PSI - Issue 59

Leonid Lobanov et al. / Procedia Structural Integrity 59 (2024) 43–49 Leonid Lobanov et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Table 1 gives the distribution of some detected defects, depending on the tower structure elements, based on visual inspection results.

Table 1. Total number of damaged tower structure elements from some detected defect types without allowing for cracks and their distribution. Structure element Nо N К К1 D D1 D2 D3 D4 D5 D6 D7 Leg А 91 42 0.46 3.21 135 80 19 20 10 2 2 2 Leg B 91 5 0.05 1.40 7 3 1 3 0 0 0 0 Leg C 91 17 0.19 1.65 28 9 1 18 0 0 0 0 Leg D 91 30 0.33 1.80 54 18 1 34 1 0 0 0 Drum 246 58 0.24 2.35 136 54 5 33 5 0 34 5+ 72.7+ mark 32 6 0.19 1.83 11 4 3 0 0 0 4 0 Stripes and octagons 32 13 0.41 2.15 28 18 9 0 0 0 0 1 Elevator shaft 38 18 0.47 4.00 72 52 3 15 0 0 2 0 Total 720- 189- - - 471 238 42 123 16 2 42 8

Note: N о - the total number of examined structural elements, N - the total number of damaged elements, K=N/No. K1=D/N. Types of defects: D - the total number of detected defects in structural elements. D1 - the total number of detected damages of one wall of the pipe all the way through in the structural elements. D2 – the total amount of damage to the two walls of the pipe through and through (lumbago). D3 – the total number of detected dents in structural elements. D4 - the total number of unrecognizable defects (defect or corrosion in the node) D5 - the total number of deformed elements. D6 - defects with partial damage to one "crater" wall (partially determined), D7 - the total number of destroyed structural elements. Moreover, the reliability of defect detection using UAV was determined depending on the defect type and its geometrical dimensions, and factors which influenced their assessment were taken into account. In order to determine the geometrical characteristics of the defects, a 3D model of the Kyiv TV tower was constructed using 3DF Zephyr software. This software contains the main photogrammetric algorithms for the determination of camera parameters, establishing their spatial position and calculation of 3D coordinates of points in each image. The method of photogrammetry was used in the work to create a 3D model. Photogrammetry can be defined as “ science of measurement on photographs ” . In order to determine the distance or area, the main task is obtaining the coordinates of the object and any point on the photograph, which can then be used to calculate the geometrical data or create a drawing of a 3D model of the objects. At present practical application of photogrammetry is highly relevant, which is described in many contemporary publications, by Linder (2006) and Rodríguez Quesada (2014). The process of construction of a 3D model of the TV tower is complicated and labour-consuming, primarily because of its real dimensions. Therefore, a methodology of model construction in successive stages was developed, namely of each support leg separately, with their further connection, which led to a significant shortening of computation time. Moreover, all the available software options were analyzed, and it was determined that the Vertical structure, by explained 3Dflow (2023), is the optimal one for the construction of the model of the Kyiv TV tower. Such an approach allowed solving the posed tasks. A base from 2351 photographs was used to construct the model, and 1292 photographs were included in the final result (Fig. 4). A 3D model of the TV tower helped detecting and identifying the defective areas. It was noted that significant complications arose during the assessment of damage to the surface anticorrosion protection and of partial penetration of fragments, as they practically do not differ from each other. In order to separate these defects, it became necessary to mount additional filters and use approximations for analysis. Defect dimensions were determined using «Measures» tool of 3DF Zephyr software. In this case , its diameter is 2.2 cm (Fig. 5).