Study On The Evolution Law Of Service Behavior Of Long-span Steel Truss Girder Cable-stayed Bridge Based On Temperature Effect-time-space Degradation

Based on the structural health monitoring system(SHMS)of a rail-cum-road steel truss cable-stayed bridge,this thesis explores the spatial and temporal distribution of temperature field and the characteristics of temperature-induced effect of long-span steel truss cable-stayed bridge.The purpose of this thesis is to study the evolution law of service performance of long-span steel truss cable-stayed bridge under the comprehensive consideration of temperature effect-spatial and temporal deterioration,which can provide some guidance for the maintenance decision of bridge structure.The main research work and chapter arrangement of this bridge are as follows :(1)IntroductionFirstly,the background and significance of the research on the evolution law of service performance of long-span steel truss cable-stayed bridge based on temperature effect-space-time deterioration are expounded.Then,the research status of bridge structure temperature field,bridge structure temperature effect,bridge structure temperature field simulation model,bridge structure time-space degradation,bridge structure service performance evolution law and prediction at home and abroad are briefly described,and the above research status at home and abroad is summarized.Finally,the main research contents and innovations of this thesis are described.(2)Establishment and correction of temperature field simulation model of longspan steel truss cable-stayed bridgeFirstly,the engineering background of the steel truss cable-stayed bridge is introduced.Secondly,the formation,characteristics and main influencing factors of temperature effect of bridge structure are expounded.Thirdly,the basic theory of temperature field of long-span steel truss girder cable-stayed bridge is expounded.Based on the field measured data of bridge structure health monitoring system(SHMS),according to the main influencing factors of bridge structure temperature,considering the particularity and actual situation of steel truss girder structure,the boundary conditions of bridge structure temperature field are calculated,and the modified simulation analysis model of bridge structure temperature field is established.Finally,the spatial and temporal distribution of the temperature field of the steel truss girder structure under the action of solar radiation,convective heat transfer and radiation heat transfer is studied,and the time-varying mathematical model of the ambient temperature and the uneven temperature field of the bridge structure is obtained.According to the field measured data,the simulation analysis model of the structural temperature field is tested and corrected.(3)Study on the correlation of temperature-induced effect of bridge structure based on ICEEMDANFirstly,the theoretical basis of ICEEMDAN method and Hilbert spectrum is expounded.Then,based on the field measured data of typical dates(extreme high temperature and extreme low temperature)in the whole year,aiming at the problem of noise residue and aliasing in signal separation,the improved adaptive noise complete ensemble empirical mode decomposition method(ICEEMDAN)is used to separate the temperature effect in the field measured data(cable force,mid-span deflection and beam end rotation angle).Finally,from the practical level,the time lag and spatial difference of temperature effect are analyzed,and the mechanism and correlation of temperature effect of bridge structure are studied from the theoretical level.(4)Study on the correlation of temperature-induced effect of bridge structure considering time-space deterioration of stay cablesFirstly,the common disease types and causes of long-span steel truss girder cablestayed bridge are briefly described.Secondly,the spatial and temporal distribution characteristics of the temperature field of the bridge structure are studied,and the temperature conditions of the bridge structure are established.Thirdly,the spatial and temporal distribution characteristics of bridge structure deterioration are studied,and the chemical condition of bridge structure deterioration is established.Finally,combined with the above established temperature conditions and poor chemical conditions,the finite element simulation analysis software ANSYS is used to simulate the temperature effect-time-space deterioration model of the whole bridge.Based on the field measured data and numerical simulation data,the time-varying characteristics of the temperature input response output characteristics during the deterioration of the bridge structure are studied.The causal relationship between the time-varying characteristics of the temperature input response output and the deterioration of structural performance is obtained,and the correlation mechanism between structural performance and temperature-induced effect is revealed.(5)Research on performance evolution and prediction of bridge structure based on artificial intelligence algorithmFirstly,the theoretical basis of ARIMA,BP neural network,weighted,combined forecasting model and permutation entropy algorithm is expounded.Secondly,the evolution law of service performance considering the time-space degradationtemperature effect of cable-stayed structure is studied,and the long-term performance evolution model of bridge structure is determined.Based on ICEEMDAN-ARIMA-BP neural network,the long-term performance evolution law of bridge structure is studied.Thirdly,based on the time-varying reliability analysis,the future performance and remaining service life of the structure are predicted and studied.The structural performance identification method and evaluation model based on the change of the temperature input response output characteristics of the bridge structure are established,and the typical disease development state of the component is effectively identified.Finally,the maintenance decision of bridge structure is studied based on life cycle cost analysis.(6)Conclusion and prospectFirstly,the relevant conclusions of the above research are summarized.Then,the existing shortcomings of the related research in this thesis are deeply considered.Finally,the future research on the temperature field and temperature effect of bridge structure is prospected.In this thesis,the long-span steel truss girder cable-stayed bridge is taken as the research object,and the service performance and state evolution of the bridge structure under complex operating environment are taken as the foothold.Based on the theory of thermodynamics and structural elasticity,the finite element simulation analysis(ANSYS),empirical mode decomposition(ICEEMDAN)and artificial intelligence(ICEEMDAN-ARIMA-BP neural network)are used.Combined with the field measured data and numerical simulation data of the bridge structure,the temperature problem of the long-span steel truss girder cable-stayed bridge is studied from theory to practice.