How to model perforated cold formed rack column and horizontal beams

[JoeH78]

DEar ALL,

I'd like to know how can I model accurately with software a perforated column and horizontal beams made up from cold formed steel, I already have an idea in my mind how to start and model itt but I'd like to hear also from colleagues how would be their approach to solve such problem.

Since I tested to modrl the whole perforated column as shell or solid which has holes in it, is great workload on computer which was not accurately modeled in software. So I decided to calculate hole areas proporitonally to column surface and in such way I'll apply the section overwrites to reduce the sectional area and bending stiffness ( especially that bending and shear part is tricky). Bending and shear reduction is not totally conceivable to my mind but since I have no better idea I belive that I'll stick to it.

I definitely will appreciate guidance of those who have done such calculation in the past, especially with drive-in and back to back racks.

Regards,

 

[driftLimiter]

I would definitely try to find equivalent section properties for simple beam/column elements and model it that way. Then take the forces and do a section strength check elsewhere I wouldn't trust any (FEA) software design results on such sections.

 

[JoeH78]

I wouldn't trust any software design results on such sections.

Say that I have %2 hole on surface area of section calculated, if I take conservative reduction percentage for bending, shear area etc. such as %5~7 even say %10, wouldn't convince you that I'm on safe side?

 

[driftLimiter]

No. 1, you can calculate the actual section properties at the reduced locations, and 2. this doesn't address any potential instabilities due to perforations.

 

[SWComposites]

Using area out calcs can work well for stiffness. Will not likely work well for strength.

 

[dvd]

There is information in the perforator's handbook that you may find helpful -

 

[centondollar]

Then take the forces and do a section strength check elsewhere I wouldn't trust any (FEA) software design results on such sections.

Most software doesn't have beam elements with warping degrees of freedom, and a beam model cannot capture local buckling, which is the main challenge of CFS sections. If the material is steel and sufficiently dense shell mesh is used, the shell model FE result and design based on that (linear buckling, non-linear buckling and von Mises stress) will be as accurate or more accurate than code formulas.

For many designs, this may not matter, but for anything beyond scope of code equations - particularly box and plate girders with odd proportions -, the FE result is usually the only results available.