Tilt up strongback

[JStructsteel]

For a new window cut into a panel, how far above the opening would you go? Just enough to get the anchors to work? I was going to be around 18" above the opening, such that the anchors are not influenced by the new edge distance. Thoughts?

 

[Aesur]

Many times I use a plate on the bottom of the new lintel beam that is inserted into a sawcut precast panel, assuming you are using goalpost setup, similar to masonry, many times this only requires 6 to 8" for the anchors.

 

[JStructsteel]

Aesur, this is for the vertical legs. I am not worried about the header. I will have a HSS vertical next to the new openings.

 

[Aesur]

Ah, misunderstood what you were asking there. In that case I tend to take the jambs all the way up to just below the ledger unless it can be proven the panel reinforcing still works as a jamb, which in my experience is fairly rare.

 

[JStructsteel]

Thanks. The panel is 22' wide. Above the windows, the panel is adequate for the load (no modification) the window is only being cut 8' above the slab. I dont see a reason for a 22' tall stongback on a 8' tall opening

 

[KootK]

If you don't run the strongback all of the way to the top, then you need to consider what stabilizes the joint between the strongback and the remaining spandrel panel with respect to out of plane displacement. That, arising from both:

1) Directly applied lateral loads such as wind and;

2) Stability at the joint under axial load in combination with any lateral loads.

Some possibilities for dealing with this include:

3) Create a moment connection between the post and the spandrel above. Yuck.

4) Demonstrate that the spandrel above the opening can span to the neighboring panels as a girt of sorts, checking the following:

a) that the spandrel panel is strong and stiff enough to perform as a girt and brace for the hybrid post/pier thing.

b) that the neighboring panels can support the lateral loads imposed by the girt.

c) that the connections between the remaining spandrel and the neighboring panels can support the lateral loads transferred to them by the girt.

That's a lot of stuff that isn't always straight forward to evaluate. For this reason, I often run the posts most of the way up.