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RE: Large pipe column

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>Rich Lewis wrote:

>Is there a separate standard for the design of large round

>pipe columns for billboard signs?  Would the AISC code

>apply to an 8ft. diameter column?  Or does the design

>standards need to be different for that size section since

>the thickness of the wall would be rather thin compared

>to the diameter?


The AISC Specification is not written explicitly for every application involving steel, but may be useful to you anyway. Section A1 of the 2005 AISC Specification recognizes its applicability to “other structures”, which means those with systems and elements that behave like the systems and elements in buildings. I can envision a sign support that behaves very much like a cantilevered column would in a building, but the applicability of the following to the specific case you have is for your engineering judgment.


In a large diameter pipe, elastic local buckling is likely to control the design (that is, the wall will likely be slender). I’ll assume so in this answer. You can check the slenderness in Table B4.1. If it winds up being noncompact, the section and equations references will change slightly.


For compression the design is based upon QFy, where Q accounts for the slenderness of the wall. See Section E7 of the 2005 AISC Specification. For flexure, the critical stress will be controlled by Equation F8-4 (which is a function of the D/t ratio). For shear, Section G6 also accounts for D/t and its effect on shear strength. Interaction is then handled through Chapter H (H1 or H2, if shear does not need to be considered concurrently, H3.2 if it does require concurrent consideration).


Alternatively, I think AASHTO has a specification for sign structures that may be helpful.