Curtain Wall connec. to Beam 1

[palk7 EIT]

Hi,

I am new to exterior CFS walls as curtain wall and curtain glazing window units, I attached a sketch showing the lateral connection for both the cases, by having an L-angle welded to top flange of the beam and attach the lateral connection. In the case of window units the cantilever of the angle is 4-1/4" away from the edge of the beam so provided with a 1/4" stiffener there, also the mullion cap is below the beam so is it common to attach the spandrel panel to this L-angle, not that much load on top only a 2 or 3' heigh parapet wall will be above that. So curious if this is a common detail or any concern to be noted in this connection.

Thank you for your time!

 

[DaveAtkins]

The detail on the left is fine, but at the detail on the right, you need a connection just above the head of the window, going back to the beam web. That way, you will have two connections for your spandrel studs above the window.

DaveAtkins

 

[palk7 EIT]

DaveAtkins, on the right is there any specific reason for two connections (one to Web of the beam & one at the L-angle at the top), why cant just one connection at the top L-angle alone be used for the right side?

 

[BAretired]

why cant just one connection at the top L-angle alone be used for the right side?

Indeed, why not? If all you need is lateral bracing for the curtain wall, then I agree. The curtain wall is light enough and strong enough to carry its own weight without assistance from the structure.

But then you might ask: "what is the point in using such a hefty angle with stiffeners at 2'-0" centres underneath?" and "why not move the beam a little more to the right?"

BA

 

[KootK]

I suspect that Dave's point is that, for a spandrel condition, one would normally want the healthy lever arm between connection groups that would be provided by having connection points at both the top and bottom of the beam. There are other ways to achieve a satisfactory result but that is a popular one.

 

[palk7 EIT]

BAretired, yes angle is only for lateral and small gravity of the parapet wall above. Oh the angle not intentionally put it hefty but to cover that distance made it 7" longer, but yeah could move the beam 1" right and get rid of that hefty angle

 

[DaveAtkins]

If you don't have two connections, you need a moment connection to the angle. There will be a lot of lateral force induced by the top of the curtain wall. I don't recommend a moment connection.

DaveAtkins

 

[BAretired]

BAretired, yes angle is only for lateral and small gravity of the parapet wall above. Oh the angle not intentionally put it hefty but to cover that distance made it 7" longer, but yeah could move the beam 1" right and get rid of that hefty angle

If the curtain wall and parapet are continuous, the connection resists only lateral load, similar to the detail on the left; that would be okay.

If the curtain wall is pin connected to the spandrel panel, there is a wind moment from the cantilevered parapet and from the eccentric reaction of the curtain wall. In that case, two connections would be needed and torsion of the W12x26 would be a consideration.

BA

 

[DaveAtkins]

If the curtain wall and parapet are continuous, the connection resists only lateral load, similar to the detail on the left; that would be okay

I have never seen a curtain wall supplier include a solid parapet as part of their curtain wall. I suppose it is possible, but they would have to continue their aluminum extrusions up into the parapet.

DaveAtkins

 

[palk7 EIT]

Please find the attached detail, it will be like that where the curtain wall will be continuous upto the top and again a lateral connection to the HSS girt at the top typically done?

 

[DaveAtkins]

Your new detail works, except you are now putting torsion into the beam. You will need kickers every so often (4' on center, for example) to brace the beam from twisting. See the attached sketch.

DaveAtkins

 

[palk7 EIT]

DaveAtkins, I beg to differ I think isn't it the same detail as before, so how come in the new one the torsion is going into the beam if it was not previously going. The end (at the top) will be connected to the Girts and the girts back into the extended column. Then the other connection will be to beam web or L-Angle at the top flange of the beam.

 

[palk7 EIT]

Adding on to that, is that upstand 6X6 welded to top flange of beam that is specified is to reduce the span distance of the tracks (Top & bottom of the parapet stud wall) in between the columns or that upstand has something else to do with the beam rotation?

 

[DaveAtkins]

You said you were going to connect the curtain wall to the HSS girt at the top. If you connect the curtain wall to the rake angle, then there won't be any torsion.

DaveAtkins

 

[palk7 EIT]

My apologies, what I meant to say was, one at the angle section (top flange of beam) and the other at the top part so that, that 2'-6" or 3' Heigh above beam doesnt act like a cantilever and is connected at the top to the girt. Attached is the detail at the top which I got for this particular case, is it the typical way of doing it?

 

[DaveAtkins]

Looks reasonable to me. Make sure the curtain wall supplier knows he is also required to attach to the rake angle.

But now that I think about it, the portion of wind load which goes into the HSS will cause torsion in the beam. You still need the kickers.

DaveAtkins

 

[palk7 EIT]

From the girt its connected to the main vertical columns, so it will travel in that path right and not into the beam as a torsion, if I am not wrong

 

[DaveAtkins]

Yes, if the HSS girt spans column to column, it will not cause torsion in the beam.

I still recommend verifying your design with the curtain wall supplier--he may not want to connect to both the HSS girt and the rake angle.

DaveAtkins