A Lifecycle Cost Based Design Optimization Model for Stormwater Management Systems
This chapter presents a novel approach to optimizing the design of stormwater management systems based on lifecycle cost. A new mathematical model coupled with PCSWMM, and Genetic Algorithms are employed to search for a global optimal design solution for a new stormwater management system. The model also ensures that the global optimization meets a set of design constraints including design guidelines and objectives.
With the implementation and integration of graph theory and search algorithms in the advanced optimization model, this mathematical model can not only identify the best mix of pipe sizes for a given layout of pipes, but can also configure and size new stormwater management network components in a formal way rather than in an intuitive fashion. A deterministic method that can construct a multi-root shortest-path tree is developed for a network configuration. The method is based on a modified form of Dijkstra's algorithm. A layered assignment method is also developed for pipe sizing and pipe slope determination.
Lifecycle cost is used as the evaluation function for design optimization. An environmental cost, viz. flood damage lifecycle cost, is evaluated in the design optimization process as well. A detailed design configuration and a unit cost database are used instead of an empirical cost estimation function to conduct the cost estimation. The approach implemented in this study makes the cost consideration more comprehensive and the result more accurate than the traditional approach. The model thus improves the design quality significantly.
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