Study On Dynamic Behaviors Of Iced Bundled Conductor Model Based On Geometric Strong Nonlinearity

Conductor will endure the comprehensive action of dead weight, ice load, windpressure and dynamic load generated by the big amplitude galloping of conductorsunder icing states. When the conductor internal tension reaches or exceeds design load,it may cause serious disaster such as wire breakage, tower collapse. Frequentgalloping of iced conductors made transmission line system face a serious threat, sodomestic and foreign scholars have devoted to solve this practical engineeringproblem. Theoretical models of iced conductors galloping are basically based onsingle degree of freedom or multi-degree of freedom coupled concentrated parametersmodel at present, research on conductor galloping based on nonlinear dynamicssystem theories are very limited. Focusing on these problems, the main research workin this thesis disserting as following:(1). In order to fully embody certain sag and flexibility the transmission linehas, the vertical, horizontal and torsional coupled vibration partial differentialequations of3-dimensional continuum of iced4-bundled conductors was establishedbased on elastic mechanics and aeroelastic theory. By means of modal hypothesistechnique, it has converted them into ordinary differential equations by Galerkinmethod and all following analysis was conducted to determine the effect of structureparameters on the modal linear nature frequencies. The application of numericalsimulation method to study vibration characteristics of iced4-bundled conductors atdifferent wind for different spans, and simulation results were basically agreementwith the finite element model analysis.(2). In this topic, the range of conductor horizontal tension that made verticalvibration with geometry strong nonlinear characteristics for different span conditionswere determined in this paper. Through the study of various factors on the impact ofgalloping, the inherent mechanism of transmission line galloping was revealed, therich nonlinear dynamic phenomenon was found, and the existing mechanism ofgalloping was developed, and those were based on iced conductor with typical strongnonlinear characteristics. The analysis results showed that a geometry strongnonlinear characteristic of iced conductor caused by flexibility and large vibrationamplitude is universal existence for different span distance.(3). On basis of normal form theory, by applying the undetermined naturefrequency method that is suitable for strong nonlinear vibration system and universal programs by means of software Mathematica to compute the normal form of system,amplitudes and frequencies of the first three modes of vertical vibration were obtained.Analysis results showed that the modal amplitudes were increased with wind velocity,the first order modal vibration frequency deviated from the nature frequency anddecreased with the increase of amplitude, but the second and the third order modalvibration frequency deviated from relevant order nature frequency and increased withamplitude, and the change laws of modal vibration frequencies with amplitude wererelated to quadratic or third-order nonlinear terms in kinetic equations.(4). By selecting initial attack angle as bifurcation parameter, dynamic stabilityof the system was analyzed. The center manifold of vertical and torsional coupledvibration system and the ninth order Hopf bifurcation A normal form in polarcoordinates were obtained by using universal programs. The range value of initialattack angle that caused conductor galloping was confirmed, simultaneously,research showed that the initial attack angle was main factor to control the occurrenceof galloping and the galloping amplitude.The research can provide theoreticalguidance to anti-galloping in engineering practice, and alleviate even eliminatedamage caused by conductor galloping.