| The optimization design of stormwater network is currently carried out by considering of only the construction cost or hydraulic performance. A method of multi-object optimization design is presented. As an example, the method considering the cost and overflow as the optimization object is studied by the optimization algorithm and simulation software. After determining the weight of cost and overflow according to the design purpose, the best scheme is picked out. The main results are:(1)According to Tianjin municipal engineering budget price of 2008,the cost functions of stormwater pipe and manhole are fitted out by using the genetic algorithm. A complete objective cost function of network is obtained to provide cost optimization.(2)Based on the principle of graph theory, the complex structure of stormwater network is represented by correlation matrix. The hydraulic parameters of different schemes are obtained by making use of hydraulic model and the planned flow, origination buried depth and length of pipe.(3)The optimization is processed by emumeration algorithm. By satisfying the optimization of the branch pipes and main pipes at the same time, five low-cost schemes are found by applying global search. The costs are 10.13%,9.47%,6.25%,5.57% and 4.82% lower than the planning scheme, respectively.(4)The stormwater network hydraulic model is established by making use of SWMM and the overflow of the above five network structure for nine return periods are determined. The risk of overflow of every structure is obtained.(5)The change of overflow compared with planning scheme of different pipe network structure is quantitatively estimated. By considering the probability of return period in Tianjin, the percentage of comprehensive overflow changes of different schemes is got. Determining the weight of cost and overflow according to planned targets, a variety of optimization schemes are provided.The optimization algorithm combined cost and hydraulic model is used to choose the best scheme. The study puts forward the theory of multi-angle optimum design for the optimization design of city stormwater network. |
