Semi-active Control Algorithm And Reliability Research For Long-span Continuous Girder Bridges

Continuous girder bridges have advantages of high structural rigidity,good integrity,material saving,large overload capacity,and good dynamic performance.It is currently one of the most widely used bridge types in China.The long-span continuous girder bridge structure is not conducive to earthquake resistance.Therefore,it is of great significance to reduce vibrations and reduce the damage caused by earthquakes to the structure.In this thesis,a study on vibration reduction control of long-span continuous girder bridges is carried out,with the intention of reducing the seismic response of the continuous girder bridge structure.The main achievements of the work are as follows:(1)A semi-active control algorithm for vibration reduction of large-span continuous girder bridges considering fault tolerance is proposed.The genetic algorithm is used to optimize the control force of the LQR classical optimal control algorithm,the reasonable control parameters are determined and the optimal active control force is obtained.The active control algorithm is used as the theoretical basis of the semi-active control scheme.Aiming at the situation that the magnetorheological damper in the control part may fail during operation and affect the normal control,the failure mode of the actuator is analyzed,and the fault-tolerant control is considered in the semi-active control scheme based on this.The purpose of maintaining the expected vibration effect of the semi-active control scheme is achieved by supercharging compensation for the fault output.(2)The accurate electro-mechanical conversion dynamic model of the magnetorheological damper is established,and the dynamic analysis model of the continuous girder bridge vibration reduction system is established by using it as the control device.Based on physical properties of the magnetorheological fluid and the nonlinear dynamic characteristics,the Spencer model is used as the forward model,and the Sparrow Search Algorithm-BP neural network model is used as the reverse model,so that the magnetorheological damper can be used in vibration reduction.The dynamic finite element analysis model of long-span continuous girder bridge is established based on the background of actual engineering bridges.The element type,structural characteristics,modeling method and grouping method of each component of the structure are expounded,and the seismic response of continuous girder bridge is solved based on the model.(3)Deterministic seismic response analysis of long-span continuous girder bridge under various operating conditions was carried out,and the vibration reduction control scheme applied in each working condition is evaluated.The seismic responses of continuous girder bridges in the state of uncontrolled,the state of active control,the state of normal working of semi-active control,the state of taking compensatory measures in the event of a fault,and the state of no compensating measures in the event of a fault are compared.The comparison of the damping results shows that semiactive control scheme considering fault tolerance is effective and necessary.(4)Based on random vibration theory,combined with probability density evolution method,random seismic response analysis and seismic reliability analysis of large-span continuous girder bridges are carried out.Taking the displacement response of the pier top as an example,the dynamic reliability of the structure under the action of 0.6g random seismic wave is evaluated by three working conditions: no control state,state of taking compensation measures at fault,and state of no compensation measures at fault.Comparative analysis shows that the seismic reliability decreases rapidly with the decrease of failure threshold.Under the same failure threshold index,the semiactive control scheme considering fault tolerance has the highest seismic reliability.The analysis results further show that the semi-active control scheme considering fault tolerance can still achieve the expected control effect for continuous girder bridges when the control system has faults.