Flag pole design

[engr567]

I need to design a flag pole (wind pressure of 20 psf, 5" dia pipe, 21' tall). How do I proceed? What are the design steps? I would appreciate your help.

 

[StructTaco]

There are embedded pole equations in the IBC for Flagpole foundations. If you have a slab at the ground level it is considered constrained, if not, use the unconstrained equation, equations 18-1, 18-2 and 18-3 in Chapter 18. The pole itself is a cantilever, M=wl^2 / 2, check against allowable stresses for steel...

 

[engr567]

StructTaco, per equation 18-1, P is applied lateral force in pounds. How do I calculate P? Also, please note that I have a cloth flag (4'x4') at the top of the pole. Is this P the resultant of lateral forces on flag (if we need to consider it) and on pole itself because of its diameter (5" diameter in this case)?

 

[nutte]

You need the NAAMM Flagpole Manual, and Guide Specifications For Design of Metal Flagpoles, which cover this exact thing, including wind effects from the flag.

http://www.naamm.org/items.aspx

 

[BAretired]

Vortex shedding is a feature which ought to be investigated. It can cause severe oscillations on a cylindrical object exposed to wind.

http://en.wikipedia.org/wiki/Vortex_shedding

http://folk.ntnu.no/nilsol/cases/cylinder/

BA