Edge beam torsion

[Timbo9]

Hi there

I have a cold rolled floor fixing to a universal beam, the typical way we do this is to keep the cold rolled and UB top flanges at the same level and weld plates at 600 ctrs to accept the cold rolled floor panel. Please see the attached sketch.

Since the load is offset from the CL there will be a torsion but I can't make my mind up if the beam should be designed for torsion and considered unrestrained or if the cold rolled floor is sufficient to restrain the beam against torsion and lateral buckling so it can design it as fully restrained and torsion ignored.

Any thoughts would be appreciated.

Tim

 

[a2mfk]

Once the slab is placed and cured, you have full top flange and lateral/torsional bracing like any normal WF floor beam with a deck and slab. Maybe it should be braced during construction, or just shored?

 

[dik]

Is that a steel beam framing into the outside beam? Can you cope the flange to get it to attach to the web?

Dik

 

[WARose]

You will definitely have some torsion from condition 2. (Especially before the concrete hardens.)

One thing I don’t follow about either sketch is: is that subframing coming into the main girder? If so, than why not use a standard clip angle connection? It will minimize torsion, and does provide some torsional restraint for the girder.

If you are counting on the deck/slab to provide restraint after the concrete hardens, I would have some sort of physical connection between the two (i.e. puddle weld, studs, etc).

 

[Timbo9]

It is subframing but it comes to site as a completed panel with an end track, therefore I can't use clip angles or notch the cold rolled flanges.

I think my conclusion will be to make sure they fix the deck to the top flange with shot fired fixings and design the beam as fully restrained. For condition 2, I will either detail diagonal struts from the bottom flange back to the joists to control any possible rotation, or lift up the UB so the panel can fix below the flange direct to the web.

Thanks for your help

 

[hokie66]

As shown, that is a terrible detail. Bringing the joists in below the flange of the supporting beam is much better, as indicated in your last post. I would change the beam in "condition 1", so that it is deeper than the floor joists to allow connection to the web. Providing a slightly larger beam will prevent having to fabricate and weld all those strange seats.

 

[Timbo9]

hokie66 I agree it is a terrible detail. All changed now to allow connection to the direct to the web with bolts.

Thanks for your comments