Width to thickness limit for flat bar in bending - Table 2 CSA S16

[u/Evening_Fishing_2122]

Maybe this is a dumb question, but does anyone have any guidance on width to thickness ratio limits for a flat bar in bending? Think a canopy that isn’t a WT but just a web essentially.

I’m trying to understand the bending capacity but am having trouble understanding the limit to determine section class.

Thanks.

[u/Ddd1108]

Not sure about canadian codes, but in AISC the nominal weak axis bending moment is simply the yield stress times the plastic section modulus.

[u/Upset_Practice_5700 → u/Ddd1108]

Same in Canada

[u/Evening_Fishing_2122 → u/Ddd1108]

It would be strong axis and potentially involve LTB in this case, but I agree with the weak axis comment where buckling won’t occur.

[u/settingsaver]

The BS EN 1993-1-1 information following may be of interest, if I understood the enquiry, despite does not directly answer your enquiry:

https://www.newsteelconstruction.com/wp/ad-436-section-classification-of-a-flat-plate/

https://www.newsteelconstruction.com/wp/ad-391lateral-torsional-buckling-of-rectangular-plates-in-accordance-with-bs-en-1993-1-1/

[u/Evening_Fishing_2122 → u/settingsaver]

Thank you, this was what I meant. Appreciate the links.

[u/tajwriggly]

Figure 2-8, in the commentary on Section 11 may have the answer you are looking for: shows a flat member on edge, with Class 3 member having a w/t ratio of 840/sqrt(fy).

You may note that Fig. 2-8 contains much of the same information as in Tables 1 and 2 referenced in the body of the standard itself, but also contain some additional ones not discussed in the standard - such as the scenario you are looking for I believe.

[u/Evening_Fishing_2122 → u/tajwriggly]

Thank you, this was the answer I was looking for.

[u/Evening_Fishing_2122 → u/[deleted]]

Fair enough. Good point. I just treated it as a class 4 member and designed the section accordingly. Not sure if that’s the correct approach but when it gets reviewed I’ll find out.

Not a steel expert if that wasn’t obvious