| The continuous rigid frame bridge has been widely used in China’s expressway because it has unique advantages of strong bearing capacity and high stiffness.The safety problems such as beam cracking and stiffness reduction are also slowly revealed because of the complex environment and the increase of operation time.When the situation is serious,there will have a collapse accident of the bridge.The emergence of these problems has a great impact on the safe operation of expressway.Therefore,based on the health monitoring of Luohe grant bridge and the monitoring data,this paper evaluates the safety state of the bridge structure from three aspects: static deflection,stress response and dynamic displacement,so as to provide a practical basis for the management and maintenance of the bridge and ensure the safe and stable operation of the bridge.The main research elements and conclusions are as follows:（1）The static deflection monitoring data of Luohe grand bridge and the bridge temperature monitoring data were used as the basis of the study.The collected deflection monitoring data were processed to separate the deflection changes generated by long-term load action by LMD method.And the accuracy of the separation results was verified.Then the correlation between temperature and deflection,the correlation between deflection between different sections within the same span and the correlation between deflection between different spans were analyzed with the separated completed monitoring data.Finally,the long-term variation of bridge deflection was evaluated using the linear variation assessment method.Three warning levels were also set according to the characteristics of the temperature and deflection monitoring data.（2）The stress monitoring data in the monitoring system were processed and analyzed.The distortion data in the stress monitoring data were classified and the characteristics of each type of data distortion were summarized.Different calculation methods are used to correct the distorted data according to these characteristics.For the processed monitoring data,the envelope calculation of the stress monitoring data is performed based on the principle of calibration coefficients.Meanwhile,the stresses in the maximum period of the bridge monitoring cycle are evaluated in the envelope with the calculated stress maximum value as the upper limit and the calculated stress minimum value as the lower limit.Finally,with the help of the finite element model,the three-level relative stress warning values established for the actual monitored stresses in the field are used as a percentage of the calculated stress values under the most unfavorable loading conditions.（3）The characteristics of the displacement monitoring data are analyzed based on the information of lateral and vertical dynamic displacement monitoring in the monitoring system.The lateral and vertical displacement calibration coefficients are calculated with the simulated values under the same conditions as the monitored displacement values.At the same time,the maximum displacement values are used to calculate the envelope evaluation analysis of the transverse and vertical displacements by relevant codes.Finally,in order to reflect the real-time status of the bridge more intuitively,a three-level warning is set based on the monitored and calculated displacement values.Based on the bridge in operation period,this paper designs the monitoring scheme,puts forward the corresponding evaluation methods according to different monitoring items,and evaluates the safety of the bridge from the three monitoring dimensions of static deflection,stress and dynamic displacement.The results show that the three indicators are within the safety range.The implementation of bridge monitoring and safety assessment can provide reliable theoretical support to ensure the normal operation of the bridge.This study also has a certain reference significance for the safety evaluation of the same type of bridges. |
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