Need advice for solving a static freebody with torsion

[ddendy]

I am a young structural engineer trying to solve a static freebody with a torsion problem. I need help trying to figure out how to apply a solution method to solve for the torsion on an equipment rack. Basically I have a structure made up of steel tubing that is going to house various pieces of electronic equipment. I have solved for the overall reactions of the freebody but one of the reactions is at the top of the rack and is not located in the middle which causes unsymmetrical loading. I need to show that this torsion does not adversely affect the structure. Basically it is a rectangular box, 37 in. tall, with 4 reactions at the feet and one at the top. The one at the top is 3 in. off of center. The torsion examples I find address solid objects and not assemblies of components.
I would appreciate some ideas on how to simplify this problem and make it workable without making a career of the solution.

Thanks!

 

[dik]

The loads and stiffnesses appear to be symmetric... what, causes the torsion? minor imperfections?

Dik

 

[msquared48]

I think I see what he is talking about here. R5 is the reaction in question with components in the X and Z directions.

The component in the Z direction will not cause any torsion as the tube member only beams out the force between reactions R1 and R3.

The component in the X direction causes the torsional forces here which will have to be resisted by the torsional rigidity of the four corner tube columns as distributed to them by the top tube frame (in the XY plane).

Mike McCann
McCann Engineering

 

[ddendy]

msquared48 is right. R5 is 3 in. off center and I need to show that the top of the rack can resist the forces. The rack is made of 1 in. square tubes with 3 in. gussets in the corners. The entire assebly is welded. I was thinking I need to show that the gussets can take out the torsion. My first attempts at this have been cumbersome and I was hoping for a better suggestion.