Torsion on Structural Tee Shapes

[VaStruct]

Has anyone ever performed a combined torsional and bending analysis on a Structural Tee shape? The only reference that I have been able to locate is the AISC design guide 9 which has all of one paragraph regarding Structural Tees?

Thanks.

 

[racookpe1978]

T's are an asymetrical shape, and what parts of that shape that are resisting an axial rotational load are not very efficiently located to resist that load, so there has been limited reason to closely analyze that problem.

Probably going to have to break down an use an FEA program.

 

[Lion06]

I just want to say that a WF in torsion is bad enough. Don't cut it in half and subject it to torsion!

 

[BAretired]

The torsional stresses and rotations should be fairly straightforward. If you stay within the elastic range, bending stresses and deflections are not difficult to determine from elementary theory.

The difficult part is assessing lateral torsional buckling. If the flange is on top, it is good for positive moment regions and bad for negative moment regions because the web has virtually no resistance to lateral buckling.

Why use a T shape at all? Wouldn't a WF be more suitable?

BA

 

[ishvaaag]

You have also info on this in the spanish codes (both not standing by now) EA-95 and MV-103. Essentially adding effects of flexion and torsion; for the analysis normally a 3D able structural analysis program would be first made.

Then, torsion effects are quite sensible to end constraints so I myself if looking at my references (most books on structural steel have sections on torsion, and also those dealing with reinforced concrete shearwall nucleus dealing with taking wind forces) would be quite atent to what I was doing to avoid errors in something one makes not everyday. Probably would check against FEM.

Doing the analysis by FEM as racookpe1978 recommends, say, by steel plate elements, will produce sure certainty in both the placement of the loads and the quality of the restraints, so I think if only for that should be preferred by anyone of us that normally does not make this kind of calculation.

 

[VaStruct]

The structure is an existing monorail supporting a hoist and it has several 90 degree and S-curve portions of the rail that are intermittently supported. Thereby creating torional loads when the hoist is positioned between hanging supports. The Structural Tee is hung such that the stem is upwards and the flange of the Tee is what the hoist trolley rides along.

Further research has revealed that it is not a true Structural Tee but rather a proprietary product made by US Monorail (see attached).

 

[ishvaaag]

Still it is possible to approximate the behaviour in FEM. Model each side with component plates of their thickness and put rigid links at intersection points of plates for the fasteners, and see how the raik work. This for a program like RISA 3D, for example.

You can do even better with say Visual Nastran 4D, at least the extruded shapes could be made by sweep functions in autocad true to the rail; constraints not easy I assume to model yet some things can be made. And surely in Ansys and its likes you can get exact shape and constraints, only that there are lesser people proficient at these more complex programs.