Damage Detection Of Connection In Transmission Tower Structure Based On Nonlinear Vibration

As an important lifeline engineering of human society, transmission towers in theevent of damage or collapse will bring very serious economic losses, and even a threatto personal safety. Transmission tower bolted steel is generally used, it is possible underthe long-term effects of wind and air will cause the bolts loose or even fall off, if thetransmission tower is not detected in time, the consequences could be disastrous, so it isvery important to identify the damage of the transmission tower. In the damageidentification of the bolt, the traditional methods have some considerable limitations,this is because of the traditional method of low technology content, constructiondifficulty, high operating cost. In this paper, this paper use the nonlinear characteristicsof the transmission tower components vibration under the artificial incentives andenvironmental excitation to identify the damage of bolted connections, the mainmethods used include random decrement, blind source separation techniques, numericalintegration and the Hilbert transform. Finally, this paper use frequency-amplitude ofthe curve, the mean and standard deviation of frequency fluctuations separatedaccording to the above method to determine the degree of nonlinear vibration of thesecomponents and identify damage of these transmission tower components. Finalconclusions prove that the method is feasible, is worthy of further study.The contents of this paper include the following aspects:(1) This paper outlines the development status of structural damage identificationand introduces the traditional non-linear vibration theory. This paper introduces theidentification method about the modal parameters of the structure and highlighting therandom decrement technique, blind source separation techniques and Hilbert transform.And numerical simulation examples demonstrate the feasibility of blind sourceseparation technology.(2) This paper introduces the experiment, including experiment conditions design,experiment environment and data collection, field.(3) For the non-linear characteristics analysis under the artificial excitation, thispaper use blind source separation techniques to extract the first-order component of thefree vibration signal, reuse integration in order to get the speed signal, displacementsignal and frequency-amplitude curve of these component under varying degrees ofdamage with the Hilbert transform. This paper analyzes these curves to find the nonlinear vibration law of the transmission towers components bolted.(4) For the non-linear characteristics analysis under the ambient excitation, thispaper use the random decrement technique to remove the impact of environment noiseand get the free vibration signal and the frequency-time curve of the structure. Thispaper analyzes the difference of signal under the ambient excitation and artificialexcitation, and finally compare the degree of nonlinear under varying degrees ofdamage with the mean value and standard deviation of the frequency fluctuations.(5) This paper summarizes the conclusions and deficiencies and propose somesuggestions for future research.