Structural Support of Curtain Walls / Deflection Limits

[JVK2060]

Hi Everyone,

From the attached screenshot, I am to support an exterior wall with steel framing. The blue line represents a line of steel members that support the dead load of a stud wall (green shade). The blue line also provides lateral support at the top of a glass curtain wall (red) and the stud wall (green). The glass curtain wall is supported entirely by a floor system at the base of the red triangle. With regards to deflection, I am looking to determine the limits to set the supporting steel members (blue line) or if my limits are provided by others. The glass curtain wall and the stud wall are delegated designs.

 

[jayrod12]

I believe most curtain wall systems have the ability to accommodate up to a 1/2" sometimes even 3/4" at the head. Might not be a bad idea to have a chat with a supplier if you've got access to someone.

 

[ntattose]

Regarding vertical deflection; The allowable deflection is a function of the caulk joint. The max deflection should be limited to about 1/2 the caulk joint. The curtain wall designer will set the caulk joint based upon the deflection of the head condition. If the caulk joint gets too big they will use a subhead. That's like a deflection track. You will also need to consider out of plane deflection. It's not as tight as vertical deflection but it still needs looked at.

 

[RenHen]

Not sure about code limits for supporting steel like this, but from the curtain wall delegatee side, I am usually just provided a deflection by the steel engineer & have to detail around that. There's plenty of ways to isolate/minimize the effect of support deflection on the curtain wall & the limits will vary a lot depending on the detailing.

 

[JVK2060]

@RenHen - To your comment I was looking to avoid reevaluating my design later if it the deflection limits were stricter than the standard serviceability limits.

It seems that without knowing this information up front that it is not unreasonable to design with the standard limits and then notify the owner that the members are subject to change following confirmation with the delegated design engineer. At the least I would have a limit that the stud wall/curtain wall engineer could start with an they would let me know if it is too much for their design.