The Degradation Prediction And Maintenance Strategy Of Medium&Short Span Concrete Girder Bridges

In the road network,there is a large number of medium and short span bridges,and the majority of them are concrete girder bridges.In the service life of bridges,long-termexposure to the natural environment combined with the increasing traffic,overloaded vehicles and other adverse factors cause bridges all sort of disease and defects,which affect the normal operation.Thus bridge maintenance management has obtained more attention,and various countries and regions have developed bridge management systems,the degradation model and maintenance strategy function module are important comonents of bridge management system.This paper analyzes the typical diseases of medium and short span concrete gieder bridges in Ningbo,and then focuses on the study of their degradation and maintenance strategies.Firstly,based on the Markov Chain,the degradation predictions of project-leveland road network-level medium and short span concrete girder bridges are carried out.For the degradation prediction of road network-level bridges,two optimization models for solving the state transition probability matrix are proposed in this paper.The results show that the optimized model can make full use of the bridge detection data,and the state transition matrix obtained has high precision in degradation prediction of road network-level bridges.Secondly,the composition and calculation model of bridge life cycle cost arestudied.The project-level medium and short span concrete girder bridge maintenance strategy optimization model is established with the objective of minimizing the life cycle cost of bridges during operation,and the maintenance measures and maintenance time are regarded as independent variables.The constraint conditions are reliability indicator,state indicator,reliability and state indicator.Matlab is used to program the optimization model based on genetic optimization algorithm.The optimization results show that the maintenance frequency of maintenance strategy based on reliability indicator is the lowest,the maintenance cost of maintenance strategy based on state indicator is the lowest,the maintenance cost based on reliability indicator and state indicator is the highest and the maintenance frequency is also the highest.Finally,the maintenance priority of road network-level medium and short spanconcrete girder bridges is analyzed.Under the condition of limited funds for maintenance,based on the periodic inspeetion data of bridges,combining the particle swarm optimization algorithm and the comprehensive evaluation method,the maintenance order of road network-level bridges was determined.By using this method,the priority analysis of 55 small and medium and span concrete girder bridges in a certain area of Ningbo City was carried out.The results show that the method is simple and feasible,and can serve as a guidance for bridge maintenance and management.