First designed and constructed by French engineer Freyssinet in the middle 1930s, prestressed concrete poles are used today worldwide for flag poles, sign poles, telephone poles, telegraph poles, and poles that support street lights, electric power lines, antenna masts, and overhead power lines for electric trains. Compared with normally reinforced concrete poles, prestressed concrete poles offer several advantages: prestressed poles are lighter and stronger, and they require less reinforcing steel. The concrete is generally in compression, so cracking is unlikely. They have a smoother surface that is denser and less permeable. This lower permeability in combination with the absence of cracks prevents corrosion of reinforcement or prestressing wire.
A pole generally acts as a cantilevered structure, and should be designed and analyzed as a tapered member with combined axial and bending loads.
Prestressed concrete poles can be manufactured in specialized factories by spin-casting and heated curing, or the long line method. In spin-casting, a steel form is placed on a spinning machine, partially filled with a precalculated amount of concrete, then spun for several minutes. The tremendous centrifugal force created by the spinning consolidates the concrete by forcing it against the form. In the long line method, forms are placed end to end on a casting bed up to 400 feet long. Prestressing wires are threaded through holes in the bulkheads of the forms and pretensioned against abutments at each end of the line of forms. Several poles are thus pretensioned in one operation.