AS 1664.1 Aluminium Limit State Design, finding Rb/t

[alrighty93]

Hi
I am calculating the ultimate limit state of a aluminium section using AS1644.1 clause 3.4.13. I need to find Rb/t with Rb = mid-thickness radius of curvature of curved plate and tubular beam elements and t = thickness. Below is the section I need to calculate.

http://i39.tinypic.com/2mgw41w.jpg[/IMG]]
For this image, Rb/t = (175-1-1)/2.

However I need to calculate it for a section at a 45 degree angle (image below)

What now become Rb and t? Is Rb 126 or 48, is t 2 or 2.7.

Thanks in advanced

 

[hokie66]

Is this an actual extrusion or a proposed one? If it already exists, the best way to establish design capacity is to load test it. Looks like a louvre blade, and testing should be done before placing in service.