attaching to edge of flange of w-beam

Question

attaching to edge of flange of w-beam

weron4u (Structural)

(OP)

14 Jul 03 10:45

I have an equipment removal beam that is used for lifting a motor. The beam was put in place in the 50's and was not rated.  My question lies in the connection to its support.  The lift beam is a [W10 X 22] and is supported by two steel rods that are welded to the top of the beam, directly above the web.  However, these steel rods run vertically 10 ft and are welded to the flange of a [W24 X 84].  The problem lies in how they are connected to the [W24 X 84] beam.  The rods are welded to the very edge of the flange, creating a cantilever-like connection to the flange as shown below.

               _______
                    |
                    |
               _______
               |
               |
               |
               |
               |
              ___
                |
              ___

Does anyone know how to calculate the resulting stress created in the flange of the [W24 X 84].

burtonli (Civil/Environmental) · Answer 1 · 2003-07-14 11:55:11

you need to calculate the torsion stress.
A better way is to use a box beam or connect a beam on the other side of the web.
               _______
                   |    beam
                   |------------
               _______
               |
               |
               |
               |
               |
              ___
                |
              ___

weron4u (Structural) · Answer 2 · 2003-07-14 12:20:48

I left something out of my question. I forgot to mention that this beam is highly unaccessable. I will not be able to add anything to it. I know that the beam will not fail due to torsion, but I dont know if the flange will fail due to bending. Is there any calculation that is very conservative for this type of loading.?

burtonli (Civil/Environmental) · Answer 3 · 2003-07-25 16:55:14

you only need a stiff. at the connection place.

Ron (Structural) · Answer 4 · 2003-07-30 20:32:03

The primary torsion occurs on the bottom flange of the beam. As it deflects in bending, the bottom flange is placed in tension. The torsion, assuming not extremely high, coupled with the tension in the bottom flange is not a big deal. If the torsion occurred in compressive mode, I would be more concerned.

I would be concerned about the small amount of weld holding the rods to the flanges. If the device gets used routinely and the weld stress at that point is greater than about 5000 psi, I would be concerned about fatigue of the welded connection. You should check that.

weron4u (Structural) · Answer 5 · 2003-07-31 09:28:14

Thanks Ron,
The beam was used in the 50's to lift a motor onto a skid, and may never again be used, but needs to be rated anyway. I appreciate the help.

trainguy (Structural) · Answer 6 · 2003-07-31 12:53:00

What about local bending stress on the bottom flange coupled with global bending (tensile) stresses? This must also be checked.

This might be alright, but I would definitely check it.

The torsion thing still irks me. Ask yourself: where is the concentrated torsional moment getting transferred? I'm having trouble imagining a free-body diagram for this beam (W24) in static equilibrium.

But that should be the first step...

Anyone?

dicksewerrat (Civil/Environmental) · Answer 7 · 2004-09-19 20:13:04

If you don't see it being used again, get amanlift and afork lift and cut it down.

Come Join Us!

Posting Guidelines

attaching to edge of flange of w-beam