Safety Prewarning For Guyed Mast's Fatigue State

The guyed mast is a extensive used tall and slender structure, which tends to generate wind-induced fatigue rupture that may cause the collapse of the whole guyed mast. Therefore, the avoidance of the wind-induced fatigue rupture to secure the guyed mast structure has become the advancing front of civil engineering researches. In this thesis, the problem is taken as engineering background to study the real-time assessment for the guyed mast' fatigue state, and the corresponding theory and method for it has been put forward .At the present time, the study on the safety prewarning theory of engineering structure mainly focuses on the construction of the hydro-structure and deep foundation ditch. There are few researches for the safety prewarning of the guyed mast' fatigue state. The foreign and domestic researches mostly concern the analysis method of the guyed mast's wind-induced fatigue for the wind resistance design of the guyed mast. The structural wind-induced fatigue calculation uses the wind load probabilistic model to assess guyed mast' fatigue life under its service period, and it can't realize the real-time assessment of guyed mast' fatigue state. In order to solve this problem, a dynamic load identification method about guyed mast should be established. Considering the characteristic of the guyed mast, finite sensors could be put in the guyed mast to gain the structural response which could identify the wind load. In this thesis, the dynamic load identification of guyed mast method in time domain based on modal analysis is analyzed. With the responses of the simplified model under the simulating wind load, the inverse wind process can be estimated.In the process of the calculation of the guyed mast' wind-induced fatigue, the structural finite model is just theoretical, and this theoretical model is different from the actual structure. There are some variances between them. In the guyed mast' wind resistance design, these differences are inessential if they are within the error permission. But in the system of safety prewarning for the guyed mast' wind-induced fatigue, these variances can be vital, and they could result in the failure of the whole safety prewarning system. Therefore, the establishment of the FEM correction method for guyed mast will be significant. As the steel structural model error mainly relied on the member bar's link stiff and not on its physical dimension, this paper expatiate on the FEM correction method, which select the joint link stiff as the damage indicator, and use the means of neural network to realize the structural model correction.With the purpose of establishing the theory and method of safety prewarning for guyed mast' wind-induced fatigue, this thesis put forward the real-time fatigue state' assessment method for guyed mast based on the structural FEM correctionand the dynamic load identification. In this paper, the pulsating wind loading time history of guyed mast which distribute upon the height of the mast is modeled numerically. Secondly, the FEM correction method, which selects the joint link stiff as the damage indicator, and use the means of neural network to realize the structural model correction, is discussed in detail. Thirdly, the dynamic load identification of guyed mast method in time domain based on modal analysis is discussed. Identification results indicate that the accuracy of this identification method can be to a satisfied degree. Finally, this paper expatiate on the theory and method of safety prewarning for guyed mast' wind-induced fatigue.