Research On Seismic Control Of The Tall And Slender Structure With Nonlinear Suspending Mass Pendulum

The tall and slender structure system is sensitive to the environment of strong wind, earthquake load, and easy to result in the fatigue damage due to the dynamic vibration and even the collapse in extreme conditions. In recent years, the structural vibration control method provides an effective way to solve this problem, and the suspended mass pendulum system has the advantages of good effect, simple principle, convenient installation, thus caused the wide attention of scholars. In the current study, the suspension mass pendulums is usually simplified into a simple pendulum vibration system. However, when the amplitude of vibration is obviously deviated from the equilibrium position, the linear small angle condition will not be satisfied, and the impact of the quality of the large amplitude nonlinear suspension must be considered. The research work in the thesis includes the following aspects:(1) The failure phenomena of the tall and slender structure system are listed. The basic concepts and types of structure vibration control are illustrated. And the research status of suspended mass pendulum are introduced;(2) A flexible transmission tower is studied in this dissertation. Firstly, the Finite Element Model (FEM) of the transmission tower is introduced, and the first six modals (frequencies and mode shapes) are derived by modal analysis; then the FEM of the transmission tower is simplified, and the comparison between the simplified model and the original is made for proving the accuracy of the simplified model. The nonlinear SMP motion equation is derived, and the comparison between the responses of a linear SMP system and a nonlinear SMP system excited by El Centro wave(SW) is made for proving the existence of nonlinear behavior. A sine wave is applied to the transmission tower for the parameter analysis. The relations between the Seismic Response Reduction Ratio (SRRR) and the mass and the length of a SMP are found. The existence of nonlinear behavior is further verified by the comparisons of the responses under different site conditions, which also shows the necessity of considering the nonlinear behavior of a SMP.(3) In chapter3, the equivalent linearization and the Pseudo Excitation Method (PEM) are briefly introduced. The motion equation of a nonlinear SMP system considering the effect of acceleration is proposed. The equation of motion of a linear SMP system is simplified by equivalent linearization and PEM for dynamical analysis. Excitations of individual amplitude are applied to the nonlinear and equivalent linearized equations for comparison, thus proved the correctness of the above proposed method.(4) The sensitivities of the objective function and the SMP-transmission tower coupling system are derived by PEM and the optimal algorithm based on gradient. Optimal design for the mass and length of a SMP is done by applying the optimal function fmincon in the optimal toolbox embedded in MATLAB, which further explained the necessity of considering the nonlinear behavior of a SMP system.