Research On Structural Condition Assessment Method Of Long-span Cable-stayed Bridge Based On Extension Theory

The long-span bridge structure,the key hub of transportation and national economic development,is easily affected by the increasingly heavy traffic,environmental loads and performance degradation of structure itself,which leads to the damage accumulation and affects the normal use of the bridge structure to a certain extent.Therefore,evaluating the health of bridge timely and accurately is the top priority.The traditional research work of bridge structural condition evaluation seldom combines with massive structural health monitoring data,and most of them are single factor evaluation.The corresponding evaluation results are not comprehensive and efficient to reflect the overall health of the bridge.For the above-mentioned analysis,this paper takes the health monitoring data of a long-span cable-stayed bridge structure as the basis,takes the relative change of the data as the benchmark,and introduces the extension evaluation theory to comprehensively evaluate the health status of the bridge,and provide some reference for the engineering practice.The main research work of this paper is as follows:(1)The development of condition assessment of long-span bridge structure and related theoretical research methods were expounded,meanwhile,the advantages and disadvantages of existing assessment methods were also analyzed.Based on the structural characteristics of the concrete cable-stayed bridge,the common diseases of the bridge structure were discussed combining with the relevant specifications.Preliminary discusses the establishment of the condition evaluation index of the cable-stayed bridge from the two aspects of on-site detection and health monitoring,and briefly explains the standardization of the data types from the qualitative and quantitative aspects.Based on the relative change of data,a condition assessment theory was proposed for the evaluation parameters of the index change.(2)In view of the unreasonable selection of evaluation weight indexes in bridge condition assessment,a more reasonable integrated weight solution method was proposed in this paper.Firstly,the Analytic hierarchy process(AHP)was adopted to solve the subjective weight of the evaluation indexes.Secondly,the coefficient variation method was used to solve the conceptual weight loss based on the measured data.Finally,the subjective and objective weights of the evaluation indexes were optimized by using the game theory,and the comprehensive weights of the evaluation indexes are obtained.Given the comprehensive weight indexes overcome the one-sidedness of the traditional single weight,the evaluation results of the proposed method were more reasonable.(3)Based on the relative variation of the health monitoring data of the cable-stayed bridge structure,and under the assumption of normal distribution,the numerical relationship between the classification of bridge condition level and the confidence interval of normal distribution has been established,One new condition grade division method was proposed.The matter-element extension evaluation method was introduced for the establishment of a complete bridge condition assessment model by the analytic hierarchy theory.According to the theory of bridge condition assessment model based on the MATLAB GUI platform,the corresponding interface design was carried out,and the cable-stayed bridge condition assessment systems were also preliminary developed to realize the visualization and automation for the cable-stayed bridge condition assessment.(4)Based on the actual long-span cable-stayed bridge health monitoring system and structural characteristics itself,the evaluation index system is determined.And the multi-level extension evaluation model is established.Based on the monitoring data of the actual bottom evaluation index,taking the relative change of the evaluation index as the benchmark,the extension evaluation theory was used to evaluate and analyze the actual bridge layer by layer.The final assessment results show that the overall state of the cable-stayed bridge is good,verifying the applicability of the proposed method.