Optimization Of Multi-Objective Maintenance Decision For Bridge Network Considering Carbon Emission And Cost

Bridge network needs necessary maintenance to ensure its connection and normal passage of vehicles,and its maintenance should consider the performance of bridge network,maintenance costs,route selection,personal and social losses,environmental pollution and other factors.On account of the complexity of bridge network,managers need to synthesize various factors to make scientific and reasonable decisions.Therefore,based on optimal maintenance strategy of single bridge,this paper considers total cost,total CO₂ emission and performance improvement of bridge network due to maintenance,a multi-objective decision model for bridge network maintenance and reinforcement is established.Multi-objective genetic algorithm is used to analyze the decision model and the optimal decision method is used to obtain the optimal maintenance and reinforcement decision of bridge network.The main contents are as follows:（1）The optimization of bridge maintenance and reinforcement decision considering carbon emission is studied.The calculation model of CO₂ emission generated in the bridge maintenance stage is established.Bridge maintenance optimization model is established considering CO₂ emission and maintenance cost.Non-dominated sorting genetic algorithm（NSGA-Ⅱ）is used to solve the optimization model to obtain the optimal maintenance decision.The results show that under the condition of ensuring bridge safety,the CO₂ emission and maintenance cost of combined maintenance activity is lower than that of single maintenance activity.（2）Network performance and target reliability of network bridge based on bridge importance are evaluated.The connectivity reliability of the bridge network is calculated based on the time-varying reliability of the bridge.Key bridge reliability is calculated according to the sensitivity analysis of path reliability.The reliability of bridge target is calculated through the importance coefficient of network bridge.The results show that the decreasing trend of bridge network connectivity reliability is most affected by the bridge with the lowest reliability in the network.The path sensitivity coefficient will produce data disturbance when the path reliability is close to 0,and then it will be stable.The more important the location of the bridge,the higher its target reliability.（3）Multi-objective maintenance and reinforcement decision optimization of bridge network considering network performance,CO₂ emission and maintenance cost is analyzed.The multi-objective maintenance decision model of bridge network is established with the connectivity reliability and key bridge reliability of bridge network,total maintenance cost and total CO₂ emission as the objectives.The decision model is solved by multi-objective optimization algorithm,and the improved multi-objective decision methods are used to select the optimal maintenance and reinforcement decision of bridge network.The results show that the NOR-LINMAP and NOR-TOPSIS decision methods can be used to solve the multiobjective decision problems with large difference in order of magnitode.NSGA-Ⅲ is more accurate and reasonable than NSGA-Ⅱ in solving the multi-objective optimization model of bridge network.The cost losses and CO₂ emission caused by social and individual impacts in the bridge network account for more than 90%of the total.