| With the rapid development of our economy, the scale of China's urbanization promises to continue at an increasing rate and the urban geographic environment changes greatly. Nowadays, the amount of hardened ground has been consistently rising in urban areas, the ability of absorbing water has been accordingly descending, and the surface runoff coefficient has been growing larger than before even under the same condition of rainfall intensity and water catchment areas, therefore the rain flood amount aggrandizes accordingly during rainstorm. In many old cities, the drainage systems were designed on the basis of the surface runoff coefficient, return period and other parameters determined by the urban former environment, while the development and reconstruction of urban areas must lead to increase of these design parameters'actual values, which means the drainage systems in many old cities cannot coordinate with the modern development and have been overburdened. When a heavy rainfall or continuous rain occurs, the storm flood disaster often attacks a few areas of the city, which can cause a serious threat to citizens'life and property. From the perspective of rainwater pipeline network, this thesis studies the reliability analysis of urban rainwater pipes and multi-objective optimization problem, aiming at improving the drainage ability of the urban rainwater pipe systems. The thesis conducts the research from the following aspects:Firstly, the Storm Water Management Model (SWMM) is introduced in detail, including its present application, the calculation principles and the step-by-step modelling process. Based on a series of rainwater pipeline network data of a catchment area in Nanjing city, the SWMM rainwater pipe model is established digitally. By coding the software interface program of SWMM, the calculation functions in the SWMM dynamic link library are embedded in the MATLAB calculation platform to realize the automatic data transfer between these two softwares. This skill can take full advantage of the powerful numerical calculation ability of MATLAB and the simulation technology to rainwater pipeline network of SWMM, and can simulate and obtain the drainage situation of rainwater pipe systems during a rainfall incident, reducing the manual calculation steps and improving the calculation efficiency simultaneously.Secondly, based on the theory of structural reliability, the problem about rainwater pipeline network's reliability is discussed and analyzed in this thesis. The pipe diameter, roughness coefficient and laid deviation are set as the three random variables, and from the point of the nodes in rainwater pipeline network the limit state equation is established. The Monte Carlo Method, which has been widely used in calculating and analyzing the structural reliability, is adopted in this thesis to calculate the nodes'reliability value in rainwater pipeline systems. The SWMM source program is coupled with the Monto Carlo Method program on MATLAB platform, and the nodes with low reliability values are found after running program. The results could support for the maintenance and reconstruction of rainwater pipeline network.Finally, the problem of multi-objective reconstruction optimization of rainwater pipeline is studied. To reduce the reconstruction cost, excavated earthwork quantity and overflowed volume are adopted as three goals, the hydraulic requirements in the rainwater pipe designing process are set as constraints and size of pipe diameter and the bottom elevation of inspection well are treated as optimal variables, in this way the multi-objective model is established. The model is solved by using the Multi-Objective Particle Swarm Optimization algorithm, and program of SWMM calculation functions are coupled with that of MOPSO on MATLAB platform. For each simulation, the overflowed volume is obtained and set as the input in the multi-objective reconstruction model for the optimal iteration, which improves the calculation efficiency and precision. |
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