Dynamic Characteristics And Damping Parameter Optimization Of Deck-damper System For Floating-girder Suspension Bridges

The floating suspension bridge mentioned in this paper refers to the two-span or multi-span suspension bridge system without vertical support at the joint between the pylon and the stiffening beam.The outstanding advantage of this system is that it can effectively reduce the negative bending moment at the cross section of the pylon.China's Xihoumen Bridge,the Great Belt East Bridge,the Izmit Gulf Bridge in Turkey,and the construction of the 1915 Canakkale Bridge in Turkey use this floating stiffening beam suspension bridge system.For the floating stiffened beam suspension bridge system,when the stiffening beam is subjected to vertical or torsional vibration,the stiffening beam at the joint of the tower and beam usually has a large vertical or torsional displacement,so the vertical damper is expected to suppress the vortex of the multi-order mode.Stimulate resonance to increase the critical wind speed of the flutter.The addition of longitudinal dampers to suspension bridges has been studied to reduce the longitudinal displacement of vehicles or earthquakes.However,the research on the addition of vertical dampers for stiffening beams is still lacking.For this reason,based on the study of the dynamic characteristics of the cable-damper,the dynamic characteristics of the beam-linear viscous damper coupling system and the optimization of the damper parameters are studied.Based on this,the floating suspension bridge is strengthened.The optimization of the damper parameters of the vertical linear visc ous damper with beam is added.Finally,the damping parameter identification of the stiffened beam with additional viscous damper is studied.The vertical vortex vibration of the stiffening beam of the suspension bridge is suppressed and the actual damping effect of the damper is evaluated.The foundation has been laid and the research results can also be used for damping of the damper of the arch bridge boom.The following is the main content of this article:(1)The development of the suspension bridge and its excellent mechanical properties are expounded.The vortex-induced vibration of the floating suspension bridge and the countermeasures are presented.The research progress and application examples of the viscous damper parameter optimization in the br idge engineering are summarized.The dynamic excitation of the suspension bridge is summarized.Damping identification method;finally,the main research content and technical route of this paper are expounded.(2)The theoretical results of the coupled vibration of the cable-viscous damper are reviewed and summarized,and extended to the Euler-Bernoulli beam model.The coupled vibration equations of beam-viscous dampers are derived by means of complex mode.The analytical solutions and asymptotic solutions of the frequency and damping ratio of the coupled system are obtained.The asymptotic solution is only applicable to the position of the viscous damper near the beam end..On this basis,the maximum damping ratio of the beam-damper system and the corresponding optimal damper parameters are obtained when the damper is installed near the beam end.(3)The finite element model of cable,simple supported beam,fixed beam at both ends and suspension bridge of Xihoumen is established to analyze the complex modal,and the optimal parameters of linear viscous damper for each modal control are obtained.The theoretical solutions are compared to verify the correctness of the theoretical results.The results show that the optimal damping coefficient of each model viscous damper is related to the bridge parameters,damper position and vertical bending mode order.The optimal modal dampi ng ratio is related to the position.(4)In order to obtain the damping effect after the vertical damper of the actual floating suspension bridge stiffener is set up,this paper studies a new type of suspension bridge dynamic excitation technology and damp ing ratio identification method.In this paper,the dynamic excitation method of multiple continuous jumps according to the modal period is used to simulate the dynamic response of multiple periodic impact loads and the damping ratio identification of stiffened beam-viscous damper system.Considering that the coupling vibration effect of the axle affects the damping ratio of the bridge system,this paper establishes the coupled vibration model of the vehicle and bridge.Firstly,the influence of the mobile excitation vehicle changing its own parameters on the modal parameters of the vehicle-bridge coupling system is studied.The principle of selecting the parameters of the vibrating vehicle.Then,the modal damping ratio is identified by the free decay curve obtained after continuous excitation.The analysis results show that the bridge can be effectively excited based on the method of multiple jumps according to the modal period.The continuous damping method identifies the damping ratio and the theory is ba sically the same.Therefore,the proposed method of dynamic excitation using multiple continuation jumps according to the modal period provides a new way for modal parameter identification.