The Experimental Investigation On Nonlinear Dynamics Of Cable-beam Structure

In recent years, a new type of structural system named cable-beam structure has been put forward. Cable-beam structure is provided with compact form and straightforward load. It is widely used in civil engineering, which is made use of tensile strength of cables and compressive/bending strength of beams. Both the theories and experimental studies of flexible cables or elastic beams were very widely and deeply, but it is a new subject to research the combination of flexible cables and elastic beams.The non-linear is an inherent character of the cable structure of large span, considering large deformation, large movement, small sag and so on. There is an interaction between the vibration of cable and beam, which influenced the security, amenity and service life of composite structure. Therefore, the non-linear vibrations of cable-beam structure are very important problems in theory and engineering.The nonlinear dynamics experiment of cable-beam structure is a difficult study. The main studies in this paper are as follows. In chapter 1, the domestic actuality of nonlinear dynamics experimental study of cable, beam and cable-beam composite structure is introduced respectively. And the first chapter introduces the investigative purposes, main works, innovative results of this paper. In chapter 2, the three dimensional nonlinear dynamical equations of inclined cable are deduced by Hamiltonian principle, considering the influence of bending rigidity, sagging and geometric nonlinearity. Based on the boundary conditions, the system equations are reduced to two-dimension. The internal resonance patterns of the plane motions and coupled motions of in-planar or out-planar are analyzed. The influence of bending rigidity on the internal resonance of inclined cable is studied. In chapter 3, we establishe the equations of plane motions of cable-beam structure by the connection and boundary conditions. The internal resonance characters such as bifurcation and stability of composite structure are analyzed. In chapter 4, the model design, calculation, experimental principle, testing process of nonlinear dynamics experiment of composite structure are introduced. In chapter 5, the parameters resonances of flexible cable and beam are studied in experiments, the response-amplitude to excitation-frequency curves and the response-amplitude to excitation-amplitude curves of beam and cable are gained respectively. The jump phenomenon is verified. And numerical simulation is also done. In chapter 6, the effects of lumped masses, distribution modes of counterweight and moving masses to the parameters resonance characters of counterweight stayed-cable are studied by the experiment. We found out strong coupling between in-plane and out-plane components under certain conditions. The response curves are also gained by studying the parameters resonance experiment. When the main parameters resonances of cable occur, the nonlinear increment of response-amplitude follows the excitation-amplitude. The furcation bifurcation will occur during the basic parameters resonance, and the nonlinear increment follows the excitation-amplitude when exceeding critical point. The skip of frequency- response curves occurs, and the varieties of excitation-amplitude induce the deflection of excitation-frequency which correspond to maximal response-amplitude. Because of the parameters resonance, spatial motion characters of the cable are rich, including single balloon motion and double balloon motion. In the conditions of main resonance, the bound of parameters resonance is undefined. At last, the chaos by break of quasi-periodic torus is observed. On the whole, the results of numerical simulation and experimental results are consistent. A nonlinear vibration of composite structure with single-beam and tow-cable is studied in chapter 7. Both theory analysis and experimental results show that various internal resonance may be excitated in the system.In this paper, the influences of bending rigidity to dynamics characters of stay-cable are considered. And the nonlinear dynamics characters of cable-beam composite structure are analyzed. The jump phenomenon and the coupled motions of stayed-cable of in-planar and out-planar are verified. The chaos by break of quasi-periodic torus is observed. The spatial motion characters of the cable are various. The results show that, there is a strong coupled non-linearity action between cable and beam. The influence of beam to cable is great, and the influence of cable to beam is also not negligible. The nonlinear dynamics experiments of composite structure are made firstly in China, and the results are significant for the vibration control and application.