Point load on bottom flange

[Navid.Nik]

There is structure in which they are going to use it as a training for professional climbers. The structure is a cold-formed mezzanine with C sections. They are going to connect their clamps to the bottom flange of the C-sections. The point load is about 6 kN which can be carried by the sections, but I am concerned about the local failure modes and buckling of the section. Could anyone guide me that which checks I should do on the bottom flange and the section? Is there any sample calculation for the calculation?

 

[KootK]

1) I think that you're concern is valid. I doubt that anybody's life is in danger but, if the thing gets all spongy and beat up, you'll surely hear about it.

2) Checks that I see as important:

a) Fastener pull through / punching shear / etc.

b) Flexure on an effective width where the bottom flange meets the web.

3) Some things that I'd like to see if they were possible:

a) Some bridging to the neighboring joists at or near the connections.

b) A connection directly to the web rather than the flange.

c) A bridging element underneath the joists that gets connected to the webs of the joists. Your hardware attached to that thing.

d) If this were new construction, I'd be compelled to use pairs of C-sections back to back and a connection that runs up the middle to the top flanges.

 

[jayrod12]

Someone posted a detail recently that had an angle strapped to the bottom of cold formed C sections with connection tabs that went up the side of the C-section web. It was a slick detail and looked a fair bit more robust than others.

 

[dik]

and closer to the shear centre.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[jayrod12]

Found it in here
thread507-486324

 

[Kuhladula]

The Metal Buildings Systems Manual has some information on this. You should be able to find the 2012 or 2018 editions with a quick internet search. Reference Appendix A6 - Hanging Loads on Purlins for a couple of possible details and tips on what to do or not to do. Attached is one of the recommended details.

 

[rb1957]

how thick ? how wide (the flange) ?

what is the loadpath from the load to the reaction (the web) ... bending of the flange.

what load ? 1 "guy" ... 200 lbs ? with some dynamic load factor ... 400 lbs ?

1/8" thick steel ... should be plenty for strength. stiffness may be an issue.

if there are dedicated points where the load is applied then "bath-tub" fitting (to reinforce the flange) and create a direct bending loadpath into the web would be great to add (and easy enough, and allow lighter beam, 1/16" thk).

another day in paradise, or is paradise one day closer ?

 

[Navid.Nik]

@Kootk, thank you very much for your detailed explanations, it helps me a lot.
@jayrod12 and Kuhladula, thank you for the details, they gave me some insights.
@dik, sure that's a good idea to prevent torsion
@rb1957 the thickness is 3 mm with 85 mm width. The static load from a hanging person is 1 kN, but the load will be 6 kN when they fall down and the rope hold them by the emergency break. Yes, indeed, having an extra element can help there.

I think the best is to have a double section to apply the load in the centre and transfer it to the web to avoid any damage on the flange.

Thank you very much everyone for your help.

 

[human909]

I am a recreational climber. As a climber our margins of safety and comfort are alot narrower that what we deal with in the structural engineering world. However what you describe is something I would be quite concerned about as a climber let alone as a structural engineer.

 

[Ron247]

I doubt you will find a cold-formed C that can support that much weight through the flange. Better go for attaching to web. Even then, there is torque.

 

[rb1957]

isn't that what he's saying ... "to have a double section to apply the load in the centre and transfer it to the web to avoid any damage on the flange" ?

One thing, that I think the climber will feel, is the torsion (on the C-channel from the load to the supports) which isn't helped by adding a fitting to reinforce the flange

another day in paradise, or is paradise one day closer ?