Study On Safety Evaluation System Of Existing Bridges In Tibet

The durability and bearing capacity of existing bridges in Tibet are gradually reduced due to the influence of complex external environment,human factors and structural aging,which will affect the safety of the overall structure of the bridge.Therefore,more and more attention has been paid to the comprehensive evaluation of bridge safety status.According to the results of bridge safety risk assessment,it can effectively reduce the safety risk of bridge operation and provide scientific basis for the management and decision-making of diseased bridges.Based on the analytic hierarchy process and fuzzy theory,this paper uses the maximum membership degree and its evaluation method to construct a comprehensive evaluation system for the safety status of existing bridges in Tibet,and calculates and analyzes the Deqing Bridge in Lhasa as an engineering example.The main research contents are as follows :Firstly,based on the research results of bridge evaluation at home and abroad,the mathematical methods and theories suitable for the evaluation of existing bridges in Tibet are found out,and the application principles and construction steps of analytic hierarchy process and fuzzy theory are summarized.In addition,starting from the typical diseases of bridges,the operating environment of bridges in service in Tibet was investigated and analyzed,and the main factors causing bridge diseases were summarized.Secondly,a comprehensive evaluation model for the safety status of existing bridges in Tibet is established.The analytic hierarchy process(AHP)is used to establish the analytic hierarchy model of in-service bridges in Tibet.The expert scoring method is used to determine the index weight of each factor.Based on the fuzzy theory,the fuzzy comprehensive evaluation index and its membership degree of in-service bridges in Tibet are established,and the comprehensive evaluation model of in-service bridges in Tibet is established by combining the index weight of AHP.In view of the particularity of the climate environment in the plateau area,the maximum membership degree improvement method is used to modify and improve the evaluation results in the comprehensive evaluation model,and finally the multi-level fuzzy state comprehensive evaluation system of existing bridges in Tibet is formed.Finally,taking the Lhasa Deqing Bridge as an example,the multi-level fuzzy comprehensive evaluation model is established and the fuzzy comprehensive evaluation results are obtained.The results are compared and discussed with the conventional evaluation methods.