam over HSS column (Moment Connection) 2

[Szubert80]

Hi All,

I have a roof framing plan attached to this post where you can see W16x26 beam to be framed into continuous W18x40 using moment connection(95kNm).
How would you design a moment connection in this scenerio. The main issue I`m having is how to transfer the moment through a beam`s weak axis into the column cap plate.
Provided that web stiffeners will be designed adequately to transfer the load into the bottom flange of W18 then the challenging part is the connection between bottom flange and cap plate.
I don`t know if there is any other way to make it feasible other than split the continuous beam and frame all 3 beams directly into the column. The beam was designed as continuous due to the fact that it cantilevers 12ft at one end.
Any suggestions would be greatly appreciated.

 

[KootK]

A very similar issue was discussed here yesterday where the consensus was that the column probably ought to run up through the joint as you've anticipated: it

 

[Earth314159]

You can use an exterior steel plate diaphragms that go around the outside of the column at the lower and upper flanges of the W18s. You can use a spacer on the W16 to transfer loads from the W16 bottom flange to the diaphragm on the lower flange of the W18. AT least you don't have to deal with a height difference due to an OWSJ seat. This makes the detailing simpler.

 

[CANPRO]

I would run the W18 continuous over the column if the total length was still shippable. Then I would shop-weld a W18 stub on the side of the W18 and move the W16 moment connection out away from the column. It might be cheaper to change the W16 to a W18 at that location and simplify the moment connection (design, fab, and install). Sketch is attached.

I see your W18 is sloped as well. That will complicate any moment connection, but more so with three different bolted moment connections.

 

[hokie66]

You didn't indicate the size of the SHS column, but are you sure it is strong enough for that moment, in addition to its axial load?

 

[p_kefa]

If there is no problem extending the bottom plate to the right of your sketch, extend the column up; provide a column cap plate doubling as the top moment connection plate for the 3 beams; provide a bottom moment plate extended on 4 sides. Design the width of the plate extending to the right of your sketch for half the force to be transmitted through the plate from the moments on each side of the column from the W18 beams.

 

[CANPRO]

p_kefa, it sounds like you're proposing to extend the column up and break the W18 into two pieces, as others have suggested above. I don't think that is the best choice for the cantilever for two reasons.

First, it is a 12' cantilever under a snowdrift, with a decent tributary width (not to mention it appears to also be part of a moment frame) - there will be relatively high flange forces in the W18 at the HSS. If you extend the column up, you need to build the beam around the column, its easier to build the column into the beam and let the beam be continuous. Give the right of way to the highest stressed member if possible.

Second, the slope of your cantilever will be dependant on your fabrication and installation tolerances. The W18 has a slight slope, so the wrap-around plates for the bottom flange connection will need to have a slight bevel cut and be fit near perfect. It is much easier and precise to just mitre cut the HSS and add a cap plate to get the proper slope.

 

[KootK]

 

[KootK]

Like Hokie, I question whether this is really the right column section for the job. Space permitting, I feel that a W8 oriented with it's strong axis aligned with the W16 might be a better choice, both with respect to capacity and connection alternatives.

Were I in OP's shoes and sticking to my guns with respect to the connection typology, I might do something as shown below. It's expensive and imperfect but, at the least, it provides a direct, stiff path for transimitting moments from the W16 to the HSS column. This might need some further noodling with respect to erection give that this would need to happen at both ends of the beam. Worst case scenario, maybe you shift the shear connection out to the free edge of the interior stiffeners.

 

[KootK]

I'm thinking that I may have judged CANPRO's detail too harshly. The issues of prying and flexibility are not so different from what we do with extended end plate moment connections regularly. If the numbers work, they work.