Double angle connections for hss beams.

[IngDod]

Greetings,

I am trying to design a shear connection between an hss beam and an hss column, the limiting issue in this case is that the beam is framing into the wide face of a 260x90mm column, so any force acting perpendicularly to the wide face of the column is bound to cause some troubles as the wall is slender. My initial solution was to use a pair of angles, each connected to each web of the beam; which is similar to the connections used for I-shaped beams and I believe the behavior should be very similar and has the added bonus of taking the forces close to the sidewalls of the column. However I have found a problem.. AISC uses angles with legs of 4" and 3".. and a 3" angle wont fit in this case... I would need to use a 2" angle.. however I know that this is exactly the sort of thing that could affect the rotation of the connection. My question is: Is there a way to ascertain wether the reduced leg size of the angle still works as a shear connection? This is for a relatively light load of 6.6kips.... According to my calculations it would still work with ample capacity.. but I do not know if a certain degree of fixity will creep in.

I have thought of other solutions.. such as welding a reinforcing plate to the column and directly welding the beam to the plate.. which would be a semi-rigid connection. But I much rather keep any moment away from the columns. I also thought of using an angle seat.. but given that the beam is narrow (70mm) I would be putting most of the force at the center of the column wide face.. which will probably come back and bite me in the ass when the beam carries any kind of axial force. Also... I just remembered that the 260x90 column has 260x90 beams framing in the perpendicular direction... so in theory I could use 3" or 4" angles and weld this angles at the webs of this beams... this a very non-standard connection but it takes all the load away from the wide face of the column which is my main concern.

Thanks, and I hope i made some sense.

Thanks.

 

[racookpe1978]

What is the beam size?
I see the column above 260 x 90, but no wall thickness.

 

[IngDod]

Sorry.. wall thickness is 5.5 mm for the column.

 

[hokie66]

A sketch would help to see how the beams and column are oriented, especially how the "260x90 beams framing in the perpendicular direction" work. Does the column go up or stop at this level?

 

[IngDod]

Im attaching a sketch, in the sketch the angles fit inside the column.. but I have several connections where its not possible. The columns are 7m high... this connections occur at 3m and at 7m. The 260x90 beams are bevel welded to the columns.. so the beams frame into the 90 side of the column.. its more clear in the sketch.

 

[hokie66]

I don't know why you say the 3" angle leg won't fit. (260-70)/2 = 95, which leaves 20 mm each side for the weld, if that is what you are proposing. An end plate or an angle seat extending across the column might be better.

 

[IngDod]

@hookie66... yeah sorry.. I've not been very clear... This does work.. but I also have a 120x120 beam framing into the column.. which will not fit.. and a similar 70mm beam framing into a 220mm column which will also not fit.

Regarding the angle seat... is it possible to have an angle seat that is much wider than the beam its supporting?... for example.. I would like to support the 70mm beam on an angle seat that is say 240mm wide... so I can weld the seat to the flat of the hss column close to the corners. I ask cause this connections are relatively easy to check for the limit states but it seems there's no real way to measure how flexible they are other than sticking to the AISC tables and recommended values.

The end plate is by far the easiest solution.. cheaper to erect too I wager.. but I still feel uncomfortable putting moment into the wide face of the column... these tubes are very thin... The only way i can see around this is using a very thick plate.. say 3/4" or even 1".. no chance of the column face seeing any kind of bending... it seems anti-economical... But I might have to do it for a few connections cause they are also receiving a brace which is pure axial load.

 

[hokie66]

With small members and small loads, with architectural detailing, etc., it is often necessary to deviate from 'standard' connection details. I don't see why an end plate would create more moment in the column. You only need a plate to transfer the shear load to the edges. Even if it does create some rigidity in the connection, what harm is done? The column will only take moment until it yields, then the beam will have to do the rest.