Study On Vibration-reduction Of Semi-floating Cable-stayed Bridge Based On Crawler Steel Damper

The long-span cable-stayed bridge has a large investment and important social status.Its construction is related to the economic development and transportation level of a region,and post-earthquake repair work is extremely difficult.When an earthquake occurs in the area where the long-span cable-stayed bridge is located,once it is damaged in the earthquake,it will cut off the traffic lifeline in the earthquake zone,which will delay the work of earthquake relief seriously,and increase the casualties and economic losses after the earthquake.By disposing energy-absorbing devices on large-span cable-stayed bridges to dissipate the total energy of seismic input,in some cases,these techniques are the only solution to the actual earthquake-resisting problem.Metal dampers have many advantages such as various forms,low cost,stable performance,good energy dissipation effect,and easy installation and maintenance.However,the design of damper parameters is mostly based on trial calculation,and the amount of computation is large,which impedes the application of such dampers to cable-stayed bridges to a certain extent.In this paper,the relationship between the seismic response of the key parts of the semi-floating cable-stayed bridge with the parameters of the crawler steel damper is studied.Two different damper parameter optimization methods are proposed for longitudinal bridge and transverse bridge respectively,which can provide certain reference value for similar projects.The main research contents include:(1)The formulas of elastic ultimate strength,plastic ultimate strength,initial yield displacement,initial elastic stiffness and ultimate displacement of crawler steel damper are deduced.The dynamic analysis model of crawler steel damper is established,and the influence of the geometry parameters of the damper on its mechanical parameters is analyzed,which provides the basis for the seismic response analysis of the crawler steel damper cable-stayed bridge.(2)Based on the finite element analysis,the general laws of vibration characteristics of the semi-floating cable-stayed bridge are studied.The analysis shows that the first mode of this type bridge is longitudinal floating,and the main girder and cable trestle generate large longitudinal-bridge displacement under the action of earthquakes.The metal damper should be used to control the seismic performance of the bridge.(3)Based on nonlinear time-history analysis,the relationship between the seismic response of the key parts of the bridge and the crawler parameters such as yield strength,initial elastic stiffness parameters is studied.The results show that the crawler steel damper has significant effect on the longitudinal direction displacement of the tower top and the beam of the semi-floating cable-stayed bridge.Under longitudinal excitation,the displacement decreases with the increase of the initial elastic stiffness of the damper.Under the lateral excitation,the installation of metal dampers in transition piers and auxiliary piers will cause an increase in the bending moment of the transition piers and the auxiliary bridge piers.(4)Two different damper parameter optimization methods are proposed for longitudinal bridge and transverse bridge respectively.The simplified semi-floating cable-stayed bridge is modeled as a single-mass oscillator model in longitudinal bridge direction,and the parameters of the damper are optimized based on the equivalent linearized response spectrum theory.In the transverse direction,use Simulated Annealing Algorithm to optimize damper parameters and the validity of the damper parameter optimization method described above was verified by finite element analysis.