Light Pole Design from Light Gage Steel

[JCWilson]

Problem:
A structural engineer in our firm has been charged with designing a pole to support a light over a parking deck. Complicating the design is the desire for this pole to be designed from 6"x2" 1/8" thick steel. The pole is to mount to the side of the building and extend 12' above the roof with the light fixture cantilevered approximately 3 feet over the roof. The pole is oriented such that the strong axis will take the direct cantilever of the light.

Question:
What types of codes would dictate the design criteria for a light pole? i.e. wind load application, allowable deflections, etc... We can't argue our structural issues and recommend product changes without some solid backup. "Upper management" just looks out the window at simple light poles mounted on 4 small bolts in the parking lot and can't understand our problem.

By conventional engineering principles for building design, our pole doesn't work at all - high wind loads cause excessive deflections and stresses. Not to mention the dynamic response of the pole to twisting in the wind, and the effect of handholes near the base of the pole that we haven't considered yet.

Please advise if anyone knows where to find more information on this type of design problem.

 

[wiktor]

Try the following publication: LTS-4-REV-1 - 2002 Interim to Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals, 4th Edition (), Member: $20, Non-Member: $24, from AASTHO.

 

[vmirat]

Since this is part of a building, I would say that your building code (UBC, BOCA, SBC) would govern. Table 16-H, line 7, of the 1997 UBC has a catagory that includes wind pressure coefficients for lightpoles. I think all you can do is advise 'upper management' of the engineering limitations and then get them to assume liability if they force the issue.