Add r_in argument for rectangular_hollow_section

[nelbs]

• I have searched the issues
  of this repo and believe that this is not a duplicate.
• I have searched the documentation and
  believe that my question is not already covered.

Feature Request

At the moment, the inner radius of a rectangular hollow section is calculated by subtracting the thickness (t) from the outer radius (r_out). This works well for cold-formed profiles, but it is not correrct for hot-rolled profiles; see the attached screenshot from the Dlubal website.

Therefore, I want to do a request for adding an (optional) argument for the inner radius r_in"

[github-actions]

Thanks for opening your first issue in sectionproperties 🙌 Pull requests are always welcome 😉

[robbievanleeuwen]

Hi @nelbs, thanks for raising this. I'll add this feature when I next get some time off :)

[nelbs]

Thanks!

[robbievanleeuwen]

@nelbs, had a bit of time tonight and this (should be) a simple change - do you want to checkout #493 and see if this works as expected?

[nelbs]

I tried it and it works as expected.