# A Review and Future Directions on the Deterioration Evaluation of Concrete Utility Poles
## 5 Issues for Concrete Utility Pole Maintenance
### Issues for Applying Non-Destructive Testing Methods to Concrete Utility Poles  
Regarding the application of deterioration evaluation methods discussed in previous studies to the deterioration evaluation of concrete utility poles, vibration-based deterioration evaluation appears readily applicable [30; 31; 39; 48; 49; 50; 51; 52; 53; 54; 55; 56; 57; 58; 59; 60; 61; 62], as previous studies have demonstrated its effectiveness on concrete utility poles. Vibration-based deterioration evaluation has also been frequently employed to assess deterioration in existing concrete structures [84; 85; 86; 87]. [PERSON] et al. [84] showed that impact echo and impulse response are effective nondestructive testing methods for evaluating the deterioration of concrete bridges. [PERSON] et al. [85] proposed a structural reliability evaluation method for age-related deterioration using a rebound hammer and ultrasonic pulse. [PERSON] et al. [86] proposed a method for predicting the compressive strength of concrete by comparing non-destructive testing methods using the rebound hammer and ultrasonic pulse methods and applying machine learning to a destructive test of a concrete cylinder specimen and a test specimen. As described above, evaluation methods for the deterioration of concrete structures are widely used based on non-destructive testing results such as ultrasonic waves and vibration characteristics. Therefore, applying the above method of evaluating the degree of deterioration based on the results of nondestructive testing to evaluate concrete utility poles is also considered effective. Vibration-based deterioration evaluation methods using ultrasonic waves often identify localized damage [30; 48; 49; 50; 51; 52; 53; 54; 55; 56], such as cracks in the measured area or embedded portions. However, this approach may not be suitable for assessing the overall damage to structures. If the influence of localized damage on the deterioration or failure of utility poles can be clarified, it would be possible to narrow down the critical localized damage to focus on. Collapse cases of concrete utility poles reported in previous studies have shown that, excluding collapses caused by weak ground rather than the poles' failure, failure is often observed near the ground level where the bending moment is greatest [19; 20; 21]. Therefore, ultrasonic-based deterioration evaluation methods that focus on identifying changes in damage around ground level and tracking the progression of deterioration in concrete utility poles are considered feasible. Regarding deterioration evaluation using vibration properties [31; 57; 58; 59; 60; 61; 62], such as vibration modes and natural frequencies, this approach is deemed appropriate for evaluating the overall damage condition of structures, as it involves vibrating the entire utility pole. However, factors such as differences in pole length and reinforcement, attached components like transformers and electric wires, and the ground conditions where poles are installed are thought to significantly influence vibration properties. Although previous studies have focused on changes in natural frequencies under the same boundary conditions, they have not sufficiently addressed changes in initial values under those conditions. Therefore, future challenges in vibration-based deterioration evaluation of concrete utility poles include estimating the initial values of healthy indicators, such as natural frequencies. For deterioration evaluation based on failure probability [40; 41; 42; 43; 44; 64; 65; 66; 67; 68; 69; 70; 71; 72; 73; 74; 75; 76; 77], many studies on wooden utility poles have constructed models combining time-dependent deterioration due to corrosion with mechanical damage, as demonstrated by [PERSON] et al. [64]. For concrete utility poles, while studies have organized the relationship between failure probability and the design and manufacturing costs of utility poles based on Monte Carlo simulations [88; 89], no research aligned with the purpose of this study has been conducted.