lrfd of steel monopoles
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.
i don't have the canadian or us standards, but have used the british standard, bs-5649
art 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