Multi-objective optimisation of seismic maintenance management in highway bridge groups considering CO ₂ emissions and decision-maker’s preference

Seismic structural measures of bridges are fundamental to ensure optimal seismic mechanical performance during earthquakes. However, measures implemented in earlier years are inevitably hard to comply with the requirements in current specifications and evolving seismic design concepts. This paper proposes an integrated multi-objective optimisation approach to balance conflicting objectives and provide decision-makers with an optimal maintenance plan. Utility theory is adopted to develop quantitative evaluation systems for indicators referring to performance, economy, and environmental impact. Then the Non-dominated Sorting Genetic Algorithm II (NSGA-II) is employed to optimise these indicators. Additionally, the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is used to refine decision-making. The capabilities of the proposed approach are demonstrated with a case study of 85 highway bridges in service. The results indicate that the proposed method can effectively optimise maintenance schemes to enhance the seismic performance of bridge group in scenarios with different preferences. This framework is also applicable to solve multi-objective optimisation problems for maintenance management of large-scale infrastructure.