Application of Max-min Ant System for Joint Layout and Size Optimization of Pipe Networks

The application of Max-Min Ant System for layout and size optimization of pipe networks is described in this paper. The formulation conventionally used for pipe size optimization of networks with fixed layout is extended to account for layout and pipe size determination of the networks. This is achieved by including a new constraints regarding the reliability of the network and modifying the availability constraints of the optimization problem. An engineering concept of reliability is used in which the number of independent paths from source nodes to each of the demand nodes is considered as a measure of reliability. The method is capable of designing the layout and pipe sizes of the water distribution networks of predefined reliability including tree-like and looped networks. It is also shown that a layout optimization of network followed by size optimization does not lead to an optimal or a near-optimal solution. The performance of the method for layout and pipe size optimization of pipe networks is tested against two benchmark examples in the literature and the results are presented.