Half a century of reinforced concrete electric poles maintenance: inspection,field-testing,and performance assessment

Application of reinforced concrete (RC) poles as overhead electrical transmission line supports has become of great interest during recent years worldwide. The higher strength, longer life, and the potential to span longer distances than steel poles are the key reasons behind this tendency. A great variety of architectural shapes, relatively low maintenance costs, and high electrical resistance make RC a prominent alternative to steel. The drawbacks related to the application of RC poles include the high self-weight and vulnerability to damage. Self-weight might be reduced by prestressing the reinforcement and/or forming a tubular structure for the poles. However, both of these options might increase the vulnerability of the supports. Moreover, long-term processes (deterioration of concrete and corrosion of steel reinforcement) complicate the prediction of structural properties. This paper presents results of the everlasting inspection of the overhead electric power distribution system in Lithuania: technical state of more than 500 RC supports was assessed; selected poles were tested until failure. A specific point of this research is that most of the inspected supports were under maintenance since the middle of last century. The inspection results were used for developing the technical condition of RC pole evaluation scale proposed in this paper.