Research On Assessment Method Of Bridge Security Based On Optimization Grey-Theory

Based on the long-term health monitoring data of a suspension bridge,this paper summarizes the changes in the bridge’s displacement,stress,cable force and vibration frequency during the monitoring period,and uses the optimized gray prediction model to predict the maximum value of each monitoring item,combined with finite element Calculate the results,establish an early warning system and determine the early warning indicators and their corresponding thresholds;according to the classification of the bridge safety status and the weight of each indicator,the whitening weight function of gray theory is used to score each monitoring item,and the gray cluster evaluation method is used Gradually complete the assessment of the safety status of the bridge to provide a reference for the daily maintenance and safe operation of the bridge.The main research process and conclusions are as follows:First of all,to understand the development status of health monitoring and safety assessment by consulting data,and grasp the advantages and disadvantages of the existing assessment system.The health monitoring items are determined according to the force characteristics of the bridge,the finite element model is used to calculate the internal force influence line of each member,and the most unfavorable load position and reasonable measurement point position of each member are determined according to the internal force influence line.The monitoring information is statistically analyzed through the data processing system,and through the coordination of the overall system to the subsystems,the establishment of the health monitoring system is completed to realize the efficient operation of the monitoring system.The long-term monitoring data of the system is for the subsequent establishment of an early warning system and bridge safety status assessment Provide an important basis.Secondly,study the principles and methods of the gray prediction model,analyze and summarize the strengths and weaknesses of the gray prediction model;according to the specific calculation process of Markov theory,summarize and summarize the unique properties of the model and the iconic transition probability matrix;in order to make predictions The results are more accurate.Use the Markov model to optimize the results of the gray prediction model to obtain the optimized gray prediction model,and use the prediction model to predict the results in the early warning system.The results show that,compared with the traditional gray prediction model,the optimized model has better prediction accuracy,and the prediction results of the optimized model can better match the change law of actual monitoring data.Use historical data for statistical analysis,calculate statistical parameters,and determine a reasonable yellow threshold range;through the structural analysis of the bridge,load the combination of the most unfavorable position determined according to the internal force influence line and the relevant code load,and load the most unfavorable load under the most unfavorable load.The calculated value of finite element is used as the red threshold of safety warning,two-level safety warning indicators are determined,and a complete warning system is gradually established.The results show that there are a very small number of monitored values that exceed the yellow threshold,but they can quickly return to the yellow threshold.The monitored values that exceed the yellow threshold are far away from the safe range of the red threshold.No data exceeds the red threshold,indicating a safety warning indicator reasonable.Finally,based on the health monitoring data,the bridge safety status is analyzed and researched,the overall evaluation structure is determined by the analytic hierarchy process,the weight of the uppermost layer is determined according to the judgment matrix,and the weight of the lower layer is determined according to the theoretical value calculated by the finite element.According to the real-time monitoring data,the score of each monitoring item is determined,and the gray clustering evaluation method is used for layer-by-layer assessment,and finally the assessment of the safety state of the bridge is completed.The evaluation results show that the overall condition of a certain bridge is good,the working state of each structure is stable,and the evaluation results conform to the basic state of the bridge.This evaluation method has certain practical value in actual projects.