Barabanov S.S. Ensuring the safety of the buildings and structures opera-tion taking into account the method of vibroacoustic control. – Qualifying scien-tific work on manuscript rights.
Thesis for a PhD Degree in the specialty 263 – “Civil Safety”. – Education-al and Scientific Institute “Prydniprovska State Academy of Civil Engineering and Architecture” of Ukrainian State University of Science and Technologies, Dnipro, 2024.
The dissertation is a completed research work in the field of labor protec-tion and civil safety, which provides the solution to the current scientific and technical task - to establish the regularities of changes in vibroacoustic parame-ters during the crack development in building structures and to improve methods and develop algorithms and models for controlling vibroacoustic oscillations with given amplitude and frequency characteristics for determining hidden damage in building structure elements by vibroacoustic method, which is essential for in-creasing the safety and efficiency of building and construction operations.
In the introduction, the relevance of the topic, the purpose of the research, scientific novelty, the practical significance of the obtained results, the recipient’s personal contribution and the approbation of the research results are given.
In the first chapter, safety condition of buildings and structures during their long-term operation is analyzed with taking into account the destructive effects of explosions and fires. It is established that in the conditions of an overage housing stock and buildings and a great number of emergency situations, which become more intensive due to the dynamic impacts of explosions and fires, it is absolute-ly necessary to control stability and safety of the objects and to assess their suit-ability for further operation. This applies both to the infrastructural objects, which can include production shops, structures, tunnels, etc., and residential buildings. The analysis shows that accumulation of internal damages in load-bearing walls and foundations of the buildings is one of the most common signs of potential destruction during their operation. The vibroacoustic control method has proven itself well for monitoring and diagnosing the damages, it was tested in various conditions and allows for a non-destructive assessment of the condition of concrete, reinforced concrete, brick, multi-layered walls, ceilings and other types of structures. However, in order to improve the speed and quality of de-termining condition of the objects and making quantitative assessment of the ac-cumulation of significant damages in the object elements, it is necessary to devel-op an automated exciter of complex oscillations and to improve the method of identifying hidden damages using the vibroacoustic method. Based on the analy-sis, the purpose and objectives of the research were formulated.
In the second chapter, identification of structural damages in the materials of buildings and structures using the vibroacoustic method is shown. On the ba-sis of the measurements of the velocities of elastic waves in wooden, concrete, and metal materials, these materials are assessed as an oscillating system under the impact action. The established patterns of changes in vibroacoustic parame-ters during the crack development in building structures are presented. Open cracks are determined by standing waves, the resonators for which are the surface and the edges of the cracks. Closed cracks transfer a uniform normal wave into a heterogeneous one which decays exponentially. It is further established that when structural elements of buildings and structures are damaged, ordered and chaotic systems of cracks appear, the sizes of which, in cases of partial (hidden) internal destruction, are significantly below the area under the control. This environment can be considered quasi-homogeneous, in which crack systems reveal their prop-erties only integrally. Therefore, it is proposed to determine the integral damage indicators of the structure elements that are connected to the zones of acoustic audibility of resonant waves. These waves are captured by a receiver with low-pass filters for various materials. On the basis of these indicators, it is already possible to identify the risks of loss of stability of the object under the control. Approbation of the method of vibroacoustic damage control of the building structural elements was carried out on the example of studying concrete tubings. Areas with increased stresses, zones of hidden cracks and damages in concrete were identified. It is stated that in order to increase the speed and quality of de-termining the conditions of objects and the structure of accumulation of signifi-cant damages in their elements, the automation of the vibroacoustic method, the development of models of complex oscillations, and the improvement of the reli-ability of damage assessments are required.
