Parametric Vibration And Control Of Stay Cable With Consideration Of Temperature And Tower-deck

For coupled vibration of tower-cable-deck under end excitation,The mechanism and characteristics of the parametric vibration of the cable are studied.It is divided into three parts:Coupled vibration model for tower-cable-deck of long-span cable-stayed bridge and its response analysis 、 Coupled vibration model of tower-cable-deck with temperature difference and its response analysis、Controlling analysis of parametric vibration of stayed cables with viscous dampers,The specific research contents and results are as follows:1)the refined model of tower-cable-beam was established.The nonlinear vibration differential equation of tower-cable-beam under end excitation was deduced.The effect of the frequency ratio of cable and beam,deck excitation amplitude,cable force,damping and angle were analyzed.The results show that: When the frequency ratio of cable and deck is1:2 and 2:1,the cables has great vibration between superharmonic resonance and subharmonic resonance,but the cable has greater amplitude under subharmonic vibration,and a longer resonance time.The amplitudes of cable increase with deck excitation increasing.The larger the deck excitation,the shorter the arriving time of resonance energy is.The cable amplitude decreases with cable force increasing.When the cable damping is larger than 2%,the long cable need set additional damping to effectively control cable vibration.2)The temperature stress of the structure will be produced due to the change of temperature.Introducing the temperature difference between cable and deck as the stress state and boundary condition based on refined model,The coupled motion equations of tower-cable-deck under excitations was deduced based on thermally stressed configuration of the cable,Effects of the temperature difference between cable and deck on natural frequency and coupled vibration properties are analyzed,The results show that:Temperature affects the natural frequencies of cables and decks,When the frequency ratio of tower-cable-deck is 2:1:1,Temperature rises five degrees Celsius,The natural frequency of the deck decrease by 4%-7% and the cable’s decrease by 0.17%-0.2%,The cable amplitude decreases and vibration frequency increases with positive temperature difference between cable and deck increases,The cable amplitude increases and vibration frequency decreases with negative temperature difference between cable and deck increases,The cable vibration amplitude under joint effect of temperature and support is lower and vibration frequency is higher than that of single support excitation,When the frequency ratio is 2:1:1 or 2:1:2,The cable vibration bears feature of “patting”,the deck vibration is relatively stable.3)The viscous damper is used to control the vibration of the cable,the coupled parametric vibration model of the cable stayed-beam-damper system is established,The program is used to analyze the displacement characteristics of cables before and after being controlled.The influence of damping coefficient,installation position of cable under three typical frequencies is studied.The formula of optimal viscous damper coefficient for controlling parametric vibration of cables is proposed.The results show that the vibration of the stayed cable has the characteristics of "beat" after the viscous damper is installed,but its vibration displacement shows a nonlinear attenuation trend.With the increase of damping coefficient,the maximum amplitude of the cable decreases gradually,but the amplitude attenuation rate increases first and then decreases,and there is an optimal damping coefficient in the system;The farther the damper installation position is,the smaller the amplitude of the cable is,There is a critical installation position where the attenuation rate is zero.When the installation position of the damper exceeds the critical position,The amplitude of the cable cannot be attenuated continuously.The efficiency of the damper is reduced.