material selection for a short monopole 1

[aeroo]

Hi, I am designing a 12" diameter steel monopole support that will support an LCD Display array 6m[19.7ft] x 2m[6.6ft] x 1m[3ft] from the ground. The display with framing and paneling is around 1600kg [3500lb] with some overturning moment. I normally design these systems to be installed in Europe and this one will be installed in the US and I was asked to specify a US grade material. Since the amount of material is so small, cost is not an issue. I will be welding a 500mm diameter baseplate to the bottom with stiffeners so the material must be easy to weld. It will remain indoors so corrosion isn't an issue. Yield strength would need to be above 400MPa. Basically, what is the best high strength, large diameter, commonly available steel pipe I could use if I don't care about saving a few bucks fabricating a one-off? I've looked into what Valmont uses for high strength applications which is A572 Grade 65. I've looked into 4140 but I'm not sure about the welding the baseplate + stiffeners. Any other US standards or material grades I should look at for this application? Thanks in advance!

 

[JStephen]

For structural applications, ASTM A500 is typically used. If it's a small quantity, it'd probably be easier to increase size or wall thickness than grade.

 

[BUGGAR]

Valmont folds their monotubes from plate so they typically use the A572 spec. There is a new spec, ASTM A1085 that covers HSS in your range. But the cost of this spec from A$TM is probably more than the cost of the steel you need.