BTH-1 2014 Allowable Stresses for bending

[SteveGregory]

This would apply particularly for spreader beams. Is the allowable bending stress in Section 3-2.3 based on using the plastic section modulus or the elastic section modulus?

The text only refers to these two properties, Sx and Zx in terms of the unbraced length. In my case, there is a tube section being bent in the weak axis. If I were using AISC 360-10, it would be Eq F7-1 with the plastic section modulus Z.

However, the ASME BTH-1 2014 equations look more like the ASD 9th Ed. We used the elastic section modulus for these allowable stresses.

 

[dik]

I would likely use the elastic section modulus... although you can have post elastic buckling, it's not common and with stability I tend to be a little conservative... same approach to columns...

Dik

 

[r13]

Second dik's response. Also, whenever I see the word "allowable", I would link it to ASD but LRFD, which more often use the word "strength" instead.