PSI - Issue 17

Pavel Steinbauer et al. / Procedia Structural Integrity 17 (2019) 799–805 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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But it has been shown that some poles are deteriorated well before this period (Fig. 1) while the other poles are in perfect state after 50 years of operation.

2. Motivation

There are already many non-destructive methods to determine actual state of construction, e.g. based on eddy currents, ultrasound, roentgen, static loading, frequency response functions (FRF) etc. Two categories of measurement methods can be distinguished.

Fig. 1. Typical extensive erosive damage of the pole, covered by painting

Many NDT methods measure properties of the construction (eddy currents, ultrasound etc.) at specific point only. It is therefore necessary to either investigate whole structure step-by-step or at least have previously determined critical points for regular measurement. In case of lighting poles, the most dangerous are pole heel area (both above and under the ground) and pole boom which is usually several meters above the ground. So, the measurement itself require special equipment, highly skilled worker and ability to correctly process tremendous amounts of output data (including proper linkage to the geometrical position of measured point). The static pole deflection and FRF measurement are global methods. The local changes or deterioration of the structure health are detected by one measurement or only few measured quantities. For example, commercially available Roch Test method (Roch Services GmbH, (2019)) is based on pole compliance measurement by sophisticated device, which regularly travels around pole set, loads the pole by hydraulic actuator and measures pole deflection. Such approach can estimate pole state, but it is time consuming, must be also performed by skilled worker, require installation of special and very expensive equipment, access to the pole and often provide local information only (related to the position of measurement). The experimental modal analyses (EMA) or frequency response function measurement (FRF) should reveal the change of the construction state in determined modal parameters (Salawu, O. S. (1997), Adams, R. D., Cawley, P., Pye, C. J., & Stone, B. J. (1978), Wang, Z., Lin, R. M., & Lim, M. K. (1997)) due to change of mechanical properties. However, the EMA method requires accurate measurement. It means both expensive equipment, highly skilled and trained worker for measurement and subsequent data evaluation. It is also very time demanding and access to the structure must be granted. The source of excitation force must be placed to more flexible parts of the construction, in case of the pole it means to higher, less accessible parts of the pole. So it is feasible to use these methods for large, expensive and exposed constructions and machines, not for relatively inexpensive lighting poles. Although their stability and safety is of great public interest. On the other hand, basic measurement means (MEMS transducers, AD converters, data storage and transfer) are currently getting very cheap. Huge computational power is available on demand within cloud based services and in