Return to index: [Subject] [Thread] [Date] [Author]

Question Re CFS Built-Up Beams

[Subject Prev][Subject Next][Thread Prev][Thread Next]
I have a question about detailing of connections for built-up box beams of
cold-formed steel sections.

The method for making these that seems to be most favored is to lay up two
"S" stud sections lip-to-lip, and then put a "T" track section as a "cover"
over the top and bottom of these, and connect them using #8 or #10 screws
either through the legs of the "T" sections into the webs of the "S"
sections (i.e. from the sides) , or through the webs of the "T" sections
into the flanges of the "S" sections (i.e. from the top and bottom).

First, I'd like to know what is the preferred method of you CFS experts out
there. I sort of like the latter option, if only because it will be easier
to calculate the screw shear.

Second, when you computer the section properties for the combined section,
do you include the "T" sections? If so, do you consider the local buckling
criteria for the resulting composite including the unstiffened elements of
the "T" section flanges?

Third , how do you treat the forces (if you do at all) resulting from the
desire of the "S" sections to want to pull at the tension zone because of
loading through each web and the resulting shear center eccentricity?

Last, why is this a preferable section to just laying the "S" sections
lip-to-lip and "stitch welding" the seam in the shop? That seems much easier
to deal with!

Thanks for any comments.

William L. Polhemus, Jr., P.E.
Polhemus Engineering Company
Katy, Texas
Phone 281-492-2251
Fax 281-492-8203

*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*   Questions to seaint-ad(--nospam--at) Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: