Abstract
This paper presents an improved scheduling model for waterway projects that can consider several complicating factors: (a) multiple project alternatives at each location, of which only one may be selected per location; (b) multiple budget sources or regional funding constraints; and (c) constrained precedence relationships between projects. To solve the problem, a simulation-based optimization model that uses simulation to evaluate alternative project schedules is developed. A genetic algorithm is also developed to solve this large investment optimization problem efficiently by means of some prescreening rules that reduce the number of simulated alternatives. The mutually exclusive alternatives at each location allow joint optimization of the sizing and timing of improvements. The multiple budget constraints realistically reflect actual funding practices, but considerably complicate the problem because project sequencing no longer uniquely determines the schedules and projects that may now be funded concurrently. The numerical example shows how the additional factors considered here can be properly incorporated into the analysis and how the quality and reliability of results from such a relatively complex model can be verified.
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