Light poles or lampposts are "engineered" structures, designed to support single or multiple luminaires. They may also be used to support signs, pennants, banners, flower pots and other decorative items. This guide covers the selection of light poles.
Function of light poles
The primary function is to resist the physical forces of luminaire weight, ice and wind loads that light poles may encounter during their expected design life. Along with the foundation system, the primary force a pole must withstand is from wind. Because of the variety of pole shapes and heights as well as the size and quantity of luminaires to be supported, including other items that may be attached to the pole, an engineering analysis must be done to ensure the customer will receive a pole adequate for the task.
The light pole must be capable of providing a long service life, require little maintenance and be aesthetically pleasing. Due to the possibility of unforeseen loadings and wind events, the light pole should also have an ample margin of structural capacity.
Factors affecting pole selection
The following factors should be considered when determining pole selection. It can be helpful to create a worksheet that lists all required data in order to finalize pole requirements.
- Mounting height (MH): Usually determined by the lighting survey, which will also include the number of poles, luminaire model number(s) and quantity of luminaires per pole.
- Luminaire selection: The type of luminaire model may be determined by the lighting survey or recommended by a lighting consultant. Note its EPA, weight, mounting method (side mount, top mount, floodlight brackets, etc.) and the distance from the centerline of the pole to the luminaire center.
- Brackets and arms: Brackets, when used, also have weight and EPA ratings and should be listed.
- Wind speed (in mph): It is critical that the proper wind speed be determined for the job site. Should the job site fall near or between two wind zones, the higher value should be used. A 50-year mean recurrence interval wind map is recommended. In special wind regions, local authorities should be consulted for the correct wind speed data. When a customer specifies or requests a wind speed requirement outside of the ASCE 7-93 (fastest mile) wind map, it should be noted as to the source of wind speed. Other wind maps have been produced by the ASCE, and it is important to know this in order to apply the correct wind force formulas and ensure that correct pole size can be selected.
- Terrain and special wind areas: Flat and open terrain may cause wind-induced pole vibrations that require special attention. In "special wind zones" such as mountain passes, where hills and local topography may create a funnel effect or other anomalies, it is advisable to contact local authorities for wind speed values.
- Pole material: The designer or owner may select the pole material. Common materials include steel, aluminum and fiberglass, with steel being the most common. Poles can also be made from concrete, cast-iron and wood.
- Pole shape and style: The most common shapes are round and square in cross-section. Poles may also be tapered. Some customers may request special designs such as ornamental and "nostalgia" period poles.
- Height above grade: This is the elevation distance from grade to pole base (e.g. locations on top of parking decks or on a bridge). The height above grade is important, since wind velocity increases with elevation. When poles are mounted above grade, please contact the factory for assistance.
- Environment: Consideration should be given to job sites near coastal areas (e.g. due to saltwater corrosion). Sewage treatment plants may also have corrosive conditions and may require special finishes and coatings for poles.
- Finish and color: Generally, the powder coat finishes used today are excellent for most environments due to their durability and color retention. Bronze is the most common, but many colors are available.
- Auxiliary lighting: Aside from general purpose area lighting, poles may also frequently be used for special task lighting applications such as building or sign illumination. These lights may be mounted at various locations on the pole. The EPA, quantity and MH of these lights should be recorded.
Have you already selected your light poles? Read this article on light pole installation.
Have questions about light pole selection, installation or maintenance? Contact the experts at Eaton's Lighting Division.