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Design Considerations

Wind Considerations


50-Year Wind Map
Wind Forces
Wind tunnel testing is one of the most reliable methods of determining wind forces for use in designing structures exposed to natural winds. HAPCO has conducted wind tunnel tests on some luminaries and traffic signals and on sections of various round and elliptical tubes. Several other manufacturers have also tested luminaries in wind tunnels. Wind tunnel test data is also available on other objects of similar shape to lighting equipment. These data are used whenever possible in calculating wind loads on HAPCO structures. EPA ratings of luminaries are based on wind tunnel test data.

Wind Velocity Section

A copy of the 50 Year Wind Map produced by the Environmental Data Service (National Oceanic and Atmospheric Administration, U.S. Department of Commerce) is linked to below. This wind map should be used to determine wind velocity for your specific location. If you are located between two different isotach lines, the higher velocity should be used. HAPCO uses 80 mph as the minimum design velocity although lower velocities are shown on the map. We feel that the use of 80 mph minimum design velocity provides us with some additional control over the strength and stiffness of the poles as well as helping to protect against isolated high wind areas not shown on the map.

A gust factor of 1.3 is applied to the isotach wind velocity to account for gusts in calculating design wind forces. For example, 104 mph gust velocity is used to calculate wind forces to 80 mph isotach.

HAPCO has learned from years of experience that there are many local isolated high wind conditions not reflected by the wind map. These local isolated high wind conditions can be devastating to poles and luminaries not designed for such conditions. Also, constant winds in the 10-25 mph range can severely damage certain poles and luminaries by vibration. Please advise HAPCO of any unusual wind conditions peculiar to your location prior to purchase of poles. Heavier poles and/or vibration dampers may be necessary to avoid wind damage at your location.

Click the link below to download a printable PDF version of our 50-Year Wind Map.

Download PDF file »

Application Recommendations

Transformer Base
The transformer base is a one-piece casting of aluminum alloy 356-T6 with hinged or removable access door, held in place with a stainless steel screw. The access door opening is 13" high, 8 3/4" wide at the top, and 9 1/4" wide at the bottom. The base is designed to be attached to 1" anchor bolts located on 15" diameter bolt circle for the 20" high base and on a 22" diameter bolt circle for the 24" high base.

Four 1" diameter x 3 3/4" long galvanized steel hex-head machine bolts with nuts and washers shall be supplied to attach the transformer base to the base flange of the pole shaft. Eight trapezoidal aluminum washers shall be provided to properly distribute the bolt forces in the top and bottom flanges.

EPA Ratings

Effective Projected Area
Throughout this web site will be found maximum effective projected area ratings for lighting equipment to be supported by each of the poles and bracket arms listed. Effective Projected Area (EPA) of a luminaries is its actual projected area times its coefficient of drag. Most luminaries manufacturers list EPA ratings of their fixtures in their catalog. The EPA of floodlight cross arms such as the "63" Series, and any other such equipment used, must be added to the luminaries EPA to determine the total EPA capacity of the pole.

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