PSI - Issue 32

I.O. Glot et al. / Procedia Structural Integrity 32 (2021) 216–223

223

8

Shestakov A.P./ Structural Integrity Procedia 00 (2021) 000 – 000

• The main stage of vibration diagnostics is the analysis of the lowest natural frequencies. This is due to the fact that: the spectrum of the lower frequencies is sparse and the determination of frequencies is not very difficult; a large number of sensors are not required to register vibrations; registration of vibrations is possible without the use of actuators (the lower frequencies are excited due to wind gusts or seismic vibrations of the earth's surface). However, the change in lower frequencies with local damage to the structure is small. It is rather difficult to localize damage sites in large-scale metal structures. • The analysis of the shapes of the lowest natural frequencies of the structure makes it possible to better determine the places of damage, however, this method requires a significantly larger number of sensors than in the previous approach. The information content of the method increases with the number of forms participating in the analysis. Thus, vibration control of a complex metal structure is possible when analyzing natural frequencies, the shapes of which correspond to the scale of its structural elements. The range of these frequencies is not excited by wind and seismic factors; therefore, other sources of vibration must be used. The construction investigated in this work can be influenced by various technological processes. These processes are sources of vibrations that can excite a wide range of natural frequencies. The use of such vibration sources requires special operating modes from the measuring system. The system must have the ability to continuously collect data and select certain time intervals corresponding to technological processes. The strongest vibration effect on the structure is exerted by dropping of ore. In this technological process, vibration can be detected at almost all points of the structure. However, this effect has specific features: during dropping a large number of shock impact are realized, which form the frequency response of the structure. The use of the Fourier transform over the entire time interval corresponding to the drop does not allow the eigenfrequencies of the structure to be identified without additional processing. One of the options for solving this problem is the calculation of a spectrogram with its subsequent averaging over the time coordinate. The lack of high-frequency response at most measuring points indicates a rapid attenuation of vibrations as it propagates through the structure. In order to obtain information about the construction over the entire possible frequency range, it is necessary to use actuators at all measuring points. This will increase the reliability of the assessment of the current state of the structure. References Fan, W., Qiao, P., 2011. Vibration-based damage identification methods: a review and comparative study. Structural Health Monitoring 10(1), 83 111. Jesus, J. Y.-B., Martin, V.-R., David, C.-M., Juan, P. A.-S., 2020. Statistical time features for global corrosion assessment in a truss bridge from vibration signals. Measurement 160 Narges, F., Seyed, V., Ali, M., 2018. Multi-damage identification of large-scale truss structures using a two-step approach. Journal of Building Engineering 19, 494-505. Parviz, M., Tommy, H.T., Chaminda, G., 2017. Benchmark Studies for Bridge Health Monitoring Using an Improved Modal Strain Energy Method. Procedia Engineering 188, 194-200. Rongrong, H., Yong, X., 2021. Review on the new development of vibration-based damage identification for civil engineering structures: 2010 – 2019. Journal of Sound and Vibration 491. Roumaissa, Z., Idir, B., Samir, K., Magd, W., 2018. A damage identification technique for beam-like and truss structures based on FRF and Bat Algorithm. Comptes Rendus Mecanique 346, 1253-1266. Samim, M., Yasunao, M., Hiroki, Y., 2018. Vibration-Based Health Monitoring of an Existing Truss Bridge Using Energy-Based Damping Evaluation. Journal of Bridge Engineering 346. Shardakov, I., Bykov, A., Shestakov, A., Glot, I., 2017. Crack control in concrete using shock wave techniques. Procedia Structural Integrity 5, 210-216. Shardakov, I., Shestakov, A., Tsvetkov, R., Glot, I., 2018. Investigation of the effect of cracks on the vibration processes in reinforced concrete structures. Frattura ed Integrità Strutturale 12, 383-390.