Research On Health Assessment And Multi-objective Decision Making Methods For Preventive Maintenance Of Large-scale Bridge Structures

With the continuous improvement of China’s transportation infrastructure network,the stock of large-scale bridges continues to grow,and more and more large-scale bridges have entered the maintenance period.From the perspective of sustainable development,in order to prolong the service life of large-scale bridges,it is necessary to strengthen the health management in the operation stage while paying attention to the construction of bridges.Large-scale bridges are exposed to the external environment for a long time,and the influence factors of structural damage are numerous and complicated.The rise of structural health monitoring technology realizes the real-time monitoring of bridge structural health and provides data support for preventive maintenance and management research of large-scale bridges.How to accurately grasp the healthy state of large-scale bridge structure,take appropriate ways to maintain at the appropriate time,and then ensure the high quality and sustainable development of large-scale bridges,has become a major problem related to social and economic development.Based on the research status at home and abroad,the health assessment and multiobjective decision making methods for preventive maintenance of large-scale bridge structures is studied in the dissertation.The whole life cycle management theory,accident cause theory and "preventing disease" theory are taken as the theoretical basis.Meanwhile,research methods such as literature analysis,system analysis,model analysis and empirical analysis are used comprehensively.Firstly,based on the analysis of the nature and maintenance characteristics of large-scale bridge structural damage,the influencing factors of large-scale bridge structural damage are identified from the perspective of the whole life cycle.On this basis,the FISM model and improved FTA model are constructed to analyze the cause chain of structural damage.Secondly,with the large-scale bridge structure damage cause analysis results as the important basis,the contents and means of large-scale bridge health monitoring are defined,and BIM technology is integrated to carry out visual integration of monitoring information during the whole life period and structural safety monitoring and early warning.Based on massive monitoring data,the comprehensive evaluation model of large-scale bridge structural health is established to accurately understand the structural health status.Thirdly,according to the data of structural health monitoring and evaluation,a multi-objective decision-making model of preventive maintenance measures and timing is established to improve the scientific nature of preventive maintenance decision-making by taking economic,social and environmental factors into consideration.Finally,on the basis of the aforementioned research content,modern information technology is integrated to build a cloud platform for intelligent maintenance decision-making of large-scale bridges,providing technical support for further improving the scientific nature of maintenance decision-making.The main innovations of the research are as follows:(1)An improved FTA model for damage analysis of large bridge structures is established.Based on the traditional FTA model,the correlation of basic events is considered,Hamacher operator is introduced to calculate the occurrence probability of minimum cut set,and the feasibility of the model is verified by the data of long-span cable-stayed bridge.The improved FTA model is closer to the actual situation of structural damage and improves the reliability of analysis results.(2)A G1-entropy weight matter-element extension structural health comprehensive evaluation model for massive monitoring data is established.The G1-entropy weight combination method is used to set the weight,and the idea of matter element is introduced to evaluate the membership degree of the health grade and the structure health state by solving the evaluation index.The feasibility of the model is verified by a case.This model can reflect the degree difference of the same evaluation level and improve the degree of refinement of evaluation.(3)A multi-objective decision model of preventive maintenance measures and maintenance timing for large-scale bridges is proposed.Considering engineering,society,environment and other factors,a multi-objective decision model of preventive maintenance measures is established and solved by analytic hierarchy process and fuzzy comprehensive evaluation method.The performance curve method is used to construct a multi-objective decision model of preventive maintenance timing based on costeffectiveness,and particle swarm optimization is used to solve the model.The feasibility of the model is verified by a case.This method can effectively improve the scientific decision of maintenance and prolong the service life of the bridge.