Intelligent Control For Wind Vibration Responses Of Guyed Mast By MR Damper

The guyed mast structure is a high-rise system made up of soft cable and slim mast. The interaction between the inclined guys and the mast makes its nonlinear dynamics very complex. The damage probability of guyed mast is especially high under normal designing and constructing in civil engineering fields. In this thesis, the problem is taken as engineering background to study the application of semi-active control for wind vibration responses of guyed mast by MR damper.The principles and mechanical model of magnetorheological fluid are first introduced and then the basic principles, constitution , mechanical model and mechanical behaviors of MR damper are discussed. According to the possible problems in the wind-resistance design of guyed mast and the characteristic of the structure form, the concept of the MR damper-spring system is presented in this paper.Guyed mast present high deformation under horizontal forces, so geometrical non-linearity must be considered in the static and dynamic analysis of guyed mast. The large displacement stiffness matrix of the 4-node space cable element is derived based on the updated Total Lagrangian Formulation and FEM theories. Based on guyed mast FEM model of 4-node space cable element and space beam element, the method to analyze along-wind induced nonlinear oscillation in the time domain is established, which breaks the traditional analysis in the frequency domain using stochastic theory on the linearization premise. And the results of imitation analysis reflect the essential character of guyed mast.In accordance with the MR damper-spring system presented in this paper and non-linear FEM model of guyed mast, an "Off-on Energy Dissipation" Semi-control strategy based upon MR damper's displacement is proposed, in which the control force of MR damper is close to the instantaneous optimal active control force and dissipate energy as possible as it can. System imitation analysis in the time domain indicates that the amplitude and peak of displacement at the joint between cable and mast are both reduced, and the fatigue life of guyed mast is increased. Adjusting the location of MR damper can efficiently reduce the displacement on the top of guyed mast induced by wind.Some research progress of fuzzy control at home and abroad is introduced in this thesis and the research on fuzzy control of wind response of guyed mast is made. In line with three different combinations of displacement, velocity and acceleration, double-input and single-input fuzzy control is applied in vibrant control. The results indicate that fuzzy control strategy is effective in the vibrant control of wind response of guyed mast and the structures under control with different input variables show remarkably different responses under earthquake excitation. In practical application, input variable can be selected on the basis of different control aims to obtain different control effects.