Citation: Iwaniec, J.; Iwaniec, M.; Kurowski, P.; Szopa, K. Investigation into Power Line Supporting Structure Dynamic Properties by Means of Impulse Test. Energies 2022, 15, 5707. https://doi.org/10.3390/en15155707 Academic Editor: Djaffar Ould-Abdeslam Received: 21 June 2022 Accepted: 3 August 2022 Published: 5 August 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). energies Article Investigation into Power Line Supporting Structure Dynamic Properties by Means of Impulse Test Joanna Iwaniec 1, * , Marek Iwaniec 2 , Piotr Kurowski 1 and Krystian Szopa 3 1 Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Mickiewicz Alley 30, 30-059 Krakow, Poland 2 Department of Biocybernetics and Biomedical Engineering, Faculty of Electrical Engineering, Automatics, Computer Science and Biomedical Engineering, AGH University of Science and Technology, Mickiewicz Alley 30, 30-059 Krakow, Poland 3 Department of Power Systems and Environmental Protection Facilities, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Mickiewicz Alley 30, 30-059 Krakow, Poland * Correspondence: jiwaniec@agh.edu.pl Abstract: Dynamic analysis of a large, full-scale construction requires proper excitation in order to induce vibrations that can be measured and further processed. The amount of delivered energy over the frequency band must be sufficient to excite all the mode shapes in the studied range. The paper concerns the pseudo-impulse pull-and-release method that allows to determine frequency response functions of a large, lightly damped structure and estimate its modal parameters. The main advantage of the developed method is the great independence of the repetitiveness of the experiment’s operational parameters. The output time histories from subsequent partial experiments are accurately synchronised and normalised without measuring the signal of input excitation. The research conducted for the full-scale transmission tower results in modal parameters, estimated by classical and pseudo-impulse methods. The applied pseudo-impulse improves the conditioning of the excitation and results in the better readability of stabilisation diagrams as well as in a better stabilisation of the poles that are not clearly represented in the input data. The proposed method allows for the visualisation of poles which are non-detectable in cases of classical analysis. Keywords: over-stiffened truss structures of complex geometry; modal analysis; technical diagnostics; impulse test; supporting structure 1. Introduction Truss systems are frequently used in civil engineering in the construction of bridges, towers, chimneys, power pylons or other supporting structures. Continuous technical development provides tools for ever-better structure optimisation in terms of maximizing strength while reducing weight and costs of construction and exploitation [1]. Assessment of the technical state of such structures is one of the most important ways to ensure structural integrity, security and to avoid major financial losses caused by failures [2]. Among the most popular and responsible engineering structures, the power line supporting structures deserve special attention since power line breakdowns have serious technical and financial consequences [3,4]. Due to a lack of knowledge regarding the weakest link (the particular pole), usually the renovation is carried out for the whole line. Moreover, weakening of the load capacity of a single supporting structure (e.g., due to incorrect welds, loose screw connections, too shallow foundations, poorly recognised type of soil) affects the reliability of the entire line, which consists of hundreds or even thousands of such supporting structures [5,6]. It is typical for failures of transmission lines to be experienced by thousands of people, to last from several hours to several days, and to have a wide territorial range and destructive effects on all areas of life, including industry and transport [7,8]. In practice, they mean paralysis of cities and entire regions. Energies 2022, 15, 5707. https://doi.org/10.3390/en15155707 https://www.mdpi.com/journal/energies