| In recent years,China’s small and medium-sized towns have developed rapidly,but the infrastructure construction generally lags behind,and the problem of insufficient fire-fighting water supply capacity of water distribution systems(WDSs)is particularly prominent.In the process of retrofitting WDSs in tourist towns with high fire risk,the traditional method ignores the actual fire risk and the difference of fire-fighting water demand in different areas,so the design scheme may not achieve the expected fire-fighting purpose and is uneconomical.In response to the abovementioned problems,this article conducted a study on the optimization and reconstruction of the WDS in tourist towns based on fire risk.The main research contents and achievements include:(1)Research on the calculation of fire-fighting water demand in tourist towns based on fire risk.When determining the fire-fighting design flow of the WDS,the traditional method is generally based on the urban population,and selects the lower limit specified in 3.2.2 of the " Technical Code for Fire-fighting Water Supply and Hydrant Systems ".The obtained the fire-fighting design flow is far less than the actual fire-fighting water demand.In response to this problem,this chapter carried out the calculation of the fire-fighting water demand of tourist town buildings based on the fire risk,using the actual fire-fighting water demand as the fire-fighting design flow.Based on the existing research results and practical engineering cases,the Gustav method is introduced to evaluate the fire risk of typical buildings in a tourist town,and the ISO method is selected to calculate the fire-fighting water demand.(2)Evaluation of fire-fighting water supply capacity of the WDS based on hydraulic model.The fire water supply capacity of the WDS refers to the maximum amount of water that can be provided by the the WDS in case of fire.It is not only an important basis for the WDS transformation,but also an important basis for regional fire risk analysis and determination of urban safety level.Based on the comparative analysis of modeling software and evaluation methods,this chapter selects water GEMS software is used to build the hydraulic model and evaluate the fire-fighting water supply capacity.Combined with the actual case,the pipe diameter distribution,node elevation,fire-fighting water supply capacity of fire hydrant and water pressure change of control points in LJ city of Yunnan Province are analyzed.Finally,the WDS of Zone B(DY ancient town)is selected as the optimization object.(3)Optimization of the WDS based on differential evolution algorithm based on optimal sorting selection strategy.Aimed at the problem of low computational efficiency of evolutionary algorithms in the optimal design of large-scale WDSs,a differential evolution algorithm based on optimal sorting selection strategy was proposed.In the selection phase,RDEA added the current optimal solution vector repeatedly to each generation to form the parent generation population,reduced the population diversity properly to guide the population to evolve in a better direction,and obtained the near-optimal solutions quickly.The proposed algorithm is used to solve the optimization design problem of the "Balerma" benchmark pipe network,and the performance of the algorithm(calculation efficiency,search speed and solution quality)is discussed.The results show that the proposed algorithm can improve the computational efficiency by 62.768% while ensuring the solution accuracy,and can quickly and effectively obtain the approximate optimal solution of the WDS optimization problem.(4)Optimization of the WDS in tourist town based on multiple fire-fighting conditions.In view of the insufficiency of the fire-fighting capacity of WDSs in tourist towns,and the issues existing in the traditional method such as the relatively small value of fire-fighting design flow and the unreasonable selection of fire-fighting conditions,this paper proposes a method for the optimal design of WDSs in tourist towns based on multiple fire-fighting conditions.The proposed method first selects typical buildings in different areas of ancient tourism towns and calculates their fire water demand by ISO method to build fire-fighting conditions,and then take the minimum required water pressure under different conditions as constraints,and the pipe diameter as decision variables to formulate the optimization problem with the network cost as the objective function.The differential evolution algorithm is applied to solve the optimization problem which minimizes the network cost and satisfies the constraints of different design conditions.The proposed method is applied to the optimal design of the WDS in DY ancient town.The application results show that the overall fire-fighting capacity of the optimized scheme is about 6L/s higher than that of the traditional scheme,and the network cost is about 8% lower than that of the traditional scheme.Besides,after optimization,the fire-fighting capacity of the WDS for typical buildings meets the design requirements,which shows that the proposed method is feasible. |
