| Since the reform and opening up,with the acceleration of urbanization and the rapid growth of traffic demand,urban rail transit has played an important role in solving urban traffic problems and promoting urban development with its efficiency,quickness,cleanness and environmental protection,and the operation scale continues to grow at a high speed.As the key node of urban rail transit,the urban rail transit bridge-building integrated structure leads to the accumulation of structural damage and the attenuation of structural resistance due to the influence of environmental erosion,load,fatigue effect and material aging in the process of long-term service,so as to accelerate the deterioration of structural safety performance,and even lead to structural failure in extreme cases.Therefore,this paper establishes a safety performance degradation analysis method for the existing urban rail transit bridge-building integrated structures to predict the structural safety performance of the urban rail transit bridgebuilding integrated structures in the service period.The main work and research results are as follows:1.According to the inspection results of urban rail transit bridge-building integrated structure in service for many years,summarize the main defect types of the urban rail transit bridge-building integrated structure,develop the characterization methods of the existing defects,determine the existing damage parts of the structure and reasonably characterize the existing defects.2.A finite element model for structural state inversion of urban rail transit bridge-building integrated structure with existing damage is established.Based on the spatial grid model method,a finite element model of urban rail transit bridge-building integrated structures considering existing damage is established,which solves the significant spatial effect of the structure and the hinge simulation of the upper substructure.Based on the model parameter sensitivity analysis and optimization algorithm,according to the results of the model parameter sensitivity analysis,the finite element model of urban rail transit bridge-building integrated structures considering existing damage is modified based on the optimization algorithm and the measured structural dynamic characteristics.The research results show that the error of the modified finite element model is within 5%,the modified finite element model of urban rail transit bridgebuilding integrated structure can more accurately reflect the current service state of the structure.3.A dynamic analysis model for vehicle-bridge-building coupling of urban rail transit considering longitudinal dynamic action is established.Based on the type of operating train and the finite element model of urban rail transit bridge-building integrated structure with existing damage,the motion equation of urban rail train considering longitudinal dynamic action is deduced from the principle of energy method.According to the wheel rail interaction relationship,the dynamic equation of vehicle-bridge-building coupling system is solved by using the whole process iterative method with track irregularity and train braking force or starting force as excitation,This paper analyzes the dynamic response of urban rail transit bridge-building integrated structure with existing damage when the train enters the station after braking,verifies the rationality of the dynamic analysis model for vehicle-bridge-building coupling according to the measured structural response data,evaluates the current operation state of the structure,and analyzes the influence of different braking conditions and full load rate on the dynamic response of the structure,The results show that the peak value of the measured acceleration of the urban rail transit bridge-building integrated structure is close to the calculated value,which verifies the reliability of the vehicle bridge construction coupling dynamic analysis model and calculation method in this paper;The existing urban rail transit bridge-building integrated structure is in good operation status and meets the requirements of the specification on the control indicators of the normal operation status of the structure;Braking acceleration and full load ratio have little influence on the dynamic coefficient of urban rail transit bridge-building integrated structure;Braking acceleration has little effect on the maximum deflection of urban rail transit bridge-building integrated structure,and the full load rate has a significant effect on the maximum deflection of urban rail transit bridge-building integrated structure;Braking acceleration and full load ratio have significant effects on the maximum vibration acceleration of urban rail transit bridge-building integrated structure.4.Based on the dynamic response analysis of the finite element model of the urban rail transit bridge-building integrated structure with existing damage,the vulnerable parts of the key steel members in urban rail transit bridge-building integrated structures are determined.A multi-scale finite element model of urban rail transit bridge-building integrated structure with existing damage for fatigue performance analysis is established,the vehicle-bridge-building coupling dynamic analysis is carried out,the stress time history of the vulnerable parts of the key steel components in the urban rail transit bridge-building integrated structure is obtained,the stress amplitude is extracted by rain flow counting method,and the fatigue damage law in the vulnerable area is analyzed by nonlinear high cycle fatigue damage equation,The results show that the fatigue damage of steel structure in the urban rail transit bridge-building integrated structure considering the existing damage is a nonlinear cumulative process,and the growth rate is relatively slow in the early stage of damage evolution;In the later stage of damage evolution,the damage growth rate increases significantly.The maximum value of fatigue damage of vulnerable parts of key steel members during the service period is 0.0065.Due to the small fatigue damage value,macro cracks can’t be initiated in the weld connection area,and the possibility of fatigue failure of the structure during the service period is very low.The impact of fatigue damage on the safety performance of the structure can be ignored.5.The main line of the analysis is concrete carbonization,reinforcement corrosion,structural deterioration and the deterioration of the overall safety performance of the structure.Based on the evaluation of the stability of urban rail transit structure,the safety index of urban rail transit is determined.Based on the structural carbonization theory,the calculation formula of the critical time of structural deterioration under carbonization is determined,and the damage process of structural members under carbonization is simulated from the deterioration of material properties and section degradation.Based on the time-varying material model,structural carbonization theory and vehicle bridge construction coupling dynamic theory,the deterioration law of the safety performance of the existing urban rail transit bridge-building integrated structures during the service period is analyzed and predicted from the perspective of structural vibration,so as to actively grasp the evolution law of the safety performance of the existing urban rail transit bridge-building integrated structure.The research results show that the maximum damage degree of the components of the urban rail transit bridge-building integrated structure during the service period is 0.12998;Although the safety performance of urban rail transit bridge structure is reduced during the service period,the urban rail transit bridge structure has sufficient safety performance reserve to ensure the safe operation of trains;The safety performance of urban rail transit building structure decreases during the service period.Under the action of train excitation,the safety performance reserve of urban rail transit building structure is insufficient,and there is a risk of vibration damage in the later service period;The maximum derailment coefficient and maximum wheel load reduction rate of urban rail transit train change little.Although the safety of urban rail transit bridge-building integrated structure is reduced during the service period,the train can maintain safe operation during the service period of the structure. |
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