Research On The Damage Detection Of Bolted Looseness On The Jiont Of Flange In Steel-tube Transmission Tower Structures

High-rise tower structures such as transmission tower, mast and television tower etc are one kind of structure shape directly relating with the human lifeline, which are widely applied in the many fileds of national economy construction. Due to the characteristic of its highness and flexibility, the structures are senstive to the action of wind.Under the action of strong wind, it occures to suffer from the collapes of structures.For example, there are more 10 transmission towers in every year which suffer from collapes in the typhoon or strong wind, especially the collapse accidents of transmision tower from the southward snow calamity in 2008 is most serious.As for thees sturctures, one of most average damage types is the damage of bolt looseness in the jiont of flange. Taking into account that it is hard to be found and serious damage of bolt looseness would great reduce the wind-resistant capability, it is more necessary to make some research on the damage detection method to guarantee the safety of steel stower structures.Based on equaling the bolt looseness of flange as the reduction of parameter values including the elastic modulus, size of section and etc, an optimization equivalent method of conjugate gradient method is put forward on the principal of minimizing the error term between stiffness matrix of refined model and one of equivalent simple model. By the method, an equivalent model of transmission tower reflecting the bolt looseness of flange is set up which provides the solid foundation for the establishment of damage detection system of bolt looseness on the high-rising steel structure.Based on this, the refinement finite element model of large-scale transmission line tower system with the equivalent flange bolt joint is established, and the influence of wire geometry misalignment on the the tower structure response has been studied.The sensitivity of bolt looseness damage on the jiont of flange on the modal parameter of transmission tower structure is analyzed, and the validity of strain modal or strain response as the damage index has been authenticated, at the same time the way to get the strain modal based on the manual drive is proposed, at last, the sensitivity of the strain modal and gain way's validity is validated by the simulation analysis and model experiment.An updating detection approach of Fuzzy-pattern recognition based on strain mode is also presented in order to locate the specific bolted looseness damage by the reduplicative detection of distance nest degree and proportion nest degree. Performance of the proposed damage detection approach is demonstrated with analysis of the Xiang-jiang transmission tower structure. The result turns up trumps with certain application value.This paper elaborates the actual difficulty of large-scale multiple structure's damage diagnosis, and fractional-step detection method of bolted looseness damage in transmittance tower structures is presented. The first step is to identify the damage region by the neural network, then locate the detailed damage location and degree by the hybrid genetic algorithm; Performance of the proposed damage detection approach is demonstrated with analysis of a tower structure. The result turns up trumps. The genetic algorithm's optimized performance under the noise environment has been elaborated; taking into account the genetic algorithm's traditional flaws, such as "premature", "stagnation", excessive variable and so on, technologies such as multi-father body hybrid,microhabitat and drifting operator and etc based on variable level has been introducedSecondly, based on the method of probability, statistical property of noise contribution from the objective function respectively under the absolute and relative noise environment is inferred, the objective function has been effectively improved by eliminating the statistical noise value. Finally, this improved method has been effectively applied in the damage diagnosis of bolt becomes on the jiongt of flange in the transmission tower. The simulation result indicates that this method can effectively enhance the convergence performance of genetic algorithm under the noise environment and can make the correct diagnosis and appraisal to the structure damage.This paper has carried on the fundamental research on the damage diagnosis of bolt looseness on the jiont of flange in the transmission tower under the wind load drive. By deducing the damage characteristic which is senstive to damage and independent of load, effective diagnosis of damage of bolt looseness on the jiont of flange is realized by applying the wavelet transform method with strong abatement ability and sensitive characteristic to the wave signal. Through the simulation analysis under the action of different wind load, the results indicate that this method can effective carry on the recognition of bolt loseness damage with excellent anti-noise ability.In order to confirm the validity of damage diagnosis theory in this paper, the experimental study of bolt loose damage on the joint of flange is carried on, respectively under the initial manual drive and the earthquake drive. The results have confirmed the validity of damage diagnosis method which provides a experimental material for the actual project's application.