Safety Evaluation Of Half-Through Continuous Tied-Arch Bridge By Structural Health Monitoring

With the rapid development of China’s transportation industry,bridge engineering is often the key project in the road network construction,and the structural form of new bridges is constantly innovating.When the service life of bridge structure is increasing,due to the influence of external environment and traffic load,the safety of bridge structure will inevitably appear some hidden dangers.How to find the hidden danger of bridge structure efficiently and take effective measures to prevent the occurrence of major accidents endangering the safety of people’s lives and property has become a major problem during the operation period.In the "Opinions on further strengthening the maintenance and management of highway bridges" issued by the general office of the Ministry of Communications,it is mentioned that "the maintenance and management department of large,special structure and particularly important bridges should use modern information technology to establish their own maintenance and management system and structure health monitoring system".Therefore,it is of great significance to design a targeted structural health monitoring system for some special structural bridges.Firstly,this paper takes a half-through continuous tied-arch bridge as the research background,response surface method combined with static and dynamic test data is adopted to modify the initial finite element model which has good correction effect.Thus,the basic finite element model for subsequent structural response analysis and safety warning is obtained.Secondly,the detailed static analysis and multi condition vehicle bridge coupling vibration analysis are carried out for the basic model.According to the results of multi condition static analysis and vehicle bridge coupling vibration analysis of each structural member,the vulnerable sensitive section is selected as the key monitoring section of the structural health monitoring system.According to the design principle of structural health monitoring system,the bridge structural health monitoring system is established,and the monitoring scheme of each monitoring item is designed for bridge structural health monitoring.Thirdly,by analyzing the relationship between the historical strain and the temperature of the measuring point,it is found that the ambient temperature has a great influence on the measured value of the strain.According to the difference between the cut-off frequency of vehicle load and temperature effect,the wavelet analysis method is used to decompose the measured signal value to obtain the strain response caused by vehicle load and temperature effect respectively.The quadratic polynomial fitting regression relationship between temperature and strain is established to predict temperature effect strain and peel temperature strain.Finally,two levels of early warning for bridge structure are designed.The yellow early warning threshold of each monitoring item is set based on the statistical value of measured historical data and the red early warning threshold of each monitoring item is set based on the calculation value of the most unfavorable design load effect model.In addition,the safety warning application is carried out for the measured data of structural strain,suspender force and deflection in a period of time.Based on the monitoring results,it can be judged that the data of the bridge structure is relatively stable under the operation state and the bridge performance has no obvious degradation.