Collaborative Optimization of Cost, Reliability, and Carbon Emissions for a Bridge Network Maintenance Strategy Based on the Improved NSGA-III

The multiobjective optimization of the maintenance strategy for bridge networks becomes more complex with the increasing environmental problems. A maintenance strategy model of bridge networks considering the coordination of cost, reliability, and carbon emissions is proposed to reduce the environmental impact during the bridge maintenance. The model comprehensively considers the connectivity reliability of bridge networks, reliability of key bridges, and comprehensive cost and further considers the influence of carbon emissions under the time effect. At the same time, the improved nondominated sorting genetic algorithm III (NSGA-III) algorithm is first proposed to optimize the maintenance strategy. To enhance the search capability of the algorithm and avoid local optima, the rotation transform operator and axial transform operator are added in the selection operation stage, while a dynamic cross-mutation mechanism is also introduced. Case study shows that the improved NSGA-III, compared with the original NSGA-III, can obtain nondominated solutions with higher diversity and the stronger convergence. Therefore, the improved NSGA-III can provide a better solution to the maintenance strategy for bridge networks, i.e., obtaining higher connectivity reliability and critical bridge reliability under the condition of lower maintenance costs and CO2 emissions.