Research On Early Warning And Evaluation Method Of Curved Beam Bridge Structure Based On Long-term Monitoring Data

Curved beam bridges are mostly used in urban interchanges and viaducts,and play a vital role in alleviating traffic pressure in cities.With the increase of urban traffic flow,vehicle speed and vehicle weight,coupled with the curved beam bridge's own lateral force and bending-torsion coupling effect,the curved beam bridge exhibits performance degradation phenomena such as lateral deviation and cracking,and the small span It is not valued by people.Over time,various diseases appeared one after another and even overturned and collapsed.This article is based on the data collected by the long-term real-time health monitoring system of the F ramp bridge at Huayuankou Interchange,analyze its temperature field,displacement and strain changes,and study the structure warning and evaluation methods.The main contents are as follows:(1)Pre-process the temperature,displacement and strain data monitored by the long-term optical fiber system,and use the average value within 10 minutes to represent the temperature,displacement and strain values of this period to study its change law,which effectively simplifies the massive data and improves the analysis and processing s efficiency.(2)The temperature field data of long-term optical fiber monitoring are systematically studied.Extreme value analysis and statistical methods are used to investigate the distribution of temperature and temperature difference between the top and bottom of the box girder,inside and outside.Through statistical analysis and hypothesis testing,it is concluded that the vertical and horizontal maximum daily positive temperature differences of the box beam obey the Weibull distribution.The fitting values of its parameters are obtained,and a method for calculating the representative values of the temperature difference between the vertical and horizontal of the curved beam bridge is proposed.(3)The displacement data of long-term optical fiber monitoring are systematically studied.The data at 1-6 hours at night are used to eliminate the effects of temperature differences and vehicle loads.The structural state index SSI is proposed to evaluate the performance degradation state of the bridge.Using the mean control chart for longitudinal displacement data can intuitively express 8%of abnormal changes in expansion joints,and using mean control chart for lateral deviation data can intuitively express 3%of abnormal changes in support.(4)The strain data of long-term optical fiber monitoring are systematically studied.It is concluded that the strain generated during the service of the bridge is mainly composed of the strain S_acaused by temperature,the strain S_bcaused by the temperature difference,and the strain S_ccaused by the vehicle load.The wavelet packet decomposition method was used to eliminate the influence of vehicle load,and then the principal component analysis and multiple linear regression analysis were used to study the correlation with the temperature structure of the bridge structure.A correlation model between the strain of the main beam and the temperature field was established.Based on this,three models of performance degradation laws of main beams were established,and the evaluation method of main beam safety is obtained.According to the evaluation results of the measured data,the current F-ramp bridge is in good condition and no performance degradation has occurred.