Study On The Dynamic Behaviors And Power Flow Features Of Frequency-variable Absorber And Beam Bridge Coupling System

In recent years, study on vibration of bridges under travelling loads has been one of the hot topics in traffic, civil engineering, mechanical engineering. It can reduce resonance when the frequency of vehicle and bridge system equals or closes to the natural frequency of the beam bridge, which will affect the service life and working condition of the vehicle and bridge directly. Vibration reduction is one of the important aspects of vibration of bridges under travelling loads. In fact, different moving loads lead the frequency of the coupled system to change. Therefore, it becomes an urgent topic of science and engineering research to find a new kind of frequency-variable nonlinear absorber. The frequency of SD(smooth and discontinuous) oscillator changes depend on the smooth parameter. In this paper, we will study the dynamic behavior and power flow characteristics of frequency-variable vibration absorber and bridge coupling system. The concrete contents are as follows.The first chapter is introduction. We introduced topic background and significance of this paper. Dynamic damping device, the SD oscillator and the related research and application problems of power flow theory at home and abroad are reviewed in this chapter.The second chapter is the research of the 2-DOF coupling system composed of the shock absorber and bridge under the action of axial load. First, we will found the motion equation of the system, and the dimensionless equations are obtained by Galerkin Method. Second, the expressions of vibration power flow are obtained by the method of harmonic balance method. Finally, we will study the effects of various parameters on the vibration rule through numerical simulation. Results show that the SD absorber can sometimes act as a linear damper and sometimes as a nonlinear one. We can achieve the ideal vibration reduction by adjusting the smooth parameters.The third chapter is research of the 3-DOF coupling system consisting of mobile quality and spring, vibration absorber and axial loading bridge. First, we establish the equation use a function which can show system motion in the infinite long time, and get the dimensionless equation. Second, we get the amplitude- frequency response function of the steady state motion use average method in multiple degree of freedom system. And the expressions of power flow are given. Finally, we find out that the bare beam system has complex dynamic behavior, such as periodic, almost periodic, chaotic motion and bifurcation phenomenon. The power flow curve of vehicle and bridge-SD damper coupling system is smooth. Thus, we achieve the goal to inhibit chaos. Also have a damping effect by adjusting the parameters of SD absorber.The fourth chapter is the research of a 2-DOF bridge system under interval girder load. First, we establish a vibration equation. Second, we get the condition of chaos using Melnikov method system and get the amplitude frequency response function using average method. Also the expression of system power flow is given. Finally, we find the bare beam has abundant dynamic phenomena through numerical simulation.In the fifth chapter, we summarize the main achievements and innovations of the full text, and point out the existing problems and future research direction.