Research On Displacement Response Of Cable-Beam Coupled Structure Under Wind And Rain Loads

Cable-beam coupled structure is one of the most widely used structures in modern civil engineering.However,when analyze the wind-rain induced vibration of stay cables,scholars usually choose the cable only as the research object.Considering that the beam and cable work together in practical engineering,the coupling effect between them cannot be ignored.With the increase of the span of cable-stayed bridge,the flexibility of the beam increase,the geometrical nonlinearity of cable and the interaction between the modes of members intensifies the nonlinear mechanical behavior of the cable,making its characteristics more different from that of a single cable.Therefore,this paper takes cable-beam coupled structure as the research object and analyzes the influence of external excitation forms,cable-beam frequency ratio and other parameters on structural vibration of the beam under wind and rain loads,so as to provide suggestions for cable-beam coupled structure design and vibration reduction.The specific research contents are as follows:The vibration control equation of cable-beam coupled structure under static rivulet is established and its accuracy is verified.The nonlinear dynamic and physical responses of the structure are analyzed by numerical method.The vibration displacement response of cable and beam under different external frequencies and its influencing factors are studied in detail.According to the calculation results of the dynamic response,the nonlinear physical response of the cable and the beam is analyzed under the condition that the natural frequency ratio of the beam is 1:2 and the external excitation forms the main resonance with the beam.The effects of four factors,namely,frequency difference between external excitation and beam,frequency difference between cable and beam,amplitude of external load,and wind speed,on nonlinear physical responses of cable and beam are discussed.The vibration control equation of cable-beam coupled structure under moving rivulet is established and its accuracy is verified.The effects of different resonance forms on the wind-rain induced vibration of stay cable are studied.For each type of resonance,the influence of external excitation amplitude on the vibration of the cable is analyzed,and the law of the amplitude of the cable changing with the excitation amplitude is obtained.On the basis of this calculation,the conditions that can show the classic wind and rain vibration are selected.Considering the influence of the fluctuating wind,a formula for calculating the net damping of cables is proposed,and the influences of wind amplitude and frequency on the vibration of cables are investigated.Considering the influence of the modal coupling of the cable and beam,the dynamic characteristics of the structure are calculated and analyzed.Based on thevibration control equation of coupled structure,the vibration characteristics of cable under static and dynamic rivulet are obtained with considering the influence of modal coupling.Compared with the actual observation results,the rationality of considering the modal coupling is verified,and the result shows that the modal coupling aggravates the complexity of the nonlinear mechanical behavior of the structure.By means of bifurcation diagram,poincare maps and phase portraits,bifurcation and chaos analysis are carried out on the vibration behavior of cable and main beam in two cases above.