Analysis Of Wind Induced Vibration Fatigue Of Steel Towers

The wind-excited vibrations of structure make it produce fluctuating stresses around mean stress states that lead to fatigue damage accumulation and may induce structural failure fatigue damage under the reciprocating actions of various levels of wind loads below design wind load。 Because the wind load and the structural wind-induced response have the fluctuating property of wide frequency and varied amplitude, the fatigue damage should be considered in the design of slender steel towers always under wind action。 But the fatigue problem hasn't been paid enough attention to in the recent design of the steel tower。 So it is necessary to study the fatigue damage for the steel stower structure, and roughly estimate its fatigue life in theory。Faced with the growing importance of the problem and the evident lack of engineering calculation criteria, this paper carries some research on the calculation of fatigue life for steel lattice towers in the frequency domain under wind action。 The main contents of the thesis are as following:(1) On the assumption that the average wind velocity follows a weibull distribution, and equivalent focused mass cantilever beam model is adopted for the steel tower, on the basis of classic fatigue failure model Basquin equation and Palmgren — Miner linear accumulation law, this paper carries a fatigue analysis for the steel tower whose stucrural response is wide band response using the equivalent stress method。(2) Assuming that the standard deviation of the fluctuating stress of the structural response can be expressed a function of mean wind speed, using continuous random fatigue theory, the calculation formulas of the fatigue damage and the fatigue life for the steel stower are derived, and a method of prediction of fatigue life for the steel stower which has constant or continuously changing height mass and stiffness characteristics under wind action is raised。(3) On the assumption that the structural response depends on only the first mode and the ratio between the fluctuating and the mean value of the stress is equal to the ratio between the fluctuating and the mean value of the displacement, using dispersed random fatigue theory, the reduced calculation formulas of the damage accumulation and the fatigue life for the steel stower are derived, and a engineering calculation method of fatigue damage for the steel stower which has constant or continuously changing height mass and stiffness characteristics is raised。(4) On the basis that Steel tower strctures such as steel tv towers mass and stiffness are not uniform along height may need to consider several modes, a method of numerical analysis on the basis of mode superposition is raised to analysis its fatigue <>(5) Because it is not enough to calculate the fatigue life of one member only for the evaluation the fatigue life of the whole steel tower structure, it is necessary to predict the fatigue life of the whole steel tower structure besides members <> This paper raises the method and procedure for the prediction of wind vibration fatigue life of steel tower structure system(6) In order to escape the fatigue damage which is induced by the frequent vibration of the steel tower, this paper gives a method which adopts raising the fatigue property of members and carrying wind-induced fatigue control design to raise the fatigue life for the steel tower oThis paper has done some beneficial research on the wind-induced fatigue of the steel tower, and it provides some references for further research0...