Storefront / Window Anchorage - No T or F Anchor

[RFreund]

Is my understanding correct? ->

For most large curtain wall systems there are T and F anchors which fit inside the vertical mullion. These anchor the system to the substrate and allow for vertical movement of the substrate and thermal/expansion contraction of the mullion. However for most single story storefront systems, these anchors are not used. Typically the vertical mullion is fastened to the head and sill mullion (via a shear block) and the head and sill mullions are fastened to the substrate. However, a gap is present between the storefront and the substrate (say 3/8 - 1/2 or whatever is needed). In order to achieve this gap, the anchor is checked in bending. Typically a fixed-guided end conditions are assumed. I could see anchoring into steel, concrete or wood as being fixed, but what about cold formed steel? I could see the aluminum mullion, if it were a tube section as providing as a guided condition, but what about when it is a channel, or you are fastening through the thermal break material? Find attached for further explanation.

Also I typically see extra fasteners at jambs, maybe for wind load or door weight? I don't normally see calcs for door weight or operable windows but it's possible I just haven't seen enough examples.

EIT
www.HowToEngineer.com

 

[XR250]

As a light gage steel designer, I don't know how they get this stuff to work. It probably does not work out on paper but they seem to perform OK in reality.

 

[RFreund]

Thanks for the response.
We also do a fair amount of CFS and I know what you mean. I have been going over some example projects from other companies and it seems like what I am describing is what they are assuming. However most projects are for larger curtain walls with the T&F anchors and all works out a little easier. With a storefront or window, it seems that the anchor is the cantilever member. I'm not sure how this works with CFS though. I suppose you could still resolve the moment caused by the eccentricity with a tension in the anchor and compression on the edge of the mullion.

EIT

http://www.HowToEngineer.com

 

[Ingenuity]

Please excuse my ignorance, but what are "T & F" anchors?

 

[jimstructures]

Thank you Ingenuity, I was hoping somebody would ask that question or it would become clear from context.

Jim.

 

[wannabeSE]

They are connections used to anchor vertical mullions to a horizontal surface (e.g. slab). They are typically used with 2 post-installed anchors. The 'T" has one anchor on each side of the mullion. The "F" has 2 anchors on one side of the mullion. The "F" are used in places such as door openings.

 

[RFreund]

Yes, as explained by WannabeSE. The 'stem' of the "T" fits into the vertical mullion so that the Vertical mullion can slide up/down. The stem does not actually fasten to the Vertical Mullion.

So I'm guessing that there really is no standard way for the storefront situation...

EIT

http://www.HowToEngineer.com

 

[Ingenuity]

Thanks wannabeSE and RFreund.

Found this, jimstructures, that helped me 'picture' what they are exactly:

 

[Ingenuity]

...and there are J anchors too...maybe other letters of the alphabet are represented too ;-)