Structural Analysis of Solar Array Systems 2

[Mustafinho]

I am a recent grad and I just landed a job with a company that doesn't have an engineering department. I am required to do some preliminary engineering analysis for some custom/extruded shapes of steel and/or aluminum. Simply put, I want to determine the unsupported span for the shapes.

I have been toying with RISA 3D and Virtual Analysis but it appears that code checks won't show up in the results. I have used ShapeBuilder to get the shape properties but when I import that in analysis it won't work.

Is there a way to perform preliminary analysis using a standard shape that is similar to the custom shape's properties? Any hints or tricks would be greatly appreciated.

Thank you in advance for your responses.

 

[JoshPlumSE]

For the most part, you're not going to see programs give you code checks on custom extruded shapes. I know there is a program for custom cold formed sections (CFS), so that might be an option for you. But, it doesn't analyze the structure. Only the cross section.

I don't know of anything like that for aluminum. It may exist, but I don't know of it.

Others may have more sage advice. But, my recommendation would be to do two things:
1) Use the closest section you can make out of the more standard shapes that the program has available in it.
2) Pull open some tables from manufacturers for similar shapes.

Validate the two methods against each other. And, when all else fails, use Excel or MathCAD to start in on some manual calculations.

 

[Lomarandil]

As I recall, RISA won't perform code checks for custom shapes -- presumably because without knowing the type of shape, it can't determine what limit states and code provisions may apply.

Of course, you can always output stress-based results (if the shape is defined with the full data, not just as a section set) and compare that fairly easily to an allowable-stress based limit state.

 

[Mustafinho]

Thank you Josh and Lomarandil.

@JoshPlum, I will certainly do that. It appears that I would have to do some manual calculations. I have never used MathCAD or Excel for that purpose. Any starting tips?

@lomarandil, would it be possible to elaborate on your second point a little bit. Excuse my lack of experience with structural analysis.

Thank you.

 

[structSU10]

To what lomarandil is saying, you can run the analysis in RISA to find the forces on the section. Within Shapebuilder, you can apply forces to a section to see the stresses. If you can figure out what your allowable stresses are, you can compare it to the stress from shapebuilder to see if the shape is adequate. If you have to do a lot of this in the future though, you would want a hand calculation that give you the allowable axial load, moment, and shear so you can use the appropriate interaction equations to find the capacity.

 

[BUGGAR]

In addition, check the elements in you section for b/t, h/t and all the other ratios noted in the Aluminum De$ign Manual. From these ratios, you can get the allowable stress limits for your section based on its non linear (buckling) properties.

 

[Lomarandil]

StructSU10 is correct, although RISA also has the capability to output stresses directly if it knows the distance from the centroid to the extreme tip of the shape in each direction (rather than parsing that through Shapebuilder).