Beam made of back-to-back channels
Beam made of back-to-back channels
(OP)
Is there a standard procedure for analyzing a beam made of back to back channels?
I'm acutally working backwards. I know the I-beam size for what I need, but want to fabricate it out of channel so I can place hooks between the channel to make it a spreader bar..
Questions, comments, jokes?..
I'm acutally working backwards. I know the I-beam size for what I need, but want to fabricate it out of channel so I can place hooks between the channel to make it a spreader bar..
Questions, comments, jokes?..






RE: Beam made of back-to-back channels
RE: Beam made of back-to-back channels
Thanks, thats' how I started, then realized that my beam was a W610x372 (thats metric - w24x207 imperial)and I can't get channel that big.
I'll likely have to go with MC18 as heavy as I can get then do a lot of reinforcing.
Likely have a 1" x 24" top plate at the lifting point, with stiffeners at the sides. Its 50T capacity.
RE: Beam made of back-to-back channels
RE: Beam made of back-to-back channels
Can you detail the connection with a Standard Wide Flange Beam.
Best regards
Rarebug
RE: Beam made of back-to-back channels
RE: Beam made of back-to-back channels
Steve - I'm glad you then afterward mentioned lateral torsional buckling as this statement by itself is not true.
RE: Beam made of back-to-back channels
RE: Beam made of back-to-back channels
There is going to be a lot of time spent on your part to analyze this 2 channel configuration (possibly a lot of trial and error) and to determine how to reinforce it. Plus it's going to end up being a lot of material. Not to mention the amount of fabrication required. Quite honestly I doubt the channels will work without a lot of plate scabbed onto it.
Unless there is some specific reason for using the channels, other than the hooks, I would suggest staying with the W24 and using lifting lugs with hooks attached to lugs to achieve the lifting points. In fact, you could consider a smaller beam and weld vertical plates on either side to create a box. This will help with torsion.
RE: Beam made of back-to-back channels
We have switched to square and rectangular members for all lifting beams we design. The strength in both axes makes for an excellent member for resisting the primary bending from the applied load as well as resisting the commpressive forces of the rigging and the need to provide adquate strength ro resist buckling.
Coming up with a basic lifting lug detail out of plate can make a reproducible detail that can be cut in mass during fabrication.
We typically design for two lifting points on the top of the member and provide a continuous punched plate on the bottom with rigging points @ 24"o.c. for rigging and analyze accordingly.
Good luck!
Daniel
RE: Beam made of back-to-back channels
It was a client spec (the two C-channels). I've recommended we use a smaller beam and box it in, and add attachment points underneath for the hooks.
We'll see if they accept the modifications..
Thanks again.
RE: Beam made of back-to-back channels
It is a free publication to members and is only $10 or so (US) for non members. It is a pretty good read for design and analysis of beam members.
I know your specific discussion was about using the as specified case, but this is a good article to have around.
I have struggled for years with some of the "built up" bolted members we use in construction. I was hoping this thread would have some good simple answers. Much of the data I use with our back to back channel beams comes from testing to support various conservative assumptions.
The newest AISC Steel manual came with a companion cd with some back to back angle design examples that i have considered working through to try to resolve the test and performance data with the codified building related info, but have not found time for the exercise.
Best of luck with the client. And do pick up the article.
Daniel
RE: Beam made of back-to-back channels
RE: Beam made of back-to-back channels