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Concurrent bilevel multi-objective optimisation of renewal funding decisions for large-scale infrastructure networks

Abstract Infrastructure fund-allocation is a complex multi-dimensional decision-making problem. It involves multiple stakeholders, thousands of assets with multiple alternative renewal types and timings for each intervention over the planning horizon. Decision-makers need to satisfy stakeholders’ preferences, and determine which and when assets will be funded (network-level decisions) and what repair strategy to use for each asset (project-level decisions). Most of the existing research efforts that addressed both levels have suffered from: consideration of a single objective, fragmented optimisation formulation, and scalability issues in handling large networks of assets. Accordingly, a concurrent bilevel optimisation model that combines both levels into one mathematical formulation while satisfying the varying objectives of infrastructure stakeholders is developed. A pavement case study is used to evaluate its performance against existing phased techniques. Afterwards, two multi-objective formulations have been examined: penalty and compromise. Results demonstrated that the proposed concurrent bilevel model: (1) out-performed comparable phased models, (2) was able to arrive at near-optimum solutions in a feasible processing time for large-scale infrastructure networks, and (3) is capable of dealing with conflicting stakeholder objectives in a flexible manner, using multi-objective formulation, that is extendable to include other objectives that exist in the context of infrastructure fund-allocation problems.