Research On Control Scheme Of Longitudinal Vibration Of Long-span Railway Cable-stayed Bridge

Long-span cable-stayed bridges have become one of the main bridge types of railway bridges due to their good spanning ability,wind resistance performance and economic indicators,and they play an important role in material circulation,personnel travel,and disaster relief.In order to reduce the internal force response under earthquakes and resist temperature deformation,long-span cable-stayed bridges often adopt semi-floating or floating seismic isolation systems.However,due to the lack of effective constraints in the longitudinal direction,it is easy to produce large structural response under the action of occasional seismic loads and frequent train braking forces.According to the dynamic characteristics of the semi-floating system cable-stayed bridge and its response characteristics under the excitation of earthquake and train braking force,this paper proposes a scheme to control the longitudinal vibration of the structure.Mainly completed the following research work:(1)This paper takes a steel-concrete composite girder railway cable-stayed bridge with a main span of 330 m as the research object.Based on the use of Midas/civil to construct a three-dimensional model of the full bridge,through dynamic characteristics analysis,the period,frequency and mode feature of the bridge are obtained.Under rare earthquakes,the selection of damping coefficient and velocity index is analyzed,and the optimal value of the parameters is determined according to the change law of the maximum value of the seismic response of key parts with the damper parameters;(2)Install viscous dampers in the longitudinal direction of the cable-stayed bridge.By comparing and analyzing the seismic response results of the original structure and the damping structure,the control effect of the viscous dampers on the structure response under different earthquakes is studied.(3)In view of the structural response characteristics caused by the braking force of the train,the lock-up device with pressure relief valve with special function is adopted to control the longitudinal displacement of the main beam and the internal force of the tower bottom.Taking the structural response of key parts as the control objective,under the same train braking force,the control effect of the lock-up device with pressure relief valve and the viscous damper on the structural vibration is compared and analyzed.Furthermore,the influence of lock-up devices in different positions on the control effect of train braking force is analyzed.So as to select the most effective control plan for the train braking force.(4)In order to determine the additional damping ratio of the cable-stayed bridge of the energy dissipation system,the strain energy method and the free vibration attenuation method are used for analysis and calculation in this paper.On this basis,the influence of different earthquake intensities and different analysis methods on the calculation results is studied.Aiming at the forced vibration of a long-span railway cable-stayed bridge under earthquake and train braking force,this paper conducts a research on the longitudinal vibration control scheme of the structure.Not only the solution is given,but also the calculation method of the additional damping ratio of the bridge with energy dissipation system is discussed,which can provide a reference for similar projects.