LRFD of Steel Monopoles

[VoyageofDiscovery]

I am looking for imperial local buckling limits for various multi-sided steel monopoles designed to LRFD. I have seen these for ASD in AASHTO Commentary and for LSD (Limit State Design) in the Canadian Standard CSA S37-01. The S37-01 has these limits for metric units, however these limits cannot be converted to imperial. I want to stick with imperial.

 

[RHK]

I don't have the Canadian or US Standards, but have used the British Standard, BS-5649art 7:1985 "Lighting Columns". This has the cross-section fully effective for plastic moment capacity up to D/t=40 for circles and polygons in 350MPa/23tsi/50ksi steel. The effective cross-section is about 80% of the total for D/t=80, again for circles and polygons. At D/t=120, circles and 10 or more sided polygons are about 70% effective, and octagons 60%.

Plastic section modulus is 4.0.R^2.t for circles, and 4.32.R^2.t for octagons, where R is mean radius for circle, and mean "inner" radius for octagon. For 10 and 12 sided figures the factor is somewhere between 4.0 and 4.32.

Hope this helps. Russell Keays