# A Review and Future Directions on the Deterioration Evaluation of Concrete Utility Poles
## 2 Existing Standards of Japanese Concrete Utility Poles  
This section summarizes the background surrounding the maintenance of Japanese concrete utility poles. The utility pole standards are organized according to various regulations in each country [6; 7; 8; 9; 10; 11; 12]. These regulations are based on the International Electrotechnical Commission (IEC), a globally recognized authority responsible for creating international standards across all fields of electrical engineering. While the specific standards may differ, the underlying principles are generally similar. Regarding the strength design of utility poles, IEC-60826 specifies that wind loads are to be determined based on the average design wind speed over 10 min at a height of 10 m, as well as snow loads, which are adapted to the environmental conditions of each country. In Japan, the 10 min average design wind speed is set at 40 m/s, and in regions where snow loads occur, adjustment coefficients are considered during the design process [6]. It is worth noting that while these standards comprehensively address product quality and strength design of utility poles, they do not sufficiently cover inspection and maintenance.  
The structure of the Japanese concrete utility poles under this study is illustrated in the figure. As shown in Figure 1, the structural type is a prestressed concrete (PC) structure, and the external shape is that of a tapered pole with a cross-section that decreases from the base (root) to the top (tip). The arrangement of the steel reinforcement includes both tensioned and non-tensioned materials of varying lengths, which are placed circumferentially along the same circle as the main reinforcing bars. One distinctive feature of the manufacturing process is that the poles are produced with a hollow cross-section due to centrifugal casting for concrete placement. The concrete used is densified by the centrifugal effect, which removes water accumulated in the center, resulting in a highly dense state and generally higher strength.  
Regarding the maintenance of concrete utility poles, preventive maintenance efforts for utility poles are conducted through regular inspections. However, the deterioration assessment methods involve visual inspection, focusing on vertical and horizontal cracks, surface roughness, cross-sectional damage, and rebar corrosion. These are categorized into \"deterioration levels\" defined for each \"type of deterioration\" and are evaluated while taking into account \"surrounding environmental factors\" such as salt damage and frost damage [13].  
\begin{table}
\begin{tabular}{c c c} \hline
**Country** & **Total Electric Line Length (km)** & **Undergrounding Rate (\%)** \\ \hline Japan & 1,765,457 & 0.3 \\ \hline Germany & 1,152,138 & 87.5 \\ \hline Italy & 762,616 & 33.1 \\ \hline France & 685,413 & 38.9 \\ \hline United Kingdom & 408,875 & 82.6 \\ \hline Spain & 383,202 & 36.9 \\ \hline Sweden & 306,019 & 77.2 \\ \hline Finland & 237,966 & 37.5 \\ \hline Greece & 121,409 & 11.2 \\ \hline Belgium & 120,643 & 56.8 \\ \hline Denmark & 96,093 & 95.9 \\ \hline Ireland & 69,200 & 17.5 \\ \hline \end{tabular}
\end{table}
Table 2: Comparison of total electric length [3].  
Currently, there is no well-established quantitative evaluation method focusing on the dynamic performance, such as the remaining load capacity of utility poles, nor is there a comprehensive evaluation system using non-destructive testing equipment beyond visual inspections.