Research On Safety Prognosis Of Prestressed Concrete Continuous Grider Bridge Based On Structural Health Monitoring

In the complex service environment,the material performance of existing bridges is deteriorating,and the diseases of bridges are becoming more and more serious.However,with the increase of actual load level,the process is greatly accelerated.The safety of the bridges is worrying.Thus,how to effectively evaluate the state of the bridge,and to predict its structural behavior in the future is becoming an important issue in the bridge engineering.Based on health monitoring,this paper studies the safety assessment and safety warning of bridge,and the prediction of its structural behavior prediction in the future.This is of great significance to ensure the safe operation of the bridge and to promote the preventive maintenance of the bridge.This paper takes the Outer Qinhuaihe Bridge(Prestressed Concrete Continuous Girder Bridge with Variable Cross Section)of Jiangsu Provincial Highway 243 as the engineering background,and a safety prognosis method based on structural health monitoring was established.The main research contents are as follows:(1)The design and installation of the health monitoring system of Outer Qinhuaihe Bridge were carried out,and the monitoring data were processed preliminaryly and analyzed.(2)Based on the ambient vibration test,the dynamic characteristics of the bridge are obtained,and the model updating is carried out based on the response surface method.In the end the baseline finite element model which can reflect actual condition of Outer Qinhuaihe Bridge is established.(3)Based on the theories which contains uncertain analytic hierarchy process,a group of judge,and set-valued statistics principle,etc,the safety assessment method of Outer Qinhuaihe Bridge is established and applied for operating condition.(4)A three-level safety warning system of Outer Qinhuaihe Bridge is established by the combination of baseline finite element model and wavelet neural network model.Then,the system is operated combined with the monitoring data.(5)The probability distribution model of bridge structural parameters is obtained by model validation.Taking material variation,vehicle load growth and other factors into consideration,the applicability life and safety life of the bridge are predicted based on the reliability method,completing the safety prognosis of the bridge.The main results are listed as follows:(1)The safety assessment method established in this paper realizes the organic combination of online monitoring project and offline monitoring project.This method can solve the problem of fuzziness and uncertainty in bridge evaluation effectively,and improve the reliability of the assessment results.The safety assessment score of Outer Qinhuaihe Bridge in January is 93.5 points,which indicates that the overall safety of the bridge is in good condition(2)A three-level safety warning system containing blue,yellow and red,is established,which achieve real-time warning of the key monitoring projects of the bridge.The monitoring data shows that there is a small amount of data in each monitoring project exceeding the blue warning threshold,no data exceeds the yellow or red warning threshold.The bridge is running well.(3)The results of safety prognosis indicate that when considering material variation and vehicle load level increase(annual growth rate is 0.2%),the applicability life of the Qinhuaihe Bridge under the service limit state is about 51 years,and the safety life in the strength limit state is about 74 years.