Flagpole supports 1

[ACtrafficengr]

A state legilature wants us to place a flagpole in the center of a roundabout. Since it will be in an intersection, we are considering giving it a breakaway base.

Could we bolt a flagpole to a standard light pole frangible base? How much wind load moment can they take? If not, does anyone have any other ideas?

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[engrbon]

Compute the wind forces based on the codes being used in your region. (You can use ASCE 7-05 as a reference)

Calculate the overturning moment and start your design.

Earthquake forces must also be considered in places of high seismic activity.

 

[rb1957]

is the flag pole significantly taller than a standard light pole ?

 

[ACtrafficengr]

@ rb1957: Probably not. We want to keep it low enough to use the existing street lights to illuminate it, rather than having to raise and lower the flag every day. I suspect a flag may have more drag than a luminaire, though.

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[graybeach]

The National Association of Architectural Metal Manufacturers (NAAMM) published a metal flagpole manual and guide specifications which cover how to calculate the wind force on a flag.

 

[JedClampett]

I'm not sure how tall this flagpole is or how big the roundabout is, but is it a good idea to make a flagpole in this situation break away? If it gets hit, it might fall on another vehicle, multiplying the hazard. This is different than a sign or light pole off-road, where the debris is likely to be out of traffic.
Maybe you can get the state legislator to seal the design.

 

[slickdeals]

I am with Jed on this one. I think you may be better off designing the flag pole to sit on a pedestal (say 4' high) and design the pedestal and foundation to resist a vehicular impact. I don't know what the requirements for such an impact would be? A vehicle traveling 40 mph head-on?

 

[slomobile]

Jed & Slick bring forward good points. Maybe also consider some strategically placed bollards in the landscaped area of the median to prevent impact with the actual flagpole if raising the pedestal is not possible. Between a curb and a bollard someone would have to be determined to plow through a flagpole on a roundabout.

 

[JStephen]

I just ran across this video on youtube, and it reminded me of this post:

http://www.youtube.com/watch?v=iBtwFdi901c