A Time-Frequency Damage Identification Method And Experimental Study For Guyed Masts

As a typical high slender structure coupled with cables, guyed masts have wide applications in the essential lifeline engineering. However, the failure proportion of guyed masts is prominent under natural design, construction and usage. Much attention has been paid to this problem. Analysis on accidents of guyed masts showed that many occurred under mild atmospheric conditions. The inspection of many a guyed mast also revealed that damages to some extent, caused by wind-induced vibrations or other factors such as constructions and environments, often exists at components or joints. These damages lower the carrying capacity of the structure and may cause a sudden catastrophe when load is much less than ultimate design value. If they can be detected earlier, lots of expenses for structure maintenance can be saved and many failures may be avoided. Therefore, the research of damage identification for guyed masts is critical to improve the safety of lifeline engineering structures.The inducements for damages of guyed masts are of diversity. It is difficult for practical application either to predict structure damages by theoretical analysis or to inspect mass components and joints at high-altitude individually. The recent development of numerical theory, test technology and signal analysis makes it possible for damage identification based on signal process. It was revealed by researches that the guyed mast is a complicated coupling system. Its stiffness and modal parameters depend not only on guy equilibrants but also on excitation and environment. This leads many efficient methods and index difficult to be applied for damage identification of guyed masts. So far, research works for guyed masts still focus on the test of wind-induced vibration and seismic effects. Both in the Code for High Slender Structure Design and in the Technical Specification for High-lifted Transmission Line Design, regulations are not listed.Guyed masts are pre-stressed space structures. Its dynamic characteristics are significantly influenced by guy equilibrants. In the dissertation, the guy's characteristics are analyzed on the basis of the continuous partial differential equations. By employing multi-node cable element, the dynamic increment equation of guyed masts is established. To avoid the guy's pre-tension loss due to deformation in FEM, the initial pre-tension identification method is forwarded to improve the numerical precision of analysis. The FEM established is more authentic in describing the dynamic behaviors of...